Abstract:China generates over 10 million tonnes of electroplating sludge annually, which contains high concentrations of heavy metals such as Cr, Cu, and Ni. Conventional hydrometallurgical techniques (e. g. , acid, alkaline, and ammonia leaching) face challenges including secondary pollution and equipment corrosion. Amino acids exhibit high affinity for chalcophile metals (e. g. , Cu, Ag, Au) and form stable complexes, making them a research focus in hydrometallurgy. This study proposes a copper leaching process from electroplating sludge using amino acid complexation. The effects of different amino acids on copper leaching efficiency were systematically investigated. Lysine was identified as the most effective leaching agent, and optimal leaching conditions were determined through single-factor experiments and comprehensive tests. The resulting products were characterized, leading to the following key conclusions: Among arginine, citrulline, glycine, glutamine, theanine, and lysine, lysine achieved near-complete copper leaching (>99%) within 6 h at a relatively low concentration of 0.2 mol/L, demonstrating strong industrial application potential; other amino acids did not meet production requirements. The optimal parameters for copper leaching with lysine were: lysine concentration 0.75 mol/L, liquid-solid ratio 50:1, temperature 328 K, and leaching time 5 h, under which the copper leaching rate reached 93%. Meanwhile, other valuable metal components were scarcely leached, indicating that lysine selectively extracts copper from electroplating sludge. The mechanism involves complexation of Cu2?with -COO? and -NH? groups in lysine, with -NH? showing stronger coordination ability than -COO?. Kinetic analysis revealed that the leaching process follows a mixed diffusion-controlled mechanism, with an apparent activation energy of 36.5 kJ/mol. Compared with existing glycine-based systems, lysine offers significantly faster leaching rates and superior selectivity for copper. These findings provide new insights into the eco-friendly disposal of heavy metal contaminants and green recovery of valuable metals.
