The pH and anion effects on the heterogeneous photocatalytic degradation of o-methylbenzoic acid in TiO2 aqueous suspension

This investigation used UV light of 365 nm and titanium dioxide in aqueous suspension to study the photocatalytic reaction of o-methylbenzoic acid und er the influence of pH values, anion additives and the varieties of titaniu m dioxide. From experimental results, under the condition of 5 g/l TiO2, pH 3 and light intensity of 2.45 mW/cm(2), 0.1 mM of o-methylbenzoic acid cou ld be completely decomposed in 2 h. The reaction was faster with lowering p H, and was found to be apparent first-order following Langmuir-Hinshelwood model. In the presence of anion additives, the inhibitive effect of chlorid e ions was larger than that of sulfate ions under acidic condition for Degu ssa brand titanium dioxide, but without influence using Janssen brand. Both brands, however, promoted the mineralization of o-methylbenzoic acid (o-MB A). (C) 1999 Elsevier Science Ltd. All rights reserved.