Effect of the radiation wavelength on the rate of photocatalytic oxidation of organic pollutants

The effect of the radiation wavelength upon the rate of oxidation of a model organic pollutant, 2-chlorophenol (2-CP), on titanium dioxide MOO 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 LTV-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 degreesC when UV-ABC radiation was used. The effect of temperature was found to be negligible when the suspension was irradiated with LTV-A radiation alone.