EP0599911A1

EP0599911A1 - Copper recovery process

Info

Publication number: EP0599911A1
Application number: EP92917245A
Authority: EP
Inventors: Joseph M. Sierakoski
Original assignee: Henkel Corp
Current assignee: Henkel Corp
Priority date: 1991-08-14
Filing date: 1992-08-06
Publication date: 1994-06-08
Also published as: ZA925990B; AU2414492A; JPH06509845A; MX9204666A; FI940526A0; FI940526A7; FI940526L; AU668358B2; WO1993004208A1; CA2115160A1; BR9206321A; ZM4092A1

Abstract

Procédé amélioré de récupération du cuivre contenu dans un concentré de sulfure de cuivre, la calchocite, et consistant à lessiver partiellement le concentré de calchocite au moyen d'une solution ammoniacale aqueuse telle que l'ammoniaque et le sulfate d'ammonium, sans qu'il se produise de lessivage sensible de soufre ou de conversion en sulfate, et à extraire le cuivre de la solution ammoniacale aqueuse de lessivage partiel obtenue à l'aide d'un produit d'extraction insoluble dans l'eau, de préférence la bêta-dicétone, qui présente une capacité de charge de cuivre élevée, une capacité de charge d'ammoniaque faible, et qui est généralement dissous dans un solvant organique non miscible dans l'eau.Improved process for recovering copper from a copper sulfide concentrate, calchocite, and which consists in partially leaching the calchocite concentrate using an aqueous ammonia solution such as ammonia and ammonium sulfate, without there occurs substantial leaching of sulfur or conversion to sulphate, and in extracting the copper from the aqueous ammoniacal solution of partial leaching obtained with the aid of an extract product insoluble in water, preferably beta- diketone, which has a high copper carrying capacity, a low ammonia carrying capacity, and which is generally dissolved in a water-immiscible organic solvent.

Description

COPPER RECOVERY PROCESS

BACKGROUND OF THE INVENTION

Field of the Invention:

This invention relates to a process for the recovery of copper from chalcocite concentrates by a process of partial leaching of the concentrate and extraction of the resulting aqueous ammoniacal leach solution.

Statement of Related Art:

Practice in the recovery of copper from its sulfidic ores involves subjecting the ores to a froth flotation operation to produce a concentrate of the valuable metal sulfides and to reject in the flotation tailings of valueless sulfides, silicates, aluminates and the like. One of such concentrates provided is a chalcocite concentrate containing chalcocite and covellite.

In U. S. Patent 4,022,866 to Kuhn and Arbiter, and in their subsequent paper, "Physical and Chemical Separations via the Arbiter Process" 11th International Mining Congress, April, 1975 Cagliari, Italy; Proc.-Int. Miner. Process. Congres., Paper 30; pp.831-847; there is described the leaching of copper sulfide concentrates with ammonia/ammonium sulfate and oxygen whereby the sulfide is converted to sulfate, and the dissolved copper may then be recovered by solvent extraction. In the patent complete leaching of the copper from the ore is preferred although Fig. 3 also describes an embodiment in which a partial leaching is contemplated. The solvent extraction reagents are described in the patent only generally as those which preferentially load copper from alkaline solutions. In the paper, which describes the operation of the Arbiter process, the focus is on complete

(or nearly complete) leaching of the sulfide concentrates. On page 834 a chalcocite concentrate is specifically discussed and diagrammed, with all the copper and associated sulfur being dissolved.

In another Kuhn and Arbiter paper, "Anaconda's Arbiter Process for Copper", Hydrometallurgy, CIM Bulletin, Feb. 1974, pp. 62-73, makes reference to "complete dissolution of copper" and on page 65, refers to the known conversion of chalcocite to covellite, but points out that the chalcocite and covellite "are observed to be completely attacked and dissolved in our leaching system within 1 to 1 1/2 hours".

U.S. Patent 4, 563,256 describes a solvent extraction process for the recovery of zinc values from ammoniacal solutions, which may also contain copper values, employing various oximes as the extractants.

A paper by Anthony 0. Filmer et al, "Oxidation of Copper Sulfides in Aqueous Ammonia" part III,"Kinetic Characteristics", Austr. J. Chem. 1979,.32.,pp. 2597-2609, gives a detailed study of the ammoniacal oxidation of chalcocite, first to covellite, then to complete dissolution.

U.S Patent 2,727,818 describes a method of leaching copper sulfide materials with ammoniacal leach solutions, indicating that the first Cu from Cu₂S (chalcocite) dissolves without dissolution of sulfur, and the Cu from CuS (covellite) dissolves only when its sulfur also dissolves. No solvent extraction is discussed.

U.S. Patents 4,065,502 and 4,175,012 describes beta- diketones which may be employed as metal extractants in a

SUBSTITUTESHEET liquid ion exchange process for recovery of metals, such as nickel or copper, from aqueous solutions containing the metal values, including aqueous ammoniacal solutions.

DESCRIPTION OF THE DRAWING Figure 1 is a diagrammatic flow chart illustrating a partial leaching of a copper concentrate and a liquid-liquid extraction of the copper values from the resulting leach solution, followed by recovery of the copper, either in the form of copper sulfate crystals or as cathode copper by electrowinning.

DESCRIPTION OF THE INVENTION In this description, except in the operating examples or where explicitly otherwise indicated, all numbers describing amounts of ingredients or reaction conditions are to be understood as modified by the word "about".

It has now been discovered that the combination of a partial leaching of chalcocite and the use of a high copper- transfer, low ammonia-loading extraction reagent provides a very efficient process of recovery of copper. Because of the partial leaching, up to 50% leach, there is no conversion of the sulfur from sulfide to sulfate, which results when complete dissolution of the concentrate is carried out. With the conversion to sulfate, as practiced in the Arbiter process, much of the ammonia is tied up as ammonium sulfate. In order to liberate the ammonia, the sulfate must be treated in an energy intensive process. In the present invention ammonia recovery is simplified as, in the solvent extraction using the reagents employed in the present invention, ammonia is automatically regenerated during extraction and is simply recycled back via the raffinate for further leaching. Since the sulfur is not converted to sulfate in the partial leaching of the present invention, the sulfur, which remains in the leach residue, is concentrated by flotation and is removed to a smelting process as shown in Figure 1, where sulfuric acid may conveniently and efficiently be produced.

SUBSTITUTESHEET In the copper recovery process of the present invention, a chalcocite concentrate is subjected to a partial leaching with ammonia and ammonium sulfate solution. While ammonium sulfate is preferred in order to maintain the sulfate matrix throughout the system and ensure consistent quality of product, other ammonium compounds, such as the carbonate, nitrate and chloride may be employed; however, these may require specialized equipment or additional processing stages. Chalcocite concentrate is typically composed of about 75-90% chalcocite (Cu₂S) , though some may contain in excess of 90%, with the remainder being substantially covellite (CuS) , with trace amounts of chalcopyrite (CuFeS₂) or other forms of copper.

As shown in the Figure, the chalcocite concentrate is contacted with ammonium sulfate solution and free ammonia, preferably in the form of ammonium hydroxide, with agitation to form a slurry which may range from about 10% to about 75% solids, typically about 30-60%, with 35-50% being preferred. The higher the percent solids attained, the smaller the size of the leaching vessel which is required and the higher the concentration of the copper contained in the aqueous phase. The leaching is conducted at a pH in the range of about 8.5 to 11 to produce cupric ammonium sulfate and is conducted at ambient temperature and pressure, until the remaining copper is present as covellite (CuS) . Thus the chalcocite (Cu₂S) is leached so as to remove sufficient copper (half of the Cu₂) to leave a residue comprised substantially of CuS (covellite) . While one of the advantages of the present invention lies in the use of ambient temperature and pressure and does not require elevated temperatures or pressures, elevated temperature and pressure may be employed, if desired, or where specialized ambient conditions exist, such as extreme cold conditions. Since the sulfur is not being converted to sulfate, no oxygen is required, however, air may be sparged into the leach vessel which tends to expedite the dissolution

SUBSTITUTESHEET of the chalcocite in the presence of free ammonia and the conversion of Cu⁺ ion to Cu⁺⁺ ion to provide the cupric ammonium sulfate. Leach retention time is dependent on the desired percentage of copper to be solubilized, however, typically 30 to 90 minutes is generally sufficient to solubilize 20-35% of the total copper contained in the form of chalcocite, using an air sparge at typical ambient temperatures and pressures, i.e. 20-23 degrees Centigrade and atmospheric pressure. In the leaching step of the present invention the leaching should not substantially exceed the conversion of the chalcocite to covellite, e.g. removal of one part of copper from chalcocite compound which contains 2 parts of copper. If the resulting covellite is leached in the present process, there would occur an oxidation of the contained sulfur to sulfate, which is to be avoided or minimized in the present invention, since with any increase in sulfate, it is then required to incorporate a sulfate bleed stream and a subsequent make-up of ammonia lost in the form of ammonium sulfate. Desirably the only losses of ammonia in the process of the present invention will be only a small amount contained in the solids which is lost in the solid/liquid separation step shown in the flow diagram of Figure 1.

The leaching is preferably conducted in a continuous fashion with the original concentrate entering the first stage of leach and mixing with the raffinate from the subsequent extraction step. Anhydrous ammonia or ammonium hydroxide is added as needed to maintain a leach pH between about 8.5-11. Ammonium sulfate should be maintained at a level of at least the stoichiometric quantity required to solubilize the desired amount of copper contained in the concentrate. Preferably the ammonium sulfate is maintained at a level slightly in excess of the stoichiometric amount, typically at about 10-20% excess, and preferably at about 15% excess. This amount of excess will ensure the amount of copper desired to be

SUB_STITUTESHEET solubilized (one Cu from the Cu₂S) , without any substantial solubilization of Cu from the covellite and without any substantial conversion of sulfidic sulfur to sulfate.

As shown in Figure 1, after the leaching, the leach slurry is discharged from the leaching vessel and a liquid/solid separation is performed, which may be simple decantation or a filtration step. The solids are preferably washed with water, and/or ammonia water solution, free of copper to remove any copper in solution entrained in the solids. As further shown in Figure 1, the washed and filtered solids may be subjected to flotation, to produce a new copper concentrate, composed primarily of covellite, CuS. The new covellite sulfide concentrate will contain a higher fuel value for subsequent pyrometallurgical treatment than the original chalcocite concentrate in regard to the copper-sulfur ratio therein. Any precious metals such as silver or gold, or other sulfide minerals, such as molybdenite, which were initially present will also be found in the new flotation concentrate, from which they may be further processed and recovered. The copper pregnant leach solution, along with the washing solutions from washing of the solids as described above, will then be sent to the extraction stage of the process, preferably after clarification to remove any fine solids which may be present from the previous step. Such clarification is preferably carried out by filtration. In the extraction stage, the pregnant copper leach solution which now will contain from about 15-100 grams per liter (g/1) copper, typically about 30-40 g/1, at about pH 9 to 10 is contacted with a water-immiscible, organic solvent solution of an extractant compound having a high copper loading, low ammonia loading, capacity so as to result in a transfer of the copper to the organic solvent solution which forms an organic phase substantially immiscible with the aqueous copper pregnant leach solution. In Figure l, the extraction stage is shown as a single

EET block. In practice, the extraction would be carried out in a continuous countercurrent process, typically employing up to three extraction stages, in a series of mixer-settler units in which the outlet of a mixer continuously feeds a large settling tank where the organic solvent (organic phase) , now containing the copper extractant complex in solution is separated from the depleted aqueous solution (aqueous phase) . This part of the process is referred to as the phase separation. Usually the extraction process is repeated through two or more mixer-settler units in order to more completely extract the copper. Where two mixer-settler units are employed, the copper pregnant leach solution will be introduced to the first mixer-settler unit extraction stage (often designated E-l) where it is contacted with the organic phase exiting from the second mixer-settler extraction stage (often designated E-2) , thereby involving a countercurrent flow of the organic phase and the aqueous copper solution phase. The aqueous phase from the first extraction unit (E-l) is introduced into the second mixer-settler extraction unit (E-2) , which contact the incoming organic phase, recycled from the stripping stage of the process. The copper loaded organic phase exits E-l and is introduced to a washing step prior to stripping of the copper from the organic phase. The aqueous raffinate (ammonia and ammonium sulfate solution) from the extraction (unit E-2) , now substantially barren of copper, typically containing less than 1 g/1 (and preferably about 0.1 g/1) is recycled to the leach step and solids wash steps earlier described.

The washing step may consist of only one stage or, as in the case of the extraction step, may consist of more than one. The purpose of the washing step is primarily to remove any entrained, or chemically loaded, ammonia solution which may have been loaded into the organic phase along with the copper. If significantly low ammonia loading extractant compounds are employed, so that no significant amounts of ammonia are loaded

SUBSTITUTESHEET into the organic phase, the washing step may be omitted and is thus an optional step. It is however preferred that at least one water washing step, pH controlled at a pH of 6-7 with a suitable pH adjusting acid, be employed to conserve ammonia and to minimize contamination of stripping agent employed in the next step of the process. If washing is employed after separation of the aqueous washing phase from the organic phase, the resulting aqueous solution from the washing is returned to the leaching step, while the copper loaded organic phase is then contacted with a stripping agent to form the stripping stage of the process. Again the stripping step may be carried out in a single stage or, as in the case of the extraction step, may typically be carried out countercurrently in more stages or units, i.e. in two stages. As in the extraction step the stripping, if carried out in two units, has the loaded organic phase introduced into the first stripping unit (S-l) , where it contacts the stripping agent (preferably sulfuric acid) exiting from the second stripping unit (S-2) , again a countercurrent processing. Sulfuric acid solution containing about 60-180 g/1 sulfuric acid is the preferred stripping agent, as it permits the subsequent recovery of the copper either in the form of copper sulfate crystals or by electrowinning to cathode copper. Other inorganic mineral acids may be employed as stripping agents, such as hydrochloric acid or nitric acid, however such may require other recovery methods or specialized handling equipment. The stripped organic, now substantially barren of the copper and typically containing less than 1 g/1 copper will exit unit S-2 and be introduced to the unit E-2 of the extraction step. The copper in the acidic stripping solution, now containing the copper in a concentrated amount, about 50- 60 g/1, and typically about 50 g/1, is then recovered in conventional manner either by crystallization or electrowinning, as shown in Figure 1. In electrowinning, the preferred recovery method, cathode copper is recovered as electrolytic copper at a 99.99%+ copper. The spent electrolyte, after deposition of the cathode copper, is then returned to stripping unit S-2. As this is being recycled into the process, the amount of copper present in the spent electrolyte may be relatively high, though lower than the 50 g/1 in the solution from the stripping step, and typically may contain from about 20-30 g/1 copper. If recovery is by crystallization, the copper is recovered in the form of copper sulfate crystals, which will typically require the introduction of some water to provide the water of hydration for copper sulfate crystals. The spent solution from the crystallization, aqueous sulfuric acid, will be recycled to the stripping step, into unit S-2.

As indicated earlier, the copper pregnant leach solution from which the copper is to be recovered by extraction will contain about 15-100 g/1 copper, and typically about 30-40 g/1 copper at pH about 8.5-11. The extraction compounds for use in the practice of this invention on these leach solutions, are those which will load, i.e. at least about 15 g/1, or extract, copper to a high degree, from high ammonia concentration solutions preferablywithout significant loading of ammonia. Such compounds, which are preferred for use as an extractant reagent in the present invention because of their low ammonia loading properties, are certain beta-diketones such as those described in U. S. Patents 4,065,502 and 4,015,980. One such extractant found to be particularly suitable for use in the present invention is l-phenyl-3- heptyl-l,3-propanedione, available commercially from Henkel Corporation as LIX^R 54. Other beta-diketone compounds which may be employed are defined by the following formula:

0 O R - C - CH - C - R' R" where R is phenyl or alkyl substituted phenyl, R' is alkyl, alkyl substituted phenyl or chloro substituted phenyl and R"

SHEET _iUB?πιyϊ5 is H or CN with the provisos that (1) when R is phenyl, R' is a branched chain alkyl group of at least seven carbon atoms and (2) when R is alkyl substituted phenyl, the number of carbon atoms in the alkyl substituent is at least 7 and at least one such alkyl substituent is a branched chain. R is desirably monoalkyl substituted and preferably contains 9 or more carbon atoms. The various alkyl groups are preferably free from substitution and contain less than 20 carbon atoms. Further when R¹ is alkyl, the carbon alpha to the carbonyl group is desirably not tertiary. Preferably, R" is H, R¹ is a branched 7, 8, 9, 12, or 17 carbon chain or a chlorophenyl or short chain (1-5 carbon) alkyl substituted phenyl and R is phenyl or a 7, 8, 9, or 12 carbon alkyl substituted phenyl group. While the beta-diketone compounds are preferred for use in the present invention as the water insoluble extractant compounds because of their low ammonia loading properties, other water insoluble copper loading extractants capable of loading copper from aqueous ammoniacal solutions may be employed. With such other reagents it may however, be necessary to include additional treatment of the organic phase because of ammonia loading, before stripping and recycling of materials in the continuous process. Other high copper loading extractants, which may be desirably employed, either alone or in admixture, are certain oximes, of those described in U.S. Patent 4,563,256. Oximes which may be employed in the present invention are those generally conforming to the formula:

where R¹ is a saturated aliphatic group of 1-25 carbon atoms or an ethylenically unsaturated aliphatic group of 3-25 carbon atoms or -OR³, where R³ is a saturated or ethylenically unsaturated group as defined above, a is an integer of 0, 1, 2, 3 or 4 and R² is H or a saturated or ethylenically unsaturated group as defined above, with the proviso that the total number of carbon atoms in R¹ and R² is from 3-25, or phenyl or R⁴ substituted phenyl where R⁴ is a saturated or ethylenically unsaturated group as defined above which may be the same or different from R¹. Illustrative of some of the oxime compounds are 5-heptyl salicylaldoxime, 5-octyl salicylaldoxime, 5-nonyl salicylaldoxime, 5-dodecyl salicylaldoxime, 5-nony1-2-hydroxyacetophenoneoxime, 5-nonyl- 2-hydroxyacetophenone oxime, 2-hydroxy-5-nonyl benzophenone oxime and 2-hydroxy-5-dodecyl benzophenone oxime. While it is preferred that a single extractant compound be employed, mixtures of extractants may be employed to meet particular system requirements.

A wide variety of essentially water-immiscible liquid hydrocarbon solvents can be used in the copper recovery process of the present invention. These include aliphatic and aromatic hydrocarbons such as kerosenes, benzene, toluene, xylene and the like. A choice of essentially water-immiscible liquid hydrocarbon solvents, or mixtures thereof for commercial operations will depend on a number of factors, including the plant design of the solvent extraction plant

(mixer-settler units, Podbielnak extractors) and the like. The preferred solvents for use in the recovery process of the present invention, are the aliphatic and aromatic hydrocarbons having flash points of 130 degrees Fahrenheit and higher, and preferably at least 150 , and solubilities in water of less than 0.1% by weight. The solvents are essentially chemically inert. Representative commercial available solvents are Chevron ion exchange solvent (available from Standard Oil of California, having a flash point 195 F, Escaid 100 and 110

^uSsrøiπΕ^^El (available from Exxon-Europe having a flash point of 180 F.), Norpar 12 (available from Exxon-USA, flash point 160 F.), Conoco-C1214 (available from Conoco, flash point 160 F.), Aromatic 150 (an aromatic kerosene available from Exxon-USA, flash point 150 F.), and the other various kerosenes and petroleum fractions available from other oil companies.

In the process of the present invention, the organic solvent solutions will preferably contain from about 0.005 up to about 75% by weight of the oxime compounds, which typically will be employed at about 10-15%. In the case of the beta- diketone compound, it may be used in an amount approaching 100% solids, but typically will be employed at about 20-30% by weight. Additionally, volume ratios of the organic:aqueous (0:A) phase will vary widely since the contacting of any quantity of the diketone organic solution with the copper containing aqueous leach solution will result in extraction of the copper values into the organic phase. For commercial practicality, however, the organic:aqueous phase ratios for extraction are preferably in the range of about 50:1 to 1:50. It is desirable to maintain an effective O to A ratio of about 1:1 in the mixer by recycle of one of the streams. In the stripping step, the organic:aqueous stripping medium phase ratio will preferably be in the range of about 1:2 to 20:1. For practical purposes, the extracting and stripping are normally conducted at ambient temperatures and pressures, although higher and/or lower temperatures and/or pressures are entirely operable. While the entire proces can be carried out as a batch operation, as described earlier, most advantageously the entire process is carried out continuously with the various solutions or streams being recycled to the various operations in the process for recovery of the copper, including the leaching, extraction and stripping steps.

As indicated, in the extraction process the extractant reagent should be soluble in the organic water-immiscible solvent. In general the diketone compounds, and other

SU BSTITUTE 5H EET extractants, described above will be soluble to such extent in the amounts described above. If necessary or desirable to promote desired properties of extraction, a solubility modifier may be employed. Such solubility modifiers, include long chain (6-30 carbon) aliphatic alcohols or esters, such as n-hexanol, n-2-ethylhexanol, isodecanol, dodecanol, tridecanol, hexadecanol, octadecanol, isohexadecanol, 2- (1,3,3-trimethyl butyl)-5,7,7-trimethyl octanol and 2,2,4- trimethyl-l,3-pentanediol mono- or di- isobutyrate; long chain alkyl phenols, such as heptylphenol, octylphenol,nonylphenol and dodecylphenol; and organo-phosphorus compounds, such as tri-lower alkyl (4-8 carbon) phosphates, especially tributyl phosphate and tri-(2-ethylhexyl) phosphate.

The invention may be illustrated by means of the following example in which all parts and percentages are by weight unless otherwise indicated. It is understood that the purpose of the example is entirely illustrative and is in no way intended to limit the scope of the invention.

Example

This example will serve to illustrate the utility and general operation of the present invention. For this purpose a sample of chalcocite concentrate, greater than 90% chalcocite, containing 29.83% copper was obtained from Mexicana de Cananea, in Cananea, Sonora, Mexico.

The dry concentrate (350 grams) was slurried in a baffled, one liter beaker with 525 milliliters (mis) of ammonia sulfate and ammonium hydroxide solution. The ammonium sulfate concentration was 150 grams/liter (g/1) as ammonium sulfate and the ammonium hydroxide concentration was 25 g/1 as ammonium hydroxide. The pH of the ammonium sulfate-ammoniu hydroxide mixture was 9.5. The slurry was agitated with a six vaned, single shrouded impeller to keep the solids suspended in the liquid phase for the duration of the leaching phase. Air was sparged through a glass frit to add some air to the

SUBSTITUTESHEET slurry and expedite the leaching of the copper. The test was conducted at ambient temperature, about 23 C. , and ambient pressure. Ammonium hydroxide was added as necessary to maintain a pH range of 9.3-9.8 for the duration of the leaching activity. The concentrate was leached in the described fashion for 90 minutes.

The unleached copper solids were filtered and washed with distilled water to recover essentially all of the dissolved copper. The filtrate was collected as pregnant leach solution with some wash water and a second volume that was essentially wash water with some contained copper in solution. The higher grade filtrate has a volume of 780 mis and contained 20.3 g/1. The weaker wash solution had a volume of 490 mis and contained 0.93 g/1 copper. The washed solids from the leaching stage were treated by flotation to produce a second copper concentrate. The solids were slurried with tap water and the pH was adjusted with calcium oxide to pH 10.5 prior to flotation. The float was conducted at about 11% solids and Aerofloat 208 Promoter (sodium diethyl and sodium di-secondary butyl dithiophosphate) was used at 0.15 pounds per ton as collector. Dowfroth 250 was used as a frother and the dosage was also 0.15 pounds per ton. Flotation time was 10 minutes and a new concentrate and tailings were produced. The concentrate (305.1 grams) contained 26.85% copper and the tailings (24.3 grams) contained 22.0% copper. The new concentrate is suitable for processing at a smelter.

The higher grade filtrate, which contained about 20 g/1 copper was used as the aqueous feed to solvent extraction. The organic extractant was l-phenyl-3-heptyl-l.3-propanedione

(LIX^R 54) , at 20 weight percent, diluted in Escaid 100, a high flash point kerosene.

The aqueous solution of cupric ammonium sulfate was adjusted to pH 9.5 and containing 20.1 g/1 copper. This solution was contacted with the mixed kerosene-diketone

SUBSTITUTE SHEET organic solution at an organic to aqueous ratio of 1:1 in a separatory funnel for 10 minutes. The volumes used were 500 mis of aqueous and 500 mis of organic. The solutions were allowed to separate and analyzed for copper. The copper loaded organic contained 15.0 g/1 and the aqueous or raffinate contained 5.1 g/1 copper The copper loaded organic phase was contacted with a synthetic spent electrolyte containing 30.3 g/1 copper and 170 g/1 sulfuric acid at an organic to aqueous ratio of 1:1 for 10 minutes. The phases were allowed to separate and then analyzed for copper. The stripped organic contained 0.08 g/1 copper and the rich electrolyte contained 44.8 g/1 copper. The stripped organic was then contacted with the aqueous raffinate (5.1 g/1 copper) from the first contact to extract additional copper. The second contact was also for 10 minutes and the two phases were analyzed after separation. The second loaded organic contained 5.02 g/1 copper and the final aqueous raffinate contained 0.35 g/1 copper. The copper may be removed from the rich electrolyte by electrowinning or copper sulfate crystallization.

T

Claims

What is claimed is:

1. A process for recovering copper from a chalcocite concentrate containing Cu₂S and CuS comprising

(A) contacting said chalcocite concentrate with an aqueous ammoniacal solution at a pH of about 8.5 up to about

11 to partially leach Cu from the chalcocite leaving a solid residue of CuS and providing a copper pregnant aqueous ammoniacal partial leach solution;

(B) separating said covellite solid residue from said copper pregnant ammoniacal partial leach solution;

(C) contacting said copper pregnant aqueous ammoniacal partial leach solution containing copper values with a water insoluble extractant selected from the group consisting of a beta-diketone, an oxime or mixtures thereof, dissolved in a water immiscible organic solvent to extract copper values from said aqueous ammoniacal partial leach solution into said organic solution thereby forming a copper pregnant organic phase and a copper barren aqueous phase;

(D) separating said aqueous phase and said organic phase; (E) contacting said copper pregnant organic phase with an aqueous acidic stripping solution whereby copper values are stripped from said organic phase into said aqueous acidic stripping solution;

(F) separating said aqueous acidic stripping solution from said organic phase; and

(G) recovering said copper values from said aqueous acidic stripping solution.

2. A process as defined in claim 1, wherein said extractant comprises a beta-diketone of the formula: 0 0

II II R - C - CH - C - R' I R" where R is phenyl or alkyl substituted phenyl, R¹ is alkyl, alkyl substituted phenyl or chloro substituted phenyl and R" is H or CN with the provisos that (1) when R is phenyl, R" is

SUBSTITUTESHEET a branched chain alkyl group of at least 7 carbon atoms and (2) when R is alkyl substituted phenyl, the number of carbon atoms is at least 7 and at least one such alkyl substituent is a branched chain.

3. A process as defined in claim 1, wherein said chalcocite concentrate consists essentially of about 75-85% Cu₂S and the remainder is substantially CuS and wherein said aqueous ammoniacal solution contacts said chalcocite concentrate so as to leach one Cu from the Cu₂S leaving a substantially CuS solid residue, without substantial leaching of S from said concentrate.

4. A process as defined in claim 3, wherein said aqueous ammoniacal solution comprises ammonia and ammonium sulfate solution.

5. A process as defined in claim 2, in which in said diketone R" is H, R¹ is a branched chain alkyl group having from about 7-17 carbon atoms and R is phenyl.

6. A process as defined in claim 5 wherein said diketone is 1- phenyl-3-heptyl-l,3-propanedione.

7. A process as defined in. claim 2, in which in said diketone R" is H, R¹ is an alkyl group containing less than 20 carbon atoms and R is an alkyl substituted phenyl group in which the alkyl group contains at least 7 carbon atoms and at least on of the alkyl groups in said diketone is branched.

8. A process as defined in claim 1, wherein after separation of the covellite solid residue from said copper pregnant aqueous ammoniacal leach solution in step (B) , said residue is washed with water and said wash solution after separation from said solid residue is added to said leach solution for contact with said organic solution in step (C) .

9. A process as defined in claim 1 wherein said aqueous acidic stripping solution in step (E) is a sulfuric acid solution containing about 60-180 g/1 sulfuric acid.

10. A process as defined in claim 1, wherein said copper pregnant aqueous ammoniacal leach solution from step (A)

SUBSTITUTESHEET contains about 15-100 g/1 copper before extraction of the copper values in step (C) and said aqueous acidic stripping solution after stripping of copper from said organic phase in step (E) contains about 50-60 g/1 copper.

11. A process as defined in claim 10, wherein said copper is recovered from said aqueous acidic stripping solution containing copper by electrowinning to provide cathode copper.

12. A process as defined in claim 10, wherein said copper is recovered from said aqueous acidic stripping solution containing copper by crystallizing said copper as copper sulfate crystals.

13. A process as defined in claim 1, wherein said water immiscible organic solvent is an aliphatic or aromatic hydrocarbon solvent having a flash point of at least 150 F.

14. A process as defined in claim 13, wherein said organic solvent is kerosene.

15. A process for recovering copper from a chalcocite concentrate comprised of about 75-90% Cu₂S and the remainder being substantially CuS, said process comprising (A) contacting said chalcocite concentrate with an aqueous ammoniacal solution comprised of ammonia and ammonium sulfate solution at a pH of about 8.5 up to about 11 to leach about 1 part of Cu from the Cu₂S providing a substantially CuS solid residue and a copper pregnant aqueous ammoniacal partial leach solution;

(B) separating said CuS solid residue from said copper pregnant aqueous ammoniacal partial leach solution;

(C) contacting said copper pregnant aqueous ammoniacal partial leach solution containing copper values with a water insoluble diketone extractant, alone, or dissolved in a water immiscible organic solvent to extract said copper values from said aqueous ammoniacal partial leach solution into said organic solution thereby forming a copper pregnant organic phase and a copper barren aqueous phase; (D) separating said aqueous phase and said organic phase;

SU_BSTITUTESHEET (E) contacting said copper pregnant organic phase with an aqueous acidic sulfuric acid stripping solution whereby copper values are stripped from said organic phase into said aqueous sulfuric acid stripping solution; (F) separating said aqueous sulfuric acid stripping solution from said organic phase; and

(G) recovering said copper values from said aqueous sulfuric acid stripping solution; wherein said extractant comprises a beta-diketone of the formula:

where R is phenyl or alkyl substituted phenyl, R¹ is alkyl, alkyl substituted phenyl or chloro substituted phenyl and R" is H or CN with the provisos that (1) when R is phenyl, R" is a branched chain alkyl group of at least 7 carbon atoms and (2) when R is alkyl substituted phenyl, the number of carbon atoms is at least 7 and at least one such alkyl substituent is a branched chain, and wherein said water immiscible organic solvent is an aliphatic or aromatic hydrocarbon having a flash point of at least 150 F.

16. A process as defined in claim 15, wherein said diketone is l-phenyl-3-heptyl-l,3-propanedione.

17. A process as defined in claim 16, wherein said organic solvent is kerosene.

18. A process as defined in claim 15, wherein said aqueous ammoniacal solution contains free ammonia, ammonium sulfate and ammonium hydroxide 19. A process as defined in claim 15, wherein said copper pregnant aqueous ammoniacal leach solution from step (A) contains about 15-100 g/1 copper before extraction of the copper values in step (C) and said aqueous acidic stripping solution after stripping of copper from said organic phase in step (E) contains about 50-60 g/1 copper.

S_UB_STITUTESHEET

20. A process as defined in claim 15 wherein said process is continuous and said copper barren aqueous phase from step (C) is recycled to the leaching step (A) , said organic phase from which copper has been stripped in step (E) is recycled to the extraction step (C) , and said aqueous acidic sulfuric acid stripping solution after recovery of copper therefrom in step (G) is recycled to the stripping step (E) .

21. A process for recovering copper from a chalcocite concentrate containing Cu₂S and CuS comprising (a) contacting said chalcocite concentrate with an aqueous ammoniacal solution at a pH of about 8.5 up to about 11 to partially leach Cu frOOom said Cu₂S leaving a solid residue of substantially CuS and providing a copper pregnant aqueous ammoniacal partial leach solution; (b) contacting said copper pregnant aqueous ammoniacal partial leach solution containing copper values with a water insoluble, high copper loading extractant to extract copper values from said aqueous ammoniacal partial leach solution; and (c) recovering said copper values.

22. A process as defined in claim 21 wherein said extractant is a beta-diketone.

SUB_STITUTESHEET