超声辅助硫酸水解法制备银杏果壳纳米纤维素及其特性表征

Ultrasound-assisted Sulfuric Acid Hydrolysis Method for Preparation and Characterization of Nanocellulose from Ginkgo Nut Shell

为充分利用银杏的工业生产副产物,以银杏果壳为原料,采用超声辅助硫酸水解法制备银杏果壳纳米纤维素(nanocrystalline cellulose isolated from ginkgo nut shell,NCC-GNS)。通过单因素实验研究了硫酸质量分数、反应温度和反应时间3个因素对NCC-GNS得率的影响,并应用正交试验进行优化,获得NCC-GNS的最佳制备条件。以常规硫酸水解法(未加超声辅助)制备的纳米纤维素(nanocrystalline cellulose,NCC)为对照,通过扫描电镜(scanning electron microscopy,SEM)、透射电镜(transmission electron microscopy,TEM)、Zeta电位和动态光散射(dynamic light scattering,DLS)、X-射线衍射(x-ray diffraction,XRD)、傅里叶变换红外光谱(fourier transform infrared spectroscopy,FT-IR)、热重(thermogravimetric analysis,TGA)等分析超声辅助处理对NCC-GNS的影响。结果表明:超声功率120 W时,制备NCC-GNS的最佳条件为硫酸质量分数48%、反应温度60℃、反应时间25 min,最优条件下NCC-GNS得率为37.01%;超声辅助和常规硫酸水解法制备的NCC-GNS均为长棒型,尺寸无明显差异,超声辅助制备的NCC-GNS长度和直径的分布范围相对集中,长度80~180 nm、直径3.5~5.5 nm;超声辅助制备的NCC-GNS结晶度为88%,高于常规硫酸水解的75%;两种方法制备的NCC-GNS均具有较低的Zeta电位和有良好的热稳定性。综上,超声辅助硫酸水解法制备的NCC-GNS得率较高,获得的NCC-GNS结晶度高、热稳定性好,在生物质复合材料领域表现出良好的应用前景。

In order to make full use of the by-products of industrial production of ginkgo,this study used ginkgo nut shell as raw materials and adopt ultrasonic-assisted sulfuric acid hydrolysis to prepare ginkgo nut shell nanocrystalline cellulose(nanocrystalline cellulose isolated from ginkgo nut shell,NCC-GNS).The effects of three factors(e.g.sulfuric acid mass fraction,reaction temperature,reaction time)on nanocellulose yield were investigated by single-factor tests,and orthogonal experiments were used to optimize them to obtain the best preparation conditions for NCC-GNS.Taking nanocrystalline cellulose(nanocrystalline cellulose,NCC)prepared by conventional sulfuric acid hydrolysis(without ultrasound assistance)as a control,analyzed the impact of ultrasound-assisted processing on NCC-GNS through scanning electron microscopy(SEM),transmission electron microscopy(TEM),Zeta potential and dynamic light scattering(DLS),X-ray diffraction(xray diffraction,XRD),Fourier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),etc.The results showed that the optimal conditions for preparing NCC-GNS were sulfuric acid mass fraction of 48%,reaction temperature of 60℃,reaction time of 25 min under the condition of ultrasonic power of 120 W.The NCC-GNS yield under optimal conditions was 37.01%.The NCC-GNS prepared by ultrasonic-assisted and conventional sulfuric acid hydrolysis methods were long rods with no significant difference in size.The length and diameter of the NCC-GNS prepared by ultrasonicassisted were relatively concentrated with a length of 80~180 nm and a diameter of 3.5~5.5 nm.The crystallinity of NCCGNS prepared by ultrasound was 88%,which was higher than 75%of conventional sulfuric acid hydrolysis.The NCC-GNS prepared by the two methods had lower Zeta potential and good thermal stability.In summary,the yield of NCC-GNS prepared by ultrasonic-assisted sulfuric acid hydrolysis was high,and the obtained NCC-GNS had high crystallinity and good thermal stability,which was expected to have better applications in the field of biomass composite materials.