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

Abstract

The sequestering capacity of synthetic and naturally occurring polycarboxylate ligands towards monomethylmercury(II) was evaluated by stability quantitative data on the interaction of CH3Hg+ with different 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 evaluated by measurements on the CH 3Hg+-polyacrylate systems in NaNO3 medium at different ionic strengths (0.10, 0.25, 0.50 and 0.75 mol L-1), and a Debye-Hückel type equation was used for the dependence of complex formation constants on ionic strength. Measurements on the CH3Hg +-alginate system were carried out at l = 0.10 mol L-1 in NaNO3 medium. By using the stability data, the sequestering capacity of both ligands towards monomethylmercury(II) was determined at different pH values. Results obtained show that the binding ability of polyacrylic ligands (PAA) is stronger than the alginate (AA), following the trend PAA (20kDa)>PAA (2kDa)>AA.