Impacts of inorganic anions and natural organic matter on thermally activated persulfate oxidation of BTEX in water.

The present study investigated the impacts of water matrix constituents (CO, HCO, Cl, Br, PO, HPO, HPO, NO, SO and natural organic matters (NOM) on the oxidation of a mixture of benzene, toluene, ethylbenzene, and xylenes (BTEX) by thermally activated persulfate (PS). In the absence of matrix constituents, the BTEX oxidation rates decreased in the following order: xylenes > toluene ≈ ethylbenzene > benzene. HCO/CO and NOM inhibited the BTEX oxidation and the inhibiting effects became more pronounced as the HCO/CO/NOM concentration increased. SO, NO, PO and HPO did not affect the BTEX oxidation while HPO slightly inhibited the reaction. The impacts of Cl and Br were complex. Cl inhibited the benzene oxidation while 100 mM and 500 mM of Cl promoted the oxidation of m-xylene and p-xylene. Br completely suppressed the benzene oxidation while 500 mM of Br strongly promoted the oxidation of xylenes. Detailed explanations on the influence of each matrix constituent were discussed. In addition, various halogenated degradation byproducts were detected in the treatments containing Cl and Br. Overall, this study indicates that some matrix constituents such as NOM, HCO, CO, HPO, Cl and Br may reduce the BTEX removal efficiency of sulfate radical-based advanced oxidation process (SR-AOP) and the presence of Cl and Br may even lead to the formation of toxic halogenated byproducts.