DEPENDENCE OF PHOTOCATALYTIC REACTION-RATE ON TITANIUM-DIOXIDE CONCENTRATION IN AQUEOUS SUSPENSIONS

The dependence of kinetic parameters in Langmuir-Hinshelwood rate expression on photocatalyst (titanium dioxide) concentration in aqueous suspensions was examined theoretically, based on the theory of Turchi and Ollis for single photocatalyst particle. The results are as follows: (1) Rate constant k shows the transition from first-order to square-root dependency with increasing photocatalyst concentration C(s) at high illumination intensity. (2) At low illumination intensity k shows the transition from first-order to zero-order dependency with increasing C(s). (3) Equilibrium constant of adsorption K is independent of C(s) when either of two species(hydroxyl radical and reactant) is adsorbed. These results are in good agreement with the experimental results reported previously.