Assessment of new immobilized photocatalysts based on TiO2 for wastewater decontamination

Abstract

With the main objective of overcoming the main drawbacks in the actual application of semiconductors in slurry in solar photocatalysis, new immobilized photocatalysts based on TiO2 supported on glass wool and silica material have been evaluated for tertiary/quaternary treatment of urban wastewater treatment plant effluents. Preliminary tests were carried out under different operating conditions in a solar simulator SUNTEST XLS+ with 30 W/m2 irradiation average. Demineralized water was spiked with sulfamethoxazole (SMX) (at 1 mg/L initial concentration) as water model pollutant. The mere effect of only irradiance as well as the photocatalytic performance of TiO2-P25 in slurry over SMX abatement were also investigated as references. The highest SMX removal (> 98% in 25 min) was obtained with SiO2_TiO2 photocatalyst (0.5 g/L). The efficacy of SiO2_TiO2 was demonstrated to be stable for 5 cycles of reusing and 66% of mineralization was also obtained through the degradation of 25 mg/L of SMX after 360 min of treatment. SiO2_TiO2 photocatalyst was also assessed for the elimination of SMX present in a more complex water matrix, in simulated urban wastewater, obtaining 50% of SMX removal in 120 min. In addition, 7 transformation products (TPs) were identified by UPHLC-QTOF-MS/MS and a tentative degradation pathway was elucidated. Assessment on actual implementation of supported TiO2 photocatalysts in solar photoreactors must be tackled in the future.