EPA-R2-73-260
MAY 1973 Environmental Protection Technology Series
Study of
Gamma Induced Low Temperature
Oxidation of Textile Effluents
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-R2-73-260
May 1973
STUDY OF GAMMA INDUCED LOW TEMPERATURE OXIDATION
OF TEXTILE EFFLUENTS
By
F. N. Case
E. E. Ketchen
Oak Ridge National Laboratory
Oak Ridge, Tennessee
Project 12090 FWD
Project Officer
Edmond Lomasney
Environmental Protection Agency
1421 Peachtree Street, N.E.
Atlanta, Georgia 30309
Prepared for
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
Price 90 cents domestic postpaid or 66 C3nts QPO Bookstore
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£E?A Rev Jew... Not ice
This report has been reviewed by the Environmental Protection
Agency and approved for publication. Approval does not
signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
11
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ABSTRACT
Gamma irradiation of textile mill effluents under oxygen
pressures up to 1500 psi, with and without activated char-
coal present, was studied as a method for removing color
and removal of substances contributing to the chemical
oxygen demand (COD). Both color and COD reduction are
directly related to the radiation dose and pressure of the
oxygen over the dye solution samples during irradiation.
Color removal was achieved in solutions of dye prepared
in the laboratory for process evaluation and for authentic
textile mill waste effluents. The study revealed a new
method for in-situ reactivation of charcoal by gamma-
radiation-induced oxidation of organic compounds adsorbed
on charcoal. This discovery permits a large reduction in
the gamma source size required for processing textile mill
effluents because the water fraction of the effluent does
not need to be irradiated to the same degree as the organic
material contained in the effluent. A mathematical model
for the process, developed late in this study, has not yet
been experimentally verified.
This report was submitted in fulfillment of Project Number
12090FWD, under the (partial) sponsorship of the Office of
Research and Monitoring, Environmental Protection Agency.
111
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CONTENTS
Page
I. Conclusions 1
II. Recommendations 3
III. Introduction 5
IV. Equipment 7
V. Single-Batch Irradiations ll'
VI. Products of Radiolytic Oxidation of Standard Dyes. . 19
VII. Adsorption on Charcoal 23
VIII. Continuous Flow Irradiations 27
IX. Acknowledgments 39
X. References 41
XI. Glossary 43
XII. Appendices 45
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FIGURES
Page
1. Cobalt-60 Gamma Irradiator 7
2. Schematic of High Pressure Irradiator 8
3. Continuous Charcoal Irradiator 8
4. Spectrophotometric Plot of Absorbance vs Wavelength
for Disperse Blue 3 Dye Solution and Irradiated
Disperse Blue 3 Dye Solution 14
5. Chemical Formula for Direct Blue 106 Dye 19
6. Chemical Formula for C.I. Acid Black 26A Dye • 20
7. Chemical Formula for C.I. Disperse Blue 3 Dye 21
8. Radiation Oxidation Product of C.I. Disperse Blue 3
Dye 21
9. 1900 Magnification of Activated Charcoal After 500 hr
of Irradiation at a Flux of 107 26
vii
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TABLES
No. Page
1. Acid and Chrome Dyes Used in Single Batch Irradiation
Studies of Radiation- Induced Oxidation ........... 11
2. Changes in Light Transmission of Acid and Chrome Dye
Solutions After Irradiation Under 1500-psi Oxygen ..... 12
3. Change in the COD of Acid and Chrome Dye Solutions After
Irradiation Under 1500-psi Oxygen ............. 12
4. COD and Color Changes in C.I. Direct Blue 106 Dye Solution
After Gamma Irradiation Under 1500-psi Oxygen ....... 13
5. COD and Color Changes in Direct Black 26A Dye Solution
After Irradiation under 1500-psi Oxygen .......... 13
6. COD and Color Changes in C.I. Disperse Blue 3 Dye Solution
After Irradiation Under 1500-psi Oxygen ........ . . 14
7. Effect of FeSOit Additions on Color Reduction on Gamma
Irradiation of Disperse Blue 3 Dye Solution When Irradiated
Under 1500-psi Oxygen ................... 15
8. COD and Color Changes in Reactive Red 3 Dye Solution After
Irradiation Under 1500-psi Oxygen ............. 15
9. Color and Odor of Authentic Dye Effluent .......... 16
10. The Effect of Irradiation Under 1500-psi Oxygen on the Light
Transmission of Six Authentic Textile Mill Effluents. ... 16
11. The Effect of Irradiation Under 1500-psi Oxygen on COD of
Six Authentic Textile Mill Effluents ............ 17
12. The Effect of Radiation Under 1500-psi Oxygen on COD and
Light Transmission on Azo Dyestuff Manufacturing Waste. . . 17
13. The Effect of the Presence of Activated Carbon on Color
Removal by Gamma Irradiation ................ 23
14. Color Removal from Dye Solutions Irradiated in Contact With
Dye Saturated Charcoal ................... 24
15. Reactivation of Charcoal by Gamma Radiation- Induced
Oxidation ......................... 25
16. Decolonization Efficiency of Charcoal and Gamma Radiation
as a Function of Oxygen Pressure .............. 28
17. Comparison of Decolorization Efficiency of Gamma Radiation
Only Compared With Gamma Irradiation Plus Oxygen at
1500-psi .......................... 29
IX
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TABLES
No. Page
18. The Effect of Flow Rate on Color Removal of Direct Blue
106 Dye Solution in a Continuous Flow System Under
1500-psi Oxygen in a 107 R/hr Gamma Flux 30
19. COD and Color Removal From Direct Blue 106 Dye Solution by
Radiation-Induced Oxidation in a 5 x io5 R/hr Radiation
Flux Under 500-psi Oxygen 30
20. COD and Color Changes in Authentic Textile Mill Effluent at
a Dose of IO6 R Gamma Under 1500-psi Oxygen 31
21. Color and COD Removal From Silk Screen Textile Plant
Effluent by Gamma Radiation at a Dose Rate of 5 x io5
R/hr With Charcoal and 500-psi Oxygen 32
22. The Effect on Light Absorbance of Solids 33
23. Dyeing and Finishing Plant Effluent Color and COD Reduction
by Gamma Radiation at a Dose Rate of 5 x io5 R/hr With
Granular Charcoal and 500-psi Oxygen 34
24. Dyeing and Finishing Plant Effluent. The Effect on Color
Absorbance Factor of Removal of Solids From Sample 34
25. Reduction in Bacteria Count by Irradiation Processes on
Dyeing and Finishing Plant Effluent 35
26. Color Removal From Dyeing and Finishing Plant Effluent by
Gamma Radiation at a 5 x io5 R/hr Dose Rate With Granular
Coconut Charcoal and 500-psi Oxygen .... 36
27. Color Removal From the Product of an Activated Sludge
Treatment Plant by Gamma Radiation (5 x io5 R/hr) at
500-psi Oxygen With Granular Coconut Charcoal 37
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SECTION I
CONCLUSIONS
•4
1. Gamma radiation in combination with oxygen under pressure has
been demonstrated to be effective in the removal of color and
COD of many dyes and other organic components in textile mill
effluents. A large variation exists in the radiation dose
required to decolorize and reduce the COD of the various dye
compounds which were investigated. In the case of some dis-
perse dyes, the dye compounds became more soluble at low and
intermediate doses of gamma radiation, thus causing the con-
centration of the dye in solution to increase. The radiation-
induced oxidation occurs at ambient temperatures and the rate
of oxidation is controlled by the radiation dose and avail-
ability of oxygen in solution.
2. While the oxidation reaction terminates at carbon dioxide,
intermediate products are produced when the radiation dose or
oxygen supply is insufficient for complete oxidation. In the
case of most of the single dye compounds studied, it was not
necessary to completely oxidize the compound to carbon dioxide
and water to destroy color.
3. Radiation-induced oxidation appears to be effective in de-
colorizing refractory dyes that persist through many of the con-
ventional textile mill waste treatment processes.
4. A promising method for applying radiation-induced oxidation to
the treatment of textile mill effluents involves adsorbing
organic materials from the effluent onto an activated charcoal
column located in the irradiator. The study has shown that
in situ reactivation of the charcoal can be achieved when the
process is operated at 500 to 2000 psi oxygen pressure. Thus,
by removing organic from the water as it passes through the
irradiator, the organics can be retained for sufficient time
to receive a radiation dose adequate for destruction without
the necessity of providing this same high dose to the large
volume of water from which the organics were adsorbed. This
saving in radiation is due to the fact that the residence time
of the water in the irradiator is reduced to the level required
only for removal of organics by adsorption onto charcoal;
therefore, the total radiation dose to the water is greatly
reduced when compared to the dose it would receive if the entire
mass of water was-required to remain in the irradiator until the
small organic fraction present received the large dose necessary
for destruction of the organic.
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5. COD increases were observed when several of the standard dye
solutions were irradiated at relatively low total gamma doses.
This is believed to be due to the alteration of refractory
structures to those more easily oxidized by the COD determina-
tion reagents.
6. Pretreatment of effluents that have filterable solids is
necessary since charcoal non-adsorbables receive radiation doses
too low to be effective in causing oxidation.
7. The color and COD is lowered as the oxygen pressure is increased.
8. Engineering cost estimates for the process have not been made
since the research involved only the radiation demands for the
process.
Estimates for radiation cost alone were based on a 10% organic loading
on the charcoal, a 106 R dose to the adsorbed organic, and a 10-minute
effluent residence time in the irradiator. Under these conditions
the radiation costs only are approximately $0.01 per 1000 gallons of
throughput.
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SECTION II
RECOMMENDATIONS
1. The data from this study shows that the presence of charcoal
increases the rate of oxidation of the organic materials present
in aqueous effluents when these are irradiated in the presence
of oxygen over the rate observed with radiation in the presence
of oxygen alone. This effect needs to be studied to determine
the mechanism involved.
2. Other oxidants in combination with gamma radiation should be
studied.
3. The mathematical model describing the charcoal adsorption and in
situ reactivation should be experimentally tested before it'is
used as a basis for determination of the theoretical limits of
the process.
4. The concept of in situ carbon reactivation at ambient temperature
is new and additional studies should be made to fully understand
and optimize the process.
5. Since the process should be used in conjunction with low cost
primary treatment (coagulants, filtration, etc.) integration of
the process with these primary treatments should be evaluated.
6. Additional bench scale test and developmental experiments are
recommended to solve problems related to specific plant waste
effluents.
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SECTION III
INTRODUCTION
Methods used to remove color from textile dye effluents include
coagulation with alum, lime and other chemicals, biological pro-
cessing through activated sludge processing .and oxygen, lagoon re-
tention, adsorption on charcoal, incineration, and reverse osmosis.
Since oxidation processes for treatment of waste effluents are gen-
erally assumed to yield products that are easily assimilated into
the natural environment, these processes are desirable for the de-
struction of the organic constituents that contribute to color in
effluents. Aeration in retention lagoons in the presence of ultra-
violet light is an effective oxidation process when easily oxidizable
compounds are present; however, because of the need for color fast
dyes in the textile dyeing operation, many of the dye compounds now
used are resistant to oxidation by aeration. Many synthetic fibers
require the use of disperse dyes which as a class are more difficult
to degrade than many of the dyes used for natural fibers (wool, cotton,
flax, etc.).
Gamma radiation has been shown to be effective in the destruction of
color in various organic compounds. It also induces oxidation of many
organic compounds when a source of oxygen is available. This reaction
occurs at ambient temperatures, and compounds that are difficult to
oxidize can often be oxidized in the presence of gamma radiation and
high pressure oxygen.
Gamma irradiation of dye effluent under oxygen pressures up to 2000
psi was investigated and was shown to be effective in the decoloriza-
tion of most dye solutions.1
The objectives of the work described in this report were (l) to in-
vestigate the radiation-induced oxidation of various dye compounds
for the destruction of color, (2) to make general identification of
oxidation products, (3) to evaluate the process using authentic textile
plant effluents, and (4-) to estimate the radiation cost of treating
effluents by this method.
The high-pressure radiolytic oxidation of a number of dyes selected
by class was performed. As the work progressed, it became evident
that it would be better to select a small number of standard dyes
currently in use by the textile industry in order that the color loss
by radiolytic oxidation-could be compared with other treatment methods.
Hence, the American Association of Textile Chemists and Colorists (AATCC)
chose four of the most frequently used dyes for the comparison study.
-------
They were C.I. Direct Blue, C.I. Acid Black 26A, C.I. Disperse Blue 3,
and Reactive Red 3.
The individual dyes prepared in water solution with additives as they
are used by the textile industry were treated in a batch irradiator at
various pressures of oxygen and at different total dose ranges of gamma
radiation. The results of this study are given in this report. The
efficiency of color removal by gamma-radiation-induced oxidation is
compared with other methods in a report by the AATCC.2 Irradiation of
authentic dye effluents were studied with a batch irradiator and two
small dynamic irradiation systems.
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SECTION IV
EQUIPMENT
Two 60Co gamma irradiators (one containing V70,000 Ci 60Co and the
other containing ^50,000 Ci 60Co) were used for this study. These
irradiators are water shielded, immersed in an ^10-ft-deep canal.
Figure 1 shows the arrangement of the 6^Co around a cavity that
could be reached by lowering vessels to be irradiated through the
water shield. The gamma dose rate provided by this irradiator was
107 R/hr gamma at the center of the source holder. The second
irradiator was loaded to provide a dose rate of 5 * 106 R/hr in the
center of the cobalt array.
VKTER LEVEL
WttTh
Samples for single batch
irradiation studies were placed
in a bottle inside a pressure
vessel and pressurized with
oxygen (500-1500 psi), and the
sealed vessel was lowered into
the center of the radiation
source for a period of time
required to obtain the desired
radiation dose.
12 SLUGS
Fig. 1. Cobalt-60 Gamma Irradiator
A dynamic irradiator arrange-
ment, shown in Fig. 2, permitted
solutions to be pumped from a
reservoir by a Lapp pump through
a pressure vessel located in the
center of the 60Co array shown
in Fig. 1. The pressure was
controlled by a pressure regu-
lator valve on the exit line
from the pressure vessel. Oxygen
was injected (by a compressor) into the feed stream between the Lapp pump
and the pressure vessel. The flow rate of solution through the irradiator
could be adjusted in the Lapp pump from 0.33 to 3 liters/hr. Solution
entered the pressure vessel through a nozzle near the bottom of the bomb
and was removed near the top through an overflow tube.
The pressure vessel was replaced with a 20-ft-long, l/8-in.-diam stain-
less steel pipe, coiled to fit into the inside cavity of the 60Co array,
and filled with 130 g of granular (6-14 mesh) activated charcoal.
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%-h. AUTO CUVE
TUWNG
Fig. 2. Schematic of High
Pressure Irradiator
in the irradiator was adjusted
with a throttle valve on the
exit end of the column. Thirteen
pounds of granular coconut char-
coal was placed in the coil.
A Beckman Spectrophotometer
Model DB was used for color eval-
uation of feed and product solu-
tions. The transmissions of
filtered solutions were reported
directly as percent transmission.
The absorbances of solutions which
were filtered through 0.80-u
Millipore filter media were used
in the calculations of the color
intensity [Eq. (1)].
Color intensity = (X + Y + Z) D (1)
where X, Y, and Z are the absorbances
at the selected wavelengths, and D is
the dilution factor.
A second and larger dynamic irra-
diator system was fabricated, making
it possible to operate at flow rates
up to 10 gal/hr. Feed to this
irradiator was pumped from a 55-gal
reservoir by a piston pump at 500 psi
through a 30-ft-long, l-l/2-in.-diam
pipe coiled to form a 20-in.-diam
circle (Fig. 3). A 60Co array (Fig.
l) was placed inside this coil to
provide an average dose rate of
5 x 106 R/hr to the volume inside
the coiled pipe. A bypass valve on
the pressure side of the pump was
used to recycle part of the pump
flow back into the reservoir to
provide flow rate control. Oxygen
was injected into the stream between
the pump and the column. The pressure
ORNL-OW6 72-1790
-I U
2 in.
-20 in.
Fig. 3. Continuous Charcoal
Irradiator
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Equation (2) can be used to calculate the color reduction of a sample.
A — B
Color reduction = —?— (2)
A
4
where A is the color intensity on the untreated sample and B is the
color intensity on the treated sample.
The chemical oxygen demand (COD) of feed and products was measured by
a standard method.3 An appropriate size sample was diluted to 20 ml
and added to 10 ml of standard 0.25 N_ potassium dichromate and 0.4- g
of mercuric sulfate. Thirty milliliters of concentrated I^SO^ con-
taining silver sulfate was added to the mixture, and the mixture was
refluxed 2 hr. The solution was cooled and the excess potassium
dichromate was titrated with standard 0.25 N^ ferrous ammonium sulfate
to a brown end point using ferroin indicator. A blank was run at the
same time. The COD can be calculated by Eq. (3).
™r> /• /-I-.L. \ (a - b) Npe x 8000 /ox
COD (mg/liter) = . e (3)
ml of organic sample
where a = volume of ferrous ammonium sulfate used on sample,
b = volume of ferrous ammonium sulfate used on blank,
Npe = normality of ferrous ammonium sulfate.
A Beckman Infrared Spectrophotometer IR-18A was used to measure the
infrared spectra in samples prepared as KBr pellets.1*
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SECTION V
SINGLE BATCH IRRADIATIONS
(Without Charcoal)
Acid and Chrome Dyes
The high-pressure, radiation-induced oxidation of five acid and chrome
dyes was studied. The dyes, their type, and general structures are
shown in Table 1, and the composition of solutions prepared from these
dyes is shown in Appendix A. Each dye solution except Neolan Yellow BG
contained Glaubers salt (Na2SOit-10H20) and acetic acid or sulphuric
acid at the concentrations used in commercial dyeing of wool. The
Neolan Yellow BG solution contained only sulphuric acid. The dye solu-
tions were irradiated under a 1500-psi oxygen atmosphere in a pressure
vessel at 106 and 5 x io6 R total radiation dose.
Table 1. Acid and Chrome Dyes Used in Single Batch
Irradiation Studies of Radiation-Induced Oxidation
Name Type Structure
Benzyl Fast Yellow GNC Weak Acid Dye Monoazo
Benzyl Blue GL Weak Acid Dye Azine
Benzyl Cyanine 6B Weak Acid Dye Triphenylmethane
Neolan Yellow BG Premetalized Acid Dye Azo
Chrome Fast Flavine A Chrome Fast Dye Monoazo
Light transmission measurements and COD determinations of the untreated
effluent, the effluent after a 106 R gamma dose, and after a 5 x io6 R
gamma dose are shown in Tables 2 and 3. In all weak acid dye experiments
the odor of acetic acid almost disappeared after a dose of IO6 R and was
completely absent after a 5 x io6 R dose. In all irradiations the color
of the solution decreased as the radiation dose increased over the range
106 to 5 x 106 R. When the Benzyl Blue GL and Chrome Fast Flavine A
solutions were irradiated, some of the dye precipitated from the solution.
The yellow color of the Chrome Fast Flavine A solution changed to orange-
olive after a IO6 R gamma radiation dose and to green after 5 x ioe R.
11
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Table 2. Changes in Light Transmission of Acid and Chrome
Dye Solutions After Irradiation Under 1500-psi Oxygen
Wavelengt
Dye (my )
Benzyl Fast Yellow GNC
Benzyl Blue GL
Benzyl Cyanine 6B
Neolan Yellow BG
Chrome Fast Flavine A
350
396
450
600
700
400
550
700
400
500
600
350
500
570
h % Light Transmission
No irradiation
41
34
22
0
45
54
0
41
1
1
67
0
34
17
106 R 5
64.5
69.5
67
16
60
75
35
75
1
6
69
2
38
17
After
x 106 R
65
71
83
65
90
95
88
98
36
83
91
32
56
21
Table 3. Change in the COD of Acid and Chrome Dye Solutions
After Irradiation Under 1500-psi Oxygen
COD (mg/ liter) After
Benzyl
Benzyl
Benzyl
Neolan
Chrome
Dye No
Fast Yellow GNC
Blue GL
Cyanine 6B
Yellow BG
Fast Flavine A
Irradiation
1
11
11
9
,795
,680
,900
920
,300
106
2,
4,
10,
8,
R 5
052
130
900
800
500
x
2
3
10
8
106 R
,713
,800
,300
570
,000
Dye Solutions Used to Compare Various Color Removal Methods
C.I. Direct Blue 106, C.I. Acid Black 26A, C.I. Disperse Blue 3, and
Reactive Red 3 dyes, chosen because they are widely used in textile
processing, were prepared as standard solutions (see Appendix A for
composition). These standard solutions were evaluated by others using
various decolorization methods, and the results are reported in the
literature.5 These solutions were irradiated under 1500-psi oxygen to
gamma doses of 106 and 5 x 106 R. In the case of C.I. Direct Blue 106
12
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dye solution, the solution changed from dark blue to a light blue
after a gamma dose of IO6 R and to water-white after 5 x io6 R
exposure. The results are shown in Table 4.
Table 4. COD and Color Changes in C.I. Direct Blue 106 Dye
Solution After Gamma Irradiation Under 1500-psi Oxygen
Oxygen Absorbances at
Pressure Irradiation COD 480 580 680 Color % Color
(psi) Dose (R) (mg/liter) my my my Intensity Removal
0
1500
1500
No irradia-
tion
10 6
5 x io6
182
102
65
0.52 2.44 0.84
0.04 0.13 0.05
000
3.80
0.22
0.0
0
94.4
100
Solutions of C.I. Acid Black 26A changed from a dark purple to
colorless after a dose of IO6 R, and the COD decreased from 104 to
30 mg/liter. The sample that received the 1Q6 R dose contained a
black precipitate which was removed by filtration before COD mea-
surements. Because this precipitate was removed, the COD of this
filtered solution was less than the solution receiving 5 x io6 R
exposure, indicating that the precipitate that formed at the IO6 R
dose level was redissolved at the higher dose of 5 x io6 R. The
results are shown in Table 5.
Table 5. COD and Color Changes in Direct Black
26A Dye Solution After Irradiation Under
1500-psi Oxygen
Oxygen
Pressure
(psi)
0
1500
1500
Absorbances
Irradiation
Dose (R)
No irradia-
tion
IO6
5 x io6
COD
(mg/liter )
104
30a
71
0
0
0
460
my
.128
0
0
0
560
my
.268
0
0
0
at
660
my
.098
Color
Intensity
1.48
0
0
% Color
Removal
0
100
100
clack precipitate was filtered from the sample before COD analysis.
C.I. Disperse Blue 3 dye was partially oxidized to a light blue after a
dose of 5 x io6 R exposure [a 48% color reduction (Table 6)]. The COD
was reduced from 725 to 347 mg/liter at 5 x io6 R.
13
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Table 6. COD and Color Changes in C.I. Disperse Blue 3
Dye Solution After Irradiation Under 1500-psi Oxygen
Oxygen
Pressure
(psi)
0
1500
1500
Absorbances
Irradiation
Dose (R)
No irradia-
tion
10 6
5 x io6
COD
(ing/liter)
752
555
347
0
0
0
430
my
.120
.200
.33
0
0
0
530
my
.166
.182
.32
0
0
0
at
630
my
.232
.212
.35
Color
Intensity
2.072
2.376
1.000
% Color
Removal
0
-14.7
48.2
The gain in color intensity after a gamma dose of IO6 R is believed to
be due to solid particles of dye that are suspended in solution prior to
irradiation and that become solubilized during the irradiation.
The absorbance curves for Disperse Blue 3 dye solution before and after
a IO6 R gamma radiation dose under 1500-psi oxygen are shown in Fig. 4.
The peak absorbance at about 600 my wavelength was lowered from about
0.247 in the original dye solution
31 i ' • i ' i i i > i i i i i'iii'i' i i i i i * i i * i i to about 0.220 in the irradiated
solution. The minimum absorbance in
the original dye solution of 0.108
at 460-my wavelength was shifted
upward in the treated dye solution
to 0.160 at 480 my. Radiation treat-
ment reduced the height of the color
absorbance peak and increased the
range of wavelengths over which color
absorbance was observed.
It has been observed that ferrous
iron can be precipitated from a
solution that has been exposed to
gamma radiation.6 To determine
whether or not this effect can be
utilized to' remove dyes from solu-
tion during irradiation, FeSO^ at a
concentration of 200 and 400 ppm was
added to a solution of Disperse Blue
3 dye prior to irradiation. The
results of this test are shown in
Table 7.
400
500 6OO
WAVELENGTH (millimicronsL
700
Fig. 4. Spectrophotometric Plot
of Absorbance vs Wavelength for
Disperse Blue 3 Dye Solution
and Irradiated Disperse Blue 3
Dye Solution
The addition of 0.2 to 0.4 g/liter of FeSO^ to the dye effluent enhanced
the decolorization at the 5 x io6 R gamma dose. The 400-ppm addition
caused a color reduction of 95% after a 5 x io6 R gamma dose.
14
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Table 7. Effect of FeSOit Additions on Color Reduction
on Gamma Irradiation of Disperse Blue 3 Dye Solution
When Irradiated Under 1500-psi Oxygen
Radiation FeSO^
Exposure Concentration
(R) (g/liter) pH
None
10 6
5 x io6
None
IO6
5 x io6
None
IO6
5 ^ T Q
0.2
0.2
0.2
0.4
0.4
0.4
0.4
0.4
6
6
6
6
6
6
12
12
12
Absorbances
430
my
0.300
0.712
0.160
0.368
1.192
0.010
2.200
1.860
0.592
530
my
0.368
1.240
0.119
0.352
0.724
0.014
1.804
1.340
0.328
at
630
my
0.480
1.220
0.089
0.288
0.680
0.015
2.145
1.640
0.260
Color
Intensity
1.148
4.172
0.368
1.008
2.596
0.039
6.149
4.840
1.180
% Color
Removal
0
-263a
68
0
-157a
96.6
0
21.3
80.9
Color increase.
The Reactive Red 3 dye solution was decolorized at 106 R exposure. The
COD was reduced from 123 to 84 mg/liter after a dose of 5 x io6 R. The
results are shown in Table 8.
*
Table 8. COD and Color Changes in Reactive Red 3 Dye
Solution After Irradiation Under 1500-psi Oxygen
Oxygen
Pressure
(psi)
0
1500
1500
Absorbances at
Irradiation
Dose (R)
No irradia-
tion
10 6
5 x io6
COD
(mg/liter )
123
98
84
420
my
0.40
0
0
520
my
2.24
0
0
620
my
0
0
0
Color
Intensity
2.64
0
0
% Color
Removal
0
100
100
Authentic Textile Mill Dye Effluents
The high-pressure, radiation-induced oxidation of six authentic textile
mill effluent samples was studied. Each sample contained a mixture of
50-65 dyes and textile additive chemicals. Each sample was irradiated
without charcoal under 1500-psi oxygen pressure in a pressure vessel a
radiation doses of 106 and 5 x io6 R. The color and odor of the original
solution are characterized in Table 9.
15
-------
Table 9. Color and Odor of Authentic Dye Effluent
Sample
Number Color Odor
1 Red-brown with red-brown precipitate Slight odor
2 Green haze with green precipitate Fish-like odor
3 Blue-green with red-brown precipitate Sour rancid odor
4 Magenta with magenta precipitate Fish-like odor
5 Hazy, beige with beige precipitate Fish-like odor
6 Hazy, grey with grey precipitate Slight fish-like odor
The results of the radiation-induced oxidation are shown in Tables 10
and 11. The odor of the solutions disappeared or nearly disappeared
after a 106 R radiation dose. The light transmission increased as the
radiation dose increased. The COD increased slightly after a 106 R
radiation dose, but after a 5 x io6 R radiation dose the COD of four of
the six samples decreased.
Table 10. The Effect of Irradiation Under 1500-psi
Oxygen on the Light Transmission of Six
Authentic Textile Mill Effluents
Sample No.
1
2
3
4
5
6
Wavelength
(my)
500
700
500
700
390
420
700
500
525
700
500
700
500
700
% Transmission After
No Radiation
65
80
58
76
15
24
55
39
37
70
55
76.5
70
83
106 R 5 x 106 R
74
85
67
81
29
41
64
49
51
73
62.5
82.5
72
83.5
75
89
67
81
47
52
72
57
60
78
62.5
82.5
72
84
16
-------
Table 11. The Effect of Irradiation Under 1500-psi Oxygen
on COD of Six Authentic Textile Mill Effluents
COD (mg/liter) After
Sample No.
1
2
3
4
5
6
No Radiation
445
428
1174
811
706
1280
106 R
622
711
1213
808
1180
1200
5 x 106 R
347
462
860
493
773
822
Azo Dyestuff Manufacturing Waste
An azo dyestuff manufacturing waste mixture was irradiated at doses of
106 and 5 x io6 R under 1500-psi oxygen (without charcoal). The phenolic
odor was reduced by the radiation process, but some odor remained even
after the 5 x io6 R exposure. The brown color of the non-treated solu-
tion was so intense that a 10:1 dilution had to be made before it was
possible to make light transmission measurements. The light trans-
mission increased and the COD removal (Table 12) were insignificant.
No additional experiments were performed to determine the dose required
for significant color and COD removal.
Table 12. The Effect of Radiation Under 1500-psi Oxygen
on COD and Light Transmission on Azo Dyestuff
Manufacturing Waste
Pressure% Transmission at
Oxygen Radiation COD 450 550 650 Dilution
(psi) Dose (R) (mg/liter) my my my Factor
0 No radia- 21,600 0 17 58 10
tion
1500 IO6 20,900 3 22 'ei 10
1500 5 x IO6 20,100 4 27 65 10
17
-------
SECTION VI
PRODUCTS OF RADIOLYTIC OXIDATION OF STANDARD DYES
Analyses of the irradiated dyes were made to identify the products of
the radiation-induced oxidation of the dye. The first dye investigated
was Direct Blue 106, having the chemical formula shown in Fig. 5. The
pure dye was dissolved in water to simplify separation from other con-
stituents of the dye effluent after the irradiation.
-N=
Figure 5. Chemical Formula for Direct Blue 106 Dye
A solution containing 400 mg/liter of dye was prepared for irradiation.
About 150 ml of the solution was irradiated without charcoal under
1500-psi oxygen in the pressure vessel to a total dose of 7.5 x io6 R.
Carbon dioxide was identified in the exhaust gas. The irradiated solu-
tion was evaporated to dryness to recover the solids from solution. The
final solid content of the irradiated solution contained about 75% of the
starting material by weight and was light gray color.
The infrared spectra of the Direct Blue dye prepared for analysis in a
KBr pellet was compared with the spectra of the light gray solids
obtained from the irradiated sample. The spectra were difficult to
interpret due to the large number of groups yielding bands in the 1000-
1200 cm"1 region of the spectra. Secondary amines were observed in both
samples. An aryl peroxide group was observed in the irradiated solid.
The band due to the chlorine appears in both samples. It also appears
that the CO group was responsible for lines found at 1700 cm"1 in the
irradiated sample spectra, indicating oxidation of the benzene ring. The
S0§~ bands at 910 and 1000 cm"1 did not appear in the irradiated sample,
and the band was too wide in the 1000-1200 cm"1 region to determine the
presence of S0[*~; however, the S0^~ group was believed to be present.
19
-------
The second dye investigated was C.I. Acid Black 26A. Its chemical
formula is shown in Fig. 6.
—N=N—
\^ \-S
Na03S
\_/ X
S03Na
Figure 6. Chemical Formula for C.I. Acid Black 26A Dye
A standard solution containing 268 mg/liter was prepared. About 150 ml
of solution was gamma irradiated without charcoal under 1500-psi oxygen
to a total dose of 3 * 107 R. The solution was taken slowly to dryness
to recover the solids for the analysis. Carbon dioxide was identified
in the waste gas. The solid weight yield was approximately the same as
present in the feed solution.
The infrared spectra for the unirradiated and the irradiated dye were
determined from samples prepared in KBr pellets. Some of the S0|~ was
oxidized to give S0£~ identified by peaks at 610, 64-0, and 1130 cm'1.
The S0|~ peaks corresponded to the original dye spectra found at 900 and
980 cm"1. Two broad new peaks at 1440 and 1620 cm"1 were found and are
due to a COO" group produced by oxidation of the CH^ group. The strong
broad peak at 3420 cm"1 was found in both the original and the irradiated
sample and is believed to be due to secondary amine structure. Un-
fortunately, no identification of the —N=N— group was possible because
this group is infrared inactive. This dye compound seems to be quite
stable, but when it is oxidized with gamma radiation and oxygen the
structure is easily altered from highly colored to colorless.
The third dye investigated was C.I. Disperse Blue 3. Its chemical formula
is shown in Fig. 7. A solution containing about 400 mg/liter of dye was
used for this work. One hundred fifty milliliters of solution was irra-
diated under 1500-psi oxygen to a total dose of 3 x io7 R. The exhaust
gas contained carbon dioxide. The solution was evaporated to dryness to
collect solids for infrared spectra analysis. The final solid content of
the irradiated solution was approximately 25% of the original material by
weight.
20
-------
NHCH3
NHCH2-CH2OH
Figure 7. Chemical Formula for C.I. Disperse Blue 3 Dye
The infrared spectra obtained from the non-irradiated blue dye in a
KBr pellet was compared with the infrared spectra from the light-gray-
colored solid recovered from the irradiated sample.1 Solids from the
irradiated sample were shown to have an anthraquinone structure with
some of the secondary amine destroyed or converted to a primary amine.
The two C=0 groups were identified by the CO bands at 1660 and 1710 cm"1,
These CO bands did not appear in the original dye spectra. A proposed
H-bond resonance structure shown in Fig. 8 might help to account for
the bands shown. This resonance did not appear in the original dye.
Figure 8. Radiation Oxidation Product of C.I.
Disperse Blue 3 Dye
21
-------
SECTION VII
ADSORPTION ON CHARCOAL
A major bar to the treatment of process effluents with radiation is
the necessity for irradiating large quantities of water in order that
the small amount of organic present in the effluent can be irradiated.
For optimum efficiency the radiation should be totally absorbed in the
organic fraction of the effluent that is to be destroyed or altered.
One approach to this ideal condition is to separate the organic fraction
from the water fraction onto charcoal that is placed in the irradiator;
this reduces the radiation dose to the water since the residence time of
the water would be limited to that necessary for adsorption of the
organic onto the charcoal. Tests were made to determine whether or not
the decolorization of dye solutions by gamma-radiation-induced oxidation
is increased by the presence of activated charcoal in contact with the
solution during irradiation over that expected by gamma irradiation alone
plus treatment with charcoal separately.
A standard dye solution (Disperse Blue 3, Appendix A) was used for all
tests, and decolorization was determined by light absorbance changes in
the 350-, 450-, and 550-my wavelengths. To cancel the effect of the
physical adsorption of dye from the solution by charcoal, the charcoal
was presaturated with dye by adding 100-ml portions of the solution to
10 g of charcoal until the color reduction of the dye solution was less
than 5% after the final dye solution portion had been exposed to the
charcoal for 16 hr.
This saturated charcoal was then added to 100 ml of the standard dye
solution and irradiated under 1000-psi oxygen. The results of this
experiment are shown in Table 13. In this test, the presence of char-
coal increased the color removal by 72% over that obtained by irradiation
alone.
Table 13.
Carbon
Irr. Dose (R)
Irr. Exposure
Time (min )
Color Intensity
% Color Removed
The Effect of the Presence of Activated
on Color Removal by Gamma Irradiation
Std. Dye
Solution
None
None
1.375
None
100 ml Std. Dye
Solution Irr.
Without Charcoal
10 6
72
0.685
50
100 ml Std. Dye
Solution Irr. With
Saturated Charcoal
106
72
0.187
86
23
-------
The enhanced color removal is believed to be due to the reactivation
of charcoal by radiation-induced oxidation of organic material held
on adsorptive sites on the charcoal; thus, the increase in color
removal is due to the availability of adsorptive sites as this re-
activation occurs.
Experiments were conducted to test this hypothesis. In these tests
10 g of charcoal saturated with dye from the standard solution by the
saturation method described above was repeatedly irradiated to a dose
of 106 R gamma in the presence of 100 ml of new standard dye solution
under 1000-psi oxygen. The results of this experiment are shown in
Table 14.
Table 14-. Color Removal from Dye Solutions Irradiated
in Contact With Dye Saturated Charcoal
SampleSample Description andColor Intensity% Color
Number Treatment (color factor) Removal
1 100 ml std. dye solution on
saturated charcoal
5 x 105 rads of gamma
delivered in 36 min 0.440 83
2 100 ml std. feed on charcoal
used with sample 1
1 x 105 rads of gamma
delivered in 72 min 0.488 81
3 100 ml std. feed on charcoal
used with sample 2
1 x 106 rads of gamma
delivered in 72 min 0.454 83
4 100 ml std. feed on charcoal
used with sample 3
2 x 106 rads of gamma
delivered in 144 min 0.2Q4 92
Based on std. solution color intensity of 2.615 obtained after
106 R radiation under 1000 psi oxygen without charcoal.
In this test the removal of color from the standard dye solution was
nearly constant through four additions of untreated dye solution to the
dye-saturated charcoal. Since the color removal to be expected by ir-
radiation of the standard under 1500-psi oxygen at a dose of 106 R
without charcoal was only 50%, the repeated achievement of 80 to 90%
color removal with saturated charcoal present during gamma irradiation
to a dose of 106 R leads one to conclude that reactivation of the char-
coal is achieved, making new sites available for acceptance of dye from
solution.
24
-------
Tests were made to determine the effect of gamma irradiation with
oxygen present on the reactivation of dye-saturated charcoal. In
these tests 10 g of charcoal saturated with dye solution was ir-
radiated in 100-ml of distilled water under a pressure of 1000-psi
oxygen for 72 min to a total gamma dose of 106 R. "Hie charcoal
was then exposed for 16 hr to another 100-ml of standard dye solu-
tion to determine whether or not its adsorptive capacity for dye from
the standard dye solution had been restored. The results of this test
are shown in Table 15.
Table 15. Reactivation of Charcoal by Gamma
Radiation-Induced Oxidation
Saturated Charcoal
(before irradia-
tion under 1000-
psi oxygen)
Exposed to 100 ml
Std. Dye Solution
Saturated Charcoal
After Irradiation
Under 1000-psi
Oxygen With 100-ml
Distilled Water
(then exposed to
100 ml Std. Dye
Solution)
Wt. of charcoal, g
Radiation exposure
time, min
Radiation dose, R
Charcoal
Treatment
Color reduction of std. dye
solution after 16 hr
shaking with charcoal
10
None
None
5%
10
72
106
91%
Carbon loss during irradiation with oxygen saturated solutions was mea-
sured by weighing. No measurable loss was determined after 160 hr of
irradiation under oxygen at 1500-psi and at a dose rate of 107 R/hr.
The irradiated carbon was examined under an electron microscope (Fig. 9)
in an attempt to determine physical changes in the carbon structure.
Comparison of images of the carbon before and after irradiation with
solutions saturated with oxygen under 1500-psi failed to demonstrate any
apparent structural change.
25
-------
Figure 9. 1900 Magnification of Activated Charcoal
After 500 hr of Irradiation at a Flux of 107
26
-------
SECTION VIII
CONTINUOUS FLOW IRRADIATIONS
Since processing of textile mill effluents for color removal will re-
quire continuous flow treatment, studies were made to determine the
efficiency of a dynamic irradiator in which charcoal is used to adsorb
organic compounds from solution and retain them in the irradiator until
oxidation can occur. These studies were made with dye solutions of
known concentrations and authentic textile mill effluents.
The capacity of granular (6-14- mesh) activated coconut charcoal for a
0.3% solution of Benzyl Fast Yellow GNC dye was established as 1,700 ml
of dye solution for 10 g of charcoal (composition of solution shown in
Appendix A). Tests were made (with this solution as a standard mix)
to determine the decolorization efficiency of a dynamic irradiator con-
sisting of a simple column fabricated from l/2-in.-diam pipe bent in
the form of a U-tube that could be placed in the center of a 60Co array,
as described in the section on equipment. This arrangement provided a
5 * io6 R/hr radiation field. The capacity of the U-shaped column was
35 g of charcoal over a length of approximately 20 in. Tests were made
to determine the capacity of the charcoal under flow conditions of
2 liters/hr without irradiation. After 8 liters of solution was passed
through the column, a sharp break in decolorization occurred (from
approximately 90% color removal to approximately 80%) as determined by
percent light transmission in the 420-my wavelength. The capacity of
the charcoal without radiation for the dye solution was considered to
be 7 liters.
The column was then recharged with 35 g of new charcoal and placed in
the 60Co irradiator. Benzyl Fast Yellow GNC dye solution was passed
through the column at a flow rate of 2.7 liters/hr while 50-psi oxygen
was introduced into the feed to the column. The data obtained from this
run were normalized to 210 g of charcoal in order that a direct com-
parison could be made with a second experiment in which this larger
quantity of charcoal was used. Table 16 shows the data obtained from
this experiment.
Under the conditions of this experiment, only a small gain in de-
colorization efficiency over charcoal alone was observed, and it was
assumed that the flow rate was too great to provide an equilibrium
condition of dye adsorption on the charcoal versus dye destruction by
radiation-induced oxidation of dye adsorbed on the column.
27
-------
Table 16. Decolorization Efficiency of Charcoal
and Gamma Radiation as a Function of
Oxygen Pressure
Treatment
5 x 1Q6 R/hr field
50-psi oxygen
5 x 106 R/hr field
1500-psi oxygen
Weight charcoal, g
Flow rate, liter s/hr
Capacity of charcoal,
liters of dye solution
% transmission at 420 my
of feed solution
35
2.7
7
10
210
2.0
42
10
% transmission at 4-20
of solution after
(throughput of liters
shown)
88 after 42 liters'
82 after 48 liters'
72 after 52 liters2
97 after 105 liters
when experiment
was discontinued
formalized to 210 g charcoal.
A second experiment was performed using the same dye solution in a pres-
sure irradiator consisting of a pressure vessel in which 210 g of char-
coal was placed. The pressure of the oxygen feed was increased to 1,500
psi introduced into the feed solution, passing through the irradiator at
a rate of 2 liters/hr. Table 16 shows the results of this experiment.
Under these conditions, the decolorization efficiency was 97%, and equi-
librium for the destruction of dye on the charcoal with dye in feed to
the charcoal was achieved.
An irradiation chamber consisting of a 20-ft-long, l/8-in.-diam stain-
less steel pipe formed into a 4-in.-diam coil and loaded with 150 g of
6-14 mesh activated coconut charcoal was prepared and used to irradiate
a solution containing 0.09 g/liter of Benzyl Cyanine 6B dye. The normal
capacity of the charcoal under conditions of no irradiation was deter-
mined by flowing the standard Benzyl Cyanine 6B dye solution at a rate
of 2 liters/hr through the column. The breakthrough point without ir-
radiation or oxygen present was considered to be 25 liters of this solu-
tion per 150 g of charcoal measured by an end point of 82% light trans-
mission at the 550-my wavelength (maximum transmission wavelength)
compared with a 91% transmission constant obtained over a 24-liter total
flow.
Data from this experiment were used to make a comparison of the de-
colorization efficiency of gamma radiation only versus gamma radiation
plus oxygen at 1,500 psi. The results are shown in Table 17.
28
-------
Table 17. Comparison of Decolorization Efficiency of
Gamma Radiation Only Compared With Gamma Irradiation
Plus Oxygen at 1,500 psi
Treatment
107-R/hr field
No Oxygen
107-R/hr field
1500-psi Oxygen
Weight of charcoal, g
Flow rate, liters/hr
Capacity charcoal, liters,
without irradiation at a
flow rate of 2 liters/hr
% light transmission of
feet at 550 my
% light transmission at
550 my after throughput
shown, liters
COD feed, mg/liter
COD, mg/liter, after
throughput shown
150
2.0
25
2.5
91 after 24 liters
82 after 27 liters
59
16.8 after 24 liters
19.0 after 27 liters
150
2.0
25
2.5
96.5 after 108 liters
59
19.3 after 58 liters
13.0 after 108 liters
In this experiment the decolorization efficiency was 96.5% even after
108 liters of solution was passed through the column; the experiment was
discontinued at this point. The COD of the solution was decreased from
59 to 19 at the point where a color breakthrough was considered to have
occurred in the solution being irradiated without oxygen. It is not
clear why the COD was 19.3 mg/liter after 58 liters and 15 mg/liter after
108 liters. A plausible explanation is variation in analysis.
In this experiment the oxygen supply to the solution being irradiated
was stopped to determine the effect of oxygen on the decolorization
efficiency. When the oxygen flow was interruped, the transmission in
the 550-my wavelength decreased from >95% to <80% after one column volume
of flow. Decolorization was restored when the oxygen flow was restored.
Direct Blue 106 dye solution (composition in Appendix A) was processed
through the 20-ft-long, l/8-in.-diam irradiator containing 130 g of
charcoal. The effluent was sampled only after equilibrium was reached,
as determined visually for various flow rates. Table 18 shows the results
of this experiment. The method for measuring color was changed from one
of transmission to absorbance since several absorbance wavelengths could
be summed to provide a color factor based upon a wider color range.
29
-------
Table 18. The Effect of Flow Rate on Color Removal of
Direct Blue 106 Dye Solution in a Continuous Flow
System Under 1500-psi Oxygen in a 107 R/hr Gamma Flux
0
Flow Rate
(liter /hr)
(control std.
solution)
1.25
0.50
0.35
Dilution
Factor
4
3
3
3
Absorbances
480
0.
0.
0.
0.
my
13
08
08
07
580
0.
0.
0.
0.
my
61
11
08
07
at
680
0.
0.
0.
0.
my
21
80
06
04
Color
Factor
3.
0.
0.
0.
80
81
66
54
% Color
Removal
0
79
83
86
A larger dynamic irradiator was fabricated from a 30-ft-long,
l-l/2-in.-diam pipe. The pipe was coiled to form a 20-in.-diam spiral
which was placed around a °°Co source array. The average gamma radia-
tion flux in the irradiator coil was determined to be 5 x 105 R/hr by
Fricke solution dosimetry. This column was loaded with 11 Ib of granular
activated coconut charcoal, and the charcoal fines were washed from the
column. The maximum operating pressure for this system was 500 psi.
Table 19. COD and Color Removal From Direct Blue 106 Dye
Solution by Radiation-Induced Oxidation in a 5 x io5 R/hr
Radiation Flux Under 500-psi Oxygen
Amt . Through
Sample Irradiator
No. (gal)
Original
4
7
11
15
18
21
24
29
32
37
42
47
52
58R
62R
(control)
7
8.5
12.5
16.5
18
21
22.5
25.75
28
31.25
34.5
37.75
41
48.75
53.75
Time From
Start of
Run (hr)
_
2
2.5
4.5
6.5
8
9.5
11
13.5
15
17.5
20
22.5
25
28.5
30.5
Flow
Rate
(gal/hr)
_
3
3
2
2
1
2
1.5
1.5
1.5
1.5
1.5
1.5
1.5
4
3
Color
Factor
3.80
0.137
0.055
0.132
0.153
0.110
0.154
0.141
0.218
0.318
0.274
0.245
0.245
0.293
0.459
0.145
% Color COD
Removal ( mg/ lit er )
_
96.4
98.7
96.5
96.0
97.1
96.0
93.3
94.3
91.5
92.8
93.5
93.5
92.3
88.0
96.2
182
12b
ND
ND
12
12
15
14
ND
ND
ND
ND
ND
ND
ND
ND
Calculated from light absorbance measurements over the 480-, 580-,
and 680-my wavelengths.
Not determined.
30
-------
Fifty-five gallons of Direct Blue 106 dye solution was prepared for
tests with this irradiator. The normal capacity of the charcoal with-
out irradiation for dye from this solution was determined to be equi-
valent to 32 gal of solution per 11 Ib of charcoal. The solution was
passed through the irradiator at 500-psi oxygen pressure with varia-
tions in the flow rate from 1 to 4 gal/hr. COD determinations were
made on six different samples, but they were discontinued after the
COD values appeared to have reached an equilibrium. Table 19 shows
the results of this experiment.
Authentic Textile Mill Effluents
Four samples of authentic textile mill effluents (^1 gal each) were
provided by the American Association of Textile Chemists and Colorists
(AATCC) members. These samples were processed through a small pres-
sure vessel equipped with an inlet and outlet for dynamic operation.
Approximately 3 liters of each sample was pumped through the pressure
irradiator without charcoal at 1.6 liters/hr under 1500 psi; the
radiation dose to the solution at this flow rate was 106 R. The
results are shown in Table 20.
Table 20. COD and Color Changes in Authentic Textile
Mill Effluent at a Dose of 106 R Gamma Under
1500-psi Oxygen
COD (mg/liter)
Sample No.
1
2
3
it-
Original
445
428
1174
811
Treated
742
631
1220
811
Original
65
80
58
76
15
24
55
39
37
70
% Transmission
Treated
60
76
59
74
17
30
59
43
44
72
Wavelength (my)
500
700
500
700
390
420
700
500
525
700
Samples 3 and 4, the most highly colored of the as-received effluent,
were slightly decolorized by the treatment. The increase in COD in all
samples following treatment has been observed in other irradiated samples
and may be due to a. partial decomposition of refractory materials that do
not contribute to COD prior to irradiation.
31
-------
A 40-gal batch of total plant effluent from a silk screen print
textile mill and a 55-gal batch of total plant effluent from a
weaving, dyeing, and finishing plant were supplied by the AATCC.
The effluents were typical for silk screen print mills and for
synthetic fabric mills.
Both of the authentic effluents were collected over a 1-hr period from
a process stream that feeds themmill effluent treatment plant. The
silk screen plant effluent contained disperse dye in the form of
printing inks dispersed in organic solvents such as varsol, pine oil,
terpentine, and binder resins to form an emulsion. The dyeing and
finishing plant effluent consisted of detergents, disperse dyes and
dye additives. Both plants incorporated their sanitary sewage into
the feed. One plant produces a total of 3.5 x io6 gal/day, with
approximately 4-000 people contributing to the sanitary sewage input.
Both effluents were filtered through a sintered polyethylene filter to
remove large particulates prior to treatment in the irradiator; however,
all solid materials were not removed. These effluents were processed
in the l-l/2-in.-diam column, charcoal-loaded irradiator. Both ef-
fluents were quite turbid when introduced into the irradiator. When the
silk screen mill effluent was treated with charcoal alone, only 51% of
the color was removed by a combination of charcoal adsorption and
Millipore filtration, based upon light absorbance as measured in the
350-, 450-, and 550-mu wavelengths. After the effluent was processed
through the irradiator under 500-psi oxygen, 82% color removal was
achieved. Results are shown in Table 21.
Table 21. Color and COD Removal From Silk Screen Textile Plant
Effluent by Gamma Radiation at a Dose Rate of 5 x 105 R/hr
With Charcoal and 500-psi Oxygen
AmountTime
Through From Flow
Irradiator Start of Rate Color % Color COD
Sample No. (gal) Run (hr) (gal/hr) Factor Removal (mg/liter)
Feed: Filtered
through-
sintered
polyethylene
10
18
22
25
30
37
10
18
23
28
33
38
5.5
10.5
12.5
14.5
17.0
20.0
2
2
2
2
2
2
1.555
0.159
0.489
0.300
0.174
0.332
0.188
90
69
81
89
79
88
1065
262
293a
aCOD after removal of solids with clay was determined to be 92
mg/liter.
32
-------
The color intensity determined by light absorbance is sensitive to the
presence of any solids present in the sample. These solids are not
removed when the effluent is passed through 0.80-y Millipore filter
membranes. The solids material is white and, while it does not con-
tribute to color as such, it does disperse and attenuate light, as
shown in Table 22. Also the COD was reduced from 293 to 92 mg/liter
after solids removal.
Table 22. The Effect on Light Absorbance of Solids Removal
Sample
No.
22
25
30
37
Color Factor
% Color
Before Removal Removal
of Solids
0.300
0.174
0.332
0.188
from Original
81
89
79
88
Color Factor % Color
After Solids Removal
Removal
0.089
0.059
0.029
0.032
from Original
99.4
99.6
99.9
99.8
It is apparent from these experiments that color due to dissolved material
is effectively removed from the effluent by irradiation in the presence
of charcoal under 500-psi oxygen. Also, the solids that persist through
the irradiation process can be easily removed by the addition of a floc-
culating agent producing a marked decrease in the light attenuation used
in the measurement of color.
The charcoal column does not remove the solids. Samples that had been
processed through the irradiator to a 82% color removal (includes solids)
were not further depreciated in color value by exposure to 20 hr to an
excess of new granular charcoal.
The silk screen textile effluent is especially difficult to treat due
to the disperse dyes present and the organic materials used in the
printing inks. The effluent as received had a very strong solvent odor —
varsol/pine oil combination — which was completely removed in the radia-
tion processing.
Effluent from the dyeing and finishing plant was processed in the same
way as the silk screen plant effluent. The feed solution appeared pink
in color and contained small solids that could not be removed by filtra-
tion through a polyethylene sintered filter (filter pore size is greater
than 500 y). Data from this run are shown in Table 23.
The problem of solids in the product was very severe with this effluent;
however, the solids in the product coagulated within 6 hr after removal
from the irradiator from samples 1 through 14 and less slowly thereafter
as the run progressed. This can be seen in the effect on the color
33
-------
factor shown in Table 23. As was observed with the silk screen effluent,
when the solids in the product were removed by the addition of a flocc-
lating agent, the color removal (absorbance) reached 99% (Table 24).
Table 23. Dyeing and Finishing Plant Effluent Color and COD
Reduction by Gamma Radiation at a Dose Rate of
5 * 105 R/hr with Granular Charcoal and 500-psi Oxygen
Sample
No.
Feed
4
9
14
19
28
35
43Rd
Amount
Through
Irradiator
(gal)
-
3
10.5
15.5
18.0
31.5
42.0
54.0
Time
From
Start of
Run (hr)
-
1
3
6
8.5
13.0
16.5
20.5
Flow
Rate
(gal/hr)
-
3
3
3
1
3
3
3
Color
Factor
2.255
0.018
0.049
0.145
0.210
0.253
0.185
0.575
% Color
Removal
from
Original
-
99.5
98.0
95.6
91.0
88.8
92.0
74.5
COD
(mg/liter)
1894^
1710b
46
116
123
200
NDC
154
160
, Before Millipore filtration.
After Millipore filtration.
,Not determined.
Sample treated with chlorine prior to irradiation.
Table 24. Dyeing and Finishing Plant Effluent. The Effect on
Color Absorbance Factor of Removal of Solids From Sample
Sample
No.
28
30
39
47R
Color
Before
of
0.
0.
0.
0.
Intensity
Removal
Solids
253
365
488
550
% Color
Removal
from
Original
88.8
84.0
78.6
76
Color
After
of
0.
0.
0.
0.
Intensity
Removal
Solids
077
017
018
031
% Color
Removal
from
Original
99.7
99.9
99.9
99.8
COD
77
77
NDa
58
Not determined.
The dyeing and finishing plant effluent was examined for coliform
bacteria; the results are shown in Table 25.
34
-------
Table 25. Reduction in Bacteria Count by Irradiation
Processes on Dyeing and Finishing Plant Effluent
Sample
No.
Feed
1
2
Flow Rate
(gal/hr)
-
3
2
Colonies Coliform Bacterial
per 100-ml Sample
1,000
90
22
Two additional 55-gal batches of authentic textile mill effluent were
processed through the 500-psi charcoal irradiator. One effluent con-
sisted of detergent, dyes, and dye additives, along with some sanitary
sewage input and was representative of the mill effluent as it was
received by the mill's activated sludge treatment plant. The other was
the product from the activated sludge treatment plant. Both effluents
were filtered through a sintered polyethylene filter prior to the ir-
radiation treatment to remove the large particles from the waste. Both
effluents were turbid after the filtrations.
The color of effluent samples taken during the irradiation was deter-
mined by measuring the light absorbances at 350-, 450-, and 550-my
wavelengths after the samples were filtered through a 0.80-y Millipore
membrane filter. Color factors were calculated from these results.
Data obtained from these runs are shown in Table 26.
As the run progressed, the quantity of solid material in the product
increased. Since these solids contribute to the color as measured by
adsorbance, a flocculating agent was added to the effluent sample to
remove them, and the sample was filtered through a 0.80-y Millipore
membrane. The color factor and percent color removal from samples after
this step are shown in Table 26. After 18 gallons had been treated,
the color removal was constant at 88 to 89%.
About 12 gallons of the treated dye effluent was recycled for a second
pass through the irradiator. Before this second pass treatment, 200 ppm
of chlorine was added. The second irradiation treatment before solids
removal lowered the color intensity of the effluent by about 35%, and
after solids removal by 86-90%. The addition of 200 ppm of chlorine did
not appreciably aid in color removal.
The activated sludge plant product was prepared for irradiation by
treating with agricultural lime (ground limestone) to raise the pH of
the solution from 6.7 to approximately 7.5 and was then refiltered to
remove large particles'. Thirteen pounds of new (10-30 mesh) coconut
charcoal was loaded into the pressure vessel for this treatment. This
35
-------
Table 26. Color Removal From Dyeing and Finishing Plant
Effluent by Gamma Radiation at a 5 x io5 R/hr Dose Rate
With Granular Coconut Charcoal and 500-psi Oxygen
Sample No.
Original
4
8
12
15
18
21
25
29
31
35
40
43
Recycle Feed
51R
55R
Amount
Through
Irradiator
(gal)
4.5
8.5
11.5
13.0
17.5
22
28
34
36
40
45
48
200 ppm C12
8
12
Flow
Rate
(gal/hr)
3
2
1.5
1.0
3
3
3
3
2
2
2
2
Before Solids
Removal
Color
Factor
3.030
0.336
0.360
0.296
0.264
0.595
0.675
0.864
1.381
1.440
1.600
1.905
1.955
% Color
Removal
88.9
88.1
90.2
91.3
80.4
77.7
71.5
54.4
52.5
47.2
37.3
35.5
After Solids
Removal
Color
Factor
\
0.270
NDD
0.243
0.241
0.329
0.336
0.324
0.363
0.328
0.326
0.358
0.361
% Color
Removal
91>1b
mr
92.0
92.0
89.1
88.9
89.3
88.0
89.2
89.3
88.2
88.1
added before second pass through irradiator
2
2
0.881
0.821
33.5
38.1
0.189
0.138
85.7
89.6
Sample filtered through a 0.80-y Millipore membrane filter before
absorbance measurements.
Not determined.
change in charcoal mesh size was made in an attempt to increase the
adsorption rate of dye onto the charcoal which would permit a greater
flow rate through the irradiator. The color absorbances at 350-, 450-,
and 550-my wavelengths were measured after filtration through an 0.80-y
Millipore membrane filter and were used to calculate the color factor
shown in Table 27. There was a continuous increase in the color factor
before solids removal from sample 1 through sample 29 (during which
43.5 gallons of effluent was processed). This was due to an increased
quantity of solids in the sample. After 36 gallons of effluent had been
processed to coagulate these solids, 200 ppm of potassium aluminum
sulfate was added to the activated sludge plant product in the column
feed reservoir. Another 200 ppm addition was made after 43 gallons had
been processed. Sample 31 represents a total of 400 ppm addition of
potassium aluminum sulfate and has lower color factor than the four
preceding samples reported.
The column effluent samples contained a greater quantity of solids as
the run progressed. These solids, which contributed to the measured color
intensity, were removed by the addition of a flocculating agent before the
Millipore filtration. The color removal and color intensity after the
36
-------
solids removal are also shown in Table 27. The addition of the first
200 ppm of AlK(SOit)2'12H20 increased the color removal from 81 to 87%.
The 400 ppm of AlK(SOit)2'12H20 further increased the color removal to
the 92-95% range. Hence, the AlK(SOlt)2-12H20 addition to the effluent
before the treatment enhanced the color removal.
Table 27. Color Removal From the Product of an Activated
Sludge Treatment Plant by Gamma Radiation (5 x 105 R/hr)
at 500-psi Oxygen With Granular Coconut Charcoal
Sample
No.
Original
6
10
14
18
22
26a
29
31b
Amount
Through
Irradiator
(gal)
9
15
21
27
33
39
43.5
46.5
Flow
Rate
(gal/hr)
3
3
3
3
3
3
3
3
Before Solids
Removal
Color
Factor
1.975
0.512
0.477
0.731
0.990
1.080
1.047
1.084
0.815
% Color
Removal
74.1
75.8
63.0
49.9
45.3
47.0
40.1
58.7
After Solids
Removal
Color
Factor
0.402
0.388
0.312
0.388
0.365
0.248
0.157
0.108
% Color
Removal
79.6
80.3
84.1
80.4
81.5
87.4
92.1
94.5
^200 ppm
200 ppm more AlK(SOit)2-12H20,
37
-------
SECTION IX
ACKNOWLEDGMENTS
The authors gratefully acknowledge the guidance a ance of the
AATCC Technical Committee RA-58, Environmental Sc.^^^ .v-ehnology,
in this study. Mr. George J. Mandikos, Technical Secretary, provided
liaison between the various participants of the study. Other individual
members provided effluent samples and valuable consultation, and we are
particularly indebted to Mr. T. A. Alspaugh, Cone Mills Corp.; J. D.
Lesslie, Spring Mills, Inc.; Clarke A. Rodman, Fram Corporation;
Joseph M. Eaddy, Jr., J. P. Stevens & Co., Inc.; H. E. Williams,
Fielderest Mills, Inc.; and J. S. Ameen, Burlington Industries, Inc.
We acknowledge Dr. David W. Hill and Dr. Wayne Garrison of the EPA
Office of Research and Monitoring, Southeast Environmental Research
Laboratory for valuable counsel and initial program planning.
Development of the mathematical model to describe activated carbon
adsorption and in situ regeneration was provided by K. H. Lin, Oak
Ridge National Laboratory Isotopes Division.
The experimental program was aided by A. F. Rupp and J. H. Gillette,
Oak Ridge National Laboratory Isotopes Division, who provided useful
suggestions and administrative help during the course of this study.
39
-------
SECTION X
REFERENCES
1. F. N. Case, D. L. Kau, D. E. Smiley, Radiation Induced High Pres-
sure Oxidation of Process Effluents, Use of Nuclear Techniques
in the Measurement and Control of Environmental Pollution, IAEA
Vienna, 1971, IAEA-SM-142a/50.
2. Clarke A. Rodman, Removal of Color From Textile Wastes, Rhode
Island Section of the American Association of Textile Chemists
and Colorists, 1971.
3. American Public Health Associates Inc., Standard Method for the
Examination of Water Waste. 12 ed., 1965, pp. 510-14.
4. Robert T. Conley, Infrared Spectroscopy, Allyn and Bacon, Inc.,
Boston, (1966), pp. 50-53.
5. "Removal of Color fromTextile DyeWastes," Textile Chemist
and Colorist 3(11), pp. 239/45-247/53 (1971).
6. U.S. Patent 3,537,966, Radiation Treatment of Mine Waste Waters,
USAEC Assignee.
-------
SECTION XI
GLOSSARY
Radiation-induced oxidation - Oxidation processes initiated by gamma
radiation usually at room temperatures.
Authentic effluents - Effluents produced by a process during routine
production operations.
In situ carbon reactivation - Reactivation of activated charcoal by
destruction of adsorbed material at the same time the charcoal is
exposed to adsorbable materials from a solution passing through the
column.
Batch irradiator - A vessel placed in a gamma radiation field in which
single batches of a material may be irradiated.
Dynamic irradiator - A vessel placed in a gamma field equipped with
flow through capability in which materials may be continuously flowed
and exposed to gamma radiation.
Rad (R) - A measure of radiation adsorbed and equals 100 ergs/g.
Radiation dose - A general term denoting the quantity of radiation or
energy adsorbed in a specified mass.
Dose rate - The adsorbed dose per unit of time.
-------
SECTION XII
APPENDICES
Page
A. Composition of Acid, Chrome Dye Solutions 46
B. Composition of Four Standard Dye Solutions 47
C. Calculation of Radiation Cost 51
Table 1: Variation in Irradiation Cost as a Function of
Organic Loading on Charcoal and Dose Rate to a
Total Dose of 106 R 53
D. Mathematical Model to Describe Effluent Treatment by
Irradiation of Dye Effluent on a Fixed Charcoal Bed ... 54.
Figure 1: Packed Charcoal Bed 54
Figure 2: Differential Volume Element in Charcoal Bed . . 55
-------
APPENDIX A
Composition of Acid, Chrome Dye Solutions
Benzyl Fast Yellow GNC
0.3% dye
10% Glaubers salt
2% of 28% acetic acid
Benzyl Blue GL
0.05% dye
10% Glaubers salt
2% of^28% acetic acid
Benzyl Cyanine 6B
Q.18% dye
10% Glaubers salt
2% of 28% acetic acid
Neolan Yellow BG
0.3% dye
4% of concentrated sulfuric acid
Chrome Fast Flavine A
0.4% dye
5% Glaubers salt
3% of 28% acetic acid
-------
APPENDIX B
Composition of Four Standard Dye Solutions
C.I. DIRECT BLUE 106
Preparation:
1. Dissolve dyestuff in one liter of boiling water.
2. Add dye solution to remainder of the warm water.
3. Add in the following sequence:
Intravon G, TSPP, sodium sulfate
For 1 Gallon
Dyestuff, g 0.50
Tetra sodium pyro phosphate, g 5.04
Sodium sulfate, g 0.25
Intravon G (wetting agent), g 0.50
Warm tap water, 5 gal 1
3.79 liters
NOTE 1:
Based upon a 2000+ pound solution (approximately 267 gallons)
100 pounds of cloth treatment theoretical batch. Ref.
Intracolor Ex 5.0.1 (1/1/68). Cloth ratio 20/1.
-------
C.I. ACID BLACK 26A
Preparation:
1. Dissolve dyestuff in one liter of boiling water.
2. Add dye solution and other chemicals to the remainder
of the warm water (not over 120°F). In making the
one-gallon solution, be sure to cool the dye solution
before adding other ingredients.
3. Adjust pH to 5.5 - 6.0 with acetic acid.
For 1 Gallon
Dyestuff, g 0.34
Sodium sulfate, g 21. Oil-
Ammonium sulfate, g 2.10
Intravon G (alkylaryl sulfate wetting agent, g 0.084
Warm tap water, gal 1
3.79 liters
Acetic acid (50%) To adjust final pH to 5.5 - 6.0
NOTE 1:
Based upon a 2000+ pound solution (approximately 267 gallons)
100 pounds of cloth treatment theoretical bath. Ref.
Intracolor Ex 6.2.1 (3/3/69). Dye bath. Cloth ratio 40/1.
48
-------
DISPERSE BLUE 3
Preparation:
1. Add Carolid to warm water bath and adjust pH to 6.5 with
monosodium phosphate; then add Intravon G.
2. Disperse dyestuff in one liter of water at 110-120°F. In
making the one-gallon formulation, be sure to use one liter
of the amount of warm water specified because of the effect
of reduced volume on the colorization.
3. Add dispersed dye solution to bath.
For 1 Gallon
Warm tap water, gal 1
3.79 liters
Carolid (ortho phenylphenol; Tanatex Co.), g 1.51
Monosodium phosphate To adjust bath to pH of 6.5
Dyestuff, g 1.51
Intravon G (wetting agent), g 0.084-
NOTE 1:
Based upon a 2000+ pound solution (approximately 267 gallons)
Theoretical dye application for 100 pounds cloth
Ref: Intracolor Ex-2.11.1 (1/1/68) Cloth ratio
-------
REACTIVE RED 3
Prepare a concentrate of this dye as follows:
Lantex
Dyestuff
Sodium bicarbonate
Urea
Ludigol
Tap water
10 parts
10 parts
5 parts
18 parts
2 parts
155 parts
by wt,
by wt,
by wt,
by wt,
by wt,
by wt,
Dilute this dye concentrate as follows:
Concentrate, ml
Warm tap water, gal
For 1 Gallon
4.7
1
3.79 liters
NOTE 1:
Formulation by William Turner of Cranston Print Works.
50
-------
APPENDIX C
Calculation of Radiation Cost
Gamma radiation is a major cost element for this process. Since
pilot plant design was not a part of this study, a determination of
radiation cost only was made. Other costs such as pretreatment for
solids removal, storage of effluents, and plant capital equipment
costs were not made but are expected to be approximately the same as
for conventional processes. Cobalt-60 costs to yield the required
gamma radiation were estimated.
The tank volume provides 10 min of solution/charcoal contact time
at a flow rate of 5 x io5 gal/day. The diameter was selected for
maximum utilization efficiency of 60Co gamma.
Assumptions Charcoal adsorption tank size 5 ft diam
23.6 ft high
Tank volume, ml 1.315 x io7
Weight of charcoal in tank 6.58 x io6 g
Percent by weight of organic adsorbed on charcoal at equilibrium
(equilibrium is defined as the rate of organic adsorption onto charcoal
being equal to the rate of removal by oxidation and requiring a 106 R
gamma radiation dose to the adsorbed organic) is 2.88%. The time chosen
for this equilibrium to occur is 24 hr.
Organic content of feed effluent 100 ppm
Effluent flow rate 5 x io5 gal/day
Cobalt-60 required
To deliver 106 R dose to organic in 24 hr, the dose rate to the organic
i fl^ P
will be . 2^ = 4.17 x io4 R/hr.
The energy of the 60Co gamma is 1.17 and 1.33 MeV or 2.50 MeV per dis-
integration.
The yield per curie of 60Co in ergs/hr is:
3.7 x 10*0 dis/sec x 2.5 Mev/dis x 3600 sec/hr _ 8 , . .
6<24 x 105 Mev/erg 5.33 x 10 erg/hr/Ci
51
-------
The density of the media in which the organic is irradiated (charcoal
plus water) is approximately 1 g/ml (determined experimentally); therefore,
1.315 x io7 g x 4.17 x io4 R/hr x 100 erg/g/R = 5.48 x 1Q13 erg/hr
(total grams in (dose rate)
tank to be ir-
radiated)
(required total
dose)
Curie cobalt-60 =
us x ml3
' ° "
v
D.OO * _LUO X U.
1-283 x io5 Ci of 60Co required
= fo* delivery of a IO6 R dose in
i_ _i_ -i o • • j • j_
24 hr to load in irradiator
Required total dose
Dose/Ci x efficiency
of energy utilization
Summary
Flow:
Quantity of Charcoal:
Organic loading on charcoal
Curies of 60Co
Cost of 60Co ($0.40/Ci)
Cost of 60Co/yr (T1/2 = 5 yr)
Cost of 60Co/day
Cost of 60Co/1000 gal of throughput
5 x 10 5 gal/ day or 7470 gal/min
463 ft3, 6^| ^ 1°bg = 14,500 Ib
2.88%
128,300
$51,320
$6,620
$18.18
3.6$
52
-------
Table 1. Variation in Irradiation Cost as a Function of
Organic Loading on Charcoal and Dose Rate to a
Total Dose of 106 R
Organic
loading,
(%) 2.88 5.76 8 10 20
Exposure
time
available
for organic
oxidation,
(hr) 24 48 66.7 83.3 166.5
Required
dose
rate
(erg/hr) 5.48 x io13 2.74 x io13 1.97 x io13 1.58 x io13 0.79 x io13
Curies of
6°Co
Cost of
6°Co
C$0.40/
Ci)
Cost of
60Co/yr
(Tl/2 -
5 yr)
Cost of
60Co/
1000 gal
12.83 x io4 6.415 x IO4 4.62 x IO4 3.70 x IO4 1.85 x IO4
$51,320 $25,660 $18,480 $14,800 $7,400
$6,620 $3,310 $2,380 $1,909 $955
3.6$ 1.8$ 1.3$ 1.0$ 0.5$
53
-------
APPENDIX D
Mathematical Model to Describe Effluent Treatment by Irradiation of
Dye Effluent on a Fixed Charcoal Bed
A packed charcoal bed (Fig. 1) is initially saturated with radiation-
sensitive colored organic contaminants "A" from untreated plant ef-
fluents. The contaminants "A" under gamma irradiation in the presence
of oxygen are either degraded or converted to colorless compounds "B".
Under steady-state operation, the untreated plant effluents containing
C.. (mole/volume) of "A" are fed through the bed continuously at a rate
of v (volume/time). In the charcoal bed, the colorless compounds "B"
are preferentially eluted by the solution while the contaminants "A"
are adsorbed onto the bed. The treated solution being discharged at v
from the system contains C (mole/volume) of "A".
The process scheme in the packed bed system is:
" j
ads
(In Charcoal Bed)
CO]
B
Desorption
B**
Colorless Compds. Gamma Rays ads (In Charcoal Bed)
B
(In Solution)
*Colored Contaminants (In Solution)
**Colorless Compounds (In Solution)
ORNL-DWG 72-2141
PACKED CHARCOAL BED-
GAMMA SOURCE
UNTREATED
PLANT -
EFFLUENTS
-«-|
-------
Development of Mathematical Model
Mass Transport
Mass Transport
in Charcoal Bed
,mole v
time
A
MA
Mole
dV
1
(Unit Bed Mass) Timel
C. + dC.
A A
MA + dMA
Figure 2. Differential Volume Element in Charcoal Bed
Assumptions :
1. Plug flow condition prevails in the packed charcoal bed system,
i.e., there is no composition gradient in the radial direction,
and the composition varies only in the longitudinal direction.
2. The gamma radiation sources are arranged in such a way that the
dose rate is constant and uniform throughout the charcoal bed.
3. A steady-state isothermal operation is in progress.
4. Physical properties (solution density, bulk density of charcoal
bed, viscosity, etc.) of the system remain constant.
Consider a differential volume element dV in the bed. Transport of
organic contaminants "A" takes place in two separate streams, one in
solution occupying the void volume and the other in the charcoal bed.
Material balance on "A" in the solution stream is:
= 0
(1)
Material balance on "A" in the charcoal bed is:
=0 (2)
where ,
55
-------
(-r^) = rate of disappearance of "A" by radiolysis in solutions,
moles/ (volume ) (time )
(-r.) = rate of disappearance of "A" from solution by adsorption
onto charcoal bed, moles/ (wt. of bed) (time)
(-r.) = rate of disappearance of "A" by radiolysis in charcoal bed,
moles/ (wt. of bed) (time)
(-r ) = rate of disappearance of "A" from charcoal bed due to
— desorption from charcoal bed by solution, moles/ (wt. of bed)
(time)
e = porosity of charcoal bed
p, = bulk density of charcoal bed.
From Eqs. (l) and (2), neglecting the second-order differential:
-vdCA = C(-rA)edV + (-rA)p
(3)
Integrating between the inlet and discharge ends of the charcoal bed:
dC
V CA .
(-rA)
,,,
or
eV
v = e
•^ A •
Ax
(-rA)
(5)
where t is the residence time of the untreated plant effluent solutions
in the charcoal bed. Integration of the right-hand side of Eq. (5) can
be completed only after the functional forms of (-r') and (-*1.) have been
established.
For the proposed process to be economically attractive, the rate of
radiolysis in the charcoal bed (-?,>) must be considerably greater than
that in the solution (-r^). That is, (-rA) » (-*A). This probably woul
be the case since the concentration of "A" in the charcoal bed would be
much higher than that in the solution, provided that a sufficient amount
of oxygen is available for the radiolysis reaction to proceed. If (-^A)
is small enough to be neglected, Eq. (5) becomes:
56
-------
(6)
Thus, Eq. (5) or (6) with a given value of C . and known functional
Al
forms of C-rO and (-r.) would describe how the contaminant concentra-
tion of the solution discharged from the charcoal bed, C.,., varies with
1 Ai
the residence time t.
Experimental Data to be Acquired
To confirm the mathematical model developed above, the experimental data
listed below are required.
1. Bulk Density (p, ) and Porosity (e) of charcoal bed:
These two properties are related to the true density of charcoal
being used (p) by p^ = (1 - e)p.
2. Radiolysis Rate Expressions (-r^) and (-r ):
A A
The bulk density and the porosity of charcoal bed are known.
The radiolysis rates are presumably functions of several parameters
as in:
dCA
dM
and (_r) = -_=f2(1, M,M) (8)
where t is time, 1 represents the gamma radiation dose rate, and C and
M are the oxygen concentrations in the solution and in the charcoal bed,
respectively. Both equilibrium values of C and M are related to the
partial pressure of oxygen in the fixed charcoal bed system.
One of the possible functional forms for Eqs. (7) and (8) may be a power
function of the type:
57
-------
c-r;> = k'isc*cm (9)
and (-r.) = klbM*MC (10)
A A O
where the rate constants k' and k, and exponential constants s, n, m,
b, a, c can be determined by the batch type of experiments. Fre-
quently, it may be more convenient to use the partial pressure of
oxygen (P ) instead of concentrations, and Eq. (9) and (10) are
rewritten as:
If the gamma irradiation source can be designed such that 1 is kept
constant and uniform throughout, two dependent variables (concentration
of "A" and P ) would be left in each of the above two equations. Further-
more, if P could be fixed at a value that is technically and economically
most desirable, only one variable (concentration of "A", C., or M ) remains.
Thus, Eqs. (11) and (12) can be simplified to give Eqs. (13) and (14) to
yield functional forms for (-r') and (-r.).
A A
Although this model was proposed for a dye mixture, it could be most
easily checked for a single dye solution. A sample of the dye solution
could be irradiated in equilibrium with charcoal under the selected
pressure and selected radiation dose. These irradiations could be made
over a suitable range of dye concentrations to get the necessary data to
determine the constants in Eqs. (13) and (14). The solution with the
charcoal could be agitated during the period of time of irradiation with
a mechanical shaker. The C . and CA_ could be read directly on the
Al AJT
spectrophotometer as absorbance and the constants of Eq. (13) could be
58
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determined. The determination of M is more difficult. Since the
Ax
ratio of C.^/M _ should be constant for each value of C.,. when agitated
in the same manner and for the same period of time, it should be possible
to calculate the M.-. from the C. _. The C.^/M.,: could be determined for
the range of C... as needed in an experiment without radiation and without
oxygen agitating the mixture for the same length of time. Hence, it
should be possible to find the amount of A on the charcoal (M ). The
Ai
constants of Eq. (14) can be determined.
3. Equilibrium Relationship:
The functional forms of (-r^) and (-r.) determined in the preceding step
are to be substituted into Eq. (5) to obtain an explicit relation between
C.,. and t. However, before Eq. (5) can be integrated, a relation between
AX*
C and M must be known. Their relation can assume the form:
A A
MA = KC« (15)
The constants K and a in such a relation can also be determined by the
batch experiments. Since in an actual operation a true equilibrium
condition is not obtainable within a convenient time, it will be necessary
to investigate how fast the system approaches the equilibrium.
The absorption of A on charcoal can be investigated for this same dye by
using an equivalent shaking (by mechanical shaker). A plot of absorption
of A on charcoal (M.) is made as a function of time until there is no
further increase of M.. The K and a can be determined for Eq. .(15).
A
Treatment of Experimental Data
Rate expressions (-rjT) and (-r.) together with the relation of Eq. (15)
can-now be employed in Eq. (5) to perform an integration. Equation (6)
can be used if the experimental data confirm that (-r') is negligibly
A
small compared with (-r.). The integration can be carried out analytically
if rate expressions are relatively simple. When complex expressions are
obtained, Eq. (5) or (6) is integrated more conveniently by the graphic
method or solved by the method of numerical integration. It is to be noted
that the relation between t and C in Eq. (5) is also valid for the constant
volume batch system since physical properties of the system are assumed to
be constant in the present case.
59
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The mathematical model developed in this section is confirmed when the
values of C.f at various residence times t predicted from Eq. (5) or
C6) agree with the experimental values within a desired accuracy.
Otherwise need for modification of the model is indicated.
60
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1
Accession Number
w
5
2
Subject Field & Group
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization Oak Ridge National Laboratory, Oak Ridge, Tennessee
Isotooes Develonment Center
Operated by Union Carbide Corp. for the U.S. Atomic Energy Commission
Title
Study of Gamma Induced Low Temperature Oxidation of
Text!le Effluents
I Q Authors)
Case, i-orrest N.
Ketchen, Eugene E.
16
21
Project Designation
Project Contract #12090
FWD
Note
22
Citation
Environmental Protection Agency report number
EPA-R2-73-260, May 1973.
23
Descriptors (Starred First)
*Color Removal, *COD Removal, Reactivation of Charcoal
25
Identifiers (Starred First)
*Color Removal, Textile Effluents
07 Abstract
1 Gamma irradiation of textile mill effluents under oxygen pressures up to 1500
psi, with and without activated charcoal present, was studied as a method for removing
color and removal of substances contributing to the chemical oxygen demand (COD). Both
color and COD reduction are directly related to the radiation dose and pressure of the
oxygen over the dye solution samples during irradiation. Color removal was achieved
in solutions of dye prepared in the laboratory for process evaluation and for authentic
textile mill waste effluents; however, the variation in the radiation dose required for
various dye compounds was large. The study revealed a new method for in-situ reactivation
of charcoal by gamma-radiation-induced oxidation of organic compounds adsorbed on charcoal.
This discovery permits a large reduction in the gamma source size required for processing
textile mill effluents because the water fraction of the effluent does not need to be
irradiated to the same degree as the organic material contained in the effluent. A
methematical model for the process, developed late in this study, has not yet been
exper i menta11y ver i f i ed.
Abstractor
Forrest
N.
Case
Inst
tution
Oak
Ridge
Nat i ona 1
Laboratory
WR:102 (REV. JULY 1969)
WRS1C
SEND. WITH COPY OF DOCUMENT, TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
* OPO: 1970-389-930
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