Photocatalysis in a slurry reactor

A series of experiments have been conducted on the photocatalytic reduction of methylene blue with zinc oxide catalyst in a slurry reactor. It is shown that by using a procedure involving separate experiments to determine the shielding effects of the suspended solid (inert solid of similar particle size with a standard actinometric solution) it is possible to identify experimentally the region in the reaction system where imperfect solids mixing influences the rate of reaction. The reactor employed here is also shown to provide a relatively simple means for kinetic measurements in photocatalytic reactions. The rate constants obtained in this study for methylene blue reduction were weakly dependent on zinc oxide concentration in the suspension. A value of 3·67 M^?1 sec^?1 at 0·1 wt.% ZnO at 31·9°C was obtained, where M is the molarity of the solution in methylene blue. This may be compared with 1·25 × 10⁴M^?1 sec^?1 reported by Yoneyama [14] for methylene blue reduction on a rutile crystal of titanium dioxide at room temperature, and 3·33 M^?1 sec^?1 for p-nitrosodimethylaniline reduction in a 0·1 wt. % ZnO suspension, also at room temperature[13].