Optimization of selective gold recovery from electronic wastes through hydrometallurgy and adsorption

Abstract

The feasibility of hydrometallurgy for metal extraction from electronic wastes was investigated in the current work. Samples were ground and preliminary extracted by nitric acid and aqua regia. The gold concentrations in nitric acid and aqua regia were measured as 1.82 mg L1 and 29.45 mg L1, respectively. In addition, extraction performances using Cl2 (oxidizer) were studied. Experiments were conducted by connecting an extraction reactor to an oxidizing electro-generator. It was found that copper and gold were mostly extracted by adjusting different extraction conditions, such as extraction time, HCl concentration, extraction temperature, current density, particle size range, sample mass (solution density), and stirring speed. Two specific extraction steps were employed to selectively extract copper and gold. It was detected that 98.1 % of copper was extracted using the first extraction step twice, whereas, in the final step, 95.1 % of gold was extracted from the residue sample of the first step. The gold recovery performances of five different resins were investigated, and IRA402 Cl and HPR9700 resins manifested the highest adsorption ability and selectivity. The adsorption mechanism was found to be a monolayer adsorption process, and the adsorption capacities of IRA402 Cl and HPR9700 resins reached 303.8 mg g1 and 295.4 mg g1, respectively. Finally, gold desorption from these resins was successfully performed using an acetone-HCl mixture as the eluent. Reusability tests revealed that these two resins could be reused at least 6–7 times with an adsorption capacity loss of less than 10 %.