High-efficiency recycling of copper-cadmium slag by ozonation with ultrasonic catalysis

Abstract

Copper-cadmium slag, a kind of hazardous metallurgical solid waste, has attracted attention in the fields of environmental protection and resource recovery because of its high output and richness of valuable metals. However, it is difficult to separate and recycle efficiently due to its oxidation resistance and strong wrapping property. To address this challenge, the ozonation with ultrasonic catalysis method is proposed for leaching of copper-cadmium slag in this work. Mechanical and cavitation effects of ultrasound can break wrapping layer and renew reaction interfaces. The active free radicals produced by ultrasonic/ozone can enhance the oxidation of reaction system and cause the inert metal copper to oxidize more easily. The leaching percentage of copper is 99.3%, which is 45.7% higher than that of conventional condition. Diffusion is proved to be the restrictive link in the copper dissolution process via kinetic experiment with a low activation energy of 3.71 kJ/mol under ultrasonic/ozone condition. The hydroxyl radical is detected by electron paramagnetic resonance and confirmed that it is beneficial to increase the recovery rate of metal in slag by quenching experiment. This study illustrates the value of ozonation with ultrasonic catalysis technology in efficient and green economy separation and recovery of various metals from hazardous waste.