Sequestration of organometallic compounds by synthetic and naturally occurring polycarboxylate ligands. Binding of monomethylmercury(II) by polyacrilic and alginic acids.

The sequestering capacity of synthetic and naturally occurring polycarboxylate ligands towards mono-methylmercury(II) was evaluated by stability quantitative data on the interaction of CH3Hgþ withdifferent molecular weight synthetic polyacrylates (2 and 20 kDa average M.wt) and alginate (70–100 kDa) extracted from brown algae Macrocystis pyrifera. The influence of ionic medium was evaluatedby measurements on the CH3Hgþ-polyacrylate systems in NaNO3 medium at different ionic strengths(0.10, 0.25, 0.50 and 0.75mol Lÿ1), and a Debye–Hu¨ ckel type equation was used for the dependence ofcomplex formation constants on ionic strength. Measurements on the CH3Hgþ - alginate system werecarried out at I ¼0.10mol Lÿ1 in NaNO3 medium. By using the stability data, the sequestering capacityof both ligands towards monomethylmercury(II) was determined at different pH values. Resultsobtained show that the binding ability of polyacrylic ligands (PAA) is stronger than the alginate (AA),following the trend PAA (20 kDa)4PAA (2 kDa)4AA.