Authors
Abstract
The microwave assisted preparation and characterization of chitosan-surfactant modified NaMMT clay composite material is discussed, followed by its interesting application to detoxify heavy metal chromium. Cr(VI) could be effectively adsorbed in a weakly acidic medium (pH 5) from a large sample volume. The composite material before and after the adsorption of chromium was scrupulously characterized using FT-IR, SEM, XRD and EDX techniques. The XRD study revealed the crystalline nature of the composite material with sharp and symmetric peaks. The bichromate ion forms an ion-pair with the protonated amine group in chitosan and this is reflected in the appearance of a Cr=O peak at 916 cm -1 in IR study. The surface hydroxyl groups in clay can be protonated and this could also serve as a source of electrostatic interaction with the bichromate oxyanion. The material exhibited a superior adsorption capacity of 133 mg g -1 and the adsorption data fitted well with Langmuir and Freundlich isotherm models. The composite adsorbent material exhibits a pore size of 3.5 nm at a maximum pore volume of 0.16 cm 3 g -1 . The BET surface area of the material obtained from N2 adsorption was found to be 52 m 2 g -1 . The experimental data also showed a good correspondence to the pseudo-second-order kinetics and the sorption thermodynamics correlated to the endothermic nature of the adsorption. The adsorbent could be regenerated using ascorbic acid or sodium sulfite which is indicative of the greener aspect in the methodology.
Keywords
)