From the perspective of green chemistry, it is of great significance to produce cellulose nanofibers (CNFs) with more environmentally friendly and sustainable materials. This study investigated the efficient cleavage of strong hydrogen bonds occurred in sugarcane bagasse (SCB), ultrafast fabrication of CNFs through a 20 min microwave-assisted ternary carboxylic acid deep eutectic solvent (Mw-TCADES) deconstruction and sweep frequency ultrasonic (SFU) separation pretreatment. It also investigated the subsequent high-intensity ultrasonication (HIU) fibrillation process. After pretreating SCB with two different TCADES (choline chloride: oxalic acid: AlCl₃·6H₂O, and choline chloride: lactic acid: AlCl₃·6H₂O, molar ratio 1:1:0.2), the cellulose content of the SCB was 56.2 and 62.6%, respectively. The CNFs obtained after the two Mw-TCADES treatments contained 0.74 and 0.84 mmol/g carboxylic acid groups, and the crystallinity was 58.05 and 60.71%, respectively. Meanwhile, the CNFs obtained under the optimum treatment conditions (Mw-TCADES, 100 °C, 20 min and HIU) showed high thermal stability, which exhibited promising potential for further applications. Under the optimum conditions, the CNFs had a length of about 400–600 nm, width of around 15–17 nm, and a height of about 6–7 nm. The results showed that the TCADES can be used effectively as an alternative to the traditional acid–base pretreatment method and provide a green and efficient method for the utilization of lignocellulosic materials and the separation of CNFs.

Graphic abstract

中文翻译：

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三元酸性深共熔溶剂并超声处理有效地裂解甘蔗渣中的强氢键，以方便地制备纤维素纳米纤维

从绿色化学的角度来看，用更环保，更可持续的材料生产纤维素纳米纤维（CNF）具有重要意义。这项研究调查了甘蔗渣（SCB）中发生的强氢键的有效裂解，通过20分钟微波辅助三元羧酸深共熔溶剂（Mw-TCADES）解构和扫频超声（SFU）分离预处理超快制备CNF的过程。它还研究了随后的高强度超声（HIU）原纤化过程。用两种不同的TCADES（氯化胆碱：草酸：AlCl ₃ ·6H ₂ O和氯化胆碱：乳酸：AlCl ₃ ·6H _2）对SCB进行预处理之后。O，摩尔比为1：1：0.2），SCB的纤维素含量分别为56.2和62.6％。两次Mw-TCADES处理后获得的CNF分别含有0.74和0.84 mmol / g的羧酸基团，结晶度分别为58.05和60.71％。同时，在最佳处理条件（Mw-TCADES，100°C，20分钟和HIU）下获得的CNF显示出高的热稳定性，为进一步的应用展示了有希望的潜力。在最佳条件下，CNF的长度约为400-600 nm，宽度约为15-17 nm，高度约为6-7 nm。结果表明，TCADES可以有效替代传统的酸碱预处理方法，并为绿色纤维素材料的利用和CNF的分离提供了绿色高效的方法。

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