Removal Of Elemental Sulfur Research Articles

Application of Highly Selective Adsorbent in the Removal of Elemental Sulfur and Other Corrosive Sulfur Compounds From Mineral Insulating Oils

The presence of corrosive sulfur in the oil increases the risks of power transformer failures. This is very pronounced in the case of the presence of elemental sulfur (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> ) in the oil a compound found to be highly reactive to metals, especially to silver at lower operating temperatures causing formation of conductive silver sulfide deposits on the contacts of on-load tap changers. Highly selective adsorbent (HSA) as new mesoporous material is synthesized in the novel procedure to be applied in the removal of corrosive sulfur compounds from the oil. The removal of corrosive sulfur compounds by HSA is obtained by chemical reaction, i.e., chemisorption. The procedure for the preparation of HSA consists of deposition of silver ions on the silicon dioxide support. Both compounds added in well-defined and optimal concentration range are necessary to produce adsorbent of high efficiency in the removal of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> and other corrosive sulfur compounds and to obtain good oil properties after treatment. HSA is characterized by nitrogen adsorption–desorption isotherms to define specific surface area, particle size distribution, and porosity. Since the efficiency of conventional adsorbents is found to be lowest in the case of elemental sulfur, among all corrosive sulfur compounds, the efficiency of HSA application in the removal of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> is verified on lab-scale system, pilot-scale system, and on-site oil treatment on 35-kV power transformer. Adsorption kinetic study is performed in order to better understand the mechanism of sorption process and potential rate-controlling steps. The pseudo-second-order model adequately fits the S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sub> kinetic data confirming that chemisorption is the rate-limiting step.

Regeneration and sulfur recovery of Lanxess Lewatit AF 5 catalyst from the acidic Albion leaching process using toluene and tetrachloroethylene as organic solvents

The removal of elemental sulfur from the final leach residue produced during the atmospheric oxidative leaching of chalcopyrite concentrates is both a technical and an economic challenge. Lanxess Lewatit® AF 5 catalyst is a promising candidate material that can collect this elemental sulfur during the leaching process. However, to be cost-effective it is necessary to develop methods to regenerate and recycle the AF 5. In the present research, toluene and tetrachloroethylene were studied as potential organic solvents for the removal of the sulfur from the sulfur loaded AF 5. Also, the recovery of elemental sulfur from the resulting liquor was investigated. The effects of temperature, time and AF 5 to solvent ratio on sulfur removal from the sulfur loaded AF 5 were examined. The optimum desulfurization conditions were 100 °C for toluene and 110 °C for tetrachloroethylene for an AF 5 to solvent ratio of 1:50 and a processing time of 120 min. For toluene and tetrachloroethylene, the sulfur removals were 89.8% and 88.1%, respectively. Toluene was considered to be the most promising solvent due to its higher sulfur removal efficiency and a reduced effect on the behavior of the recycled AF 5 in the leaching process. After three consecutive leaching and regeneration cycles the sulfur absorption capacity and the copper and iron leaching recoveries were essentially unchanged. Copper and iron recoveries of greater than 95% and greater than 80%, respectively, were achieved with the recycled AF 5.

Effect of gas-liquid flow pattern and microbial diversity analysis of a pilot-scale biotrickling filter for anoxic biogas desulfurization

Hydrogen sulfide removal from biogas was studied under anoxic conditions in a pilot-scale biotrickling filter operated under counter- and co-current gas-liquid flow patterns. The best performance was found under counter-current conditions (maximum elimination capacity of 140 gS m−3 h−1). Nevertheless, switching conditions between co- and counter-current flow lead to a favorable redistribution of biomass and elemental sulfur along the bed height. Moreover, elemental sulfur was oxidized to sulfate when the feeding biogas was disconnected and the supply of nitrate (electron acceptor) was maintained. Removal of elemental sulfur was important to prevent clogging in the packed bed and, thereby, to increase the lifespan of the packed bed between maintenance episodes. The larger elemental sulfur removal rate during shutdowns was 59.1 gS m−3 h−1. Tag-encoded FLX amplicon pyrosequencing was used to study the diversity of bacteria under co-current flow pattern with liquid recirculation and counter-current mode with a single-pass flow of the liquid phase. The main desulfurizing bacteria were Sedimenticola while significant role of heterotrophic, opportunistic species was envisaged. Remarkable differences between communities were found when a single-pass flow of industrial water was fed to the biotrickling filter.

Study on the formation, determination, and removal of elemental sulfur in ultra-low sulfur gas oil

The question as to the formation of elemental sulfur in petroleum has never been definitely settled, although there are many references in the literature to the presence of elemental sulfur in distillates. In connection with studies on sulfur compounds in petroleum distillates, the presence and behavior of elemental sulfur in gas oil, especially in ultra-low sulfur gas oil are important. A rapid and accurate method for the analysis of elemental sulfur by GC–PFPD was developed and a series of experiments was carried out to clarify the formation mechanism of elemental sulfur. The results showed that (NH4)2Sn was found to be easily oxidized to free sulfur when contacted with air and the oxidation of ammonium polysulfide was the main formation mechanism of elemental sulfur in the hydrotreating of gas oil. It was revealed that nitrogen-containing molecules in the oil feed and NH4+ contained in the HDS catalyst can result in the formation of (NH4)2Sn. A method with high efficiency and selectivity to remove elemental sulfur from hydrotreated gas oil by Na2S washing was developed for analysis purpose.

Bio-reduction of elemental sulfur to increase the gold recovery from enargite

The mineral enargite can be of interest to the mining industry as a copper and precious metal source. The mineral has a refractory character towards oxidation, which is attributed to the formation of elemental sulfur that seals off the mineral surface. In this study it was investigated whether elemental sulfur resulting from oxidation during industrial milling can be converted into hydrogen sulfide via bio-reduction. The removal of elemental sulfur in this process will clean the mineral surfaces for subsequent oxidation, prevent interference with the gold extraction process and reduce consumption of chemicals such as cyanide.HPLC analysis confirmed that indeed elemental sulfur was formed during industrial milling of an enargite–pyrite gold concentrate. Removal of elemental sulfur via bio-reduction was successful and improved the gold leachability from 48.9% to 69.6%. The combination of milling and bio-reduction was therefore concluded to be a possible route to liberate metals. Further research is necessary to investigate if the enargite to sulfur conversion can be improved to obtain economically satisfactory (>90%) gold recoveries.

Interaction of copper with fatty acids in Soxhlet extraction and its influence

Treatment with metallic copper for the removal of elemental sulfur from bitumen extracted from sedimentary rocks or petroleum is the most widely used method. Little attention has been paid, however, to its disadvantages. It was observed that copper can interact with some polar organic substances during conventional sulfur removal, which can strongly influence the quantitative and qualitative determination of bitumen, as has been confirmed by interaction of long-chain fatty acids with copper. The copper soap generated was analyzed by element analysis, inductively coupled plasma optical emission spectrometry (ICP-OES), thermal analysis (TG-DSC) and Fourier Transform Infrared spectroscopy (FTIR). Mechanism of the interaction was investigated and elucidated. Our experimental results would necessitate improvement of the present method for sulfur removal and/or a search for a new one.

Determination of pesticides associated with suspended sediments in the San Joaquin River, California, USA, using gas chromatography‐ion trap mass spectrometry

An analytical method useful for the quantification of a range of pesticides and pesticide degradation products associated with suspended sediments was developed by testing a variety of extraction and cleanup schemes. The final extraction and cleanup methods chosen for use are suitable for the quantification of the listed pesticides using gas chromatography‐ion trap mass spectrometry and the removal of interfering coextractable organic material found in suspended sediments. Methylene chloride extraction followed by Florisil cleanup proved most effective for separation of coextractives from the pesticide analytes. Removal of elemental sulfur was accomplished with tetrabutylammonium hydrogen sulfite. The suitability of the method for the analysis of a variety of pesticides was evaluated, and the method detection limits (MDLs) were determined (0.1–6.0 ng/g dry weight of sediment) for 21 compounds. Recovery of pesticides dried onto natural sediments averaged 63%. Analysis of duplicate San Joaquin River suspended‐sediment samples demonstrated the utility of the method for environmental samples with variability between replicate analyses lower than between environmental samples. Eight of 21 pesticides measured were observed at concentrations ranging from the MDL to more than 80 ng/g dry weight of sediment and exhibited significant temporal variability. Sediment‐associated pesticides, therefore, may contribute to the transport of pesticides through aquatic systems and should be studied separately from dissolved pesticides.

Oszillationsphänomene bei der Elektrolyse von Alkalisulfidlösungen an Platinelektroden

The anodic oxidation of alkaline sulfide solutions on a platinum electrode results in a cyclical formation and removal of elemental sulfur. The formation and removal of sulfur is associated with regular current-potential oscillations. At low potentials (>−0.1 V), a surface layer of platinum sulfide is formed. This process can be compared with the passivation of an active metal. The sulfide film inhibits the expected oxidation of sulfide ions and the deposition of elemental sulfur. The passivation of the platinum electrode is accompanied by an increase of the potential (∼1.5 V) and a decrease of the current (∼0 mA). However, the sulfide film can be removed by anodic oxidation to platinum oxide at these higher potentials (>1 V). Now, sulfur formation is possible on the oxide surface layer. The current increases, too, but the potential decreases (∼0.7 V). At lower potentials (<1 V), the oxide film is slowly removed by formation of a passivating platinum sulfide layer; the potential increases (<1.5 V) and the current decreases (∼0 mA). The thick sulfur deposition is disolved by formation of a yellow polysulfide solution until the platinum surface appears, the sulfide film is oxidized, and a new oscillation cycle begins.

97/00152 Dynamic mixer process with continuous caustic phase for removal of elemental sulfur from organic fluids

97/00152 Dynamic mixer process with continuous caustic phase for removal of elemental sulfur from organic fluids

Determination of organophosphorus pesticides in sediment from Alexandria‐Coast, Egypt

Several homogenized spiked samples are subjected to the different analysis methods. Soxhlet extraction with acetone gives best recovery (96.0%). The concentrated extract is cleaned up by florisil chromatography and analyzed by capillary gas chromatography using a nitrogen‐phosphorus detector. The influence of a number of variables on the extraction efficiency and interference problems such as the solvent extract, and removal of elemental sulfur are discussed. Seven Samples are collected within a short distance from Abu Quir bay, and three samples which were collected from Diffisho drain in front of a pesticide factory. The most important phosphorus compounds were chloropyrifos 86.4 ppm at Abu Quir and parathion at Diffisho drain 157.0 ppm.

An advantageous reagent for the removal of elemental sulfur from environmental samples

Polymeric triphenylphosphine is introduced as an efficient reagent for the removal of elemental sulfur from environmental samples. It is compared with several traditional reagents, particularly heavy metals. For all reagents, ultrasonication was much preferable to stirring or shaking the reaction solution. Advantages of the new reagent include quantitative reaction with sulfur, few side-reactions with analytes, ease of handling and non-hazardous products. The used reagent can be regenerated and reused.

A study of the extraction conditions of sedimentary humic acids to estimate their true in situ sulfur content

Precautions are necessary to extract the humic acid fraction from anoxic marine sediments without artificially raising its sulfur content. Elemental sulfur and free sulfides must be removed from the sample before proceeding with alkaline extraction. Also, the extent of sulfur contamination from coextracted pyrite and greigite must be estimated. In my procedure the sediment samples were freeze‐dried immediately after their extrusion under a nitrogen atmosphere onboard ship. Humic substances were extracted by 0.5 N NaOH after removal of elemental sulfur from the dried sediment with benzene, which also removed the lipid materials. Humic acids were precipitated from the alkaline solutions by acidification to pH 2 with HCl. The formation of elemental sulfur by the oxidation of H2S produced by decomposition of coextracted acid‐volatile sulfides was minimized by precipitating humic acids under a vigorous stream of nitrogen. Precipitates were freeze‐dried and their elemental composition determined. Subsequently, samples were treated with a freshly prepared CrCl2 solution, and the amount of H2S produced was measured to estimate the sulfur contribution of coextracted pyrite and greigite.

An auger and eels study of iron sulfide (FeS 2, F 7S 8 and FeS) surfaces

Auger and electron energy loss spectroscopy (EELS) were used to study the iron sulfide (FeS 2, Fe 7S 8 and FeS) surfaces. A characteristic M 2.3VV Auger doublet with a separation of 5.0 eV was observed on the Sulfides. An assignment of the electron energy loss peaks was made based on the energy dependence of the loss peaks and previous photoemission results. In addition to interband transitions and core level excitations, two volume plasmons and two surface plasmons were tentatively identified. The effect of argon ion bombardment was studied by monitoring the changes observed in the EELS spectra with sputtering time. Peaks with strong iron and sulfur character were observed. Heating the damaged sulfides results in reconstruction of the sulfide surfaces through migration of sulfur. For the undamaged sulfides, changes in the EELS spectra are due to variations in surface composition and crystallographic structure. For all the sulfides under study, some evidence of sulfur segregation to the surface was observed. Finally, the reactions of the sulfides with simple gases, such as H 2, CO and O 2 were studied. Heating with H 2 results in removal of elemental sulfur from the surface. CO reacts with Fe on the damage FeS 2 and Fe 7S 8 surfaces. The reaction products can be removed with H 2. All the sulfides are easily oxidized by oxygen to form α-Fe 2O 3. The reactions of H 2S and CO with clean Fe surfaces were also studied using EELS.

Removal of Elemental Sulfur from Environmental Samples.

Removal of Elemental Sulfur from Environmental Samples.

Removal of Elemental Sulfur from Hydrocarbon Fractions

Removal of Elemental Sulfur from Hydrocarbon Fractions