Removal of nitrate from water by acid-washed zero-valent iron/ferrous ion/hydrogen peroxide: influencing factors and reaction mechanism

Abstract

In this paper, a system consisting of acid-washed zero-valent iron (ZVI), ferrous ion (Fe²⁺), and hydrogen peroxide (H₂O₂) was employed for the removal of nitrate (NO₃^-) from water, and the reaction mechanism for this is discussed. The effects of acid-washed ZVI, Fe²⁺, H₂O₂, and initial NO₃^- concentration on nitrate removal were investigated. Acid-washed ZVI before and after reaction with nitrate were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results reveal that the combined system can enhance the corrosion of ZVI and facilitate aqueous nitrate reduction. The products of nitrate reduction are mainly ammonium, with some N₂. The ZVI particles after reaction may have a core of ZVI with an oxidation layer mainly consisting of Fe₃O₄.