Facile Green Production of Chitin Nanomaterials from Shrimp Shell Chitin Using Recyclable Maleic Acid and Microwave Irradiation

This study presents a facile, green, and sustainable method for the integrated production of chitin nanocrystals (ChNCs) and nanofibers (ChNFs) from shrimp shell chitin using recyclable maleic acid and microwave irradiation. Maleic acid, a mild organic acid, is employed for hydrolysis and functionalization, with 88.5% recovery for reuse, contributing to the sustainability of the process. Optimal production conditions, determined using response surface methodology (RSM), were an 85% acid concentration, 26.63 min of reaction time, and 315.41 W microwave power, yielding 26.28% ChNCs and 64.04% ChNFs. Transmission electron microscopy (TEM) revealed rod-like ChNCs (543.71 nm length, 48.70 nm width) and web-like ChNFs (61.15 nm width). Fourier-transform infrared spectroscopy (FTIR) confirmed successful surface carboxylation, with degrees of substitution of 0.32 for ChNCs and 0.28 for ChNFs. Both nanomaterials exhibited high crystallinity (91.55% for ChNCs, 87.65% for ChNFs), negative zeta potential values (−44.56 mV for ChNCs, −16.93 mV for ChNFs), and enhanced thermal stability compared to raw chitin. The process, evaluated using sustainability metrics, yielded an E-factor of 3.317, highlighting significant waste reduction over conventional acid hydrolysis. This eco-friendly approach aligns with green chemistry principles and offers a sustainable, scalable solution for chitin nanomaterial production, suitable for diverse industrial applications.