Realistic and sustainable phosphate adsorption using intercalant-engineered exfoliated serpentinite: mechanistic insights and real-water validation

This study investigates phosphate adsorption using exfoliated serpentinite produced by intercalation with potassium nitrate (KN/SP), urea (U/SP), and potassium acetate (KC/SP), with emphasis on performance, mechanism, and realistic applicability. All modified adsorbents showed strongly improved phosphate uptake, reaching maximum capacities of 127.85 mg g -1 (KN/SP), 154.18 mg g -1 (U/SP), and 183.54 mg g -1 (KC/SP), confirming the advantage of acetate-assisted exfoliation. Kinetic behavior followed the pseudo-first-order model, indicating rapid, surface-controlled adsorption. Equilibrium was best fitted by the Langmuir isotherm, supporting monolayer adsorption on energetically uniform sites. Statistical physics modeling provided steric and energetic descriptors, revealing high densities of accessible sites (Nm = 39.22–63.51 mg g -1 ), with KC/SP showing the highest site density. The number of adsorbed species per site (n ≈ 4) suggests multisite/multidocking adsorption via cooperative interactions with multiple surface functionalities. Adsorption energies (