Turning trash into treasure: conversion of agroresidue rice straw into carboxymethylcellulose biopolymer

Abstract In the present study, rice straw‐derived cellulose was converted into carboxymethylcellulose (CMC) using alkalization followed by an etherification reaction. The synthesis conditions for this chemical modification were optimized such that CMC with a high degree of substitution (1.02) was obtained. Infrared spectra of the synthesized CMC clearly showed an increased intensity of the C═O bond at 1600 cm −1 , confirming successful carboxymethylation. Further, X‐ray diffraction analysis demonstrated a decrease in cellulose crystallinity owing to partial rearrangement from a crystalline to an amorphous phase during initial alkalization reaction. The obtained CMC biopolymer was subsequently cross‐linked to form a composite hydrogel matrix reinforced with bentonite clay. The hydrogel showed about 91% adsorption capacity for methylene blue dye as a model contaminant in aqueous media. Therefore, this study shows that lignocellulosic agrowaste is a rich source of cellulose, and its derivatives such as CMC possess the potential to realize the waste to wealth sustainability goal.