• Al³⁺, Ca²⁺, Na⁺ modify Amberlyst-15 to boost phosphate adsorption capacity. • Phosphate removal enhanced by electrostatic, ion exchange, and complexation. • Al³⁺ and Ca²⁺ improve selectivity for phosphate over competing anions. • Adsorption follows pseudo-second-order kinetics, suggesting chemisorption. • Removal order: Al³⁺ > Ca²⁺ > Na⁺; Selectivity: PO₄³⁻ > HCO₃⁻ > Cl⁻ > NO₃⁻ > SO₄²⁻. Phosphorus pollution from domestic, agricultural, and industrial sources accelerates eutrophication, leading to algal blooms and water quality issues. This study evaluates a macroporous resin, Amberlyst-15(H), modified with Na⁺, Ca²⁺, and Al³⁺ ions for phosphate adsorption under varying time and temperature conditions. In single-component systems, removal efficiencies followed the order: Amberlyst-15(Al³⁺) (99.9%) > Amberlyst-15(Ca²⁺) (96.1%) > Amberlyst-15(Na⁺) (92.7%). In binary systems, Amberlyst-15(Al³⁺) showed selectivity in the sequence PO₄³⁻ (99.9%) > HCO₃⁻ (98.9%) > Cl⁻ (96.6%) > NO₃⁻ (93.9%) > SO₄²⁻ (75.7%). Phosphate adsorption on Amberlyst-15 was strongly dependent on the counter-cation form, exhibiting a clear adsorption pattern of Na + < Ca 2 < Al 3+ . This behavior suggests that phosphate uptake is influenced by the increasing cation charge density, leading to stronger interactions for multivalent forms. Al 3+ -exchanged Amberlyst-15 demonstrated excellent reusability, with phosphate effectively desorbed using 0.5 M NaOH and adsorption capacity well maintained over five successive adsorption-desorption cycles, confirming its superior performance among the tested resins. Characterization using FTIR, TGA, BET, XRD, SEM, and EDS confirmed successful ion incorporation and provided mechanistic insights. SEM–EDS verified metal ion loading onto the resin surface. Adsorption isotherms, Langmuir and the Freundlich, and adsorption kinetics pseudo-first-order and pseudo-second-order models fit best, while thermodynamic parameters (Ea, ΔH, ΔS, ΔG) derived from Arrhenius and Eyring equations confirmed the feasibility and energetics of the process. Overall, Amberlyst-15(Al³⁺) demonstrated exceptional phosphate removal capacity, highlighting its potential for scalable application in domestic and pilot-scale water treatment.
Kazim et al. (Sun,) studied this question.