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 Fe-57 Mossbauer 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. N-15 isotopic analysis reveals that NH4+ 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.