AU465112B2 - Hydrometallurgical process for treating copper-iron sulphides - Google Patents

Description

3 9,661 72 This invention relates to a process for treat-

ing copper-ircn sulphides and, more particularly, is extrac- directed to a process for the hydrometallurgical form from tion of copper values and sulphur in elemental

copper-iron sulphides. Many processes have been developed for the hydro-

metallurgical extraction of copper values from complex

sulphide ores and concentrates. According to one such sulphates process, iron values are converted to dissolved which are not separately recovered and thereby not only

cause a loss of acid values but also pose disposal prob- More- lems, with attendant pollution of the environment.

over, a significant portion of such iron values are not

removed and not only lead to production of undesirable

acid but remain to impede copper separation and sulphur

recovery. Other processes comprise the extraction of cop-

per values and the production of iron oxide and elemen-

tal sulphur from sulphides by direct oxidizing pressure

leaching. In these processes, iron is converted to iron to oxide simultaneously with the conversion of copper

copper sulphate and the conversion of sulphide sulphur to elemental sulphur. As a result, the recovery of sul- of the phur from the residue is impeded by the presence

iron oxide. Co-pending patent application -Sefka No.1/V 1 teaches a process for the hydrometallurgical

treatment of copper-iron sulphides whereby copper-bearing

materials are subjected to an activation leach with an

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copper sulphate whereby acidic solution containing of ferrous sulphides and a solution insoluble simple copper separation, After a liquid-solids sulphates are obtained. of iron from copper values, for the effective separation and hydrolyzed the solution is oxidized the ferrous sulphate in the proces, which is removed from to precipitate the iron, are treated sulphuric acid. The copper sulphides and to regenerate acid solution in a gas and with sulphuric with an oxygen-bearing sulphide sulphur to oxidizing leach to oxidize the multiple-stage as euDric ion for to liberate the copper elemental sulphur and elemental form. subsequent recovery in process therefore provides a The present invention of sulphides for the recovery for treating copper-iron sulvhides comprises leaching copper-iron copper and sulphur which acid-in the presence containing sulphuric with acidic solution sulphides to convert said copper iron of metallic copper to sulphate, and recovering a solution of ferrous cuprous sulphide and said cuprous sulphide. copper and sulphur from for also provides a process The present invention copoer values sulphides to extract treating copper-iron the steps of: elemental sulphur therefrom which comprises and con- with an acidic solution reacting said sulphides in an and with metallic copper taining sulphuric acid range of from a temperature in the activation leach at the amount of metallic 700 to 1000C. and maintaining about at a molar ratio of copper to soluble iron and a of cuprous sulphide unity, for the production solution of ferrous sulphate;

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separating the solution 6f ferrous sulphate from the

cuprous sulphide;

3. concurrently oxidizing and hydrolyzing the ferrous

sulphate for the precipitation of iron compounds

and the regeneration of acidic solution containing

sulphuric acid;

4. separating the precipitated iron compounds from the regenerated acidic solution;

returning regenerated acidic solution to said

activation leach;

6. Subjecting the cuprous sulphide to an oxidizing leach

for oxidation of sulphide sulohur to elemental sulphur

and for dissolution of copper as cupric ion to form a

copper bearing solution.

7. discharging a mixture of copper bearing solution,

elemental sulphur and residual solids from the oxidizing

leach; and

8. recovering copper values from said copper bearing

solution.

A 465.112

39.661n The process will now be described in detail with schematical- reference to the accompanying flowsheet which of the process. ly illu~trates the relaticnship of the steps Materials processed according to the present in- ores which vention have been obtained from copper bearing whereby unde- have been beneficiated according to methodj The minerals sirable gangue material3 have been removed. comprise present in the copper bearing materi3ls normally bornite, copper-iron sulphides such as chalcopyrite and and chalco- copper sulphides such as covellite, diyinite and gold, cite, as well as precious metals such as silver nickel, and sulphides of other base metals such as iron,

molybdenum, lead and zirc. Copper containing concentrates are fed to the having at activation leach 10 in finely divided form, to ensure least SW pass a 325 mesh screen (Tyler series), The con- satisfactory activation of the sulphide minerals. either centrates can be added to the activation leach

as dry solids or in the form of an aquecus slurry. in The copper containing concentrates are treated and an acidic the activation step with metallic copper 11 activation solution 12 containing sulphuric acid. In this converted to sim- leach complex copper-iron sulphides are sulphate ple insoluble copper sulphides and to ferrous evolution of which dissolves in the liquid phase with the sulphides is hydrogen sulphide gas. Soluble iron in the from which it dissolved into solution as ferrous sulphate whereby the cop- can be recovered as a solid compound and insoluble simple per in the sulphides is tr-ansformed into

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39.6 61/72 copper sulphides which will react completely and rapidly

under subsequent oxidizing leaching conditions.

The principal reaction occurring in the activa-

tion step can be illustrated for chalcopyrite by equa-

tion

CuFeS 2 Cu -H2SO 4 Cu2 S FeSO4 H2 S (1)

After a separation, the insoluble simple copper sulphide

can be readily oxidized while the iron can be separately

treated. A secondary reaction consumes some copper by reacting with hydrogen sulphide. The copper is converted

to insoluble copper sulphide which must be treated to

enable recovery of the copper. We have found that this reaction takes place only to a limited degree and the

amount of copper consumed by the reaction is small.

The metallic copper 11, which is fed to the activation step 10, can be from various sources. For example, copper scrap, cement copper, or copper produced

by the process according to the present invention may be

utilized with equal results. Regardless of its source,

the copper must be in a finely divided form. A particle

size of the copper of less than 150 mesh (Tyler series)

is satisfactory, but a particle size of less than 400

mesh is preferred.

The acidic solution 12 is fed to the activation

step from a subsequent process step to be described and

comprises sulphuric acid in a concentration in the range

of from abeou 40 to 150 grams per litre and iron

in amount of from about 0 to 60 g/l in the form of fer-

rous and ferric sulphate, as well as small amounts of

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issolved zinc. magnesium and ralcium compounds. in There are a number of important variables ratio of the he prccess of the activation step. The amouAt of soluble mount of added metel ic copper to che the degree of ron present in the concentrate controls the zopper contain- Lissolution of the soluble iron from to iron in .ngconcentrate, while the rato of copper activation step :he solids containing residue from the on to the sub- etermines the amount of iron that passes activity of the equent oxidizing leach as well as the 3olid residue. The ratio o. the added copper to the soluble expressed as a iron in the concentrate is conveniently provides a satis- molar ratio and a value of about unity iron from factory degree of dissolution of the soluble above unity, the concentrate. Values of the molar ratio to unneces- using an excess of added copper, lead be desirable sary expense, although a slight excess may reactions and to allow for copper consumed in secondary in the feed to react with such metals as are present soluble than concentrate as sulphides which are more sulphide. The copper csulphide, such as for example zinc is reached when lower limiting value of the molar ratio residue is either the activity of the solids containing leach, or not sufficient for a satisfactory oxidizing leach. excess iron passes into the oxidizing of iron The ratio of copper to iron in the form from the acti- sulphides, in the solids containing residue should be vation step expressed ir aweight ratio, 7 465,1 12

39.661 P2 and preferably greater maintained at greater than 4:1 activity of the solids. than 1:1 to ensure a sufficient step is ai-other The acidity in tne activation acidity of the reaction important variable in that the of the solids from the ni::ture affects the separation separation step liquid in the subsequent liquid-solids dissolved iron from the and it affects remo,al of the iron precipitation step. leach solution in the sabsequent range of between -abet We have found that a pH in the requirements for a good and 2 is preferred to meet both removal. separation and a successful iron mixture de- The retention time of the reaction which is being treated, pends on the kind of concentrate the activation reaction as well as the rate with which of completion of the ac- proceeds and the desired degree that a retention time in tivation leach. We have found o 6 hours gives the de- the order of from I hour to-a sired results. at atmospheric The activation step is conducted in the range of from abet* pressure and at temperatures from abeo 700 to 100 0 a temperature in the range of may be injec- 900 to- 950 C. being preferred. Steam within the desired range. ted to maintain the temperature sufficiently to main- The reaction mixture is agitated in suspension. The acti- tain the solids in this mixture or in a continuous vation is conducted either batchwise Concentrate, aci- fashion, the latter being preferred. copper 11 are added to the dic solution 12 and elemental reaction vessel. During reaction mixture in a su.table

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tic reaction a froth calised by the evolution of hydrogen If so sulphide gas fcrm3 on top of the reaction mixture.

desired, means for breaking this froth may be provided, may be facilitating the release of the gas. These means the de- one of a number well known in the art to obtain of water, rired effect, e.g. a spinning disc, or a qpray or steam.

A slurry, comprising activated solids and an sulphide acidic ferrous sulphate solution, and hydrogen The hydro- gas are dischargcd from the reactijon v~essel. according gen sulphide is recovered and may b~e processed

to one of a number of methods. Preferably, the hydrogen

sulphide gas is absorbed in a copper sulphate solution copper with which it reacts to form a precipitate of recovery sulphide, which is subsequently treated for the is of copper and sulphur. Thus, the hydrogen sulphide sul- fed to precipitation step 13, reacted with a copper are phate containing solution and the reaction products 30. The fed directly to the subsequent o:.idizirg leach from copper sulphate containing solution may be drawn to be the solution obtained after the oxidizing leach

described below. Alternatively, the hydrogen sulphide for may be separately processed to recover the sulphur,

example, by the Claus process. The solids in the slurry discharged from the en- reaction vessel contain, in addition to sulphides and riched in copper, compounds of silver, molybdenum of lead. The solids may contain an amount of copper completion up to 65% by weight, depending on the degree of 9 465112

39,6 61 /72 of the activation step, and the amount of gangue mater- ials and other metal sulphides. The iron content of the solids likewise depends mainly on the degree of com- pletion of the activation leach. The discharged reaction mixture is subjected to a liquid-solids separation step 14. The various liquid- solid separations in tae process according to the inven- tion are carried out by using conveational methods such as, for example, settling, filtration, centrifuging and the like, either alone or in combination. The solids fraction from step 14 is fed to oxidizing leach 30 and the liquid fraction is directed to the iron precipitation step In the iron precipitation step 20, the ferrous sulphate in the solution from the liquid-solid separa- tion step 14 is converted into insoluble iron compounds and sulphuric acid by a combination of oxidation and hy- drolysis reactions. The reactions must be carried out in such a way that loss of copper, by coprecipita- tion with the iron product, is kept to a minimum. To prevent environmental pollution, the solid product from the iron precipitation Is impounded. The oxidation and hydrolysis reactions are carried out Simultaneously, preferably in a continuous manner, in a reaction vessel. The iron containing solution from the liquid-solids separation 14 is fed to this reaction vessel together with a sufficient amount of an oxygen bearing gas to give an oxygen partial pres- sure in the range of frora abeii 50-to abet, 200 pounds

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per square inch The contents of the reaction

vessel are maintained at a temperature of above 180°C.,

preferably in the range cf from 1800 to 230 0 C.

It will be evident from the flowsheet that the iron circuit,

comprising the dissolution 6f the iron in the activation

the separation 14 from the copper sulphides, the precipitation from the solution and the separation 21 of solid iron com-

pounds from the acidic solution 12, is independent from no the remainder of the flowsheet with regard to iron because the iron and/or copper containing solutions are recycled from free rest of the process to this circuit. We are, therefore, is to to choose the iron concentration of the solution which

be treated. We have found that by controlling the concentra-

tion of iron in the solution fed to the iron precipitation

a not more than 40 g/l, under the conditions of temperature

and pressure as discussed above, iron can be precipitated

mainly as stable iron oxide in a one stage precinitation level by The concentration of iron may be maintained at this fed to the the addition or removal of water from the solution desired, the reaction vessel of the iron precipitation 20. If separation precipitated iron compounds may be subjected, after hydrolysis from the liquid phase, to a second oxidation and pressure treatment, not shown, at similar temperature and

to reclaim further sulphate values. The oxidation and hydrolysis treatment may be carried

out in the presence of ammonium or alkali-metal

465.112

39.6 61 /n compounds, such ds, for example, ammoniu1, hydroxide, sodium hydroxide or sodium sulphate, whereby the ircn and sulphate are precipitated as jarosite.

The liquid phase from the separation step 21 comprises acidic solucion 12 which is returned to the activation step 10. This solution contains sulphuric

acid in an amount of from eabu 20 to 75 g/l H2 SO4 a

minor amount of both ferrous and ferric ion and all other ions present in the feed to the iron precipita- tion step. Because the ferric ion contained in solution will react with elemental copper in the activation step, it may be desirable to reduce the ferric ion to the ferrous state prior to feeding the solution to the ac- tivation step. The solids fraction from the liquid-solids se- paration step 14 is repulped, not shown, with return acid 31 which is recovered in the subse.uent copper re- covery steps and the pulp is fed to a multiple stage oxidizing leach wherein the activated solids are reac- ted with an oxygen bearing gas such as air, oxygen and mixtures thereof to oxidize the sulphide sulphur to elemental sulphur and to bring the copper into solution as copper sulphate. The accompanying flowsheet illustrates the oxi- dizing leach for a leach in two stages, 30 and 33 respec- tively. The discharge from the first stage oxidizing leach 0 is subjected to a liquid-solids separation 32. The solids from this separation are fed to the second stage

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puri- the licuid is fed to a subsequent oxidizing leach 33, while understood that in an operation fication operation. It willbe liquid-solids the oxidizing leach 30 and with more than two stages, with the to provide, in combination separation 32 may be repeated as those of stages. Sulphides such last stage, thedesired number iron, i.e. pyrite and precious of silver, molybdenum and leach and femain as solids in the metals, are not dissolved materials and elemental residue together with the gangue

sulphur. to the process of The oxidizing leach according copper sulphate in solution the present invention produces sulphur, while only a and a precipitate of elemental ferric sulphate is formed. minor amount of ferrous and different from In this, our process is significantly which do not first realize a other oxidizing leach processes of the soluble iron compounds substantially complete seperation the processes oxidize and hydrolyse from the copper. Such other or hydrated sulphates and hydroxides iron compounds in situ to:basic sulphate to separate from the copper oxides which are difficult from the the recovery of sulphur solution while, moreover, is diff- precipitated iron compounds mixture of sulphur and and sulphur other processes do not produce icult to achieve. Still After the sulphur to sulphate. in elemental form but oxidize in the form this sulphate is recovered the recovery of copper, acid which is in the form of sulphuric of sulphate is recovered an excess acid in the circuit recirculated and which creates removed. which must necessarily be is returned from the subsequent The return acid 31, which of the which is fed to each stage copper recovery step and I 465,112

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oxidizing leach, contains from 40 to 120 g/l H 2 SO4 from

0 to 40 g/l cupric ions and from 0 to 10 q/l ferrous ions. The

composition of the return acid will depend largely on the methods of copper recovery used.

The operating parameters under which the oxidizing leach is

pefformed are highly critical. The most critical operating

parameter is the temperature.

We have found that at temperatures above 100 C the oxidation

reaction proceeds initially at a high rate but this rate decreases

sharply with time. We believe that this reduction in the reactic

rate is due to the activity of the solids and the exothermic nat-

ure of the reaction which causes localized overheating with conse

quent melting of sulphur. The molten sulphur blinds the surfac

of the particles thereby preventing continuing oxidation. We have found that the temperature to achieve a good rate

of extraction at a staisfactory efficiency is in the range of fr< 0 that tempera- 700 to about 110 C. The limiting temperature is

ture at which the iron in solution starts to hydrolyze add

precipitate with an associated loss of silver'and molybdenum. We have also found that by maintaining the temperature in

the first, or earlier stages, of the oxidizing leach in the lowe

end of the range, within the range of from 700 to

100 0 the blinding of particle surfaces is effectively prevent

while the temperature in the later, or last, stages of the leach

may be maintained in the higher end of the range, within

the range of 900 to 1lOoC.

The oxidizing leach can be performed under a wide range of

pressures. We have found that in the presence of an oxygen cont

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leach may be up to 400 P.5.1. ing gas pressure in the oxidizing Pressures above 400 p.5.1., to provide satisfactory extractions. pressure equipment necessitating although effective, require high it is possible to conduct the oxid- additional capital cost. Thus, gas under pressures in the izing leach with an oxygen bearing p.s.a-. range of from atmospheric to 400 be obtained by maintaining An effective oxidizing leach can

the pressure in the first, or earlier, stages of the oxidizing stated pressure range, while leach in the lower end of the above later, or last stages in the higher maintaining the pressure in the example, we have found that a end of the disclosed range. For sulphides will be oxidized in substantial portion of the copper gas in the first stage oxidizing the presence of an oxygen bearing atmospheric pressure. leach wherein the pressure is substantially pressure in the first, or earlier It is preferred to maintain the to the range of from atmospheric stages of the oxidizing leach, the last, or later 300 p.s.i. and to maintain the pressure in to 400 stages, in the range of from 200 mixture in each of the The retention time of the reaction and is may vary within a broad range stages of the oxidizing leach extraction in each stage but dependent not only on the required stage. mhus we have found that also on the conditions in each the retention time may be at lower temperatures and pressures at higher temperatures and pressures between 2 and 48 hours, while 30 minutes and 12 hours. the retention time may vary between in the oxidizing leach is The acidity of the reaction mixture controlled to ensure a high dissolut- critical and must be carefully to prevent the precipitation ion of the copper as well as

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of iron compounds and associated loss of silver and molybdenum.

The discharge from the oxidizing leach 33 is passed

directly to a froth flotation operation 40, wherein the elemental

sulphur, residual metal sulphides and precious metals are

separated from the gangue materials and solution. By using a

collector for sulphur such as an organic diethiophosphate, a

flotation concentrate is obtained which contains the elemental

sulphur, as well as substantially all of the silver and molybdenu as sulphides, precious metals, iron compounds and unleached coppe

sulphides,,as well as some gangue materials. We have found

that the concentrate may contain up to 85% So by weight. If so

desired, the flotation concentrate may be subjected to a liauid-

solids separation and the solids washed to recover additional

dissolved copper values. The elemental sulphur is separated

from the sulphides in a sulphur recovery step 50 followed by a

liquid-solids separation 51. This receovery can be accomplished

using one of a number of methods. Becuase of the very high is 1 concentration of sulphur, a conventient and efficient method heat the concentrate above the melting point of sulphur, separat:

the molten sulphur in liquid-solids separation 51 by a convenien method such as filtration, and recovering the sulphur. The

residue of the concentrate after separation of the sulphur may

be treated in a recovery step 60 to recover the copper, molybden silver and other precious metals.

The flotation tailings, which contain the copper solution an

the insoluble non-sulphide gangue materials, such as silicates

and magnetite from the feed concentrate, are subjected to a

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the copper liquid-solids separation 41 to separate The resulting copper bearing bearing solution from the solids.

solution is combined with the liquid

465.112 portion from the liquid-solids separation step 32. This combined solution contains abee~ 20 to 80 g/l copper as cupric ions, abou± 5 to 25 g/l sulphuric acid

-ind aot3 to 15 g/l iron as ferrous and ferric iron. The combined solution ia then treated it.a purification operation. In the purification, at least a portion of the in iron is removed to maintain the concentration of iron the circuit at a predetermined lot. level while the iron in the remaining portion present in the ferric state must be red~uced to the ferrous state. Residual silver,

as well as selenium and tellurium are simultaneously precipitated in the purification and can be recovered. It is advantageous to conduct the purification step in two stages, as illustrated. In the first purif-

ication stage 70, the iron in solution is oxidized and hydrolysed continuously at a temperature of above 1600C., preferably in the range of from abe4M. 1800 to 2300C., under a partial pressure of oxygen in the range of from ahout 50 to 200 p.s.i. The retention time is 30 minutes

or less. After a liquid-solids separation 71 to remove the precipitated iron compounds, copper powder is added 72 to the liquid fraction in the second stage purification/ and the solution is separated from the copper powder with the precipitated elements in liquid-solids separa- tion 73. The residue containing silver, selenium, tellurium and copper may be further treated to recover these valuable constituents. The purified solution from liquid-solids separ- ation 73 is fed to a recovery step 80 wherein elemental 18 465.112

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the solution. For recovery copper is precipitated from solution any one of a number of copper from the purified employed, such as electro- of well known methods may be with subsequent reduction, winning, chemical precipitation a reducing gas. We have found or direct reduction with hydrogen gas at elevated that direct reduction with is very in a continuous fashion temperature and pressure economic advantages over rapid and offers significant in a reaction other methods. The reaction is conducted a pressure of about 1800C., under vessel at a temperatura with agitation. The retention of about 450 p.s.i. and sulphate reduction of the cupric time required for the five of several minutes, e.g. solution is in the order minutes. from the liquid-solids The purified solution from adoav 25 to 80 g/l separation 73 may contain acid from 5 to 25 g/l sulphuric copper as cupric ions, The g/1 ircn as ferrous ions. and from a trace to 10 vessel is treated in a dischdrge from the reaction 81 to separate the precipitated liquid-solids separation liquid. A portion of the copper copper powder from the step directly to the activation powder may be returned is dried and sintered in while the remaining portion product. and recovered as final an atmosphere of hydrogen stage 31 which is fed to each The liquid is return acid This in an amount as required. of the oxidizing leach aebea 40 to 120 g/l sulphuric return acid contains from ions and 40 g/l copper as cupric acid, from abes 0 to iron as ferrous ions. from .beaU' 0 to 10 g/1 build-up of concen- In order to prevent the 19 465.112

396 61 1fn

magnesium, or zinc, trations of minor elements, such as it is necessary to and sulphate ions in the process, at any convenient provide one or more bleed-streams place, or places. The amount of bleed depends on the the concentrate; gener- amounts of magner'ium and zinc in Z in the process ally a circulating load of kMg++ and acceptable. Any of -abeet 20 to 30 g/l has been found is recovered, copper which is present in the bleedstreams or cementation on for example, by chemical precipitation treated to iron. The residual solution may be further discarded after neutral- recover other values, or may be pollution. ization of the acid content to prevent now be described The process of our invention will with reference to the following example: EXAMPLE portions A copper concentrate containing major to about 99% of chalcopyrite and bornite was ground and had a composition minus 325 meshl (Tyler Screen Series) 22.4% sulphur, the comprising 40.8% copper, 13.8% iron, remainder mostly gangue. 1,000 grams of this ground litres of an acidic concentrate were suspended in 4 which solution obtained from an iron precipitation 10 g/l iron as ferrous contained 65 g/l sulphuric acid and and 157 sulphate. The suspension was heated to 959C. finely divided elemental grams of electrolytic copper in slowly added over a period form, i.e. minus 400 mesh, were hydrogen sulphide gas of 5 hours.. During this period of foam on top of the was evolved which formed a layer foam reaction mixture. A spinning disc was used in this the gas. 46 112 layer to facilitate the release of

39.661 /72

the solids residue After the specified period, The solution by filtration. das separated from the and contained 52.1% copper, solids weighed 1,084 grams

4.3% irQn and 16.5% sulphur. the above data that It will be evident from elemental copper to scluble the molar ratio of added ratio was unity, that the weight iron in the concentrate that solids xesidue was 12, of copper to iron in the in the concentrate and all copper which was present in the solids residue, that which was addeu reported the had been dissolved from and that 66% of the iron

concentrate. in an autoclave at The solution was treated partial pressure of oxygen, 2000C. and at 200 p.s.i. and an acidic solution whereby the iron was precipitated suspended in 12 was obtained. The solids residue was with obtained from the reduction litres'of return acid The containing solution. hydrogen of a copper sulphate in the g/l copper, 3 g/l iron return acid contained 20.5 The 109 g/1 sulphuric acid. form of ferrous ions and subjected in the return acid was solids residue suspended at a leach in an autoclave to a first stage oxidizing at an oxygen partial pressure temperature of 950C. and 1.5. After of 200 p.s.i. The pH of the leach was separated from the solution minutes, the residue was iron. copper and 5.1 g/l total which analyzed 64.1 g/l stage leach was The residue from the first acid and treated in the suspended in 3 litres return of a partial pressure of oxygen second stage at 950C. at 5 hours. The pH in the leach p.s.i. for a period of

was less than one. 21 465.112

3 9. 661 /n

stage The material discharged from the second oxidizing lea~h was subjected to flotation using e as collector. The flotation "Aerofloat 25" 1.2% copper, concentrate weighed 258 grams and contained From this concen- 0.8% iron and 74s elemental sulphut. in elemental trate was recovered 190 grams of sulphur 4% form, while the residue weighing 68 grams contained elemental copper, 4.1% iron, 3.1% total sulphur, 1% sulphide sulphur as well as about 90% of the mol:-bdenum the concen. and silver which wer2 originally present in trate. After separation of the solution from the tailings, the solids in the tailings, weighing 236 grams, being contained 0.1% copper and0.3% iron, the remainder mainly silicates. The solution from the tailings and was contained 27.7 g/l copper and 13.4 g/1 iron stage oxidizing combined with the solution from the first purif- leach. The combined solution was subjected to a was ication whereby the iron content of the solution reduced to 3 g/l. The purified solution was reduced 450 p.s.i. with hydrogen in an autoclave at 2000C. and metallic to recover a major portion of the copper in as form, while the residual solution was recirculated return acid to the oxidizing leach. It will be understgod, of course, that the foregoing example is illustrative only of typical embod- that modific- iments of the process of our invention and ations can be made in the process as described and hereinbefore without departing from the scope purview of the appended claims. 465.112 22 i

39661 /2

1. A process for treating copper-iron sulphides for

the recovery of copper and sulphur which comprises leaching

copper-iron sulphides with an acidic solution containing metallic sulphuric acid in the presence of metallic copper to sulphide and copper to convert said copper iron sulphides to cuprous a solution of ferrous sulphate, and recovering copper and sulphur

from said cuprous sulphide.

2. A process for treating copper-iron sulphides to extract comprises the copper values and elemental sulphur therefrom which steps of: reacting said sulphides with an acidic solution containing sulphuric acid and with metallic copper in an activation leach at a temperature in the range

of from 700 to 1000C. and maintaining the amount of

metallic copper to soluble iron at a molar ratio of about unity, for the procution of cuprous sulphide and a solution of ferrous sulphate;

separating the solution of ferrous sulphate from the cuprous sulphide;

concurrently oxidizing and hydrolvzing the ferrous

sulphate for the precipitation of iron compounds and the regeneration of acidic solution containing

sulphuric acid; the separating the precipitated iron compounds from regenerated acidic solution;

returning regenerated acidic solution to said activation leach;

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Subjecting the cuprous sulphide to an oxidizing leach for oxidation of sulphide sulphur to

elemental sulphur and for dissolution of copper

as cupric ion to form a copper bearing solution;

discharging a mixture of copper bearing solution, elemental sulphur and residual solids from the

oxidizing leach; and

recovering copper values from said copper bearing solution.

3. A process as claimed in claim 1 or 2, which comprises metallic reacting said sulphides with said acidic solution and

copperat a pH in the range of from 0.5 to which 4. A process as claimed in anyone of claims 1 to 3, solution and comprises reacting said sulphides with said acidic at the metallic copper at the vapour pressure of the system reaction temperature.

A process as claimed in anyone of claims 1 to 3 which solution comprises reacting said sulphides with said acidic of from and metallic copper at a temperature within the range to 95 C. 5, in 6. A process as claimed in anyone of claims 1 to group consisting which the metallic copper is selected from the and of scrap copper, cement copper, electrolytic copper

hydrogen reduced copper. to 9, in 7. A process as claimed in anyone of claims 2 copper to iron which residue from the activation leach has

weight ratio of greater than 4:'1. to 6, in 8. A process as claimed in anyone of claims 2 a copper to iron which residue from the ativation leach has

weight ratio of greater than 7 1.

9. A process as claimed in anyone of claims 2 to 8, in 24 465.112

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in the activation leach is absorbed which hydrogen sulphide envolved the oxidizing leach. in copper sulphate solution from of claims 1 to 9 which A process as claimed in anyone the ferrous sulphate at compris'es oxidizing and hydrolysing 0 0 from 180 to 230 and a pressure a temperature in the range of to 200 p.s.i. in the range of from 50 p.s.i. 10 which comprises, controlling 11. A process as claimed in claim in the solution fed to the oxidzing the ferrous iron concentration than 40 grams per litre. and hydrolysing step at not more of claims 1 to 11, whiich 12. A process as claimed in anyone sulphide to a multiple stage comprises subjecting the cuprous up to 400 p.s.i. oxidizing leach at a pressure of claims 1 to 11, 13. A process as claimed in anyone stage cuprous sulphide to a multiple which comprises subjecting the in the range of from 70 0 to oxidizing leach at a temperature 1100 C. claim 12 or 13 twhich comprises 14. A process as claimed in leach at a pressure in maintaining the first stage oxidizing to 300 ps.s.i. and the last the range of from atmospheric in the range of from 200 stage oxidizing leach at a pressure to 400 p.s.i.

A process as claim in claim 14 which comprises maintain- a temperature in the range of ing,the first stage oxidizing~at oxid 6zing from 70 0 to 100 0 and maintaining tne last stoge range of from 90 to 110 C. leach at a temperature in t he of claims 2 to 16. A process as claimed in anyone sulphur and sulphides from the which comprises floating elemental leach to produce a concentrate mixture discharges from the oxidizing metal sulphides and precious containing elemental sulphur,

465.112

Claims (1)

1. 39.661 In

   metals, and flotation tailings which contain the copper solution

   and the insoluble non-sulphide gangue materials such as

   silicates and magnetite.

   17. A process as claimed in claim 16 in which the floatation

   tailings are subjected to a liquid-solids separation to sep-

   arate the copper bearing solution from the solids.

   18. A process as claimed in claim 16 or 17 which comprises

   separating the elemental sulphur from the metal sulphides

   and precious metals.

   19. A process as claimed in anyone of claims 2 to 18 which comprisei

   reducing the ferric iron in the copoer sulphate solution to ferrous fc iron and subjecting the resultant solution to hydrogen reduction production of metallic copper and return acid.

   A process claimed in claim 19 which comprises return- reduction to the ing said return acid produced in the hydrogen oxidizing leach. said return 21. A process as claimed in claim 20, in which ions. acid contains from 0 to 10 grams per litre ferrous 2 to 18 which 22. A process as claimed in anyone of claims sulphate comprises recovering copper values from said copper metallic solution by electrowinning for the production of copper and return acid.

   23. A process as claim in claim 22, which comprises return- to the oxid- ing said return acid produced by electrowinning izing leach.

   24. A process as claimed in claim 23, in which said return ferrous ions. acid contains from 0 to 10 grams per litre preceding claims A process as claimed in anyone of the

   465,112

   39.661 72

   in which said sulphides have a particle size such that at

   least 98% of said sulphides pass a Tyler 352 mesch screen.

   26. A process as claimed in anyone of the preceding

   claims in which the metallic copper has particle size smaller

   than tyler 150 mesh. 27. A process as claimed in anyone of the preceding claims

   in which the metallic copper has particle size smaller than

   Tyler 400 mesh.

   28. A process as claimed in anyone of Claims 2, 10 or 11,

   which comprises oxidizing and hydrolyzing the ferrous sulphate

   in the presence of ammonium or alkali metal compounds whereby the ferrous sulphate is precipitated as jarosite.

   29. A process as claimed in claim 28 in which said a ammonium or alkali metal compounds are selected from the group consist-

   ing of ammonium hydroxide, sodium hydroxide and sodium sulphate.

   A process substantially as hereinbefore described and

   illustrated with reference to the accompanying drawings.

   D A T E D this 18th day of of JUNE, 1975.

   COMINCO LTD. By its Patent Attorneys.

   CALLINAN AND ASSOCIATES.

   465.112

   39, 6 61 /72

   465, 112