CA2115160A1 - Copper recovery process - Google Patents

Abstract

An improved method for the recovery of copper from a copper sulfide concentrate, chalcocite, comprising partially leaching the chalcocite concentrate with an aqueous ammoniacal solution, such as ammonia and ammonium sulfate, with no substantial leaching of sulfur or conversion to sulfate, and extracting the copper from the resulting aqueous ammoniacal partial leach solution with a water insoluble extractant, preferably a beta-diketone, having a high copper loading, low ammonia loading capacity, typically dissolved in a water immiscible organic solvent.

Description

WO 93~04208 2 ~ /us~2/~ 8 COPPER RECOVERY PROCESS

~=Y~

5 Field~of the~ Inventic)n:
This inv~ntion rel~es to a proc~ss for the recovery of copper from chalcocite corlce.ntrates by a proces~ of partial leaching t~f the cc: ncentrate and ex~raction of the r~sulting aqueous ammoniacal leach solution.
Statement s:~f Related Art:
Practice in the r~covery of copper from its sulfidic ores voIves subj~c:ting the ores to a fro~h flotation operation to ~: p~oduce a corc ntrate of the valuable metal sulfidQ~ and to 15 reject in the flotation tailing~ of valueless sul~ides, silicates, aluminat~s and the like. One of such concentrates ;provided is a chalcocite concentrate containing chalcocit~ and c~vellite.
In U~ S . Patent 4, 022, 866 to Kuhn and ~biter, and in 20: tlheir ~ubsequent paper, "Physical and Chemical Separations vi~
the Arbiter Proce~s" 11th International Mining Congr ~s, Aprilr 1975 Cagliari, Italy; Proc.-Int. Miner. Process.
~ongres~, Paper 30; pp~831-847; there is described the leac:hing of copper sulfide concentrates with am~nonia/ammonium sulfate and oxygen whereby the sulfide is converted to sulf~te, and the dissolved copper may then be recovered by ~3UB~;TITOTE ~;HEET

WO 93~04208 2 1 1 ~ ~ 6 0 P~r/llS92/064g~

solvent extraction. In the patent complete leaching of the copper from the o:re is preferred althollgh Fig. 3 alsc:
descxibes an embodiment in which a partial leaching is contemplated. The solvent extraction reagents are des::ribed in the patent only generally a5 those which preferentially lo~ad copper from alkaline solutions. In the paper, whic:h describes the operation of the Arbiter process, the focus is on complete (or nearly complete) leac:hing of the sulfidP corlc:erltrat s~ On page 834 a chalcocite concentrate is specifically discussed and diagraDed, with all the copper and associated ~;ulfur being dissolved.
In another Kuhn and Arbiter paper, "Anaconda ' s Arbiter Proc~ss ~Eor Copper"/ Hydrometa~lurgy, CII~ Bulletin, Feb. 1974, pp. 62-73, make5 reference to '~complete dis~olu~ion of c:opper~' and on page 65, refers to the known conversic:n of chalcocite to covellite I but points out that th ::halcclcite and covellite "are observed to be completely attaGked and dissolved in our leachin~ system within 1 to 1 1/2 hours~'.
U. S . Patent 4, 563, 256 des ::ribes a solv~nt extraction process for the recovery of zinc values from ammoniacal solutions, which ma~ al~o corltain c~pper values, employing various oximes as the extractants.
A paper by Anthony 0. Filmer et al, "Oxidation of Copper Sulfides in Aqueous Ammonia" part III, ~'Kinetlc ChararteristiCS", Austr. J. Chem~ 1979,32,pp. 2597-2609, gi~ves a de~ailed study of the ammoniacal oxidation of chalcocite, f irst to co~ellite, then to complete dissolution .
U. S Patent 2, 727, 818 descri}:Jes a method of leaching copper ~;ulf ide materials with ammoniacal leach sslutions, indicating that the first Cu from Cu2S (chalcocite~ dissolves without dissolutiorl of sulfur, and the Cu from CllS (covellite) dissolves only when its sulfur also dissolves. N~ solvent extras::tion is discussed.
U. S . Patents 4, 065, 502 and 4 ,175, 012 describes beta-diketones which may be employed as metal extrac:tants in a ~3U~3STITUTE ~iHEET

WO ~3/0'120~ PCr/US92/06~08 lic~uid i~n exchange process for recovery of metals, such as ni~kel or copper, from aqueous solutions containing the metal values, including aqueous ammoniac:al ~olutions.
DESCRIPTION OF THE_DRAWING
Figure 1 is a diagrammatic f low chart illustrating a partial leaching of a copper c:oncentrate and a liquid-liquid extractiorl of the coppQr vallles ~rom the resulting leach solution, followed by recovery of the copper, either in the f orm of copper sulf ate crystals or as athode copper by elec:trowinning.
DESCRIPTlON OF_T~ INVENTT~N
In thi~ descriptiorl; except in the operating examples or where explicitly other-wise indicated, all number~; describ~ ng ..... amounts of ingredients or reaction condiltic3ns are to be under~tos~d as modif ied by the word "about'l .
It has now b2en disc:c)v~red that t~e combination of a partial laaching of chalcocite and the use of a high copper-transfer/ low ammonia-loading extraction reagent provides a very e~ficient process o~ recovery of copper. Because of the partial leaching, up to 50% leach, there is no conversion of the sulur from sulfide to sulfate, which results when complete dissolution of th concentrate is carried out. With the conversion t~ sulfate, as practiced in the Arbiter process~ much of the ammonia is tied up as ammonium sulfate.
: 25 In order to liberate the a~monia, the sulfate must be treated in an energy int~nsive proces~. In the present invention a~monia recov~ry i~ simplifi~d as, in the solvent extraction u ing the reagents employed in the pre~ent nvention, ammonia is automatically regenerated during extraction and is simply recycled back via the raffinate for further leaching. Since the sulfur is not convexted to sulfate in the partial leaching of the present inv~ntion, the sul~ur, which remains in the leach residue, is concentrated by flotation and is removed to a smelting process as ~hown in Figure 1, where sulfuric acid may con~eniently and efficiently be produced.

~;IVBSTITUTE SHEET

2 1 1 5 1 6 0 PCll~lS92/064~8 In the copper recovery process of the present invention, a chalcocite concentrate is subjected to a par~ial leaching with ammonia and ammonium sulfate solution. ~hile ammoniu~n sulfate is preferred in order to mainkairl the sulfate matrix 5 throughout the system and ensure consistent quality of product, other ammonium cs~mpounds, such as the carbonate, nitrate and chloride may be employed; however, these may re~uire specialized eqlaipment or additional proc:essing stages.
Ch2l1cocite cs:nc~ntrate is ltypically compo~ed of about 75-90%
10 chalcocite (Cu2S~, though some may contsin in excess of 90% , wi~h the rem~inder bQing substalttially s: ovellite (CuS), with trace a~aounts of chalcopyrite ~CuFeS2~ or other form~ o~
copper .
~ s shown in the Figure, the chalcoeite concentrate is 15 contacted with ammonium sulfate solution and free ammonia, prei~erably in the for~a of am~aonium hydroxide, with agitation to ~o~m a slurry which may r~nge frc~m about 10% to about 7596 ~;olids, typically about 30-60%, with 35-50% bein~ preferred.
The higher the percent solids. attained j the smaller the size 20 o~ the leac:hing vessel whis::h is require:31 and the higher the c:oncentration of the copper contained in the aqueous phase.
The lea ::hing is conducted at a pH in the range of abc3u~ 8 . 5 to 11 to produce cupric: anunonium sulfate and is conducted at ambient temperature and pres~;ure, until the remaining copper 25 is present as covellite (CuS). Thus the chalc~cite (Cu2S) is leached so as to rem~ve suffic:ient copper (half of the Cu2) to leave a residue comprised substantially of CuS ( covellite) ..
While one of the advantages of the pr~sent ir veT~tion lies ~n the use of ambient temperature and pressure and does not 3 0 require elevated tempsratures or pre~;sur~s, elevated temperature and pressure may be employed, if desired, or where specialized ambient conditiorls exist, s~ch as extreme c:old conditions. Since the sulfur is not being converted to sulfatg, no oxygen is required, however, air may be sparged 35 into the leach ve5sel which tends to expedite the dissolution SUBSTITUTE~ 5HEET

WC) 93/lD4~08 P~/US9~/064~g 2 ) ~

of the chalcocite in the presence of free ~mmonia and the conversion of Cu+ ion to Cu~+ ion to provide the cupric ammonium sulfate. Leach rekention time is deperldent on the desired percentage of copper to be solubilized, however, 5 typically 30 to 90 minutes is generally sufficient to solubilize 20-35% of the total copper c::ontained in the form of chalcocite, using an air sparge at typical ar~ient temperatures and pre~;sures, i~e. 20-23 degrees t:~ntigrade and atmospheric pressure.
In the leaching step of the present invenl;ion the leachirls~ should not substarltially exceed the conversion DiE the chalr::ocite to covellit~, e. g. r~moval of c~ne part of copper ~rom c:halcocite compound which contains 2 parts of copper. If ~ the resulting covellite is leached in the present process, 15 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 i:ncrease in sulf ate, it is then required to incorporate a sulf ate bleed stream and a sub~e~uerlt make-up of ammoni.a 105t in the f orm of amms: nium 20 ~ulfate. Desirably the only :Losses of ammonia in the process of the presellt invention will be only a small amourlt contained in the solids which is lost n the solid/liquid ~eparation step shown in the f low diagram of Figure 1.
The leaching is pref erably conducted in a continuous 25 fashion with the original conc:entrate entering the first stage of l each and mixing with the raf f irlate from the subsequent extraction step. Anhydrous ammonia or ammonium hydroxide i~
added as needed to maint~in a leach pH betwean about 8 . 5~11.
Ammonium sulfate ~hould be maintained at a level c: f at least 30 khe stoichiometric quantity rç~uired to solubilize the desired amount of copper contained in the concentrate. Preferably the ~mmonium sulfate is maintained at a level slightly ill excess of the stoichiometric amount, typically at about 10-20~6 excess, and pref erably at about 15~ excess . This amount of 3 5 excess will ensure the amount of copper desired to be SUI~STllrlJTE~ 5HEI~

WO 93/1~4~08 ~ 1 1 5 ~ ) P~/U~92/06408 solubilized (one Cu from the Cu2S), without any substantial solubilization Cf CU from the c:ovellite and without any substan~ial conversion of sulfidic sulfur to sulfate.
~s shown in Figure 1, a~ter the leac::hing, t:he leach slurry is di~charged from the leaching ve~sel and a li~uid/~;olid separation is performed, whic:h may be simple dec:antation or a filtration step. The solids are preferably wash~d with water, and/or ammonia water solu1:ion, free of copper tc) remove any cc:pper in solution entrained in the ~0 solids. As further shown in Figur~ 1, the washe~ and filtered solids may be subj0cted to flotation, to produc~ a new copper concentrate, c:omposed primarily of covellite, CuS. The new covellite sulfide concentrate will contain a higher fuel value f or s~absequent pyrometallllrgical treatment than the original 1~ chalcocite concentrate in regard to the copper~sulfur ratio ~herein. Any preciolls metals ~uch as silver or goldr or other sulfide minerals, suc:h as molybdenite, which were initially present will also be found in the new ~lotatic)n concentra~e from whish they may be ~Eurther processed and rec:overed.
The copper pregnant l~ach ~olution, along with the washing solutions from washing of the solids a~; described ab~ve, will then be sent to the extraction stage of the process, preferably after clarification to remove any fine soll ds which may be present from the previous step . Such clarif ication is preferably carried ou~ by f iltration . In the extraction stage, the pr~gnant copper leach solution whis::h now will c:ontain from about 15 100 grams per liter (g/l) copper, typically about 3 0~4 0 g/ 1, at abs:~ut pH 9 to 10 is contacted with a water-immiscible, organic solvent solution of an extractant compound havin~ a high copper loading, low ammonia loading, capac:ity so as to result in a tran~f er of the copper to the organic solvent solution whi~h f orms an organic phase substantially immisc:ible with the as~U80us copper pregnant leach solution.
In Figure 1, the extractiorl stage is shown as a single SUBSTlTlJTI~ SHE~ET

WO 93/042~ 2 1 1 5 1 6 ~lPcr/US92/0640~

block. In practice, the extractiorl 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 continuous~y feed~; a large 5 ~ettling ~ank where the organic ~;olvent (orga:n ic pha~;e~, now c:ontaining the copper extract~nt complex in solution is separated from the depleted a~ueous ~olution (a~ueous pha~
This part of the process is ref erred to as the phase separation. Usualïy the extra::tion proGess is repeated thrc:uqh 10 two or more mixer~;ettler UllitS ~ n order to more completely extract the copper. Where two mixer ~ettler units are employed, the copper pregnant leach solution will be introduced to the f irst mixer-settler u~it extraction ~;tage r~ (often de~ignated E-1) where it is contacked with the organic:
15 phase exiting from th~ sec:on~ mixer-settler extraction stage toften designat~d E-2), thereby invvlving a count~rcurrent f low of the orgarlic phase and the aqueous copper solution phase. The aqueous ph~se ~rom the first extraction unit (E-l) is introduced into th~ ~econd mixer~settler ex~raction unit 20 (~ 2), which contact the incomin~ organic phase) recycl~d from the stripping stage of the proces~. The coppar loaded organic phase exits E-1 and iB introduced to a washing ~tep prior to stripping of the copper from the organic phase. ~he aqueous raffinate (a~nonia and ammc:nium sulfate soIution) from the 25 extraction (unit E:~ 2~, now sub~tantially barr~n of copper, typically containing less than 1 g/l (and preferably about 0.1 g/l) is re~ycled to the leach step and solids wash steps earlier described.
The wa~hing st~p may consist of only one stage or, as in 30 the s:ase of the extraction step, may consist of more than one.
The purpose of the wa~hing step is primarily to remove any entrained, or chemically loaded, ammorlia solution which ~nay have been loa~ed into the or~anic phase along with lthe copper~
If signif icantly low ammonia loading extractant compounds are 35 employ~d, so that no significant amolmts of ammonia are loaded SUI~STITUTE~ ~;HEl~

WO 93~)4~8 PCr/~JS9~/06408 2~5~ 8 into the organic phase, the washing ~;tep may be oraitted and is thus an optional step . It is hs:~waver pref erred that at least one water wa~hing step, pH ~ontrolle~l at a pH of 6-7 with a suitable pH adjusting acid, be employed to conserve ammonia and to minimize contamination of :~;tripping agent employed in the next step of the process~ If washing is employed after separatie:n of the aqueous washing pha~e from the organic phase, the resulting aqueous solutil~n from the washing is returned to the leaching stepr while the c:opper loaded organic phase is then contacted with a stripping agent to form the stripping stage of the process, Pagain the stripping step may be carried out in a singl~ ;tage or, as in the c:ase of the extractiorl step, may typically be carried out count~rcurrently in more s~ages or UllitS, i~e~ in two stages.
As in the extraction step lthe stripping, if carried out in two units, has the loaded organic phase introdu ed int~ the f irst strippin~ unit ( S-l ~, where it COl~lt2C:tS the strippillg agent ~pra~erably sulfuric acid) exiting from the seGorld s~ripping unit ( S-2 ~, again a countercurrent processing r Sulfuric acid solution corlt~ining about 60 180 g/l sulfuric ~cid is the preferred stripping agent, as it permits ~he subsequent recovery of the copper either in the form of copper ~ulfate crystal~ or by electrowinning to c:athode c:opper. Other inorganic min~ral acids may be employed as skripping agents, such as hydrochloric acid or nitric acid, however s~ch may require other recovery methods or specialized handling equipment. The ~tripped organic, now substantially barren of the copper and typically containing less th~n 1 g/ l copper will exit unit S-2 and be introduced to the ~mit E-2 of the extractic~n ~tep. The copper in the acidic ~tripping solution, now c:ontainiIlg the copper in a concentrated amount ~ about 50-60 g/ 1, and typically about 50 g/ 1, is then rec:overed in conventiorlal manner either by crystallization or electrowinning, as shown in Figure 1. In elec:trowinning, the 3 5 pref erred recovery method, cathode c:opper is recovered as ~E3UE~SlRlTUTE SHEET
_. .. . ... .

WO 93/04208 2 1 1 ~ ) Pcr/~S92/064~8 electrolytic: copper at a 99 . 99%+ copper. The spent electrolyte, after deposition of the cathode c:opper, is then returned to stripping unit S-2. As this is being recycled irato the proc:ess, the amount of copper lpresent in the spent electrolyte may be relatively high, thou~h lower than the 50 g/l in the ~;olution from the strippi3~g step, and tyE~ically may contain from about 20-30 g/l c~pperO If recovery is by c:rystallization, the c:opper is rec:overed in thP form of copper sulfate crystal~;, which will typic:ally require the introduction of ~ome water to lprovide the water o~ hydration for copper sulfate crystals. The spent solutiorl from the cryE;tallization, aqueous sulfuric acid, will be recycled t~
the stripping ~;tep, into unit S-2.
As indicated earlier, the copper pregnant leach solution from which the copper is to be recovered by extraction will c:ontai3l about 15-100 g/l copp~,r, and typically about 30-40 g/l copper at pH about 8.5-11. The extraction compounds for u~;e in the prac:~ice of this imrention on these leach solutions, are those which will load, i . e ,. at least about 15 g/ l, or extract, ~opper to a high degree, from high ammonia concenltration solutions preferably without significant loading of ammonia. Such compounds, which are preferr~d for use as an extractant reagent in the present invention because of their low ammonia loading prop~rties, 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 ~or use in the pr~ent inventivn is l~phenyl-3-heptyl~ 1,3~propanedione, a~railable commercially from Henkel Corporatioll as LIXR 54~ Other beta-diketone compounds which may be employed are defined by the following ~ormula:
O O
R ~ CH - C - R~
R"
whe:re R is phenyl or alkyl substituted phenyl, R ' is alkyl, alkyl substituted phenyl vr chloro substituted phenyl and R"

'~3~

WO 93/0~208 PCY'/VS92/064~8 21~160 lO
is H or CN with the provisos that ( 1 ) when R is phenyl, R ' is a br~nched 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 5 least one such alJcyl substituent is a branched chain. R is desirably monoalkyl substitut:ed and preferably contains 9 or more c:arbon atoms . The various alkyl groups are pref erably free from substitution and contain less than 20 carbon altc)ms.
Further when R ' is alkyl, the carbon alpha to the carbonyl 10 group is de~;irab~y not tertiaxy,. Preferably, R" is H, R' is a branched 7, 8, . 9, 12, or 17 ~arbon ::hain or a c~lorophenyl or short chain ( 1-5 carbon) a7 kyl substitu~ed phe~l and R is phenyl or a 7, 8, 9, or 12 carbon alkyl substituted phenyl ~ yroup.
While the beta diketorle compounds are preferred for use in th~ present inverltion as the water insoluble extra6 tant compound~; b~cause of their :lo~ ammonia loading properties, uther water in~oluble copper loading extractants capable of loading copper from aqueou!; aramoniacal solutions may be 20 employed. ~ith such other reagents it may ~ however, be nece~sary to include additional trea~ment of the organic phase because of ammonia loadin~f, before stripping and rec::ycling of materials in the continuous process. Other high copper loading extractants, which may be desirably employed, either alone or 25 in admixture, are certain oximes, of those ~escribed in U~ S .
Patent 4,563,256, Oximes which may be employed in the pre~ent invention are those generally conforming to the formula:

OH NOH
3~
~ ~ C --R2 Rla SU13STITUTE SHEE~

W093/04208 2 1 1 5 1 ~ ~J P~T/US~2~0~0~

where Rl 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, l, 2, 3 or ~ and R2 is H or a saturat~d or ethylenically - unsaturated group as defined above, with the proviso that the total number of carbon atoms in Rl and R2 i~ from 3-25, or phenyl or R4 substituted phenyl where R4 is a saturated or ethylenlcally unsaturated group a5 defined above which may be the same or different from Rl. Illustrative of some of the oxime compounds are 5-heptyl ~alicylaldoxime, 5-octyl salicylaldoxime, 5-nonyl salicylaldoxime, 5-dodecyl salicylaldoxime,5-nonyl-~-hydroxyacetophenoneoxime,5-nonyl~
~ hydroxyacetophenone oxime, 2-hydroxy-5-nonyl ~enzophenone oxime and 2-hydroxy-5-dodecyl benzophenone oxime. ~hile it is preferred that a single ~xtractant compound be employed, mixture~ of extra~tants may be employed to meet particular system r~quirement~.
A wide variety of essentially water~immiscible liquid hydr~carbon solvents can be used in the copper recovsry process of the present invent.ion. These include aliphatic an~
aromatic hydrocarbons such as kerosenes, benzene, toluene~
xylen~ and the like. A ch~ice of essentially water-immiscible liquid hydrocarbon solvents, or mixtures thereof for commercial operations will depend on a numb~r of factors, including the plan~ design of the solvent extraction plant ~mixer-~ettler unitsr Podbielnak extractor~) and the like. The pre~erred ~olvents for use in the recovery process of the present invention, are the allphatic and aromatic hydrocarbons having flash points of 130 degre~s Fahrenheit and higher~ and preferably at least ~50 , 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 '~u~ H~n WO 93/0~120X PCI/US92/0640~s i 1 6 ~ 12 (available from Exxon-Europe having a flash point of 180 F. ~, Norpar 12 (available from Exxon-USA, iElash point 160 F. ), Conoco-C1214 (available from Corloco, flash point 160 F. ), Aromatic: 150 (an aromatic kerosene available from Exxon~USA~
5 flash point 150 F. ), and the o~her various kerosenes and petroleum fractions availi~ble from other oil companies.
In the process of the present inverlt ion, the organic solvent solutions will preferably contain from about 0.005 up to about 75% by wei~ht of the oxime compounds, which typically will be employed at abc3ut 10-15~. In the ca~;e of the beta-diketone compound, it may be used in an amount approaching 100% solid~, but typic:ally will be employed at about 20-30g6 by weight. Additionally, volume ratios of the organic: aqueous (V:A) phase Will vary widely ~:ince the cont~cting of any 15 quantity of the diketone organic solution with the c:opper containing aqueous leach solution will r~sult in e~traction of the copper values into the organic phas~. For commercial practi::ality, however, the organic:a~uaous pha~;e ratios for extraction are preferably in ll:he range of about 50 :1 to 1: 50 .
20 It is desirable to maintain an effec:tive O ~o A ratit~ 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 wi.ll preferably be in the range of about 1:2 to 20:1.
For practical purposes, the extractirlg and skripping axe 25 normally conducted at ambient temperatures and pressures, although higher and/or lower temperakures 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 contintlc)usly 3 0 with the various solutions or streams being recycled to the ~arious operations in the process for recovery of the copp!r, includiny the leaching, extraction and stripping steps.
As indicated, in the extract ion process the extr~ctant reagent should be soluble in the organic water-immiscible 35 solvent. In general the dilcetone compounds, and other ~UB~;TITUTE ~HEE~T

W093/0420X 2 1 l r~ PcT/us92/o~

extractants, described aboYe will be svluble 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-ethylhexa~ol, isodecanol, dodecanol, tridecanol, hexadecanol, octadecanol, is~hexad~canol, 2 (1,3,3-trimethyl butyl3-5,7,7-trimethyl octanol and 2,2,4-trimethyl-1,3-pentanediol mono- or di- isobutyrate; long chain alkyl phenols, such as heptylphenol, octylphenol~nonylphenol and dodecylphenol î and organo-pho~phorus compounds, such as tri-lower alkyl (4-8 carbon) pho~phates, especially tributyl phosphate and ~ri-(2-ethylhexyl) phosphate.
~ The invention may be illustrated by means of the following example in which all parts and percentages are ~y weight unless otherwise indicated. It i5 understood that the purpose of the ~xample is entirely illustrative and is in no way int~nded to limit the scope of the inventiQn.

Exlample This example will serve to illu~trate the utility and general operation of the present invention. For this purpose a sample of chalcocite conc~ntrate, greater than 90% chalcocite, containing 29.~3% copper was obtained from Mexicana de Cananea, in Cananea, Son~ra, Mexico.
The dry concentrate (350 grams) was slurried in a baffled, one liter beaker with 525 milliliter~ (mls) of ammonia sulfate and ammonium hydroxide solution. The ammonium ~ulfate concentration was 150 grams/liter (g/l) as ammonium sulfate and the ammonium hydroxide concentration was 25 g/l ~s ammonium hydroxide. The pH of the ammonium sulfat*-ammonium 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 glas5 frit to add some air to the SUB5TITLITE~ 5HEIET

WO93/(1420X PCT/US9~/0~08 21151G~J

slurry and expedite the leaching of the copper. The test was conducted at ambient tPmperature, about 23 c., and ambient pressure. ~mmonium hydroxide was added as necessary to maintain a pH range of 9.3-9.8 for the duration of the leaching activity. Th~ concentrate was leached in the described fashion for 90 minutes.
The unleached copper solids were filtered and washed with distilled water to ~ecover 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 ml5 and contained 20.3 g/l.
The weaker wash solution had a volume of 490 mls and contain2d . 0.93 g/l copper.
The wa~hed solids from the leaching 5tage were treated by flotation t~ produce a second copper concentrate. The solids were slurried with tap wate:r and the pH was adju~ted with cal ium oxide to pH 10.5 pr:ior to flotation. The float was conducted at about 11% sol:ids and Aerofloat 208 Promoter (sodium diethyl and sodium di-secondary butyl dithiophosphate) was used at 0.15 pounds per ton as collector. DQwfroth 250 was used a~ a frother and the dosage was also Onl5 pounds per ton.
Flotation time was 10 minutes and a new concentrate and tailings were produced. The concentrate ~305.1 grams) contained 26~85% coppQr and the tailings (24.3 ~rams) contained 22.0% copper. The new con~entrate is suitable for processing at a smelter~
The higher grade filtrate, which contained about 20 g/l copper was used as the aqueous feed to solvent extraction. The organiG extractant was 1-phenyl-3-heptyl-1.3-propanedione (LIXR 54) t a~ 20 weight percent, diluted in Escaid 100, a high flash point keros2ne.
The aqueous solution of cupric ammonium sulfate was adjusted to pH 9O5 and containing 20.1 g/l copper. This solution was contacted wi~h the mixed kero~ene-diketone 5U E~STITUTE~ lEET

WO 93/0~208 2 1 l C) 1 6 !) PCI/US92/06~OX

organic solution ~t an organic to aqueous ratio o~ 1 in a separatory funnel fc)r 10 minutes. The volumes used were 500 mls of aqueous and 500 mls of organic. The solutions were allowed to separate and analyzed for copper. The copper loaded 5 organic contained 15. 0 g/l and the aqueous or raffinate contained 5 .1 g/ 1 copper The copper loaded organic phase was c:ontacted with a synthel:ic spent electrolyte con~aining 30. 3 g/ 1 c:opper and 17 0 g/ 1 sul~uric acid at an organic to aqueous ratio o~ 1:1 for lO minutes. The phases were allowed ~o 10 separa~e and then analyzed for copper. The stripped organic contained 0. 08 ~/l copper and the rich electrolyte contained 44.8 g/l copper. The stripped organic was then contac:ted with the a~ueo~s raffinate (5.1 g/l c:opper) from the first contact ~ to extract additional copper. The secorld contact was also f~sr 15 10 minutes and the two lphases were analyzed a~ter separation.
The second loaded organic contained 5. û2 g~l copper and the finaI aqueous raffinate cc)ntained 0.35 g/l copper,. The copper may be remoYed from the rich electrolyte by electrowinning or ~opper ~;ulf ate crystalliæatio;n .

S`UE3 5TlT.l~TE ~E~ET

Claims (22)

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:

where R is phenyl or alkyl substituted phenyl, R' 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.

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, R' 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-1,3-propanedione.

7. A process as defined in claim 2, in which in said diketone R" is H, R' 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 a 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/l sulfuric acid.

10. A process as defined in claim 1, wherein said copper pregnant aqueous ammoniacal leach solution from step (A) contains about 15-100 g/l 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/l 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, along, 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;

(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, R' 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 haying a flash point of at least 150 F.

16. A process as defined in claim 15, wherein said diketone is 1-phenyl-3-heptyl-1,3-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/l 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/l copper.

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 fr00om 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 value 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.