both in the external liquid film and within the resin particles. To evaluate the kinetic behavior of the studied resins, ion exchange assays were conducted in batch and continuous flow systems, using the monitoring of residual ionic concentration over time as the analytical basis (ROBSHAW, et al., 2019). The experimental procedure commenced with the immersion of 10 g of resin in a beaker containing 200 mL of a 1 mol·L⁻¹ LiOH solution, maintained under constant stirring at room temperature, as illustrated in Figure 1. Solution samples were collected at 15-minute intervals to monitor the ion exchange process over time. Subsequently, the system containing the resin was subjected to filtration using a filter assembly equipped with JP42 filter paper (15 cm diameter, Quanty® brand), allowing the separation of the solid phase for subsequent analysis of the filtered solution. The concentrations of calcium, magnesium, sodium, and lithium were determined by flame photometry using Digimed® equipment, model DM-64-5E. The loading capacity of the resin (qt), defined as the amount of ions adsorbed per unit mass of the material at a given time t, was calculated according to Equation (01), following the methodological reference described by Abusultan et al., (2023). = 0− ( ) . (1) Onde: o qt: Ion exchange capacity over time “t” (mg·g-1). o C0: Initial ion concentration in the solution (mg·L-1). o Ct: Ion concentration in the solution at time “t” (mg·L-1). o V: Total volume of the solution (L). o m: Resin mass utilized (g). Figure 1: Batch kinetic test. (1) Heating plate; (2) Resins; (3) 1 mol·L⁻¹ LiOH solution; (4) Beaker; (5) Magnetic stirrer; (6) Thermometer. Source: Authors. The fixed-bed column system operating under continuous flow conditions is schematically presented in Figure 2. The experimental procedure consisted of percolating a lithium hydroxide (LiOH) solution, at a concentration of 1 mol·L⁻¹, through the polymeric bed. To ensure 105
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