ADSORPTION PROPERTIES OF TIO2 RELATED TO THE PHOTOCATALYTIC DEGRADATION OF ORGANIC CONTAMINANTS IN WATER

The purpose of this study was to correlate the photocatalytic degradation of water contaminants with the adsorption phenomena, taking both the equilibrium state and kinetics into consideration. 1,2-Dichloroethane (DCE) was chosen as a test pollutant. The adsorption isotherm was found to follow the Langmuir model. The kinetics of adsorption were studied and interpreted as a mass transfer process. The kinetics of photocatalytic degradation were analysed with special attention given to the influence of the reactant concentration. A kinetic model is proposed, which includes mass transfer, leading to an apparent Langmuir-Hinshelwood equation for the degradation rate, even when the kinetics are controlled by mass transfer. The experimental results show an agreement with the model at concentrations above 0.5 mmol.l(-1), but at lower concentrations the rate is lower than expected, possibly due to a loss of DCE or hydroxyl radicals.