Microwave-assisted carboxymethylation of cellulose extracted from brewer's spent grain

Cellulose was extracted from brewer's spent grain (BSG) by alkaline and bleaching treatments. The extracted cellulose was used in the preparation of carboxymethyl cellulose (CMC) by reaction with monochloroacetic acid in alkaline medium with the use of a microwave reactor. A full-factorial 23 central composite design was applied in order to evaluate how parameters of carboxymethylation process such as reaction time, amount of monochloroacetic acid and reaction temperature affect the average degree of substitution ((DS) over bar) of the cellulose derivative. An optimization strategy based on response surface methodology has been used for this process. The optimized conditions to yield CMC with the highest (DS) over bar of 1.46 follow: 5g of monochloroacetic acid per gram of cellulose, reaction time of 7.5 mm and temperature of 70 degrees C. This work demonstrated the feasibility of a fast and efficient microwave-assisted method to synthesize carboxymethyl cellulose from cellulose isolated of brewer's spent grain. (C) 2015 Elsevier Ltd. All rights reserved.