Use of curcumin as a sensitizer with ZnO nanoparticles for the visible light photocatalytic degradation of methylene blue

This work aims to examine the application of ZnO/Curcumin nanocomposite materials, in which curcumin (natural dye) is used as a photosensitizer in the photocatalytic degradation of methylene blue (MB) under visible light irradiation. The ZnO/x% curcumin nanocomposite materials (with x = 3, 5, 7, 10 and 20) are prepared by the wet impregnation method. These nanocomposite materials are characterized using various techniques; including Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet-visible spectroscopy and scanning electron microscopy. Optimal MB degradation of similar to 99% was obtained with a concentration of 0.5 g L-1 of 5% curcumin/ZnO nanocomposite catalyst material, at natural pH and initial MB concentration of 10 mg L-1 for 90 min exposure to visible light irradiation. The kinetic indicates that the Langmuir-Hinshelwood (L-H) model is well adapted to the experimental data. Pseudo-first order kinetics were obtained with a rate constant (k) and half-life time (t(1/2)) of 0.0423 min(-1) and 16 min. The significant improvement in the photocatalytic properties of ZnO under visible light irradiation induced by the addition of curcumin as a photosensitizer could be due to the increase in the concentration of reactive radical species in the solution, such as superoxide (O-2(center dot)) and hydroxyles (OH center dot).