Degradation mechanism of losartan in aqueous solutions under the effect of gamma radiation

Highlights: • Gamma radiation degradation of a Losartan was studied in aqueous solutions. • Identification of degradation by products by LC/MS was performed. • Losartan degradation mechanistic scheme was proposed. • The radiation induced losartan degradation followed pseudo first order kinetics. • Ionizing radiation is a promising way to remove losartan from water and wastewater. In this paper, the impact of gamma radiation on one of emerging pharmaceutical pollutant was investigated. Deriving from sartan class, losartan, one of the most consumed antihypertensive drug was irradiated at doses of 0.5–4 kGy in aqueous solutions. The removal of chemical oxygen demand (COD) and total organic carbon (TOC) during the irradiation process reflects that the mineralization efficiency increases with increasing radiation dose. During the mineralization process some aromatic intermediates such as 4-[2-(1H-1,2,3,4-tetrazol-5-yl) phenyl] phenol, 2-butyl-4-chloro-5-(hydroxymethyl) imidazole-1-ol, 2,4′-dihydroxybiphenyl, tetrazole, 1,2,4 benzentriol, 1,4-hydroxyquinone and quinone were identified by LC/MS. These results show that degradation process starts with cleavage of the starting molecule by hydroxyl radicals, which are generated by the radiolysis of water. Based on these observations, a mechanistic schema of losartan was proposed. At the end, losartan kinetic study was performed indicating a pseudo first order degradation process.