without the requirement for additional chemical reagents. The efficacy of this separation arises from the specific interaction between the functional groups of the polymeric matrix and the contaminants, although the economic viability of the system demands rigorous control of the competitive adsorption of the analyte of interest, lithium (Li+), to prevent significant mass losses during purification (BING et al., 2020). The objective of this study was to evaluate the efficiency of IRC 747 and IRC 748 ion-exchange resins in the purification of lithium hydroxide ($LiOH$) solutions intended for crystallization and subsequent lithium-ion battery manufacturing, as an innovative technique to replace chemical precipitation. Although ion exchange is a consolidated method for obtaining lithium compounds from brines, its application in the refining of $LiOH$ derived from spodumene ore still lacks extensive scientific and industrial exploration. To substantiate such feasibility, the work investigated the ion-exchange capacity of the resins, the adsorption kinetics in batch systems, and the dynamic behavior of the system under continuous flow in a fixed-bed regime. 2. METHODS AND MATERIALS The Amberlite™ IRC747 and IRC748 cation exchange resins, manufactured by DuPont®, were evaluated regarding their efficiency in purifying lithium-containing solutions, a precursor stage in the crystallization process aimed at obtaining battery-grade LiOH. The IRC747 resin is applied for the separation of ions such as zinc and lead, as well as for brine purification (Abusultan et al., 2023). Similarly, the IRC748 resin is utilized for brines, notably in the removal of trace metals and metal recovery. Table 1 presents the primary characteristics and technical specifications for each resin. Table 01: Characteristics of IRC747 and IRC748 resins. IRC747 IRC748 nic Form as Shipped a+ a+ niformity Coefficient 1.2% 1.2% hipping Weight 55 g·L-1 50 g·L-1 Water Retention apacity 4 – 69% 0 – 69% article Diameter 50 ± 50 μm 75 ± 75 μm otal Exchange Capacity 1.75 eq·L-1 35 eq·L-1 unctional Group CH2–NH–CH2–PO3–Na minodiacetic acid Source: Adapted from Dupont® (2023A-B). The kinetics of processes involving ion exchange resins describe the rate at which ions in solution are replaced by counter-ions associated with the polymeric matrix of the adsorbent material. Unlike conventional homogeneous chemical reactions, this phenomenon is predominantly governed by mass transfer mechanisms, especially diffusive processes occurring 104
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