Amount Of Sulfur Research Articles

Characterization of municipal solid waste for effective utilization as an alternative source for clean energy production

Renewable energy resources become an alternative to fossil fuels and help to mitigate the issues relevant to environmental sustainability. Some organic waste materials are harmful to the environment, but they offer a useful bioresource for renewable energy production. In this study, municipal solid waste (MSW) collected from Chattogram City was characterized for its effective utilization of energy production. Proximate analysis showed that the MSW has high ash and moisture content which needs further separation and purification. Elemental analysis reveals the presence of a lower amount of sulfur and nitrogen content. Fourier transform infrared (FTIR) spectroscopy analysis depicted that it has hydrocarbons with some compounds of sulfur and nitrogen. Thermogravimetric analysis (TGA) showed that MSW can be degraded through three stages corresponding to the presence of moisture content, lower hydrocarbons, and higher hydrocarbons. Based on the characterization and subsequent analysis, it can be concluded that municipal solid waste has potential for utilization as an alternative source of energy, after proper separation and purification.

Doping of porous carbons with sulfur and nitrogen markedly enhances their surface activity for formaldehyde removal

The surfaces of phosphoric acid activated carbon, referred to as CG, and steam activated one, referred to as SX, were modified through an introduction of S- and N- groups originated from thiourea. The prepared samples were used for formaldehyde removal at room temperature. Heating at 450, 600 and 950 °C altered both surface chemistry and porosity. The extents of these modifications depended on the type of carbon. Using thiourea as the modifier resulted in an incorporation of significant amounts of nitrogen and sulfur to the carbon matrices. Their speciation depended on the heat treatment conditions. The activity of samples heated at 450 °C was governed by amine groups of thiourea retained on the surface. A further heat treatment converted gradually amine nitrogen into pyridines/pyrroles and quaternary nitrogen, shifting the adsorption mechanism to rather specific interactions than a direct chemical reactivity. Carbons with few times less nitrogen than in their amine-modified counterparts, but in quaternary form and with the small amount of sulfur in thiophenic configurations, regardless the origin, worked as very efficient adsorbents of HCHO. Due to the modification of the carbon matrix electronic structure, resulting in a positive charge on carbon atoms in the vicinity of the heteroatoms incorporated to carbon rings, the density of specific adsorption centers on the surface in larger pores was significantly higher than that in ultramicropores. This markedly contributed to efficient utilization of pores/surface, where heteroatom can exist and where otherwise the dispersive adsorptions forces would be weak, for HCHO removal at ambient conditions.

Failure analysis of the 304SS nut in rural atmosphere

An unexpected cracking of a 304SS nut exposed to a rural atmosphere caused gas leakage. Aiming at identifying the failure cause, this study has conducted crack morphology analysis and corrosion product analysis using X-ray computed tomography, electron backscatter diffraction, and scanning electron microscope. The results revealed that the primary failure is attributed to intergranular corrosion cracking, where corrosion has played a predominant role. Initial corrosion was induced by MnS inclusions and chromium carbides. The application of additional force during re-examination promoted crack propagation. MnS inclusions played an auxiliary role in crack propagation due to the high stress concentration around them. The main contributing factor to the failure is the unqualified material, which contains excessive amounts of carbon and sulfur, significantly reducing the corrosion resistance and toughness. Based on these findings, recommendations for preventing further failures were proposed. This study has provided a failure case in mild environment and demonstrate that failure of 304SS would also occur even if the environment is the rural atmosphere, as long as the material is sensitized.

Failure analysis of eccentric bushings in large gyratory crusher

Shortly after the start-up of the loaded gyratory crusher, a severe failure issue occurred in the eccentric bushing of the crusher. Based on the analysis of working conditions and force, the failure mechanism of the eccentric bushing is studied in detail by combining macroscopic analysis, finite element analysis, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The macroscopic analysis results indicate that the failure of the eccentric bushing occurs at the contact position with the mantle shaft, where strong oxidation takes place. The finite element analysis results show that stress concentration occurs at the contact position between the eccentric bushing and the mantle shaft. Nevertheless, the maximum von Mises stress in the eccentric bushing remains significantly below the material's yield strength. Furthermore, the maximum deformation of the eccentric bushing is minor. Therefore, the failure of eccentric bushings is not caused by insufficient material strength or large deformation. It should be noted that the finite element analysis results show that the minimum clearance δ between the beam bushing and the mantle bushing has a great influence on the contact position between the eccentric bushing and the mantle shaft. SEM and EDS analysis of the undamaged samples indicate the presence of numerous micro-pits on the surface of the eccentric bushing. Meanwhile, a large amount of sulfur and oxygen elements and their chemical compounds are found on the fracture surface, exhibiting local enrichment phenomena. The SEM and EDS analyses conducted on samples around the crack reveal pronounced corrosion and spalling phenomena on the surface of the lead-tin bronze alloy. The comprehensive analysis shows that the failure of the eccentric bushing is mainly due to sulfur contamination, which leads to sulfidation and oxidation under elevated temperature conditions, thus promoting corrosion and corrosion-induced cracking.

Transcription factor OxyR regulates sulfane sulfur removal and L-cysteine biosynthesis in Corynebacterium glutamicum.

Sulfane sulfur, a collective term for hydrogen polysulfide and organic persulfide, often damages cells at high concentrations. Cells can regulate intracellular sulfane sulfur levels through specific mechanisms, but these mechanisms are unclear in Corynebacterium glutamicum. OxyR is a transcription factor capable of sensing oxidative stress and is also responsive to sulfane sulfur. In this study, we found that OxyR functioned directly in regulating sulfane sulfur in C. glutamicum. OxyR binds to the promoter of katA and nrdH and regulates its expression, as revealed via in vitro electrophoretic mobility shift assay analysis, real-time quantitative PCR, and reporting systems. Overexpression of katA and nrdH reduced intracellular sulfane sulfur levels by over 30% and 20% in C. glutamicum, respectively. RNA-sequencing analysis showed that the lack of OxyR downregulated the expression of sulfur assimilation pathway genes and/or sulfur transcription factors, which may reduce the rate of sulfur assimilation. In addition, OxyR also affected the biosynthesis of L-cysteine in C. glutamicum. OxyR overexpression strain Cg-2 accumulated 183 mg/L of L-cysteine, increased by approximately 30% compared with the control (142 mg/L). In summary, OxyR not only regulated sulfane sulfur levels by controlling the expression of katA and nrdH in C. glutamicum but also facilitated the sulfur assimilation and L-cysteine synthesis pathways, providing a potential target for constructing robust cell factories of sulfur-containing amino acids and their derivatives. IMPORTANCE C. glutamicum is an important industrial microorganism used to produce various amino acids. In the production of sulfur-containing amino acids, cells inevitably accumulate a large amount of sulfane sulfur. However, few studies have focused on sulfane sulfur removal in C. glutamicum. In this study, we not only revealed the regulatory mechanism of OxyR on intracellular sulfane sulfur removal but also explored the effects of OxyR on the sulfur assimilation and L-cysteine synthesis pathways in C. glutamicum. This is the first study on the removal of sulfane sulfur in C. glutamicum. These results contribute to the understanding of sulfur regulatory mechanisms and may aid in the future optimization of C. glutamicum for biosynthesis of sulfur-containing amino acids.

Sulfur Interaction and Regeneration of CaMn0.775Ti0.125Mg0.1O2.9-δ Perovskite as Oxygen Carrier during Combustion of Sour Gas in a 500 Wth Chemical Looping Combustion Unit.

In the present study, the performance of a CaMn0.775Ti0.125Mg0.1O2.9-δ perovskite used as an oxygen carrier to burn sour gas with different H2S concentrations (up to 3000 vppm) in a continuous 500 Wth chemical looping combustion (CLC) prototype was investigated. After 29 h of sour gas combustion, the combustion efficiency had dropped by 18% in comparison with the reference test without sulfur addition. The characterization of the used particles of the perovskite confirmed that the presence of sulfur in the fuel gas had a poisonous effect through the formation of undesired compounds, such as CaSO4. The reactivity with CH4 and oxygen uncoupling capacity decreased, which could explain the decrease in the combustion efficiency. Two regeneration processes, one at high temperature (1273 K) and another one at low temperature (773-873 K), were carried out in a batch fluidized bed reactor to remove the amount of sulfur accumulated in the oxygen carrier particles. The detection of appreciable amounts of gaseous sulfur-based compounds (SO2 and H2S) during the experimentation and the postcharacterization results obtained through different techniques such as X-ray diffraction, ultimate analysis, and thermogravimetric analysis confirmed the effectiveness of both processes. Finally, the feasibility of implementation of the regeneration processes in a commercial CLC unit was thoroughly analyzed.

Long-Term Sulfur Tolerance of Solid Oxide Fuel Cells with Alternative Titanate-Based Fuel Electrodes

The future renewable energy system relies on devices capable of energy conversion and storage. Solid oxide fuel cells (SOFCs) convert the chemical energy of a fuel into electricity and heat with high electrical efficiency. The fuel flexibility of SOFCs allows for the use of not only hydrogen, but also C-containing fuels, including biogas and green fuels from power-to-X. Such fuels contain trace amounts of sulfur, either being present from the original source or added for safety reasons as odorant, which causes loss of performance in state-of-the-art (SoA) SOCFs with Ni-based cermet fuel electrodes, due to sulfur adsorption on the Ni. An upstream desulfurization unit mitigates this problem in commercial SOFC-systems, increasing CAPEX and system complexity.Hence, alternative S-tolerant fuel electrode materials are highly desirable. All-ceramic doped strontium titanates perovskite compounds (ABO3) are interesting candidates due to their high electronic conductivity and chemical stability. Among these, La0.4Sr0.4Fe0.03Ni0.03Ti0.94O3 (LSFNT), is particularly interesting, due to its B-site exsolution of electrocatalytically active Fe and Ni nanoparticles under reducing conditions. However, the electrochemical activity from the exsoluted catalyst is not sufficient and integration of additional electrocatalyst by infiltration ensures electrochemical performance comparable to SoA.In this study, the electrochemical performance and sulfur tolerance of three different, electrolyte supported cells are examined: Cell 1 contains a standard Ni/CGO cermet fuel electrode, Cell 2 contains a LSFNT electrode backbone with Ni:CGO electrocatalyst and Cell 3 contains LSFNT electrode backbone with Fe-Ni:CGO electrocatalyst.. Fe is added to the Ni:CGO to investigate if alloy formation on the nanoscale can improve the sulfur tolerance. All the cells contain LSM-YSZ oxygen electrodes. The cells were integrated in a short, 5-cell stack and tested at HEXIS AG. The fuel was a natural gas directly supplied from the grid, pre-reformed in a catalytic partial oxidation (CPOx) unit, where a desulfurization unit was connected or by-passed for determining the sulfur tolerance. The electrochemical performance was investigated for each cell in the stack individually by iV-curves and electrochemical impedance spectroscopy (EIS) with and without the use of an upstream desulfurization unit. This was followed by a durability test for ca. 400 hours with sulfur exposure. While the initial performances with short term exposure to sulfur indicate reversible degradation on both types of infiltrated LSFNT fuel electrodes, Cell 1 with the Ni/CGO cermet fuel electrode experiences loss of performance related to an increase in the Ohmic resistance. Cell 1 together with Cell 2 (LSFNT infiltrated with Ni:CGO) are both stable over several hundred hours of operation in sulfur, whereas accelerated degradation of cell voltage is observed on Cell 3 where Fe is present in the infiltrate. Details on electrochemical behavior during the durability test and origins of degradation will be presented together with a microstructural analysis. Figure 1

Influence of Microstructure on the Sulfur Tolerance of Ceria-Based Anodes in Low Temperature SOFC

Hydrocarbon fuels such as natural gas, propane or biogas commonly contain small amounts of impurities like sulfur which result in a strong degradation of the cell performance in the intensively studied Ni/YSZ cermet anode [1-3]. The sulfur poisons the nickel catalyst and hinders the electrooxidation of hydrogen [2-3].At common SOFC operation temperatures of 700 to 900 °C the polarization resistance of a Ni/CGO fuel electrode is less influenced by sulfur [3-5]. With a modification of the surface by infiltration of Ni and / or ceria nanoparticles the impact can be even reduced [5-6]. The trend to a much lower operating temperature of SOFCs [7-8] even below 600 °C raises the question to what extend the sulfur tolerance of ceria-based fuel electrodes is maintained.In this study we analyze the impact of H2S on the polarization resistance of ceria-based fuel electrodes at operation temperatures around 600 °C. Ni/ceria anodes, differing in their microstructure, are investigated by electrochemical impedance spectroscopy (EIS). The distribution of relaxation times (DRT) analysis is applied to deconvolute the electrochemical processes followed by a complex nonlinear least square approximation to quantify the loss processes and the impact of sulfur amounts of 0.1-3 ppm. Compared to previous results [5] the polarization resistance increases more significantly at 600 °C than at 750 °C. The influence of the microstructure will be discussed in detail.

Alkaline pretreatment of a polymetallic sulfide (Fe-Pb-Mn) ore containing silver increases the efficiency of cyanidation by decreasing elemental sulfur content and by exposing sulfide surfaces

Polymetallic sulfide ores are often not amenable to cyanide leaching due to the presence of several elements and minerals capable of interfering with this process. Thus, various strategies, such as chemical pretreatments, are often studied to improve the efficiency of cyanidation. Beyond the results of such strategies, it is important to understand the changes occurring on the mineral samples during these pretreatments. Herein, an alkaline pretreatment was applied to a silver concentrate (∼8 kg Ag/t) composed of polymetallic sulfides (Fe-Pb-Mn), which increased the silver extraction during subsequent cyanidation from 40% to 80% and decreased the cyanide consumption in half (from approximately 60 to 30 kg NaCN/t). X-ray diffraction (XRD) and ICP-MS indicated that the pretreatment could remove significant amounts of elemental sulfur, which is a known cyanicidal agent. The dissolution of significant amounts of sulfur was confirmed by chemical analysis, which also demonstrated that the dissolution of iron, lead, manganese, and silver were negligible during pretreatment. At surface level, X-ray photoelectron spectroscopy (XPS) demonstrated that the pretreatment exposes fresh sulfide surfaces (e. g. pyrite). In addition, the XPS spectra indicated that the pretreatment facilitated the exposure of clean mineral surfaces. The presence of cleaner surfaces suggested a more uniform and less hindered diffusion of leaching agents through the mineral. Indeed, fitting the extraction data to the shrinking core model showed that pretreated samples featured a nearly ideal diffusion-controlled process, while in the case of untreated samples this fitting was less adequate. During cyanidation of both untreated and pretreated samples, lead build-up was detected on the surface (readsorption), which suggested that this phenomenon does not affect the efficiency of a leaching process. This study highlights the importance of combining bulk analytical methods with surface-sensitive techniques to obtain a more complete understanding of leaching processes.

Determination of Total Sulfur Content in Fuels: A Comprehensive and Metrological Review Focusing on Compliance Assessment.

Sulfur-containing compounds are naturally found in crude oil, and they can be partially removed during the refining process. The wide use of fossil fuels has a significant contribution to sulfur emissions into the atmosphere, and Governments are striving to reduce the amount of the fuels by environmental regulations. The reduction of sulfur levels in diesel and other transportation fuels is beneficial from economic and environmental points, but meeting this standard represents a major operational and economic challenge for the oil and gas industry. Quantitative measurement of the sulfur amount must be taken along the oil refining chains guided by standards of measurement and recommended analytical methods such as various American Society for Testing and Materials methods (ASTM D2622, ASTM D5453, ASTM D7039, and ASTM D7220). Advancement in the refining processes and environmental regulations also require reliable measurements and well-defined criteria for compliance assessment. This work presented a brief review of the ASTM Standards used in the laboratories of the Brazilian oil and gas industry to determine the total sulfur content in fuels. We also presented an approach based on the reproducibility of the measurement methods and the guard band concept to evaluate the conformity statement.

Separation of sulfur compounds from petroleum using hydrodesulfurization method to reduce SO2 emission: Process optimization and validation

Preparation of clean fuels from petroleum need decent removal of sulfur compounds from the petroleum which can be done using the well-known hydrodesulfurization (HDS) method. The removal of sulfur compounds from crude oil would be essential in order to control the emission of gas pollutants such as SO2. However, due to the complexity of the sulfur separation process, predictive modeling and computations are required to improve the separation efficiency. In this research, we have collected some experimental data for optimization of separation process. Each data point has four input features: temperature, pressure, initial sulfur content, and dose. On the other hand, the outputs included left sulfur amount in the feed, value of SO2 emission, and process cost ($). Adaboost technique integrated with three core models of DT, Lasso, and KNN is used for modeling. The models are tuned using LOA method on the available dataset, thereby the optimum models’ parameters were determined for the best fitting. For sulfur concentration and emission parameters, the ADA-DT technique is the best one among other methods, but for the HDS cost, the ADA-LASSO framework works the best. Using these models, the R2-score for outputs is, respectively, 0.940, 0.923, and 0.999. This work makes significant contributions by providing accurate predictive models that would enhance the understanding and optimization of sulfur separation process. These models pave the way for more efficient and environmentally-friendly production of clean fuels from petroleum, contributing to reduced gas pollutants emissions.

New insight into the pyrophoricity and mechanism of ironic sulfide from synergistic effect of FeS and FeS2

The pyrophoricity of ironic sulfide of sulfur corrosion products in oil tanks is a critical safety and environment concern that may trigger fire and explosion accidents. This paper focused on mixtures of FeS with FeS2 and aimed to systematically investigate their influence on the pyrophoricity of ironic sulfide. The results showed that the mixtures’ oxidation spontaneous combustion processes are generally similar, including low-temperature heating, oxidation decomposition, and burning-out stages. The more unstable molecular configuration and uneven surface morphology of FeS made it more prone to spontaneous combustion than FeS2. As the proportion of FeS2 in the sample increased, it absorbed the energy used to activate FeS during the early stages of oxidation and decomposition, causing the sample’s activation energy to increase and its pyrophoricity to weaken. When the proportion of FeS2 reached a certain level, the reaction may produce a large amount of elemental sulfur, which further oxidized and released heat, thus promoting the sample’s pyrophoricity. The study results suggest that the oxidation process of ironic sulfide involved a spontaneous, multistage exothermic reaction and produced intermediate products such as elemental sulfur, leading to a synergistic effect that influenced the reaction process.

Effect of extracts of petroleum ether, dichloromethane and methanol on thiophenic sulfur release during coal pyrolysis

The existing forms and thermal transformation of sulfur in high sulfur coal directly influence the efficiency of coal clean utilization by the staged pyrolysis conversion. Low molecular compounds distributed in coal are very different from the macromolecular structure of coal and play an important role during coal pyrolysis. In order to investigate the effects of low molecular compounds on the release of typical thiophenic sulfur species during coal pyrolysis by Py-GC/MS, petroleum ether, dichloromethane, and methanol were used for sequential ultrasonic extraction of Linfen coal (LFC). The compositions of extracts were detected by GC×GC/MS. Results show that three primary kinds of thiophenic sulfur species (2-methyl thiophene, benzothiophene, and dibenzothiophene) were released during coal pyrolysis and they are mainly derived from the cracking of macromolecular skeleton containing thiophenic sulfur in coal. The amounts of thiophenic sulfur released during raw coal and residues pyrolysis both increase with temperature. Besides, extracts with different compositions have different effects on the release of thiophenic sulfur during pyrolysis. In detail, the cyclization of aliphatic compounds could provide active hydrogen. On the one hand, the active hydrogen promotes the break of bridge bonds around thiophenic sulfur. On the other hand, active hydrogen may attack sulfur atoms of thiophenic sulfur, reducing the energy barriers of thiophenic sulfur decomposition. Aromatic compounds polymerize with sulfur-containing groups converting to benzothiophene and dibenzothiophene with larger molecular weight. In addition, thiophenic sulfur may be oxidized by esters to sulfones or sulfoxides, which further decompose, resulting in the inhibition effect on thiophenic sulfur formation during coal pyrolysis.

Ce-Doped Three-Dimensional Ni/Fe LDH Composite as a Sulfur Host for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have become the most promising choice in the new generation of energy storage/conversion equipment due to their high theoretical capacity of 1675 mAh g-1 and theoretical energy density of 2600 Wh kg-1. Nevertheless, the continuous shuttling of lithium polysulfides (LiPSs) restricts the commercial application of LSBs. The appearance of layered double hydroxides (LDH) plays a certain role in the anchoring of LiPSs, but its unsatisfactory electronic conductivity and poor active sites hinder its realization as a sulfur host for high-performance LSBs. In this paper, metal organic framework-derived and Ce ion-doped LDH (Ce-Ni/Fe LDH) with a hollow capsule configuration is designed rationally. The hollow structure of Ce-Ni/Fe LDH contains a sufficient amount of sulfur. Fe, Ni, and Ce metal ions effectively trap LiPSs; speed up the conversion of LiPSs; and firmly anchor LiPSs, thus effectively inhibiting the shuttle of LiPSs. The electrochemical testing results demonstrate that a lithium-sulfur battery with capsule-type S@Ce-Ni/Fe LDH delivers the initial discharge capacities of 1207 mAh g-1 at 0.1 C and 1056 mAh g-1 at 0.2 C, respectively. Even at 1 C, a lithium-sulfur battery with S@Ce-Ni/Fe LDH can also cycle 1000 times. This work provides new ideas to enhance the electrochemical properties of LSBs by constructing a hollow capsule configuration.

A physicochemical model-based digital twin of Li–S batteries to elucidate the effects of cathode microstructure and evaluate different microstructures

We are presenting a physicochemical model-based digital twin of Li–S batteries which involves continuum, volume-averaged ion transport equations including species migration, dissolution and precipitation, and electrochemical reactions, where the cathode microstructure is taken into account in terms of pore size distribution, hierarchy and tortuosity. The digital twin is applied in simulations of galvanostatic charge-discharge of a Li–S cell, exploring three types of cathode microstructure, activated carbon, graphene and hollow particles, two different amounts of sulphur and two different cathode coating thicknesses. Very good agreement is observed between predictions and experimental data in all case-studies. The best cathode is 70 wt% sulphur in host with porous hollow particles which trap the polysulphides from migrating to the anode. The simulations reveal that other reasons for low sulphur utilization, preventing the Li–S cell from reaching its theoretical capacity, are undissolved sulphur in micropores and sulphur leaching to macropores, especially in the cathode region near the separator, and reprecipitating.

Chemical Composition of Wet Atmospheric Deposition in a Natural Urban Reserve, Conservation of Green Urban Areas: a Mexico City Case Study

Green areas are essential for life in cities and for the conservation of ecosystem services in the case of megacities such as Mexico City. Green areas mitigate air pollution, reduce the temperature, and promote infiltration to feed the aquifers that, in the case of Mexico City, supply 68% of the water. Additionally, food production and recreational usage are important for the population. In the years 2017 and 2018, the chemical composition of wet deposition in the southern part of Mexico City was analyzed, daily and weekly. The study area is located in the greenest part of Mexico City, an important site for water recharge and carbon sequestration. Mexico City, like other megacities of high- and low-income countries, faces serious problems of air pollution. The purpose of this study was to measure the amount of total nitrogen and sulfur that is available in a natural reserve located inside the National Autonomous University of Mexico, and conductivity, pH, rain volume, and anions and cations were analyzed as well. Eighteen months of data were analyzed in order to understand the atmospheric deposition in and anthropogenic influence on an urban green natural area from the southern part of the city. Although both stations are less than 2 km apart, there are significant differences in their chemical composition; however, no differences were found for precipitation and pH, indicating that each station provides a local contribution, depending on local events and sources. Samples included rain events match for both sampling sites, with 67% of the samples in the same rain event match. Nonetheless, when only volume is compared for each year, both tests showed no significant difference (pv = 0.520). Throughout the year, various rainfall rates occur at the CU-CCA and REPSA stations, and the rainy season presents during the May–October period; the median value registered for both monitoring stations was 780 mL, and maximal rainfall was 4780 mL presenting at the CU-CCA station.

The influence of composition of asphaltenes of different genesis on the properties of carbon materials manufactured from them by plasma processing

The results of experimental studies of carbon materials, which are formed in the plasma of a direct current (DC) arc discharge initiated in open air from the asphaltenes of different origins, extracted from the natural asphaltite and from the oil of the Sredne-Ugutskoye Oilfield, are presented. The influence of the initial asphaltene composition on the composition and properties of the resulting carbon materials is analyzed. The initial asphaltenes and the samples of the carbon materials are characterized by the methods of X-ray diffraction, differential thermal analysis, X-ray fluorescence analysis, IR-Fourier spectroscopy, laser diffraction, transmission and scanning electron microscopy. The changes in the composition and structure of the asphaltenes are determined before and after their plasma treatment and the hypotheses are put forward concerning the chemical processes causing the changes in the molecular structure of the samples. As a result of plasma treatment of asphaltenes (100 A, 30 s), it was shown that graphitization occurs, as well as oxidation, and a decrease in sulfur content. Moreover, nanotubes and nano-onions have been detected using electron microscopy. Petroleum asphaltenes after plasma treatment give a less thermostable carbon material, but with a lower content of heteroatoms, and with a large amount of sulfur in the composition of sulfoxide structural fragments. This method is shown to be a promising technology for processing the petroleum feedstock enriched with heavy asphaltene components for the manufacture of carbon nanomaterials: nanotubes, nano-onions and polyhedral graphite.

A paleo-bioclimatological study on gondwana coal deposits in northwestern Bangladesh and the associated environment reflected by pollen and geochemical analysis

To comprehend the realistic paleo-bioclimate and depositional environment, we need to clearly grasp the methods that can be used to track paleoclimate in the past. The present research has focused on palynological investigation, X-ray Diffraction analysis, and elemental analysis of the core coal samples of the Gondwana coal of the Barapukuria Basin. The palynological study identifies two Palynoassemblage zones (Zone I and Zone II). A non-striate desiccate Scheuringipollenite, Crucisaccites, Parasaccites palynoassemblages are identified as Zone I and denotes as Lower Barakar Palynozone in the Early Permian where Zone II is dominated by striate desiccate Barakarites, Faunipollenites, Callumispora Palynoassemblages in the Late Permian. The Glossopterid plant family ruled the botanical affinity of Zone I and Zone II. It rendered the Gymnosperm group of plants as the rapid deglaciation assisted dissemination of Glossopteris flora. Higher percentages of clay minerals in X-ray diffraction (XRD) analysis and higher amounts of carbon content, lower sulfur, and higher C/S>10 ratio in the elemental analysis have been identified. All evidence from the research suggests that coals were deposited when glaciers retreated in the Early Permian, and the Gymnosperm group of plants prevailed and accumulated in the warm and humid climatic conditions under the braided fluvial influence in the terrestrial environment. J. Asiat. Soc. Bangladesh, Sci. 49(1): 101-119, June 2023

Novel Sulfate Reduction Coupled to Simultaneous Nitrification and Autotrophic Denitrification Process for Removing Nitrogen and Organics from Saline Wastewater.

Highly efficient sulfate reduction coupled to autotrophic denitrification plus nitrification is demonstrated by integrating an anaerobic membrane bioreactor (AnMBR) with a membrane aerated biofilm reactor (MABR). Concurrent chemical oxygen demand (COD) removal and sulfate reduction were accomplished in the AnMBR, while simultaneous nitrification and autotrophic denitrification were carried out in the MABR. Separate operation of the MABR achieved >90% total nitrogen (TN) removal when the N/S ratio was controlled at 0.4 gN/gS. The integrated AnMBR-MABR system efficiently resisted influent variability, realizing >95% COD removal in the AnMBR and >75% TN removal in the MABR when the influent COD/N ratio was above 4 gCOD/gN. Membrane fouling did not happen during ∼170 days of operation. Due to sulfide oxidation, a large amount of elemental sulfur (S0) accumulated in the MABR biofilm, where it served as an electron donor for denitrification. Microbial community analysis indicated that Nitrospira and Thiobacillus played key roles in nitrification and sulfide-driven denitrification, respectively, and that they occurred in different layers of the biofilm. This novel process offers advantages of a small land-area footprint, modular operation, and high efficiency electron-donor and oxygen utilizations, particularly for wastewater with a low COD/N ratio.

The role of organic carbon in the Southern Uplands-Down-Longford Terrane accretionary prism, Scotland and Ireland

Carbonaceous shales in the Southern Uplands-Down-Longford Terrane accretionary prism had extremely high potential for hydrocarbon generation in the Lower Paleozoic. Structural thickening in the prism enhanced the rapid generation of oil. Shale horizons are separated by thick turbidites composed of low-permeability greywackes, so oil under high fluid pressure either pooled along shale bedding surfaces or migrated into fractured greywackes. Pooled oil became solidified to bitumen, which locally formed deposits on a scale of tonnes, mined as coal. The carbon-rich shale also sequestered large amounts of sulfur from seawater, which precipitated as pyrite firstly during early diagenesis, then further during fluid flow through the shale beds. The oil was also sulfur-bearing. Deformation focused on the shale beds during the evolution of the accretionary prism would have been closely related to the fluid flow which precipitated bitumen and sulfides. The palaeo-fluids were also anomalously rich in methane and hydrogen, similar to fluids venting from modern accretionary prisms. Supplementary material: details of localities searched for coal in Lower Palaeozoic, Southern Uplands-Down-Longford Terrane (locations shown in Fig. 6 ) are available at https://doi.org/10.6084/m9.figshare.c.6691597