Removal of cadmium (11) ions by using Alkali Blue 6B attached poly(EGDMA-HEMA) microspheres

In the present study, poly(ethyleneglycoldimethacrylate (EGDMA)-hydroxyethylmethacrylate (HEMA) microspheres (150-200 μm in average diameter) were produced by suspension copolymerization of EGDMA and HEMA in an aqueous medium. Toluene was included in the formulations in order to produce water-swellable microspheres. Poly(vinylalcohol) and benzoyl peroxide were used as stabilizer and initiator, respectively. Alkali Blue 6B was attached to the microspheres, as a metal chelating ligand for specific adsorption of heavy metal ions. These dye attached microspheres were characterized by optical microscopy and FTIR spectroscopy. Adsorption/desorption of cadmium(II) ions from aqueous solutions on these sorbents were investigated in batch equilibrium experiments by using an atomic absorption spectrophotometer. The rate of interaction between Alkali Blue 6B and cadmium(II) was very fast (15-60 min). The maximum cadmium(II) adsorption onto the dye-attached microspheres (i.e., by complex metal chelate formation) was about 5.43 mg cadmium(Il)/g polymer, which was observed at pH = 6.7. While adsorption onto the plain poly(EGDMA-HEMA) microspheres (i.e., nonspecific adsorption) was about 0.93 mg cadmium(Il)/g polymer at the same conditions. Up to 92% of the adsorbed cadmium(II) ions was desorbed in 2 h using 0.1 M HN0₃ (pH = 1.0) as an eluant. The resorption capacity of the sorbent did not significantly decrease during repeated sorption-desorption cycling.