Sustained-release alkali source used in the oxidation degumming of ramie

Sodium hydroxide is commonly used as the main alkali source in the oxidation degumming of ramie in the current studies for natural fiber extraction. However, due to the strong alkalinity of sodium hydroxide, the oxidation reaction speed of hydrogen peroxide is difficult to control and thus results in great damage to the treated fibers. In this paper, magnesium hydroxide was selected as an effective sustained-release alkali source to improve the tensile properties of degummed fibers and reduce the chemical oxygen demand (COD) values of degumming wastewater. This novel reagent can adjust and buffer pH values in the degumming solution. The chemical components and structure properties of degummed fibers were characterized by Fourier transform infrared spectroscopy and X-ray diffraction, respectively, and the as-developed oxidation degumming solution performance was monitored by an oxidation–reduction potentiometer. The results showed that the optimal substitution rate of magnesium hydroxide was 20% during the oxidation process. Compared with the degummed fibers without magnesium hydroxide, the tenacity, work of rupture and degumming yield of treated fibers increased by 39.82%, 46.15% and 5%, respectively. Moreover, the COD values of wastewater decreased by 20% at the same time.