Enhanced dechlorination of triclosan by hydrated electron reduction in aqueous solution

•Hydrated electron reduction of TCS in aqueous solution is first investigated.•The photochemical transformation of TCS is enhanced in the presence of eaq−.•Several further dechlorination products are obtained in the presence of eaq−.•eaq− accelerates dechlorination and ether cleavage of TCS.

In this study, different methods of electron beam (EB) irradiation and potassium ferrocyanide (K4Fe(CN)6) activated by simulated sunlight irradiation (λ ⩾ 290 nm) were adopted to generate hydrated electron (eaq−), respectively. Steady-state and laser flash photolysis experiments were conducted to evaluate the feasibility of using eaq− reduction to enhance the dechlorination of TCS in aqueous solution. Under the EB irradiation, eaq− was proved to be an effective radical, and significant degradation of TCS was observed. Under simulated sunlight irradiation, TCS degradation efficiency within 60 min increased from 70.3% (without K4Fe(CN)6) to 100% ([TCS]0/[K4Fe(CN)6]0 = 1/5), and the average dechlorination percentage after 2 h increased from 62.7% to 90.7%, respectively. The degradation of TCS in the presence of eaq− adhered to the apparent first-order kinetics, and the optimal rate constant (kp) was (1.54 ± 0.02) × 10−3 s−1. Several enhanced dechlorination products were obtained and a primary reaction mechanism was proposed.