Advancing phosphate batch adsorption: Comprehensive modeling and scalability with granulated clay adsorbent in single and binary systems

Phosphate pollution from industrial and agricultural wastewater threatens aquatic ecosystems, promoting eutrophication and water quality deterioration. This study investigates the potential of granulated clay (GC) as a low-cost, high-capacity adsorbent for phosphate removal. The clay undergoes calcination at 830 °C, significantly enhancing its adsorption capacity and mechanical stability. The impact of clay dosage, initial phosphate concentration, and agitation speed on adsorption efficiency was examined. A kinetic model, the Film-Pore-Concentration-Dependent Surface Diffusion (FPCDSD) model, was developed to predict adsorption behavior in single and binary systems. Results show that calcined GC achieved a maximum adsorption capacity of 54.29 mg/g for phosphate. The FPCDSD model provided a better fit to experimental data compared to the Film-Pore Diffusion (FPD) and Film-Concentration-Dependent Surface Diffusion (FCDSD) models. The adsorption process is governed by external mass transfer, pore diffusion, and surface diffusion. Competitive adsorption in binary systems with phosphate and nitrate revealed GC's selectivity for phosphate due to its higher affinity. These findings highlight the potential of granulated clay as an effective, eco-friendly adsorbent for phosphate removal from wastewater, offering insights into adsorption kinetics, diffusion mechanisms, and competitive adsorption behavior. This study combats eutrophication with clay adsorbents, efficiently removing phosphate, scaling water treatment, and offering insights via modeling and prediction. • Explores affordable local clay adsorbent. • Introduces Film-Pore-Concentration-Dependent Surface Diffusion model. • Studies factors: concentration, agitation speed, dosage, size, porosity • Identifying key controlling mechanisms and mass transfer resistance • Predicts batch adsorption scalability potential.