Using Recyclable Hydrated Deep Eutectic Solvents for Extraction of High-Purity Chitin and Preparation of Acylated Chitin Nanofibers to Reinforce PVA Films

Traditional methods for extracting chitin and preparing acylated chitin nanofibers (O-ChNFs) often rely on harsh reaction conditions and large quantities of acid–base solvents, leading to inefficiency and a substantial environmental impact. In this study, a hydrated multicarboxylic acid deep eutectic solvent composed of choline chloride (ChCl), malonic acid (MA), and water was employed to efficiently extract high-purity chitin from shrimp shell waste and further prepare acylated chitin nanofibers. This process significantly reduced the treatment time, requiring only 10 min to obtain chitin with a purity as high as 94.08%. The resulting O-ChNFs exhibited a high degree of substitution and a yield of 82.3%. The deep eutectic solvent (DES) maintained an excellent treatment efficiency even after 10 recycling cycles. Furthermore, PVA/O-ChNFs nanocomposite films were fabricated, in which O-ChNFs served as nanoreinforcements, significantly enhancing the mechanical properties and thermal stability of the composite films. In summary, this work presents a green and efficient strategy for converting shrimp shell waste into high-value nanomaterials, offering new insights into chitin biorefining and demonstrating the broad application prospects of the O-ChNFs in the field of sustainable packaging materials.