Improving gold recovery in carbonaceous gold ores using naphthalene sulphonate as a blanking agent

Abstract

Naphthalene sulphonate was used as a blanking agent to treat a gold ore with an 87% preg-robbing index with the aim of improving the gold recovery during carbon-in-leach (CIL). The adsorption of naphthalene sulfonate, an anionic surfactant, was significantly higher under acid conditions: 0.51 µmol/g at pH 2.4 and 0.24 µmol/g at pH 11.3. However, conditioning the ore at the expected pH for 30 mins prior to adsorption led to a similar loading of naphthalene sulfonate regardless of the initial solution pH. The gold recovery of the ore was improved from 57% to 80% during CIL, after the ore was treated with 4.48 mM naphthalene sulfonate at pH 11.3 adjusted by 4.36 mM Ca(OH)2. The main factor, that was likely responsible for the improved gold recovery, was the passivation of the adsorption sites on the carbonaceous matter in the ore. The impact of electrostatic repulsion of Au(CN)2- was negligible due to relatively unchanged surface potential before and after naphthalene sulphonate adsorption.