Calcium and magnesium rejection from sulphate solutions in lateritic nickel solvent extraction using Versatic 10 acid-lix 84-IC system

Transcription

1 SAIMM_43-49:Templte Jounl 5/7/08 8:17 AM Pge 223 Clcium nd mgnesium ejection fom sulphte solutions in lteitic nickel solvent extction using Vestic 10 cid-lix 84-IC system by B. Ndlovu* nd T. Mhlngu* Ppe witten on poject wok cied out in ptil fulfillment of B Eng (Met. Eng.) degee J o u n l Synopsis The wold minel industy hs ove the yes expeienced gowth in the poduction of nickel (Ni) due to its use not only in the ctlytic industy but minly lso to its demnd in the stinless steel poduction industy. Hence thee is need to poduce moe pue nd mketble gdes of Ni though the use of efficient puifiction outes such s solvent extction. The V10-LIX 84-IC system esulted in nickel (Ni) extction isothem shifting to lowe ph levels. The ph window of oppotunity fo the extction of Ni subsequently incesed in solution contining mgnesium (Mg) nd clcium (C) even though the system lso esulted in slight shifts to less positive ph vlues fo Mg nd C cuves. Results showed synegistic effect of LIX 84-IC when dded to V10 fo ll elements, Ni, Mg nd C. The ph 50 vlues fo elements Ni, Mg nd C in the V10-LIX 84-IC system wee 2.95, 8.10 nd 7.70 espectively. Comping esults obtined when using V10 lone poduced fo Ni, Mg nd C being 3.35, 0.15 nd 0.70 espectively, which ws confimtion of the synegistic shifts fo ll the elements. The (Mg-Ni) vlue ws 1.95 with no synegism nd 5.15 with synegism nd tht fo (C-Ni) ws 2.10 with no synegism nd 4.75 with synegism. This showed tht the Ni-Mg seption fcto ws eltively lge thn the Ni-C. Impoved loding nd stipping kinetics wee lso obseved. Keywods: Nickel solvent extction seption, mgnesium, clcium, vestic 10 cid nd LIX 84-IC. Intoduction The wold minel industy hs ove the yes expeienced gowth in the poduction of nickel (Ni) due to its demnd in stinless steel poduction used in consume goods, chemicl pocessing nd constuction. Moe ecently, the demnd hs been invigoted by the gowth in Chin nd the industil gowth in Euope, Jpn nd USA. Anothe pticul use is in the poduction of hydide electicl stoge cells. Figue 1 shows the wold nickel poduction sttistics since 1900, which illusttes genel incese in both poduction nd pice. Hence thee is need to poduce moe pue nd mketble gdes fo Ni though the use efficient puifiction outes such s solvent extction. Extction outes fo Ni cn be pyometllugicl nd/o hydometllugicl, with the fome hving been eplced gdully by the lte method due to expected svings on cpitl nd opeting costs s well s wy of execising moe envionmentlly fiendly metllugicl woks. Vious pocesses nd methods hve been developed to ecove Ni fom eithe the sulphide concenttes o its oxide oes, lteites, with oxide oes ccounting fo 70% of the wold s Ni esouce but only contibuting 30% of the wold s Ni equiements. Lteite oes e egded s oxidized sulfides tht hve undegone the wetheing pocess to fom oxides becuse of being close to the sufce. Lteite oe pocessing now ccounts fo the gowing popotion of Ni poduction due to the depletion of known sulphide deposits nd lso the bundnce of known, unexploited lteite esouce. Lteites e genelly low gde oes contining high mounts of cid consuming gngue. Lteite oes e difficult to concentte using the noml eduction ostleching method but new technologies such s high pessue cid lech (HPAL) hve mde Ni ecoveies fom these oes moe ttctive. Thus, gowing inteest in Ni extction fom lteite oes though HPAL nd solvent extction-electowinning pocess hs since been estblished. Thee e five well-known pocesses tht tet lteite oes by solvent extction s the min puifiction step. These include the Cwse poject, Bulong, Muin Muin, Goo nd Queenslnd Nickel pocesses. All except the Queenslnd pocess, which uses the ostlech pocess, use HPAL method lthough the down-stem pocesses fo the seption of Ni fom impuities diffe fo ech one of them (Denegn, 2006; Sole, 2001 nd 2007; Tskiidis, 2003 nd 2004). Solvent extction (SX) plys mjo pt in hydometllugicl Ni pocessing. SX is method used fo the emovl, seption nd concenttion of metllic species in n queous * Deptment of Mteils Science nd Metllugicl Engineeing, Univesity of Petoi, South Afic The Southen Aficn Institute of Mining nd Metllugy, SA ISSN X/ Ppe eceived Feb. 2008; evised ppe eceived M P p e The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 108 NON-REFEREED PAPER APRIL

2 SAIMM_43-49:Templte Jounl 5/7/08 8:17 AM Pge 224 Clcium nd mgnesium ejection fom sulphte solutions Figue 1 Wold nickel poduction nd pices since 1900 (Goonn T.G. et l., 2006) medi. Common impuities dissolved in solution include clcium (C), zinc (Zn), mgnesium (Mg), ion (Fe) nd mngnese (Mn). Fo Mg, up to 16g/l in solution hs been found to esult fom leching of nontonitic clys, lteite oe, in the Bulong pocess (Kdkis et l., 2005) pio to Ni solvent extction. Clcium lso occus in significnt mounts nd thus the emovl of these two elements is essentil to void build-up in eciculting stems. Exmples of extctnts mostly used in the ecovey of Ni in solution e Vestic 10 (V10), di-2-ethylhexyl phosphoic cid (D2EHPA) nd Cynex 272 nd 301. V10 hs been found to give vey positive esults nd thus been extensively used in mjo Ni SX woks. Howeve, V10, cboxylic cid, displys eltively poo selectivity towds Ni ove some common impuities such s Mg, C nd feous Fe (Peston et l., 2000) when used s stndlone egent. Futhemoe, V10 hs disdvntge of high wte solubility t elevted ph levels of 6 7 equied fo Ni ecovey; 150 ppm t ph 6.5 (Schekes et l., 2006). Extction t low ph levels will vstly educe its losses. The sech fo ltentive extctnts nd the genel eluctnce to develop new egents by mnufctues due to costs hs led to the development of mixtues of solvents with impoved extction powe nd enhnced mss tnsfe nd kinetics though phenomenon clled synegism. Numeous synegistic systems hve been studied, which use V10 s the mjo extctnt due to its eltively impoved selectivity, vilbility nd low cost when mixed with solvents such s lkylpyidines (Peston et l., 2000) nd hydoxyoximes such s LIX 63 (Cheng, 2006). Synegism between ketoxime nd V10 hs not yet eceived much ttention even though pevious epots declined this possibility due to ssumed significnt intection between the oxime nd V10 vi hydogen-bond fomtion, which educes the mount of fee extctnt vilbility (Peston, 1983). This obsevtion ws the dive of the cuent investigtion. Conty to the ppe by Peston (1983), n investigtion into the possibility of using ketoxime, LIX 84-I, s n extctnt in Ni SX poved successful (Mckenzie et l., 2006). In s much s LIX 84-I hs extensive use in coppe SX cicuits (Sole, 2007), its use in HPAL Ni lteite tetment is eqully significnt in pocesses such s the Cwse nd the Queenslnd. LIX 84-I bsed cicuits hve emeged s stong cndidtes fo mny new lteite nickel pojects (Mckenzie et l., 2006). Fo this eson, LIX 84-I, lso known s 2-hydoxy-5 nonylcetophenone oxime, cn be consideed to be n effective extctnt, which my be enhnced in synegistic system with n eqully poweful egent such s V10. Although Co in mny Ni extction cicuits is bypoduct, it is egded s n impuity when it comes to Ni solvent extction. Selectivity fo Ni in the pesence Co is poo. Howeve, impovements cn be mde by contolling the oxidtion stte of Co (Sole, 2007). Coblt co-loding in Ni SX by LIX 84-I cuses ognic degdtion in the pocess (Mckenzie et l., 2006). Pio Co emovl is theefoe essentil nd this cn be done by using Cynex 272 (Tskiidis, 2003 nd 2004). The cuent wok dopted system whee Co hs been emoved nd the only impuities pesent e Mg nd C. Fom this citeion, the Bulong pocess fits into this desciption s it lso pocessed sulphte bsed solutions. Expeimentl pln Ognic solution Vestic 10 (V10) cid used in this study ws supplied by Chem Quest South Afic. V10 is synthetic C10 cboxylic cid, lso known s Neodecnoic cid. It is deived fom C9 olefin nd displys specific bnching t the lph position nd hs high tetiy cid content, whilst lso exhibiting low cid stength nd outstnding solubility in ognic diluents, nd emining negligibly soluble in wte (Vestic 10 poduct dt sheet, Chem quest). The stuctue of V10 my be epesented s follows: whee R 1 nd R 2 e lkyl goups, contining 9 cbon toms togethe. The molecul weight is 172 nd the density (24 C) is 0.91 g/cm3. The woking ph of V10 is genelly between 4 nd 8. The ode of extction of metl ctions by V10 follows the ode of hydolysis constnts of metl ions (Tskiidis et l., 2004). LIX 84-IC ws supplied by the Cognis Cop. South Afic (SA). LIX 84-IC flls unde the LIX 84-I seies, which includes LIX 84-INS. These egents e blend of the ketoxime 2-hydoxy-5-nonylcetophenone oxime in hydocbon diluent. LIX 84-IC is concentted vesion of LIX 84-IC, concentted by fcto of 1.4 on volume bsis. The stuctue of LIX 84-IC my be epesented s follows: whee A is CH 3 nd R is C 9 H 19 o C 12 H 25 The molecul weight of LIX 84-IC is 263 nd hs density (25 C) of ound 0.94 g/cm3. Both extctnts wee used without futhe puifiction. The ognic solution ws peped by diluting V10 nd LIX 84-IC to 0.5 M in xylene obtined fom Meck Chemicls SA. 224 APRIL 2008 VOLUME 108 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

3 SAIMM_43-49:Templte Jounl 5/7/08 8:17 AM Pge 225 Clcium nd mgnesium ejection fom sulphte solutions Aqueous solution The test ws specificlly pefomed to lteitic HPAL type lech solution pio to electowinning. An ssumption mde ws tht most of the Co would hve been emoved elie in the pocess. A synthetic Bulong pocess Ni SX feed contining 3.0 g/l Ni2+, 15.0 g/l Mg2+ nd 0.5 g/l C2+ ws peped by dissolving AR gde NiSO 4.6H 2 O, AR gde MgSO 4.7H 2 O nd AR CSO 4.2H 2 O espectively in distilled wte. These chemicls wee supplied by Meck Chemicl SA. No initil ph djustments wee mde to the solution except on equilibium. Shke-out tests All btch tests wee conducted t 40 C t n O:A tio of 1:1. A 200 ml ecto ws used fo mixing the ognic nd the queous solutions using mgnetic stie using 20 mm mgnetic followe to sti t 750 pm. Anlyticl gde sulphuic cid (H 2 SO 4 ) nd sodium hydoxide (NOH) wee used to djust the ph of the solution s equied. Afte mixing fo 15 minutes, pedetemined time, the mixtue ws llowed to settle fo 3 minutes to septe. A 20 ml smple of the queous phse ws tken fo ph mesuement nd the ph djusted by eithe ddition of H 2 SO 4 o NOH. Afte mixing fo nothe 15 minutes, the mixtue ws llowed to septe nd the ph ws mesued nd djusted. The test ws continued until the equilibium ph ws obtined, fte which n queous solution smple ws tken fo chemicl nlysis. The schemtic expeiment set-up is shown on Figue 2. highe vilbility of LIX 84-IC to extct Ni thn V10 only. Two moles of LIX 84-IC (Sole, 2007) s comped to fou moles of V10 e equied to tke up single Ni mole. This is illustted by Equtions [2] nd [3] fo LIX 84-IC loding nd V10 espectively. LIX 84-IC : 2RH (og) + Ni2+ (q) R 2 Ni (og) + 2H+ (q) [2] V10: 4RH (og) + Ni2+ (q) R 2 Ni2RH (og) + 2H+ (q) [3] The fct tht the LIX 84-IC cuves e t eltively highe ph vlues thn the V10-LIX 84-IC mixtue is evidence tht LIX 84-IC is not the only ctive egent to extct Ni but synegistic effect esulted due to the ddition of LIX 84-IC to V10. A shift to lowe ph vlues hs n dded benefit of educing V10 losses to the queous solution nd lso educes the cost of neutlizing egent dditions. Veifiction of esults ws done by sending set of smples to n extenl J o u n l P p e Chemicl nlysis All the chemicl nlyses wee conducted on the queous phse using GBC909 tomic dsoption (AA) mchine. Fo esults, veifiction puposes, some smples wee submitted to n extenl lbotoy, UIS Anlyticl Sevices, which used the ICP type nlysis by OES Pekin Elme Optim 3000 mchine. The mount of metl loded on the ognic ws clculted s the diffeence between the initil concenttion nd tht fom queous solution nlysis. The % extction ws clculted by the following fomul: Figue 2 Expeimentl set-up [1] whee %E = Extction (%) n M,q,i = Initil mount of metl in queous solution n M,q,f = Finl mount of metl in queous solution (ffinte) Results nd discussion ph-metl extction isothems ph-extction isothems fo Ni, Mg nd C wee detemined by shke-out tests t diffeent equilibium ph vlues with O:A tio of 1:1. The ph-extction isothems t 40 C of the thee elements of inteest wee detemined fo 0.5 M V10 (Figue 3), 0.5 M LIX 84-IC (Figue 4) s well s mixtue of 0.5 M V10 nd 0.5 M LIX 84-IC (Figue 5). The V10- LIX 84-IC system esulted in the shift of the Ni ph-extction isothem to lowe ph levels, theeby widening the gp between Ni nd the impuities Mg nd C. A ph window of oppotunity ws obseved to be between ph 5 nd 6 (Figue 5). The explntion ws ssumed to be due to Figue 3 ph dependence of 0.5 M V10 in xylene with Ni, Mg nd C t 40 C with O:A = 1:1 Figue 4 ph dependence of 0.5 M LIX 84-IC in xylene with Ni, Mg nd C t 40 C with O:A = 1:1 The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 108 NON-REFEREED PAPER APRIL

4 SAIMM_43-49:Templte Jounl 5/7/08 8:17 AM Pge 226 Clcium nd mgnesium ejection fom sulphte solutions Figue 5 Extction ph isothems of Ni, Mg nd C by mixtue of 0.5 M V10 nd 0.5 M LIX 84-IC in xylene t 40 C with O:A = 1:1 Figue 6 Vlidtion of esults obtined fom expeiment (AA mchine) with those fom n extenl lbotoy UIS (ICP) lbotoy, UIS nlyticl lbotoies. A compison between the esults obtined fom the AA nd those supplied by UIS is shown in Figue 3, in the fom of eo bs, nd Figue 6. It is ppent tht the two sets of esults e eltively in good geement. Futhe nlysis ws done by plotting the esponse fo individul elements Ni (Figue 7), Mg (Figue 8) nd C (Figue 9) to V10, LIX 84-IC s well s the mixtue of V10 nd LIX 84-IC. These plots wee mtched to those fom pevious studies in which V10 diluted in Shellsol 2046 (S2046) ws used s n extctnt t 40 C with O:A tio of 1:1 (Denegn, 2006). It is impotnt to note tht compison ws done with system tht used diffeent diluent, S2046 insted of xylene. Howeve, it hs been epoted by Peston (2000) tht the extction of Ni is not getly ffected by the diluent in the ognic phse (Peston, 2000). The plots showed get similities in isothems involving extctions by 0.5 M V10 fo both the expeiment nd those by Denegn. The significnt shift in Ni extction isothem to lowe ph levels ws clely illustted in the V10-LIX 84-IC system s well s slight shifts to less positive ph vlues fo Mg nd C cuves, with C hving mjo shift. This showed synegistic effect of LIX 84-IC fo ll elements Ni, Mg nd C. The ph 50 (the ph fo 50% extction) vlues fo Ni, Mg nd C in the V10-LIX 84-IC system e shown on Tble I, with ll vlues being positive. This ws confimtion of the synegistic shifts obseved of ll the elements unde considetion. The ovell seption fctos between Ni nd the impuities consideed wee shown by the (metl-ni) (the diffeence between the ph vlues fo 50% extction of the impuity nd Ni befoe nd fte LIX 84-IC ddition) vlues. Tble II is summy of the esults. The diffeence in (Metl-Ni) vlues show tht the Ni-Mg seption fcto is eltively lge thn tht of Ni-C. Effect of vibles In ode to obtin the optimum conditions fo extcting Ni nd effectively ejecting C nd Mg, fctoil design ws pefomed to investigte the effects of vibles on extction. Fistly the ph ws fixed t ph 4 nd the effect of LIX 84-IC concenttion on extction ws detemined t constnt V10 concenttion of 0.5 M nd fixed tempetue of 40 C. The effect of vious combintions on two-level vible bsis ws lte tested t fixed tempetue of 40 C. Fo chosen combintion of ph, LIX 84-IC concenttion nd O:A tio tempetues of 25, 35, 40 nd 50 C wee eventully tested. Figue 7 ph dependence of 0.5 M V10 in xylene, 0.5 M LIX 84-IC in xylene, 0.5 M V10 nd 0.5 M LIX 84-IC in xylene nd 0.5 V10 in Shellsol 2046 fo Ni t 40 C with O:A = 1:1 Figue 8 ph dependence of 0.5 M V10 in xylene, 0.5 M LIX 84-IC in xylene, 0.5 M V10 nd 0.5 M LIX 84-IC in xylene nd 0.5 V10 in Shellsol 2046 fo Mg t 40 C with O:A = 1:1 Figue 9 ph dependence of 0.5 M V10 in Xylene, 0.5 M LIX 84-IC in Xylene, 0.5 M V10 nd 0.5 M LIX 84-IC in xylene nd 0.5 V10 in Shellsol 2046 fo C t 40 C with O:A = 1:1 226 APRIL 2008 VOLUME 108 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

5 SAIMM_43-49:Templte Jounl 5/8/08 1:36 PM Pge 227 Clcium nd mgnesium ejection fom sulphte solutions Tble I Expeimentl esults fo the 0.5 M V10-0.5LIX 84- IC system t 40 C with O:A = 1:1 Expeiment 0.5 M V10 ph Ni Mg C No Synegism ph M LIX 84-IC ph LIX 84-IC concenttion effects Figue 10 shows the effect of LIX 84-IC concenttion t ph 4. Thee is genel incese in Ni extction with LIX 84-IC concenttion ccompnied by simultneous decese in Mg nd C extctions. This shows the high selectivity of the system fo Ni ove Mg nd C. Futhemoe, esults showed tht thee is no need to incese LIX 84-IC concenttion beyond 0.45 M, othewise ny benefits in tems of extction cn only be elized t 0.6 M. Vious combintions of vibles A two-level sttisticl design ws pefomed to obtin the optimum conditions. Tble III shows the fctos, vibles nd the levels investigted fo vious combintions fo fixed tempetue of 40 C. The fixed fctos tht wee consideed wee; 0.5 M V M LIX 84-IC ph 5.00 O:A tio of 1:1 The esults fo the unique combintions fo diffeent tetment codes e shown in Tble IV. The bc tetment code with 0.5 M V10, 0.45 M LIX 84-IC, ph 5.00 nd O:A tio of 1:2 ws chosen s the one which gve optimum condition due to low mounts of Mg nd C being coextcted with Ni. The othe benefits of this combintion e the cost svings on ognic utiliztion since the concenttion of LIX 84-IC used is low 0.45 M t n O:A tio of 1:2. Effect of tempetue The effect of tempetue ws then studied fo the bc combintion. Figue 11 illusttes the plot obtined fom this test. Thee is genel incese in Ni extction with tempetue. The esults showed tht the optimum esonble tempetue to wok t is 40 C being in mind tht woking t 50 C my esults in extensive evpotion of the ognic phse, esulting in eltive incese in ognic losses. Ovell 0.5 M V10, 0.45 M LIX 84-IC, ph 5.00, O:A tio of 1:2 nd tempetue of 40 C wee consideed s the optimum conditions fo Ni extction fo this pticul study. Loding nd stipping kinetics wee then investigted unde these conditions. Kinetics Loding Loding expeiments wee conducted t 0.5 M V10, 0.45 M LIX 84-IC, ph 5.00, O:A tio of 1:2 t tempetue of 40 C. Figue 12 shows the esults of this test. In compison to the V10-LIX 63 system (Cheng, 2006), the V10-LIX 84-IC hs impoved kinetics with 95% extcted within 1 minute s comped to ppoximtely 60% fo the V10-LIX 63 system. Tble II Results fo the V10 lone (no synegism) nd the V10-LIX 84-IC system t 40 C with O:A = 1:1 0.5 V10 Diffeence (synegism No synegism 0.5 M LIX 84-IC no synegism) (Mg-Ni) (C-Ni) Figue 10 Effect of LIX 84-IC concenttion on Ni, Mg nd C extction t ph 4 nd T = 40 C Tble III Tetment code, vible nd level of investigtion Fcto Vible Level High Low ph b [LIX 84-IC] c O:A J o u n l P p e Tble IV Expeiment esults t 40 C fo the diffeent tetment codes to investigte the effects of vible levels Tetment Code [V 10] [LIX 84-IC] ph O:A Temp ( C) Ni Mg C %Extction %Extction %Extction : b : b : c : c : bc* : bc : * Chosen combintion The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 108 NON-REFEREED PAPER APRIL

6 SAIMM_43-49:Templte Jounl 5/7/08 8:17 AM Pge 228 Clcium nd mgnesium ejection fom sulphte solutions Stipping Stipping kinetics investigtions wee conducted on the loded ognic, loded unde the elie detemined optimum conditions. The loded ognic solution ws initilly scubbed with solution contining 15 g/l Ni t n A:O tio 4:1. No ph djustments wee mde. Depending on the vilbility of the loded ognic solution, between ml, stipping kinetic tests wee conducted. As comped to the V10-LIX 63 system (Cheng, 2006), impoved stipping kinetic on the loded V10-LIX 84-IC system wee obtined t n A:O of 1:1 fo the 40 C tempetue. Figue 13 shows the esults obtined. Within 5minutes 95% of Ni ws stipped s comped to the 32% in the V10-LIX 63 system. Figue 11 Effect of tempetue on Ni extction by the 0.5 M V M LIX 84-IC in xylene t ph 5.00 with O:A = 1:2 Figue 12 Nickel loding kinetics fo V10-LIX 63 t O:A tio 1:1 nd V10- LIX 84-IC systems t 40 C with O:A = 1:2 t ph 5.00 Figue 13 Nickel stipping kinetics fo V10-LIX 63 nd V10-LIX 84-IC systems t 40 C with A:O = 1:1 t ph 5.00 Conclusion The conclusions dwn up e s follows: LIX 84-IC hs synegistic effect when mixed with V10 fo Ni, Mg nd C. The Ni extction cuve ws shifted most significntly while those fo Mg nd C wee slightly shifted to lowe ph levels when LIX 84-IC ws dded to V10. This showed highe selectivity fo Ni by the V10-LIX 84-IC system. A ph window of oppotunity between ph 5 nd 6 esults in 100% Ni extctions. Impoved loding nd stipping kinetics wee obseved. Aspects of costs of using combintion of the two egents fo possible commecil use cn lso be looked t. The system my offe svings on ognic egent costs since n O:A tio of 1:2 cn give eqully good esults. Anothe benefit to this system is the extction of Ni t low ph vlues (100% extction ph 5 to 6), which lso offes svings on neutliztion egent dditions comped to woking t typicl Ni SX ph levels of ound 6.5 o moe. Futhe test wok is equied in ode to consolidte these esults. Acknowledgements The uthos wish to cknowledge the ssistnce povided by Angus Fethe fom Cognis Cop South Afic with the supply of LIX 84-IC nd its dt. The geneous ssistnce of Ms Lilin (LD) Blow fom the deptment of mteil science nd metllugy, Univesity of Petoi, is getly ppecited. We would like to expess ou sincee thnks to UIS nlyticl lbotoies fo the dditionl chemicl nlysis. Deon vn Rensbug fom Chem Quest South Afic fo the supply of vestic 10 cid is lso thnked. Sthembile Mkont nd Nkhumeleni Tshiongo, thei suppot is lso ppecited. Refeences 1. CHENG, C.Y. Solvent extction of nickel nd coblt with synegistic systems consisting of cboxylic cid nd liphtic hydoxyoxime, Hydometllugy, 2006, vol. 84, pp DENEGAN, S. Diect solvent extction of nickel t Bulong opetions, Minels Engineeing, 2006, vol. 19, pp GOONAN, T.G. nd KUCK, P.H. Nickel sttistics, U.S. Bueu of Mines nd U.S. Geologicl suvey Minels Yebook, Octobe KARADAKIS T., AGTZININI-LEONARDOU, S. nd NEOU-SYNGOUNA, P. Removl of mgnesium fom nickel lech liquos by chemicl pecipittion using clcium hydoxide nd the potentil use of the pecipitte s fille mteil, Hydometllugy, 2005, vol. 76, pp MACKENZIE, M., VIRNIG, M. nd FEATHER, A. The ecovey of nickel fom high-pessue cid lech solutions using mixed hydoxide poduct LIX84-INS technology, Minels Engineeing, 2006, vol. 19, pp PRESTON, J.S. Solvent extction of nickel nd coblt by mixtues of cboxylic cids nd non-chelting oximes, Hydometllugy, 1983, vol. 56, no. 1, pp PRESTON, J.S. nd DU PREEZ, A.C. Seption of nickel nd clcium by solvent extction using mixtues of cboxylic cids nd lkylpyidines, Hydometllugy, 2000, vol. 58, pp SCHEKERS, M.J. nd DUPREEZ, H. Solvent extction fo seption of goups of bse metls, United Sttes Appliction, June SOLE, K.C. Solvent extction in moden bsed-metl hydometllugy, 6th Wold Congess of Chemicl Engineeing, Melboune, Austli, Septembe SOLE, K.C. Shot couse: Solvent extction nd ion exchnge, Anglo Resech nd Mtomo Pojects TSAKIRIDIS, P.E. nd AGATZINI, S.L. Pocess fo the ecovey of coblt nd nickel in the pesence of mgnesium nd clcium fom sulphte solutions by Vestic 10 nd Cynex 272, Minels Engineeing, 2004, vol. 17, pp TSAKIRIDIS, P.E. nd AGATZINI-LEONARDOU, S. Pocess fo the ecovey of coblt nd nickel in the pesence of mgnesium fom sulphte solutions by Cynex 272 nd Cynex 302, Minels Engineeing, 2004, vol. 17, pp APRIL 2008 VOLUME 108 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy