Enhanced phosphate removal using nanostructured hydrated ferric-zirconium binary oxide confined in a polymeric anion exchanger

Abstract

Phosphate removal is an important measure required to control eutrophication of water bodies as it inhibits excessive algal growth. Currently available phosphate removal methods have various limitations and function poorly under wide pH ranges. This study successfully prepared and characterized a novel nanocomposite adsorbent, nHFZO@I402, which has high capacity and specific affinity towards phosphate. The nHFZO@I402 constituted of nanostructured hydrated ferric oxide and hydrated zirconium oxide loaded on the surface and inside the pores of a polymeric anion exchanger. Batch experiments were conducted to investigate the effects of varied conditions on phosphate adsorption. The results demonstrated that nHFZO@I402 achieved high phosphate removal efficiencies over a wide pH range (4–11), which indicates higher adaptability towards varying environmental conditions. In addition, nHFZO@I402 exhibited enhanced phosphate adsorption capacity regardless of coexisting anions (chloride, nitrate, sulfate, and carbonate) at different concentrations. Kinetic analysis suggested that the adsorption process best-fitted with the pseudo-second-order kinetic model, suggesting chemical sorption mechanism. Furthermore, the underlying mechanism of phosphate adsorption by nHFZO@I402 was assessing through XPS analysis. Phosphate removal was effected by the replacement of hydroxyl groups by phosphate species and interaction between ammonium groups and phosphate. In general, these results indicated that nHFZO@I402 is a highly efficient adsorbent for phosphate removal with excellent adaptability to varying and undesirable environmental conditions.