Photoelectrocatalytic oxidation of chlortetracycline using Ti/TiO2 photo-anode with simultaneous H2O2 production

Highlights: ► The TiO2 coatings were found to be of rutile and anatase nanostructured morphology. ► The PECO process applied under optimal conditions oxidized 98.0 ± 0.2% of CTC. ► TOC concentration could be optimally diminished up to 67.3 ± 2.15%. ► The degradation rate follows the L–H kinetic with a rate of 6 × 10−4 L mg−1 min−1. ► Biotests revealed that treated effluent was not toxic versus untreated effluent. - Abstract: This study investigated the photoelectrocatalytic oxidation (PECO) of chlortetracycline (CTC) in aqueous solution using a Ti/TiO2 photocatalyst. The Ti/TiO2 used as photo-anode was prepared by a pulsed laser deposition (PLD) method. The PLD TiO2 coatings were found to have rutile and anatase structures consisting of nano-crystallites of approximately 10 nm and 15 nm in diameter, respectively. The influence of various parameters such as crystallographic structure of Ti/TiO2, cathode material and pH were evaluated. Experimental results revealed that a current intensity of 0.39 A under UV irradiation (245 nm) for a period of treatment of 120 min was beneficial for CTC oxidation. The initial CTC concentration (25 μg/L) could be optimally diminished up to 98.0 ± 0.2% while using a Ti/TiO2 photo-anode having a crystallographic structure of anatase and using vitreous carbon as cathode. Under these conditions, a relatively high mineralization of CTC (67.3 ± 2.15% of TOC removal and 69.3 ± 3.10% of TN removal) was recorded. The initial rate of photoelectrocatalytic degradation of CTC can be well described by the Langmuir–Hinshelwood (L–H) kinetic model (R2 = 0.9996) with a reaction rate constant of 17.3 μg/L min. Likewise, microtox (Vibrio fisheri), microalga (Pseudokirchneriella Subcapitata) and Daphnia (Daphnia magna) biotests revealed that the treated – effluent was not toxic compared to the untreated effluent.