Abstract for presentation at 14th IUAPPA World Congress

This study investigates photocatalysis of monobromdiphenyl ether (MBDE) under the illumination of near-UV light by using P-25 TiO2 as the photocatalyst. The investigated parameters including water vapor from dry to 27000 μM, oxygen concentration from 400 to 8000 μM, and reaction temperature from 150 to 270 oC are tested. Experimental results show that water vapor promotes degradation rates of MBDE in the presence of enough water vapor due to less accumulation of reaction intermediates and more formation of hydroxyl radicals on the catalyst. The highest reaction rate is as water concentration equal 13400 μM. The degradation rates are inhibited in too humid conditions due to adsorption competition for active sites. Besides, typical heterogeneously catalytic reactions are observed for MBDE degradation respected to different oxygen content. A first-order reaction kinetic is detected for the decomposition of MBDE for low concentration oxygen, but a zero-order reaction kinetic is observed as the catalyst saturated with oxygen. The decomposition rate of MBDE increases exponentially with reaction temperature. Faster surface reaction rates are expected in high temperature conditions even though less adsorption of reactants by the photocatalyst. For reaction intermediates formation, both high water vapor content and reaction temperature would cause less formation concentrations of the intermediates but cause more different types of the intermediates yield. The intermediates may include diphenyl ether, 4-methoxycinnamic acid, 2-ethylhexyl ester, butylated hydroxytoluene, benzoic acid, myristic acid isopropyl ester, benzene, bromoform and dibromomethane.