Interaction of Inorganic Mercury(II) with Polyamines, Polycarboxylates, and Amino Acids

Abstract

A study on chemical equilibria of different Hg2+−organic ligand systems is reported to establish the sequestration power of N/O donor groups versus metal. Ligand classes considered are: O-donors (succinate, 1,2,3,4-butanetetracarboxylate, 1,2,3,4,5,6-benzenehexacarboxylate, polymethacrylate, and polyacrylates); N-donors (ethylenediamine, diethylenetriamine, spermidine, triethylentetramine, tetraethylenpentamine, poly(allylamine), and poly(ethylenimine)); and amino acids (glycine, histidine, and aspartic acid). Equilibria were studied potentiometrically in NaNO3 at I = 0.1 mol·L−1 and t = 25 °C. For some systems, the dependence on ionic strength in the range (0 ≤ I ≤ 1) mol·L−1 (NaNO3) and the overall enthalpy changes, by calorimetric measurements, were also determined. The sequestering ability of ligands toward Hg2+ was evaluated, defining the amount of ligand necessary to sequester 50 % of the total metal cation concentration, pL50. The dependence on temperature and on ionic strength of pL50 was determin...