Abstract
The dye-sensitized photodegradation of aqueous phenol using rose bengal was carried out batchwise in the chemical region by using an annular bubble-column photoreactor, to evaluate the use of sunlight in wastewater treatment. Effects of both the partial pressure of oxygen and the initial concentration of phenol, [A]0, on the initial reaction rate were analyzed according to the reaction scheme including the quenching reaction of triplet dye 3D* with phenol, in order to determine the kinetic parameters. The reaction rate constant of phenol with singlet oxygen increased with increasing pH and was 2.66 ×108 dm3/mol-s at pH 10.3. The reaction quantum yield at pH 10.3 was limited to a maximum of 0.29 at [A]0=3 ×10-3 mol/dm3 for O2-bubbling and 0.13 at [A]0=1.4 ×10-3 mol/dm3 for air-bubbling by the quenching reaction of 3D* with phenol, of which the rate constant was 4.0×108 dm3/mol• s. p-Benzoquinone, the primary main product, underwent further degradation with both alkaline and ground-state oxygen to yield final products such as carboxylic acids. The reaction curves were simulated closely up to high conversions by taking account of the quenching effect of both phenol and the quinone-type intermediate products on 3D*.
