Institute of Food Engineering for Development, Universtitat Politècnica de València, 46022 Valencia, Spain.
Institute of Food Engineering for Development, Universtitat Politècnica de València, 46022 Valencia, Spain.
Carbohydr Polym. 2023 Jul 15;312:120805. doi: 10.1016/j.carbpol.2023.120805. Epub 2023 Mar 11.
Cellulose aerogels were obtained from purified rice straw cellulose fibres (CF) by applying different extraction methods: the conventional alkaline treatment (ALK) and alternative aqueous extraction based on the ultrasound combined with reflux heating (USHT) and subcritical water extraction (SWE) (160 and 180 °C). The composition and properties of the CFs were significantly affected by the purification process. The USHT treatment was as efficient as the ALK at eliminating the silica content, but the fibres maintained a notable ratio of hemicellulose (∼16 %). The SWE treatments were not so effective at removing silica (15 %) but greatly promoted the selective extraction of hemicellulose, especially at 180 °C (3 %). The CF compositional differences affected their hydrogel formation capacity and the properties of aerogels. A higher hemicellulose content in the CF led to better-structured hydrogels with better water-holding capacity, while the aerogels exhibited a more cohesive structure with thicker walls, higher porosity (99 %) and water vapour sorption capacity, but lower liquid water retention capacity (0.2 g/g). The residual silica content also interfered with the hydrogel and aerogel formation, giving rise to less structured hydrogels and more fibrous aerogels, with lower porosity (97-98 %).
纤维素气凝胶是通过应用不同的提取方法从纯化的稻草纤维素纤维（CF）中获得的：传统的碱性处理（ALK）和基于超声结合回流加热（USHT）和亚临界水提取（SWE）的替代水溶液提取（160 和 180°C）。CF 的组成和性质受到纯化过程的显著影响。USHT 处理在去除二氧化硅含量方面与 ALK 一样有效，但纤维保持了相当比例的半纤维素（约 16%）。SWE 处理在去除二氧化硅（15%）方面效果不佳，但极大地促进了半纤维素的选择性提取，特别是在 180°C（3%）时。CF 的组成差异影响其水凝胶形成能力和气凝胶的性质。CF 中较高的半纤维素含量导致具有更好持水能力的结构更好的水凝胶，而气凝胶具有更具凝聚力的结构，壁更厚，更高的孔隙率（99%）和水蒸气吸附能力，但较低的液态水保留能力（0.2 g/g）。残留的二氧化硅含量也会干扰水凝胶和气凝胶的形成，导致结构较差的水凝胶和更多纤维状的气凝胶，孔隙率较低（97-98%）。
