TiO2 MOCVD coating for photocatalytic degradation of ciprofloxacin using 365 nm UV LEDs - kinetics and mechanisms

Thibaut Triquet (1) , Claire Tendero (2) , Laure Latapie (1) , Marie-Hélène Manero (1) , Romain Richard (1) , Caroline Andriantsiferana (1)

1 LGC - Laboratoire de Génie Chimique
2 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux

This work presents a solution for the photocatalytic degradation of the antibiotic ciprofloxacin (CIP) in water, without using P25 TiO2 powder and thus getting rid of expensive separation steps. It consists in using a TiO2 coating that is directly deposited on the optical window of a photocatalytic micro-reactor and 365 nm UV LEDs as radiation source. P25 TiO2 powder was also studied as reference. HPLC-MS was used to determine the transformation products and the pathways reactions. CIP was slowly degraded by the photolysis reaction at 365 nm: (75 % removal after 8 h of UV irradiation). However, no significant decrease of the total organic carbon (TOC) was noticed, thus showing the presence of transformation products not degraded by the action of UV-light alone. For a low catalyst amount (i.e 0.12 g of TiO2, whatever the form, powder or coating, per liter of contaminated water,), excellent CIP degradation by photocatalysis was observed. Complete CIP degradation after 1 h of irradiation was required using P25 and 8 h using TiO2 coating. Different preferential reaction pathways were identified for both TiO2 catalysts. The Langmuir-Hinshelwood model showed a very good representation of the kinetics, unlike its simplified pseudo-first order model. Photocatalysis experiments did not show a complete mineralization (60–70 % of TOC removal), but most of the aromatic transformation products were degraded. The last transformation products were identified as small aliphatic acids. There is therefore a real interest in using MOCVD coating of TiO2 for sustainable wastewater treatment to avoid expensive catalyst separation. A study with a spiked real effluent from a wastewater treatment plant was performed and a satisfactory degradation was obtained. Slower kinetics were found due to the presence of additional organic products and scavenger compounds such as HCO3-.

Mots clés: Photocatalysis; MOCVD; Langmuir-Hinshelwood; HPLC-MS; Antibiotic; Transformation products

Domaines: Génie chimique; Génie des procédés

Thibaut Triquet, Claire Tendero, Laure Latapie, Marie-Hélène Manero, Romain Richard, et al.. TiO2 MOCVD coating for photocatalytic degradation of ciprofloxacin using 365 nm UV LEDs - kinetics and mechanisms. Journal of Environmental Chemical Engineering, 2020, 8 (6), pp.104544. ⟨10.1016/j.jece.2020.104544⟩. ⟨hal-02975294⟩