Iron(III) (hydr)oxides play an important role in the geochemical cycling of arsenic in aquatic systems. Using in situ, simultaneous small angle x-ray scattering (SAXS)/grazing incidence SAXS setup, we observed and quantified the homogeneous and heterogeneous precipitation of iron(III) (hydr)oxide in the presence of arsenate on quartz substrates. To provide comprehensive information about nanoparticle�water interactions in the presence of arsenate, we also conducted complementary techniques such as atomic force microscpy, electrophoretic mobility measurements, thermal gravimetric analysis, and high resolution X-ray diffraction. Our results show that the presence of arsenate can have a significant impact on the nucleation and growth of iron(III) (hydr)oxides and the extent of water molecules in their structure. The presence of arsenate enhances growthand promotes heterogeneous precipitation relative to systems without this oxyanion. Changes in size and water content in newly formed iron(III) (hydr)oxide nanoparticles can affect their reactive surface area toward contaminants in the environment. This new quantitative and qualtitative information can be used to develop more rigorous reactive transport models of contaminant fate and transport in relevant natural and engineering aquatic systems, such as arsenic-contaminated groundwater aquifers and acid mine drainage sites.

Arsenate-promoted water content in heterogeneously formed iron (hydr)oxide nanoparticles

247th National Meeting (2014)

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