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

Jonathan C Espíndola; Raquel O Cristóvão; Sara G S Santos; Rui A R Boaventura; Madalena M Dias; José Carlos B Lopes; Vítor J P Vilar

doi:10.1016/j.scitotenv.2019.05.066

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

Sci Total Environ. 2019 Sep 1:681:467-474. doi: 10.1016/j.scitotenv.2019.05.066. Epub 2019 May 7.

Authors

Jonathan C Espíndola¹, Raquel O Cristóvão², Sara G S Santos³, Rui A R Boaventura³, Madalena M Dias³, José Carlos B Lopes³, Vítor J P Vilar⁴

Affiliations

¹ Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal; CNPq - National Council for Scientific and Technological Development, Brazil.
² Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal. Electronic address: raquel.cristovao@fe.up.pt.
³ Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
⁴ Laboratory of Separation and Reaction Engineering - Laboratory of Catalysis and Materials (LSRE-LCM), Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal. Electronic address: vilar@fe.up.pt.

PMID: 31117018
DOI: 10.1016/j.scitotenv.2019.05.066

Abstract

This study focuses on the intensification of heterogeneous TiO₂ 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 m²_catalyst m^-3_reactor) or on the network of channels and chambers imprinted in the back stainless-steel slab (SSS) (FSI mechanism; 989 m²_catalyst m^-3_reactor) using a spray system. OTC removal was also assessed as a function of TiO₂ 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.

Keywords: Contaminants of emerging concern; LEDs; NETmix mili-photoreactor; Process intensification; TiO(2) photocatalysis.