Adsorption of phosphate by two iron oxides in relation to their porosity

Adsorption and desorption of phosphate by lepidocrocite and hematite, the latter obtained by thermal decomposition of the former, were studied and related to changes in mesoporosity of the solid surface. Differences between the oxides in the accessibility of their surfaces to phosphate seems to control the fractional amounts of ‘rapidly’ and ‘slowly’ adsorbed phosphate. Results of isotopic exchange of the phosphate adsorbed at high surface coverage can also be explained in terms of the mesoporosity of the surfaces.