Abstract:Spent copper-containing etchants produced in metallurgical and chemical processes are classified as typical hazardous wastes. These effluents are highly corrosive and characterized by high copper (Cu) concentrations (up to 10 wt.%) and high salinity. Comprehensive resource utilization is crucial for the effective treatment and Cu recovery of these spent etchants. This paper reviews the latest research advances in technologies for the comprehensive utilization of such wastewater, including electrowinning, solvent extraction, metal replacement, and chemical precipitation. The mechanisms of Cu recovery are elucidated, and key processes and development trends are analyzed. Among these technologies, electrochemical deposition is frequently employed for the in situ recovery of Cu and etchant regeneration from acidic spent etchants. The Cu recovery efficiency and purity can be as high as 100% and 99.99%, respectively. Future development of this technology should focus on mitigating chlorine gas emissions and further improving product purity. Solvent extraction is primarily utilized for the regeneration of alkaline spent etchants, as well as the extraction and enrichment of Cu, with extraction rates reaching 99.9%. Furthermore, combining extraction with other methods (e.g., electrochemical deposition and neutralization-precipitation) enables the recovery of various high-value products, such as high-purity copper and copper sulfate. Metal replacement using iron and aluminum is commonly applied for the recovery of sponge copper from spent acidic etchants. However, the purity of the resulting sponge copper is relatively lower (approximately 80%). Moreover, the pH of the post-reaction wastewater is typically less than 3, and the residual copper concentration remains around 1 wt.%, necessitating further treatment. Chemical precipitation is the most widely applied technology for treating both acidic and alkaline spent etchants, facilitating the recovery of various products (e.g., copper sulfate and basic copper chloride). Considering the characteristics of spent etchants, such as copper speciation, concentration, and pH, future research should focus on: (1) intergrating multiple technologies (e.g., solvent extraction and electrochemical deposition) to achieve stepwise resource utilization and comprehensive wastewater treatment, (2) developing corresponding reaction equipment to promote the industrial application of these technologies, and (3) exploiting new, high-value copper products to increase the potential economic benefits from spent etchant recovery. Close-