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)/H 2 O 2 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 μg L −1 (4.73 nM), a H 2 O 2 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 H 2 O 2 concentration from 10 to 50 mg L −1 . The second order rate constant ( k HO·,2,3,6-TCA ) in competition kinetic trials was determined to be 8.17 × 10 7  M −1 s −1 . Degradation products generated during both the UV photolysis and UV/H 2 O 2 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 − , HCO 3 − 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/H 2 O 2 has significant potential with regard to controlling TCAs as pollutants in water.