Study on extracting hemicellulose, cellulose, and carboxymethyl cellulose from Vietnamese rice straw waste

Abstract

Vietnam is an agricultural country with a large amount of rice straw waste amounting to 55-60 million tons annually. Rice straw contains about 35-40% dry weight of cellulose and 25-30% hemicellulose, and 10-15% lignin. Cellulose and hemicellulose were successfully extracted from Vietnamese rice straw waste. The maximum hemicellulose yield of the process was 22.60% with 1.5 M NaOH at 90^oC for 1.5 h. The pure cellulose obtained from the rice straw was prepared by refluxing the rice straw powder with a 1.0 M HNO3solution at 90^oC for 1.5 h. The Vietnamese rice straw cellulose was converted to carboxymethyl cellulose (CMC) by etherification. The extracted cellulose was soaked in a mixed solution of isopropyl alcohol and NaOH solution for 1.5 h. After that, it was reacted with monochloroacetic acid at 70^oC for 1.5 h. The optimum conditions for carboxymethylation were 5 g cellulose, 4.0 g monochloroacetic acid, and 15 ml 25% w/v NaOH and the obtained product had a degree of substitution (DS) of 0.70.