Corn husk is an abundant agricultural waste. It has great potential for use as a cellulose source for the production of carboxymethyl cellulose (CMC). The chemical composition of corn husk, such as cellulose, hemicelluloses, lignin, fatty and waxy matter, pectic matter and aqueous extract was determined. The cellulose extracted from corn husk was carboxymethylated using sodium hydroxide (NaOH) and monochloroacetic acid (MCA), in aqueous ethanolic medium, under heterogeneous conditions. The carboxymethylation reaction was optimized as to the NaOH concentration, MCA concentration, reaction temperature, reaction time and cellulose particle size. The degree of substitution (DS) was determined with respect to the reaction conditions using chemical methods. The produced CMC was identified by FTIR and the crystallinity of the CMC was determined by XRD. The CMC product had an optimized DS of 2.41 and the optimal conditions for carboxymethylation were NaOH concentration, 7.5 mol/L; MCA concentration, 12 mol/L; reaction temperature, 55 °C; reaction time, 3.5 h and cellulose particle size, 74 μm. These optimization factors allowed to prepare highly substituted CMC with higher yield, 2.40 g/g, providing plenty of opportunities for its many applications.
Keywords: Carboxymethyl cellulose; Carboxymethylation; Cellulose; Corn husk waste; Degree of substitution.
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