Adsorption of Anionic Dyes on Poly(N-vinylpyrrolidone) Modified Bentonite

Abstract

A composite based on poly(N-vinylpyrrolidone) (PVP) and sodium bentonite was prepared by a simple method. Structural characterizations of the bentonite and the composite were performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The TGA analysis showed a low loading of the polymer in the bentonite. XRD analysis confirmed a modification in the structure of the bentonite without affecting its crystalline nature. The prepared composite was used for the removal of Telon-Blue, Telon-Orange and Telon-Red dyes in aqueous solution. Batch adsorption experiments were used to study the effect of the experimental parameters on the dyes equilibrium adsorption. At 23 °C, the maximum adsorption capacity obtained for the Telon-Blue dye was 36.6 mg.g-1 (73.10 %) after 120 min equilibrium time, 28.8 mg.g-1 (59.57 %) after 40 min for Orange-Telon, whereas, with the Telon-Red, we obtained 24.6 mg.g-1 (50 %) after 60 min. The kinetic data of the adsorbed dyes were defined by the pseudo second order and the equilibrium data were fitted well with the Freundlich isotherm. The thermodynamic parameters were determined for Telon-Bleu dye, as the more important adsorption capacity values were achieved with it. The adsorption process is non spontaneous and exothermic.