FE 0 -INITIATED REDOX SYSTEMS FOR DEGRADING TRICHLOROETHYLENE

This paper presents innovative reaction systems for degrading a pollutant of human health concern, trichloroethylene (20 mg/L). Based on the use of zero-valent iron (Fe 0 ) powder (0.5 g/L), the reduction and oxidation (redox) systems were constructed in the presence of H2O2 (9 and 311 mg/L) and UV irradiation (128 watts). The redox systems of Fe 0 /H2O2 and Fe 0 /H2O2/UV for degrading TCE involve reaction modes such as photon absorption, electron reduction (corrosion/photo-corrosion of Fe 0 ) and hydroxyl radical oxidation (Fenton/photo-Fenton, H2O2/UV, and Fe 3+ /UV). As a result, TCE itself is sensitive to photolysis, and its degradation follows a first order reaction kinetics, while the releasing of Cl - can be expressed by a hyperbola function. In addition, irradiation of UV light appeared to enhance the corrosion of Fe 0 , which was advantageous for inducing photo-Fenton oxidation removal of TCE as H2O2 was dosed into the reaction system. The results show that the Fe 0 /H2O2 system was capable of degrading TCE by a molar fraction of 0.66 on the basis of moles of chloride releasing and chlorine atoms in TCE, whereas the Fe 0 /H2O2/UV system degraded TCE by 0.99. The remaining molar fraction was responsible by the stripping of TCE in the open system due to mixing. To achieve the best performance of such redox systems, the dosage and the dosing time sequence of H2O2 need to be optimized. In addition, UV light photon in the studied redox system appears to play a key role and it may result in multiple synergistic effects on TCE degradation.