Kinetic study of methylene blue photocatalytic decolorization using zinc oxide under UV-LED irradiation

Kinetic study of methylene blue photocatalytic decolorization using zinc oxide was carried out under UV-LED lamp irradiation. Zinc oxide was prepared by precipitation method. Zinc oxide was characterized by XRD, FESEM, and N2 adsorption-desorption. Characterization results show that zinc oxide has a hexagonal crystal face, particle size between 0.125-0.3 µm, specific surface area (SBET), micropore volume, and mesopore volume are 60.20 m2/g, 0.541 cm3/g, and 0.02 cm3/g, respectively. The variations of pH and concentration of methylene blue solution were observed. The results show that the alkaline conditions had the highest methylene blue photocatalytic decolorization rate. At initial low concentration, the methylene blue photocatalytic decolorization is very high and decrease when the initial concentration of methylene blue increase. Photocatalytic decolorization reaction kinetics follow the first-order kinetic. The Langmuir-Hinshelwood kinetic analysis results show that photocatalytic reaction constant and Langmuir-Hinshelwood constant value are 2.2621 L.mg−1.min−1 and 0.0144 L.mg-1, respectively.