COMPETITIVE ADSORPTION OF HEAVY-METAL IONS ON MONODISPERSE POLYSTYRENE MICROSPHERES CARRYING DITHIOCARBAMATE GROUPS

Competitive adsorption of heavy-metal ions, i.e., Cd(II), Cu(II) and P b(II), from aqueous media onto monodisperse polystyrene (PS) microsphe res carrying dithiocarbamate groups were investigated. The crosslinked PS microspheres (2 mu m in diameter) were produced by dispersion poly merization, and then dithiocarbamate groups were incorporated by a two -step procedure. The adsorption rate and capacity of these sorbents fo r selected heavy metal ions from aqueous media containing different am ounts of these ions (0.05-600 ppm) and at different pH of 3.0-8.0 were investigated. Very high adsorption rates were observed at the beginni ng, and adsorption equilibria were then gradually achieved in about 5- 90 minutes. The maximum adsorptions of metal ions onto the dithidcarba mate modified PS microsphere were 205.8 mg, 126.0 mg and 129.1 mg per gram of the sorbent microspheres for Pb(II), Cd(II) and Cu(II), respec tively. When the metal ions competed (in the case of the adsorption fr om their mixture) the amounts of adsorption of metal ions were quite c lose. Desorption of metal ions were studied by using different eluent volume (20-200 ml) with 0.5 M NaCl. High desorption ratios (more than 90%) were achieved in all cases. Adsorption-desorption cycles showed t he feasibility of repeated uses of this sorbent system.