Optimization of phosphate removal from aqueous solution using activated carbon supported zero-valent iron nanoparticles: application of RSM approach

Abstract

In this study, activated carbon (AC) prepared from cork powder was used in synthesis of AC stabilized nano-zero-valent iron (AC/NZVI) composite and evaluated phosphate (PO₄³⁻) removal efficiency from aqueous solution. The as-obtained AC/NZVI was characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD) analysis. Response surface methodology based on a three-level, three-factor, Box–Behnken design (B.B.D.) has been employed for determination of optimal combination of three significant process factors or variables such as temperature, solution pH and AC/NZVI dose, for maximum removal of PO₄³⁻ from aqueous solution. Based on B.B.D. experimental design, a limited number of experiments were performed in a cost-effective manner at initial PO₄³⁻ concentration of 211 mg L⁻¹ as a fixed input parameter. A statistically validated quadratic model was developed to predict the responses in the form PO₄³⁻ removal capacity from aqueous solution and adequacy of the model was evaluated using regression analysis and analysis of variance. The model predicted maximum PO₄³⁻ removal capacity of the AC/NZVI was 152.12 mg g⁻¹ under the optimal condition of process variables (temperature 60 °C, pH 3.5, and AC/NZVI dose 0.4 g L⁻¹) which was strictly closer to the experimental value (151.10 mg g⁻¹) obtained in batch experiment under the same optimize condition of process variables. The result of the study inferred that all three factors had a significant impact on removal of PO₄³⁻.