2552 Table 01: Characteristics of IRC747 and IRC748 resins. IRC747 IRC748 Ionic Form as Shipped Na+ Na+ Uniformity Coefficient ≤ 1.2% ≤ 1.2% Shipping Weight 755 g·L-1 750 g·L-1 Water Retention Capacity 64 – 69% 60 – 69% Particle Diameter 550 ± 50 μm 575 ± 75 μm Total Exchange Capacity ≥ 1.75 eq·L-1 1.35 eq·L-1 Functional Group –CH2–NH–CH2– PO3–Na2 Iminodiacetic 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 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). qB = (CC −CB m ).V (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).
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