Various Forms Of Sulfur Research Articles

Analysis of the Formation Mechanism of Hydrogen Sulfide in the 13# Coal Seam of Shaping Coal Mine.

In order to accurately predict the law of occurrence and migration of hydrogen sulfide (H2S) in the underground and effectively solve the problem of excessive concentration of H2S gas, laboratory experiments on the content of various forms of sulfur in coal, sulfur isotopes, thermal evolution history, and coal seam water samples were carried out by applying the theories of coal mine geology, microbiology, and analytical chemistry, and based on the experimental results, the cause of H2S gas was explored. Through the analysis of the geological conditions of the coal seam mined, it can be seen that the coal mine experienced the alternation of marine and continental phases in the process of coal formation and that there was no magma intrusion. The experimental results showed that iron sulfide in coal accounts for 73.25% of the total sulfur, indicating that the coal seam was rich in pyrite. The results of the isotope test showed that the sulfur isotopes in coal samples were all negative, indicating that the sulfur isotope fractionation in coal was large, the loss was serious, and the coal seam was greatly affected by seawater. According to the experimental results of vitrinite reflectance, it can be concluded that the highest temperature during the thermal evolution of the coal seam is 108.12 °C, which has not reached the temperature condition of sulfate thermochemical reduction. Comparing the concentration of acid ions in coal seam water and tap water, it was found that the concentration of SO42- in coal seam water is low, while the concentration of HCO3- is high. According to the experimental results and theoretical analysis, the H2S gas in the high-sulfur coal mine was caused by microbial sulfate reduction. Finally, the transformation path of sulfur in the coal seam was deduced and analyzed. The results showed that sulfur in coal is positively correlated with H2S gas concentration.

APPLICATION OF SULFUR RADICAL ANIONS IN ORGANIC SYNTHESIS. DETERMINATION OF FORMS OF SULFUR

The study of reactions involving sulfur anion radicals in organic synthesis has become an area of active research in the last few years. The role of polysulfide radicals in the electrochemical processes of lithium-sulfur (Li-S) batteries has been particularly discussed. Understanding the pathways of the electrochemical reactions is crucial for improving the performance of Li-S batteries. In order to summarize and analyze the most relevant literature data, the review presents information on the application and study of sulfur anion radicals in organic synthesis and methods for the determination of sulfur forms. We have classified and discussed in detail the spectra of various forms of sulfur in the ultraviolet and visible ranges. The article describes the choice of solvent, the correlation between the properties of solvents, the influence of the nature of the solvent on the absorption band shift of sulfur particles and on the stability of the anion radical, the identification of sulfur forms in the ultraviolet and visible spectrum regions, and the possibility of stabilizing anion radicals by complexation with crown ethers. The absorption bands for S22-, S32-, S52-, S72- strongly overlap with other particles while having lower intensities, leading to different conclusions regarding the distribution of polysulfides and different forms of sulfur in aqueous media. The data presented in the review have an applied meaning, contribute to the understanding of the application of sulfur anion radicals in organic synthesis and can be used for the choice of method for the determination of sulfur forms and solvent. This review article may be of interest to specialists in the field and will help to plan studies on the study of sulfur forms and the interpretation of spectra of different sulfur forms.

Study on influencing factors of Coal Microbial Flotation Desulfurization

This study systematically investigates the influence of various factors on microbial flotation desulfurization of coal, with a particular focus on removing organic sulfur. The parameters examined encompass particle size, pretreatment time, bacteria species, bacterial concentration, forms of sulfur occurrence, ash yield, and coal rank. The study aims to develop a thorough understanding of the desulfurization process and establish a theoretical framework for advancing clean coal technology and efficient coal utilization. Stringent control was maintained over parameters such as particle size, pretreatment time, bacterial species, and bacterial concentration. Various forms of sulfur and coal rank were considered to evaluate their impact on desulfurization. Correlation analysis was conducted to investigate the relationship between ash yield reduction and the extent of desulfurization. Thiobacillus ferrooxidans and Rhodotorula mucilaginosa were employed in the experimental setup to assess their efficacy in microbial flotation desulfurization. The results demonstrate that microbial flotation desulfurization achieved the highest removal efficiency for organic sulfur, reaching 79.65%. Notably, the desulfurization of organic sulfur exhibited an increasing trend with decreasing coal rank. Correlation analysis reveals a positive correlation between ash yield and desulfurization, suggesting that high mineral matter content in coal facilitates microbial flotation desulfurization and enhances biological oxidation. Comparative analysis of single strain and mixed strain experiments revealed varying degrees of improvement in desulfurization extent, with the mixed-bacteria system exhibiting the most effective removal of organic sulfur, which suggests that Rhodotorula mucilaginosa can significantly enhance microbial flotation desulfurization. Overall, this research provides systematic insights into the influence of process conditions and geological factors on coal desulfurization. The study establishes a theoretical foundation for the development of clean coal technology and the efficient utilization of coal resources, contributing to the advancement of environmentally friendly practices in the coal industry.

Exploring the potential of sulphur forms in Northeastern Indian coals: Implications in environmental remediation and heavy metal sensing

The Sampar Coalfield in Northeastern India is a source of plentiful coal reserves, which are burnt for energy production and industrial applications, resulting in the release of pollutants such as sulphur , arsenic, and lead, which are hazardous to the environment and public health. In this work, samples from the Sampar coalfield have been analyzed to understand the origin, distribution, and various forms of sulphur and their ability to detect toxic heavy metals. The total sulphur concentration ranged from 4.31% to 6%, with organic sulphur being the predominant form at 69.21%, followed by pyritic sulphur at 16.49% and sulphate sulphur at 14.28%. With high sulphur content, this coal indicates a marine influence in the peat-forming swamps. The samples have also been examined for petrographic and elemental analysis, which have revealed the presence of vitrinite, liptinite, inertinite, carbon, hydrogen, nitrogen, oxygen, and mineral matter. In addition, the same coal sample has also been used for electrochemical sensing-based detection of toxic heavy metals like arsenic and lead, and the findings indicate an improved efficacy. These results are expected to have significant implications in the development of effective bio-based remediation strategies in the region to mitigate the harmful effects of coal-related pollution.

Geochemical transformations of sulfur in salt lakes (Transbaikalia)

The water column in brackish and saline lakes hosts various forms of sulfur including sulfide (hydrosulfide), elemental, thiosulfate, and sulfate sulfur. The unequal distribution of these reduced sulfur species indicates the presence of two opposing processes - sulfate reduction and oxidation of newly formed hydrogen sulfide. The scale of these processes varies among lakes, resulting in differing proportions of reduced sulfur forms. The bacterial reduction of sulfate ions is confirmed by a significant separation of sulfur isotopes into sulfide and sulfate ions, with the lighter isotope accumulating in the former and heavier isotope in the latter. In most soda, chloride, brackish, and salt lakes, sulfate reduction is the principal process responsible for relatively low sulfate ion content. Additionally, the presence of an oxidizing environment and sulfides in host rocks provide additional sources for sulfates, leading to the formation of sulfate-type lakes. The formation of specific types and subtypes of brackish and salt lakes is determined by processes such as water evaporation, dissolution of aluminosilicates, sulfate reduction, and oxidation of sulfides. The dominance of these processes contributes to the geochemical diversity of lakes.

Transformation of sulfur in coal during rapid pyrolysis at high temperatures

ABSTRACT The Guizhou high-sulfur coal and its demineralized coal were rapidly pyrolyzed in a drop tube furnace under an argon atmosphere at the high temperatures ranging from 700°C to 1200°C. The effects of temperature and minerals on the transformations between various forms of sulfur, including sulphidic sulfur and thiophenic sulfur, were studied using X-ray photoelectron spectroscopy (XPS) during rapid pyrolysis. The total sulfur content was determined by the infrared-red sulfur analyzer (ISA) and confirmed by XPS analysis. The total sulfur retention in chars did not simply decrease with increasing temperature but increased at a specific temperature in both raw coal and demineralized coal. Thiophenic sulfur was the primary sulfur compound found on the char surface during rapid pyrolysis at different temperatures. Sulfur in different forms decomposed and transformed at high temperatures and this was evidenced by the complete decomposition of sulphidic sulfur at 1000°C and the increase of thiophenic sulfur content at 1100°C. These results indicate that other forms of sulfur could transform into thiophenic sulfur.

Preliminaries of the Decay of Metals versus Petroleum Oils

Petroleum oils are predominantly made of various hydrocarbons with trace compounds including corrosive aided compounds that basically known as the salts, organic acids and various forms of sulfur. The scope of the current research was based on the investigations of the effect of salts, organic, elemental sulfur and Mercaptans of crude oils on the corrosion rates of seven different types of ferrous metals that important in the industry of crude oil refining. As the procedure the important corrosive properties of two different selected crude oils and the chemical compositions of the selected ferrous metals were analyzed by the standard instruments and methods. There were determined the corrosion rates of prepared metal coupons from selected ferrous metals with the similar dimensions after certain immersion time periods with respect to both crude oils by the weight loss method while analyzing the corroded metal surfaces through the microscope also simultaneously analyzed the decayed metallic elemental concentrations from metals into crude oils and the variations of initial hardness of the metals. As the foremost outcomes of the existing analysis there were obtained the significantly lower corrosion rates from stainless steels which are having at least 12% of chromium with sufficient amount if nickel, relatively higher corrosive impact from salts especially at the lower temperatures, formations of ferrous sulfides, ferrous oxides, corrosion cracks and pitting corrosion, significantly decay of copper from Monel metal, higher decay of ferrous from some of carbon steels and slight reductions of the initial hardness of metals after the formations of the corrosion on the metal surfaces.

BACTERIAL DESULPHURIZATION OF COALS

The review contains literature data about the amount of various forms of sulfur in coals and its impact on the qualitative characteristics of coal. The technological and environmental problems resulting from the combustion of high-sulfur coals are shown. The problems of coal enrichment are considered and an overview of modern methods for their desulfurization are presented. Particular attention is paid to the biotechnological methods with using microorganisms of various taxonomic groups. Data about the reduction of sulphur content in the coals, mainly pyrite, under the action by representatives of mesophilic and moderately thermophilic acidophilic chemolithotrophic bacteria are given. A comparative analysis of the ability of the bacteria of the genera Pseudomonas, Bacillus, Brevibarterium and others to destroy the sulfur-containing heteroatom included in the structural matrix of coal are else given. The data on the role of heterotrophic bacteria in the oxidation of organic sulfur are shown.

Investigation of transient forms of sulfur during biological treatment of spent caustic

ABSTRACTIn the present study, the production of various transient forms of sulfur during biological oxidation of sulfidic spent caustics under haloalkaline conditions in a stirred tank bioreactor is investigated. Also, the effects of abiotic aeration (chemical oxidation), dissolved oxygen (DO) concentration and sodium concentration on forms of sulfur during biological treatment are demonstrated. Thioalkalivibrio versutus strain was used for sulfide oxidation in spent caustic (SC). The aeration had an important effect on sulfide oxidation and its final products. At DO concentrations above 2 mg l−1, majority of sulfide was oxidized to sulfate. Maximum sulfide removal efficiency (%R) and yield of sulfate production was obtained in Na+ concentration ranging from 0.6 to 2 M. Abiotic aeration, which is the most important factor of production of thiosulfate, resulted in the formation of an undesired product-polysulfide. However, abiotic aeration can be used as a pretreatment to biological treatment. In the bioreactor the removal efficiency was obtained as 82.7% and various forms of sulfur such as polysulfide, biosulfur, thiosulfate and sulfate was observed during biological treatment of SC.

Assessment of the effects of land use pattern on distribution of sulphur fractions in soil

In the present investigation, various forms of sulphur (S) viz., total S, organic S, inorganic S and available S were estimated in soils under four different land uses viz., Rice-rice, rice-green gram, mango orchard and a fallow. Soils samples were taken up to a profile depth of 0.60m at 3 depths i.e. 0-0.20m, 0.20-0.40m and 0.40-0.60m. Thesoils were found to be slightly acidic to moderately acidic in reaction (5.83-6.59), showing an increase along the depth irrespective of the land use pattern. Soil organic carbon (SOC) content (mean 5.5 gkg-1) was found well above the low level of SOC in soils. Calcium carbonate content, bulk density and clay content of soils didn’t maintain any definite pattern along the depth. All forms of S were found to decrease along depth irrespective of the land use patterns. The available S content ranged from 12.2 to 21.4mgkg-1 of soils. The relative preponderance of all the forms of S followed the order: mango orchard> fallow> rice-rice> rice-green gram. On an average organic S and available S fractions constituted 93 and 6 per cent of total S respectively. A correlation matrix revealed that all the forms of S maintained a significant positive correlation with SOC content while a negative correlation with pH of the soils. The results of the study will be useful in managing the different fractions of S in soils in order to maintain its availability well above the critical level.

Investigating the Distribution of Chemical Forms of Sulfur in Prostate Cancer Tissue Using X-ray Absorption Spectroscopy.

The use of synchrotron radiation may shed more light on the study of prostate cancer, one of the leading diseases among men. In the presented study the microbeam setup at the PSI Swiss Light Source combined with fluorescence detected X-ray absorption spectroscopy (XAS) was applied to determine two-dimensional (2D) imaging of distributions of various chemical sulfur forms in prostate cancer tissue sections, since sulfur is considered important and essential in cancer progression. The research focused on prostate tissues obtained during routine prostatectomies on patients suffering from prostate cancer.Our previous studies using μ-XAS point measurements on prostate cancer cell lines showed the differences in fractions of various forms of sulfur between cancerous and non-cancerous cells. Therefore, in this experiment the chosen areas of prostate cancer tissues were scanned to get the full picture of the chemical composition of tissue, which is highly heterogeneous. The incident X-ray beams of energies tuned to spectroscopic features of the near-edge region of sulfur K-edge absorption spectra were used to provide contrast between chemical species presented in the tissue. Next, the relative content of the three main sulfur forms, found in biological systems, was calculated and the results are presented in a form of 2D color maps. These maps are correlated with the microscopic histological image of the scanned area.The main findings show that sulfur occurs in prostate tissue mainly in reduced form. The oxidized form of sulfur is present mostly in prostatic stroma, while sulfur in intermediate oxidation state is present in trace amount.

Study of Chlorophyll Pigments in Beans (Phaseolus vulgaris) in terms Of Heavy Metal Complexation with Various Forms of Sulfur, in Order to Reduce Their Toxicity

In this paper we intended to find the effect of the complexation of heavy metals with various forms of sulfur on the content of chlorophyll pigments in dwarf beans ( Phaseolus vulgaris var. Compressius ellipticus ). The effect of two heavy metals, cadmium and respectively lead, in different concentrations, on the content of chlorophyll pigments in the leaves of beans plantlets, by extracting the pigments by the hot process. These were the variants: V 1 Cd 1mg/l, V 2 Cd 1mg/l + 100mg Cys, V 3 Cd 1mg/l + 100mgK 2 SO 4 , V 4 Cd 50mg/l, V 5 Cd 50mg/l+100mg Cys, V 6 Cd 50mg/l+100mgK 2 SO 4 , V 7 Pb 1mg/l, V 8 Pb 1mg/l+100mg Cys, V 9 Pb 1mg/l+100mg K 2 SO 4 , V 10 Pb 50mg/l, V 11 Pb 50mg/l+100mg Cys, V 12 Pb 50mg/l+100mg K 2 SO 4 , V 13 – control sample. Following the experimental research, we can state that the contents of chlorophyll pigments in leaves is negatively influenced by organic sulfur (cysteine) and positively influenced by inorganic sulfur (K 2 SO 4 ), towards inhibition and, respectively, stimulation. Cysteine inhibits with 7% at high concentration of Cd (50mg/l), and K 2 SO 4 stimulates with 1.2% at the same concentration of Cd. In case of Pb (1 mg/l), cysteine inhibits it with 5%, and inorganic sulfur with 1% less as the control. Inorganic sulfur in combination with high concentration of Pb stimulates the pigments production in leaves with 3% more than the control, and concentrated Cd inhibits it with 15%.

Studies of the correlation between mercury content and the content of various forms of sulfur in Polish hard coals

Similarities concerning the occurrence of mercury and sulfur in coal are the reasons for studying the correlation between mercury content and the content of the various forms of sulfur such as: total sulfur, pyritic sulfur, sulfate sulfur, and organic sulfur. For this purpose a wide range of different coals and rejects were used. Selected samples differed significantly in the content of ash, mercury, sulfur and its various forms. In the examinations, both steam and coking coals were studied. For coking coals, samples of raw coals, clean coals, middling products and rejects derived from coal preparation plants were examined. To verify the correlation a statistical analysis was performed. The Spearman’s rank correlation coefficient and the correlation coefficients R for polynomial functions of degree 1 and 2 were determined.Based on the obtained results, it can be concluded, that mercury occurs in Polish hard coals both in the organic matter and the inorganic constituents. For the organic matter a significant correlation between the content of mercury and the content of total sulfur and organic sulfur was obtained for subset of examined samples characterized by a relatively low ash yield (clean coals derived from the coal cleaning process). In the case of the inorganic constituents a significant correlation between the content of mercury and the content of pyritic sulfur was obtained for the examined subset of samples characterized by a very high ash yield (rejects derived from the coal cleaning process). An analysis of the subsets of samples derived from individual mines showed that the modes of occurrence of mercury in coal were different for various Polish mines. These differences may be explained by the genetic diversity of coal i.e. various diagenetic, coalification and post-diagenetic conditions, including such phenomena as mineralization that post-dates coal formation and magmatic intrusion, etc.In order to explain the mercury and sulfur behavior in the analyzed processes of coal cleaning the percentage share of those elements in rejects in relation to raw coal was also determined. The mercury removal efficiencies recorded for the cleaning process of Polish hard coals ranged from about 33% to as much as 67%.Results of the statistical analyses did not, however, provide necessary evidence allowing for the formulation of final conclusions regarding the modes of occurrence of mercury in Polish coals, its association with sulfur present in coal as well as proportioning of mercury in the processes of coal cleaning. The results did make it possible, though, to identify the major scientific problems, which, if solved by relevant methods (e.g. XRD, SEM, EPMA), will facilitate the understanding of the Hg-modes of occurrence in various Polish hard coals. The results of the statistical analyses will also make it easier to appropriately select samples in order to explain these scientific problems.

Vliv vybraných faktorů pěstování na výnos a obsah dusíkatých látek v zrnu sladovnického ječmene

The objective of the three-year small-plot trial was to assess the effect of the weather of the year, forecrop, variety, form of sulphur (elementary and sulphate) and additional nitrogen fertilising on the yields and the content of N-substances of the malt barley varieties Jersey and Sebastian. The trial was carried out in 2006–2008 at the experimental site of the Mendel University of Agriculture and Forestry in Brno, the Žabčice locality. The Jersey and Sebastian varieties were grown after three different forecrops – winter wheat with ploughed down straw, sugar beet with ploughed down tops and maize for grain with ploughed down straw. The fertilising treatments differed in the form of sulphur (elementary and sulphate) and date of the additional nitrogen fertilising. As the sulphate form we chose ammonium sulphate (40 kg . ha−1 N and 45.6 kg . ha−1 S) and the same amount was supplied in the form of elementary sulphur; nitrogen was in the form of urea. A dose of 30 kg . ha−1 of ammonium nitrate with limestone (ANL) was applied as additional nitrogen fertilising. The results show that the weather conditions of the respective years had an almost 94 % effect on yields. The very strong effect of the weather overshadowed the effect of the forecrop (3.8 %); the effect of the variety was only half that of the forecrop (1.8 %). The form of additionally applied sulphur and nitrogen during cultivation had a relatively little effect on the yields (0.2 %). The forecrop affected the content of N‑substances most of all (47.3 %). The quality of barley grain is markedly dependent on the course of the weather of the year (40.1 %); the effect of the variety on the content of N‑substances was relatively low (1.6 %). Applications of various forms of sulphur had a small effect on the grain quality (0.01 %), while the effect on additional nitrogen fertilising on the content of N-substances was 8.5 %.

The effect of various forms of sulphur and nitrogen on calcium and magnesium content and uptake in spring wheat (Triticum aestivum L.) and cocksfoot (Dactylis glomerata L.)

The study assessed the effect of various forms of sulphur (Na 2 S 2 O 3 , elemental S and Na 2 SO 4 ) and nitrogen (UAN-30, NH 4 NO 3 ) on calcium and magnesium content and uptake in spring wheat and cocksfoot. A two-year pot experiment was conducted on soil material of clayey silt granulometric composition. Before the experiment, the soil was characterized by slight acidity and low content of assimilable forms of phosphorus, potassium, magnesium and sulphur. The results show that the experimental factors caused noticeable variation in the content and uptake of calcium and magnesium in spring wheat and cocksfoot. Among the sulphur fertilizers, the greatest increase in calcium and magnesium content and uptake was produced by application of sodium sulphate. The increase in calcium and magnesium uptake was more marked in the case of plants fertilized with nitrogen in the form of ammonium nitrate. The effect of nitrogen fertilization on the analyzed parameters also depended on the species of plant. Wheat grown in the series with ammonium nitrate was characterized by higher Ca and Mg content and uptake than plants fertilized with nitrogen in the form of liquid UAN 30. Calcium uptake by wheat fertilized with NH4NO3 was on average 15% higher for grain and 9% higher for straw compared to wheat fertilized with UAN 30. As for magnesium, the increase was 24.5% and 18%, respectively. Concerning cocksfoot, fertilization with UAN 30 had a greater affect on content and uptake of the analyzed nutrients than ammonium nitrate.

Innovative Desulfurization Process of Coal Water Slurry under Atmospheric Condition via Sodium Metaborate Electroreduction in the Isolated Slot

This electrochemical reductive desulfurization (ERD) method for coal water slurry (CWS), which was an offshoot of the research Novel Desulfurization Method of Sodium Borohydride Reduction for Coal Water Slurry (Shen, Y. F.; Sun, T. H.; Jia, J. P. Energy Fuels 2011, 25, 2963–2967.), utilized cathodic reduction to change some chemical compounds into strong reducing substances that convert various forms of sulfur (S) in coal into H2S and S2–, thus releasing S from coals. It was an effective way to enhance S removal from coal by adding divalent metal catalysts (Ni2+, Mn2+, etc.). Using the atmospheric conditions of 12 g/L of NaBO2, 3.0 V of electrolytic voltage, 4 h of electrolytic time, 50 g/L of CWS, ≤140 mesh of coal particle size, 1.0 g/L of NaOH, and 1 mM (about 0.13 g/L) of NiCl2 catalyst, the total sulfur (TS) of CWS can be dramatically reduced by 58.5%. The ERD described here was a predominant desulfurization process, such as mild (slight improvement of the combustion characteristics), high desulfuriz...

The effect of applications of various forms of sulfur on the yields and quality of grass forage

The objective of our study was to assess the effect of soil application of sulfur in ammonium sulfate and gypsum and of either soil or foliar application of elemental sulfur on yield of grass forage and its qualitative parameters. The effect of various forms of sulfur on the yields of grass forage and its qualitative parameters was explored in the form of a small plot experiment in the Bohemian-Moravian Uplands in 2004–2006 involving the following variants: 1) sulfur unfertilised control; 2) ammonium sulfate; 3) elemental sulfur; 4) gypsum; 5) foliar elemental sulfur. Sulfurous fertilisers and foliar elemental sulfur were applied to the soil in doses of 40 kg and 8 kg S per ha, respectively. Nitrogen applied in ammonium sulfate was added to all the other variants in the form of ammonium nitrate. Application of the fertilisers was repeated at the beginning of each vegetation season. The stand was cut twice in the course of vegetation. In the harvested biomass we assessed the content of sulfur, nitrogenous substances, and net energy of lactation. The effect of various forms of sulfur on the grass biomass yields was not significant in either of the two cuts. Yields increased after sulfur fertilisation only in the 1st cut, especially after the application of sulfate sulfur and gypsum, and/or after foliar application of elemental sulfur. In the individual years the sulfur content in the biomass gradually increased significantly (0.17–0.23–0.29%). In the first year the sulfur content did not reach the critical deficiency limit (0.2%). Sulfur fertilisation increased the S concentration in grass forage in all the fertilised variants; the highest S content was detected in the variant where gypsum was applied (0.27%). No significant correlation was established between the values of water-soluble sulfur in the soil and the sulfur content in grass forage. Sulfur fertilisation had no significant effect on the N/S ratio, but was the highest in the variant not fertilised with sulfur and the lowest in the gypsum variant. The content of nitrogenous substances and net energy of lactation were significantly the highest after fertilisation with elemental sulfur and was related, among others, to the lowest yields of this variant. Sulfurous fertilisers did not significantly affect the exchangeable soil reaction and the highest content of water-soluble sulfur after the 2nd cut was seen in the gypsum-applied variant.

Transformation of organic and inorganic sulphur in a lignite during pyrolysis: Influence of inherent and added inorganic matter

The transformation of organic and inorganic sulphur during pyrolysis of a Western Australian lignite has been studied using several complimentary techniques. The lignite contains high moisture, oxygen, volatile matter, organic sulphur and inherent inorganic matter. FTIR and solid state 13C TOSS NMR spectroscopic studies revealed that the high oxygen content is attributed to the oxygenated functional groups, which is saturated with organically bonded inherent inorganic matter. Sodium and chlorine are the dominant inorganic matter and present in the form of sodium chloride. TGA-MS studies of the raw lignite showed that SO 2 is the dominant sulphur-bearing gases evolved during the pyrolysis of the raw lignite. The effect of inherent and added inorganics was studied by comparing the amounts of various forms of sulphur retained in the chars of the raw lignite, the acid washed lignite and the acid washed lignite doped with sodium and kaolinite following pyrolysis in a fixed-bed reactor in nitrogen. Inherent inorganic matter was shown to reduce the decomposition of organic sulphur but has little effect on the decomposition of inorganic sulphur. Sodium helps the retention of sulphur in the chars between 400 and 500 °C while kaolinite has a better ability to retain sulphur above 600 °C.

The state of cluster SH and S2- of aconitase during cluster interconversions and removal. A convenient preparation of apoenzyme.

During the interconversion of the various cluster types observed in aconitase ([4Fe-4S]1+,2+, [3Fe-4S]0,1+, cubane, or linear types) and production of apoenzyme, changes int he state of the sulfur ligands (RSH and S2-) are bound to occur. We have attempted to obtain information on such changes by interception of SH groups and/or by analysis of the resulting cluster or apoprotein for various forms of sulfur and enzymatic activity. During cluster interconversions no evidence was obtained for changes in SH titer that could be associated with cluster ligands. We conclude from this that the ligand exchange at the cluster is too rapid to allow trapping even by SH reagents of low Mr. The possibility that released SH becomes buried in the protein structure and unreactive cannot be entirely discounted. On formation of the apoenzyme by oxidation with ferricyanide, four SH groups per molecule became unavailable for reaction with 5,5'-dithiobis(2-nitrobenzoic acid); instead, while the holoenzyme contains no disulfides or S(0), two di- or polysulfides were found in the apoenzyme indicating that, on an average, four SH groups and three of the original four S(2-) ligands are trapped as RS-Sx-SR. In agreement with this conclusion is the fact that the apoenzyme can be reconstituted without addition of S(2-). A convenient preparative procedure for reconstitutable apoenzyme in 75% yield is [3Fe-4S] and [4Fe-4S] clusters with a variety of combinations of iron and sulfur isotopes as required for Mössbauer, resonance Raman, and electron nuclear double resonance studies.

An analytical scheme for determining forms of sulphur in oil shales and associated rocks

An analytical scheme for determining various forms of sulphur in oil shales and associated rocks is presented. Acid-soluble sulphate, sulphur contained in monosulphide and in disulphide minerals, and organically-bound sulphur are all quantitatively recovered as separate fractions. Finely-ground oil-shale samples are treated in an inert atmosphere with 6 M hydrochloric acid to dissolve the acid-soluble sulphate minerals and form H 2S from the decomposition of monosulphide minerals. The acid-soluble sulphate is precipitated as barium sulphate and the H 2S is collected and weighed as silver sulphide. Disulphide minerals in the solid residue from the acid treatment are reduced by an acidified Cr(II) solution in an inert atmosphere, releasing the sulphide as H 2S. The H 2S is collected as silver sulphide. An Eschka fusion oxidizes and solubilizes all sulphur remaining within the Cr(II)-treated residue. This sulphate represents organically-bound sulphur and is collected as barium sulphate. The analytical procedures have been verified by using 57Fe Mössbauer spectroscopy. Good agreement between the chemical and Mössbauer data substantiated the sequential removal of the forms of sulphur and also demonstrated the ability of Mössbauer spectroscopy to determine the absolute quantities of iron present in specific minerals.