Photocatalytic degradation of 2-chloro and 2-nitrophenol by titanium dioxide suspensions in aqueous solution

This investigation used a specifically built jacketed cylindrical type reactor with suspended titanium dioxide under W-light of 365 nm for feasibility studies of decomposition of mono-substituted phenols. The factors to be studied were the effects of pH, anion additives and the influence of co-existing reactants competing for reaction. Finally, the degree of mineralization of reactants was conducted in order to survey the effectiveness of treatment. From experimental results, under the condition of 7.5 g/l TiO2, pH 3, and light intensity of 2.25 mW/cm(2), 0.1 mM of substituted phenol could be completely decomposed in 2 h. The reaction was found to be apparent first-order following Langmuir-Hinshelwood model. In the presence of chloride ions, a significant inhibition of reaction was found at pH 3, but not at higher pH levels. At pH 3, a slight inhibition was found for nitrate ions, but uncertain for sulfate ions. For the experiment with co-existing 2-chloro and 2-nitrophenol, the result differed from that of the individual specie. In the mineralization experiments, substitution in the phenol ring had no applicable influence on the reaction rate, however, complete mineralization to carbon dioxide could not be completed within 9 h. (C) 1999 Elsevier Science B.V. All rights reserved.