scholarly journals Chromium (VI) Inhibition of Low pH Bioleaching of Limonitic Nickel-Cobalt Ore

2022 ◽  
Vol 12 ◽  
Author(s):  
Ana Laura Santos ◽  
Agnieszka Dybowska ◽  
Paul F. Schofield ◽  
Richard J. Herrington ◽  
Giannantonio Cibin ◽  
...  
Keyword(s):  
Iron Reduction ◽  
New Caledonia ◽  
Raw Materials ◽  
Total Chromium ◽  
Edge Structure ◽  
Chromium Vi ◽  
Microbial Inhibition ◽  
Nickel Cobalt ◽  
Target Metal ◽  
X Ray Absorption

Limonitic layers of the regolith, which are often stockpiled as waste materials at laterite mines, commonly contain significant concentrations of valuable base metals, such as nickel, cobalt, and manganese. There is currently considerable demand for these transition metals, and this is projected to continue to increase (alongside their commodity values) during the next few decades, due in the most part to their use in battery and renewable technologies. Limonite bioprocessing is an emerging technology that often uses acidophilic prokaryotes to catalyse the oxidation of zero-valent sulphur coupled to the reduction of Fe (III) and Mn (IV) minerals, resulting in the release of target metals. Chromium-bearing minerals, such as chromite, where the metal is present as Cr (III), are widespread in laterite deposits. However, there are also reports that the more oxidised and more biotoxic form of this metal [Cr (VI)] may be present in some limonites, formed by the oxidation of Cr (III) by manganese (IV) oxides. Bioleaching experiments carried out in laboratory-scale reactors using limonites from a laterite mine in New Caledonia found that solid densities of ∼10% w/v resulted in complete inhibition of iron reduction by acidophiles, which is a critical reaction in the reductive dissolution process. Further investigations found this to be due to the release of Cr (VI) in the acidic liquors. X-ray absorption near edge structure (XANES) spectroscopy analysis of the limonites used found that between 3.1 and 8.0% of the total chromium in the three limonite samples used in experiments was present in the raw materials as Cr (VI). Microbial inhibition due to Cr (VI) could be eliminated either by adding limonite incrementally or by the addition of ferrous iron, which reduces Cr (VI) to less toxic Cr (III), resulting in rates of extraction of cobalt (the main target metal in the experiments) of >90%.

scholarly journals Microscale Investigation of Arsenic Distribution and Species in Cement Product from Cement Kiln Coprocessing Wastes

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Yufei Yang ◽  
Jingchuan Xue ◽  
Qifei Huang
Keyword(s):  
Cement Paste ◽  
Raw Materials ◽  
Cement Clinker ◽  
Cement Kiln ◽  
Edge Structure ◽  
X Ray ◽  
Mineral Phases ◽  
Arsenic Distribution ◽  
Investigation Methods ◽  
X Ray Absorption

To improve the understanding of the immobilization mechanism and the leaching risk of Arsenic (As) in the cement product from coprocessing wastes using cement kiln, distribution and species of As in cement product were determined by microscale investigation methods, including electron probe microanalysis (EPMA) and X-ray absorption spectroscopy. In this study, sodium arsenate crystals (Na3AsO412H2O) were mixed with cement production raw materials and calcined to produce cement clinker. Then, clinker was mixed water to prepare cement paste. EPMA results showed that As was generally distributed throughout the cement paste. As content in calcium silicate hydrates gel (C-S-H) was in low level, but higher than that in other cement mineral phases. This means that most of As is expected to form some compounds that disperse on the surfaces of cement mineral phases. Linear combination fitting (LCF) of the X-ray absorption near edge structure spectra revealed that As in the cement paste was predominantly As(V) and mainly existed as Mg3(AsO4)2, Ca3(AsO4)2, and Na2HAsO4.

scholarly journals Determination of Chromium(VI) Reduction by Acinetobacter haemolyticus using X-ray Absorption Fine Structure Spectroscopy

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Quek Hsiao Pei ◽  
Shafinaz Shahir ◽  
Liu Tao ◽  
Wan Azlina Ahmad
Keyword(s):  
Fine Structure ◽  
Enzymatic Reactions ◽  
Edge Structure ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Absorption Fine ◽  
Chromium Vi ◽  
X Ray Absorption ◽  
Acinetobacter Haemolyticus ◽  
Exafs Spectra

Several types of microorganisms have been reported to reduce Cr(VI) to the less toxic Cr(III) via enzymatic reactions. The main purpose of this study is to determine the reduction of Cr(VI) by a locally isolated bacterium, Acinetobacter haemolyticus (A. haemolyticus) using the x-ray absorption fine structure (XAFS) spectroscopy. XAFS analysis consisted of both the x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra. XANES spectra of the rinsed Cr(VI)-laden A. haemolyticus biomass indicated that chromium was only present in the form of Cr (III). The nearest atoms coordinated to Cr(III) were oxygens in an octahedral geometry. The longer Cr-O bond lengths (~1.97 Å) obtained from the EXAFS spectra corroborated the presence of chromium as Cr(III) bonded to oxygen. These findings demonstrate the ability of A. haemolyticus to reduce Cr(VI) to Cr(III) that was bound to oxygen atoms of the ligands in A. haemolyticus.

scholarly journals Manganese distribution in the Mn-hyperaccumulator Grevillea meisneri from New Caledonia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Camille Bihanic ◽  
Eddy Petit ◽  
Roseline Perrot ◽  
Lucie Cases ◽  
Armelle Garcia ◽  
...  
Keyword(s):  
Large Scale ◽  
New Caledonia ◽  
Tissue Level ◽  
Cluster Roots ◽  
Edge Structure ◽  
X Ray ◽  
Mining Sites ◽  
Primary Roots ◽  
Counter Ions ◽  
X Ray Absorption

AbstractNew Caledonian endemic Mn-hyperaccumulator Grevillea meisneri is useful species for the preparation of ecocatalysts, which contain Mn–Ca oxides that are very difficult to synthesize under laboratory conditions. Mechanisms leading to their formation in the ecocatalysts are unknown. Comparing tissue-level microdistribution of these two elements could provide clues. We studied tissue-level distribution of Mn, Ca, and other elements in different tissues of G. meisneri using micro-X-Ray Fluorescence-spectroscopy (μXRF), and the speciation of Mn by micro-X-ray Absorption Near Edge Structure (µXANES), comparing nursery-grown plants transplanted into the site, and similar-sized plants growing naturally on the site. Mirroring patterns in other Grevillea species, Mn concentrations were highest in leaf epidermal tissues, in cortex and vascular tissues of stems and primary roots, and in phloem and pericycle–endodermis of parent cluster roots. Strong positive Mn/Ca correlations were observed in every tissue of G. meisneri where Mn was the most concentrated. Mn foliar speciation confirmed what was already reported for G. exul, with strong evidence for carboxylate counter-ions. The co-localization of Ca and Mn in the same tissues of G. meisneri might in some way facilitate the formation of mixed Ca–Mn oxides upon preparation of Eco-CaMnOx ecocatalysts from this plant. Grevillea meisneri has been successfully used in rehabilitation of degraded mining sites in New Caledonia, and in supplying biomass for production of ecocatalysts. We showed that transplanted nursery-grown seedlings accumulate as much Mn as do spontaneous plants, and sequester Mn in the same tissues, demonstrating the feasibility of large-scale transplantation programs for generating Mn-rich biomass.

Chemical and orientational imaging of polymeric samples

1994 ◽  
Vol 52 ◽  
pp. 68-69
Author(s):  
H. Ade ◽  
B. Hsiao ◽  
G. Mitchell ◽  
E. Rightor ◽  
A. P. Smith ◽  
...  
Keyword(s):  
Ethylene Terephthalate ◽  
National Laboratory ◽  
Brookhaven National Laboratory ◽  
Carbonyl Groups ◽  
Aromatic Rings ◽  
Edge Structure ◽  
X Ray ◽  
Scanning Transmission ◽  
Polymeric Samples ◽  
X Ray Absorption

We have used the Scanning Transmission X-ray Microscope at beamline X1A (X1-STXM) at Brookhaven National Laboratory (BNL) to acquire high resolution, chemical and orientation sensitive images of polymeric samples as well as point spectra from 0.1 μm areas. This sensitivity is achieved by exploiting the X-ray Absorption Near Edge Structure (XANES) of the carbon K edge. One of the most illustrative example of the chemical sensitivity achievable is provided by images of a polycarbonate/pol(ethylene terephthalate) (70/30 PC/PET) blend. Contrast reversal at high overall contrast is observed between images acquired at 285.36 and 285.69 eV (Fig. 1). Contrast in these images is achieved by exploring subtle differences between resonances associated with the π bonds (sp hybridization) of the aromatic groups of each polymer. PET has a split peak associated with these aromatic groups, due to the proximity of its carbonyl groups to its aromatic rings, whereas PC has only a single peak.

Full-Field Calcium K-Edge X-ray Absorption Near-Edge Structure Spectroscopy on Cortical Bone at the Micron-Scale: Polarization Effects Reveal Mineral Orientation

2016 ◽  
Vol 88 (7) ◽  
pp. 3826-3835 ◽  
Author(s):  
Bernhard Hesse ◽  
Murielle Salome ◽  
Hiram Castillo-Michel ◽  
Marine Cotte ◽  
Barbara Fayard ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Edge Structure ◽  
Full Field ◽  
Polarization Effects ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Database of ab initio L-edge X-ray absorption near edge structure

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yiming Chen ◽  
Chi Chen ◽  
Chen Zheng ◽  
Shyam Dwaraknath ◽  
Matthew K. Horton ◽  
...  
Keyword(s):  
High Throughput ◽  
Scattering Theory ◽  
Research Community ◽  
Metal Compounds ◽  
Edge Structure ◽  
X Ray ◽  
Initial Release ◽  
Computational Workflow ◽  
X Ray Absorption

AbstractThe L-edge X-ray Absorption Near Edge Structure (XANES) is widely used in the characterization of transition metal compounds. Here, we report the development of a database of computed L-edge XANES using the multiple scattering theory-based FEFF9 code. The initial release of the database contains more than 140,000 L-edge spectra for more than 22,000 structures generated using a high-throughput computational workflow. The data is disseminated through the Materials Project and addresses a critical need for L-edge XANES spectra among the research community.

Theoretical and experimental investigation of point defects in cubic boron nitride

MRS Advances ◽  
2017 ◽  
Vol 2 (29) ◽  
pp. 1545-1550 ◽  
Author(s):  
Nicholas L. McDougall ◽  
Jim G. Partridge ◽  
Desmond W. M. Lau ◽  
Philipp Reineck ◽  
Brant C. Gibson ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Cubic Boron Nitride ◽  
Optical Emission ◽  
Wide Band ◽  
Wide Band Gap ◽  
Edge Structure ◽  
X Ray ◽  
Substitutional Defects ◽  
X Ray Absorption ◽  
Annealing Experiments

ABSTRACTCubic boron nitride (cBN) is a synthetic wide band gap material that has attracted attention due to its high thermal conductivity, optical transparency and optical emission. In this work, defects in cBN have been investigated using experimental and theoretical X-ray absorption near edge structure (XANES). Vacancy and O substitutional defects were considered, with O substituted at the N site (ON) to be the most energetically favorable. All defects produce unique signatures in either the B or N K-edges and can thus be identified using XANES. The calculations coupled with electron-irradiation / annealing experiments strongly suggest that ON is the dominant defect in irradiated cBN and remains after annealing. This defect is a likely source of optical emission in cBN.

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