Some thermodynamic and kinetic properties of H2SO4–H3PO4–H2O–Fe(III) system

2021 ◽  
pp. 1-9
Author(s):  
Ya.G. Avdeev ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Platinum Electrode ◽  
Molar Fraction ◽  
Redox Couple ◽  
Kinetic Properties ◽  
Cyclic Voltammogram ◽  
Electrode Potentials ◽  
Half Wave ◽  
Sulfate Complexes

The values of the electrode potentials of the redox couple Fe(III) / Fe(II) and the half-wave potentials of the reactions Fe3+ + e– = Fe2+ и Fe2+ — e– = Fe3+ on the cyclic voltammogram of a platinum electrode in acid solutions containing Fe(III) salts have been measured to characterize the oxidizing ability of the H2SO4—H3PO4—H2O—Fe(III) system. The values of these experimentally obtained parameters are close. A decrease in the oxidizing ability of H2SO4 and H3PO4 mixtures containing Fe(III) with an increase in the molar fraction of H3PO4 in them occurs due to the formation of Fe(III) complexes with phosphate anions which are inferior to their hydrate and sulfate complexes in the oxidizing ability. The temperature coefficients of the electrode potential (dE / dt) of the redox couple Fe(III) / Fe(II) in the H2SO4—H2O, H2SO4—H3PO4—H2O and H3PO4–H2O systems were determined experimentally. The diffusion coefficients of Fe(III) in the studied solutions were calculated based on the Randles—Shevchik equation. The temperature dependence of the diffusion coefficients of Fe(III) cations is satisfactorily described by the Arrhenius equation. The parameters of this equation are calculated.

Diffusion Coefficients of Interest for the Simulation of Heat Treatment in Rare-Earth Transition Metal Magnets

2012 ◽  
Vol 727-728 ◽  
pp. 163-168 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Activation Energy ◽  
Rare Earth ◽  
Transition Metal ◽  
Impurity Atom ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Atom Diffusion ◽  
Essential Input

In the case of the modeling of sintering and heat treatments, the diffusion coefficients are an essential input. However, experimental data in the literature about diffusion coefficients for rare-earth transition metal intermetallics is scarce. In this study, the available data concerning diffusion coefficients relevant for rare-earth transition metal magnets are reviewed and commented. Some empirical rules are discussed, for example the activation energy is affected by the size of the diffusing impurity atom. Diffusion coefficients for Dy, Nd and Fe into Nd2Fe14B are given according an Arrhenius equation D=D0exp (-Q/RT). For Dy diffusion into Nd2Fe14B, Q 315 kJ/mol and D08 . 10-4m2/s.

scholarly journals Elements in the Interpretation of Platinum Electrode Potentials in Biological Treatment

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1335-1344 ◽  
Author(s):  
A. Heduit ◽  
D. R. Thevenot
Keyword(s):  
Dissolved Oxygen ◽  
Biological Treatment ◽  
Platinum Electrode ◽  
Surface Characteristics ◽  
Electrode Potentials ◽  
Zero Current ◽  
Experimental Values ◽  
Mixed Potentials ◽  
Ionic Forms ◽  
Current Potential

The zero current potential of a platinum electrode in a biological medium (wastewater, activated sludge) is strongly dependent on the surface characteristics of the metal. It is also influenced by pH (probably Pt/PtO system), dissolved oxygen (O2/OH- system), and ionic forms of nitrogen (NO2-/NH4+ and NO3-/NO2-systems). The experimental values of the coefficients relating the stabilized potential of a platinum electrode to the logarithm of the concentration of the elements under consideration (Nernst equations) are significantly different from the thermodynamic coefficients corresponding to each reaction. The platinum is thus not in equilibrium with the dissolved redox reactants and is likely subject to mixed potentials in which the adsorbed components play an important role.

Estimation of Li-Ion Diffusion Coefficients in C60 Coated Si Thin Film Anodes Using Electrochemical Techniques

2012 ◽  
Vol 326-328 ◽  
pp. 87-92 ◽  
Author(s):  
Arenst Andreas Arie ◽  
Joong Kee Lee
Keyword(s):  
Thin Films ◽  
Diffusion Coefficients ◽  
Electrochemical Impedance ◽  
Silicon Film ◽  
Electrochemical Techniques ◽  
Lithium Ion ◽  
Chemical Vapor ◽  
Film Coating ◽  
Kinetic Properties ◽  
Silicon Thin Films

C60coated Si thin films were prepared sequentially by a plasma enhanced chemical vapor deposition and a plasma assisted thermal evaporation technique. The films were then utilized as anode materials for lithium ion batteries. The diffusion coefficients of Li-ions in the film electrodes were then estimated by typical electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. The diffusion coefficients determined by both methods were found to be consistent each other. The diffusion coefficient of coated samples was obviously higher than that of bare silicon thin films, indicated that the kinetic properties of lithium ion transport in silicon film electrodes were enhanced by the C60film coating on its surface.

Irreversibility of Se(VI)/Se(IV) Redox Couple in Synthetic Basaltic Ground Water at 25°C and 75°C

1986 ◽  
Vol 84 ◽  
Author(s):  
Donald D. Runnells ◽  
Ralph D. Lindberg ◽  
John H. Kempton
Keyword(s):  
Time Series ◽  
Electron Transfer ◽  
Ground Water ◽  
Computer Model ◽  
High Purity ◽  
Sodium Selenite ◽  
Platinum Electrode ◽  
Redox Couple ◽  
Infinite Time ◽  
Acidic Solutions

AbstractSynthetic basaltic ground water was spiked with different ratios of high-purity solium selenate and sodium selenite, to yield ratios of aqueous SeO42to SeO 42from 2100/1 to 1/44000, at temperatures of 25°C and 75°C. The apparent 2h of the solutions was measured by means of a platinum electrode. The time series Eh data were extrapolated to infinite time using the method of Muller [1,2]. Results show no relationship between the analyzed ratios of Se(VI)/Se(IV) in solution and the observed+Eh plues at the platinum electrode. In contrast, acidic solutions of Fe /Fe show nearly perfect Nernstian behavior and rapid electron transfer at the platinum electrode. Based on the results of this study, it is probably invalid to use Eh measurements as input to any equilibrium computer model for purposes of predicting the behavior of a pure selenium system.

scholarly journals Standard rate constants of charge transfer for the redox couple Ti(IV)/Ti(III) in chloride-fluoride melts with the different cationic composition

2021 ◽  
Vol 12 (2-2021) ◽  
pp. 60-65
Author(s):  
D. A. Vetrova ◽  
◽  
S. A. Kuznetsov ◽  
Keyword(s):  
Charge Transfer ◽  
Rate Constants ◽  
Diffusion Coefficients ◽  
Redox Couple ◽  
Cationic Composition ◽  
Fluoride Melts ◽  
Alkali Metal Halides ◽  
Cyclic Voltammetry Method ◽  
Standard Rate ◽  
Kinetics Of

The influence of the second coordination sphere of titanium complexes on the charge transfer kinetics of the Ti (IV)/Ti (III) redox couple in melts of alkali metal halides was studied by cyclic voltammetry method. Diffusion coefficients in the CsC-CsF (10 wt. %) melt were calculated. The standard rate constants of charge transfer have been determined by the Nicholson method. The activation energies of the charge transfer process in (NaCl- KCl)equimol-NaF (10 wt. %) — K2TiF6, KCl-KF (10 wt. %) — K2TiF6 and CsCl-CsF (10 wt. %) — K2TiF6 melts were calculated.

scholarly journals Calculation of Electrochemical Parameters Starting from the Polarization Curves of Ferrocene at Glassy Carbon Electrode

2013 ◽  
Vol 9 ◽  
pp. 37-45 ◽  
Author(s):  
N.S. Neghmouche ◽  
Touhami Lanez
Keyword(s):  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Diffusion Coefficients ◽  
Polarization Curves ◽  
Carbon Electrode ◽  
Half Wave ◽  
Electrochemical Parameters

This work is a contribution to the calculation of electrochemical parameters from the polarization curves of ferrocene. The parameters are: The anodic (Epa) and the cathodic (Epc) peak potentials, as well as the corresponding anodic (ipa) and cathodic (ipc) peak currents, were obtained at different scan rates (0.05, 0.10, 0.30, 0.50 V.s-1). The half-wave potentials (E1/2) of the couple in the investigated solvents have been evaluated. The diffusion coefficients (D) have been calculated using the Randles-Sevcik equation.

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