FEASIBLITY OF ZnO/UV IN DEGRADATION OF METHYLENE BLUE AND CONGO RED

Abstract

This study aims to evaluate the feasibility of ZnO/UV in degrading organic dyes including methylene blue (MB) and congo red (CR) in aqueous solution. The synthesized materials were analyzed by X-ray diffraction and scanning electron microscopy. The obtained materials were in the form of single phase ZnO with spherical shapes and sizes ranging from 20 to 70 nm. The influence of factors such as ZnO content, pH, initial dye concentration and time on the degradation efficiency was studied. The optimal ZnO contents for MB and CR degradation were 1.2 g/L and 1.5 g/L, respectively. The suitable pH value for MB decomposition reaction was 7 and for CR was 6. As the concentration of organic dyes increased, the reaction time increased. The decomposition efficiency was above 90% for solutions with organic dye concentration from 5 to 20 mg/L. The decomposition kinetics followed a first-order kinetic model with the reaction rate constants for MB and CR were 0.0579 and 0.0609 (min-1), respectively. The results show that the ZnO/UV system has good ability to degrade MB and CR with concentrations of 20 mg/L or less.