Solvent Impregnated Resins for the Recovery of Gold from Gold(I)Thiourea Solutions

Solvent Impregnated Resins (SIRs) are high surface area, macroporous, polymeric resins which have been physically impregnated with an organic solvent. In this research, three resins have been impregnated with Di-2-ethylhexyl phosphoric acid, a solvent which has shown selectivity to gold. The ability of the resins to recover gold (1) thiourea perchlorate from solution has been investigated. The resins have been studied both bare and when impregnated with the solvent and their efficiency was seen to increase upon impregnation. The overall efficiency of the resins was found to be pH dependent. It is also related to the level of impregnation of the resins. Recovery by the resins compares favourably with liquid/liquid solvent extraction using the same solvent. The overall capacity of the resins was estimated by determination of the maximum gold loading of the resins. Gold from the resins was eluted by washing with methanol and mass balances of gold approaching 100% have been achieved. The effect of interferents in solution, in particular, excess thiourea and ferric and cupric ions was also investigated. Scanning electron micrographs and X-Ray fluorescence spectra of the bare and impregnated resins were obtained and the effect of sulphur formation on the resins was established