Preparation of modified chitosan microspheres for the removal of Sc(III)

Chitosan modified with polyethylene glycol-200 and crosslinked with glutaraldehyde (MCS) was synthesized for the recovery of Sc(III) ions from aqueous solutions. The prepared adsorbents were characterized by FT-IR, TGA, BET, XRD, XRF, and SEM. The effects of solution pH, adsorbent dosage, contact time, initial concentration, and temperature on the adsorption performance were systematically investigated. The characterization results confirmed the successful fabrication of MCS, and the PEG-200-assisted pore-forming strategy improved the accessible pore structure and Sc(III) adsorption performance of MCS relative to glutaraldehyde-crosslinked chitosan (GCS). A working pH of 5, an adsorbent dosage of 50 mg, a contact time of 100 min, and a temperature of 30 °C were selected for the subsequent adsorption experiments. The adsorption kinetics, isotherms, and thermodynamics of Sc(III) onto MCS were further investigated. The adsorption data were best described by the pseudo-second-order kinetic and Langmuir isotherm models, and the Langmuir model predicted a maximum monolayer adsorption capacity of 55.28 mg·g −1 at 30 °C. The adsorption of Sc(III) was mainly associated with coordination interactions, electrostatic attraction, and hydrogen bonding involving the N/O-containing functional groups of MCS. The synergistic combination of PEG-200-assisted pore formation and GA crosslinking helped balance acid stability and pore accessibility, indicating that MCS has potential as an adsorbent for Sc(III) recovery from acidic aqueous media.