Improving reductive performance of zero valent iron by H₂O₂/HCl pretreatment: A case study on nitrate reduction

This study demonstrates a simple method to prepare zero valent iron (ZVI)-based agent (prtZVI) with outstanding reducing power via pretreating ZVI with H₂O₂/HCl. Characterization of the prtZVI system with ⁵⁷Fe Mössbauer spectroscopy, XRD, TEM and chemical analysis indicates that it is a well dispersed system, containing nanosized solids such as ZVI, magnetite, Fe^II-associated iron oxides/(oxy)hydroxides, as well as soluble species like Fe²⁺ and Cl⁻. Highly effective reduction of nitrate (20 mg N/L initially) by prtZVI could be realized in a broad pH range (4–10), short reaction time, and at low solid dosage, which is much superior to ZVIs pretreated by H₂O₂, HCl, or NaCl alone and the traditional ZVI systems as well. Long-term storage of the prtZVI system (30 d) did not pose any negative effect on the nitrate reduction. ¹⁵N isotopic analysis reveals that NH₄⁺ is the major aqueous product (>95%) and N₂ is the only gaseous one. Considering the outstanding reduction efficiency, simple synthesis, and long-term stability, the prtZVI system could serve as a promising ZVI technology for reductive removal of contaminants of concern.