BACKGROUND: This paper describes the use of cottons talk, 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: m(cotton stalk cellulose) : m(sodium hydroxide) : m(sodium 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 mu m. 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. (C) 2011 Society of Chemical Industry