Recovery of valuable metals from spent lithium-ion batteries by complexation-assisted ammonia leaching from reductive roasting residue

Recycling valuable metals in spent LIBs is not only in line with the purpose of resource recycling but also an important measure for environmental protection. In this article, a process using biomass reduction roasting followed by a unique complexation-assisted ammonia leaching is proposed. Using waste areca powder (WAP) as a biomass reducing agent, the roasted residue is leached in an aqueous solution for the carbonate. The leaching efficiencies of Ni, Co, and Mn reach over 99% under ammonia leaching conditions of 1.5 M ammonium citrate (AC), 3 M ethylenediamine (EDA). The kinetics of ammonia leaching indicates the activation energies of Ni, Co, and Mn are 51.8 kJ mol^-1, 47.7 kJ mol^-1, and 40.8 kJ mol^-1, respectively, which shows the whole duration is controlled by chemical reactions. Most importantly, this study systematically explores the mechanism of ammonia leaching and provided a useful recommendation for selecting the right ammonium salt.