木质纤维的绿色分离及其重组复合材料的性能研究

Green Separation of Lignocellulose and Properties of Reconstituted Composites

为了实现废弃木质纤维的高值化利用,以竹粉为原料,用氯化胆碱(ChCl)/乳酸(LA)构建的低共熔溶剂(DES)来分离竹粉组分,采用简单的热压法将解离的木质素和纤维素进行重组制备木质纤维板。探究低共熔溶剂的组分、氯化铁的添加量、反应温度和反应时间对木质纤维组分分离的影响,并通过红外光谱(FT-IR)、X射线衍射(XRD)仪、扫描电子显微镜(SEM)、Zeta电位测试仪和万能试验机对DES分离的木质素(DESL)和纤维素(DESC)、DES/FeCl_(3)分离的木质素(DESL-FeCl_(3))和纤维素(DESC-FeCl_(3)),以及木质素纤维板的结构和性质进行分析。结果表明:木质纤维分离的较佳工艺条件为n(氯化胆碱)∶n(乳酸)=1∶2,FeCl_(3)添加量2%,反应温度140℃,反应时间6 h,此条件下木质素和纤维素的产率分别为85.57%和48.40%。所提取木质素(DESL-FeCl_(3))的酚羟基值和Zeta电位分别为12.86 mmol/L和-32.26 mV,且粒径尺寸较小,所提取纤维素具有更多的活性位点,有利于与木质素之间的分子重构和界面结合。低共熔溶剂在经过5次循环利用后,依旧对木质纤维具有较好的分离性能。所制备的木质纤维板的水稳定性和力学性能得到改善,水接触角达到58.6°,拉伸强度从8.4 MPa提升至53.1 MPa,具有替代石油基塑料的潜力。

In order to realize the high-value utilization of waste lignocellulose,bamboo powder was used as raw material,and the deep eutectic solvent(DES)composed of choline chloride(ChCl)/lactic acid(LA)was used to separate the components of bamboo powder.The lignin and cellulose were reconstructed by a simple hot-pressing method to prepare lignocellulosic board.In this paper,the effects of the components of DES,the amount of ferric chloride,reaction temperature and reaction time on the separation of lignocellulosic components were investigated.The structure and properties of DES-separated lignin(DESL)and cellulose(DESC),DES/FeCl_(3)-separated lignin(DESL-FeCl_(3))and cellulose(DESC-FeCl_(3)),and lignin fiberboards were analyzed by infrared spectroscopy(FT-IR),X-ray diffractometer(XRD),scanning electron microscope(SEM),Zeta potential tester,and universal testing machine.The results showed that the optimum process conditions were choline chloride and lactic acid with a molar ratio of 1∶2,FeCl_(3)addition amount of 2%,reaction temperature of 140℃,and reaction time of 6 h.The yields of lignin and cellulose under these conditions were 85.57%and 48.4%,respectively.The phenolic hydroxyl number and Zeta potential of the extracted lignin were 12.86 mmol/L and-32.26 mV,respectively,and the particle size was small.The extracted cellulose had more active sites,which were favorable for the molecular reconstruction and interfacial bonding with lignin.After five cycles of recycling,DES still had good separation performance for lignocellulose.The water stability and mechanical properties of the prepared lignocellulosic board had been improved,water contact angle reached to 58.6°,and its tensile strength increased from 8.4 MPa to 53.1 MPa,which had the potential to replace petroleum-based plastics.