REMOVAL OF CADMIUM(II) IONS BY USING ALKALI-BLUE-6B ATTACHED POLY(EGDMA-HEMA) MICROSPHERES

In the present study, poly(ethyleneglycoldimethacrylate (EGDMA)-hydrox yethylmethacrylate (HEMA) microspheres (150-200 mu m in average diamet er) were produced by suspension copolymerization of EGDMA and HEMA in an aqueous medium. Toluene was included in the formulations in order t o 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 micros pheres were characterized by optical microscopy and FTIR spectroscopy. Adsorption/desorption of cadmium(II) ions from aqueous solutions on t hese sorbents were investigated in batch equilibrium experiments by us ing an atomic absorption spectrophotometer. The rate of interaction be tween Alkali Blue 6B and cadmium(II) was very fast (15-60 min). The ma ximum cadmium(II) adsorption onto the dye-attached microspheres (i.e., by complex metal chelate formation) was about 5.43 mg cadmium(II)/g p olymer, which was observed at pH = 6.7. While adsorption onto the plai n poly(EGDMA-HEMA) microspheres (i.e., nonspecific adsorption) was abo ut 0.93 mg cadmium(II)/g polymer at the same conditions. Up to 92% of the adsorbed cadmium(II) ions was desorbed in 2 h using 0.1 M HNO3 (pH = 1.0) as an eluant. The resorption capacity of the sorbent did not s ignificantly decrease during repeated sorption-desorption cycling.