Development of Fe0/Fe3O4 composites with tunable properties facilitated by Fe2+ for phosphate removal from river water

Abstract

Phosphorus (P) has been overused for decades in agriculture and industry, such that excess phosphorus inevitably enters natural waters, especially river water, via runoff. Trace phosphate in natural water will cause eutrophication, and it is important to achieve low concentration phosphate removal effectively because of the increasingly stringent standards. In this study, a new technology, using Fe0/Fe3O4 composites facilitated by Fe2+ for low concentration phosphate removal was developed. The amount of Fe3O4 on the Fe0 surface was tuned and Fe0/Fe3O4-2 was proved to have best performance in phosphate removal and iron corrosion. The initial Fe2+ concentration of 0.5 mg/L was chosen for effective phosphate removal and meeting an acceptable total iron concentration below 0.3 mg/L after treatment. The generated iron corrosion products showed a high phosphate removal capacity and favorable selectivity towards phosphate in the presence of co-existing anions and NOM. The phosphate in real river water was decreased from 0.4 mg-P/L to 0.010 mg-P/L by using 0.5 g/L Fe0/Fe3O4-2 facilitated by 0.5 mg/L Fe2+. Adsorption, co-precipitation and precipitation contributed to phosphate removal, and the main removal mechanism was adsorption, which included electrostatic attraction and inner-sphere complexation. This study highlights a promising new method for the removal of low concentrations of phosphate from river water.