Ma Chen-Yan

Effect of sodium chloride on sulfur speciation of chalcopyrite bioleached by the extreme thermophile Acidianus manzaensis.

The influence of sodium chloride on dissolution of chalcopyrite and surface sulfur speciation during bioleaching of chalcopyrite with the extreme thermophile Acidianus manzaensis YN-25 was studied. The addition of sodium chloride accelerated the dissolution of chalcopyrite by reducing the accumulation of elemental sulfur layers on the mineral surface, resulting in an increase in the concentration of copper ions from 2.37g/L to 2.67g/L. Jarosite and elemental sulfur were found in the bioleached residues, while the amount of elemental sulfur accumulating on the mineral surface decreased drastically from 25.4% to 3.0% when 0.66g/L of sodium chloride was present during bioleaching. Therefore, the accumulation of elemental sulfur on the mineral surface is likely mainly responsible for the slowdown in the dissolution rate. The results indicated that bioleaching chalcopyrite with extreme thermophiles possessing high sulfur oxidation activity likely enhances dissolution of chalcopyrite by effectively removing elemental sulfur accumulating on the mineral surface.

Investigation of sulfur speciation in particles from small coal-burning boiler by XANES spectroscopy

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy was employed to study the speciation of sulfur in raw coal, ash by-product and fine particulate matter from a small coal-burning boiler. By means of least square analysis of the XANES spectra, the major organic and inorganic sulfur forms were quantitatively determined. The results show that about 70% of the sulfur in raw coal is present as organic and a minor fraction of the sulfur occurs as other forms: 17% of pyrite and 13% of sulfate. While in bottom ash, fly ash, and PM(2.5), the dominant form of sulfur is sulfate, with the percentage of 80,79 and 94, respectively. Moreover, a number of other reduced sulfur including thiophenic sulfur, element sulfur and pyrrhotite are also present. During coal combustion, most of organic sulfur and pyrite were oxidized and released into the atmosphere as SO(2) gas, part of them was converted to sulfate existing in coal combustion by-products, and a small part of pyrite was probably reduced to elemental sulfur and pyrrhotite. The results may provide information for assessing the pollution caused by small boiler and developing new methods for the control of SO(2) pollution.

Iron L-edge and sulfur K-edge XANES spectroscopy analysis of pyrite leached by Acidianus manzaensis

Iron L-edge and sulfur K-edge X-ray absorption near edge structure (XANES) spectroscopy analysis of pyrite leached by extreme thermophilic Archaea strain Acidianus manzaensis (A. manzaensis) was carried out. Leaching experiments show that the oxidation of pyrite can be accelerated by A. manzaensis. Leaching results show that with the increase of leaching time, pH value in the leaching solution gradually decreases, redox potential increases rapidly from day 0 to day 3, and then increases slowly. The SEM results show that the pyrite surfaces are corroded gradually by A. manzaensis, and the XRD results show that the leaching residues contain new compositions of jarosite and elemental sulfur (S-0). The iron L-edge XANES spectroscopy analysis of pyrite during biooxidation indicates that pyrite is gradually converted to Fe(III)-containing species. The sulfur K-edge XANES spectroscopy analysis indicates that elemental sulfur is produced during bioleaching and maintains mass fractions of 3.2%-5.9%. Sodium thiosulfate was also detected from day 2 to day 4, indicating the existence of thiosulfate during biooxidation of pyrite.

Differential utilization and speciation transformation of orthorhombic α-S8 and amorphous μ-S by substrate-acclimated mesophilic Acidithiobacillus ferrooxidans

The utilization and speciation transformation of alpha-S-8 and mu-S by the typical mesophilic acidophilic strain Acidithiobacillus ferrooxidans ATCC 23270 were investigated. A. ferrooxidans cells first acclimated to the energy source alpha-S-8 or mu-S, respectively. The results of cell growth and sulfur oxidation behavior showed that the strain grown on alpha-S-8 entered slowly (about 1 d later) into the exponential phase, while grew faster in the exponential phase and attained higher maximal cell density and lower pH value than that on mu-S. After bio-corrosion, both of the two sulfur samples were evidently eroded and modified by A. ferrooxidans cells. After growth of A. ferrooxidans, the surface composition of amorphous mu-S became 63.1% mu-S and 36.9% alpha-S-8, and that of orthorhombic alpha-S-8 became 68.3% alpha-S-8 and 31.7% mu-S, while the surface compositions of alpha-S-8 and mu-S in sterile experiment were not changed, indicating that these two elemental sulfur species can be interconverted by A. ferrooxidans.

Determination of the calcium species in coal chars by Ca K-edge XANES analysis

Ca-based additives have been widely used as a sulfur adsorbent during coal pyrolysis and gasification. The Ca speciation and evolution during the pyrolysis of coal with Ca additives have attracted great attention. In this paper, Ca species in the coal chars prepared from the pyrolysis of Ca(OH)2 or ...

Relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleaching by mixed thermophilic Archaea culture at 65 °C

The relatedness between catalytic effect of activated carbon and passivation phenomenon during chalcopyrite bioleaching by mixed thermophilic Archaea culture (Acidianus brierleyi, Metallosphaera sedula, Acidianus manzaensis and Sulfolobus metallicus) at 65 °C was studied. Leaching experiments showed that the addition of activated carbon could significantly promote the dissolution of chalcopyrite for both bioleaching and chemical leaching. The results of synchrotron-based X-ray diffraction, iron L-edge and sulfur K-edge X-ray absorption near edge structure spectroscopy indicated that activated carbon could change the transition path of electrons through galvanic interactions to form more readily dissolved secondary mineral chalcocite at a low redox potential (<400 mV) and then enhanced the copper dissolution. Jarosite accumulated immediately in the initial stage of bioleaching with activated carbon but copper dissolution was not hindered. However, much jarosite precipitated on the surface of chalcopyrite in the late stage of bioleaching, which might account for the decrease of copper dissolution rate. More elemental sulfur (S0) was also detected with additional activated carbon but the mixed thermophilic Archaea culture had a great sulfur oxidation activity, thus S0 was eliminated and seemed to have no significant influence on the dissolution of chalcopyrite.

Formation and evolution of secondary minerals during bioleaching of chalcopyrite by thermoacidophilic Archaea Acidianus manzaensis

Abstract The formation and evolution of secondary minerals during bioleaching of chalcopyrite by thermoacidophilic Archaea Acidianus manzaensis were analyzed by combining synchrotron radiation X-ray diffraction (SR-XRD) and S, Fe and Cu Kα X-ray absorption near edge structure (XANES) spectroscopy. Leaching experiment showed that 82.4% of Cu2+ was dissolved by A. manzaensis after 10 d. The surface of chalcopyrite was corroded apparently and covered with leaching products. During bioleaching, the formation and evolution of secondary minerals were as follows: 1) little elemental sulfur, jarosite, bornite and chalcocite were found at days 2 and 4; and 2) bornite and chalcocite disappeared, covellite formed, and jarosite gradually became the main component at days 6 and 10. These results indicated that metal-deficiency sulfides chalcocite and bornite were first formed with a low redox potential value (360–461 mV), and then gradually transformed to covellite with a high redox potential value (461–531 mV).

Quantitative Measurement of the Proportions of High-Order Harmonics for the 4B7B Soft-X-Ray Source at Beijing Synchrotron Radiation Facility

A transmission grating coupled with an X-ray charge coupled device (CCD) is used to quantitatively measure the proportion of high-order harmonics of the soft-X-ray source of beam line 4B7B. The results show that the monochromatic X-ray has third-order and second-order harmonics. The proportion of second-order harmonic of 4B7B is less than 9.0% and the third-order harmonic is below 0.7% when no suppressing method is applied. When suppression methods are used, the proportion of second-order harmonic is less than 1.7% and the third-order harmonic is ignorable.

Transfer characterization of sulfur from coal-burning emission to plant leaves by PIXE and XANES

The impact of coal-burning emission on sulfur in camphor leaves was investigated using Proton Induced X-ray Emission (PIXE) and synchrotron radiation technique X-ray Absorption Near-Edge Structure (XANES) spectroscopy. The PIXE results show that the sulfur concentrations in the leaves collected at the polluted site are significantly higher than those in controls. The Sulfur XANES spectra show the presence of organic (disulfides, thiols, thioethers, sulfonates and sulfoxides) and inorganic sulfur (sulfates) in the leaves. The inorganic sulfur in the leaves of camphor tree polluted by coal combustion is 15% more than that of the control site. The results suggest that the long-term coal-burning pollution resulted in an enhanced content of the total sulfur and sulfate in the leaves, and the uptake of sulfur by leaves had exceeded the metabolic requirement of plants and the excess of sulfur was stored as SO(4)(2-). It can monitor the sulfur pollution in atmosphere.

Soft X-Ray Magneto-optical Faraday Effect around Ni M2,3 Edges

We present magneto-optical (MO) Faraday spectra measured around the M2,3 edges (60–70eV) of Ni films at the Beijing Synchrotron Radiation Facility (BSRF). A polarization analysis of the final state of the transmitted radiation from the Ni film is employed to determine the Faraday rotation at the edges. The MO effect becomes resonantly enhanced at the M2,3 edges, and accordingly large values for the rotation angle β of 1.85 ± 0.19° for this ferromagnetic Ni film with thickness of 31 nm are measured. Without the magnetic field, the azimuthal angles do not shift; with parallel and antiparallel magnetic field the rotation angles shift in the opposite way and they are symmetrical. The uncertainty of Faraday rotation angles mainly comes from the data fitting and the state change of the beamline when the angles are measured.