Nanoscale zerovalent iron (nZVI) has often been reported to have a high efficiency of contaminant removal for several contaminants of great concern, including aqueous arsenic species, yet the transformations and translocation of contaminants at and within the nanoparticles are not clearly understood. Investigations of surface reactions between nZVI and arsenite, As(III), using high-resolution X-ray photoelectron spectroscopy (HR-XPS) demonstrated for the first time stratified distributions of multiple arsenic valence states within the iron nanoparticles and revealed that As(III) oxidation and reduction can occur in parallel in separate regions of the nanoparticles. In situ time-dependent X-ray absorption spectroscopy (XAS) measurements of the arsenic core level for nZVI in anoxic As(III) solutions have further illuminated the role of intraparticle diffusion and reduction in affecting the chemical state and spatial distribution of arsenic in nZVI materials. In other studies we investigated surface modifications of iron oxide nanoparticles to tune the transport properties toward more desirable retention in porous media. Iron oxide nanoparticles were synthesized and coated with different amounts of poly(acrylic acid) polymers, and analyses were then performed on these particles, including sorption/desorption of the polymer onto the iron nanoparticles, particle size, zeta potential, transport in sand and soil columns, and bioavailability of the Fe(III) in the absence and presence of the coating to iron reducing organisms. These results suggest that augmentation of soils with iron to enhance biological processes such as uranium reduction via iron reducing bacteria, e.g., Geobacter sp., might be achieved via the injection of iron nanoparticles into the subsurface.

Surface reactions and modification of nanoscale zero-valent iron (nZVI) and iron oxide nanoparticles for environmental remediation

251st National Meeting (2016)

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