Preparation of peanut shell lignin nanocellulose by aluminum trichloride acid deep eutectic solvent pretreatment

Nanocellulose holds great potential as a material, however, traditional separation methods have utilized dangerous chemicals and substantial energy use chemical reagents. The deep eutectic solvent (DES) has attracted considerable interest because of its non-toxic, biodegradable, and recyclable characteristics. It offers distinct advantages in the preparation of nanocellulose. In this study, environmentally friendly acid binary (choline chloride-oxalic acid/lactic acid (ChCl-OA/LA), molar ratio 1:1) and ternary carboxylic acid (ChCl-OA/LA-AlCl3 <middle dot> 6H2O, molar ratio 1:1:0.1) were utilized. The lignin nanocellulose (LNCs) was isolated from peanut shell (PS) through DES pretreatment combined with mechanical treatment. The findings indicate that in comparison to binary DES, the LNCs separated by tri-component DES demonstrate elevated charge density and increased carboxyl content, resulting in a higher negative charge. Under the reaction conditions of 100 degrees C for 3 h, the carboxylic acid content of LNCs were 0.81 and 0.88 mmol/g, respectively, and their Zeta potentials were -25.5 and -25.9 mV, respectively. Compared to OA-based DES, LA-based DES exhibits superior light transmission in the visible range of LNCs suspensions. Specifically, binary DES achieves a light transmission level of 83.89 +/- 2.14%, and ternary DES reaches 76.41 +/- 1.03% at a wavelength of 630 nm. Furthermore, the width distribution of LNCs separated by ternary DES is more narrowly defined. The average width of nanofibers falls within a range of 28 nm to 44 nm, while the diameter of lignin nanoparticles in LNCs varies between 30 and 53 nm. Concurrently, the LNCs derived from the optimal pretreatment conditions exhibit both high crystallinity and excellent thermal stability. Overall, the DES pretreatment employing AlCl3 <middle dot> 6H2O offers a sustainable and efficient approach for extracting LNCs from lignocellulosic materials, promising broad application potential.