Calcium Sulfide Research Articles

Green Emitting Cerium Doped CaS Whiskers Grown by Solid State Diffusion Method.

Undoped and cerium doped Calcium sulfide (CaS) phosphors were synthesized using solid state diffusion method. The X-ray diffraction pattern revealed that both undoped and doped CaS crystallites have cubic structure with average crystallite size varying from 20 to 30nm. Scanning electron micrographs indicated that Ce doped CaS phosphors were composed of whiskers with different dimensions and orientations. The optical properties of undoped and Ce doped particles were characterized using Photoluminescence (PL) and UV-Vis absorption spectroscopy. The PL emission spectrum of cerium doped CaS phosphors for an excitation wavelength 465nm showed a main peak at 500nm and a shoulder peak at 556nm due to 5d → 4f transition in Ce3+ ions. The variation of PL intensity with cerium concentration was investigated and the maximum PL intensity was obtained for a doping concentration of 3wt.%. The optical band gap of the samples was estimated from the diffuse reflectance spectrum and was found to increase with increase in cerium concentration. The enhanced optical properties of these phosphors can be exploited in various optoelectronic devices including displays and bioimaging techniques.

Experimental study on the recovery of sodium in high sodium fly ash from thermochemical conversion of Zhundong coal

Zhundong (ZD) coal gasification/combustion fly ash is a high Na content residual product and contains a large quantity of harmful elements, including as Cl, S, and Na that must be removed and recovered. Water-soluble Na is the predominant Na form in ZD coal fly ash, accounting for 34.7–92.8% of the total Na. The main minerals of Na identified were NaCl and Na2SO4. Most of the water-soluble Na in the ZD coal fly ash can be effectively removed by water washing, the removal yields have been found to be 31–93%. Increasing the washing time, water temperature, liquid–solid ratio and acid concentration can increase the Na removal yield. For the ZD coal combustion fly ash (SEHcf) and gasification fly ash (SEHf), NaCl particles are present on the fly ash surface, most water-soluble Na was washed by water in 5 min at 30 °C. However, the removal of Na by water washing was inhibited by the water insoluble calcium oxides and sulfides that covered the surface of the ZD coal gasification fly ashes (TCf and SHf), Na removal required higher wash water temperatures and longer washing times. It is feasible to recover Na from ZD coal fly ash by water washing, and the recovered Na products are primarily NaCl and Na2SO4. The recovery yields of Na in the SEHcf, SEHf and TCf were 49.4%, 81.2%, and 65.4%. But the recovery yield of Na in SHf was 16.6%. SEHcf, SEHf and TCf were more suitable for recovering Na. the recovery of Na from ZD coal fly ash is economically feasible.

Model of Inclusion Evolution During Calcium Treatment in the Ladle Furnace

Calcium treatment of steel is typically employed to modify alumina inclusions to liquid calcium aluminates. However, injected calcium also reacts with the dissolved sulfur to form calcium sulfide. The current work aims to develop a kinetic model for the evolution of oxide and sulfide inclusions in Al-killed alloyed steel during Ca treatment in the ladle refining process. The model considers dissolution of the calcium from the calcium bubbles into the steel and reduction of calcium oxide in the slag to dissolved calcium. A steel–inclusion kinetic model is used for mass transfer to the inclusion interface and diffusion within the calcium aluminate phases formed on the inclusion. The inclusion–steel kinetic model is then coupled with a previously developed steel–slag kinetic model. The coupled inclusion–steel–slag kinetic model is applied to the chemical composition changes in molten steel, slag, and evolution of inclusions in the ladle. The result of calculations is found to agree well with an industrial heat for species in the steel as well as inclusions during Ca treatment.

Effect of Calcium Sulfide Nanoclusters in the Migration of Non‐Small Cell Lung Adenocarcinoma cell line HCC827

Lung cancer is the most common malignancy worldwide independently of gender. Non‐small cell lung carcinoma (NSCLC) is responsible for 80% of diagnosed cases. Prognosis for patients suffering this cancer is poor, with only 7% of patients surviving five years after the diagnosis. Current treatments include surgery, radiotherapy, and chemotherapy. Although the aforementioned seem successful, they do not address the development of secondary tumors due to cell migration resulting in metastasis. Evidently, there is a need for developing novel therapeutic approaches specifically targeting malignant cells. In our laboratory, we evaluate calcium sulfide (CaS) nanostructures as potential multi‐cancer malignant‐cell targeted specific treatment. The objective of this study was to determine the effect of CaS nanoclusters in the migration of NSCLC HCC827 cells. We hypothesized that CaS will decrease the area of migration compared to the control vehicle (DMSO), will increase the number of dead cells and decrease the live cells in the collected supernatant. We used the Scratch Wound Healing Assay, to determine the area of migration after 24, 48, and 72hrs upon a single exposure at time 0 of CaS treatment and controls (DMSO: vehicle control; etoposide: positive control; and media: negative control). We also collected the supernatant to characterize detached cells in suspension. Preliminary data shows that at 72hrs, cells treated with CaS exhibited a significant decrease in cell migration. We categorized the cells in the supernatant as live or dead. Although there were not statistically significant differences when compared CaS treatment with the controls, we observed a time‐dependent trend. This trend showed a decrease of the number of dead cells and an increase of live cells as the time increases. Based on this preliminary data, we partly accept our hypothesis due to the observed decreasing of migration in CaS treatment. However, the supernatant data was the opposite to what we hypothesized. We are currently optimizing experiments to increase statistical power and correlate the area of migration with the supernatant findings. In the next step of this project, I will be determining the effect of CaS by means of migration and number of live and dead cells in the supernatant in the non‐malignant lung cells MRC5.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Determination of Apoptotic Stage of HCC827 Lung Adenocarcinoma Cell Line, Following Calcium Sulfide Nanoclusters Treatment

Lung cancer is the number one cause of death independently of gender. By the time of the initial diagnosis, more than 50% of all lung cancer patients have already developed secondary tumors due to metastases. Despite current treatments such as surgery, chemotherapy, and radiotherapy, the prognosis for these patients still poor. Subsequently, there exists the need for more efficient treatments in order to increase the survival rate of patients suffering this disease. Previously, in‐vitro experiments in our lab demonstrated that Calcium Sulfide (CaS) nanoclusters induced apoptosis and necrosis in the non‐small lung cell adenocarcinoma (NSCLC) cell line HCC827. Using the Flow Cytometry technology, in this project we aimed to determine the effect of CaS in these cells evaluating apoptotic markers including, Caspase‐3/7 activity, Bcl‐2 phosphorylation, mitochondria potential, DNA‐damage, and oxidative stress. We hypothesized that CaS will show significant differences in these assays when compared to the Dimethyl sulfoxide (DMSO) control. We added a single dose of CaS [3.8μM] (experimental treatment), DMSO (control vehicle) or Etoposide [10 nM] (positive control) at time 0 and then collected the data after 24, 48, and 72 hours. As our results, we did not observe any statistically significant effect on apoptotic markers, Caspase‐3/7 and Bcl‐2. Analysis of the Mitopotential assay showed an statistical increase (p≤0.01) of dead cells population at 48 hours and of depolarized/lives cells at 72 hours compared to DMSO, in HCC827 cells treated with CaS. However, at 48 hours cells treated with CaS decrease the numbers of non‐affected cells (p≤0.05), increase DNA double‐strand breaks (p≤0.001), decrease the activation of Ataxia‐telangiectasia mutated kinase (ATM) and the phosphorylation of H2A.X significantly (p≤0.01). These results suggested that the detrimental effect of CaS on malignant HCC827 cell line is influenced by the accumulation of oxidative stress damage also affecting the cell cycle as our lab previously reported. Additional studies are ongoing to validate these results. Within the next month we plan to study the lung non‐malignant cells MRC‐5 using the same assays.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of Calcium Sulfide Nanoclusters in Cell Proliferation of Malignant Lung and Pancreatic Cell Lines

Lung and pancreatic cancer are leading cause of cancer deaths in the United States. Despite significant developments in treatments, survival rate for lung and pancreatic cancer patients is low. The diagnosis of these cancers is usually done at later stages, are very aggressive and when treated it affects negatively the quality of life of the patients. Recently, there have been advances in nanomedicine particularly in drug delivery and carrier systems developed to treat many types of cancers including lung, pancreas, breast, and prostate, among others. Calcium and sulfur are expected to be biocompatible with human body due the availability of these elements in our system. We propose the use of Calcium Sulfide (CaS) nanoclusters as an anti‐proliferation agent acting selectively in malignant non‐small cell lung adenocarcinoma (NSCLC HCC827) and pancreatic epithelial carcinoma cells (Mia Paca‐2) without affecting non‐malignant lung cells (MRC5). We hypothesize that CaS nanoclusters will decrease the cell replication in HCC827 and in Mia Paca‐2 cell lines without affecting the MRC5. Cells were treated with DMSO [1%] (vehicle control), etoposide [10μM] (positive control), or CaS nanoclusters [3.8μM] (experimental treatment) at 0‐hours. We performed each assay in quadruplicates according to their incubation time: 24, 48 and 72 hours after a single‐dose exposure to the correspondent treatments. To evaluate the effects of the CaS nanoclusters, we performed BrdU Proliferation Assay to quantify the newly synthesized DNA. The preliminary results showed that there was no significant changes in the pancreatic cell lines Mia Paca‐2 and HCC827 treated with CaS when compared to the controls at 24, 48, and 72 hours. In the MRC5 cell line there was only a borderline significance of 0.056 at 48 hours, which showed an increase in proliferation that confirm previous findings using other methods in our lab. In the following step, we plan to evaluate the effect of CaS in apoptotic and autophagy markers using the same cell lines.Support or Funding InformationNIH‐NIGMS #2R25GM096955This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Performance Evaluation of a Gypsum-Based Desulfurizer for Sulfur Recovery from the Smelter Off-Gas: Experimental Analysis and Thermodynamic Performance

To find some new desulfurizers for the smelter off-gas containing high levels of SO2, both the sulfur recovery performance and the regeneration performance of the sulfides of alkali metals and alkaline-earth metals were compared in both simulation and experiment. Although sodium sulfide(Na2S) showed a good sulfur recovery performance, its regeneration performance was poor due to the production of polysulfides. Calcium sulfide(CaS) was a feasible option of the desulfurizer because both its sulfur recovery performance and regeneration performance were satisfactory. CaS was prepared after the reduction of the commercial CaSO4(Red-Ca), the flue gas desulphurization gypsum(Red-FGD), the phosphogypsum(Red-P) and the titanogypsum(Red-Ti), respectively. The results showed that the performances of Red-Ca and Red-FGD were quite similar and both of them were distinctly better than Red-P and Red-Ti. According to XRF analysis and XRD patterns, the impurities in Red-P and Red-Ti reduced the activity of CaS. Both the su...

Wound Healing According to Biochemical Laws by Highly Potentized Homeopathic Remedies Containing Magnetic Photons

Homeopathy, a holistic therapy, is believed to cure only acute symptoms of a beginning illness according to the Laws of Similars; but not deep, bleeding, septic wounds. The homeopaths refuse to heal according to special medical indications. Based on Lenger’s detection of magnetic photons in homeopathic remedies a biochemical and biophysical model of homeopathic healing was developed Biochemical, pathological pathways can be treated by their highly potentized substrates and inhibitors. Three groups of patients with moderate, severe and septic wounds had been successfully treated with the suitable remedies depending on the biochemical pathological state. The wounds of the patients can be divided into 3 groups: 1. Moderate injuries 2. Surgeries of the abdomen, tooth extraction and 3. Deep wounds with pus and putrescent flesh The first group mostly children, had bruises on their skin after accidents such as push, collission or a little cut with a knife. High potencies of Arnica montana, regulating blood circulation, and Hypericum perfoliatum, curing the attacked nerves, were given. In order to close the wounds the calcium pathway was stimulated with Calcium phosphoricum and Silicea. More severe wounds after surgeries of the abdomen or tooth extraction, demanded additional remedies to heal the wounds. Staphisagria was applied supporting the calcium regulation too. Additional moderate inflammation was healed by the following remedies: Kaliumbi chromicum, Mercurius solubilis, Silicea, Hepar sulphuris, Calcium fluoricum, Calcium phosphoricum and Aconite. To cure the wounds, the inhibitors as matters of the calcium pathway were given as potentized remedies: Kalium bichromicum, Mercurius solubilis and Silicea. At the top of the second main group of the periodic table are the elements magnesium and calcium, the natural elements working in a living body; below follow the elements from barium untill mercury. All these elements are the poisons of the calcium biochemical pathway; at the top of the third main group there is alumina serving to support the body’s structure. At the top of the fourth main group there are the elements carbon, below that silicon, and lead (latin: plumbum). They form the structures of a living body and as homeopathic remedies they are necessary for healing deep wounds. Severe inflammation with pus and swelling is cured by the following highly potentized remedies: Anthracinum, Pyrogenium. The snake venoms of Elaps corallinus, Crotalus horridus, Lachesis mutus stimulate the regeneration of the cells. These potentized snake venoms are used very often for healing inflammation of the veins. The toxicology of the used remedies as substance is described in toxicological books and in the symptom pictures of the Materia Medica. At the beginning of the therapy the remedies were given 3 times daily. When the symptoms were improving the remedies were taken twice daily, and then later once a day. In general the wounds were cured softly, more quickly and without any sideeffects. This new, advanced treatment is against the ideas of homeopaths, who give only one dose of one remedy and wait for the reaction. Reaction chains were developed for the homeopathic therapy of different sorts of wounds based on their pathological biochemistry and in this way according to the Law of Similars. This biochemical thinking may give a guideline for curing wounds and ulcers with homeopathic remedies.

Two-stage leaching of manganese and silver from manganese–silver ores by reduction with calcium sulfide and oxidation with copper(II)

The development of a hydrometallurgical process to recover manganese and silver from manganese–silver ores is reported. Insoluble manganese(IV) was reduced to soluble manganese(II) in an aqueous medium with calcium sulfide (CaS) as the reductant, and the resultant residue was then leached by a sulfuric acid solution. Thiosulfate (S2O32−) was produced in situ in the reduction stage. The S2O32− by-product was reserved and used as the lixiviant for the subsequent silver leaching step with copper(II) and ammonia additives. The production of S2O32− was 0.168mol/L in the reduction stage and the recovery of manganese reached 98.0% in the acid leaching stage under the optimum conditions. Notably, 57.5% of silver was recovered when only the S2O32−-containing liquor from the reduction stage was used, and 92.0% of silver was recovered when a small amount of supplementary S2O32− was used.

Experiments on Condensation of Calcium Sulfide Grains To Demarcate Environments for the Formation of Enstatite Chondrites

To achieve a better understanding of material evolution in the early solar system, experiments have been performed to constrain the environments in which many of the dust grains formed. Sulfur is an element whose chemical processes and mineralization of related grains are poorly understood. The high reactivity of sulfur makes it difficult to perform experiments in conventional metallic chambers, because these become heavily contaminated. Nevertheless, sulfur is expected to be a key element to understand processes in the early solar system. Here, we performed experiments on the condensation of calcium sulfide (CaS) in a glass chamber in an attempt to identify constraints on the possible formation environments of components of enstatite chondrites in terms of the effects of oxygen. Condensation experiments showed that calcium sulfate (CaSO4) or solid-solution particles of CaS and calcium oxide (CaO), i.e., [Ca(S,O)], were formed at various partial pressures of oxygen. Our results expand the range of possibl...

The gypsum reduction process and its validation using the Mintek Pyrosim model

ABSTRACTWaste gypsum is produced as a by-product from the fertilizer, mining industries, and acid mine water neutralization using calcium carbonate and/or lime and desalination processes using reverse osmosis and ion-exchange processes, resulting in environmental and storage problems. The purpose of the study was to establish optimum operating conditions for the recovery of valuable products, e.g., sulfur and precipitated calcium carbonate, from waste gypsum, hence, offer an attractive solution to the gypsum waste problem. The paper presents results on thermal studies of waste gypsum in a tube furnace and its validation using the Mintek Pyrosim model. Gypsum was homogeneously mixed with coal and the reduction experiments conducted. The following findings were made: (i) reduction of waste gypsum is an endothermic reaction since, ΔH values were greater than 0 (ΔH > 0) when the reduction temperature was increased from 25 to 1200°C, (ii) energy requirement is dependent on temperature and gypsum to coal ratio. Gypsum to calcium sulfide conversion of 83.5 and 83.8% was obtained at the optimum temperature range of 1100–1200°C and gypsum to calcium sulfide conversion of 85.4% was obtained at the optimum coal to gypsum mole ratio of 2.1:1, (iii) excess coal gave a lower conversion, and (iv) the predicted data using Mintek Pyrosim were found to be similar to the experimental data.

Impact of interfacial charge transfer on the start-up of bioelectrochemical systems

In order to increase the efficiency of microbial fuel cells and related bioelectrochemical systems (BESs), one of the common approaches is to lower the resistance of the anode surface to increase the extracellular electron transfer (EET) of anode respiring bacteria (ARB). As our work demonstrates here, this approach is not ideal when dealing with common species of ARB. Bacteria colonized an electrode surface modified with graphite material doped with nonconductive calcium sulfide (CaS) more favorably than the conductive magnetite (Fe3O4) or semiconductive iron (II) sulfide (FeS). Average anodic current densities of 8.2±0.25Am−2 (Fe3O4), 10.7±0.46Am−2 (FeS) and 21.3±1.12Am−2 (CaS) were achieved as compared to that of non-doped activated carbon (5.04±0.12Am−2). Bioelectrochemical evaluation during growth using simple low-scan (1mVs−1) cycle voltammetry (LSCV) indicated variations in patterns which reflect the variability of the ARBs growth. On the other hand, despite the high affinity of bacteria to grow at a faster rate on Fe3O4-anode and CaS-anode, as indicated by the maximum specific growth rate during the start-up exponential phase, the kinetic scan rate study of derivative cycle voltammetry (DCVs) during growth indicated accumulation of bacteria-produced mediators on iron containing anodes which reduced their electrochemical activity. Thus, irrespective of surface resistance, the CaS doped graphite represented a promising anode material which is suitable for highly efficient BES.

Enhanced luminescence of triethanolamine capped calcium sulfide nanoparticles synthesized using wet chemical method

Semiconductor nanophosphors have smart technological applications in optoelectronic devices and in nanomedicine. Here we report the synthesis of Calcium sulfide nanophosphors by wet chemical method using Triethanolamine (TEOA) as capping agent. The structural characterization of the prepared nanoparticles was done using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The XRD pattern confirmed the cubic CaS phase with an average grain size of 21nm of the formed samples. From TEM images, the TEOA capped nanoparticles were found to have a spherical morphology with diameter in the range 5–15nm. The optical studies of the capped nanoparticles were carried out using Photoluminescence spectroscopy and UV–vis absorption spectroscopy. We obtained a highly intense blue emission on exciting the TEOA capped nanoparticles at 318nm which was found to be greater than the luminescence intensity of uncapped CaS nanoparticles. The optical band gap of the capped nanoparticles was estimated from the Diffuse Reflectance Spectra and an increase in bandgap was observed which can be explained on the basis of quantum size effect. Thermogravimetric analysis and Fourier Transform Infrared Spectra analysis confirmed the presence of capping agent in the synthesized CaS nanoparticles.

Chemotherapeutic Effect of Calcium Sulfide Nanostructures in non‐small cell lung carcinoma by intrinsic and extrinsic apoptotic pathways

Apoptosis or programed cell death is characterized by metabolic changes and energy‐dependent mechanisms aimed to ensure cell viability and proper function. A failure in the activation of pro‐apoptotic processes is considered a major contributor to the survival of tumor cells, induction of malignant transformation, tumor growth and subsequently, cancer as a disease. The apoptotic cascade can be triggered by a variety of internal and external stimuli, the results of which are classified into two signaling pathways: Extrinsic and Intrinsic, based on the origin of the stimuli and the mediators involved. The principal mediators are caspases‐8 and ‐9, which are responsible for a subtype of apoptosis known as Caspase dependent apoptosis. Previous studies in our laboratory showed that non‐small lung cell carcinoma cells (NSCLC) (HCC827) treated with proprietary calcium sulfide nanostructures (CaS) exhibited induction of apoptosis starting at 48 hours after treatment (p<0.05). In the new stage of this project, we aimed to determine the expression of apoptotic factors (Bax, Caspase‐3, Casapse‐8), the electron transport chain component Cytochrome C (CytoC), and the metabolic enzyme GAPDH, 24‐, 48‐ and 72‐hours after a single dose addition of CaS nanostructures. We hypothesized that CaS nanostructures treatment in HCC827 cells will selectively activate the intrinsic and extrinsic pathways; increasing the cytosolic CytoC expression and decreasing the expression of GADPH when compared to non‐malignant MRC5 cells. The HCC827 and MRC‐5 cells were treated with DMSO [1%] (vehicle control), etoposide [10μM] (positive control), and CaS nanostructures [3.8μM] (experimental treatment) at 0‐hours. To study the target proteins, we performed Western Blot analysis, densitometry and statistical analyses to evaluate changes in expression of the studied proteins. Our preliminary results showed that Bax expression decreased through time in the MRC‐5 cells treated with CaS compared to DMSO; while its expression increased in the HCC827 cells at 48 hours (p<0.05). At 24 hours, the expression of caspases‐8 and ‐3 in HCC827 increased when compared to DMSO, but it was not statistically significant. In MRC‐5 cells, caspase‐8 was observed at 24 hours. In contrast, caspase‐3 expression increased compared to DMSO and remained constantly increased at 24‐ and 48‐ hours. The expression of CytoC was observed in the HCC827 cells after 48 hours of exposure to CaS nanostructures; while it was not detected in MRC‐5 at any time point. These results suggest that CaS structures have a pro‐apoptotic effect, involving both intrinsic and extrinsic pathways, accepting this part of the hypothesis. As well CytoC was detected only in HCC827, suggesting release from the mitochondria that would promote the intrinsic apoptotic pathway. However, our hypothesis was not accepted for the GADPH protein expression, by obtaining the opposite results. This may be explained as an attempt of the malignant cells to survive. We are currently studying additional pro‐apoptotic factors, such as caspase‐9 and caspase‐7, to elucidate the mechanism CaS nanostructures within these pathways, which may represent a selective chemotherapeutic agent for NSCLC.Support or Funding InformationNIH‐NIGMS#2R25GM096955

A novel method for direct fabrication of ferromolybdenum using molybdenite via self-propagation high temperature synthesis

Direct production of ferromolybdenum from molybdenite (MoS2), in the presence of lime as a desulfurizing reagent using combustion synthesis process is investigated. Thermodynamic calculations and measurement of the adiabatic temperature of the reaction denoted that the process is in agreement with the Merzhanov criterion for self-sustaining processes. The experimental results indicated a relatively complete separation between the molten metal droplets and the co-existing slag. The slag and metal phases were characterized by X-ray diffraction, electron microscopy and wet chemical analysis techniques. It was found that sulfur is mainly distributed into the slag in the form of solid calcium sulfide (CaS). The Lack of calcium oxide in the slag indicated a complete desulfurization reaction between lime and the sulfur in molybdenum sulfide. Characterization of the molted metal revealed that only two phases namely Fe3Mo3C and Fe3Mo exist in the melt. Mass balance calculations showed an Iron-molybdenum recovery greater than 85%. Analyses of the phases indicated that a significant amount of Fe3Mo3C phase (60–70 wt%) is present in ferromolybdenum molten droplets even though the raw materials were low in carbon. Chemical analysis and microstructural studies of the raw materials and the products showed that carbon is not present in sufficient quantities to produce this amount of Fe3Mo3C; therefore the structure of this phase should contain a high concentration of carbon vacancies. The deviation of Fe3Mo3C1−x peaks in X-ray diffraction pattern compared to its standard reference peaks and a calculated 0.02% decrease in the lattice parameter of this phase are evidence of the presence of these carbon vacancies.

Inclusion evolution after calcium addition in Al-killed steel with different sulphur content

ABSTRACTThe inclusion evolutions after calcium treatment in Al-killed steel with different sulphur content were determined by chemical experiments and thermodynamics calculations. The results show that the inclusions are calcium aluminate with a little amount of calcium sulphide in low content sulphur steel after calcium treatment. As the sulphur content in steel increases, the typical inclusions generated in steel are layered or homogeneous irregular oxysulphides. A number of pure sulphides can be observed in higher content sulphur steel, and the morphology of sulphides with different CaS/MnS mass ratio has different shape. Thermodynamics calculations of Al–Ca–O–S–Mn system inclusions in steel at 1873 K and during solidification process were comprehensively conducted, considering all types of inclusions. The experimental results are in good agreement with thermodynamic calculations, which can predict the formation of the inclusions in Al-killed steel with different sulphur content.

The performance of 3-D graphite doped anodes in microbial electrolysis cells

Abstract This study investigated the use of granular activated carbon (GAC) as high surface area 3-dimensional (3-D) anode in MECs systems. The interfacial anodes' charge transfer resistance of the doped GAC did not impact the overall performance of MECs. Based on our finding, the 3-D anode packed with GAC-doped with nonconductive calcium sulfide (CaS) outperformed the more conductive iron (II) sulfide (FeS), magnetite (Fe 3 O 4 ), or GAC without doping. The results showed higher current densities for 3-D CaS (40.1 A/m 3 ), as compared with 3-D FeS (34.4 A/m 3 ), 3-D Fe 3 O 4 (29.8 A/m 3 ), and 3-D GAC (23.1 A/m 3 ). The higher current density in the 3-D CaS translated to higher coulombic efficiency (96.7%), hydrogen yield (3.6 mol H 2 /mol acetate), and attached biomass per anode mass (54.01 mg COD biomass/g GAC). Although the 3-D MEC achieved similar hydrogen yield, hydrogen recovery efficiency, and COD removal rate to a conventional sandwich type MEC, the current density, coulombic efficiency, and overall energy efficiency were higher.

Electrochemical Behavior of Anode-Respiring Bacteria on Doped Carbon Electrodes.

Cultivating anodic respiring bacteria (ARB) on anodes doped with metal-enhanced biological growth and affected higher electocatalytic activity (ECA). The anode doped with calcium sulfide (CaS) proved more favorable for ARB than the magnetite (Fe3O4) or iron(II) sulfide (FeS). Average anodic current densities of 8.4 Am2- (Fe3O4), 11.1 Am2- (FeS), and 22.0 Am2- (CaS) were achieved as compared to that of nondoped carbon (5.1 A m-2). Thus, CaS-doped graphite represents a promising anode material which is suitable for highly efficient bioelectrochemical systems (BES). Electrochemical evaluation during turnover and starvation using simple cycle voltammetry (CV) and derivative cycle voltammetry (DCV) indicated several extracellular electron transfer (EET) pathways characterized with lower potentials for biofilms. However, despite the high affinity of bacteria to iron, their lower ECA was kinetically attributed to the accumulation of self-produced mediators on iron-doped anodes.

Direct elemental sulphur recovery from gold acid mine drainage streams

The metal precipitates resulting from the neutralization and desalination processes of acid mine water with lime, limestone and barium carbonate are wastes identified as sludge. The composition of these sludges generally comprises hydrated manganese, magnesium hydroxides, gypsum and large amount of barite. Legislation requires that these sludges be disposed in an environmentally acceptable manner to prevent metals from leaching and entering the environment. However; the enormous volumes of sludge produced and the limited disposal spaces present major environmental and economic concerns for the development of a viable technology for acid mine water treatment. This paper assesses the conversion of CaSO4/Mg(OH)2 and BaSO4/CaCO3 generated in the water stage of the Alkali Barium Calcium desalination process into sulphur. Africa is a major importer of large tonnages of sulphur at high cost often inflated by the cost of transportation whilst sulphur itself remains a relatively cheap product. This paper investigates a) the reduction of BaSO4/CaCO3 and CaSO4/Mg(OH)2 sludges to barium and calcium sulphide; b) the stripping of the sulphide with CO2 gas and the production of sulphur. Thermal reduction study shows that BaSO4/CaCO3 and CaSO4/Mg(OH)2 sludges can be reduced to BaS/CaS with duff carbon in a muffle furnace operating at about 1100°C with BaS/CaS yield between 70 and 76%. The BaS/CaS formed was slurried in water and CO2 was used for the stripping of sulphide to form H2S gas and BaCO3/CaCO3 precipitate. The H2S generated was reacted with ferric sulphate to form elemental sulphur. Sulphur with purity between 95.2% and 99.1% was recovered from the sulphate rich wastes.

Features of Nonmetallic Inclusion (Precipitates) Evolution During Heating of Structural Steel for Rolling

Evolution of nonmetallic inclusions on heating a billet for rolling is studied using contemporary methods of electron microscopy and local x-ray spectral analysis for steels 20-KSKh and 13KhFA from an industrial melt. It is established that it is controlled by the occurrence of three main processes. The first consists in the deposition of manganese sulfide on the surface of aluminum-magnesium spinel and other oxide composites MgO–Al2O3–CaO both from solid solution and from soluble MnS precipitates, as a result of which inclusions become corrosion-active and their amount increases. An increase in metal heating duration leads to the coalescence of sulfide components from smaller to larger sizes. As a result of this, the number of inclusions exhibiting corrosion activity decreases. The majority of titanium nitride inclusions are retained with the metal composition outside a dependence on billet heating temperature and duration, and there may be formation of complex TiN inclusions with niobium nitride, with calcium and manganese sulfides, and also of even more complex composition, including aluminum-magnesium spinel, and these inclusions may have an unfavorable effect on the steel’s properties. In contrast, a favorable process is deposition during subsequent cooling on the surface of sulfide and other forms of inclusions of cementite and other carbides, which may lead to a marked increase in strength properties without a reduction in steel ductility. On the basis of results obtained, a number of effective production methods are suggested for improving steel resistance to local corrosion and other service properties.