Environmentally-Friendly Extraction of Cellulose Nanofibers from Steam-Explosion Pretreated Sugar Beet Pulp.

Wengang Yang,Zhitao Yang,Hezhi He,Yanhong Feng

doi:10.3390/ma11071160

Wengang Yang, Zhitao Yang + Show 2 more

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https://doi.org/10.3390/ma11071160

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Abstract

Cellulose nanofibers (CNFs) with an average diameter of 22 nm were prepared from sugar beet pulp (SBP) via an environmentally-friendly method. Steam-explosion pretreated SBP was treated with hydrogen peroxide (H2O2) bleaching, high-speed blending, and ultrasonic treatment. Thermogravimetric analysis showed that hemicellulose was partially hydrolyzed in the steam-cooking stage, pectin was removed in the explosion stage, and lignin was removed by H2O2 bleaching. The removal of non-cellulosic components was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. Morphological analysis showed that steam-explosion pretreatment largely extracted the binder materials of hemicellulose and pectin. This exposed the microfibrillated cellulosic fibers, which promoted subsequent nanofibrillation. X-ray diffraction showed that the CNFs had a crystallinity index of 62.3%. The CNFs had good thermal stability, and thus have potential for use as fillers in polymer matrices. The only chemical reagent used in this green method was H2O2. Combining H2O2 bleaching with steam explosion, high-speed blending, and ultrasonic treatment reduced the overall energy consumption and increased the efficiency of the CNFs extraction. The method, therefore, has potential application in industrial processes.

Highlights

As a common agricultural plant in north-eastern China, sugar beet is usually used to squeeze sugar
Was due to acetyl and uronic ester groups of hemicelluloses and the ester linkage of carboxylic groups of the ferulic and p-coumaric acids of lignin [24]. This peak was noticeably weaker in the spectrum of sugar beet pulp (SBP)-SC, and was moved to a lower wavenumber (1728 cm−1 ). This was because hemicellulose and pectin were partially hydrolyzed in the steam-cooking stage
The present study showed that cellulose nanofibers (CNFs) with an average diameter of 22 nm can be obtained from steam-explosion pretreated SBP, using an environmentally-friendly mechanochemical method involving H2 O2 bleaching, high-speed blending, and ultrasonic treatment

Summary

Introduction

As a common agricultural plant in north-eastern China, sugar beet is usually used to squeeze sugar. The waste from this process is sugar beet pulp (SBP), which is currently mostly applied in animal feed [1]. Researchers used physical and chemical methods to extract pectin from SBP [3,4]. Another possibility for using SBP is extracting cellulose from its parenchymal cell wall for further use. Nanocellulose is the cellulosic fiber with at least one dimension less than 100 nm, including cellulose nanofibers (CNFs), cellulose nanocrystals, and bacterial nanocelluloses [5]. CNFs are an important group, possessing characteristics such as renewability, high strength and toughness, low thermal expansion, good biocompatibility, and a larger aspect ratio

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