Photocatalytic Degradation of 2-Chlorophenol in Water with Direct Solar Light using Pristine and Kaolinite Supported ZnO

The photocatalytic degradation of 2-chlorophenol in water under direct sun light was studied using ZnO as semiconductor photocatalyst. Different forms of catalyst were used, namely commercial ZnO, synthetic ZnO and for the first time using composite of ZnO/Kaolinite. These forms were characterized by photoluminescence and UV-visible spectra and the results indicate that the ZnO particles varied in size as: ZnO/Kaolinite < synthetic ZnO < commercial ZnO. The photodegradation of 2-chlorophenol was investigated under different conditions including effect of contaminant concentration, effect of catalyst amount and effect of pH. To study catalyst efficiency, values of overall rate, turnover number (T.N.), turnover frequency (T.F.), degradation percentage and quantum yield (Q.Y.) were all calculated. Under neutral conditions, different ZnO forms catalyzed the photodegradation of 2-chlorophenol in water. The results were compared between ZnO forms, synthetic ZnO showed higher efficiency than commercial ZnO. Commercial ZnO/Kaolinite composite showed higher efficiency than commercial ZnO and synthetic ZnO. The order of efficiency using different form of ZnO system is commercial ZnO< synthetic ZnO< commercial ZnO/Kaolinite. Increasing contaminant concentration, catalyst amount and pH increased photodegradation rates. A mechanism is provided to explain how the photodegradation occurs.