Note: Descriptions are shown in the official language in which they were submitted.
- ~2~0593
.
.... 1 --
PROC~S ~OR ~HE SU~FA~IZA~IO~ O~
: ~0~-~3RROUS M~TA~ SU~FlDES
~ield of the Invention
This invention is concerned with the extraction o,
certain non-ferrous metals from their ores and more
particularly with a process for the sulfatization of such
metal values from their sulfide ores.
~ac~ground of the In~ention
Metals are commonly extracted from their ores by
processes in which the minerals are concentrated and .the
concentrate roasted to convert complex or otherwise
difficult-to-extract metal compounds into compounds which
can more easily be separated for recovery of the metal
content.
In one such process, applicable to sul~ide minerals,
sulfide~ are converted by roastlng into water soluble
sulfates which may readily be recovered by leaching with
water.
It is generally agreed that the mechanism involved in
converting sulfides to sulfates proceeds via an oxide as
follows:
MS + 3/2 2 ~ MO + S02 (1)
S02 + 1/2 2 so3 -(2)
MO + S03 ~ 4
wherein M represents metal. (See Palperi, M. and
Aaltonen, O., Sul~atizing Roasting and ~eaching o~ Cobalt
Ores at Outokumpu Oy, Journal o~ Metals, February 1971,
pP--34~
. . For the sulfatization ~rocess to be economicaI,
suf~iciently high ~per.centages o~ the metals must be
converted under reasonable operating conditions to easily
extractable water soluble sulfates while other, undesired
materials remain insoluble. In particular, it is
important that the iron content of the ore remains
~5 insoluble so that it can easily be disposed of as a solid
by-product, rather than being leached as a water soluble
~210593
product which wculd require subsequent, difficult
separation and disposal steps. ---
Some of the desired non-ferrous metals in sulfide
ores can be difficult to recover as water soluble
sulfates in the sulfatization process. ~ickel in
particular is difficult ~to sulfatize efficiently.
- Attempts to sulfatize nic~el sulfides were unsuccessful
until ~hornhill, in U.~. Patents 2,81~,015 and 2,81~,016,
showed that the addition of sodium sulfate to the roaster
feed promoted the sulfatization of nickel sulfide. The
sodium sulfate is used to control particle size in a
fluidized bed and is said to render unstable the nickel
ferrites in pyrrhotite according to the following
equation:
~i~e204 + ~a2S4 ~ ~a~e204 + ~i~04 (4)
- ., . -- . . . . . . . .
~hese patents also describe- sodium sulfate taking part in
reactions providing sodium pyrosulfate, a strong
sulfating agent, and sulfur trioxide for sulfatization of
the metal oxide:
~a2S04 + ~03 ~ ~a2S2o7 (5)
NiO + ~0 ` NiSO (6)
~ 4
lhus, these -patents demonstrate the addition of a
sulfate material as a requirement to enhance the
sulfatization of nickel. While the use of sodium sulf~te
in the roast does provide significant improvement--in the-
amount-o~ metal extracted as water soluble sulfate~ the
percentage of such metal extracted from the raw material
needs to be increased for improved process economics.
Unfortunately, the addition of sodium sulfate to the
roaster increases the sulfur content of the roast and
contributes to the generation of sulfur dioxide and
sulfur trioxide gases during the roasting procedure.
~21059;~
. .
~his is undesirable because these gases are subject to
pollution control regulations so tha~ increasing their
quantity in the off gases increases the cost of pollution
control and thereby 'also increases the cost of the
extraction process.
At-tempts have been made to decrease the amount of
toxic sulfur gases liberated in the sulfatization
process. In U.S. Patent I~o. 3,791,812, copper, nic~el,
cobalt and manganese are extracted as water soluble salts
from sulfide oreæ by roasting the ore in the presence of
sodium chloride. ~he use of sodium sul~'ate is'avoided
and the amount of sulfur dioxide in the off gases is
reduced by conducting the roasting in at least two stage~'
ana using sulfur dioxide liberated in the first stage as
a sulfatizing agent in a subsequent stage.
~nfortuna~ely, iron as well as~~the nsn-ferrous metals is
extrac~ed as a ~water soluble s~alt, necessitating the
expense of further separation steps to remove the iron.
Other alkali metal salts beside~ sodium sulfate and
chloride have been used in the extraction o~ non-~errous
metals from their ores~ U.~. Patent No. 2,775,517
discloses a process for separating nickel from low sulfur
content iron oxide ores. The ore is roasted with alkali,
such as sodium hydroxide, carbonate or bicarbonate and
the roasted product leached with water to extract
chromium and aluminum. ~he nickel remains in a water
insoluble state and is subsequently removed by treatment
in an auto~lave 'with ferric or ferrous chloride or
~ sulfate. ~his process'is not æ sulfatization process
~0 because t~e raw ma~eri'al is not a sulfide ore. The
process suffers from the disadvantages that the nickel is
not converted into a readily-leachable, water soluble
- salt and that an autoclave is required, thereby
increasing plant and operating costs and processing
complexity.
,
32105~3
~ here is, therefore, a need for a process or
extracting non-ferrous metals from sulfide ores by
sulfatization of such metals into readily leachable salts
which extracts high percentages of the metals in the ore
in an economical and environmentally acceptable process~
Summary of the Invention
-
We have now found that these objectives may be
achie~ed by including alkali metal carbonate or
bicarbonate in the sulfatizing roast. It is quite
unexpected that the addition of carbonate should have
this effect since ~hornhill's hypothesis, mentioned
above, clearly requires the addition of sul~ate
material. Moreover, we ha~e surprisingly found that the
addition of carbonate material in this invention still
forms water soluble sulfate3 in the sulfatizatiorl process
rather than soluble carbonate-products. Utilization of a
- carbonate or bicarbonate additive, instead of a sulfate,
eliminates the addition of further sulfur to the roast
and improves the sulfatization process and in doing so
uses more of the natural sulfur in the sulfides in the
ore and produces less sulfur-containin~ off gases. ln
addition, the additives in this invention are less
expensive~ ~oaium carbonate, for example, - is less
expensi~e on a bulk scale than sodium sul~ate.
According to the invention there is provided a
process for the sulfatization of non-ferrous metal
sulfide which comprises roasting sulfide mineral
containing said metal sulfide in the presence of alkali
metal carbonate or bicarbonate and coverting at least a
portion of saia metal suIf;ae into water soluble
non-ferrous metal sulfate.
In one embodiment of the invention, the sulfatization
process is used in a process for the extraction of
non-ferrous metal from sulfide mineral containing
non-ferrous metal sulfide. ~he extraction process
~o~sa
comprises roasting the mineral in the presence of alkali
metal carbonate or bicarbonate and converting at least a
portion of the non-ferrous metal sullide into water
soluble, non-ferrous metal sulfate. The roasted product
containing the soluble sulfate is washed with water to
leach out the soluble met~al sulfate from the solid
materials and the non-ferrous metal content of the
sulfate solution is recovered.
~he process - of the invention is particularly
applicable to the sulfatization of at least one o~
cobalt, copper, nickel and zinc.
In the process of the invention, a sulfide ore, such
as a low grade copper-nickel-cobalt ore, is milled to
reduce the particle size of the ore and then, preferably,
concen~rated such as by flotation. Alkali metal
carbonate or bicarbonate is mixed with dried concentrate
-- -~- or ore and the ~ixture is fed to a furnace for roasting.
Typical roasting conditions are a temperature of from
about 400C. to 650C., ~enerally including a period
at about 550C. to 630C., and a time of from 2 to 6
hours. ~he roasted material is allowed to cool and the
soluble sulfates leached into solution by washing the
roasted product with water. The sulfate solution is
separated from insoluble residues by filtration and the
metal values recovered by conventional means such as
solvent extraction and electrowinning.
~rief Description of the Drawings
- ~I&URE 1 is a flowsheet illustrating the steps in the
p~ocess of the invention~
30FI~URE 2 is a flo~sheet illustra'ing representative
changes in chemical composition of the products through
the steps of the process of the invention;
~IGURE 3 is a graph showing the effect of roasting
temperature on the extraction of copper, iron and nickel
in the process of the invention.
~210S93
Detailed Description of the Preferred ~mbodiments
Referring to ~igure 1, the process of the invention
uses sulfide ore as the raw material. ~he ore contains
one or more of the metals copper, cobalt, nickel and zinc
and may be a high or low grade ore. ~he process is
economically attractive for use on low grade ores and for
this reason such ores are the preferred starting
material. Preferred ores include copper-nickel-cobalt
and copper-lead-zinc sulfide ores. A typîcal low grade
copper-nic~el-cobalt ore is illustrated as the starting
- material in Figure 2 and contains approximately 0.4%
copper, 0.4~ nickel, 0.04~ cobalt, 23% iron and 12%
sulfur. All percentages herein are by weight unless
otherwise specified.
15The ore is milled by conventional methods to a
suitable particle size and then--concentrated with respect
- -to sulfide minerals. ~he concentration step is-- not
, . . . ., . - . ..
necessary in order to achieve optimum response with the
roasting process of the invention. While unconcentrated
ores may be used in the process of this invention it is
preferred that the ore be concentrated as shown in
~igure 1. ~he concentration process is simply a case of
processing economics. Ideally, through the concentration
process, a considerable P~ount of ore weight will be
rejected with only a minor loss in metal values. In the
process depicted in ~igure 2, flotætion concentration
recovers 83% of the copper, 79% of the nickel and 79% of
- the cobalt in 15% of the original ore weight. With the
. .
concentrate representing onIy t5~- of~ the weight of the
original feed ore, a considerable reduction in capital
and operating costs in the subsequent treatment stages is
realized. In the ore exemplified in ~igure 2, it can be
seen that the concentration process substantially
increases the percentage content of non-ferrous metals
and therefore provides a material for subsequent
~210593
-- 7 --
processing fro~ which it is easier to extract the desired
metals. Of the yarious concentration techniques
available, froth flotation has been found to yield the
best metallurgical results with this particular ore.
~he concentrate may then be ground to further reduce
the particle size and is aried, for example at about
120C. Alkali metal carbonate or bicarbonate is mixed
with the dried concentrate, pre~erabl-y in an amou~t of
from 5% to 50%, more preferably from about 10 to 20%,
based on the weight of dry concentrate, or ore if the
concentration step is omitted.
Sodium or potassium carbonates or bicarbonates may be
- used as the al~ali metal additive. ~he sodium compounds
are preferred, particularly sodium carbonate which has
been found to provide optimum results while being
~elatively inexpensive and readily obtainable.
- The carbonate-concentrate mixture is fed to~a furnace
for roasting to convert the metal sulfides to sulfates.
During roasting the roast may be rabbled periodically to
maximize reaction.
Reactions for some typical sulfide minerals ores ar~e
show~ below:
2 CuFeS2 ~ 6 /2 2 -~ 2CuO ~ Fe203 + 4S02 (7)
CuO + ~03 ~ CuS04 (8)
2(Ni,Fe)S + 4l/2 2 --~ 2~iO + Fe203 + 2S02 - (9)
(assu~ing equiualent quantities of Ni and Fe)
I~iO ~ S~ iS04 (tO~
,~0 ,. . ~ . . . . -
2~eS ~ 3 /2 2~ 2 3 2 (11)
Fe203 + ~SO~ ~ Fe2(S04)3 (12)
. . .
~12~0593
- 8 -
Roasting temperature is dictated by the decomposition
temperatures of the sulfates of the metals to be
extractea. Optimwm temperatures for the conversion of
the mineral sulfides to the sulfate state (for a given
roasting time and atmospheric condition) exist when the
decomposition temperatures are approached. ~y
maintaining the reaction temperature either ~elow or
above the decomposition temperature, more or less of the
particular sul~ate can be obtained. ~his characteristic
provides the means for setting conditions that
theoretically will selectively sulfatize the non-ferreus
metal values, such as Cu, Co, ~i and Zn9 while the iron
sulfates are decomposed. However, when a sulfatizing
roast is conducted on several different sulfide minerals,
even under optimum roasting conditions, only a partial
sulfatization is effected and the metallurgical response
of the copper and cobalt sulfides is mu`ch more ~avorable
than the response of the nickel sulfides. Similarly, in
practice, decomposition of the iron sulfates is not ideal
since decomposition is usually incomplete and therefore
it is important that the leaching step extracts the
maximum amount of non-ferrous wa~er soluble sulfates but
the minimum amount of iron sulfates.
Accordingly, the temperatures used in the process of
this inventibn depend on the metal or metals to be
extracted. Where an individual m~tal is to be extracted,
the temperature will approach the decomposition
temperature of the sulfate of thæt metal. Where a number
of metals are to be~ extracted~ as is usuall~ the case,
the temperature will approach the lowest decomposition
temperature of the metal sulfates in question. lhe
energetic decomposition temperatures of ~eSO~, ZnS04~
CuS04, CoS04 and NiS04 are 480, 600 , 670 ,
735 and 764C., respectively (~odgman, C.D. ed.
Handbook of Chemistry and Physics~ 37th edition, 1955, p.
~Z~0593
g
1812 and 48th edition, 1967 pp. ~-172, -241). Preferred
roasting temperatures~ in th proces~ of the invention
range from about 400 to 650C. Temperatures from
about 400 to 500C. may be used for a proportion of
the roasting period but a temperature greater than the
decomposition temperature ~ of iron sulfate, about
500C., is required for a significant proportion of
that period so as to promote con~ersion of the iron
sulfate to insoluble iron oxide. More preferred roasting
temperatures are from about 550C. to 650C.,
conveniently about 550 to 600C., - such as about
570C. As can be seen from Figure 3, high percentages
of copper and nickel and low percentages of iron are
extracted over a wide range of temperature.
Roasting time has a significant effect on the
efficiency of the process ol -the invention. Generally
longer roasting times convert more sulfide mineral to
sulfate but long roasting times decrease the economy of
the process. A preferred time is from two to six hours,
for example about four hours.
~ he roasted product is allowed to cool and is then
leached with water, convenientiy with suf~icient water to
provide a 15 to 20% solid~ slurry. ~he slurry is then
agitated, for example for about two hours, to maximize
extraction of the water soluble sulfates. The slurry is
filtered and optionally washed with more water to ensure
that any residual water soluble sulfates are carried into
the product solution. ~he liquid or filtrate portion
- . . - - . ~ - . . - . .:. .-.
contains the wa~er soluble sulfates of nickel, cobalt~
copper or zinc. As can be seen ~rom Figure 2, on a
laboratory scale high percentages of copper, nickel and
cobalt are extracted into the filtrate with very little
iron. The non-ferrous metals may be recovered from the
solution by conventional means. For example, the
sulfates may be recovered by precipitation or by solvent
extraction and electrolysis.
~2~1S93
-- ,. .
- 10 -
Various parameters o~ the process of the invention
were investigated in the laboratory to determine their
effect on the efficiency of the process. In the tests
which follow it is shown that the process of the
invention enhances the extraction of nickel, cobalt,
copper and zinc as wate~ soluble sulfates in the
sulfatization of their sulfide ores while minimizing the
extraction of iron as water soluble sulfate.
- ~ST SERI~S 1
In a first series of tests, numbers 1 to 4, a
copper-nickel-cobalt sulfide concentrate was composited
from products of various froth flotation tests. ~he
composite assayed the following percentages: 0.69 Cu,
1.23 Ni, 5~.0 ~e~ and 30.4 S. ~he composite was wet
ground to 200 mesh in a laboratory ball mill, dried at
120C, and split into 200 gram batches for comparison
roasting tests. ~he specified amount of -additive was
-blended into the sample with a mortar and pestle just
prior to roasting. ~he sample was then placed in a
refractory boat. The material in the boat had an
approximate depth of 1 cm. The boat was then placed in
an urlvented muffle furnace, which was at room
temperature9 and the temperature controller was then set
to 420C. ~he heating period to 420C was fairly
linear and took approximately 40 minutes. The
temperature was then held at 420 for 140 minutes.
Upon completion of this initial roasting period, the
temperature controller was set to 610C. It took
approximately 30 minutes to reach 610C and was then
held at tni;s temperature for 210 minutes. Upon reaching
610C, the ore was rabbled e~ery 30 minutes for the
duration of the roast. After the ore was subjected to
this second stage roast, the furnace was turned off and
allowed to cool before the boat was removed.
After completing the roasting procedure, the roasted
material was removed from the refractory boat and 130
~2~0sa3
grams were split out for leaching. ~he remainder of the
material was submittea for chemical analysis. The leach
sample was then placea in a 1 liter beaker containing 600
grams of distilled water. ~his slurry was then agitated
for 2 hours. ~each tests were conducted in an open
vessel beaker at room temperature. After 2 hours of
agitation, the slurry was filtered and washed with ~00
gram~ of distilled water. The filtrate and wash solution
was collected and its volume was measured. The filtered
leach residue was dried and weighed. Both the filtrate
solution and leach residue were submitted for chemical-
analysis in order to evaluate the metal extractions.
Presented in Table 1 is a descriptive tabulation of
the roasting tests performed. ~he four roasting tests
were conducted in the exact same manner with the
exception of types and amounts of additive.
: - Presented in ~able 2 is a partial chemical analysis
of the leaching products and the metal extractions. ~he
extractions represent the amount of metal (Cu, ~is Fe,
20 Co) that was leached from the roasted material which
reports to the leach filtrate. The calculated head for
each test represents an analysis of the roasted products
calculated from the analyses of residue and filtrate
material. ~he addition of sodium carbonate greatly
increased the copper, nickel, and cobalt extractions over
the test that was void of an additive and significantly
increased the extractions, especially that of nickel,
over those tests containing the sodium sul~ate additive.
.
- ~or exampIe, an extraction of ~4.8 percent nickel waq
~0 experienced when the ore was roasted with sodium
carbonate. When the ore was roasted without an additive,
a nickel extraction of 20.6 percent was experienced. ~he
two tests that csntained sodium sulfate average an ~4.5
psrcent nickel extraction.
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- 13 --
~2~05~3
. .
-- ~4 --
- T~ST S~RI~S 2
In a second series of tests, nu~bQrs 5 to 7, a
copper-nickel-cobalt sulfide concentrate was again
composited from products of various froth flotation
tests. ~his composite assayed the following
percentages: 1.80 Cu, 1.19 Ni, 51.2 ~e, 30.5 S, and 0.11
Co. ~he second test series of roasting tests were
conducted in a similar manner as was the first series of
r~asting tests. The composite was wet ground to 200 mesh
in a laboratory ball mill, dried at 120C, and split
into 150 gram batches ~or comparision roasting tests.
Again the specified amount of additive was blended into
the sample with a mortar and pestle just prior to
roasting. The sample was then placed in a refractory
boat. In this test series, the ore was subjected a less
severe, single stage roas~. -After the refractory boat
wa8 placed in an unvented muf~le furnace, which was at
.. . . ,, . - .
room temperature, the temperature controller was set to
610C~ The heating period was fairly linear and too~
approximately 70 minutes. The temperature was then held
at 610C for 150 minutes with the ore being rabbled
every ~0 minutes for the duration of the roast. After
150 minutes at 610C, the furnace was turned off and
allowed to cool before the boat was removed.
The leaching procedure in test series 2 was conduc~ed
in the exact manner as was the leaching procedure in test
series 1 with the exception of a réduction in both the
amount o~ roasted ma~erial and water used in the leaching
- process The leach process consiste~ of 1~Q grams of
30 roasted material combinea and agi~ate~ with 500 grams of
water.
Presented in Table- 3 is a descriptive tabulation of
the roasting tests performed and a partial chemical
analysis of the roasted products. The three roasting
~5 tèsts were conducted ih the exact same manner with the
exception of types and amounts of additives.
1210S~3
. . .
1,5
Presented in ~able 4 is a partial chemical analysis
of the leaching products and the metal extractions. ~he
extractions represent the amount of metal (Cu, ~i, Fe)
that was leac,hed from the roasted material which reports
~o the leach filtrate. Although cobalt extractions were
succeæsful in both the sodium carbonate and sodium
sulfate roast-leach, they were not accounted ~or because
of the minor amount of cobalt present in the composite.
Again the addition of sodium carbonate greatly increased
the copper, nickel, and cobalt extractions over the test
that was void of an additive and increased the
extractions over that test conducted with an equal amount
of sodium sulfate.
. .
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12~S93
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`` ~2~0593
- 18 -
~ST SERI~S 3
In a third series of tests, numbers 8 to 20, various
ores and concentrates were tested. One 150 gram batch
was roasted per test. ~he specified amount of additive
was blended into the sample with a mortar and pestal just
prior to roasting. An unvented muffle furnace was heated
to sioc and each sample, uniformly spread in -a
refractory boat, was placed in the furnace for four
hours. ~he samples were rabbled every 30 minutes during
the roast. ~he refractory boat was removed from the
~urnace immediately upon completeion of the roast and
allowed to cool. One hundred grams was split from the
roasted sample, placed in a beaker and distilled water
was added to produce a 15 percent solids solution. The
slurry was agitated $or two hours at room temperature and
then filtered and washed A~chemic~ nal~sis sf the
-- residue and filtrate was -pérformed to determine the
recovery of the metals in soluble form.
The various ores and concent~ates are listed in Table
5. Core samples were used as mineral æourceæ for ~ests 8
to 17. ~ince core samples are not homogeneous, samples
for individual tests which are taken from different
portions of a core sample will have slightly different
assays~
Tests 8 to 17 were conducted on copper-nickel-cobalt
¢oncentrates and ores. Tests 8, 9 and 10 used
concentrate from a core sample ~A) which was taken from
the same ar~a as the sam~les used to prepare the
concentrates in;~est-Series I and 2. Tests 11-to 15 were
~0 conducted on ~oncentràte from a differen~ core sampIe tB)
but which had a mineralogy very similar to (A) and was
taken from the same area as sample (A). Tests:16 a~d 17
were conducted on ore~ and concentrate respectively of a
core sample (C) of a massive sul~ide ore containing
quantities o$ copper, nickel and cobalt taken $rom a
different area than samples (A) and (B).
~2~05g3
- 19 -
Tests 18, l9 and 20 were conducted on ore (D) which
~as a copper, lead and zinc bearing ore.
Presented in ~able 6 are the metallurgical results of
~ests 8 to 17. ~he results demonstrate the excellent
extraction efficiencies achieved by the process of the
invention and show that potassium carbonate as well as
sodium carbonate gives good results. Test 16 shows that
the process of the invention is applicable to ores as
well as concentrates. Although extractions ~rom the
concentrate, in Test 17, were better than from the ore,
the tests demonstrate that sulfiae ores as well as
concentrates are susceptible to the process of the
invention. Unfortunately, the small quantity of ore (C)
available did not allow optimization testing on this ore.
Presented in Table 7 are the metallurgical results of
lests 18, 19 and 20 conducted-on copper, lead and zinc
; bearing ore (D). The results show not only-that- ores are
susceptible to the process-o~ the invention but also that
zinc may be extracted by the roast-leach process with
high percentage extraction. ~ead sul~ide materials are
not susceptiblé to the extraction process. Although lead
sulfate may be produced in the roaæt, it is not water
soluble and therefore is not extracted in the leach
process.
.
.
~5
~2~0~;93
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~210~93
- 24 -
~ST ~RIES 4
~aboratory roasting tests were performed on low grade
copper-nickel concentrates. The effects on sulfatization
of roasting time (one to six hours), roasting temperature
(490 C to 650C) and additives (l~a2S04,
~a2C03, CaO, CaCO~, CaS04) were investigated.
A factorial design investigating levels of roasting
temperature~ roasting time and, amount of sodium carbonate
added to the roast was conducted. The results
demonstrated that within the parameters of the
experiment, the amount of sodium carbonate added to the
roæst was the most significant factor for sulfatization
followed by roasting time.
Several bench scale flotation concentrates were
composited to provide enough material for several
, roasting tests. Although fIotation composites varied
'~ slightly between test series,, ~he dif~erence was not
great enough to effect the results. The ore used to
prepare the concentrates was from a 'core sample obtained
in the same area as Sample (A) in Test Series 3.
The flotation composite was wet ground to 200 mesh in
a laboratory ball mill, dried at 110C, and split into
150 gram batches for comparison roasting tests.
One 150 gram batch was ro~sted per test. The
specified amount of additive was blended into the sample
with a 'mortar and pestl~ just prior to roasting. The
unvented ~uffle furnace was preheated to the specified
~ temperature. ~he concentrate sample was then uniformly
- spread in a refractory boat and placed in the furnace.
Ihe sample was rabbled every 30 minutes for the duration
of the roast. The -refractory boat was removed
immediately upon completion of the roast and allowed to
cool. In order to evaluate the degree of sulfatization,
a standard leaching procedure was followed. One hundred
grams was split from the roasted sample. The sample was
~2~0S93
.
- 25 - -
placed in a beaker and distilled water wæs added to
produce a 15 percent solids solution. ~he slurry was
agitated for two hours at room temperature and then
filtered and washed. A chemical analysis of the residue
and filtrate solution was performed to determine recovery
of copper, nickel and iron in soluble form.
In a first series of roasting tests, 21-26, an
investigation was conducted in order to study the
sulfatization effects of various additives: sodium
sulfate, calcium sulfate, calcium oxide, calcium
carbonate and soaium carbonate. The flotation composite
used in this test series assayed the following
percentages; 1.80 Cu, 1.19 Ni, 51.2 ~e, 30.5 ~, and ~.11
Co. In each test the specified additive was blended into
the sample to equal 10 percent of the total weight. The
sample was then roasted at 610~ for-150 minutes
- Presented in Table 8 are the metallurgical results of
these tests. A chemical analysis of the residues and
filtrate solutions along with the metal distributions for
each leach test is tabulated. The results of the tests
indicate that sodium carbonate is the most effective
promoter for the sulfatization of the Cu-~i values.
.
- ~ - -
~2~0~
-- 26 --
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lZ'10593
- 27 -
The effect of temperature was investigated in ~ests
27-~5 when the roasting time was held constant employing
a 10 percent by weight sodium carbonate addition.
Roasting temperatures between 490C and 650C were
5 investigated; a roasting time of 240 minutes was used.
~he flotation concentrates composited for this test work
assayed the ~ollowing percentages: ~.22 Cu, 1.41 Ni,
54.5 ~e, and 29.4 S.
Presented in ~able 9 are the ro~sting conditions and
10 the metallurgical results of the temperature dependept
roasting tests. A chemical analysis of the residues and
filtrate solutions along with the metal distributions for
each test is tabulated. Presented in ~igure 3 is a graph
illustrating Cu~ e recoveries in soluble form as a
15 function of temperature. ~he results indicate that the
copper recoverïes span a narrow range throughout the
- -- range of~ temperatures. ~ickel recoreries are at a L
.. , ..... .. . . ...... .. , . .. , .. , .. . . ,_ . . ,.. ,.,, .. ,. .. . ...... . I
maximum ~etween 550 and 590C and shærply decrease with ~
increasing temperatures. Iron recoveries span a narrow t
20 range and are inversely proportional to temperature.
~5
- :'. ~ . ''' -., ' -
-. ~0
- , - .: . .. .
- ' ' - '' - ' ' , . . , ' ~ -
. . .
~2~0S93
-- 28 --
~ ~ ~ ~ N 00 ~ N ~ N 0~
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~ ~ C~
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D~ r I :(~ N - . el~ l C~l O L~ td
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t~ ~31~ r-- ~ ~ O C~ ~) ~ h
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O r~:J h 'd F- rc5 ~I rd h ~ h ~ ~ rd ~ 'd ~ rc5 ~ ~
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-P:; ' P~
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V¢ o~ ' ' . ' ' ,~
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N N N N N N ~ N 01
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1 Tests were conducted in order to a~alyze the inter-
active effects of the roasting variables; time, temperature
and amount of additive. Again, several bench scale flotation
concentrates were composited to provide enough material for the
test series. The composite assayed the following percentages:
2.74 Cu, 1.49 Ni, 47.7 Fe, 27.3 S and 0.10 Co. The variables
in this test series were quantified from the results of the
previous tests and are listed in Table 10 as Tests 36-52~
Three levels each of roasting temperature, roasting time, and
percent sodium carbonate addition were incorporated in this
experiment. The temperatures selected were 550, 570 and 590C,
which are above the decomposition temperature of iron (Fe++)
sulfate but below the decomposition temperatures of copper ~Cu~+)
sulfate and nickel (Ni++) sulfate. The roasting times selected
were 2, 4, and 6 hours. The sodium carbonate addition levels
were 0, 10, and 20 percent. With three levels each of roasting
temperature, roasting time, and percent sodium carbonate additions,
27 combinations of roasting conditions are possible. The tests
employed 0 and 20 percent sodium carbonate additions and were
part of a limited factorial design series. The previous test
work indicated that the addition of sodium carbonate is
necessary to establish nickel sulfatization. However,
increasing the sodium carbonate in excess of 10 percent was not
determined to be a critical factor in the sulfatization process.
The roasting time appeared to be the most significant ~actor and
was therefore emphasized in this investigation. Roasting times
of 2, 4 and 6 hours were used at temperatures of 550, 570 and
590C.
The results of these tests indicate that there are
interactions between the sodium carbonate addition ana the
roasting time, and between the roasting temperature and roasting
time.
S~3
-- 30 --
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-- 32 --
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~2~0sg3
Analyses were made of sulfide concentrates before
and after roasting in the presence of alkali metal
carbonate to determine whether sulfæte or carbonate
products were formed.
~ach concentrate was blended with 20~ by weight of
sodium carbonate and subjected to a four-hour roast at
570C.
~he analyses are presented in Table 11, and it can
be seen that, surprisingly, while only a small amount of
sulfate (S04) is present in the concentrate prior to
roasting, esse~tially all the sulfur (S) is present as
sulfate (-S0~) in thé roasted product~ ~he amount of
carbon (C) present in the concentrates is reduced to
only a trace amount by the roasting process. When
roasted concentrate ~) was subjected to water
dissolution, copper, nickel, cobalt, and iron
extractions we~e 93.4%, - 72.4%, 88.8~, and 3.7%,
respectlvely. When roasted concentrate (C) was
subjected to water dissolution, copper, nickel, cobalt,
and iron extractions were 96.7%, 85.6%, 92.0%, ~nd
12.8%, respectively.
- . ' -. . - ~. . :
.
. . ' . , - - - .
.: :' . . '
12I~
.
~ o ~ o
Vl
o o o
t~ ~ ~D
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o ~ o
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P:~ O ~ ~ O
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m
a~
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~ ~ - . . r~ t~
c~ H - - - ~ .
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c) a~
O
h O q I O q-l
V ¢ V ¢
~210~3
~ his invention is applicæble to the mining and metal
industry. ~he process of the invention is useful in the
extraction of non-ferrous metals from sulfide ores by
sulfatization of such metals into water soluble salts
which may readily be leached into aqueous solution for
recovery of the metals.
~0
:
~5
