Aquatic Geochemistry

, Volume 13, Issue 4, pp 339–355 | Cite as

Use of Pitzer Equations to Examine the Formation of Mercury(II) Hydroxide and Chloride Complexes in NaClO4 Media

  • Melchor González-Dávila
  • J. Magdalena Santana-Casiano
  • Frank J. Millero
Original Paper

Abstract

The thermodynamic stability constants for the hydrolysis and formation of mercury (Hg2+) chloride complexes
$$ \hbox{Hg}^{2+} + n\hbox{H}_{2}\hbox{O} = \hbox{Hg(OH)}_n^{(2-n)+} + n\hbox{H}^{+ } \quad\quad \beta_n $$
$$ \hbox{Hg}^{2+} + n\hbox{Cl}^{-} = \hbox{HgCl}_n^{(2-n)+ } \quad\quad \beta_i $$
have been used to calculate the activity coefficients for Hg(OH) n (2–n)+ and HgCl n (2–n)+ complexes using the Pitzer specific interaction model. These values have been used to determine the Pitzer parameters for the hydroxide and chloro complexes \((\beta_{\rm ML}^{(0)}, \,\beta_{\rm ML}^{(1)}\) and C ML). The values of \(\lambda_{ij}\) and \(\zeta_{ijk}\) have been determined for the neutral complexes (Hg(OH)2 and HgCl2). The resultant parameters yield calculated values for the measured values of log \(\beta^{\ast}\) to  ±0.01 from I  =  0.1 to 3 m at 25°C. Since the activity coefficients of \(\hbox{Hg(OH)}_n^{(2-n)+}\) and \(\hbox{HgCl}_n^{(2-n)+}\) are in reasonable agreement with the values for Pb(II), we have estimated the effect of temperature on the chloride constants for Hg(II) from 0 to 300°C and I = 0–6 m using the Pitzer parameters for \(\hbox{PbCl}_n^{(2-n)+}\) complexes. The resulting parameters can be used to examine the speciation of Hg(II) with Cl in natural waters over a wide range of conditions.

Keywords

Mercury(II) hydroxide Chloride complexes NaClO4 Speciation Activity coefficients Pitzer equations 

Notes

Acknowledgements

We acknowledge the support of the Oceanographic Section of the National Science Foundation, the National Oceanic and Atmospheric Administration and the Spanish Ministerio de Educacion y Ciencia project CTM2006-09857. MGD wishes to acknowledge the support of the Ministerio de Educacion y Ciencia (PR2007-0163) for his stay in the USA. JMSC acknowledges the support of the Canary Islands Government for her stay in the USA.

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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Melchor González-Dávila
    • 1
    • 2
  • J. Magdalena Santana-Casiano
    • 1
    • 2
  • Frank J. Millero
    • 1
  1. 1.Rosenstiel School of Marine and Atmospheric Science, Marine and Atmospheric ChemistryUniversity of MiamiMiamiUSA
  2. 2.Department of ChemistryUniversity of Las Palmas Gran CanariaLas Palmas Gran CanariaSpain

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