RATE PARAMETER INDEPENDENCE ON THE ORGANIC REACTANT - A STUDY OF ADSORPTION AND PHOTOCATALYTIC OXIDATION OF SURFACTANTS USING MO(3)-TIO2 (M=MO OR W) CATALYSTS

The adsorption of dodecylbenzene sulphonic acid sodium salt (DBS), cet ylpyridinium chloride (CPC) and triton X-100 (TX-100) in aqueous solut ion on to TiO2, MoO3-TiO2 and WO3-TiO2 photocatalysts has been studied . The sulphite group in DBS, the pyridinium ion in CPC and the ethoxyl group in TX-100 fix these surfactant molecules to the catalyst surfac e, leaving the hydrocarbon chains perpendicular to the surface plane o f the catalyst. Irradiation of these surfactants in the presence of th e above photocatalysts caused their degradation into carbon dioxide. A fter a 6 h irradiation period, over 80% reduction in chemical oxygen d emand relative to its initial value was achieved. The first-order rate constants (k) and dark absorption equilibrium constants (K) were comp ared. It was found that k corresponds to a reaction step wherein surfa ctant molecules do not participate.