Dithiocarbamate-Incorporated Monodisperse Polystyrene Microspheres as Specific Sorbents: Adsorption of Organomercury Species

Abstract

Adsorption of organomercury species, CH₃Hg⁺, C₂H₂Hg⁺ and C₆ H₅ Hg⁺ from aqueous media onto monodisperse polystyrene (PS) microspheres carrying dithiocarbamate groups were investigated. The crosslinked PS microspheres (2 μm in diameter) were produced by dispersion polymerization, and then dithiocarbamate groups were incorporated by a two-step procedure. Adsorption rate and capacity of these sorbents for selected organomercury ions from aqueous media containing different amounts of these ions and at different pH of 3.0-8.0 were investigated. Very high adsorption rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 40 min. The maximum adsorption of metal ions onto the dithiocarbamate modified PS microspheres were 123.2 mg, 113.6 mg and 20.1 mg per gram of the sorbent microspheres for CH₃Hg⁺, C₂H₅Hg⁺ and C₆H₅Hg⁺ respectively. C₆H₅Hg⁺ ion concentrations higher than 100 μg/mL could not be studied due to its limited solubility. When the metal ions competed (in the case of the adsorption from their mixture) the amounts of adsorption of the ions were equal. Desorption of metal ions were studied by using 2.0 M NaCl and 5% thiourea solutions. High desorption ratios (more than 90%) were achieved in all cases. Adsorption-desorption cycles showed the feasibility of repeated uses of this sorbent system.

Key Words:

• Monodisperse microspheres
• adsorption
• organomercury ions GC/AAS technique