Production of cellulose nanofibrils and films from elephant grass using deep eutectic solvents and a solid acid catalyst.

A new strategy was developed to produce cellulose nanofibrils (CNFs) and films from raw elephant grass using deep eutectic solvents and a recyclable spent coffee-derived solid acid (SC-SO 3 H) catalyst with assistance of ultrasonic disintegration and a suction filtration film forming method. The effects of a solid acid and reused solid acid were comprehensively studied by comparing with catalyst-free conditions and using sulfuric acid as the catalyst. The CNF fibers obtained from this novel SC-SO 3 H catalyst method showed the longest fiber length. The corresponding films achieved the strongest tensile strength of 79.8 MPa and the elongation at break of 13.6%, and best thermostability. In addition, the performance of CNFs and films prepared by the fourth recovered SC-SO 3 H-4 catalyst was close to that obtained with the first use. The SC-SO 3 H could be reused by a simple decantation method, meaning this novel method has the potential for green and sustainable preparation of CNFs and films.