A KINETIC STUDY OF ORTHOPHOSPHATE SORPTION ON METAL OXIDES

The kinetics of phosphate sorption on thorium and zirconium oxides are described by a rate equation which contains both a linear surface site depletion term and a term in which the fraction of surface coverage occurs exponentially. This is interpreted to mean that the activation energy increases linearly with the quantity of phosphate sorbed. The activation energy for the phosphate sorption on crystalline thorium oxide at zero phosphate coverage was found to be 3.0 ± 0.3 kcal mol-1; the sorption process thus is very probably solution diffusion controlled.