One-step leaching mechanism for total elemental recovery from spent lithium-ion batteries utilizing ethylene diamine tetraacetic acid

Abstract

A process capable of leaching full component valuable metals including Ni, Co, Mn, and Li from spent lithium-ion batteries (LIBs) without additional reducing agents has been proposed. As a strong chelating organic acid, ethylene diamine tetraacetic acid (EDTA) is suitable for recovering up to 99.9 % of each metal element under optimal conditions of EDTA concentration of 0.5 M, liquid-solid ratio of 30:1 mL g−1, the temperature of 353 K, and leaching duration of 2 h. Kinetic analysis shows that the entire leaching process is controlled by the chemical reaction, accompanied by the apparent activation energy of 56.6 kJ mol−1 for Ni, 68.2 kJ mol−1 for Co, 49.5 kJ mol−1 for Mn, and 53.0 kJ mol−1 for Li, respectively. The thermodynamic mechanism indicates that EDTA acts as a proton chelating agent and Fe/Al exhibits a synergistic reduction effect during leaching process. In addition, the whole process is divided into three stages, where the behavior of each substance is specified. The individual ions in the leachate are separated by precipitation with different reagents and the filtrate can be recycled for the next stage of leaching, which also provides a novel approach for an industrial one-step leaching process.