RESUMEN
Demand for lithium-ion batteries (LIBs) is projected to maintain unprecedented acceleration for decades, towards satisfying international climate and source objectives. LIB wastes pose a threat to the environment, but also may be considered a strategic, high-grade resource. Yet, recycling the black mass of waste LIBs, which contains plastic, C, Li, Fe, Ni, Co, Mn, Cu, and Al, is very complex. Herein, the direct selective leaching of Li from the industrial-grade black mass powder of waste LIBs is proposed for the first time. Results demonstrated that the leaching efficiency of Li is shown to exceed 97%, while other metals remain below 1%. The mechanism of selective leaching was also investigated in this study. Under the experimental conditions, Fe is not leached out and remains in the form of solid FePO4. As for other impurity metal elements, they are removed from the solution due to the alkaline environment of the post-leaching solution and the adsorption effect of the anodic carbon. Furthermore, the alkaline post-leaching solution can avoid the neutralizing stage before the precipitation of lithium salts. This highly efficient and Li-selective leaching strategy offers a broadly applicable approach to reclaiming critical energy minerals from the black mass of wasted LIBs.
RESUMEN
Layered H2TiO3 has been studied as an ionic sieve material for the selective concentration of lithium from solutions. The accepted mechanism of lithium adsorption on H2TiO3 ion sieves is that it occurs via Li+-H+ ion exchange with no chemical bond breakage. However, in this work, we demonstrate that lithium adsorption on H2TiO3 occurs via O-H bond breakage and the formation of O-Li bonds, contrary to previously proposed mechanisms. Thermogravimetric analysis results show that the weight loss due to dehydroxylation decreases from 2.96 wt % to 0.8 wt % after lithium adsorption, indicating that surface hydroxyl groups break during lithium adsorption. Raman and Fourier transform infrared spectroscopy studies indicate that H2TiO3 contains isolated OH groups and hydrogen-bonded OH groups. Among these two hydroxyl groups, isolated OH groups present in the HTi2 layers are more actively involved in lithium adsorption than hydrogen-bonded OH groups. As a result, the actual adsorption capacity is limited by the number of isolated OH groups, whereas hydrogen-bonded OH groups involved are for stabilizing the layered structure. We also show that H2TiO3 contains a high concentration of stacking faults and structural disorders which play a crucial role in controlling lithium adsorption properties.
