Dopamine triacrylamide-crosslinked chitosan/polyacrylic acid cryogels for rapid and efficient adsorption of anionic dyes from wastewater.

Developing three-dimensional composite materials with high adsorption capacity, environmentally friendliness, and facile processability is essential for removing organic dyes from wastewater and enhancing ecological protection. In this study, a Friedel-Crafts alkylation reaction was employed to introduce multiple double bonds into the benzene ring of dopamine hydrochloride monomer, resulting in dopamine triacrylamide (DAHAM) compounds. Dopamine triacrylamide crosslinked chitosan (CTS)/polyacrylic acid (PAA) cryogels (CTS/PAA@DAHAM) were prepared to achieve efficient and specific adsorption of anionic dyes. The structure and properties of the material were revealed by SEM, BET analysis, FTIR spectroscopy, TGA, UV-vis spectroscopy, and XPS characterization techniques. The cryogels demonstrated high mechanical strength, a porous structure, and abundant functional groups, including NH3+ and OH. The maximum adsorption capacities for Direct Yellow 12 (DY 12), Direct Brown 1 (DB 1), and Direct Red 13 (DR 13), determined by the pseudo-second-order (PSO) model, were 2088 mg/g (experimentally 2096 mg/g), 2765 mg/g (experimentally 2728 mg/g), and 1315 mg/g (experimentally 1397 mg/g), respectively, at natural pH and 298 K. The adsorption process followed the PSO and Freundlich isotherm models. The adsorption capacities of CTS/PAA@DAHAM exceeds that of most previously reported adsorbents. This study demonstrates the potential of CTS-based cryogels for efficiently removing anionic dyes from wastewater.