Synthesis of imidazolium-crosslinked chitosan aerogel and its prospect as a dye removing adsorbent

Abstract

The potential utility of Debus–Radziszewski imidazole synthesis in the fabrication of crosslinked chitosan was studied. Three-component crosslinking was achieved by using glyoxal and propionaldehyde to connect amine groups of chitosan via imidazolium crosslinking. A water-insoluble (at pH range of 2–10) chitosan was obtained at room temperature with a degree of substitution of 0.45 and aerogel was obtained after freeze-drying. The ability of the imidazolium-crosslinked chitosan (ICC) aerogel to absorb an anionic dye, Direct Yellow 27, from a model water was then studied. Based on the Langmuir isotherm, at a pH of 4, an adsorption maximum of 2340 mg g⁻¹ (3.5 mmol g⁻¹) was obtained. In addition, due to the permanent cationic charge of imidazolium group, ICC exhibited excellent adsorption capacity, even under alkaline conditions. Methylglyoxal and benzaldehyde were also used to obtain other types of ICC, demonstrating the versatility of Debus–Radziszewski imidazole synthesis for fabrication of modified chitosan.