ADSORPTION OF WATER-VAPOR BY IRON-OXIDES .1. PREPARATION AND CHARACTERIZATION OF THE ADSORBENTS

The preparation and interconversion of iron(III) oxides and hydroxides and their characterization by X-ray diffraction and small angle neutron scattering (SANS) are described. The solids, i.e. alpha-Fe2O3 (haemoatite), gamma-Fe2O3 (maghemite), Fe3O4 (magnetite), alpha-FeOOH (goethite), beta-FeOOH (akaganeite), and gamma-FeOOH (lepidocrocite) were all characterized by X-ray diffraction. The various chemical transformations are compared with nominally similar processes published in the literature and some significant discrepancies are noted. With SANS, alpha-Fe2O3, gamma-Fe2O3, gamma-Fe2O3 (calcined), and Fe3O4 show nonlinear Guinier behavior but the Debye analysis gives linear plots indicating random structure; the corresponding specific surface areas generally show good agreement with gas adsorption values. alpha-Fe2O3 and gamma-Fe2O3 (calcined) follow the Porod law, but gamma-Fe2O3 and Fe3O4 show deviation.