Photodegradation performance of 1,1,1-trichloroethane in aqueous solution: In the presence and absence of persulfate

Photodegradation of 1,1,1-trichloroethane (TCA), a chlorinated solvent, with VUV and VUV/S2O82- processes was investigated. The effects of various parameters including solution pH, Cl- and HCO3- anions, and humic acid (HA) were evaluated. The results indicated that TCA can be effectively removed under VUV irradiation, and the addition of S2O82-, significantly enhanced TCA removal. TCA decomposition in both processes follows the pseudo-first-order kinetic model. In the pH adjusted solutions (from pH 3 to 11), maximum TCA degradation rate occurred at pH 3 and remarkable inhibition at pH 11 in the two processes. Both Cl- and HCO3- anions, as well as HA, adversely affected TCA degradation performance. Moreover, TCA degradation in the VUV/S2O82- process was more sensitive to all the influence factors than in the VUV process. The organic chlorine in TCA was released completely to chloride ion as a final product in both processes. Several reaction intermediates, including 1,1-dichloroethylene, 1,1,1,2-tetrachloroethane, perchloroethylene, carbon tetrachloride, chloroform, and dichloromethane were identified during TCA degradation in the presence of S2O82- . In summary, it can be concluded that the presence of persulfate was much more effective than the VUV alone, but the latter was more environmentally friendly due to the formation of nontoxic intermediates. (C) 2012 Elsevier B.V. All rights reserved.