-
The pre~ent invention r~late~ to the treatment o~
chalcopyrite and i~ particular to the treatmen-t of chalco-
pyrito ore~ and concentrate~ with ga~eous sulphur dioxide in
the ~ub~tantial ab~ence of oxygenO
Chalcopyrite i~ a complex copper-iron ~ulphide
mlneral generally glven in the for~ula CuFeS2,. Chalcopyrite
i~ one o~ the most abundant miner~ls o~ copper. A number
of techniques ~ay b~ u~ed to obtaln copp~r f~om chalcopyrit~
ores or conc0ntrate~. One such technique co~lpriæes a smelt-
~ng process in which the copper 3ulphide is con~erted toblister copper, the iron is converted to an i~ert s~ ate
clag and the ~ulphur is liberated a~ 3ulphur dioxide. Pure
metallic copper may then be obtained by~ ~or example, elec-
trolytic technique~. How~v~r, in this process the lib~rated
~ulphur dioxid2 1~ a potentlal ~ollution problcm. Cha:Lco~
pyrite L~ di~lcult to lcach without prior troatment to con-
Yert the copper-iron sulphide (CuFeS2) into another form.
For example, chalcopyrite ma~ be con~erted i~to copp~r ~ul-
phide ~Cu8) and pyrite (F~S2) by treatment with æulphur at
~levated temper~tures, a~ i8 di~clo6ed in C~nadian Patent
783J52~ of A.I. V~soly~ ~t al which i~u~d April 23, 1958.
The chal~opyrite ~o treated is more readlly leachable but
the ~ulphur content o~ the or~ has b~en lncrea~d and the
pyrlte may be in a ~orm that i8 partiall~ soluble, one or
both o~ which may be undesirable in subsequent steps to re-
cover copper.
The treatment o~ molte~ pyrite (FeS2) and pyrrhotite
(Fel_xS) ore with oxygen, hydrogen, ~ulphur dioxide and/or
water has been di~clo~ed by C~ Kennicott i~ U.S~ Patent
1~958J581 which i~ued May 15, 1934.
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~- ~L0~(~767
It has now been found that when chalcopyrite ore or
concentrate is treated wlth gaseous sulphur dioxide ~n the
substantial absence o~ oxygen, the copper and iron con~ents of
the chalcopyrite are converted to forms that facilitate
recovery of metallic copper and that at ~he same time the
sulphur conten~ of the chalcopyrite is decreased, elemental
sulphur being produced.
Accordingly, the present invention provides a pro-
cess for the treatmen~ of chalcopyrite ore or concentrate
comprising contactin~ said chalcopyrite with an excesæ o~
gaseou~ sulphur dioxide in the sub~tantial absence of oxygen
at a temperature in the range between 700C and the fusion
point of the chalcopyri-te.
Xn an embodiment of ~he process of the present in-
vention the temper~ture is in the range 700-900C.
In another embodiment the sulphur formed is sep-
arated from the chalcopyrite so treated.
In yet another embodiment the lron oxides formed
are separated from the chalcopyrite so treated.
Ln the process of the invention chalcopyrite i8
contacted wlth sulphur dioxide in the substantial absence of
oxygen, The chalcopyrite may be in the form of an ore or a
concentrate, Chalcopgrite concentrates are normally obtained
from the ore by physical separatlon techniques, ~or example,
by froth flotation.
The chalcopyrite is treated with an excess of sul
phur dloxide. As used herein an excess of sulphur dioxide is
defined as an amount of sulphur dioxide in excess of the stoich-
iometric amount of sulphur dioxide actually required to convert
the iron in th~ chalcopyrite into magnetite (Fe304) and the
copper into copper sulphides (CuxS) Other copper-iron
~, ;- , . .,.,.,... , .
~ L~5~3~67
sulphides, e g , bornite (Cu.5FeSI~) o~ lower copper:sulphur ratios
than chalcopyrite may ho~rever be f7Ormed in the process o~ the
present in~ention I~ is preferred~ espeoially in view of
eguilibria that may exist, e~g. between sulp~lur dioxide and
sulphur, to treat ~tlth at least five ~lmes and in particular
with at lea~7t twenty times the .stoichiometric amount of sulphur
dioxide 1,e. a ~wenty-~old excess o~ sulphur dio~ide. Other
process condi~ions may a~fect the optimum excess o~ sulphur
dioxide, Unreacted sulphur d~oxide may be utilized for removal
10 of sulphur from ~e treAtment zone o~ the proces5. After :~
removal of sulphur the sulphur d~oxide may be recycled to the
treatment zone.
Sulphur, which is also obtained in the treatment
process, volatizes at the temperature~ used in the process and
is pre~er~bly remo~ed ~rom the reac~ion zone. The process
1~ operated in the substantial ab~ence o~ oxygen primarily to
avoid oxidation Or the copper ~7ulphides, magnetite (Fe304) or
elemental sulphur wh~ch may result in process problems. The
term "subs~antial absence o:f oxy~en" is u~7ed to indicate
that level of oXy~en tha~ would 7~e ach~eve~ in practical process
o~ the type described herein when operated so as to exclude
oxygen.
The proce~s is opera~ed at a temperature ln the
range betwe~n 700C. and the fusion polnt of the chalcopyrite
ore or concentrEte and pre~erably between 700C and 900C. ;.
The process may be operable at lower temperatures but the
rate of treatment may be uneconomically sl~w At higher ~emp-
eratures fusi~n may limit the rate of reactlon by reducing
the surface area of the çhalcopyrite
As stated hereinabove the sulphur liberated during
the process is pre~erably removed ~rom the reaction zone.
The treated chalcopyrite preferably a~ter re-grinding, may
~ 3 --
,
,.
5`~7~
be u~ed a~ such or subjected to a further concentratio~ proce~æ,
which may be, for example~ a magnetic separation or a ~lotat~on
process, to increase the concentratio~ o~ copper and to reduce
the concentration of iron in the treated chalcopyrite. In
partlcular3 magnetite may be separated ~rom the treated
chalcopyxlte. me ef~ectlveness o~ this separation will
depend on, at lea~t in part, the reaction co~ldition~ the
grlnding conditions and the separation technique UB~d,
me tr~ated chalcopyrit~ either as such or a~ter
concentration may be treated ~o a6 to obtain metallic copper
or compounds capable of being converted into metallic copper
by techniques known in the art. Such techniqueæ include
treatment with oxygen in a pyrometallurgical process whe~eby
sulphur dioxide, which may be r~cycled, will be liberated,
and leached in hydrometallurgical processes the latter
processes will more selectively leach copper, as opposed to
iron, and produc~ less oxyanions of ~ulphur in solution
when u~ed on the treated chalcopyrlte of the prese~t invention
th~n on untreated chalcopyrite. Typlcal leaching agentæ are
nitric acid, 3ulphuric acid, or ammonia solutions in -the
presence o~ oxygen, or by electrolytic tec~niques. Techniques ..
~or the treatment of copper coneentrates are discus6ed in an
article by R.J. Roman and B.R. Benner, Minerals Sci. Engin~
oering 5, 3-24 (1973).
In a~ embodlment of the process o~ the present in-
vention th~ tre~ted chalcopyrite is heated to molten state
in ~he ~ubstantial absence of oxygenD As is exemplified her~-
ina~ter the copper-rich phase coalesce~ and this coalesced
copper-rich phase ma~ be ~eparated while in a ~olten state
or cooled to solidl~y the phase before separation is ~f~ected.
I~ a preferred embodiment o~ the proceæs of the pre-
sent invention ~he sulphur dioxide used in the treatment of
chalcopyrit~ contain3 water. As ex~mplified hereina~ker the
767
addition of water to the sulphur dioxlde results in an increase
in the rate of treatment o~ the chalcopyrite.
Chalcopyrite may contain pyrrhotite (Fel xS) and/or
pyrite/marcasite (FeS2) In the process o~ the present in- ..
vention the pyrrhotite and pyrite/marcasite will be largely .
con~erted to Fe304 and sulphur~ .
The presen.t invent~on is illustrated by the following .:
examples
A ~230 TYL~R* mesh sample of a chalcopyrite con-
centrate, containing 28~6~ Cu, 26.1~ Fe and 3401~ S that
had been prepared by flotation of a chalcopyrite ore~ was
pelletized lnto pellets o~ -5~10 TYIER mesh s~ze using 1%
Wyoming bentonite as a b~nder Approximately 20 g. of pellets
were weighed and then heated, in the ~ubstant~al absence of
oxygen, to 850C while sulphur dioxide was passed o~er the
pellets at a rate o~ 650 cm3/min. The pellets were then
cooled, weighed and then crushed to -325 TYLER m~sh size and
analyzed qualitatively by X-ray diffraction techniques.
This technique allowed the extent of the reaction
to be monitored using the absorptions due to chalcopyrlte,
bornite, magnetite and CuxS (x c 108 ' 2, 0), ~uantitative
analys0s were subsequently carried out by atomic abæorption
(copper and iron) and X-ray fluorescence (sulphur)0
The a~ove method o~ treatment o~ chalcopyrite was
repeated using sulphur d~ox$de that had been saturated with
water at 100C.
The results are gi~en ~n Table Io The theoretical ~-
results for complete con~ersion of chalcopyrite to Fe304 and
Cu2S are a weight loss o~ 15 8~ and a product analyzing, 8,5%
sulphur ~or the chalcopyrite used in this example. The results `
show the effect o~ water on the treatment process
denotes trade mark
. ~ 5
', :
.
~ ~ S~ 7 ~ 7
me accuracy Or the analy~s rep~rted in th~ examples
is belleved to be as follows: copper and sulphur ~ 4% iron
6% relatlve.
EX~MPlE II
The products of Runs 3 and 6 of Example I were further
treated to increase the copp~x content of the treated chal~o-
pyrite by sub~ecting the products to magnetic separation and ~ .
~lotation technique~. me results given in Table II
illu~trate the effect of the two separatisn techniquesO
The ~iagnetic separation was made on 8 g. samplesu ing a wet magnetic separation technique in a DAVIS* tubeq
The flotation was carri~d out on 4 gO samples that had been
condit~on~d in distilled water ~or 48 hours. 200 ml o~ water
containing DOW z-200* (0.005~ concent~atiQn), methyl isobutyl
carbinol (1.5 ~g/~OO ~1) and ~u~ficient calcium oxide to ..
ad~ust the pH to 10~7 - 11.0 was u~ed ~or the flotatio~.
The use of a DAVIS tube is de~cribed in "Handbook
of Mineral Dressing - Ores and Indu~trial Minerals", 2nd
Edition, Section 19-174 by A.F. Taggart.
* denotes trade mark
.
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<IMG>
<IMG>
-8-
[)7~7
A -170~230 mER mesh sample of chalcop~rite con-
centrate was pelletized into pellets of -5-~10 TYIER mesh size
using 1% Wyoming bentonit~ as a binder, The pellets had the
following analysis: 26,8~ copper, 29,7~ iron~ 33,8% sulphur
and 9,0~ silica. Approxima-tely 24 g, o~ pel~Lets were weighed
and then heated to 850C in the substantial absence o~ o~ygen,
for 4,5 hour~, Sulphur ~ioxide was passed over the sample at
1090 cm3/min, The weight loss of the treated pellets was
14,3~ and analysis of the treated pellets showed a sulphur
content of 807~, .
Samples of untreated chalcopyrite (A) and of the
treated chalcopyrite pellets (B) were separately ground under
identical conditions to approximately -230 ~Y~ER mesh size,
3.0 g, samples of the ground material were then leached wlth
several leaching system~, The resulks are given ln Table III,
TABLE III
Leaching
Time opper Iron
20 Run Leach _ nditions (hours~ A B A B
9 Concentrated ammon-
la in water in ~re~-
ence of alr, 20-C 28 11,2 19~5 - -
Dilute HN0 /~ SOI
20C 3 2 ~ 28 8,2 49,0 9,~ 29,8
11 Conc, HN03
75C 28 98,o 94,5 85,o 1~6,1
67
~V
Using the procedure of Example I pellets were heated
at 850C in the substantial absence of oxygen for 3 hours under
a flow of 650 cm3/min, o~ sulphur dioxlde~ The weight loss of
the pe~lets was 1},8% and the pellets contained 17~2% sulphurO
Analysis by X-ray diffraction showed that the pellets
containsd crystalline phases of Fe304 and Cu5FeSL~ together
with residual CuFeS2 and some gangue, A port~on of the pel- ;-
lets was heated under nitrogen at 1200C for 3 hours, A
further weight loss of 6,6~ was obtained, I~o layers were
~ormed and these were mechanically separated, The top layer
(2,3 g,) was shown by X ray diffraction to be primarily
Fe2SiO4 and analyzed 6,7~ copper~ 34,6% iron and 36,o% silicà,
The lower layer (3,8 g,) was shown to be mainly Cu5FeS~ with
~ome metallic copper and iron; analys~s showed 59,4% copper,
25,6~ iron and 0~ sllica, Copper recovery in the lcwer layer
was 93~, ;
Example V
Using the procedure of Lxample I pellets were heated
at 850C under nitrogen ~or 2 hours and then ~or 4 hours
under a flow of 650 cm3/min, of sulphur dioxide, The weight
loss was 14,3% and product analysis showed 30~2~ copper,
28,2~ iron and 7,5$ sulphur, The product was shown by X-ray
di~raction to be primarily Fe301~, Cu5FeS4 and Cul.8_2,0S-
A portion of this product was ground to -400 TYLER mesh and
magnetically wet separated using a DAVIS tube, m e fractions
obtained were:
Magnetic fraction: 28,3% Cu, 33,3% Fe,
weight 7,80 g,
Non-magnetic fraction: 37,7% Cu, 5,2~ Fe,
weight 1,09 g,
Copper recovery was 16~
- 10 --
50767
The above magnetic ~raction was furkher treated by
heating at 1200C under nitrogen for two hours. After cool-
ing ~he copper-rich phase existed as large pellets which could
be mechanically separated~ The copper-rich phase was 2.47
g. and analyzed 77.4~ copper and 2,2% iron and raised the
copper recovery from 16~ to 89~,
- 11
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