Kinetics of the Natural Wolframite Interaction with Sodium and Potassium Carbonates

2020 ◽  
Vol 989 ◽  
pp. 440-447
Author(s):  
E.N. Selivanov ◽  
K.V. Pikulin ◽  
R.I. Gulyaeva ◽  
L.I. Galkova
Keyword(s):  
Manganese Oxides ◽  
Atomic Ratio ◽  
Water Soluble ◽  
Isothermal Kinetics ◽  
X Ray ◽  
Unit Cells ◽  
Subsequent Phase ◽  
Kinetics Of ◽  
Sodium And Potassium ◽  
Iron And Manganese

The kinetics and mechanism of the natural wolframite interaction with sodium and potassium carbonate, when they are heated in the air, are studied. Using X-ray phase and X-ray structure microanalysis, it was established that the initial single crystal wolfram consists of Fe0.5Mn0.5WO4 and Fe0.3Mn0.7WO4. The method of differential thermal and subsequent phase analysis of products has shown that the interaction of wolframite with sodium and potassium carbonates begins above 450-470 °C with the formation of tungstate and ferrites of sodium and potassium, iron and manganese oxides. Conducting the model experiments on sintering with the subsequent removal of water-soluble compounds (alkalization) made it possible to follow the change in the structure of wolframite. Unit cells parameters of wolframites in solid products (cakes) of leaching do not change if sintering is carried out in the range up to 600 °С. In samples, the preparation of which is coupled with heating to 700–800 °C, the atomic ratio of Fe/Mn in wolframite decreases to 0.2. This allows to specify the mechanism of the process and judge the greater reactivity of wolframites with an increased proportion of iron. Thermal analysis with data processing using the methods of non-isothermal kinetics has established that the studied interactions proceed according to a two-stage mechanism, which in the first stage is limited by diffusion. The appearance of a low-melting eutectic Na2WO4 – Na2CO3 и K2WO4 – K2CO3 in the system contributes to the process transition to the autocatalytic mode.

scholarly journals Kinetics of Cadmium and Cobalt Desorption from Iron and Manganese Oxides

1995 ◽  
Vol 59 (3) ◽  
pp. 778-785 ◽  
Author(s):  
Clare A. Backes ◽  
Ronald G. McLaren ◽  
Andrew W. Rate ◽  
Roger S. Swift
Keyword(s):  
Manganese Oxides ◽  
Kinetics Of ◽  
Iron And Manganese

scholarly journals Kinetics of the Thermal Decomposition of Rhodochrosite

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 34
Author(s):  
Iván A. Reyes ◽  
Mizraim Flores ◽  
Elia G. Palacios ◽  
Hernán Islas ◽  
Julio C. Juárez ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Mass Loss ◽  
Manganese Oxides ◽  
Absorption Spectrometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Decomposition Reactions ◽  
Mass Losses ◽  
Rate Controlled ◽  
Kinetics Of

Manganese is a widely used element in the steel industry; its main source is a mineral named rhodochrosite (MnCO3). For industrial usage, rhodochrosite is reduced to different manganese oxides by means of nodulation furnaces. In this study, rhodochrosite was thermally analyzed at temperatures ranging from 100 °C to 1200 °C. XRD (Powder X-ray diffraction), XRF (X-ray fluorescence), AAS (Atomic Absorption Spectrometry), and FESEM-EDX (Field Emission Scanning Electron Microscopy-Energy Dispersive X-Ray Spectrometry) were used to characterize the mineral and the residues were analyzed by XRD and FTIR (Fourier-transform infrared spectroscopy) to determine the stoichiometry of the thermal decomposition reactions. Three mass losses were observed, the first attributed to the transformation from carbonate to manganese (III) oxide, the second to the reduction to manganese tetroxide, and the third to the decomposition of calcium carbonate (CaCO3) present as a contaminant in the studied mineral. Thermal decomposition kinetics shows that the first mass loss required 17.91 kJ mol−1, indicating a control by mass transport-controlled process. For the second and third mass loss, the apparent activation energy of 112.41 kJ mol−1 and 64.69 kJ mol−1 was obtained respectively, indicating that both mass loss events were rate-controlled.

Trace analysis: soils

1990 ◽  
Vol 333 (1628) ◽  
pp. 160-161
Keyword(s):  
Trace Elements ◽  
Manganese Oxides ◽  
Soil Extract ◽  
Water Soluble ◽  
Plant Availability ◽  
Soil Solutions ◽  
Freshwater Biota ◽  
Solute Chemistry ◽  
Trace Concentrations ◽  
Iron And Manganese

Determinations of constituents present in soils and soil solutions at trace concentrations are conducted primarily because of interest in soil as a medium for plant growth or because of its influence upon the solute chemistry of fresh waters and ground waters. Interest may arise from concern over potential toxicity effects or over adverse effects of deficiency of trace nutrient elements essential to soil or freshwater biota. In the above context, total amounts of elements present in soil are generally of less interest than water-soluble or labile, plant available forms (Marr & Cresser 1983). Rhizosphere soil may be more relevant than bulk soil in assessing plant availability. Over recent decades, optimal chemical extractants (such as EDTA or DTPA for Zn and Cu) have been selected which reflect plant availability of trace elements in terms of high correlations between plant tissue and soil extract concentrations. Occasionally full speciation is conducted. M. S. Cresser & E. El-Sayad (unpublished results), for example, have measured water-soluble, exchangeable and organically bound trace elements, and those in carbonate and amorphorus and crystalline iron and manganese oxides, and residual sand, silt and clay minerals. Such detailed analysis is valuable in elucidation of soil pedogenesis (El-Sayad et al . 1988).

Synthesis of Sulfoquinovose and Sulfoquinovosyl Diacylglycerides, and a Fluorogenic Substrate for Sulfoquinovosidases

2019 ◽  
Author(s):  
Yunyang Zhang ◽  
Janice Mui ◽  
Thimali Arumaperuma ◽  
James P. Lingford ◽  
ETHAN GODDARD-BORGER ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Fluorogenic Substrate ◽  
Potassium Salts ◽  
X Ray ◽  
Sulfoquinovosyl Diacylglycerol ◽  
Sodium And Potassium

<p>The sulfolipid sulfoquinovosyl diacylglycerol (SQDG) and its headgroup, the sulfosugar sulfoquinovose (SQ), are estimated to harbour up to half of all organosulfur in the biosphere. SQ is liberated from SQDG and related glycosides by the action of sulfoquinovosidases (SQases). We report a 10-step synthesis of SQDG that we apply to the preparation of saturated and unsaturated lipoforms. We also report an expeditious synthesis of SQ and (<sup>13</sup>C<sub>6</sub>)SQ, and X-ray crystal structures of sodium and potassium salts of SQ. Finally, we report the synthesis of a fluorogenic SQase substrate, methylumbelliferyl a-D-sulfoquinovoside, and examination of its cleavage kinetics by two recombinant SQases.</p>

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

Non-isothermal Kinetics of Free Radical Polymerization of 2-Phenylethyl (Meth)acrylate

2018 ◽  
Vol 8 (3) ◽  
pp. 585-594
Author(s):  
Khdbudin Mulani ◽  
Ravindra Ghorpade ◽  
Surendra Ponrathnam ◽  
Nayaku Chavan ◽  
Kamini Donde
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Free Radical Polymerization ◽  
Isothermal Kinetics ◽  
Kinetics Of
Sign in / Sign up

Export Citation Format

Share Document