AN INVESTIGATION OF NANOSTRUCTURED IRON ANDVANADIA/TITANIA CATALYSTS FOR OXIDATION OFCHLOROBENZENES AND POLYCHLORINATED BIPHENYLS

摘要

In this study, the effectiveness of iron powder, nanostructured iron, iron(III) oxide andV2O5/TiO2 catalysts to control emissions of selected pollutants was investigated. Thefocus of this study was the destruction of two classes of pollutants, namely, chloro-benzenes(CBz) and polychlorinated biphenyls (PCBs). The nanostructured V2O5/TiO2catalyst (5% vanadia loading) was prepared by the wet incipient method. The ironnanoparticles used in this study were prepared by reducing ferric chloride solution withsodium borohydride. A PCB mix, Arochlor 1254, was used to investigate the potential ofthe proposed catalyst system to destroy PCB contaminants and 1, 2-dichlorobenzene wasthe CBz used in this study. The PCB or CBz mix was added to the reactor flow byplacing the pollutant mix in the injector at room temperature and then heating the injectorto 300°C. The reactor inlet concentration of pollutants was maintained at 1000 ppm. Thetransport efficiency of this sample introduction system has already been validated. Forthis study, the fixed bed reactor was made of 0.1 g of catalyst and the total reaction timewas kept at 60 minutes. Air (combustion) or nitrogen (pyrolysis) was used as reactor gasduring reaction time. The reactor exit gas was collected in a XAD trap held at roomtemperature. After each experiment, the catalyst and XAD trap were extracted separatelyby soxhlet extraction (solvent-dichloromethane) and then concentrated. The productswere analyzed using gas chromatography-mass spectrometry (GC-MS). The resultssuggest that pollutants are destroyed more efficiently under combustion condition andthat V2O5/TiO2, iron(III) oxide and nanostructured iron can all be effective in controllingemissions (destruction >80%) of PCB and CBZ emissions. As expected, iron powderwas the least effective catalyst. The results also suggest that under the conditions of thisstudy, deep oxidation and not dechlorination is the dominant pollutant destructionmechanism.