Recovery of base metals from a sulphate-based bioleach solution using commercially available chelating ion exchange resins and adsorbents

Liebenberg, Cornelius Johannes (2012-12)

Thesis (MScEng)--Stellenbosch University, 2012.

Thesis

ENGLISH ABSTRACT: Lonmin Plc. is currently investigating a hydrometallurgical process route for the recovery of base metals (BMs) and platinum group metals (PGMs) from a low grade PGM bearing ore originating from the Platreef deposit in the northern limb of the Bushveld Complex. The front-end of the flow sheet entails recovering the BM values from the ore in a heap bioleach carried out at a temperature of 65 C after which the PGMs are recovered from the solid residue of the bioleach in a second stage heap cyanide leach (Mwase et al., 2012; Mwase, 2009). Commercially available chelating ion exchange resins and chelating adsorbents, Dow M4195 (bispicolylamine functionality), Dow XUS43605 (hydroxypropylpicolylamine functionality), Amberlite IRC748 and Purolite S930 (iminodiacetic acid functionality), and Purolite S991 (mixed amine and carboxylic functionality), were investigated in this thesis for the recovery of copper, nickel and cobalt (metals of interest, or MOI) from the bioleach solution. Screening tests indicated that Dow M4195 and Dow XUS43605 were able to selectively adsorb copper to the preference of all other metals in the solution at pH 3 and 4, while the other resins only succeeded in this purpose at pH 4 in the presence of little ferric iron. Only Dow M4195 proved to be able to selectively recover nickel over other metals in the solution at pH 4. Dow M4195, Dow XUS43605 and Amberlite IRC748 were selected for further investigation. Batch kinetic and equilibrium studies were performed on these resins and they were compared on the basis of their metals uptake rate and equilibrium concentrations of the MOI. The rate of metal uptake equilibrium attainment was found to be the fastest for Dow XUS43605, followed by Amberlite IRC748 and Dow M4195. Langmuir and Freundlich isotherm models were tted to equilibrium data for copper adsorption with Dow XUS43605 and nickel adsorption with Dow M4195, and copper and nickel capacities of these two resins at pH 4 were found to be 26 g/L and g/L 30.86 g/L, respectively. Column adsorption experiments revealed that flow rate and temperature were the parameters that had the most significant effects on the copper loading achieved on Dow XUS43605 at copper breakthrough. A 36% increase in copper loading on Dow XUS43605 at copper breakthrough was observed when the temperature increased from 25 to 60 ºC, and the co-loaded nickel decreased proportionally. This increase was ascribed to the faster kinetics of copper adsorption at 60º C than at 25º C. Regarding nickel and cobalt recovery, the same trends were observed for increasing the flow rate and temperature. In addition to flow rate and temperature, an increase in initial solution pH also significantly increased metal adsorption, as would be expected. Elution studies revealed that a split elution could be performed to remove the majority of the nickel from the resin with 2 bed volumes (BV) of 20 g/L sulfuric acid to remove the majority of the co-loaded nickel, followed by 2-3 BV of 100 or 200 g/L sulfuric acid to elute the copper, thus a purer copper-rich eluate fraction could be obtained. The same was true for nickel and cobalt elution from Dow M4195. The effect of flow rate in the range of 2 to 10 BV/h did not signi cantly influence metal elution from either Dow XUS43605 or Dow M4195, whereas temperature was found to increase the rate of metal elution. Finally, two flow sheets were proposed for the recovery of the MOI. The overall recoveries of copper, nickel, cobalt and zinc for both flow sheets were 100%, but 14% nickel was lost to the copper eluate for both flow sheets, while the nickel lost to the cobalt rich effluent of the lag column was reduced from 8.3% for ow sheet option 1 to 5.6% for ow sheet option 2. By reducing the flow rate at which the process is carried out, these losses could be reduced. Also, by modifying flow sheet 2 and carrying out the copper recovery with Dow XUS43605 at a lower pH (pH 2 or 3), nickel losses to the copper eluate could be minimized as the resin's selectivity towards nickel is lower at lower solution pH values. It was further concluded that additional processing of the cobalt-rich eluate fraction of the lag column (in the lead-lag con guration of Dow M4195) is necessary to recover cobalt in a pure form.

AFRIKAANSE OPSOMMING: Lonmin Plc. is tans besig met die ontwikkeling van 'n hidrometallurgiese proses om basismetale (BMe) en Platinum Groep Metale (PGMe) te herwin vanuit 'n laegraad erts afkomstig van die Platinumrifneerslag in die Bosveldkompleks. Aan die voorent van die proses word die BMe in 'n hoopbiologingsproses, waarna die PGMe uit die soliede oorskot van die biologingsproses geloog word met 'n sianiedoplossing. Hierdie tesis ondersoek kommersieël-beskikbare chelerende ioonuitruilingsharse asook chelerende adsorbente om koper, nikkel en kobalt uit die oplossing mee te herwin. Die harse wat ondersoek word in hierdie studie, Dow M4195 (bispikolielamien funksionaliteit), Dow XUS43605 (hidroksiepropielpikolielamien funksionaliteit), Amberlite IRC748 (iminodiasetaatsuur funksionaliteit), en Purolite S991 (gemengde amien en karboksieliese funksionaliteit) is ondersoek in hierdie tesis vir die herwinning van koper, nikkel en kobalt vanuit die biologingsoplossing. Die harse was onderwerp aan 'n siftingsproses en resultate het getoon dat Dow M4195 en Dow XUS43605 die enigste harse was wat koper selektief bo yster kon adsorbeer by pH 3 en 4, terwyl die ander drie harse slegs in hierdie doel kon slaag by 'n oplossing pH van 4 (in die teenwoordigheid van min Fe3+). Slegs Dow M4195 was in staat om nikkel en kobalt selektief bo ander metale in die oplossing te adsorbeer. Dow M4195, Dow XUS43605 en Amberlite IRC748 is gekies om onderwerp te word aan verdere kinetiese en ekwilibrium toetse. Die tempo waarteen metaaladsorpsie met Dow XUS43605 ekwilibrium bereik het was die vinnigste, gevolg deur Amberlite IRC748 en Dow M4195. Langmuir en Freundlich isoterme is gepas op die ekwilibriumdata van koperadsorpsie met Dow XUS43605 en nikkeladsorpsie met Dow M4195, en die koper- en nikkelkapasiteite van hierdie twee harse was bevind om 26 g/L en 30 g/L, onderskeidelik, gewees. Kolomladingstoetse het aan die lig gebring dat vloeitempo en temperatuur die parameters was wat die grootste invloed op die koperlading op Dow XUS43605 by koper deurbraak gehad het. 'n 36% toename in koperlading op die hars was waargeneem toe die temperatuur verhoog was van 25 to 60º C, en die ooreenstemmende nikkellading het proporsioneel afgeneem. Die toename in koperlading by koper deurbraak was toegeskryf aan die vinniger kinetika van die hars by 60 ºC as by 25º C. Dieselfde neigings is waargeneem vir nikkel en kobalt herwinning met Dow M4195 as vir koper herwinning met Dow XUS43605; toenemende vloeitempo het gelei tot 'n laer konsentrasie van teikenmetale op die hars, terwyl verhoogde temperatuur die teenoorgestelde effek gehad het. Verder het 'n verhoging in die oplossing pH ook daartoe gelei dat meer kobalt en nikkel geadsorbeer word deur Dow M4195. Dit was bepaal dat 'n twee-stadium eluering uitgevoer kan word deur die nikkel eerste van die hars te verwyder met 2 bed volumes 2% swawelsuur, gevolg deur die eluering van koper met 10-20% suur binne 2-3 bed volumes. Sodoende kan die koper-ryk fraksie meer suiwer wees. Dieselfde beginsel geld vir die eluering van nikkel en kobalt vanaf Dow M4195. Verdere bevindings sluit in dat vloeitempo's tussen 2 en 10 bed volumes per uur van die elueringsmiddel nie 'n merkwaardige invloed het op metaaleluering vanaf enige van die twee harse nie, maar dat 'n toename in temperatuur wel die tempo van metaaleluering laat toeneem het. Ten slotte was twee vloeiskemas voorgestel vir die herwinning van koper, nikkel en kobalt met ioonuitruiling. Die algehele herwinning van koper, nikkel en kobalt vir beide vloeiskemas was 100%, alhoewel 14% van die nikkel verloor was na die kopereluaat in beide vloeiskemas, terwyl die nikkel verlies na die kobalt-ryke eluaat van die volg-kolom afgeneem het vanaf 8.3% in die eerste vloeiskema na 5.6% in die tweede vloeiskema. Die bogenoemde verliese kan verminder word deur die vloeitempo waarby die proses uitgevoer word te verlaag. Verder kan die tweede vloeiskema só aangepas word dat die herwinning van koper met Dow XUS43605 by 'n laer pH geskied (pH 2 of 3) aangesien die a niteit van hierdie hars merkbaar laer is vir nikkel by hierdie pH's en sy affiniteit vir koper byna onveranderd bly. Die gevolgtrekking was ook gemaak dat die kobalt-ryke eluaat van die volg-kolom verder geprosesseer moet word om kobalt in 'n suiwer vorm te herwin.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71962
This item appears in the following collections: