The occurrence of anticancer drugs in the environment has attracted wide attention due to its potential environmental risks. The aim of this study was to investigate degradation characteristics and mechanism of anticancer drug capecitabine (CPC) by electron beam (EB) irradiation. The results showed that EB was an efficient water treatment process for CPC. The degradation followed pseudo-first-order kinetics with dose constants ranged from 1.27 to 3.94 kGy-1. Removal efficiencies in natural water filtered or unfiltered were lower than pure water due to the effect of water matrix components. The degradation was restrained by the presence of NO2-, NO3- and CO32-, and fulvic acid due to competition of reactive radical •OH. It demonstrated that oxidizing radical played important role in irradiation process. The appropriate addition of H2O2 and K2S2O8 providing with oxidizing agents •OH and •SO4- was favorable to improve degradation efficiency of CPC. The possible transformation pathways of CPC including cleavage of the ribofuranose sugar and defluorination were proposed based on intermediate products and were consistent with the theoretical calculation of charge and electron density distribution. Toxicity of CPC and intermediate products were estimated by ECOSAR program. It was found that CPC was transformed to low toxicity products with EB.
Keywords: Capecitabine; Degradation mechanism and pathway; Density functional theory; Electron beam irradiation; Kinetics; Toxicity evaluation.