Luo Xitao, Sun Lingling, Shou Qinghui, Liang Xiangfeng, Liu Huizhou
CAS Key Laboratory of Bio-Based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences (CAS), Qingdao 266101, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Membranes (Basel). 2023 Feb 21;13(3):256. doi: 10.3390/membranes13030256.
Acid saccharification of hemicelluloses offers promising pathways to sustainably diversify the revenue of the lignocellulose biorefinery industry. Electrodialysis to separate inorganic acids from acid hydrolysate in the hemicellulose saccharification process could realize the recovery of sulfuric acid, and significantly reduced the chemical consumption than the traditional ion exchange resins method. In this work, the deacidification of corncob acid hydrolysate was conducted by a homemade electrodialysis apparatus. The results showed that: (1) more than 99% of acid can be removed through the electrodialysis process; (2) A non-negligible membrane fouling occurred during the electrodialysis process, which aggravated with the repeated batch running The final global system resistance rose from 15.8 Ω (1st batch) to 43.9 Ω (10th batch), and the treatment ending time was delayed from 120 min (1st batch) to 162 min (10th batch); (4) About 90% of protein, 70% of ferulate acid, and 80% of -coumarate acid precipitated from the corncob acid hydrolysate during the electrodialysis process. The zeta potential of corncob acid hydrolysate changed from a positive value to a negative value, and an isoelectric point around pH 2.3 was reached. HSQC, FTTR, and GPC, along with and analysis, revealed that the fouling layers mostly consisted of hydrolysates of protein and lignin. The result of HSQC indicated that the membrane foulant may exist in the form of lignin-carbohydrate complexes, as the lignin component of the membrane foulant is in the form of -coumarate and ferulate. From the result of FTIR, a strong chemical bonding, such as a covalent linkage, existed between the lignin and protein in the membrane foulant. Throughout the electrodialysis process, the increased pH decreased the stability of colloidal particles, including lignin and proteins. Destabilized colloidal particles started to self-aggregate and form deposits on the anion exchange membrane's surface. Over time, these deposits covered the entire membrane surface and the spaces between the membranes. Eventually, they attached to the surface of the cation exchange membrane. In the end, a suggestion to control and minimize membrane fouling in this process was discussed: lower pH as a process endpoint and a post-treatment method.
半纤维素的酸糖化提供了可持续使木质纤维素生物精炼行业收入多样化的有前景途径。在半纤维素糖化过程中通过电渗析从酸性水解产物中分离无机酸可以实现硫酸的回收，并且与传统离子交换树脂方法相比显著降低了化学品消耗。在这项工作中，使用自制的电渗析装置对玉米芯酸性水解产物进行脱酸。结果表明：（1）通过电渗析过程可以去除超过99%的酸；（2）在电渗析过程中发生了不可忽视的膜污染，随着批次的重复运行而加剧。最终的总系统电阻从15.8Ω（第1批）上升到43.9Ω（第10批），处理结束时间从120分钟（第1批）延迟到162分钟（第10批）；（4）在电渗析过程中约90%的蛋白质、70%的阿魏酸和80%的对香豆酸从玉米芯酸性水解产物中沉淀出来。玉米芯酸性水解产物的ζ电位从正值变为负值，并在pH约2.3处达到等电点。HSQC、FTTR和GPC以及 和 分析表明，污垢层主要由蛋白质和木质素的水解产物组成。HSQC结果表明，膜污染物可能以木质素 - 碳水化合物复合物的形式存在，因为膜污染物的木质素成分以对香豆酸和阿魏酸的形式存在。从FTIR结果来看，膜污染物中的木质素和蛋白质之间存在强化学键，如共价键。在整个电渗析过程中，pH值的升高降低了包括木质素和蛋白质在内的胶体颗粒的稳定性。失稳的胶体颗粒开始自我聚集并在阴离子交换膜表面形成沉积物。随着时间的推移，这些沉积物覆盖了整个膜表面和膜之间的空间。最终，它们附着在阳离子交换膜的表面。最后，讨论了在此过程中控制和最小化膜污染的建议：将较低的pH值作为过程终点和一种后处理方法。
