Complexation of CH3Hg+ with chloride,sulfate and carbonate in NaClO4: construction of thermodynamic models

The complexation of CH₃Hg⁺ with major ions present in sea and estuary waters (Cl^?, SO₄^2? and CO₃^2?) was studied potentiometrically in an NaClO₄ medium in the ionic strength range 0.1–3.0 mol dm^?3 at 25 °C. The potentiometric data, treated with non‐linear least squares computer programs, led us to establish the formation of the species CH₃HgCl in equilibrium with chloride, CH₃Hg(SO₄)^? species with sulfate and no complex with carbonate. The stoichiometric stability constants obtained at the different ionic strengths were correlated by means of the modified Bromley methodology (MBM) to determine the corresponding thermodynamic constants and interaction parameters. This study is the second of a series designed to simulate, using the MBM thermodynamic model, the behaviour of methylmercury in different conditions of sea and estuary waters. In the first study of the series, the hydrolysis equilibria of methylmercury in NaClO₄ ionic media were established. Copyright © 2002 John Wiley & Sons, Ltd.