Radiolysis of carbamazepine by electron beam: Roles of transient reactive species and biotoxicity of final reaction solutions on rotifer Philodina sp.

Electron beam (EB) has proven to be an effective advanced oxidation reduction process (AORP) to degrade the psychiatric drug carbamazepine (CBZ); however, the degradation mechanism and the toxicity of the final reaction solutions to aquatic microorganisms needed further investigation. In this study, CBZ was eventually degraded and even mineralized by EB treatment, where the degradation of CBZ followed the pseudo-first-order kinetics with R2 > 0.98. Acidic conditions, presence of an additional oxidant (2.5 mmol L-1 H2O2), and O2/air-saturated conditions improved the degradation efficiency of CBZ, as well as the radiation chemical yield (G-value defined as the efficiency of the irradiation process). Concentrations of transient reactive species (TRS) caused by EB were quantified under different conditions at doses of 0.956 and 3.17 kGy, and the apparent quantum yield of CBZ degradation was in the order of OH > H > eaq-. However, the contribution of these species to CBZ degradation was in the order of OH > eaq- >H due to the generation of only a small amount of H. Findings regarding the changes of in CBZ degradation intermediates, short-chain fatty acids (SCFAs), and total organic carbon showed that CBZ can gradually be mineralized into CO2/CO32-, H2O, and NH3/NH4+ by the EB process. Additionally, an excellent rotifer survival rate after 5-day culturing in the reaction solutions resulting from 5-kGy treatment indicated that EB can be a safe AORP to mineralize CBZ in solution. These findings provide scientific proof for the EB being an effective AORP for removal of psychiatric drugs from aqueous solutions, laying the foundation for future remediation research.