Intensification of heterogeneous TiO2 photocatalysis using the NETmix mili-photoreactor under microscale illumination for oxytetracycline oxidation

Abstract This study focuses on the intensification of heterogeneous TiO 2 photocatalysis for the removal of a contaminant of emerging concern (CEC), oxytetracycline (OTC), as a polishing step of urban wastewaters, using an innovative NETmix mili-photoreactor under UVA-LEDs illumination. The effect of catalyst coated surface per reactor volume and the illumination mechanism, back-side (BSI) or front-side (FSI) irradiation, on OTC oxidation were evaluated. For that, a thin film of photocatalyst was uniformly deposited on the front borosilicate slab (BS) (BSI mechanism; 333 m 2 catalyst m −3 reactor ) or on the network of channels and chambers imprinted in the back stainless-steel slab (SSS) (FSI mechanism; 989 m 2 catalyst m −3 reactor ) using a spray system. OTC removal was also assessed as a function of TiO 2 film thickness immobilized on both slabs. The photocatalyst reactivity in combination with photoreactor was significantly enhanced (3.4 times) from 0.64 to 2.19 mmol OTC m −3 illuminated reactor volume s −1 , when considering the BSI and FSI mechanisms, respectively. In addition, the influence of UVA-LEDs intensity on OTC oxidation rate was investigated. UVA-LEDs plates were placed on the top of the NETmix borosilicate window. Moreover, the effect of water matrix was assessed using a secondary effluent from an urban wastewater treatment plant fortified with OTC. OTC oxidation rate was only inhibited in about 1.3 times in the presence of the real matrix, showing the ability of the NETmix to overcome matrix effects due to its unique characteristics. Catalyst film stability over four consecutive reaction cycles was evaluated using synthetic and real matrices fortified with OTC.