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

The purpose of this study was to correlate the photocatalytic degradat ion of water contaminants with the adsorption phenomena, taking both t he equilibrium state and kinetics into consideration. 1,2-Dichloroetha ne (DCE) was chosen as a test pollutant. The adsorption isotherm was f ound to follow the Langmuir model. The kinetics of adsorption were stu died and interpreted as a mass transfer process. The kinetics of photo catalytic degradation were analysed with special attention given to th e influence of the reactant concentration. A kinetic model is proposed , which includes mass transfer, leading to an apparent Langmuir-Hinshe lwood equation for the degradation rate, even when the kinetics are co ntrolled by mass transfer. The experimental results show an agreement with the model at concentrations above 0.5 mmol.l(-1), but at lower co ncentrations the rate is lower than expected, possibly due to a loss o f DCE or hydroxyl radicals.