Photocatalytic degradation of pyridine in water solution using ZnO as an alternative catalyst to TiO2

The degradation of pyridine, widely used in the synthesis of vitamins, drugs, rubber chemicals, herbicides and pesticides, can be photocatalyzed by semiconductor catalysts. Since zinc oxide promotes faster pyridine photocatalytic oxidation reactions than TiO2, the former appears to be a suitable alternative to TiO2 for water treatment contaminated with pyridine. The photodegradation efficiency was negligible when the photolysis was carried out in the absence of any catalyst. The formation and eventual disappearance of intermediate organic reaction products during the photocatalytic oxidation of pyridine was monitored by a combination of analytical techniques such as UV-Vis, HPLC, TOC and NMR. Based on experimental observations, an alternative mechanism is proposed for the photocatalytic oxidation of pyridine. In addition, the kinetic parameters of the Langmuir-Hinshelwood model that describe the initial reaction rate for the photocatalytic degradation of pyridine over TiO2 and ZnO are presented.