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Sjöberg, Staffan
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Publications (10 of 80) Show all publications
Lutzenkirchen, J. & Sjöberg, S. (2018). Speciation and equilibria in the H+-Al3+ - polyacrylic acid system. Monatshefte fuer Chemie, 149(2), 423-429
Open this publication in new window or tab >>Speciation and equilibria in the H+-Al3+ - polyacrylic acid system
2018 (English)In: Monatshefte fuer Chemie, ISSN 0026-9247, E-ISSN 1434-4475, Vol. 149, no 2, p. 423-429Article in journal (Refereed) Published
Abstract [en]

Equilibria between Al3+ and the polyelectrolyte polyacrylic acid (PAA) were studied in 0.1 M NaCl medium at 25 A degrees C (M = mol dm(-3)). The measurements were performed as precise potentiometric titrations in which OH- was in most cases generated coulometrically. The total concentration of Al(III) and PAA varied within the limits 6.23 x 10(-5)-2.01 x 10(-4) M and 7.20 x 10(-4)-1.12 x 10(-3) M, resp., with a 4-18 fold excess of ligand. The value of - log{[H+]/mol dm(-3)} varied between 3 and 5-7, the upper limit set by drifting EMF potentials caused by the onset of a precipitation reaction. The constant capacitance model was utilized to model the experimental data. With the objective of finding a model as simple as possible that gives an acceptable fit to data, the two species AlPAA(2+) and Al(OH)(2)PAA are postulated. The polyelectrolyte effect resulting in pH-dependent formation constants is demonstrated. Furthermore a comparison between the stability constant of the 1:1 complexes of Al3+ with acrylate(-) and PAA(-), respectively, shows the logK value of the latter to be five units higher and is ascribed to particular properties of the polyelectrolyte.

Keywords
Stability constants, Carboxylic acids, Acidity, Potentiometric titrations, Surface complexation delling, Constant capacitance model
National Category
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-145596 (URN)10.1007/s00706-017-2096-4 (DOI)000425536700022 ()
Available from: 2018-03-29 Created: 2018-03-29 Last updated: 2018-06-09Bibliographically approved
Sundman, A., Karlsson, T., Sjöberg, S. & Persson, P. (2016). Impact of iron–organic matter complexes on aqueous phosphate concentrations. Chemical Geology, 426, 109-117
Open this publication in new window or tab >>Impact of iron–organic matter complexes on aqueous phosphate concentrations
2016 (English)In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 426, p. 109-117Article in journal (Refereed) Published
Abstract [en]

Abstract The close linkage between iron (Fe) and phosphorus (P) suggests that changes in Fe speciation may have a strong effect on the bioavailability of P. At the same time Fe speciation in natural oxic environments is known to be affected by the presence of organic matter (OM), pH and total Fe concentrations, thus these parameters should also influence the Fe–P interactions. The main objective of the present work was to study how OM affected the distribution of P(V) in the presence of Fe(III) and to address the questions if and by what mechanism(s) OM influenced the concentration of aqueous phosphate. This was accomplished by investigating the ternary P(V)–Fe(III)–OM system over a wide range of chemical conditions; [Fe]tot = 5000–50,000 μg g− 1, Fe/P = 0.5–2.0 at pH 2.9–7. Iron speciation was probed via Fe K-edge X-ray absorption spectroscopy, P speciation and concentrations were analyzed via infrared spectroscopy, and chemical equilibrium modeling was conducted to simulate the distribution of chemical species of the system. The collective results showed that the dominating species were Fe(III)–OM complexes and ferric phosphate (FePO4(s)). At low concentrations, the Fe(III)–OM complexes suppressed the formation of FePO4(s), which resulted in elevated aqueous phosphate concentrations. At high concentrations, FePO4(s) was formed and co-existed with Fe(III)–OM complexes; ternary P(V)–Fe(III)–OM complexes were not detected under any experimental condition. The collective spectroscopic and equilibrium modeling results offer a mechanistic and thermodynamic consistent explanation to why OM contributes to elevated concentrations of soluble P and thereby to increased bioavailability of P in soils and waters.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Iron, Phosphate, Organic matter, X-ray absorption spectroscopy
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-117463 (URN)10.1016/j.chemgeo.2016.02.008 (DOI)000371214700010 ()
Available from: 2016-03-01 Created: 2016-03-01 Last updated: 2018-06-07Bibliographically approved
Powell, K. J., Brown, P. L., Byrne, R. H., Gajda, T., Hefter, G., Leuz, A.-K., . . . Wanner, H. (2015). Chemical speciation of environmentally significant metals: an IUPAC contribution to reliable and rigorous computer modelling. Chemistry International, 37(1), 15-19
Open this publication in new window or tab >>Chemical speciation of environmentally significant metals: an IUPAC contribution to reliable and rigorous computer modelling
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2015 (English)In: Chemistry International, ISSN 0193-6484, E-ISSN 1365-2192, Vol. 37, no 1, p. 15-19Article in journal (Refereed) Published
Abstract [en]

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)…).

Place, publisher, year, edition, pages
Walter de Gruyter, 2015
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-108892 (URN)10.1515/ci-2015-0105 (DOI)
Available from: 2015-09-17 Created: 2015-09-17 Last updated: 2018-06-07Bibliographically approved
Sand, K. K., Pedersen, C. S., Sjöberg, S., Nielsen, J. W., Makovicky, E. & Stipp, S. L. (2014). Biomineralization: long-term effectiveness of polysaccharides on the growth and dissolution of calcite. Crystal Growth & Design, 14(11), 5486-5494
Open this publication in new window or tab >>Biomineralization: long-term effectiveness of polysaccharides on the growth and dissolution of calcite
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2014 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 11, p. 5486-5494Article in journal (Refereed) Published
Abstract [en]

Our results demonstrate that in addition to being used for controlling morphology during calcite growth, polysaccharide (PS) that has been designed for biomineralization is also extremely robust, influencing calcite reactions even after millions of years. We investigated calcite (CaCO3) behavior in solutions with very small concentrations of PS that was produced similar to 70 Ma ago by coccolithophorids. We used atomic force microscopy (AFM) and the constant composition method to monitor calcite growth in the presence of this ancient PS. The ancient PS is still very active and has a high affinity for calcite step edges. Adsorption, even at extremely low concentrations (0.5 mu g/mL), results in decreased growth rate and dramatic morphology changes during growth and dissolution. The experimental results are complemented with surface complexation modeling for adsorption of components of polysaccharide from a modern coccolithophorid, Emiliania huxleyi. We generated surface complexation constants for the branch components: malonate: 14.25 +/- 0.17, succinate: 11.91 +/- 0.06, tricarballylate: 14.86 +/- 0.04, and citrate: 15.25 +/- 0.04. The implication is that complex PS could hold promise for smart material engineering and for preventing scaling.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
National Category
Chemical Sciences Materials Engineering
Identifiers
urn:nbn:se:umu:diva-97220 (URN)10.1021/cg5006743 (DOI)000344516800020 ()
Available from: 2014-12-18 Created: 2014-12-12 Last updated: 2018-06-07Bibliographically approved
Sundman, A., Karlsson, T., Sjöberg, S. & Persson, P. (2014). Complexation and precipitation reactions in the ternary As(V)–Fe(III)–OM (organic matter) system. Geochimica et Cosmochimica Acta, 145, 297-314
Open this publication in new window or tab >>Complexation and precipitation reactions in the ternary As(V)–Fe(III)–OM (organic matter) system
2014 (English)In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 145, p. 297-314Article in journal (Refereed) Published
Abstract [en]

The predominant forms of arsenic (As) in anoxic and oxic environments are As(III) and As(V), respectively, and the fate of these forms is influenced by interactions with mineral surfaces and organic matter (OM). Interactions between As(V) and OM are believed to occur mainly via iron(Fe)-bridges in ternary Fe–arsenate complexes, but direct evidence for these interactions are scarce. Furthermore, since the speciation of Fe in the presence of organic matter varies as a function of pH and Fe concentration, a central question is how different chemical conditions will affect the As–Fe–OM interactions. In order to answer this, the As(V)–Fe(III)–OM system have been studied under a large range of experimental conditions (6485–67,243 ppm Fe(III) and Fe(III):As(V) ratios of 0.5–20 at pH 3–7), with Suwannee River natural organic matter and Suwannee River fulvic acid as sources of OM, using Fe and As K-edge X-ray absorption spectroscopy (XAS), infrared (IR) spectroscopy and chemical equilibrium modeling. Our collective results showed that interactions in the ternary As(V)–Fe(III)–OM system were strongly influenced by pH, total concentrations and ratios among the reactive species. In particular, the high stability of the Fe(III)–OM complexes exerted a strong control on the speciation. The predominant species identified were mononuclear Fe(III)–OM complexes, Fe(III) (hydr)oxides and FeAsO4 solids. The experimental results also showed that at low concentrations the Fe(III)–OM complexes were sufficiently stable to prevent reaction with arsenate. The chemical equilibrium models developed corroborated the spectroscopic results and indicated that As(V) was distributed over two solid phases, namely FeAsO4(s) and Fe(OH)1.5(AsO4)0.5(s). Thus, neither ternary As(V)–Fe(III)–OM complexes nor As(V) surface complexes on Fe(III) (hydr)oxides were necessary to explain the collective results presented in this study.

National Category
Geochemistry
Identifiers
urn:nbn:se:umu:diva-96841 (URN)10.1016/j.gca.2014.09.036 (DOI)000344945800016 ()
Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2018-06-07Bibliographically approved
Exley, C. & Sjöberg, S. (2014). Silicon species in seawater [Letter to the editor]. Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, 117, 820-821
Open this publication in new window or tab >>Silicon species in seawater
2014 (English)In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 117, p. 820-821Article in journal, Letter (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2014
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-85446 (URN)10.1016/j.saa.2013.09.002 (DOI)000328179900109 ()24113207 (PubMedID)
Available from: 2014-02-04 Created: 2014-02-04 Last updated: 2018-06-08Bibliographically approved
Powell, K. J., Brown, P. L., Byrne, R. H., Gajda, T., Hefter, G., Leuz, A.-K., . . . Wanner, H. (2013). Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH–, Cl–, CO32–, SO42–, and PO43– systems (IUPAC Technical Report). Pure and Applied Chemistry, 85(12), 2249-2311
Open this publication in new window or tab >>Chemical speciation of environmentally significant metals with inorganic ligands. Part 5: The Zn2+ + OH, Cl, CO32–, SO42–, and PO43– systems (IUPAC Technical Report)
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2013 (English)In: Pure and Applied Chemistry, ISSN 0033-4545, E-ISSN 1365-3075, Vol. 85, no 12, p. 2249-2311Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
chemical speciation; environmental chemistry; inorganic ligands; IUPAC Analytical Chemistry Division; stability constants; zinc.
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-85447 (URN)10.1351/PAC-REP-13-06-03 (DOI)000328194000009 ()
Available from: 2014-02-04 Created: 2014-02-04 Last updated: 2018-06-08Bibliographically approved
Viipsi, K., Sjöberg, S., Tõnsuaadu, K. & Shchukarev, A. (2013). Hydroxy- and fluorapatite as sorbents in Cd(II) - Zn(II) multi-component solutions in the absence/presence of EDTA. Journal of Hazardous Materials, 252-253, 91-98
Open this publication in new window or tab >>Hydroxy- and fluorapatite as sorbents in Cd(II) - Zn(II) multi-component solutions in the absence/presence of EDTA
2013 (English)In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 252-253, p. 91-98Article in journal (Refereed) Published
Abstract [en]

Apatites are suitable sorbent materials for contaminated soil and water remediation because of their low solubility and ability to bind toxic metals into their structure. Whereas in soil/water systems different complexing ligands are present, it is important to examine how these ligands affect apatite metal sorption process. The removal of cadmium (Cd) and zinc (Zn) ions from aqueous solutions by hydroxyapatite (HAP) and fluorapatite (FAP) was investigated by batch experiments with and without EDTA being present in the pH range 4 to 11. The surface composition of the solid phases was analysed by X-ray photoelectron spectroscopy (XPS). The surface layer of apatites (AP), according to the (Ca + Cd + Zn):P atomic ratio, remained constant (1.4 ± 0.1) through an ion exchange. The amount of Cd2+ and Zn2+ removed increased with increasing pH. The removed amount of Zn2+ was higher than Cd2+. In the Cd-Zn binary system, competitive sorption reduced the individual removed amounts but the total maximum sorption was approximately constant. In the presence of EDTA, Cd2+ and Zn2+ removal was reduced because of the formation of [CdEDTA]2− and [ZnEDTA]2− in solution. XPS revealed an enrichment of AP surface by Cd2+ and Zn2+ and formation of new surface solid-solution phase with the general composition Ca8.4-xMex(HPO4)1.6(PO4)4.4(OH)0.4.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Apatite, Heavy metals, Sorption, EDTA, XPS
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-66931 (URN)10.1016/j.jhazmat.2013.02.034 (DOI)000320288800012 ()
Available from: 2013-03-07 Created: 2013-03-07 Last updated: 2018-06-08Bibliographically approved
Nelson, H., Sjöberg, S. & Lövgren, L. (2013). Surface complexation modelling of arsenate and copper adsorbed at the goethite/water interface. Applied Geochemistry, 35, 64-74
Open this publication in new window or tab >>Surface complexation modelling of arsenate and copper adsorbed at the goethite/water interface
2013 (English)In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 35, p. 64-74Article in journal (Refereed) Published
Abstract [en]

The co-adsorption of Cu(II) and arsenate onto the surface of goethite has been studied by performing adsorption experiments and potentiometric titrations, and a surface complexation model has been developed to describe the experimental results. Models for the binary systems, Cu-goethite and arsenate-goethite, were acquired separately and the model parameters were then included in the ternary system, together with the solubility products of solid Cu(II) arsenates reported in the literature. The adsorption of Cu(II) was described applying a model in which Cu(II) forms bidentate bridging mono- and binuclear surface complexes. According to recent interpretations of ATR-FTIR and EXAFS data the arsenate ions are assumed to be coordinated in a monodentate fashion to singly coordinated hydroxyl groups at the surface, and hydrogen-bonded to neighbouring triply coordinated surface oxide sites. In the case of co-adsorption of Cu(II) and arsenate, the adsorption could not be predicted by applying the combined model from the two binary systems. Two ternary Cu(II)-arsenate-goethite surface complexes must be included, one complex in which an arsenate ion is coordinating to surface Fe(III) (≡FeOAsO3Cu0.5-) and one complex in which arsenate is bound to the surface by coordinating to an adsorbed Cu(II) ion (≡(Fe3OFeOH)Cu2(OH)2HAsO41-). No solid Cu (II) arsenate phases were formed under the experimental conditions in the present study. From constructed predominance area diagrams, the significance of adsorption and precipitation processes are discussed. Furthermore, calculated solubility of Cu(II) and As(V) is used to indicate optimum conditions for the cleaning of contaminated natural waters.

Place, publisher, year, edition, pages
Oxford: Elsevier, 2013
Keywords
initio molecular geometries, solid solution interface, alpha-FeOOH, exafs spectroscopy, aqueous solution, oxide minerals, adsorption, (hydr)oxides, speciation, water
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-52960 (URN)10.1016/j.apgeochem.2013.03.007 (DOI)000322065800008 ()
Available from: 2012-03-07 Created: 2012-03-07 Last updated: 2018-06-08Bibliographically approved
Lützenkirchen, J., Preocanin, T., Bauer, A., Metz, V. & Sjöberg, S. (2012). Net surface proton excess of smectites obtained from a combination of potentiometric acid–base, mass and electrolyte titrations. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 412, 11-19
Open this publication in new window or tab >>Net surface proton excess of smectites obtained from a combination of potentiometric acid–base, mass and electrolyte titrations
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2012 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 412, p. 11-19Article in journal (Refereed) Published
Abstract [en]

Difficulties in the determination of absolute net proton and hydroxide surface consumption of clays from potentiometric acid–base titration are due to the fact that unlike for oxide minerals curves of relative proton related surface charge densities for several electrolyte concentrations are shifted and do not exhibit a common intersection point. Moreover, the isoelectric point (pHiep) of clays is usually in the acidic region and differs from the point of zero net proton and hydroxide consumption (pHncph). As a simple experimental procedure for clays we propose to perform potentiometric mass titrations in combination with potentiometric electrolyte titrations for the determination of the pHncph at different electrolyte concentration.

Potentiometric acid–base titrations (pH of the suspension monitored as a function of the volume of added acid or base) and mass titrations (pH of the suspension monitored as a function of the mass concentration of added solid) of two pretreated clay samples (SAz-1 and SWy-2) were carried out in sodium chloride media. Due to the pre-treatment samples SAz-1 and SWy-2 contain ≥92 wt.% montmorillonitic smectite. The mass titrations were supplemented by electrolyte titrations (pH of the suspension of high mass concentration measured as a function of electrolyte concentration). The observed decrease in the mass-titration endpoint pH due to additional salt clearly corroborates previous reports that the point of zero net proton and hydroxide consumption of smectites depends on the electrolyte concentration.

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
Mass titration, Montomorillonite, Smectite, Adsorption, Acid–base properties, Surface charge
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-59585 (URN)10.1016/j.colsurfa.2012.06.024 (DOI)
Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2018-06-08Bibliographically approved
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