Effect of coexisting ions on the selective adsorption and mechanism of lithium by ion sieve

The recovery of lithium from coal-based solid wastes has attracted increasing attention because, of their higher strategic importance. However, the coexisting ions in the leaching solution take challenges to selective adsorption. This study systematically investigates the influence of silicon, aluminum, and calcium ions on the adsorption behaviors of lithium. In this study, three manganese-based ion sieves, HMn₂O₄ (HMO-1), H₁.₃₃Mn₁.₆₇O₄ (HMO-2) and H₁.₆Mn₁.₆O₄ (HMO-3), derived from LiMn₂O₄, Li₁.₃₃Mn₁.₆₇O₄ and Li₁.₆Mn₁.₆O₄ precursors, were synthesized and employed as adsorbents for Li+ recovery. Adsorption experiments were conducted in simulated leaching solutions with varying ion concentrations. The results show that SiO32- and Al(OH)4− significantly restrain lithium adsorption by competing for active sites in the one-impurity ion system, whereas Ca2+ has a lower effect on HMO-1 but reduces Li+ adsorption on HMO-2 and HMO-3 by charge repulsion. The coexisting ions hinder Li+ adsorption by altering surface chemistry. The formation of MnSiO₃ sediment reduces available Mn for redox-based Li+ exchange, while surface sediment of Al(OH)₃ and adsorption of Ca2+ hinder Li+ and Mn2+ mass transfer through physical blockage and electrostatic repulsion. This study provides insights into the competitive interactions in multi-ion systems, offering guidance for optimizing the selective recovery of lithium from coal-based solid wastes leaching solution.