WATER POLLUTION CONTROL RESEARCH SERIES 12010 DIM 08/70
Pyrite Depression by Reduction
of
Solution Oxidation Potential
ENVIRONMENTAL PROTECTION AGENCY WATER QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH
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PYRITE DEPRESSION BY REDUCTION
OF
SOLUTION OXIDATION POTENTIAL
Department of Mineral Engineering
University of Utah
Salt Lake City, Utah 84112
for
ENVIRONMENTAL PROTECTION AGENCY
WATER QUALITY OFFICE
Grant Number 12010 DIM
December, 1970
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EPA Review Notice
This report has been reviewed by the Water Quality Office of the
Environmental Protection Agency and approved for publication.
Approval does not signify that the contents necessarily reflect
the views and policies of the Water Quality Office of the
Environmental Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or recommendation
for use.
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ABSTRACT
A study of pyrite depression by reducing agents with
potassium ethylxanthate as collector indicates that pyrite
may be depressed effectively in the flotation of both lead
and copper sulfide ores without the use of poisonous cyanide
salts. More specifically, the use of sodium sulfite as the
depressant may result in metallurgical, economical, environ-
mental and safety advantages over the poison, cyanide. For
example, in the case of the copper ore, the best results
with cyanide as the depressant were a rougher concentrate
recovery of 90.2% and a grade of 4.3% Cu. However, when
sulfite was used as the depressant for the same recovery
a grade of 7.3% Cu was obtained.
Experimental results support the theory that dixanthogen
is the collector species responsible for pyrite flotation.
The study shows that pyrite depression is possible by
maintaining a reduced solution oxidation potential thus
preventing dixanthogen formation. Depression was effected
with the following reducing agents and in all cases the
results were similar; sulfite, sulfide, thiosulfate, hypo-
phosphite and oxalate. The proposed mechanism of depression
involves the adsorption of the reductant on surface active
sites, thus preventing the adsorption and dissociation of
molecular oxygen to nascent oxygen. In the case of sulfite
the adsorption reaction is shown below:
-------
ss ss cr
/ . / V /
Fe + S03 aqueous * F\ /°~S\
X ^S £ \
SS SS 0
Pyrite Surface Pyrite Surface
This report was submitted in fulfillment of Grant
Number 12010 DIM between the Environmental Protection Agency
(EPA) and the Grantee.
Key Words :
f 1 otati on
py ri te
depression
reducing agents
cyanide
sulfite
ethyl xanthate
oxidation potential
11
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CONTENTS
SECTION PAGE
ABSTRACT 1
CONCLUSIONS & RECOMMENDATIONS vii
INTRODUCTION 1
EXPERIMENTAL TECHNIQUES 5
Reagents 5
Flotation Experiments with Singular Minerals 6
Zeta Potential Experiments 8
Oxidation Potential Measurements 9
Froth Flotation Experiments with Ore Samples 10
EXPERIMENTAL RESULTS 12
Flotation Experiments with Singular Minerals 12
Zeta Potential Experiments 21
Oxidation Potential Experiments 21
Froth Flotation Experiments with Ore Samples 27
DISCUSSION 39
ACKNOWLEDGEMENTS 46
REFERENCES 47
PUBLICATIONS 50
ill
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FIGURES
FIGURE PAGE
1 Schematic diagram of flotation apparatus 7
2 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 M KEX and at four levels
of addition of sodium sulfite 13
3 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 M KEX in the presence
and absence of zinc sulfite 14
4 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 M KEX and at four levels
of addition of sodium sulfide 16
5 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 ^ KEX in the presence and
absence of sodium thiosulfate 17
6 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 M KEX in the presence and
absence of sodium hypophosphite 18
7 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 M_ KEX and at three levels
of addition of sodium oxalate 19
8 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 1Q-4 M. KEX and 1 x 10'3 M
sodium sulfite for two different conditioning times . . 20
9 Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH at two levels of addition of KEX .... 22
10 Flotation recovery of pyrite, 65 x 100 mesh, as a
function of pH with 2 x 10~4 N[ KEX in the presence and
absence of sodium sulfite 23
11 Flotation recovery of pyrite, minus 200 mesh, as a
function of pH with 2 x 10-4 M^ KEX in the presence and
absence of sodium sulfite 24
12 Flotation recovery of galena, 100 x 200 mesh, as a
function of pH with 10-3 ^ additions of several
reducing agents and 2 x 10-4 M KEX 25
i v
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FIGURE PAGE
13 Zeta potential of pyrite as a function of pH in the
absence and presence of various additions of sodium
sulfite ........................ 26
14 Solution oxidation potential as a function of pH,
pyrite (100 x 200 mesh), 2 x TO"4 M KEX, and various
levels of addition of sodium sulfide (European
Convention) . ..................... 28
15 Percent recovery and grade percent of chalcopyrite-
pyrite ore with KEX as a function of sodium cyanide
addition ....................... 31
16 Percent recovery and grade percent of chalcopyrite-
pyrite ore with KEX as a function of sodium sulfite
addition ....................... 32
17 Percent recovery and grade percent of galena-pyrite
ore with KEX as a function of sodium cyanide
addition ....................... 36
18 Percent recovery and grade percent of galena-pyrite
ore with KEX as a function of sodium sulfite
addition ....................... 37
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TABLES
TABLE PAGE
I Experimental Flotation Results Obtained with
Chalcopyrite-Pyrite Ore with 2.0 Ib. per ton CaO
and Various Amounts of Sodium Cyanide Depressant ... 29
II Experimental Flotation Results Obtained with
Chalcopyrite-Pyrite Ore using Various Amounts of
Sodium Sulfite Depressant at pH 8 30
III Experimental Flotation Results Obtained with Galena-
Pyrite Ore using Various Amounts of Sodium Cyanide
Depressant at pH 8.0 34
IV Experimental Flotation Results Obtained with Gal ena-
Pyrite Ore using Various Amounts of Sodium Sulfite
Depressant at pH 8.0 35
vi
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CONCLUSIONS AND RECOMMENDATIONS
As was anticipated from the fact that dixanthogen is
the collector species responsible for pyrite flotation, all
reducing agents studied had the ability to depress pyrite
when ethylxanthate was used as collector. Sulfite, a good
reducing agent, appears to function exceptionally well as
a pyrite depressant. Sulfite can be used as effectively as
cyanide in galena-pyrite and chalcopyrite-pyrite ores with
ethyl xanthate as the collector. In fact, sulfite exhibits
no depressant effect on chalcopyrite, whereas excessive
cyanide can completely depress chalcopyrite. In the case
of the chalcopyrite-pyrite ore, a significant improvement
in concentrate grade was obtained when sulfite rather than
cyanide was used as the depressant. Equivalent metallurgical
results were obtained with either sulfite or cyanide as
depressants in the galena-pyrite ore.
Sulfite was shown to be potential determining for pyrite,
which supports the mechanism proposed for pyrite depression
by reducing agents. The solution potential reducing agents
adsorb at the pyrite surface, preventing the adsorption and
dissociation of molecular oxygen to nascent oxygen and in
this manner, prevent oxidation of xanthate to dixanthogen
and subsequent flotation. Meaningful oxidation potentials
could not be obtained with a platinum electrode when oxyanion
reductants were used to effect pyrite depression. However,
the platinum electrode can be used as a monitor when sulfide
vii
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ion is used as the depressant.
Laboratory study has shown that poisonous cyanide salts
need not be used, both from metallurgical and economical
criteria, for the depression of pyrite in sulfide flotation
systems. This is a most important conclusion in view of
the recent interest of government and society on water
pollution and safety. Consequently, it is recommended that
this study be broadened in order to demonstrate that
similar results can be obtained on an industrial scale. For
such a study to be feasible an united effort and complete
cooperation between the University, EPA ,and industry is
requi red.
vi i i
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INTRODUCTION
One of the principle means of processing the Nation's
raw materials involves the technique of froth flotation.
Froth flotation is the process whereby surfactants (termed
collectors) are adsorbed on selected minerals in a particulate
suspension. This renders the selected minerals hydrophobic
and on passing air through the suspension, the hydrophobic
particles concentrate in a froth column thus effecting their
separation from the worthless gangue particles. Almost all
sulfide ores are processed by the froth flotation technique,
and in so doing the rejection or depression of pyrite, a
common sulfide mineral, to the worthless gangue or tailing
product is frequently required to make an effective
separation. Industrially this is most readily accomplished
with xanthate as collector for the valuable sulfides such
as chalcooyrite and galena, and poisonous cyanide salts
as a pyrite depressant, i.e., the cyanide salts prevent
adsorption of the collector on the pyrite surface and
subsequent flotation.
Dixanthogen, an oxidation product of xanthate, is the
species responsible for pyrite flotation . In most sulfide
flotation systems pyrite depression is desired, therefore,
it should be possible to use various chemicals to reduce
the oxidation potential of the solution and depress pyrite
by preventing the formation of the collector, dixanthogen.
On this basis,the purpose of our research was to establish
1
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that pyrite could be effectively depressed with non-toxic
reducing agents which do not have the adverse ecological
and emotional problems associated with the poisonous cyanide
sal ts.
p -3
The first industrial technique of flotation ' was to
collect mineral particles in an oily layer which could then
be separated from the gangue and water. The oil flotation
procedure has been replaced by a method known as froth
flotation, where bubbles carrying mineral particles rise to
the surface and are removed in the froth, leaving the gangue
behind.
The observation that different collectors changed
flotation results and the patenting of xanthate, dithio-
carbonate, in 1925 increased the use of flotation as a
separation technique in mineral processing operations.
Attention was then centered on means of floating one sulfide
mineral away from others. This was accomplished by using
various chemical reagents as depressants and activators.
The depressants allowed one or more minerals to float while
suppressing others with the gangue, while the activators
caused otherwise unfloatable minerals to become floatable.
The first depressants were alkalis and cyanide compounds
which were followed by many organic and inorganic compounds.
The depressant effect of alkalis was investigated by Wark
ef-
5-9
and Cox , and the depressant effect of cyanide has been the
topic of many investigations
2
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Gaudin has shown that many anions act as depressants
for sulfide minerals, but little information on mechanisms
was given. The mechanisms for depression of sulfide
minerals have remained obscure, because the mechanisms for
flotation have been obscure. This is evidenced by the
number of theories proposed to explain the flotation
mechanisms Gaudin proposed that the adsorption of
xanthate on sulfide minerals was the result of an ion
1 2
exchange mechanism. Wark proposed that xanthates adsorb
on a sulfide mineral by exchanging with hydroxyl and sulfur
ions on the surface. Mellgren presented evidence which
supports a theory of insoluble salt formation between the
collector and the mineral as a mechanism for flotation.
Another mechanism,, given by Cook and Nixon , is the chemical
adsorption of a neutral molecule on the surface.
The mechanism for xanthate flotation of pyrite has
been considered extensively ' 5~zo. Recently, Fuerstenau
showed that the oxidation product, dixanthogen, is the species
responsible for pyrite flotation when xanthate is used
as the collector. Majima and Takeda18 verified the exist-
ence of dixanthogen on pyrite with infrared spectroscopy.
Most probably dixanthogen is formed by adsorbed nascent
oxygen oxidation of xanthate.
Since the pyrite flotation mechanism has been well
established, it should be possible to analyze the depression
of pyrite. The cyanide depression mechanism of pyrite has
3
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been determined . However, the mechanism of pyrite
depression with other depressants, especially reducing
agents, has not been analyzed in light of the recent theory
advanced for pyrite flotation. Because of the environmental
and safety problems presented by cyanide depress ion, research
was initiated to determine the flotation response of pyrite
in the presence of non-toxic reducing agents.
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EXPERIMENTAL TECHNIQUES
The investigation included the four following tech-
niques: flotation experiments with singular minerals,
zeta potential experiments, oxidation potential measurements,
and froth flotation experiments with ore samples.
Reagents
The reagents as discussed here, will apply to all of
the experiments in this investigation.
Commercial potassium ethylxanthate (KEX) was purified
by dissolving the xanthate in a minimum amount of acetone
and recrystal1izing the xanthate by the addition of cold
?n
petroleum ether . After recrystal1ization the material
was filtered, washed with petroleum ether, and dried. This
purification method gives a purity of better than 99 percent.
The purified xanthate was stored in an airtight container
in a refrigerator until used.
Deionized, distilled water was used in all experiments
except for the froth flotation experiments on ore samples,
where tap water was used.
Pure pyrite mineral specimens and the galena-pyrite
ore were obtained from Park City, Utah. Pure galena was
obtained from Minerals Unlimited. The chalcopyrite-pyrite
ore was typical of the southwestern copper porphory ores.
All of the chemicals used in this investigation were
of reagent grade quality or better.
5
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Flotation Experiments with Singular Minerals
21
A modified Hallimond tube flotation cell was used
to determine the effect of certain reducing agents on the
flotation response of pyrite and galena with potassium
ethylxanthate as the collector. The apparatus, described
in Figure 1, consisted of a fritted-glass bottom tube
through which air was controlled by a manometer, constant
head reservoir, and a gas measuring burette. A magnetic
stirrer with a teflon-coated stirring bar was used to
maintain constant agitation.
The following procedure was used for both pyrite and
galena mineral samples:
1. The mineral was dry-ground with a porcelain mortar
and pestle, then sized with Tyler standard sieves within
24 hours prior to the flotation test.
2. A sized 1.0 gram sample was used as the flotation
sample.
3. The flotation sample was deslimed 5 times with
deionized water prior to each test.
4. Deionized water, xanthate, and reducing agent
were mixed to yield the desired concentration of 130 mill-
iliters total volume.
5. The desired solution pH was obtained with either
KOH or HC1.
6. The deslimed mineral was added to the solution.
7. The pulp was conditioned for 3 minutes.
6
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Constant head
water tank
Manometer
Air measuring
burette
Compressed- Air Reservoir
air Line
Hallimond tube
floation cell
Figure 1. Schematic diagram of flotation
apparatus.
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8. The pH of the pulp was measured and recorded after
conditioning.
9. The pulp was transferred to the Hallimond tube
flotation cell and floated for 2 minutes at constant agitation
and at 70 milliliters per minute air flow rate.
10. The pH was measured after flotation to determine
if a significant change occurred.
11. The concentrate and tailing products were dried,
weighed and the percent recovery calculated.
Zeta Potential Experiments
The zeta potential of pyrite was determined at various
concentrations of sodium sulfite and at various pH values.
The pH at which the zeta potential of the pyrite surface
reached zero was determined graphically, and this pH is
called the zero-point-of-charge (ZPC).
The equipment consisted of a Zeta Meter to determine
the zeta potential at the pyrite surface and a Beckman
Zeromatic II pH meter to measure pH. A magnetic stirrer
with a teflon-coated magnetic stirring bar was used to
maintain agitation during conditioning.
The following procedure was used to obtain the desired
sample conditions for the zeta potential determinations.
1. The pyrite was dry-ground with a porcelain mortar
and pestle, then screened through a 200 mesh Tyler sieve.
2. The minus 200 mesh pyrite was weighed out into
50 milligram samples.
8
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3. Deionized water and sodium sulfite were added
to a 150 mi Hi liter beaker to give a total volume of 100
milliliters and the desired concentration of sodium sulfite.
4. The 50 milligram pyrite sample was added to the
water and sodium sulfite solution.
5. The pK of the sample was adjusted with either HC1
or KOH.
6. The sample was conditioned for 3 minutes to
approximate the flotation conditions of the pyrite.
7. The pH of the sample was measured and recorded.
8. The resulting suspension was decanted into a
plexiglass electrophoretic cell, electrodes inserted, and
placed under the microscope.
9. A potential was applied across the electrodes.
10. The average time for a particle to move horizon-
tally between two lines of the grid was recorded. This time
was translated into zeta potential from standard charts.
The measured zeta potentials were plotted against pH, and
a ZPC was determined from the resulting curve.
Oxidation Potential Measurements
The apparatus used in these measurements consisted of
a Beckman Zeromatic II pH meter, a calomel reference
electrode, a platinum electrode, a glass electrode, magnetic
stirrer with teflon-coated magnetic stirring bar, and a
250 milliliter beaker.
The following procedure was used in preparing the samples
9
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and making measurements.
1. The pyrite was dry-ground with a porcelain mortar
and pestle, then sized with Tyler sieves.
2. A 1.0 gram sample, 100 X 200 mesh, was used as in
flotation experiments.
3. Deionized water, xanthate, and reducing agent were
mixed to yield the desired concentrations of 130 milliliters
total volume.
4. The pH was adjusted with either KOH or HC1.
5. The deslimed pyrite was added to the above solution.
6. The pulp was conditioned for 3 minutes.
7. The pH was measured and recorded.
8. The solution oxidation potential was measured and
recorded.
9. The Eh was calculated from the cell potential,
Eh = Ecell + Eref.
Froth Flotation Experiments with Ore Samples
Experimental equipment consisted of an ore crusher, a
rod mill, a Wemco froth flotation cell, a Beckman Zeromatic
II pH meter, and a Mettler top load electronic balance.
The following procedure was used on both the galena and
the chalcopyrite ores.
1. Approximately 100 Ibs of ore was crushed, then
coned and quartered, and split with a riffle until approx-
imately 500 gram samples resulted.
3. 500 grams of a sample was weighed out on the top
10
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loading balance and placed in the rod mill with 333
milliliters of tap water.
3. The ore was ground at 60 percent solids in the rod
mill for 3 minutes and the resulting pulp was transferred
to the flotation cell with 1667 milliliters of tap water.
4. Varying amounts of sodium sulfite or sodium cyanide
and 0.05 pounds per ton KEX were added to the cell.
5. The pH was adjusted and the pulp was conditioned
at 20 percent solids for 5 minutes.
6. 3 drops of Aerofroth 65 were added, the air was
turned on, and the sample was floated for 8 minutes.
7. The concentrate and tailing products were dried,
weighed, and analyzed to test the effectiveness of the
depressant.
11
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EXPERIMENTAL RESULTS
The flotation response of pyrite and galena in a
Hallimond cell with KEX as the collector and various reducing
agents as depressants was investigated. Zeta potential
and solution oxidation potential measurements were made on
these systems. Flotation tests with lead and copper ore
samples were made to compare the effectiveness of sodium
cyanide and sodium sulfite as depressants for pyrite. The
experimental data from these tests are presented in this
section.
Flotation Experiments with Singular Minerals
Various reducing agents at different concentration levels
were tested to determine their ability to depress pyrite
and to establish the mechanism for depression with KEX as
the flotation collector.
The flotation response of pyrite with KEX in the presence
of various additions of sodium sulfite is shown in Figure 2.
When no sodium sulfite is present, complete depression is
effected above pH 10; whereas, with increasing sulfite
additions the pH for depression is lowered to what appears
to be a minimum of pH 5 for additions of 10"3 M, and greater.
The flotation response of pyrite with KEX in the presence
and absence of zinc sulfite is shown in Figure 3. When
zinc sulfite is present, complete depression is effected
above pH 5.
12
-------
u>
oc
UJ
§
u
UJ
IT
U
O
cr
UJ
a.
100
80
60
20
Sodium Suffite
None
o
D |x|o"2M
6 8 10
FLOTATION pH
14
Figure 2
Flotation recovery of pyrite,
of pH with 2 x 10-4 M KEX and
sodium sulfite.
TOO x 200 mesh, as a function
at four levels of addition of
-------
100
80
o:
u
IĞ>
40
20
u
o:
Zinc Sulfite:
o None
a Ixio"3M
468
FLOTATION pH
10
12
14
Figure 3. Flotation recovery of pyrite, TOO x 200 mesh, as a function
of pH with 2 x 10~4 M_ KEX in the presence and absence of
zinc sulfite.
-------
The flotation response of pyrite with KEX in the
presence of various additions of sodium sulfide is shown in
_3
Figure 4. Addition of 10 M. sodium sulfide is required
-5
to depress pyrite, while additions of 10 M_ sodium sulfide
have no effect on the flotation response.
The flotation response of pyrite with KEX in the presence
and absence of sodium thiosulfate is shown in Figure 5.
Sodium thiosulfate acts as a depressant at pH 7 and above,
but shows little effect below pH 7.
The flotation response of pyrite with KEX in the presence
and absence of sodium hypophosphite is shown in Figure 6.
Sodium hypophosphite is a pyrite depressant above pH 6, but
shows little effect on pyrite below pH 6.
The flotation response of pyrite with KEX in the
presence of various additions of sodium oxalate is shown
in Figure 7. Sodium oxalate is not as effective as the
other reducing agents in pyrite depression. Depression
occurs only above pH 8.
Figures 2 thorugh 7 show that sulfite is one of the
most effective depressants tested. These figures aloo show
that the best pyrite depression occurs in basic media and
that below pH 4.5, no depression is observed with any
depressant.
Figure 8 indicates that the effectiveness of sodium
sulfite is long-lasting, in that pyrite is depressed as
well, or even better, after a ten minute conditioning time
15
-------
100
60
OL
UJ
O 60
u
LJ
cc
u
g
bJ
40
20
Figure 4.
Sodium Suffide:
o None
a lxlo"5M
ix io"4M
lx|0~*M
6 8 10
FLOTATION pH
12
14
Flotation recovery of pyrite, 100 x 200 mesh, as a
function of pH with 2 x 10-4 y\ KEX, and at four levels
of addition of sodium sulfide.
-------
IOO
80
tr
UJ
UJ
or
ui
o
(T
bl
a.
40
20
Figure 5
KEX: 2x 1C)4 M
Sodium Thiosulfote
o None
n lxio"5
6 8
FLOTATION
IO
12
PH
Flotation recovery of
of pH with 2 x 10-4 M
sodium thiosulfate.
pyrite, 100 x 200 mesh,
KEX in the presence and
14
as a function
absence of
-------
100
oo
cc
UJ
I
bJ
CC
z
UJ
u
cc
80
60
40
20
Sodium Hypophosphite
o None
n |x io"5M
Figure 6,
6 8
FLOTATION pH
10
12
Flotation recovery^of pyrite, 100 x 200 mesh,
of pH with 2 x 10 4 M^ KEX in the presence and
sodium hypophosphite.
14
as a function
absence of
-------
100
>-
QC
80
8 60
ui
a:
u
ac
in
a.
4O
20
KEX: 2xlO~4M
Sodium Oxalatc:
None
o I x lo"4 M
a I x |0"SM
46 8 10
FLOTATION pH
12
14
Figure 7. Flotation recovery of pyrite, 100 x 200 mesh as a function
of pH with 2 x TO'4 n KEX and at three levels of addition
of sodium oxalate.
-------
ro
o
too
> 80
or
Id
§60
u
a:
UJ
o
oe
40
Figure 8.
KEX= 2 x |Q"4M
Sodium Sulfite: IO"3M
o 10 Minute
P 3 Minute
n
4 6 8 10
FLOTATION p H
12
14
Flotation recovery of pyrite, 100 x 2QO mesh, as a function
of pH with 2 x 10-4 j^ KEX and 1 x 10~ M sodium sulfite
for two different conditioning times.
-------
as it was after a three minute conditioning time.
As can be seen in Figure 9, pyrite flotation response
does not change considerably from a KEX concentration of
2xx 10 mole per liter to a KEX concentration of 5 x 10~
mole per liter. This determination was made because the
ore samples were floated at a KEX level of about 5 x 10~
mole per liter.
Figures 10 and 11 illustrate that the size of the pyrite
particles are relatively unimportant in the sodium sulfite
depression system.
Oxyanion reductants do not affect the flotation response
of galena, as Figure 12 illustrates. The galena floats as
well in the presence of the reductants as in their absence.
Zeta Potential Experiments
The zeta potential of pyrite in the absence of sulfite
and at two levels of sulfite addition was determined as
a function of pH. See Figure 13. It appears that the
sulfite anion has a special affinity for the pyrite surface,
in that the ZPC is pH 7 with no sulfite addition, pH 6
with 10"4 M sulfite, and pH 5 with 10"3 M sulfite.
Oxidation Potential Measurements
Solution oxidation potential measurements of each
pyrite flotation system were attempted; however, in oxyanion
reductant systems, it was not possible to obtain meaningful
measurements. No variation in the platinum-calomel cell
potential could be detected, even though the concentration
21
-------
too
ro
or
UJ
I
UJ
oc
UJ
o
tr
ui
a.
80
60
40
20
o 2 x io"4M KEX
n 5 x 10"5M
KEX
4 6 8 IO
FLOTATION pH
12
14
Figure 9. Flotation recovery of pyrite, 100 x 200 mesh as a function
of pH at two levels of addition of KEX.
-------
ro
100
>80
QL
LJ
8 60
UJ
40
UJ
0.
20
Figure 10
KEX*. 2 x |0"4 M
Sodium Sulfite:
o None
D |x|o"5
4 8 10
FLOTATION pH
12
14
Flotation recovery.of pyrite, 65
of pH with 2 x 10 M. KEX in the
sodium sulfite.
x 100 mesh, as a function
presence and absence of
-------
100
>
OC
LU
O
80
PO
LJ
O
QC
UJ
0.
40
20
Sodium Sulfite: _
o None
a I x I0"3 M
6 8 10
FLOTATION pH
14
Figure 11. Flotation recovery of pyrite
function of pH with 2 x 10~4
absence of sodium sulfite.
minus 200 mesh, as a
M KEX in the presence
and
-------
ro
on
100
> 80
oc
UJ
O
Ğ M
u 60
o:
h-
w 4O
o
o:
Q.
20
I
KEX
V w . -i VX 0 w - u ^fc , ,
-4 \
:2x|Q U \
Depressant: \
\
a None I
o I
1
|
-
i
0 2
xlO"3M Sodium Sulfite 1
ttr I
xlO"3M Sodium Thiosulfote 1
xlo"5M Sodium Hypophosphite 1
1
A
i
I
-
iii it i
46 8 10 12 14
FLOTATION pH
Figure 12. Flotation recovery of galena, 100 x 200 mesh, as a
function of pH with 10'3 M, additions of several reducing
agents and 2 x 1Q-4 KEX.
-------
no
+ 50
+40
*Ğ
? +30
>
I +20
j +10
UJ
o
a.
£
-IO
- 20
-40
-50
No2S03 Addition:
None
I x 10
I x
8
10
12
14
PH
Figure 13
Zeta potential of pyrite as a function of pH in the absence
and oresence of various additions of sodium sulfite.
-------
of reductant was changed by several orders of magnitude.
Meaningful solution oxidation potential readings were
obtained in the sodium sulfide system, as illustrated in
Figure 14. The potential readings in this figure have been
converted to Eh (hydrogen electrode reference), and are
plotted against pH. The dotted line drawn through the data
represents the 50 percent recovery isotherm, as determined
from flotation experiments. Above the dotted line, good
flotation response is obtained and below the dotted line,
poor flotation response is obtained.
Froth Flotation Experiments with Ore Samples
Tables I and II show the flotation results of the
chalcopyrite-pyrite ore when sodium cyanide and sodium
sulfite, respectively, were the depressants. By comparing
these two tables the relative effectiveness of each depressant
can be determined. The columns labeled Fe Units and Cu Units,
are weights of the respective elements based on a total
weight of 100 grams. The distribution percentages of Fe and
Cu show that sodium sulfite is just as effective as sodium
cyanide for depressing pyrite in a chalcopyrite ore.
Graphical representation in Figures 15 and 16 show that
Fe percent recovery falls off with increasing depressant
addition in both cyanide and sulfite systems. This means
that both sodium cyanide and sodium sulfite can effectively
depress pyrite.
Comparison of the Cu percent recovery of both curves,
27
-------
IS5
00
+0-5
+0-4
+0-3
+0-2
o
bj -i
-0-2
-03
-0-4
Figure 14.
KEX' 2 x I0"4 M
Sodium Sulfide
o None
D I x K>~* M
I x 10 M
A |xlO"5M
8
10
12
14
PH
Solution oxidation potential as a function of pH, pyrite
(100 x 200 mesh), 2 x 10-4 M KEX, and various levels of
addition of sodium sulfide TEuropean Convention).
-------
TABLE I
Experimental Flotation Results Obtained With
Chalcopyrite-Pyrite Ore With 2.0 1b per ton
CaO and Various Amounts of NaCN Depressant
vo
PH
8.5
8.65
8.65
8.80
Depressant
Amount
None
0.05 Ib
per ton
0.10 Ib
per ton
0.50 Ib
per ton
Product
Product Wt, grains
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
82
412
72
425
60
443
40
434
Wt,%
16.6
83.4
100.0
14.5
85.5
100.0
12.0
88.0
100.0
8.5
91.5
100.0
Fe,
20.
2.
15.
2.
16.
6.
9.
4.
%
4
6
7
9
6
4
3
6
Cu,%
4.30
0.09
4.30
0.08
4.60
0.12
2.30
0.67
Fe
Units
3.39
2.17
5.56
2.26
2.46
4.72
2.00
5.67
7.67
0.74
4.00
4.74
Cu
Units
0.710
0.075
0.785
0.620
0.067
0.687
0.560
0.106
0.666
0.180
0.580
0.760
Fe Distri-
bution^
60.9
39.1
100.0
47.8
52.2
100.0
26.1
73.9
100.0
15.6
84.4
100.0
Cu Distri-
bution,%
90.5
9.5
100.0
90.2
9.8
100.0
84.2
15.8
100.0
31.0
69.0
100.0
-------
CO
o
TABLE II
Experimental Flotation Results Obtained With
Chalcopyrite-Pyrite Ore Using Various Amounts
of Sodium Sulfite Depressant at pH 8
Depressant
Amount
None
0.25 Ib
per ton
0.50 Ib
per ton
0.75 Ib
per ton
1.00 Ib
per ton
Product
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Product
Wt, grams
53
443
55
443
44
453
43
453
39
461
Wt,%
10.7
89.3
100.0
11.0
89.30
100.0
8.9
91.1
100.0
8.7
91.3
100.0
7.8
92.2
100.0
Fe,%
26.8
2.3
24.4
2.3
28.0
7.7
23.8
4.9
28.0
14.5
Cu,%
5.90
0.08
5.80
0.08
7.30
0.08
6.20
0.13
7.70
0.10
Fe
Units
2.84
2.04
4.88
2.68
2.04
4.72
2.46
7.00
9.46
2.04
4.44
6.48
2.18
13.34
15.52
Cu
Units
0.620
0.070
0.690
0.640
0.070
0.710
0.640
0.072
0.712
0.536
0.118
0.654
0.600
0.092
0.692
Fe Distri-
bution,/^
58.3
41.7
100.0
56.8
43.2
100.0
26.0
74.0
100.0
31.6
68.4
100.0
14.1
85.9
100.0
Cu Distri
bution,%
90.2
9.8
100.0
90.2
9.8
100.0
89.9
10.1
100.0
82.0
18.0
100.0
86.0
13.4
100.0
-------
10
Iron Recovery
o Copper Recovery
A Copper Grode
0-2 0-4 06 0-8 1-0 1-2
SODIUM CYANIDE ADDITION (Pounds/Ton)
1-4
100
80
UJ
60 §
u
40
20
ui
u
flC
Ul
Q.
Figure 15,
Percent recovery and grade percent of chalcopyrite-pyrite ore
with KEX as a function of sodium cyanide addition.
-------
10
CO
ro
Iron Recovery
o Copper Recovery
Copper Grade
100
80
o
I-
40 g
o
cr
UJ
Q.
20
0-2 0-4 0-6 0-8 1-0 1-2
SODIUM SULFITE ADDITION (Pounds/Ton )
1-4
Figure 16,
Percent recovery and grade percent of chalcopyrite-pyrite
ore with KEX as a function of sodium sulfite solution.
-------
reveals that sodium cyanide not only depressed pyrite
but also depressed the chalcopyrite. Recovery dropped
from about 90 percent at .05 Ib per ton to 30 percent
at 0.5 Ib per ton. Sodium sulfite had little effect on
the flotation recovery of chalcopyrite. Recovery decreased
from 90 percent at 0.25 Ib per ton to 86 percent at 1.0
Ib per ton. Comparison of concentrate grade, percent Cu,
of the cyanide and sulfite systems indicates the same
results, sulfite is a depressant for pyrite but not for
chalcopyrite whereas, cyanide can be depressant for both
pyrite and chalcopyrite. For example, with sodium sulfite
the percent copper in the concentrate increases from about
6 percent at 0.25 Ib per ton to almost 8 percent at 1.0 Ib
per ton. This is to be compared with results in the cyanide
system in which the percent copper in the concentrate
drops from about 4.5 percent at low levels of cyanide to
about 2.5 percent at 0.5 Ib per ton.
Table III and IV show the flotation results of the
galena-pyrite ore when sodium cyanide and sodium sulfite
were the depressants. Again, the columns labeled Fe Units
and Pb Units refer to the weight of the respective elements
based on a total weight of 100 grams. Comparison of these
tables gives the relative effectiveness of each depressant.
Both depressants are effective for pyrite depression.
Figures 17 and 18 graphically demonstrate that both
cyanide and sulfite depress pyrite in a galena-pyrite ore.
33
-------
CO
TABLE III
Experimental Flotation Results Obtained With
Galena-Pyrite Ore Using Various Amounts of
Sodium Cyanide Depressant at pH 8.0
Depressant
Amount
None
0.10 Lb
Per Ton
0.25 Lb
Per Ton
0.50 Lb
Per Ton
0.75 Lb
Per Ton
1.00 Lb
Per Ton
Product
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Product
Wt, grams
251
244
102
393
106
389
99
400
112
387
117
380
Wt,*
50.7
49.3
100.0
21.6
79.4
100.0
21.4
78.6
100.0
19.8
80.2
100.0
22.5
77.5
100.0
23.6
76.4
100.0
Fef%
20.9
12.8
5.8
32.6
4.7
22.7
11.6
22.1
5.8
18.3
8.1
23.3
Pb.X
30.5
2.0
46.0
6.0
54.6
6.2
49.0
8.0
43.3
7.0
43.3
7.8
Fe
Units
10.6
6.3
16.9
1.19
25.85
27.04
1.00
17.85
18.85
2.30
17.70
20.00
1.30
14.20
15.17
1.91
17.80
19.71
Pb
Units
15.50
0.99
16.49
9.48
4.76
14.24
11.70
4.88
16.58
9.71
6.42
16.13
9.75
5.42
15.17
10.20
5.95
16.15
Fe Distri-
bution,/^
62.7
37.3
100.0
4.4
95.6
100.0
5.4
94.6
100.0
11.5
88.5
100.0
8.4
91.6
100.00
9.7
90.3
100.0
Pb Distri-
bution,%
94.0
6.0
100.0
66.4
33.6
100.0
70.6
29.4
100.0
60.4
39.6
100.0
64.2
35.8
100.0
63.0
37.0
100.0
-------
CO
CJ1
TABLE IV
Experimental Flotation Results Obtained With
Galena-Pyrite Ore Using Various Amounts of
Sodium Sulfite Depressant at pH 8.0
Depressant
Amount
None
0.25 Lb
Per Ton
0.50 Lb
Per Ton
0.75 Lb
Per Ton
1.00 Lb
Per Ton
Product
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Concentrate
Tail
Total
Product
Wt, grams
251
244
148
349
111
383
87
410
91
407
Wt,%
50.7
49.3
100.0
29.8
70.2
100.0
22.5
77.5
100.0
17.5
82.5
100.0
18.2
81.8
100.0
Fe,*
20.9
12.8
11.6
20.9
16.3
23.0
9.9
25.0
7.6
12.5
Pbt%
30.5
2.0
43.3
4.7
46.6
4.3
44.0
4.7
56.6
6.0
Fe
Units
10.6
6.3
16.9
3.5
14.6
18.1
3.4
17.8
21.5
1.7
20.6
22.3
1.4
10.2
11.6
Pb
Units
15.50
0.99
16.49
12.90
3.30
16.20
10.50
3.33
11.58
7.70
3.88
11.58
10.30
4.90
15.20
Fe Distri-
bution^
62.7
37.3
100.0
19.1
80.9
100.0
17.0
83.0
100.0
7.8
92.2
100.0
11.8
88.2
100.0
Pb Distri-
bution^
94.0
6.0
100.0
79.5
20.5
100.0
76.0
24.0
100.0
66.7
33.3
100.0
68.0
32.0
100.0
-------
CO
too
Iron Recovery
o Lead Recovery
A Lead Grode
0-2 0-4 0-6 0-8 1-0 1-2
SODIUM CYANIDE ADDITION (Pounds/Ton)
1-4
100
80
>-
a:
a:
20
IS
Figure 17
Percent recovery and grade percent of galena-pyrite ore with
KEX as a function of sodium cyanide addition.
-------
100
too
Iron Recovery
o Lead Recovery
Lead Grade
0-2 04 0-6 0-8 1-0 1-2
SODIUM SULFITE ADDITION (Pounds/Ton)
1-4
Figure 18.
Percent recovery and grade percent of galena-pyrite ore with
KEX as a function of sodium sulfite addition.
-------
The lead recovery drops slightly in both the cyanide and
sulfite systems, which is an indication that both cyanide
and sulfite may have a small depressing effect on galena.
Lead recovery in the cyanide system drops quickly from
about 95 percent to about 65 percent with small additions
of the depressant. On the other hand, lead recovery in the
sulfite system is not affected to the same extent. In this
case, the lead recovery decreases slowly and only at large
additions of sodium sulfite (1.0 Ib per ton) is the recovery
less than 70 percent. In both systems iron recovery is
reduced to 10 percent at moderate additions of depressant.
38
-------
DISCUSSION OF RESULTS
The common technique of cyanide depression of pyrite
in flotation milling of a complex sulfide ore has been
r o
thoroughly investigated " . The mechanism responsible
for depression is the formation of a ferrocyanide complex
5
on the pyrite surface . The industrial use of cyanide is
undesirable, however, both from the standpoint of the
potential pollution problem and safety hazard it presents.
The depression of pyrite with reducing agents has not
been investigated as extensively as has cyanide. However,
22
reducing agents have been observed to depress pyrite
Sulfite, which is a good reducing agent, has been observed
22 25
to depress pyrite . In addition, ferrous ion, which
is also a good reducing agent, has been observed to depress
pyrite .
Since dixanthogen is the species responsible for pyrite
flotation, any chemical which is more reducing than the
xanthate-dixanthogen couple should be capable of depressing
pyrite. The average value of the standard half cell
potential (E°), according to the European sign convention,
for the xanthate-dixanthogen system was found to be minus
0.044 volt by Huiatt20 and minus 0.049 volt by Majima17.
The half cell reactions and their corresponding potentials
for the reducing agents considered in this study are
presented in the following equations, written according
26
to the European sign convention :
39
-------
SOg" + 20H" = S0^~ + H20 + 2e" E° = -0.93
H2PO~ + 30H" = HPO~~ + 2H20 + 2e~ E° = -1.57
S" = S + 2e" E° = -0.48
H2C2°4(aq) ' 2C02(^ + 2H+ + 2e" E° = -°'49
2
60H" = 2SOI" + 3H00 + 4e" E° = -0.58
The flotation results of pyrite using the reducing agents,
which are represented in the preceding half cell reactions,
are shown in Figures 2 through 7. The figures indicate
that all these reducing agents act as depressants for pyrite.
These results present more evidence that dixanthogen is the
species responsible for pyrite flotation, since in these
systems the dixanthogen molecule would be thermodynamically
unstable. Other indirect evidence for dixanthogen as the
collector species for pyrite arises because: ferric xanthate
is an unstable compound, decomposing into ferrous ion and
dixanthogen; ferrous xanthate is too soluble to form at
the concentration used, and while electrostatic adsorption
is possible in acid solutions it should not be possible in
basic solutions where both the pyrite surface and xanthate
ion are negatively charged.
Comparison of Figures 2 through 7, indicate that sulfite
is one of the better depressants for pyrite. This can
be accounted for, since sulfite is such a strong
40
-------
reducing agent (E° = -0.93) and since sulfite is potential
determining for pyrite, as shown in Figure 13.
Because sulfite is potential determining for pyrite,
the depressant effect should arise both from its reducing
interactions in solution and its adsorption on the pyrite
surface. The latter effect is probably more important,
because recent work indicates that the oxidation of
xanthate to dixanthogen is accomplished catalytically by
1 8 20
nascent oxygen on the pyrite surface ' . The sulfite
would then prevent the adsorption of molecular oxygen and
formation of active nascent oxygen sites as indicated by
the following reaction:
SS SS 0=
\
Fe + SOI + Fe 0 S
\ (aqueous) \
"(surface) SS °
Such a mechanism accounts for depression by occupying the
sites for the effective oxidant and is substantiated by
zeta potential measurements. The results illustrated in
Figure 13 show that the zeta potential becomes more negative
as sulfite is added. This is in accord with the proposed
mechanism. Other reducing agents, which also act as
depressants, probably function in a similar manner.
Figure 12, shows that reducing agents are not depressants
for galena and that it should be possible to separate galena
41
-------
from pyrite in an ore containing both minerals. This may
he somewhat surprising because galena as well as all other
sulfides adsorb oxygen at their surface readily. Conse-
quently, one might expect depression as in the case of
pyrite. Such is not the case, because unlike ferrous
ethyl xanthate, lead ethyl xanthate is a very stable compound
and has been observed by infrared techniques on the galena
27
surface . As a result, galena is not depressed by
reducing agents.
To depress pyrite from galena and other sulfides, it
would be desirable to be able to monitor the solution
oxidation potential and determine whether enough reducing
agent is in solution to prevent dixanthogen formation.
Meaningful measurements of solution oxidation potentials
were not possible with oxyanion reductants because these
reductants are not reversible to the platinum electrode,
probably due to the fact that there is an oxygen transfer
involved in the oxidation-reduction couple, in addition to
the simple electron transfer. However, meaningful measure-
ments were made using sulfide ion for the depressant, as
shown in Figure 14. Comparison of Figure 14 with Figure 4
indicates that for a pH less than 8, pyrite depression
occurs at Eh values less than 0.1 volt; and that good
flotation occurs at Eh values greater than 0.1 volt. Above
pH 8, it is believed that pyrite depression occurs for an
entirely different reason. It is well known that pyrite is
42
-------
depressed 1n a basic media of pH ]1 and above. This
phenomenon is attributed to the formation of ferric hydroxide,
on which dixanthogen cannot adsorb. This reasoning is
supported by the fact that flotation cannot be effected at
high pH even when a moderate oxidizing agent is added to
the system to form dixanthogen. If measurements of oxyanion
solution potentials were possible, it is expected that an
Eh response similar to the sulfide system would exist.
Sodium sulfite has relatively long-lasting effectiveness,
since it depresses pyrite well, even after a ten minute
conditioning time. This is demonstrated in Figure 8 and
indicates that the oxidation kinetics of sulfite in the
pyrite system is slow and therefore not a hindering factor
in depression.
The flotation results shown in Figures 2, 10 and 11
indicate that depression of pyrite is not a function of
particle size, since almost identical flotation curves were
obtained for three different mesh sizes.
An evaluation of the theory proposed was made by
testing both a lead and copper ore. The results of tests
on the copper ore are shown in Table I and II. These
results show that both sodium cyanide and sodium sulfite
are depressants for pyrite, since in both cases the weight
percent of concentrate, the percent of iron in the concentrate
and the iron distribution in the concentrate decrease as
the level of depressant addition increases. The copper
43
-------
distribution in the concentrate drops from 84 percent with
0.10 Ib per ton sodium cyanide to 31 percent with an addition
of 0.5 Ib per ton. This response is not observed when
sodium sulfite is used as the depressant, since recovery is
still 86 percent even at an addition of 1.0 Ib per ton.
These results indicate that cyanide will depress both
chalcopyrite and pyrite with additions of more than 0.10
Ib per ton, but that sulfite is a depressant for pyrite only
and will not influence chalcopyrite flotation at any level.
Figures 15 and 16 illustrate these results graphically.
Approximately five times more sulfite than cyanide is
required for adequate depression of pyrite; however, the
rougher concentrate grade is significantly greater with
sulfite, 7 percent Cu, than with cyanide, 4.3 percent Cu,
at the same recovery. The minimum price of alkaline sulfites
is 4 cents a pound, while the price of sodium cyanide is
28
about 20 cents a pound . At these prices.the cost of using
sulfite is the same as the cost for using cyanide. Because
the economics are the same and because sulfite is more
efficient metallurgically, it appears that sulfite would
be a better depressant for pyrite in copper porphory ores.
In addition,pol1ution danger is reduced and monitoring costs
for the poisonous cyanide are eliminated.
It has been reported that sulfite is an effective
23
depressant for galena and that galena is not influenced
2Q
by cyanide . However, the results of this investigation
44
-------
tabulated in Tables III and IV and illustrated in
Figures 17 and 18, do not support prior findings. Galena
floats as well with sulfite additions as with cyanide
additions. Both cyanide and sulfite appear to depress
galena to a slight extent in ore flotation but the effect
seems greater with cyanide than with sulfite. Pyrite is
effectively depressed with both cyanide and sulfite, but
more sulfite is required than cyanide to accomplish the
same results. Other than the level of reagent addition,
there seems to be little difference in metallurgical results
of sulfite and cyanide in the case of the lead ore. To
depress pyrite more sulfite than cyanide is required; however,
this is offset by the fact that cyanide is five times more
expensive than sulfite. Therefore, on the basis of both
metallurgy and economics, sulfite and cyanide are equivalent
as pyrite depressants for lead ore.
45
-------
ACKNOWLEDGMENTS
This work was accomplished under the direction of Dr. Jan D.
Miller, Assistant Professor of Metallurgy, Department of Mineral
Engineering, University of Utah with the assistance of Walter G.
Peterson, former graduate student in metallurgy. Mr. Peterson
did much of the experimental work on this project and his Master's
thesis was the basis for this report.
This work was performed in fulfillment of Environmental Protection
Agency Grant No. 12010 DIM.
-------
REFERENCES
1. Fuerstenau, M. C., Kuhn, M. C.f and Elgillani, D. A., "The Role
of Dixanthogen in Xanthate Flotation of Pyrite," AIME Trans.,
241 (1968) 148-156.
2. Fuerstenau, D. W. ed., Froth Flotation, Fiftieth Anniversary
Volume, The American Institute of Mining, Metallurgical, and
Petroleum Engineers, Inc., N.Y., 1962, 39-68.
3. Adamson, A. W., Physical Chemistry of Surfaces, Second Edition
Interscience Publishers, N.Y., 1967, 478.
4. Fuerstenau, D. W., Froth Flotation. Fiftieth Anniversary Volume,
The American Institute of Mining, Metallurgical and Petroleum
Engineers, Inc., N.Y., 1962, 144-164.
5. Mark, I. W. and Cox, A. B., "Principles of Flotation, III. An
Experimental Study of the Influence of Cyanide, Alkalis, and
Copper Sulfate on the effect of Xanthates at Mineral Surfaces,"
AIME Trans., 112 (1934) 245.
6. Elgillani, D. A. and Fuerstenau, M. C., "Mechanisms Involved in
Cyanide Depression of Pyrite," AIME Trans., 241 (1968) 437-443.
7. Majumdar, K. K., "On the Role of Alkali Cyanides in the Depression
of Pyrite," J. Sci. Ind. Res., 11B (1952) 344.
8. Majumdar, K. K., "Depression of Pyrite by Cyanide Ions," The
Mining Magazine, 97 (1957) 137-139.
9. Majumdar, K. K., "On the Mechanism of Depression of Pyrite," J.
Sci. Ind. Res., 13B (1954) 586.
10. Gaudin, A. M., Flotation, McGraw-Hill Book Co., Inc., N.Y., 1957,
308.
11. Gaudin, A. M., Flotation, McGraw-Hill Book Co., Inc., N.Y., 1957,
242.
12. Sutherland, K. L. and Mark, I. W., Principles of Flotation.
Australasian Institute of Mining and Metallurgy, Melbourne, 1955,
110.
13. Taggart, A. F., Handbook of Mineral Dressing. John Wiley and Sons,
Inc., N.Y., 1945, 12.
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47
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15. Mellgren, 0., "Heat of Adsorption and Surface Reactions of
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Tangel, 0. F., "Reactions of Xanthates with Sulfide Minerals,"
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Mines, Metals, and Fuels, 8 (I960) 18.
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Collectors Potassium Ethylxanthate and Ammonium Diethyl Dithio-
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49
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PUBLICATIONS
1. Peterson, Walter G., "Pyrite Depression by Reduction
of Solution Oxidation Potential", M.S. Thesis, University
of Utah, 1970.
2. Miller, Jan D. and Peterson, Walter G. , "Pyrite Depression
by Reduction of Solution Oxidation Potential", to be
presented at the Annual A.I.M.E. Meeting, New York,
February, 1971. The same will be submitted for publication
to the Transactions of A.I.M.E.
50
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Accession Number
Subject
Field it Group
10
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
c Organization
University of Utah
PYRITE DEPRESSION BY REDUCTION OF SOLUTION OXIDATION POTENTIAL
10
Author! a)
Miller, Jan D.
11
Date
August 1970
12
Pages
50
i X 1 Project Number
21
, c Contract Number
EPA Grant No. 12010 DIM
Note
Citation
23
Descriptors (Starred First)
Flotation, PyHte, Sulflte, Oxidation Potential
25 Identifiers (Starred First)
Ethyl Xanthate, Depression, Cyanide^Reducing Agents, Complex Sulfide Ores
27
Abstract
A study of pyrlte depression by reducing agents with potassium
ethylaxanthate as collector Indicates that pyrlte may be depressed
effectively 1n the flotation of both lead and copper sulfide ores
without the use of poisonous cyanide salts. More specifically, the
use of sodium sulflte as the depressant may result in metallurgical,
economical, environmental and safety advantages over the poison,
cyanide as the depressant were a rougher concentrate recovery of 90.2%
and a grade of 4.3% Cu. However, when sulflte was used as the depres-
sant for the same recovery a grade of 7.3% Cu was obtained.
Aba tractor
Jan D. Miller
Institution
University of Utah
WRSIC
(REV. OCT. i9ea)
SEND TOl WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U ğ. DEPARTMENT OP THE INTERIOR
WASHINGTON, D.C. 20240
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