Ion-Exchange Resins For Lithium Hydroxide Purification C. R. dos S. Brigido¹*, J. G. Sanches¹, L. da C. Bastos¹, J. M. S. R. dos Santos¹, P. F. A. Braga¹ ¹Centre for Mineral Technology (CETEM), Av. Pedro Calmon, 900, Cidade Universitária, Rio de Janeiro 21941-908, Brazil, e-mail: cbrigido@cetem.gov.br (*Presenting author: cbrigido@cetem.gov.br) Abstract This study evaluates the performance of fixed-bed column systems for the selective removal of metallic impurities, specifically sodium and calcium, from a 1 mol·L⁻¹ LiOH solution. The methodology is based on the application of functional chelating resins, IRC 747 and IRC 748, operating under continuous flow rates of 10, 20, and 30 mL·min⁻¹. Regarding ion exchange capacity, the results demonstrate that the IRC 748 resin exhibits superior values, reaching 2.00 meq·g⁻¹, while the IRC 747 shows a capacity of 1.90 meq·g⁻¹. The analysis of the breakthrough curves reveals that process efficiency is strictly dependent on system hydrodynamics and the intrinsic selectivity of the matrices. Lower flow rates (10 mL·min⁻¹) provide an extended residence time, which promotes the full utilization of active sites and results in a superior breakthrough time, essential for long-term purification processes. Conversely, high flow rates (30 mL·min⁻¹) reduce interfacial contact, leading to premature bed saturation and a less efficient mass transfer zone. Both resins demonstrate high selectivity for calcium, maintaining residual concentrations below 5 mg·L⁻¹ in the purified effluent. Additionally, the study indicates that IRC 747 possesses a robust affinity, capable of removing up to 76% of Ca2+ and 92% of Mg2+ under specific conditions, confirming the effectiveness of these materials in the treatment of contaminated solutions. Keywords Lithium hydroxide, Ion-exchange resin, Battery grade. 1. INTRODUCTION The production of battery-grade lithium hydroxide (LiOH) requires the rigorous removal of metallic contaminants, specifically magnesium (Mg2+), calcium (Ca2+), and sodium (Na+), a process in which the use of ion-exchange resins is based on the final polishing capacity of concentrated solutions through the exploitation of the affinity between ions in solution and the functional groups of the polymeric matrix. This methodology presents substantial technical advantages compared to conventional chemical precipitation methods, as precipitation is limited by the solubility product constant (Ksp) of the solid phases, which frequently results in residual impurity concentrations above the permitted limits, whereas ion exchange allows for purification levels in the parts per billion (ppb) range. Furthermore, the use of resins avoids the introduction of additional chemical precipitating agents and provides more precise kinetic control over ionic selectivity; however, the success of the process depends on the minimization 102
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