Degradation of cardiovascular drug furosemide in aqueous by electron beam irradiation: Mechanisms, degradation pathways and toxicity assessment

Furosemide (FRSM) is a cardiovascular drug with high concentration (up to mu g L-1) in the surface water environment, which are not properly removed by traditional wastewater treatment plants, resulting in negative impact on organisms. In this study, the use of characteristic electron beam (EB) irradiation degraded FRSM with high efficiency. The degradation process precisely conformed to the pseudo first-order kinetic model (R-2 > 0.99). The radical scavenger experiments indicated that center dot OH was the main free radical for the degradation of FRSM. Adding oxidants such as H2O2 (1 mM) had a positive effect on the degradation of 150 mg L-1 FRSM, while adding more than 10 mM H2O2 resulted in the negative effect. The addition of K2S2O8 enhanced the degradation and mineralization of FRSM, with a mineralization rate of 57.1% under 1.5 kGy, which was 2.14 times that of the control group. The degradation of FRSM by EB irradiation in actual water was studied, and the results showed that the presence of NO3 - and CO2- (3) (10 mM) inhibited the degradation of FRSM, while the presence of SO32- , SO2- (4) and Cl- slightly accelerated the degradation. The degradation effect of adding tap water and river water was similar to that of the control group. Moreover, transformation products (TPs) were identified (11 types) and FRSM was mainly oxidized and ultimately converted into small molecule acids, inorganic ions and CO2. Based on toxicity assessment, most TPs have much lower acute and chronic toxicity than maternal FRSM, suggesting EB irradiation is an alternative advanced treatment process to degrade FRSM in wastewater.