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

Abstract

The complexation of CH 3 Hg with major ions present in sea and estuary waters (Cl À , SO 4 2À and CO 3 2À ) was studied potentiometrically in an NaClO 4 medium in the ionic strength range 0.1± 3.0 mol dm À3 at 25°C. The potentiometric data, treated with non-linear least squares computer programs, led us to establish the formation of the species CH 3 HgCl in equilibrium with chloride, CH 3 Hg(SO 4 ) À 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 NaClO 4 ionic media were established.

Bioconcentration of methylmercury in microzooplankton in a temperate river

“…This indicates that spatial distribution of the MeHg K d cannot be explained by a passive diffusion model. Alternatively, the particle solubility of MeHg would be increased in response to increasing Cl concentrations, if MeHg speciation were dominated by Cl complexation [33,34]. Indeed, the modeling result presented in Figure 5 is consistent with this hypothesis, suggesting that most of the microseston is not composed of phytoplankton and bacteria.…”

Influence of initiators on the growth of poly(ethyl 2-cyanoacrylate) nanofibers

“…Table 2 lists the anionic initiators along their respective pK s and pK a values and the corresponding morphology of the polymer observed by SEM. The pK s and pK a values shown in Table 2 were obtained from reports published in the literature [20][21][22][23][24]. For certain anions whose pK s values were unavailable, estimations were made for their values.…”

Adsorption of aqueous inorganic mercury and methylmercury on suspended kaolin: influence of sodium chloride, fulvic acid and particle content

“…High NaCl content provides (i) Na cations, which effectively compete with mercury species for the anionic binding sites of kaolin, and (ii) Cl À anions, which promote the formation of very stable and negatively charged chloro-complexes of mercury, especially HgCl 4 2À , 9 and MeHgCl. 26 Both facts facilitate desorption of mercury species from the suspended particles. In our experiments, increasing the concentration of NaCl leads to significantly lower removals in all the situations checked.…”