Methylene Blue Adsorption from Aqueous Solution Using Malonic Acid Crosslinked Sodium Carboxymethylcellulose‐hydroxyethyl Cellulose Hydrogel Films

ABSTRACT Water pollution by dyes released from various industries is an issue of major concern. Adsorption is a widely used water treatment process for the removal of dyes from industrial wastewater, as it is a less expensive but efficient technique. This work details the synthesis of biodegradable, sodium carboxymethyl cellulose (CMCNa) and hydroxyethyl cellulose (HEC) based mixed hydrogel crosslinked with malonic acid (MA) and its effectiveness for the removal of methylene blue (MB) from aqueous solution. Characterization of the hydrogel was done by FTIR spectroscopy, TGA, PXRD, and SEM. From the adsorption studies, the adsorption equilibrium was obtained within 150 min for methylene blue (MB). The evaluation of kinetic parameters provided a good fit in the pseudo‐second order kinetic model, indicating probable chemisorption. Furthermore, the Langmuir, Freundlich, and Temkin isotherm models were used to study the adsorption mechanism, and the adsorption isotherm was best described by the Langmuir isotherm model with a maximum adsorption capacity of about 429.2 mg g −1 . Moreover, with positive ∆H 0 and negative ∆G 0 values obtained from the thermodynamic calculations, adsorption capacity was observed to increase with an increase in temperature, indicating the reaction to be favorable, spontaneous, and endothermic.