DECONTAMINATION OF NITRATES AND NITRITES IN WASTEWATER BY ZERO-VALENT IRON NANOPARTICLES

The chemical reduction of nitrate or nitrite species by zero-valent iron nanoparticle (ZVIN) in aqueous solution and related reaction kinetics or mechanisms using fine structure characterization were investigated. Experimentally, ZVIN of this study was prepared by borohydride reduction method at room temperature. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20–50 nm were observed with FE-SEM analysis. The kinetic model of nitrites or nitrates reductive reaction by ZVIN is proposed as a pseudo-first-order kinetic equation. The nitrite and nitrate removal efficiencies using ZVIN were found 65–83% and 51–68%, respectively, based on three different initial concentrations. By using XRD patterns, the quantitative relationship between nitrite and Fe(III) or Fe(II) becomes similar to the one between nitrate and Fe(III) in the ZVIN study. The possible reason is linked with a faster nitrite reduction by ZVIN. In fact, the occurrence of the relative faster nitrite reductive reaction suggested that the passivation of the ZVIN have a significant contribution to iron corrosion. The XANES spectra show that the nitrites or nitrates reduce to N₂ while oxidizing the ZVIN to Fe₂O₃ or Fe₃O₄ electrochemically. It is also very clear that decontamination of nitrate or nitrite species in groundwater via the in-situ remediation with a ZVIN permeable reactive barrier would be environmentally attractive.