Enhanced photocatalytic degradation of ciprofloxacin by black Ti3+/N-TiO2 under visible LED light irradiation: Kinetic, energy consumption, degradation pathway, and toxicity assessment

In this work, the photocatalytic degradation of ciprofloxacin (CIP) by black Ti3+/N-TiO2 under visible LED light irradiation (b-N-TiO2/LED) was studied for the first time. Characterization of the prepared photocatalyst was performed by XRD, UV-Vis DRS, FE-SEM, EDS, HRTEM, and BET techniques. The b-N-TiO2 nanoparticles with high surface area of near 100 m(2) g(1) and narrow band gap of 2.0 eV, exhibited a remarkable photocatalytic performance on the degradation (100 %) and mineralization (82 %) of CIP under visible LED light irradiation. The maximum degradation was found at reaction time = 70 min, initial CIP concentration = 0.5 mg L-1, pH = 6.7, and catalyst dosage = 0.43 g L-1. Based on the results, both the hole (h(+)) and hydroxyl radical ((OH)-O-center dot) played a major role than the superoxide radical (O-center dot(2)-) in CIP degradation. Although common coexisting anions in water had a slight negative effect on CIP degradation; humic acid (HA), especially in higher amounts, showed a considerable inhibitory effect on degradation process. Besides, the intermediates of CIP degradation were ultimately transformed into simple compounds. Accordingly, toxicity assessments revealed that the treatment of CIP solution by b-N-TiO2/LED process remarkably resulted in diminished toxicity compared to the untreated controls. The energy utilized in this study was far less than that used in other studies. Moreover, we found that b-NTiO2 had desirable stability and can be reused for more than five runs of experiments. Collectively, based on our findings, the b-N-TiO2/LED process is a promising, low cost and feasible candidate can be used for degradation and mineralization of antibiotics like CIP in real water samples. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.