Phosphate Removal from Water Using Novel Fe2+-KMnO4 Process: Significant Role of In Situ–Formed Fe(III)

This paper investigated the phosphate removal from aqueous solutions using the Fe2+-KMnO4 process. Results indicated that the reaction of Fe2+ and KMnO4 in the Fe2+-KMnO4 process could synergistically increase the removal of phosphate compared with those achieved by Fe(III) coagulation and MnO2 adsorption at pH≥7. It was necessary that the optimal Fe/P molar ratio was above 3 for effective phosphate removal because of effects of coexisting substances. At pH 7.0, phosphate removal approached a maximum within approximately 5 min. Competing effects of sulfate, bicarbonate, and silicate on phosphate removal were slight. The presence of Ca2+ and Mg2+ had limited effects on phosphate removal at pH≤4 but resulted in a significant increase at pH≥5. Coprecipitation was considered as the dominant mechanism about phosphate removal in the Fe2+-KMnO4 process. Fe(III) formed in situ was primarily responsible for phosphate removal. Additionally, in-situ-formed MnO2 also contributed to the phosphate removal through complexation adsorption. The Fe2+-KMnO4 process had the potential to be utilized in natural water and municipal wastewater treatment for phosphate removal.