酸解法制备纤维素纳米晶体水解残液的糖酸分离

Separation of Acid and Sugar in the Waste Liquid from Acid Hydrolysis for Preparing Cellulose Nanocrystals

硫酸法制备纤维素纳米晶体(CNC)的水解残液中含有大量的硫酸、一些未充分水解的纤维素片段以及以单体和寡聚形式存在的糖,直接丢弃不仅会污染环境,更是对资源的一种极大浪费。通过向水解残液中加入硫酸(质量分数80%)的方法,调节水解残液中的硫酸浓度,并通过水浴加热使残液中未充分水解的物质转化为葡萄糖;然后用阴离子交换膜将水解残液中的硫酸和葡萄糖分离,再将分离后的液体用旋转蒸发仪浓缩,以提高硫酸和葡萄糖的浓度。研究结果表明,调节水解残液中硫酸质量分数为56%,在45℃水浴中反应3 h,水解残液中葡萄糖含量达到最大值13.73 g/L;处理后的水解残液通过2次阴离子交换膜过滤,硫酸的回收率达到90.31%,浓缩可得到10.06 mol/L的浓硫酸和36 g/L的葡萄糖溶液。回收得到的硫酸和副产品葡萄糖溶液可分别用于CNC的制备和用作生物发酵的碳源。

There were lots of sulfuric acid, some of not fully hydrolyzed cellulose fragments, monomer sugars and oligo in the waste liquid from preparing cellulose nanocrystals （CNC） by sulfuric acid hydrolysis process. If the waste liquid was discarded directly without recycling, and it could cause environmental pollution and a great waste of resource. This paper studied the method for recovering both sulfuric acid and glucose. The concentration of sulfuric acid in the waste liquid was adjusted by adding 80% （wt） sulfuric acid, then the materials not fully hydrolyzed were converted to glucose by heating in water bath. The sulfuric acid and glucose were separated by anion exchange membrane, then concentrated by using rotary evaporating and concentrating system. Results showed that glucose concentration in the waste liquid reached maximum when sulfuric acid concentration was 56% （wt） and heating at 45℃ for 3 h in water bath. The recovery rate of sulfuric acid was 90.31% after the liquid was treated twice by anion exchange membrane, 10.06 mol/L sulfuric acid and 36 g/L glucose solution were obtained after being concentrated.