While a high efficiency of contaminant removal by nanoscale zero-valent iron (nZVI) has often been reported for several contaminants of great concern, including aqueous arsenic species, the transformations and translocation of contaminants at and within the nanoparticles are not clearly understood. By using in situ XAS analysis of the As core level for nZVI-As(III) aqueous reaction systems, we have observed that As(III) undergoes two stages of transformation upon adsorption at the nZVI surface. The first stage corresponds to breaking down As(III) complexes at the particle surface, and the second stage involves gradual migration of arsenic across the thin oxide layer enclosing the nanoparticles. This second stage ends with complete loss of As-O bonds and the formation of a disordered As-Fe intermetallic phase. These results highlight the role of the nZVI microstructure in shaping its chemical reactivity and the relevance of intra-particle diffusion and reduction in contaminant sequestration processes.

Investigation of intra-particle contaminant transformations in nanoscale zero-valent iron with in situ X-ray absorption spectroscopy (XAS)

243rd National Meeting (2012)

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