Gold recovery from pregnant thiosulfate solution by ion exchange resin: Synergistic desorption behaviors and mechanisms

The behaviors and mechanisms of gold desorption from its loading resin with the mixed solution of Na2SO3 and NaCl were studied. The desorbent displayed evident "synergistic role" on the gold desorption and had good desorption performance over wide ranges of reagent concentration, flow rate and gold loading amount. Based on the thermodynamic analysis, a two-step desorption mechanism was proposed: (1) SO32- reacted with [Au (S2O3)2]3-to generate [Au(S2O3)(SO3)]3-; (2) The resin had weak affinity for the two-ligand gold complex which was thus replaced by Cl- readily. SEM-EDS, characteristic color of gold complex, Raman spectra and binding energy calculation results indicated SO32- could react with [Au(S2O3)2]3- to form [Au(S2O3)(SO3)]3-, and the affinity of the resin for the newly-generated complex was weaker than that for Cl-, which demonstrated the above mechanism. The mechanism model of gold recovery from pregnant thiosulfate solution by ion exchange resin was finally constructed.