Selective lignin extraction by deep eutectic solvents for the green preparation of bagasse fibers with different lignin contents

Abstract

In this work, a series of deep eutectic solvents (DES) were prepared using varying proportions of choline chloride and lactic acid. The DES were then employed to selectively extract lignin from bagasse fibers, resulting in bagasse fibers with varying lignin contents. By manipulating the lactic acid composition, bagasse fibers with lignin content ranging from 3.79 to 11.73 wt% of the total weight of the original bagasse were successfully produced, retaining most of the cellulose. Furthermore, the dissolution mechanism of the DES was experimentally characterized. These findings indicate that an increase in the lactic acid level leads to a finer particle size and dissolved cellulose shape. Furthermore, the mechanism by which lactic acid content influences the extraction of lignin units was investigated along with the morphological and elemental changes of cellulose within bagasse fibers after extraction. Additionally, the changes in structural composition, molecular weight, and β-d-xylopyranoside content of lignin were analyzed. This study offers novel perspectives on the environmentally friendly processing of cellulosic material with various lignin contents.