Co-treatment of copper electrolytic sludges and copper scraps for the recycled utilization of copper and arsenic

The Cu electrolytic sludge is a hazardous waste because of its high Cu and As contents. In contrast, As content in Cu scraps is low but causes massive floating slime to be formed during its electrolytic refining, thus decreasing quality of the obtained cathode Cu. In this study, an innovative process was developed to transfer As from the electrolytic Cu sludge into Cu scraps, realizing the recycled utilization of As and Cu from them. The Cu electrolytic sludge was firstly subjected to oxidization roasting in the presence of Ca(OH)2, where the As2O3, Cu3As, and elemental As from the sludge were oxidized and immobilized into Cu3(AsO4)2 and Ca3(AsO4)2. The Cu3(AsO4)2 and Ca3(AsO4)2 retained in the roasted residue. The As volatilization efficiency was only 3.7% under the optimized roasting condition. In the next co-fire-refining of the roasted residue and Cu scraps, the As in Cu3(AsO4)2 and Ca3(AsO4)2 was reduced and transferred into the refined Cu at a content of 0.17 wt%. Although a volatile As2O3 could be generated in this co-fire-refining, the molten Cu scraps restricted As volatilization by forming a Cu–As alloy. With the obtained As-containing refined Cu used in electrolytic refining, the formation of floating slime could be decreased and consequently the quality of the cathode Cu would be increased. This research provided an alternative technology for Cu and As recycling by co-treating Cu electrolytic sludges and Cu scraps. © 2023 Elsevier Ltd