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In this paper we present a two-dimensional (2-D) analysis of a narrow-slit, flat-plate, single-pass, flow-through photocatalytic reactor for air purification. The continuity equation for convection and diffusion in two dimensions, under un-steady-state conditions, was coupled with radiation field modeling and photocatalytic reaction kinetics to model the transient and steady-state behavior of the reactor. The model was applied to the photocatalytic oxidation of trichloroethylene (TCE) in humidified air streams under different experimental conditions. The kinetic parameters determined by a three-dimensional (3-D) computational fluid dynamics model of the reactor were used in the 2-D model simulations. Under the experimental conditions in the reactor, the 2-D model was shown to approximate closely the experimental results of the oxidation of TCE and to give predictions that approach very well those of the 3-D model. The 2-D model, when applicable, provides a simpler and less time-consuming approach than the...

The effect of the radiation wavelength upon the rate of oxidation of a model organic pollutant, 2-chlorophenol (2-CP), on titanium dioxide (TiO2) aqueous suspensions was investigated using UV-A radiation alone and concomitant UV-A, -B, and -C radiation. The rates of degradation and mineralization of 2-CP were significantly enhanced with UV-ABC radiation compared to the use of UV-A radiation alone. This rate enhancement was found to be caused by the combined effect of photolysis, photocatalysis, and synergistic effects due to concomitant photolysis and photocatalysis. In the initial stage of the oxidation reaction, 2-CP is preferentially photolyzed to yield catechol as the main intermediate which is mineralized further to CO2 and water via a photocatalytic process. A significant effect of temperature was found in the experiment using UV-ABC radiation. The rate of mineralization of 2-CP was found to double with a temperature increase from 20 to 40 °C when UV-ABC radiation was used. The effect of temperature...

A novel, thin-film, slurry “fountain” photocatalytic reactor for water treatment and purification is presented. The novelty of the reactor centers on the design of a special nozzle through which water is pumped to create a thin film. The film emerges from the nozzle in the shape of a smooth and radially expanding water fountain. A radiation source (solar or UV lamps) is situated above the fountain. Two dimensionless mathematical models for the photoreactora flat fountain model and a parabolic fountain modeland simulation results under a number of different conditions including the effects of nozzle setting (radius, aperture, and angle), flow rate, and light scattering are presented. The model simulations suggest that optimal photoreactor design is given by fountains with large surface areas. Photocatalysts with scattering albedos smaller than 0.3 result in optimal photoreactor performance. The models presented may be used as a tool for the design, scale-up, and optimization of these types of reactors.

The photocatalytic oxidation of single-component and multicomponent systems consisting of chlorophenols in aqueous TiO2 suspension was investigated using long, medium, and short wavelength UV radiation. In the single-component experiments, 2-chlorophenol (2-CP), 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol, and 4-chloro-3-methylphenol (4-Cl-3-MP) were found to degrade at the same rate. The rate of mineralization of 4-Cl-3-MP was higher than that of the others. Power law kinetic models for the temporal prediction of the degradation and mineralization profiles fitted the experimental results well for the single-component systems. The application of these models to represent the simultaneous oxidation of a binary mixture of 2-CP and 4-Cl-3-MP was examined for several equimolar and nonequimolar mixtures. Competitive inhibition kinetics were observed. Under equimolar feed conditions the rates of degradation of the total mixture were comparable to those for single-component systems and could be ...

Laminar falling film slurry (LFFS) photocatalytic reactors are one of the most efficient reactor configurations for conducting heterogeneous photocatalytic reactions, particularly for wastewater treatment. This paper presents a study on the oxidation of an aqueous salicylic acid waste in a pilot continuous flow LFFS photocatalytic reactor which has an optimum design for light absorption. In conducting the oxidation reaction, heterogeneous photocatalysis was supplemented with other photon-assisted processes. The effect of light intensity, radiation wavelength, oxidizing-enhancing agents, substrate and photocatalyst concentration, and exposure time were studied. A comparison of six different photon-based processes showed that higher oxidation rates of salicylic acid were obtained when there was concomitant photocatalysis, photolysis, and UV peroxidation. The oxidation rates of salicylic acid with this combined process were at least 1 order of magnitude higher in comparison with those for UVA photocatalysis and 3-fold higher in comparison with homogeneous UVC photolysis/UVC peroxidation.