Journal articles: 'Chromium sulphide'

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Eric, R. H. "Chromous capacities of ferrochromium and matte smelting slags." Archives of Materials Science and Engineering 2, no. 93 (October 1, 2018): 49–58. http://dx.doi.org/10.5604/01.3001.0012.7354.

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Purpose: of this paper is to extend the slag capacity concept to sparingly soluble cationic species encountered for example in matte smelting and ferrochromium processing in terms of chromous capacities. Design/methodology/approach: In this context in order to develop the chromous capacity the experimental data on slag-metal equilibrium for ferrochromium smelting and on chromium distribution between slag and matte phases encountered in sulphide smelting of PGM (Platinum Group Metals) and chromium containing copper nickel concentrates were used. Findings: The calculated chromous capacities were in the 10-8 range for ferrochrome smelting slags and 10-4 range for matte smelting slags. These values indicate the very low and moderate chromous ion dissolving ability of ferrochromium smelting slags and matte smelting slags respectively. Research limitations/implications: Due to highly reducing conditions in ferrochromium smelting and the imposed low oxygen partial pressures in sulphide smelting of chromium and PGM containing concentrates chromium in the slag was assumed to be in its divalent state. The slag-metal/matte reaction for dissolution of chromium into the slag as a cation under reducing conditions -in contrast to reactions for dissolution of species such as sulphur and phosphorus into the slag as anions under oxidizing conditions – required the release of electrons. Thus to maintain charge neutrality the dissolution of chromium from the metal or the matte phases into the slag as Cr2+ ions was accompanied by consumption of these electrons by reduction of Fe2+ ions in the slag into metallic Fe which dissolved in the metal/ matte phase. This was supported by the experimental equilibrium data. Hence the slagmetal/ matte reaction defining the chromous capacity involved both O2- and Fe2+ ions of the slag phase. Moreover for matte smelting the thermodynamic activities of species in the matte phase were assumed to conform to ideal associated solution model due to lack of data. For future work it is advisable to determine such activities. Practical implications: The calculated chromous capacities were in the 10-8 range for ferrochrome smelting slags and 10-4 range for matte smelting slags. The results clearly indicate that in matte smelting lower basicity slags would be preferable to render chromium more soluble in the slag in contrast to ferrochromium smelting where higher basicity slags would be suitable to minimize chromium losses to the slag. Originality/value: This research and hence the paper is probably the first on dissolution of chromium as chromous ion in slags, thus it is novel and original.

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BACKLUND, K., A. BOMAN, and S. FRÖJDÖ. "An analytical procedure for determination of sulphur species and isotopes in boreal acid sulphate soils and sediments." Agricultural and Food Science 14, no. 1 (December 4, 2008): 70. http://dx.doi.org/10.2137/1459606054224147.

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An analytical scheme suitable for boreal acid sulphate (AS) soils and sediments was developed on the basis of existing methods. The presented procedure can be used to quantify and discriminate among acid volatile sulphide, cold chromium reducible sulphur, hot chromium reducible sulphur, elemental sulphur, sulphate sulphur, organic sulphur, total reducible sulphur and total sulphur. The sulphur fractions are recovered as either Ag2S or BaSO4 precipitates and can further be used for isotope analysis. Overlaps between sulphur species are common during speciation, and must be minimized. Some of these overlaps are caused by poor sampling and storage, inappropriate conditions during the distillation, or natural variations in the sample (e.g. Fe3+ interference and grain size). The procedural impact was determined by conducting tests on both artificial and natural samples containing one or several sulphur species. The method is applied on reduced sediment from an AS soil locality (Överpurmo) and a brackish lake (Larsmo Lake) in western Finland and the results, including S-isotopes, are discussed.;

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Schmid, Alexander, Gregor Mori, and Roland Haubner. "Metallographic Documentation of the Degradation of Iron and Nickel Based Alloys in HCl and H₂S Containing Environments, between 480 – 680 °C." Defect and Diffusion Forum 405 (November 2020): 26–32. http://dx.doi.org/10.4028/www.scientific.net/ddf.405.26.

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Corrosion behavior of the alloys 1.7386 (P9), 1.4462, 1.4841, 1.4959 (Alloy 800HT) and 2.4816 (Alloy 600) was tested for 24, 72 and 240 h between 480 – 680 °C. The testing gas atmosphere contained 3.8 vol. % HCl, 200 ppm H2S and CO, CO2 and N2. It simulated conditions present in a thermal cracking process for post-consumer plastics. Samples were analyzed by metallography, SEM/EDX and XRD after corrosion experiments. Additionally, their mass loss during the test was evaluated. A multilayered structure of corrosion products grew on the samples during the corrosion experiments. The composition of the corrosion products depended not on the material, but on the testing temperature. At 680 °C chromium sulphide formed the outer layer, followed by a chromium oxide layer. Below these two layers a chlorine containing layer was observed. At 480 °C mainly nickel sulphide was detected, besides chromium oxide and iron- and chromium chloride. Especially at higher testing temperatures FeCl2 was not observed directly on the samples, but as colorless crystals at the colder parts of the testing equipment. At 680 °C the mass loss of the samples decreased with increasing nickel content. However, this effect changed entirely at lower testing temperatures. At 480 °C 1.7386 and 2.4816 showed nearly the same mass losses.

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Salman, Rehab Ahmed, Gurashi A. Gasmelseed, and Rawia S. Hassan. "Recycling of (Soaking, Deliming and Retannage) Solutions in Amatong Tannery in the Sudan." European Journal of Engineering Research and Science 4, no. 1 (January 31, 2019): 123–25. http://dx.doi.org/10.24018/ejers.2019.4.1.1081.

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Tanneries use much of chemicals such as sodium sulphide ,calcium hydroxide, ammonium sulphate, acids, basic chromium sulphate bactericide and fungicide. All these substances contribute to the environment pollution, although biological and chemical treatment methods are required, but still these methods are not effective enough to reduce pollution to the international standard level required. This pollution problem has to be solved completely via recycling through all wet processes from soaking to retannage.In this study the spent solutions were recycled for soaking, deliming and retannage processes many times with addition of makeup of chemicals and water ,that normally used , The produced crust quality was tested and the results were found to be satisfactory.

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Hutchison, R. "Chromian-manganoan augite in the interchondrule matrix of the Tieschitz (H3) chondritic meteorite." Mineralogical Magazine 51, no. 360 (June 1987): 311–16. http://dx.doi.org/10.1180/minmag.1987.051.360.14.

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AbstractThe Tieschitz chondrite is a disequilibrium assemblage of silicate, metal and sulphide occurring together or separately as chondrules and clasts that generally have opaque rims (matrix) of fine-grained material. Translucent, silicate-rich matrix fills channels that occur sporadically between chondrules and clasts. An angular fragment of twinned ‘clinoenstatite’ was found to be rimmed with chromium- and manganese-rich augite and surrounded by opaque matrix. The whole is set within the largest area of translucent (white) interchondrule matrix encountered. It is suggested that reaction between crystallizing undersaturated translucent matrix, opaque matrix, and clinoenstatite probably led to the partial replacement of clinoenstatite by chromian-manganoan augite at high temperature.

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Dampc, Jan, and Marek Szkodo. "Effect of some Sulphur Additives on the Degradation of 9Cr-1Mo Steel after its 10 Years Service in the CCR Platforming Unit." Solid State Phenomena 225 (December 2014): 139–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.225.139.

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The work shows the results of the tests of 9Cr-1Mo steel, which was for 10 years operated in the CCR platforming unit in Group Lotos SA in Gdańsk, and then in the laboratory was sulphidised during 166 h at a temperature of 600 °C. Sulphidation was performed in a mixture of H2-H2S gases at the vapour pressure of sulphur 4.1·10-14 atm, so the order of magnitude of vapour pressure was less than that of the dissociation pressure of FeS. Although sulphidising took place in conditions which preclude any iron sulphide formation, research results have demonstrated that after 166 hour exposure in reaction mixture in 9Cr-1Mo steel produces iron and chromium sulfides. Sulphide precipitates form under a layer of fine carbides, located directly on the surface of steel. Formation of scale sulphide here is most likely caused by the penetration of hydrogen sulphide through the porous layer of carbides that increases the pressure of hydrogen sulphide. Thus the vapour of sulphur in apertures and narrow passages occurs between the layer of carbides and the rest of oversaturated carbon layer top, until its pressure value is reached allowing the formation of sulphide scaling.

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Davydov, S. V., and A. O. Gorlenko. "The Wear Resistance of Mottled Iron with Stabilized Carbide Phase." Solid State Phenomena 265 (September 2017): 22–26. http://dx.doi.org/10.4028/www.scientific.net/ssp.265.22.

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There is investigated the wear resistance of mottled irons with stabilized carbide phase, obtained by alloying iron with copper, chromium and sulfur. It is shown that during heat treatment the outer shell of the carbide phase inclusions, destabilized with copper, dissolves, leaving a core stabilized with chromium. Carbon from the carbide phase dissolution coats the surface of manganese sulphide inclusions, forming additional wear-resistant structural component of mottled iron. The resulting structures can be attributed to compositional structures, which morphology and phase composition can be controlled by alloying and heat treatment.

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Meng, Fan Sheng, and Ye Yao Wang. "Remediation of Hexavalent Chromium Polluted Ground Water by PRB." Advanced Materials Research 726-731 (August 2013): 1724–31. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.1724.

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The zero-valent iron (Fe0) and the activated carbon were used as reaction mediums, the reactivity characteristics and removal effect of hexavalent chromium (Cr (VI)) contaminated ground water using Fe0/AC-PRB were investigated. The results showed that AC adsorbed Cr (VI) under the pH conditions of influent, and Cr (VI) was removed. Also, the chromium could be deoxidized by zero-valent iron effectively, when simulated groundwater containing 10mg/L hexavalent chromium was continuously input. During the process, the redox products, Fe3+ and Cr3+, precipitated on the reaction media without transferring into downstream water. The pH value increased from 7.0 in influent to 8.0 in effluent, and the total iron concentration of effluent was below 0.30mg/L. Chromium was distributed mainly in the form of organic/sulphide fraction and residue fraction when the aquifer was flushed with deionized water, Moreover, bioavailable weak acid extractable fraction was not detected, indicatinga low ecological risk of chromium remained in the aquifer.

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9

Grzesik, Z., and S. Mrowec. "High Temperature Corrosion of Metallic Materials in Composed Oxidizing Environments." High Temperature Materials and Processes 31, no. 4-5 (October 30, 2012): 539–51. http://dx.doi.org/10.1515/htmp-2012-0091.

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AbstractBasing on actual theoretical approach and experimental results, the mechanism of sulphide formation beneath the oxide scale grown on metals in SO2-O2 atmospheres has been described. It has been shown that in spite of much lower sulphur partial pressure in the oxidizing atmosphere than the dissociation pressure of the sulphide to be formed, the sulphidation process takes place beneath the oxide scale. This, at the first sight, unexpected behavior results from the fact that sulphur is diffusing inwards through the primary oxide scale in the molecular form, i.e. SO2 molecules. Reaching thus metal-scale interface, where the oxygen partial pressure is very low, virtually equal to the dissociation pressure of the oxide forming the scale, SO2 ⇔ O2 + ½S2 equilibrium is shifted to the right, as a result of which the partial pressure of sulphur vapor dramatically increases, reaching the value several orders of magnitude higher than that needed for sulphide formation.Analogous situation is observed during oxidation of chromium steels in CO2-O2 atmospheres. In this case, namely, carburisation process is observed beneath the oxide scale, in spite of the fact that carbon activity in this environment is several order of magnitude lower than that required for chromium carbide formation. This again unexpected situation becomes understandable if one assumes – like in the case of metal oxidation in SO2 containing atmosphere – that carbon is transported through the oxide scale in the form of CO2 molecules.The final conclusion is, that the explanation of the mechanism of sulphide formation beneath the oxide scale on metals and of carburization beneath the oxide scales on steels constitutes the important step forward, leading to the better understanding of high temperature corrosion mechanisms of metallic materials, observed in multicomponent agresive gases.

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10

Shaybekov, R. I., M. M. Gaikovich, and S. S. Shevchuk. "Sulphide mineralization in the chromium ores of Lagortinsko-Kershorskoy area (Polar Urals)." Vestnik of Institute of Geology of Komi Science Center of Ural Branch RAS 8 (2012): 13–17. http://dx.doi.org/10.19110/2221-1381-2012-8-13-17.

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11

Azizi, Asghar, Seid Ziaoddin Shafaei, Mohammad Noaparast, and Mohammad Karamoozian. "Galvanic Interaction between Chalcopyrite and Pyrite with Low Alloy and High Carbon Chromium Steel Ball." Journal of Chemistry 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/817218.

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This study was aimed to investigate the galvanic interaction between pyrite and chalcopyrite with two types of grinding media (low alloy and high carbon chromium steel ball) in grinding of a porphyry copper sulphide ore. Results indicated that injection of different gases into mill altered the oxidation-reduction environment during grinding. High carbon chromium steel ball under nitrogen gas has the lowest galvanic current, and low alloy steel ball under oxygen gas had the highest galvanic current. Also, results showed that the media is anodic relative to pyrite and chalcopyrite, and therefore pyrite or chalcopyrite with a higher rest potential acted as the cathode, whilst the grinding media with a lower rest potential acted as the anode, when they are electrochemically contacted. It was also found that low alloy steel under oxygen produced the highest amount of EDTA extractable iron in the slurry, whilst high carbon chromium steel under nitrogen atmosphere led to the lowest amount.

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12

Wiegant, W. M., T. J. J. Kalker, V. N. Sontakke, and R. R. Zwaag. "Full scale experience with tannery water management: an integrated approach." Water Science and Technology 39, no. 5 (March 1, 1999): 169–76. http://dx.doi.org/10.2166/wst.1999.0236.

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In this article, an overview is given of the proposed and actual activities that are undertaken to reduce the pollution from the approximately 180 tanneries in Kanpur, Uttar Pradesh, India. As a part of an action plan to reduce the pollution of the river Ganga, this project includes in-house measures to reduce the output of chromium by the tanneries, and pre-treatment at the tanneries to reduce the solids content of the wastewater and to facilitate maintenance of the sewer system. A treatment plant consisting of two Upflow Anaerobic Sludge Bed (UASB) reactors, followed by a post-treatment facility, reduces the wastewater pollution by approximately 80% of BOD, COD, and TSS. However, sulphide output is still high, owing to the high sulphate concentrations in the wastewater. The sludge produced during the operations is projected to be used as a fertilizer.

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Patil, H. B., and S. V. Borse. "Optimization of Chemical Bath Deposited Mercury Chromium Sulphide Thin Films on Glass Substrate." Indian Journal of Materials Science 2013 (September 12, 2013): 1–4. http://dx.doi.org/10.1155/2013/694357.

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Semiconducting thin films of ternary () have been deposited on glass substrate by the simple and economical chemical bath deposition method. We report the deposition and optimization of the solution growth parameters such as temperature, complexing agent, thiourea, and deposition time that maximizes the thickness of the deposited thin film. The X-ray diffraction deposited thin films having cubic structure. The thin films were uniform and adherent to substrate. The composition was found homogeneous and stoichiometric by EDAX analysis.

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14

Godlewski, K., E. Godlewska, S. Mrowec, and M. Danielewski. "Sulphide corrosion of pure and chromium-modified β-NiAl intermetallic compound at high temperatures." Materials Science and Engineering: A 120-121 (November 1989): 105–9. http://dx.doi.org/10.1016/0921-5093(89)90726-0.

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Mazlan, Siti Nur Farhana, Azzura Ismail, Lokman Mohd Noh, and Sufizar Ahmad. "Failure Analysis on Heat Exchanger Tube Bundle Exposed to Naphthenic Acid Corrosion." Key Engineering Materials 791 (November 2018): 95–101. http://dx.doi.org/10.4028/www.scientific.net/kem.791.95.

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Naphthenic acid is a sort of organic acid which present in crude oil and cause severe corrosion in certain circumstances. This type of acid will lead to the corrosion phenomenon known as naphthenic acid corrosion (NAC). Damage mechanism by NAC attack can be analysed using Scanning Electron Microscope (SEM), Electron-dispersive X-ray (EDX) and X-ray Diffraction (XRD). These characterization methods aim to observe the morphology, element content, and crystal structure of the NAC. The objective of this research is to apply failure analysis (FA) on heat exchanger (HE) tube bundle made form stainless steel 410 (SS410). SEM reveals the inter-granular attack initiate to crack propagation. A particular result of interest is that nickel catalytically decomposes naphthenic acids at high temperatures (e.g. 270°C) via a catalytic mechanism. For XRD testing, the corrosion product have been known and the main causes that lead to the corrosion has been detected which there is a formation of chromium carbide continuously along the pipe tube. However there is also formation of iron sulphide and chromium sulphide obtained in the XRD analysis where both are the reaction element that can retard the formation of NAC. Material selection is the most crucial task to resists from corrosion attack especially in high temperature applications. The mechanism of resistance of these elements provides insight into the failure mode of 304 and 400 series stainless steel in NA service.

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ÅSTRÖM, M., and K. RÖNNBACK. "Concentration levels and spatial distribution of sulphur and metals in fine-grained sediments in western Finland." Agricultural and Food Science 14, no. 1 (December 4, 2008): 14. http://dx.doi.org/10.2137/1459606054224093.

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On the coastal plains of Finland, widespread Holocene marine and lacustrine sediments have developed into acid sulphate soil as a result of extensive artificial drainage for agricultural purposes. This has caused a variety of environmental problems. The aim of this study was to determine the concentration levels and spatial distribution of sulphur, carbon and metals [titanium, vanadium, chromium, manganese (Mn), iron, cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn)] in these sediments, in order to increase the geochemical understanding of the parent materials from which acid sulphate soil develops. Sediment samples were collected at 317 sites from a depth of 1.53 m. While the sediments have high S (sulphide) concentrations (median = 0.54%) and thus a strong acidification potential, they carry transition metals mainly in smallsized silicates close to background concentrations far below contamination limits. The previously documented extensive release of Co, Cu, Mn, Ni and Zn from oxidised and acidified layers of these sediments (i.e. acid sulphate soil) is thus not explained by anomalously high natural or anthropogenic metal concentrations of the soils/sediments, but by an inherent highly mobile metal pool. Spatial-distribution maps highlight areas of elevated S and Mn concentrations, where it is likely that ditching and subsequent oxidation will result in an exceptionally large release of protons and Mn respectively.;

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Kulkarni, Swapnil, Saee Gharpure, Ujjal Kumar Sur, and Balaprasad Ankamwar. "Hydrothermal biosynthesis of chromium sulphide nanoparticles using egg yolk and its catalytic activity in degradation of dyes." Nano Express 1, no. 1 (April 14, 2020): 010019. http://dx.doi.org/10.1088/2632-959x/ab844c.

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Tanko, M. A., B. Y. Sanda, and M. H. Bichi. "Application of Moringa Oleifera Seed Extract (Mose) in the Removal of Heavy Metals from Tannery Wastewater." Nigerian Journal of Technological Development 17, no. 2 (July 22, 2020): 70–78. http://dx.doi.org/10.4314/njtd.v17i2.1.

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The main focus of this research work is to investigate the possibility of applying Moringa oleifera seed extract for the removal of heavy metals from tannery wastewater. Samples were collected from effluent discharge points of the GB tannery, Muhaza tannery and Z-tannery which are located in Challawa Industrial Area, Kano, Nigeria. The samples analyzed for physico-chemical parameters are pH, temperature, hardness, conductivity, turbidity, alkalinity, total suspended solid, total dissolved solid, calcium, magnesium, chloride, nitrates, sulphates and sulphide and heavy metals such as cadmium, chromium, copper, cobbalt, iron, lead, manganese and zinc. The results show that the final levels of heavy metals after the application of Moringa Oliefera seed extracts were within NESREA acceptable limits. The heavy metal removal efficiencies were as follows; 99.29% for cadmium, chromium and iron while 96.03%, 95.56%, 96.84%, 87.41%, 91.35% for copper, cobalt, lead, manganese and zinc, respectively. The cheap, easy and environmentally friendly material called Moringa oleifera could be recommended to tannery companies for effective removal of heavy metals so as to have a safe, non-polluting environment and also prevent endangering the lives of aquatic organisms andHUMANS Keywords: Moringa Oleifera, tannery, wastewater, heavy metal, wastewater

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Kassem, Taher S. "Kinetics and thermodynamic treatments of the reduction of hexavalent to trivalent chromium in presence of organic sulphide compounds." Desalination 258, no. 1-3 (August 2010): 206–18. http://dx.doi.org/10.1016/j.desal.2010.03.011.

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Roš, Milenko, and Anton Gantar. "Possibilities of reduction of recipient loading of tannery wastewater in Slovenia." Water Science and Technology 37, no. 8 (April 1, 1998): 145–52. http://dx.doi.org/10.2166/wst.1998.0319.

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The leather industry is well known as a high consumer of water (30 to 80 m3 for 1 ton of processed raw skins). At the same time this industry is known for the high specific pollution of wastewater. The main characteristics of tannery wastewater are: high salinity, high organic loading (COD, BOD5), high content of ammonia and organic nitrogen, and presence of specific pollutants (sulphide, chromium). The largest Slovenian tannery (IUV Vrhnika) processing 40 to 50 t of pig skins daily has a good system of physico-chemical pre-treatment of their wastewater (coagulation and flocculation with Al-sulfate and anionic polyelectrolyte). In pre-treatment, about 60% of organic substances are removed (COD and BOD5) and above 95% of sulfide and chromium. Concerning Slovenian regulations and taking into consideration the fact that this tannery is located on the relatively small and slowly running river Ljubljanica such pre-treatment is not sufficient. The company would like to supplement pre-treatment with biological treatment. Laboratory and pilot scale feasibility experiments including conventional biological treatment with activated sludge and combined anaerobic-anoxic-aerobic treatment with fixed biomass using mechanical pretreated wastewater and pretreated wastewater with flotation were performed. It became clear that effective biological treatment requires long retention times (several days) for applicable effluent.

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Yatim, Siti Rohana Mohd, N. A. Zainuddin, Nurul Shahirazni Mokhtar, Hanin Nazhifah Syahjidan, and Siti Nor Hazliyana Kamsuri. "Competitiveness in removing copper, zinc and chromium trivalent in plating industrial effluent by using hydroxide precipitation versus sulphide precipitation." IOP Conference Series: Materials Science and Engineering 1053, no. 1 (February 1, 2021): 012084. http://dx.doi.org/10.1088/1757-899x/1053/1/012084.

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Merkle, Roland K. W. "Platinum-group minerals in the middle group of chromitite layers at Marikana, western Bushveld Complex: indications for collection mechanisms and postmagmatic modification." Canadian Journal of Earth Sciences 29, no. 2 (February 1, 1992): 209–21. http://dx.doi.org/10.1139/e92-020.

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The platinum-group minerals in a drill core taken through the middle group of chromitite layers in the Critical Zone at Marikana in the western Bushveld Complex were found to consist mainly of laurite as inclusions in chromite grains. The platinum-group minerals containing Pt, Pd, and Rh are concentrated in the intercumulus silicates and frequently associated with base-metal sulphides. Up to about 20% of all platinum-group minerals in the investigated chromitite layers contain sub stantial amounts of As. The base-metal sulphides are strongly modified in the postmagmatic stage, which led to a significant loss of Fe and S, in this way concentrating Cu, Ni, and the platinum-group elements by factors of up to 10. Interaction between chromite and base-metal sulphides cannot account for all the Fe lost in chromite-poor samples, and the importance of additional processes is indicated. Inclusions in chromite and orthopyroxene indicate the formation of discrete platinum-group minerals and As-rich phases before the formation of an immiscible sulphide melt. Resorption of earlier formed platinum-group minerals into the immiscible sulphide melt and postmagmatic sulphidation destroyed most of the evidence of the early formed platinum-group minerals.

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Smyk, Mark C., and James M. Franklin. "A synopsis of mineral deposits in the Archean and Proterozoic rocks of the Lake Nipigon Region, Thunder Bay District, Ontario." Canadian Journal of Earth Sciences 44, no. 8 (August 1, 2007): 1041–53. http://dx.doi.org/10.1139/e07-013.

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A variety of metallic and non-metallic mineral deposit types occur within Archean and Proterozoic rocks in the area encompassing the Lake Nipigon Region Geoscience Initiative. Archean deposit types include Algoma-type banded iron formation-hosted iron (e.g., Lake Nipigon iron range); volcanogenic massive sulphide copper–zinc (e.g., Onaman–Tashota belt); ultramafic intrusion-hosted chromium (e.g., Puddy–Chrome lakes); mafic to ultramafic intrusion-hosted copper–nickel – platinum group element (PGE) (e.g., Lac des Iles); and pegmatite-hosted deposits of rare metals (Li, Ta, Be), uranium, and molybdenum (e.g., Georgia Lake field, Black Sturgeon Lake, and Anderson Lake, respectively). Mesothermal lode gold deposits are prominent in the Beardmore–Geraldton camp. Superior-type iron formation occurs in Paleoproterozoic Gunflint Formation. "Red-bed" copper occurs in Mesoproterozoic Midcontinent Rift-related Osler Group volcanic and interflow sedimentary rocks. Native copper and copper sulphides occur in Mesoproterozoic Sibley Group sedimentary rocks, adjacent to ultramafic intrusions. These mafic to ultramafic intrusions, associated with Midcontinent Rift magmatism, host copper–nickel–PGE deposits (e.g., Seagull, Great Lakes Nickel). Silver-bearing veins occur in Paleoproterozoic Animikie Group sedimentary rocks in proximity to Midcontinent Rift-related mafic intrusions (e.g., Silver Islet, Silver Mountain). Lead–zinc–barite veins, uranium-bearing veins, and amethyst vein and replacement-type deposits may be cogenetic and formed at or near the unconformity between Sibley Group basal sandstone and underlying Archean granitic basement (e.g., Dorion, Black Sturgeon Lake, McTavish Township). The hydrothermal systems that produced all of these veins were probably driven by heat associated with Midcontinent rifting. Many occur in structures related to rift-bounding faults. Iron oxide – copper–gold deposits may occur near the English Bay intrusion.

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Khosravi, Vahid, Faramarz Doulati Ardejani, Asa Gholizadeh, and Mohammadmehdi Saberioon. "Satellite Imagery for Monitoring and Mapping Soil Chromium Pollution in a Mine Waste Dump." Remote Sensing 13, no. 7 (March 27, 2021): 1277. http://dx.doi.org/10.3390/rs13071277.

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Weathering and oxidation of sulphide minerals in mine wastes release toxic elements in surrounding environments. As an alternative to traditional sampling and chemical analysis methods, the capability of proximal and remote sensing techniques was investigated in this study to predict Chromium (Cr) concentration in 120 soil samples collected from a dumpsite in Sarcheshmeh copper mine, Iran. The samples’ mineralogy and Cr concentration were determined and were then subjected to laboratory reflectance spectroscopy in the range of Visible–Near Infrared–Shortwave Infrared (VNIR–SWIR: 350–2500 nm). The raw spectra were pre-processed using Savitzky-Golay First-Derivative (SG-FD) and Savitzky-Golay Second-Derivative (SG-SD) algorithms. The important wavelengths were determined using Partial Least Squares Regression (PLSR) coefficients and Genetic Algorithm (GA). Artificial Neural Networks (ANN), Stepwise Multiple Linear Regression (SMLR) and PLSR data mining methods were applied to the selected spectral variables to assess Cr concentration. The developed models were then applied to the selected bands of Aster, Hyperion, Sentinel-2A, and Landsat 8-OLI satellite images of the area. Afterwards, rasters obtained from the best prediction model were segmented using a binary fitness function. According to the outputs of the laboratory reflectance spectroscopy, the highest prediction accuracy was obtained using ANN applied to the SD pre-processed spectra with R2 = 0.91, RMSE = 8.73 mg/kg and RPD = 2.76. SD-ANN also showed an acceptable performance on mapping the spatial distribution of Cr using the ordinary kriging technique. Using satellite images, SD-SMLR provided the best prediction models with R2 values of 0.61 and 0.53 for Hyperion and Sentinel-2A, respectively. This led to the higher visual similarity of the segmented Hyperion and Sentinel-2A images with the Cr distribution map. This study’s findings indicated that applying the best prediction models obtained by spectroscopy to the selected wavebands of Hyperion and Sentinel-2A satellite imagery could be considered a promising technique for rapid, cost-effective and eco-friendly assessment of Cr concentration in highly heterogeneous mining areas.

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Tuurna, Satu, Sanni Yli-Olli, and Liisa Heikinheimo. "The Effect of Water Vapour and Sulphur on Corrosion Mechanisms of Steels." Materials Science Forum 595-598 (September 2008): 841–49. http://dx.doi.org/10.4028/www.scientific.net/msf.595-598.841.

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It is well known that water vapour accelerates oxidation; however different gas conditions and material compositions affect the mechanism. The paper addresses this issue from two different application areas; biomass and kraft recovery boilers. In these applications water vapour and sulphur are simultaneously affecting the corrosion mechanism, though the mechanisms are different. Low-alloyed steels were exposed to an atmosphere containing different amounts of water vapour at temperatures of 420, 550 and 600°C. Under oxidising conditions increasing water content generally accelerates oxidation. However, presence of SO2 in moist atmosphere retards oxidation at high temperatures. The phenomenon is seen at low temperatures with higher chromium contents. Stainless steel 304L was tested in an atmosphere containing hydrogen sulphide and carbon monoxide with and without water vapour at a temperature of 440°C to simulate elevated kraft recovery boiler furnace conditions. The tests showed that water vapour in the test atmosphere produces a protective spinel oxide on the metal surface. In tests without water vapour, the initial scales at metal surface were different sulphur compounds and intensive sulphidation occurred. The effect of water vapour on the sulphidation mechanism is addressed in the paper through the described tests and thermodynamic modelling.

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Yavorovskiy, Oleksandr, Sergii Omelchuk, Lyudmyla Sokurenko, Tetyana Zinchenko, Nina Solokha, Vasyl Aleksiichuk, and Roman Brukhno. "ENVIRONMENTAL AND OCCUPATIONAL HAZARDS OF METAL NANOCOMPOUNDS PRODUCTION AND APPLICATION: HYGIENIC, CLINICAL AND TOXICOLOGICAL ASPECTS." Wiadomości Lekarskie 72, no. 8 (2019): 1504–11. http://dx.doi.org/10.36740/wlek201908117.

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Introduction: Nanometals are the most common nanoobjects, used nearly in all industrial branches. Considerable advances in the nanotechnological production have led to progressive use of nanomaterials in industry, though occupational safety of the nanoindustry staff is insufficiently studied. The aim: Estimation of labor safety during production of metal nanoparticles for the purpose of defining necessary and efficient preventive measures. Materials and methods: The personnel of the hygienic departments of the O.Bogomolets National medical university have conducted numerous physiological, hygienic, biochemical, morphological and toxicological studies. The scientists have studied and revealed hazardous workplace factors of various metal nanoparticle production technologies, particularly those of metal nanoparticles: nanosilver, titanium nitride, chromium disilicide, lead sulphide, etc. Results and conclusions: The authors have developed method of the occupational exposure metal nanoparticles exposure air control, assessed and analyzed health of the personnel engaged in production of the nanometals. The paper contains data of the blood cells functional activity assessment, with the detected possible molecular nanoparticles toxicity mechanisms due to the altered gene expression. The authors have studied effect of nanoaerosols onto the laboratory rats respiratory organs, evaluated their blood biochemical characteristics, liver lipid content of fatty acids as well as defined morpho-functional hepatic transformations of the laboratory animals which underwent lead sulfide nanoparticles treatment.

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Leta, S., L. Gumaelius, F. Assefa, and G. Dalhammar. "Identification of Efficient Denitrifying Bacteria from Tannery Wastewaters in Ethiopia and a Study of the Effects of Chromium III and Sulphide on Their Denitrification Rate." World Journal of Microbiology and Biotechnology 20, no. 4 (June 2004): 405–11. http://dx.doi.org/10.1023/b:wibi.0000033069.24982.6e.

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Eliseeva, Olga V. "Application of atomic absorption spectroscopy for the analysis of chemical composition of Brassica rapa." Butlerov Communications 61, no. 2 (February 29, 2020): 46–50. http://dx.doi.org/10.37952/roi-jbc-01/20-61-2-46.

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This paper presents the study of the chemical composition of Petrovskaya variety of turnip after the non-root treatment of vegetating plants with the solution of trivalent chromium. The treatment has been performed with the solutions of chromic potassium sulphate with chromium concentrations of 0.002% and 0.005%. The experiment has been conducted according to the following scheme: 1. NPK (background) – control version; 2. NPK + HO Cr 0.002%; 3. NPK + HO Cr 0.005%. Nitroammophoska was used as the background macro fertiliser during the sowing at the rate of 30 g/m2. In the control versions plants have been treated with the distilled water. The content of chromium in root vegetables has been assessed using the method of atomic absorption spectroscopy. It is shown that after the treatment with the solution of chromic potassium sulphate the average content of chromium in root vegetables increased by 31.3% in NPK + Cr 0.002% version and by 55.6% in NPK + Cr 0.005% version in comparison with the control version. At the chromium concentration of 0.002% the content of dry matter in turnip remained at the level of control version, the content of dry soluble matters and ascorbic acid decreased down to 5.9% and 28.60 mg/100 g, the level of nitrates in root vegetables increased up to 286.0 mg/kg of wet mass. At the chromium concentration of 0.005% the content of dry matter in turnip decreased down to 10.4%, the content of dry soluble matters increased up to 7.3%, the content of ascorbic acid and nitrates decreased down to 27.81 mg/100 g and 210.2 mg/kg of wet mass, respectively.

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Fomichev, V. T., A. V. Savchenko, and G. P. Gubarevich. "Functional Galvanic Coatings of the Cr-Zn System." Materials Science Forum 945 (February 2019): 688–94. http://dx.doi.org/10.4028/www.scientific.net/msf.945.688.

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The authors have studied the influence of the electric current density, temperature, electrolyte composition on the properties of electroplating Chromium-Zinc deposits. The dependence of the maximum yield of metal on the physico-chemical characteristics of the solutions for electroplating of Chromium and Cr-Zn alloy has been shown. Chromium-Zinc coatings have been obtained from electrolytes based on chromic acid in the presence of organic additive (4-methylaminophenol). Abrupt nonlinear changes in density, viscosity, surface tension, specific electrical conductivity due to structural transformations in electrolytes are observed at the concentration of zinc sulphate of 4070 gramm / litr (further in the text - g/l), and the organic additive of 2-5 g/l. The obtained model has been applied to predict the optimal electrolyte compositions for the processes of Cr-Zn alloy formation, which will allow reducing the research efforts concerning the electrochemical studies of the given process when chromic acid solutions are used. The coatings exhibit high hardness, corrosion resistance, wear resistance, low internal stresses.

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de Vooys, A. C. A., J. H. O. J. Wijenberg, and M. T. M. Koper. "Cyclic voltammetry study of trivalent basic chromium sulphate electrolytes contaminated with sulphite." Electrochimica Acta 269 (April 2018): 700–705. http://dx.doi.org/10.1016/j.electacta.2018.02.169.

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Kotzé, E., and C. Gauert. "PGE distribution in the chromitite layers at Eastern Chrome Mine, Eastern Bushveld Complex, South Africa: A descriptive study with comparison of EPMA and LA-ICP-MS methods for detection of trace PGE in base metal sulphides." South African Journal of Geology 123, no. 4 (October 26, 2020): 551–72. http://dx.doi.org/10.25131/sajg.123.0033.

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Abstract A descriptive petrographic study was carried out on the chromitites (LG-6 to UG-3a) of a single borehole from the Winterveld Chrome Mine, Eastern BC, along with analysis by both EPMA and LA-ICP-MS of the PGE contents of base metal sulphides (BMS) found within these layers. EPMA measurements were optimized to measure trace amounts of PGE by increased probe current and counting time, yielding very low detection limits for this method (12 to 38 ppm). However, analytical error proved to be very high (over ~30%) in samples that showed PGE values below 100 ppm. Also, the possibility of interference on PGE spectra by other elements, especially on Rh, is high. Therefore, these measurements can only be considered semi-quantitative indicators of elemental PGE concentration. Our findings confirmed that pentlandite of the BC chromitites contains Pd and Rh, probably in solid solution. Pt was found in discrete minerals (braggite, cooperite) throughout the sequence, and Ru, Ir and Os were found as early-stage minerals such as laurite, associated with chromite rather than sulphide. The PPGE increase upwards in the chromitite layers relative to the IPGE. An immiscible sulphide phase contributed to collection of the PGE in the chromitites of the MG-4 and above. The chromitites of the LG-6 to MG-1 show less evidence of hosting an immiscible sulphide phase, and pentlandite of these layers does not appear to host Rh, although Pd was found. Although this borehole is located only 1.5 km away from the centre of the Steelpoort Fault Zone, a possible feeder zone for the BC, large-scale disruption of the chromitite layers was not observed. An intrusive pegmatoidal pyroxenite was found to occur beneath the LG-6, and contained PGE-bearing sulphides, although the origin of this mineralization is most likely from the LG-6 chromitite itself. A sulphide vein occurring in silicate was also analysed and was found to be PGE-deficient compared to the sulphides of the chromitite layers.

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Bindi, Luca, Federica Zaccarini, Elena Ifandi, Basilios Tsikouras, Chris Stanley, Giorgio Garuti, and Daniela Mauro. "Grammatikopoulosite, NiVP, a New Phosphide from the Chromitite of the Othrys Ophiolite, Greece." Minerals 10, no. 2 (January 31, 2020): 131. http://dx.doi.org/10.3390/min10020131.

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Grammatikopoulosite, NiVP, is a new phosphide discovered in the podiform chromitite and hosted in the mantle sequence of the Othrys ophiolite complex, central Greece. The studied samples were collected from the abandoned chromium mine of Agios Stefanos. Grammatikopoulosite forms small crystals (from 5 μm up to about 80 μm) and occurs as isolated grains. It is associated with nickelphosphide, awaruite, tsikourasite, and an undetermined V-sulphide. It is brittle and has a metallic luster. In plane-polarized light, it is creamy-yellow, weakly bireflectant, with measurable but not discernible pleochroism and slight anisotropy with indeterminate rotation tints. Internal reflections were not observed. Reflectance values of mineral in air (R1, R2 in %) are: 48.8–50.30 at 470 nm, 50.5–53.5 at 546 nm, 51.7–55.2 at 589 nm, and 53.2–57.1 at 650 nm. Five spot analyses of grammatikopoulosite give the average composition: P 19.90, S 0.41, Ni 21.81, V 20.85, Co 16.46, Mo 16.39, Fe 3.83, and Si 0.14, total 99.79 wt %. The empirical formula of grammatikopoulosite—based on Σ(V + Ni + Co + Mo + Fe + Si) = 2 apfu, and taking into account the structural results—is (Ni0.57Co0.32Fe0.11)Σ1.00(V0.63Mo0.26Co0.11)Σ1.00(P0.98S0.02)Σ1.00. The simplified formula is (Ni,Co)(V,Mo)P and the ideal formula is NiVP, which corresponds to Ni 41.74%, V 36.23%, P 22.03%, total 100 wt %. The density, calculated on the basis of the empirical formula and single-crystal data, is 7.085 g/cm3. The mineral is orthorhombic, space group Pnma, with a = 5.8893(8), b = 3.5723(4), c = 6.8146(9) Å, V = 143.37(3) Å3, and Z = 4. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2019-090). The mineral honors Tassos Grammatikopoulos, geoscientist at the SGS Canada Inc., for his contribution to the economic mineralogy and mineral deposits of Greece.

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Zhang, Bo, Wen Hai Chi, Pei Yang Shi, Cheng Jun Liu, and Mao Fa Jiang. "Study on the Clean Production Process of Basic Chromium Sulphate." Advanced Materials Research 887-888 (February 2014): 651–56. http://dx.doi.org/10.4028/www.scientific.net/amr.887-888.651.

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The pollution of chromium salt industry is increasingly serious in China and becomes a worldwide problem with the rapid development of chromium salt industry. Then a new clean production process with a high recovery rate of chromium and pollution-free was proposed according to the comprehensive summary of existing processes of basic chromium sulphate. Furthermore, a small amount of slag will be discharged in this short process with lower energy consuming. The design concept is also applicable to the preparation of other chromium salts products, which will eliminate the pollution of Cr6+ during the process of chromium salt production and be helpful to the comprehensive utilization of chromium salt. In addition, the guidance of scholar research and the broad application prospects of this work cannot be neglected.

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Valverde, J. L., J. Lobato, I. Fernández, L. Marijuán, S. Pérez-Mohedano, and R. Talero. "Reducción de cromo hexavalente en cementos usando sulfato ferroso mono y heptahidratado: eficacia y almacenabilidad." Materiales de Construcción 55, no. 279 (September 30, 2005): 39–52. http://dx.doi.org/10.3989/mc.2005.v55.i279.197.

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35

Bonny, Sandy M., and Brian Jones. "Barite (BaSO4) biomineralization at Flybye Springs, a cold sulphur spring system in Canada's Northwest Territories." Canadian Journal of Earth Sciences 44, no. 6 (June 29, 2007): 835–56. http://dx.doi.org/10.1139/e06-126.

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The Flybye Springs, Northwest Territories, consist of 10 active vents and numerous small seeps that discharge sulphide- and barium-rich spring waters at an average temperature 8.5 °C. Oxidation of sulphide to sulphate drives precipitation of stellate and platy barite microcrystals in the proximal flow paths. Downstream, and in vent- and tributary-fed ponds, barite is precipitated among streamer and mat forming colonies of sulphur-tolerant microbes, including Thiothrix, Beggiatoa, Thioploca, Chromatium, Oscillatoria, fungi (dominantly Penicillium), and unicellular sulphate reducing bacteria. These microbes mediate barite saturation by adjusting redox gradients and via passive adsorption of barium ions to cell surfaces and extracellular polymeric substances. Passive biomineralization produces barite laminae in floating microbial mats, nanometric coatings, and micrometric encrustations around microbial cells and filaments, and local permineralization of Thiothrix, Beggiatoa, and Oscillatoria outer cell walls. Intracellular barium enrichment and (or) metabolic sulphur oxidation may be important to "active biomineralization" that produces nanometric barite globules on the tips of fungal hyphae, barite-filled cell cavities in Beggiatoa and Thiothrix, and baritized sulphur globules. Degradation of biomineralized cells generates detrital "microfossils," including barite tunnels, layered cylinders, solid cylindrical grains and chains of barite beads. The diversity of inorganic and biomineralized barite in the Flybye Springs flow path highlights the influence of ambient chemistry, microbial metabolism, and cellular structure on barite solubility and on the taphonomy of microfossils preserved in barite.

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Orlov, Victor, Leonid Levkov, Vladimir Dub, Alan Balikoev, and Dmitry Shurygin. "New approach to development and manufacturing technologies of duplex steel." E3S Web of Conferences 121 (2019): 04010. http://dx.doi.org/10.1051/e3sconf/201912104010.

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We conducted a brief review of current production and application of duplex and super duplex steels for manufacture of equipment exposed to the hazard of sulphide stress-corrosion cracking, sea water and other corrosive environment. The super duplex steel with enhanced corrosion-mechanical characteristics in comparison with the known steels of austenitic-ferritic class was developed. Based on the concepts of formation of a special structure of two-phase austenitic-ferritic steels in the process of crystallization, the possibilities of compositional, technological, thermal and special impact techniques are considered and advanced ways of controlling physical, chemical, structural homogeneity and properties of super duplex steels are developed. Electroslag remelting with the application of low-frequency alternating current provides effective control over the length of the two-phase area, the size of the primary dendrites of the austenitic and ferritic phases, the average distance between their axes, the parameters of the crystallizing cell, the development of liquation phenomena and the size of the growing non-metallic phases. Within framework of the proposed approach, the thermodynamic and kinetic conditions for the formation and growth of hardening phases are assessed, a new composition and a complex technology for the manufacture of corrosion-resistant super duplex steels for gas and oil production equipment has been developed. Thermodynamically stable, having sizes of 30-300 nm, niobium nitrides and carbonitrides are located inside the grains of the ferritic phase. At the same time, the sigma phase and chromium carbide precipitates at the intergrain boundaries are not observed. The results of the determination of mechanical and corrosion properties in accordance with the NACE TM 0177 standard (method A), tests of corrosion witness-samples in field conditions demonstrate the advantages and prospects of using new super duplex steel for the manufacture of oil and gas production equipment operating in an environment with high H2S content and CO2 under significant mechanical loads, without the risk of brittle fracture.

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Karlsson, S., J. Pettersson, J. E. Svensson, and L. G. Johansson. "KCl-Induced High Temperature Corrosion of the Austenitic Stainless Steel 304L – The Influence of SO₂." Materials Science Forum 696 (September 2011): 224–29. http://dx.doi.org/10.4028/www.scientific.net/msf.696.224.

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The effect of SO2 on the oxidation of alloy 304L in O2+H2O and O2+H2O+KCl environment has been investigated at 600°C. Exposure time was 1-168 hours. The exposed samples were analyzed by SEM/EDX, XRD and IC. In dry O2, a protective and chromium-rich corundum-type oxide forms. In the presence of H2O(g), chromium is volatilized in the form of CrO2(OH)2(g). The corresponding chromium depletion of the protective oxide triggers a partial loss of protective properties resulting in the formation of oxide islands on the alloy grain centers. The oxide islands consist of an outward growing hematite layer and an inward growing FeCrNi spinel layer. By coating the samples with KCl the chromia depletion of the protective oxide dramatically increases due to the formation of K2CrO4. This leads to breakaway corrosion, a rapidly growing scale forming all over the surface. The resulting thick scale has a similar structure as the oxide islands formed in the absence of KCl. The addition of 300 ppm SO2 to the O2+H2O and O2+H2O+KCl environments results in a drastic reduction of corrosion rate. In O2+H2O environment the effect of SO2 is attributed to the formation of a thin sulphate film on the oxide surface that impedes chromium volatilization and decreases the rate of oxygen reduction on the oxide surface. In O2+H2O+KCl environment the corrosion mitigating effect of SO2 is mainly attributed to the rapid conversion of KCl to K2SO4. In contrast to KCl, K2SO4 does not deplete the protective oxide in chromium by forming K2CrO4.

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R.N. Palomar, P. Jensen, and V.K. Sulc. "EXPOSURE TESTS OF SURFACE TREATED SAWN COCONUT TIMBER." CORD 5, no. 01 (June 1, 1989): 34. http://dx.doi.org/10.37833/cord.v5i01.224.

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An investigation was made to determine the relative performance of three readily available inorganic chemicals containing either copper or chromium when applied singly or in combination to sawn coconut timber surfaces. The treating solutions, consisting of chromic acid (H2CrO4) sodium chromate (Na2CrO4) and copper sulphate (CuSO4), were applied by trush to wood surfaces with one coating at the rate of approximately 155 grams per square meter. The specimens were exposed outdoors on racks inclined at 450 angle and facing south. Results after 3 years of test showed that treatments with mixture of H2CrO4 and CuSO4 or combination of Na2CrO4 and CO4 performed better than single application of either H2Cr4 or Na2CrO4. The former treatments still showed uniform and pleasing appearance after the exposure period.

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Kumar, D. B. Rohini, B. S. Sitaramam, and N. Krishnamurti. "Reutilisation of Waste Chromium Sulphate Liquor." Chemie Ingenieur Technik 64, no. 8 (August 1992): 734–35. http://dx.doi.org/10.1002/cite.330640815.

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40

Anami, Wisni Rona, Mamay Maslahat, and Dian Arrisujaya. "PRESIPITASI LOGAM BERAT LIMBAH CAIR LABORATORIUM MENGGUNAKAN NATRIUM SULFIDA DARI BELERANG ALAM." Jurnal Sains Natural 10, no. 2 (September 29, 2020): 61. http://dx.doi.org/10.31938/jsn.v10i2.283.

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Precipitation of Laboratory Wastewater Heavy Metals by Natural Sulphur Sodium Sulfide Sodium sulfide (Na2S) from natural sulfur has been used for heavy metal precipitation from laboratory wastewater. Heavy metals in laboratory wastewater include mercury (Hg), lead (Pb), chromium (Cr) and zinc (Zn). Initial laboratory wastewater testing was performed by measuring the initial pH and the concentration of heavy metals in the wastewater prior to precipitation using the atomic absorption spectrophotometer. Sulphide precipitation phase consists of variations in the concentration of NaOH, time, temperature, and volume of dissolving Na2S. Parameters for the efficiency of Hg, Pb, Zn and Cr heavy metal precipitation were the initial pH, concentration and rate of stirring of the solution. Results showed that the optimum precipitation efficiency for Zn is achieved by using 10 % Na2S solution with an efficiency of 97.93 %. The most significant reduction in Cr and Hg was the use of 20 % Na2S solution with a precipitation efficiency of 99.24 % and 99.76 % respectively. The optimal efficiency for Pb with a 30 % Na2S solution was 99.68 %. Natural sulfur can reduce the levels of heavy metals in laboratory wastewater by precipitation.Key words: Natural sulfur, Heavy metals, Precipitation, Sodium sulfide, ABSTRAKPresipitasi logam berat dari limbah cair laboratorium telah dilakukan dengan menggunakan natrium sulfida (Na2S) dari belerang alam. Logam berat yang terkandung dalam limbah cair laboratorium diantaranya adalah merkuri (Hg), timbal (Pb), kromium (Cr) dan seng (Zn). Pengujian awal limbah laboratorium dilakukan dengan mengukur pH awal dan kadar logam berat yang terdapat dalam limbah sebelum presipitasi menggunakan pH meter dan spektrofotometer serapan atom. Tahapan presipitasi limbah oleh sulfida meliputi pembuatan variasi konsentrasi NaOH, waktu, suhu, dan volume pelarutan Na2S. Parameter efisiensi presipitasi logam Hg, Pb, Zn, dan Cr meliputi pH, Konsentrasi dan Kecepatan pengadukan. Hasil penelitian menunjukkan efisiensi pengendapan optimal untuk logam Zn terdapat pada penggunaan larutan Na2S 10% dengan efisiensi 97,93%. Larutan Na2S 20% paling banyak menurunkan logam Cr dan Hg dengan efisiensi masing-masing sebesar 99,24% dan99,76%. Efisiensi optimal untuk logam Pb berada pada penggunaan larutan Na2S 30% dengan efisiensi 99,68%. Belerang alam mampu menurunkan kadar logam berat dalam limbah cair laboratorium dengan metode presipitasi.Kata kunci: Belerang alam, Logam berat, Presipitasi, Natrium sulfida

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Journal, Baghdad Science. "Spectrophotometric Determination of Sulphite in Various Water Samples Via Chromium-1,5-Diphenylcarbazide Complex." Baghdad Science Journal 15, no. 2 (June 3, 2018): 181–88. http://dx.doi.org/10.21123/bsj.15.2.181-188.

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A simple and rapid spectrophotometric method for the determination of sulphite SO3-2 is described. The method is based on the rapid reduction of known amount of chromate CrO4-2 in the presence of sulphite in acidic medium of 2N H2SO4. The amount of excess of chromate was measured after it reactions with 1,5-diphenylcarbazide which finally gives a pink-violet, water soluble and stable complex, which exhibit a maximum absorption at 542 nm. Beer's law was obeyed in the concentration range from 0.004-6.0 µg of sulphite in a final volume of 25 ml with a molar absorbtivity of 4.64×104 l.mol-1.cm-1, Sandal's sensitivity index of 0.001724 ?g .cm-2 and relative standard deviation of ±0.55 - ±0.83 depending on the concentration level. The present method has been developed for the determination of sulphite in the presence of thiosulphate. Good recoveries of sulphite from various water samples are achieved using the proposed method.

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Jorge, F. C., T. M. Santos, J. Pedrosa de Jesus, and W. B. Banks. "Fixation of Chromium in Wood from Trivalent Chromium Salt Solutions." Holzforschung 53, no. 5 (September 10, 1999): 465–73. http://dx.doi.org/10.1515/hf.1999.077.

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Summary The aim of this study was to fix chromium chemically in wood from trivalent chromium solutions. Chromium(III) nitrate, chloride and sulphate salts were applied, both in aqueous and in methanolic solutions. To improve chromium fixation metallic zinc was used as a strong reductant to generate labile Cr(II) species from Cr(III), and base was added (NaOH for water and NaMeO for methanol). Aqueous solution reaction conditions were always acidic in spite of base addition, leading to unacceptable levels of wood degradation (e. g., weight loss), although relatively high chromium levels were attained in some cases. Methanolic solutions did not lead to wood degradation, and there was fixation of high levels of chromium. Although the addition of NaMeO seemed to improve chromium fixation, a chromium precipitate always formed, usually after a long reaction time (> 4h). Therefore the following experimental conditions for chromium fixation are suggested: alcoholic solution of Cr(III) chloride or nitrate, addition of metallic zinc, at reflux. To avoid using large amounts of zinc, Cr(III)-solutions can also be reduced electrochemically.

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Yoshikuni, N. "Rapid dissolution of chromite with sulphuric acid—lithium sulphate mixture containing ceric sulphate, manganese dioxide or periodate, and spectrophotometric determination of chromium." Talanta 38, no. 5 (May 1991): 515–19. http://dx.doi.org/10.1016/0039-9140(91)80173-w.

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44

Alguacil, F. J., A. G. Coedo, T. Dorado, and I. Padilla. "The removal of toxic metals from liquid effluents by ion exchange resins. Part I: Chromium(VI)/Sulphate/Dowex 1x8." Revista de Metalurgia 38, no. 4 (August 30, 2002): 306–11. http://dx.doi.org/10.3989/revmetalm.2002.v38.i4.412.

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45

Dunham, A. C., and F. C. F. Wilkinson. "Sulphide droplets-and the Unit 11/12 chromite band, Rhum: a mineralogical study." Geological Magazine 122, no. 5 (September 1985): 539–48. http://dx.doi.org/10.1017/s0016756800035457.

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AbstractA microscopic and electron microprobe investigation has been made of six samples of the allivalite–chromitite–peridotite band at the junction of Units 11 and 12, Eastern Layered Series, Rhum. Analyses are presented of olivine, plagioclase and pyroxene, the plagioclase showing reverse zoning in the chromitite. Sulphide droplets occur within and above the chromitite, and contain pyrrhotite, pentlandite, cubanite, bornite, digenite, chalcocite, native copper and electrum, as well as chromite zoned to magnetite, spinel and ilmenite. The variation from aluminous chromite to chromite in the chromitite is confirmed by analyses of five new traverses. The rocks formed during and just after the time when new magma entered the magma chamber. The variation in the chromite compositions is ascribed mainly to magmatic variation in composition due to the mixing process.

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Philipot, J. M., F. Chaffange, and J. Sibony. "Hexavalent Chromium Removal from Drinking Water." Water Science and Technology 17, no. 6-7 (June 1, 1985): 1121–32. http://dx.doi.org/10.2166/wst.1985.0207.

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A series of tests were performed with a view to solving the problem of chromium pollution in the Meulan district near Paris, due to the proximity of long-established metal-working plants. It was found that the accumulated pollution not only originated from the groundwater source but also from atmospheric contamination through fall-out from smoke and fumes issuing from local metal-works' stacks. Among the interesting features of this paper is the fact that, since the profound penetration by the pollutant affects potable feedstock, chromium removal studies have been made on potable water for the first time on record. Several methods are reviewed, among which the only economically feasible one appears to be the reduction of hexavalent chromium by a sufficient quantity of iron sulphate, the problem attached to iron-sulphate overdose being solved by the application of high-rate filtration on very fine sand. This arrests the fine precipitates and reduces the residual ferrous-iron by catalysis. Reliability of the treatment is ensured by a system of continuous metering that automatically controls reagent dosing.

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Cassano, A., R. Molinari, and E. Drioli. "Saving of Water and Chemicals in Tanning Industry by Membrane Processes." Water Science and Technology 40, no. 4-5 (August 1, 1999): 443–50. http://dx.doi.org/10.2166/wst.1999.0621.

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Some results on pressure-driven membrane operations able to improve chromium recovery from spent chromium tanning baths and to desalinate water discharged from filterpress after Cr(III) precipitation are reported. Nanofiltration was employed to concentrate chromium(III) using a spiral-wound module. Chromium concentration and COD in permeate were respectively about zero and 2–3 g/l as compared to initial feed values of 2.8 and 5.2 g/l; the high chloride concentration in the permeate suggested to reuse this solution in the pickling step saving fresh water and salts. The concentrate solution presented a higher chromium purification with respect to initial feed. It was tested in retanning, and after further concentration by chemical precipitation-dissolution method, in tanning operations. Chemical and physical analyses on leather treated with these solutions showed similar characteristics with respect to use of traditional chromium solution. Reverse osmosis was employed to reduce the high salt content in waste water from filter pressing of chromium hydroxide panels. Good rejection of reverse osmosis membrane to chloride and sulphate ions suggested the use of this operation for obtaining water, to be used in washings, or to sent to biological treatment of final waste water.

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Cetin, Gulten, Sevgi Kocaoba, and Goksel Akcin. "Removal and Recovery of Chromium from Solutions Simulating Tannery Wastewater by Strong Acid Cation Exchanger." Journal of Chemistry 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/158167.

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The process in this study was conducted on removal of chromium(III) in a solution simulating a typical spent chrome tanning bath by the resin having matrix of styrene-divinylbenzene-based macroporous sulphonate, Amberjet 1200Na. The column experiments were carried out with the bed volumes of the resin as 751 mL and 1016 mL for different installation systems of the laboratory-scale pilot plant. The feeding solutions in the bed volumes of 200 and 190 were used for each installation system. The regeneration behaviour of the resin was determined by using reverse regeneration procedure with the solution of hydrogen peroxide in alkaline. The regeneration kinetics of the exhausted resin was examined with a range of the solutions having different concentration series of the alkaline hydrogen peroxide. The solutions of the basic chromium sulphate were recycled for each installation system following the regeneration cycles. The chromium ions in effluent were quantitatively eluted, and satisfactory removal of chromium(III) and recovery of chromium(VI) were achieved.

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Polischuk, S. D., Yu A. Stekolnikov, D. G. Churilov, N. V. Byshov, S. N. Borychev, I. A. Uspenskiy, and I. S. Arapov. "Peculiarities of Chromium Coating in Low-Concentrated Electrolytes when Repairing Details." Key Engineering Materials 836 (March 2020): 151–57. http://dx.doi.org/10.4028/www.scientific.net/kem.836.151.

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The physical-mechanical properties of chromium coatings from low-concentrated electrolytes with additions of organic substances were studied when comparing with similar ones from standard sulphate electrolyte. It has been established that the properties of chromium coatings from low concentrated electrolytes are superior to those of standard sulphate electrolyte. An additional advantage of low-concentrated electrolytes is less carry-over of chromium anhydrate through ventilation and wash water, which reduces the cost of cleaning them when they are discharged. However, under operating conditions, more frequent adjustment of the composition of such electrolytes is required. The electrolyte is distinguished by a good scattering over the surface of parts and covering power when restored to size on a thickness of 250-300 μm of hydraulic cylinders of agricultural and mining equipment, having a length of up to 4 m and a diameter of up to 0.5 m, an increased current output of up to 24-36 % and up to 3-4 times higher corrosion resistance, micro hardness of up to 1,300 kg / mm2, determined by the conditions of deposition relative to the standard sulfate electrolyte of chromium plating. Chromium coatings from a low-concentration electrolyte with organic additives passed the recommended tests for adhesion, tearing, wear and micro hardness according to GOST methods. Their use at the enterprises of technical service for repair of agricultural parts promises economic advantages in the field of practical application (higher deposition rate and less application time), as well as lower costs for environmental protection.

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Chattopadhyay, P., and M. Mistry. "Rapid chromite dissolution using a manganese dioxide-lithium sulphate-sulphuric acid mixture for matrix-independent determination of chromium." Analytica Chimica Acta 295, no. 3 (September 1994): 325–30. http://dx.doi.org/10.1016/0003-2670(94)80238-6.

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Journal articles on the topic 'Chromium sulphide'

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