Preparation of nanochitin hydrogels via ice templated chemical/physical crosslinking for microplastic removal

Formaldehyde (FO) and nanochitin suspension (DEChN) were combined to synthesize stable hydrogels via ice-templated chemical/physical crosslinking. The synthesis process involved the mixing of formaldehyde and nanochitin, followed by ammonia-induced gas phase coagulation to achieve dual crosslinking, thereby enhancing the mechanical properties of the hydrogels. The chemically crosslinked hydrogel exhibited a storage modulus of 680.05 Pa, whereas the demonstrated an approximately 5-times increase in storage modulus of 3110.34 Pa for DEChN(5)/FO(1), along with a reduced surface area and improved structural stability. Filtration experiments revealed that the dual-crosslinked hydrogel achieved nearly complete removal of microplastics (∼3 μm in diameter), with a flux of 8.22 mL cm h, outperforming both the chemically (5.05 mL cm h) and physically (3.01 mL cm h) crosslinked samples. This enhanced performance was attributed to the larger pore size and robust channel structure in dual crosslinked hydrogels. The nanochitin hydrogels offered a more straightforward fabrication process, superior filtration efficiency, and cost-effectiveness, highlighting their scalability for practical water purification systems.