Effect of mass transfer and catalyst layer thickness on photocatalytic reaction

Semiconductor photocatalytic processes have been studied for nearly 20 year s dire to their intriguing advantages in environmental remediation. A ratio nal approach in determining the effect of mass transfer and catalyst layer thickness during photocatalytic reactions is proposed. The reaction occurs at the liquid-catalyst interface, and therefore when the catalyst is immobi lized, both external and internal mass transfer plays significant roles in overall photocatalytic processes. Several model parameters-external mass-tr ansfer coefficient dynamic adsorption equilibrium constant adsorption rate constant, internal mass-transfer coefficient, and effective diffusivity-wer e determined either experimentally or by fitting realistic models to experi mental results using benzoic acid as a model component. Even though all the se parameters are critical to the design and development of photocatalytic processes, they are not available in the literature. The effect of the inte rnal mass transfer on the photocatalytic degradation rate over different ca talyst layer thicknesses under two different operating configurations was a nalyzed theoretically and experimentally verified. It was observed that an optimal catalyst layer thickness exists for substrate-to-catalyst illuminat ion.