Copper(II) phosphate as a promising catalyst for the degradation of ciprofloxacin via photo-assisted Fenton-like process.

This work aims to unravel the potential of copper(II) phosphate as a new promising heterogenous catalyst for the degradation of ciprofloxacin (CIP) in the presence of H2O2 and/or visible light (λ > 400 nm). For this purpose, copper(II) phosphate was prepared by a facile precipitation method and fully characterized. Of our particular interest was the elucidation of the kinetics of CIP degradation on the surface of this heterogeneous catalyst, identification of the main reactive oxygen species responsible for the oxidative degradation of CIP, and the evaluation of the degradation pathways of this model antibiotic pollutant. It was found that the degradation of the antibiotic proceeded according to the pseudo-first-order kinetics. Copper(II) phosphate exhibited ca. 7 times higher CIP degradation rate in a Fenton-like process than commercial CuO (0.00155 vs. 0.00023 min-1, respectively). Furthermore, the activity of this metal phosphate could be significantly improved upon exposure of the reaction medium to visible light (reaction rate = 0.00445 min-1). In a photo-assisted Fenton-like process, copper(II) phosphate exhibited the highest activity in CIP degradation from among all reference samples used in this study, including CuO, Fe2O3, CeO2 and other metal phosphates. The main active species responsible for the degradation of CIP were hydroxyl radicals.

Phosphate doping as a promising approach to improve reactivity of Nb2O5 in catalytic activation of hydrogen peroxide and removal of methylene blue via adsorption and oxidative degradation.

This study is devoted to the evaluation of the influence of phosphate dopants on the reactivity of Nb2O5-based nanomaterials in the combined catalytic activation of H2O2 and the elimination of methylene blue (MB) from an aqueous solution via adsorption and chemical degradation. For this purpose, several niobia-based catalysts doped with various amounts of phosphate were prepared by a facile hydrothermal method and subsequent calcination. Phosphate doping was shown to strongly enhance the ability of Nb2O5 to activate H2O2, as well as to adsorb and degrade MB. The most pronounced differences in the reactivity of the parent Nb2O5 and phosphate-doped samples were observed under strongly acidic conditions (pH ~ 2.4), at which the most active modified catalysts (Nb/P molar ratio = 5/1) was approximately 6 times more efficient in the removal of MB. The observed enhancement of reactivity was attributed to the increased generation of singlet oxygen 1O2, which was identified as the main oxidizing agent responsible for efficient degradation of MB. To our knowledge, it is the first report revealing that phosphate doping of Nb2O5 resulted in an improved activity of niobia in the adsorption and degradation of organic pollutants.