Optimization of gold sorption from ammoniacal thiosulphate solution on anion exchange fiber using Taguchi experimental design

Abstract : Taguchi experimental design was used to optimize the experimental parameters for Au sorption from ammoniacal thiosulfate solutions containing 2 mg/L Cu complexed as cuprous thiosulfate [Cu(S2O3)3] 5− onto anion exchange fiber (METALICAPT® MFH11). An L9 orthogonal array was chosen to study the effect of three parameters, namely Au initial concentration (10-30 mg/L), fiber quantity (0.05-0.55 g) and temperature (20-30°C). The sorption tests were carried out in batch mode at a stirring rate of 500 rpm and pH of 9.3. The experimental data were processed using signal-to-noise ratio and the analysis of variance was used to determine the most significant parameters. The optimal conditions for Au sorption were found to be 30 mg/L Au concentration, 0.05 g of fiber and temperature of 20°C. The obtained results indicated fiber quantity as the most influential parameter on Au sorption with a contribution of 66%, followed by Au initial concentration with a contribution of 33%. In the optimal conditions, the sorption capacity of the fiber was found to be 16.8 mg/g, in good agreement with the predicted result by Taguchi method (16.7 mg/g). Further investigations are necessary to examine the elution behavior of gold from the fiber.