Synthesis and characterization of superabsorbent chitosan-starch hydrogel and its application for removal of direct red 80 dye

ABSTRACT: In this study, an eco-friendly superabsorbent hydrogel was prepared by crosslinking chitosan and starch using glutaraldehyde as the crosslinking agent. The chitosan-starch hydrogel (CSH) as an adsorbent was then successfully used for the sorption of Direct Red 80 (DR80) dye from aqueous medium. The adsorbent was evaluated using batch adsorption process by performing a series of batch investigations to identify the maximum sorption kinetics, thermodynamics and isotherms of DR80 onto the adsorbent by assessing different operational conditions such as pH, sorbent dose, initial DR80 concentration, salts and temperature. The sorption process was studied using the pseudo-first order, the pseudo-second order kinetic equations alongside the Freundlich and Langmuir isotherm equations at different temperatures.The equilibrium data was observed to follow the Freundlich model and was observed that DR80 sorption process favored the pseudo-second order kinetics correlation coefficient (R2) value obtained. The negative and positive values of ΔG° and ΔH° demonstrated that the sorption process of DR80 onto the adsorbent was spontaneous and endothermic, respectively. FT-IR characterization was used to demonstrate presence of the various functional groups; -NH2, -CONH2, -CO and -OH on the adsorbent. From the data obtained from the experimental measurements, conclusion were drawn based on the eco-friendly, low cost and economical nature of the adsorbent material and thus may be a reliable material for treatment of contaminants from aqueous solutions. Key words: Superabsorbent, Chitosan-Starch Hydrogel, Direct Red 80, Eco-friendly 4. …………………………………………………………………………………………………………………………………………………………………………………………………………