木质纤维素预水解液的纳滤分离规律及膜污染机理研究

Treating lignocellulosic prehydrolyzates with nanofiltration could achieve removal of pretreatment inhibitors and concentration of monosaccharides simultaneously, possessing the characteristics of environmental protection, economy and high-efficiency. The separation performance and fouling mechanism during nanofiltration filtration of lignocellulosic prehydrolyzates were unclear due to the complication of compositions and physical properties of the prehydrolyzates feed. Therefore, it is urgent to elucidate the quantitative relationship between the compositions and physical properties of prehydrolyzates and the separation performance and fouling mechanisms of nanofiltration filtration, and to develop research of membrane fouling control strategies during nanofiltration processes. According to the phenomenon of rejection variation and flux decline during nanofitration treatment of lignocellulosic prehydrolyzates, we will investigate the effect of compositions and physical properties of lignocellulosic prehydrolyzates on nanofiltration separation; explore the necessity of treating prehydrolyzates using microfiltration; investigate the interaction between solutes in prehydrolyzates on mass transfer of nanofiltration membrane; analyze the process characteristics and membrane fouling during nanofiltration filtration. Through above research we will propose economical and effective membrane fouling control technology and membrane regeneration cleaning technology. The development of the project will provide theoretical foundation and technical support for the application of nanofiltration in the high-value utilization of cellulosic materials.

通过纳滤处理木纤维素预水解液可以一步实现预水解液中抑制物的去除以及木糖和葡萄糖等单糖的浓缩，具有环保、经济、高效等特点。但木质纤维素预水解液成分与物性复杂，纳滤膜在过滤预水解过程中的过滤规律和污染机理尚不清楚，所以亟需阐明预水解液成分、物性与纳滤膜分离规律和污染机理间的定量关系和开展纳滤膜污染控制策略研究。本项目针对纳滤膜在处理木质纤维素预水解液时膜的截留率变化及膜通量衰减现象，研究预水解液中的主要成份和物性对纳滤分离特性的影响，探讨对预水解液进行微滤处理的必要性，研究预水解液中溶质之间相互作用对纳滤膜传质的影响，分析纳滤过滤的过程特征和膜污染形式，提出经济有效的膜污染控制技术和膜再生清洗技术，为纳滤技术应用于纤维原料的高值化利用提供理论依据和技术支持。

木质纤维素预水解液成分复杂，既有可发酵利用的单糖（木糖和葡萄糖），又有预处理抑制物（乙酸、糠醛和酚类化合物等），还有固体悬浮物。本项目围绕木质纤维素预水解液的纳滤分离技术以及预水解液对纤维素酶水解的影响展开研究。经过三年研究，取得了以下研究成果：（1）考察了秸秆不同组织茎和叶对预处理与酶水解的影响，发现秸秆的茎和叶经预处理后得到的预水解液组分以及水不溶性固体组分存在显著差异，预处理茎和叶的酶解糖产率与预处理方法有关；（2）对秸秆酸预水解液进行静置或微滤预处理（0.2，0.8和1.4 微米），对降低后续纳滤分离过程中的膜污染无显著作用；对秸秆稀酸预水解液进行活性炭吸附，能去除酚类和色素类物质，显著提升秸秆稀酸预水解液的纳滤分离效果；（3）在正常的纳滤操作压力下（10-20 bar），主要抑制物乙酸和糠醛对纳滤分离稀酸预水解液中的主要单糖木糖没有显著影响；（4）秸秆稀碱预水解液中的碱溶性木质素促进纤维素酶水解，并且随着木质素分子量的增加，促进作用逐渐增强；秸秆稀碱预水解液中的香草醛是纤维素酶的非竞争性抑制剂，香草醛中起抑制作用的基团是酚羟基和醛基；（5）超滤处理秸秆碱预水解液不仅能回收木质素，还能实现碱液的回用。碱液循环预处理秸秆4次，水和碱的消耗量分别降低了42%和50%；超滤后的秸秆碱预水解液可进一步用纳滤回收羟基肉桂酸，其纯度可达到91.4%；（6）已发表SCI收录论文4篇，培养博士研究生1名。