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Chemical Engineering

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Articles 241 - 247 of 247

Full-Text Articles in Chemical Engineering

A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer Jan 1983

A Model Of The Bromine/Bromide Electrode Reaction At A Rotating Disk Electrode, Ralph E. White, S. E. Lorimer

Faculty Publications

A mathematical model is presented for the Br2/Br– electrode reaction at a rotating disk electrode. The model includes current density-overpotential expressions for the electrode reaction according to either the Volmer-Heyrovsky (V-H) or the Volmer-Tafel (V-T) mechanism and the transport equations including the effect of ionic migration. The model is used to predict current-overpotential curves for various cases of interest. Qualitative comparison of the model predictions to literature data shows that either the V-H or the V-T mechanism, with V controlling, may be acceptable for the Br2/Br– reaction.

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Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby Jan 1983

Prediction Of The Current Density At An Electrode At Which Multiple Electrode Reactions Occur Under Potentiostatic Control, Ralph E. White, S. E. Lorimer, R. Darby

Faculty Publications

It is often desirable to be able to predict the total current density at an electrode when multiple electrochemical reactions occur there under potentiostatic control. It is also sometimes desirable to include the effect of ionic migration within the diffusion layer upon the predicted total (1) and partial current densities (2). A procedure for doing this can be illustrated by considering the rotating disk electrode (RDE) system and the associated potential distribution near the RDE as shown in Fig. 1 and 2.

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An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White Jan 1983

An Analysis Of A Back Fed Porous Electrode For The Br2/Br Reaction, John Van Zee, Ralph E. White

Faculty Publications

An experimental analysis of the Br2/Br– redox reaction in a porous back fed ruthenium-coated titanium electrode is described. A mathematical model of the steady-state process is presented. Nonlinear regression of the model against the experimental data gives physically meaningful parameter estimates; these parameters and the model provide a design equation for the porous electrode current as a function of specific surface area, bulk Br2 concentration, average total overpotential, and the Reynolds number. The design equation shows that the back fed electrode could reduce the loss of Br2 across the separator and the ohmic loss in …

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Potential-Selective Deposition Of Copper From Chloride Solutions Containing Iron, Ralph E. White, James A. Trainham, John Newman, Thomas W. Chapman Jan 1977

Potential-Selective Deposition Of Copper From Chloride Solutions Containing Iron, Ralph E. White, James A. Trainham, John Newman, Thomas W. Chapman

Faculty Publications

The hydrometallurgy of copper may involve leaching of the metal from its ore with an aqueous solution containing cupric and ferric chloride. The subsequent deposition of copper from such a process stream is modeled here in an idealized electrochemical cell with a rotating-disk electrode. The potential distribution and concentration profiles within the diffusion layer are predicted for given potential differences between the electrode and the solution. The cuprous ion, which is formed by the reduction of the complexed cupric ion at the electrode, is stabilized in the chloride solution and can react either at the electrode or with ferric species …

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Electrochemical Reduction Of Molybdate In The Presence Of Zinc Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, R. Cvetkovic, Branko N. Popov, H. A. Laitinen Jan 1975

Electrochemical Reduction Of Molybdate In The Presence Of Zinc Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, R. Cvetkovic, Branko N. Popov, H. A. Laitinen

Faculty Publications

Two chronopotentiometric waves were observed for the electrochemical reduction of molybdate in the presence of zinc chloride, with quarter-wave potentials of –1.5V and –1.75V vs. the Pt(II)/Pt reference electrode, respectively. It was observed that an increase in the molybdate concentration causes a decrease of the first transition time indicating a chemical reaction between ZnCl2 (which is reduced at –1.5V) and Li2MoO4 in the melt forming ZnMoO4 which is sparingly dissociated in LiCl-KCl eutectic. The equilibrium constant for the observed reaction was calculated. X-ray powder diffraction patterns of the reduction product of ZnMoO4 have been …

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Electrochemical Reduction Of Molybdenum(Vi) Compounds In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen Jan 1973

Electrochemical Reduction Of Molybdenum(Vi) Compounds In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen

Faculty Publications

Molybdenum (VI) oxide reacts with molten LiCl-KCl eutectic at 450° to form MoO2CI2, which probably is present as an anion MoO2Cl4=, and pyromolybdate, Mo2O7=. Both of these species are electrochemically reduced to MoO2, which can be reoxidized to MoO2Cl2 by current reversal. A second reduction step, observed whether MoO3 or Mo2O72− is added to the melt, can be attributed to the reduction of MoO4−−, formed as a secondary reaction product in the first …

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Electrochemical Reduction Of Chromate In The Presence Of Nickel Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen Jan 1970

Electrochemical Reduction Of Chromate In The Presence Of Nickel Chloride In Molten Lithium Chloride-Potassium Chloride Eutectic, Branko N. Popov, H. A. Laitinen

Faculty Publications

Chronopotentiometry of chromate in the presence of NiCl2 in molten LiCl-KCl eutectic reveals a diffusion controlled, three electron reduction step. In the presence of excess NiCl2, chromate is reduced at −0.35V vs. Pt(II)/Pt reference electrode and the electroactive species responsible for the chrono-potentiometric wave is estimated to have a diffusion coefficient of 1.06 · 10−5 cm2 sec−1 at 450°C. The stoichiometry of the reduction product depends mainly on the temperature at which the deposit is formed. At 500°C the deposit approaches the composition LiNi2CrO4. X-ray powder diffraction shows the deposit …

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