Three-dimensional porous adsorbent based on chitosan-alginate-cellulose sponge for selective and efficient removal of anionic dyes

A three-dimensional porous adsorbent, chitosan-alginate-cellulose (CAC) sponge, for efficient and selective adsorption of anionic dyes from aqueous systems was developed using a ternary deep eutectic solvent as the cellulose solvent, polyvinyl alcohol as the porogen, and glutaraldehyde as the crosslinking agent. Compared with unary and binary sponges prepared by chitosan, alginate, and cellulose, the CAC sponge exhibited better adsorption capacity, mechanical property, and water stability. The three-dimensional porous structure of CAC sponge was significantly improved by combining the three polysaccharides and introducing the polyvinyl alcohol and glutaraldehyde. A series of characterizations was performed to investigate the properties of the CAC sponge. The CAC sponge performed high adsorption capacity (105.9–203.7 mg/g) and excellent selectivity to anionic dyes, with the selectivity factor up to 26.5, and the experimental data followed the Langmuir and pseudo-second-order models. The adsorption behavior of the CAC sponge exhibited temperature stability and strong pH dependence. The adsorption mechanism and energy were determined using density functional theory, and electrostatic interactions were the main forces for the adsorption of anionic dyes. Finally, the CAC sponge combined with high-performance liquid chromatography was applied to adsorb and detect anionic dyes from river water, tap water, and beverage samples with outstanding enrichment ability (enrichment factors: 31.16–69.69) and selectivity.