3D porous tubular network-structured chitosan-based beads with multifunctional groups: Highly efficient and selective...

Herein, an effective adsorbent, 3D porous tubular network-structured citric acid-chitosan/Fe/polyethyleneimine beads (CCFPB) with multifunctional active groups and strong selectivity, was prepared for the selective removal of Cu²⁺ from simulated wastewater. Compared with pure chitosan beads (CB), the adsorption capacity of CCFPB for Cu²⁺ was increased by 127 mg g^-1 (238%), and the adsorption equilibrium time was shortened by 480 min. The CCFPB showed porous surface and a novel 3D porous tubular network structure in interior, which were benefit to the diffusion of Cu²⁺ from surface to interior of the CCFPB and the shortening of adsorption equilibrium time. The common coexisting ions in the simulated wastewater had almost no effect on the adsorption of Cu²⁺ by CCFPB, and the adsorption was fast and reached equilibrium within 10 h. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model (q_m = 240.9 mg g^-1 for Cu²⁺). The adsorption mechanism of CCFPB for Cu²⁺ was mainly the synergistic interaction with amino, carboxyl, and hydroxyl groups. This strategy shows great potential for developing a variety of novel, highly active, and reusable immobilized functional beads materials for effective separation of Cu²⁺ from multi-ion wastewater.