Removal of cetirizine dihydrochloride from different matrices waters using Bi₂O₃/TiO₂ photocatalyst under simulated solar irradiation: Kinetics, mechanism, and effect of environmental media

In this study, the photodegradation of cetirizine dihydrochloride (CET) by Bi₂O₃/TiO₂ heterojunctions under simulated solar light irradiation (300-800nm) was examined in detail for the first time. A hydrothermal synthesis of the photocatalyst was carried out, and several analytical techniques were used to characterize the product. The resulting Bi₂O₃/TiO₂ photocatalyst effectively removed CET from an aqueous solution. The Bi₂O₃/TiO₂ (5.0%/95.0%) ratio exhibited the highest photocatalytic performance for CET degradation, degrading 75.85% of CET after 60 min of irradiation, with a high pseudo-first-order rate constant (k_app = 0.022 min⁻¹; t_1/2 = 31.50 min; natural pH). Moreover, TOC decreased by 40.45% after 420 min of irradiation. The Bi₂O₃/TiO₂ photocatalyst has also been proven effective in degrading CET in different real aqueous matrices (Seawater (99.89%) > spring water (68.44%) > tap water (52.62%)), and the degradation under natural solar irradiation is more effective and faster than under artificial irradiation. Additionally, the Bi₂O₃/TiO₂ photocatalyst demonstrated excellent photo-stability in a five-cycle photocatalytic experiment. The influence of various parameters showed that the removal of CET was heightened with a dose of 1 g/L of the Bi₂O₃/TiO₂ and enhanced under acidic conditions (pH = 2.3). Moreover, the involvement of different reactive species was investigated by introducing diverse scavengers, revealing that hydroxyl radicals and photo-holes were the main reactive species involved in the CET photodegradation process over the Bi₂O₃/TiO₂ photocatalyst. The primary photodegradation byproducts were identified using HPLC–MS analysis, and a possible mechanism was proposed.