Strategy of combining radiation with ferrate oxidation for enhancing the degradation and mineralization of carbamazepine.

In this study, the strategy of combining radiation with ferrate oxidation was proposed to decrease the adsorbed dosse and enhance the mineralization of carbamazepine in aqueous solution. Compared to single radiation (800 Gy), the combined process of ferrate pretreatment and radiation required lower dose (600 Gy) for totally removing carbamazepine. During the combined process, the removal efficiency of total organic carbon (TOC) reached 22.2%. However, the removal efficiencies of carbamazepine and TOC decreased when ferrate and radiation were used simultaneously, indicating that the addition of ferrate during the radiation process had negative effect on the removal of carbamazepine. In contrast, the radiation followed by ferrate oxidation presented the best performance in decreasing the absorbed dose and enhancing the mineralization of carbamazepine. Carbamazepine could be completely removed under all conditions. TOC removal efficiency reached 18.3%, 31.3%, 52.9% and 60.6%, respectively, at the adsorbed dose of 100, 300, 600 and 800 Gy when 0.4 mM ferrate was adopted. The enhanced TOC removal could be due to the enhanced oxidation capacity of ferrate caused by the pH decrease at the end of radiation and the further oxidation of intermediate products formed during the radiation process by ferrate. Seven degradation products were identified in total, and thus the degradation pathway of carbamazepine was proposed. This study provides a possible way to decrease the adsorbed dose and enhance the mineralization of carbamazepine by radiation.