EXAFS characterization of ferric oxyhydroxides

The EXAFS method has been used for investigating the local structures of fe rric oxyhydroxides which are reaction products formed on an iron surface ex posed to air or immersed in salt water. Fe K EXAFS spectra of two reference s of ferric oxyhydroxides, i.e. goethite and lepidocrocite, which are often detected as components of reaction products, have been also studied for co mparison thereof. The two reference oxyhydroxides demonstrated different EX AFS spectra, which are interpreted based on the atomic local structures. Fe K EXAFS spectra and their radial distribution functions of the reaction pr oducts formed on an iron surface have been compared with those of the refer ence oxyhydroxides. This comparison shows that the first and second nearest neighboring structures around ferric ions in the reaction products are dif ferent from those of the two references. These results indicate that the lo cal structures around ferric ions in the reaction products are disordered, although the atomic local structures of Fe-O may be described as being loca l structural units. (C) 2001 Elsevier Science B.V. All rights reserved.