Preferential adsorption of mercury(II) ions in water: chelation of mercury, cadmium, and lead ions to silica derivatized with meso-2,3-dimercaptosuccinic acid

Abstract

Meso-dimercaptosuccinic acid (DMSA) covalently attached to silica gel via amide bond linkages (DMSA-[silica]) was evaluated as a chelate for Hg(II), Cd(II), and Pb(II). All three metal ions are separately chelated by DMSA-[silica]; 95% of Hg(II) is chelated, 81% of Cd(II), and 74% of Pb(II). When equal molar concentrations of the three metals are allowed to react simultaneously with DMSA-[silica] for 2 h, mercury is preferentially bound (99%) compared to cadmium (13%) or lead (0.4%). Attachment of DMSA to silica surfaces via amide bond formation, which increases the thiol to carboxylic acid ratio over free DMSA, is suggested as a factor in enhancing the preference of DMSA-[silica] for mercury.

Keywords:

• Metal chelation
• Mercury(II)
• DMSA
• Silica derivatized chelate

Acknowledgment

We thank Professor Aria Amirbahman for his helpful discussions.