Removal of Phosphate from Aqueous Solution Using Anion Exchange Resin: Equilibrium Isotherms and Kinetics

Phosphate removal before discharging wastewater into the receiving environment is important since eutrophication has become an environmental problem on a global scale. In this study, phosphate ion removal from aqueous solutions was investigated using a strong anion exchange resin, Purolite A200E. The effects of initial phosphate ion concentration, initial pH value of the solution, resin dosage, stirring speed, presence of some anions in solution, and temperature on the ion exchange process were researched. Resin dosage, stirring speed, and temperature increases were determined to increase the phosphate removal rate. The highest phosphate removal efficiency was observed in the pH interval 7-9. With initial phosphate concentration of 10 and 20 mg/L, 1.50 g/500 mL resin dosage fully removed phosphate at the end of 120 min. However, at phosphate concentrations higher than 20 mg/L, increasing phosphate concentrations caused a reduction in removal efficiency. The competitive anion with the most effect on phosphate removal was sulfate while adding bicarbonate did not affect phosphate removal. Pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models were used to assess experimental data. Kinetic studies revealed that the ion exchange process can be explained better by the PFO kinetic model. Equilibrium isotherm data were analyzed with the Freundlich and Langmuir equations, and the Freundlich isotherm model fitted the equilibrium data better.