EPA-R2-73-255
MAY 1973 Environmental Protection Technology Series
Ion Exchange Color
and Mineral Removal
from Kraft Bleach Wastes
Office of Research and Monitoring
U.S. Environmental Protection Agency
Washington, D.C. 20460
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
degradation from point and non-point sources of
pollution. This work provides the new or improved
technology required for the control and treatment
of pollution sources to meet environmental quality
standards.
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EPA-R2-73-255
May 1973
ION EXCHANGE COLOR AND MINERAL REMOVAL
FROM KRAFT BLEACH WASTES
by
Dr. Robert L. Sanks
Montana State University
Bozeman, Montana 59715
EnviTv>--.v:-i-1-.".'\ "'-: - -'-.tion Agenoy
Li ' , -
1 £)..., , .vi'iva
CMougu, Illinois 60606
Project # 12040 DBD
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, B.C. 20402
Price $2.38 domestic postpaid or $2.00 GPO Bookstore
Project Officer
Dr. H. Kirk Willard
National Environmental Research Center
Environmental Protection Agency
Corvallis, Oregon 97330
U.S. Env;-"r--' ' r<-0iection Agency
Region ;;)( i - '-MX
77 Wpct '- i .,
// *»\-ui^_Jtj,^ , jjjf^'/sr/i 1 OtK ci
Chicago, IL 60..C4-3590 °°f
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
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EPA REVIEW NOTICE
This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the con-
tents necessarily reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names of commercial
products constitute endorsement or recommendation for use.
ENVIRONMENTAL *;.Z:~X
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ABSTRACT
Twenty resins and seven carbons were evaluated in the laboratory for
the removal of color and minerals from the four-stage kraft bleach plant
waste of the Hoerner Waldorf Corporation.
Resins were equal to carbon for decoloring ditch waste (the combined
waste of the bleach plant). With a few exceptions, resins were unsuited
for decoloring wastes from the chlorine, hypochlorite, and chlorine
dioxide stages. Except for success in the use of weak wash to regener-
ate Amberlite XAD-8 resin, attempts to utilize mill liquors for
regenerating resins were unsuccessful. Sulfuric acid, caustic, and
ammonia were good regenerants, but lime was poor.
" j Single stage ion exchange with starvation regeneration produced water
'ri adequate for unbleached pulping. Two-stage desalination produced
water adequate for bleached pulping. Any of the continuous counter-
current ion exchange processes are probably adequate for producing
water for bleached pulp manufacture.
The estimated cost for desalination by ion exchange including amortiza-
tion over a 10 year period at 9 percent interest, labor, chemicals,
maintenance, and repairs are estimated to vary from $1..38/_LOOO gal (for
the non-optimized process actually used in the laboratory) to $O.A2/
1000 gal (with estimated 90 percent cation regeneration efficiency, 85
percent anion regeneration efficiency, and 87 percent product recovery).
This report was submitted in fulfillment of Project 12040 DBD under the
sponsorship of the Water Quality Office, Environmental Protection
Agency in cooperation with the Department of Civil Engineering and
Engineering Mechanics, Montana State University.
Key words: bleach plant waste, ion exchange, desalination, color
removal, cost.
iii
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CONTENTS
Section
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
CONCLUSIONS . .
RECOMMENDATIONS
INTRODUCTION .
Page
1
5
7
EQUIPMENT 19
MATERIALS 29
LABORATORY PROCEDURES 41
RESULTS AND DISCUSSION 59
ECONOMICS 157
ACKNOWLEDGEMENTS 173
REFERENCES 175
GLOSSARY 183
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FIGURES
Page
1. SCHEMATIC DIAGRAM OF ION EXCHANGE PLANT 20
2. CIRCUIT DIAGRAM FOR ION EXCHANGE PLANT AUTOMATIC
SHUT-OFF DEVICE 22
3. SCHEMATIC DIAGRAM OF 16-STATION ION EXCHANGER 26
4. SCHEMATIC BLEACH PLANT FLOW DIAGRAM 32
5. FLOW DIAGRAM OF BLEACH PLANT 33
6. CALIBRATION OF SPECTROPHOTOMETER 60
7. FREUNDLICH ISOTHERM FOR DOWEX 11 AND CAUSTIC 65
8. FREUNDLICH ISOTHERM FOR DOWEX 11 AND DITCH WASTE 65
9. FREUNDLICH ISOTHERM FOR DUOLITE A-7 AND CAUSTIC 66
10. FREUNDLICH ISOTHERM FOR DUOLITE A-7 AND DITCH WASTE .... 66
11. FREUNDLICH ISOTHERM FOR DUOLITE A-57 AND CAUSTIC 67
12. FREUNDLICH ISOTHERM FOR DUOLITE ES-33 AND DITCH WASTE ... 67
13. FREUNDLICH ISOTHERM FOR DUOLITE S-37 AND DITCH WASTE ... 68
14. FREUNDLICH ISOTHERM FOR FILTRASORB 300 AND CAUSTIC WASTE . 69
15. FREUNDLICH ISOTHERM FOR FILTRASORB 300 AND
CHLORINE WASTE 69
16. FREUNDLICH ISOTHERM FOR FILTRASORB 300 AND DITCH WASTE . . 70
17. FREUNDLICH ISOTHERM FOR NUCHAR WVL AND CAUSTIC WASTE ... 70
18. FREUNDLICH ISOTHERM FOR NUCHAR WVL AND DITCH WASTE .... 71
19. AMBERLITE IRA-68 RESIN, COLOR SORPTION 72
20. AMBERLITE IRA-93 RESIN, COLOR SORPTION 72
21. DOWEX 11 RESIN, COLOR SORPTION 73
22. DUOLITE A-6 RESIN, COLOR SORPTION 73
23. DUOLITE A-7 RESIN, COLOR SORPTION 74
24. DUOLITE S-37 RESIN, COLOR SORPTION 74
25. FILTRASORB 300 CARBON, COLOR SORPTION 75
26. COLOR REMOVAL FROM CAUSTIC EXTRACT BY LIME PRECIPITATION . 91
27. CAUSTIC EXTRACT SEDIMENTATION RATES IN LIME PRECIPITATION . 91
28. HARDNESS AFTER LIME PRECIPITATION OF CAUSTIC EXTRACT ... 92
29. CALCIUM AFTER LIME PRECIPITATION OF CAUSTIC EXTRACT .... 92
vii
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(Figures continued) Page
30. COLOR REMOVAL FROM DITCH WASTE BY LIME PRECIPITATION ... 94
31. DITCH WASTE SEDIMENTATION RATES. LIME PRECIPITATION ... 94
32. HARDNESS AFTER LIME PRECIPITATION OF DITCH WASTE 95
33. CALCIUM AFTER LIME PRECIPITATION OF DITCH WASTE 95
34. COLOR SORPTION OF LIME-PRECIPITATED CAUSTIC
WASTE BY RESIN 98
35. COLOR SORPTION OF LIME-PRECIPITATED CAUSTIC
WASTE BY CARBON 101
36. COLOR BREAKTHROUGH FOR HALF-INCH AND ONE-INCH COLUMNS ... 105
37. CHANGE OF pH FOR HALF-INCH AND ONE-INCH COLUMNS 105
38. COMPARISON OF COLOR REMOVAL IN HALF-INCH AND
ONE-INCH COLUMNS 106
39. COMPARISON OF pH IN HALF-INCH AND ONE-INCH COLUMNS .... 106
40. SORPTION OF COLOR AT VARIOUS FLOW RATES IN DUOLITE
A-6 RESIN. HALF-INCH COLUMN 108
41. EFFECT OF FLOW RATE ON SORPTION. HALF-INCH COLUMN .... 108
42. IRA-68 COLOR SORPTION. HALF-INCH COLUMN 109
43. IRA-93 COLOR SORPTION. HALF-INCH COLUMN 109
44. S-37 COLOR SORPTION. HALF-INCH COLUMN 110
45. A-6 COLOR SORPTION. HALF-INCH COLUMN 110
46. FILTRASORB 400 COLOR SORPTION. HALF-INCH COLUMN Ill
47. IRA-68 COLOR SORPTION. ONE-INCH COLUMN 114
48. IRA-93 COLOR SORPTION. ONE-INCH COLUMN 114
49. S-30 COLOR SORPTION. ONE-INCH COLUMN 115
50. A-6 COLOR SORPTION. ONE-INCH COLUMN 115
51. FILTRASORB 400 COLOR SORPTION. ONE-INCH COLUMN 116
52. EFFECT OF CONCENTRATION ON REGENERATION OF A-6 RESIN . . . 118
53. COLOR BREAKTHROUGH IN THE REGENERATION OF A-6 RESIN .... 118
54. EFFECT OF CONCENTRATION ON REGENERATION OF S-37 RESIN ... 119
55. COLOR BREAKTHROUGH IN THE REGENERATION OF S-37 RESIN ... 119
56. EFFECT OF CONCENTRATION ON REGENERATION OF IRA-68 RESIN . . 120
57. COLOR BREAKTHROUGH IN THE REGENERATION OF IRA-68 RESIN . . 120
58. EFFECT OF FLOW RATE UPON REGENERATION EFFICIENCY
OF A-6 RESIN 121
viii
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(Figures continued) Page
59. EFFECT OF FLOW RATE ON REGENERATION EFFICIENCY
OF S-37 RESIN 123
60. EFFECT OF FLo i;/.,^ ON Ah^NERATION EFFICIENCY
OF IRA-68 RESIN 123
61. COLOR REMOVAL B\ DUOLI1E A-6 RESIN REGENERATED WITH
WHITE LIQUOR 125
62. COLOR REMOVAL BY DUOLITE S-37 RESIN REGENERATED WITH
WHITE LIQUOR 125
63. COLOR REMOVAL BY DUOLITE A-6 RESIN REGENERATED
WITH CAUSTIC 127
64. COLOR REMOVAL BY DUOLITE S-37 RESIN REGENERATED
WITH CAUCriC 127
65. COLOR AND TOC BREAKTHROUGH IN 13TH CYCLIC RUN.
DUOLITE A-6 RESIN. CAUSTIC REGENERATION 128
66. ELUTION OF COLOR AND TOC IN COUNTERCURRENT CAUSTIC
REGENERATION OF DUOLITE A-6 RESIN IN 13TH CYCLIC RUN . . . 128
67. COLOR AND TOC BREAKTHROUGH IN 14TH CYCLIC RUN.
DUOLITE S-37 RESIN. CAUSTIC REGENERATION . . .' 129
68. ELUTION OF COLOR AND TOC IN COUNTERCURRENT CAUSTIC
REGENERATION OF DUOLITL o 37 RESIN IN 14TH CYCLIC RUN ... 129
69. FOURTH RUN OF COLOR SORPTION FROM RAW DITCH
WASTE BY XAD-8 131
70. REGENERATION OF XAD-8 WITH WEAK WASH 132
71. COLOR AND TOC BREAKTHROUGH IN VIRGIN FILTRASORB 400 CARBON 132
72. EXHAUSTION BREAKTHROUGH CURVES OF IONS AND PARAMETERS
OF PERFORMANCE IN CATION EXCHANGE 134
73. REGENERATION BREAKTHROUGH CURVES IN CATION EXCHANGE .... 134
74. EXHAUSTION BREAKTHROUGH CURVES OF CHLORIDE ION AND
PARAMETERS OF PERFORMANCE IN ANION EXCHANGE 137
75. SERIAL BATCH REGENERATION OF DUOLITE A-6 RESIN WITH 4%
LIME SLURRY AND AIR MIXING 138
76. COLUMN REGENERATION OF DUOLITE A-6 RESIN WITH LIME SLURRY . 138
77. COLUMN REGENERATION OF DUOLITE A-6 RESIN WITH AMMONIA ... 140
78. COLUMN REGENERATION OF DUOLITE A-6 RESIN WITH CAUSTIC ... 140
79. REGENERATION EFFICIENCY. C-25D RESIN 141
80. TRUE EFFICIENCY AND PRODUCT WATER. C-25D RESIN 141
ix
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(Figures continued) Page
81. REGENERATION EFFICIENCY. A-6 RESIN 143
82. TRUE EFFICIENCY AND PRODUCT WATER. A-6 RESIN 143
83. PRODUCT VOLUME IN CYCLIC CATION EXCHANGE. C-25D RESIN . . 145
84. SUPERFICIAL EFFICIENCY IN CYCLIC CATION EXCHANGE.
C-25D RESIN 145
85. PRODUCT VOLUME IN CYCLIC ANION EXCHANGE. A-6 RESIN .... 146
86. SUPERFICIAL EFFICIENCY IN CYCLIC ANION EXCHANGE.
A-6 RESIN 146
87. PRODUCT VOLUME AT 60°C IN CYCLIC CATION EXCHANGE.
C-25D RESIN 147
88. SUPERFICIAL EFFICIENCY AT 60°C IN CYCLIC CATION
EXCHANGE. C-25D RESIN 147
89. PRODUCT VOLUME AT 60°C IN CYCLIC ANION EXCHANGE.
A-6 RESIN 148
90. SUPERFICIAL EFFICIENCY AT 60°C IN CYCLIC ANION EXCHANGE.
A-6 RESIN 148
91. SECOND STAGE COLOR CONCENTRATION HISTORIES 150
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TABLES
Page
1 COMPONENTS OF ION EXCHANGE PLANTS 21
2 SOKBENTS EVALUATED 29
3 CHEMICALS IN BLEACH PLANT 34
4 CHEMICALS IN ENTIRE PLANT EXCEPT BLEACH PLANT 34
5 COMPARISON OF DITCH AND ARTIFICIAL DITCH WASTES 36
6 CHEMICAL ANALYSES OF ARTIFICIAL DITCH WASTES
AFTER PRETREATMENT 37
7 TYPICAL ANALYSIS OF ANION EXCHANGER FEED WATER 38
8 CHEMICAL ANALYSIS OF WHITE LIQUOR 39
9 WEAK WASH COMPOSITION 40
10 CHEMICAL ANALYSES OF ARTIFICIAL DITCH WASTES
AFTER PRETREATMENT 44
11 PROCEDURES FOR CHEMICAL ANALYSES 56
12 SUMMARY OF DATA FOR COLOR SORBENCY 75
13 COLOR PRECIPITATION FROM CAUSTIC WASTE WITH LIME 87
14 COLOR PRECIPITATION FROM DITCH WASTE WITH LIME 88
15 COLOR PRECIPITATION FROM ARTIFICIAL DITCH WASTE WITH LIME . 89
16 COLOR PRECIPITATION FROM CHLORINE, HYPO AND CHLORINE
DIOXIDE WASTES WITH LIME 90
17 RESIN SORPTION OF CAUSTIC COLOR AFTER LIME PRECIPITATION . 98
18 CARBON SORPTION OF CAUSTIC COLOR AFTER LIME PRECIPITATION . 102
19 BED VOLUMES OF WASTE REQUIRED TO REACH COLOR
BREAKTHROUGH OF 50% Ill
20 ESTIMATED OPTIMUM QUANTITIES OF WHITE LIQUOR REGENERANT . . 122
21 COLOR ELUTED AT OPTIMUM QUANTITIES OF WHITE
LIQUOR REGENERANT 124
22 TYPICAL CONCENTRATION OF IONS IN CATION FEED 136
23 TYPICAL CONCENTRATION OF IONS IN ANION FEED . , 136
24 TWO-STAGE COLOR REMOVAL . 150
25 EXCHANGE CAPACITIES IN LIFE TESTS , 151
26 PHYSICAL CHARACTERISTICS OF RESINS ...... 153
27 APPEARANCE OF RESINS .............. 154
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(Tables continued) Page
28 RANGES OF DESIRED PROPERTIES OF PROCESS WATER
FOR KRAFT MANUFACTURE 159
29 TYPICAL WATER QUALITY IMPROVEMENT BY ION EXCHANGE 159
30 OPERATING CONDITIONS FOR ION EXCHANGE 161
31 ESTIMATED CAPITAL COST OF FIXED BED CATION-ANION
EXCHANGERS 163
32 OPERATING COSTS FOR SINGLE STAGE ION EXCHANGE 165
33 COST VERSUS OPERATING CONDITIONS OF SIMPLE ION EXCHANGE . . 165
34 ESTIMATED CAPITAL COST OF A PROGRESSIVE MODE ION
EXCHANGE SYSTEM 168
35 OPERATING COSTS FOR PROGRESSIVE MODE ION EXCHANGE 169
XI1
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SECTION I
CONCLUSIONS
After pretreatment by massive lime precipitation, water desalinated by
a single stage, strong acid exchanger followed by a weak base anion
exchanger is adequate for use in the manufacture of the unbleached pulp.
Excluding pretreatment, storage, and hook-up of the ion exchange units
to the rest of the mill the cost was estimated to vary from $1.38/1000
gal to $0.42/1000 gal. The larger cost was based on duplication of
laboratory conditions in full scale operation namely: 75 percent acid
regeneration efficiency, 84 percent caustic regeneration efficiency,
3 BV of rinse, no recovery of regenerants, and a resin life of two
months. With optimization to increase regeneration efficiency and to
decrease the rinse volume, this cost can be substantially reduced.
Assuming a Progressive Mode ion exchange system, 87 percent regeneration
efficiency, sulfuric acid for regenerating cation resins, ammonia for
regenerating anion resins, 1.3 BV of rinse, 87 percent product recovery,
a one year resin life and amortization over 10 years at 9 percent
interest, the cost was estimated to approximate $0.49/1000 gal of
product water. If the aggressiveness of the bleach plant waste (85 per-
cent chlorination and 15 percent caustic extraction stage effluents) can
be reduced by pretreatment to increase the useful life to five years for
cation resins and three years for anion resins, the cost was estimated
to approach $0.43/1000 gal. The cost of single stage strong acid-weak
base ion exchange could, perhaps, be reduced to $0.42/1000 gal but the
quality of the product water would be inferior to the product from a
Progressive Mode system. The prices for chemicals used in these cost
estimates are April, 1973 prices actually paid for chemicals delivered
to the Hoerner Waldorf Mill at Frenchtown, Montana. The cost of ammonia,
however, was conservatively estimated by a local supplier, but no doubt
this chemical could be obtained at a lower cost.
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Although every effort was made to ensure reasonable cost estimates with
a lack of bias, more accurate cost estimates depend upon extended opera-
tions of large pilot plants at the mill site where pretreatment, 24-hour
operation, and procedures which can be realized in practice can be main-
tained. Nevertheless, the cost of ion exchange is competitive with
reverse osmosis and deserves further study for improving the quality of
bleach plant wastes and to achieve closed systems.
The most pressing problems requiring further research are: (1) reduction
or elimination of the aggressiveness of the wastes, (2) integration of
regenerating chemicals into the mill process, (3) inexpensive recovery
or disposal of concentrated wastes from the ion exchange plant, (4)
development of new resins more resistant to attack, (5) optimization in
the selection and operation of necessary pretreatment methods, (6)
optimization of ion exchange with respect to selection of system and its
operation, (7) careful consideration for the integration of other proc-
esses including reverse osmosis, carbon sorption, and the use of newly-
developed ion exchange processes for pretreatment, and (8) elimination
of slime, foaming, and corrosion problems.
The best resins were approximately equal to the best activated carbon
for the removal of color from ditch waste, the composite waste consisting
of 15 percent caustic extract and 85 percent chlorination stage wastes
from the bleach plant. The best sorbents were weak base porous resins
with phenolic matrices. While resins generally performed well with
ditch waste and caustic extract stage wastes, they performed poorly
with waste from chlorination, hypochlorite, and chlorine dioxide stages.
By contrast, carbon performed better on chlorine, hypochlorite, and
chlorine dioxide stage wastes than on caustic or ditch waste. These
observations do not apply to Amberlite XAD-2 nor XAD-8 as no data on
color sorbency curves were obtained for them. Later tests indicated
XAD-8 was effective for sorption of color from ditch waste.
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Of those anion resins tested for color removal from ditch waste, the
best appeared to be Duolite A-6, a weak base resin with secondary amine
functional groups on a phenolic matrix. The second best resin was
Duolite A-7 which is a similar but less expensive resin.
The small amount of color remaining in the product of single stage
desalination of ditch waste could not be removed at neutral pH either
with phenolic resins or with carbon. But residual color was effectively
removed by phenolic resin at pH 3 (obtained by adding acid or by further
decationization).
Of the regenerants tested, hydrochloric acid, sulfuric acid, and sodium
hydroxide produced excellent results, ammonia was good, lime was poor,
and white liquor was very poor. At a concentration of 5 percent sul-
furic acid, calcium sulfate precipitated in the column, but the diffi-
culty disappeared when the acid concentration was reduced to 3 percent.
Ammonia appeared to be about 80 percent as effective as caustic, but
with operation optimized for ammonia regeneration, Sanks and Kaufman
(1965) were able to achieve nearly 90 percent regeneration efficiency
in fixed-bed ion exchange. Regeneration with white liquor produced
rapidly declining capacities caused by calcium carbonate precipitation
in the resins. When treated with hydrochloric acid, large quantities
of gas evolved, and the resin was restored to virgin capacity. However,
a regeneration process which requires daily renovation of resin seems
impractical.
Optimum rates of flow vary markedly for different resins. In general,
optimum rates of flow for service and for regeneration are considerably
higher than those listed by manufacturers whose literature pertains to
the production of high quality water. Optimization for flow rate should
include considerations of leakage, efficiency, and amortization of
capital because high flow rates result in fewer or smaller reactors.
The required rinse volumes for desalination practice is much less than
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rinse volumes listed by resin manufacturers. In general, service flow
rates can be very high, regenerant flow rates may be optimum at 20 to
30 BV/hr, and rinse at 1.3 BV (10 gal/cu ft) has been found adequate.
Ditch waste from the Hoerner Waldorf Mill was apparently abnormal
because the pH was usually above 5 whereas, according to Button (1972)
the pH of the effluent from most bleach plants is less than 3. The
lower pH of wastes at other mills would enhance the removal of color
by resins.
Ion exchange resins and resin sorbents offer considerable promise for
aid in producing closed water systems in pulp manufacture. Several
new and superior resins have recently become available including
Amberlite XAD-8 and an improved version of Duolite A-6. New processes
have recently been developed with better integration into mill processes
such as the regeneration of Amberlite XAD-8 with weak wash and the
process described by Anderson, Broddevall, and Lindberg et al (1973)
in which the resin is regenerated with black liquor which is then
burned in the recovery furnace. The integration of processes such
as these with desalination by ion exchange might remain the cheapest
means of achieving closed systems.
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SECTION II
RECOMMENDATIONS
As the cost of ion exchange appears to be competitive with the cost
of reverse osmosis, both at the present time and potentially, more
research effort is recommended for ion exchange. At the present time
much research effort is now being lavished upon reverse osmosis whereas
comparatively little is being devoted to ion exchange. The results of
this investigation and of other new products and processes in ion
exchange are encouraging.
It is recommended that additional investigations be made concerning
reduction of the aggressiveness of bleach plant wastes toward resins.
Such efforts should include basic research to develop a means for
predicting the aggressiveness of waters because the only method now
available is the time-consuming "life" tests.
When a satisfactory means for reducing aggressiveness of waters has
been developed to extend resin life to approximately a year or more,
a large scale pilot plant should be constructed with reactors one to
two feet in diameter. These must be versatile enough to permit a wide
range of residence times and flow rates in each reactor or each part of
reactors. The pilot plant should permit a continuous countercurrent
ion exchange process or a close approximation thereof. Satisfactory
processes would include: Chem-Seps, Graver CCIX, and Progressive
Mode. Whichever process is selected, it should be readily possible to
make field alterations of residence times, flow rates, and distribution
of time for service, regeneration, and rinse. Optimization for regen-
erant flow rates, rinse volume, reduction of waste, and pretreatment
(especially for particulate matter) should be studied long enough to
ensure successful prototype operation over extended periods of time.
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The use of inexpensive regenerants such as ammonia, weak wash, and
white liquor, should be studied together with possible recovery and
reuse, integration into other mill processes, or at least innocuous
disposal methods.
The tendency of investigators and government agencies to limit research
to one process should be rejected and replaced by a philosophy of
considering all processes and combinations of processes. A team con-
sisting of experts in ion exchange, reverse osmosis, and pulp mill
practice and chemistry is needed.
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SECTION III
INTRODUCTION
HISTORY OF ION EXCHANGE
Although there are early references to phenomena that might be con-
strued to have been ion exchange, the discovery of ion exchange is
attributed to Thompson (1850) who in 1847 discovered that ammonium
sorbed on soil could not be eluted with water. Investigating Thompson's
discovery, Way (1850) determined the phenomenon was (1) an exchange
of equivalent ions, (2) a function of concentration, (3) less effected
by temperature than other types of chemical reactions, and (4) a func-
tion of selectivity.
The first commercial application of softening by ion exchange was
promoted by Cans (1905), and the development of synthetic cation and
anion zeolites by Adams and Holmes (1935) made demineralization by
ion exchange possible. The modern era of ion exchange began with the
invention of synthetic resins by d'Alelio (1944) and only a decade
later the annual sales of ion exchange products reached $40 million.
After another decade there were approximately 17,000 ion exchange plants.
Because many firms now manufacture ion exchange products, equipment and
systems are highly competitive, much of it is so standardized that
it can be obtained virtually "off-the-shelf."
In the early sixties, ion exchange was used mostly for water softening
and the production of demineralized water of high quality principally
for boiler feed. A small proportion of the synthetic resin production
was used for production of Pharmaceuticals, decolorization of sugar,
and other industrial purposes. The production of high quality water
required thorough regeneration and extensive rinsing so the use of ion
exchange for the partial demineralization of brackish waters could
not be justified by desk-top analyses due to the extensive portion
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of the water produced required for rinsing and regeneration. It was
generally conceded ion exchange could be dismissed as impractical for
the demineralization of high solids water unless the regenerants could
somehow be recovered for reuse or unless the resins could be regenerated
by some method of heat exchange or the use of electrical current. Early
in that decade, however, several workers applied themselves to the
demineralization of high solids water, notably Kunin, Higgins, Odland
and Pabich, the Asahi Chemical Corporation, and Sanks and Kaufman.
Desal Process
The Desal Process developed by Kunin (1965) typically utilizes a 3-bed
system containing weak-electrolyte resins. In the first bed, Amber-
lite IRA-68 resin (in bicarbonate form) exchanges influent chlorides
and sulfates in raw water for bicarbonate. The second exchanger,
Amberlite IRC-84 (in hydrogen form) exchanges influent cations for
hydrogen ions. In the last exchanger, IRA-68 (in hydroxyl form) the
bicarbonate is exchanged for hydroxyl ions and the water is consequently
demineralized. The first reactor is regenerated to the hydroxyl form
with caustic, ammonia, or lime, and the second reactor is regenerated
to the hydrogen form with sulfuric acid. The third reactor is left in
its exhausted state which is the bicarbonate form. Hence, at the
beginning of the second cycle, the position of the exchangers is
reversed with respect to right and left, and raw water enters the
"third" reactor first. Several modifications, such as a 2-reactor
system, are possible. Kunin and Downing (1970) estimated an operating
cost of $0.20/1000 gal to produce potable water from a brackish water
containing 1000 mg/1 of total dissolved solids in a 1 mgd plant for a
capital cost of $250,000.
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Chem-Seps Process
Higgins (1964) explained the use of a continuous, moving bed ion
exchange process for demineralizing high solids water. The resin
in the reactor is confined to a closed loop divided by butterfly
valves into separate reaction sections: (1) loading or exhaustion,
(2) feed-rinse, (3) rinse elimination, (4) regeneration, (5) regeneration-
rinse, and (6) second water elimination. At frequent intervals the
resin is pulsed a few inches around the loop countercurrently to the
solution flow. By means of ports and conductivity probes, mixed liquor
at the liquid interfaces is eliminated to prevent contamination of
the product. Its advantages are: the last of the resin contacted
by the influent feed is fully regenerated and only fully exhausted
resin is regenerated. The system permits high flow rates limited only
by pressure drop. Higgins (1965) proposed nitric acid for regenerating
cation resin and ammonia for regenerating weak base anion resin. Thermal
decomposition of the nitrate salts in the spent cation regeneration
can be utilized to recover nitric acid and metallic hydroxides. Ammonia
can be evolved by reacting the spent anion regenerant with the metallic
hydroxides. Efficiencies of regenerant reclamation varied from 50
to 80 percent in laboratory tests. The overall efficiency of the process
with respect to chemical regeneration can be 95 percent or more.
Sul-biSul Process
In the Sul-biSul process evaluated in the field by Schmidt et al (1969)
cation removal is accomplished conventionally, but anions are removed
by a strong base exchanger operating between the sulfate form and the
bisulfate form. During exhaustion the anion bed is converted to the
bisulfate form by the acidic influent. It is regenerated to the sulfate
form with either raw water or lime. Its capacity is only half the
capacity of a conventionally operated ion exchanger, but regeneration
is cheap, and the strong base electrolytes are not subject to fouling
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by organic materials. Odland and Pabich (1965) made extensive analyses
of costs required to demineralize high solids water. For example,
a 1 mgd plant could remove 1500 mg/1 from water containing 2000 mg/1
total dissolved solids at a cost of approximately $0.56/1000 gal.
Graver CCIX Process
The Graver CCIX Process is a fully automatic continuous countercurrent
ion exchange process which uses three reactors for cation exchange and
three more for anion exchange. Service or exhaustion is carried out
in the first column. At intervals, the influent feed is halted for
30 seconds and the exhausted horizon of resin is pumped to the second
column for regeneration. The fully regenerated horizon of resin in the
second column is pumped to the third column for rinsing. During this
30 second interval, resin in the first column drops downward in the
reactor and rinsed resin from the third column is pumped into the top
of the reactor through a special valve. All of the reactors operate
with an upward flow of liquid. The first reactor always has a freshly
regenerated horizon of resin to polish the feed water. As with the
Chem-Seps method invented by Higgins, the Graver CCIX Process utilizes
regenerant at very high efficiency according to Levendusky, Limon, and
Ryan (1965).
Progressive Mode
As explained by Adams (1970), the Progressive Mode system (marketed by
The Permutit Company) utilizes three or more reactors each for cation
and for anion exchange. The reactors are regenerated and rinsed in
place and in a sequence such that the feed water first contacts partly
exhausted resin in one reactor and finally leaves a last reactor full
of freshly regenerated resin. The advantages of progressive mode are:
each reactor is of the simple type that has been commonly used for at
least the last 30 years, and a wide variety of flow regimes coupled with
10
-------
operational flexibility can be used to accomplish almost any desired
effluent quality at high efficiencies of chemical regeneration.
Simple Fixed Bed Systems
Working with the simplest ion exchange system (a strong acid cation
exchanger followed by a weak base anion exchanger) Sanks and Kaufman
(1966) optimized the exchange cycle to produce low solids water from
2000 IDS feed at higher chemical efficiencies than those previously
reported.
Acid efficiencies of 93 percent were obtained by a combination of
reutilizing partly spent regenerant and by "starvation" regeneration.
Regeneration efficiency decreased to 80 percent when only fresh acid
was used. However, by adding a layer of weak acid resin on top of
the strong acid resin, Sanks (1967) found the efficiency of regenera-
tion using fresh acid only could be increased to 92 percent. Abrams
and Poll (1967) termed it the "Duo-Cat" Process. It is effective only
when the proportion of bicarbonate ion exceeds 20 percent of the total
anions. Efficiencies of weak base resins were 89 percent using caustic
and 86 percent using ammonia. Sanks and Kaufman found it cost $0.15/1000
gal in a 10 mgd plant to remove 350 mg/1 of total dissolved solids
from sewage treated by activated sludge, coagulation, sand filtration,
and carbon sorption. They experienced no difficulty with blinding or
irreversible sorption.
Fouling and Blinding
The effects of organics in blinding strong-base ion exchange resins and
the difficulty of renovating them has been studied by Wilson (1959) and
others. Using many radio-active labeled compounds, Ward and Edgerley
(1965) studied the role of various functional groups in blinding strong-
11
-------
base resins. The mechanism and kinetics of poisoning was discussed by
Olson (1968).
Countercurrent Regeneration
Countercurrent regeneration is universally known to be much more
efficient than concurrent regeneration. But Lux (1971) pointed out
slight shifts in the resin bed, due to counter-flow conditions, reduced
efficiency. In the Econex process, inert granular synthetic material
in the plenum keeps the resin bed firmly in place and improves regenera-
tion efficiency. Some of the inert material is pumped out of the
plenum for backwashing.
Summary of Federal Programs
By the e:.d of 1966, a considerable body of knowledge had been developed
on the desalination of high solids water by ion exchange. The
Advanced Waste Treatment Research Program of the Public Health
Service was initiated in 1960 to alleviate growing water pollution
problems and to renovate wastewater for direct reuse or recycling.
The Advanced Waste Treatment Research Program was transferred to the
Environmental Protection Agency which is now striving for "closed"
systems in water use by industries. The advancements in ion exchange
have lead to the inclusion of this process for evaluation in this
program.
PULP INDUSTRY
The pulp industry is the fifth largest industry in the United States.
Kraft pulp accounts for the largest tonage of any process. Large
quantities of water are required for this process and particularly
for the bleaching of kraft pulp. Not only is the quantity of water
required for bleaching large (15,000 to 60,000 gallons per ton of
12
-------
bleached pulp) but the bleach waste is by far the most highly colored
and objectionable of all the liquid wastes discharged from a kraft
plant. Furthermore, it contains high total dissolved solids, a fairly
high COD, a moderate BOD, and it possesses a moderately high toxicity.
Reuse
The reuse of water in the pulp industry is increasing. Cooper (1968)
showed how more careful housekeeping reduced water use at one plant
to 28 percent of its previous amount per ton of pulp. Haynes (1966),
reporting on the reuse of water by 10 kinds of pulp and paper mills,
showed overall water reuse in 1965 was about 220 percent of total intake,
In a more recent TAPPI survey, Haynes (1968) showed the reuse of water
to be increasing toward a target figure of 300 to 400 percent. Nelson
et al (1972) discussed the possibility of reducing water use to 6000
gal/ton pulp and Yankowski (1972) proved (by laboratory tests confirmed
by mill tests) it was possible to reduce bleach wash water by 50 percent
with no effect on brightness of pulp. Factors inhibiting reuse are
(in order of their importance): slime, suspended solids, color, dis-
solved solids, foaming, corrosion, and scale. Berger (1966) stated
advanced treatment of kraft mill waste will become common practice
before long. Secondary treatment of kraft mill wastes cost more than
$1.50 per ton in 1966 and complete treatment (primary sedimentation,
biological oxidation, color removal, and sludge disposal) would cost
more than $3.00 per ton of production or $0.05/1000 gal assuming 60,000
gal of effluent per ton of production. He stated desirable water
quality limits for bleached kraft manufacture are:
Color 5 CU Alkalinity 75 mg/1 CaC03
Hardness 100 mg/1 CaC03 Iron 0.2 mg/1
IDS 250 mg/1 Manganese 0.1 mg/1
Chloride 150 mg/1 COD 8 mg/1
Turbidity 5 JTU BOD 2 mg/1
13
-------
Massive Lime Precipitation
In the massive lime precipitation process patented by Berger, Gehm, and
Herbet (1964) for color removal the colored waste is mixed with the
entire lime budget used to caustisize the green liquor. Transferring
the resulting filter cake to the caustisizer, the color bodies dissolve
in the white liquor, pass through the digestion process, and are finally
burned in the black liquor recovery furnace. The process, fully des-
cribed by the National Council for Stream Improvement (1962) , removes
88 to 95 percent of the color which renders the water suitable for
reuse for some plant purposes. Bennett et al (1971) determined the
color reduction is due not to sorption but to reaction of lime with
very weakly acidic groups to form insoluble calcium salts. Remaining
color is attributable to the more soluble calcium salts of low molecular
weight. A more extensive discussion of this work is given by National
Council for Air and Stream Improvement, Inc. (1970). Interstate
Paper Corporation (1971) found it possible to reduce color from the
effluent of an unbleached linerboard mill to 125 CU with only 1000
mg/1 of lime, which is a much smaller dose than that used for massive
lime precipitation.
Color sorption. The potential use of granular carbon to polish the
waste effluents after massive lime precipitation has been given by
McGlasson, Thibodeaux, and Berger (1966). Rimer, Calahan, and
Woodward (1971) estimated costs for carbon sorption of combined munici-
pal and pulp mill effluents. The mechanism, effectiveness, and cost
analysis of carbon sorption were the subject of intensive study by
the National Council for Stream Improvement (1965, 1967), and the council
concluded carbon should be used as a polishing agent only after massive
lime precipitation.
Many other studies of sorption might well apply to decoloring bleach
plant effluents. The West Virginia Pulp and Paper Company (1969)
14
-------
recommended mixed pulverized carbons for sorption over a wide range
of molecular sizes. Recovery and regeneration of powdered carbon poses
difficult problems which are yielding to current research efforts. A
promising technique is the manufacture of carbon by "scorching" black
liquor, using the carbon to sorb color from wastes, then burning sorbed
organics and carbon for heat recovery.
Dickinson and Barrett (1969) found finely divided sorbents consisting
of polar resins, activated carbon, and inorganic sorbents mutually
enhance and complement one another for removal of color and haze.
Rebhun and Kaufman (1967) concluded the performance of resinous sorbents
was comparable to carbon for sorbing color from treated wastewaters.
However, virgin carbon was nearly twice as effective as virgin resins
for sorbing gross organic material.
Rohm and Haas Company (1970) developed a sorbent resin XAD-2 which
was intended to polish pulp mill effluents after massive lime precipi-
tation. By using white liquor for regeneration, the process can be
integrated into the mill process in which the color bodies are eventually
burned in the recovery furnace. Later, Rohm and Haas Company (1971)
found a more effective sorbent, XAD-8, had sufficient capacity to remove
color from raw bleach wastes and the color could be eluted with weak
wash. Unfortunately, their literature did not mention the pH must be
less than 2.5 for effective sorption nor that concentrated eluants like
white liquor are too strong for effective regeneration.
Ruzickova (1970) found Ostion-SL(L-33), a weakly basic gel-type
Czechoslovakian anion exchanger obtained by condensation of aromatic
amines with formaldehyde, to be suitable for decoloring sulfite mill
wastes, sulfate mill wastes, and bleaching wastes after biological
treatment. The resin was also able to remove residual phosphates.
15
-------
Desalination for Reuse
Desalination of the bleach wastes can be accomplished by many processes,
among them: reverse osmosis, electrodialysis, and ion exchange. Pilot
plant studies of reverse osmosis have been reported by Wiley, Ammerlaan,
and Dubey (1967) who found it possible to concentrate solids to
10 g/liter or more and to obtain high yields of colorless, non-foaming
product water. In a later work, Ammerlaan, Lueck, and Wiley (1968)
reported difficulty with the fouling of membranes. Wiley, Dubey, and
Ba, 1 (1972) concluded membrane replacement, required at least once
per year, represented 60 to 80 percent of the operating costs and
commercial application would depend upon success in attaining membrane
life far beyond present limitations.
Thibodeaux and Berger (1967) found the Desal process effective in
desalinization of caustic stage bleach and further studies by Thibo-
deaux and Wright (1970) led to cost estimates of 60.4c/1000 gal to
reduce IDS from 2500 mg/1 to 25 mg/1. The fixed capital investment was
estimated at $1,280,000 for six 20 ft ID x 15 ft high columns, regen-
erant tanks, and pumps. Regenerants were one percent solutions of
sulfuric acid (for the IRC-84 resin) and ammonia (for the IRA-68 resin).
OBJECTIVES
Relatively little attention has been given to the use of resins as
sorbents. Although resins are more expensive than carbon and although
they can be blinded, poisoned, or oxidized under some conditions, they
can be regenerated in situ with cheap chemicals and with little or no
loss in capacity. Their kinetic properties are equal to or better than
those of carbon, their capacities are high and their properties can be
varied and controlled by the manufacturer. Resins can be used to sorb
organics and to reduce dissolved solids at the same time.
16
-------
General Objectives
The general objectives were to determine the economic potential of
synthetic resins for the control of pollution from kraft bleach wastes
particularly in reuse and recycle systems. It includes the investiga-
tion for the removal of color, other organics, and dissolved minerals
from the waste streams of kraft bleach mills and an estimate of the
economics for comparison with other methods.
Specific Aims
The specific aims were:
1. to determine the relative merit of various resins and carbons by
determination of sorption isotherms,
2. to optimize fixed bed ion exchange for the removal of color and
for demineralization combined with color removal,
3. to verify the best types of resins for sorption and demineraliza-
tion,
4. to seek more economical methods and chemicals for regeneration,
5. to investigate acceptable means of waste regenerant disposal,
especially methods which permit reuse of chemicals,
6. to compare sorption and ion exchange using resins with other
methods for renovating water,
7. to estimate the cost of treatment by resins alone or in conjunction
with other methods, and
8. to establish criteria for the design and operation of a pilot plant.
SCOPE
The study was limited to the investigation of commercially available
resins only and to the bleach waste from one kraft pulp plant.
Only the simplest ion exchange system (strong acid cation exchange
17
-------
and either strong or weak base anion exchange) was to be considered
so the results could be as universally applicable as possible.
The work was divided into the following phases: exploration, color
sorbency in columns, ion exchange, life tests, and economic evaluation.
The exploratory tests were designed to establish operating procedures
and to make a preliminary evaluation of each resin which would result
in eliminating all but the most favored resins for further
investigations.
PROPRIETARY PRODUCTS
Manufacturers and trade names are listed with reluctance and a warning.
Disguising the names of resins places an undue hardship on the reader
with respect to interpreting results. The mention of trade names in
no way constitutes either endorsement or rejection of a product. A
slight change in feed water analysis can make a great deal of difference
in the life or efficiency of a resin, and the reader is cautioned that
the results reported herein might not apply to another waste under
other conditions.
18
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SECTION IV
EQUIPMENT
ION EXCHANGE
Pilot Plant
To facilitate laboratory operations, such as the collection of fractions,
ending a run at a precise value of color, pH, or conductivity break-
through, switching from downflow to upflow, etc., two semi-automatic
pilot plants shown schematically in Figure 1 were constructed. The
columns were Corning double-tough Pyrex conical glass pipe. Top and
bottom sections were separated by a central distributor which permitted
rapid draining of the plenum or block flow (compressed-bed upward flow).
Liquids were carried in 1/4 x 1/8 R3603 Tygon (vinyl) tubing connected
to the column with Swagelok double-end-shut-off quick-connects (labeled
QC) made of 316 stainless steel. They permitted instant switching
of feed, waste, and drain hoses to either bottom, center, or top of
the column. The components are described in Table 1.
Control of breakthrough. The conductivity meter was altered by the
installation of a rise-fall switch connected to a separate manual-reset
relay box. The wiring diagram for the relay is shown in Figure 2.
This apparatus makes it quick and easy to stop the feed pump on a rise
or on a fall of conductivity to any preset value from 10 to 10,000
micromhos/cm .
The Sargent recorder was modified so it can also shut off the pump
motor at any predetermined value of pH, color, or any other quantity
that can be monitored by the Hitachi Perkin Elmer M-139 spectrophotometer.
A large washer was clamped to each of the two chart pen drive wheels
in such a manner as to allow its rotation to any position. A pin welded
19
-------
pH cell
I
Waste
Conductivity cell
Bourdon gage
Flow meter
Conductivity meter
Metering valve
1 -
Feed
To fraction collector
V J
FIGURE 1. SCHEMATIC DIAGRAM OF ION EXCHANGE PLANT
20
-------
TABLE 1
COMPONENTS OF ION EXCHANGE PLANTS
Part
pH electrode
Conductivity cell
QC (Quick Connect)
Bourdon gage
Flowmeter
Conductivity meter
Relay
Metering valve
Fraction collector
Pump
Not shown in Figure 2:
pH meters
Recorder
Spectrophotometer
Description
Sargent S-30072-15 combination, glass
Beckman JD-2. K = 2.00
Swagelok 400-1/4QC-200 DESO 316
US Gage 19001
Fischer Porter 10A3135M
Beckman RE104-Y11 Solu Bridge
Advance 964 D54 with manual reset
Nupro SS-4MX with micrometer handle
Isco Golden Retriever 326
Sigmamotor T-65, Bodine 54SH DC motor and
Minarik 76 SH Controller
Sargent DR and Orion 404
Sargent dual channel DSRG equipped with two
Micro JV26 microswitches
Hitachi Perkin-Elmer M-139 equipped with a
flowthrough cell
to each washer is used to trip the microswitch which carries electric
current to the pump motor. When the pen reaches a preset position
on the chart, the microswitch is activated which stops the motor. Two
channels can be operated simultaneously and independently.
Small Columns
Half-inch ID columns were used for screening tests in order to conserve
the limited quantities of wastewater. They were made from heavy wall
Pyrex glass tubing two feet long. End closures were rubber stoppers
ground to fit and bored for a short tube to fit the rubber tubing. A
21
-------
110 va
To
conductivity
cell
©
Wall
outlet
To relay
LI-
Rise-fall
switch
Solenoid
0
Manual
reset
Double
relay
Conductivity meter
terminal strip
110 vac
RELAY BOX
Wall outlet
oo
To alarm-1 LTo pump
FIGURE 2. CIRCUIT DIAGRAM FOR ION EXCHANGE PLANT AUTOMATIC SHUT-OFF DEVICE
22
-------
tuft of glass wool supported the resin bed. The feed was placed in
a five gallon plastic jug pressurized to 3 psi with compressed air.
A manifold of rubber hose and glass tees led to five half-inch columns
operated simultaneously. Flow rate, regulated by Hoffman hose clamps,
was measured with a stopwatch and a small graduated cylinder.
Appurtenant Equipment
Shakers. Batch tests for isotherms were carried out in 250 ml
erlenmeyer flasks containing 100 ml of liquid agitated in a Blue M
Model MSB1122 A-l water bath shaker holding 10 flasks. Preliminary
tests showed the optimum amplitude to be one and one half inches and
the optimum speed 112 rpm. The temperature of the flasks was maintained
between 17 and 20°C. To augment the limited capacity of the Blue M
water bath shaker, a special shaker was constructed to hold 54 flasks.
It consisted of a 20 gage galvanized iron tray mounted on a 3/4 inch
angle iron frame to which four roller skate wheels were attached. The
tray was driven by a connecting rod attached at a radius of 3/4 inch
to the pulley of a Bodine motor. It was crude but effective and
reliable.
Environmental cabinet. Most tests were conducted at room temperature
maintained between 68 and 75°F. Elevated temperature tests were con-
ducted in a custom made environmental cabinet 6'3" high by 6'8" long
by 2'10" deep inside dimensions. The temperature controller, built
especially for this cabinet, maintained any given temperature within
23
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LIFE TESTS
Ion Exchange Reactors
Sixteen ion exchange reactors were made of Corning double tough conical
Pyrex pipe reducers specially fabricated to have a one-inch ID section
3 1/2 inches long expanding to 1 1/2 inch ID with an overall length
of 7 1/4 inches. They were fitted with standard aluminum flanges
and gaskets with end closures made of lucite fitted with nylon Swagelok
tubing connections. The resin was supported by 80 mesh stainless steel
screens. All tubing was 1/4" x 1/8" Tygon R3603 tubing connected to
a nest of plastic tees in such a way so that the total length of inlet
or outlet to each column was the same.
The combination of upflow operation and the larger diameter above the
resin bed completely prevented any plugging of resin columns. The
apparatus was quite successful.
Pumr
A sixteen channel roller pump similar in concept to the Sage Model
375 Peristaltic pump was constructed especially for the project. It
was powered by a Bodine NSH-11D3 variable speed reversible motor con-
trolled by a Minarik SL14P converter-controller equipped with a 10-turn
helipot. The unit can be set for any speed between 3 and 44 rpm with
an error of less than 1 percent.
The tubing in the pump was silastic rubber 1/4" OD by 1/8" ID. By
stretching each tube as needed, it was easy to regulate the flow
within 1 percent of the desired value.
As first constructed, the pump tended to cut certain of the rubber
tubes badly. The pump was remodeled by removing the hinges and holding
24
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the cover with four vertical threaded studs and by widening the
pressure plates by gluing to each plate a strip of Teflon sheet wide
enough to reduce gaps to a minimum. No further trouble occurred and
no tubing ever again required replacement.
Automatic Cycler
The automatic cycler consisted of a Cramer type 540 timer in a custom
chassis. Four 3-way switches were provided to override the timer
switches for control. The timer switches activate Asco Catalog no.
826206 stainless steel solenoid automatic valves. The four valves
were connected respectively to: (1) the acid storage tank, (2) pretreated
bleach plant waste, (3) caustic storage tank, and (4) cation reactor
product water.
The apparatus is shown schematically in Figure 3. Essentially it
consisted of two separate systems: one for cation exchangers and one
for anion exchangers. One of the automatic valves failed after a few
hours of operation and required replacement. Otherwise the apparatus
worked perfectly without attendance save for the necessity of refilling
the tanks with liquor.
CHROMATOGRAPHY
The chromatographic column was a Pharmacia type K9/60, 9 mm in diameter
and 60 cm long. The flow of the eluent, 0.02 molar NaCl, was maintained
at 10 ml/hr by a Sage Model 375 tubing pump. Fractions were collected
in an Isco Golden Retriever Model 326 fraction collecter.
25
-------
-lucite
lucite
Corning glass
reducer7
Swagelok tube fittings
COLUMN DETAILS
To Waste
t t t t t t t t f t t t t t t t
16 station tubing pump
11
tl
II
Cation
Feed
111
0
H
n U W:
M V:.'
111111111
F As co
solenoid
valves
Acid
Regen-
erant
Anion
Feed
Base
Regen-
erant
FIGURE 3. SCHEMATIC DIAGRAM OF 16-STATION ION EXCHANGER
26
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ANALYTICAL EQUIPMENT
Spectrophotometer
Color was measured with an Hitachi-Perkin Elmer Model 139 spectro-
photometer at a wave length of 422.2 my and at a slit width of 0.32 mm.
The spectrum is continuous and varies slowly, so a wave length of 420
my would give essentially the same results. Because the concentration
of color varied greatly, cells with effective light paths of 10 cm,
1 cm, and 0.036 cm were used. The effective light path 0.036 cm, used
to avoid tedious dilution, was made by placing a polished lucite block
with an effective thickness of 0.964 cm into the 1 cm cells. The unit
was calibrated with several colored solutions to insure accuracy,
repeatability, and conformance with the standard 1 cm cell.
Sodium and potassium. The M-139 spectrophotometer was fitted with
a flame photometer for measuring sodium at a wave length of 589 my and
a slit width of 0.01 mm and potassium at a wave length of 768 my and
a slit width of 2.0 mm. The photo-multiplier was connected to a Sargent
Model SLRG 10-inch strip chart recorder for precise determination of
average photometer response.
Carbon Analyzer
During all of the preliminary investigations, total organic carbon was
measured with a Beckman carbonaceous analyzer belonging to another
department and operated by the personnel of that department. The
instrument was out of commission so much of the time that most of the
organic carbon measurements could not be made. During the last part
of these investigations, total organic carbon was measured on a new
Beckman Model 915 Total Organic. Carbon Analyzer, an instrument which
gave reliable results.
27
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Amperometric Titrater
Due to the difficulty of titrating highly colored solutions with color
indicators, a Wallace and Tiernan Amprometric Titrater was obtained
for the measurement of chlorine. It functions independently of color
and measures total residual chlorine at pH 4 and free available
chlorine at pH 7. As determined by iodometric titration, the accuracy
was found to be satisfactory.
pH Meters
Several meters were used to measure pH including an Orion Model 404
lonalyzer, a Beckman Zeromatic II and a Sargent Model DR. All were
equipped with combination electrodes. Calibrations were made frequently
and always with solutions within 3 pH units of the unknown solution.
28
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SECTION V
MATERIALS
RESINS AND CARBON
Carbon was used in these investigations only to provide comparison in
color sorbency with synthetic resins. All sorbents and ion exchangers
are described in Table 2.
TABLE 2
SORBENTS EVALUATED
Designation
Name No .
Cation resins
Dowex HCR-W
Duolite C-25D
Amberlite IRC-84
Amberlite IRC-50
Amberlite IR-120+
Anion resins
Dowex 11
Dowex WGR
Amberlite IRA-93
Amberlite IRA-402
Amberlite IRA-68
Duolite A-6
Duolite A-7
Functionality
Strong Acid
Strong Acid
Weak Acid
Weak Acid
Strong Acid
Strong Base
Weak Base
Weak Base
Strong Base
Weak Base
Weak Base
Weak Base
Porosity
Gela
^ a
Porous
Gel3
Gelb
Gelb
GelC
Geld
Macro-
reticular
Gelb
Gelb
Macro-
c
porous
Macro -
c
porous
-,a
Composition
Active
Matrix group
Polystyrene SOJSIa
Polystyrene SO~Na
Acrylic COOH
Methacrylic COOH
Polystyrene SO,.Na
Polystyrene N(CH ) Cl
Epoxy-amine NR_
Polystyrene t>7R«
PC' ;-3tyrene NCCH^Cl
Acrylic NR«
Phenolic NR0
£
Phenolic NR0
2.
29
-------
(Table 2 Continued)
Sorbents
Amberlite XAD-2
Amberlite XAD-8
Duolite S-37
Duolite ES-33
Duolite S-30
Filtrasorb 100
Filtrasorb 200
Filtrasorb 300
Filtrasorb 400
Nuchar WV-L
Nuchar WV-G
Nuchar WV-W
r\
mesh size 20 x
mesh size 16 x
mesh size 14 x
Sorbent
Sorbent
Weakly Basic
Weakly Basic
Sorbent
Sorbent
Sorbent
Sorbent
Sorbent
Sorbent
Sorbent
Sorbent
50 mesh
50 mesh
50 mesh
Porosity
Gela
Macro-
reticular
Macro-
c
porous
Macro-
c
porous
Semi-
c
porous
Porous
Porous
Porous
Porous8
Porous
Porous8
a
Porous0
size 20 x 40
size 20 x 60
size 8 x 30
Matrix
Phenolic
Phenolic
Phenolic
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
8 mesh
h ,
mesh
mesh
Active
group
NR2
NR2
00H
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
Carbon
size 12 x 40
size 8 x 20
size 12 x 30
PROCESS STREAMS
All wastewaters were originally obtained from the Hoerner Waldorf
kraft pulp mill locaced at Frenchtown, near Missoula and 2.36 miles
from Bozeman.
Hoerner Waldorf Mill
The mill was constructed in 1957 and expanded in 1960 and again in
1966. It now produces 900 tons per day of kraft paper board or
30
-------
unbleached pulp and between 130 and 150 tons per day of bleached pulp.
The species of wood utilized varies but all are soft woods.
Pulping
All bleached pulp is produced in batch digesters. Each of the eight
digesters holds a 10 ton charge on a dry basis (20 tons wet as loaded)
and the total capacity is 60 3-hour cooks per day for a gross ultimate
capacity production of 600 tons per day. However, 150 tons of pulp
(dry basis) is the maximum that is actually bleached. All flow dia-
grams and all chemical usages are figured on the basis of a 150 day
production of bleached pulp.
Bleaching
The bleaching process, shown schematically in Figure 4, consists of
four stages: (1) chlorination, (2) caustic extraction, (3) sodium
hypochlorite, and (4) chlorine dioxide. The flow diagram in Figure 5
shows extensive countercurrent reuse of water so that the only waste
produced by the plant is 2930 gpm from the chlorination washer, 460 gpm
from the caustic washer, other small sporadic flows due to leakage in
wash-down operations and it may also contain some black liquor. The
flows do not always balance exactly. The discrepancies are thought
to be due to leaky valves.
Chemical Inventory
The chemical inventory and the chemical purchases for the bleach plant
on a daily basis for 150 tons per day are given in Table 3. Those
for the rest of the entire plant are given in Table 4.
31
-------
Unbleached
Pulp
Chlorine
Storage
Chlorine
Bleach
Tower
Zenith
Presses
Caustic
Storage
Recycled
Water
Chlorine
Dioxide
Washer
Chlorine
Washer
Fresh
Wash
Water
Waste
Water
Recycled
Water
Caustic
Bleach
Tower
Chlorine
Dioxide
Bleach Tower
Recycled
Water
Chlorine
Dioxide
Storage
Caustic
Washer
Hypochlori te
Washer
Chlorine Dioxide
Reactor
2NaC10
NaClO-,
H^SO
Waste
Water
Hypochlorite
Storage
Hypocnlorite
Bleach
Tower i
Hypochlorite
Reactor
2NaOH + Cl
Centri
Screens
NaOCl+NaCl+H20
FIGURE 4. SCHEMATIC BLEACH PLANT FLOW DIAGRAM.
32
-------
33
-------
TABLE 3
CHEMICALS IN BLEACH PLANT
(Based on 150 tons bleached pulp per day)
Chemical
Chlorine, as Cl«
Caustic, 50% Na20
Sulfuric acid
as H2SO,
Sodium chlorate
SCL as SO
Pitch dispersant
Usage
Cone.
5%
93.6%
96%
Storage
Cone.
100%
50%
93.6%
96%
100%
a
Usage
tons/day
13.65
9.75
0.68
0.98
1.12
Cost, $/ton
fob Freight
54.50 14.00
56.25 11.20
17.47 7.90
Total
68.50
67.45
25.37
143.40
68.72
771.40
3.
fiscal year November 1968-September 1969
bApril 1973
°Vanzak 112, R. T.
Vanderbilt Co.
Inc. , 230
Park Avenue, New York, NY
TABLE 4
CHEMICALS IN ENTIRE PLANT EXCEPT BLEACH PLANT
(Based on 1000 tons unbleached pulp per day)
Chemical
Salt cake, as
Na2S04
Caustic, 50%
Spent
as
Lime,
Bulk
Alum,
caustic
as CaO
Starch
17% A12
Sulfuric acid
as H2S04
fiscal year
Usage
Cone.
98%
Na20 5%
100%
95%
100%
03 50%
93.6%
Storage
Cone.
98%
50%
100%
95%
100%
50%
93.6%
Usage
tons/day
61
35
1
15
39
39
20
.5
.0
.5
.5
.0
.0
November 1968-September 1969
Cost,
fob
16
56
_
16
101
-
17
$/tonb
Freight
.50
.25
_
.00
.40
-
.47
bApril
12
11
_
14
9
-
7
.50
.20
_
.20
.00
-
.90
Total
29
67
25
30
110
63
25
.00
.45
.00
.20
.40
.35
.37
1973
34
-------
Lime
The capacity of the three lime kilns is 290 tons CaO/day although
the plant is usually operated at 250 tons/day. The lime is slaked and
reacted with 800 gpm of green liquor (equivalent to 52 g/1). If massive
lime precipitation were practiced and the maximum lime output of the
mill were slaked with the 460 gpm wasted from the caustic washer seal
tank, the lime dose would equal 105 g/1. If all the 3390 gpm of ditch
waste were to be precipitated with the 290 tons lime/day, the dosage
would be 14.2 g/1.
Bleach Wastes
During the early part of the investigations, the characteristics of
the ditch waste varied considerably and upset the results of the experi-
ments. Hence, an "artificial" ditch waste was manufactured by combining
15 percent caustic extract with 85 percent chlorine waste. Direct com-
parisons of ditch waste and artificial ditch waste showed close agree-
ment, an example of which is indicated in Table 5. Only pH, suspended
solids, and total alkalinity are greatly different. These differences
can be accounted for by floor sweepings from the lime kiln area which
are present in ditch waste but not in artificial ditch waste. In
October 1970, the waste collection piping system of the Hoerner Waldorf
Mill was combined with waste from the paper machines so it was no
longer possible to obtain unadulterated bleach plant wastes. All sub-
sequent experiments were, perforce, made with the artificial ditch
waste. The maximum and minimum values of the various parameters which
characterize the wastes are given in Table 6.
Liquors from the bleach plant were transported to Bozeman in plastic
containers. During the investigations for batch tests, the liquors
were stored at 4°C in a refrigerator. Low temperature storage for
35
-------
TABLE 5
COMPARISON OF DITCH AND ARTIFICIAL DITCH WASTES
Characteristic
Residual free
chlorine, mg/1
Jar Test:
% color removed
CaO, mg/1
Specific conductivity
pmhos/cm
TOC, mg/1
Type of Waste
Ditch Waste
7/31/70
88
1200
2340
270
Artificial Ditch Waste
15% caustic extract,
85% chlorine waste
7/31/70
PH
Suspended solids, mg/1
TDS, mg/1
Color
CU, orig. pH
CU, pH 7.6
Total Alkalinity,
mg/1 as CaCO
COD, mg/1
9.4
500
1690
2820
2420
570
415
5.4
22
1490
2730
3170
44
550
40
92.5
1200
1990
250
36
-------
TABLE 6
CHEMICAL ANALYSES OF ARTIFICIAL
DITCH WASTES AFTER PRETREATMENT
Cation Concentration, me/1 Anion
Na
K
Ca
Mg
TDS
max
24.0
tr
6.9
tr
(Computed) , mg/1
min
16.8 HCO
tr Cl
4.8 NO,,
tr SO,
Concentration, me/1
max
7.0
23.1
0.03
2.7
2157
min
4.1
13.6
tr
1.4
1700
large quantities of liquor needed for column runs was quite impractical.
Furthermore, the characteristics of liquors stored at room temperature
did not change sufficiently to affect test results.
Anion Feed
Feed to the anion column is the effluent from the cation column either
with or without decarbonation. If the effluent from the cation column
is to be carbonated, the decarbonation tower would normally discharge
into an intermediate reservoir. Hence, feed to the anion column would
consist of a mixed, uniform cation effluent. To expedite the prepara-
tion of anion feed, a two-inch diameter cation column 24 inches deep
was operated to 35% breakthrough of the sodium ion. The product was
mixed by sparging until the C0~ concentration was reduced to 2 mg/1,
which required approximately two hours. A typical analysis of the
decarbonated cation product water is shown in Table 7.
37
-------
TABLE 7
TYPICAL ANALYSIS OF ANION EXCHANGER FEED WATER
Effluent from 2-inch column, decarbonated
Cation
H
Na
Ca
Mg
Concentration
me/1
9.9
3.1
0.0
0.0
13.0
Anion
H2C°3
Cl
N03
so4
S
Concentration
me/1
0.1
13.2
tr
0.1
tr
13.4
pH = 2.0
REGENERANTS
Acid
Regenerant for pilot plant cation exchange was technical grade sulfuric
acid. Difficulty with calcium sulfate precipitation using 5 percent
acid was elminated by reducing the concentration to 3 percent. Hence,
resin was regenerated with 3 percent acid.
To avoid difficulty with calcium sulfate precipitation in life tests
in which the columns operated automatically, 1 N hydrochloric acid was
used for regeneration.
Base
Several bases were used to regenerate sorbents and anion exchangers:
1 N technical grade sodium hydroxide, 4 percent NH,OH, and white liquor.
The concentration of white liquor (equivalent to caustic) is kept at
3.0 N by the Hoerner Waldorf Mill. When it was necessary to use a
38
-------
lower concentration, the white liquor was diluted with Bozeman tap
water. Bozeman tap water is essentially a calcium carbonate water
with little sodium, chloride, or sulfate, and the dissolved solids
content varies from 60 to 110 mg/1. The chemical analysis of white
liquor is given in Table 8.
TABLE 8
CHEMICAL ANALYSIS OF WHITE LIQUOR
Cation
Na
K
Mg
Ca
Sum
Concentration
me/1 Anion
4000
100
1.0
0.7
4101.7
OH
co3
Cl
s
so4
Sum
Error: 5.5%
Concentration
me/1
2100
785
5
900
94
3884
.4
.4
TDS (Computed): 216,700 mg/1
pH: 13.3
r
Dilute specific conductivity: 781,000 pmhos/cm
Weak wash is essentially a dilute form of white liquor. Whereas white
liquor contains about 6.2 Ibs Na_0/cu ft, weak wash contains only 0.5
Ibs Na?0/cu ft. Table 9 is an analysis given by Weeks (1972) .
39
-------
TABLE 9
WEAK WASH COMPOSITION
Constituent Concentration, Ib/cu ft
Active Na 0 0.5
Total alkali 1.0
NaOH ---
Ca(OH)2 saturated
Na SO, tr
CHROMATOGRAPHY
Chromatographic separations were carried out with Sephadex G-10 and
Bio-Gel P-2, 100 to 200 mesh. The eluant was 0.02 N sodium chloride,
Baker Analyzed reagent grade. The gel was calibrated with a mixture
of Dextran Blue (molecular weight - 5000) and potassium ferricyanide
(molecular weight = 329).
40
-------
SECTION VI
LABORATORY PROCEDURES
EXPLORATORY TESTS
Isotherms in Batch Tests
All anion resins were presoaked for 30 minutes to cause the beads
to swell. About a liter was backwashed with tap water in a 2-in.
ID x 6 ft column at a rate sufficient to cause 60 percent bed expansion
and the fine debris was allowed to wash out of the column. After drain-
ing to an inch above the top of the resin column, two bed volumns
of 1 N NaOH were passed downward at a rate of 12 BV/hr followed the
same flow rate by a rinse of 5 BV of tap water. This was followed
by a 1 N HC1 acid treatment with the same volumes, flow rates, and
rinses. The entire cycle was repeated again and then the resin was
converted to free base form with 2 bed volumes of 1 N NaOH followed
by a distilled water rinse to pH 8. Resins exhibiting much swelling
during conditioning (such as Duolite A-57 and S-33) were regenerated
upflow to prevent undue pressure within the glass column.
Cation resins were cycled in the same way except the sequence of acid
and base was reversed.
Duolite S-30 sorbent resin was treated like the anion resins except:
the concentration of NaOH was 2 percent, the concentration of HCl
was 1 percent, and the last treatment with NaOH was omitted leaving
the resin neutralized with acid. All other sorbent resins were left
in the OH form.
The carbons were presoaked approximately 30 minutes, loaded into a
2-inch ID x 6 ft column and backwashed to remove carbon dust. In
early tests the carbon granules abraded so much that the turbidity
41
-------
interfered with color measurements. Preshaking the carbon in distilled
water to remove sharp edges was unsuccessful and the carbon continued
to abrade. Turbidity caused by carbon dust was removed by pressure
filtration through a 0.45 u filter in a Millipore filter syringe con-
verted to filter by pressure rather than by suction.
Samples of liquors were prepared for sorbency testing by filtration
through a Whatman No. 30 filter paper and by pH adjustment to 7.6 +
0.1. Acidic samples were neutralized with 1.5 N NaOH. Basic samples
were neutralized with 8 N and 0.1 N HCl for early tests and later
with gaseous CO,,. An initial color measurement was made on the filtered
liquor (neutralized to pH 7.6 before the start of each run. Several
concentrations of sorbents were used for each isotherm run, usually
0.1, 0.25, 0.5, 0.75, 1.0, 2.5, and 5.0 grams (wet, drained weight)
per 100 ml of liquor. In addition, a blank containing no resin was
included for comparison.
Color measurements were taken at 1/2, 1, 2, 4, 8, and 24 hour intervals
and thereafter at 24 hour intervals until no further change in color
could be observed. But even a period of a week was not always sufficient
to achieve true equilibrium.
Color Sorbency in Batch Tests
Sample and sorbent preparation were identical to those used for isotherms
except 100 ml of the filtered neutralized waste was added to a 250 ml
flask containing 5 grams (wet, drained weight) of the sorbent. The
flask was immediately placed in the shaker, and color measurements
were taken after shaking 10, 20, and 40 minutes and at 1, 2, 3, and
4 hours after the start. The starting times were staggered to permit
8 or even 10 runs per day with five minute intervals between color
readings except at the 2 hour and 3 hour readings when three simultaneous
readings were scheduled. These three readings were taken at a total of
three minutes, a time span too short to cause significant error.
42
-------
Pretreatment by Massive Lime Precipitation
Pretreatment consisted of massive lime precipitation followed by two-
stage recarbonation. Lime was slaked by adding 5 ml of the liquor
being investigated per gram of lime. The mixture was heated on the
hot plate until the reaction began. The vessel was removed from the
hot plate and the reaction allowed to complete itself, and the contents
were then cooled to room temperature before the slurry was used for
precipitation.
Precipitation runs were planned so six samples could be started almost
simultaneously. The liquor to be pretreated was quickly added to
the previously slaked lime to increase the volume to one liter. The
samples were immediately placed in position under the stirrer, where
they received five minutes of high speed stirring at about 140 rpm to
insure complete mixing, and 15 minutes of slow stirring at 50 rpm.
Upon completion of the stirring the samples were transferred without
delay to one-liter graduated cylinders (liquid height 28 cm) in which
the settling rates of the lime solids were timed. After two hours
of settling the supernatant liquor was siphoned out of the cylinder,
filtered, and kept in tightly stoppered flasks. At this stage aliquots
were removed for physical and chemical analyses. Typical analyses are
shown in Table 10.
Recarbonation. Recarbonation was performed in two stages. A sample
of supernatant liquor was transferred to a 250 ml graduated cylinder,
the recarbonater nozzle was placed at the bottom, and the air-CO~
mixture was introduced at a flow rate of about 450 ml/min. The liquid
height was always 28 cm in all experiments. The pH was monitored con-
tinuously. The gas flow was stopped when the pH reached 11.5. The
settling rate of the calcium carbonate precipitate was timed. After
the precipitate was removed by vacuum filtration, the liquid was poured
into a second cylinder and the second recarbonation step was continued
43
-------
TABLE 10
CHEMICAL ANALYSES OF ARTIFICIAL DITCH WASTES AFTER PRETREATMENT
(Lime precipitation and recarbonation to pH 7.6 and 300 CU)
Cation Concentration
me/1
Na
K
CA
Mg
Sum
IDS
All
Na
K
Ca
Mg
Sum
Collection
24.0
Tr
6.9
Tr
30.9
(computed): 2157 mg/1
Collection
used for color sorbency.
Collection
16.8
Tr
4.8
Tr
21.6
Anion Concentration
me/1
Date 1/4/71
HC03
Cl
N03
S
so4
Sum
Error: 3.1%
Date 2/23/71
No chemical analysis made.
Date 4/6/71
HC03
Cl
N03
S
so4
Sum
Error: 1.8%
4.1
23.1
0.03
Tr
2.7
29.93
7.0
13.6
Tr
Tr
1.4
22.0
TDS (computed): 1700 mg/1
44
-------
to pH 7.6. Chemical and physical analyses were made of the final
products.
Storage
Liquors obtained from the Hoerner Waldorf Plant were transported by
truck or bus to Bozeman and placed in refrigerators set at 4°C with
the least practical delay (8 to 15 hours after collection). The samples
from the chlorination, hypochlorite, and chlorine dioxide stages were
taken from the caustic washers whereas caustic was taken from the
caustic seal tank. The bleach ditch sample was taken from an open
ditch about 600 yards from the mill.
After completion of batch tests, the quantities of liquor needed were
so large it was impractical to store them in a refrigerator. Therefore,
samples were stored at room temperature. Ditch waste and artificial
ditch waste were found to be quite stable for several weeks under room
temperature conditions.
Gel Permeation Chromatography
The proper gel for fractionation of the kraft bleach wastewater was
selected by calibrating with a mixture of Blue Dextran (molecular
weight - 5000) and potassium ferricyanide (molecular weight = 330).
Of the Sephadex gels, only G-10 gave adequate separations, but Bio-Gel
P-2, 100 to 200 mesh appeared to be better for the purpose and most of
the results were obtained with it.
One ml of the mixture, or the liquid to be analyzed, was placed at the
top of the column and eluted with 0.02 N sodium chloride (Baker
analyzed reagent grade). The elution flow rate was 0.166 ml/min
regulated by a Sage Model 375 tubing pump. Ten samples/hr were
45
-------
collected by the Isco Model 326 fraction collector until 36 ml of
samples (equal to the volume of the column) were collected.
The collected fractions were too small to be tested for color or for
sorbency at 265 my, so TOG (measured on the Model 915 Total Organic
Carbon Analyzer) was used as the concentration parameter for each
fraction collected.
The general procedure for gel permeation chromatography has been
described by Determann (1968) and Sephadex (1970).
COLOR SORBENCY IN COLUMNS
Feed Preparation
Lime-precipitated waste for column runs was prepared in 50 gallon
barrels by adding enough slaked lime to produce 90 percent color
removal. After 6 to 12 hours of sedimentation, the supernatant liquor
was decanted and recarbonated to pH 11.5, the precipitate was allowed to
settle 6 to 12 hours, and the supernatant liquor was again decanted
and recarbonated in a second stage to pH 7.6 + 0.1.
Single Runs on Virgin Resins
Resins were preconditioned with two cycles of acid and base followed
by thorough rinsing as described in Exploratory Tests.
Regeneration optimization. Optimization regeneration was begun with
preconditioned resins exhausted at a rate of 20 BV(bed volumes)/hr to
partial breakthrough with lime-precipitated ditch waste in a 1-inch
ID x 24-inch deep bed. Duolite A-6 was exhausted to 90 percent break-
through whereas Duolite S-37 and Amberlite IRA-68 were exhausted to
30 percent breakthrough. After exhaustion, the resin bed was backwashed,
46
-------
rinsed, removed from the column, and thoroughly mixed. Each bed was
divided into 24 packets of 13.1 ml each. Each packet provided a bed
1 inch in diameter x 1 inch deep for regeneration tests.
Each preliminary regeneration test was performed on a fresh packet
of 13.1 ml of exhausted resin. The packet of resin was placed in a
3 inch long column 1 inch in diameter and was then backwashed with
distilled water. Water was drained to the top of the resin bed.
Regenerant was applied downflow to the resin bed at a constantly
monitored flow rate of 2.5 to 40 BV/hr. The effluent was collected
in numerous successive fractions. Flow was continued until the effluent
became almost colorless, which showed that regeneration was essentially
complete.
Cyclic Tests
Duolite A-6 and S-37 were the resins selected for color sorbency in
cyclic runs. In all cyclic color sorbency runs, the feed was pumped
downward through the column at the rate of 20 BV/hr. The resin beds
were 1 inch in diameter and 24 inches deep in their regenerated, back-
washed, and settled state. Runs were halted at a color breakthrough
of 50 percent (150 CU). In all but a few runs this criterion was
closely approached.
Regeneration was always countercurrent at an upflow rate of 20 BV/hr.
The regenerant was pumped into the bottom of the column and the efflu-
ent was removed through a screened port located just above the top
of the resin bed (30 1/2 inches above the bottom screen). The feed
remaining in the 30 inch high plenum (upper part of reactor) was not
disturbed. Samples of the regeneration effluent were collected at
one minute intervals for color measurement.
47
-------
Immediately following regeneration, the resin was rinsed upflow with
5 BV of distilled water. Then the direction of rinse was changed to
downflow with 15 BV of distilled water pumped into the column at the
middle port.
Two cyclic series of runs were made with: (1) white liquor and (2)
technical grade NaOH regenerants. With white liquor as a regenerant,
9 cycles were obtained, after which it was necessary to rejuvenate the
re^in. No rejuvenation was necessary in the second series of runs
in ,iich 1 N technical grade NaOH was used for 15 cycles.
Single runs were made using three different solutions of lime: (1)
a saturated solution of lime, (2) a 2 percent lime slurry, and (3)
a 4 percent lime slurry. Regenerant at rates of 16 to 20 BV at a rate
of 20 BV/hr was passed upflow through the column followed by 10 to
15 BV of distilled water rinse upflow and then 30 BV of distilled
water rinse downflow.
In another series of runs, the resin was removed from the column and
placed in an Imhoff cone with 500 ml of 4 percent lime slurry. The
blend was mixed 10 minutes with air and then rinsed. This treatment
was repeated a total of six times to determine how much additional
color could be removed by repeated regeneration.
Ammonia regeneration was studied by passing 5 BV of a 4 percent solution
of NH.OH through the resin upflow at 20 BV/hr, followed by the same
procedure for rinsing used with lime regeneration. This procedure was
repeated three different times on the same resin.
Rejuvenation. During rejuvenation experiments, 15 ml aliquots of used,
regenerated resins were placed in 1/2 inch diameter tubes in beds 12
inches deep. Various chemicals such as methanol, 10 percent NaCl, and
1 N HC1 were passed downward through the columns at 12 to 16 BV/hr.
48
-------
DESALINATION IN SINGLE RUNS
The objective of the single runs was to establish near-optimum condi-
tions for operating the time-consuming, difficult cyclic runs.
Cation Exchange
The influent to the cation column was the artificial ditch waste treated
by massive lime precipitation and recarbonation to 300 CU and pH 7.6.
It was applied at the rate of 20 BV/hr downflow because preliminary runs
indicated such a flow rate was near optimum. Duolite C-25D porous
cation resin was chosen because its low rinse requirement, high efficiency
in regeneration, and good kinetics outweighed the disadvantage of its
low capacity as compared to gel type resin. The resin bed, 1 in. ID x
24 in. deep, was a compromise between applicability to prototype con-
ditions and conservation of time and expensive liquor.
During the first test, feed was applied until complete breakthrough
of all ions occurred. The column was then backwashed with 10 BV (75
gal water/cu ft resin) of distilled water at a rate of 20 BV/hr which
produced a bed expansion of approximately 50 percent. After backwashing,
the plenum was dewatered through the middle port and 5 BV of 1 normal
HCl (11.4 lb HCl/cu ft resin) was applied upflow at a rate of 20 BV/hr.
The acid was immediately followed with 5 BV of distilled water applied
upflow at the same rate followed by 10 BV of distilled water rinse
applied downflow.
Later in the test program, H-SO, was used instead of HCl and at different
flow rates and volumes. Rinse volumes were monitored by conductivity
and pH. The breakthrough during the service run was limited to 35
percent.
49
-------
Anion Exchange
Because the amount of product water from the cation column was so
small, feed for the anion column was produced by using a larger cation
column, 2 inches ID by 24 inches deep filled with Duolite C-25D, H-
form resin. The cation run was stopped when the sodium ion breakthrough
reached 35 percent and the specific conductivity had dropped from 6500
to 4000 micromhos. At the pH of the combined effluent, which was
about 2, the alkalinity was converted to (XL, which was stripped by
sparging with compressed air until the C0? level was approximately 2
mg/1.
In the first run, feed to the anion column was applied downflow at
the rate of 20 BV/hr until all anions broke through completely. But
after the first run, feed was stopped at a Cl breakthrough of approxi-
mately 35 percent. Immediately following the service part of the
cycle, the resin was backwashed with 10 BV of distilled water applied
at an upflow rate of 16 BV/hr. Then the water was drained from the
plenum and typically 5 BV of 1 normal NaOH was applied upflow at 16
BV/hr followed by 5 BV of distilled water at the same rate. Typically
upflow rinse was followed by 10 BV of downflow rinse with distilled
water at the rate of 16 BV/hr. The column was then ready for a new
service run. Nine such preliminary runs were completed with variations
of operating parameters to optimize flow rates and volumes of regenerant
and rinse.
Regeneration Efficiencies
Regeneration efficiencies were determined in a number of ways. Screening
tests were made with several acids and bases and different volumes
and rates. Efficiencies were determined by measuring ions sorbed by
resins and checked by measuring ions eluted by the regenerant.
50
-------
The rinse requirement was determined by monitoring conductivity and
pH. The volume of rinse was deemed sufficient when the conductivity
of the rinse effluent was approximately equal to the conductivity of
the feed.
DESALINATION IN CYCLIC RUNS
Feed to the cation column was artificial ditch waste pretreated by
massive lime precipitation and two-stage recarbonation to a residual
color of 300 CU. The feed was pumped downward through a 1 in. ID
column containing 24 inches of Duolite C-25D resin at a flow rate of
20 BV/hr because preliminary tests showed such a flow rate was near
optimum. Flow was continued to a 35 percent breakthrough of the
sodium ion.
The resin was regenerated with 1.3 BV of 3 percent technical grade
H-SO, applied at the rate of 16 BV/hr in upward flow. Regeneration
was immediately followed by 3 BV of distilled water at the same rate.
The cation product water was stored in a barrel, degasified by air
sparging to a residual concentration of 2 mg/1 C0«. This well-mixed
product was pumped to the anion column (also 1 in. ID filled to a depth
of 24 inches with Duolite A-6 resin) at the rate of 20 BV/hr downflow.
The run was continued to a 35 percent breakthrough of the chloride ion.
The resin was regenerated with 1.3 BV of 3 percent technical grade
NaOH applied upflow at the rate of 16 BV/hr. The caustic was followed
with 3 BV of distilled water at the same flow rate.
The flow rates, volumes, and concentrations of regenerants and volumes
of rinse were nearly optimum values determined from the preliminary
tests. With only a minimum of compromise, the operating parameters
could therefore be made the same for both resins. This was done in
the interests of ease of operation.
51
-------
One series of runs was made at a temperature of 60°C to simulate the
temperatures to be found under actual mill conditions. The feed to
the columns was preheated in a Blue M water bath before introduction
into the environmental cabinet which contained all of the ion exchange
equipment held under a temperature of 60°C + 1°.
REMOVAL OF RESIDUAL COLOR
The high rate of flow, starvation regeneration, and the limited bed
depth of 24 inches permitted an average leakage of about 80 color
units. Several procedures were tried for the removal of residual
color after desalination by ion exchange.
Decoloring methods tried unsuccessfully on desalinated water included
virgin Duolite S-30 in OH form, Filtrasorb 400 carbon, Carbo-Dur
carbon, Duolite A-7 resin ground to 100 x 200 mesh in virgin OH form,
and A-6 in 40 to 80 mesh virgin base form. The various sorbents were
tested at a downflow rate of 20 BV/hr in 1 inch ID by 24 inch deep beds.
Finally, second stage demineralization was tried for the removal of
residual color with used C-25D cation resin and used A-6 anion resin.
The cation resin was conditioned with 2 BV of 3 percent H~SO, and the
anion resin was conditioned with 2 BV of 3 percent NaOH. The slightly
colored (80 CU) effluent from the first stage was put through the
cation column at a downflow rate of 20 BV/hr, the effluent was collected,
stripped of residual CO- by air sparging, and then put through the anion
column downflow at a rate of 20 BV/hr. Samples were collected at
intervals of 5, 10, 20, 40, 80, 120, etc. BV for color monitoring.
52
-------
LIFE TESTS
Column Operations
All resins and sorbents were confined in beds _ inch ID oy 2 inches deep,
a volume of 28 ml. The resins tested included the following strong
acid resins: C-25D, Amberlite 200, HCR-W, IR-120+; the following weak
acid resins: IRC-50, and IRC-84; the following strong base resins:
Dowex 11 and IRA-402; the following weak base resins: A-6, A-7, IRA-68,
and IRA-93; and the following synthetic sorbents: S-37, S-30, ES-33,
and XAD-8.
Feed. All columns were operated simultaneously on the same cyclic
times. Feed to the cation resins was artificial ditch waste pretreated
to 300 CU and pH 7.6. Feed to the anion column was a well-mixed cation
effluent at pH 2 from which the CO was removed by air sparging. The
cation column was operated until the sodium breakthrough at the end
of the run was 35 percent. The average sodium leakage was 2.2 percent
or about 0.28 me/1.
Regenerants. Regenerant for the cation column was 3 percent technical
grade hydrochloric acid and, for the anion and sorbent resins, 3 percent
technical grade NaOH.
Cyclic regime. The flow rate was 8.0 ml per minute which was equiva-
lent to 17 BV/hr. The regeneration time was 5 minutes, and the service
time was 140 minutes. All the flows were applied upward to prevent
plugging the column, but the flow rates were so low no expansion of
the resin bed nor movement of resin particles occurred. This scheme
allowed particles in the feed to be washed right through the resin
column. The effluent was only monitored for the determination of
flow rate which was kept well within + 5 percent.
53
-------
Inspections
An inspection consisted of visual examination using a 30 power stereo-
scopic microscope with both direct and reflected light and for the
determination of exchange capacity. At the beginning and the end of
the life tests the volume and weight of the resin were determined
under standard conditions.
Preparation. Resins were prepared for inspection by conditioning
with 5 BV of 1 N reagent grade NaOH (for anion resins) or HCl (for
cation resins) downflow at 8 ml/min. They were rinsed until the effluent
pH was approximately neutral.
Exchange capacity. Exchange capacity was determined by exhausting the
resin at the rate of 8 ml/min in downflow. Feed for strong acid resins
was 0.5 N reagent grade NaCl to a neutral effluent, which required
approximately 800 ml of liquor. The exchange capacity of strong base
resins was determined by feeding 5 percent reagent grade NaCl to a
neutral effluent which required approximately 650 ml of liquor. The feed
for weak base and sorbent resins was 810 ml of 0.135 N reagent grade
HCl, and the feed for weak acid resins was 1250 ml of 0.10 normal
reagent grade NaOH. Effluents were collected, and titrated to neutrality
with 0.5 N reagent grade NaOH or HCl. These procedures varied somewhat
from manufacturers' recommendations, but they were found to give the
same results and possess the advantage of ease and quickness of
operation.
Sorptive capacity was tested by thoroughly regenerating the resin with
N/12 NaOH until the effluent was colorless. It was rinsed with dis-
tilled water to neutral pH. Then 30 BV of a "standard" artificial
ditch waste acidified to pH 2.2 was passed upward through the column at
12 BV/hr.
54
-------
The exhausted resins were returned to the life cycling apparatus which
was set to regenerate them as the first step in the cycle.
Frequency. Inspections were made of the resins periodically as follows;
virgin resin, after 20 hours of service, then at intervals increasing
up to 200 hours.
CHEMICAL ANALYSES
The procedures used for chemical analyses are described in Table 11.
55
-------
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58
-------
SECTION VII
RESULTS AND DISCUSSION
EXPLORATORY TESTS
Several kinds of tests and experiments were performed to ensure accur-
acy in measurements and to determine the effect of several test vari-
ables. They included tests for: sorption of color bodies on the walls
of spectrophotometer cells, effect of temperature on sorption, variation
of color with pH, means for the measurement of true color of turbid
suspensions, effect of time of storage, calibrations, and determining
the most reliable methods for chemical analysis of these highly colored
solutions.
Isotherms and color sorbency tests were run on a wide variety of sor-
bents and anion exchange resins. The results from these tests were
the basis for selecting resins to be investigated in the more time-
consuming column operations.
Miscellaneous Tests
Spectrophotometer cells. Adherence of organic material to the walls
of spectrophotometer cells has been known to cause spurious readings.
But a series of tests using bleach wastes indicated organic material
did not adhere to the cell walls enough to effect results appreciably.
Color measurement. Several means were tried for removing the turbidity
which interferred with color determinations including: filtration
through Whatman No. 30 filter paper and through 0.45 y, 0.2 u and
0.8 p Millipore filters, and centrifugation at 2000 rpm and 17,000 rpm
for 20 minutes each.
59
-------
The results were not greatly different. For the small volume of samples
required, filtration through a 0.45 y Millipore filter held in a 25 mm
Swinnex filter holder was the quickest and the most satisfactory treatment
for routine work. The Swinnex filter holder was attached to a Millipore
Sanitarian's syringe modified to filter by pressure instead of vacuum.
A typical calibration curve is shown in Figure 6. Color measured
at 422.2 my is practically the same as color measured at 420 my because
the spectrum is flat in this region. The odd wave length was used
because it is one of the wave lengths specified in obtaining tristimulus
values.
100
90
80
70
60
50
.240
in
30
c
cu
o
cu
a.
20
10
Cell:
X:
Slit:
Lamp:
10 mm
122.2 my
0.32mm
Tungsten
1000 2000 3000
CU (APHA color units)
FIGURE 6. CALIBRATION OF SPECTROPHOTOMETER
60
4000
-------
Total organic carbon. During the first two years of the investigation,
the carbonaceous analyzer was often inoperative. A new Beckman Model
915 Total Carbon Analyzer was obtained during the last stages of this
investigation, so a few reliable results of total organic carbon were
obtained. Unfortunately, most of the value of total organic carbon
measurements pertained to the preliminary phases of the work.
The National Council for Stream Improvement, Inc. (1962) found TOC
was directly proportional to color in 20 different caustic stage
effluents. In the tests reported herein, proportionality did not
occur between color and organic carbon during sorption runs by carbon
and resins.
Mixing and sorption. The rate of sorption in batch tests is strongly
influenced by mixing due to the renewal of the average concentration
at the liquid-solid interfaces. Tests to establish the effect of
agitation rate showed an increase of sorption with increasing agitation
up to 100 cpm. Above this value there was no increase of sorption
with an increase in agitation. Consequently, all batch sorption tests
were made at an agitation rate of 112 cpm.
Storage. The problem of preventing changes in stored wastes was thought
to be a serious difficulty. Dugal (1969) concentrated and preserved
wastes by vacuum distillation followed by freeze-drying to a powder.
Samples of our wastes were sent to Dugal for trial freeze-drying. The
caustic extract cot Id not be concentrated by vacuum distillation because
freezing made the product gummy and sublimation to a powder did not
occur. Freeze-drying without previous concentration by vacuum distilla-
tion was successful, but this was too time consuming for the preserva-
tion of large quantities.
61
-------
Freezing might be thought to preserve the wastes almost unchanged,
but Abrams (1969) and others found precipitates often form as the
temperature is reduced. The precipitates do not redissolve as the
temperature is raised. An exploratory check of this observation was
made with some filtered black liquor extract. After thawing the frozen
liquor, large particles were seen and the color increased 7 percent.
Refiltering had no affect upon the color.
Cold storage did not appear to be particularly advantageous. Color in
chlorine stage wastes decreased about 4 percent in a month. Color in
caustic waste declined from 4 to 20 percent in about the same period.
Color in ditch waste declined from 30 to 40 percent, and color in
hypochlorite and chlorine dioxide liquids were drastically reduced on
a percentage basis. However, the latter two liquors were not highly
colored at the time of collection (approximately 40 CU) so a large
percentile change was comparatively insignificant.
At room temperature, color in the chlorine waste decreased only 10 per-
cent in 70 days and color in the caustic waste increased only 7 percent.
Thereafter, wastes were stored at room temperature.
In this exploratory phase of the program, some alteration of the waste
was tolerable. If it were known that only the amount, and not the
character, of the color bodies were changed, alteration could have been
tolerated throughout all the investigations. Insofar as has been
determined, there seems to be no apparent change in the distribution of
molecular sizes as determined by gel permeation chromatography u.sing
a Sephadex column. But such tests are relatively crude and inconclusive.
Temperature and sorption. In general, the rate of sorption increases
with an increase in temperature. Several tests indicated the increase
in sorption rate between 15°C and 20°C was scarcely detectable. Above
20°C the rate of sorption increased markedly. Hence, sorption tests
62
-------
were run between 17°C and 20°C. Closer temperature control was
unnecessary.
Isotherms in Batch Tests
Twelve isotherms were run before the program of establishing isotherms
for each waste and each resin was modified to the determination of
4-hour color sorbency tests. The time required to reach apparent
equilibrium varied greatly but was usually more than a week. Moreover,
true equilibrium was elusive because at the end of a week color was
often sorbed so slowly that the determination of whether true equilib-
rium was achieved itself required several days. As the capacities of
the shaking machines were limited, the use of isotherms for selecting
the best resins for column tests became impractical.
While isotherms are useful for selecting carbon they are less so for
selecting resins. Each point on an isotherm represents equilibrium.
Because even highly colored wastes contain relatively small amounts of
organic material and because carbon has a high equilibrium capacity
for organic material (up to 25 percent of its own weight) the lower
layers in a deep carbon column would be expected to approach equilibrium
in an upflow reactor. But resins, on the other hand, should be. regen-
erated frequently to prevent irreversible sorption or poisoning. Since
resins would not be subject to equilibrium in service, isotherms for
resins and carbons cannot be compared. To be valid, the pilot plant
operation must simulate the prototype, and the costs of equipment and
operation must be measured against the efficacy of treatment. Hence,
it is proper to compare carbons by means of isotherms and to compare
resins by means of short sorbency tests, but it is unreasonable to
use either of these methods to compare carbon with resins. Therefore,
the modification of original plans to obtain isotherms for all sorbents
and wastes detracted little from the program.
63
-------
Both Langmuir and Freundlich isotherms were plotted. The Langmuir
isotherm is considered to be rational and the Freundlich isotherm
empirical. Neither, however, explains the phenomenon of sorption and
as both are only a means for fitting data, the choice is largely one
of preference. Because the Freundlich isotherm invariably fit the
data better, it was the isotherm of choice. The more complex Brunauer-
Emmett-Teller isotherm, which is adapted to multiple layers of sorbed
molecules, was not considered.
These data are not invariably good. Some points lie at considerable
distance from the best straight line. Plots of time versus sorbency
indicated no sorbent reached full equilibrium at all doses over the
time periods tested, namely 120 to 196 hours.
All carbons abraded severely creating particles fine enough to pass
through Whatman No. 31 filter paper. Some resins abraded too, although
not as much as carbon. Probably tumbling at short, intermittent
periods would reduce abrasion and would seem to be superior to constant,
violent shaking.
Resins. Isotherms for caustic extract and ditch waste are shown in
Figures 7 to 13 for the following types of resins: strong base gel,
weak base phenolic exchanger, weak base epoxy-amine, and two weakly
basic phenolic sorbents.
None of the resins tested were effective on caustic waste, but all were
effective on ditch waste. The sorption of color from ditch waste must
have included the sorption of some components of caustic extract color,
because total color sorption was considerably greater than the color
contribution of chlorine waste. This synergistic effect was observed
many times.
64
-------
300,000
g 100,000
-Q
s_
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T3
01
O
£
*- 10,000
o
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E
X
1,000
1,000
FIGURE 7.
10,000 100,000
CU, color remaining
FREUNDLICH ISOTHERM FOR DOWEX 11 AND CAUSTIC
1 ,000,000
10,000
10
10,000
FIGURE 8.
100 1,000
CU, color remaining
FREUNDLICH ISOTHERM FOR DOWEX 11 AND DITCH WASTE
65
-------
300,000
| 100,000
JD
s-
o
1/1
-o
Ol
s-
o
r
o
o
10,000
1,000
1,000
1,000,000
FIGURE 9.
10,000 100,000
CU, color remaining
FREUNDLICH ISOTHERM FOR DUOLITE A-7 AND CAUSTIC
C.
01
JD
S-
o
I/)
en
^-^
-o
o>
o
I
S-
o
'o
o
e
X
10,000
1 ,000
100
30
10
10,000
FIGURE 10.
100 1,000
CU, color remaining
FREUNDLICH ISOTHERM FOR DUOLITE A-7 AND DITCH WASTE
66
-------
10,000
QJ
-Q
O
(/)
CD
T3
01
O
-------
i.
o
I/)
O)
"O
OJ
>
q
0)
S-
o
o
o
10,000
1,000
100
10
10 100 1,000 10,000
CU , col 2r renainirr
FIGURE 13. FREUNDLICH ISOTHERM FOR DUOLITE S-37 AND DITCH WASTE
The resins listed in order of merit for sorbing color from ditch waste
are: Duolite A-7, Dowex 11, Duolite S-37, and Duolite ES-33. Duolite
A-7 was much better than all the others. Abrams (1969) found phenolic.
matrices to be superior to polystyrene and weak base to be better than
strong base functional groups for sorption of some kinds of organic
materials. The results obtained herein confirm this viewpoint.
Carbon. Isotherms of sorption of color by carbon from caustic extract,
ditch waste, and chlorine waste are shown in Figures 14 to 18. All
carbons tested were effective on all wastes tested.
Filtrasorb 300 appeared to be slightly superior to Nuchar VWL in the
sorption of color from caustic extract and somewhat inferior for
ditch waste, but the difference was not great. Both carbons performed
68
-------
100,000
o
O)
o
o
E
X
100
10
FIGURE 15.
"1 10 100 1,000
CU, color remaining
FREUNDLICH ISOTHERM FOR FILTRASORB 300 AND CHLORINE WASTE
69
-------
10,000
c:
cu
.o
s-
o
I/)
>
o
O)
i-
o
o
o
>ooo
100
FIGURE 16.
3°10 100" "~ 1,000 " 10,000
CU, color remaining
FREUNDLICH ISOTHERM FOR FILTRASORB 300 AND DITCH WASTE
100,000
O
1/1
en
O)
S-
S-
o
o
o
10,000
.- 1,000
300
100
100,000
1,000 10,000
CU, color remaining
FIGURE 17. FREUNDLICH ISOTHERM FOR NUCHAR WVL AND CAUSTIC WASTE
70
-------
Hi
x".
S-
c
-a
CD
>
c
fc.
a>
o
o
e-
X
1C,000
1,000
100
0
1C 100 1,000 10,000
CU, color repaininn
FIGURE 18. FPEUNDLICH ISOTHERM FOR NUCHAR WVL AND DITCH WASTE
well. In contrast to resins, carbon sorbed color from caustic extract
waste much better than from ditch waste. Sorption from ditch waste was
better than from chlorine wastes.
Color Sorbency in Batch Tests
Representative curves of color sorbency over a four-hour period are
shown for several sorbents in Figures 19 to 25. The conditions for
these and all other color sorbency tests are given in Table 12.
It must be noted that these curves cannot be taken at face value for
many reasons, among them:
71
-------
FIGURE 19.
1 2 3
Time, hours
ft-ISERLITE IPA-68 REST!, COLOR SORPTi:
200
(0
^
,2100
o
QJ
O
\
5 g resin wet, drained
100 ml bleach waste
pH 7.6
20°C
J0 1 " 2 3
Time, hours
FIGURE 20. AWBERLITE IRA-93 RESIN, COLOR SORPTION
72
-------
FIGURE 21
Time5 hours
DOWEX 11 RESIN, COLOR SORPTION
200
Cn
c
E
O)
o
o
O)
o.
/
/
/ OC1
5c resin , wet, drained
100 ml bleac!" waste
pH 7.6
20°C
Caustic
Ditch
0123
Time, hours
FIGURE 22. DUOLITE A-6 RESIN, COLOR SORPTION
73
-------
200,
O)
c
03
0)
O 100
'o
u
0}
CJ
s-
-------
200r
5g carbon, wet, drained
100 ml bleach waste
pH 7.6
20°C
=a **
CIO. Vo Vi
J0 1 2 3
Time, hours
FIGURE 25. FILTRASORB 300 CARBON, COLOR SORPTION
TABLE 12
SUMMARY OF DATA FOR COLOR SORBENCY
Type
Bleach.
Waste
APHA Color Units
Raw
End
Red.
AN ION RESINS
Amberlite IRA-68
C12
Caustic
Hypo
C102
Ditch
Amberlite IRA-93
ci2
Caustic
570
25400
25A
168
4860
57
25900
570
13400
214
54
3010
80
14000
0
47
16
68
48
-40,'
46
75
-------
(Table 12 continued)
Hypo
CIO
Ditch
Dowex 11
C10
2
Caustic
Hypo
C100
Ditch
Dowex WGR
C10
2
Caustic
Hypo
CIO
Ditch
Duolite A-6
C10
2
Caustic
Hypo
CIO 2
Ditch
Duolite A-7
C10
2
Caustic
Hypo
C10_
Ditch
Duolite A-57
Cl.
2
Caustic
Hypo
CIO 2
Ditch
254
170
4860
57
26900
270
155
4710
57
26400
258
18
4860
130
25400
105
140
4590
57
26900
270
160
4710
57
26300
269
167
4860
219
39
895
715
22400
277
360
3550
149
25400
245
7
4450
35
2950
230
60
840
485
3300
296
392
1260
352
24000
261
360
3730
14
77
82
-1150
17
-3
-132
25
-161
4
5
61
7
73
-88
-119
57
82
-751
88
-10
-145
33
-518
9
7
-116
23
76
-------
(Table 12 continued)
CATION RESINS
Dowex HCR-W
ci2
Caustic
Hypo
CIO
Ditch
Duolite C-25D
ci2
Caustic
Hypo
CIO
Ditch
SORBENTS
Amberlite XAD-2
ci2
Caustic
Hypo
cio2
Ditch
Duolite S-30
ci2
Caustic
Hypo
C10?
Ditch
Duolite ES-33
ci2
Caustic
Hypo
cio9
Ditch
Duolite S-37
C12
Caustic
140
16300
130
230
4500
140
16300
130
230
4500
57
25300
253
163
4860
135
18000
55
145
4590
57
26300
219
168
4710
58
26300
970
16600
970
1210
5390
230
16600
100
205
4590
123
20000
269
102
3290
120
14000
170
145
2350
59
18000
222
168
1620
115
12950
-593
-2
-646
-424
-20
-64
-2
23
11
-2
-116
21
-6
37
35
11
22
-209
0
49
-4
32
-1
0
66
-98
51
77
-------
(Table 12 continued)
Hypo
cio9
Ditch
Filtrasorb 100
C10
2
Caustic
Hypo
CIO
Ditch
Filtrasorb 200
Cl_
2
Caustic
Hypo
CIO
Ditch
Filtrasorb 300
Cl_
2
Caustic
Hypo
CIO
Ditch
Filtrasorb 400
C10
2
Caustic
Hypo
CIO-
9
Ditch
Nuchar WVG
C10
9
Caustic
Hypo
CIO
Ditch
218
168
4710
50
18400
50
125
4230
50
18400
50
130
4230
30
18000
50
120
4230
30
18000
50
120
4230
105
18000
55
170
4360
190
95
650
5
13000
20
10
2540
3
12000
3
2
1990
0
9990
0
1
1450
1
5850
0
0
1000
1
7000
5
0
1400
13
43
86
90
29
60
93
40
94
35
94
98
53
100
44
100
99
67
97
67
100
100
77
99
61
91
100
78
78
-------
(Table 12 continued)
Nuchar WVL
Cl
Caustic
Hypo
CIO
Ditch
Nuchar WVW
ci2
Caustic
Hypo
CIO
Ditch
Negative indicates
105
18000
55
170
4360
105
18000
55
170
4360
increase not
0
6500
0
0
1530
0
8700
5
0
1470
reduction
100
64
100
100
65
100
52
91
100
66
(1) All the batch tests were run at pH 7.6 whereas in a prototype
situation the pH might be very different and the effectiveness of the
sorbent likewise very different. This would be true especially for
wastes to be demineralized.
(2) Some of the wastes were lightly colored so percentile reductions
are of different significance for different wastes.
(3) In some cases the color actually increased, probably indicating
oxidation of the sorbent.
(4) The effect of multiple exhaustion and regeneration cycles was
missing and hence utilizing these curves to draw conclusive comparisons
between strong and weak electrolyte resins would be premature. Some
generalizations, however, are apparent. When there was little or no
color sorption or desorption within a four-hour period, the sorbent was
obviously ineffective. Specificity for different color bodies can
be assessed. And, finally, effectiveness can be approximately judged.
Anion Resins. Anion resins produced great variations in results. All
free residual chlorine was gone before the batch tests were begun, but
79
-------
nevertheless there often appeared to be an antagonistic reaction as
the color in chlorine, hypo, and chlorine dioxide wastes often
increased. Color in caustic and ditch wastes always decreased, some-
times by more than 70 percent.
Amberlite IRA-68. This resin was moderately effective on chlorine
dioxide and caustic wastes. It had little effect on hypo and none at
all on chlorine waste. Considering that ditch waste was 15 percent
caustic and 85 percent chlorine waste, the expected color removal was
Co, ited to be 36 percent. As the measured color reduction of ditch
waste was 35 percent (from Table 12) it is evident that only the
caustic fraction of the waste was being sorbed.
In spite of its failure to sorb chlorine waste and its mediocre per-
formance on other wastes this resin rated testing in a column because
it is one of the two resins needed for the Desal process.
Amberlite IRA-93. This is a hard, strong macroreticular resin noted
for its resistance to fouling and to chemical attack so it is surpris-
ing to observe an immediate color increase of more than 100 percent
when it was exposed to chlorine waste as shown in Figure 20. A curve
like this would be expected of a resin from which some colored compon-
ent was quickly leached. A synergistic effect occurred with ditch waste
where the small amount of caustic mixed with a large amount of chlorine
waste effectively muzzled the initial color jump, and 81 percent of
the color was removed. This was a greater color reduction than was
obtained with any other waste.
Amberlite IRA-93 merits considerable attention in column tests. It
appears to be effective for color reduction and Sanks and Kaufman
(1965, 1966) found it to be both readily regenerated and resistant to
fouling.
80
-------
Dowex 11. This resin, too, caused an immediate, drastic increase in
the color of all except caustic and ditch wastes upon which it had
little effect. The pH increased from 7.6 to 8.3 but this is entirely
insufficient to account for such a gross increase of color. Strong
base resins require an excess of caustic for regeneration and they
tend to foul irreversibly, so it seems unlikely that any of the strong
base resins are economical. A possible use for such resins might be
the lowest horizon of a multilayered bed. Until such use is contemplated,
there is little reason to test this resin in column operation.
Dowex WGR. This resin had almost no effect upon any but chlorine
waste for which the color was increased more than 100 percent. Most
of the color reduction in chlorine dioxide occurred after three hours,
so the kinetics are not attractive. As a color sorbent, this resin
can be dismissed.
Duolite A-6. This resin gave the best overall performance of any.
Color removals were at least 50 percent for all except hypo waste.
The color in ditch waste was reduced 84 percent whereas the color
reduction in chlorine and caustic waste (the two main ingredients of
ditch waste) were reduced 60 and 77 percent respectively. Hence,
mixing the wastes was clearly beneficial.
Duolite A-7. In general Duolite A-7 was inferior to Duolite A-6, but
the A-7 was superior for treating hypo and caustic. As both Duolite
A-6 and A-7 are similar in all but functional groups there is no reason
to expect column tests to reverse the findings of the batch tests.
Duolite A-57. This resin had little effect on the wastes. It can be
summarily dismissed.
Cation Resins. The cation resins in hydrogen form did not prove to be
effective in sorbing color.
81
-------
Dowex HCR-W. This resin is typical of the gel-type polystyrene-
divinylbenzene resins so widely used for demineralization. It drasti-
cally increased the color of all wastes except caustic. There was no
reason to test this resin in columns.
Duolite C-25D. This resin is like Dowex HCR-W except for its porous
matrix. It requires less regenerant and rinse water than do gel-type
resins. Some increase of color was found with chlorine waste. There
was either a slight sorption of color from other wastes or no effect
at all. Duolite C-25D appears to be superior for demineralization.
But it is not an effective sorbent and column tests are not required
for color sorbency.
Organic Sorbents. The synthetic organic sorbents exhibited various
degrees of selectivity in sorbing color from wastes. None sorbed all
wastes. All increased the color in one or more wastes, sometimes by
significant amounts.
Amberlite XAD-2. This resin had but little effect on most wastes.
After 2 hours the color in chlorine waste began to increase at an
accelerating rate. There was no such effect in ditch waste. During
the investigations of color sorbency, the extreme dependence upon low
pH was unknown, and a decision was made to abandon further tests with
Amberlite XAD-2. Later, a better resin, XAD-8, was developed, so there
was no reason to reconsider the decision.
Duolite S-30. This resin sorbed 45 percent of the color from ditch
waste during the 4-hour period, most of it within the first hour, so
the kinetic characteristics are good. However, the color of hypo
increased about 100 percent, and the effects on other wastes were
negligible. In neutral acid form, at least, the resin is not a parti-
cularly effective sorbent for these wastes. Further testing is not
required.
82
-------
Duolite ES-33. This resin resembles S-30 in performance but it was
somewhat superior with every waste. It might prove to be a useful
sorbent, but no further tests were made.
Duolite S-37. Of the several sorbent resins, this was the best except
with chlorine waste. The removal of color from ditch waste reached
70 percent within an hour and 86 percent in four hours.
The matrix and functional groups of Duolite ES-33 and Duolite A-6 are
similar and Duolite A-7 is similar to Duolite S-37. In free base form
secondary amine functionality was better and in chloride form, a
functional mixture of secondary and primary amines was better. More
color was sorbed from ditch waste by S-37 than by any other resin
or carbon.
Carbon. Carbon sorbed color more uniformly than did resins. Color
never increased. The best results were obtained with chlorine, hypo,
and chlorine dioxide wastes and the poorest results were experienced
with caustic and ditch wastes. These results are opposite to those
obtained with resins which suggests that resins and carbon would
complement each other.
The carbon was pretreated by being shaken in distilled water (to reduce
abrasion during the tests), washed, and drained. The weight of carbon
(and resin) per flask was 5 grams on a saturated, drained basis. The
moisture varied from 53 to 86 percent of the dry weight which corre-
sponds to carbon dry weights of 3.3 to 2.7 grams. While this compares
resins and carbon on the same basis, it is awkward for comparison on
the basis of purchase price. Were the tests to be run again the carbon
would be weighed dry and presoaked afterward.
Filtrasorb. This carbon, although very hard, abrades significantly
during shaking, so it was necessary to filter the liquor to obtain
83
-------
a valid color reading. Sorbance of color increased with decreasing
particle size. Nearly 100 percent of the color was sorbed from chlorine,
hypo, and chlorine dioxide wastes. But it should be noted that none
of these three raw wastes contained more than 150 CU.
Filtrasorb 300 seems to be the most popular size in industrial use.
It combines good kinetic properties with ease of handling and resistance
to abrasion. It contained 74 percent water when loaded so the dry
weight was 2.9 grams. Had 2.1 grams more dry carbon been loaded, it
would have further reduced the color of caustic from 44 percent to
about 65 percent. (This figure is based on calculations using a
Freundlich isotherm which fits sorbency over a four-hour time period
quite well.) The 67 percent reduction of color in ditch waste would
have been 80 percent on the same basis.
Filtrasorb 400 was the best of all carbons tested. Sorption of color
from chlorine, hypo, and chlorine dioxide wastes was essentially 100
percent. As loaded, the moisture content was 77 percent so the dry
weight was 2.8 grams. Had the dry weight been 5 grams the color
reduction of 67 and 75 percent for caustic and ditch waste respectively
would have been 87 and 94 percent respectively. As this was the best
of the carbons, it was chosen as the basis for comparison with resins.
Nuchar. Nuchar carbons performed about the same as Filtrasorb carbons.
Nuchar WVL was slightly superior to the others except for the sorption
of color in ditch waste. Its overall performance was nearly equal to
Filtrasorb 400.
Lime Precipitation
The purpose of lime precipitation experiments was to provide enough
information to select an optimum lime dose for producing a good super-
natant liquor. No attempt was made to optimize massive lime floccula-
84
-------
tion because this has been thoroughly studied by the National Council
for Stream Improvement (1962). Several forms of lime were tried: lime
slurry, 60 percent 1 ;ue r!, -- eborned lime. The liquors were limited
to caustic waste, dit'.'h *ast* .Mid artificial ditch waste.
Lime Slurry. Lime slurry obtained from the mud washer with a moisture
content of 278 percent (dry basis) was only moderately e/tective in
removing color from caustic waste. Reductions in colo'- of 41 and 76
percent were obtained with 50 grams dry mud/liter and luO grams dry
mud/liter respectively. Because far better results wire obtained
with reburned j.i;ue, experiments with lime slurry were Jis^outiaued.
Lime Mud. Limp mud cake (or 60 percent lime mud) obtained from the
microscreen f QJ ': owing the mud washer was tested on caustic and ditch
waste with indifferent results. At a dosage of 10 grams dry mud/liter
only 14 per..-a> 01 color was removed from ditch waste. With massive
amounts of muc 97 percent of Li .olor could be removed. Color in
caustic waste was reduced 25 percent with 50 g dry mud/liter and 61
percent with 100 g dry mud/liier.
In previous investigations, Sanks (1969) found lime mud to be much more
effective. This is not surprising because its chemical characteristics
are likely to vary considerably. But variations, if large, preclude
its use in a process unless: (1) it always occurs in excess, (2) its
effect can be reliably monitored, and (3) its dosage can be controlled
by an automatic, feed-forward mechanism.
Experiments at the Hoerner Waldorf plant in 1965 which showed a 1/4
inch cake of lime mud removed 90 percent of the color from ditch waste
prompted a few exploratory experiments with a filter leaf using lime
and lime mud. Usually cakes built up to 1/4 inch within 20 seconds
but occasionally it required as much as 60 seconds. Cracking time was
always less than 15 seconds. However, the National Council for Stream
85
-------
Improvement (1962) stated the cake tends to crack on microscreen drums
permitting color leakage and furthermore vacuum filtration is expensive
compared to sedimentation. For these reasons the experiments with
filtration were not pursued beyond an exploratory phase.
Lime. By a wide margin, reburned lime was the most effective coagulant
for the removal of color. The experiments with lime, summarized in
Tables 13 to 16, indicate color removals in excess of 95 percent are
readily achieved with the massive lime precipitation method patented
by Berger et al (1964). The plant can produce enough lime (290 tons
CaO/day maximum) to dose the waste caustic extract (460 gpm) at 106,000
mg/1. The same quantity of lime would dose the entire waste stream
of 3390 gpm at 14,200 mg/1. The quantity of C0? required for recarbona-
tion was measured but the data are omitted because correlation between
model (a one-liter cylinder) and prototype is too uncertain. Suffice
it to say the Hoerner Waldorf plant produces so much stack gas (16
percent CO- and 84 percent air) the amount required to reduce the
pH to 7.6 is but a fraction of production.
The following explanation clarifies some of the data given in the
tables. The reburned lime contains some impurities, so only about 90
percent is CaO. Doses are given as CaO rather than as gross weight.
The mud depth ratio is the depth of precipitate divided by total depth
of mud and liquor after two hours of settling in a one-liter cylinder.
The carbon dioxide gas was bubbled until the pH fell to 7.6 but due to
problems of mixing in a one-liter cylinder, the final pH of the mixed
liquor sometimes differed from pH 7.6 by as much as pH 0.2. The percent
color removal was based on the color of the waste neutralized to pH
7.6. A pH of 7.6 corresponded closely to the average pH of the Clark
Fork River. Also pH 7.6 was readily achieved but pH values much less
than that required excessive time and volumes of gas.
86
-------
TABLE 13
COLOR PRECIPITATION FROM CAUSTIC WASTE WITH LIME
Caustic
Original pH 11
Color at pH 7.6, CU 18,
TDS, mg/1 4,
Ca as CaCO~, mg/1
Hardness as CaCO.,, mg/1
Jar No.
Lime dose, g/1 CaO
PH
Sludge depth ratio
Gas to pH 11.5:
Color, CU at pH 11.5
Appearance of supernatant
Alkalinity, mg/1 as CaCO»
Calcium, mg/1 as CaCO-
Hardness, mg/1 as CaCO_
Gas to pH 7.6:
Appearance
Color, CU
Color removal, %
TDS, mg/1
Alkalinity, mg/1 as CaCO,.
Calcium, mg/1 as CaCO»
Hardness, mg/1 as CaCO,,
Reburned lime
.42
200
330
54
150
1
0
11.40
-
18,200
opaque
1,396
54
150
opaque
17,920
0
4,308
1,469
67
170
CaO
2
25
12.22
0.11
3,835
clear
3,050
480
1,254
clear
1,950
89
4,364
1,862
14
36
, %
3
50
12.20
0.16
1,140
turbid
3,786
570
1,536
clear
545
97
5,008
2,370
6
18
90
4
100
12.23
0.27
830
turbid
5,424
497
1,244
clear
460
97
7,740
3,127
7
22
5
200
12.40
0.88
220
clear
6,751
144
430
clear
155
99
9,212
6,960
200
203
87
-------
TABLE 14
COLOR PRECIPITATION FROM DITCH WASTE WITH LIME
Jar No.
Lime dose, g/1 CaO
PH
Sludge depth ratio
Gas to pH 11.5:
Color, CU at pH 11.5
Appearance of supernatant
Alkalinity, mg/1 as CaCO
Calcium, mg/1 as CaCO,.
Hardness, mg/1 as CaCO,.
Gas to pH 7.6:
Appearance
Color, CU
Color removal , %
TDS, mg/1
Alkalinity, mg/1 as CaCO.,
Calcium, mg/1 as CaCO,.
Hardness, mg/1 as CaCO
Ditch waste
Original pH
Color at pH 7.6, CU
TDS, mg/1
Ca as CaCO.-, mg/1
Hardness as CaCO,., mg/1
1
0
8.1
-
4,420
opaque
403
301
385
opaque
4,420
-
1,904
370
329
395
8.1
4,420
4,452
301
385
2
1
11.8
0.06
380
sit tura
1,053
881
953
clear
300
93
1,544
283
182
205
3
2.5
12.1
0.06
300
sit tur
1,985
1,816
1,885
clear
140
97
1,524
300
183
218
Reburned
CaO, %
4
5
12.3
0.07
275
sit tur
2,630
2,440
2,460
clear
125
97
1,608
355
198
215
lime
90
Slightly turbid
88
-------
TABLE 15
COLOR PRECIPITATION FROM ARTIFICIAL DITCH WASTE WITH LIME
Jar No.
Lime dose, g/1 CaO
PH
Sludge depth ratio
Gas to pH 11.5:
Color, CU at pH 11.5
Appearance of supernatant
Alkalinity, mg/1 as CaCO-
Calcium, mg/1 as CaCO,,
Hardness, mg/1 as CaCO.,
Gas to pH 7.6:
Appearance
Color, CU
Color removal, %
TDS, mg/1
Alkalinity, mg/1 as CaCO.,
Calcium, mg/1 as CaCO.,
Hardness, mg/1 as CaCO_
Constituent, %
Lime, % CaO
Original pH
Color at pH 7.6, CU
TDS, mg/1
1
0
5.05
-
1820a
clear
14
146
190
clear
1820a
0
887
14
146
190
Caustic
20
10.42
18,200
4,330
2
2.0
12.15
0.05
450
clear
1730
1828
1830
clear
180
90
1352
235
300
384
3
3.0
12.70
0.05
365
clear
2125
2220
2260
clear
100
95
1316
230
290
360
Chlorine
80
2.56
253
2
4
4.0
12.25
0.04
320
clear
2150
2278
2260
clear
100
95
1336
318
280
382
Lime
90
5
5.0
12.34
0.05
260
clear
2745
2810
2810
clear
75
96
1372
262
235
338
pH 5.05
89
-------
TABLE 16
COLOR PRECIPITATION FROM CHLORINE, HYPO AND
CHLORINE DIOXIDE WASTES WITH LIME
Waste
Original
color at
PH
pH 7.6, CU
Chlorine
3.72
520
Hypo
9.30
180
Chlorine
Dioxide
7.25
380
Lime dose, g/1 CaO 2 5 2525
Appearance at pH 7.6 cloudy cloudy clear clear clear clear
Color after recarbonation
to
Color
pH 7.6,
removed ,
CU
, %
240
74
70
85
0
100
0
100
0
100
0
100
Significantly, the optimum dose of lime to declorize caustic extract
waste was less than the entire lime budget of the plant. About half
of the lime budget, or 50,000 mg/1 reduced the color 97 percent,
produced little more than the minimum obtainable TDS (total dissolved
solids), and gave a low mud depth ratio. As shown, by Figure 26 doses
less than 50,000 mg/1 were much less effective. The sedimentation
rate of the 50,000 mg/1 dose was near optimum whereas high doses
resulted in much slower sedimentation rates as shown in Figure 27.
Furthermore, both hardness and calcium remaining in the supernatant
liquor were at or near the theoretical minimum after recarbonation to
pH 7.6 as shown by Figures 28 and 29. The calcium lost in the super-
natant liquor at this dosage would amount to only about 0.1 ton as CaO
per day in plant operation.
Ditch waste, which varied greatly but was essentially 15 percent caustic
extract and 85 percent chlorine waste was of an entirely different
character than either of its two main constituents. As shown by Table
14 and Figure 30, the amount of lime required to reduce color in 3390
90
-------
o
o
cr
si
o
re
i-
O
O
o
Total CaO budget,
TOO 200
Rebiirned lime, g/1 as CaO
FIGURE 26. COLOR REMOVAL FROM CAUSTIC EXTRACT BY LIME PRECIPITATION
100
0>
O)
CD
a
50
0
lOOq CaO/1
50g CaO/1
25q CaO/1
0 1
Time, hours
FIGURE 27. CAUSTIC EXTRACT SEDIMENTATION RATES IN LIME PRECIPITATION
91
-------
o
o
O
l/l
1C
O
tr
0>
C
a
s-
2r> r\f
J W 'V V.
1,500
1,000
500
C
Before recarbonaticn
After recarbcnation
pH 7.6
Total CaO budcet
25
CO
175
75 100 125 150
Reburneci lirae, :;/! as CaO
FIGURE 28. HARDNESS AFTER LIME PRECIPITATION OF CAUSTIC EXTF.ACT
200
1,000
PO
o
o
ITS
o
I/I
e
r
O
o
500
-Before recarbcnation
After recarbonation
pH 7.6
Total CaO budcet
FIGURE 29.
50 100 15C
Reburned line, q/1 as CaO
CALCIUM AFTER LI.".E PRECIPITATION OF CAUSTIC LXTRAC
92
-------
gpm of ditch waste by 95 percent was less than required for 460 gpm of
caustic extract. To reduce color by 95 percent in caustic extract
required about 40 percent of the total lime budget of the plant. To
reduce color by 95 percent in ditch waste requires about 1,200 mg/1 or
nearly 9 percent of the lime budget. Furthermore, the residual color
in the treated ditch waste was less than 300 CU whereas if untreated
chlorine waste were to be blended with precipitated caustic extract,
the final color would be about 600 CU. Hence, it appears massive lime
precipitation would be more effective if applied to ditch waste rather
than to the caustic extract only.
In some plants, massive lime precipitation might interfere with recaus-
ticizing which could eliminate massive lime precipitation as a color
control method. But it might not be difficult for such plants to
carry a lime budget increase of about 10 percent for precipitation.
The findings reported herein, if consistent, are significant.
Plots of sedimentation rates in Figure 31 show there is little choice
between the various dosages. All precipitates settled well. After
recarbonation to pH 7.6 the supernatant liquors for all doses were
clear and the floe settled quickly.
The removal of hardness and especially of calcium after recarbonation,
shown in Figures 32 and 33, was poor in this experiment. About 180
mg/1 of calcium remained in the supernatant liquor after reuarbonation.
The process is the same as the well-known and commonly used excess
lime softening process in which hardness can be commercially reduced
to 80 mg/1 as CaCO- at 20°C, and it should not be difficult to reduce
the calcium content of the ditch waste to such a value. As the calcium
content of the untreated ditch waste was about 300 mg/1, some lime could
be recovered by this process.
93
-------
Before C02 (pH 12
After C09 (pH 7.6)
0 2.5
Returned lir.e, p/1 as CaO
FIGURE 30. COLOR REMOVAL FRO'! DITCH WASTE BY LIME PRECIPITATION
5c CaO/1
2.5gCaO/l
0
_L
-Time, hours
FIGURE 31. DITCH WASTE SEDIMENTATION RATES. LIME PRECIPITATION
94
-------
co
o
Cl
fO
CO
to
O)
2500
2COC
1500 -
fO
re:
Before recarbonation
Afterrecarbcnation to oH 7.6
1000 -
1 2 3
Reburned li^e, c/1 as CaO
FIGURE 32. HARDNESS AFTER LIME PRECIPITATION OF DITCH WASTE
25CO
o
o
-------
Anomalies and variations experienced with ditch waste prompted making
an artificial ditch waste. The first artificial ditch waste was made
of 20 percent caustic extract and 80 percent chlorine waste to give
a calculated color of 3,730 CU to approximate the real ditch waste.
But the measured color, as shown in Table 15, was only 1820 CU. When
the pH of both wastes was adjusted to 7.6 before mixing, the calculated
and measured colors were the same. Apparently, the acid-base reaction
of the raw wastes profoundly affected the color bodies. Later, artifi-
cial ditch wastes contained 15 percent caustic extract and 85 percent
chlorine waste.
As Table 15 indicates, the dose of lime required to reduce the color
by 90 percent was about 20 percent of the lime budget. Mixing the
waste liquors before decoloring was advantageous.
As the liquor from the chlorine, hyopchlorite, and chlorine dioxide
stages is returned to the process in counter-current flow, none of it
except accidental spills or minor leaks goes to waste. Hence experi-
ments with flocculation of these wastes were only exploratory. The
procedure was the same employed in testing caustic and ditch wastes,
and Table 15 summarizes the effects on color.
Small amounts of lime (2000 mg/1 or less) removed 100 percent of the
color of hypochlorite and chlorine dioxide liquors but 5000 mg lime/1
resulted in only 85 percent reduction of color from chlorine waste.
However, none of the raw wastes are highly colored, so a color reduction
of 85 percent produces a nearly colorless product.
Color Sorbency After Lime Precipitation
The National Council for Stream Improvement (1967) stated carbon is
uneconomical for the removal of concentrated color and its role is
logically one of polishing effluents after most of the color is removed
96
-------
by massive lime precipitation. Certainly, very large amounts of carbon
are required to decolor raw ditch wastes. Obviously, decolorization
by chemically regenerated sorbents is only feasible if little or no
product water is required for regeneration and rinsing. The efficiency
of carbon and resins for polishing the effluent from the precipitation
process is explored in this section.
Waste. Tests of lime-precipitated waste were confined to caustic extract
because it is the most troublesome fraction. It contains the most color
and even after lime precipitation, it was still more highly colored
than the other raw wastes except ditch wastes.
Lime precipitation of caustic extract was repeated several times.
Inevitably, there were slight variations in the percentage of color
removed, and hence there were variations in the initial color of the
various batches of waste.
Resin. Typical time-sorbency curves are shown in Figure 34. Table 17
shows the color and total organic carbon remaining after four hours
of sorption.
Lime precipitation clearly has benefits that reach beyond gross color
removal. The performance of resins in removing color from raw caustic
waste is poor as can be seen in Figures 7, 9, 11, 19, 20, and 21. But
the percentage removal of color from lime-precipitated caustic waste is
fair to excellent. For example, Dowex 11 at a dose of 5 g/100 ml
removed only 17 percent of color from untreated caustic. But even a
dose of 1 g/100 ml removed 100 percent of the color from lime-
precipitated caustic.
Table 17 shows the best performance was obtained with Dowex 11 followed
in order of merit by Amberlite IRA-93, Duolite A-57, Amberlite IRA-68,
and Duolite A-6. The performance of Duolite S-37 was only fair with
97
-------
c
r-
rtl
o
4J
£
Ol
CJ
i.
2.5 g resin wet, drained
100 nil caustic waste
oH 7.5
FIGURE
Tire, hours
34. COLOR SORPTION OF LIME-PRECIPITATED CAUSTIC WASTE 3Y
RESIN
TABLE 17
RESIN SORPTION OF CAUSTIC COLOR AFTER LIME PRECIPITATION
Untreated color :
Lime dose:
18,200 CU
35g CaO/1
Color after precipitation:
Color removal by precip :
TOG after precipitation:
450 CU
97.5%
725 mg/1
After 4 hrs. sorption
Sorbent
Amberlite IRA-68
Amberlite IRA-93
Duolite A-6
Dose
8/1
1
2.5
5
1
2.5
5
1
2.5
5
Color, CU TOG, mg/1
60 600
55 600
50 575
80 565
50 575
0 575
80 600
50 600
70 575
Removals
Color
87
88
89
82
89
100
82
89
85
.
TOC
17
17
21
22
21
21
17
17
21
98
-------
(Table 17 continued)
Duolite S-30
Untreated color:
Lime dose:
Amberlite XAD-2
Dowex 11
Dowex WGR
Duolite A- 7
Duolite A-57
Duolite ES-33
Duolite S-37
1
2.5
5
18,200 CU
50g CaO/1
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
395
350
290
Color
Color
525
500
500
after precipitation:
removal by precip:
TOG after precipitation:
305
270
240
0
0
0
270
270
270
305
445
700
40
35
40
250
250
285
150
90
90
640
600
600
600
540
480
620
640
630
680
600
580
625
625
500
600
620
600
625
575
600
12
22
36
360 CU
99%
725 mg/1
15
25
33
100
100
100
25
25
25
15
-24
-95
89
90
89
31
31
21
58
75
75
28
31
31
12
17
17
17
26
34
15
12
13
6
17
20
14
14
31
17
15
17
14
21
17
85 percent of the color removed. Other resins such as Duolite ES-33,
Dowex WGR, Amberlite XAD-2, and Duolite S-30 removed only 30 percent
or less of the color, and Duolite A-7 increased the color somewhat.
Except for Amberlite 1RA-93, the resins appeared to sorb color rapidly.
Hence little color was sorbed after one hour of contact. A high rate
of sorption is beneficial in column operation as it permits frequent
regeneration which in turn tends to prevent blinding.
99
-------
Removals of total organic carbon were low. Furthermore, there seems
to be little correlation between color removal and TOG removal. Duo-
lite S-30 removed little color but on the other hand, it performed
better than other resins on TOG removal. The amount of TOG was not
large and it is possible that some solvents or other organic material
from the resin were dissolving in the liquor.
Table 17 shows occasional anomalies. Such anomolies can result from
an error of only 1 percent on the transmittance scale of the spectro-
photometer and such errors are occasionally to be expected. Anomalies
in the values of TOG also occur and are not surprising considering the
accuracy of the TOG analyzer in use at that time.
Carbon. Lime precipitation also benefited sorption of color by carbon
and the carbons were very effective. Their rate of sorption was some-
what less than the rate of resins, but sorption was usually more complete
as shown in Figure 35 and Table 18.
There was little difference between Nuchar and Filtrasorb. After four
hours of sorption the color removal was independent of particle size.
The removal of TOG was better and more consistent than removal by resins,
but again there does not appear to be a direct relation between color
and organic carbon.
GEL CHROMATOGRAPHY
Principle
Gel chromatography is a method for separating compounds of different
molecular weights. The gel is a very porous material with holes of
varying sizes. When mixtures of different compounds are eluted through
the gel column, molecules larger than any of the holes will be found
only in the surrounding liquid, whereas smaller molecules will exist
100
-------
1 01
re
-------
TABLE 18
CARBON SORPTION OF CAUSTIC COLOR AFTER LIME PRECIPITATION
Color after precipitation:
Untreated color:
Lime dose:
Sorbent
Filtrasorb 100
200
300
400
Nuchar WVG
WVL
WVW
18,200 CU
35g CaO/1
Dose
g/1
I
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
1
2.5
5
Color removed by
precip :
TOC after precipitation:
After 4
Color, CU TOC
250
70
0
240
230
0
90
55
0
25
25
0
50
0
0
80
0
0
200
60
0
450 CU
97.5%
725 mg/1
hrs. sorption
, mg/1
530
500
510
570
540
500
540
500
500
540
520
500
580
500
470
450
450
440
470
460
460
Removals
Color
44
85
100
47
49
100
80
88
100
95
95
100
89
100
100
82
100
100
56
87
100
%
TOC
27
31
30
21
26
31
26
31
31
26
28
31
20
31
35
38
38
39
35
37
37
102
-------
Artificial Ditch Waste
The artificial ditch waste apparently consists of many different organic
compounds because there were no real peaks except for very small
molecules. These results were found also by Luner, Dence, Bennett,
and Rung (1970). Loras (1965) found spent liquor from the chlorination
of spruce sulfite pulp to have two principle fractions with weight-
average molecular weights greater and smaller than 5000. By use of
Sephadex G-50 and LH-20, Collins, Webb, Didwania, and Lueck (1969)
were able further to fractionate molecular weights of less than 5000 in
spent chlorination liquors from sulfite and kraft pulps.
The data of our studies show Duolite A-6 appears to remove some of
the compounds of every weight but preferentially those just under a
molecular weight of 1800.
Demineralization through Duolite C-25D and A-6 appears to remove more
of the larger molecules than were removed by A-6 alone.
Filtrasorb 400 carbon columns appear to remove smaller molecules
preferentially. Hence, it would appear advantageous to manufacture
a resin which would remove all molecules with equal efficiency or else
to combine resins (or resins and carbon) of complementary characteristics.
The results of gel chromatography, limited though they were, explains
the failure of a sorbent to effect substantially greater reduction in
color after the first pass through the resin.
103
-------
COLOR SORBENCY IN COLUMNS
Column Size
An internal diameter of one inch is ordinarily considered to be minimum
in ion exchange columns because of excessive wall effects for lesser
diameters. But even one-inch columns require large amounts of feed.
Were they reliable, half-inch columns would conserve liquor, so several
runs were made to compare half-inch columns with one-inch columns. The
resin beds in each were 24" deep and the flow rate in BV/hr were the
same for both.
The feed for the columns was caustic bleach waste precipitated with
approximately 35 grams of lime as CaO/1 and recarbonated to a pH of 7.6
with a concentration of about 300 CU. The flow rate was 20 BV/hr.
Typical results, shown in Figures 36 and 37, indicate only a fair com-
parison between the half-inch and one-inch columns.
Several runs with Amberlite IRA-93 and Duolite A-6 are compared in
Figures 38 and 39. The figures themselves and a regression analysis in
which the coefficient of correlation is 0.97 with 13 degrees freedom in
Figure 5, indicates the comparison to be rather poor. However, several
different batches of wastes were used, so the comparison includes not
only the size effect, but also the effect of variation in feed. Vari-
ations in feed greatly affect column performance and leads to a scatter-
ing of test results that are as important as the difference between half-
inch and one-inch columns. Hence, it was concluded half-inch column
tests are adequate but only for screening runs.
104
-------
TOO
cr
c
c:
50
o
o
(J
i-
o;
(X
Caustic bleach (35 g CaO/1)
Duolite A-6
One-inch column-
I
I
I
Half-inch column
r
i
J I 1 L.
100
Bed-volumes
200
FIGURE 36. COLOR BREAKTHROUGH FOR HALF-INCH AND ONE-INCH COLUMNS
12
11
10
Caustic bleach (35 g CaO/1)
Duolite A-6
Half-inch column
r
One-inch column
-I L
_l L.
0 100
Bed volumes
FIGURE 37. CHANGE OF pH FOR HALF-INCH AND ONE-INCH COLUMNS
200
105
-------
E
o
u
o
c
(O
100
ex
'I 50
O)
s_
S-
o
o
o
O)
o
Ol
Q_
0
o Duolite A-6, Ditch, Set 1
Q Same, Set 2
A IRA-93, Ditch
0 50 100
Percent color remaining, one-inch column
FIGURE 38. COMPARISON OF COLOR REMOVAL IN HALF-
INCH AND ONE-INCH COLUMNS
o
12
11
S 10
^ 9
03
Duolite A-6, Ditch, Set 1
Same, Set 2
IRA-93, Ditch
9 10 11
pH, one-inch column
12
FIGURE 39. COMPARISON OF pH IN HALF-INCH AND
ONE-INCH COLUMNS
106
-------
Half-Inch Column Screening Runs
The screening runs comprised several series of fixed-bed ion exchange
operations to compare the resins selected in batch studies for further
study and to compare operating parameters and different wastes.
Flow rate for exhaustion. The effect of flow rate on color break-
through is shown in Figures 40 and 41 for Duolite A-6. resin fed with
ditch waste in which color was reduced to 275 CU by lime precipitation.
There is no readily apparent optimum rate of flow. Sorption decreased
more or less steadily with an increasing flow rate. The desirability
of low flow rates is certainly evident from the standpoint of effective-
ness of the resin, but on the other hand low flow rates result in
large reactors and a large capital expenditure. As there is no evident
optimum flow rate, 20 BV/hr (2.5 gpm/cu ft) was selected with considera-
tion for operational efficiency and speed in performing laboratory runs.
Wastes. The countercurrent operation in the Hoerner Waldorf Mill
discharges wastes only from the chlorine and the caustic extract stages.
Approximately 15 percent of the waste is caustic extract and 85 percent
is chlorine waste. As shown in Figure 5 the wastes from the other
stages are recycled to the preceeding stage. Nevertheless, to obtain
a better idea concerning the refractory character of other wastes,
each waste was tested with each of the sorbents selected in batch
tests for further study. These results are shown in Figures 42 to
46 and in Table 19.
In general, the waste most easily decolored was ditch waste followed
by caustic extract. Hypochlorite, and particularly chlorine and chlorine
dioxide liquors tended to be refractory. However, the juxtaposition
of the different wastes were different with the various resins, which
supports the supposition that resinous sorbents can be selected or
even tailored to accomplish different jobs at different mills.
107
-------
100
Ditch waste (4/13/70)
450 mg CaQ/1
275 CU (color units)
to
OJ
$-
S-
o
o
u
£=
01
o
CD
50
100 200
Bed volumes
300
FIGURE 40. SORPTION OF COLOR AT VARIOUS FLOW RATES IN DUOLITE A-6
RESIN. HALF-INCH COLUMN
2000
O)
»->
X
o
*\
un
o
it
3 1000
o
-------
lOOr
C12
en
r
C
i
(O
O)
s-
s_
O
*0
O
+J
c
u
O)
Q.
50
cio2
1 Plugged
OC1
Ditch
Caustic
P1ugged
100
Bed volumes
FIGURE 42. IRA-68 COLOR SORPTION. HALF-INCH COLUMN
200
100
3.08, C102
-t
Cl,
.-J
2 ,
OC1 . ^ I
1 plugged
O)
s_
O
O
O
c
CD
O
s-
O)
50
-T'
I
Ditch f
-\ Plugged
100
Bed volumes
FIGURE 43. IRA-93 COLOR SORPTION. HALF-INCH COLUMN
200
109
-------
100
ng
re
OJ
_-
S_
o
o
o
+->
c:
cu
u
s_
OJ
Q-
en
o
HPluqqec
100
Bed volumes
FIGURE 44. S-37 COLOR SORPTION. HALF-INCH COLUMN
200
100
Bed volumes
FIGURE 45. A-6 COLOR SORPTION.
110
200
HALF-INCH COLUMN
-------
100
CT
C
C
to
o
s_
O)
Q-
50
0
CIO
2 J
OC1
Cb
I
Caustic j
Ditch
____
i
Plugged
I
Plugged
0
100
Bed volumes
FIGURE 46. FILTRASORB 400 COLOR SORPTION. HALF-INCH COLUMN
200
TABLE 19
BED VOLUMES OF WASTE REQUIRED TO REACH
COLOR BREAKTHROUGH OF 50%
(Half-Inch Column)
Sorbent
IRA-93
IRA-68
S-37
A-6
Filtrasorb 400
ci2
44
1
84
80
82
Caustic
80
200
95
145
138
Waste
cio2
1
100
1
90
25
OC1
22
110
88
95
70
Ditch
160
150
180
165
160
111
-------
Sorbents in virgin state. In half-inch column runs, carbon performed
better than did resin sorbents on ditch waste. But IRA-68, IRA-93,
S-37, and A-6 resins also performed well. IRA-68 resin was by far
the most effective sorbent for removing color from caustic waste
followed by A-6 resin and carbon. The other sorbents were less
effective.
A-6 and IRA-68 resins were superior for chlorine dioxide waste whereas
t^ - other sorbents were relatively ineffective. Amberlite IRA-68
at: ;> appeared to be the best resin for sorbing color from hypochlorite.
However A-6, S-37 and carbon appeared to be almost as effective as
IRA-68. The best sorbents for removing color from chlorine waste
were S-37, A-6, and carbon. The other sorbents were poor.
Because of the time required to make the column runs and because the
liquors needed for the runs were augmented by newly flocculated and
recarbonated batches from time to time, the comparison of sorbents is
not completely definitive. Furthermore, as explained above, the half-
inch columns tend to give rather wide variations in results. Neverthe-
less the screening runs show ditch waste is more readily decolored than
are other wastes and all of the sorbents are reasonably competitive
for ditch waste. Evidently color in other wastes is preferentially
sorbed in different order by the different resins. Resins are also
competitive, in general, with carbon for color sorption from liquors
other than ditch waste.
One-Inch Colunn Runs
Virgin resins. All five sorbents (IRA-68, IRA-93, S-37, A-6, and
Filtrasorb 400 carbon) were tested in this series. The only feed used
was ditch waste in which approximately 90 percent of the color was
removed through massive lime precipitation followed by recarbonation
to pH 7.6. In the first two sets of experiments, the remaining color,
112
-------
280 CU versus 450 CU, varied by 50 percent. (Afterward it was possible
to obtain a residual color of exactly 300 CU.) But the first two
batches of wastes produced anomalies which could not be accounted for
by the difference in residual color. Each of the two batches were used
for one-inch column runs and the first batch gave good correlation
with the previous half-inch column runs as shown by a comparison of
Figures 47 and 48 with Figures 42 and 43. The second batch with the
higher residual color gave abnormally short column runs as shown by
Figures 49 to 51.
Because of the evident difference between the two feeds used in this
phase of the investigation it is dangerous to compare all sorbents on
the same basis. Nevertheless it is possible to conclude that the
performance of IRA-68 is nearly identical with that of IRA-93. S-37
was somewhat more effective than A-6 and both were superior to Filtra-
sorb 400 carbon.
Regeneration With White Liquor
The general purpose of this phase of the work was to establish the
feasibility of using white liquor to regenerate resin columns in single
runs. The white liquor was used as received from the Hoerner Waldorf
Mill or diluted to less than its natural concentration of 3 normal
as required. The resins, partly exhausted with lime-flocculated ditch
waste, were divided into packets of 28 ml to make resin beds one inch
in diameter and one inch deep.
The regeneration of each of three resins, Duolite A-6, Duolite S-37,
and Amberlite IRA-68, was optimized in single runs with respect to
three variables: concentration of regeneration, flow rate, and amount.
To save time and liquor, regeneration experiments were carried out in
columns one inch in diameter and one inch deep. For evaluating relative
performance, such a column size is entirely adequate.
113
-------
100
Ditch waste (4/13/70)
450 mg CaO/1
280 CU
c
I
c
«3
I 50
-------
100
en
O)
50
O)
o
O)
£X
Ditch waste (4/13/70)
300 mg CaO/1
425 CU
J_
50
Bed volumes
FIGURE 49. S-30 COLOR SORPTION. ONE-INCH COLUMN
100
100
en
fO
CD
50
o
o
OJ
o
S-
O)
Q_
Ditch waste (4/13/70)
300 mg CaO/1
425 CU
50
Bed volumes
FIGURE 50. A-6 COLOR SORPTION. ONE-INCH COLUMN
100
115
-------
100
en
c
c
to
o>
50
o
o
OJ
(J
O)
Q.
Ditch waste (4/13/70)
300 mg Ca 0/1
425 CU
50
Bed volumes
TOO
FIGURE 51. FILTRASORB 400 COLOR SORPTION. ONE-INCH COLUMN
Concentration. It is desirable to regenerate the resins with undiluted
white liquor because the spent regenerant can then be transferred to
the digesters with the rest of the white liquor. Such an operation
would not interfere with mill operations and therefore the resins could
be regenerated cheaply. On the other hand, if it is necessary to
dilute the regenerant, some interference with mill operations would
occur. Dilution of the process chemicals is, in general, critical.
Although the effects of dilution of white liquor on the mill operations
have not been investigated it seems nevertheless desirable to avoid any
dilution.
In exploring the effect of the concentration of regenerant upon the
efficiency of regeneration, all flow rates were 20 BV/hr. Therefore
as the concentration was reduced the rate of application in me of
NaOH per hour decreased.
116
-------
As shown in Figures 52 and 53, undiluted white liquor at 3.0 normal was
the best regenerant for Duolite A-6 resin. After regeneration with
nearly 400 me the r in ft -pea" -,o be like. new. No signs of damage
(such as physical disintegration) were detectable in these single runs.
As shown in Figures 54 and 55 Duolite S-37 appeared to be insensitive to
concentrations between 1 and 3 normal. Concentrations less than 1
normal were less efficient. After regeneration the reain appeared
to be like new with no visible damage.
Figures 56 and 57 show Amberlite IRA-68 is very sensitive to the con-
centration of the white liquor. The best concentration was 0.25 normal.
The inefficiency of regeneration at higher concentrations can probably
be explained on the basis of the high shrinkage observed at these con-
centrations which showed the resin matrix closed around the sorbed
color bodies thereby decreasing the solid diffusivity. Inspection of
the resin beads showed not all color was eluted from the resin at
any of the concentrations or volumes of throughput investigated. The
resin remained very dark.
The maximum amount of color eluted in these tests was 5,200 CU-liters
with nearly 400 me of 3 normal caustic in Duolite A-6 resin. The most
color removed from Duolite S-37 was 900 CU-liters with nearly 300 me
of 1 normal caustic, and no more color could be eluted even with 700 me
of 3 normal caustic. Although superficially Duolite A-6 appears to
be superior to Duolite S-37, it may not be so because the A-6 was
more completely exhausted than the S-37.
The maximum amount of color removed from Amberlite IRA-68 was about
330 CU-liters at a regeneration level of about 100 me of 0.25 normal
white liquor. In single runs, at least, the regeneration of Duolite
S-37 and A-6 was superior to Amberlite IRA-68.
117
-------
6000
CD
4500
s_
O)
3000
o
o
1500
03
4->
O
0
Regenerant: white liquor
Flow rate: 20 BV/hr
1" x 1" resin bed
0
1
Normality
FIGURE 52. EFFECT OF CONCENTRATION ON REGENERATION OF A-6 RESIN
6000
CD
O)
HI
4500
3000
1500
0,
Regenerant: white liquor
Flow rate: 20 BV/hr
1" x 1" resin bed
100
300
400
200
me white liquor
FIGURE 53. COLOR BREAKTHROUGH IN THE REGENERATION OF A-6 RESIN
118
-------
1000
800
CD
l/l
|J600
400
o
o
-200
0
Regenerant: white liquor
Flow rate: 20 BV/hr
1" x 1" resin bed
0
FIGURE 54
1000
1234
Normality
EFFECT OF CONCENTRATION ON REGENERATION OF S-37 RESIN
3N
Regenerant: white liquor
Flow rate: 20 BV/hr
1" x 1" resin bed
200
800
400 600
me white liquor
FIGURE 55. COLOR BREAKTHROUGH IN THE REGENERATION OF S-37 RESIN
1000
119
-------
CD
400
360
320
i-
^ 280
co
S 240
r
x 200
3 160
n
° 120
ro
+->
O
80
40
0
Regenerant: white liquor
Flow rate: 20 BV/hr
1" x 1" resin bed
01234
Normality
FIGURE 56. EFFECT OF CONCENTRATION ON REGENERATION OF IRA-68 RESIN
Regenerant: white liquor
Flow rate: 20 BV/hr
1" x 1" resin bed
100
300
400
FIGURE 57.
200
me white liquor
COLOR BREAKTHROUGH IN THE REGENERATION OF IRA-68 RESIN
120
-------
Flow rate. The effect of flow rate upon regeneration efficiency was
determined using the optimum concentration of regenerant for each resin,
namely: 3.00 normal white liquor for Duolite A-6 and Duolite S-37 and
0.25 normal for Amberlite IRA-68 resin.
As shown in Figure 58 the optimum flow rate for Duolite A-6 was 5 BV/hr.
However at flow rates of 7 to 25 BV/hr, the efficiency was nearly as
great. Beyond a flow rate of 25 BV/hr and below 5 BV/hr the efficiency
decreased. These results appeared to be somewhat anomalous, but
corroborating runs were made with confirming results. Glueckauf (1955)
has shown theoretical considerations can lead to peculiarities with
respect to flow rates in resin columns. Because a flow rate of 5 BV/hr
(which produced the highest efficiency) results in excessively long
regeneration times, 25 BV/hr was considered optimum.
10,000
c
0)
8,000
O)
s_
O)
6,000
s." 4,000
0
2,000
0
0!
0
Regenerant: white liquor
Exhaustion
breakthrough: C/C = 0.9
1" x 1" resin bed
30
35
5 10 15 20 25
Flow rate, BV/hr
FIGURE 58. EFFECT OF FLOW RATE UPON REGENERATION EFFICIENCY OF A-6 RESIN
121
-------
The optimum flow rate in Duolite S-37 was approximately 25 BV/hr as
shown in Figure 59. No anomalies were found in these runs. Efficiency
decreased below 20 BV/hr and above 30 BV/hr.
As shown in Figure 60, the best flow rate tested for Amberlite IRA-68
was 10 BV/hr. From the shape of the curve it seems likely that higher
efficiencies might be found at still lower rates. The low concentra-
tions and the low flow rates combine to require a long time for
efficient regeneration.
Regeneration level. The optimum quantity of regenerant can be only
approximately determined from these short-column experiments. The
regenerant does not pass through the column in plug flow. Instead,
there is dispersion of the front and tailing of the end. Shallow
resin beds give little indication of this action. However, a first
approximation of the optimum quantity of regenerant can be gleaned by
estimating the point where a plateau begins in the elution history
shown in Figures 53, 55, and 57. These estimated points are given in
Table 20, and the amount of color eluted is given in Table 21.
TABLE 20
ESTIMATED OPTIMUM QUANTITIES OF WHITE LIQUOR REGENERANT
Quantity Regenerant , me NaOH/ml resin
Resin
A-6
S-37
IRA-68
3N
24.6
17.2
18.3
2N
16.5
14.5
14.5
IN
10.2
12.6
12.8
0.5N 0.25N
3.8
12.0 7.6
122
-------
1000
c:
o>
3
800
O)
I/)
S-
O)
- 600
400
o
o
200
0
0
10
30
40
20
Flow rate, BV/hr
FIGURE 59. EFFECT OF FLOW RATE ON REGENERATION EFFICIENCY OF S-37 RESIN
1000
800
eu
^5600
°400
o
o
200
(C
4->
O
0
Regenerant: white liquor
Exhaustion
breakthrough: C/C = 0.3
1" x 1" resin bed
0
10
40
50
20 30
Flow rate, BV/hr
FIGURE 60. EFFECT OF FLOW RATE ON REGENERATION EFFICIENCY OF IRA-6a RESIN
123
-------
TABLE 21
COLOR ELUTED AT OPTIMUM QUANTITIES OF WHITE LIQUOR REGENERANT
Total color eluted, CU-liters/me NaOH
Resin
A-6
S-37
IRA-68
3N
15.9
3.8
0.3
2N
18.6
4.4
0.7
IN
27.5
5.4
1.3
0.5N 0.25N
7.5
1.9 3.3
Comparison of Resins in Single Runs
Comparing one resin with another on the basis of a series of single
runs can be quite misleading. Conclusive comparisons can only be
made with cyclic runs in which the resins reach cyclic stability.
Irreversible sorption, blinding, and chemical and physical degradation
are factors which cannot be judged from single runs.
Cyclic Runs
During the cyclical runs, the capacity of resins regenerated with
white liquor continued to decline. Rejuvenation with hydrochloric acid
fully restored the resin, but the procedure would have to be repeated
about every 10th cycle, which in a prototype would mean a daily rejuvena-
tion procedure. Hence, other regenerants were tried, some in single
runs, others in a few cyclical runs, and still others in a lengthy
series of cyclical runs.
White liquor regeneration. As shown in Figures 61 and 62 both Duolite
A-6 and S-37 gradually lost capacity to sorb color from bleach waste
when regenerated at 16 BV/hr with white liquor. After 9 cycles of
sorption runs, the original capacity of the resin was reduced to less
than 50 percent. Neither rejuvenation with 4 BV of methanol nor with
124
-------
l£>
0
X
l/l
S-
0)
X
S-
° 0.5
o
o
n
Rejuvenation-
\ i
M
4 BV 1 N HC1
Sorption o Ry i M Nar,L
O D V L ! i iiG'-'i
Regeneration
3
/
\
r
/
/
/
^m
^
7"
''/
\
/
rj ii
/
/
/
(
/
/
MB
/
/
kXXXXXI
-
NSXNXNXV
456
Number of cycles
10
FIGURE 61. COLOR REMOVAL BY DUOLITE A-6 RESIN REGENERATED «'ITH HHITE LIQUOR
1. 3
o
~
X
01
s_
S 1.0
T
^
ft
S-
° 0.5
0
o
rO
1
n
i Sorption
-
_
^^
7
/
'V
/
/
/;
^
Regeneration Rejuvenation
.
71
^
/
/
'/
^
^
^
4 BV 1 N HC1
8 BV 1 N NaOH
r
^
^
/
/
^
/
/
/
'f
~
7
/
/
'.
',
/
/
_
/
/
',
/
/
/
n_
7
/
/
/
/
/
/
j>
71
*
*
/
^
_
/
/
/
a
^
^
-
[
i
/
/
^
Number of cycles
FIGURE 62. COLOR REMOVAL BY DUOLITE S-37 RESIN REGENERATED WITH WHITE LIQUOR
125
-------
4 BV of 10 percent NaCl had much affect. However, rejuvenation with
4 BV of 1 N HC1 followed by 8 BV of 1 N NaOH restored both resins
to their original, virgin appearance and nearly to their original
capacity for the sorption of color.
The loss of capacity appeared to be associated with some sulfide
precipitation as well as precipitation of carbonates. When the resins
were treated with hydrochloric acid, great quantities of CCL gas were
evolved.
Caustic regeneration. When the resins were regenerated with 1 N NaOH,
there was little or no decline in the sorption capacity of Duolite
A-6 after the first cycle. As Figure 63 shows, the sustained sorption
capacity was approximately 80 percent of the virgin sorptive capacity.
Duolite S-37 resin exhibited somewhat anomalous behavior. It's
sorptive capacity, as shown in Figure 64, was greater in the second
cycle than for the virgin resin. After the third cycle its capacity
began to rise slowly. At the 9th cycle, its capacity decreased
abruptly to less than 60 percent of its virgin capacity. Although
the two resins (Duolite A-6 and S-37) are nearly equal, Duolite A-6
was more consistent in performance.
Sorption and elution breakthrough curves for color and total organic
carbon are shown in Figures 65 to 68 for one of the last runs in a series
after cyclic equilibrium was established. In general, approximately
30 percent of the color broke through almost immediately with a gradual
increase of color breakthrough to the end point of the run.
Little organic carbon was sorbed by the resin. Duolite A-6 was con-
siderably better than Duolite $-37 in this respect.
126
-------
1.5
co
% 1.0
-I-)
o 0.5
"o
o
(O
4->
o
0
I Sorption
Regeneration
171
1 2
4 5
6 7 89 10 11 12 13 14 15
Number of cycles
FIGURE 63. COLOR REMOVAL BY DUOLITE A-6 RESIN REGENERATED V.'ITH CAUSTIC
1.5
to
o
i/>
t-
1 0
A
0.5
o
o
fO
4J
o
0
Sorption
- Regeneration
1
3 4
6 78 9 10 11 12 13 14 Ic>
Number of cycles
FIGURE 64. COLOR REMOVAL BY DUOLITE S-37 RESIN REGENERATED WITH CAUSTIC
127
-------
0
20 40 60 80 100 120 140
Bed volumes
160 130 200
FIGURE 65. COLOR AND TOC BREAxTiiROUGH JN 13TH CYCLIC PUN.
'J'JOLITI A-6 RESIN. CAUSTIC REGENERATION
5 BV 1.000 N aC !
= 1575 me '"''
Upflow (3 20 BV/hr
56789
Bed volumes
FIGURE 66. ELUTION Or COLOR A.\D TOC IN COUNTERCLRRENT CAU3TIC
REGENERATION 0" DUOLITE A-6 RESIN IN 13TH CrCLIC ?.UN
128
10
-------
1.0
0.9
0 = 8-
0.7
0.6
o
" 0.5H
0.4
0.3
0.2
0.1
FIGURE 67.
Color
I
50
100
Bed volumes
150
200
COLOR AND TOC BREAKTHROUGH IN 14TH CYCLIC RUN,
DUOLITE S-37 RESIN. CAUSTIC REGENERATION
5 BV 1.000 N *!aOH
- 1575
pflow ? 20 BV/hr
2 * 3
Bed volumes
FIGURE 68. ELUTION OF COLOR AND TOC IN COUNTERQjRRENT CAUSTIC RE3EN-
ERATION Of DUOLITE S-37 RESIN IN 14TH CYCLIC RUN
129
-------
Amberlite XAD-8 and weak wash regeneration. News of a new resin,
Amberlite XAD-8, was received late in 1971 after the program on color
sorbency was completed. A decision was made not to interrupt desalination
runs with more color sorbency runs, and nothing was done with XAD-
8 until the life cycling runs were begun. The results of the few
preliminary tests were poor, so little interest in -XAD-8 was aroused.
In discussing these results, Button (1972) stated very low pH of the
feed was necessary for good operation of this resin, and furthermore
regenerants containing one normal equivalent NaOH were too strong.
Button reported excellent results on many artificial bleach plant
effluents (blends of chlorine and caustic wastes) in which the pH
was always less than 3, and since, in his experience, the pH of bleach
plant liquors was invariably low, the need for low pH was not mentioned
in the literature. The experiments described herein follow the
recommendations of Rohm and Haas literature (1971). No attempt was
made to optimize operating conditions.
Raw artificial ditch waste (pH 6.5) was acidified to pH 2.2 by adding
0.1 percent H?SO, by weight. Corrected to pH 7.6, the intensity of
color was 2800 CU. Figure 69 shows the fourth run in a series in which
the XAD-8 was regenerated countercurrently (as shown in Figure 70) with
2 BV of weak wash at a flow rate of 1 BV/hr upflow. The sharp drop in
color at the beginning of the run in Figure 69 is due to the displacement
of the regenerant by the ditch waste, and the low color at about 3
BV shows the resin is capable of sorbing nearly all kinds of color
bodies. It suggests that a series of columns (as in Progressive Mode)
would be capable of producing a colorless effluent.
These results are significant because they indicate resins can indeed
be tailored for optimum operation. If the operation of such resins
can be integrated sufficiently well into the pulping process, the use
of resinous sorbents for the color reduction of raw wastes might be
the most satisfactory and economical of all methods developed to date.
130
-------
1.0
0.8
0.6
0.4
0.2
Artificial ditch waste (Nov. 1972)
0.1% H2S04 added.
2800 CU
pH 2.2
12 BV/hr down-flow
1" x 24" column
Date: November 1972
20
40
Bed
60
volumes
80
100
FIGURE
60. FOURTH RUN OF COLOR SORPTION FROM RAW
UITCH WASTE BY XAD-8.
Although little attempt was made to optimize the regeneration conditions
shown in Figure 70, a few runs proved concentrated bases such as white
liquor and 1 N NaOH were not as good as weak wash. Attempts to regen-
erate at high flow rates were unsuccessful. If no improvement in
these low flow rates can be made, the amount of resin required to
treat the bleach waste of the Hoerner Waldorf Mill would have to be
large.
Carbon. Sorption of color by carbon as shown in Figure 71 was far
superior to the results obtained for carbon in any of the previous
experiments. Previously, virgin resins were always competitive with
or superior to carbon for the sorption of color.
131
-------
400,000
300,000-
15200,000
'o
o
100,000-
XAD-8 regeneration
Weakwash 1 BV/hr upflow
1" x 24" column
Date: November 1972
Ditch waste rinse
1234
Bed volumes
FIGURE 70. REGENERATION OF XAD-8 WITH WEAK WASH
l.U
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
o
i i i i
Filtrasorb 400
Art ditch, 300 CU
20 BV/hr
-
-
r *~
f -J
TOC
_ r- _ J
1
1 1 J 1
i .1
-
_
Color
i
0 100 200 300 400 50
Bed volumes
FIGURE 71. COLOR AND TOC BREAKTHROUGH IN ViRGKi FILTRASORB 400 CARBON
132
-------
DESALINATION
The first run on both cation and anion resins in both exhaustion and
regeneration were carried far beyond initial breakthroughs to help
assess a satisfactory breakthrough limitation for subsequent cyclic
runs.
Virgin Resins
Cation exchange. Breakthrough histories for cations and for the para-
meters pH, TOG, and specific conductivity are shown in Figure 72 for
the first run of a series. There was no effect on color, so color is
not shown. As would be expected, sodium is the first ion to break
through, and a corresponding sharp decrease of specific conductivity
heralds this event. Specific conductivity is an easy parameter to
monitor for the control of this kind of ion exchange. At this level
of regeneration (11.4 Ib HCl/cu ft resin) about 60 BV of feed pass
through the column before breakthrough. About 140 BV of feed pass
through the column before calcium begins to appear. The relative
amounts of sodium and calcium in the effluent can be controlled by
altering the end point.
Breakthrough curves for regeneration (with 5 BV of 0.915 N HLSO.) of
resin exhausted only to 35 percent breakthrough of Na are shown in
Figure 73. The large surplus of H ions as compared to Na plus Ca
ions show that the regeneration efficiency is low approximately 22
percent. The regeneration efficiency can be increased in a number of
ways: (1) by using less regenerant (starvation regeneration), (2) by
the addition of a weak acid resin to the column which makes a "Duo-Cat"
column, and (3) by use of a more sophisticated ion exchange system such
as: 2-stage cation-anion-cation-anion columns, a Progressive Mode
system, or by continuous countercurrent ion exchange such as the Graver
133
-------
"O
c;
O
o
CL'
r>
4
F 9
Q
CL
20
16
- E 12
- * 8
^Dr-^Q^
I
I
1 e
7^
J D a) 1 ^*- *~
«
> tft\
S '
/ i
ii
i
ii
r . J*
\
,, ^ Total cations
\ ?H
» ^ ~
\
V Na
Bed: C-25D, 1" X 24'' TOC
Downvlovv (?
--eed: Art
pH 7
Spec
Na
Ca
*-0 0 C
1 , .
! \
.V \ ^f
r,' A I ~-
20 BV/hr
ditch @ 300 CU
.55, TOC 76 ma/1
Cond 1750
13.2 -,ie/l
5.9 ^e/1 Ca , ,
1 f , _ ' M C \^ JL. \J 1 1 '^i ^-^
1 ""I" "^^^^f^^f ~~^~ ^^^ Q^MbA ^_M "^J
y
^
i
100
200
300
Bed volumes
FIGURE 72. EXHAUSTION BREAKTHROUGH CURVES OF IONS AND PARAMETERS OF PER--
FORdANCE IN CATION EXCHANGE
\^ 5 BV 0.915 N H2S04_
-- 1440 Tie H
Upflow @ 20 BV/hr -
456
Bed volumes
FIGURE 73. REGENERATION BREAKTHROUGH CURVES IN CATION EXCHANGE
134
-------
CCIX system or the Chem-Seps continuous countercurrent ion exchange
system.
The feed for the first cation run was artificial ditch waste pretreated
by massive lime precipitation and two-stage recarbonation to a pH of
7.6. The concentration of ions are shown in Table 22.
Anion exchange. Analysis of the feed to the anion column, the decarbon-
ated cation effluent, is shown in Table 23. Discrepencies between
analyses of cation and anion feeds are the result of treatment of
different batches of bleach plant waste. Treatment by massive lime
precipitation results in a fluctuation of ionic concentrations. These
fluctuations are likely to be typical of those that would be experienced
in the operation of a prototype and hence no attempt has been made
to reduce the normal fluctuations.
Figure 74 shows the complete breakthrough curve for the chloride ion.
No other anions appeared in more than trace quantities in the effluent.
The run was halted at this point because the other ions were present
in such small amounts that equilibrium of effluent with feed would
require inordinate volumes of liquor. Effluent color never reached
40 percent of the influent color. The control of the anion exchange
column could be achieved by monitoring conductivity, instantaneous
pH, or the pH of the total mixed effluent. As the pH of process streams
is important, control of the column by monitoring the pH of the mixed
effluent is probably the most desirable means.
For the study of regeneration, it was desirable to begin with a resin
partially exhausted to approximate the condition to be found in cyclic
operation. Consequently, columns of Duolite A-6 resin were exhausted
to a chloride breakthrough of approximately 35 percent or 4.5 me/1.
This corresponds to a throughput of 80 to 90 BV and a mixed liquor
pH of approximately 6.8. Such a mixed liquor pH is somewhat too low
135
-------
Cation
TABLE 22
TYPICAL CONCENTRATION OF IONS IN CATION FEED
Concentration
me/1
An ion
Concentration
me/1
K
Na
Ca
Mg
Sum
Run #2
tr
18.0
6.6
tr
24.6
Run #3
tr
13.2
5.9
tr
19.1
HC03
Cl
NO,.
3
so4
S
Run #2
5.3
17.2
tr
0.6
tr
23.1
Run #3
4.3
12.9
tr
1.4
tr
18.6
TABLE 23
TYPICAL CONCENTRATION OF IONS IN ANION FEED
Effluent from 2-inch column
Cation
H
Na
Ca
Mg
Concentration
me/1
9.9
3.1
0.0
0.0
13.0
Error
Anion
H0COQ
2 3
Cl
N03
so4
S
= 3.0%
Concentration
me/1
0.1
13.2
tr
0.1
tr
13.4
pH = 2.0
136
-------
ro
i
olO
,(
^ 9
o
I 8
o
o
o
Q)
c/o
FIGURL 74.
lied: A-6, 1" X 24"
'Jo 'if! oi<, @ 20 BV/hr
7eed: Cation effluent (3 300
Cl
Spec. Cond.
Color
pH of stored
effluent.
PH
50
100
Bed volumes
700
EXHAUSTION BREAKTHROUGH CURVES OF CHLORIDE ION AND PARAMETERS
OF PERFORMANCE Iu ANION EXCHANGE
for process water in the plant, but examination of Figure 74 shows the
pH of the mixed liquor to be changing very rapidly with small changes
of throughput volume. In a prototype, it would be easy to produce any
desired pH of the mixed effluent.
Lime slurry regeneration. Attempts to regenerate Duolite A-6 resin with
4 percent lime slurry were only partially successful. In one set
of experiments, the resin was removed from the column and stirred by
air for 10 minutes in one liter of a 4 percent lime slurry. The lime
slurry was then drained and replaced for a second treatment. This
was repeated five times as shown in Figure 75. Most of the color
and the chloride ion were removed in the first treatment, but elution
of chloride continued in succeeding treatments.
137
-------
o. u
2.5
o2.0
(_;
i." 1.5
o
o
o
1.0
0.5
n
- OUU
- 250
- ^200
o>
E
QJ - i- /-\
- -o 150
o
- 5100
50
n
_ i
-
-
-
-
i i i
500 )nl 1.164 N1 (4%) Ca(OH)?
per exposure - 582 ^e
-
-
-
C1
Color | i,ni ,r- !_
0
1
23
10 minute exposures
FIGURE 75. SEPJAL BATCH RE3ENERATION Or DUOLITE A-6 ?E3IN MITH 4% LIf'E
SLURRY AND AIR MIXING
iUU
O
"" 90
X
^ 80
OJ
70
a>
TJ
L60
j .
5 50
TD
« 40
o
0
o 30
f
o 20
o
0 10
f
III 1 1 1 1 1 1
_
5 BV 0.676 N Ca(OH)?
= 1065 ne ^
Upflow @ 20 BV/hr
_
-
-
-
j i
j ol G vo 1 ume
r»
/ V1
/ \
/
/ \
'«o> *^^
// \ Color ^-^.^
j|( iV^_|-n ^ oi~~~~~~* T * ^
0
1
8
10
3456
Bed volumes
FIGURE 76. COLUMN REGENERATION OF DUOLITE A-6 RESIN WITH LIME SLURRY
138
-------
The regeneration efficiency for the first treatment was 48 percent, where
regeneration efficiency is defined as "milliequivalents anions eluted
divided by milliequivalents of regenerant used." The efficiency of
regeneration for the first two treatments was 28 percent.
Regeneration of the resin within the column by upward flow of 4 percent
lime slurry at the rate of 20 BV/hr is shown in Figure 76. Using five
BV of 4 percent lime slurry, the regeneration efficiency was 15 percent.
The removal of color was somewhat better than the removal of chloride
ion.
Ammonia regeneration. The elution of color and chloride during column
regeneration of Duolite A-6 resin with ammonia is shown in Figure 77.
Five BV of 4 percent ammonia (1710 me) was used at an upflow rate of
20 BV/hr. The regeneration efficiency was 12 percent. It is obvious
the regeneration would have been nearly as complete with much less
ammonia. Hence, it can be expected that regeneration efficiencies
with ammonia could be vastly improved.
Caustic regeneration. Column regeneration with caustic (1 N NaOH) is
shown in Figure 78. Five BV of 1 N NaOH was used at an upflow rate of
20 BV/hr. The overall regeneration efficiency was 19 percent.
Cyclic Runs
Sulfuric acid regeneration. Regeneration of Duolite C-25D resin with
1 N H-SO, gave rise to problems with calcium sulfate precipitation.
Decreasing the concentration to 3 percent H-SO, (0.6 N) eliminated
the problem with calcium sulfate.
The quantity of acid for optimum regeneration is shown in Figures 79
and 80. On the basis of these figures, 1.3 BV of 3 percent H SO, was
chosen as the optimum volume. Superficial efficiency of regeneration
is calculated as
139
-------
100
90
80
70
o°60
o
^ 50
I 40
30
20
10
0
5 BV 1.086 M N
= 1710 tne
Upflow (a 20 BV/hr
456
Bed volumes
FIGURE 77. COLUMN REGENERATION OF DUOLITE A-6 ?£SI.'-: /IITH ^"MO
100 r- 1000,
To 120
Void volume
Color
Cl
T
T
T T
5 BV 0.955 N a^H
= 1503 ne
Upflow @ 20 BV/h -
1
i
8
Bed volumes
FIGURE 78. I.U-J1N REGENERATION OF DUGLITE A-6 RESIf! ;ITH CAUSTIC
10
140
-------
100
80
60
c
-------
,. . n ,-,-.. (me H in)-(me H out) me cations eluted
Superficial efficiency = -7 TT .- :* = -.
v (me H in) me H in
..... . me cations sorbed from net product water
True efficiency = ;
J me H in
Net product water is the total throughput minus the rinse and minus
the acid dilution water.
Regeneration efficiency at 1.3 BV of 3 percent H«SO, was close to 71
percent. Restated, regeneration was 141 percent of stoichiometry.
Although this is excellent efficiency for a strong acid resin, the
efficiency can be improved in a number of ways as previously explained.
Economy of regeneration in a prototype reactor is complicated by many
factors. As Figure 80 shows, an increase in the volume of acid reduces
the efficiency slightly. On the other hand, it increases the quantity
of useable product water. For any given size and configuration of
reactor, there will be an optimum which depends not only upon these
relationships but also upon the capital expenditure for the equipment,
the interest rate, cost of chemicals, and sometimes practical considera-
tions such as convenience in operation.
Caustic regeneration. The optimum amount of caustic regeneration for
Duolite A-6 resin was obtained from Figures 81 and 82. The equation
for the efficiency of regeneration for anion resin is the same as
given for cation resin where "OH" is substituted for "H" and "anion"
for "cation." The optimum bed volumes of 3 percent NaOH was also
close to 1.3 BV, and for simplicity in operating both anion and cation
columns, the flow rates, concentrations, volumes of regenerant, and
volumes of rinse were chosen to be the same for both anion and cation
resins.
142
-------
1.0
0.8
^0.6
o
c
(U
o
£0.4
LU
0.2
Based on utilization of OH
Based on anions eluted
2 3
Ib caustic/cu ft resin
FIGURE 81. REGENERATION EFFICIENCY. A-6 RESIN
100
80
E
OJ
OJ
O)
OJ
CQ
60
40
20
E
True efficiency
Total effluent
0.5
Usable product water
1.5
FIGURE 82.
1.0
Bed volumes 3% NaOH
TRUE EFFICIENCY AND PRODUCT WATER. A-6 RESIN
2.0
143
-------
The efficiency of 1.3 BV of 3 percent NaOH was approximately 84 percent.
Restated, regeneration was 119 percent of stoichiometry.
Cation exchange. The product volume of the cation exchange column
decreased during the first three cycles as shown in Figure 83 and
then remained constant at 33 BV at 35 percent Na breakthrough. Because
Figure 84 shows the superficial efficiency of regeneration was uniformly
77 percent, it is apparent some cations were irreversibly (at this
regeneration level) sorbed during the first three cycles.
Ariion exchange. Figure 85 shows the production volume in anion exchange
remained constant at 55 BV per cycle at 35 percent chloride breakthrough.
As shown by Figure 86, the superficial regeneration efficiency remained
reasonably steady at about 84 percent.
High temperature operation. A series of runs at the temperature of the
caustic extract in the caustic seal tank at the Hoerner Waldorf Mill
resulted in a significant impairment in product volume and a slight
decrease in regeneration efficiency as shown in Figures 87 and 88
respectively. Hence, for these resins at least, there would be a
disadvantage in ion exchange of hot liquor as compared with cold liquor.
As with cation exchange, elevated temperatures did not improve the per-
formance of the anion exchanger. Figure 89 shows the production
volume increased somewhat but was more erratic. The efficiency
decreased as shown in Figure 90. Hence, there was an increase in
leakage.
Two-Stage Color Removal
Color leakage through the cation-anion pair of columns averaged 80 CU,
a concentration too great for many uses in the mill. The object of a
144
-------
100
80
en
3
o
S-
1 60
s~
_o
s-s
un
00
CQ
40
20
Art ditch, 300 CU , pH
20 BV/hr downflow
Regenerant 1.3 BV 3% H
@ 16 BV/hr upflow
Room temperature
7.6
°0 2 4 6
Number of cycles
FIGURE 83. PRODUCT VOLUME IN CYCLIC CATION EXCHANGE.
10
C-25D RESIN
100
80
^ 60
o
c:
O)
40
20
0
Art ditch, 300 CU , pH 7.6
20 BV/hr downflow
Regenerant 1.3 BV
@ 16 BV/hr upflow
Room temperature
3%
I
1
I
0
8
FIGURE 84.
246
Number of cycles
SUPERFICIAL EFFICIENCY IN CYCLIC CATION EXCHANGE.
10
C-25D RESIN
145
-------
100
-§,80
^
o
"I 60
C_3
oo
o
CQ
20
0
A-6 exhausted w/cation
effluent 20 BV/hr downflow
Regenerant: 1.3 BV 35K NaOH
@ 16 BV/hr upflow
Room temperature
0
FIGURE 85.
100
2 4 6 8 10
Number of cycles
PRODUCT VOLUME IN CYCLIC ANION EXCHANGE. A-6 RESIN
80
I 60
c
(O
cu
L)
40
20
A-6 exhausted w/cation
effluent 20 BV/hr downflow
Regenerant: 1.3 BV 3% NaOH
@ 16 BV/hr upflow
Room temperature
8
10
246
Number of cycles
FIGURE 86. SUPERFICIAL EFFICIENCY IN CYCLIC ANION EXCHANGE. A-6 RESIN
146
-------
100
₯ 80
o
-Q
60
(13
40
o
-M
CQ
20
0
Art ditch, 300 CU, pH 7.6
20 BV/hr downflow
Regenerant 1.3 BV 3% H2S0
(? 16 SV/hr upflow
ex,
-o-
t
J0 2 4 6 8 10
Number of cycles
FIGURE 87. PRODUCT VOLUME AT 60°C IN CYCLIC CATION EXCHANGE. C-250 RESIN
o
c
O)
o
100
80
60-
40
20
0
Art ditch, 300 CU, pH 7.6
20 BV/hr downflow
Regenerant 1.3 BV 3% H2SO/
@ 16 SV/hr upflow
8
10
246
Number of cycles
FIGURE 88. SUPERFICIAL EFFICIENCY AT 60°C IN CYCLIC CATION EXCHANGE. C-25D RESIN
147
-------
TOO
CD
80
O
s_
£60
CQ
20
0
0
A-6 exhausted w/cation
effluent 20 BV/hr downflow
Regenerant: 1.3 BV 3% NaOH
@ 16 BV/hr upflow
8
246
Number of cycles
FIGURE 89. PRODUCT VOLUME AT 60°C IN CYCLIC ANION EXCHANGE
10
A-6 RESIN
100
80
o
o
c
60
40
20
0
A-6 exhausted w/cation
effluent 20 BV/hr downflow
Regenerant: 1.3 BV 3% NaOH
@ 16 BV/hr upflow
024 6 8 10
Number of cycles
FIGURE 90. SUPERFICIAL EFFICIENCY AT 60°C IN CYCLIC ANION EXCHANGE. A-6 RESIN
148
-------
second stage of treatment was to find some way to reduce the color to
acceptable levels 8 to 10 CU.
The feed for second stage treatment was the mixed effluent from the
anion column operated to a breakthrough of 35 percent of the chloride
ion which resulted in a mixed liquor pH of about 6.8. In one run, the
feed was acidified to a pH of 2.4 and in another run the feed was pre-
treated by putting it through a second cation resin column which reduced
the pH to 2.15, so essentially this run was two-stage ion exchange.
The conditions for seven of the eight runs are given in Table 24, and
the breakthrough curves are shown in Figure 91.
A second column of used regenerated 16 x 50 mesh Duolite A-6 resin was
ineffective, but fine (40 x 80 mesh) virgin A-6 was very effective.
All other sorbents including Duolite A-7 and S-30 resins and even two
carbons were only moderately effective. However, second stage desalina-
tion was very effective indeed. Neither color nor anion breakthrough
occurred in 250 bed volumes. The success of two-stage desalination
suggests a modification of the Progressive Mode system to permit two-
stage desalination would produce very high quality water at regeneration
efficiencies approaching 90 percent.
LIFE TESTS
Exchange Capacity
The exchange capacity of the resins is the most significant single
test, and the results are given in Table 25. Four of the resins tested
were received after the tests had begun and consequently there were
essentially two time schedules.
In general, strong base resins i-cirformed poorly. None withstood 100
cycles. The performance of the strong acid resins was only a little
149
-------
A-6, _pH 2.4 / /-A-6, 40x80
S-30
Filt 400
Carbo-Dur
A-6, 16x50
decat to pH 2.15
100 150
Bed volumes
200
250
FIGURE 91. SECOND STAGE COLOR CONCENTRATION HISTORIES
TABLE 24
TWO-STAGE COLOR REMOVAL
Feed: Artificial ditch at 300 CU desalinized to pH 6.8 and 80 CU
Additional Treatment
of Feed
None
None
None
None
None
Acidify to pH 2.4
Decat ionize to pH 2.15
Sorbent
A-6
A-7
S-30
Filt 400
CarboDur
A-6
A-6
Mesh
40 x 80
100 x 200
14 x 50
12 x 40
20 x 50
16 x 50
16 x 50
Throughput ,
BV
120
100
140
160
140
100
250+
Average
Color,
CU
9
41
61
41
36
28
8
150
-------
co
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151
-------
better than the performance of the strong base resins. This is a
serious matter. Unless a way can be found to improve the life of the
strong electrolyte resins, they cannot be used. Perhaps the strong
electrolyte resins could be protected by preceeding them with weak
electrolyte resins or sorbent resins, but there was no time to try such
measures in this project.
The weak acid resins performed very well indeed. Neither IRC-84 nor
IRC-50 lost appreciable capacity in more than 300 cycles.
Weak base resins generally performed well. But all had lost approxi-
mately half their capacity at the end of 405 cycles. The best were
Duolite A-6 and A-7. Of the sorbent resins, S-37 was slightly superior
to both Duolite A-6 and A-7. Because the procedures used for deter-
mining exchange capacity was a simplified and more rapid method of
determination than the methods recommended in manufacturer's manuals,
it is not likely that the tests are accurate to the nearest 0.1 me/ml.
Physical Characteristics
The damp weights and the minimum tamped volumes are given in Table 26.
These characteristics have sometimes been used as indicators of the
stability of resins. Excessive gain of moisture or excessive swelling
is supposed to indicate lack of stability. But the results of Table
26 do not seem to confirm those suppositions, because resins with large
changes in physical characteristics appear to retain their exchange
capacities better than some other resins. The tests themselves are
subjective and by their very nature liable to produce relatively large
errors.
The physical appearance of resins at the beginning and end of the
tests are given in Table 27. These tests are significant in showing
irreversible sorption of color on the resin beads, but, more important,
152
-------
TABLE 26
PHYSICAL CHARACTERISTICS OF RESINS
Strong acid
C-25D
Amb 200
HCR-W
IR-120+
Weak acid
IRC-84
IRC -50
Strong base
Dow 11
IRA-402
Weak base
A-6
A- 7
IRA-68
IRA-93
Sorbent
S-37
S-30
ES-33
XAD-8
Damp
Virgin
21.8
22.3
22.6
22.7
21.9
19.1
20.0
18.8
18.8
19.0
19.8
18.4
19.0
17.7
18.0
22.0
weight, g
Terminated
20.0
17.6
21.8
22.7
20.0
17.8
21.2
19.8
20.1
23.6
21.7
18.7
22.8
20.0
19,8
18.1
Minimum
Virgin
27.4
26.8
27.8
28.0
27.4
26.8
27.6
28.6
27.4
27.2
29.0
26.2
27.2
27.0
27.0
29.0
Tamped vol, ml
Terminated
26.6
26.0
27.2
28.2
33.0
25.2
28.8
27.6
28.2
35.6
30.0
26.2
34.0
31.2
31.0
26.0
153
-------
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li-ij-i 33 4JO 4Jj-i tfl 3
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154
-------
the physical stamina of the resins. The reported number of cracked
or broken beads is not precise but nevertheless accurate enough to
furnish insight into the physical strength and durability of the beads.
Summary
On the basis of the limited number of cyclic tests, it would appear:
(1) Weak electrolyte resins are much superior to strong electrolyte
resins.
(2) Gel type strong acid resins are somewhat superior to porous strong
acid resins.
(3) IRC-50 is superior to IRC-84.
(4) Duolite A-6 and A-7 are the best of the weak base resins.
(5) Duolite S-37 sorbent resin is slightly superior to Duolite A-6
and A-7 weak base resins.
(6) XAD-8 appears to be essentially unaffected.
155
-------
SECTION VIII
ECONOMICS
Refinements in estimating costs of sorption of color and desalination
by ion exchange are premature for several reasons. The operation of
the ion exchange columns was not completely optimized. Furthermore,
it seems likely that one of the more advanced ion exchange processes
(such as Progressive Mode or continuous counter-current ion exchange)
will be more economical than a simple cation-anion system. And a
refined cost estimate should be based on experience with a large pilot
plant operated for many months at a kraft mill. Life tests showed
serious deterioration of all but one of the resins within little more
than a month of severe operation, and as this was discovered at the
end of the program, there has been no opportunity to study means of
prolonging the resin life. Uncertainty concerning resin life makes
the accurate prediction of costs impossible.
Several items of costs are omitted from the estimates. The disposal of
the highly colored regenerant waste depends upon local circumstances.
Unless the regenerant waste can be stripped of unwanted ions for reuse
in the mill, it must be sewered, lagooned, pumped into deep wells or
discarded in some other innocuous way. A truly acceptable means for
the disposal of these wastes has not been found. The cost for modify-
ing the process piping in an existing mill to accomodate an ion
exchange plant and the added cost for extra piping in a new mill would
depend upon the specific circumstances and is also omitted.
Ion exchange is a well-established process with a long history of suc-
cessful commercial use. In spite of the seeming complexity of the
equipment, ion exchange plants are reliable and can operate fully
automatically with only about an hour of preventative maintenance and
attention per day. In general, the life of the equipment may exceed
157
-------
15 years. However, an amortization period of 10 years at an interest
rate of 9 percent is assumed herein.
DESALINATION AND COLOR REMOVAL FOR REUSE
Water Quality
The ranges in the desired properties of process water for reuse in kraft
manufacture as given by Thibodeaux and Berger (1967) are reproduced in
Table 28. The typical improvement to be expected in water quality
obtained by ion exchange after massive lime precipitation is given in
Table 29, but it should be emphasized that the figures are only typical
and not absolute. The cation column was operated to a 35 percent break-
through of the sodium ion which gave a high average leakage of 13 per-
cent. In practice it might be desirable to operate to a higher leakage
for greater efficiency or a lower leakage for improved quality. Further-
more, leakage is a complex function of several factors including
regeneration level, relative concentration of ions, flow rates, rinse
volume, countercurrent versus concurrent regeneration, and the design
and operation of the reactor vessel. In general, leakage for the most
economical operation of a simple cation-anion pair of reactors lies
between about 8 and 20 percent for high solids feed. A second stage
cation-anion pair could easily reduce the TDS to 20 mg/1 and reduce
the chloride to 10 mg/1.
The leakage from the first pair of reactors can be reduced in a number
of ways. One means is to stop the run at a lesser throughput, although
at some reduction of efficiency. Another is to add a layer of weak
acid resin on top of the strong acid resin which transforms the simple
cation reactor into a Duo-cat reactor described by Abrams and Poll
(1967). The added cost consists only of the cost of the extra resin
and a somewhat deeper reactor. Weak acid resin is lighter than strong
acid resin and rises to the top during backwashing. The regenerating
158
-------
TABLE 28
RANGES OF DESIRED PROPERTIES OF PROCESS WATER
FOR KRAFT MANUFACTURE
Constituent
Turbidity, mg/1
Color, CU
pH
Total alkalinity, mg/1 CaCO
Hardness, mg/1 CaCO,.
Dissolved solids, mg/1
Chloride, mg/1
Iron, mg/1
Manganese, mg/1
Chemical oxygen demand, mg/1
Biochemical oxygen demand, mg/1
Unbleached
5-25
10-80
6.5-8.0
20-150
5-200
50-500
10-150
0.5
0.3
0-12
0-5
Bleached
0-5
0-5
6.8-7.3
20-75
5-100
50-250
10-150
0.2
0.1
0-8
0-2
TABLE 29
TYPICAL WATER QUALITY IMPROVEMENT BY ION EXCHANGE
Constituent
Typical Concentration After:
Massive Lime First Stage Approx
Precip, Ion Exchange, Leakage,
me/1 me/1 %
Second Stage
Ion Exchange
Na+K
Ca
Mg
HC03
Cl
N03
so4
S
Cations,
Total Anions
Total Mineral
Acidity
TDS
Color
18.0-13.0
7.8-5.9
tr
5.3-4.3
17.2-12.9
tr
0.1-2.2
tr
24.6-19.1
23.1-18.6
18.5-13.4
1509-1209 mg/1
300 CU
3.1
0
0
0.1
2.4
0
0
0
3.1
2.8
2.8
162 mg/1
80 CU
20
0
0
2
16
0
0
0
14
15
17
12 mg/1
27 CU 8 CU
159
-------
acid must flow upward to contact the strong acid resin first. The
weak acid resin is regenerated at nearly 100 percent efficiency even
though the regenerant is both weak and contaminated. In the succeeding
service cycle the weak acid resin removes cations up to the equivalence
of the alkalinity. In bleach plant waste, alkalinity comprises 20 per-
cent of the anions so the use of a Duo-cat reactor is feasible. Sanks
(1968) found an overall efficiency of 72 percent in a cation reactor
could be increased to 92 percent by the addition of 26 percent of
weak acid resin. The leakage, originally 30 percent, was decreased to
16 percent. Another way to improve performance is to use a continuous,
countercurrent ion exchange system (or an approximation, such as
Progressive Mode) in which leakage is low and efficiency is typically
90 percent.
The raw waste quality varies considerably and the TDS after massive
lime precipitation has varied from about 1100 to 1800. Some variation
in quality of finished water can also be expected if the ion exchangers
are operated on the basis of a preset time or volumetric basis. The
reactors can, however, be operated on the basis of the quality of
effluent to provide a nearly uniform product.
In summary, single stage operation can produce water adequate in quality
for the manufacture of unbleached pulp. Water adequate in quality for
bleached pulp manufacture can be produced by two-stage ion exchange
and probably by single stage continuous counter-current ion exchange
or by Progressive Mode. Decolorization to very low levels requires low
pH, low leakage, and deep anion beds.
Estimated Cost for Single Stage Ion Exchange
The size of the reactors are based on the operating conditions given
in Table 30. These in turn are based on the bench scale pilot plant
160
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TABLE 30
OPERATING CONDITIONS FOR ION EXCHANGE
Item Value
Cation Exchange
Feed flow rate, BV/hr (ditch waste after
massive lime precipitation) 20
Feed to breakthrough, BV of 19.1 me/1 feed 33
Regenerant and rinse flow rate, BV/hr 16
Regenerant (3% H2SO.) volume, BV 1.30
Regenerant level, ID H~SO,/cu ft resin-cycle 2.43
Rinse volume, BV 3.00
Efficiency (me ions removed/me acid), % 75 (71-78)
Cycle time:
Service, hrs 1.65
Backwash (every 6th cycle) per cycle, hrs 0.04
Regeneration, hrs 0.08
Rinse, hrs 0.19
Downtime (maintenance, repairs at 5%), hrs 0.10
Total cycle time, hrs 2.06
Cycles per day 11.65
Service volume per cu ft resin, gpd 2880
Total resin required, cu ft 1700
Water required for rinse and acid dilution, gpd 634,000
Acid required for 4,882,000 gpd, tons as R SO,/day 24.0
Anion Exchange
Feed flow rate, BV/hr 20
Feed to breakthrough, BV of 18.5 me/1 Cl in feed 54
Regenerant and rinse flow rate, BV/hr 16
Regenerant (3% NaOH) volume, BV 1.30
Regenerant level, Ib NaOH/cu ft resin-cycle 2.51
Rinse volume, BV 3.00
Efficiency (me ions removed/me base), % 85 (81-88)
Cycle time:
Service, hrs 2.70
Backwash (every 6th cycle), hrs 0.04
Regeneration, hrs 0.08
Rinse, hrs 0.19
Downtime, hrs at 5% 0.15
Total cycle time, hrs 3.16
Cycles per day 7.59
Service volume per cu ft resin, gpd 3070
Total resin required, cu ft 1600
Water required for rinse and base dilution, gpd 390,000
Net product water, 4,882,000-634,000-390,000, gpd 3,858,000
Base required for 4,882,000 gpd, tons as NaOH 15.2
161
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operations used in the laboratory. More extensive pilot plant experi-
ment would result in obtaining more efficient operating conditions.
The capital equipment costs in Table 31 are based on the following
conditions. Reactors are epoxy-lined mild steel equipped with multi-
port 304 stainless steel valves. Inlet and regeneration distributors
are also of 304 stainless steel. Alkalinity is removed more cheaply
by degasification than by ion exchange. Furthermore, weak base resins
do not remove bicarbonate well. At times the feed water alkalinity
has been as much as 350 mg/1 as CaCO_. To reduce this to 10 mg/1 at
140°F requires 46 trays in a 12 ft x 12 ft x 16 ft high countercurrent
uegasification tower.
Regenerant storage, product storage, and process piping are omitted
from tne estimated capital cost of the ion exchange plant in Table 31.
Regenerant might be stored in tank cars because, for such large amounts,
there would be little or no demurrage. The requirements of product
storage depend on the fluctuations of water use. Without fluctuations,
there is no need for storage, and since unbleached pulp at the Hoerner
Waldorf plant is made in a continuous Kamyr digester, little product
storage is required. Some mills operating with batch digesters might
require several hours of product storage. The cost of process piping
depends upon the location of the ion exchange plant relative to the
rest of the plant and an allowance for connecting the ion exchangers
to the rest of the plant and is impractical to estimate. Furthermore,
it would be entirely different for each mill, so an estimate would be
merely speculative.
The costs of chemicals in Table 32 were taken from Tables 3 and 4.
They are actual costs for chemicals delivered at the Hoerner Waldorf
Mill, Frenchtown, Montana in April 1973. The cost for labor in Table
32 is uncertain. Ion exchange plants can operate at a minimum of
labor despite the seeming complexity of the equipment. The charges
162
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TABLE 31
ESTIMATED CAPITAL COST OF FIXED BED CATION-ANION EXCHANGERS
Item Cost
Cation exchange: 8 reactors
10 ft ID x 7 ft reactors with multiport valve control
1700 cu ft resin
4 inch automatic reset meters
Inlet regeneration distributors, 304 SS
100 psi code vessels
Automatic unit controls
2 sets if 4-unit system controls
Pipe and valves
2 sets H SO, regeneration systems
Skid mounted, piped, wired
Manufacturers engineering
Subtotal cation exchangers 310,440
Degasifier: Forced draft, fiberglass
For reducing 350 mg/1 alkalinity as
CaCO to 10 mg/1 at 140°F
12 ft x 12 ft x 16 ft high with 46 trays 24,000
Clearwell, buried 100,000 gal, neoprene lining 18,000
Supports and piping 8,000
Subtotal degasifier 50,000
Anion exchange: 8 reactors
10 ft ID x 7 ft reactors with multiport valve control
100 psi.,code vessels
1600 ft resin
8 conductivity meters
Inlet and regenerant distributors, 304SS
Automatic unit controls
2 sets 4-unit system controls
Interconnecting piping and valves
2 sets NaOH regeneration systems
Skid-mounted, piped, and wired
Manufacturers engineering
Subtotal anion equipment 365,560
Building and foundations, 162 x 48 at $18/sq ft 84,480
Feed pump, rubber covered, 4 @ 1700 gpm and 20 hp motors 18,000
Total equipment cost 829,280
Engineering at 10% total equipment cost 82,928
Erection and hook-up at 10% total equipment cost 82,928
Contractor's profit and overhead at 12% equipment + erection 109,465
Freight: cation, anion, degasifier 43,000
Start up 5,OOP
Total capital cost excluding storage and process piping
to ion exchangers 1,152,601
Capital cost per gallon of product (3,858,000 gal)/day 0.30
163
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for amortization may or may not be realistic. Amortization periods
in industry rarely exceed 7 years and interest rates are often more
than 9 percent. On the other hand, the equipment life is probably
in excess of 15 years. But combining life and amortization periods
into one value, 10 years, is not far amiss and avoids complex cost
analyses.
The operational costs shown in Table 32 and in the first line of Table
33, are based on a resin life of 12 months and if the aggressiveness
of the wastewaters can be reduced to permit resins to last a year,
the costs shown are reasonable. Abrams (1973) stated there are several
ways to reduce the attack on resins including: treatment of feed with
sulfur dioxide or (occasionally) with sodium hydrosulfite, cold tempera-
ture, and use of weak regenerants. Pretreatment by Amberlite XAD-8
can give colorless feeds, but its effect on aggressiveness is quite
unknown. If the life of the resin cannot be prolonged, the resins
must be replaced every 2 months, and the costs would be increased to
$1.38/1000 gallons as shown in line 2 of Table 33.
The water required for dilution of regenerants and for rinsing and
backwash need not, necessarily, be product water. For this economic
analysis, it was assumed regenerant dilution water and rinse water was
product water and backwash water was feed that could be reused in the
process. The quantities used are given in Table 30. The most economi-
cal operating conditions require considerably more investigation.
Acid and base dilution water cannot be reduced greatly, but 3 BV of
rinse is much more than is required. In previous work with waters
containing higher TDS than bleach plant effluent Sanks and Kaufman (1965)
found rinse volumes of 1.3 BV to be adequate and this lower rinse
requirement would reduce costs to $1.24/1000 gallons as shown by line
3 of Table 33.
164
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TABLE 32
OPERATING COSTS FOR SINGLE STAGE ION EXCHANGE
Item
Cost $/Day
Electric power at lc/kw hr
Sulfuric acid, 24 tons H?SO, at $25.37/ton,
75% efficiency
Caustic, 15.2 tons NaOH at $67.45/ton as 50% Na 0,
85% efficiency
Maintenance at 0.0075% equipment cost
Taxes and insurance at 0.006% capital cost
Cation exchanger, 100% replacement/year
Anion exchanger, 100% replacement/year
Operating labor
1 hr supervision/day at $7.50/hr 7.50
4 hrs labor/day at $6.00/hr 24.00
Benefits at 15% 4.73
Overhead at 50% 18.12
Contract 16 hrs/month inscrument service
at $20.00/hr 10.52
Subtotal 2807.58
Amortization, 10 yrs at 9% interest
Total
Total cost, $/1000 gal net product (3,858,000 gpd)
Total cost, $ per ton bleached pulp (150 tons/day)
11.58
608.88
1589.52
62.20
69.16
116.44
284.93
2807.58
492.05
3299.63
0.86
22.00
TABLE 33
COST VERSUS OPERATING CONDITIONS OF SIMPLE ION EXCHANGE
Conditions
Cost,
Resin $/1000 gal
% Acid % Base Rinse, Product, Life, of net
Efficiency Base Efficiency BV % of Feed Months product
75
75
75
90
90
Caustic
Caustic
Caustic
Ammonia
Ammonia
85
85
85
85
85
3
3
1.3
1.3
1.3
79
79
87
87
87
12
2
2
12
36
0.86
1.38
1.24
0.48
0.42
165
-------
The cost of base is the largest item because caustic is very expensive.
Other possibilities for reducing the regenerant cost include: the
integration of spent regenerant into the mill process to eliminate
waste, the use of lime, and the use of ammonia with or without ammonia
recycle by recovery with lime. The integration of spent regenerants
with mill processes was not pursued in this investigation due to lack
of time and financial resources. Certain difficulties can be foreseen
such as the high concentration of chlorides and the separation of other
ions, but the rewards of success are so great that serious efforts
should be made to overcome these difficulties. Lime was not an effective
regenerant with Duolite A-6 resin as shown in Figure 76, but on the
other hand only limited efforts were made to optimize lime regeneration.
Odland and Pabich (1965) reported successful, low-cost regeneration
of strong base resins with lime in the Sul-biSul process but only when
the SO./C1 ratio was 9 or more. Low sulfate water, such as ditch waste,
is not suited to the Sul-biSul process according to Schmidt et al (1969).
Time ran out before cyclic runs could be made with ammonia as the
regenerant, so the sustained efficiency is unknown. In a single run,
however, regeneration with ammonia was 80 percent as effective as
regeneration with caustic as Figures 77 and 78 show. With optimization
ammonia regeneration efficiency could be increased to at least 85 per-
cent. At the delivered cost of $70/ton quoted by Whaley (1973) for
anhydrous ammonia, the cost of ammonia is 28 percent of the cost of
caustic on a pound-equivalent basis. Hence, the daily cost for anion
regeneration with ammonia would be about $452/day which would reduce
the demineralization cost to $0.48/1000 gallons assuming a 12-month
resin life and the regeneration efficiencies (shown in Table 33) pre-
viously determined by Sanks and Kaufman (1965) and by Sanks (1967).
The recovery of ammonia with lime is a well-known process, but it
would require careful investigation to determine whether such an
operation would be economical. If resin life can be increased to three
years, the cost of ion exchange would be reduced to $0.42/1000 gallons
166
-------
assuming: ammonia for base regenerant, Duo-cat cation columns, and
optimum operating conditions with respect to flow rate, regeneration
level, and rinse volume.
Estimated Cost for Progressive Mode System
Any of the continuous countercurrent ion exchange systems (Chem-Seps
or Graver and their approximations) possess the advantages of low
leakage combined with highly efficient regeneration. The Progressive
Mode system closely approximates continuous countercurrent ion exchange,
the efficiency is good, the leakage is low, and it possesses distinct
advantages in versatility. The operation can be changed in the field
and at will by altering the timer settings. It can even be operated
as a simple single stage cation-anion system. Its disadvantages are
the complexity of operation which requires an expert to adjust the timers
and the high head loss resulting from the high flow rates employed.
As neither disadvantage is serious, a comparison of Progressive Mode
with simple ion exchange is illuminating.
The capital equipment costs shown in Table 34 are based on the same
considerations as the capital equipment costs in Table 31. To protect
the Permutit Company, the costs of individual items are omitted in
favor of a total sum.
Because pilot plant experience and optimization are not available, the
operating costs of Progressive Mode ion exchange are somewhat uncertain.
However, acid and base regeneration efficiencies are higher than in
simple fixed-bed cation-anion pairs and on the basis of experience
with other installations it appears likely that regeneration efficiencies
of approximately 87 percent can be realized. Accordingly acid and base
quantities of 115 percent of cations and (except for alkalinity) anions
were used for the operating cost estimates in Table 35.
167
-------
TABLE 34
ESTIMATED CAPITAL COST OF A PROGRESSIVE MODE ION EXCHANGE SYSTEM
Item Cost, $
Cation reactors: 2 trains of 4 units
8 ft ID x 10 ft reactors with valve nest
1700 cu ft resin
8 sets inlet and regeneration distributors 304SS
100 psi code vessels
Automatic controls for 2 4-unit trains
Interconnecting piping and valves
2 - HLSO, regeneration systems
Skid mounted, piped, and wired
Manufacturer's engineering
Subtotal cation exchangers $ 310,440
Degasifier (See Table 30) 50,000
Anion reactors: 2 trains of 4 units
8 ft ID x 10 ft reactors with valve nest
100 psi code vessels
1600 cu ft resin
8 sets inlet and regeneration distributors 304SS
Automatic controls for 2 4-unit trains
Interconnecting piping and valves
2 - NaOH regeneration systems
Skid mounted, piped and wired
Manufacturer's engineering
Subtotal anion exchangers 365,560
Building and foundations 84,480
Feed pumps 23,000
Total equipment 833,480
Engineering at 10% 83,348
Erection and hook-up at 10% 83,348
Contractors profit and overhead at 12%
equipment and erection 110,019
Freight: cation, anion, degasifier 43,000
Start up 8,000
Total capital cost except for storage tanks, and
process piping to ion exchanger 1,161,195
Capital cost per gallon product(4,265,000 gal)/day, $ 0.27
168
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TABLE 35
OPERATING COSTS FOR PROGRESSIVE MODE ION EXCHANGE
Cost
Item $/day
Electric power at l
-------
COLOR REMOVAL
Color removal from kraft bleach wastes at the pH ranges encountered in
the Hoerner Waldorf Mill was not notably successful. At the low pH
(about 2.2) of decationized waters, color removal was successful when
combined with anion exchange. Because complete (or nearly complete)
color removal without desalination was not obtained, cost estimates for
color removal without desalination are not warranted at the present
stage of development.
The Rohm and Haas Company (1973) reported 78 percent reduction in color
from a bleach plant waste stream consisting of equal parts of caustic
extraction liquor and chlorine stage liquor at an estimated cost of
3.5C/1000 gal or $0.84/ton pulp for treating 5 mgd from a plant producing
800 tons of bleached pulp per day. Rubber-lined steel vessels and
maintenance and repair were included in the cost estimates. Labor was
excluded. The life of Amberlite XAD-8 resin assumed to be 5 years.
The amortization was based on a 20 year life at 5 percent interest.
The total capital cost was $1,300,000 including filtration and all
process piping. Of course, greater color reduction can be achieved
but at a higher cost.
During the final stages of preparation of this manuscript, Anderson,
Broddevall, and Lindberg (1973) reported success after many years of
experimentation in decoloring bleach plant effluents by ion exchangers.
They were able to decolor caustic extract stage liquor completely.
However, with more conservative practice (allowing 35 percent color
breakthrough at the end point) color was reduced by 96 percent, COD
was reduced by 90 percent, and BOD was reduced by 60 percent. The
resin was regenerated by black liquor and the eluant was then burned
in the recovery furnace. The capital cost of a plant for treating
the caustic extract stage of a 300 ton per day bleach plant was esti-
mated to vary from $500,000 to $1,000,000. Kamyr, Inc. is marketing
170
-------
the method in North America. Such a process might well be incorporated
into desalination by ion exchange.
PRETREATMENT
None of the costs yet discussed include pretreatment. Wright (1972)
stated the cost for massive lime precipitation might be as high as
$1.80/ton of pulp which would increase the total cost in Table 35 to
$15.67/ton of pulp or $0.56/1000 gal. Pretreatment by ion exchange
using the Rohm and Haas Company (1973) method with Amberlite XAD-8
resin would certainly cost more than $0.035/1000 gallons but it might
well replace massive lime precipitation. Furthermore, as pretreatment
by XAD-8 removes compounds causing color, it may also remove other
substances that attack the resins used for desalination. The ion
exchange method of Anderson, Broddevall, and Lindberg (1973) might
also be used in place of massive lime precipitation for pretreatment
preceeding desalination. The necessity for further pretreatment for
such as filtration has not been determined. A large pilot plant
operating at the mill for an extended period of time would afford
the best basis for this judgment.
COMPARISON WITH REVERSE OSMOSIS
The only serious competitor with some form of the ion exchange process
appears to be reverse osmosis. Extensive research over a number of
years by Wiley, Dubey, and Bansal (1972) culminated in predicted
capital costs of $0.82 to $1.48 per daily gallon of permeate water for
plants producing 0.1 mgd to 1 mgd of kraft bleach effluent. Total
operating costs were estimated at $1.32/1000 gallons of product water.
The use of improved membranes (which apparently became available too
late for testing) might reduce capital and operating costs to $0.58
per daily gallon and $0.82/1000 gallons of product water respectively.
171
-------
Cost comparisons are frought with uncertainties. Amortization periods,
interest rates, chemical prices, life of equipment, labor, pretreatment,
waste disposal, integration of the process into the rest of the plant,
bias of the estimator, and other factors all contribute to the uncer-
tainty. But it has been shown, under conditions of the actual testing,
the cost of ion exchange is about the same as the cost of reverse
osmosis. Under the best conditions, the speculative cost of ion
exchange is about $0.43/1000 gallons compared with $0.82/1000 gallons
for reverse osmosis. These figures are based upon different assump-
tions concerning life, interest, plant hook-up, pretreatment, waste
disposal, etc., and therefore they are not directly comparable.
Whether ion exchange will eventually prove to be less costly in full
scale plants depends on the solution of pretreatment problems, the life
of membranes and resins, the relative costs of waste disposal and the
ease of integration into the pulp mill facilities. But in any event
it is sate to conclude ion exchange is competitive and the method
deserves more research effort to bring it into focus with reverse
osmosis.
172
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SECTION IX
ACKNOWLEDGEMENT S
The project was initiated and directed throughout by R. L. Sanks,
Professor of Civil Engineering and Engineering Mechanics, Montana
State University, Bozeman, Montana. Mr. Ralph H. Scott and Dr. H.
Kirk Willard, Paper and Forest Industries, Environmental Protection
Agency acted as Project Officers. The help of Mr. William J. Lacy,
Chief, Applied Science and Technology, Environmental Protection
Agency, and Mr. George R. Webster, his former assistant and now Chief,
Technical Information and Analysis, is gratefully acknowledged.
Most of the laboratory work was done by Mr. C. Frank Reid, Engineering
Associate. For a short time he was assisted by Dr. Nancy Roth. Mr.
Robert Anderson and Mr. Gerald Funk, graduate students worked on phases
of the project.
Many have contributed to the project in various ways including:
Dr. Glen L. Martin, Head, Department of Civil Engineering and
Engineering Mechanics, Montana State University,
Mr. Lawrence Kain, Assistant to Vice President for Research,
Montana State University,
Mr. Herbert F. Berger, Regional Engineer, National Council for
Stream Improvement, Inc.,
Dr. I. M. Abrams, Technical Director, Ion Exchange Division,
Diamond Shamrock Chemical Company,
Mr. Gerald D. Button, Ion Exchange Department, Rohm and Haas
Company,
Mr. Roy Countryman, General Manager, Hoerner Waldorf Corporation,
Frenchtown, Montana,
Mr. Lawrence Weeks, Chief Chemist, Hoerner Waldorf Corporation,
Frenchtown, Montana,
173
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Mr. Robert Sorensen, Purchasing Agent, Hoerner Waldorf Corporation,
Frenchtown, Montana,
Mr. William Murray, Plant Engineer, Hoerner Waldorf Corporation,
Frenchtown, Montana,
Mr. Joe Manley, Chief Estimator, Edsall Construction Company, and
Mr. Lloyd P. Lee, The Permutit Company.
Several companies supplied resins and carbons including:
Dow Chemical Company,
Diamond Shamrock Chemical Company,
Calgon Corporation, and
Rohm and Haas Company.
174
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SECTION X
REFERENCES
1. Abrams, I.M. Technical Director Duolite Division Diamond Shamrock
Company. Private communication (1969).
2. Abrams, I.M. Private communication (January, 1973).
3. Abrams, I.M. and R.F. Poll. "The 'Duo-cat' system in the ion
exchange refining of beet-sugar extracts," presented at 153rd
National Meeting of the American Chemical Society, Miami Beach,
Florida (April, 1967).
4. Adams, R.C. "Progressive Mode a new approach to ion exchange."
Technical Bulletin VIII No 1, Permutit Sybron Corporation (April,
1970).
5. Adams, B.A. and E.L. Holmes. Journal Society of Chemical Industry,
London. 5^, pp ITff (1935).
6. Ammerlaan, A.C.F., B.F. Lueck, and A.J. Wiley. "Membrane process-
ing of dilute pulping wastes by reverse osmosis," presented at
Technical Association of the Pulp and Paper Industry Conference,
Portland, Oregon (April, 1968).
7. Anderson, L.G., B. Broddevall, and S. Lindberg. "Color removal
from effluents in forest industries by ion exchange," presented at
Annual Meeting Canadian Pulp and Paper Association, Montreal
(January 23-26, 1973).
8. Bennett, D.J., C.W. Dence, F.L. Kung, P. Luner, and M. Ota. "The
mechanism of color removal in the treatment of spent bleaching
liquors with lime," Journal of Technical Association of Pulp and
Industries, 54^(12), pp 2019-2026 (December, 1971).
175
-------
9. Berger, H.F. "Evaluating water reclamation against rising costs
of water and effluent treatment." Journal of Technical Association
of the Pulp and Paper Industry, ^9_(8) , pp 79A-82A (August, 1966).
10. Berger, H.F., H.W. Gehm, and A.J. Herbet. "Decolorizing kraft
waste liquors," U.S. Patent 3,192,464 (February 4, 1964).
11. Button, G.B. Ion Exchange Department, Rohn and Haas Company.
Private communication (October, 1972).
12. Collins, J.W., A.A. Webb, H.P. Didwania, and B.F. Lueck. "Com-
ponents of wood pulp bleach effluents," Environmental Science
and Technology, 3_, pp 371-377 (April, 1969).
13. Cooper, S.R. "Water reuse in a large integrated bleached kraft
mill," presented at Technical Association of the Pulp and Paper
Industry, Portland, Oregon (April, 1968).
14. d'Alelio, G.F. General Electric Company. U.S. Patent 2,340,110
(1944).
15. Determann, H. Gel Chromatograpy, (New York: Springer-Verlag, Inc.,
1968).
16. Dickinson, B.N. and H.E. Barrett, Jr. "Complimentary refining
with pulverulent mixtures of polar resinous adsorbents, activated
carbon, and inorganic adsorbents," I&EC Product Research and
Development 8, pp 199-204 (June, 1969).
17. Dugal, H.S. Institute of Paper Chemistry, Appleton, Wisconsin.
Private communication (1969) .
176
-------
18. Cans, R. Jahrbuch der Preussischen geologischen Landesanstalt,
Bergakademie. Berlin, 26, pp 179ff (1905).
19. Gel Filtration in Theory and Practice, (Uppsala, Sweden: Pharmacia
Fine Chemicals AB, 1970).
20. Glueckauf, E. "Principles of operation of ion exchange columns,"
Ion Exchange and Its Applications, Society Chemical Industries,
pp 34-46 (1955).
21. Haynes, D.C. "Water reuse. A survey of the pulp and paper
industry," Journal Technical Association of the Pulp and Paper
Industry, 49/9), pp 51A-52A (September, 1966).
22. Haynes, D.C. "Progress report on water reuse," presented at
Technical Association of the Pulp and Paper Industry Conference,
Portland, Oregon (April, 1968).
23. Higgins, I.R. "Use ion exchange when processing brine," Chemical
Engineering Progress. ^p_j pp 60-63 (November, 1964).
24. Higgins, I.R. "A unique process for demineralizing waste water,"
Industrial Water Engineering, _2, pp 26-29 (August, 1965).
25. Interstate Paper Corporation. Color Removal from Kraft Pulping
Effluent by Lime Addition, Water Pollution Control Research Series,
12040 ENC, U.S. Environmental Protection Agency (December, 1971).
26. Kunin, R. "Deionization of high solids water," Industrial Water
Engineering, 2_, pp 12-15 (1965) .
27. Kunin, R. and D.G. Downing. "New ion exchange systems for treating
municipal and domestic waste effluents," Chemical Engineering
Symposium Series, Water, 67, pp 575-580 (1970).
177
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28. Levendusky, J.A., L. Limon, and L.F. Ryan. "Continuous counter-
current ion exchange a proven low-cost process," presented at the
International Water Conference of the Engineer's Society of Western
Pennsylvania, Pittsburgh, Pennsylvania (October 20-22, 1965).
29. Loras, V. "Removal of lignin and carbohydrates during bleaching,"
Technical Association of the Pulp and Paper Industry, 48, pp 125-
128 (February, 1965).
30. Lux, Werner. "The new counterflow regeneration process for ion
exchange plants cuts operating costs and improves quality," BAMAG
Verfahrenstechnik GmbH. Facts of publication unknown.
31. McGlasson, W.G., L. J. Thibodeaux, and H. F. Berger. "Potential
uses of activated carbon for waste water renovation," Technical
Association of the Pulp and Paper Industry, 49, pp 521-526 (1966).
32. National Council for Stream Improvement, Inc. A Process For
Removal of Color from Bleached Kraft Effluents Through Modifica-
tion of the Chemical Recovery System. Technical Bulletin 157
(June, 1962).
33. National Council for Air and Stream Improvement, Inc. Decoloriza-
tion of Pulp Mill Bleaching Effluents Using Activated Carbon,
Technical Bulletin No. 181 (May, 1965).
34. National Council for Stream Improvement, Inc. Treatment of Pulp
Mill with Activated Carbon, Technical Bulletin No. 199 (January,
1967).
35- National Council for Air and Stream Improvement, Inc. The
Mechanisms of Color Removal in the Treatment of Pulping and
Bleaching Effluents with Lime. 1. Treatment of Caustic Extraction
178
-------
Stage Bleaching Effluent, Technical Bulletin No. 239 (July, 1970),
36. Nelson, G.G., Jr., A.A. Yankowski, G.H. Trostel, and M.P. Clark.
"Water reuse in bleaching - panel discussion," Journal Technical
Association of Pulp and Paper Industry, ,55_(6) , pp 933-936 (June,
1972).
37. Odland, K. and H.L. Pablich. "Desalinization by the Sul-biSul
process," presented at International Water Conference of the
Engineer's Society of Western Pennsylvania, Pittsburgh,
Pennsylvania (October, 1965).
38. Olson, J.H. "Rates of poisoning in fixed-bed reactors,"
Industrial and Engineering Chemistry Fundamentals, 7(2), pp
185-188 (May, 1968).
39. Rebhun, M. and W.J. Kaufman. Removal of Organic Contaminants.
Sorption of Organics by Synthetic Resins and Activated Carbon.
SERL Report No. 67-9, Sanitary Engineering Research Laboratory,
University of California (December, 1967).
40. Rimer, A.E., W.F. Calahan, and R.L. Woodward. "Activated carbon
system for treatment of combined municipal and paper mill waste-
waters in Fitchburg, Mass.," Journal Technical Association of the
Pulp and Paper Industry, 54, pp 1377-1584 (September, 1971).
41. Rohm and Haas Company. Decolorization of Pulp Mill Effluents
Using Synthetic Polymeric Adsorbents, Bulletin IE-172-70 (Phila-
delphia: Rohm and Haas Company, April 1970).
42. Rohm and Haas Company. Decolorization of Kraft Pulp Bleaching
Effluents Using Amberlite XAD-8 Polymeric Adsorbents, Bulletin
IE-201 (Philadelphia: Rohm and Haas Company, August 1971).
179
-------
43. Rohm and Haas Company. "Report of experience. Mill site effluent
decolorization studies utilizing Amberlite XAD-8 polymeric adsor-
bent," (Philadelphia: Rohm and Haas Company, 1973).
44. Ruzickova, D. "Treatment of pulp mill effluents on sorption resins,1
presented at 5th International Water Pollution Research Conference,
San Francisco (July, 1970).
45. Sanks, R.L. "Improving the efficiency of cation exchange,"
Proceedings American Power Conference, 29, pp 808-814 (1967).
46. Sanks, R.L. and W.J. Kaufman. "Partial demineralization of
brackish waters by ion exchange," Journal Sanitary Engineering
Division Proceedings American Society of Civil Engineers, (SA6),
pp 57-84 (December, 1966).
47. Sanks, R.L. and W.J. Kaufman. "Recycling of saline wastes,"
Advances in Water Pollution Research, 3_, pp 333-359 (1967).
48. Schmidt, K., et al. Sul-biSul Ion Exchange Process: Field
Evaluation on Brackish Waters, Research and Development Progress
Report No. 446, U.S. Department of the Interior (May, 1969).
49. Sephadex. Gel Filtration in Theory and Practice, (Uppsala,
Sweden: Pharmacia Fine Chemicals AB, 1970).
50. Standard Methods for the Examination of Water and Waste Water,
13th Ed (New York: American Public Health Association, 1971).
51. Thibodeaux, L.J. and H.F. Berger. Laboratory and Pilot Plant
Studies of Water Reclamation, NCSI Technical Bulletin No. 203,
National Council for Stream Improvement (June, 1967).
180
-------
52. Thibodeaux, L.J. and R.L. Wright. Deionization of Paper Industry
Wastewater via Ion Exchange, proposed as a Technical Bulletin of
the National Council of ths- Paper Industry for Air and Stream
Improvement Inc. (rough draft, 1970).
53. Thompson, H.S. Journal Royal Agricultural Society of England,
LI, pp 68ff (1850).
54. Ward, R.F. and E. Edgerley, Jr. "Organic fouling of anion
exchange resins," presented at Symposium on Sanitary Engineering
Research Development and Design, Pennsylvania State University,
University Park, Pennsylvania (July, 1965).
55. Way, J.T. Journal Royal Agricultural Society of England, ll,
pp 313ff (1850).
56. Weeks, L. Plant Chemist, Hoerner-Waldorf Corporation. Private
communication (October, 1972).
57. West Virginia Pulp and Paper Company. Study of Powdered Carbons
for Waste Water Treatment and Methods for Their Application, Water
Pollution Control Research Series, 17020 DNQ 09/69, U.S. Depart-
ment of the Interior, Federal Water Pollution Control Administration
(September, 1969).
58. Whaley, D. Vice President, Dyce Sales and Engineering Services.
Private communication (April, 1973).
59. Wiley, A.J., A.C.F. Ammerlaan, and G.A. Dubey. "Application of
reverse osmosis to processing of spent liquors from the pulp and
paper industry," Journal Technical Association of the Pulp and
Paper Industry, 50^(9), pp 455-460 (September, 1967).
181
-------
60. Wiley, A.J., G.A. Dubey and I.K. Bansal. Reverse Osmosis Concen-
tration of Dilute Pulp and Paper Effluents, Water Pollution
Control Research Series, 12040 EEL 02/72, U.S. Environmental
Protection Agency, Water Quality Office (February, 1972).
61. Wilson, A.L. "Organic fouling of strongly basic anion-exchange
resins," Journal Applied Chemistry, 9_> PP 352-359 (1959).
62. Wright, R.S. "Color removal from kraft pulp mill effluents by
massive lime treatment," presented at Southern Regional Meeting,
National Council of the Paper Industry for Air and Stream Improve-
ment, Inc. (July 26-27, 1972).
63. Yankowski, A.A. "Reducing the water consumption in a kraft
bleacher," Journal Technical Association of Pulp and Paper
Industry, 55(6), pp 939-940 (June, 1972).
182
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SECTION XI
GLOSSARY
ALKALINITY
ANION
BACKWASHING
BED DEPTH
BED EXPANSION
BED VOLUME
(BV)
BV/hr
BIOCHEMICAL OXYGEN
DEMAND
(BOD)
BLACK LIQUOR
The buffering capacity of water. Specifi-
cally, it is CO + HC03 + OH - H. Also it
includes other weak acid anions such as
borates, silicates, and phosphates. It is
expressed in milligrams per liter of equivalent
calcium carbonate or in milliequivalents.
A negatively charged ion in solution attracted
to the anode under the influence of electric
potential.
The operation of cleansing a resin bed by an
upward flow of water sufficient to expand the
bed and aggitate the particles. Backwashing
reclassifies the bed so lighter, smaller
particles are lifted to the top. Channels
formed during the service cycle are eliminated
which promotes uniform flow in the following
service cycle.
The effective height of resin in the reactor.
The added height to which resin rises during
backwashing expressed as a percentage of the
unexpanded bed depth.
The total volume of the resin particles plus
the pore volume between particles in the
unexpanded bed.
Flow rate expressed as bed volumes per hour.
The quantity of oxygen used in the oxidation
of organic matter by bacteria under standard
conditions of temperature, time, quiescence,
and absence of light. It is a measure of
readily oxidizable organic material.
The product of white liquor after being used
to digest wood chips. It contains less
caustic, more carbonates, and large quantities
of lignin. This black fluid is burned for
the recovery of chemicals and when the ash is
redissolved the resulting fluid is called green
liquor.
183
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BOD-5
BREAKTHROUGH
Biochemical oxygen demand over a five day
period at 20°C.
The rapid increase in the concentration of an
ion or color in the effluent. It is expressed
as a percentage of the concentration of the
substance in the feed water.
CALCIUM CARBONATE
EQUIVALENT
(CaCO )
CAPACITY
A means for expressing the number of equiva-
lents of a constituent in terms of an
equivalent weight of calcium carbonate
commonly used for ease in calculation and
elimination of ambiguity.
1 equivalent.
50 mg/1 CaC03 =
The amount of ions that can be held by a resin.
It is usually expressed as kilograins (as
calcium carbonate) per cubic foot, but it
can also be expressed in other ways. For
example, 1 me/ml = 21.85 kilograins per cubic
foot.
CATION
A positively charged ion which migrates to the
cathode in a solution.
CAUSTIC EXTRACT
CHEMICAL OXYGEN DEMAND
(COD)
cm
COLOR UNIT
(CU)
CU-liter
A stage in the bleaching process. Waste from
this stage contains much more color than
wastes from other stages.
A measure of the organic material in water in
terms of its oxygen-consuming capacity when
subjected to boiling in acid solution with
an excess of a strong oxidant.
Centimeter.
A measurement of the intensity of color com-
pared to a standard solution of 1 mg/1 Pt in
the form of chloroplatinate ion augmented
with 0.5 mg CoCl« as Co.
The quantity of color in one liter at a con-
centration of 1 CU.
CONCURRENT
Operation of an ion exchange bed in which
direction of flow in the service cycle is
the same as the direction of flow of the
regenerant.
184
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COUNTERCURRENT
CONDUCTIVITY
Cwt
DECATIONIZATION
DEMINERALIZATION
DESALINATION
DITCH WASTE
DUO-CAT
EFFLUENT
ELUTION
EQUIVALENT
(eq)
ENDPOINT
Operation of an ion exchange bed in which the
direction of flow during the service cycle is
opposite to that of the regenerant.
The ability of water to conduct electricity
expressed in the reciprocal of resistance as
micromhos/square centimeter or, more simply
pmhos.
Weight expressed in hundredths of pounds.
Ion exchange with a cation resin in which the
cations are replaced by hydrogen ions.
The removal of the mineral content of water.
It can also mean reduction of the mineral
content.
The partial removal of salts from water by
physical or chemical means.
In this report, ditch waste is the aggregate
waste leaving the bleach plant. It consists
of approximately 15 percent caustic extract,
85 percent chlorination stage effluent, minor
spills, floor sweepings from the lime kiln
area, and sporadic flows of black liquor.
A layer of weak acid cation resin on top of
a bed of strong acid cation resin. The com-
bination of the advantages of both resins
produces low leakage plus high efficiency in
regeneration.
The liquid that emerges from a reactor or a
tank.
Removal of sorbed ions from an ion exchanger
by regeneration with concentrated chemical
solutions. The regenerant solution is the
eluant. The effluent is the eluate.
An amount of substance equivalent to one mole
of hydrogen ions.
The end of the service cycle defined as some
desired percentage of breakthrough.
185
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EXCHANGER
EXHAUSTION
FEED
FIXED-BED
HOOK-UP
ID
INFLUENT
JTU
LEAKAGE
LIME
LIFE TEST
me/1
MICROMHOS
(ymho)
Any substance, such as ion exchange resins,
sulfonated coal, or zeolite which can
reversibly exchange one ion for another.
Exhaustion and service are synonymous. That
part of the service cycle in which feed is
pumped through the resin bed. The resin is
exhausted at the endpoint.
The solution introduced into a reactor.
An ion exchange system in which the resin
does not leave the reactor. Temporary dis-
turbances of the bed by backwashing does not
alter its status as a fixed-bed reactor.
Connect, join, or attach any device, reactor
or pump to the remainder of the plant.
Internal diameter.
Synonymous with feed. The solution introduced
into a reactor or tank.
APHA Jackson Turbidity Units.
turbidity.
A measure of
The unsorbed ions present in the effluent.
In general, any of a family of chemicals com-
posed of calcium and sometimes containing
magnesia. In this report, lime which is dry
is CaO, and lime in water is Ca(OH)?.
Continuous cyclic tests of exhaustion and
regeneration in rapid sequence to determine
the degradability of resins. The "life" of
a resin is its operating period during which
it retains sufficient physical and chemical
integrity for use.
Milliequivalents (1000th of an equivalent)
per liter.
Electrical conductivity equal to 1 millionth
of a reciprocal ohm.
186
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MOVING BED
NORMAL
(N)
OD
PLENUM
ppm
PRODUCT
PRODUCT RECOVERY
REGENERANT
REGENERATION
REGENERATION EFFICIENCY
RINSE
SALT SPLITTING
SELECTIVITY
In moving bed reactors, resins are pumped
from one portion of a reaction into another
portion of the same reactor or into a different
reactor for different parts of the service
cycle such as exhaustion, regeneration, and
rinse.
A concentration of acid of base equal to one
equivalent per liter.
Outside diameter.
The space between the top of the resin bed
and the top of the reactor.
Parts per million and approximately equal to
mg/1.
The finished water or effluent from an ion
exchange system.
The product remaining after utilization of
some of the feed for acid and base dilution
and rinse.
The chemical solution used to restore the
exchange capacity of a resin. Also eluent.
The portion of the service cycle in which the
regenerant flows through the resin bed.
The milliequivalents of ions eluted from the
resin divided by the milliequivalents of ions
supplied in the regenerant and usually expressed
as a percentage. See true and superficial
efficiency.
The part of the service cycle in which regen-
erant in the reactor is displaced by water,
usually product water.
The conversion of neutral salts to their
corresponding acids or bases.
The preference of a sorbent for one ion over
another. It is a function not only of the
resin itself but of the absolute and relative
concentrations of ions in the solution.
187
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SERVICE
STARVATION REGENERATION
STRONG ACID RESIN
STRONG BASE RESIN
SUPERFICIAL EFFICIENCY
THROUGHPUT
TOTAL ORGANIC CARBON
(TOG)
TDS
tr
TRUE EFFICIENCY
WEAK ACID RESIN
The part of the ion exchange cycle in which
feed is converted to product.
Regeneration in which small amounts of chemicals
are used in order to increase regeneration
efficiency.
A cationic exchanger with strong acid functional
groups such as sulfonic acid. Such exchangers
exhibit high selectivity for other ions over
hydrogen ion and will operate in a pH range
of less than one to 14.
An anion exchanger with strongly basic func-
tional groups such as quaternary ammonium.
Such exchangers exhibit high selectivity of
other ions over OH and can operate in any
pH range from 0 to 13.
Milliequivalents of ions eluted from resin
divided by milliequivalents of ions in the
regenerant.
The amount of feed that passes through a resin
bed, usually expressed in bed volumes.
The concentration of organic carbon found by
oxidizing the carbon at high temperature in
a stream of pure oxygen aided by a catalyst.
Total dissolved solids
Trace. It indicates the presence of a chemical
in quantities smaller than is convenient to
tabulate or to measure.
Milliequivalents of ions sorbed from the net,
useable product water divided by milliequivalents
of ions in the regenerant.
An exchanger containing weak acid functional
groups such as carboxylic acid. Such exchan-
gers cannot split strong electrolyte salts
such as sodium chloride but can split salts
of weak acids such as sodium bicarbonate.
They can operate between pH 5 and 14.
188
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WEAK BASE RESIN An exchanger containing weak base functional
groups such as primary, secondary, or tertiary
amines. Such exchangers can only operate
between pH 0 and pH 7 or 8.
«US GOVERNMENT PRINTING OFFICE 1973 514-156/347 1-3
189
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
w
Ion Exchange Color and Mineral Removal From
Kraft Bleach Wastes.
S. » iforr,i Org* siioi
Sanks, R.L.
Department of Civil Engineering
Montana State University
Bozeman, Montana 59715
12040 DBD
1. Ty:> flep-- and
!3, S tsorit 'trgaf -two
.Environmental Protection Agency Report No. EPA-R2-73-255, May 1973
Laboratory evaluations of twenty resins and seven carbons for removing color
and minerals from a four-stage kraft bleach plant showed resins were equal to
carbon for decoloring the combined waste. With few exceptions, resins were unsuited
for decoloring wastes from each stage separately. Except for success in the use of
weak wash to regenerate Amberlite XAD-8 resin, utilization of mill liquors for
regeneration was unsuccessful. Sulfuric acid, caustic, and ammonia were good rege-
nerants, but lime was poor.
Single stage ion exchange produced water adequate for unbleached pulping.
Two-stage desalination produced water adequate for bleached pulping. Any of the
continuous counter-current ion exchange processes are probably adequate for producing
water for bleached pulping.
The estimated cost for desalination including amortization over a 10 year
period at 9 percent interest, labor, chemicals, maintenance, and repairs are estimatec
to vary from $1.38/1000 gal (for the non-optimized process used in the laboratory)
to $0.42/1000 gal (with estimated 90 percent cation regeneration efficiency, 85
percent anion regeneration efficiency, and 87 percent product recovery).
Pulp & Paper Industry, Effluents, Resins, Lime, Water Reuse, Costs, Color
Bleach plant wastes, ion exchange, desalination, color removal, demineralization.
IS. Security duns,
'Rept> /
21, No. of
2'ages
:. P;, ,-'
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
US DEPARTMENT OF THE INTERIOR
WASHINGTON 11 C 2024O
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