Cobalt recovery and microspherical cobalt tetroxide preparation from ammonia leaching solution of spent lithium-ion batteries

Abstract

A process for recovering Co and preparing microspherical Co3O4 through NH3 distillation and phase transformation from ammoniacal solution was investigated. As the basis of thermodynamics, the solubility of Co at different NH3 and CO32− concentrations was studied, and then the effects of different NH3 distillation conditions on Co recovery rate were discussed. Over 94% Co and 96% NH3 were recovered through NH3 distillation, and the cobalt was precipitated in form of cobalt carbonate ammonium compound salt. Through the analysis of the formation mechanism of the precursor, the precipitation process of cobalt could be divided into two stages, and the cobalt precipitation rate was significantly accelerated in the second stage. In phase transformation, the effect of temperature on the roasted product was investigated. The microspherical Co3O4 with a microporous structure was prepared at 300 °C, and Co3O4 with a mesoporous structure and high-spin state was obtained at 750 °C.