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 H 2 O 2 /HCl. Characterization of the prtZVI system with 57 Fe 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 Fe 2+ 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 H 2 O 2 , 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. 15 N isotopic analysis reveals that NH 4 + is the major aqueous product (>95%) and N 2 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.