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Showing 1 to 20 of 71 for “"Cr(VI)"”.
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Cr(VI) Generation and Stability in Drinking Water
The current US Environmental Protection Agency (USEPA) maximum contaminant level (MCL) for total chromium of 100 ppb is under revision to consider a specific level for Cr(VI), which has a proposed MCL of 10 ppb in California. Cr(VI) is a suspected carcinogen, and interconverts with the other most …
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Extractant Impregnated Membranes for Cr(III) and Cr(VI)
… removal and enrichment of the anionic forms of Cr(VI) and cationic forms of Cr(III), respectively. Results show Aliquat-336 and DEHPA effectively remove Cr(VI) and Cr(III) from aqueous solutions. Extraction efficiency is independent of source concentration from 1-50 ppm but is dependent upon …
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Microbial CR(VI) reduction in indigenous culture of bacteria: characterization and modelling
South Africa currently faces multiple Cr(VI) contamination problems which are unsuccessfully remediated using available technologies. Cr(VI) is highly toxic, carcinogenic and mutagenic in nature and it is exclusively released through anthropogenic activities. A new treatment approach is proposed …
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Development of teawaste based bio-sorbent materials for removal of Cr(VI) from wastewater
… health and the stability of the ecological environment. Hexavalent chromium in industrial waste water is a common typical heavy metal ion. Therefore, how to effectively treat heavy metal pollution in water has become a hot topic in the field of water pollution control. <br/><br/>In this …
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Síntesis de tecnologías de membranas para el tratamiento de efluentes y recuperación de Cr(VI)
En esta Tesis se presentan resultados vinculados al modelado, diseño, optimización operativa y síntesis de plantas basadas en nuevas tecnologías de membranas para la extracción y concentración de compuestos altamente contaminantes pre-sentes en efluentes acuosos. Se centra el análisis en el …
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Isotopic fractionation of chromium and uranium during Cr(VI) reduction by ascorbate and U(VI) reduction by sulfide
… conditions which control their chemical behavior in near surface settings. Reduction of hexavalent chromium (Cr(VI)) and uranium (U(VI)) greatly decreases their solubility and mobility, and therefore their toxicity in groundwater. Redox transformations have been shown to induce predictable …
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Isotopic fractionation of chromium and uranium during abiotic and microbial Cr(VI) reduction and microbial U(VI) reduction
Reduction of hexavalent chromium (Cr(VI)) influences the chemical behavior of Cr in a variety of geochemical settings such as ancient and modern oceans, lakes and groundwater and surface water systems. Cr(VI) reduction immobilizes the toxic form of Cr to less toxic and insoluble Cr(III). Several …
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Preparation and characterisation of poly (vinyl alcohol)/chitosan/silicon dioxide (PVA/CS/SiO2) beads for the chromium (VI) (Cr(VI) removal
… have been developed for the removal of Chromium (VI) (Cr(VI)) from wastewater. In this study, blend polymer absorbent beads which was poly (vinyl alcohol)/chitosan/silicon dioxide (PVA/CS/SiO2) beads were prepared by dropwise method by crosslinking with sodium hydroxide and ethanol and further …
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Investigation of Hexavalent Chromium Reduction by Aerobic Bacteria in Water and Soil
<p>Hexavalent chromium (Cr(VI)) has been identified as a high priority pollutant by the U.S. Environmental Protection Agency because of its high toxicity and carcinogenicity. Cr(VI) is commonly used in electroplating, pigment, leather processing and mining resulting in widespread Cr(VI) pollution, …
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The kinetics of the Arsenic(III)-Chromium(VI) reaction in various buffer solutions
The oxidation of arsenic(III) by chromium(VI) requires the postulation of uncommon oxidation states as reactive intermediates. The possible intermediates of chromium are the divalent, tetravalent, and pentavalent states. Recently arsenic(IV) has been postulated as a reactive intermediate in certain …
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Synthesis of anion exchange/activated carbon fiber hybrid materials for aqueous adsorption of toxic hexavalent chromium
… Point-of-Use (POU) based technology to remove Cr(VI) in tap water is urgently needed to protect human beings against this carcinogen. Due to the inadequate state-of-the-art technology for rapid, selective removal of Cr(VI), a unique hybrid activated carbon/anion exchange system (HACAX) has been …
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Bioremediation of hexavalent chromium using gram-negative bacteria.
Hexavalent chromium (Cr (VI)), the most toxic form of chromium, is widely used in industrial processes. As a result substantial amounts of Cr (VI) contaminated wastes are produced. The use of microbial cells as bioremediation of heavy metals is a potential alternative to conventional chemical …
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Coupling of Oxidation-Reduction Reactions of Chromium, Iron and Manganese: Implications for the Fate and Mobility of Chromium in Aquatic Environments
… States and internationally, hexavalent chromium (Cr(VI)) is a contaminant of concern in drinking water supplies. The U.S. Environmental Protection Agency is considering a Cr(VI)-specific standard. Thus improved technologies for Cr(VI) removal in drinking water are needed. Iron electrocoagulation …
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The application of iron oxide based photocatalysts in chromium photoredox chemistry
Chromium(VI) is a reactive and highly toxic pollutant species which is present in certain industrial effluent streams as well as sea water and polluted ground water. Chromium(III), however, is relatively inert and less toxic. Conventional methods used to eliminate Cr(VI) from aqueous phase include …
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A kinetic study of the chromium (VI) - arsenic (III) reaction in pyridine-pyridinium buffer solutions containing oxalate
The oxidation of arsenic (III) by chromium (VI) has been studied in pyridine - pyridinium buffers with and without added oxalate ion. The rate law at pH 4.6 for the reactions without oxalate is best described as - d[Cr(VI)]/dt = (0.535 [As(III)]² [Cr(VI)])/(1+187 [As(III)]) This is in accord with …
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Chromium and uranium isotopic exchange kinetics and isotope fractionation during oxidation of tetravalent uranium by dissolved oxygen
Chromium (Cr) and Uranium (U) isotopes (53Cr/52Cr and 238U/235U ratios) are very powerful new geochemical tools in environmental remediation and paleoredox reconstruction studies. Correctly interpreting Cr and U isotopic compositions in groundwater and sed- imentary rock samples requires thorough …
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Corrosion protection mechanisms of trivalent chromium based passivations on γ-ZnNi coated Al6061-T6 alloy
… the underlying substrate. Optical and electron micrographs indicated physical changes such as crack thickness, crack density, passivation porosity, and passivation thickness existed between the TCP and cobalt-free TCPs but had contradictory results on corrosion performance. Electrochemical …
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Investigating chromium cycling in global oxygen deficient zones with chromium isotopes
Chromium (Cr) isotopes have shown great potential as a paleo-redox proxy to trace the redox conditions of ancient oceans and atmosphere. However, its cycling in modern environments is poorly constrained. In my thesis, I attempt to fill in the gap of our understanding of chromium cycling in the …
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Investigating Chromium Cycling in Global Oxygen Deficient Zones with Chromium Isotopes
Chromium (Cr) isotopes have shown great potential as a paleo-redox proxy to trace the redox conditions of ancient oceans and atmosphere. However, its cycling in modern environments is poorly constrained. In my thesis, I attempt to fill in the gap of our understanding of chromium cycling in the …
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