Synthesis and characterization of poly(ethylene glycol dimethacrylate-1-vinyl-1,2,4-triazole) copolymer beads for heavy-metal removal

Abstract

We prepared poly(ethylene glycol dimethacrylate-l-vinyl-1,2,4-triazole) [poly(EGDMA-VTAZ)] beads (average diameter = 150-200 mu m) by copolymerizing ethylene glycol dimethacrylate (EGDMA) with 1-vinyl-1,2,4-triazole (VTAZ). The copolymer composition was characterized by elemental analysis and found to contain five EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA-VTAZ) beads had a specific surface area of 65.8 m(2)/g. Poly(EGDMA-VTAZ) beads were characterized by Fourier transform infrared spectroscopy, elemental analysis, surface area measurements, swelling studies, and scanning electron microscopy. Poly(EGDMAVTAZ) beads with a swelling ratio of 84% were used for the heavy-metal removal studies. The adsorption capacities of the beads for Cd(II), Hg(II), and Pb(II) were investigated in aqueous media containing different amounts of these ions (5-750 mg/L) and at different pH values (3.0-7.0). The maximum adsorption capacities of the poly(EGDMA-VTAZ) beads were 85.7 mg/g (0.76 mmol/g) for Cd(II), 134.9 mg/g (0.65 mmol/g) for Pb(II), and 186.5 mg/g (0.93 mmol/g) for Hg(II). The affinity order toward triazole groups on a molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). pH significantly affected the adsorption capacity of the VTAZ-incorporated beads. The equilibrium data were well fitted to the Redlich-Peterson isotherm. Consideration of the kinetic data suggested that chemisorption processes could have been the rate-limiting step in the adsorption process. Regeneration of the chelating-beads was easily performed with 0.1M HNO3.