Summary The reduction of pollutants such as inorganic metals is an important environmental chemical reaction. This proposal focuses on the reduction of chromate(Cr(VI)) using zerovalent iron(Fe0) as a solid phase remediation material. Numerous studies have investigated Cr(VI) reactions with Fe0 but there remains significant outstanding questions about the mechanism of reduction and the products formed on the surface of the corroded Fe0. In addition, Fe0 creates reactive surfaces and solid Fe(II)/Fe(III) hydroxide products with high surface areas that have proven difficult to quantify. The overall goal of this proposal is to combine [Surface Data Analysis-cue why ]X-ray spectroscopy with electron microscopy imaging to identify and quantify the Cr reaction products and to develop 3D stereoscopic model for measuring surface area based on SEM images. It is expected that the proposed research will result in an improved approach to analyzing the morphology and specific surface area of complex materials. Background The reduction of Cr(VI) to Cr(III) by Fe0 has been studied using several analytical techniques including X-ray photoelectron spectroscopy(XPS) and extended X-ray absorption fine structure spectroscopy(EXAFS), X-ray diffraction(XRD) and scanning electron microscopy(SEM). Using these techniques it has been determined that the reduction of Cr(VI) is coupled with the oxidation of Fe0 Fe? Fe3+ + 3e- (1) CrO42- + 3e- + 8 H+ Cr3+ +4H2O (2) ------------------------------------------- Net equation : CrO42- + Fe?+ 8 H+ Cr3+ +Fe3+ + 4H2O (3) An additional reaction includes the adsorption and co-precipitation of Cr(III) by Fe(III) oxide surface Fe3+ +Cr3+ + 3OH- (Fe, Cr)(OH)3(s) (4) The reaction forms a mixed Fe(III)/Cr(III) hydroxide solid that is insoluble and effectively removes Cr(VI) from solution. The reduction of Cr(VI) to Cr(III) also decreases the toxicity by converting the toxic Cr(VI) form to the insoluble, non-toxic Cr(III) hydroxide form. Zerovalent iron surfaces oxidize in water and produce Fe(III) hydroxide (Fe(OH3)) which generates reactive surface for adsorption of pollutants. The Fe0 solid particles oxidize and produce an oxide growth shell around the Fe0 core making a “core-shell” solid structure. This structure has been studied using transmission electron microscopy(TEM) and a typical image of oxidized Fe0 Acknowledgements Thanks to Drs Manning and Skalars and NIC Granted Goals and objectives Goals and objectives More detailed information is needed about the Fe oxide/hydroxide core-shell structure and the specific surface area of complex surface features. The overall goal of this proposl is to use Cr(VI) as a model pollutant to study the surface structures and surface area measurement by a new approach using SEM imaging. The specific objectives of the proposal are: ? Investigate the reduction of Cr(VI) to Cr(III) by Fe0 using XPS; ? Use XAS (EXAFS and XANES) to provide structural information ( inter-atomic distances and coordination shell) about the Fe/Cr products; ? Use SEM to develop images of Fe0 oxides and Cr(VI)-treated Fe(0) to define the effects of Cr(V) treatment on the morphology of the Fe oxide/hydroxide crystals; ? Develop the application of a computer software approach to calculating the specific surface area of complex Fe0 oxidation products. ? Promote internal database combined with X-ray beam line such SSRL. Thereare benefits of internal database for advanced