Elimination of trichloroanisoles by UV/H2O2: Kinetics, degradation mechanism, water matrix effects and toxicity assessment

The elimination of 2,3,6-trichloroanisole (2,3,6-TCA), which produces a musty-earthy off-odor in water, by an ultraviolet (UV)/H2O2 process was assessed. The removal of 88.1% of 2,3,6-TCA in ultrapure water (UPW) was achieved using an initial 2,3,6-TCA concentration of 1 mu g L-1 (4.73 nM), a H2O2 concentration of 20 mg L-1 (0.588 mM), a UV intensity of 1.44 mW cm(-2) and a pH of 8.2. The reaction was found to be pseudo first order with a rate constant (k(obs)) of 0.0340 min(-1). Both the removal efficiency and k(obs) increased significantly upon increasing the H2O2 concentration from 10 to 50 mg L-1. The second order rate constant (k(HO)(center dot),2,3,6-TCA) in competition kinetic trials was determined to be 8.17 x 10(7)M(-1)s(-1). Degradation products generated during both the UV photolysis and UV/H2O2 treatment of 2,3,6-TCA solutions were analyzed using ultrahigh resolution gas chromatography/mass spectrometry, and the degradation mechanism was proposed. The toxicities of water solutions during both processes were assessed via a luminescence method in conjunction with Vibrio fischeri. The pH and Cl-, HCO3- and natural organic matter concentrations of the aqueous medium were all found to significantly affect the removal of 2,3,6-TCA. The degradation rates of trichloroanisoles (TCAs) in real-world water samples demonstrated that UV/H2O2 has significant potential with regard to controlling TCAs as pollutants in water. (C) 2019 Elsevier Ltd. All rights reserved.