NaOH/硫脲/尿素溶液溶解麦草分离纤维素的研究

Extracting Cellulose from Wheat Straw with NaOH / Thiourea / Urea Aqueous Solution

采用Na OH/硫脲/尿素溶液在低温下溶解提取麦草中的纤维素。通过正交试验确定了预处理麦草在复合溶剂中的溶解条件为溶剂配比每100 g水中Na OH/尿素/硫脲为9∶7∶7(m∶m∶m),溶剂用量为50m L/g,在-10℃溶解90 min。此条件下溶解率可达53.19%,用稀硫酸作为沉淀剂析出富含纤维素的白色絮状麦草纤维素,得率为35.03%,其纤维素含量可达90.28%。红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)分析结果表明,分离得到的纤维素结构发生了很大的变化,麦草中纤维素是典型的纤维素Ⅰ,白色絮状麦草纤维素晶型由纤维素Ⅰ型向纤维素Ⅱ型转变,结晶度很小。

Using a NaOH/thiourea/urea aqueous solution to extract cellulose from the wheat straw, an orthogonal design was used to optimize the dissolution for extracting cellulose. Results showed the optimal conditions were the mass ratio of NaOH, urea, thiourea of 9：7：7 （m：m：m） in 100 g water, the volume of the NaOH/thiourea/urea aqueous solution of 50 mL for one gram pretreated wheat straw sample, and the dissolution time of 90 min at -10 ℃. Under these conditions,53.19% wheat straw was dissolved. A dilute sulfuric acid was used as the coagulating agent to regenerate the dissolved cellulose from the solution. The regeneration rate and the percent of the cellulose was 35.03% and 90.28%,respectively. Results of fourier transform infrared spectroscopy （FTIR）,powder X-ray diffraction （XRD）,and scanning electron microscope （SEM） showed that the isolation process changed the cellulose structure from typical cellulose Ⅰ in wheat straw to cellulose Ⅰ and cellulose Ⅱ with a very small crystallinity degree in the cellulose-rich white floccules.