Co-Precipitation of Metal Oxalates from Organic Leach Solution Derived from Spent Lithium-Ion Batteries (LIBs)

Abstract

Recent studies in hydrometallurgy are focused on developing eco-friendly and selective leach agents such as organic acids. These agents can extract metal ions, which are usually separated through precipitation methods. When traditional methods are used, the separation is complex and time-consuming, and each metal cation is required to be isolated separately. Moreover, extracted metal salts are subsequently recombined in the regeneration of cathode materials. To simplify this, a novel simultaneous precipitation approach has been developed, allowing the separation of metal salts that can directly contribute to regenerating novel cathode materials, bypassing the need for separate isolation. This study aimed to recover cobalt, nickel, and manganese from the organic leach solution of spent lithium-ion batteries (LIBs) through co-precipitation of metal oxalates. The investigation includes the selection of organic acids and the best parameters for the leaching process, as well as testing different molar ratios of the metals M2+ (M = Co, Ni, Mn) to oxalic acid (1:3, 1:4.5, 1:6, and 1:7.5) to examine the effects of the precipitating agent on the recovery percentages of the metals. The findings indicate that 2 M citric acid and 4 vol% H2O2 is the optimal parameter in the leaching process. Meanwhile, in the co-precipitation process, an increase in the molar ratio leads to a corresponding rise in the resulting metal recoveries. At the ratio of 1:7.5, cobalt, nickel, and manganese were recovered to the extent of 99.26%, 98.93%, and 94.01%, respectively. Nevertheless, at the increased molar ratio, the co-extraction of lithium and aluminum was observed, resulting in reduced selectivity and decreased precipitate purity.