An Efficient Process for Recovering Copper as Cuo Nanoparticles from Acidic Waste Etchant Via Chemical Precipitation and Thermal Decomposition : Turning Waste into Value-Added Product

Due to the rapid progress in printed circuit board (PCB) industries, plenty of waste etchants, characterized by the high concentration of copper chloride and hydrochloric acid, are generated continuously, which has placed a heavy burden on the environment and metal resources. Herein, a succinct process for recovering Cu as CuO nanoparticles from acidic waste etchant (AWE) was proposed, which included efficient recycling Cu via oxalate precipitation, preparing CuO nanoparticles by thermal decomposing the precipitate, and recycling NaCl via evaporation crystallization. Comparison of copper precipitation by H2C2O4 and Na2C2O4 suggested that an excellent recovery efficiency of Cu was obtained by Na2C2O4 rather than H2C2O4. Through thermodynamic analysis, the H+-release mechanism was proposed to explain the significant difference in copper precipitation between Na2C2O4 and H2C2O4. Using the optimal conditions determined, 99.8% of Cu was recovered by Na2C2O4 without adjusting pH value. Further, CuO nanoparticles with a purity of 99.92% and particle size of 30 nm were prepared, and the phase transformation of Cu was investigated in-depth via various characterization methods. Besides, the chloride ions were recycled as sodium chloride (99.51%). This study might provide a potential environmental-friendly strategy to deal with strongly acidic waste etchant and achieve its high-value utilization