IE37279L - Extraction of copper from metallic materials - Google Patents

Abstract

1399281 Extraction of copper ISC SMELTING Ltd 6 Feb 1973 [21 Feb 1972] 7945/72 Heading C1A [Also in Division C7] Copper values are leached from copper dross separated from lead bullion produced in the blast furnace smelting of lead or zinc lead by contacting particles of the dross in the form of a metallic lead matrix containing copper and copper compound inclusions with an aqueous solution of ammonium carbonate and ammonium hydroxide to dissolve copper from the dross. The leaching may be effected in the presence of the oxidizing gas or the leachate may be subsequently treated with an oxidizing gas. The ammoniacal solution is preferably a solution of (NH 4 ) 2 CO 3 and NH 4 OA and may contain SO 4 - preferably with a mole ratio CO 3 : SO 4 of 1 : 3. The leaching may be carried out in any conventional manner. The copper may be recovered from the leachate by contact with a copper-selective organic phase, e.g. one containing a hydroxy oxime, from which it may be extracted with an aqueous mineral acid (preferably H 2 SO 4 ). This aqueous phase may be evaporated to recover a copper salt or it may be electrolysed to recover copper. [GB1399281A]

Description

*■ 1727S Biii imatioa rtlitea to tte sxtnotioo of copper fro* eoppav-oeatal&lqg metallic materials produced in the pcffiipi itilliggtoil neltiag efiae/letf or lead, sod »ere particularly to the extraction of copper from copper drott s separated from teed bull Ion profeud 1a tne blest furnace smelting of a lead oxide aeterlal.

Tfce Melting of ozldlo aaterialr.containing sine, lead and other metal values with a carbonaceous fuel in a blast furnace la veil known. The netal-containing materials 10 are first agglomerated, and If necessary roasted, in a sintering prooesa an! then charged to the blast furnaco witb a carbonaceous solid such aa coke.

Zinc vapour la condensed out of the hot gases leaving the top of the blast furnace. From the furnace is bottoa are tapped gangue in the form of a aolten slag containing oxides and allioetea of Iron and calciua as major coaponants and, as a separate phase, aolten lead bullion. Shis lead bullion carries with It a variety of metala such as sine, copper, silver, arsenic, antinony 20 and others. Where copper is present in the furnace charge it will always ha present in the lead bullion, usually in amounts of less than 5JS by weight but possibly in omouata up to 152 by weight.

Subsequently, and preferably Immediately after a tapping the bullion from the furnaco, the hot bullion is cooled in a controlled manner thereby cauqiog solid particles of compounds of copper with sulphur, arsenic and other elements and of metallic copper to rise to the surface of the bullion. These solids may be skimmed off an copper - 2 - 372?y dro*i and sethods are known for droasing in such u May that on.V/ very snail residual amounts of copper remain in the Bo]tei lead. In reaoving tha copper dross from the surface of the aolten lead soae aolten de-copperl»ed lead and 5 lead oxide are reaored, together with aoae copper oxide. Copper dross aay contain as little as 10? by weight of copper and over 80J5 by weight of lead, but with care a drooc can be obtained which contains about 35ft by weight of copper and only <>yf. b7 weight of lead. 10 Methods of working up this copper droso arc already known. For example the dross can be smelted with iron and sulphur, for example in the forn of pyrites, to form bullion containing some copper and an iron-copper matto containing aoae lead. This aatte is then converted, the blister copper 15 oast into anodes, and the anodes refined electrolytically, as in conventional copper refining practice. However, the setting up of a plant to operate such a process is scarcely economically practicable in the context of a slnc/lcad blast furnace since the amounts of copper arising in such a process are relatively 20 small.

The copper in coppor dross appears to be elemental cr combined copper, for exaaple as copper sulphides or arsenides, embedded in a matrix of de-copperised metallic lead and it has previously been believed that it would be difficult to extract 25 this copper using conventional extraction agents.

In British Patent Specification No. 1,J03,C?0 there is described a process in which copper drosa is leached - 3 - 3 7 2 7 9 with dilute aqueous sulphuric acid in the preaeno of a gau containing True oxygen to produce soluble copper salts. present The /invention consists In s method of leaching copper ▼slues fro* copper dross separated frca lead bunion produced In the saeltlng qC4 Jess oxide material, ■y blast furnsce /comprising contacting finely-divided particles of the copper dross In the forw of a Metallic lead aatrlx canuining copper and copper compound Inclusions *1th an aqueous aseonlacal solution of aoBonium carbonate and aanonliw hydroxide to dissolve copper from th..- dross. fh» leaching is preferably carried out in tho proi.osce 10 of an oxidising gas, for exaaple air or oxygen. Alternatively, the leachate solution la subsequently treated with an oxidising gas to oxidise cuprous to cuprlc ions.

Since an aaaoziiacal solution is used to leach copper dror.s by the oethod according to the preceding paragraph less 15 iopurities are extracted into the copper-rich solution than when an acid leach is used. In particular, less iron, arsonic, and antiaony are taken up by such alkaline) leaching than with acid leaching. As a result, less difficulty is encountered in purification of the solution obtained by leaching since w organic solvents are known which will selectively extract copper froo ssBOniscal solutions in preference to other elecents such as iron, sino sud arsenic.

Preferably /the leaching solution say be produced by carbonating ammoniacal liquor with carbon dioxide, for exaaple from a 5 smelting furnace.

Preferably the leaching solution contains sulphate ions in addition to carbonate ions. The mole ratio of carbonate tc sulphate in the leaching solution 1s preferably fron - 4 - J7 279 1:3 to 3:1. Tho presence of the sulphate ions in the leaching solution io bolieved to give rise to the following advantages> (a) A reduction in the ratio of impurity eleaenta, particularly lead and sine, to copper in the leacbato aolution. (b) A reduction in the amount of copper lout in the filter cuke after filtration of the residue. (c) A lower partial pressure of aaaonia over the leaching aolution.

The l^acbate solution fron the leaching process, after filtration,ia preferably contacted with an organic solvent which ia a specific extract ant for copper to talce copper into the organic phase and frco which copper can be subsequently extracted back into an aquaous solution by contact with an aqueous ainernl acid, for exasple dilute sulphuric acid or hydrochloric acid. Suitable organic extrsctants are that sold by General Mills Inc. under the trede-nase "LIX 645"/an Tho aqueous copper sulphate aolution produced by contacting the organic solvent with dilute sulphuric acid aay be utillted either in the production of copper sulphate crystals by on evaporation/crystallisation procosa op as an electrolyte for the production of cathode copper by electrowinning. In general, copper sulphata produced by this process is comparable in purity with copper sulphate frca other sources. The leachate solution aay alternatively be either boiled, to precipitate a basic copper carbonate or sulphate, or treated with a r9ducing agent to obtain metallic copper, Tor exaaple in powder form. - 5 - 37 '* t J The usociacal Is aching solution ie suitably •alntained at a t«»perature between 20° and 100°0.

Preferably i'she pH value of the leaching solution la at least 9.0, aore pr»foratly fro® 9*5 to 10. 5* 5 Advantageously the copper dross is vigorously agitated during tba laaching process, preferably la contact with an oxygen-containing gaa. The leaching solution may be circulatcd to keep the dross in suspension.

Preferably the droas is sised to -1/6 incn 10 particles before leochirg.

The leaching aolution aay suitably contain at l«aat 15 g/1 of asjionia (expressed as HB^). Preferably the leaching solution contains at least 5 grams of Cu** per litre, since it has been found that the reaction proceeds 2^ more rapidly in the presence of cupric ion.

The procoaa aay be carried out nnder a range of conditions. When parrying out the process ii; is essential to ensure good liquid/solid oontact when dissolving the copper froa the drosa, and good contact with the liquid of the 2Q oxygen-containing gas in ordex* to obtain the fasteat rates of solution of the copper in the leaching solution. Methods for achieving this are wall known; for exaaple, efficient ng in a tank by neans of a high speed turbid*, tuabling in a rotating vessel, fluidisatioc or slurry 25 circulation are suitable methods, whether batchwiae or continuous. Alternatively, percolation leaching say be eoployed in which the liquid is allowed to flow through a heap or bed of the granular dross. In this case it is particularly preferred that the liquid contains sose pre- - G - 173 70 formed cupric asminc to diesolve the metallic copper ainc* little oxidation is possible in the bed, and that tbe resultant cuprous f*?*i" 6a oxidised separately, partly for recycling and partly for clarification and extraction. 5 lae ammonia, carbonate and sulphate concentration are not critical. At tbe lower concentrotions tbe 11sito are primarily economic in that excessively dilute solutions require proportionately large tankage and pumping energj consumption. At tba upper concentrations tbe limits are set by knows 10 solubility and stability considerations.

The proportions of amacnia to amconiua calt arc not critical. The actual copper dissolved is frequently in excosa cf atoichioaetric for the complex carbonate Cu(KHj)^COj, for exaaple fron about 1.? gA Cu to lH(NH^)pCO^, 2K TfE^ and is 15 linitad by ammonia plus ammonium ions in solution rather than by tha cation. Lower proportions of aaaorxia tend to permit basic carbonate to be precipitated while higher proportions give solutions of unnecessarily high ammonia partial pressures and lead to troubleaone loss of ammonia by entrainment in spent oxidising 20 gas. Higher proportions of ammonia also load tbe extractant, reducing copper transfer, and hinder clean and easy disengagement of tha axtractant.

The preferred molar proportions of ammonia to ammonium salt are 0.5 to 4.0 : l.OCNH^JpX, where 2 is carbonate and/or 25 sulphate, but ratios of about 0.1 to 10:1 may be used. The total free and combined ammonia should amoupt to about 5*0 to 4.0 H: IgA Cu to be dissolved, plus suitable allowance for vaporisation and loss. The preferred copper concentration in leach liquor is 20 to 100 gpl with appropriate acconia and 30 ammonium salt in proportion, but - 7 - 37279 efficient operation of tbe process is possibio at about 1 to 200 StA coppor.

The initial leeching solution aay be copper fro a provided that enough oxygen is present to allow ths dealred copper dissolution, hot it is preferred tc have an appreciable aaouat of cupric n* in solution which can then quickly dissolve aetallic copper. in nr.cor'Innoe with the reaction Cu(NHj)4^(aq) ♦ Cu(A) > Cu2(' It should be noted that one gram atom of cupric ion as oassine yields two gran atoss of cuprous ion as aamine after reaction without ths need for oxidation in the actual leaching reactor, so that it ia desirable to feed a raffinato solution containing 50?» of tbe required copper concentration to the leaching reactor, vhioh will yield a leach liquor containing the required concentration as cuprous aaaine, given enough copper and adequate reaction conditions in the reaotor. This solution can then be oxidised separately, thus allowing design freedoo in plant construction and operation. The temperature of reaction is conveniently at or near 20°C, but nay be from 0° to 1C0°C, given adequate plant design and operation. The range 20° to 50°C is preferred.

Recovery of the copper is preferably carried out by a solvent extroction process, particularly by contact with a - 8 - J7279 solution in kerosene of a hydroxy oxima ouch aa Lix Li* €A or Lix 64K, which are proprietary materials nanufactured and sold by General Mills Inc., or with the oxtrnctant described by Van der Zeeuw in Dutch Patent Application ITo. 71-06C5O. extrnct.-.nt io diluted with an inert orcanic solvent subsl'antially insoluble in water, for exanple a h-igh flash point kerosene, and iG used at 1 to AO;.' v/v. The extraction ia carried out by countercurrent contacting c. the two liquid phases by procesoes and ia equipment known in the art. The aim io to sake the copper dissolve substantially in the organic phase as ita conplex with the extractant, followed by rapid and clean separation of the two phases for subsequent processings -The most useful equipment is a aixer-sefctler, but variants such as spray columns, packed columns, pulsating plate coluans, rotating disc contactors, and centrifugal contactors aay be used. The nuabor of stages of extraction required is not critical. In a cyclic process, it may be desirable to leave some copper, for example 5 to 10 gpl, in the raffinate to speed copper dissolution. In this ca«e, extraction is not carried out to completion, and in general fewer stages ore needed than where complete extraction ia desired. A. single or two stages are frequently adequate.

The loaded organic phase containing copper and trace elements may be waahod with weak a£id, for exfmplo aqueous sulphuric acid solution pH 2 to to rexove nine and aaaonia before stripping. Stripping is carried 278 out by treatment of the loaded organic aolution vrLtb strong aqueous acid, in particular with sulphuric acid at about 150 to 200 gpl frea acid, in similar equipment to that uced for extraction. Again the nuaber of stages required aay vary with eirauBatanca* and ia not critical. Tho priae requirement is to reduce the copper content of stripped organic to an economically low levjl, .'or cxruarle about 0.5 gpl» in order to obtain auxiau-; practicable copper transfer capacity of the organic phase. In the case of Lix 64H, about 0.4g copper dissolves in 1 lit of kerosene solution containing 10 al of extract^nt, and proportionately for higher Lix 64H concentrations. About AO v/v % of Lix 64H is the usual maxiarua concentration, that ia about 16 gpl copper. If 0.5 gpl i» left in atripped organic, the transfer of 15.5 gpl copper is defined aa the transfer capacity. The relative flow rate^ and copper transfer of the leach liquor/raf filiate, loaded/stripped organic, and atrip/recycle liquor sruat relate to the aasa of copper transferred in unit tiae.

When leaching copper dross obtained from lead blast furnace bullion, tho copper compounds generally require more vigorous oxidation conditions to dissolve the copper values than does sine/lead blast furnace droas. In particular, super-atmospheric proasurea of oxyc^n and elovated tesperutures ore required to obtain acco^voblo r^tos of dissolution for a production unit, for exacple 1 to 5 ntfflOHpherea oxygen partial prensure and tespcr&turea of J0° to 100°C are suitable ranges of conditions Tor use - 10 - 3 7 2 7 S) with tbia antcrial. *ho invention will b<5 further described with reference to the accompanying drawing which la a flow-sheot illustrating the extraction of oopper from copper droao obtained from pyro-metallurgleal lead bullion.

In tho flow aheet ohown in the drawing, copper dross (reduced to -1/8 inch particlea) together with aqueous uamonia/aausoniua carbonate solution and air are fed into a leaching tank 1. Pregnant liquor, containing dissolved copper values, 1s fed after filtration in a filter la into a solvent oxtraction contactor 2.

Raffinate,separated froa the organic phase La the contactor 2, ia recycled to the leaching stage, with a ble^d being fed to a still 3 which peraita removal of impurities such as zinc, nickel and arsenic fro® the let>ch circuit. The slurry from the still is filtered by a filter 5 to give Insoluble inorganic salta, inch as Bine and nickel hydroxides nryi carbonates and calcium arsenate.

The loaded organic phasa froa the solvent extraction contactor 2 is fed to a stripper 4 where copper values are extracted into an aqueous sulphuric acid solution and th^nc.' recycled to the contactor 2. This solution is fed to a tank house 6 in which copper is recovered, by electrolytic deposition, as cathode copper. Spent electrolyte reinforced with aajce up sulphuric acid is recycled to the strapper 4. Spent liquor from the filter 5 discharged to waste as is a bleed of spent electrolyte necessary to control impurity lcvols. r Tbe invention will b« further dencribed with reference to tbe following exiuaplos.

EXAfTLK l.

The extraction of artnl vnlnou from c.onr Dry copper dros3(118.£'t~., P.().hi:Zu-. -10 2. -. J.) wan suspended in an aqueous solution (5C0 al) of 4M JTB^ CH, 2K(NH^)200j whilst air (liitre/min.) was introduced froa a sintered glass disc imcersed in tbe liquid. The toaperature rose from 19° to 33° ovei 2 to 2.5hr, tk*n dropped to 21° at 5 hr. The spent air was scrubbed with acid. Periodic analysis of the le.icbate and of the aaaonia entrained in spent uir gave the following results : Time - hr. 1 2 3 4 5 Copper concentration, gpl. 16 35 42 46 50 Average oxygen efficiency, c/. 12 13 10 9 7 ammonia * removed,^ 3.9 7.9 1C.S 13.8 15.2 \pr>roxiE;tte • copper extraction, 5S L 25 I 56 j 1 60 73 c.c • Based on total input acconia/asmcnius, and copp.;r The ni:cture gave on filtration n filter cake (96.36«» washed and -Iried at 100°C) and a dark blue curiru=~oniu;2 37270 carbonito aolution (MO cj-J.) which waa r.tnoa distillod, forming n dark green impuro copper carbonate (59.9g., 5?.55&u, ttttohcd *nd dried). The maen balancc for tho aajor elomenta wu* oa given in the Table below. \ - 15 - r u w -J e > 1 1 " Copper Load Zinc — Iron —-——— Antimony r Ar««nlc SIlvc r ri i i» en Uro s a 2*i. 67 57. 9 3.66 3-5'« 1. 11 1. 74 0, 146 Co:ic : in Leachate (g/l) 49. 1 0.795 3.975 0. 1136 0. 318 2. 27 1 0.0068 1 (s> * (s) * («) * (f) % <«> * (g) ; % 1 (5) * Lr achate Wsahi ngs 23.3 79.5 0. 39 0.5 7 1.9<» 44.6 0.06 1.43 0.16 12. 12 1.11 53.6 0.003 73 j Washed & dric-J dross ■ res i due 6.0 20. 5 68.4 99.43 2.4l 55.4 4.15 98.57 1.16 87.78 u.96 46.4 0. 17 98.5:7 J To t 0 1 6 1 29.3 100 6B.79 100 *». 35 100 4.21 100 1. 3"2 100 2.07 100 O «vl U 100 1— -- - | Ha s i c j C .•* Ti«c («ins) 0 5 15 ; 30 90 Copper contont of initial oolut i on(g/) ) Temp. (*C) Copper in solution(g/l) Cun.incrunse(g/l) 1*.5 0 0 16. i 1.21 t.21 17.6 h.52 <1.52 19.7 a. 55 8.55 19.'« 10.70 10.70 0 Tenp. CO Copper in solution(g/l) Cum. increase(g/l) l8.8 6.57 0 20. 5 9.66 3.09 22.8 13.60 7.03 22.3 16.'i0 9.83 19.8 17. 15 10.55 6.57 Testp. CO Copper in solution(g/l) Cua.increase(g/l) 18.8 9.2<» 0 20.5 13.06 3.82 22.8 17.08 l.bk 22. 3 18.77 9.53 19-8 20.08 10.8^ 9. 2'i Temp.(*C) Copper in solution(g/l) Cum.iucreaso (g/l) 21.6 12.52 0 23-7 16.86 U. 3'» 23.7 20.7 8. 19 21.8 22. 10 9.58 20. 3 2 3. 26 10. ?'i 12. 52 r This table shows that at lco.it rjfJ 1 of copper in the leaching solution considerably spends up the lcaching process.

- - A r "vo 1 ca«~>» t n«^ orn.inu i'»ti mc I i on , ■■ t i i ppi up •">«! c.l i*«" I ' I val » c i rent t Kivc cycli'H wire operated »s roll own; ( ii) !•< acM n>; Droat, (-i]' . Cu. , ) w.i : It ... carbonate ( 100 ml.) with aeration (1 litri'/.in) I'cr .. -l.X ui: Ammonia and carbon dioxide wore added as make up wlmn About 10JS of the copper was left in the re*i> (c ) Strii'pin; into Aqueous Phase Stripping was accoaplishod with synthetic spent electrolyte ()0 gpl Cu, 180 gpl. H,S0, ) by shaking portions (6 x BO ml . ) viI Lix solution, progressing from ghakcr-sctth-r 6 to l. - 10 - 37*78 8uboaquint tit-ripping cyclcn used electrolyte from the oloctrolyaiH otage. The prceiant electrolyte frothed with oir or wanhud with keroeone befora oleetrolyais to separate tracoa of entrained Lix aolution which interfered . -.th ccpr>or -epoaitioi;. (d) l%lor.tro1 vt1<*. T)or cr,i'.ion Electrolysis wan carried out in a standa- ^ aiv.-.r »*>•'-'-for coppor analysis by deposition, usinc platinum electrodes, giving bright, clean and even copper doposito froo pregnant electrolyte which had been frothed, but luapy uneven deposits from that which had only • been washed with kerosene. The copper was finally stripped with nitric acid for analysis.

Results The results obtained froa the operation are given below.

Analysea Solution Cycle No. — ———! ; i Analyses gpl • Solut ion Voluui*. i ml. | Cu Aa Pb Zn P« [ Sb N1 Aomin* Hrtffinat« 3 5 2.4 2.6 6.1 7.5 0.023 0.023 ..3 1.3 0.02 0.02 78 j 78.5 ! i Spent Klnctrolytw 1 3 5 29.6 28. 1 30.0 0.03 0.05 0.03 0.01 0.01 0.01 0.02 0. 11 0. l6 0.023 0.039 0.0*7 0.08 0.0* 0.0* *30 *66 | *59 ; Cpthoda Coppar* l 1 -- 1 3 5 *1.9 40.* 30.8 L- £0.01 <0.01 *0.0i CO.Ol <0.01 O.Ol <0.01 <0.01 0.01 <.0.007 <0.007 CO.007 0.03 0.0* <0.01 j 100 j too : j 100 1 • After dissolution in /i<|ii«oiis nitric ac 3 7 2 7 0 /..

Tho bohoviour of tho impurity olfmniln is briefly .is follow Largely left am n notnllie and corlioii-itcd residue, i m follows copper into tho extr/tc t.int noluti on.

Arsenic: Builds up to Z. 5 - 3 Ki'l *•'> r.ifl'in 5 on coppor (Xtrnction, and th«* i-vm.i i n U-r r.-ji- in dross residue.

Nickel: Builds up in raffinate, probnbly follows coppor through the process.- Zinc: Dull da up to about 7-10 gpl in raffinate, rcmiinulor 10 rejected in dross retidue, but somo follows copper through process.

Iron: Trace aamunts go through procoss, most is rc tec ted in dross residue.

Antimony: Largely rejected in dross residue, but some fo1lo*s 15> copper through proccss. - 1ft - 37279 Kxnwpln 4 Effect of Sulnltatii on Loaching Prncru Til* follovin| leaching experimcnts were carried out in a spherical glass flask tittrf. w;*h a pa Dio coppcr dross contained 29.7% coppcr, and was screened to -i" (ca 3 ma). Aqueous solutions containing mixture of ammonia and anaoniun carbonato and/or sulphate were prepared as follows. 2 molar taooniun hydroxide, plus: (a) 1M (NH,)tCO, (b) 0.75M 0.25M(I«^ ),S(\ (c) 0.5M (MV).CO, , 0.5M (Ni^ ),S<\ (d) 0.25« (N)^ ), CO, , 0.75M(Nlk )«SC\ (•) 1M (NH.),S(\ » - The flask was charged with the appropriate solution (11.) at about 20eC. Whilst stirring vigorously, coppor droas (200*.) was added, the flask sealed and air (ll/atiu) bubbled through the liquid. Coppor dissolution started fairly quickly, and roaction was continued for 2 hr. except when noted. T } temperature rose spontaneously to about HO'C, oxcept that when no carbonnto wan present, thn dissolution of coppur was ao slow th.it tht CXOthSlfllC1 ty was Vfry much Iosn pronounced^ - 19 - 37270 / -7 Itch slurry of drosa reaiduo and loach liquor vna filtcrcl undsr standard conditions, and tho claar liquor oxtr/icted by shcklnj with Lix 6*N (G^noral Mills Trsds natoo) In k#ri smu (25 >*) until all tho copper had boon loaded into Ihr- orj.JUL phase. Tho loaded organic was washed with water, then stripptti with aqueous sulphuric acid ( lS^gpl.) yielding an acidic copper sulphate solution and a stripped organic phase suitable for recycle. The ammonium liquor, raffinate, stripped of coppor, was sultsblo for treatment of a fresh quantity of droas oftcr mak-: up of losses.

The results of the experiments are given as follows.

A. Leaching mid leach liquor details Leach Liquor 2M KH,jP"» (N'k, * (X«CO, " and/or SU ") pH ■ t •w' * i » 'AnaYyais gV>l • 'Kilter Entrainrri VH, . n (51 Initial Final Cu Pb in Fe Ni "■SB" r Xi Cake (*) Moisture A 10.15 11. 25 85 50.6 0.27 3.9 <>.0l 0.07 0. * 1.6 7. 1 7-8 h 10.15 10.80 8i *7.9 0.23 *.* o.oj9 0.07 0.6 1.2 *. 3 6.5 C 10.15 10.50 78(2) *6. i 0. 13 *.* 0.078 0.07 0.6 0.8 2.8 5.* 10. 10 10.10 8l *7.8 0.05 *.0 0.023 0.07 0.5 0. * 1.9 5.7 V 10.05 9-75 26(3) 15.5 0. 15 *.* <0-01 0.02 (*) Volume of entrained liquid ."is pcic en t .ijc of tot.il liquor. (5) Anuuonin entrained in spent oir based on tot.il aumoiuii/iinmonuim.

- PC - 372 70 D. Pr~>poi 1 I oin of Iwp'iri tv cli'ment ^ rrh .ictcil f i ■•nil .immino It.ichntf l>g»c<1 nn unit weight of irupiiT Seriea 1 r— Cu Pb "r* Tc Xi Sb I a 1.0 0.0022 0.0091 <0.0002 0. 001 0.0011 • 0.002 b 1.0 0.0033 0.030 0.0008 0. 001 '1 0.0023 1 0 c 1.0 0.0028 0.019 0.0017 0. 0012 0.0035 i : 1 0 1 d 1.0 0.0010 O.O176 0.000"} 0. 00l'» 0.0033 | 0.002 : « 1.0 0.0097 0.09B 0 0 c c V -0. 001 <0.006 I ; — 0 I ! i i It ia apparent that several advantages arise when using carbonate plus sulphate nixture to leach 'chis coppor dross, and that several disadvantages arise with sulphate a a tho only ■ anion thus: (1) The rapid reaction rate of a system containing only carbonate anion is maintained, at least to 75W# sulphate ?5K5» carbonate. It is very slow with only sulp&ate present* (2) Progressively less areenio, an'.imony and lead are dissolved by the loach liquor in proportion to the • coppor as tho sulphate content incrouscs. Very substantial amounts of load can be dissolved when only oulphote is prosont. - 21 - r The drone rosidue (npprcmantely half of which in the case of carbonate only la a very fine, slow settling and filterinc moteriul) h'»cooes progressively coarser, »ore readily filtered and holda less liquor in the cake as tho sulphate content is incrn.-iani.

Progressively lass amnonia ie lost by eatr:iins:t:nt in spent air aa the sulphate content increased. Uhon extracting with specific copper oxtractent.s, lead transfer in relation to copper decreases steadily with increasing sulphate content in tbe liquor, but then increases sharply at a 1 CC% sulphate liquor. This is particularly important sjb lead transferred to such extroctants ia stripped in the acid troataent stage. *Jhen sulphuric acid is used, such of the lead sulphate forss a precipitate which collects at the interface between the cxtractant solution ar.A the acid, enhancing "crud" formation and rendering difficult the clean separation and cosplete recovery of the exnensivo extractant. The remainder dissolves in the sulphuric solution enforcing measures to avoid contamination of the cathode copper or copper salt. - 22 -

Claims (10)

CLAIMS 372 79

1. * A asthod of leaching oopper values from copper dross separated froa- tead bullion produced in tit* blast fsmiting of a lead oxide aaterlal, coapr1s1ng contacting 0art1c1«s of the copper dross In tfw> form of a wUllfc lead ustrla containing copper and copper coapound inclusions with a* aqusous solution of aatanlua carbonate and i—onIta hydroxide to >J1isol coppcr froa theiron.

2. * A Mthod m claimed Id dale 1 wherein the lo aching .a carried out ia tbe preaence of an oxidising gon.

3. * A Mthod as claimed in claim 1 wherein the leachate solution is subsequently treated with an oxidising gas to oxidise cuprous to cupric ions. dales 1 to 3

4. A asthod as claimed in any of / wherein the leashing solution further contains sulphate ions.

5. A asthod as claimed in claim 4 wherein the mole ratio of carbonate to sulphate in the leaching aolution is froa 1:3 to 3:1.

6. A asthod as claimed in any of claims 1 to 5 wherein the temperature of the leaching solution is maintained at between 20° and 100°G.

7.j A net hod as claimed in any of claims 1 to 6 wherein the pH value of ths leaching solution is at least 9.0.

8. A aethod as claimed in claim 7 wherein tbe pH value of the leaching solution is between 9.5 and 10.5°

9. A method as claimed in any of claims 1 to 8 whcroir. the leaching oolution contains at least 15B»/litre of anoonia expressed as 37279

10. A aethod as dadoed in sty of claima 1 to 9 wLeretn the leaching solution contain* at laast 3g./litre of cuprio ions. *1 - A asthod as claiaed in aay of claixvs 1 to 10 wherein tha oopper dross Is agitated during the leaching process. 5 12. A net hod as claiaed in aay of olaias 1 to 11 wherein tho leaching solution is circulated to keep the copper droca in suspension. 13. A net hod as olaioed in any of claiaa 1 *o wherein the copper droas has bean sized to -1/8 inch particles 13 before leaching. 14. A method as claiaed in any of clalias 1 to 13 wherein the leachate solution froa the leaching process is contacted with a copper-selective organic solvent to take copper into the organic phase. is, & aethod as claiaed in claim 14 wherein the organic phase is contacted with sa aqueous aineral acid to extract copper hack into cn aqueous solution. 16. A method as claiaed in claia 15 wherein the acuoous eolutioa is evaporated to crystallise a copper salt. 20 17. a asthod as claiaed ia claia IS wherein the aqueous solutioa is electrolysed to deposit aetallic copper at the cathode. 18. A aethod as claimed in claia 15 wherein the aqueous mineral acid is dilute sulphuric acid and wherein tbe aqueous 25 solution is subsequently evaporated to crystalline copper sulphate froa the sulphate solution. 19. A aethod as claiaed in claim 15 whereir. the aqueous mineral acid is dilute sulphuric acid and wherein the aqueous solution is aubcoquently electrolysed to J-jpooi^ -c-p; er at •'<7 2? it tha oathode froa tha sulphate solution. 29. - A aethod at claiaed is any of claims 1 to 13, wherein tha laachate aolution ia stripped of aiusocia to yield aolid copper salt praeipitate. 21. . A aethod a* claiaed in any of clairw 1 to 13. wherein copper values in the leachate sjlution nre rccDVcr-ed aa netal by treatment with a recusing agent. ia recovered aa copper powder. 23. A aethod of leaching copper values from copper dross substantially as herein described, with reference to, and as shown in, the accompanying drawing. 24. A aethod of leaching copper valuee froa copper drosa substantially aa herein described with reference to any of the foregoing exaaplea. 25. Copper values obtained froa copper drosa by the aethod claiaed in any of claiaa 1 to 24.. 26. Coppor sulphate when produced hy the method aa claiaed in claia '8. ol&ia 19. 28. Copper salt when produced by the method as claimed in claia 20. 29. Copper powder when produced by the aethod as claimed in claia 22. Dated tM$ 12th day of February 1973. TOM KIKS ft CO. . A aethod as claiaed in claim wherein the copper Copper when produced by the aethod aa claimed in Agents, S Oartaouth Road, DUBLIN 6. - 25 - r M*tt11urg1c«1 toctSMt Halted and t.S.C. Smiting t1«1Ud On* shMt csrryim on business togatMr In th« ItfiiHt undtr t>« mm 37279 sad style cf NsUllurglctl OiwIopMut CoapMy. Cu omk*Q\ TO LEAD RECOVERY PLAIT Fllfh 6 TA*f HOUSE » SPENT LIQUOR (TO WASTE) MAffUP -SPOIT temTE