Photocatalytic degradation of carbamazepine by tailored BiPO4: efficiency, intermediates and pathway

Abstract

This study firstly explored the photodegradation of carbamazepine, one of the most frequently detected pharmaceuticals, with tailored BiPO4 nanomaterials. BiPO4 was synthesized with a hydrothermal method. The physicochemical properties of the obtained samples were characterized and the results indicated that both the hydrothermal temperature and reaction time influenced the phase, morphology and optical properties of the BiPO4 catalysts, which may further determine their specific photocatalytic performances. The intrinsic microstructure and optical properties reflected the crystal properties of the catalysts to some extent. The BiPO4 prepared at 180°C for 72h (BPO-180-72) displayed the best photocatalytic activity under UV irradiation, during which carbamazepine was nearly completely eliminated from ultrapure water after 60min irradiation. The good photocatalytic activity was ascribed to the synergistic effect of monoclinic phase and relatively ordered morphology of the resulting BiPO4. Particularly, the monoclinic phase was firstly proved to be more active than the hexagonal phase for BiPO4 samples. BPO-180-72 removed approximately 72.4% of carbamazepine from lab-prepared simulated wastewater after 60min irradiation, suggesting the potential application of this material in wastewater treatment. Ten reaction intermediate products were observed and identified by HPLC–MS/MS, and a tentative reaction pathway was proposed. Results indicated that photogenerated holes and hydroxyl radicals were the main reactive species for the photodegradation of carbamazepine in the system.