Adsorption of Cr(VI) onto PEI immobilized acrylate-based magnetic beads: Isotherms, kinetics and thermodynamics study

Magnetic poly(GMA–EGDMA) beads were prepared from glycidylmetharylate (GMA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of Fe3O4 nano-powder via suspension polymerization. After polymerization, the magnetic beads were coated with polyethyleneimine (PEI). Elemental analysis of PEI immobilized beads for the free amine group content was estimated as 258.8 (mu)mol/g polymer. The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), and scanning electron microscopy (SEM). ESR data revealed that the beads were highly super-paramagnetic. The magnetic beads were used for the removal of Cr(VI) ions from aqueous solutions in batch mode. Adsorption equilibrium was established in about 120 min. The maximum adsorption of Cr(VI) on the magnetic beads was observed at around pH 2.0. The maximum adsorption capacity of the magnetic beads was 137.7 mg/g. The effects of adsorbent dosage, ionic strength and temperature have been also reported.