Equilibrium of the reaction between dissolved sodium sulfide and biologically produced sulfur

W.E. Kleinjan, A. de Keizer, A.J.H. Janssen

Research output: Contribution to journalArticleAcademicpeer-review

56 Citations (Scopus)

Abstract

The equilibrium of the heterogeneous reaction between dissolved sodium sulfide and biologically produced sulfur particles has been studied. Biologically produced sulfur was obtained from a bioreactor of a hydrogen sulfide removal process in which the dominating organism is Thiobacillus sp. W5. Detailed knowledge of this reaction is essential to understand its effect on the process. The results were compared with the equilibrium of the reaction of sulfide with 'inorganic' elemental sulfur. The equilibrium between dissolved sodium sulfide and biologically produced sulfur particles can be described by an equilibrium constant, Kx, which consists of a weighted sum of constants for polysulfide ions of different chain length, rather than a true single equilibrium constant. For biologically produced sulfur pKx = 9.10 ± 0.08 (21°C) and 9.17 ± 0.09 (35°C) with an average polysulfide chain length x = 4.91 ± 0.32 (21°C) and 4.59 ± 0.31 (35°C). The pKx value for biologically produced sulfur is significantly higher than for reaction of dissolved sodium sulfide with inorganic sulfur (pKx = 8.82; 21°C). This difference is probably caused by the negatively charged polymeric organic layer, which is present on biologically produced sulfur but absent with "inorganic" sulfur. Specific binding of polysulfide ions to the organic layer results in a higher polysulfide concentration at the reaction site compared to the bulk concentration. This results in an apparent decrease of the measured equilibrium constant, Kx.
Original languageEnglish
Pages (from-to)228-237
JournalColloids and Surfaces. B: Biointerfaces
Volume43
Issue number3-4
DOIs
Publication statusPublished - 2005

Keywords

  • polysulfide ions
  • elemental sulfur
  • aqueous-solutions
  • 25-degrees-c
  • globules
  • water

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