Fabrication of 3D Hierarchically Porous Chitosan Monoliths by Thermally Induced Phase Separation of Chemically Modified Chitin

Chitosan (CS), an amino-polysaccharide, has applications in various areas such as drug delivery, biotechnology, food technology, and numerous industrial applications. Monoliths have been developed continuously for several decades, and today, they hold an impressively strong position in highly efficient separation, ion exchange, catalysis, and chromatography. In our previous study, a hierarchical chitin (CT) monolith was fabricated using chemically modified CT through the thermally induced phase separation (TIPS) method. This report generated a template-free approach to prepare highly effective, stable, and reusable hierarchically porous CS monoliths by deacetylation of CT monoliths. The acquired CS monoliths exhibited a high surface area at 144.1 m2 g-1 owing to the presence of hierarchical macro-and mesopores. The monoliths demonstrated efficient removal of metal ions from an aqueous solution in a flow system (adsorption capacity at 92.1 mg g-1). To gain durability of CS monoliths in acidic and basic environments, epichlorohydrin (ECH) was used as a cross-linking agent. The cross-linked monoliths also exhibited excellent performance in the adsorption of Cu(II) ions from the solution (64.4 mg g-1) and good reusability in multiple adsorption-desorption cycles without losing significant performance (with 90.7 +/- 6.1% adsorption efficiency and 88.5 +/- 7.2% desorption efficiency). The fabricated CS monolith can be modified and applied to various fields such as protein separation, catalysis, and drug delivery.