| 1. |
- Powell, Kipton J., et al.
(författare)
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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)
- 2005
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Ingår i: Pure and Applied Chemistry. - : Walter de Gruyter GmbH. - 0033-4545 .- 1365-3075. ; 77:4, s. 739-800
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Tidskriftsartikel (refereegranskat)abstract
- This document presents a critical evaluation of the equilibrium constants and reaction enthalpies for the complex formation reactions between aqueous Hg(II) and the common environmental inorganic ligands Cl-, OH-, CO32-, SO42-, and PO43-. The analysis used data from the IUPAC Stability Constants database, SC-Database, focusing particularly on values for 25 ° C and perchlorate media. Specific ion interaction theory (SIT) was applied to reliable data available for the ionic strength range I-c ≤ 3.0 mol dm(-3). Recommended values of log(10) β(p,q,r)° and the associated reaction enthalpies, &UDelta;H-r(m)°, valid at I-m = 0 mol kg(-1) and 25 ° C, were obtained by weighted linear regression using the SIT equations. Also reported are the equations and specific ion interaction coefficients required to calculate log(10) β(p,q,r) values at higher ionic strengths and other temperatures. A similar analysis is reported for the reactions of H+ with CO32- and PO43-. Diagrams are presented to show the calculated distribution of Hg(II) amongst these inorganic ligands in model natural waters. Under typical environmental conditions, Hg(II) speciation is dominated by the formation of HgCl2(aq), Hg(OH)Cl(aq), and Hg(OH)(2)(aq).
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| 2. |
- Powell, Kipton J, et al.
(författare)
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Chemical speciation of environmentally significant metals : an IUPAC contribution to reliable and rigorous computer modelling
- 2015
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Ingår i: Chemistry International. - : Walter de Gruyter. - 0193-6484 .- 1365-2192. ; 37:1, s. 15-19
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Tidskriftsartikel (refereegranskat)abstract
- The mobility and bioavailability of metal ions in natural waters depend on their chemical speciation, which involves a distribution of the metal ions between different complex (metal-ligand) species, colloid-adsorbed species and insoluble phases, each of which may be kinetically labile or inert. For example, in fresh water the metal ions are distributed among organic complexes (e.g., humates), colloids (e.g., as surface-adsorbed species on colloidal phases such as FeOOH), solid phases (e.g., hydroxide, oxide, carbonate mineral phases), and labile complexes with the simple inorganic anionic ligands commonly present in natural waters (e.g., for ZnII, the aqueous species, Zn2+, ZnOH+, Zn(OH)2(aq), Zn2OH3+, ZnSO4(aq), ZnCO3(aq)…).
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| 3. |
- Powell, Kipton J., et al.
(författare)
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Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu2+-OH-, Cl-, CO32-, SO42-, and PO43- systems (IUPAC Technical Report)
- 2007
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Ingår i: Pure and Applied Chemistry. - : Walter de Gruyter GmbH. - 0033-4545 .- 1365-3075. ; 79:5, s. 895-950
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Forskningsöversikt (refereegranskat)abstract
- Complex formation between CuII and the common environmental ligands Cl-, OH-, CO32-, SO42-, and PO43- can have a significant effect on CuII speciation in natural waters with low concentrations of organic matter. Copper(II) complexes are labile, so the CuII distribution amongst these inorganic ligands can be estimated by numerical modeling if reliable values for the relevant stability (formation) constants are available. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log10βp,q,r° valid at Im = 0 mol kg-1 and 25 °C (298.15 K), along with the equations and specific ion interaction coefficients required to calculate log10βp,q,r values at higher ionic strengths. Some values for reaction enthalpies, ΔrHm, are also reported where available. In weakly acidic fresh water systems, in the absence of organic ligands, CuII speciation is dominated by the species Cu2+(aq), with CuSO4(aq) as a minor species. In seawater, it is dominated by CuCO3(aq), with Cu(OH)+, Cu2+(aq), CuCl+, Cu(CO3)OH-, Cu(OH)2(aq), and Cu(CO3)22- as minor species. In weakly acidic saline systems, it is dominated by Cu2+(aq) and CuCl+, with CuSO4(aq) and CuCl2(aq) as minor species.
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| 4. |
- Powell, Kipton J, et al.
(författare)
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Chemical speciation of environmentally significant metals with inorganic ligands. Part 3: The Pb2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)
- 2009
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Ingår i: Pure and Applied Chemistry. - 0033-4545 .- 1365-3075. ; 81:12, s. 2425-76
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Tidskriftsartikel (refereegranskat)abstract
- Complex formation between PbII and the common environmental inorganic ligands, Cl–, OH–, CO32–, SO42–, and PO43–, can be significant in natural waters with low concentrations of organic matter. Numerical modeling of the speciation of PbII amongst these inorganic ligands requires reliable values for the relevant stability (formation) constants. This paper provides a critical review of such constants and related thermodynamic data. It recommends values of log10 βp,q,r° valid at Im = 0 mol kg–1 and 25 °C (298.15 K), along with the equations and empirical coefficients required to calculate log10 βp,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Some values for reaction enthalpies, ΔrH, are also reported. In weakly acidic fresh water systems (–log10 {[H+]/c°} < 6), the speciation of PbII is similar to that of CuII. In the absence of organic ligands, PbII speciation is dominated by Pb2+(aq), with PbSO4(aq) as a minor species. In weakly alkaline solutions, 8.0 < –log10 {[H+]/c°} < 9.0, the speciation is dominated by the carbonato species PbCO3(aq) and Pb(CO3)22–. In weakly acidic saline systems (–log10 {[H+]/c°} < 6), the speciation is dominated by PbCln(2–n)+ complexes, (n = 0–3), with Pb2+(aq) as a minor species. In this medium (and in seawater), the speciation contrasts with that of CuII because of the higher stability of the Pb2+-chlorido- complexes. In seawater at –log10 {[H+]/c°} = 8.2, the calculated speciation is less well defined, although it is clearly dominated by the uncharged species PbCO3(aq) (41 % of [Pb]T) with a significant contribution (16 %) from Pb(CO3)Cl– and minor contributions (5–10 %) from PbCln(2–n)+, (n = 0–3) and Pb(CO3)22–. The uncertainty in calculations of PbII speciation in seawater arises from (a) the large uncertainty in the stability constant for the apparently dominant species PbCO3(aq), (b) the reliance on statistical predictions for stability constants of the ternary species Pb(CO3)Cl– and Pb(CO3)OH–, and (c) the uncertainty in the stability constant for PbCl42–, the available value being considered "indicative" only. There is scope for additional detailed high-quality measurements in the Pb2+ + CO32– + Cl– system.
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| 5. |
- Powell, Kipton J., et al.
(författare)
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Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)
- 2013
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Ingår i: Pure and Applied Chemistry. - 0033-4545 .- 1365-3075. ; 85:12, s. 2249-2311
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Tidskriftsartikel (refereegranskat)abstract
- The numerical modeling of ZnII speciation amongst the environmental inorganic ligands Cl–, OH–, CO32–, SO42–, and PO43– requires reliable values for the relevant stability (formation) constants. This paper compiles and provides a critical review of these constants and related thermodynamic data. It recommends values of log10 βp,q,r° valid at Im = 0 mol·kg–1 and 25 °C (298.15 K), and reports the empirical reaction ion interaction coefficients, ∆ε, required to calculate log10 βp,q,r values at higher ionic strengths using the Brønsted–Guggenheim–Scatchard specific ion interaction theory (SIT). Values for the corresponding reaction enthalpies, ∆rH, are reported where available. There is scope for additional high-quality measurements for the Zn2+ + H+ + CO32– system and for the Zn2+ + OH– and Zn2+ + SO42– systems at I > 0. In acidic and weakly alkaline fresh water systems (pH < 8), in the absence of organic ligands (e.g., humic substances), ZnII speciation is dominated by Zn2+(aq). In this respect, ZnII contrasts with CuII and PbII (the subjects of earlier reviews in this series) for which carbonato- and hydroxido- complex formation become important at pH > 7. The speciation of ZnII is dominated by ZnCO3(aq) only at pH > 8.4. In seawater systems, the speciation at pH = 8.2 is dominated by Zn2+(aq) with ZnCl+, Zn(Cl)2(aq), ZnCO3(aq), and ZnSO4(aq) as minor species. This behaviour contrasts with that for CuII and PbII for which at the pH of seawater in equilibrium with the atmosphere at 25 °C (log10 {[H+]/c°} ≈ 8.2) the MCO3(aq) complex dominates over the MCln(2–n)+ species. The lower stability of the different complexes of ZnII compared with those of CuII, PbII, and CdII is also illustrated by the percentage of uncomplexed M2+ in seawater, which is ca. 55, 3, 2, and 3.3 % of [MII]T, respectively.
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| 6. |
- Simpson, Stuart L, et al.
(författare)
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Pyrocatechol Violet Complexation at the Boehmite–Water Interface
- 2000
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 229:2, s. 568-74
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Tidskriftsartikel (refereegranskat)abstract
- Acid/base reactions and pyrocatechol violet complexation at the boehmite–solution interface have been investigated in 0.10 M K(Cl) solution at 298.2 K in the range 5.0≤−log h≤9.0. Equilibrium measurements were performed as potentiometric titrations complemented by spectrophotometric analysis of a ligand (batch adsorption experiments). The experimental data were evaluated on the basis of the extended constant capacitance model, allowing for inner-sphere and/or outer-sphere complexation. The acid/base properties are described by the equilibria: H++≡AlOH ≡AlOH2+; log β1,1,0(int)=7.46±0.04 and ≡AlOH ≡AlO−+H+; log β−1,1,0(int)=−9.87±0.12. The specific capacitance was determined as 1.00 F m−2. The binding of pyrocatechol violet {PCV, 2-[(3,4-dihydroxyphenyl)(3-hydroxy-4-oxocyclohexa-2,5-diene-1-ylidene)methyl]benzenesulfonic acid}, H4L, was described by the formation of a single inner-sphere complex according to the reaction ≡AlOH+H4L≡AlL3−+3H++H2O. Allowing for a charge distribution of this complex between the inner plane and β-plane (−2, −1), a significant improvement of the fit was obtained. The adsorbed complex exhibited a dark blue color over the pH range 5–8.5, indicative of proton loss from the 1,2-dihydroxyl moiety. Furthermore, DRIFT spectra showed the bonding environment of PCV bound to the surface to exhibit similarities with corresponding catechol adsorption to different aluminium (hydr)oxides. These spectral features turned out to be very similar to soluble catechol complexes of Al(III). Thus, it is suggested that PCV forms a mononuclear chelating complex at the boehmite–water interface. The maximum surface coverage reached was ca. 33%, indicating that the high negative charge of the species may result in surface charge “saturation” rather than saturation of surface binding sites. Steric hindrances caused by the large size of PCV may also contribute to the low surface coverage.
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