One-step extraction of high-purity CuCl2·2H2O from copper-containing electroplating sludge based on the directional phase conversion

Highlights: • A novel process was developed for copper extraction from electroplating sludge. • 97% of the Cu was selectively recovered via precise phase directional regulation. • High-purity product CuCl₂·2H₂O was directly extracted in one step. • A valuable reference was provided for disposal of polymetallic solid wastes. The recovery of heavy metals is a vital way to turn electroplating sludge into resources and reduce its environmental hazards. However, the complex compositions of the polymetallic electroplating sludge severely limit the selective recovery of metal resources such as copper. In this study, we took a kind of copper-containing electroplating sludge (C-ES) as an example present and investigated the process of copper extraction. The copper and other metals were directional converted through an accurate phase transformation process carried out by chlorination combined with thermal regulation. Eventually, the copper was selectively recovered in the form of CuCl₂·2H₂O, while the rest of the metals were converted into stable metal salts or oxides. The HCl solution was the best regulator for selective copper recovery. Under the optimal conditions, the recovery of copper approached 97% and the purity of the CuCl₂·2H₂O product was about 95%. The kinetic reaction equation of the CuCl₂ volatilization process can be described by Power Low, G(α) = α^1/15. The economic estimate based on experimentation indicates the profit of recycling CuCl₂·2H₂O is about $23.2/kg. This work provides a novel, simple, and efficient approach to the selective recovery of heavy metal from polymetallic solid wastes.