Adsorption of Methylene Blue Dye on Hydrothermally Prepared Tungsten Oxide Nanosheets

METHYLENE blue (MB) dye was successfully adsorbed on hydrothermally prepared tungsten oxide (WO3) nanosheets. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and energy-dispersive X-ray spectroscopy (EDS) were used to characterize the prepared powder. Different parameters affecting the adsorption process were investigated such as, contact time, tungsten oxide dose, MB concentration, pH and temperature. In order to detect the kinetic of adsorption process, first, second-order kinetics and intra-particle diffusion models were considered. The second-order model exhibited the best description of MB adsorption onto WO3 center dot H2O. Adsorption equilibrium data obtained from Langmuir, Freundlich and Tempkin isotherm models showed that the dye uptake is a chemisorption process and the dye species prefer to adsorb on the WO3 center dot H2O surface as a monolayer with adsorption capacity Q degrees = 13.33 mg g(-1). Thermodynamic data revealed that the adsorption reaction is exothermic and spontaneous. The effect of different crystalline phases of tungsten oxide nanosheets was also investigated. The hydrated form (WO3 center dot H2O) nanosheets (orthorhombic)showed higher adsorption performance than the non-hydrated structure WO3 nanosheets (monoclinic).