Removal of phosphate from aqueous solution using nanoscale zerovalent iron (nZVI)

Nanoscale zerovalent iron (nZVI) was used to remove phosphate from aqueous solution, and the influence of pH, ionic strength and coexisting anions on phosphate removal was investigated. The results agree well with both Langmuir model and Freundlich model, and the calculated maximum adsorption capacity of phosphate was 245.65 mg/g, suggesting significantly higher and excellent uptake of phosphate by nZVI. The removal of phosphate obviously decreased with an increasing pH due to the isoelectric point (IEP) of nZVI, but exhibited no change with ionic strength and coexisting anions (except carbonate anion). The microstructure of fresh and reacted nZVI was characterized by FT-IR, XRD and XPS and these results indicated that no redox reaction occurred to the P(V). These observations shed light on the mechanisms of phosphate removal were mainly adsorption and coprecipitation processes. The higher uptake of phosphate indicates that nZVI was a suitable and effective material for phosphate removal.