Thiosulphate leaching of gold in the presence of carboxymethyl cellulose (CMC)

Carboxymethyl cellulose (CMC) was introduced as a surfactant in the leaching of pure gold as well as a sulphide ore using ammoniacal thiosulphate medium. Competing with thiosulphate anions to complex with the cupric ion at the axial coordinate sites, CMC in small quantities reduced the consumption of thiosulphate in the ammoniacal thiosulphate leaching system. The dissolution of pure gold in thiosulphate solution was enhanced in the presence of CMC, and this beneficial effect became more pronounced with an increase in the CMC concentration up to a certain level. Extraction rates of gold and silver from the sulphide ore were improved greatly, while the consumption of thiosulphate was reduced in the presence of CMC especially at a higher CMC concentration. The enhanced leaching performance was attributed to the stabilisation of thiosulphate, likely reduced leaching passivation and the dispersion of mineral particles in the slurry system. Addition of CMC facilitates satisfactory gold extraction at low reagent consumption in thiosulphate leaching.