Modeling the Adsorption of Mercury(II) on (Hydr)oxides II: α-FeOOH (Goethite) and Amorphous Silica

✍ Scribed by Pascale Bonnissel-Gissinger; Marc Alnot; Jean-Paul Lickes; Jean-Jacques Ehrhardt; Philippe Behra

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 124 KB
• Volume: 215
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1999.6263

✦ Synopsis

The surface complexation model is used to describe sorption experiments of inorganic mercury(II) in the presence of an amorphous silica, Aerosil 200, or an iron (hydr)oxide, the goethite ␣-FeOOH (Bayferrox 910). In the simulations, one assumes the formation of a monodentate surface complex 'SOOHg ؉ and of ternary surface complexes with OH ؊ surface groups, 'SOOHgOH and 'SOOHgCl, when chlorides are present in solution. Participation of the complex 'SOOHgCl has been especially evidenced. The mercury(II) surface complexation on oxides can be described by the following equilibria (298.15 K, I ‫؍‬ 0):

with log K SOOHg ؉ int ‫؍‬ 4.9 for goethite; 'SOOH ؉ Hg 2؉ ؉ H 2 O 7 'SOOHgOH ؉ 2H ؉ , with log K SOOHgOH int ‫؍‬ ؊3.7 and ؊2.3 for amorphous silica and goethite, respectively; 'SOOH ؉ Hg 2؉ ؉ Cl ؊ 7 'SOOHgCl ؉ H ؉ , with log K SOOHgCl int ‫؍‬ 5.8 and 8.0 for amorphous silica and goethite, respectively. Comparisons with other data from the literature have been made to investigate the influence of the nature of the oxide on the mechanism of mercury(II) adsorption. X-ray photoelectron spectroscopy was used to characterize the surface of the (hydr)oxides prior to adsorption and to observe when possible the mercury surface compounds.