Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg2+– Cl–, OH–, CO32–, SO42–, and PO43– aqueous systems (IUPAC Technical Report)

Powell, Kipton J.; Brown, Paul L.; Byrne, Robert H.; Gajda, Tamás; Hefter, Glenn; Sjöberg, Staffan; Wanner, Hans

doi:10.1351/pac200577040739

Cited by 213 publications

(66 citation statements)

References 14 publications

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“…The results derived from Raman measurements are comparable to the recommended CODATA values given in Ref. [38]. With modern Raman equipment it is possible to produce high quality data on aqueous acid-base equilibria, such as the determination of the second dissociation step of H 2 SO 4 [28] and the current data on phosphoric acid as a function of temperature up to subcritical temperatures.…”

Section: Quantitative Temperature Dependant Raman Measurements On H 3supporting

confidence: 77%

Raman-Spectroscopic Measurements of the First Dissociation Constant of Aqueous Phosphoric Acid Solution from 5 to 301 °C

Rudolph

2012

J Solution Chem

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Dilute aqueous phosphoric acid solutions have been studied by Raman spectroscopy at room temperature and over a broad temperature range from 5 to 301°C. R-normalized spectra (Bose-Einstein correction) have been constructed and used for quantitative analysis. The vibrational modes of H 3 PO 4 (aq) (pseudo C 3v symmetry) have been assigned. The band with the highest intensity, the symmetric stretch ν s {P(OH) 3 }(ν 1 (a 1 )) is strongly polarized while ν 4 (e), the antisymmetric stretch ν as P(OH) 3 ) is depolarized. The stretching mode of the phosphoryl group (-P=O), ν 2 (a 1 ) occurs at 1178 cm −1 and is polarized. In the range between 300 and 600 cm −1 , the deformation modes are observed. The deformation mode, δ{PO-H}, involving the O-H group has been detected at 1250 cm −1 as a very weak and broad mode.In addition to the modes of phosphoric acid, modes of the dissociation product H 2 PO − 4 (aq) have been observed. The mode at 1077 cm −1 has been assigned to ν s {PO 2 }, and the mode at 877 cm −1 to ν s {P(OH) 2 } which is overlapped by ν s {P(OH) 3 } of H 3 PO 4 (aq). The modes of H 2 PO − 4 (aq) have been measured in dilute solution and were assigned and presented as well. H 3 PO 4 is hydrated in aqueous solution, which can be verified with Raman spectroscopy by following the modes ν 2 (a 1 ) and ν 1 (a 1 ) as a function of temperature. These modes show a strong temperature dependency. The mode ν 1 (a 1 ) broadens and shifts to lower wavenumbers. The mode ν 2 (a 1 ) on the other hand, shifts to higher wavenumbers and broadens considerably with increases in temperature. At 301°C the phosphoric acid is almost molecular in nature. In very dilute H 3 PO 4 solutions at room temperature, however, the dissociation product, H 2 PO − 4 (aq) is the dominant species. In these dilute H 3 PO 4 (aq) solutions no spectroscopic features could be detected for a hydrogen bonded dimeric species of the formula H 5 P 2 O − 8 (or the neutral dimeric acid H 6 P 2 O 8 ). Pyrophosphate formation, although favored at high temperatures, could not be detected in dilute solution even at 301°C due to the high water activity. In highly concentrated solutions, however, pyrophosphate formation is observable and in hydrate melts the formation of pyrophosphate is already noticeable at room temperature.

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Section: Quantitative Temperature Dependant Raman Measurements On H 3supporting

confidence: 77%

Raman-Spectroscopic Measurements of the First Dissociation Constant of Aqueous Phosphoric Acid Solution from 5 to 301 °C

Rudolph

2012

J Solution Chem

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“…The boldfaced molecules in Reactions indicate the so‐called “tracer” molecules to construct the pseudo first‐order reactions. The p K a values for H 3 O + , H 2 O, H 3 PO 4 ,

{normalH}_{2} {PO}_{4}^{-}

, and HPO 4 2− are −1.7, 15.7, 2.1, 7.2, and 12.3, respectively . The p K a value for HA was chosen from the p K a values of the protonated amine (R‐NH 4 + ) in glutamic acid, which was 9.67, and the protonated guanidine (R‐C(NH 2 ) 2+ ), or guanidinium, in creatine, which was 11.02.…”

Section: Numerical Study I: Protonated Amine and Guanidiniummentioning

confidence: 99%

“…The “tracer” molecules are presented as boldfaced. For numerical calculations, the same values were used for all the parameters other than the chemical shift difference, which was set to be 1.0 ppm, and the p K a values for HA and H 2 A + , which were, respectively, set to be 16 and −2.4 assuming that HA is a primary alcohol …”

Section: Numerical Study Ii: Primary Alcoholsmentioning

confidence: 99%

Bloch equations for proton exchange reactions in an aqueous solution

Lee

Regatte

Jerschow

2016

Concepts Magnetic Resonance

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The extension of the Bloch equations for acid-base reactions in an aqueous solution is revisited. The acid-base reactions are second-order, and several reactions catalyzed by distinct catalysts may happen simultaneously. By constructing pseudo first-order reactions and assuming fast dissemination of protons from catalysts to solvent water, this extension converges to the well-known Bloch-McConnell equations for a two-site first-order exchange. Thus, explicit relationships between the parameters appearing in the reactions and the Bloch-McConnell equations are established. The dependencies of exchange rates and chemical exchange saturation transfer effects on pH were numerically and experimentally investigated for representative examples.

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“…Thermodynamic calculations were performed using the Geochemist's Workbench modeling package with a modified version of the Lawrence Livermore National Laboratory (LLNL) thermodynamic database (Delany and Lundeen, 1990) augmented with the “cemdata 07” thermodynamic database (Lothenbach and Winnefeld, 2006) and with recently compiled thermodynamic data for inorganic Hg species (Powell et al, 2005). …”

Section: Methodsmentioning

confidence: 99%

Mechanism of Hg(II) immobilization in sediments by sulfate-cement amendment

Serrano

Vlassopoulos²,

O’Day

2016

Applied Geochemistry

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Reactive amendments such as Portland and super-sulfate cements offer a promising technology for immobilizing metalloid contaminants such as mercury (Hg) in soils and sediments through sequestration in less bioavailable solid forms. Tidal marsh sediments were reacted with dissolved Hg(II) in synthetic seawater and fresh water solutions, treated with Portland cement and FeSO4 amendment, and aged for up to 90 days. Reacted solids were analyzed with bulk sequential extraction methods and characterized by powder X-ray diffraction (XRD), electron microscopy, and synchrotron X-ray absorption spectroscopy at the Hg LIII- and S K-edge. In amended sediments, XRD, SEM and sulfur K-edge XANES indicated formation of gypsum in seawater experiments or ettringite-type (Ca6Al2(SO4)3(OH)12.26H2O) phases in fresh water experiments, depending on the final solution pH (seawater ∼8.5; freshwater ∼10.5). Analysis of Hg EXAFS spectra showed Cl and Hg ligands in the first- and second-coordination shells at distances characteristic of a polynuclear chloromercury(II) salt, perhaps as a nanoparticulate phase, in both seawater and fresh water experiments. In addition to the chloromercury species, a smaller fraction (∼20-25%) of Hg was bonded to O atoms in fresh water sample spectra, suggesting the presence of a minor sorbed Hg fraction. In the absence of amendment treatment, Hg sorption and resistance to extraction can be accounted for by relatively strong binding by reduced S species present in the marsh sediment detected by S XANES. Thermodynamic calculations predict stable aqueous Hg-Cl species at seawater final pH, but higher final pH in fresh water favors aqueous Hg-hydroxide species. The difference in Hg coordination between aqueous and solid phases suggests that the initial Hg-Cl coordination was stabilized in the cement hydration products and did not re-equilibrate with the bulk solution with aging. Collectively, results suggest physical encapsulation of Hg as a polynuclear chloromercury(II) salt as the primary immobilization mechanism.

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Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg2+– Cl–, OH–, CO32–, SO42–, and PO43– aqueous systems (IUPAC Technical Report)

Cited by 213 publications

References 14 publications

Raman-Spectroscopic Measurements of the First Dissociation Constant of Aqueous Phosphoric Acid Solution from 5 to 301 °C

Raman-Spectroscopic Measurements of the First Dissociation Constant of Aqueous Phosphoric Acid Solution from 5 to 301 °C

Bloch equations for proton exchange reactions in an aqueous solution

Mechanism of Hg(II) immobilization in sediments by sulfate-cement amendment

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