OA10135A - A process for the extraction and separation of nikel and/or cobalt - Google Patents

Description

01 G ! 3 5 -1-

Α PROCESS FOR THE EXTRAÇT1ON AND SEPARATION OF

NICKEL AND/OR COBALT

I

FIELD OF THE INVENTION

This invention relates to hydrometallurgy, and more partîcularly to the5 recovery and séparation of nickel and/or cobalt by liquid-liquid extraction from aqueous solutions derived from the acid Ieaching of ores. BACKGROUND OF THE INVENTIONIn solvent extraction processes, organic phases consisting of an organic extractant, organic diluent, and optionally organic soluble compounds commonly called10 "phase-modifiers," are contacted with a métal value loaded aqueous phase in a counter- current, cross-current, or co-current fashion over one or more stages. The organicphase is selected in such a way so as to be immiscible with the aqueous phase.Hydrogen ions from the organic phase exchange with métal ions from the aqueousphase so that the organic phase becomes loaded with métal values while the aqueous 15 phase emerges depleted in these métal values. The pH of the aqueous phase is usually -2- "'01 Οΐ35 controlled to maintain the efficiency and to adjust the métal selectivity of the exchangeprocess. After the extraction, the métal loaded organic phase is contacte/! wilh acid in acounter-current, cross-current, or co-current fashion over one or more stages to transfermétal values to the aqueous solution. The métal values from this aqueous solution canthen be recovered by various means, for example, by electrowinning.

Effective nickel and cobalt recovery from dilute acidic leach solutions,such as those from leaching lateritic ores, has been known to be possible byprécipitation with hydrogen sulfide. When precipitating with hydrogen sulfide, theresulting mixed nickel/cobalt sulfide precipitate may be further refined by operationsthat optionally may inelude solvent extraction. Advantageously, solvent extraction isperformed on the leach solution directly to bypass the sulfide précipitation step. This;direct solvent extraction route éliminâtes the costs associated with the difficultproduction and handling of hydrogen sulfide gas and has the potential to directlyproduce market products.

Direct solvent extraction processes hâve been commercially applied torecover copper for many years. With respect to cobalt and nickel, solvent extractionhas been limited almost exclusively to the refming of intermediate nickel-cobaltproducts (Bautista, R., "The Solvent Extraction of Nickel, Cobalt, and their AssociatedMetals." Extractive Metallurgy of Copper, Nickel and Cobalt, vol. I; FundamentalAspects, R. Reddy and R. Weizenbach (Editors), The Minerais, Metals, and MaterialsSociety, 1993, pp. 827-852). The only exception is for the direct nickel / cobaltrecovery from ammoniacal leach liquors as described, for example, in U.S. Pat. Nos.3,907,966 and 3,981,968.

Attempts to adapt existing solvent extradants for recovery of nickel andcobalt from solutions obtained as a resuit of direct acid leaching of ores or concentrâtesusing, for example, sulfuric acid hâve been largely unsuccessful. One main reason iîthat these solutions typically contain significant amounts of dissolved manganèse,magnésium and/or calcium, and these metals are often extracted together with nickeland cobalt. For example, organophosphorus and carboxylic acid extradants extractcobalt and nickel, but also co-extract, often even preferentially, manganèse (and to a -3- m 1 3 5 lesser extent calcium and magnésium). The co-extraction of these métal ions, consumesa significant portion of the extractant loading capacity and does not allow the obtainingof pure strip liquors. This eventually renders the extractant commercially unacceptable.Furtherrnore, excess aqueous solubïlîty is typically a problem for extradants such ascarboxylic acids.

Extradants comprising a mixture of carboxylic acids and non-chelatingoximes hâve demonstrated nickel and cobalt selectivity over manganèse, magnésium,and calcium. However, the non-chelating oximes usually hâve high aqueous solubilitiesand tend to hydrolyse. Chelating hydroxyoxime extradants, such as ketoximes andsalicyl aldoximes, most of them commercially developed for the extraction of copper(II) from sulfuric acid leach solutions, hâve also demonstrated selectivity for nickel andcobalt (II) over manganèse, calcium, and magnésium. However, once loaded into thesechelating oximes, cobalt (II) tends to oxidize to cobalt (III), which adversely affectsstripping and may dégradé the oxime reagent. Furtherrnore, the rate for nickelextraction using chelating oxime extractants has been reported as being very slow(Szymanowski, J., Hydroxyoximes and Copper Hydrometallurgy, CRC Press, 1993, p.281). Mixtures of chelating hydroxyoximes with di-nonyl naphthalene sulphonic acid(DNNS) hâve demonstrated improved nickel extraction, however, the DNNS acceleratesthe dégradation of the oxime (Oliver, A.J., and Ettel, V.A., "LIX 65N and Dowfax2AO Interaction in Copper Solvent Extraction and Electrolysis," CIM 14th AnnualConf., Edmonton, August 1975, pp. 383-88).

Brown et al., in U.S. Pat. No. 4,721,605 disclose a method whereby themetals selected from r.he group consisting of zinc, silver, cadmium, mercury, nickel,cobalt, and copper can be separated from calcium and/or magnésium, présent in anaqueous solution, by solvent extraction using dithiophosphinic acids. Furtherrnore, B.T. Tait reported in "Cobalt-Nickel Séparation: The Extraction of Cobalt (II) andNickel (II) by Cyanex 301, Cyanex 302, and Cyanex 272," Hydrometallurgy, 32(1993) pp. 365-372, that Cyanex 301 extractant (Cyanex is a trademark fororganophosphorus extractants distributed by Cytec Canada Inc.) extracts both nickel andcobalt and may also be used to selectively remove cobalt from nickel-containingsolution. However, the différence in the pH values at which 50% of the cobalt and -4- 5055 of the nickel is extracted is a relatively small value of only 1.1 units. In thisarticle, Tait also noted the disadvantage of requiring a strong acid to strip cobalt whenusing Cyanex 301 extradant. Tait also suggested in "The Extraction of Some BaseMétal Ions by Cyanex 301, Cyanex 302 and Binary Extradant Mixtures with Aliquat336," Solv. Extr. Ion Exch., 10(5) (1992) pp. 799-809, that manganèse is alsoextracted by Cyanex 301 at some higher pH values than nickel and cobalt. Sole et al.in "Solvent Extraction Characteristics of Thiosubstituted Organophosphinic AcidExtradants," Hydrometallurgy, 30 (1992) pp. 345-65, illustrâtes almost no séparationbetween nickel and cobalt for Cyanex 301. Contrary to Tait, Sole et al. hâve indicatedthat Cyanex 301 displays a slight preference for nickel over cobalt. Furthermore, Coteand Bauer hâve described in "Métal Complexes with Organothiophosphorus Ligandsand Extraction Phenomena," Reviews in Inorganic Chemistry, Vol. 10, Nos. 1-3, (1989) pp. 121-144, that the class of organothiophosphorus acid extradants can beoxidized to disulphides by Fe (III) présent in the solution as well as by Co (III) whichmay form in the organic phase as a resuit of oxidation of Co (II) by atmosphericoxygen. Cote and Bauer further noted that the oxidation of Co (II) to Co (III) may beavoided in the presence of oxygen donor reagents in the organic phase such as tri-octyl-phosphine oxide (TOPO), tri-butyl-phosphate (TBP), or octanol (ROH).

None of the foregoing discloses a commercially viable process for thesélective recovery of metals such as nickel and/or cobalt against metals such asmanganèse, calcium and magnésium in acidic solutions. The acid leaching ofnickeliferous lateritic ores, for example, generates leach solutions containing nickel andcobalt, often combined with appréciable amounts of impurities such as manganèse andmagnésium. Therefore, a welcome contribution to the art would be a methocl for thesélective solvent extraction of only nickel and cobalt from aqueous solutions containingthese metals as well as manganèse, magnésium and the like. After the primaryséparation of nickel and cobalt from other metals by solvent extraction, addit ionalsolvent extractants are often required for the séparation of nickel from cobalt. A singleextradant capable of separating nickel and cobalt from other metals and separatingnickel from cobalt would further contribute to the field of nickel and cobalt recovery. -5- / : C 1 0 ! 3 5

It is an object of the invention to provide a process to selectively recovernickel and/or cobalt values from acidic aqueous solutions using solvent extraction andavoiding the co-extraction of other métal values, présent in the same solution, such as,but not limited to, manganèse, calcium, and magnésium.

It is a further object of the invention to provide a simple and economicalprocess consistent with the preceding object.

It is a further object of the invention to provide reusable stripped organicphase consistent with one or both of the preceding objects.

It is a further object of the invention to provide séparation of nickel fromcobalt by their sélective stripping from loaded organic phase consistent with one ormore of the preceding objects.

It is a further object of the invention to provide séparation of nickel fromcobalt by their sélective loading into an organic phase consistent with one or more ofthe preceding objects. SUMMARY OF THE INVENTIONThe invention provides a hydrometallurgical process for the recovery of metals. In particular, an aqueous feed solution originating from acid leaching isprovided. The aqueous feed solution contains nickel and/or cobalt ions. The pH of thesolution is maintainecl at a level between aoout 2 and 6. The aqueous feed solution iscontacted with a water-immiscible organic phase containing an extradant to load thenickel and/or cobalt métal ions to form a metal-bearing organic phase. The extradanthas at least one organic soluble dithiophosphinic acid, alkali, alkaline earth métal orammonium sait thereof. The aqueous feed solution has sufficiently low levels ofchromium (VI) ions, iron (III) ions and copper ions to allow repeated use of theextractant. The metal-bearing organic phase is then separated from the metal-containingaqueous feed solution. Finally, after séparation from the aqueous feed solution, themetal-bearing organic phase is contacted with an aqueous strip solution to recover theloaded nickel and/or cobalt from the metal-bearing organic phase. -6- CÎ0Î35

DESCRIPTION OF THE PREFERRED EMBOD1MENTS

OF THE INVENTION

It has been discovered that organic dithiophosphinic extradants, may beused to effectively separate nickel and/or cobalt from acid leach solutions by 5 maintaining chromium (VI), iron (III) and copper ions at levels that allow repeated useof the extractant.

It has further been discovered that nickel/cobalt séparation is achieved byexlracting nickel and cobalt together with an organic dithiophosphinic extractant andthen selectively stripping the co-loaded cobalt from the organic dithiophosphinic 10 extractant with a dilute water-soluble acid solution, while the nickel is subsequently stripped with a more concentrated solution of the same or a different water-soluble acid.

It has further been discovered that nickel/cobalt séparation mayalternatively be achieved by selectively loading only the nickel onto an organicdithiophosphinic extractant, leaving essentially the cobalt in the aqueous raffinate and 15 then extracting this cobalt with the same or another extractant operating in a separatecircuit. After preferential loading, the nickel and cobalt are stripped with solutions ofthe same or different kÈnd of water-soluble acid from the respectively loaded organicextractant(s).

It has also been discovered that organic dithiophosphinic extradants may 20 be used to effectively separate by solvent extraction nickel and/or cobalt frommanganèse (II), présent in acidic leach solutions of oxide ores. The organicdithiophosphinic extractant readily combines with nickel and cobalt ions in the organ ephase, leaving the manganèse ions in the aqueous raffinate.

The process of the invention uses a dithiophosphinic extractant to 25 separate nickel and/or cobalt from acidic leach solutions. Spécifie examples of ores suitable for acid leaching include oxide ores, sulfide ores and manganèse or sea nodulesthat contain nickel and/or cobalt. Most advantageously, the process of the invention isused for lateritic ores. -7- V 1 ό â ΰ b

The leach solution must be maintained at a pH between about 2 and 6 prior to loading of nickel and/or cobalt ions onto the extradant. Advantageously, theleach solution is maintained at a pH between about 3 and 6 prior to loading. Mostadvantageously, the leach solution is maintained at a pH between about 3 and 5.5 priorto loading. Advantageously, the leach solution is partîally neutralized to remove freeacid prior to the extraction step. Removing free acid during partial neutralizationminimizes or even éliminâtes the need for base addition during the subséquent solventextraction operations. During partial neutralization the majority of iron (III), chromium(III), aluminum and copper ions precipitate, leaving a majority of the nickel and cobaltions in solution. After précipitation, the ions are readily separated from the aqueousfeed solution in a solid/liquid séparation step. In some cases, it may be désirable tooxidize Fe (II) ions to Fe (III) ions prior to the partial neutralization step.Advantageously, Fe (II) ions are oxidized to Fe (III) ions by contact with an oxygen-containing gas. In some instances, when manganèse (IV) ions are présent in the leachsolution, manganèse (IV) ions are also precipitated during partial neutralization. Partialneutralization may be accomplished using any suitable base reagent. Mostadvantageously, the pH of the leach solution is adjusted with calcium carbonate.

Advantageously, after removal of Fe (III) ions, remaining iron (III) ions are reduced to Fe (II) ions to prevent unnecessary dégradation of the extractarit. TheFe (III) ions may be reduced using Chemical réduction agents such as SO2, sulfite,bisulfite, soluble sulfides and the like.

In order to extract nickel and/or cobalt from the leach solution., the solution is contacted with an organic soluble dithiophosphinic acid, alkali, alkaline earthmétal or ammonium sait thereof. The dithiophosphinic extractant is advantageouslyrepresented by the formula: R1

SM

R1 S

R2 SM -8- Ό1' 01 σ 5 wherein R1 and R2 are the same or different and are substituted alky 1, cycloalkyl,alkoxyalkyl, alkylcycloalkyl, aryl, alkylaryl, aralkyl, or cycloalkylaryl radicals havingbetween 2 and 24 carbon atoms. Most advantageously, R* and R2 are each 2,4,4-trimethylpenty 1 radicals; this bis (2,4,4-trimethylpentyl) dithiophosphinic acid isavailable from Cytec Canada Inc. as Cyanex 301 extradant. The M may be hydrogen,when the extradant is used in its acid form. Alternatively, M may be an alkali,alkaline earth métal ion or an ammonium ion when the extradant is used in its saitform. Most advantageously, M is hydrogen. During solvent extraction, nickel and/orcobalt ions are substituted for M, thus loading the extradant with the mdal icns.Extradants are advantageously loaded at températures between freezing and 85 °C.

During métal stripping, a water-soluble acid solution provides thenecessary hydrogen to replace the extracted métal in the M position of the extradant.The extradant, stripped in this manner, is then recycled for repeated loading of nickeland/or cobalt ions.

It has been found that chromium (VI) ions, if présent in the feed aquecussolution, will cause a substantial and rapid decrease of the métal extraction ability of idieorganic dithiophosphinic extradant. Commercially viable operations require repeateduse of the extractant. Advantageously, the extradant may be used at least 10 timeswith only about a 10% or less réduction in extraction ability. Therefore, in order toprotect the extradant and optimize its performance during its use over a number ofmétal extraction and stripping operations, oxidizing species that would not hydrolyzeduring the partial neutralization step such as chromium (VI) ions, are advantageouslyremoved prior to the solvent extraction with the organic dithiophosphinic extractant. Itis recognized that when chromium (VI) concentrations are very low, a chromium (VI)removal step may not be required. The chromium (VI) removal can be accomplishedby a variety of techniques. For example, chromium (VI) may be readily removed byréduction and précipitation as chromium (III) during the partial neutralization step.Advantageously, the reductant used for reducing of chromium (VI) ions is a reducingsulftir species such as a metabisulfite, a sulfur dioxide gas or an aqueous solublesulfide. Alternatively., hydrogen peroxide may be used for chromium (VI) réduction.Most advantageously, sulfur dioxide gas is used for chromium (VI) réduction. -9- * · λ 3 ΠΠ 3 5

It has fiirther been found that copper ions, if présent in the feed aqueoussolution, bond very strongly to the organic dithiophosphinic extradant. The bondformed between dithiophosphinic extradants and copper ions is so strong thaï it isvirtually impossible to strip the copper with common minerai acids. Therefore, inorder to optimize the performance of the extradant, copper ions are advantageouslyremoved prior to the solvent extraction with the organic dithiophosphinic extradant. Il:is recognized that when copper concentrations are very low, a copper removaJ step maynot be required. This copper removal can be accomplished by a variety of technique».

For example, copper ions may be removed by using an ion-exchange resin. Mostadvantageously, the ion-exchange resin is a chelating resin with iminodiacetic acidfunctionality. Other techniques that may be employed for copper removal include, forexample, cementation and précipitation as copper sulfide.

The organic dithiophosphinic extradant may be used undiluted.

However, it is advantageous to use a water-immiscible organic diluent. This diluentmay represent from 1 to 99 parts by volume of the organic extractant/diluent mixture .Optionally, the organic extractant/diluent mixture may contain from 1 to 20 parts byvolume of one or more addïtional organic soluble and water-immiscible compounds,denoted generally as "phase-modifiers," which rôle, among others, is to improve theséparation of the aqueous and organic phases. In addition, these compounds may helpin preventing the oxidation of Co (II) to Co (III) upon loading into the organic phase,for example, when the solution is in contact with an oxidizing atmosphère such as air. A broad variety of water-immiscible organic liquids may be used as thediluent. Suitable diluents include, but are not limited to, kerosene, toluene, xylene,naphtha, hexane, decane, cyclohexane, and the like. Advantageously, the diluent is analiphatic or aromatic petroleum product. Most advantageously, the diluent is analiphatic petroleum liquid. The aliphatic petroleum liquid may optionally containnaphthenic and/or aromatic compounds. Examples of suitable phase-modifiers include,but are not limited to, iso-decanol, tridecyl alcohol, nonyl phénol, tributyl phosphate,trioctyl phosphine oxide, and the like. -10- i»,

The solvent extraction process may be carried ou! under an airatmosphère, n'owever, when operating in air, some dégradation of the extradant mayoccur during the solvent: extraction (from the step of contacting the feed solution withan organic phase to the step of contacting the loaded organic phase with a stipper 5 solution). Thus, it is aCvantageous to carry out the solvent extraction process under aninert gas or a reducing gas atmosphère in order to avoid or limil the detrimental effects,or the formation, of oxidizing species, such as Fe (III) and Co (III). For purposes ofthe spécification inert gas is defined as a gas that does not oxidize cobalt (II) to cobalt(III) or iron (II) to iron (III) in the aqueous solution and/or the organic phase. 50 Examples of suitable gasses include, but are not limited to, carbon dioxide, nitrogen, argon, sulfur dioxide and the like. Advantageously, if oxidizing species such as Fe (111)are présent in the feed aqueous solution, then Chemical reducing reagents, such as, butnot limited to SO2, sulfites, bisulfites, water soluble sulfides and the like, areadvantageously added to reduce the oxidizing species. The Chemical reducing reagents 15 may be added befcre or during métal extraction.

For carrying out the solvent extraction process of the invention, mixer -settlers, extraction columns, such as puise columns, columns with internai stirring usingrotating impeliers, reciprocating-plate extraction columns, tubular reactors with in-linemixers and the like may be used. 20 At a steady-state pH of less than about 4, and advantageously of less than about 3, cobalt and nickel are loaded onto the organic dithiophosphinic extradant.

Most advantageously, the cobalt and nickel are loaded onto the organic dithiophosphinicextradant at a steady-state pH of less than about 2.5 to ensure that manganèse is not co-loaded onto the extradant. If the pH of the aqueous feed is higher than about 2,5, 25 addition of base to neutralize released hydrpgen ions during the extraction may not beneeded. 'The avoidance of base addition significantly facilitâtes minimizing theoperational costs of the solvent extraction process. Advantageously, the pH forextraction is higher than about 1.0 to ensure efficient extraction of nickel and/or cobalt:.Advantageously, at least about 60% of the nickel ions are loaded onto the extradant. 30 Most advantageously, at least about 95% of the nickel ions are loaded onto the extradant. It has been discovered that a nickel to manganèse loading ratio of at least -11- about 100 is readily achievable when at least about 60% nickel is extracted. In fact,séparation ratios of at least 400 to 700 are typically achieved with the process of theinvention. This exceptional ratio provides for effective nickel and/or cobalt séparationfrom manganèse, as well as, calcium, magnésium and the like.

The métal extraction reaction is very fast, thus allowing operation atambient température. However, the extraction may also be carried out at elevatedtempératures. Advantageously, the organic/aqueous mixture during extraction ismaintained at a température between freezing and 85°C. The aqueous to organic phaseratio during extraction is advantageously maintained between 10 and 0.1, moreadvantageously, between 5 and 0.5, and most advantageously, between 3 and 1.

After loading the organic dithiophosphinic extradant with nickel andcobalt, the nickel and cobalt metals can be stripped with a water-soluble acid, separatelyor together. Cobalt ions advantageously may be separately stripped with aqueoussolutions having acidity between about 0.1 and 2.0 N, and most advantageously lessthan 1 N HCl, or its équivalent for another acid or combination of acids. After cobaltremoval, nickel advantageously may be stripped with the same or a different kind ofwater-soluble acid with the concentration of the acid being at least 1.0 N HCl or itséquivalent for another acid or combination of acids. Most advantageously, the acidconcentration is between about 2.0 N and 8.0 N for nickel removal. The métalstripping can be achieved by using, for example, common minerai acids such as sulft rieor hydrochloric acid, and the like, or mixtures thereof. Advantageously, eitherhydrochloric or sulfurit: acid is used. Most advantageously, hydrochloric acid is usedfor métal stripping. Advantageously, nickel is stripped with the organic phase andaqueous acidic solution being at a température between 45 °C and 85 °C.

Advantageously, the acid strip solutions are internally recycled, within the strippingoperation, in order to cbtain more concentrated nickel and/or cobalt strip solutions.

Alternatively, nickel and cobalt may be separated by sélective loading of nickel over cobalt. Under the conditions close to the maximum métal loading capacity of the organic dithiophosphinic extradant, the nickel ions présent in the aqueous feed solution may be loaded onto the extradant by displacing cobalt to the aqueous phase. -12-

The organic extradant is thus essentially loaded with nickel only. The cobalt in theaqueous solution may be conveniently extracted using the same or another extradant ma separate extraction step. When using separate cobalt extraction steps, the later cobz.ltextraction step may require an upward pH adjustment for improved efficiency. Thedisplacement of cobalt by nickel during extraction achieves a nickel/cobalt séparationthat may be advantageous over the sélective nickel/cobalt stripping with different acidconcentrations for situations wherein the initial feed concentration of nickel issignificantly higher than the concentration of cobalt.

Alternatively, nickel and cobalt may be stripped together from the loadeddithiophosphinic extradant with water-soluble acid with the concentration of the acidbeing at least 1.0 N. More advantageously, the acid is hydrochloric acid and is used inconcentrations between 2.0 N and 8.0 N. Nickel and cobalt may then subsequently beseparated by known solvent extraction processes. Advantageously, the nickel and the:cobalt are separated by selectively extrading the cobalt with an amine solventextradant. Most advantageously, the amine extradant is triisooctylamine.

It is advantageous, for économie reasons, to regenerate the acid from lhenickel and/or cobalt strip solutions. For example, thermal décomposition of therespective nickel and/or cobalt salts of the strip solutions can be used to produce nickeland/or cobalt oxide and regenerate the acid so that the acid is advantageously recycledfor further nickel and/or cobalt stripping.

The following Examples only provide an illustration and should not beconstrued as limiting the invention in any way, as variations from the invention arepossible which do not départ from the spirit and scope of the appended daims.

Example 1: This Example illustrâtes that complété nickel (II) and cobalt (II) extractionis possible, without extracting manganèse (II), calcium (II), magnésium (II), orchromium (III), with an organic dithiophosphinic extradant at low pH conditions.

A sample of 15 vol% solution of Cyanex 301 extradant in Iscpar M diluent (an aliphatic organic solvent from Impérial Oil) was coritacted at a température -13- of 23°C and at various pH values (adjusted with sodium hydroxide solution) fer 5minutes, and at an aqueous to organic (A/O) ratio of 2, with a sulfate solutioncontaining, in g/L, 0.045 copper (II), 3.86 nickel (II), 0.35 cobalt (II), 0.002 iron (III),2.24 manganèse (II), 0.54 calcium (II), 1.54 magnésium (II), 0.094 zinc (II), 0.004 5 chrornium (III) and 0.005 aluminum (III). Samples from each phase were withdrawnafter the five minute contact time. The analyzed métal concentrations in the resultingaqueous phase are given in the Table la below:

Table la pH Raffinate Assay (g/L) Cu (Π) Ni (II) Co (II) Μη (II) Zn (II) 1.46 <0.001 0.410 0.040 2.28 0.001 1.61 <0.001 0.057 0.033 2.28 <0.001 1.83 <0.001 0.006 0.016 2.23 <0.001 2.01 <0.001 0.002 0.008 2.19 <0.001 2.54 <0.001 <0.001 <0.001 2.18 <0.001 15 The concentrations of Cr (III), Al (III), Ca (II), and Mg (II) remained the same as those in the aqueous feed. The respective percent extractions for Ni (II),Co (II) and Mn (II) are provided in Table lb below: 20

Table 1b pH Extraction (%) Ni Co Mn 1.46 89.4 88.6 0 1.61 98.5 90.6 0 -14- ΙΗίΠ pH Extraction (%) Mn 1.83 99.8 95.4 0.4 2.01 99.95 97.7 2.2 2.54 >99.9 >99.9 2.7

Examnle 2; This Exarnple illustrâtes the alternative of selectively loading nickel (II)into an organic dithiophosphinic extradant to achieve an effective nickel/cobaltséparation. i) the sélective loading of nickel A sample of 15 vol% Cyanex 301 extradant in Isopar M diluent wascontacted at a température of 23°C for 5 minutes at an A/O ratio of 2 and pH 2.5(adjusted with sodium hydroxide solution) with a feed sulfate solution containing, ing/L, 0.002 copper (II), 2.15 nickel (II), 0.25 cobalt (II), <0.001 iron (III), 1.18manganèse (II), 0.51 calcium (II), 0.58 magnésium (II), 0.037 zinc (II), 0.020chromium (III) and 0.007 aluminum (III). After separating the two phases, the aquecusraffinate contained, in g/L, <0.001 copper (II), <0.001 nickel (II), <0.001 cobalt(II), <0.001 iron (III), 1.09 manganèse (II), 0.51 calcium (II), 0.56 magnésium (II),<0.001 zinc (II), 0.028 chromium (III) and 0.004 aluminum (III).

The loaded organic phase was then contacted, for a second time, withanother portion of the same feed sulfate solution at an A/O ratio of 3 and underotherwise the same conditions. After 5 minutes of contact time, followed by phaseséparation, the aqueous raffinate phase contained, in g/L, <0.001 copper (II), 0.78nickel (II), 0.36 cobalt (II), <0.001 iron (III), 1.2 manganèse (II), 0.51 calcium (II),0.58 magnésium (II), <0.001 zinc (II), 0.021 chromium (III) and 0.006 aluminum(ΙΠ).

The loaded organic phase was then contacted, for a third time, with another portion of the same feed sulfate solution at the same A/O ratio of 3 and the -15- 010ÎG5 same other conditions. After 5 minutes of contact time, and then phase separa'.ion, theaqueous raffinate contained, in g/L, <0.001 copper (II), 2.30 nickel (II), 0.31 cobalt(II), <0.001 iron (III), 1.2 manganèse (II), 0.52 calcium (II), 0.59 magnésium (II),0.005 zinc (II), 0.022 chromium (III) and 0.004 aluminum (III).

Following these three conséquent contacts of the same organic phase withfresh portions of the sarne feed sulfate solution, the obtained loaded organic phase wasanalyzed and found to contain, in g/L, 0.023 copper, 9.33 nickel, 0.038 cobalt, 0.004iron, <0.005 manganèse and 0.272 zinc. ii) stripping of nickel A portion of a similarly loaded organic phase was contacted with 5 Nhydrochloric acid solution for 40 minutes at a température of 55"C. After phaseséparation, the strip liquor was found to contain, in g/L, <0.001 copper (II), 5.99nickel (II), 0.03 cobalt (II), <0.001 iron (III), 0.003 manganèse (II), 0.002 calcium(II), 0.003 magnésium (II), 0.51 zinc (II), 0.002 chromium (III) and 0.004 aluminum(m).

Example 3: This Example illustrâtes the stripping of nickel and cobalt from loadedorganic dithiophosphinic extradant with sulfuric acid. A sample of 15 vol% Cyanex 301 extradant in Isopar M diluent, loadedto about 7.6 g/L Ni (II), 0.5 g/L Co (II), and 0.12 g/L Zn (II), was contacted with 3.0N sulphuric acid solution at an A/O ratio of 1 at a température of 55°C for 50 minutes.The obtained aqueous strip liquor contained 3.7 g/L Ni (II), 0.5 g/L Co (H), and 0.02g/L Zn (II), which was équivalent to the stripping of 49% of the nickel, >99.9% of thecobalt, and 15% of the zinc.

Example 4: This Example illustrâtes the complété nickel (II) and cobalt 01) extraction with an organic dithiophosphinic extradant with the simultaneous total rejection of manganèse 01), calcium (II), magnésium (II), and chromium (III). This Example ftirther illustrâtes the séparation of nickel 01) and cobalt 01) by sélective stripping from -16- the organic dithiophosphinic extradant in a continuons multi-stage counter-cu rrentsolvent extraction operation.

An aqueous sulfate solution containirig, in g/L, 5.05 nickel (II), 0.53cobalt (II), <0.001 iron (III), 2.93 manganèse (II), 0.48 calcium (II), 1.03 magnésium(II), 0.074 zinc (II), 0.044 chromium (III) and 0.005 aluminum (III), having a pH of3.66 at a température of22°C, was contacted in a counter-current fashion in threeconséquent extraction stages (stages Ll, L2, and L3; the aqueous solution enters theoperation through stage L3 and leaves the operation (as raffinate) through stage Ll) at aflow-rate of 10 mL/min and at a température of 41°C with a 15 vol% solution ofCyanex 301 extradant in Isopar M diluent. The organic solution enters the operationthrough stage Ll and bas the same flow-rate of 10 mL/min to give an A/O ratio of cne,with a rétention time of 6 minutes per stage. No base was added to any of theextraction stages for pH adjustment or control. The loaded organic solution leavingstage L3 was contacted in a counter-current fashion in two conséquent stripping stag<ïs(stages C1 and C2) at a température of 33°C with a l N solution of hydrochloric acidhaving a flow-rate of 0.8 mL/min to give an organic to aqueous (O/A) ratio of 12.5(the 1 N solution of hydrochloric acid entered the operation through stage G2 and exitedthe operation (as cobalt strip solution) through stage Cl). The organic solution wasremoved through stage C2 and contacted in a counter-current fashion in one washingstage (stage Wl) at a température of 32°C with water, having a flow-rate of 0.5mL/min to give an O/A ratio of 20. The partially stripped and washed organic phasewas contacted, aller leaving the washing stage, in a counter-current fashion in fourconséquent stripping stages (stages NI, N2, N3, and N4) with a 6 N solution ofhydrochloric acid having a flow-rate of 2.3 mL/min to give an O/A ratio of 4.3 (the 6N solution of hydrochloric acid entered the operation through stage N4 and wasremoved from the operation as nickel strip solution through stage NI). The strippingstages were maintained at a température of 60°C. The métal-stripped organic phase wasremoved through the N4 stage and was contacted in a counter-current fashion in onewashing stage (stage W2) at a température of 34°C with water, having a flow-rate of0.4 mL/min to give ari O/A ratio of 25. The metal-stripped and washed organic phasewâs then recycled back to the extraction stages (stage Ll). -17-

The typical aqueous solution compositions after each stage, alorg withtheir pH values where appropriate, are summarized in Table 2.

Table 2

Stage Temp CC pH * : Aqueous Solution Analyses (mg/L) Ni (II) Co (II) Mn (II) Cr (III) Ca (II) Mg (II) Zn (II) L1 (raffmate) 41 1.30 43 46 3,040 52 560 1,240 <1 L2 41 1.53 680 990 3,030 52 560 1,230 <1 L3 40 2.36 3,510 1,630 3,050 53 560 1,230 3 Cl (cobaltstrip liquor) 33 0.28 1,960 3,730 2 3 < 1 1 160 C2 33 0.23 1,260 550 <1 <1 <1 <1 110 NI (nickelstrip liquor) 60 - 18,200 35 <11 4 <1 <1 270 N2 60 - 5,380 2 <1 <1 <1 <1 <1 N3 60 - 1,580 <1 <1 < 1 <1 <1 <1 N4 60 - 450 <1 <1 <1 <1 <1 <1 W2 34 2.36 <1 <1 <1 <1 <1 <1 <1 * Measured at the corresponding température.

Example 5: This Example illustrâtes the treatment of a nickel and cobaltcontaining acidic solution involving the réduction of chromium (VI) with sulfurdioxide gas and partial neutralization.

An aqueous sulfate solution, containing, in g/L, 0.017 copper, 3.29 nickel, 0.33 cobalt, 0.24 iron (III), 2.45 manganèse, 0.5 chromium (VI),0.18 calcium, 0.89 aluminum, 0.079 zinc and 2.44 magnésium, having a pH ofabout 1.0 and a redox potential of 800 mV, measured against a saturatedcalomel electrode, was contacted with sulfur dioxide gas at about 60°C to lower -18- C HH 3 5 the redox potential to about 550 mV, as measured against a saturated calomelelectrode. Following this treatment, calcium carbonate was added to thesolution to raise the pH to 4.5 at 60°C. After removing the précipitâtes solid:;,the solution contained, in g/L, <0.008 copper, 3.18 nickel, 0.31 cobalt, <0.01iron, 2.18 manganèse, 0.074 chromium (ΠΙ) (no chromium (VI) was found), 0.89 calcium, 0.01 aluminum, 0.077 zinc, and 2.18 magnésium.

Example 6: This Example illustrâtes that relatively small amounts of copper (II)which may be présent in the aqueous feed solution, can be selectively removedprior to solvent extraction by using chelating ion-exchange resins.

An aqueous sulfate feed solution, containing, in g/L, 0.20 copper(II), 3.5 nickel (II), 0.33 cobalt (II), 2.2 manganèse (II), 0.5 calcium (II), 1.5magnésium (II), and 0.087 zinc (II), was fed at an upflow velocity of 1.2 m/hand at a température of 23°C through a column, containing 100 mL ofResinTech SIR-300 chelating resin (from ResinTech, Inc.) with iminodiaceticacid functionality. After the passing of 80 bed volumes of solution, the treatedsulfate solution still contained less than 0.001 g/L of copper (II), while theconcentrations of nickel (II) and cobalt (II) remained the same as those in thefeed solution.

The process of the invention provides several advantages. Theinvention provides a process to selectively recover nickel and/or cobalt valuesfrom acidic aqueous solutions using solvent extraction that avoids the co-extraction of manganèse, calcium and magnésium. The process of the inventionfacilitâtes simple and economical sélective recovery of nickel and/or cobalt.

The organic phase is typically reusable over many extraction/stripping cycles.The process further provides effective séparation of nickel from cobalt bysélective strippirig or sélective loading process options. Finally, base additions -19- C ί C1 3 5 during the métal loading step are often not necessary when partial neutralizationis used to remove impurities.

While in accordance with the provisions of the statute, there isillustrated and described herein spécifie embodiments of the invention. Those 5 skilled in the art will understand that changes may be made in the form of theinvention covered by the daims and that certain features of the invention maysometimes be used to advantage without a corresponding use of the otherfeatures.

Claims (10)

1. -20- co The embodiments of the invention in which an exclusive propertyor privilège is claimed are defmed as follows:

   1. A hydrometallurgical process for the recovery of metalscomprising the steps of: a) providing an aqueous feed solution, said aqueous feedsolution originating from acid leaching and said aqueousfeed solution having at least one métal selected ;from thegroup consisting of nickel and cobalt ions, b) maintaining pH of said aqueous solution at a levelbetween about 2 and 6, c) contacting said aqueous feed solution with a water-immiscible organic phase containing an extractant to loadmétal of said aqueous feed solution onto said extractantand to form a metal-bearing organic phase, said extractanthaving at least one organic soluble dithiophosphinic acidor alkali or alkaline earth métal or ammonium sait thereofand said aqueous feed solution having sufficiently lowlevels of chromium (VI) ions, iron (III) ions and copperions to allow repeated use of said extractant, d) separating said metal-bearing organic phase from saidmetal-containing aqueous feed solution, and e.) contacting said metal-bearing organic phase with anaqueous strip solution to recover said loaded métal fromsaid metal-bearing organic phase. -21- •Ί Ο JW .1 7
2. 2. A hydrometallurgical process for the recovery of metalscornprising the steps of: a.) providing an aqueous feed solution, said aqueou:; feedsolution originating front acid leaching of an ore and saidaqueous feed solution having a first métal group and asecond métal group, said first métal group having at leastone métal selected front the group consisting of nickel andcobalt ions and said second métal group having at leastone métal selected from the group of iron (III), chromium,aluminum and copper ions, b) partially neutralizing said aqueous feed solution to a pHbetween about 2 and 6 to remove free acid front saidaqueous feed solution and to precipitate metals of saidsecond métal group, said neutralizing leaving a majority ofions from said first métal group in said aqueous feedsolution, c) separating said precipitated métal from said aqueous feedsolution, d) contacting said aqueous feed solution with a water-immiscible organic phase containing an extradant to Ioadmétal of said first métal group onto said extradant and toform a metal-bearing organic phase, said extradant havingat least one organic soluble dithiophosphinic acid or alkalior alkaline earth métal or ammonium sait thereof and saidaqueous feed solution having sufficiently low Ievels ofchromium (VI) ions, iron (III) ions and copper ions toallow repeated use of said extradant, -22- e) separating said metal-bearing organie phase from saidmétal-containîrig aqueous feed solution, and 0 contacting said metal-bearing organie phase with anaqueous strip solution to recover said métal of said firstmétal group from said metal-bearing organie phase.
3. 3. A hydrometallurgical process for the reeovery of metalscomprising the steps of: a) providing an aqueous feed solution, said aqueous feedsolution originating from acid leaching of lateritie ore andsaid aqueous feed solution containing chromium (VI) ionsand having a first métal group, a second métal group anda third métal group, said first métal group having at leastone métal selected from the group consisting of nickel andcobalt ions, said second métal group having at least onemétal selected from the group of iron (111), chromium(III), aluminum and copper ions, and said tliird métalgroup having at least one métal selected from the group ofmanganèse, calcium and magnésium, b) reducing chromium (VI) ions in said aqueous feed solutionto chromium (III) ions and partially neutralizing saidaqueous leach solution to a pH between about 3 and 6 toremove free acid from said aqueous feed solution and teprecipitate metals of said second métal group, saidneutralizing leaving a majority of ions from said firstmétal group in said aqueous feed solution, c) separating said precipitated métal from said aqueous feedsolution, -23- d) contacting said aqueous feed solution with a water-immiscible organic phase containing an extractant to loadmétal of said first métal group onto said extradant and toform a metal-bearing organic phase, said extractant havingat least one organic soluble dithiophosphinic acid or alkalior alkaline earth métal or ammonium sait thereof to leavesaid ions of said third métal group in a resulting raffinatesolution and said aqueous feed solution having sufficientlylow levels of chromium (VI) ions, iron (III) ions <indcopper ions to allow repeated use of said extractant, e) separating said metal-bearing organic phase from saidraffinate solution containing said ions of said third métalgroup, and f) contacting said metal-bearing organic phase with anaqueous strip solution to recover said métal of said firstmétal group from said metal-bearing organic phase.
4. 4. The method of daim 3 induding the additional step of removing copper ions from said aqueous feed solution prior to said contactingwith said water-immiscible organic phase.
5. 5. The process of daim 3 wherein said organic soluble dithiophosphinic acid or alkaîi or alkaline earth métal, or ammonium sait thereofis represented by the formula: R1 S R2 SM R1 S R2 SM wherein R1 and R2 are selected from the group consisting of substituted alkyl, cydoalkyl, alkoxyalkyl, alkylcydoalkyl, aryl, alkylaryl, aralkyl, or -24- cycloalkylaryl radicals having between 2 and 24 carbon atoms and wherein M iseither hydrogen or an alkali or alkaline earth métal ion or an ammonium ion.
6. 6. The method of daim 3 wherein said extractant is bis (2,4,4-trimethylpentyl) dithiophosphinic acid.
7. 7. The method of daim 3 wherein said aqueous feed solution contains nickel and cobalt ions, and said extractant is loaded with nickel andcobalt ions and said nickel and cobalt ions are recovered together during saidcontact with said aqueous strip solution.
8. 8. The method of daim 7 wherein said nickel and cobalt ions 10 are separated by a solvent extraction using an amine extractant.
9. 9. The method of daim 3 wherein said métal from said aqueousstrip solution is recovered as an oxide by thermal décomposition wherebyregenerated acid from said acid aqueous strip solution depleted of métal isrecyded to step f).
10. 10. The method of daim 3 induding the additional step of reducing Fe (III) ions to Fe (II) ions after step c) and before or during step d) andwherein steps d) to f) are operated under an atmosphère that limits oxidation ofan ion selected from the group consisting of cobalt (II) ions and iron (II) ions insaid aqueous feed solution or said organic phase. 20