Upcycling cotton gin byproducts into bioplastics: A sustainable approach to Co-dissolution of lignin and cellulose using a DES/NMMO binary solvent

Abstract

In this work, a sustainable and efficient approach was developed to address the challenges associated with the dissolution of the entire biomass lignocellulosic components. This was carried out using a deep eutectic solvent (DES) and N-methylmorpholine N-oxide (NMMO), together as a binary solvent system for direct dissolution and film fabrication of cotton gin trash (CGT) and cotton gin motes (CGM), two underutilized agricultural residues. The DES facilitated the selective dissolution of lignin and hemicellulose, while NMMO effectively dissolved crystalline cellulose. The synergistic action of DES and NMMO enabled efficient co-dissolution of lignin, hemicellulose and cellulose without fractionation. XRD and ¹³CNMR confirmed a transition from crystalline cellulose structure to a more amorphous network in the regenerated films, particularly in CGT-rich compositions. The films showed enhanced thermal stability, with the 1:1 CGT/CGM blend film exhibiting the highest onset temperature. The mechanical testing indicated that the 1:1 CGT/CGM blend films achieved an optimal balance between tensile strength and flexibility through combining CGM's crystalline cellulose reinforcement with CGT's amorphous lignin and hemicellulose content. This study demonstrates the potential of CGT and CGM as sustainable raw materials and the proposed DES/NMMO system as an effective green solvent for processing whole lignocellulosic biomass into high-value-added products.