Radiation-induced degradation of doxazosin: Role of reactive species, toxicity, mineralization and degradation pathways

State-of-the-art technologies based on advanced oxidation processes (AOPs) are currently being developed for the removal of environmental pollutants such as pharmaceuticals from water matrices. Such studies are very important and should include the impact of inorganic and organic matrix on the degradation process of pollutants. One of the AOPs that is in focus of investigations nowadays, is ionizing radiation. Doxazosin (DOX) is a widely used pharmaceutical for the treatment of hypertension, which can be potentially harmful due to its occurrence in the aquatic environment. This study reports the radiation-induced degradation of DOX in aqueous solution. Removal of 10 mg L-1 DOX reached almost 100 % at irradiation doses of 200 Gy regardless of the dose rate used. The effect of saturated solutions with N2, N2O, air and the addition of radical scavengers such as 2PrOH and thiourea on DOX degradation was investigated. The efficiency of degradation increased in the order: thiourea < 2-PrOH < N2 < air < N2O. The effects of pH, various inorganic ions and water matrix on DOX degradation were also studied. DOX degradation was lower in underground water than in ultrapure water. Under prolonged irradiation, mineralization of about 60 % of DOX solutions was observed based on the dissolved organic carbon (DOC) evaluation. Toxicity tests with V. fischeri luminescent bacteria showed higher toxicity of samples irradiated at 500 Gy. The main degradation products were identified using LC-HRMS and degradation pathways were proposed. Overall, irradiation technology could be a promising technique for the removal of micropollutants, such as pharmaceuticals in real water matrices.