Synthesis and characterization of new chitosan-based nanocomposite gel and its application towards dye removal

Abstract: We present a nanocomposite gel that efficiently adsorbs a toxic and non-biodegradable cationic dye (methylene blue) from water. This nanocomposite gel is synthesized using chitosan, silica, and titanium dioxide nanoparticles (TiO2 NPs) as precursors. The structure of the nanocomposite gel is characterized by X-ray diffraction (XRD) and cryogenic-scanning electron microscopy (cryo-SEM). Its viscoelastic properties are analyzed using a rheometer, and the mechanical rigidity is noted to significantly improve upon the incorporation of TiO2 NPs. The nanocomposite gel is then utilized to adsorb methylene blue dye (1-20mg/L) from its aqueous solution using batch method. Effects of contact time, pH of the solvent, amount of adsorbent dose, and initial dye concentration on the dye removal percentage are probed systematically. The kinetic studies indicate that the adsorption process follows pseudo-second-order kinetics. Among various isotherms, Freundlich isotherm describes the adsorption best with the highest regression coefficient. Furthermore, preliminary results show that the nanocomposite synthesized here even has the capability of adsorbing heavy metal ions such as chromium (Cr(VI)). This nanocomposite gel is, therefore, a promising candidate for the treatment of wastewater containing dyes and other contaminants from wastewater.