Fine structure characterization of zero-valent iron nanoparticles for decontamination of nitrites and nitrates in wastewater and groundwater

Abstract

The main objectives of the present study were to investigate 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. This work also exemplifies the utilization of field emission-scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and x-ray diffraction (XRD) to reveal the speciation and possible reaction pathway in a very complex adsorption and redox reaction process. Experimentally, ZVIN of this study was prepared by sodium borohydride reduction method at room temperature and ambient pressure. The morphology of as-synthesized ZVIN shows that the nearly ball and ultrafine particles ranged of 20-50 nm were observed with FE-SEM or TEM 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. Based on the XRD pattern analyses, it is found that the quantitative relationship between nitrite and Fe(III) or Fe(II) is similar to the one between nitrate and Fe(III) in the ZVIN study. The possible reason is due to the 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 extended x-ray absorption fine structure (EXAFS) or x-ray absorption near edge structure (XANES) spectra show that the nitrites or nitrates reduce to N 2 or NH 3 while oxidizing the ZVIN to Fe 2 O 3 or Fe 3 O 4 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.

Green Synthesis of Iron Nanoparticles and Their Environmental Applications and Implications

“…Among these metallic nanoparticles, iron nanoparticles (FeNPs) have promising advantages that can combat environmental pollution. The interest in nanoscale zero-valent iron (nZVI) in environmental remediation is increasing due to the reactivity of nanoscale iron having a large surface area to volume ratio [6,7]. The production of iron nanomaterials, such as metallic iron and oxide of iron via a more convenient greener route, is a great step forward in the development of nanomaterials.…”

Activation process of air stable nanoscale zero-valent iron particles

“…Besides organic (halogenated) compounds, nZVI can reduce and/or immobilize harmful metals and metalloids [2,3] and other ions: PO4 3- NO3 -, NO2 - [4]. Depending on the nature of the contaminant, there are many proposed mechanisms and pathways of iron action: reduction, adsorption, reduction and adsorption, adsorption and precipitation or oxidation [5,6].…”

Nitrate removal from water using iron nanoparticles produced by arc discharge vs. reduction

“…Therefore, its innovative applications can often be found for in situ groundwater remediation or for the treatment of industrial waste streams contaminated with redox active toxic materials [12][13][14][15][16][17][18][19][20][21][22][23][24][25]. In addition to nitrate, extensive laboratory studies have indicated that FeNps are effective for the transformation of a wide range of common environmental contaminants such as chlorinated organic solvents [26], organo-chlorine pesticides [27], PCBs [28], organic dyes [29], and metal ions such as As(III), Pb(II), Cu(II), Ni(II), and Cr(VI) [30].…”