Thermodynamic study on reaction path of Hg(II) with S(II) in solution

Abstract

The mercury sulfidation experiments were conducted in the pH range from 1 to 13. The results show that Hg(Ⅱ) reacted with equimolar S(Ⅱ) has the lowest remained Hg(Ⅱ) concentration (9.7 µg/L) at pH 1.0 and the highest remained concentration (940.8 µg/L) at pH 13.0. Meanwhile, the changes of pH values were monitored exactly, which reveal that solution pH values change when mixing the same pH value solutions of HgCl 2 and Na 2 S. In order to explain the phenomena and determine the reaction paths of Hg(Ⅱ) reacting with S(Ⅱ) in the solution, the concerned thermodynamics was studied. Species of S(Ⅱ)-H 2 O system and Hg(Ⅱ)-H 2 O system at different pH values were calculated, and then the species distribution diagrams of S(Ⅱ)-H 2 O system, Hg( Ⅱ )-H 2 O system and Hg( Ⅱ )-Cl − -OH − -H 2 O system were drawn. Combining the experimental data and thermodynamic calculation, the mechanism of Hg(Ⅱ) reacting with S(Ⅱ) was deduced. The results indicate that different species of S(Ⅱ) and Hg(Ⅱ) have the diverse reaction paths to form HgS precipitate at different pH values and the standard Gibbs free energies change ) (∆ Θ m r G of those equations are also calculated, which can provide a guidance for mercury-containing wastewater treatment with Na 2 S.

Water-dispersible few-layer graphene flakes for selective and rapid ion mercury (Hg2+)-rejecting membranes

“…6b, the regeneration mechanism of the membranes in the presence of highly alkaline conditions (0.5 M Bu 4 NOHÁ30H 2 O) is then attributed to the formation of mercury hydroxide complexes (Hg(OH) 3 À ). 219 These negative complexes are electrostatically repulsed by the negative sites of the graphene surfaces. 45,46,220 Meanwhile Hg(OH) 3…”

Comparative Study of Mercury(II) Removal from Aqueous Solutions onto Natural and Iron-Modified Clinoptilolite Rich Zeolite

“…This indicates that mercury is sorbed over the entire surface of the particle, where some sites on the surface are more energy efficient, i.e., they act as active centers for crystal formation and growth probably in the form of HgO or Hg(OH) 2 . When saturation conditions are reached, Hg(OH) 2 can precipitate or transform into the HgO form [37,40]. The resulting formations are irregular in shape because the sorption process was conducted under well-mixed conditions.…”