Gold Leaching from Printed Circuit Boards (PCBs) as one of the Urban Mine Resources using Thiosulphate: Optimization using Response Surface Methodology (RSM)

Abstract

Along with the decrease of metal resources in the natural ores, urban mine comes up as an alternative with two aspects of both resource and environmental protection due to recycle. Broken printed circuit boards (PCBs) as one of the urban mine resources contains valuable metals, such as, Au, Ag, and Ti, with high concentration, however, it has not been seriously managed in some developing countries, such as Indonesia. Focusing on gold extraction, safer leaching agent using thiosulphate has been applied in this study and scrutinized the optimum leaching conditions with respond surface methodology. Temperature and concentration of thiosulphate were varied and designed in accordance with three factorial. Leaching time was set for two hours and the shaking speed of waterbath was set at fixed value of 200 rpm. In order to quantify the final concentration of gold in the solution, Atomic Absorption Spectroscopy (AAS) was applied for all samples. Response Surface Method (RSM) is utilized to know the optimum result of Au extracted. The result shows that the optimum result of Au extracted by using ammonium tiosulphate is 0.5114 mg/L respectively with correlative equation as follow; Gold Concentration = 0, 127+0, 00268*T+0, 66*C-0, 000021*T2+1, 74*C2- 0, 0038*T.C. With T = temperature (°C) and C = thiosulphate concentration (M) The obtained R2 is 0.94 and the p-value is 0.037 showing the significance of the variable correlation in the equation.