EPA-670/2-75-029
April 1975
Environmental Protection Technology Series
RECOVERY FROM
BRASS MILL DISCHARGE BY
CEMENTATION WITH SCRAP IRON
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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EPA-670/2-75-029
April 1975
COPPER RECOVERY FROM BRASS MILL DISCHARGE BY
CEMENTATION WITH SCRAP IRON
By
Oliver P. Case
The Anaconda Co. - Brass Division
Research and Technical Center
Waterbury, Connecticut 06720
Grant No. S-803226-01-0
Program Element No. 1BB036
Project Officer
Richard Tabakin
Industrial Waste Treatment Research Laboratory
Edison, New Jersey 08817
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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REVIEW NOTICE
The National Environmental Research Center --
Cincinnati has reviewed this report and approved its
publication. Approval does not signify that the con-
tents necessarily reflect the views and policies of
the U. S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
ii
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FOREWORD
M«n and his environment must be protected from the adverse
effects of pesticides, radiation, noise and other forms of pol-
lution, and the unwise management of solid waste. Efforts to pro-
tect the environment require a focus that recognizes the inter-
play between the components of our physical environment -- air,
water, and land. The National Environmental Research Centers
provide this multidisciplinary focus through programs engaged in
studies on the effects of environmental
contaminants on man and the biosphere, and
a search for ways to prevent contamination
and to recycle valuable resources.
This report covers attempts to develop an economical way
of recovering copper in brass mill discharge which otherwise
might be wasted. The recovery process is non-polluting and
incidentally reduces hexavalent chromium in an economical
fashion.
A. W. Breidenbach, Ph.D.
Director
National Environmental
Research Center, Cincinnati
111
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ABSTRACT
This report presents the results of studies of copper recovery and
incidental simultaneous reduction of hexavalent chromium in brass mill
discharge by passage of the discharge over scrap iron in a rotating
drum. Effluent from the cementation system was treated by neutraliza-
tion for the precipitation of residual copper and other metals which
are settled in a clarifier and subsequently dewatered on a vacuum
filter. The drum feed consisted of normal production discharge of
combined pickle rinse water and spent sulfuric acid and sulfuric
acid - dichromate pickle. About half of the total mill waste discharge
over a period of 16 weeks was processed.
Four modes of drum operation were studied:
1. Continuous rotation
2. No rotation
3. Intermittent rotation (1 hr off - 5 min on)
4. Intermittent rotation (2-1/2 hr off - 10 min on)
Each mode was studied at 2 flow levels and 2 scrap iron surface area
levels.
Data were evaluated in terms of percent cementation of available copper,
excess iron consumption over theoretical, and completeness of chromium
reduction.
Results indicate that the over-riding factor in the efficiency of
copper cementation is the level of copper in the feed solution. Copper
concentrations of over 300 ppm may yield recoveries of over 507. of the
copper; concentrations below 100 ppm yield recoveries too small to be
economically practical. Normal levels of hexavalent chromium are
effectively reduced under a variety of conditions providing the pH is
below 2.5.
This report was submitted in fulfillment of Grant No. S-803226-01-0 by
the Anaconda American Brass Company under the partial sponsorship of
the Environmental Protection Agency.
Work was completed as of November 1974.
iv
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CONTENTS
Page
Review Notice ii
Foreword lit
Abstract iv
Table of Contents v
List of Figures vi
List of Tables vii
Acknowledgments viii
Sections
I Conclusions 1
II Recommendations 3
III Introduction 4
IV Waste Treatment System 7
V Experimental Program 13
VI Experimental Results 21
VII Economic Considerations 34
VIII References 38
IX Appendices 39
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FIGURES
No. Pace
1 Schematic Flow Sheet for Waste Treat- 6
tnent Plant
2 General View of Waste Treatment Plant 8
3 Schematic Diagram of Cementation Drum 11
4 Typical Scrap Iron Punchings 16
5 Miscellaneous Scrap Iron Punchings 17
6 Appearance of Scrap Iron Surface After 23
Various Periods of Use
7 Net Annual Return Realized from Recovered 37
Copper at Various Cementation Efficiencies
vi
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TABLES
No. Page
1 Treated Waste Discharge Sampled 9
September 5, 1974
2 Characteristics of Typical Pieces of 18
Scrap Iron in Drum Charge
3 Summary of Data for Operation in the 23
Continuous Mode
4 Suimnary of Data for Operation in the 24
Static Mode
5 Summary of Data for Operation in the 25
Intermittent Mode (A)
6 Summary of Data for Operation in the 26
Intermittent Mode (B)
7 Summary of Data for Operation in all 27
Modes
8 Data for Runs Giving 50% or Better 28
Copper Recovery
vii
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ACKNOWLEDGMENTS
Charles R. Chamberlin manned the Waste Treatment Plant
during the experimental runs and was responsible for
all monitoring, sampling, field analytical work and
data recording.
Kenneth F. Schneider performed the regression analysis
of the data.
viii
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SECTION I
CONCLUSIONS
The inclusion of cementation facilities as part of the total wastewater
treatment system for brass mill discharge is economically justified only
if copper removal efficiencies approaching 50% can be achieved.
Cementation efficiencies high enough to be economically viable can only
be achieved if the concentration of copper in the feed solution is kept
at a high level; 300 ppm or greater.
A high concentration of copper in the feed solution can be maintained by
water conservation measures which prevent unnecessary dilution of the
waste stream.
Low pH enhances cementation of copper; a high concentration of hexavalent
chromium inhibits it.
Any material likely to form a film on the surface of the iron reductant,
such as oil or surfactants, may inhibit the cementation reaction. How-
ever, in practice the effect does not appear to be serious unless the
contamination is gross.
A high cementation efficiency results in dissolution of considerably less
EXCESS iron than a low cementation efficiency.
The mode of operation of the cementation drum and the flow/iron surface
level combination have considerably less effect on the cementation
efficiency than the characteristics of the feed solution. However,
regression analysis of the data indicates the continuous mode of drum
operation to be optimum and that f low/iron surface area and copper
concentration/iron surface area ratios should be kept as small as
practical.
The cemented copper can be converted to usable metal by conventional
smelting and refining techniques.
The present study indicated an annual potential of approximately 77,000
pounds of copper in the waste stream, as well as an annual loading of
1,500 pounds of hexavalent chromium. Assuming the value of the copper
in a usable form to be 75 cents per pound, the net annual return using
15-year amortization of equipment would be approximately:
$22,600 at 90% Copper Recovery
$16,200 at 75% " "
$ 5,200 at 50% " "
Break-even at 35% " "
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These returns DO NOT include the value of the simultaneous reduction
of the hexavalent chromium which would have an annual cost of approxi-
mately $5,000 if another process were used.
Based on the results of this study the Anaconda American Brass Company
will continue to utilize cementation for the recovery of copper and
the simultaneous reduction of hexavalent chromium. Attempts will be
made to increase the efficiency of copper recovery by in-plant water
conservation measures designed to concentrate the copper in the waste
s treams .
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SECTION II
RECOMMENDATIONS
Since the efficiency of cementation is dependent on the concentration
of copper in the feed solution, means of concentration through water
conservation should be explored.
Gross amounts of oil, soaps and similar film-forming materials must
be removed from the waste stream prior to passage over the iron re-
ductant. Segregation and separate disposal of such materials is
recommended. Where this is not practical, gravity separation or
similar pretreatment should be considered.
An alternate means of copper recovery through treatment of the clari-
fier sludge filter cake should be studied. This route offers poten-
tially complete copper recovery and lower over-all waste treatment
cost. The high-density clarifier sludge achieved through sludge re-
circulation should be especially suitable for such a process.
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SECTION III
INTRODUCTION
The Valley Divisions of the Anaconda American Brass Company at Water-
bury and Ansonia, Connecticut, are typical brass mills.
The Waterbury Division consists of three tube mills producing both
copper and copper-alloy tube, while the Ansonia Division is essen-
tially a rod mill which also produces some drawn copper shapes. Annual
production from both divisions exceeds 100 million pounds.
Also located in the Waterbury area is the Anaconda Metal Hose Division
which fabricates flexible hose from galvanized steel, stainless steel,
aluminum and copper alloy strip and tube.
In all divisions, in-process material, as well as end products, may be
pickled in su If uric acid, or sulfuric acid plus sodium dichr ornate, or
a combination of the two. Rinsewaters utilized in the process, as well
as the spent pickles which are discarded, contribute copper, zinc,
nickel, chromium and sulfuric acid to the waste stream; all of which
must be separated or neutralized before discharge. All brass mills,
and mills processing copper alloys, face similar problems in treating
effluents.
To provide suitable treatment for the waste streams generated in the
Naugatuck Valley Plants, the Anaconda American Brass Company has built
treatment plants at Ansonia and Waterbury, each having a capacity of
500,000 gpd. Both plants are identical and utilize a unique process
for simultaneously precipitating metallic copper in a recoverable form
and reducing hexavalent chromium.
Similar plants are in operation at Anaconda American Brass Company
divisions at Toronto, Ontario and Kenosha, Wisconsin.
All of these plants perform in admirable fashion as far as waste treat-
ment is concerned; however, the recovery of copper has been disappointing.
Analyses of raw waste streams from the Valley Mills show the following
copper potentials:
Waterbury 77,000 Ibs/yr
Ansonia 75,000 Ibs/yr
At current prices for copper, this is worth over $110,000 less recovery
costs. Experience indicated that less than 50% of this potential was
being realized.
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The reason for the Low copper recovery in the full-scale plant opera-
tions is not evident. A laboratory study carried out for the Connecti-
cut Research Commission^ and a similar study carried out for the En-
vironmental Protection Agency-* both demonstrated the feasibility of
over 90% copper recovery, coupled with complete reduction of hexavaient
chromium.
The present study was undertaken to determine the most significant
factors influencing cementation efficiency under actual mill operating
conditions and to determine the optimum procedure for operation of the
cementation drums.
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RAW
WASTE
A
CEMENTATION SYSTEM
I
FLOCCULENT
LIME AID
1 COPPER Mil)
I TO REFINERY
CLEAR DISCHARGE
TO RIVER
SLUDGE TO
LANDFILL
RECYCLED SLUDGE
A - EQUALISATION BASIN
B - CEM1NTATION CHAMBER
C - SETTLING PIT
D - TRANSFER WELL
E - NO. 1 NEUTRALIZATION TANK
F - NO. 2 NEUTRALIZATION TANK
G - CLARIFIER
H - VACUUM FILTER
Figure 1. Schematic flow sheet for Waste Treatment Plant
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SECTION IV
WASTE TREATteNT SYSTEM
GENERAL
The flow of waste material through the plant is shown schematically in
Fig. 1 and the general plant layout is shown in Fig. 2.
Waste is collected and blended in a 100,000-gal. equalization basin
where the pH is monitored, and adjusted to pH 2.5 or less by addition
of su If uric acid, if necessary. The blended waste is pumped to one of
two revolving drums filled with scrap iron.
Passage of the feed solution through the scrap bed reduces hexavalent
chromium and precipitates metallic copper. The finely divided metallic
copper is carried in the stream flowing over the lip of the drum, and
settles in a baffled pit.
Copper mud removed from the settling pits is air-dried to approximately
30 to 40% moisture and shipped to a copper refinery for recovery of the
copper.
The overflow from the settling pit flows by gravity to a preliminary
neutralizing tank where it is blended with settled sludge pumped from
the bottom of a clarifier. The mixture flows by gravity to a second
neutralizing tank where it is treated with lime slurry to bring the pH
to 9.0. Polyelectrolyte floe aid is added and the neutral slurry passes
to a clarifier where the sludge settles. The two-stage neutralization
produces a dense sludge which is periodically dewatered on a vacuum
filter.
The dewatered sludge has a solids content of approximately 357. and is
disposed of as landfill.
The clarifier overflow meets all applicable effluent specifications
and is discharged to the Naugatuck River.
The analysis of a typical discharge from the Water bury Treatment Plant
by the Connecticut Department of Environmental Protection Laboratory
is shown In Table 1 on page 9. The effectiveness of the total treat-
ment system may be judged by comparison of this analysis with the
composition of the blended raw waste streams given on page ]_o.
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X
Figure 2. General view of Waste Treatment Plant
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Table 1. TREATH) WASTE DISCHARGE SAMPLED SEPTEMBER 5, 1974
Clarifier Effluent Clear
PH 8.2
Methyl Orange A Ik - pH 3.7 26 ppm
Phenolphthaletn A Ik - pH 8.3 0 ppm
Solids - Total 1798 ppm
- Fixed 1606 ppm
- Volatile 192 ppm
P04 - P 0.2 ppm
NH3 - N 0.4 ppm
Tot Org Carbon (TOG) 6 ppm
Cyanide (CN) 0 ppm
Free Chlorine 0 ppm
Iron (Fe) 0.2 ppm
Copper (Cu) 0.3 ppm
2inc (2n) <0.1 ppm
Cadmium (Cd) <0.1 ppm
Nickel (Ni) <0.1 ppm
Chromium - Total (cr ) <0.1 ppm
Aluminum (Al) <1 ppm
WASTE STREAM
The waste stream treated at the Waterbury Division Waste Treatment Plant
consists of effluent from four mills:
1. East Tube
2. West Tube
3. Small Tube
4. Metal Hose (flexible tube)
All of these mills process copper and copper alloy tube, including
pickling in sulfuric acid or sulfuric acid-dichrornate solution to re-
move surface oxides. Effluents consist essentially of rinse water from
pickling operations and the spent pickles themselves.
Although oils, alkaline cleaners, soaps, drawing lubricants and similar
organic materials are not intentionally included in the waste stream,
in practice small amounts of these materials do find their way into
the stream and gradually form a sludge in the Treatment Plant equaliza-
tion basin and occasional scum or foam on the surface.
Discharge from the East Tube Mill is collected in a sump in the mill
and pumped to an intermediate lift station from which it is pumped to
the Treatment Plant equalization basin.
Discharge from the West Tube Mill is collected in a sump in the mill
from which it is pumped directly to the Treatment Plant equalization
basin.
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The Small Tube Mill Is some distance away from the Treatment Plant,
hence wastes are transported by tank truck and discharged into the
lift station sump. In addition to sulfuric acid, dichromate and solu-
ble metal salts this discharge may contain small amounts of hydrazine
and elemental copper.
Discharge from the Metal Hose operation flows directly to the lift sta-
tion. The lift station is equipped with two 1.14-klm (300-gpm) pumps
which may be used singly or combined. The West Mill sump is equipped
with two 0.757-klm (200-gpm) pumps which also can be used singly or in
combination. It will be apparent that if all pumps are in operation a
total of about 3,79 klra (1,000 gpm) can be delivered to the equaliza-
tion basin. In practice the waste flow will rarely exceed half this
amount.
The equalization basin is roughly 11.28 m (37 ft) long x 10.97 m (36 ft)
wide x 3.66 m (12 ft) deep and has a capacity of about 453 kl (120,000
gal.). Thus, there is capacity for retaining at least 4 hours normal
flow of effluent. The waste collected in the basin is blended by a
2.65-klra (700-gpm) recirculation pump.
The Cementation Drums are fed from inlets located 22.86 cm (9 in.) from
the bottom of the basin. Three pumps of 0.662-klm (175-gpm) capacity
feed the Drums. The pump valves are so arranged that the flow may go
to either Drum or be split between them. However, not more than 1,32
klm (350 gpm) may be fed to one Drum.
The composition of the blended waste streams as fed to the Cementation
Drums may vary widely as follows:
Copper 50-1300 ppm
Total Chromium 10- 750 ppm
Hexavalent Chromium 0- 40 ppm
Zinc 10- 90 ppm
Nickel 10- 35 ppm
Oil 5- 130 ppm
pH 1.5- 6.0
The high metal and low pH values correspond with pickle dumps, whereas
the lower metal values and high pH values are characteristic of dilute
rinse water.
CEMENTATION DRUM
A cementation drum is shown schematically in Fig. 3.
It consists of a Type 316L stainless steel cylinder 1.372 m (4.5 ft) ID
and 2.438 m (8 ft) long which may be inclined 25 to 35 degrees from the
horizontal.
10
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BEARINGS
DEFLECTORS
MANIFOLD
NOZZLES
Figure 3. Schematic diagram of Cementation Drum
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The Influent end of the drum Is fitted with a circular manifold 29.2 cm
(11.5 in.) CD containing 18 spray nozzles 1.27 cm (0.5 in.) ID, 12 of
which are directed in a lateral direction and 6 in a horizontal direction,
The discharge end of the drum is fitted with a flared lip which extends
64.14 cm (25.25 in.) from the cylinder and has a diameter of 2.438 m
(8 ft) at the face.
The interior of the drum is fitted with four deflectors arranged to
impart good tumbling action to the scrap iron charge.
A removable hatch cover approximately 50 cm x 50 cm (20 in. x 20 in.)
is provided on one side of the drum for removing the scrap charge if
this becomes necessary.
The drum may be rotated in a counter clock-wise direction at speeds
varying from 0 to 10 RPM.
Variation in speed of rotation and angle of inclination are provided to
permit optimum tumbling action for scrap iron shapes of widely varying
geometrical configuration.
At an inclination of 30° the drum has a total capacity of 2.166 m3
(76.5 ft-*). An installation normally includes two drums which may be
operated simultaneously or separately. The drums are covered by U. S.
Patent 3,748,124. L
COPPER SETTLING PITS
Each drum discharges into a settling pit of trapezoidal shape approxi-
mately 5.626 m x 2.781 m (18.46 ft x 9.13 ft) at the top, 5.283 m x
2.438 m (17.33 ft x 8 ft) at the bottom and 4.115 m (13.5 ft) deep,
having a total capacity of 58.70 m3 (2073 ft3).
The end of the pit into which the drum discharges is segregated by a
baffle which extends 1.194 m (3.92 ft) below the surface.
The discharge from each settling pit flows over a weir into a common
transfer well, from which it flows by gravity to the neutralization
system.
Cemented copper and other particulate matter discharged from the drum
collects in the settling pit. After the pit becomes about one third
full of particulate material the supernatent liquid is pumped down
and the copper mud removed with a clam-shell bucket.
This is an inefficient method of removal, and settling pits in future
installations will be modified so that the mud layer can be transferred
to a decant storage tank at periodic intervals before it becomes too
dense to pump.
12
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SECTION V
EXPERIMENTAL PROGRAM
GENERAL
Factors known, or suspected, to Influence the efficiency of copper
cementation include:
1. Temperature
2. pH of feed solution
3. Concentration of copper in feed solution
4. Concentration of other metals in feed solution, especially
hexavalent chromium
5. Oily material in feed solution
6. Flow rate of feed solution
7. Composition of iron contact material
8. Geometry of iron pieces
9. Surface area of iron
10. Surface films on iron, especially oil
11. Oxidation of cemented copper
12. Mode of operation of cementation drums; i.e., static, continuous
or intermittent rotation
13. Geometry of settling pit
14. Flow pattern through settling pit
15. Particle size of cementate
Of these factors the only ones which can be controlled to a reasonable
degree under mill operating conditions are:
1. Flow rate of feed solution
2. Surface area of iron contact material
3. Mode of operation of cementation drum
Some recent work^ has indicated that copper previously deposited on an
iron surface greatly increases the cementation rate by forming nucleii
for subsequent cementation. Essentially the same conclusion was reached
in an independent study of the cementation of copper on zinc.5
These findings led to the belief that the efficiency of copper cementa-
tion might be enhanced by leaving the scrap bed quiescent in the drum
for various intervals, limiting rotation of the drum to brief periods
for dislodging some of the deposited copper and realigning the scrap
surfaces.
When the drum is operated without rotation it becomes essentially a
plug-flow reactor, whereas with normal rotation it is a back-mix reactor,
13
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It was decided to operate the drum in the following modes:
1. Continuous rotation
2. Static (no rotation)
3. Intermittent rotation
A (1 hr off - 5 min on)
B (2-1/2 hr off - 10 min on)
It was planned to study each mode of operation for one week at each of
two flow levels for two iron contact surface levels. Thus, a total ex-
perimental period of 16 weeks was projected. Because of flow control
problems operation in the Continuous Mode at low flow/low iron surface
was repeated. Operation in the Intermittent Mode B at high flow/high
iron surface was eliminated due to previous unpromising results in this
mode.
Nadkarni and Wadsworth have studied the effect of ferric iron on the
cementation of copper in considerable detail^. They concluded that
ferric iron not only consumed excess metallic iron but also had a ten-
dency to redissolve deposited copper and promote other undesirable side
reactions. For this reason the percentage of ferric iron in the drum
discharge was monitored each day.
It must be pointed out that there are inherent difficulties in attempting
to carry out a controlled experiment under mill production conditions,
since there are fluctuations in production schedules which affect the
composition of the discharge and flow rates. It was found especially
difficult to maintain uniform flow rates at desired levels. However,
a substantial differential between high and low flow rates was fairly
consistently achieved.
Occasional problems were encountered with unauthorized dumps of deter-
gents which resulted in foaming and drawing lubricants which formed a
scum on the surface of the equalization basin.
IRON REDUCTANT
The reducing medium utilized consisted of scrap punch ings of low carbon
steel (SAE 1009).
The material as received from the scrap dealer consisted of a large
variety of configurations averaging about 0.25 cm (0.1 in.) in thick-
ness and ranging from 0.6 cm (0,25 in.) to 7.5 cm (3 in.) in the largest
dimension.
Previous experience had shown that the smallest pieces of scrap, es-
pecially disks, had a tendency to plug up the feed injection nozzles in
the drum. Therefore, all scrap used in the experimental runs was classi-
fied with a metal screen having openings of a diamond configuration,
the long axis being 3.81 cm (1.5 in.) and the short axis 1.75 cm
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(0.6875 in.). This method of classification was found very effective
in rejecting the smaller pieces of scrap.
A representative portion of screened scrap weighing approximately
6.48 kg (14 Ibs) contained individual pieces as shown in Figs. 4 and 5.
Data relating to the individual pieces are given in Table 2,pg. 18. The
material contained a slight amount of oil equivalent to 13 g/m2. The
packing density of the screened scrap was estimated by filling a tared
wooden box having a capacity of 0.0339 m3 (1.2 ft3) and weighing. Four
trials gave an average packing density of 1540 kg/in3 (96 Ibs /ft3).
Considering the density of 1009 steel as 7.871 g/cm3, the packing den-
sity of the loose scrap (1.540 g/cm3) indicates that the solid volume
of the scrap is 1.540 x 100 » 19.577. of the loose scrap volume.
7.871
The surface area per unit volume of the screened scrap was estimated
by dividing the solid volume by the weighted average thickness of the
individual pieces, multiplying by 2 and adding 10% for the edge area.
Thus:
0.1957X 1,000,000 2 . 16?>6 m2/m3 + 107. - 184 m2/m3 (56
0.2338 x 10,000
During the ninth week of the experiment, a fresh load of scrap was re-
ceived. This lot had slightly different geometric characteristics be-
cause of the presence of a disk 4.1275 cm (1.625 in.) in diameter with
a 1.113 cm (0.4375 in.) diameter hole in the center which had not been
present in the original lot. This piece is identified as "M" in Fig. 4.
Since the piece had a thickness of 0.2337 cm (0.092 in.) the weighted
average thickness of the scrap was not materially changed.
The characteristics of the new lot of scrap were determined as previously
described and found to be:
packing density - 199 kg/m3 (124 Ibs /ft3)
surface area per unit volume - 238 tn^/in3 (72.5 ft2/f t3) .
This material contained an oil film equivalent to 8 g/m2.
In determining intial charges for both low and high iron surface levels,
the volume of scrap was estimated by multiplying the volume of the
charging bucket (0.0566 m3) by the number of bucket loads added. This
was converted to weight by use of the appropriate factor. Periodic
additions to the charge were measured by the actual weight of the scrap
added .
15
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ooooOe
ABC
o b 1 O
G H I
Figure 4. Typical Scrap Iron Punchings
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Figure 5. Miscellaneous Scrap Iron Punch ings
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Table 2. CHARACTERISTICS OF TYPICAL PIECES OF SCRAP IRON IN DRUM CHARGE
Thickness Greatest
Type*
A
B
C
D
E
F
G
H
I
J
Misc.
Weighted
Average
cm in.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
.2337 0
.1702 0
.2108 0
.2134 0
.2032 0
.2210 0
.2337 0
.2311 0
.3251 0
.4674 0
Max.
. 37 34 0
Min.
.0635 0
Avg.
.2184 0
.2338 0
.092
.067
.083
.084
.080
.087
.092
.091
.128
.184
_«^v
.147
.025
.086
.092
cm
3.96
5.72
5.41
6.03
6.83
5.40
2.54
4.45
3.81
7.62
D imens ion
in.
1.56
2.25
2.13
2.38
2.69
2.13
1.00
1.75
1.5
3.00
7.00
Total
No. of
Pieces
in Sample
75
95
71
25
50
11
30
75
24
16
47
519
Percent
by Type
14.45
18.30
13.68
4.82
9.63
2.12
5.78
14.45
4.62
3.08
9.06
Total
398.1
359.1
1395.7
363.4
1735.0
197.2
180.1
595.0
160.4
491.7
608.9
6484.6
Percent
by Wt
6.14
5.54
21.52
5.60
26.76
3.04
2.78
9.18
2.47
7.58
9.39
Compos it ion ,70
C Mn Other
0.07 0
0.08 0
0.14 0
0.10 0
0.11 0
0.11 0
0.06 0
0.05 0
0.06 0
0.13 0
.29 Cu 0.02
.31
.45
.38 Pb 0.02
.34
.32
.31
.22
.23
.36
00
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The average iron contact surface area for each run was estimated as
follows: weight of iron remaining at end of previous run plus weight
of iron added during run minus weight of iron consumed during run
multiplied by the appropriate conversion factor.
Admittedly the estimation of the actual iron surface is only a very
rough approximation, and the values thus obtained should only be con-
sidered as relative magnitudes.
OPERATING PROCEDURE
Each combination of flow and iron surface level for each mode of drum
operation was run for five consecutive days, with the exception of the
run in the Continuous Mode at high f low/low iron surface and the run
in the Static Mode at low flow/high iron surface which were for four
days. Normally each day's run was for a full 8 hours, although occasion-
ally an early shutdown was necessitated by lack of feed.
In all runs the drum was inclined 30° above the horizontal and during
periods of roation was rotated at 3 RPM.
The experimental drum was cut into the line at 8:30 A.M. each morning
after recording the volume of feed which had passed through the standby
drum during the period when the experimental drum was off line and feed
flow adjusted as close to the desired level as possible.
Brailsf ord automatic samplers were set up to sample both the drum feed
and the drum d is charge.
Every two hours the pH of both feed solution and drum discharge was
checked with a glass electrode pH meter. At the same time the drum
discharge was checked colorimetrically for the presence of hexavalent
chromium and the temperature of the feed solution taken. Manual flow
measurements were also taken every two hours at the Parshal flume
through which the plant discharge passed.
In the early afternoon a grab sample of drum discharge was taken. This
was filtered and divided in half. Ferrous iron was determined in one
portion of the sample by immediate titration with standard potassium
dichromate and the total iron was determined in the other portion by
atomic absorption. From this data the percent of ferric iron in the
discharge was calculated.
During the day weighed portions of screened scrap estimated to be suffi-
cient to keep the iron surface at the desired level were added to the
drum.
At 4:30 the experimental drum was shut down and the standby drum cut
in. The Brails ford samplers were shut down and the samples removed.
19
-------
Specimens of the composite sample of feed were transferred to appropriate
containers and sent to the laboratory for the following determinations:
Copper
Chromium^
Oil (Tuesday and Thursday only)
Sine „
Nickel " "
The hexavalent chromium in the composite was determined immediately by
adding a measured excess of standard ferrous ammonium sulfate and back
titrating with standard potassium dichrornate.
The composite sample of drum discharge was filtered (to remove particu-
late copper and iron) and specimens transferred to appropriate containers
and sent to the laboratory for determination of copper and iron.
Once each week a sample of copper mud was withdrawn from the top of the
mud blanket in the settling pit and allowed to settle for 24 hrs, after
which the supernatant layer was poured off. The density of the settled
layer was determined and analysis made for moisture, copper and iron.
An attempt was made to measure the increase in depth of the mud layer
each week, but this was never reliably accomplished; perhaps due to
constant shifting of the surface of the layer by currents in the pit.
Twice a week a sample was taken of overflow from the settling pit and
the concentration of particulate copper determined. The data were not
reliable due to the ever-present possibility of including particulate
copper inadvertently dislodged from the lip of the weir. For this
reason the data are not included in the report.
Sludge which settled in the clarifier was normally vacuum filtered
once each week. The volume of the filter cake was estimated and
determination made of density, moisture, copper and iron.
Once each week representative specimens of scrap were withdrawn from
the drum and examined for the nature of any film on the surface and
the progress of dissolution.
20
-------
SECTION VI
EXPERIhENTAL RESULTS-
GENERAL
In all instances cementation efficiencies were disappointingly low.
As previously mentioned, laboratory experiments have consistently
shown copper recoveries of over 90%3. Recoveries in the present study
were not only much lower, but data related to optimum conditions for
recovery presented a confusing pattern. It is evident that many factors,
not readily isolated, bear upon the effectiveness of copper recovery in
a full-scale mill operation. One of these factors may well be the
presence of oil or other film-forming materials in the waste stream,
although the effect of oil did not appear marked unless the amount was
gross.
The single factor which appeared to bear most heavily on the effective-
ness of cementation was the concentration of copper in the feed solu-
tion. In general, the higher the concentration, the greater the per-
centage of recovery.
A high concentration of copper is invariably the result of a pickle dump
which has the concomitant effect of producing low pH and relatively
high concentrations of metal salts besides copper, such as nickel, zinc
and chromium. The low pH is desirable; high concentrations of hexavalent
chromium are not.
Little difficulty was experienced in reducing hexavalent chromium at
any level encountered. Only on one or two occasions were traces of hex-
avalent chromium detected for short periods in the discharge and these
were readily corrected by the addition of sulfuric acid to the drum
feed.
CALCULATIONS
Because the primary criterion for judging the effectiveness of any set
of parameters was the cementation efficiency attained, data were arranged
according to the conditions under which maximum and minimum cementation
was obtained for each series of runs. Also included in the data are
the AVERAGE conditions for the series of runs and the AVERAGE cementa-
tion efficiency attained.
Note that data related to maximum and minimum cementation define the
conditions ONLY for the respective run. Averaged data are the arithmetic
means of weekly (5-day) data.
Calculations from data were made as follows:
21
-------
Vol Feed, 1 x 10"6 =
Ayg dally flow in I/min x hrs of operation x 60
1,000,000
Cu Cemented, kg •=
Cu in drum feed in ppm - Cu in drum discharge in ppm
x vol feed in 1 x 10'6
Reduced, kg
in drum feed in ppm - Cr+6 in drum discharge in
ppm x vol feed in 1 x 10~*>
Fe dissolved, kg »
Fe in drum discharge in ppm x vol feed in 1 x 10"6
Fe required, kg «
Cu cemented in kg x 0.8789 -I- Cr+6 reduced in kg x 1.611
Fe excess, 7. «
Fe dissolved in kg - Fe required in kg
. , , —- 100
Fe required in kg
Cu cemented, 7.
Cu in drum feed in ppm - Cu in drum discharge in ppm
Cu in drum feed in ppm x °
22
-------
OPERATION IN THE CONTINUOUS MODE
Data and calculations are given in Appendices A and B, pages 40and 41
Table 3 summarizes the significant data for the four combinations of
flow and iron surface levels.
Table 3. SUMMARY OF DATA FOR OPERATION IN THE CONTINUOUS MODE
Combination
Cementation
Efficiency, %
Composition
of Drum Feed
Composition
of Drum Discharge
Cu
ppm
ppm pH
Fe
Fe
excess ,%
Low flow/
Low
Low
High
High
Low
High
High
iron surface
flow/
iron surface
flow/
iron surface
flow/
iron surface
60
35
42
35
17
27
28
14
22
30
16
21
.00
.71
.24
.61
.20
.20
.50
.29
.49
.00
.22
.95
max
min
avg
max
min
avg
max
min
avg
max
min
avg
345
700
431
132
93
92
200
56
150
100
74
82
3.5
12.6
9.7
6.5
2.0
3.5
10.8
1.52
11.8
2.0
2.0
1.7
2.5
2.3
2.4
2.3
2.7
2.6
2.3
3.1
2.5
2.7
2.9
3.0
8
7
4
5
7
3
13
14
13
9
5
10
.14
.81
.91
.37
.62
.83
.75
.10
.89
.75
.00
.60
1
112
99
205
704
283
92
280
82
190
307
227
.83
.03
.75
.28
As previously mentioned, the original run in the Continuous Mode with
the low flow/low iron surface level was repeated because of flow con-
trol problems. The data, however, are given in Appendix I, page 48 .
Considering the averaged data, the low flow/low iron surface combina-
tion appears to have a significant advantage, although the efficiency
in terms of excess iron requirements is not quite as good as that of
the high flow/low iron surface combination. Note that by chance the
low flow/low iron surface combination had by far the highest copper
concentration in the feed solution and this fact may well overbalance
any other influence.
The fact that for the low flow/low iron surface combination a lesser
cementation efficiency was obtained at a higher level of copper in the
feed solution is an anomaly. The reason may possibly be related to the
high chromium level in the feed.
The proportion of ferric iron in the drum discharge is least for the
low flow combinations, probably because of the longer contact periods
per unit iron surface area.
23
-------
OPERATION IN THE STATIC MODE
Data and calculations are given in Appendices C and D, pages 42 and 43.
Table 4 summarizes the significant data for the four combinations of
flow and iron surface levels.
Table 4. SUMMARY OF DATA FOR OPERATION IN THE STATIC MODE
Combination
Cementation
Efficiency,?.
Compos it ion
of Drum Feed
Composition
of Drum Discharge
Low flow/
Low iron surface
Low flow/
High iron surface
High flow/
Low iron surface
High flow/
High iron surface
21.61
15.97
18.12
28.50
20.92
24.67
23.67
7.53
13.56
50.00
15.63
31.63
max
min
avg
max
min
avg
max
min
avg
max
min
avg
Cu
ppm
545
119
470
107
76.5
86
414
146
163
600
160
245
Cr-r0
PPm
0.0
0.88
1.56
2.2
2.0
1.2
6.5
3.5
2.4
0.0
8.2
3.2
PH
2.2
2.7
2.5
2.3
2.4
2.4
2.2
2.4
2.6
1.9
2.6
2.4
Fe+3 %
10.42
5.68
12.75
6.94
2.70
2.62
37.65
33.52
17.96
5.36
52.01
19.57
Fe
excess %
52.36
179
58.86
141
103
96.85
74.72
91.40
124
52.59
0
55.58
It should be pointed out that due to previously mentioned difficulty in
flow control, the difference in flow between the low flow/high iron sur-
face combination and the high flow/high iron surface combination is
much less than desired.
The data indicate the high flow/high iron surface combination to give
the best results. That this is not entirely due to a higher copper
concentration in the feed solution is attested to by the fact that
equivalent or higher copper concentrations did not give as good re-
coveries in other flow/iron surface combinations. In all combinations,
however, higher copper concentrations gave the best recoveries.
Generally large excess iron dissolution was associated with lower copper
recoveries, however, in the high flow/high iron surface combination
this phenomenon was reversed, although the excess iron dissolved was
not great.
24
-------
OPERATION IN THE INTERMITTENT MODE (A)
Data and calculations are given in Appendices E and F, pages 44 and 45
Table 5 summarizes the significant data for the four combinations of
flow and iron surface levels.
Table 5. SUMMARY OF DATA FOR OPERATION IN THE INTERMITTENT MODE (A)
Combination
Cementation Composition
Eff iciency,% of Drum Feed
Composition
of Drum Discharge
Cu Cr+6
ppm ppm pH
Fe
+3
Fe
excess 7,
Low flow/
Low iron surface
Low flow/
High iron surface
High flow/
Low iron surface
High flow/
High iron surface
17
7
11
57
22
37
13
2
8
23
6
15
.27
.38
.66
.71
.73
.51
.58
.08
.04
.53
.60
.69
max
min
avg
max
min
avg
max
min
avg
max
min
avg
139
122
125
584
110
220
81
96
82
170
212
197
1.3
3.0
2.4
2.0
3.0
2.2
0.4
2.6
1.2
2.0
37.3
14.3
2
3
2
2
2
2
2
2
2
2
2
2
.4
.2
.7
.1
.6
.4
.65
.8
.6
.7
.5
.8
7
52
22
.68
.54
.51
-
0
4
6
4
8
4
14
.57
.93
.82
.51
.82
-
.48
197
323
279
108
241
123
287
285
297
77
29
50
.00
.81
.57
It is evident that the low flow/high iron surface combination gave the
best results. However, this is not conclusive since the copper in the
feed solution was much higher during this run than in others.
The low flow combinations showed less excess iron dissolution for the
higher cementation efficiencies as expected; however, this was reversed
for the high flow combinations.
The minimum cementation efficiency for the high flow /high iron surface
combination is surprisingly low when it is considered that the concen-
tration of copper in the feed solution was over 200 ppm. Again, this
appears to be due to a higher than normal concentration of hexavalent
chromium in the feed solution. It is also of interest to note that the
effect of the hexavalent chromium appears to have superseded the nor-
mally positive cementation effect of a low pH. The concentration of
hexavalent chromium was sufficiently high so that for a short period,
complete reduction was not achieved, and during this period at least,
no cementation of copper would occur.
25
-------
OPERATION IN THE INTERMITTENT MODE (B)
Data and calculations are given in Appendices G and H, pages 46 and 47
Table 6 summarizes the significant data for three combinations of flow
and iron surface levels.
Table 6. SUMMARY OF DATA FOR OPERATION IN THE INTERMITTENT MODE (B)
Combination
Cementation
Efficiency,
Composition
of Drum Feed
Composition
of Drum Discharge
Low flow/
Low iron surface
Low flow/
High iron surface
High flow/
Low iron surface
High flow/
High iron surface
12.00 max
1.12 rain
7.64 avg
55 . 37 max
4.59 min
21.74 avg
9.68 max
1.32 min
5.82 avg
Not
Run
Cu
ppm
50
89
85
1183
54.5
290
62
76
85
Cr+6
ppm
0.1
1.3
2.9
2.0
1.3
1.5
0.7
2.0
1.4
PH Fe+3 7.
2.9 0
2.3 9.41
2.7 13.60
1.9 32.72
3.0 1.76
2.7 11.02
2.9 0
2.8 0
2.8
Fe
excess %
907
2,549
501
35.04
574
51.31
243
533
278
As previously explained, the high flow/high iron surface combination was
not run in this mode due to generally unpromising results for other com-
binations .
The low flow/high iron surface gave a fair maximum copper recovery, but
it will be noted that the copper concentration in the feed solution was
enormously high. It is interesting to note that even with such a high
concentration of copper, the excess dissolution of iron was extremely
low.
The concentration of copper in the feed solution for all of the other
combinations run was too low for data to be interpreted, except in a
very general way.
26
-------
SUMMARY OF DATA FOR OPERATION IN ALL MODES
Data are summarized in Table 7.
Table 7. SUMMARY OF DATA FOR OPERATION IN ALL MODES
Max Cu Fe Cu in Cr"1"6
Recovery Excess Fe+-* Feed, in Feed,
% 7. % ppm ppm pH
Continuous Mode
Low flow/low Fe surface 60.00 1.83 8.14 345 3.5 2.5
Low flow/high Fe surface 35.61 205 5.37 132 6.5 2.3
High flow/low Fe surface 28.50 92.75 13.75 200 10.8 2.3
High flow/high Fe surface 30.00 190 9.75 100 2.0 2.7
Static Mode
Low flow/low Fe surface 26.61 52.36 10.42 545 0.0 2.2
Low flow/high Fe surface 28.50 141 6.94 107 2.2 2.3
High flow/low Fe surface 23.67 74.72 37.65 414 6.5 2.2
High flow/high Fe surface 50.00 52.59 5.36 600 0 1.9
Intermittent Mode (A)
Low flow/low Fe surface 17.27 197 7.68 139 1.3 2.4
Low flow/high Fe surface 57.71 108 - 584 2.0 2.1
High flow/low Fe surface 13.58 287 6.93 81 0.4 2.65
High flow/high Fe surface 23.53 77.00 4.82 170 2.0 2.7
Intermittent Mode (B)
Low flow/low Fe surface 12.00 907 0 50 0.1 2.9
Low flow/high Fe surface 55.37 35.04 32.72 1183 2.0 1.9
High flow/low Fe surface 9.68 243 0 62 0.7 2.9
High flow/high Fe surface Not Run
Data for runs where 507, or better copper recovery was achieved are
arranged in Table 8, page 28.
It is interesting to note that one run in each mode gave a copper re-
covery of 50% or better. Although in all instances the copper concen-
trations in the feed solution were higher than normal, the percentage
of recovery was not strictly proportional to the copper concentration,
indicating that other factors besides the copper concentration'exert
an influence. For instance, operation in Intermittent Mode (A) with
the low flow/high iron surface combination gave slightly better copper
recovery than operation in Intermittent Mode (B) under the same condi-
tions with twice the copper concentration in the feed solution. This,
however, was at the expense of dissolution of about 3 times the amount
of excess iron.
27
-------
Table 8. DATA FOR RUNS GIVING 50% OR BETTER COPPER RECOVERY
Mode
Cont
Static
Inter. (A)
Inter. (B)
Flow
Low
High
Low
Low
Iron
Surface
Low
High
High
High
Cu
Recovery,
%
60.00
50.00
57.71
55.37
Fe
Excess,
%
1.83
52.59
108
35.04
Fe+3
%
8.14
5.36
-
32.72
Cu in
Feed, jDpm
345
600
584
1183
Cr+6 in
Feed, ppm
3.5
0.0
2.0
2.0
Feed
PH
2.5
1.9
2.1
1.9
S3
00
-------
The data given in Appendices A through I were analyzed on an IBM 370
computer using a Stepvise Regression technique whereby only the signi-
ficant variables are retained in the final equation.
The following variables were entered into the analysis:
a) % Cu cemented • y = dependent variable
b) Mode » time drum was off » x^
There were four modes:
1) Continuous » 0
2) Intermittent (A) » 55
3) Intermittent (B) *> 140
4) Static = 450
c) Feed flow in 1/min - X9
d) Iron surface area in m* * X3
e) Feed concentration of Cu in ppm • x^
f) Feed concentration of Cr+6 in ppm » x$
g) pH of feed solution • xg
h) Feed concentration of oil in ppm « xj
i) Feed temperature in °C " xg
1) Interaction of —flow " xo
Fe area
t) Interaction of C.°nCGu- - x19
Fe area *
v) Interaction of
-------
The following equation with a multiple correlation of 0.924 was deter-
mined from the analysis:
7. Cu cemented + 13.18 = 43.34397 + .09512 (Conccu)
- .000038 (Conc2Cu) - .18312 (Mode)
+ .000333 (Mode2) - .74124 (Cr+6)
Flow v ,Conccu
- .92799
- 2.42109 (pH2)
where 13.18 » standard error at 95% confidence.
From the above equation and within the limits of the experiment, the
following conclusions can be made:
a) Better cementation efficiency can be obtained with higher concen-
trations of copper. (However, the maximum for the quadratic ex-
pression for concentration is about 1,251 ppm. )
b) A continuous mode of drum operation; i.e., time drum off - 0,
will improve the cementation efficiency.
c) The lower the hexavalent chromium, the better the efficiency.
d) The higher the pH value, the less efficient will be the cementation.
flow Conccu
e) Because both the pe area and the Fe area interaction have a nega-
tive effect on cementation efficiency, these terms should be made
as small as possible. Increases in the flow and/or copper concen-
tration will require substantial increases in iron surface area.
The Regression Analysis confirms the conclusions reached by visual
examination of the data and adds the not immediately apparent facts
that drum operation in the continuous mode is advantageous and that
flow/iron surface area and copper concentration/iron surface area
ratios have significant influence.
It seems apparent that the static mode of drum operation does not have
the hoped-for effect of increasing cementation efficiency. Even though
the previously deposited copper may have the predicted effect of nu-
cleating further cementation, other factors cut down on the over-all
efficiency. Probably the principal negative factor is the reduction
in effective iron contact surface by layering of adjacent pieces.
30
-------
COPPER MUD
The characteristics of the copper mud collected in the settling pit
during the course of the experimental runs are shown in Appendix J,
page 49.
The characteristics are those of the mud after settling for 24 hrs.
Longer settling, coupled with air-drying, of course would greatly
increase the density and diminish the moisture content.
There is no obvious correlation between the characteristics of the mud
and the conditions of drum operation.
The copper is probably largely in the elemental form, but substantial
quantities of oxides are also present.
The moist mud also contains small quantities of copper, chromium, zinc,
iron and nickel salts, as well as a small quantity of particulate iron.
A typical specimen of the mud was thoroughly washed with water and
dried. Analysis showed the following composition:
Copper 78.507.
Iron 1.32
Zinc 0.11
Nickel 0.18
Aluminum 0.05
Calcium 0.01
Obviously, part of the copper and iron are in the form of oxides.
The air-dried copper mud may be mixed with other salvaged copper-bearing
materials such as skimmings, and the copper reclaimed by conventional
smelting and refining practices. However, an attractive optional method
for recovery which eliminates the smelting operation is a hydrometallur-
gical process which involves leaching the mud with ammonium carbonate,
separating the copper by liquid ion exchange, and finally depositing the
copper electrolytically. The application of this process to copper mud
is currently being studied at The Anaconda Company, General Mining
Division, Research Laboratories, at Tucson, Arizona. Preliminary re-
sults are favorable.
SLUDGE FILTER CAKE
Any copper not precipitated by cementation and trapped In the settling
pit is included in the sludge filter cake. The characteristics of the
filter cake collected during the course of the experimental runs are
shown in Appendix K, page 50 .
31
-------
To date, in spite of considerable effort, no practical way of reclaiming
copper from the filter cake has beeu devised, and the material is dis-
carded as land fill.
The major problem in reclaiming the copper is the presence of a substan-
tial amount of chromium in the cake which attacks the lining of smelting
furnaces.
Experiments with hydrometallurgical processes for recovery of copper
from the cake are underway, and if successful a comparison will be made
as to the cost of removing all the metal by chemical precipitation vs.
the inclusion of cementation for copper recovery. This will also be
dependent on the ability to improve the cementation efficiency beyond
the capability shown in the present study.
BEHAVIOR OF IRON SCRAP
The mechanism of cementation and hexavalent chromium reduction by
metallic iron is discussed in a previous report.-^
The reactions appear to be concentrated at selected sites where pro-
gressively deeper pitting occurs. This is illustrated in F ig. 6, page
33.
During periods of continuous rotation, the pieces of scrap were coated
with a bright lustrous film of copper which was continuously ground off
and discharged as particulates .
During static operation, the copper film was dull and amorphous, and
was generally not dislodged until the drum was rotated.
Generally, the scrap pieces tumbled well, but at the higher surface
level there was a slight tendency for the pieces to stack in layers
around the inlet nozzles.
32
-------
'. *">
Figure 6. Appearance of Scrap Iron Surface After Various
Periods of Use 5 X
A. Unused piece; original surface
B. Piece after short use; still original gauge
C. Piece after prolonged use; less than half original
gauge
33
-------
SECTION VII
ECONOMIC CONSIDERATIONS
During the 16 weeks of experimental runs, the copper concentration in
the feed solution averaged 188 ppm, and the concentration of hexavalent
chromium 3.69 ppm. The average flow was 697 1/min for 8 hours per day,
and 46.60% of the total plant discharge was processed.
In terms of the total amount of available copper, this comes to:
694 1/min x 60 x 8 x 188 » 62.63 ^ Cu/day
1,000,000
62.63 kfi Cu/day x 5 x 16 . 10>751 ^ Cu/16 wecks
10,751 kg Cu x — - 34,943 kg Cu/year, or 77,047 Ibs Cu/year.
16
Calculated on the same basis, the total amount of hexavalent chromium
to be reduced is equal to 868 kg/yr (1513 Ibs/yr).
Assuming that cementation efficiency is 50%, then the annual potential
copper recovery is:
34,942 kg Cu x 0.5 • 17,471 kg Cu (38,524 Ibs) and the annual
potential value is 38,524 Ibs Cu at 75 cents - $28,893.
Whether or not any recovery of copper is attempted, it is mandatory
that treatment facilities be provided to bring plant discharge into
conformity with Federal and State effluent standards, hence only the
ADDITIONAL cost of providing facilities and services for copper recovery
need be considered in assessing the economic value of a copper recovery
program.
The cost of a complete cementation unit including two drums, scrap con-
veyor, settling pits, pumps, etc. installed in Kenosha, Wisconsin, in
1972 was $164,000. If it is considered that the present cost would be
increased by 10% and the equipment has a useful life of 15 years, then
the amortized capital cost would be:
$164,000 + 10% . $12,027/year
The iron required for cementing 17,471 kg of Cu and reducing 686 kg of
hexavalent chromium may be calculated as follows:
34
-------
17,471 kg Cu x 0.8789 » 15,355 kg Fe
868 kg Cr+6 x 1.611 - 1.105 " "
16,460 kg Fe
plus 50% excess 8,230
24,690 kg Fe
2A>69° fennn X 2>2°5 " 27 .22 tons Fe/year
& * V/x/w
27.22 tons Fe at $118 - $3,212
Annual copper recovery costs may be summarized as follows:
Equipment (15-year depreciation) $12,027
Maintenance at 57. 601
Electricity for drum operation
(40 hp x 0.7457 x 8 hrs x 6 days x 52 weeks
x 3.2 cents) 2,382
Scrap Iron 3,212
Labor (charging drum with scrap) 1,170
1.5 hr/week x 52 at $15
Removing Cu mud from settling pits - 400
16 hrs at $25
Shipping Cu mud to refinery - 48 tons 960
at $20
Refining Costs - 38,524 Ibs Cu at 7-1/2 2,889
cents _^
Total Annual Cost $23,641
Total Annual Gain $ 5,252
$28,893 - 23,641
In considering the value of the annual gain it should be pointed out
that if the cementation process were not utilized, an alternate
process for the reduction of hexavalent chromium would have to be pro-
vided on which there would be no return on either capital or operating
costs. Such a process would probably have a minimum annual cost of
$5,000.
35
-------
If only a 25% cementation efficiency is assumed, calculations on the
same basis show an annual loss of $5,573 which may not be sufficient
to cover the cost of hexavalent chromium reduction by another process.
Fig. 7, shows graphically the possible net annual return in recovered
copper value for various cementation efficiencies. Note that the
"break-even" point is at approximately 35% recovery.
The profitability of cementation is, of course, tied to the price of
copper which may fluctuate widely. At 61 cents per pound the only gain
from the cementation process (at 50% copper recovery) is the value of
the chromium reduction.
It is apparent that the process is economically viable only if a
cementation efficiency approaching 50% can be maintained. The present
study indicates that this efficiency can only be maintained by keeping
a high concentration of copper in the feed solution. This can best be
achieved by eliminating all unnecessary dilution of the waste stream.
Rinsing practices are notoriously wasteful in water usage and it is not
uncommon for water to be left running continuously and serious leaks to
go unrepaired. By implementing simple water conservation measures,
it should not be difficult to upgrade the copper content of the feed
solution to the point where copper recovery becomes profitable.
This is of especial importance because the waste stream must be treated
in any event at considerable cost, and any copper which is not recovered
by the cementation process is lost. There is at present, to our know-
ledge, no practical way of recovering copper from the filter cake pre-
cipitated by neutralization of brass mill discharges.
36
-------
o
•o
o
9
w
20,000
15,000
10,000
5,000
BREAK
EVEN
os -5,000
§ -10,000
-15,000
-20,000 I -
I I I I
10 20 30 40 50 60 70 80
CEMENTATION EFFICIENCY, %
90
Figure 7. Net Annual Return Realized from Recovered
Copper at Various Cementation Efficiencies
37
-------
SECTION VIII
REFERENCES
I. Case, 0. P., et al, "Method for Simultaneous Reduction
of Hexavalent Chromium and Cementation of Copper", U. S.
Patent 3.748.124. July 24, 1973.
2. Case, 0. P., and Jones, R. B. L., "Treatment of Brass
Mill Effluents", Conn. Research Commission RSA-68-34.
September 10, 1969.
3. Case, 0. P., "Mstallic Recovery from Waste Waters Utilizing
Cementation", Environmental Protection Technology Series,
EPA-670/2-74-008. January 1974.
4. Fisher, W. W., and Groves, R. D., "Physical Aspects of
Copper Cementation on Iron". Report of Investigations
7761. U. S. Dept. of Interior, Bureau of Mines, 1973.
5. Strickland, P. H,, and Laws on, F., "Deposit Effects on
the Kinetics of the Cementation of Copper with Zinc from
Dilute Aqueous Solution", Proc. A us tr a las. Inst. Min.
Me tall.. No. 246, June 1973, p. 1.
6. Nadkarni, R. M., and Wads worth, M. E., "A Kinetic Study
of Copper Precipitation on Iron: Part II", Trans. Met.
Soc. AIME. Vol. 239, July 1967, p. 1066.
38
-------
SECTION DC
APPENDICES
Page
A-B Data and Calculations for Operation in 40-41
the Continuous Mode
C-D Data and Calculations for Operation in 42-43
the Static Mode
E-F Data and Calculations for Operation in 44-45
the Intermittent Mode (A)
G-H Data and Calculations for Operation in 46-47
the Intermittent Mode (B)
I Data and Calculations for Operation in 48
the Continuous Mode (Original Run)
J Characteristics of Copper Mud 49
K Characteristics of Filter Cake 50
39
-------
APPENDIX A
DATA AND CALCULATIONS FOR OPERATION IN CONTINUOUS MDDE
Low Flow
Low Iron Surface
Low Flow
High Iron Surface
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surf ace ,m2
Cu , ppm
Cr4"6, ppm
CrT, ppm
d 2n, ppra
: Ni, ppm
"^
J
\ Oil, ppm
PH
Temp, °C
\ Cu, ppm
f Cr+6, ppm
J T
3 Fe , ppm
D _L.Q
j
\ PH
Vol Feed,l x 10 "6
n Cu Cemented, kg
I Cr4"6 Reduced, kg
-4
5 Fe Dissolved, kg
j
3 Fe Required , kg
ti
^ Fe Excess , %
Cu Cemented, %
379
124
345
3.5
97
18
6.1
10.2
2.5
30.5
138
0
191
8.14
2.9
6.18168
37.6
0.64
34.7
34,1
1.83
60.00
492
124
700
12.6
341
91
7
23
2.3
30
450
0
509
7.81
2.5
0.24356
60.9
3.07
124
58.5
112
35.71 ,
416
124
431
9.7
196
54.5
6.6
16.6
2.4
29
253
0
342
4.91
2.9
0.19734
35.1
1.91
67.5
33.9
99.03
42.24
727
322
132
6.5
76
11.4
19
39
2.3
26
85
0
158
5.37
2.7
0.35972
16.9
2.34
56.8
18.6
205
35.61
507
322
93
2.0
47
14
12
61
2.7
28
77
0
139
7.62
4.2
0.25105
4.02
0.50
35
4.34
704
17.20
601
322
92
3.5
53
14
12
61
2.6
26
65
0
111
3.83
3.95
0.29031
7.7
1.02
32.2
8.4
283
27.20
40
-------
APPENDIX B
DATA AND CALCULATIONS FOR OPERATION IN CONTINUOUS MODE
High Flow
Low Iron Surface
High Flow
High Iron Surface
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surface ,m^
Cu, ppm
Cr46, ppm
CrT, ppm
a an, ppm
<4
E Ni, ppm
~\
^J
j§ Oil, ppm
PH
Temp, °C
3 Cu, ppm
1 Cr+6, ppm
J -y
$ Fe1, ppm
g Fe , %
3 PH
Vol Feed,l x 10 "6
10 Cu Cemented, kg
3 Cr46 Reduced, kg
H
5 Fe Dissolved, kg
j Fe Required , leg
u Fe Excess , 7.
Cu Cemented, %
806
129
200
10.8
111
8
89
2.3
29
143
0
130
13.75
2.5
0.36279
20.7
3.9
47.2
24.5
92.75
28.50
931
129
56
1.52
22
5
3
3
3.1
25
48
0
36
14.10
3.4
0.43296
3.46
0.66
15.6
4.1
280
14.29
869
129
150
11.8
86
23
5.2
46
2.5
28
114
0
92
13.89
2.8
0.37904
13.6
4.5
35
19.2
82.28
22.49
659
281
100
2.0
39
11
6
54
2.7
25
70
0
86
9.75
4.4
0.31612
9.5
0.63
27.2
9.4
190
30.00
1105
281
74
2.0
38
12
6
36
2.9
26.5
62
0
56
5.00
4.0
0.53050
6.37
1.06
29.7
7.3
307
16.22
1002
281
82
1.7
38
11
6
54
3.0
25
64
0
61
10.60
4.2
0.44500
8
0.76
27.1
8.3
227
21.95
41
-------
APPENDIX C
DATA AND CALCULATIONS FOR OPERATION IN STATIC MODE
Low Flow Low Flow
Low Iron Surface High Iron Surface
Q
w
u
i
0!
Q
JM DISCHARGE
a
g
o
M
H
3
O
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surf ace ,n\2
Cu , ppm
Cr"1^, ppm
CrT, ppm
2n, ppra
Ni, ppm
Oi 1 , ppm
PH
Temp, °C
Cu, ppm
Cr"1"6, ppm
FeT, ppm
Fe+3, 7.
PH
Vol Feed,l x 10 ~6
Cu Cemented, kg
Cr"1"6 Reduced, kg
Fe Dissolved, kg
Fe Required , kg
Fe Excess , %
Cu Cemented, 7.
424
109
545
0
89
85
17
81
2.2
29.5
400
0
194
10.42
2.3
0.21619
31.3
0
41.9
27.5
52.36
26.61
390
109
119
0.88
43
52
7
36
2.7
30.5
100
0
51
5.68
2.8
0.18128
3.44
0.16
9.2
3.3
179
15.97 ,
420,
109
470
1.56
86
69
12
58
2.5
30
374
0
138
12.75
2.6
0.20710
19.9
0.32
28.6
18
58.86
18.12
708
329
107
2.2
54
10
11
88
2.3
30
76.5
0
73
6.94
2.4
0.34696
10.6
0.76
25.3
10.5
141
28.50
719
329
76.5
.2.0
31
9
8
46
2.4
28
60.5
0
35
2.70
2.6
0.35943
5.75
0.72
12.6
6.2
103
20.92
728
329
86
1.2
38
9
8
47
2.4
28
64.5
0
48
2.62
2.65
3.35659
7.67
0.43
17.1
8.7
96.85
24.67
42
-------
APPENDIX D
DATA AND CALCULATIONS FOR OPERATION IN STATIC MODE
Q
§
Q
8
i
u
H
Q
OS
Q
g
c
t-
1=
»••*
c.
c
High Flow High Flow
Low Iron Surface High Iron Surface
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surf ace ,m2
Cu, ppm
Cr46, ppm
CrT, ppm
2n, ppm
Ni, ppm
01 1 , ppm
PH
Temp, °C
Cu , ppm
Cr+6, ppm
FeT, ppm
Fe+3, %
PH
Vol Feed,l x 10"6
Cu Cemented, kg
Cr*6 Reduced, kg
Fe Dissolved, kg
Fe Required , kg
Fe Excess , %
Cu Cemented, %
772
117
414
6.5
220
-
-
20
2.2
29
316
0
169
37.65
2.3
0.38220
37.5
2.48
64.6
37
74.72
23.67
855
117
146
3.5
92
-
-
17.7
2.4
27
135
0
44
33.52
2.6
0.42342
4.66
1.48
18.6
9.7
91.40
7.53
800
117
163
2.4
84
-
-
20
2.6
29
135
0
64
17.96
2.75
0.39607
11.1
0.95
25.3
11.3
124
13.56
840
309
600
0
19
27
10
49
1.9
21
300
0
402
5.36
1.7
0.39072
117
0
157
103
52.59
50.00
905
309
160
8.2
81
19
9
105
2.6
25
135
0.09
43
52.01
2.8
0.40707
10.2
8.1
17.5
22
0
15.63
878
309
245
3.2
53
19
9
105
2.4
24.5
147
<0.01
142
19.57
2.5
0.39778
39
1.27
56.5
36.3
55.58
31.63
43
-------
APPENDIX E
DATA AND CALCULATIONS FOR OPERATION IN INTERMITTENT MODE (A)
Low Flow LOW Flow
Low Iron Surface High Iron Surface
Q
u
u
ffcc
O
tt
8
Q
a
§
H
|
2
Cementation Efficiency Cementation Eft iciency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surface ,m2
Cu , ppm
Cr*6, ppm
CrT, ppm
2n, ppm
Ni, ppm
Oil, ppm
PH
Temp, °C
Cu, ppm
Cr+6, ppm
FeT, ppm
F«>+3 t
re , /,
PH
Vol Feed,l x 10 "6
Cu Cemented, kg
Cr"*"6 Reduced, kg
Fe Dissolved, kg
Fe Required , kg
Fe Excess , %
Cu Cemented, 7.
643
117
139
1.3
71
13
9
26
2.4
33
115
0
68
7.68
2.5
0.31850
7.6
0.41
21.7
7.3
197
17.27
379
117
122
3.0
57
13
9
40
3.2
29.5
113
0
54
52.54
3.7
0.18735
1.69
0.56
10.1
2.39
323
7.38
537
117
125
2.4
64
13
9
26
2.7
32
111
0
61
22.51
3.0
0.26714
3.74
0.64
16.3
4.3
279
11.66
662
304
584
2.0
371
14
34
131
2.1
21
247
0
624
-
2.3
0.30800
104
0.62
192
92.4
108
57.71
583
304
110
3.0
44
10
7
77
2.6
25
85
0
78
0
3.5
0.28853
7.2
0.87
22.5
6.6
241
22.73
603
304
220
2.2
124
12
21
104
2.4
24
116
0
211
4.57
2.8
0.28923
30
0.64
61
21. U
123
37.51
44
-------
APPENDIX F
DATA AND CALCULATIONS FOR OPERATION IN INTERMITTENT MODE (A)
High Flow
Low Iron Surface
High Flow
High Iron Surface
Q
W
U
g
as
Q
a
i
§
Q
Q
g
H
H
g
a
*
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surface ,m2
Cu, ppm
Cr"1^, ppm
CrT, ppm
2n, ppm
Ni , ppm
Oil, ppm
PH
Temp, °C
Cu, ppm
Cr+6, ppm
FeT, ppm
Fe+3, %
PH
Vol Feed.l x 10 ~6
Cu Cemented, kg
Cr"^6 Reduced, kg
Fe Dissolved, kg
Fe Required , kg
Fe Excess , %
Cu Cemented, 7.
802
107
81
0.4
36
7
7
9
2.65
32
70
0
40
6.93
2.8
0.39334
4.33
0.16
15.7
4.06
287
13.58
977
107
96
2.6
46
9
7
19
2.8
30
94
0-
23
4.82
3.25
0.48338
0.97
1.26
11.1
2.88
285
2.08
887
107
82
1.2
38
8
7
14
2.6
30.5
75
0
32
8.51
2.8
0.43299
3.03
0.52
13.9
3.5
297
8.04
889
301
170
2.0
83
29
42
124
2.7
25
130
0
68
4.82
3.2
0.44029
17.6
0.88
29.9
16.9
77.00
23.53
818
301
212
37.3
127
11
6
63
2.5
26
198
12 for
< 1 hr
94
-
3.1
0.25753
3.61
9.61
24.2
18.6
29.81
6.60
896
301
197
14.3
112
20
24
94
2.8
25
166.5
< 1
75
14.48
3.3
0.35955
11
5.14
27
17.9
50.57
15.69
45
-------
APPENDIX G
DATA AND CALCULATION? FOR OPERATION IN INTERMITTENT MODE(B)
Low Flow Low Flow
Low Iron Surface High Iron Surface
Q
w
u
fa
g
Q
a
i
u
a
a
Q
£
1
H
3
u
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surface ,m^
Cu, ppm
Cr"1"6, ppm
Cr , ppm
£n , ppm
Ni, ppm
Oil, ppm
PH
Temp, °C
Cu, ppm
Cr+6, ppm
FeT, ppm
Fe+3, 7.
PH
Vol Feed,l x 10 "6
Cu Cemented, kg
Cr"1"6 Reduced, kg
Fe Dissolved, kg
Fe Required , kg
Fe Excess , 7.
Cu Cemented, 7.
579
129
50
0.1
20
15
5
81
2.9
29
44
0
55
0
2.9
0.29256
1.76
0.03
16.1
1.6
907
12.00
496
129
89
1.3
61
20
5
54
2.3
33
88
0
79
9.41
2.4
0.24781
0.25
0.32
19.6
0.74
2549
1.12
i
512
129
85
2.9
52
20
5
54
2.7
31
78
0.1
64
13.60
2.9
0.25620
1.79
0.72
16.4
2.73
501
7.64
526
284
1183
2.0
740
9
296
34
1.9
22
528
0
780
32.72
2.0
0.25253
165
0.51
197
146
35.04
556
284
54.5
1.3
25
7
4
11
3.0
18
52
0
29
1.76
3.35
0.25304
0.63
0.33
7.34
1.09
574
55.37 J4.59
569
284
290
1.5
172
8
102
22
2.7
21
152
0
187
11.02
3.1
0.26866
37
0.40
50.2
33.2
51.31
21.74
46
-------
APPENDIX H
DATA AND CALCULATIONS FOR OPERATION IN INTERMITTENT MODE(B)
High Flow
Low Iron Surface
High Flow
High Iron Surface
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surface .m^
Cu , ppm
Cr*6, ppm
CrT, ppm
d 2n, ppra
a Ni, ppm
D
§ Oil, ppm
PH
Temp, °C
g Cu, ppm
| Cr+6, ppm
j "r
3 Fe1, ppm
~* +3
"^
j
D P"
Vol Feed.l x 10 "6
to Cu Cemented, kg
2 Cr Reduced, kg
3 Fe Dissolved, kg
!j Fe Required , kg
u Fe Excess , %
Cu Cemented, %
912
104
62
0.7
25
6
4
14
2.9
28
56
0
22
0
3.1
0.43784
2.63
0.31
9.63
2.81
243
9.68
912
104
76
2
35
6
4
14
2.8
28
75
0
26
0
3.1
0.45153
0.45
0.90
11.7
1.85
533
1.32
893
104
85
1.4
34
12
6
24
2.8
28
80
0
25
3.0
0.43948
2.2
0.62
11.0
2.9
278
5.82
1
NOT RUN
47
-------
APPENDIX I
DATA AND CALCULATIONS FOR OPIillATION IN CONTINUOUS MODE (ORIGINAL P.UN)
Low Flow
Low Iron Surface
High Iron Surface
Cementation Efficiency Cementation Efficiency
Max Min Avg Max Min Avg
Flow, 1/min
Iron Surf ace ,m2
Q
w
w
§
ft
Q
8
|
u
0
OS
a
g
o
H
H
3
U
Cu , ppm
Cr , ppm
CrT, pom
2n, ppm
Ni, ppm
Oil, ppm
PH
Temp, °C
Cu, ppm
Cr+6, ppm
Fe , ppm
Fe+3, 7.
PH
Vol Feed,l x 10 "6
Cu Cemented, kg
Cr4"6 Reduced, kg
Fe Dissolved, kg
Fe Required , kg
Fe Excess , %
Cu Cemented, %
568
149
287
1.7
117
26.5
5
61
2.4
29
132
0
190
4.12
2.7
0.27252
42.2
0.46
51.8
37.8
36.96
54.01
530
149
97
0
39
17
4
79
2.8
26.5
63
0
211.5
7.94
2.75
0.21460
7.3
0
45.4
6.42
607
35.05
. 1
473
149
238
1.3
104
27
5
61
2.5
28.5
124
0
200.5
5.35
2.7
0.21954
25
0.29
44
22.4
96.25
45.92
48
-------
APPENDIX J
CHARACTERISTICS OF COPPER MUD
Mode of
Operat ion
Continuous
Flow
Iron
Surface
-p-
IO
Static
it
Inter.(A)
Inter. (B)
Total Cu
Cemented. kg
Low
Low
High
High
Low
Low
High
High
Low
Low
High
High
Low
LOW
High
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
176
39
55
40
99
31
55
195
19
129
15
46
9
186
11
Compos it ion of Mud
Dens ity,g/cc
1.0760**
1.2820
1.1290
1.3906
1.0520
1.3180
1.1758
1.2196
1.3426
1.3126
1.3320
1.2402
1.2506
1.3680
ti /"\ 9i Va °/
80.3 0.93
65 . 1 0 . 84
79.7 1.20
60 . 1 0 . 76
69.0 0.68
No Sample
63.4 1.13
76.1 0.79
71.8 0.82
60.5 1.00
64.8 1.02
62.7 0.98
67.9 1.48
66.2 0.85
58.7 0.95
No Sample
Cu.%
12.21
25.09
9.28
30.32
22.32
23.42
15.98
20.22
28.57
25.20
30.40
18.94
23.97
30.10
Other ,%
6.56
8.97
9.82
8.82
8.00
12.05
7.13
7.16
9.93
8.98
5.92
11.68
8.98
10.25
Average
1.2625
66.62 0.96
23.37
9.05
**Limited settling period; values excluded from averages
-------
APPENDIX K
CHARACTERISTICS OF FILTER CAKE
01
o
Mode of
Operat ion
Cont inuous
if
ir
it
S tat ic
ir
it
it
Inter. (A)
ii
it
ti
Inter. (B)
it
ti
ii
Flow
Low
Low
High
High
Low
Low
High
High
LOW
Low
High
High
Low
Low
High
High
Iron
Surface
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Vol Filter Composition of Filter Cake
Cake, m3 Density,g/cc
4.21
4.21
2.68
4.21
5.35
3.82
3.82
3.06
3.82
4.01
3.82
4.01
6.9
1.2366
Filter Not Run
1.1960
1.2366
1.1970
1.2306
1.2046
1.2820
1.2560
1.2486
1.2336
1.2580
1.1976
Filter Not Run
1.2606
No Sample
H20,%
69.4
68.6
64.5
68.6
67.0
66.9
66.2
68.5
65.6
67.6
65.2
68.9
67.6
Fe,7.
5.20
5.12
5.53
5.65
5.19
5.00
5.30
4.91
6.12
4.89
5.39
4.63
5.02
Cu, 7,
5.51
6.22
8.24
5.97
6.47
6.16
6.84
6.87
6.74
6.41
7.62
5.94
6.55
Average
3.59*
1.2337
67.28
5.23
6.58
*Filter cake generated per week
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-670/2-75-029
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
COPPER RECOVERY FROM BRASS MILL DISCHARGE BY
CEMENTATION WITH SCRAP IRON
5. REPORT DATE
April 1975; Issuing Date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Oliver P. Case
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORG '\NIZATION NAME AND ADDRESS
The Anaconda Co. - Brass Division
Research and Technical Center
P.O. Box 747
Waterbury, Connecticut 06720
10. PROGRAM ELEMENT NO.
1BB036; ROAP 21AZO; Task 23
11.X3WOCKXKX/GRANT NO.
S-803226-01-0
12. SPONSORING AGENCY NAME AND ADDRESS
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final 7/1/74 - 1/1/75
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report presents the results of studies of copper recovery (and incidental
reduction of hexavalent chromium) in brass mill discharge by passage of the discharge
over scrap iron in a rotating drum. The drum feed consisted of normal production
discharge of combined pickle rinse water and spent sulfuric acid and sulfuric acid -
bichromate pickle. About half of the total mill waste discharge over a period of 16
weeks was processed. Four modes of drum operation were studied: (1) continuous
rotation, (2) no rotation, (3) intermittent rotation (1 hr of - 5 min on), and (4)
intermittent rotation (2-1/2 hr off - 10 min on). Each mode was studied at two flow
levels and two scrap iron surface area levels. Data were evaluated in terms of per-
cent cementation of available copper, excess iron consumption over theoretical, and
completeness of chromium reduction. Results indicate that the over-riding factor in
the efficiency of copper cementation is the level of copper in the feed solution.
Hexavalent chromium is effectively reduced providing the pH is below 2.5.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Water pollution
*Metal finishing
*Materials recovery
Industrial wastes
Waste water
*Copper recovery
*Hexavalent chromium
reduction
Water pollution abatement
Metal finishing wastes
Metal recovery
Cementation
Iron reductant
13B
13. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
59
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
51
. GOVERNMENT PRINTING OFFICE: 1975-657-592/535't Region No. 5-11
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