Immobilization of TiO2 onto a polymeric support for photocatalytic oxidation of a paraben's mixture

Heterogeneous photocatalysis has been used as a suitable technology for microcontaminants abatement using titanium dioxide as semiconductor and UV radiation as energy source. TiO2 is usually applied as a powder which requires supplementary separation stages to remove the catalyst after the oxidation reactions. Thus, continuous operation is cumbersome. Aiming to reach a suitable supported catalyst, in this work TiO2 (Degussa P25) was immobilized over a polydimethylsiloxane (PDMS) membrane to promote the degradation of a mixture of three parabens through the photocatalytic oxidation process. Several parameters of immobilization, such as UV irradiation time, TiO2 slurry load immobilized onto support, were optimized in order to enhance the photoactivity of supported TiO2. In fact, the time considered for UV irradiation which promotes the immobilization of TiO2 onto PDMS needs to be controlled since to high exposure times (90 and 120 min) reduce the photoactivity of catalyst. The load of 140 mg/L of TiO2 allows a highest removal of parabens abatement using sunlight radiation. Higher loads can lead to particles agglomeration reducing their dispersion onto the membrane surface. During three cycles of use the membranes keep the efficiency over parabens removal. The sunlight (during autumn and summer) and UVA radiation were compared for the paraben's abatement using the supported catalysts. The toxicity assessment reveal that treated solutions present a slightly impact comparing to pattern compounds due to the by-product's formation.

Automated summary

Heterogeneous photocatalysis using TiO2 as a semiconductor has been applied to remove microcontaminants. In this study, TiO2 (Degussa P25) was immobilized on a PDMS membrane to enhance the degradation of a mixture of three parabens. The UV irradiation time and TiO2 slurry load were optimized to improve the photoactivity of supported TiO2. Results showed that 140 mg/L of TiO2 load achieved the highest removal of parabens under sunlight radiation.