Ultrasound enhanced in-situ chemical oxidation for leaching Ag from zinc leaching residue and response surface optimization

Zinc leaching residue is the important source of silver due to its high silver content. The traditional leaching process of silver from zinc leaching residue has shortcomings such as higher acid or ammonium concentration, resulting in strong corrosion and serious pollution. Here developed an acid-free in-situ chemical oxidation technology using ultrasound enhanced persulfate to leach Ag from zinc leaching residue. The effects of leaching temperature, leaching time, sodium persulfate concentration, liquid–solid ratio, and ultrasonic power on the leaching efficiency of Ag were investigated. Under the optimal conditions, the maximum leaching efficiency of silver reaches 91.09 %. The leaching efficiency is higher than that without ultrasound. Kinetic analysis revealed that the activation energy of ultrasound enhanced leaching process is 65.23 kJ/mol, and the leaching process is controlled by chemical reactions. The ultrasound enhanced leaching process can reduce the activation energy of the reaction. Response surface methodology was employed to identify significant factors influencing the efficiency of Ag, which were found that sodium persulfate concentration and ultrasonic power were the most important factors. In addition, the developed method has a certain leaching effect on transition metals and is a potential solution to recover transition metals from secondary resources.