Photodegradation of p-Nitrochlorbenzene (p-NCB) Using Nanometer-Sized ZnO Particles Prepared by Reactive Evaporation Method
PHOTODEGRADATION OF p-NITROCHLORBENZENE （p-NCB） USING NANOMETER-SIZED ZnO PARTICLES PREPARED BY REACTIVE EVAPORATION METHOD

Photocatalytic degradations of p-nitrochlorbenzene (p-NCB) with distilled water were investigated with ZnO crystals (catalyst) of 70nm in diameter under UV irradiation. The suitable experimental conditions are determined as: ZnO 0.25g, pH 7, p-NCB concentration 30mg/L. These variables in terms of the degradation rate have been discussed, which was defined as the rate of the initial degradation to the final degrada- tion of p-NCB. When all of the experimental degradation rate values are plotted as a function of irradiation time, all of the points appeared on a single line for wide range of p-NCB degradations. On the basis of these results, it has been concluded that at lower ZnO catalyst amount, much of the light is transmitted through the slurry in the con- tainer beaker, while at higher catalyst amount, all the incident photons are observed by the slurry. Degradation rates of p-NCB were found to decrease with increasing solution pH. It has been concluded that the maximum degradation rate values of p- NCB under principally the same experimental conditions mentioned above are 97.4%, 98.8% and 95.5% at 100min respectively. The results suggest that the photocatalytic degradation is initiated by an oxidation of the p-NCB through ZnO surface-adsorbed hydroxyl radicals. Absorption spectra are recorded using spectrophotometer before and after UV-irradiation in the wavelength range 200-400nm at room temperature. It is found that the variation of irradiation time over the range 20-100min resulted in change in the form of the spectrum linear absorption and a higher maximum value will be obtained at longer irradiation time.