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About: Chromium is a(n) research topic. Over the lifetime, 40874 publication(s) have been published within this topic receiving 607689 citation(s). The topic is also known as: Cr & element 24.

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Abstract: A rapid and accurate atomic absorption method for the determination of chromium in faeces samples from pasture experiments using chromic oxide ‘markers’ is described. Of the elements present after ashing and digesting the samples in a phosphoric acid—manganese sulphate—potassium bromate solution silicate, aluminium, calcium and magnesium were found to interfere in the determination. The effects of these interferences were overcome by the addition of calcium to the test solution and by the addition of silicate to the standards, which were prepared in ‘blank’ solutions.The sensitivities of a number of alternate chromium resonance lines relative to that of Cr 3578·7 A. are given. These lines may be used to increase the concentration range of the analysis.The results of a comparison of the atomic absorption method with a chemical method are given.

1,789 citations

Journal ArticleDOI
Abstract: The first three-dimensional chromium(III) dicarboxylate, MIL-53as or CrIII(OH)·{O2C−C6H4−CO2}·{HO2C−C6H4−CO2H}0.75, has been obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or CrIII(OH)·{O2C−C6H4−CO2}. At room temperature, MIL-53ht adsorbs atmospheric water immediately to give CrIII(OH)·{O2C−C6H4−CO2}·H2O or MIL-53lt (lt: low-temperature form, ht: high-temperature form). Both structures, which have been determined by using X-ray powder diffraction data, are built up from chains of chromium(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of one-dimensional large pore channels filled with free disordered terephthalic molecules (MIL-53as) or water molecules (MIL-53lt); when the free molecules are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m2/g. The transition between the hydrated form (MIL-53lt) and the a...

1,463 citations

Journal ArticleDOI
TL;DR: The sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation are provided, and particular attention is paid to comparing the sorption efficiency and capacities of commercially available activated carbons to otherLow cost alternatives.
Abstract: Hexavalent chromium is a well-known highly toxic metal, considered a priority pollutant. Industrial sources of Cr(VI) include leather tanning, cooling tower blowdown, plating, electroplating, anodizing baths, rinse waters, etc. The most common method applied for chromate control is reduction of Cr(VI) to its trivalent form in acid (pH approximately 2.0) and subsequent hydroxide precipitation of Cr(III) by increasing the pH to approximately 9.0-10.0 using lime. Existing overviews of chromium removal only cover selected technologies that have traditionally been used in chromium removal. Far less attention has been paid to adsorption. Herein, we provide the first review article that provides readers an overview of the sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation. After an overview of chromium contamination is provided, more than 300 papers on chromium remediation using adsorption are discussed to provide recent information about the most widely used adsorbents applied for chromium remediation. Efforts to establish the adsorption mechanisms of Cr(III) and Cr(VI) on various adsorbents are reviewed. Chromium's impact environmental quality, sources of chromium pollution and toxicological/health effects is also briefly introduced. Interpretations of the surface interactions are offered. Particular attention is paid to comparing the sorption efficiency and capacities of commercially available activated carbons to other low cost alternatives, including an extensive table.

1,441 citations

Journal ArticleDOI
Abstract: A sulfur analysis scheme employing the use of chromium reduction for the determination of reduced inorganic sulfur compounds (pyrite + elemental sulfur + acid volatile monosulfides) in modern sediments and shales is presented. Exhaustive testing shows that chromium reduction does not reduce or liberate either organic sulfur or sulfate sulfur; making the method specific only to reduced inorganic sulfur phases. The high degree of specificity, ease of sample analysis, and excellent analytic precision should make this technique ideally suited for routine analysis of modern and ancient sediments.

1,157 citations

Journal ArticleDOI
Abstract: Borohydride reduction of an aqueous iron salt in the presence of a support material gives supported zero-valent iron nanoparticles that are 10−30 nm in diameter. The material is stable in air once it has dried and contains 22.6% iron by weight. The supported zero-valent iron nanoparticles (“Ferragels”) rapidly separate and immobilize Cr(VI) and Pb(II) from aqueous solution, reducing the chromium to Cr(III) and the Pb to Pb(0) while oxidizing the Fe to goethite (α-FeOOH). The kinetics of the reduction reactions are complex and include an adsorption phase. About 10% of the iron in the material appears to be located at active surface sites. Once these sites have been saturated, the reduction process continues but at a much lower rate, which is likely limited by mass transfer. Rates of remediation of Cr(VI) and Pb(II) are up to 30 times higher for Ferragels than for iron filings or iron powder on a (Fe) molar basis. Over 2 months, reduction of Cr(VI) was 4.8 times greater for Ferragels than for an equal weigh...

1,063 citations

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