Application of BiOClnBrm photocatalyst to cytostatic drugs removal from water; mechanism and toxicity assessment

Abstract The photocatalytic activity of series of BiOClnBrm photocatalysts toward degradation and mineralization of the cytostatic drugs 5-fluorouracil (5-FU) and imatinib mesylate (IMA) both singly and in their mixture under simulated solar and visible light irradiation has been investigated. Screening test revealed that among BiOClnBrm photocatalysts synthesized by a solvothermal method, the one with molar 1.3Cl/0.7Br ratio was the most efficient in 5-FU removal under UV–Vis irradiation. The dose 200 mg L−1 and 6.3 pH were optimal to effective removal of 5-FU. The BiOCl1.3Br0.7 was successfully used to 5-FU and IMA removal singly and in their mixture under simulated solar and visible light irradiation. Scavenging experiments showed that h+ and •O2− were the major oxidative species participated in both drugs degradation. In presence of IMA, 5-FU removal was significantly depressed. In singly drug solutions and in the mixture of drugs, the presence of inorganic ions such as Cl−, SO42−, and NO3− significantly hindered 5-FU photocatalytic degradation, and increased the adsorption of IMA onto the photocatalyst surface in dark phase. The HCO3− anion, Fe3+ and Ag+ cations accelerated the 5-FU removal, while Ca2+ showed no impact on the process. The transformation products of 5-FU and IMA were identified by LC-MS revealing that hydroxylation and oxidation were the main transformation pathways, under the all studied systems. Some of intermediates were indicated for the first time in heterogeneous photocatalysis. The defluorination of 5-FU by the reaction with photogenerated e− was also possible. Furthermore, the alga toxicity assay was investigated using Chlorella vulgaris. A reduction of toxicity in effluents after photocatalytic degradation of both drugs singly and in their mixture was observed.