Optimization of gold recovery from copper anode slime by acidic ionic liquid

Abstract

Hydrometallurgical gold recovery from primary or secondary sources is mainly based on a cyanide process, which is very dangerous for the environment due to the high toxicity levels. In view of the environmental effect, the present study proposes a new green solvent called 1-ethyl-3-methyl-imidazolium hydrogen sulfate (EmimHSO4) ionic liquid (IL) to recover gold from copper anode slime (CAS). The optimum leaching conditions for maximizing gold recovery were determined by orthogonal array (OA) of Taguchi’s experimental design method. OA L16 (44) including four parameters with four levels each, was used to examine the effects of IL concentration (20%, 40%, 60%, 80% v/v), temperature (25, 50, 75, 95 °C), time (½, 1, 2, 4 h) and solid/liquid ratio (1/10, 1/15, 1/20, 1/25 g/mL) on leaching efficiency of the gold recovery. Statistical analysis of variance (ANOVA) was used to determine the relevance between experimental conditions and gold recovery. The selective leaching tests results showed that gold recovery up to 89.07% was attained on laboratory scale under the optimum leach conditions: 80% IL concentration, 75 °C, 4 h and 1/25 g/mL solid/liquid ratio. According to these results, EmimHSO4 IL provides a very good ambiance for the oxidative leaching of gold and can be offered as an alternative leaching agent instead of harmful cyanide-based solvents.