Mechanism and Kinetics for Copper Leaching by Complexing with Lysine Bearing Two Amino Groups

In order to overcome the environmental problems associated with ammonia volatilization during the ammonia leaching process, the leaching effects of copper by amino acids with various numbers and substitution positions of amino functional groups were systematically studied. The results showed that lysine had the best leaching efficiency for copper. When the concentration of lysine was 0.2 mol/L, the leaching temperature was 20 °C, the molar ratio of lysine to copper was 3.88, the stirring speed was 250 rpm, the pH was 10, and the leaching time was 14 h, the leaching rate of copper reached 99%. The leaching results of copper containing smelting slag showed that lysine has an excellent effect on selective leaching of copper. The leaching kinetic results indicated that the rate-limiting step of the leaching process is controlled by the interfacial chemical reaction, with an apparent activation energy of 64.8 kJ/mol. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analyses confirmed that COO^- and -NH groups in lysine can form complexes with copper ions. Compared to conventional methods, this approach not only achieves environmentally benign disposal of heavy metal pollutants but also provides a novel strategy for the green recovery of valuable metals from secondary resources.