Critical roles of Fe2+/Fe3+ in manipulating permanganate reactivity with zero-valent iron towards enhanced arsenite removal

Due to the higher toxicity and great threat to environmental safety and human health, the remediation of As(III) from wastewater attracts more and more attentions. The introduction of Fe2+ and Fe3+ into potassium permanganate (PP)-zero-valent iron (ZVI) system was used to rapidly and effectively remove arsenic (III) from wastewater. PP-ZVI system was rapidly activated by Fe2+ but Fe3+ in a slow way. The high removal efficiency of As(III) in Fe2+-PP-ZVI system was obtained at pH(ini) 1-9. The removal of As(III) by Fe2+-PP-ZVI system can be well described by the pseudo-second-order kinetic expression. The results of scanning electron micrographs (SEM) showed that the quickly enhanced corrosion of ZVI surface caused the different morphologies of ZVI surface. ZVI acted as a resource of Fe2+ for the activated generation of. OH radicals, which oxidized As(III) to As(V). High-resolution X-ray photoelectron spectrometer (HR-XPS) proved that MnFe2O4, MnO2 and MnO were formed, which controlled the generation of hydroxyl radical ((OH)-O-center dot). Most of As(III) was oxidized to As(V) but a very small proportion was reduced to As(0) during the removal process. The Fe2+-PP-ZVI system may provide an effective and new technology for the efficient and fast remediation of heavy metals from wastewater.