Functionalized mesoporous silicas SBA-15 for heterogeneous photocatalysis towards CECs removal from secondary urban wastewater

Abstract

The photocatalytic activity of TiO2 nanoparticles (NPs) supported on mesoporous silica SBA-15 (TiO2/SBA-15) was evaluated for the photodegradation of sulfadiazine (SDZ), as target contaminant of emerging concern (CEC), using either pure water solutions (PW) or a real secondary urban wastewater (UWW) spiked with SDZ. For this purpose, TiO2/SBA-15 samples with 10, 20 and 30% TiO2 (w/w) were prepared by the sol-gel post synthetic method on pre-formed SBA-15, using titanium (IV) isopropoxide as a precursor. The TiO2/SBA-15 materials were characterized by HRTEM, SAXS and XRD, nitrogen adsorption isotherms and UV–vis diffuse reflectance spectroscopy. TiO2 NPs were shown to be attached onto the external surface, decorating the SBA-15 particles. The TiO2/SBA-15 catalysts were active in SDZ photodegradation using the annular FluHelik photoreactor, when irradiated with UVA light. The 30% TiO2/SBA-15 sample presented the best performance in optimization tests performed using PW, and it was further used for the tests with UWW. The photocatalytic activity of 30% TiO2/SBA-15 was higher (56% SDZ degradation) than that of standard TiO2–P25 (32% SDZ degradation) in the removal of SDZ spiked in the UWW ([SDZ] = 2 mg L−1). The photodegradation of SDZ with 30% TiO2/SBA-15 eached 90% for UWW spiked with a lower SDZ concentration ([SDZ] = 40 μg L−1). Aside of SDZ, a suit of 65 other CECs were also identified in the UWW sample using LC-MS spectrometry. A fast-screening test showed the heterogeneous photocatalytic system was able to remove most of the detected CECs from UWW, by either adsorption and/or photocatalysis.