Counter flow silica-titania photocatalytic reactor for the simultaneous treatment of air and water contaminated with volatile organic compounds

The photocatalytic oxidation (PCO) of VOCs was investigated using a novel countercurrent flow reactor designed to enable the treatment of toluene present in the gas and the aqueous phases simultaneously. The reactor was packed with silica-titania composites (STCs) commingled with plastic high flow rings. Using this mixed packing style was advantageous as it resulted in a higher UV penetration throughout the reactor. The average UV intensity in the reactor was 220 uW/g irradiated titania.;Under dry conditions, the STCs had a high adsorption capacity for toluene; however, this adsorption was completely inhibited by the wetting of the STCs when the two phases were flowing simultaneously. The lack of adsorption hindered the PCO of toluene in the gas phase as it was found to be negligible during the two-phase operation.;Likewise, the adsorption of toluene in the aqueous phase was negligible likely due to the short mean residence time in the pilot reactor (< 60 s). However, the PCO of toluene in the aqueous phase linearly increased with concentration due to the larger driving force and decreased as function of liquid loading rate.;In the presence of both phases, toluene destruction was only observed under conditions in which the solution was initially supersaturated with respect to the gas phase. Under these conditions, the net destruction of toluene in the system reached a maximum of about 68%. For the most part, the destruction occurred in the aqueous phase, and it was observed that high gas phase flowrates could be detrimental to the toluene destruction in the two-phase reactor.;The reactor was modeled using a one dimensional plug flow with dispersion model for the aqueous phase and a plug flow model for the gas phase. The dispersion coefficient and gas-liquid and liquid-solid mass transfer coefficients were determined from correlations developed in this study. The model was calibrated using the two-phase experiments data by fitting the mass transfer coefficients. The mathematical model is a useful tool to simulate the reactor's performance for a given set of operating conditions and investigate the effects of the different variables on the net toluene conversion. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)...