umu.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Chemical Processes at the Water-Manganite (γ-MnOOH) Interface
Umeå University, Faculty of Science and Technology, Chemistry.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Kemiska Processer vid gränsytan mellan vatten och manganit (γ-MnOOH) (Swedish)
Abstract [en]

The chemistry of mineral surfaces is of great importance in many different areas including natural processes occurring in oceans, rivers, lakes and soils. Manganese (hydr)oxides are one important group to these natural processes, and the thermodynamically most stable trivalent manganese (hydr)oxide, manganit (γ-MnOOH), is studied in this thesis.

This thesis summarises six papers in which the surface chemistry of synthetic manganite has been investigated with respect to surface acid-base properties, dissolution, and adsorption of Cd(II) and the herbicide N-(phosphonomethyl)glycine (glyphosate, PMG). In these papers, a wide range of analysis techniques were used, including X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), potentiometry, electrophoretic mobility measurements and wet chemical techniques, in order to obtain a more complete understanding of the different processes occurring at the manganite-water interface.

From the combined use of these techniques, a 1-pKa acid-base model was established that is valid at pH>6. The model includes a Na+ interaction with the surface:

=MnOH2+½ --> =MnOH-½ + H+ log β0 (intr.) = -8.20 = -pHiep

=MnOH2+½ + Na+ --> =MnOHNa+½ + H+ log β0 (intr.) = -9.64

At pH<6 the manganite crystals dissolve and disproportionate into pyrolusite (β-MnO2) and Mn(II)-ions in solution according to:

2 γ-MnOOH + 2H+ --> β-MnO2 + Mn2+ + 2H2O log K0 = 7.61 ± 0.10

The adsorption and co-adsorption of Cd(II) and glyphosate at the manganite surface was studied at pH>6. Cd(II) adsorption displays an adsorption edge at pH~8.5. Glyphosate adsorbs over the entire pH range, but the adsorption decreases with increasing pH. When the two substances are co-adsorbed, the adsorption of Cd(II) is increased at low pH but decreased at high pH. The adsorption of glyphosate is increased in the entire pH range in the presence of Cd(II). From XPS, FTIR and EXAFS it was found that glyphosate and Cd(II) form inner sphere complexes. The binary Cd(II)-surface complex is bonded by edge sharing of Mn and Cd octahedra on the (010) plane of manganite. Glyphosate forms inner-sphere complexes through an interaction between the phosphonate group and the manganite surface. The largest fraction of this binary glyphosate complex is protonated throughout the pH range. A ternary surface complex is also present, and its structure is explained as type B ternary surface complex (surface-glyphosate-Cd(II)). The chelating rings between the Cd(II) and glyphosate, found in aqueous complexes, are maintained at the surface, and the ternary complex is bound to the surface through the phosphonate group of the ligand.

Place, publisher, year, edition, pages
2004. , 74 p.
Keyword [en]
Inorganic chemistry, manganite, γ-MnOOH, mineral surface, acid-base properties, adsorption, Cd(II), N-(phosphonomethyl)glycine, glyphosate, PMG, surface complex, dissolution, disproportionation, XPS, EXAFS, infrared spectroscopy, SEM, AFM, potentiometry, electrophoresis
Keyword [sv]
Oorganisk kemi
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-253ISBN: 91-7305-634-0 (print)OAI: oai:DiVA.org:umu-253DiVA: diva2:142825
Public defence
2004-05-19, KB3B1, KBC, Umeå University, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2004-04-29 Created: 2004-04-29 Last updated: 2009-12-04Bibliographically approved
List of papers
1. Characterization of hydrous manganite (γ-MnOOH) surfaces - an XPS study
Open this publication in new window or tab >>Characterization of hydrous manganite (γ-MnOOH) surfaces - an XPS study
2002 In: Surface and Interface Analysis, Vol. 34, 632-636 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-3912 (URN)
Available from: 2004-04-29 Created: 2004-04-29Bibliographically approved
2. Surface Properties of Hydrous Manganite (γ-MnOOH) - A Potentiometric, electroacoustic and XPS study
Open this publication in new window or tab >>Surface Properties of Hydrous Manganite (γ-MnOOH) - A Potentiometric, electroacoustic and XPS study
In: LangmuirArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:umu:diva-3913 (URN)
Available from: 2004-04-29 Created: 2004-04-29Bibliographically approved
3. Low pH Phase Transformation and Proton Promoted Dissolution of Hydrous Manganite (γ-MnOOH)
Open this publication in new window or tab >>Low pH Phase Transformation and Proton Promoted Dissolution of Hydrous Manganite (γ-MnOOH)
(English)Manuscript (Other (popular science, discussion, etc.))
Identifiers
urn:nbn:se:umu:diva-3914 (URN)
Available from: 2004-04-29 Created: 2004-04-29 Last updated: 2009-12-03Bibliographically approved
4. Chemical speciation of N-(phosphonomethyl)glycine in solution and at mineral interfaces
Open this publication in new window or tab >>Chemical speciation of N-(phosphonomethyl)glycine in solution and at mineral interfaces
Show others...
2004 (English)In: Surface and Interface Analysis, ISSN 0142-2421, Vol. 36, no 8, 1074-7 p.Article in journal (Refereed) Published
Abstract [en]

The chemical speciation of the zwitterionic compound N-(phosphonomethyl)glycine (PMG) was studied in solution and at the mineral/water interface at different pH. Results from vacuum techniques such as XPS were compared with previously published conventional batch experiments. It was shown that by keeping the samples frozen during XPS analyses it was possible to keep a water interface. The frozen interface enables studies of the protonation of the nitrogen group which has previously been difficult using XPS. The protonation in frozen solutions was compared with literature data and the differences discussed. Furthermore, the speciation of PMG at the surface of manganite (-MnOOH) and goethite (-FeOOH) was studied. It was found that at least one of the protonation constants for surface-bound PMG differs significantly from the protonation constants in a pure PMG solution. The formation of different surface complexes is discussed together with differences between the sorption capacities of PMG onto the minerals studied.

Keyword
XPS, cryogenics, solid-liquid interface, manganite, goethite, phosphonomethylglycine
Identifiers
urn:nbn:se:umu:diva-14084 (URN)doi:10.1002/sia.1844 (DOI)
Available from: 2007-05-22 Created: 2007-05-22 Last updated: 2011-01-12Bibliographically approved
5. Thermodynamic and spectroscopic studies of cadmium(II)–N-(phosphonomethyl)glycine (PMG) complexes
Open this publication in new window or tab >>Thermodynamic and spectroscopic studies of cadmium(II)–N-(phosphonomethyl)glycine (PMG) complexes
Show others...
2004 (English)In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 357, no 4, 1185-1192 p.Article in journal (Refereed) Published
Abstract [en]

Speciation and equilibria in the H+–Cd2+N-(phosphonomethyl)glycine (PMG, H3L) system have been studied in 0.1 M Na(Cl) medium at 25.0 °C. Formation constants for a series of mononuclear complexes, CdHL, CdL, CdL2 4− and CdL(OH)2− were determined from potentiometric titrations. The structures of the predominating species CdL, and CdL2 4− in solution were investigated using EXAFS and IR spectroscopic techniques. In the 1:1 complex bonds are formed between the Cd(II) ion and all three donor groups (amino, carboxylate, phosphonate) of the PMG molecule resulting in two 5-membered chelate rings. At the remaining three of the corners of the distorted Cd(II) octahedra oxygens were found which are replaced by donor groups of a second PMG molecule in the 1:2 complex. Furthermore, a solid phase consisting of Cd9(PMG)6(H2O)12 · 6H2O crystals was synthesized and the crystal structure was determined. The structure consists of six CdL octahedra connected through a seventh Cd–O octahedron in the centre of the entity, with two additional Cd–O octahedra located at the apices of the unit formed.

Speciation and equilibria in the H+–Cd2+N-(phosphonomethyl)glycine (PMG, H3L) system have been studied using potentiometry, and formation constants for CdHL, CdL, CdL2 4− and CdL(OH)2− were determined. The structures of CdL, and CdL2 4− in solution were investigated using EXAFS and IR spectroscopic techniques. The results indicated chelating PMG molecules forming two 5-membered chelate rings.

Place, publisher, year, edition, pages
Elsevier, 2004
Identifiers
urn:nbn:se:umu:diva-2219 (URN)doi:10.1016/j.ica.2003.10.029 (DOI)
Available from: 2007-04-03 Created: 2007-04-03 Last updated: 2017-12-14Bibliographically approved
6. Co-adsorption of cadmium(II) and glyphosate at the water–manganite (γ-MnOOH) interface
Open this publication in new window or tab >>Co-adsorption of cadmium(II) and glyphosate at the water–manganite (γ-MnOOH) interface
Show others...
2005 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 285, no 2, 493-501 p.Article in journal (Refereed) Published
Abstract [en]

The co-adsorption of Cd(II) and glyphosate (N-(phosphonomethyl)glycine, PMG) at the manganite (γ-MnOOH) surface has been studied in the pH range 6–10 at 25 °C and with 0.1 M Na(Cl) as ionic medium. Batch adsorption experiments, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy were used for the quantitative analysis and the determination of the molecular structure of the surface complexes. The adsorption of Cd(II) and PMG in the ternary Cd(II)–PMG–manganite system was compared with the adsorption in the binary Cd(II)–manganite and PMG–manganite systems. The formation of three inner sphere surface complexes was observed, a ternary Cd(II)–PMG–manganite complex, a binary Cd(II)–manganite complex and a binary PMG–manganite complex. The surface concentration of the ternary complex and the Cd(II)–manganite complex was more or less constant throughout the pH range studied. However, the surface concentration of the binary PMG–manganite complex decreased with increasing pH. The major part of the binary PMG–surface complex was protonated. The ternary surface complex displayed a type B structure (Cd(II)–PMG–manganite). The average Cd–Mn distance obtained from EXAFS (3.26 Å) indicates that the binary and ternary Cd(II)–surface complexes are formed by edge-sharing of Mn and Cd octahedra on the (010) plane of the manganite crystals.

Keyword
N-(phosphonomethyl)glycine, Glyphosate, Manganite, γ-MnOOH, Cadmium, EXAFS, XPS, FTIR, Ternary surface complexes
Identifiers
urn:nbn:se:umu:diva-2220 (URN)doi:10.1016/j.jcis.2004.12.003 (DOI)
Available from: 2007-04-03 Created: 2007-04-03 Last updated: 2017-12-14Bibliographically approved

Open Access in DiVA

fulltext(9723 kB)3468 downloads
File information
File name FULLTEXT01.pdfFile size 9723 kBChecksum SHA-1
2e61f7c90e44f374ae633dc8cf923d6bc67b841bf5ffd6e5c0686bd7bc32c050a4c9581a
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Ramstedt, Madeleine
By organisation
Chemistry
Inorganic Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 3468 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1569 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf