Beijing Key Laboratory of Wood Science and Engineering, College of Material Science and Technology, Beijing Forestry University, No. 35 Tsinghua East Road Haidian District, Beijing, PR China.
Beijing Key Laboratory of Wood Science and Engineering, College of Material Science and Technology, Beijing Forestry University, No. 35 Tsinghua East Road Haidian District, Beijing, PR China.
Ultrason Sonochem. 2021 Sep;77:105672. doi: 10.1016/j.ultsonch.2021.105672. Epub 2021 Jul 18.
It is well-known that ultrasound has been studied for its cavitation, mechanical and thermal effects. As a pretreatment technology, ultrasonic alkali treatment has attracted much attention in the field of biomass biochemical transformation. In this study, the structural and dynamic changes of wood cell walls during ultrasound-water, alkali, and ultrasound-alkali treatments were investigated by stereoscopic microscopy, confocal Raman microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. The results indicated that the ultrasound-water, alkali, and ultrasound-alkali treatments had the effect of removing extractives from conduits. The uniform self-shrinking samples with shrinkage conduits were obtained by the alkali and ultrasound-alkali treatments. All of the treatments affected the relative content, structure and distribution of the chemical components in the wood cell walls. Compared with water-immersion samples, the relative content of hemicellulose of the treated samples reduced from 32.31% to 7.02% for ultrasound-8% NaOH treated samples. For the signal intensity of lignin, ultrasound-water treated and ultrasound-alkali treated samples displayed a more significant reductions than the alkali treated samples in the cell wall region. The crystal zone and amorphous zone of cellulose coexisted before and after the treatment, for all of the treated samples, and particularly for the ultrasound-assisted treated samples, the crystallinity increased from 38.15% for water-immersion samples to 57.42% for ultrasound-8% NaOH treated samples.
众所周知，超声空化、机械和热效应已被广泛研究。作为一种预处理技术，超声碱处理在生物质生化转化领域引起了广泛关注。在这项研究中，通过立体显微镜、共聚焦拉曼显微镜、傅里叶变换红外光谱和 X 射线衍射研究了木材细胞壁在超声水、碱和超声-碱处理过程中的结构和动态变化。结果表明，超声水、碱和超声-碱处理均具有去除导管中提取物的作用。通过碱处理和超声-碱处理获得了具有收缩导管的均匀自收缩样品。所有处理均影响细胞壁中化学成分的相对含量、结构和分布。与水浸泡样品相比，超声-8%NaOH 处理样品的半纤维素相对含量从 32.31%降低至 7.02%。对于木质素的信号强度，与碱处理样品相比，超声水和超声-碱处理样品在细胞壁区域的降低更为显著。处理前后纤维素的结晶区和无定形区共存，对于所有处理样品，特别是对于超声辅助处理样品，结晶度从水浸泡样品的 38.15%增加到超声-8%NaOH 处理样品的 57.42%。
