The copper–ethanediamine–thiosulphate leaching of gold ore containing limonite with cetyltrimethyl ammonium bromide as the synergist

• Cu2 +-en-thiosulphate system was found to be suitable for the extraction of gold ore containing limonite.
• The addition of CTAB was found to increase the extraction rate of gold and reduce the consumption of thiosulphate remarkably.
• For the gold ore containing limonite, the gold extraction rate was 94.3% and the thiosulphate consuption was 1.12 kg/t.

The leaching of thiosulphate gold for a gold ore containing limonite was investigated. The results indicate that the copper ion–ethanediamine(en)–thiosulphate system was more suitable than the copper ion–ammonia–thiosulphate system for gold extraction of the gold ore. The use of cetyltrimethyl ammonium bromide (CTAB) as an effective synergistic additive in the gold extraction process was demonstrated to increase the gold extraction rate and to reduce the thiosulphate consumption for the gold ore. One possible reason for this improvement may be that CTAB hydrolyses to [CTA+] and subsequently attracts the negative charged slime, thereby causing a change in the slurry rheology, which results in the gold surface's being exposed and thus easily leached in the thiosulphate leaching system. Another reason may be the formation of ion pairs, [CTA+]3[Au(S2O3)23−]
• nH2O and [CTA+][AuBr2−]
• nH2O, which leads to the stabilisation of [ Au(S2O3)23 −] in the leaching system. The two effects of CTAB increase the gold extraction rate remarkably and sharply reduce the thiosulphate consumption. The gold dissolution rate of the gold ore could reach 94.3% and the thiosulphate consumption could be reduced to 1.12 kg/t ore in the thiosulphate gold leaching system containing 0.1 mol/L of sodium thiosulphate, 0.06 M ethanediamine, 0.005 M copper ion and 1.5 kg/t of CTAB and operated at a rate of agitation of 150 rpm.