Resin technology for gold recovery from alkaline cyanide solution.

摘要

A review of the current literature on gold recovery from alkaline cyanide solution suggests resin ion exchange as a potential process alternative, if a suitable resin can be identified. In this regard four different adsorption systems, including commercially available and new synthetic resins, were investigated for recovery of gold from alkaline cyanide solution.; Commercially available, XAD-series, polyacrylates were found to exhibit a modest capacity (200 mg gold/kg resin, at 1 ppm gold in the aqueous phase) for gold adsorption at pH 10 under ambient conditions. Lower temperatures and higher ionic strengths promoted gold adsorption from cyanide solution.; Next, a class of recently identified gold solvent extraction systems was combined with the nonfunctional, or nonderivatized, XAD-16 resin beads to prepare solvent impregnated resins. Under ambient conditions and pH 9, at 1 ppm gold in the aqueous cyanide phase, gold adsorption by 0.5 M Adogen 283/TBP/XAD-16 and 0.5 M Adogen 283/TOP/XAD-16 resins were 1200 mg gold/l organic in the resin, and 56 mg gold/l organic in the resin, respectively.; A new class of phosphonate ester based polystyrene resins was studied. Gold loading with the most effective, monoester/monoacid type, resin was found to be ca. 1 g/kg resin at 1 ppm aqueous gold concentration. No pH dependency was observed. Gold loading was promoted by higher temperature and lower ionic strength.; Finally, amine/ester type bifunctional resins showed higher gold loadings than all other types of adsorbents examined. A typical tertiary amine/ester resin exhibited ca. 10 g gold/kg resin loading at 1 ppm aqueous gold concentration under ambient conditions and at pH 10. These resins showed slight pH dependency, being more pronounced for secondary type amine functional groups.; Generally no experimental evidence was found to show any specific bonding of the gold cyanide complex during adsorption. It is proposed that the adsorption reaction occurs by ion pairing of the gold cyanide anion with a suitable cation, M{dollar}sp+{dollar}, and the subsequent solvation at active sites in the resin structure, R, can be stated as, M{dollar}sp+{dollar} + Au(CN){dollar}sb2sp-{dollar} + R {dollar}leftrightarrow{dollar} {dollar}{lcub}rmoverline{lcub}Msp+cdots Au(CN)sb2sp-cdot R{rcub}.{rcub}{dollar}; The results of this research contributed to the understanding of gold cyanide loading and elution by organic based adsorbents. However, to identify a promising commercial resin for gold recovery from alkaline cyanide solution more work still remains to be done.