Removal of the antimicrobial activity from fortified effluents with fluoroquinolones by photocatalytic processes: a comparative study of differently synthesized TiO2-N

This study presents a comparison of three methods for TiO2-N synthesis that were applied in the photocatalytic oxidation of the fluoroquinolones (FQs) ciprofloxacin, ofloxacin, and lomefloxacin in aqueous solution. The TiO2-N bandgap is small enough to allow the use of solar energy in the photocatalytic oxidation (PCO) reactions. The TiO2 doped by a sol-gel method with titanium butoxide (TiO2–N–BUT) and titanium isopropoxide (TiO2–N–PROP) as the precursor were effective as the TiO2 (P25) impregnation with urea (TiO2-N-P25) to degrade the FQs. The FQ degradation was higher by 74, 65, and 91%, respectively for TiO2–N–BUT, TiO2–N–PROP, and TiO2-N (load 50 mg L−1, 20 min of reaction under 28 W UV-ASolar). The TiO2-P25 with urea showed the best performance in FQ degradation. The reaction intermediates might present modifications in their acceptor groups by PCO and, because of that the antimicrobial activity dropped as the reaction time increased. Reactions with TiO2-N-P25 (100 mg L−1) and TiO2-N-BUT (100 mg L−1) achieved ≥ 80% of antimicrobial activity removal from the mixed FQ solution (Cciprofloxacin = 100 μg L−1; Cofloxacin = 100 μg L−1; Clomefloxacin = 100 μg L−1) after 40 min of reaction, for both for Escherichia coli and Bacillus subtilis.