scholarly journals Preferential Elimination of Ba2+ through Irreversible Biogenic Manganese Oxide Sequestration

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 53
Author(s):  
Yukinori Tani ◽  
Satomi Kakinuma ◽  
Jianing Chang ◽  
Kazuya Tanaka ◽  
Naoyuki Miyata
Keyword(s):  
Manganese Oxides ◽  
Toxic Elements ◽  
X Ray Diffraction ◽  
Oxidation Activity ◽  
Acremonium Strictum ◽  
X Ray ◽  
Mn Oxide ◽  
Sequestration Potential ◽  
Oxide Phases ◽  
X Ray Absorption

Biogenic manganese oxides (BMOs) formed in a culture of the Mn(II)-oxidizing fungus Acremonium strictum strain KR21-2 are known to retain enzymatic Mn(II) oxidation activity. Consequently, these are increasingly attracting attention as a substrate for eliminating toxic elements from contaminated wastewaters. In this study, we examined the Ba2+ sequestration potential of enzymatically active BMOs with and without exogenous Mn2+. The BMOs readily oxidized exogenous Mn2+ to produce another BMO phase, and subsequently sequestered Ba2+ at a pH of 7.0, with irreversible Ba2+ sequestration as the dominant pathway. Extended X-ray absorption fine structure spectroscopy and X-ray diffraction analyses demonstrated alteration from turbostratic to tightly stacked birnessite through possible Ba2+ incorporation into the interlayer. The irreversible sequestration of Sr2+, Ca2+, and Mg2+ was insignificant, and the turbostratic birnessite structure was preserved. Results from competitive sequestration experiments revealed that the BMOs favored Ba2+ over Sr2+, Ca2+, and Mg2+. These results explain the preferential accumulation of Ba2+ in natural Mn oxide phases produced by microbes under circumneutral environmental conditions. These findings highlight the potential for applying enzymatically active BMOs for eliminating Ba2+ from contaminated wastewaters.

scholarly journals Identification of jarosite and other major mineral Fe phases in acidic environments affected by mining-metallurgy using X-ray Absorption Spectroscopy: With special emphasis on the August 2014 Cananea acid spill

2019 ◽  
Vol 36 (2) ◽  
pp. 229-241 ◽  
Author(s):  
Ingrid Nayeli Escobar-Quiroz ◽  
Mario Villalobos-Peñalosa ◽  
Teresa Pi-Puig ◽  
Francisco Martín Romero ◽  
Javier Aguilar-Carrillo de Albornoz
Keyword(s):  
Absorption Spectroscopy ◽  
Copper Ions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selective Sequential Extraction ◽  
Metallurgical Wastes ◽  
Solid Iron ◽  
Oxide Phases ◽  
Mine Acid ◽  
X Ray Absorption

The sulfuric acid spill into the Sonora river, enriched in iron and copper ions from the Buenavista del Cobre mine (Cananea), gave way to the formation of various solid iron (Fe) phases. In this study, the mineral phases were identified by X-ray Absorption Spectroscopy (XAS) and bulk powder X-Ray Diffraction (XRD), and chemically through acid digestions for multielemental quantification, as well as a 3-step selective sequential extraction (SSE) to quantify the types of Fe oxide phases and the contribution of the associated elements. Jarosite was the only Fe mineral identified by XRD, but XAS allowed identification of jarosite with potentially toxic elements (PTEs) incorporated in its structure, making these elements less prone to leaching. In addition, very poorly crystalline phases such as schwertmannite and ferrihydrite were identified in several samples through XAS, which was confirmed by SSE. These phases are probably associated with PTEs. Other possible adsorbent Fe(III) minerals were also identified by XAS, such as maghemite and goethite; as well as mixed Fe(II)-Fe(III) minerals, such as green rust. It was possible to infer the influence of the acid spill on the different sampled areas through various Fe phases identified and/or the presence of gypsum. The influence was detected to be lower where the mineralogy was not associated to low pH and high sulfate concentrations. All precipitated Fe(III) phases downriver from the acid spill are known for their high retention capacities of PTEs either from incorporation into their structures and/or from surface adsorption, thus, contributing to the immobilization of the initial metal(loid) pollution caused by the acid spill. In addition, several other samples of mining-metallurgical wastes were analyzed by the same three techniques, suggesting many of the findings from the secondary Fe mineralogy of the Buenavista del Cobre mine acid spill as common processes occurring in mining-affected environments.

Improved Electrochemical Durability of PtRuAu/C Catalyst Synthesized by Radiolytic Process

2011 ◽  
Vol 1311 ◽  
Author(s):  
Satoru Kageyama ◽  
Akio Murakami ◽  
Satoshi Seino ◽  
Takashi Nakagawa ◽  
Hideo Daimon ◽  
...  
Keyword(s):  
Linear Sweep Voltammetry ◽  
X Ray Diffraction ◽  
Oxidation Activity ◽  
X Ray ◽  
Transmission Electron ◽  
Radiolytic Process ◽  
Significant Difference ◽  
Direct Methanol ◽  
X Ray Absorption ◽  
Methanol Fuel Cell

ABSTRACTNanoparticle catalyst of PtRuAu/C for direct methanol fuel cell anodes was synthesized by a radiolytic process. Its methanol oxidation activity and the electrochemical durability were evaluated by using the linear sweep voltammetry and the cyclic voltammety. The Au addition significantly improved the durability in comparison with PtRu/C catalyst without losing its high activity. The atomic structure was characterized with techniques of the transmission electron microscopy, the X-ray diffraction, the X-ray fluorescence spectroscopy and the X-ray absorption fine structure. These results implied that the arrangement of Pt and Ru atoms in the PtRuAu/C has no significant difference from that without Au, possessing a structure of Pt rich core and PtRu alloy shell. We concluded that the improvement in durability could originate from these PtRu nanoparticles decorated with Au, but not from particles with high Au contents.

Local atomic structure in tetragonal pure ZrO2nanopowders

2010 ◽  
Vol 43 (2) ◽  
pp. 227-236 ◽  
Author(s):  
Leandro M. Acuña ◽  
Diego G. Lamas ◽  
Rodolfo O. Fuentes ◽  
Ismael O. Fábregas ◽  
Márcia C. A. Fantini ◽  
...  
Keyword(s):  
Tetragonal Phase ◽  
Local Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Crystallite Sizes ◽  
Exafs Study ◽  
The Difference ◽  
X Ray Absorption ◽  
Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

The Relative Merits of Oxides of Hafnium, Cerium and Thorium as Surrogates for Plutonium Oxide in Calcium Phosphate Ceramics

2009 ◽  
Vol 1193 ◽  
Author(s):  
B. L. Metcalfe ◽  
S. K. Fong ◽  
L. A. Gerrard ◽  
I. W. Donald ◽  
E. S. Welch ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Calcination Temperature ◽  
Cerium Oxide ◽  
Absorption Spectroscopy ◽  
Hafnium Oxide ◽  
Intermediate Level ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Absorption ◽  
Additional Phase

AbstractThe choice of surrogate for plutonium oxide for use during the initial stages of research into the immobilization of intermediate level pyrochemical wastes containing plutonium andamericium oxides in a calcium phosphate host has been investigated by powder X-ray diffraction and X-ray absorption spectroscopy. Two non-radioactive surrogates, hafnium oxide and cerium oxide, together with radioactive thorium oxide were compared. Similarities in behaviour were observed for all three surrogates when calcined at the lowest temperature, 750°C but differences became more pronounced as the calcination temperature was increased to 950°C. Although some reaction occurred between all the surrogates and the host to form a substituted whitlockite phase, increasing the temperature led to a significant increase in the cerium reaction and the formation of an additional phase, monazite. Additionally it was observed that the cerium became increasingly trivalent at higher temperatures.

LiMn2-xCuxO4 Spineis - 5 V Cathode Materials

1997 ◽  
Vol 496 ◽  
Author(s):  
Yair Ein-Eli ◽  
W. F. Howard ◽  
Sharon H. Lu ◽  
Sanjeev Mukerjee ◽  
James McBreen ◽  
...  
Keyword(s):  
Copper Ions ◽  
Oxide Phase ◽  
Electrochemical Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spinel Compounds ◽  
Composition And Structure ◽  
Phase Spinel ◽  
Lithium Copper Oxide ◽  
X Ray Absorption

ABSTRACTA series of electroactive spinel compounds, LiMn2-xCuxO4 (0.1 ≤ x ≤ 0.5) has been studied by crystallographic, spectroscopie and electrochemical methods and by electron-microscopy. These LiMn2-xCuxO4 spinels are nearly identical in structure to cubic LiMn2O4 and successfully undergo reversible Li intercalation. The electrochemical data show slight shifts to higher voltage for the delithiation reaction that normally occurs at 4.1 V in standard Li1−xMn2O4 electrodes (1 ≥ x ≥ 0) corresponding to the oxidation of Mn3+ to Mn4+. The data also show a remarkable reversible electrochemical process at 4.9 V which is attributed to the oxidation of Cu2+ to Cu3+. The inclusion of Cu in the spinel structure enhances the electrochemical stability of these materials upon cycling. The initial capacity of LiMn2-xCuxO4 spinels decreases with increasing x from 130 mAh/g in LiMn2O4 (x=0) to 70 mAh/g in “LiMn1.5Cu0.5O4”(x=0.5). Although the powder X-ray diffraction pattern of “LiMn1.5Cu0.5 O4” shows a single-phase spinel product, neutron diffraction data show a small, but significant quantity of an impurity phase, the composition and structure of which could not be identified. X-ray absorption spectroscopy was used to gather information about the oxidation states of the manganese and copper ions. The composition of the spinel component in the LiMn1.5Cu0.5O4 was determined from X-ray diffraction and XANES data to be Li1.01Mn1.67Cu0.32O4 suggesting, to a best approximation, that the impurity in the sample was a lithium-copper-oxide phase.

scholarly journals Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Structural Evolution ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

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