The photocatalytic oxidation of benzoic acid was investigated in a pilot scale-cascade photoreactor. The photoreactor consists of an array of UV lamps (40 W, 365 nm) illuminating a cascade of three inclined 316 stainless steel plates, on which titanium dioxide (TiO2) was immobilized by electrophoretic deposition. The percentage removal of total organic carbon (TOC) of liquid samples was determined. The photocatalytic process was affected by several operating parameters. Increasing the solution temperature was found to reduce the dissolved oxygen (DO) level and to decrease the rate of the degradation process. The Langmuir-Hinshelwood equation was found to be accurate for modeling the degradation of benzoic acid with initial concentrations of 50 ppm, 75 ppm and 100 ppm. The rate of removal of TOC was positively affected by UV light intensity, but appeared to be independent of solution flowrate in the range examined. Control experiments confirmed that the effects of adsorption of the solute onto the TiO2 catalysts and photolytic degradation were negligible.

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