Isolation and characterization of cellulosic fibers from ramie using organosolv degumming process

Degumming bast fibers by organic solvents has been a promising method in recent years due to easy recovery and reuse of organic solvents. In this research, the possibility of ramie fiber degumming by glycol and a combination of acetic acid with glycol was studied, in which two steps were involved in the degumming process: distilled water boiling pretreatment and organosolv treatment by a combination of glycol/acetic acid (100/0, 90/10, 80/20, 70/30, 60/40, 50/50). Results displayed that the pretreatment could remove 6.99% of hemicellulose, 0.59% of lignin and 36.26% of other gums compared with raw ramie. While with organosolv treatment (130 °C, 6 h), fibers treated by glycol/acetic acid (50/50) had the best effect of removing gums. The hemicellulose and lignin content of fibers reduced by 44.81% and 54.12%, respectively (compared with raw ramie), while the residual gum content still failed to meet the requirements of spinning process. Besides, the tenacity of glycol/acetic acid treated fibers was lower than that of only glycol treated fibers (4.67 cN/dtex). Considering that the addition of acid could cause a decrease in fiber tenacity, the step of organosolv (only glycol) treatment was optimized by altering the degumming condition. The tenacity, linear density, non-cellulosic component ratio of fibers treated with the optimized condition (200 °C, 80 min) were 6.53 cN/dtex, 6.06 dtex, 5.78%, respectively, which met the needs of industrial production. Compared with the organosolv treated fibers, these properties of fibers with traditional alkaline treatment were better, but the yield (62.4%) was much lower than that of fibers treated with glycol in two degumming condition (77–82%). Considering impressive properties of the treated ramie, the method of organosolv degumming with high degumming efficiency and environmental protection would bring an innovative thought for natural fiber isolation. Graphic abstract