Solvent extraction test work to evaluate a Versatic 10/Nicksyn synergistic system for nickel-calcium separation

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1 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 633 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system fo nickel-clcium seption by R. du Peez*, M. Kotze, G. Nel, S. Donegn, nd H. Msiiw J o u n l Synopsis Tti Nickel is cuently opeting hydometllugicl demonsttion plnt in Botswn, using the Activox pocess developed by LionOe Technology to poduce nickel cthode nd coblt slt fom sulphide concentte. Coblt is extcted using Cynex 272. This egent lso extcts ll the ion, luminium, coppe, zinc, nd mngnese fom the nickel stem. Vestic 1 cboxylic cid is then used s extctnt to ecove nickel fom the stem, septing it fom clcium nd mgnesium, nd upgding it to povide suitble dvnce electolyte fo nickel electowinning. Howeve, the selectivity of Vestic 1 fo nickel ove clcium is limited, nd gypsum fomtion in the extction cicuit is poblem when ttempts e mde to mximize the ecovey of nickel. Mintek hs developed synegistic system with Vestic 1 fo impoved seption of nickel fom clcium nd mgnesium. Lbotoy testwok ws conducted on the ffinte of the coblt solvent extction cicuit to optimize the Vestic 1/Nicksyn (Mintek synegist) system to be employed. Extction nd stipping pmetes suitble fo this stem wee optimized in the lbotoy nd then pplied on the demonsttion plnt. A commecil btch (.5 tons) of Nicksyn egent ws poduced fo the demonsttion plnt. The lbotoy testwok esults nd the demonsttion plnt pefomnce e discussed in detil in this ppe. Intoduction Nickel cthode nd coblt slt e cuently being poduced by Tti Nickel in Botswn fom sulphide concentte. The Activox technology is employed fo leching, followed by oxidtive pecipittion of ion, pecipittion of luminium, coblt solvent extction using Cynex 272, nd finlly nickel solvent extction using Vestic 1 cid. Coblt solvent extction lso emoves esidul ion, zinc, luminium, mngnese, nd coppe quntittively fom the solution. The Vestic 1 cid cicuit pimily septes nickel fom clcium nd mgnesium. The Tti demonsttion plnt cuently uses five stges in the nickel solvent extction cicuit, nd the nickel loss to the ffinte is.8 g/l (fom n 18 g/l feed, bout.5% Ni loss). Although the Ni cicuit hs been pefoming on tget fo the lst thee yes, ecovey of nickel could be impoved by incesing the ph pofile coss the extction cicuit, o incesing the numbe of extction stges. The cuent cicuit lso elies on fesh wte being dded to the feed to the extction cicuit, which dilutes the clcium concenttion fom ound 6 mg/l to 545 mg/l. This tnsltes to n incese in the volumetic flowte of bout 1%, nd hence lowe nickel thoughput in the cuent plnt. A plnt 1% lge would be equied fo the full-scle opetion of the cuent system. To incese the ph pofile coss the extction cicuit would not esult in n incese in cpitl costs, but it cuses the fomtion of gypsum in the fist nd second extction stges (even in the diluted feed). Additionl extction stges would incese the poject s cpitl costs. It would be mjo benefit in tems of cpitl nd opeting costs if the dilution of the feed wee to be educed o no longe equied. Hence, Tti Nickel investigted the use of the Vestic 1/Nicksyn system fo the seption of nickel nd clcium fom stem stuted in clcium (ound 6 mg/l, equied no dilution of the coblt solvent extction ffinte). Mintek hs published numeous ppes since the ely 199s bout its development wok on synegistic systems fo the ecovey of nickel nd coblt fom lech liquos stuted in clcium.1,2 Moe ecently, Mintek secued commecil poduce of the Nicksyn egent. Tti Nickel subsequently puchsed commecil btch of this egent, which ws evluted on the demonsttion plnt. * Mintek, South Afic. BHP Billiton, South Afic. LionOe South Afic (Pty) Ltd. Tti Nickel Botswn. The Southen Aficn Institute of Mining nd Metllugy, 27. SA ISSN X/ This ppe ws fist published t the SAIMM Confeence, Bse Metls 27, July 27. P p e The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 17 NON-REFEREED PAPER OCTOBER

2 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 634 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Expeimentl pocedues Anlyticl methods All metl nlyses wee done by Mintek s Anlyticl Sevices Division. Aqueous smples wee nlysed fo Ni, Co, C, Cu, Zn, Mn, Fe nd Mg (detection limit 2 mg/l fo ll metls) using Inductively Coupled Plsm Opticl Emission Spectoscopy (ICP-OES). Ognic smples wee stipped with sulphuic cid (1 M) t n ognic-to-queous (O:A) phse tio of.5, fte which the stip liquos wee submitted fo nlysis. The concenttion of Vestic 1 (V1) in the ognic phse ws detemined by potentiometic tittion of smple (4 ml) dissolved in ethnol (25 ml) nd wte (1 ml) ginst stndd sodium hydoxide solution (.1 M, mde up fom Meck mpoule), using clibted combined glssefeence electode. Ognic phses Vestic 1 cid, V1 ( tetiy-bnched cboxylic cid), ws obtined fom Chemquest (poduced by Resolution Pefomnce Poducts Ltd.), whilst Nicksyn ws peped fo Mintek in lge btch (3 kg) by n independent, eputble mnufctue. The chemicl composition of, nd technicl infomtion bout Nicksyn emins the sole popety of Mintek, nd cn theefoe not be disclosed. Appopite dilutions of V1 lone nd V1 mixtues with Nicksyn wee done using n liphtic hydocbon diluent, Shellsol D7, which ws obtined fom Shell Chemicls. This diluent ws used, s it ws the diluent employed on the Tti Nickel demonsttion plnt. Ognic phses wee used s supplied, without ny futhe puifiction. Metl-distibution equilibi fo extction (ph vs. extction) Metl-distibution equilibi (ph vs. extction isothems) wee detemined by contcting the equied ognic phse (1. M V1 lone o mixed with.2 1. M Nicksyn in Shellsol D7) with Tti Co SX ffinte t n O:A phse tio of 2, using pid mgnetic stiing nd contolling the tempetue t 35ºC in wte-jcketed glss vessel. The ph vlue of the queous phse ws djusted by the ddition of mmoni solution (25 m/v%). Equilibium ws estblished between 1 to 15 minutes fte lkli dditions. Smples (15 ml queous nd 3 ml ognic) of ech phse wee tken fte ech djustment of ph. Aqueous smples wee submitted fo nlysis. No ognic smples wee stipped fo nlysis. Distibution isothems fo extction The equied potions of ognic phse ( M V1 mixed with.25.5 M Nicksyn in Shellsol D7) nd queous phse (Tti Co SX ffinte) wee contcted t diffeent O:A phse tios (1:8 to 8:1) by mens of pid mgnetic stiing nd contolling the tempetue t 35ºC, using wte-jcketed glss vessel. A contct time of 1 to 15 minutes ws llowed to ech equilibium. The ph vlues of the queous phses wee contolled s equied, using mmoni solution (25 m/v%). Smples of the queous phses wee submitted fo nlysis. Smples of the ognic phses wee tken immeditely fte the queous smples to pevent possible e-equilibtion, nd stipped with sulphuic cid solution (1 M, O:A =.5). The stip liquos wee submitted fo nlysis. Distibution isothems fo stipping Ognic phse (1.25 M V1 mixed with.31 M Nicksyn in Shellsol D7) ws btch-loded by contcting potion (5 ml) of fesh ognic with Tti Co SX ffinte (555 ml, O:A =.9), contolling the ph t 6., using mmoni solution (25 m/v%) t mbient tempetue. Smples (1 ml queous nd 9 ml ognic phse) wee tken fo nlysis. The ptilly loded ognic phse ws then contcted fo second nd thid time in the sme mnne, using fesh potion of Tti Co SX ffinte ech time. Smples of the ognic phses wee stipped with sulphuic cid (1 M, O:A =.5), nd the stip liquos s well s the queous smples tken wee tested fo nickel by mens of tomic bsoption. The btch-loded ognic phse obtined ws then contcted with synthetic spent electolyte (61 g/l nickel in 4 g/l sulphuic cid solution) t diffeent O:A phse tios (1:8 to 8:1) t 35ºC by mens of mgnetic stiing in wtejcketed glss vessel. A contct time of 1 to 15 minutes ws llowed to ech equilibium. Smples of the queous phses wee submitted fo nlysis. Smples of the ognic phses wee tken immeditely fte the queous smples, to pevent possible e-equilibtion, nd estipped with sulphuic cid (1 M). The estip liquos wee submitted fo nlysis. Acid extction by ognic phse Aliquots of n queous phse (2 ml) consisting of 4 g/l sulphuic cid nd 133 g/l sodium sulphte (simulting typicl spent electolyte contining no nickel), wee djusted to the equied ph vlue using 1 M sodium hydoxide solution, nd contcted with the ppopite ognic phse (1.25 M V1 plus.31 M Nicksyn in Shellsol D7, 2 ml) t 35ºC. A smple of the ognic phse (5 ml) ws stipped with wte (5 ml) nd the esulting queous phse ws septed nd titted ginst.1 M sodium hydoxide solution to bomothymol blue endpoint (ph ~ 8.5). The ph vlue of the ffinte ws mesued. Stbility of Nicksyn Stbility tests wee cied out by contcting potion (5 ml) of ognic phse (1.25 M V1 cid plus.31 M Nicksyn in Shellsol D7) with synthetic spent electolyte (5 ml, contining 55 g/l nickel in 4 g/l sulphuic cid) by pid mgnetic stiing in scew-top bottle of 1 lite cpcity, themosttted t 35 C, to simulte stipping conditions ove peiod of 9 dys. The bottles wee weighed peiodiclly to check fo possible evpotion losses, but none wee detected. A simil set-up ws done by contcting nothe potion (5 ml) of the sme mixed ognic phse with Tti Co SX ffinte (5 ml) nd djusting the ph vlue to 6. using mmoni solution (25 m/v%, 17.8 ml) in ode to simulte extction conditions. Smples of the ognic phse (115 to 12 ml) of the expeiment simulting stipping conditions wee tken t suitble intevls, fte which the queous phse ws eplced with the ppopite volume of fesh synthetic spent electolyte to mintin n O:A phse tio of 1. Metl-distibution equilibi (ph vs. extction) wee detemined on potion (1 ml) of these ognic smples using Tti Co SX ffinte (5 ml) feed, s descibed in Section OCTOBER 27 VOLUME 17 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

3 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 635 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Results nd discussion Feed solution The coblt ffinte used s feed ws obtined fom the coblt solvent extction cicuit (Tti Co SX ffinte) t Tti Nickel s demonsttion plnt nd povided by Tti Nickel Mining Compny. Fou btches of bout 2 L ech wee supplied. A typicl composition of this feed solution to the nickel SX cicuit is given in Tble I. Ognic phse composition The neutliztion equivlent fo V1 (supplied by Chemquest) ws found to be g/mol by potentiometic tittion of smple (169 g) of V1 ginst stndd.1 M sodium hydoxide solution. Detiled technicl infomtion concening Nicksyn emins the sole popety of Mintek nd cnnot be disclosed. The diffeent V1 nd Nicksyn concenttion mixtues diluted with Shellsol D7 (mol nd vol.%) used in this study e given in Tble II. Metl-distibution equilibi fo extction (ph vs. extction) The synegistic extction of nickel by cboxylic cid such s V1 (which exists in the fom of dimes H 2 A 2 ), with the ddition of synegistic compound (L) such s Nicksyn, is given in Eqution [1].1 [1] The bs denote the pesence of the species in the ognic phse. The diffeent behviou of nickel nd clcium, mgnesium, nd mngnese in this type of synegistic system is illustted in the esults fo the extction of metls fom Tti Co SX ffinte by 1. M V1 lone nd mixed with.5 M Nicksyn in Shellsol D7, s shown in Figue 1. Pecentge extction is clculted by the diffeence between the feed nd ffinte solutions. The ph 5 vlue (the ph t which 5% of the metl oiginlly pesent in the queous phse is extcted unde given set of conditions) of nickel shifted fom 5.8 (using 1. M V1 lone) to 4.48 (1. M V1 plus.5 M Nicksyn ), which eltes to synegistic shift (ΔpH 5 ) of 1.32 ph units. Only smll synegistic shift (ΔpH 5 =.17) fo clcium occued fo this feed solution, which contined bout 18 g/l nickel nd.6 g/l clcium. Vious concenttion mixtues of V1 nd Nicksyn wee evluted in ode to obtin esonble nickel-clcium seption, whilst minimizing the volume (o mss) equiement nd hence the costs of using Nicksyn. The esults e summized in Tble III. The seption between the extction cuves fo nickel nd clcium is indicted by ph 5 C-Ni. Synegistic shifts in the ph 5 vlues fo the extction of nickel incesed fom.9 to 1.45 units when Nicksyn ddition ws incesed fom.2 to 1. M espectively, whilst the extction of clcium ws lgely unffected. The seption between nickel nd clcium (ph 5 C-Ni) incesed fom 1.32 ph units (V1 lone) to 2.83 ph units (1. M V1 plus 1. M Nicksyn ). Consideing the dditionl costs of incesing the Nicksyn concenttion beyond tio of 5:1 Tble I Typicl composition of nickel SX feed solution Metl Concenttion, g/l Ni 18 Co.2.5 C 6 Mn <.2 Cu <.2 Mg.54 Zn <.2 Fe <.2 Tble II Diffeent concenttion mixtues of V1 nd Nicksyn used in expeimentl test wok Ognic phse Concenttion, M Concenttion, Vol.% Vestic Nicksyn J o u n l P p e b Extction, % Extction, % Equilibium ph Ni C Mg Equilibium ph Ni C Mg Figue 1 Metl-distibution equilibi fo the extction of metls fom Tti Co SX ffinte by 1. M V1 lone () nd 1. M V1 plus.5 M Nicksyn (b) in Shellsol D7 t 35ºC The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 17 NON-REFEREED PAPER OCTOBER

4 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 636 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Tble III Extction of nickel nd clcium fom Tti Co SX ffinte by mixtues of V1 (1. M) nd Nicksyn (.2-1. M) in Shellsol D7 t 35ºC Ognic phse ph5 Ni ph5 C ph5 C-Ni V1, M Nicksyn, M (ph 5 C-Ni of 2 ph units) to impove nickel-clcium seption incementlly with nothe ph unit (finl tio of 1:1), it ws decided to conside only mol tios of V1:Nicksyn of 5:1 nd 4:1 fo the demonsttion plnt. A ph vs. extction isothem ws done (Figue 2) using Tti Nickel coblt pegnnt lech solution (Tti Co PLS) nd 1.25 M V1 plus.31 M Nicksyn t 35ºC to guge the possibility of septing nickel, coblt, zinc nd coppe fom clcium, mngnese nd mgnesium fom Tti Nickel coblt SX feed. This would llow the Ni SX to be done fist, followed by Co SX to emove Co nd othe impuities fom the Ni electolyte. This would be especilly beneficil if the PLS wee diluted nd upgding of nickel tkes plce coss the Ni SX cicuit, becuse the Co SX cn be done on smlle volumetic flow. The ph 5 vlues obtined fo nickel (4.68), coblt (5.4), mngnese (6.1) nd clcium (6.61) indicte tht seption between coblt nd mngnese (ph 5 Mn-Co) of only.61 units ws chieved fo this feed solution, which would pobbly equie lge numbe of stges nd tight ph contol to fcilitte efficient seption of nickel, coblt, zinc nd coppe fom clcium, mngnese nd mgnesium. This seption between coblt nd mngnese would be impoved with highe concenttion of Nicksyn in the ognic mixtue. Distibution isothems fo extction of nickel The distibution isothem nd McCbe Thiele constuction fo the extction of nickel fom Tti Co SX ffinte geneted using 1. M V1 plus.5 M Nicksyn in Shellsol D7, t ph 5.5 nd contolling the tempetue t 35ºC, is shown in Figue 3. The esults (bsed on clcultions done bsed on the diffeence between the feed nd ffinte solutions, s well s tht deived by stipping the ognic phses nd nlysing the stip liquos) nd McCbe-Thiele constuction on the extction isothem, indicte tht loding of bout 18 g/l nickel could be chieved in thee countecuent extction stges t n O:A phse tio of 1. The clcium co-extction unde these conditions ws bout 2.3% (14 mg/l on the loded ognic). The distibution isothems fo extction of nickel using 1. M V1 togethe with lowe (.25 M) concenttion of Nicksyn t ph vlues 5.4 nd 5.8, e shown in Figues 4 nd 5 espectively. The McCbe-Thiele constuctions shown in Figues 4 nd 5 pedict nickel lodings of bout 11 nd 14 g/l t ph 5.4 nd 5.8 espectively. Although n ppecible selectivity fo nickel ws shown by the limited co-loding of clcium on the ognic phses (bout 12 mg/l nd 2 mg/l t ph 5.4 nd 5.8 espectively), optimum plnt opetion would equie highe nickel loding on the ognic phse to opete close to n O:A phse tio of unity in extction. Mximum loding expeiments indicted tht bout 2 g/l nickel loding could be chieved using 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 (V1:Nicksyn = 4) t ph 6. nd 35ºC. These conditions wee pplied in geneting the extction isothem shown in Figue 6. The McCbe-Thiele constuction confimed tht nickel loding of bout 2 g/l could be chieved in thee countecuent extction stges t n O:A phse tio of.9, with clcium loding on the ognic phse below detection limit (< 4 mg/l in stip liquo nlyses). These opeting conditions wee theefoe ecommended fo the extction cicuit on the demonsttion plnt. Distibution isothems fo the stipping of nickel The distibution isothem geneted fo the stipping of nickel fom btch-loded 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 (contining bout 2 g/l nickel) t 35ºC, using synthetic spent electolyte contining 61 g/l nickel nd 4 g/l sulphuic cid s stip solution, is shown in Figue 7. The McCbe-Thiele constuction pedicts tht loded ognic phse contining bout 21.5 g/l nickel could be stipped with synthetic spent electolyte in two countecuent Extction,% Metl on loded ognic phse, mg/l Equilibium ph Ni Co C Mn Cu Mg Figue 2 Metl-distibution equilibi fo the extction of metls fom Tti Co PLS by 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 t 35ºC( O:A = 2) Metl in queous phse, mg/l Ni queous Ni stipped og Figue 3 Distibution isothem fo the extction of nickel fom Tti Co SX ffinte by 1. M V1 plus.5 M Nicksyn in Shellsol D7 t ph 5.5 nd 35ºC 636 OCTOBER 27 VOLUME 17 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

5 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 637 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Metl on loded ognic phse, mg/l Figue 4 Distibution isothem fo the extction of nickel fom Tti Co SX ffinte by 1. M V1 plus.25 M Nicksyn in Shellsol D7 t ph 5.4 nd 35ºC Metl on loded ognic phse, mg/l Metl in queous phse, mg/l Ni queous Metl in queous phse, mg/l Ni queous N stipped og Ni stipped og stipping stges t n O:A phse tio of 1.2 nd t 35ºC. Loded stip liquo contining bout 86 g/l nickel ws obtined, s would be expected becuse of the cid content of the synthetic stip liquo. Stip liquo ph vlues mesued fo stipping done t O:A phse tios of.125,.2,.5 nd 1. wee.75,.76, 1.6 nd 1.43, espectively, which indictes tht enough (o even excess) sulphuic cid ws vilble fo complete stipping of nickel. Stipping done t O:A phse tios of 2, 5 nd 8 esulted in stip liquos exhibiting ph vlues of 5.2, 5.7 nd 5.8 espectively, which indictes unfvouble stipping conditions fo nickel. If plnt opetion equied these opeting conditions, ph contol coulde be employed (t bout 3) in ode to fcilitte efficient stipping of nickel in the minimum numbe of stges. Acid extction by ognic phse The cid uptke s function of the equilibium ph of the queous phse (4 g/l sulphuic cid plus 133 g/l sodium sulphte), using n ognic phse contining 1.25 M V1 mixed with.31 M Nicksyn in Shellsol D7, is shown in Figue 8. The extction of cid by Nicksyn fom queous solutions between ph.7 nd.9 ws 8 mm, while the vege extction of cid by Nicksyn fom queous solutions between ph 1.4 nd 3.3 ws 6.1 mm, which is negligible. Ni in queous phse, mg/l J o u n l P p e Figue 5 Distibution isothem fo the extction of nickel fom Tti Co SX ffinte by 1. M V1 plus.25 M Nicksyn in Shellsol D7 t ph 5.8 nd 35ºC Ni on ognic phse, mg/l Figue 7 Distibution isothem fo the stipping of nickel fom btch loded 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 with synthetic spent electolyte (61 g/l nickel in 4 g/l sulphuic cid solution) t 35ºC Metl on loded ognic phse, mg/l (H+)og, mm Metl in queous phse, mg/l N queous Ni stipped og Figue 6 Distibution isothem fo the extction of nickel fom Tti Co SX ffinte by 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 t ph 6. nd 35ºC ph of ffinte Figue 8 Extction of cid (s H + ) fom simulted spent electolyte (4 g/l H2SO g/l N2SO4, no Ni) by 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 t 35ºC The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 17 NON-REFEREED PAPER OCTOBER

6 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 638 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Stbility tests Stbility tests wee cied out using ognic phses contining 1.25 M V1 mixed with.31 M Nicksyn, simulting extction nd stipping conditions. Smples tken of the ognic phses t chosen time intevls (15, 29, 45 nd 9 dys fo stbility tests epesenting stipping conditions nd 9 dys fo stbility test epesenting extction conditions) wee then used (septely) to detemine the ph vs. extction cuves fo nickel nd clcium fom Tti Co SX ffinte t 35 C. These e shown in Figue 9. No intemittent smples wee tken fo the testsimulting extction conditions. A potion of the ognic phse (25 ml) ws stipped btch-wise (thee times) with 1 M sulphuic cid (5 ml) fte 9 dys to ensue complete stipping of nickel, fte which it ws used to detemine ph vs. extction dt (shown in Figue 9). The ph 5 vlues, s well s ph 5 C-Ni obtined fo nickel nd clcium, e given in Tble IV togethe with those obtined using the fesh ognic phse. It cn be seen fom Figue 9 nd Tble IV tht vitions in ph 5 vlues of nickel (4.57 to 4.63) nd clcium (6.55 to 6.67), nd theefoe vitions in ph 5 C-Ni (1.97 to 2.5) e insignificntly smll ove the 9-dy peiod of the stbility tests, epesenting stipping s well s extction conditions. All phses wee cle duing stbility tests done simulting stipping conditions. White cud ccumulted t the intefce of the phses of the stbility test simulting extction conditions. It cn be concluded tht the ognic phse mixtue contining 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 ws stble unde the given conditions tested fo peiod of 9 dys. Demonsttion plnt dt Tti Nickel cquied.5 tons of Nicksyn fom the mnufctue ppointed by Mintek. The qulity of the Nicksyn poduct ws evluted t Mintek pio to shipment to the Tti Nickel site, nd the esults confimed tht it ws of qulity equivlent to tht of the lbotoy-scle poduct. Nicksyn ws intoduced into the plnt duing Octobe 26, nd hs been in opetion since then. The opeting conditions pplied to the V1 nd V1 plus Nicksyn tils e comped in Tble V. The nickel pofiles coss the extction cicuit fo V1 lone nd V1 plus Nicksyn e given in Figue 1. The moe efficient extction of nickel by V1 plus Nicksyn system is cle, lthough it ws done t lowe ph pofile (lbeit highe O:A phse tio). As mentioned elie, the mximum nickel loding of 2 g/l ws obtined in the lbotoy testwok using 1.25 M V1 plus.31 M Nicksyn mixtue (see Section 3.4). The loding of nickel could theefoe be incesed by incesing the Nicksyn concenttion o lifting the ph vlues slightly ove the extction cicuit. The clcium ognic loding pofiles coss the extction cicuit e given in Figue 11. The pofile fo V1 plus Nicksyn system is the flt, which demonsttes the dvntge of the synegistic system. With V1 lone, significnt mount of clcium ws coloded on the ognic phse t the til end of the extction cicuit, which ws then displced by nickel s the ognic dvnced towds the font end of the cicuit. This clely demonsttes the poblem in the V1 cicuit, s ny clcium tht is displced fom the ognic could esult in gypsum fomtion in the extction cicuit if the feed contins clcium t stution. Peviously Tti Nickel minimized the poblem of gypsum by diluting the feed stem with fesh wte. This, howeve, will incese the size of the plnt by 1% (highe flow tes fo simil nickel poduction). With the synegistic system, no dilution of the feed is equied, s gypsum fomtion cn be completely voided. Figue 12 shows the nickel eltive ecoveies obtined ove peiod. With V1 lone, n vege ecovey of bout 99.3% ws chieved, while tht of the V1 plus Nicksyn ws 99.7%. With the extction cicuit contining V1 lone, the ph of extction cnnot be incesed, s this cuses highe clcium loding, nd hence n incesed likelihood of gypsum fomtion in the extction cicuit. Hence, to impove extction efficiency, moe stges would be equied. The V1 lone cicuit ledy employed five extction stges. The V1 plus Nicksyn opetion chieved highe nickel ecoveies using fou stges only, nd with vey little isk of gypsum fomtion. The ecovey of nickel cn be impoved in this cicuit by incesing the ph pofile somewht, whilst still voiding dditionl clcium loding. Regent mke-up fo the V1 nd V1 plus Nicksyn systems ws comped ove peiod of fou months. Indictive esults e given in Tble VI. The lowe egent loss expeienced using the V1 plus Nicksyn ws scibed to the much lowe ph of opetion nd the eduction in cud fomtion. The diluent nd Vestic 1 cid mke-up wee 21% nd 3% highe espectively fo the V1 lone system. ph5 vlues Figue 9 ph5 vlues fo nickel nd clcium extction by 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 (fesh nd fte use in stbility tests) t 35ºC Tble IV Ni Fesh 15 dys 29 dys 45 dys 9 dys ext 9 dys ph5 nd ph5c-ni vlues fo nickel nd clcium extction by 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 (fesh nd fte use in stbility tests) t 35ºC Smple of 1.25 M V M Nicksyn ph5 ph5 C-Ni Stipping conditions: Fesh dys dys dys dys Extction conditions: 9 dys Ni C C 638 OCTOBER 27 VOLUME 17 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy

7 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 639 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Tble V Compison of opeting conditions V1 V1 + Nicksyn Vestic 1 cid concenttion, M Nicksyn concenttion, M.27 Ni mximum loding, g/l Numbe of stges Extction 5 4 Scubbing 2 1 Stipping 2 2 Wshing 1 Vestic 1 ecovey (VR) 1 1 Totl 1 9 O:A phse tio Extction Scubbing Stipping ph pofile coss extction E E E E E Not in use Phse disenggement time, s Extction Scubbing Stipping Ni concenttion coss extction, g/l Feed E E E E4.5.7 E5.1 Not in use C concenttion in ognic coss extction, g/l E E E E E5.149 Not in use J o u n l P p e Ni in queous, g/l PLS E1 E2 E3 E4 E5 Extction Stges Ni in queous, g/l b PLS E1 E2 E3 E4 E5 Extction Stges Figue 1 Nickel queous concenttion pofile coss extction cicuit (V1 lone () nd V1 plus Nicksyn (b)) C on ognic, mg/l E1 E2 E3 E4 E5 Extction Stges C on ognic, mg/l b E1 E2 E3 E4 VR Extction Stges Figue 11 Clcium ognic concenttion pofile coss extction cicuit (V1 lone () nd V1 plus Nicksyn (b)) The Jounl of The Southen Aficn Institute of Mining nd Metllugy VOLUME 17 NON-REFEREED PAPER OCTOBER

8 SAIMM_Oct_29-36:Templte Jounl 11/5/7 8:8 AM Pge 64 Solvent extction test wok to evlute Vestic 1/Nicksyn synegistic system Ni ecovey, % Dys Figue 12 Nickel ecoveies fo V1 lone nd V1 plus Nicksyn extction systems Tble VI Regent mke-up Mke-up (L/m 3 ) V1 V1 plus Nicksyn Diluent V Nicksyn.13 The esults obtined duing the demonsttion plnt un wee used to mke techno- economic compison between the V1 nd V1 plus Nicksyn systems in ode to quntify the cpitl nd opeting cost diffeence between the two technologies. Conclusions V1 V1-NS The Mintek-developed synegist (Nicksyn ) in diffeent combintions with V1 ( commecilly vilble tetiy-bnched cboxylic cid) nd diluted with Shellsol D7 (liphtic), ws evluted s optimizing nickel ecovey nd nickel-clcium seption fom coblt solvent extction ffinte stem t Tti Nickel. This stem typiclly contined bout 2 g/l nickel, 5-6 mg/l clcium nd 54 mg/l mgnesium. Coppe, zinc, mngnese, ion nd coblt wee <2 mg/l in solution s esult of thei effective extction in the upfont Cynex 272 cicuit Extction vs. ph cuves done with 1. M Vestic 1 lone nd mixed with.2 1. M Nicksyn in Shellsol D7 t 35ºC showed tht synegistic shifts in the ph 5 (ΔpH 5 ) vlues fo the extction of nickel incesed fom.9 to 1.45 units when Nicksyn ddition ws incesed fom.2 to 1. M espectively. The extction of clcium ws insignificntly ffected. The seption between nickel nd clcium (ph 5 C-Ni) incesed fom 1.32 ph units (V1 lone) to 2.83 ph units (1. M V1 plus 1. M Nicksyn ). Consideing the highe costs of dding Nicksyn to mol tio of unity to incese the seption by futhe ph unit (fom 2 to 3 ph units), mol tios of V1:Nicksyn of 5:1 nd 4:1 wee consideed fo the demonsttion plnt A combintion of 1.25 M V1 plus.31 M Nicksyn t 35ºC ws used to guge the possibility of septing nickel, coblt, zinc nd coppe fom clcium, mngnese nd mgnesium in the Co SX feed (PLS). This would llow fo the Ni extction to be done fist, followed by Co ecovey nd impuity emovl on the Ni SX loded stip liquo. The ph 5 vlues obtined fo nickel (4.68), coblt (5.4), mngnese (6.1) nd clcium (6.61) indicte tht seption between coblt nd mngnese (ph 5 Mn-Co) of only.61 units ws chieved fo this feed solution. It would pobbly equie lge numbe of stges nd tight ph contol to fcilitte efficient seption of nickel, coblt, zinc nd coppe fom clcium, mngnese nd mgnesium. A highe popotion of Nicksyn would enhnce the seption The use of 1. M V1 plus.5 M Nicksyn in Shellsol D7, t ph 5.5, indicted tht loding of bout 18 g/l nickel could be chieved in thee countecuent extction stges t n O:A phse tio of unity. The clcium co-extction unde these conditions ws bout 2.3% (14 mg/l on loded ognic phse) The testing of 1. M V1 togethe with lowe (.25 M) concenttion of Nicksyn t ph 5.4 nd 5.8 pedicted nickel lodings of bout 11 nd 14 g/l t ph 5.4 nd 5.8, espectively The combintion of 1.25 M V1 plus.31 M Nicksyn in Shellsol D7 esulted in nickel loding of bout 2 g/l in thee countecuent extction stges t n O:A phse tio of.9, with clcium co-loding on the ognic phse below detection limit. These opeting conditions wee theefoe ecommended fo the extction cicuit on the demonsttion plnt Two stipping stges wee deemed dequte fo complete stipping No meningful cid loding, nd hence cy-ove to the extction cicuit, ws detemined fo the egent mixtue Stbility tests unde extction nd stipping conditions ove peiod of 9 dys indicted no chnge in the composition of the extction mixtue V1 lone nd V1 plus Nicksyn systems wee comped duing demonsttion plnt un t Tti Nickel. The ecovey of nickel incesed by.5% using the V1 plus Nicksyn mixtue nd fou extction stges. The co-loding of clcium ws bout 15 mg/l in E5 (using V1), which could fom gypsum if displced. The co-loding of clcium in E4 (using V1 plus Nicksyn ) ws bout 14 mg/l, with no isk of gypsum fomtion. Acknowledgements This ppe is published by pemission of LionOe nd Tti Nickel. Refeences 1. DU PREEZ, A.C. nd PRESTON, J.S. Seption of nickel nd coblt fom clcium, mgnesium nd mngnese by solvent extction with synegistic mixtues of cboxylic cids, SAIMM Jounl, July 24, 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, vol. 58, 2, pp OCTOBER 27 VOLUME 17 NON-REFEREED PAPER The Jounl of The Southen Aficn Institute of Mining nd Metllugy