TiO₂ Nanoparticles for Removal of Malachite Green Dye from Waste Water

Abstract

In this research, we present a simple and successful route for synthesis titania nanoparticles by controlled solgel progress. Chitosan as bio-template is involved in the progress of preparation to increase the surface area and manipulate defined particle and pore structure. The crystalline behavior and the nanostructure of the prepared nanoparticles were investigated using X-ray diffraction [XRD] and transmission electron microscope [TEM]. The crystalline results have pointed out the predominant existence of anatase phase that reveals the successful role of chitosan in stabilizing titania nanoparticles and preventing the growth of these particles into rutile phase. It is obvious to notice that a change in sample crystallography from anatase to completely amorphous nanoparticles upon adsorption of malachite green dye indicates a strong adsorption of this dye that destroys the crystalline feature of titania sample. TEM analysis reveals the existence of spherical nanoparticles with size about 25 nm. The adsorption isotherm indicates the adsorption capacity 6.3 mg.g-1 TiO2. The value of enthalpy change (ΔH°) for malachite green dye adsorption is 19 kJ/mol, which indicates that the removal process is endothermic. The adsorption process follows pseudo-second order rate equation and the negative values of standard free energy (ΔG°) suggest that the adsorption process is spontaneous.