SURFACE-ROUGHNESS CREATED BY ACIDIC DISSOLUTION OF SYNTHETIC GOETHITEMONITORED WITH SAXS AND N-2-ADSORPTION ISOTHERMS

The development of surface roughness of two synthetic goethites with a high, 176 m(2)/g, and a low, 7 m(2)/g, initial specific surface area by acid attack is described in terms of fractal geometry. The dissolut ion kinetics were influenced by the presence of micropores and small m esopores created during dissolution and leading to an initial increase in surface area causing S-shaped dissolution curves. The fractal dime nsions were calculated from the adsorption isotherms obtained with N-2 as adsorbate. These values of surface fractal dimension agree quite w ell with the values of the mass and surface fractal dimension obtained with small angle X-ray scattering (SAXS). (C) 1998 Academic Press.