Optimization of P25/PDMS supported catalysts preparation for the photocatalytic oxidation of parabens

Abstract

Heterogenous photocatalysis is a suitable technology for the removal of contaminants of emerging concern (CEC), such as parabens, from wastewaters. However, typically the photocatalyst is applied as a powder, which requires time-consuming and expensive supplementary separation processes, for its separation and recovery. Therefore, supported-photocatalysis has gained interest in the scientific community. To develop a suitable supported photocatalyst, commercial TiO2 (P25) powder was immobilized in polydimethylsiloxane (PDMS) membranes, to promote the degradation of three parabens (methylparaben -MP, ethylparaben -EP, and propylparaben -PP), under UV irradiation. To enhance the photocatalytic activity of the membranes, a plasma process was applied during their preparation. The plasma process operating conditions were optimized, regarding the working gas, the power applied, the pressure used and the processing time selected. Thus, the best conditions, among those analyzed, were the use of argon as the working gas, a power of 100 W, a pressure of 0.6 mbar and an operating time of 4 min. To assess the photocatalytic activity, two protocols, which varied in the P25 immobilization methodology (surface or matrix), were developed. It was concluded that PDMS membranes with P25 on the surface achieved higher removals of parabens during the photocatalytic oxidation and, when the preparation parameters were optimized, these membranes achieved removals of 53 ± 2%, 53 ± 0%, 58 ± 2% for EP, MP and PP, respectively. As such, in this study, it was possible to develop a protocol to produce hydrophilic and photocatalytic P25/PDMS membranes efficient in the abatement of parabens under UV irradiation.