Synthesis and Characterization of Poly-Methacrylic Acid Grafted Chitosan-Bentonite Composite and its Application for Heavy Metals Recovery

Abstract

Poly-methacrylic acid grafted chitosan-bentonite nanocomposite (MACB) was synthesized by g-irradiation polymerization. The nanocomposite was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) crystallography, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The MACB nanocomposite was employed for the adsorption of mercury, cadmium and lead ions from aqueous solution. The effect of various parameters such as pH, contact time, metal ion concentration and temperature on the adsorption of metal ions onto MACB nanocomposite was investigated. The experimental results indicated that the order of adsorption capacity of MACB nanocomposite for metal ions was as follows: Hg²⁺ > Pb²⁺ > Cd²⁺. The data indicating that the adsorption of the latter ions onto MACB nanocomposite followed both the Langmuir and Freundlich isotherm models. Equilibrium adsorption isotherm fitted the Langmuir model for Hg²⁺ ions and the adsorption of Cd²⁺ ions better fit the Freundlich isotherm model. The adsorption of Pb²⁺ ions followed both the Langmuir and Freundlich isotherm models.

Keywords: hydrogel; nanocomposites; clay; chitosan; ?-ray irradiation; Metal uptake