Honeycomb-inspired chitosan-based beads with pore structure and multifunctional groups: Improvement of fluoride ion...

Selective removal of F^- from industrial wastewater containing multiple anions is a major challenge. Here, we propose a biomimetic chitosan/FeOOH/AlOOH bead (CFeAlB) with a unique honeycomb porous structure and amino and hydroxyl multifunctional groups and AlOOH/FeOOH bimetallic active components for enhanced selective adsorption capacity and enrichment of F^-. The adsorption of F^- by CFeAlB (29.1 mg g^-1) was increased by 96.62 % compared to chitosan beads (14.8 mg g^-1). The adsorption of CFeAlB on F^- was found to be mainly achieved through electrostatic adsorption, ligand complexation, and ion exchange interactions by XPS, FTIR and DFT analyses. Therefore, CFeAlB can reduce the F^- concentration in wastewater containing multiple anions from 10.1 to 1.3 mg L^-1 in 20 min. The adsorption energies between CFeAlB and a variety of anions were analysed using DFT, and it was found that the highest adsorption energy was found for CFeAlB with F^-, and it was demonstrated for the first time by DFT that an Al - F bond is formed between AlOOH and F^-. Furthermore, the chelating between chitosan and FeOOH and AlOOH conferred excellent structural stability to CFeAlB. These findings provide a new research perspective for the application of chitosan novel materials in fluorinated wastewater treatment.