This review article is a comprehensive report on vanadium oxides which are interesting materials for environmental applications. Therefore, a general overview of vanadium and its related oxides are presented in the first two parts. Afterwards, the physical properties of binary and ternary vanadium oxides in single and mixed valence states are described such as their structural, optical, and electronic properties. Finally, the use of these vanadium oxides in photochemical processes for environmental applications is detailed, especially for the production of hydrogen by water splitting and the degradation of organic pollutants in water using photocatalytic and photo-Fenton processes. The scientific aim of such a review is to bring a comprehensive tool to understand the photochemical processes triggered by vanadium oxide based materials where the photo-induced properties are thoroughly discussed based on the detailed description of their intrinsic properties.

Enrofloxacin (ENR) belongs to the fluoroquinolone (FQ) antibiotics family, which are contaminants of emerging concern frequently found in effluents. Although many works studying photo-Fenton process for FQ degradation have been reported, there are no reports analysing in deep the effect of iron complexation, as well as other metals, towards FQs' photolysis, which, evidently, also contributes in the overall degradation of the pollutant. Therefore, in this work, we report a comparative study between the photochemical fate of ENR and its complex with Fe(III) under simulated sunlight irradiation. In addition, the effect of dissolved oxygen, self-sensitization process, and H2O2 addition on the studied photochemical systems are also investigated. Results indicate that, for free and iron-complexed ENR, singlet oxygen (1O2) is generated from the interaction of its triplet state with ground state oxygen. Half-life time (t1/2) of ENR under sun simulated conditions is estimated to be around 22 min, while complexation with iron enhances its photostability, leading to a t1/2 of 2.1 h. Such finding indicates that at least the presence of iron, might notably increase the residence time of these pollutants in the environment. Eventually, only with the addition of H2O2, the FQ-iron complex is efficiently degraded due to photo-Fenton process even at circumneutral pH values due to the high stability of the formed complex. Finally, after LC/FT-ICR MS analysis, 39 photoproducts are detected, of which the 14 most abundant ones are identified. Results indicate that photoproducts formation is pH and iron dependent.