Trichloroethene Degradation by UV/H₂O₂ Advanced Oxidation Process:  Product Study and Kinetic Modeling

Abstract

The broadband UV irradiation of 1.1 mM trichloroethene (TCE) aqueous solution in the presence of 10.4 mM H2O2 resulted in formic, oxalic, dichloroacetic (DCA), and monochloroacetic (MCA) acids, as organic byproducts. The organic chlorine was converted completely to chloride ion as a final product. TCE and its degradation products were completely mineralized in 30 min, under a volume-averaged UV-C irradiant power of 35.7 W/L from a 1 kW medium-pressure mercury vapor arc lamp. TCE degraded primarily through hydroxyl radical-induced reactions and onlyto a low extentthrough direct UV photolysis and chlorine atom-induced chain reactions. The experimental patterns of TCE, H2O2, and detected reaction products combined with the literature information on radical reactions in the aqueous phase were used to postulate a degradation mechanism and to develop a kinetic model to predict the TCE decay, formation and degradation of byproducts, and pH and oxygen profiles. The agreement between the model calculations and the experimental data is satisfactory.

Photo-assisted electrolytic decomplexation of Cu-EDTA and Cu recovery enhanced by H 2 O 2 and electro-generated active chlorine

“…By contrast, AOPs employing H 2 O 2 with UV irradiation, as reported in previous literatures, were effective in the degradation of organics by producing a multitude of hydroxyl radicals [10,12]. Therefore, the decomplexation of Cu-EDTA was enhanced via the homogeneous and heterogeneous oxidation process with addition of H 2 O 2 .…”

“…Under UV irradiation, a molar of H 2 O 2 was transferred into two molar of hydroxyl radicals by reaction (5) [10,12]. While the pH variation from 1 to 3 increased the oxidation ability, further increase of pH from 3.0 to 5.0 decreased the rate of H 2 O 2 production by reaction (5).…”

“…In the last two decades, Many researches have demonstrated that AOPs employing H 2 O 2 with ultraviolet (UV/H 2 O 2 ) were effective in the rapid degradation of organics [5,[10][11][12]. It was indicated that high degradation efficiency of Pb-EDTA was achieved in 10 min [5].…”

Photocatalytic degradation of dichlorvos in aqueous TiO2 suspensions

“…Evgenidou et al (2006) consider also as possible the route DCA → DCAA → CO 2 + HCl+H 2 O but without any other specification concerning the reaction mechanism. In their study on trichloroethene degradation through the UV/ H 2 O 2 process, Li et al (2007) found DCA as an intermediate byproduct and proposed a degradation mechanism via DCAA which is further oxidized to oxalic acid. An additional degradation pathway of DCAA in Li et al's paper led to phosgene which rapidly hydrolyzes to HCl and CO 2 .…”

Comparative study of diethyl phthalate degradation by UV/H2O2 and UV/TiO2: kinetics, mechanism, and effects of operational parameters

“…The excited electron and hole can react with the adsorbent substance at the surface of TiO 2 (Autin et al 2012). The excited hole has a strong capacity of oxidation, and the excited electron has the possibility of oxidation (with the oxygen molecule) (Li et al 2007;Wu 2008) and reduction (Gao et al 2012;Gu et al 2013).…”