Adsorption performance and mechanism of HFO/pumice composites for phosphate in water

Abstract

Excessive phosphorus is a principal cause of water eutrophication. Adsorption is an effective method for phosphorus removal. Yet there is little research on the adsorption performance and mechanism of phosphorus with HFO (hydrous ferric oxide)/pumice composites. In this study, the HFO/pumice composites were prepared, and the adsorption performance and mechanism of HFO/pumice composites for phosphorus were researched. The results indicated that the phosphorus adsorption performance reached a maximum value of 5.69 mg·g⁻¹ when the pH was 7. The adsorption performance increased with temperature. Moreover, when Cl^-, SO₄^2- and HCO₃^- coexisted, HCO₃^- had a greater effect on the adsorption performance of the HFO/pumice composites for phosphorus, and the adsorption performance decreased gradually with the increase of HCO₃^- concentration. The adsorption isotherms indicated that the Langmuir isotherm model was more suitable to describe the adsorption behavior of the HFO/pumice composites for phosphorus, and the correlation coefficient was 0.9785. In addition, the pseudo-second-order kinetic was more consistent with the adsorption mechanism of HFO/pumice composites for phosphorus. The internal diffusion model showed that the combination of external mass transfer and internal diffusion controlled the adsorption rate of the HFO/pumice composites for phosphorus. The experimental results showed that the adsorption mechanisms of HFO/pumice composites for phosphorus mainly involved pore filling, electrostatic interaction, and surface complexation.