20 research outputs found
Sulfur analysis of Bolu-Mengen lignite before and after microbiological treatment using reductive pyrolysis and gas chromatography/mass spectrometry
Atmospheric pressure-temperature programmed reduction coupled with on-line mass spectrometry (AP-TPR/MS) is used for the first time on microbiologically treated coal samples as a technique to monitor the degree of desulfurization of the various sulfur functionalities. The experimental procedure enables the identification of both organic and inorganic sulfur species present in the coal matrix. A better insight in the degradation of the coal matrix and the accompanying processes during the AP-TPR experiment is obtained by a quantitative differentiation of the sulfur. The determination of the sulfur balance for the reductive pyrolysis gives an overview of the side reactions and their relative contribution in the total process. The volatile sulfur species are unambiguously identified using AP-TPR off-line coupled with gas chromatography/mass spectrometry (GC/MS). In this way, fundamental mechanisms and reactions that occur during the reductive pyrolysis could be quantified, explaining the differences in AP-TPR recoveries. Therefore, this study gives a clearer view on the possibilities and limitations of AP-TPR as a technique to monitor sulfur functionalities in coal
MECHANISM OF OXIDATION OF REDUCED SULPHUR COMPOUNDS BY THIOBACILLI
The mechanism of transport sulphur both outside and inside the
cells was studied. Macroroentgen structural analysis and electronicmicroscopic
researches showed that the membrane structures of thiobacilli
carry out not only the oxidation function, but the transport
function as well, which consists in the extraction of the formed
sulphur from cell. This mechanism of sulphur deposition develops ac-—
cording to the exocytosis type.
The transport of elemental sulphur inside the cell involves the
surface membrane structures (vesicles), while oxidation of the sulphur
to sulphuric acid takes place on the outer surface of the cytoplasmic
membrane. The vesicles are supposed also to participate in
the primary dissolution of elemental sulphur at the site of contact
of the cells with the mineral.
The study of bacterial oxidation of sulphide minerals has shown
the electrochemical nature of microbiological oxidation of sulphide
minerals, which takes place at the level of its electronic structure.
Pyrite with hole conductivity (with the cation deficit in composition)
is oxidized by means of Thiobacillus ferrooxidans not only
much more intensively, but also continuously as compared to pyrite
with electron conductivity.
Thiobacilli play a leading role in the oxidation of reduced sulphur
compounds under natural conditions. The mechanism of this process
however have not been studied sufficiently well so far. The main
purpose of this work was to study the mechanism of sulphur transport,
when sulphur was deposited or oxidized by thiobacilli, by means
of cytological and cytochemical techniques. We believed that the
mechanism,of sulphur transport either from, or into, the cell must
be closely related to the submicroscopic organization of thiobacill