scholarly journals The geochemistry of antimony in hydrothermal solutions

2021 ◽  
Author(s):  
◽  
Nellie J. Olsen
Keyword(s):  
Alkaline Solutions ◽  
Sulfide Concentration ◽  
Solubility Curve ◽  
Hydrothermal Solutions ◽  
Alkaline Ph ◽  
X Ray ◽  
Antimony Sulfide ◽  
Speciation Model ◽  
X Ray Absorption ◽  
Antimony Speciation

<p>In this thesis, 30°C stibnite solubility experiments, ambient temperature X-ray absorption spectroscopic measurements of antimony in solution, and high temperature (70 to 400°C) stibnite solubility experiments were carried out in order to determine the aqueous antimony species present in equilibrium with stibnite in hydrosulfide solutions from pH = 3.5 to 12 and reduced sulfur concentrations from 0.001 to 0.1 mol kg⁻¹. Both ambient and elevated temperature solubility studies were conducted using a flow-through apparatus containing a column of stibnite grains though which solutions were pumped. Above 100°C, solubility experiments were conducted at slightly above saturated water vapour pressure to pressures of 300 bar.  At 30°C, the stibnite solubility curve was best reproduced by a scheme of five species: Sb₂S₄²⁻, HSb₂S₄⁻, H₂Sb₂S₅²⁻, H₃SbS₂O, and Sb(OH)₃. At higher temperatures (≥ 70 °C), stibnite solubility at the conditions of the experiments was due to the following four species: Sb₂S₄²⁻, HSb₂S₄⁻, H₃SbS₂O, and Sb(OH)₃. Equilibrium constants were determined for the following five heterogeneous solubility reactions for the temperature ranges listed:  [Please consult the thesis for details.]  Stibnite solubility was independent of pressure at ≤ 350°C. At ~ 400°C, the solubility of stibnite was strongly dependent on pressure and decreased from Sbtotal = 0.015 to 0.0003 mol kg⁻¹ (~2000 to 40 ppm) with a pressure decrease from 300 to 160 bars.  The Sb K-edge X-ray absorption spectroscopic (XAS) measurements of antimony in alkaline (pH = 10. 9 to 12) hydrosulfide solutions gave average first shell coordination environments that were consistent with the speciation model derived from solubility experiments for strongly alkaline solutions (i.e., Sb₂S₄²⁻ and Sb(OH)₃). XAS data enable the elimination of a speciation model involving only monomeric antimony complexes at strongly alkaline pH.  Antimony speciation in near neutral to strongly alkaline pH’s is dominated by dimeric antimony-sulfide complexes at 30°C and sulfide concentrations > 0.001 mol kg⁻¹. With increasing temperature, antimony speciation becomes increasingly dominated by Sb(OH)₃. For hydrothermal solutions with sulfide concentrations between 0.0001 and 0.01 mol kg⁻¹, antimony-sulfide complexes are predominant at < 100°C, whereas antimonous acid, Sb(OH)₃, is the main aqueous species at contributing to stibnite solubility at > 200°C with the speciation in the intervening temperature range being dependent on the pH and sulfide concentration of the solution. For higher sulfide concentrations (i.e., ~ 0.1 mol kg⁻¹), HSb₂S₄⁻ and Sb₂S₄²⁻ control stibnite solubility to higher temperatures.</p>

scholarly journals The geochemistry of antimony in hydrothermal solutions

2021 ◽  
Author(s):  
◽  
Nellie J. Olsen
Keyword(s):  
Alkaline Solutions ◽  
Sulfide Concentration ◽  
Solubility Curve ◽  
Hydrothermal Solutions ◽  
Alkaline Ph ◽  
X Ray ◽  
Antimony Sulfide ◽  
Speciation Model ◽  
X Ray Absorption ◽  
Antimony Speciation

<p>In this thesis, 30°C stibnite solubility experiments, ambient temperature X-ray absorption spectroscopic measurements of antimony in solution, and high temperature (70 to 400°C) stibnite solubility experiments were carried out in order to determine the aqueous antimony species present in equilibrium with stibnite in hydrosulfide solutions from pH = 3.5 to 12 and reduced sulfur concentrations from 0.001 to 0.1 mol kg⁻¹. Both ambient and elevated temperature solubility studies were conducted using a flow-through apparatus containing a column of stibnite grains though which solutions were pumped. Above 100°C, solubility experiments were conducted at slightly above saturated water vapour pressure to pressures of 300 bar.  At 30°C, the stibnite solubility curve was best reproduced by a scheme of five species: Sb₂S₄²⁻, HSb₂S₄⁻, H₂Sb₂S₅²⁻, H₃SbS₂O, and Sb(OH)₃. At higher temperatures (≥ 70 °C), stibnite solubility at the conditions of the experiments was due to the following four species: Sb₂S₄²⁻, HSb₂S₄⁻, H₃SbS₂O, and Sb(OH)₃. Equilibrium constants were determined for the following five heterogeneous solubility reactions for the temperature ranges listed:  [Please consult the thesis for details.]  Stibnite solubility was independent of pressure at ≤ 350°C. At ~ 400°C, the solubility of stibnite was strongly dependent on pressure and decreased from Sbtotal = 0.015 to 0.0003 mol kg⁻¹ (~2000 to 40 ppm) with a pressure decrease from 300 to 160 bars.  The Sb K-edge X-ray absorption spectroscopic (XAS) measurements of antimony in alkaline (pH = 10. 9 to 12) hydrosulfide solutions gave average first shell coordination environments that were consistent with the speciation model derived from solubility experiments for strongly alkaline solutions (i.e., Sb₂S₄²⁻ and Sb(OH)₃). XAS data enable the elimination of a speciation model involving only monomeric antimony complexes at strongly alkaline pH.  Antimony speciation in near neutral to strongly alkaline pH’s is dominated by dimeric antimony-sulfide complexes at 30°C and sulfide concentrations > 0.001 mol kg⁻¹. With increasing temperature, antimony speciation becomes increasingly dominated by Sb(OH)₃. For hydrothermal solutions with sulfide concentrations between 0.0001 and 0.01 mol kg⁻¹, antimony-sulfide complexes are predominant at < 100°C, whereas antimonous acid, Sb(OH)₃, is the main aqueous species at contributing to stibnite solubility at > 200°C with the speciation in the intervening temperature range being dependent on the pH and sulfide concentration of the solution. For higher sulfide concentrations (i.e., ~ 0.1 mol kg⁻¹), HSb₂S₄⁻ and Sb₂S₄²⁻ control stibnite solubility to higher temperatures.</p>

X-ray absorption spectroscopic studies of halide ion hydration in hydrothermal solutions

2006 ◽  
Vol 70 (18) ◽  
pp. A573 ◽  
Author(s):  
T.M. Seward ◽  
C.M.B. Henderson ◽  
O.M. Suleimenov ◽  
J.M. Charnock
Keyword(s):  
Spectroscopic Studies ◽  
Hydrothermal Solutions ◽  
Ion Hydration ◽  
X Ray ◽  
X Ray Absorption

scholarly journals A Coherent Picture of the Hydrogen Oxidation and Evolution Reactions in Aqueous Solutions

2019 ◽  
Author(s):  
Ershuai Liu ◽  
Li Jiao ◽  
Jingkun Li ◽  
Thomas Stracensky ◽  
Lynne K. LaRochelle Richard ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Hydrogen Oxidation ◽  
Alkaline Solutions ◽  
X Ray ◽  
Bifunctional Mechanism ◽  
X Ray Absorption ◽  
Kinetics Of ◽  
Coherent Picture ◽  
Soft Acid

<p>Recent studies show the limitations of catalytic activity descriptor-based approaches to rationalize the kinetics of the hydrogen oxidation and evolution reactions (HOR/HER). Herein, we deposited several transition metals (TMs) onto Pt surfaces to disturb and probe the interface in alkaline solutions. The redox transition of these TMs in association with adsorption and desorption of reaction intermediates during the HOR/HER was monitored via <i>in situ</i> X-ray absorption spectroscopy. We propose that the TM facilitates the HOR by anchoring H<sub>2</sub>O with the H-up configuration (↑H<sub>2</sub>O<sub>ad</sub>) that removes H<sub>ad</sub> on Pt via the bifunctional mechanism, based on the first in situ experimental evidence for the presence of ↑H<sub>2</sub>O<sub>ad</sub> on surface Ru. Meanwhile, the TM promotes the HER of Pt by anchoring OH<sub>ad</sub> to trigger the hard–soft acid–base (HSAB) mechanism for OH<sub>ad</sub> removal. The revised 2B theory depicts a coherent picture of the HOR/HER kinetics in aqueous solutions.<br></p>

Antimony speciation in saline hydrothermal fluids: A combined X-ray absorption fine structure spectroscopy and solubility study

2006 ◽  
Vol 70 (16) ◽  
pp. 4196-4214 ◽  
Author(s):  
Gleb S. Pokrovski ◽  
Anastassia Yu. Borisova ◽  
Jacques Roux ◽  
Jean-Louis Hazemann ◽  
Alain Petdang ◽  
...  
Keyword(s):  
Fine Structure ◽  
Hydrothermal Fluids ◽  
X Ray ◽  
Solubility Study ◽  
Absorption Fine ◽  
X Ray Absorption ◽  
Antimony Speciation

scholarly journals Evidence for the existence of Tc(IV) – humic substance species by X-ray absorption near-edge spectroscopy

2002 ◽  
Vol 90 (12) ◽  
Author(s):  
K. Geraedts ◽  
C. Bruggeman ◽  
A. Maes ◽  
Luc R. Van Loon ◽  
A. Rossberg ◽  
...  
Keyword(s):  
Fission Product ◽  
Humic Substances ◽  
Humic Substance ◽  
The Other ◽  
Alkaline Ph ◽  
X Ray ◽  
Other Hand ◽  
Solid Phases ◽  
The One ◽  
X Ray Absorption

SummaryThe redox–sensitive fission product technetium–99 has been investigated in systems containing different reducing solid phases (pyrite, magnetite, ironsulphide and Gorleben sand) on the one hand and Gorleben groundwater, which contains a high amount of humic substances, on the other hand. Initially, technetium–99 was added to these systems as pertechnetate (Tc(VII)), which was reduced in presence and absence of humic substances with the aid of the different reducing surfaces (neutral to alkaline pH). Both in absence and presence of humic substances, Tc concentrations were observed which exceeded the TcO

In Situ Co K-Edge X-Ray Absorption Fine Structure of Cobalt Hydroxide Film Electrodes in Alkaline Solutions

2000 ◽  
Vol 147 (12) ◽  
pp. 4594 ◽  
Author(s):  
Dana Totir ◽  
Yibo Mo ◽  
Sunghyun Kim ◽  
Mark R. Antonio ◽  
Daniel A. Scherson
Keyword(s):  
Fine Structure ◽  
Alkaline Solutions ◽  
Cobalt Hydroxide ◽  
X Ray ◽  
Absorption Fine ◽  
Hydroxide Film ◽  
X Ray Absorption

In situ analysis of thioarsenite complexes in neutral to alkaline arsenic sulphide solutions

2005 ◽  
Vol 69 (5) ◽  
pp. 781-795 ◽  
Author(s):  
B. C. Bostick ◽  
S. Fendorf ◽  
G. E. Brown
Keyword(s):  
Arsenic Species ◽  
Alkaline Ph ◽  
Pore Waters ◽  
Protonation State ◽  
Relative Fraction ◽  
Relative Stabilities ◽  
X Ray ◽  
Polymeric Species ◽  
X Ray Absorption

AbstractThe solubility of arsenic in anoxic soil and sediment pore waters is strongly influenced by complexation with dissolved sulphide. Despite their importance in arsenic chemistry, thioarsenite complexes have not been well characterized, and considerable questions remain regarding their structure, protonation state, and relative stabilities. Here we use X-ray absorption spectroscopy to examine the type and structure of aqueous arsenic-sulphur complexes in sulphidic solutions under neutral to alkaline pH. Arsenic formed a variety of thioarsenites, including AsS(SH)(OH)—, As(SH)S22—, AsS33—and As(SH)4— complexes. The relative fraction of each species varied strongly with the S:As ratio — with the fraction of AsS(SH)(OH)— greatest at low S:As and trithioarsenites dominating As speciation when S:As ratios exceeded 3 in solution. As much as 40% of the total As also was present as AsS3S3+x(SH)3—x—x in solutions at S:As ratios of 3 or greater. Sulphide complexation was somewhat dependent on pH, with sulphide complexation generally increasing with pH. The speciation observed in these experiments is similar to, though distinct from, speciation predicted based on As2S3 solubility (inferred to contain AsS2— and AsS3S3+x(SH)—x3—x) and chromatographic separation of arsenic species (which does not identify polymeric species). Thus, these data indicate that stability constants for arsenic sulphide complexes must be reappraised.

An investigation of extreme silver enrichment at tennantite surfaces exposed to alkaline solutions: an XPS-based study

2006 ◽  
Vol 70 (4) ◽  
pp. 445-457 ◽  
Author(s):  
E. L. Hobson ◽  
P. Wincott ◽  
D. J. Vaughan ◽  
R. A. D. Pattrick
Keyword(s):  
Photoelectron Spectroscopy ◽  
Depth Profiling ◽  
Selective Dissolution ◽  
Alkaline Solutions ◽  
Surface Species ◽  
Surface Enrichment ◽  
X Ray ◽  
X Ray Absorption ◽  
New Phase ◽  
Cu And Zn

AbstractExtreme silver enrichment at the surface of the complex sulphide, tennantite (ideal formula: Cu12As4S13), occurs following exposure to alkaline solutions, and involves the development of an Ag-rich sulphide surface species. The tennantite has a low bulk Ag content of 0.3 at.%, and a percentage surface enrichment of Ag is thirty-six times that of the bulk. The techniques of X-ray photoelectron spectroscopy (XPS) and reflection extended X-ray absorption fine structure spectroscopy show the new phase to be a Ag sulphide species compositionally similar to cupriferous proustite ((Cu,Ag)3AsS3). Solution experiments and XPS depth profiling show that the surface is most depleted in Cu and Zn, and enriched in Ag compared to the bulk tennantite. Selective dissolution and reprecipitation at the tennantite surface cannot explain the enrichment of Ag relative to the bulk. Migration must have occurred and could have been driven by the leaching out of Cu which produces a metal-depleted surface, coupled to the relative incompatibility of Ag in the tennantite lattice. To account for the extreme enrichment at the surface, Ag must have diffused from depths of up to 9 nm, probably via structural weaknesses and vacancies in the tennantite lattice.

An X-ray absorption (EXAFS) spectroscopic study of aquated Ag+ in hydrothermal solutions to 350°C

1996 ◽  
Vol 60 (13) ◽  
pp. 2273-2282 ◽  
Author(s):  
T.M. Seward ◽  
C.M.B. Henderson ◽  
J.M. Charnock ◽  
B.R. Dobson
Keyword(s):  
Spectroscopic Study ◽  
Hydrothermal Solutions ◽  
X Ray ◽  
X Ray Absorption
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