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

Abstract

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.

Extraction of Ramie Fiber in Alkali Hydrogen Peroxide System Supported by Controlled-release Alkali Source

“…Normally, the pH value and thus oxidation ability of alkali hydrogen peroxide system decreases with the increasing of substitution rate. When the reaction temperature is set at 85°C, the free radical reaction plays the main role in the system and the strong oxidation ability makes the system suitable for dissolving materials; when the reaction temperature was set at 125 °C, the free radical reaction was inhibited and a large amount of HOO existed in the system, which makes the system suitable for bleaching 19 . The limitation of this technology is that the pH value of hydrogen peroxide system can only be set at values between 10.0 to 12.0 when the controlled-released alkali source is used.…”

“…NOTE: ORP 12,19 is an important water chemistry parameter and it provides a measurement tool for the oxidizing or reducing capacity of the ambient water. Solutions with stronger oxidation property have a higher ORP value.…”

“…The effect of Mg(OH) 2 substitution rate on: (A) the DP value and crystallinity of fiber; and (B) the tensile properties of fiber19 . DP value, crystallinity, and tensile properties of fiber increased with SR from 0% to 20%, but decreased with further rising of substitution rate.…”

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“…There were mainly two approaches of ramie degumming, namely, traditional chemical degumming and bio-degumming [8]. The energy and time consumption, chemical oxygen demand (COD value) of degumming wastewater in traditional chemical degumming was rather high, for cellulose fiber was extracted by scouring raw ramie in concentrated NaOH under high pressure for 6h to 8h [9]. Bio-degumming is an eco-friendly way of ramie fiber extraction; however, the harsh reaction condition and sophisticated equipment inhibited its further industrial application [10].…”

“…Compared with traditional degumming, oxidation degumming with H 2 O 2 is effective, eco-friendly, and of high fiber yield [9]. H 2 O 2 can decompose into several kinds of free radicals (such as O -2 ·, OH·, OOH·, OH -, ect) in alkali condition, these radicals have strong oxidizing ability.…”