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Electrochemical generation of polysulfide liquor and sodium hydroxide from white liquor
KTH, Superseded Departments, Chemical Engineering and Technology.ORCID iD: 0000-0002-9392-9059
1998 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 1998. , 73 p.
Series
Trita-KET, ISSN 1104-3466 ; 80
Keyword [en]
White liquor, Kraft pulping, Polysulfides, Sodium hydroxide, Electrolysis, Autocatalysis, Cation-selective membranes, DSA, Nickel, Graphite
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-2613ISBN: 99-2513020-4 OAI: oai:DiVA.org:kth-2613DiVA: diva2:8259
Public defence
1998-02-20, 00:00 (English)
Note
QC 20100518Available from: 2000-01-01 Created: 2000-01-01 Last updated: 2010-05-18Bibliographically approved
List of papers
1. UV characterization of sulphide-polysulphide solutions and its application for process monitoring in the electrochemical production of polysulphides
Open this publication in new window or tab >>UV characterization of sulphide-polysulphide solutions and its application for process monitoring in the electrochemical production of polysulphides
1996 (English)In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 22, no 6, J187-J191 p.Article in journal (Refereed) Published
Abstract [en]

The UV spectral characteristics of some sulphur species of relevance for the electrochemical production of polysulphides have been studies. It was found that an isosbestic point exists in the hydrogen sulphide ion-polysulphide solution. The absorption at this point (249 nm) is proportional to the total sulphur concentration in the solution. The investigation also shows that the spectrum of a polysulphide solution can be regarded simply as the sum of contributions from charges hydrogen sulphide ion and zero-valent sulphur in polysulphides although a complicated equilibrium distribution of different species exists in the polysulphide solution. The spectrum provides enough information for the measurement of these forms of sulphur. Based on spectrophotometric measurements, a simple monitoring for changed hydrogen sulphide ion and polysulphide excess sulphur in the process liquor can be realized.

Keyword
spectroscopy, photometry, ultraviolet spectra, electrochemistry, oxidation, sulfides, polysulfides, sulfur, hydrogen sulfide, production, POLYSULFIDE IONS
Identifiers
urn:nbn:se:kth:diva-12871 (URN)A1996UR40800001 ()
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2010-05-18Bibliographically approved
2. Spectrophotometric in-line monitoring of the electrochemical production of polysulfides using an ATR-probe
Open this publication in new window or tab >>Spectrophotometric in-line monitoring of the electrochemical production of polysulfides using an ATR-probe
1998 (English)In: Process control and quality, ISSN 0924-3089, E-ISSN 1568-5667, Vol. 11, no 2, 153-159 p.Article in journal (Refereed) Published
Abstract [en]

With an ATR-probe For the UV-vis range it is possible to apply spectrophotometry to very concentrated process liquors without dilution. In this paper the application of a new ATR-probe to the monitoring of sulfur species during an electrochemical process for production of polysulfides is presented. In this system, the temperature and the total salt concentration are relatively constant. A linear relation exists between the ATR-probe response and the concentration of adsorbing species. Therefore, the process can be followed by simple monitoring of a few wavelengths. The ATR-probe was easily implemented and showed no signs of deterioration in the hot strongly alkaline medium. Temperature has a significant effect on measurement with ATR-probes. Other factors that might also affect the measurements using an ATR-probe an briefly discussed.

Keyword
sulfide, polysulfide excess sulfur, ATR-probe, UV-vis, in-line, process monitoring, electrochemical oxidation, SODIUM-HYDROXIDE, LIQUOR, CELL
Identifiers
urn:nbn:se:kth:diva-12873 (URN)000076338000007 ()
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2010-05-18Bibliographically approved
3. Electrochemical production of polysulfides and sodium hydroxide from white liquor .1. Experiments with rotating disc and ring-disc electrodes
Open this publication in new window or tab >>Electrochemical production of polysulfides and sodium hydroxide from white liquor .1. Experiments with rotating disc and ring-disc electrodes
1997 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 27, no 5, 507-518 p.Article in journal (Refereed) Published
Abstract [en]

Electrochemical oxidation of white liquor in a membrane cell is a process of great potential for the pulp and paper industry. The process produces polysulfide-containing white liquor in the anode chamber, and pure sodium hydroxide solution in the cathode chamber. The anode reaction has been investigated using cyclic voltammetry at temperatures between 25 and 90 degrees C on rotating disc and ring-disc electrodes. It was further investigated using chronoamperometry on rotating disc electrodes at 90 degrees C. The experiments, which were mainly run in dilute alkaline sulfide solutions, using platinum electrodes, show that the electrochemical production of polysulfide ions, at lower anode potentials (-0.1 to +0.1 V vs SCE), proceeds via formation of elemental sulfur on the electrode surface. The sulfur is dissolved by hydrosulfide and polysulfide ions producing (longer-chain) polysulfide ions. The rate of dissolution, and thus the overall reaction rate, increases strongly with temperature. Polysulfide ions have an autocatalytic effect on the anode reaction due to their ability to dissolve adsorbed sulfur. At higher anode potentials (greater than or equal to 0.2 V vs SCE), a change of reaction mechanism is observed. In this region the reaction rate depends on electrode potential and is not catalysed by polysulfide ions.

Keyword
HYDROGEN-SULFIDE CONVERSION, PLATINUM-ELECTRODE, GOLD ELECTRODES, HYDROSULFIDE IONS, REDOX REACTIONS, SULFUR, OXIDATION, SYSTEM, SPECTROSCOPY, RADIOTRACER
Identifiers
urn:nbn:se:kth:diva-12874 (URN)A1997WX63100002 ()
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2010-05-18Bibliographically approved
4. Electrochemical production of polysulfides and sodium hydroxide from while liquor .2. Electrolysis in a laboratory scale flow cell
Open this publication in new window or tab >>Electrochemical production of polysulfides and sodium hydroxide from while liquor .2. Electrolysis in a laboratory scale flow cell
1997 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 27, no 5, 519-528 p.Article in journal (Refereed) Published
Abstract [en]

Electrochemical production of polysulfide-containing white liquor and pure sodium hydroxide solution was investigated at 90 degrees C in a laboratory scale flow cell. A mixed iridium-tantalum oxide coated titanium electrode was used as the anode and the two electrolyte compartments were separated by a cation-exchange membrane. The process was demonstrated at current densities up to 5 kA m(-2), resulting in high current efficiencies for both products. The previously reported autocatalytic effect of polysulfide ions was confirmed, and its technical implications on the use of three-dimensional electrodes were demonstrated and discussed. The current efficiency was found to depend strongly on the degree of conversion of sulfur(-II) to sulfur(0). The anode material showed favourable properties, with respect to activity and selectivity, but suffered from limited durability.

Identifiers
urn:nbn:se:kth:diva-12875 (URN)A1997WX63100003 ()
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2010-05-18Bibliographically approved
5. Nickel as anode material for the electrochemical production of polysulfides in white liquor
Open this publication in new window or tab >>Nickel as anode material for the electrochemical production of polysulfides in white liquor
1999 (English)In: Journal of New Materials for Electrochemical Systems, ISSN 1480-2422, Vol. 2, no 1, 11-18 p.Article in journal (Refereed) Published
Abstract [en]

This paper is concerned with new anode materials for the electrochemical oxidation of white liquor. This electrosynthesis process is run in a membrane cell where polysulfide ions are produced in the white liquor of the anode chamber, while a pure sodium hydroxide solution is generated in the cathode chamber: If the noble metal oxide coated anodes that were used in a previous investigation could be successfully replaced by nickel, important reductions in investment costs would be possible. The stability and catalytic activity of nickel as anode material were investigated using cyclic voltammetry and chronoamperometry on rotating disc electrodes, combined with surface analysis. Furthermore, porous nickel was tested in a flow cell, with galvanostatic electrolysis. The results show that nickel has good activity for sulfide oxidation, but a nickel oxide/sulfide surface layer is formed which deactivates the electrode at E greater than or equal to -0.2 V, probably due to the increasing proportion of poorly conducting Ni(II) oxide. Carbon precipitation, and peeling of a thin film of the metal were observed with SEM. High current efficiency and an overpotential of less than 0.2 V were obtained with a porous nickel electrode at a geometric current density of 3 kA m(-2). Corrosion did not appear to be a problem, and nickel should also be suitable as substrate material for more active anode coatings.

Keyword
electrolysis, white liquor, polysulfides, anode material, nickel, SODIUM-HYDROXIDE, ELECTRODES, SULFIDE
Identifiers
urn:nbn:se:kth:diva-12876 (URN)000085276100002 ()
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2010-05-18Bibliographically approved
6. Graphite as anode material for the electrochemical production of polysulfide ions in white liquor
Open this publication in new window or tab >>Graphite as anode material for the electrochemical production of polysulfide ions in white liquor
1999 (English)In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 29, no 4, 521-524 p.Article in journal (Refereed) Published
Keyword
electrolysis, graphite, packed bed electrode, polysulfide ions, white liquor, SODIUM-HYDROXIDE, SULFIDE
Identifiers
urn:nbn:se:kth:diva-12877 (URN)000080968500015 ()
Note
QC 20100518Available from: 2010-05-18 Created: 2010-05-18 Last updated: 2010-05-18Bibliographically approved

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