Water-redispersible and high-yield α-chitin nanocrystals isolated using electron-beam irradiation as adsorbents to remove heavy metals and dye

Abstract

An innovative approach to fabricate transparent and redispersible α-chitin nanocrystals (ChNCs) with high overall yields was developed in this work for eventual commercial use. The nanomanufacturing process included electron-beam irradiation (EBI) of chitin for oxidation and degradation in the dried state, high-pressure nanoscale homogenization via swelling, CO₂ absorption, and spray-drying to obtain dehydrated products. The resulting EBI-disassociated chitins contained increased amounts of carboxylate (0.19–0.27 mmol g⁻¹) and a negligible fraction of D-glucosamine moiety (from ca. 6.5 to <1.0%) with an intrinsic structure identical to α-chitin derived from shrimp shell prior to purification by conventional methods, such as deproteination. The resulting EBI-induced ChNC series exhibited nano-sized and rod-like morphology with tunable lengths averaging 608–259 nm, uniform widths of ca. 16–12 nm, a high isolation yield of max. 81%, and sufficient anionic surface charges, as zeta potentials of −32 to −34 mV indicate that it is homogenously water-dispersible and stable with background transparency. Unlike ChNC prepared by HCl-hydrolysis, the dehydrated particles of EBI-induced ChNCs were clearly redispersible in water and retained the characteristics of the original nanomaterials. We also tested the redispersible EBI-induced ChNCs as effective adsorbents. Their anionic groups interacted with cationic heavy metals (Cu²⁺ and Fe³⁺) and organic blue dye via electrostatic attraction, forming robust hydrogels, which were self-supporting after centrifugation. The EBI-induced ChNCs produced with low environmental impact in this work offer a promising choice of adsorbents for the removal of undesirable chemicals during wastewater treatment.