Preparation and characterization of sodium carboxymethyl cellulose from cotton stalk using microwave heating

BACKGROUND: This paper describes the use of cotton stalk, an agricultural waste, for the preparation of sodium carboxymethyl cellulose (CMC) using microwave heating. The study includes the optimization of pre‐treatment and preparation processes, and the characterization of product. RESULTS: The optimal cotton stalk pre‐treatment condition involved the addition of 12% alkali to extract cellulose for 6 min at a microwave power of 200 W using the ratio of cotton stalk to solvent 1:9, giving 87.52% cellulose. Response surface methodology was applied to optimize the preparation of CMC, with the best conditions for preparation predicted by the model: mcotton stalk cellulose:msodium hydroxide:msodium chloroacetate = 1.0:1.1:1.2 with etherification at 195.5 W of microwave power for 1.97 min. Under these conditions, CMC with degree of substitution (DS) 0.77, viscosity 498.0 cps and purity 92% was produced. The results of Fourier transform infrared (FT‐IR) spectroscopy indicated that the product had the characteristics of a high DS. Scanning electron microscopy showed that the particles were nearly clava in shape with length ranging from about 12–100 µm. The product met the quality standards of GB/T1904‐2005. CONCLUSION: Preparation of CMC from cotton stalk using microwave heating can shorten the processing time and may be considered a feasible alternative, contributing to solving environmental problems resulting from cotton stalk.