Citral and aspartic acid co-modified chitosan sponge: more active amines for greatly improved indigo carmine removal

A novel green chitosan sponge crosslinked with citral and aspartic acid (CS@AA-CIT) was synthesized using chitosan modified with aspartic acid via the freeze-drying method. CS@AA-CIT demonstrated superior adsorption properties for indigo carmine dye (IC), achieving a capacity of 1068.919 mg/g. While the aspartic acid-free chitosan sponge (CS-CIT) only exhibited a capacity of 530.515 mg/g. This enhancement in adsorption performance was attributed to increased electrostatic attraction, π-π interactions and hydrogen bonding. The incorporation of aspartic acid introduced a significant number of reactive amino and carboxyl groups, which augmented the material's electrostatic attraction, thereby significantly improving its adsorption capacity for IC. Additionally, simulated wastewater experiments conducted on CS@AA-CIT demonstrated its excellent anti-interference capability. Furthermore, CS@AA-CIT maintained a high adsorption performance for IC (78 %) even after four regeneration cycles. Finally, fixed-bed column experiments on IC were conducted, and the breakthrough curves aligned well with the Thomas model, demonstrating significant application potential in real wastewater treatment. In summary, CS@AA-CIT serves as an ideal adsorbent that is environmentally friendly, highly efficient, and reusable. Looking into the future, CS@AA-CIT holds significant exploration space and application potential in treating dye pollutants.