Electrophoresis–A new approach for the determination of organic matters adsorption on irradiated TiO2

The application of electrophoretic analysis for monitoring the adsorption of organic onto TiO2 and for detecting the formation of adsorbed organic species during the photocatalytic reactions has been successfully demonstrated. When highly adsorbed organic compounds such as maleic acid, oxalic acid and 1,2,3-THB interacted with TiO2 surface at pH 3, the zeta potential of TiO2 exhibited a negative shift. On the contrary, no apparent change in zeta potential of TiO2 was recorded from the interaction of weakly adsorbed organic compounds such as methanol, sucrose, glucose and resorcinol. The electrophoretic analysis showed that during photocatalytic reaction, the weakly adsorbed resorcinol formed intermediate species that were highly adsorbing onto TiO2, while no change in TiO2 zeta potential during the photocatalytic reaction of methanol. The removal kinetics of adsorbed organic species during the photocatalytic reaction of resorcinol and 1,2,3-THB can be easily followed by monitoring the change in zeta potential of TiO2. As the adsorbed organic compounds were progressively removed from the irradiated surface of photocatalyst, the zeta potential of TiO2 gradually shifted to a more positive value and finally restored to the zeta potential of bare TiO2 when complete removal of adsorbed organic was achieved.