Influence of pH and DO on the ofloxacin degradation in water by UVA-LED/TiO2 nanotube arrays photocatalytic fuel cell: mechanism, ROSs contribution and power generation

Abstract

The influence of pH and dissolved oxygen (DO) on the degradation of ofloxacin (OFX) in water by UVA-LED/TiO2 nanotube arrays photocatalytic fuel cell (UVA-LED/TNA PFC) was investigated. The degradation pathway depended on the location of OFX frontier orbital with different ionization states and the role of reactive oxidative species (ROSs) played with varied pH and DO values. In presence of DO, the quencher tests revealed that O2− played a key role at pH 3.0, 7.0 and 11.0, while OH made its greatest contribution at pH 3.0 and the effect of h+ was largely inhibited at pH 11.0. Hydroxylation for cationic OFX was more significant, while demethylation and piperazinyl ring oxidation for anionic OFX occurred more quickly compared to other forms. Besides, zwitterionic OFX underwent decarboxylation and combination of demethylation & hydroxylation more easily. Much higher power generation was observed in presence of DO at pH 7.0, probably due to the enhanced adsorption of OFX on the TNA, and DO could amplify the electric potential between the two electrodes. The degradation efficiencies were almost the same in presence or absence of DO, but the pathways were different and e-aq may replace O2- as the leading ROSs in absence of DO.