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.