Ishida Shinnosuke, Kudo Shinji, Asano Shusaku, Hayashi Jun-Ichiro
Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Japan.
Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga, Japan.
Front Chem. 2025 Jan 23;13:1538797. doi: 10.3389/fchem.2025.1538797. eCollection 2025.
Rice husk, a widely available agricultural by-product lignocellulosic biomass, is a promising and sustainable feedstock for organic and inorganic chemicals due to the rich silica content. However, its current application is largely limited, with most being incinerated as waste. This study introduces a novel multi-step pre-treatment process to fractionate these components efficiently, enabling their comprehensive valorization.
The process begins with hydrothermal treatment, selectively extracting hemicellulose while preserving the structural integrity of other components. This is followed by an organosolv treatment using ethanol/water mixture, optimized to dissolve and extract organosolv lignin effectively. Subsequently, alkaline aqueous solution treatment under nitrogen atmosphere facilitates the recovery of silica as sodium silicate, a valuable industrial precursor. To ensure high-purity cellulose recovery, the final step employs alkaline hydrothermal processing under oxygen, achieving effective lignin depolymerization and removal.
Each step was carefully optimized, considering parameters such as temperature, solvent composition, and reaction time, to enhance selectivity and yield. Notably, this method reduces environmental negative impact by avoiding the use of acids while utilizing renewable solvents. The sequential application of these treatments resulted in separation exceeding 97% for hemicellulose, lignin, and silica, leaving high-purity cellulose with the loss of 22.8 wt%. Hemicellulose, organosolv lignin, and silica in the removed fractions were 66.5, 78.1, and 77.5 wt% at the first, second, and third treatments, respectively.
稻壳是一种广泛可得的农业副产品木质纤维素生物质，由于其富含二氧化硅，是一种有前景的可持续有机和无机化学品原料。然而，其目前的应用在很大程度上受到限制，大部分作为废物被焚烧。本研究引入了一种新型的多步预处理工艺，以有效分离这些成分，实现其综合利用。
该工艺首先进行水热处理，选择性提取半纤维素，同时保持其他成分的结构完整性。随后采用乙醇/水混合溶剂进行有机溶剂处理，优化以有效溶解和提取有机溶剂木质素。接着在氮气气氛下进行碱性水溶液处理，促进二氧化硅以硅酸钠的形式回收，硅酸钠是一种有价值的工业前体。为确保高纯度纤维素的回收，最后一步在氧气存在下采用碱性水热处理，实现木质素的有效解聚和去除。
仔细优化了每个步骤，考虑了温度、溶剂组成和反应时间等参数，以提高选择性和产率。值得注意的是，该方法通过避免使用酸同时利用可再生溶剂，减少了对环境的负面影响。这些处理的顺序应用导致半纤维素、木质素和二氧化硅的分离率超过97%，剩余高纯度纤维素的损失率为22.8 wt%。在第一次、第二次和第三次处理中，去除部分中的半纤维素、有机溶剂木质素和二氧化硅分别为66.5 wt%、78.1 wt%和77.5 wt%。
