OA10492A - Recovery of nickel and cobalt from laterite ores - Google Patents

Abstract

A process is provided for selectively recovering nickel by ion exchange absorption from a Ni/Co sulfuric acid feed solution (6) obtained from limonite ore (1) which is pressure leached with sulfuric acid (2) and then neutralized (3) and solid/liquid separated (4), containing nickel in the range of about 0.5 to 40 gpl and cobalt in the range of about 0.01 to 2 gpl as sulfates. Tailings disposal occurs at (5). The process comprises contacting the acid solution at a pH ranging from about 0.3 to 6 with a bed of protonated ion exchange resin in which protons thereof are exchangeable with nickel ions in said solution during ion exchange (7). The nickel is selectively extracted in preference to cobalt from the solution at a pH of less than about 2, thereby forming a raffinate containing the cobalt (8). The cobalt raffinate is neutralized (9), solid/liquid separated (10) and cobalt recovered therefrom (11, 12). Raffinate depleted in cobalt is sent (13) to tailings disposal (5). The absorbed nickel is stripped from said resin with sulfuric acid (16) to form a nickel sulfate solution characterized by a nickel to cobalt ratio of at least about 50:1 suitable for the recovery of substantially pure nickel by electrolysis (15). Prior to electrolysis the nickel sulfate solution is neutralized (8A) and solid/liquid separated (14).

Description

010492

Recovery of Nickel and CobaltFront Latérite Ores

Field of Invention

This invention relates to the hydrometallurgicalProcessing of nickeliferous oxide ores and, in particular,to acid leaching of nickeliferous oxide ores selected fromthe group consisting of limonite and saprolite, whichjointly are called latérites. v

Backoround Of The Invention

It is known that nickeliferous oxide ores, e.g.,limonite and saprolite, are the world's largest potentialsources of nickel and cobalt.

The ability to beneficiate these ores by conventionaltechniques has placed these ores at an économiedisadvantage in that these ores cannot be concentrated bymagnetic séparation or by froth flotation as compared tonickeliferotis sulfide ores which can be easilyconcentrated to substantially high levels of nickel bywell known methods, such as froth flotation and mattesmelting.

One process for recovering nickel and cobalt is thewell known Moa Bay process involving acid leaching atelevated températures and pressures at which iron oxideand aluminum oxysulfate are substantially insoluble.

In the Moa Bay process, limonitic ore at minus 20mesh (95% passing 325 mesh U.S. Standard) is pulped toapproximately 45% solids and the nickel and cobaltselectively leached with sufficient sulfuric acid atelevated température and pressure (e.g. 230 C to 250 C and 405 to 580 psia) to solubilizeabout 95% each of nickel and cobalt in about 60 to 90minutes. After pressure let down, the leached pulp is 010492 washed by countercurrent décantation with the washed pulpgoing to tailings. The leach solution pH, which is quitelow (e.g., between 0 and 0.5), is then neutralized withcoral mud to a pH of about 2.4 in a sériés of four tanksat a total rétention time of about 20 minutes and thethus-treated product liguor (containing about 5.65 gpl Ni,0.8 gpl Fe and 2.3 gpl Al), after solid-liquid séparation,is then subjected to sulfide précipitation. The leachliquor is preheated and the sulfide précipitation carriedout using H2S as the precipitating reagent in an autoclaveat about 12O’C (25O°F) and a pressurç of about 150 psig.

In the original scheme for treating the mixedsulfides,, the sulfide precipitate was washed andthickened to a solids content of 65%. It was thenoxidized in an autoclave at about 177-c (350*F) and apressure of about 700 psig.

The solution containing nickel and cobalt was thenneutralized with ammonia to a pH (5.35) sufficient toprecipitate any residual iron, aluminum, and chromiumprésent using air as an oxidizing agent.

The precipitate was thereafter separated frora thesolution and the nickel and cobalt solution then adjustedto a pH of about 1.5. H2S was added to precipitateselectively any copper, lead and zinc présent. Theprecipitate was separated from the solution by filtrationand the nickel recovered by various methods, one methodcomprised treating the nickel-containing solution withhydrogen at elevated température and pressure to producenickel powder.

The aforementioned process is similar to thatdescribed in "the state of the prior art" set forth inU.S. Patent No. 4,097,575, the disclosure of which isincorporated herein by reference.

The aforementioned method had certain économiedisadvantages. The conversion of mixed nickel-cobaltsulfide into salable separate nickel and cobalt products 010492 was very expensive and there was no market for mïxedsulfide précipitâtes.

It has now been discovered that a novel combinationof operational steps can be employed to separate nickelfrom cobalt and produce nickel métal directly from a leachsolution produced from a nickel oxide ore, e.g., latériteore, without going through an intermediate step ofproducing a nickel-cobalt sulfide concentrate or matte,the refining of which to recover nickel is cost-intensive.

The hydrometallurgical process employed involves theuse of a chelating ion exchange resins in which nickel ispreferentially separated from cobalt and impuritiestypically obtained in the sulfuric acid leaching oflatérite ores. While chelating ion exchange resins areknown for extracting nickel from solutions, it was notknown that, under relatively high acidic conditions,nickel can be separated from cobalt présent in latériteleach solutions and provide an eluate with a substantiallyhigh Ni to Co ratio, e.g., at least about 50:1 suitablefor recovery of substantially pure nickel by electrolysis.

In this connection, reference is made to an articledirected to Process Developments in the CobaltPurification Circuit employed at CHAMBISHI RLE COBALTPLANT of Z.C.C.M, Zambia (copyright 1993 by the Minerais,Metals & Material Society).

Reference is also made to a paper entitled"Séparation of Nickel From Cobalt in Sulphate Medium IonExchange" presented by L. Rosato et. al. at the AIMEAnnual Meeting of February 14-18, 1982, in Dallas, Texas.

The use of an ion-exchange chelating resin, such asXFS 4195, for separating nickel from a concentratedaqueous solution of cobaltous sulfate is disclosed in U.S.Patent No. 4,320,099 (March 16, 1982). 7< ' > · 4 010492

Objecta Of The Invention

It is thus an object of the présent invention toprovide a hydrometallurgical process for recovering nickeland cobalt separately from nickel oxide ores, in particular, limonite and saprolite ores.

Another object is to provide a process foreconomically recovering both nickel and cobalt.

These and other objects will more clearly appear whentaken in conjunction with the following disclosure, the .accompanying drawings and the appended daims.

Brief Description Of The Drawings

Fig. 1 is a flowsheet illustrating the process asapplied to nickel latérite ores;

Fig. 2 depicts two curves published by Dow Chemicalshowing the absorption characteristics for each of nickeland cobalt using a Dow ion exchange composition identifiedby the trade désignation XFS-4195 in which an activeingrédient thereof is comprised of bis-picolylamine;

Fig. 3 is a curve depicting the absorptionselectivity of Dow resin XFS-4195 as a function ofsolution pH;

Fig. 4 is illustrative of cumulative loading ofnickel and cobalt as a function of bed volumes of feed solutionpassed through a column of XFS-4195 resin;

Fig.5 depicts generally an ISEP configuration in the form of a carousel for carrying out the ion-exchange extractions of nickel and cobalt;

Figs. 5A and 5B are schematics shown as flow sheetsillustrating the use of said ISEP carousel configurationin carrying out the ion-exchange extraction of nickel fromsolution using the resin XFS-4915; 010492 5

Fig. 6 is illustrative of cobalt and nickel loadingat room température as a function of the number of bedvolumes (BVS/hr) passed through a column of XFS-4195resin;

Fig. 7 depicts curves illustrating the sélectivestripping of cobalt from the resin employed in extractingthe cobalt ;

Fig. 8 is a simplified schematic illustrating thecounterflow operation of the ISEP configuration through asériés of columns;

Fig. 9 illustrâtes the use of the ISEP configurationfor carrying out the Ni + Co IX (i.e. nickel plus cobaltion exchange); and

Fig. 10 is a flow sheet based on the use of a Recofloapparatus in recovering the nickel from the prégnant leachliquor, Fig. 10A being a continuation of Fig. 10.

Summarv of The Invention

Generally speaking, latérite ores (e.g. limonite andsaprolite) contain Ni, Co, Fe, Al, Mg, Mn, Cr, SiO2 and avariety of impurity éléments along with free andcrystalline water, some of which éléments and the waterare lost when the ore is heated.

An example of a limonite ore is one containing byweight 1.72% Ni, 0.14% Co, 41% Fe, 2.5% Al, 1.58% Mg, 0.8%Mn, 2.05% Cr, 12.1% SiO2 and 11.3% LOI (Loss on Ignition).

When speaking generally of latérite ores, theimportant éléments of interest are nickel and cobalt.

Such ores will generally contain by weight about 0.5%to 3% nickel and about .005 to 0.5% cobalt.

Restating it with regard to ail of the constituentsprésent, the oxide ores to which the invention is appliedmay contain by weight about 0.5% to 3% nickel, about0.005% to 1% cobalt, about 10% to 55% Fe, about 0.2% to10% Al, about 0.5% to 15% Mg, about 0.1% to 5% Mn, about 6 010492 1% to 5% Cr, about 1% to 25% Si02 and the balance loss-on-ignition constituents ranging up to about 20%.

In its broad aspects, the invention is directed to aprocess for the recovery of nickel from particulate nickeloxide ores, such as saprolites and limonites, by sulfuricacid leaching said ores to fora a prégnant solution ofmétal values, e.g., nickel and cobalt, which are recovereddirectly by ionexchange. The ore may be either atmospherically leached or pressure leached.

In a preferred embodiment, sulfuric acid leaching iscarried out at a relatively high température and pressure,e.g., 270’ and 810 psi. The advantage of employing thesulfuric acid pressure leaching process in an autoclave isthat iron is separated from the nickel by dissolving andthen reprecipitating from solution as hématite, while thenickel remains in solution. Any iron left in the leachliguor is usually in the ferrous State.

Another embodiment of the process comprises foraingan agueous slurry in the fora of a pulp of particulateoxide ore containing by weight about 1.5% Ni and about0.15% Co and leaching the ore in the présence of sulfuricacid solution at a pH of less than about 0.5. The leachingmay be carried out by either atmospheric or pressureleaching. The amount of sulfuric acid solution is atleast stoichiometrically sufficient to dissolvesubstantially the nickel and cobalt présent. In apreferred embodiment, the pulp is subjected to pressureleaching following injection of sulfuric acid at anelevated température of about 150’C to 300’C at a pressureranging from about 150 psig to 1,000 psig to solubilize atleast 80% nickel and at least about 80% of the cobaltprésent in the ore. A typical time of leaching may rangefrom about 15 minutes to 120 minutes.

Following completion of the leaching, a prégnantliquor is obtained containing said nickel and cobalt as μ·. 010492 7 sulfates and residual other éléments and undissolvedresidue as tailings.

The acid in the prégnant solution is adjusted to orprovided at a pH of about 0.5 to 4 following which theslurry is subjected to countercurrent décantation toseparate the prégnant nickel and cobalt solution from saidtailings.

The acid in the tailings is neutralized with lime orother base to a pH of about 9 and the tailings disposedof.

The prégnant nickel sulfate solution with thêcontained cobalt is contacted with an ion exchange resinunder pH conditions sélective to the absorption of nickel,while providing a raffinate containing cobalt. Theraffinate is thereafter prepared for the removal of cobaltplus any nickel remaining therein by an ion exchange resinunder conditions sélective to the absorption of cobalt andnickel.

Thus, in essence, the invention provides a processfor selectively recovering nickel by ion exchangeabsorption from a Ni/Co sulfuric acid feed solutioncontaining nickel in the range of about 0.5 to 40 gpl andcobalt in the range of about 0.01 to 2 gpl as sulfates.

The process comprises contacting the nickelcontaining acidsolution at a pH ranging from about 0.3 to 6 with a bed ofprotonated ion exchange resin in which protons associatedwith said resin are exchangeable with nickel ions in thesolution. The protonated resin selectively extracts thenickel in preference to cobalt from the solution at a pHof less than about 2. The low pH is generally achieved byproton ions entering the solution as the nickel ions areabsorbed by the resin. The absorbed nickel is thenstripped from the resin with sulfuric acid to form anickel sulfate solution characterized by a nickel tocobalt ratio of at leaSt about 50:1 suitable for therecover of substantially pure nickel by electrolysis.' 010492 8

In a preferred embodiment, the prégnant nickelsolution is passed serially through a plurality of raovingcolumns of the resin which move countercurrently to theflow of the prégnant solution entering the first coluranand exiting through the last column thereof with the bulkof the nickel removed in the initial columns and thenickel-impoverished solution containing cobalt thereafterpassing through the last column. In one embodiment, theISEP® continuous contactor manufactured by AdvancedSéparation Technologies, Inc. of Lakeland, Florida of thecarousel type is employed.

In another embodiment, the prégnant nickel solutionmay be passed serially through two stationary columns ofresin in a.Recoflo® ion exchange systera produced by Eco-Tec Inc. of Pickering, Ontario, Canada. When nickelstarts to "break through” the second column, the feedsolution is stopped and the first column only is strippedof the loaded nickel with sulfuric acid solution. Afterstripping, the feed solution is again passed through thetwo columns serially, except the second column now becomesthe ”lead” column for feeding the prégnant liquor. Whennickel begins to break through the first column, now the"lag” column, the feed solution is stopped and the secondcolumn is stripped. Then feeding commences once againwith the first column as the lead column. This iséquivalent to the counterflow ISEP® process.

The nickel absorbed by the resin is stripped withsulfuric acid to provide a prégnant solution from whichsubstantially pure nickel is recovered, such as byelectrowinning.

Similarly, the cobalt plus the remaining nickelabsorbed in a second ion exchange step is recovered bystripping with a sulfuric acid solution and the mixedcobalt nickel solution then sent to nickel/cobaltrecovery. 010492

An important économie advantage of the invention isthat sulfide précipitation of nickel and cobalt iscompletely avoided, as well as the necessity of recoveringsaid metals by pressure leaching the sulfide precipitateand refining the résultant solution which is costintensive.

The invention, on the other hand, takes a more simpleand économie route in that following the leaching of thenickel oxide ore, e.g., pressure leaching in theautoclave, the nickel is directly recovered in substantially the pure State, by pas^sing the prégnantsolution through an ion exchange resin under conditionssélective to the absorption of nickel in preference tocobalt following séparation of the leach residue from thenickel leach liguor by, for example, countercurrentdécantation of the prégnant nickel solution from thewashed residue or tailings.

Details Of The Invention

One method of carrying the invention into practice isdisclosed in the flowsheet of Fig. 1 as applied to nickel-containing oxide ores, such as limonite.

The limonite ore contained by weight 1.7% Ni, 0.15%Co, 40% Fe, 4% Al, 2% Mg, 2% Mn, 2% Cr, 10% SiO2 and 15%LOI (Loss On Ignition).

Referring to Fig. 1, the technology employed includesan ore préparation step (1) in which the coarse reject IAthereof may be used for the neutralization of excess acid.Sulfurie acid pressure leaching (2) is carried out atabout 270’C with a leaching time in the range of about 20-40 minutes and generally ranging up to 30 minutesfollowing injection of the acid into the autoclave. Leachdischarge pulp containing the tailings without prior acidneutralization is passed through a conventional countercurrent (CCD) décantation System which is used to wash soluble nickel plus cobalt values from the slurry. 010492 10

The tailings are separated from the prégnant liquor at 4and passed on.to tailings disposai at 5. Followingtailings neutralization (5) with limestone and milk oflime, in which the pH is raised to about 9, the residue isdisposed of at a tailings dam. The CCD overflow solution6 is contacted with an ion exchange resin where onlynickel (plus copper if présent) and only minor guantitiesof cobalt are loaded (7). Because nickel replaces theproton or hydrogen ion in the active part of the resin,the pH of the solution decreases during ion exchange,whereby the nickel is extracted by the resin in p'referenceto a cobalt at a pH of less than about 2.

The nickel is stripped from the ion exchange resin(7) with sulfuric acid. The nickel-containing solution isneutralized at (8A) with limestone and the neutralizedsolution subjected to solid/liquid séparation with thesolids recycled to neutralization (3) and the nickelsolution sent to nickel electrowinning (15).

The raffinate 8 with only minor amounts of nickelplus most of the cobalt and other impurities (iron,aluminum, manganèse,, magnésium, chromium, etc.), isfurther neutralized at (9) with limestone to a pH of about2 to 4. The solids and liquid are separated at (10), thesolids sent to tailings disposai (5) and the nickel/cobaltsolution (11) sent to cobalt recovery 12 with theraffinate 13 depleted in cobalt recycled to tailingsdisposai (5). The nickel/cobalt following ion exchange issubstantially pure and free of the contained impurities.

The purified cobalt solution is treated for recoveryof cobalt as a salable commodity, either by soda ashprécipitation, sulfide précipitation or electrowinning.

The nickel loaded on the resin (7) may be stripped withspent electrolyte (16) from the nickel electrowinningcircuit (15). Prior to returning the stripped resin toloading, the resin is washed with water which converts the 0 1 0492 11 resin from the bisulfate into the sulfate form, releasingsulfuric acid which can be reused for stripping.

Tests were conducted using DOW's XFS-4195 as theresin both for nickel loading as well as cobalt/nickelloading. Other resins which may be used include Rohm andHaas IR-904, Amberlite XE-318, and DOW XFS-43084. Asdisclosed hereinafter, the DOW resins hâve picolylaminesas active groups.

The DOW resins which are sold under the tradedésignations XFS-4195, XFS-4196 and XFS-43084, aremacroporous resins of polystyrene/divinylbenzene'copolymers onto which weakly basic chelating picolylaminedérivatives hâve been attached. DOW rèsin XFS 4195 is a stronger and preferredcômpleting agent for nickel than the other resinshereinabove. The functional groups in the XFS 4195 andXFS 4196 resin are more specifically referred to as bis(2-picolyl)amine and N-(2hydroxyethyl-2-picolylamine,respectively.

The XFS 43084 resin is similar to the resins above,that is, the resin is a macroporous polystyrène copolymerwith a weakly basic chelating picolylamine dérivativeattached, i.e., specifically N-(2-hydroxypropyl)-2-picolylamine.

With respect to the XFS-4195 resin, the followingTable 1 taken from the DOW literature shows the absorptionconstants of various metals. y, _ '0 12 010492 10 15 20 25 35

Table I

Table: Métal Ion Absorption by XFS-4195[Resin capacity 0.42 mol/1, sulfate solution @ pH 2) Métal ion solution (gpi) resin (gpl) resin (mol/1) K l/mole Cr(VI) 0.2 62 1.12 • Cu(H) 0.73 25 0.40 1700 V(IV) 0.68 19 • 037 560 Ni 0.88 18 031 190 Fe(IH) 0.82 19 034 84 Cd 0.73 15 0.13 69 Zn 0.83 11 0.18 59 Co(H) 0.92 83 0.14 32 Fe(H) 1.06 13 0.023 ' ' 3.1 Ca 0.16 <0.1 <0.003 <1.5 Mg 0.97 <0.1 <0.004 <03 AJ 1.07 <04 <0.004 <03

The absorption constant is really not a constant buta function of the pH, as shown in the attached Figure 2published by DOW Chemical. A DOW Chemical publicationindicates that from a practical standpoint, a resin willbe loaded to 50% of its maximum value when K=100 and when[Me] = 0.01 M (i.e. 0.6 gpl Ni). The importance of η 010492 keeping the pH low will be apparent from Figure 3. Thisfigure clearly shows that it is advantageous to keep thepH of the prégnant solution low if one wants toselectively remove nickel from latérite leach solutionscontaining nickel and cobalt. At the optimum pH of 1 theratio of the nickel and cobalt K-factors is 8 compared toaround 2 at the usual,and customary operating pH for SX orIX of 2-3. This shows an improved selectivity of about400%.

In carrying out the novel process of the invention,it is the Ni/Co ratio in the product which is important.

For example, if the Ni/Co ratio in the electro-winning ofnickel is better than 50:1 and particularly better than90:1 or 100:1,, a high quality nickel product isobtainable.

Likewise, with respect to the electrowinning ofcobalt, the Co/Ni ratios are similarly important. Anexample of a désirable ratio is a ratio which is at leàstabout 50:1 preferably 80:1 or 100:1.

Previous nickel/cobalt studies on the use of DOW XFS-4195 resin were concentrated on the removal of smallquantities of nickel from low acid, high gradecobaltiferous solutions contaminated with nickel.

Generally, these solutions contain between 20 and 100 gplCo and hâve a cobalt to nickel ratio of about 100 to 1.

Ion exchange treatment of these solutions extracted nickelbut also a great deal of cobalt. The latérite leachsolutions treated in accordance with the inventioncontained about 0.5 gpl Co and hâve a cobalt to nickelratio of 0.1 to 1. According to the method employed, ithas been possible to "crowd off" nearly ail of the cobaltfrom the resin during nickel absorption, while at the sametime extracting substantially ail of the nickel. Thus astrip solution is produced having an adéquate Ni/Co ratiofor direct electrowinning and for achieving high nickelrecovery without additional Ni-Co séparation. Thus, it is ·'<· Ψ T" 14 01 0492 now possible to extract up to 99% of the nickel withoutsignificant coextraction of cobalt (less than about 10%).

In the présent invention, much improved selectivelyof the chelating ion exchange resins with respect to 5 nickel over cobalt is achieved by controlling the conditions during resin loading to ensureêthat any cobaltloaded on the resin is displaced by nickel. Furthermore,the free acid content of the aqueous solution is alsocontrolled to prevent cobalt loading and thus increase the 10 Ni/Co ratio in the solution obtained by stripping theloaded resin with sulfuric acid. This is achieved by: 1) ensuring that "fresh" resin, i.e. resincontaining little or no extracted nickel or cobalt, iscontacted with liquor of relatively high acid content, and 15 (2) ensuring that "fresh" feed solution of relatively low acid content is contacted with resin whichhas already loaded a substantial quantity of nickel, andfurther ensuring that the resin is loaded to a level closeto its theoretical maximum capacity for nickel, i.e., the 20 level which would be achieved if a quantity of resin werecontacted repeatedly with fresh solution containing excessnickel.

Thus, cobalt loading can be substantially eliminatedand virtually-complete nickel loading can be achieved. 25 The best method of achieving these conditions is to contact resin with leach solution in-a true countercurrentfashion. Very few ion exchange Systems, however, permit resin flow and those that do suffer from the engineeringproblem of resin breakage by attrition and other 30 mechanical forces. Two other types of equipment whichallow the conditions described above to be achieved aredetailed in the examples which follow. Both of theseSystems produced "pseudo" countercurrent flow of resin andsolution, as will be described later. The first condition 35 is met because the solution naturally acidifies as nickel is loaded onto the resin by the release of protons from 15 010492 the resin. Thus, even though fresh resin may load bothcobalt and nickel, cobalt loading is impeded due to thehigh acidity (see Fig. 2). Cobalt does not load from thefresh feed solution, even though the pH may be higher,because the resin is already loaded close to its maximumcapacity with nickel and therefore thermodynamicallyincapable for cobalt to displace nickel on the resin.

Direct nickel electrowinning from latérite leachsolutions as obtained is not generally feasible because ofthe impurities présent in the solution. In particular,chromium, aluminum and iron présent a problem. In thenickel plating industry, hexavalent'chromium has to belimited to less than 10 ppm to maintain a good gualitydeposit. On the one hand, XFS-4195 has a disadvantage inthat it has a very high affinity for hexavalent chromium(it does not load trivalent Cr). Sulfurie acid strips thehexavalent chromium which normally contaminâtes theelectrolyte. Thus, it is important to keep the amount ofhexavalent Cr in the IX feed to a minimum. XFS-4195 isalso sélective for copper. Latérite leach solutions hâveup to about 50 ppm Cu and up to 300 ppm total chromium, ofwhich about 10% or more may be présent as hexavalent Cr. A pretreatment step for removing both Cu and hexavalent Crcan be included as a preferred embodiment of the

Processing invention. This pretreatment step can eitherbe a métal cementation step using iron, zinc or evennickel to reduce hexavalent Cr to the trivalent State andto cernent copper. Alternatively, an ion exchange columnmay be included that is specifically used to load bothhexavalent Cr and Cu from the leach solution. After thistreatment, the leach solution can then be treated by theion exchange approach discussed herein. Anotheralternative approach is the removal of the copper andhexavalent chromium from the prégnant electrolyte afterion exchange. 010492 16

In carrying out the invention, the best results wereobtained with a System operating under hot and acidicconditions. Both conditions are met by pressure leachingand ion exchange which provides hot and acidic solutions.Because of the natural pH of about 1 of the autoclavedischarge solution,,an efficient Ix séparation of Ni andCo obtains. Thus, the neutralization step 3 of Fig. 1 canbe omitted. In addition, ion exchange with XFS 4195 canbe carried out at températures up to at least the normalboiling point of the leach liquor? whereas, in the case ofsolvent extraction of nickel, it is generally advised tokeep the températures lower than 50 degrees Celsius andthat the pH be greater than 2. The effect of the bisulfateand sulfate equilibrium will clearly appear from thefollowing.

Nickel Ion Exchange Combined withPressure Sulfuric Acid Leaching A novel aspect of the invention is the fact that theXFS4195 resin has the ability of being converted from thesulfate to the bisulfate form by taking up sulfuric acidas follows: [R-H*. 1/2SO42’ ] + 1/2H2so4 = [R-H*.HS04‘1 (1) wherein R is the bis-picolylamine group and the bracketindicates a species in the resin phase. Alternatively, ifthe resin is in the bisulfate form, a sulfuric acidsolution can be generated when the resin is stripped withwater. (Equation 1 shifts then to the left. This abilityof the resin to extract sulfuric acid allows nickelloading onto XFS-4195 from an acidic solution becauseconversion of the resin from sulfate to bisulfate formduring nickel loading prevents the solution pH from beinglowered further, thus maintaining a relatively high nickelabsorption constant. This is illustrated by reaction (2): 2 [R-H*. 1/2SO42'] + Ni2* + SO42- = [R2-Ni2*. (HSO/) 2] (2) 17 010492

The sulfuric acid loaded on the resin at the saine time canbe stripped from it by water washing. This is clearlyadvantageous since latérite leach solutions tend to hâve ahigh acidity, which normally would hâve to be neutralizedprior to nickel recovery. A further advantage of usingacid-bearing leach solution is that Co loading can bevirtually eliminated because the solution pH is always toolow to load any appréciable amount of cobalt.

Another feature for the combined approach of theinvention is the advantages of pressure leaching with itshigh solution températures. ' There are presently· liquidorganic compounds available that can extract nickel andcobalt from latérite leach solutions. However, solutioncooling is required since solvent extraction does notoperate efficiently at températures higher than say 50'C.Ion exchange resins, on the other hand, can be beneficially used at higher températures in that theloading kinetics are favorably affected. Using naturallyhot leach solution saves on solution cooling and evenimproves the ion exchange efficiency. Another embodimentof the invention is the use of a hot resin-in-pulp (RIP)process. Solid/liquid séparation can be quite costintensive when processing chemically treated ores and thiscan be avoided by employing resin directly in the leachslurry. One example of the RIP route is illustrated byone of the following examplesï

The higher températures hâve an impact on thesulfate/ bisulfate equilibrium. Sulfuric aciddisassociates as follows:

> H* + HS04·1 > H* + SO4*2 (3) (4)

Equation (3) shifts completely to the right under ailconditions of the acid leaching process. Equation (4),however, shifts only to the sulfate side at higher pH andlower températures. The bisulfate to sulfate ratio as a 010492 18 fonction of the température and pH is calculated asfollows in Table 2. PH température HSO4‘/SO4* ratio 25* C 50e C 7FC 100° C 0.66 21 46 ν· 111 285 1.00 9.7 21 51 128 1.5 3.1 6.8 16 41 • 2.0 1.0 2.1 5.1 13 2.5 0J 0.7 1.6 4.1

It has been recommended that the IX System beoperated at a feed pH in the order of about 2 or that theraffinate has a pH of about 1. At room température, thiswill provide an HSO4/SO4 ratio of 1.0. This means that,for a solution with 50 gpl total sulfate, 50% of thesulfur or 25 gpl is présent as bisulfate and 25 gpl assulfate. Cne preferred method of carrying out theinvention is hot with about 25 gpl free acid in the leachsolution. This translates into an hso4/so4 ratio of about 50.In such a case, 98% of the sulfate is présent as bisulfatewith only 2% as sulfate, Thus, with a 50 gpl totalsulfate solution, this indicates that 49 grains arerepresented as bisulfate and only 1 gram as sulfate. Inother words, the ion exchange process can tolerate more 010492 19 free acid in solution as the process température israised.

In the flowsheet for processing lateritic ore, thekinetics of nickel loading on the resin are rather slow atroom température. It is not economically advisable toheat the solution to improve reaction kinetics. However,with respect to the invention, the leach discharge isgenerally near its boiling point and an advantage isobtained since the nickel loading will be done hot withoutthe need for additional heating. The improved kineticsusually resuit in a significant increase in resiri capacityin that, in carrying out the invention, the resin iscapable of being loaded at a rate of at 30 Bed Volumes(BV) per hour while conventionally the maximum is about 5BV/hr.

It h-as been noted that there may be a problem withrespect to both chromium and aluminura as possiblecontaminants in the electrolyte. This might occur if theion exchange resin is not washed efficiently prior tonickel stripping. Both aluminum and chromium (III) mustbe prevented from entering the nickel electrowinningcircuit. Efficient resin washing ensures they do notcontaminate the electrolyte because Cr (III) and Al do notload on the resin. The nickel sulfate feed to theelectrowinning cell generally should be at a pH of 2.5 to3.5 to obtain the best déposition characteristics. Testwork in the laboratory has shown that raising the pH ofthe eluate going to the electrolytic cell not to 2.5-3.5,but to 4.5 to 5.5, removes any aluminum and chromium whichpass through the ion exchange System, down to less thanabout 10 ppm levels. Little nickel will precipitate atthis pH. However, in order to provide the optimum cellfeed compositions, it is necessary to re-acidify the cellfeed with acid to the required lower pH.

As illustrative of the invention, the followingexample is given: 20 010492

Exemple 1

Particulate lateritic oxide ore is formed into a pulpwith water and screened at 28 mesh (U.S. Standard). Thecomposition is comprised of 1.5% Ni, 0.14% Co, 4% Al, 0.8%Mg and the balance substantially iron, i.e., 42% Fe,présent as oxides or hydroxides.

The coarse fraction (approximately +20 mesh) isseparated from the ore and may be used for atmosphericleaching by including this step in the flowsheet of Fig. 1 and thenickelcontaining solution thereof joining the prégnantleach solution at the acid neutralization station.

Preferably, the fines fraction of the ore, which ispassed to pressure leaching 2 of the flowsheet, is firstpulped with water or an aqueous solution to a pulp densityof about 35%. Sulfuric acid is added to provide an acidto ore ratio of 0.2:1 to 0.3:1 based on weight ofconcentrated sulfuric acid and the dry weight of the ore.

The pulp is pressure leached in an autoclave at atempérature of about 270eC under a total pressure of about810 psia, the sulfuric acid being added to the pulp in theautoclave by injection.

Under these conditions, the ore is leached in about15 to 60 minutes and the nickel extracted to about 95%based on the amount of nickel in the ore.

At this température, the iron and aluminum in thesolution are substantially rejected and appear in thetailings as basic aluminum sulfate (alunite) and hématite(Fe2O3) .

Following leaching, the prégnant nickel solution ispassed on to acid neutralization at (3). The solution isneutralized with limestone to a pH of about 2, after whichthe neutralized slurry is subjected to solids/liquidséparation at (4). In a preferred embodiment, theneutralization step (3) may be omitted. The separatedsolution is passed to an ion-exchange apparatus (7) 010492 21 containing an ion-exchange resin spécifie to the extraction of nickel.

In some tests, a conunercially available ion exchangeapparatus (Note Figs. 5, 5A and 5B) referred to as an"ISEP" apparatus was employed in carrying out theextraction of nickel. In other tests, the conunerciallyavailable apparatus known as "Recoflo" was used.

The ratio of nickel in the feed solution to thequantity of resin employed is such as to provide 95% ofresin loading capacity while extracting 95% of the nickel.This helps to ensure complété "crowding" off of cobalt,that is, the preferential loading of nickel over that ofcobalt.

As stated herein, a particularly advantageous ionexchange resin is one identified as DOW XFS 4195 in whichthe active ingrédient is bis-picolylamine.

Following sélective removal of nickel at (7), theraffinate remaining is subjected to acid neutralization at(9) with limestone to a pH of about 2 to 4.5, followingwhich the slurry from acid neutralization is passed tosolid-liquid séparation at (10) and the solution containing cobalt and the remaining nickel is passed on tocobalt recovery.

Reference is made to the schematic of Fig. 8 which isa simplified illustration of the general operation of theISEP configuration.

Fig. 8 is a schematic of Figs. 5, 5A and 5B,illustrating the use of a carousel, as one embodiment,comprising a sériés of resin-loaded columns 1, 2, 3 andranging up to the Nth column, arranged and adapted toprovide a serial pathway for the solution 5 from the firstcolumn to the Nth column, the interruption in the Systemat 4 indicating that other resinloaded columns may beprésent in the system between the 3rd and Nth columns.

The rotational arrangement of the columns shown in

Fig. 5 is such that the flow direction 6 of the resin- 010492 22 loaded columns of Fig. 8 (i.e., the direction of travel ofthe resin columns) is counter to the flow direction of thenickel prégnant solution through the columns as shown, i.e., countercurrent flow) whereby the resins of eachsucceeding column remove the nickel from solution with theraffinate solution 7 containing cobalt flowing out of theSystem for the subséquent recovery of said cobalt. A more detailed schematic is shown in Figs. 5A and 5Bto be discussed later.

In recovering the nickel from the prégnant solution,the acid pH is preferably maintained- at a level sélectiveto the absorption of nickel, the pH being such that thenickel crowds off or substantially inhibits the absorptionof cobalt. The nickel to cobalt ratio in the resinfollowing substantially complété recovery of nickel is atleast about 50:1 or at least 90:1 or higher.

The cobalt-containing raffinate solutionsubstantially impoverished in nickel may then be treatedafter a pH adjustment, if necessary, to recover the cobaltusing a resin and conditions sélective to the absorptionof cobalt, e.g., DOW FXS 4195.

Additional examples illustrating the novel processare as follows:

Example 2

Ion exchange tests were conducted on a nickelsulfate/cobalt sulfate.solution having a Ni/Co ratiocorresponding generally to that produced by leaching atypical limonite ore. The solution contained 12.5 gpl Niand I gpl Co and had a pH of 3. The solution had atempérature of about 25*C and was passed through a columnof diameter 1 3/16 inches containing 200 ml of DOW XFS4195 at a flow rate of 13.3 ml/min corresponding to 4BV/hr (bed volumes/hr.). Each 100 ml of the column effuentwas collected as a separate sample and assayed for Ni andCo. From the this data, the cumulative percentage loadingof Ni and Co contained in the feed solution was calculated 010492 23 and plotted as a function of the solution volume passed asshown in Fig. 4.

The curves in Fig. 4 demonstrate some selectivity forNi over Co. However, the data also show that very low Coloading, say <20%, cannot be achieved while maintainingvery high Ni loading, say >90%, in a single column. Forexample, after passing approximately 7.5 bed volumes offeed solution through the resin column, around 20% Coloading and only around 50% Ni loading were achieved. Itis apparent from this example that it would be difficultto achieve the degree of séparation,desired from a singlecolumn.

From the data of Example 1 and the selectivity dataof Fig. 3, the advantages of the présent invention arequite apparent. In such a system, fresh resin would becontacted with a solution already depleted in nickelbecause a portion of the nickel would already be loaded onthe resin further "upstream". This depleted nickelsolution would contain a higher sulfuric acidconcentration than the feed solution because acid isproduced by the ion exchange reaction as follows: [2 (RH*) (SO42')1/2] + Ni2*----> [ (R2Ni2+) (SO42-) ]+2H*

Thus, cobalt loading on the fresh resin would besuppressed due to the lower pH environment (see Figs. 2and 3), despite the fact that fresh resin normally loadsboth Ni and Co (see Fig. 4 at a low number of bed volumesfeed passed). At the solution feed inlet of the “loadingzone," partially loaded resin is contacted with fresh Niand Co bearing solution at a higher pH. At thiscondition, Co loading is suppressed because the resin isalready loaded with substantial nickel which cannot beeasily exchanged for Co, even at the higher pH of the feedsolution.

Further testwork was conducted to demonstrate that high Ni loading and very low Co loading on the resin could be achieved in a countercurrent system. For this purpose, 010492 24 two commercially available ion exchange contactors wereemployed to carry out the invention, one apparatus,(similar to Fig. 5) called an "ISEP", is manufactured byAdvanced Séparation Technologies Inc. of Lakeland,

Florida. It consists of a carousel of 30 ion exchangecolumns connected to a rotary valve arrangement at the topand bottom of the carousel as means for providing serial,flow through the columns of resin. Each rotary valveconsists of a rotating dise attached to the columns and astationary dise attached to réservoirs of the variousprocess solutions. Each stationary dise has 20 internaiports. Each column on the carousel is connected to a porton the rotating dise at the top and the bottom of thecarousel. (There are 30 columns and 30 ports in eachrotating dise.) The carousel and rotating dise portionsof.the top and bottom valve rotate continuously and theports in the rotating dise are connected to the ports ofthe stationary dise in sequence. Thus, the solutionpumped continuously into a port or ports of the stationarydise flows serially through each column in sequence as thecarousel rotâtes. A countercurrent flow of solution andresin can thus be effected in this apparatus by theaforementioned indexing means. A second ion exchange System for carrying out thenovel aspects of the invention is referred to as theRecoflo (trademark) System manufactured by Eco-Tec Inc. ofPickering, Ontario, Canada. In this System, two beds ofresin are employed. A cyclic process is used (note Fig.10) to provide in effect a partial countercurrent flowresin and solution. As will be clearly apparent from Fig.10, there are eight distinct steps in each cycle,following which the cycle is repeated.

In step 1, feed solution is passed through beds I and2 in sériés. Bed 1 has already been partially loaded withnickel in the preceding step while bed 2 contains freshresin because it was stripped and washed in the preceding 010492 25 steps. Thus, fresh feed solution is contacted withpartially loaded resin and fresh resin is contacted withpartially depleted and acidified solution as occurs in theISEP contactor.

Example 3

The stationary ports of the ISEP apparatus areillustrated in the configuration shown in Fig. 5A. Thecarousel, containing thirty 1 3/8 inch diameter by lm highcolumns of Dow XFS 4195 resin, was rotated at 0.2révolutions per hour. The direction of rotation was suchthat each column was connected to each numbered port indecreasing number sequence. For example, each columnentered the nickel loading portion of the process at port12, thus effecting a partial countercurrent flow ofsolution and resin. (Note the simplified schematic of Fig.8). As can be seen from Fig. 5A, the complété ionexchange process consisted of four steps: 1. Loading - ports 4-12 in a 3/3 series/parallelconfiguration; 2. Load wash - ports 2-3 in sériés; 3. Elution - ports 16-20 ail in parallel; and 4. Elution wash - ports 14-15 in sériés.

In addition, air was passed through ports 1 and 13 todrain out as much solution as possible between the loadingand elution zones. The load wash was required to removeimpurities in entrained feed solution from each columnprior to entering the elution zone. The elution wash wasrequired to remove entrained Ni from each column andprevent its recycle to the loading zone and also torecover sulfuric acid loaded on the resin during elution.Ail feed, wash and strip solutions were heated to 65“Cprior to entering the ISEP and each column of resin wasinsulated. 26 010492

The solution flowrates were as follows:

Feed 10.L/hr

Load Wash 2 L/hr

Strip Solution 6 L/hr

Strip Wash 6 L/hr

The compositions of the various solution streamsafter 15 hours of continuous operation in grams/liter wereas follows:

El· -Co -H. SP. Ni/Co Feed Solution 13.3 1.22 6.6 -1 (pH 3) 10.9 Dùchx’ge Ports 4-6 12.2 1.22 6.6 6.2 Dijciarge Port» 7-9 4.0 1.26 6.6 23.7 Dùchirge Pons 10-12(Fùul iùÆnjuc) Scip Solution to Ports 16-2C 0.5 1 0.88 5.3 . 17.7 108 Dùcharje Ports 16-20(Eluiie) 21.9 0.07 0.2 20.1 313 DiscEarg» Port 15(Elutioa Wuû) 0.7 -0. 0.1 93.4 Dùcharge Port 3(LoU Wuh) 12.8 1.17 Ù 2.6 There was little change in the assays of each stream with time after 15 hours of operation, indicating a closeapproach to steady-state.

Based on the raffinate and feed compositions andmeasured flow rates, the Ni and Co extractions from feedsolution were 95% and 13%, respectively, producing a Ni/Co 27 010492 ratio in the eluate of >300:1. Based on the feed solutioncomposition of 6.6 g/L Mg and the eluate composition of0.2 g/L Mg, only 1.8% of the Mg in the feed was passed tothe eluate by solution entrainment, indicating >98%washing efficiency in the load wash stage. The otherimpurities, including Al and Mn, behavéd similarly to Mg.

An examination of the free sulfuric acid assaysillustrâtes the loading and stripping of sulfuric acidwhich occurs in the elution and elution wash stages,respectively. Elution of divalent metals, such as Ni,requires theoretically 1 mole of sulfuric acid per mole ofmétal. Thus, 21.9 g/L Ni in the eluate corresponds to atheoretical acid consumption of about 37 g/L H2SO4. Theactual consumption of acid was approximately 108-20 = 88g/L H2SO4, indicating substantial loading of sulfuric acid.This occurs due to reaction (1). The high level ofsulfuric acid (93 g/L) in the elution wash streamindicates that the loaded acid is stripped from the resinin this section by reversai of reaction (1). This isimportant in order to achieve efficient utilization ofsulfuric acid in the elution stage and to ensure that theresin is in the "sulfate form" when it enters the loadingzone. If the resin entered the loading zone in the"bisulfate form", additional sulfuric acid would beliberated during loading and this would impede maximumnickel loading.

The foregoing illustrâtes the benefits of employingcountercurrent flow of resin and feed solution to achieveefficient Ni recovery and an efficient séparation of Niand Co in the feed stream. The Ni/Co ratio of 310 in theeluate is sufficient for direct electrowinning of goodquality Ni cathodes, although not of so-called Class Iquality (Ni/Co 1670:1). These cathodes would certainly beusable for stainless Steel manufacture as the main sourceof Ni for the production of stainless Steel is 28 01 0iS2 ferronickel, which typically has a Ni/Co ratio of only 30-40:1.

Example 4 5 The test configuration and flow rates in this test were exactly the same as in Example 2 except ail solutionswere maintained at ambient température, around 20’C, The various solution follows: analyses ùi_ after _ 9 hours running were as Ni/Co SQ, reed Solution 13.5 1.21 v 6.9 -l (pH 3) 11.2 Discharge Ports 4-6 10.2 1.11 5.7 7.4 . DiscHerge Ports 7*9 6.7 1.05 5.7 12.6 Dlscharge Ports 10-12(Pliai PxSùatc) 3.0 0.94 5.4 13.S Strip Solutoa to Ports 16-20 120 Discharge Ports 16-20(Eiuaw) 13.4 0.13 0.13 55.7 103 Discharge Port 15(Ziuuoa Wash) 2.3 •Ό. 0.05 111 Dlscharge Port 3 9.9$ 1.11 5.5 5.5 (Load Wuh)

In this test, Ni and Co extractions wereapproximately 74% and 6%, respectively. The advantage ofhigher solution températures is clearly seen by comparingthis resuit with the resuit of Example 3. 35 29 010492

Example 5

The configuration of the ISEP for this test was onlyslightly different from Examples 3 and 4, as shown in Fig,5B. The main différence is that the acidity of the feedsolution was 25 g/L H2SO4, which is about the naturalacidity expected for high pressure acid leach solution.Also, the strip solution was a "synthetic" spent electrolyte, as normally produced by electrowinning Nidirectly from neutralized eluate, as shown in Fig. 1.

The solution flowrates were as follows:

Feed

Load WashStrip SolutionStrip Wash 15 L/hr4 L/hr8 L/hr8 L/hr

The results of this test after 14 hours of operatingtime are given below: .....Ce Mg H, S O. f g/LKi/Cn

Ft*d Solution 10.0 0.4S 6.9 25 üiuCAig· Pca*j 4-6 5.4 0.46 3.9 22.5 üùchirp Pons 7-9 4.6 0.45 3.7 31.0 Ports 10-12(Fiaxi Rs£xau) i-.l 0.34 3.9 28.1 Strip Solution to Pons 16-20 25.3 0.13 0.54 111 Dischirse Ports 16-20(Eluxtt) 31.5 0.12 0.46 48.3 Dischvge Port 14(Elutioa Wuh) 8.8 0.03 0.15 41.3 Discbuge Port 3 10.3 0.45 3.6 20.9 (Lo*d Wuà) 010492 30

Ni and Co extractions in this test were approximately86% and 0.4%, respectively. Surprisingly, very good Niextraction was achieved despite the high acidity of thefeed solution.

Nickel and sulfüric acid mass balances using theabove data show that in the loading section net productionof H2SO4 was only 0.5 moles per mole of Ni loaded on theresin. This indicates that some sulfuric acid liberatedby Ni loading actually reloads on the resin via reaction(1), thus limiting the free acid content of the raffinateand permitting substantial Ni loading despite the highacidity of the feed solution.

The other significant advantage apparent from thisexample is that Co loading is virtually prevented bymaintaining relatively high acidity throughout the loadingzone. Thus it is possible to produce an extremely highNi/Co ratio in the eluate by this technique. The Ni/Coratio of 263 achieved in Example 4 was limited due to thepresence of Co in the synthetic nickel spent electrolyteused for elution.

From the foregoing example, it is obvious that highquality Ni cathodes could be produced by neutralizing theeluate and feeding this solution to a conventional Nielectrowinning cell.

Example 6 A test was carried out with a Recoflo apparatuscomprised of two 2 inch diameter columns 12 inches highcontaining DOW XFS 4195 resin. The two columns wereconnected in sériés and operated cyclically as illustratedin Fig. 10. The solution flow rates were maintained atabout 0.4 L/min and each solution was heated to 70*C. Thefeed solution contained 9.75 g/L Ni, 0.94 g/L Co, 2.1 g/LAl, 5.5 g/L Mg, 2.05 g/L Mn and had a pH of about 2. Thestrip solution contained 100 g/L H2SO4. A steady State 010492 31 condition was achieved after 10 complété cycles ofoperation with the following results,

The eluate was collected as two separate fractions,the first fraction consisting mainly of displaced washwater. (e/L)

SlZgA P,S.£ïclc CL) Be6 Vol. Ei £2 AJ Mg Mn Ni/Ci Feed 1.9 3.36 9.74 0.94 2.1 5.5 2.05 10.4 RaShate 1.9 3.36 .091 0.48 1.4 4.0 • 1.45 Wash 1 0.52 0.92 7.06 0.92 1.78 4.0 1.60 Eluate 1 0.30 0.53 2.53 0.34 0 0.30 0.14 Eluate 2 0.935 1.66 14.0 0.13 0.001 0.01 0.005 110 Wash 2 0.94 1.66 1.42 0.001 0.002 0.003 0.001

In practice, Wash 1 and Eluate 1 would be recycled tothe feed solution, whereas, Wash 2 would be used to makeup fresh strip solution. Based on raffinate and Eluate 2compositions, about 99% of Ni extraction and about 10% Coextraction to the product stream (Eluate 2), wêre obtainedin which'-"the product exhibits a Ni/Co ration of about110.

Example 7

Referring to the ISEP configuration, the stationaryports were arranged as shown in Fig. 9. The carousel wasrotating at 0.13 révolutions per hour. Ail feed, wash andstrip solutions were heated to 20’C prior to being fed to the ISEP apparatus. The flowas follows:

Feed

Load WashStrip SolutionStrip Wash rates of each solution were 52 L/hr5.3 L/hr 5.3 L/hr 5.3 L/hr 010492 32

After 8 hours of assays were obtained: operation, the following solution ai Ω2 Ha Feed Solution 1.04 1.06 2.14 -1.0 Discharge Ports 1-3 0.03 1.03 1.87 7.0 Discharge Ports 4-6 0.01 0.42 1.80 9.0 Discharge Ports 7-9(Final Raffinate) 0.00 0.09 1.90 10.0 Strip Solution to Ports 13-14 •195. Discharge Port 17 9.79 9.70 0.01 36. (Eluate)

Based on the eluate flowrate and composition, 96% ofNi recovery, 93% Co recovery, and «1% Mg recovery wereachieved to the product stream. 0.45 moles Ni + Co wereloaded per liter of resin in the loading step.

This example illustrâtes the ability of the ionexchange System to load both nickel and cobalt underconditions of relatively low acidity (<15 g/L H2so4) and aresin loading less than the resin maximum capacity (-0.65moles Ni+Co per liter resin). A pure cobalt plus nickelsolution is obtained which can be treated for cobaltrecovery via methods ·apparent to those skilled in the art.

Sasunpls 9, A resin-in-pulp test was carried on a prégnant leachiiquor produced as follows: A sample of limonite of 30% solids was batch leachedwith concentrated sulfuric acid in an autoclave at 270’Cto produce a leach slurry. The pH of one liter of leachslurry was adjusted to 3.7 with calcium carbonate and theslurry was then mixed with 200 mL. of Dow XFS 4195 resin 010492 33 for 2 hours at room température. The resin was recoveredfrom the slurry by screening over a 50 mesh screen. Theleach solution before and after treatment with the resinassayed as follows:

Ni Co Fe Zn Mn/ol Leach Solution 5.59 0.64 9.03 0.11 2.71 Final Solution 0.21 0.08 0.01 0.02 2.36

The pH of the solution during ion exchange, decreasedto about 2. Based on the raffinate composition Ni and Corecoveries were estimated at 96% and 88%, respectively. y

Iron and zinc were also extracted. It should be noted,however, that iron dissolution during leaching can beprevented by careful control of leaching conditions.

Thus, a substantially pure Ni and Co solution can beproduced for further processing to recover pure cobalt andpure nickel.

Although the présent invention has been described inconjunction with preferred embodiments, it is to beunderstood that modifications and variations may beresorted to without departing from the spirit and scope ofthe invention, as those skilled in the art will readilyunderstand. Such modifications and variations areconsidered to be within the purview and scope of theinvention and appended daims.

Claims (9)

1. 34 010492 WHAT IS CLAIMED IS:

   1. A process for selectively recovering nickel byion exchange absorption in preference to cobalt from aprégnant sulfuric acid solution containing about 0.5 to 40gpl Ni, about 0.01 to 2.0 gpl Co of pH ranging from about0.3 to 6, said process characterized in the steps of: neutralizing said prégnant solution toprovide a solution sélective to theion exchange absorption of said nickelin preference to cobalt by aprotonated picolylamine resin; contacting said neutralized prégnantsolution with said resin andselectively absorbing said nickel andproviding a cobalt-containingraffinate having a pH of approximately1, stripping said nickel from said resinwith a sulfuric acid solution andforming an eluate containing saidnickel; and then recovering said nickel from saideluate to provide a product in whichthe ratio of nickel to cobalt is atleast about 80 to 1. 35 010492
2. 2. The.process of claim 1, wherein cobalt is thereafter recoveredfrom said raffinate.
3. 3. The process of claim 1, wherein the absorption of nickel bythe resin is conducted at atempérature ranging from about 40° to80°C.
4. 4. The process of claim 1, wherein said resin is comprised of afirst bed and a second bed seriallyàrranged one with respect to theother, wherein said nickel-containing feedsolution is caused to flow seriallyand counter-currently therethrough bycyclically employing a plurality ofsteps, wherein during cycle operation of theion exchange process, the first bed ispartially loaded with nickel from apreceding step and wherein said secondbed is comprised of fresh resinproduced when the nickel is strippedtherefrom with sulfuric acid and theresin washed, the plurality of steps employed beingsuch that fresh feed solution iscontacted with said partially loaded resin to form a

   36 partially depleted acidified feedsolution, the partially depleted acidified feedsolution being then contacted with abed of fresh resin, such that nickel is extracted fromsaid feed solution and a cobalt-containing raffinate is obtainedhaving a pH of approximately 1.
5. 5. A hydrometallurgical sulfuric acid leachingprocess for recovering nickel from particulate nickeloxide ore containing by weight about 0.5% to about 3% Niand an amount of cobalt ranging up to about 1% by weightwhich comprises; providing an aqueous pulp of saidparticulate ore. leaching said ore at an elevatedtempérature and pressure with anaddition of an amount of sulfuric acid at least sufficient stoichiomet-rically to leach the contained nickel andcobalt and produce a prégnant solution ofnickel sulfate and cobalt sulfate at a pHof about 0.3 to 6, and produce tailings ofsaid ore, separating said prégnant solution fromsaid tailings, neutralizing said prégnant solutionsélective to the ion exchange *f·' 37 010492 absorption of nickel in preference tocobalt by a protonated picolylamineresin, contacting said neutralized prégnantsolution with said protonatedpicolylamine resin such that nickel isabsorbed in preference to cobalt and accbalt-containing raffinate isobtained having pH of approximately 1, and stripping said nickel froro said resinwith sulfurie acid and producing an eluatehaving a nickel to cobalt ratio of at leastabout 80:1.
6. 6. The process of claim 5, wherein the absorptionof nickel by the resin is conducted at a températureranging from about 40°C to 80°C.
7. 7. The process of claim 5 wherein said nickel oxideore is selected from the group consisting of limonite andsaprolite ores.
8. 8. The process of claim 1, wherein saidpicolylamine is selected from the group consisting ofbis(2-(picolyl)amine, N-(2-hydroxyethyl)-2-picolylamineand N-(2-hydroxypropyl)-2-picolylamine.
9. 9. The process of claim 5, wherein saidpicolylamine is selected from the group consisting ofbis(2-(picolyl)amine, N-(2-hydroxyethyl)-2-picolylamineand N-(2-hydroxypropyl)-2-picolylamine.