INFLUENCE OF LIGHT-INTENSITY AND MEMBRANE-PROPERTIES ON THE PHOTOCATALYTIC DEGRADATION OF FORMIC-ACID OVER TIO2 CERAMIC MEMBRANES

The photocatalytic activity of ceramic membranes for the oxidation of dissolved formic acid has been evaluated as a function of the membrane thickness and porosity, as well as the intensity of the incident ligh t. Quantum efficiencies as high as 30% have been obtained for the oxid ation of formic acid. Light absorption increased with an increase in m embrane thickness and could be fit to a Lambert-Beer expression. This increase in light absorption in thicker membranes caused more electron -hole pairs to be generated. Increasing the light intensity also incre ased the rate of carrier recombination processes. Consequently, a maxi mum in the quantum yield was observed at a particular thickness. Highe r quantum yields were obtained at the lowest intensities.