Kinetic Modeling of Phosphate Adsorption onto Algae-Saturated Chitosan Composites from Aqueous Solution under Batch Conditions

Phosphate contamination in water bodies has emerged as a major environmental concern due to its role in eutrophication and water quality degradation. This study investigates the phosphate adsorption behaviour of algae-saturated chitosan composites synthesised using Spirulina platensis under batch experimental conditions. The adsorption performance was evaluated at an initial phosphate concentration of 50 mg L⁻¹, using 1.0 g L⁻¹ of the composite, at ambient temperature and pH 5.65 ± 0.1. The maximum phosphate removal efficiency reached 24.04 %, with adsorption equilibrium achieved within 120 minutes. Kinetic modelling indicated that the pseudo-second-order model (R² = 0.983) provided a better fit than the pseudo-first-order model (R² = 0.737), suggesting that chemisorption governs the adsorption process. The equilibrium adsorption capacity (qe​) calculated from the pseudo-second-order model was 13.51 mg g⁻¹, closely matching the experimental value of 12.04 mg g⁻¹. These results demonstrate the synergistic potential of algal biomass and chitosan as a low-cost, biodegradable, and efficient biosorbent for phosphate removal from aqueous solutions. The study offers a promising approach for developing sustainable materials for water purification applications.