Chemical Engineering Commons^™

Effect Of Proton Diffusion, Electron Conductivity, And Charge-Transfer Resistance On Nickel Hydroxide Discharge Curves, John W. Weidner, Paul Timmerman

Faculty Publications

Constant-current discharge curves for the nickel hydroxide electrode are simulated assuming resistances due to diffusion of protons and conduction of electrons through the nickel hydroxide film, and charge-transfer resistance at the film/electrolyte interface contribute to the polarization losses of the electrode. Good qualitative agreement is observed between the model predictions and experimental discharge curves. The results suggest that polarization losses due to diffusional limitations of protons is a critical factor in determining the characteristics of the discharge curve. Ohmic resistance has a significant effect on the discharge curves at the end of discharge, and charge-transfer resistance is a minor contributor …

Using Electrochemical Impedance Spectroscopy As A Tool For Organic Coating Solute Saturation Monitoring, Branko N. Popov, Mohammed A. Alwohaibi, Ralph E. White

Faculty Publications

Electrochemical impedance spectroscopy (EIS) has been used to study the solute uptake for epoxy/phenolic (E/p) andepoxy/amine (E/a) thick-coated mild steel samples immersed for 160 days in 3.5 weight percent NaCl solution exposed to air. Samples with thicknesses of approximately 200 µm with an exposed surface area of 22.6 cm² were used to follow solute saturation of the organic coating. Good agreement was obtained between the calculated and measured coating capacitance when, according to the diffusion equation, the coating capacitance was plotted against exposure time.

Hydrogen Diffusion, Solubility, And Water Uptake In Dow's Short-Side-Chain Perfluorocarbon Membranes, Yu-Min Tsou, M. C. Kimble, Ralph E. White

Faculty Publications

Hydrogen gas diffusion coefficients and solubilities as well as water uptake values are reported for Dow's short-side-chain perfluoro-sulfonic and -carboxylic membranes of different equivalent weight (EW). The diffusion coefficients and solubilities were determined with an electrochemical test cell. Hydrogen solubility decreases with increasing EW in the lower EW range and tends to level off at higher EWs for both types of membranes. Both hydrogen solubility and diffusion coefficients of a sulfonic membrane with EW higher than 800 are higher than the corresponding values of a carboxylic membrane of similar EW. An unusual maximum is observed in the diffusion coefficient-EW plot …

Estimation Of The Diffusion Coefficient And Solubility For A Gas Diffusing Through A Membrane, Michael C. Kimble, Ralph E. White, Yu-Min Tsou, R. Neal Beaver

Faculty Publications

Analysis of the data obtained by the electrochemical monitoring technique for diffusion of a gas through a membrane is considered. It is shown that combining a numerical method with a nonlinear parameter estimation technique provides a means to determine values for the diffusion coefficient and the solubility of the diffusing gas. It is shown that better accuracy can be obtained for the diffusion coefficient and solubility of this gas by using the method presented and all experimental data rather than only part of the data, as has often been done in the past.

Electrodeposition Of Copper-Nickel Alloys From Citrate Solutions On A Rotating Disk Electrode, Ramona Y. Ying, Patrick K. Ng, Z. Mao, Ralph E. White

Faculty Publications

A mathematical model is developed to simulate the electrodeposition of Cu-Ni alloy from citrate solutions onto a rotating disk electrode under potentiostatic control. The model includes the influence of diffusion, ionic migration, forced convection, and homogeneous equilibria. The three major electrochemical reactions treated in the model are copper deposition, nickel deposition, and hydrogen evolution. Using experimental parameters when available, the model was fitted and tested against experimentally-obtained results for different bath compositions and operating conditions. The model agreed reasonably well with the experimental results particularly in the codeposition region, –1.0 to –1.2V vs. SCE, where hydrogen evolution is not the …

On The Use Of A Modified Square-Well Model For Prediction And Correlation Of Thermal Diffusion Factors In Binary Liquid Mixtures, Richard L. Rowley, S. C. Yi

Faculty Publications

Recently reported thermal diffusion factors obtained from heats of transport have been used to test the ability of existing theories to predict thermal diffusivities using model parameters regressed from pure component transport data. None of the theories tested were able to provide even qualitative agreement with experiment. However, predictions using a square-well Enskog theory, modified here for consistency with normal experimental definitions, were found to be approximately correct using pure-component square-well parameters regressed from viscosity and thermal conductivity and an assumed mixing rule for cross terms. Predicted values are very sensitive to the energy mixing rule, and correlation of experimental …

Heats Of Transport From Diffusion Thermoeffect Measurements On Binary Liquid Mixtures Of Carbon Tetrachloride With Benzene, Toluene, 2-Propanone, N-Hexane, And N-Octane, Richard L. Rowley, S. C. Yi

Faculty Publications

Measurements of heats of transport are reported for binary liquid mixtures containing carbon tetrachloride and benzene, toluene, 2-propanone, n-hexane, or n-octane at 298 K and ambient pressure. Additionally, measurements were made at 308 K for carbon tetrachloride with benzene, toluene, and 2-propanone. The corresponding heat-mass Onsager coefficients are also reported, from which thermal diffusion ratios have been calculated based on Onsager reciprocity. These data will be used in a companion paper to report a modified Enskog method for correlation and prediction of heats of transport.

Hard-Sphere Theory For Correlation Of Tracer Diffusion Of Gases And Liquids In Alkanes, Michael A. Matthews, Aydin Akgerman

Faculty Publications

No abstract provided.

Utility Of An Empirical Method Of Modeling Combined Zero Gap/Attached Electrode Membrane Chlor-Alkali Cells, Clifford W. Walton, Ralph E. White

Faculty Publications

An extensive survey of the Docktor-Ingenieur Dissertationen of Jakob Jörissen and Klaus-R. Menschig, both originally from the Universität Dortmund, is presented in regard to the empirical modeling of membrane chlor-alkali cells and how it can be applied to a combined zero gap/attached porous electrode layer membrane cell. Particular emphasis isplaced on Menschig's work on zero gap (ZG) and attached porous electrode layer (APEL) membrane chlor-alkali cells, the first such research to appear in the open literature. Menschig developed various computer programs to characterize these ZG and APEL membrane chlor-alkali cells. He characterized these cells by using the following parameters: the …

Heats Of Transport From The Diffusion Thermoeffect In Binary Liquid Mixtures Of Toluene, Chlorobenzene, And Bromobenzene, Richard L. Rowley, M. D. Hall

Faculty Publications

Measurements of heats of transport in binary liquid mixtures of toluene, chlorobenzene, and bromobenzene utilizing the diffusion thermoeffect, or Dufour effect, are reported at 298 and 308 K. The corresponding heat-mass Onsager doefficients are also reported, from which thermal diffusion ratios have been calculated based on Onsager reciprocity. The resultant binary thermal diffusion ratios have been correlated as a function of composition in an attempt to study the relationship between values in binary and ternary mixtures. It was found that the single independent binary values can be used to estimate the two independent thermal diffusion ratios previously reported in toluene …

A Mathematical Model For A Parallel Plate Electrochemical Reactor, Cstr, And Associated Recirculation System, T V. Nguyen, C W. Walton, Ralph E. White

Faculty Publications

A mathematical model is presented for a system comprised of a parallel plate electrochemical reactor (PPER) and a continuous, stirred-tank reactor (CSTR) under both total and partial recycle. The model is used to predict the time dependent behavior of the electrowinning of copper from an aqueous, hydrochloric acid solution. The model includes many important aspects of a PPER/CSTR system which have been neglected previously. These aspects are the kinetics of electrode reactions, the electroneutrality condition, three mass transfer processes for ionic species in the electrolyte (diffusion, ionic migration, and convection) and the electrode gap in the PPER, and the inclusion …

Using Parameter Estimation Techniques With A Simple Model Of A Diaphragm-Type Electrolyzer To Predict The Electrical Energy Cost For Naoh Production, John Van Zee, Ralph E. White

Faculty Publications

Predictions of the electrical energy cost for NaOH production are determined as a function of the independent operating variables and diaphragm characterizing properties. The predictions are based on data from a statistically designed experiment, a simple model of a diaphragm-type electrolyzer, a simple model of the cell voltage losses, and parameter estimation techniques. The data were obtained over a sufficiently large range of operating conditions so that the resulting design equation may be industrially useful. The simple model of the diaphragm is based on the mass transport of the hydroxyl ion, a linear potential gradient, and is presented in terms …

Simulation Of Particle Size Distribution In Continuous Emulsion Polymerization Through A Modified Population Balance Approach, Ying-Yuh Lu

Theses

A detailed mathematical model for particle size distribution in continuous emulsion polymerization of styrene and vinyl acetate is proposed on the basis of the population balance in the presence of several kinetic and mass transfer processes. This study is limited to the Smith-Ewart case II, which assumes instantaneous free radical termination within polymer particles. Radical desorption mechanism from polymer particles is included in the model and the desorption rate is formulated from the diffusion theory which suggests that the rate coefficient should be inversely proportional to the surface area of polymer particles.

Diffusion Thermoeffect Measurements Of Heats Of Transport In Ternary Liquid Toluene Chlorobenzene Bromobenzene Mixtures At 25°C And 3°C, Richard L. Rowley, Gerald Platt, Tevin Vongvanich

Faculty Publications

Heats of transport in ternary nonelectrolyte liquid mixtures have been directly measured for the first time. Diffusion thermoeffect measurements have been made for ternary mixtures of toluene-chlorobenzene-bromobenzene at 25 degrees and 35 degrees C. A new boundary sharpening technique was used in addition to a liquid gate withdrawal method. Both techniques yield consistent, accurate values of the heat of transport, but the new cell provides versatility in allowable densities and compositions of the initial phases. Heats of transport were obtained by nonlinear least-squares fitting of calculated to experimental temperature differences measured at positions symmetric about the initial diffusional interface. The …

Correlation And Prediction Of Diffussion Coefficients In Binary Gas Systems, Raymond Gerald Bailey

Theses

A correlation was developed for estimating binary gas diffusion coefficients by the reference substance method, in this case using the viscosity of air and subsequently its corresponding temperature. The derivation was made by the linear least square analysis of 65 different binary systems comprising 161 separate data points at temperatures ranging from 193°K. to 1200°K. At any given temperature only the critical molal volume and the molecular weights of the two gases of interest are required to calculate the diffusion coefficient. The correlation based on the viscosity of air had an average error of 7.67%. The correlation using temperature had …

Diffusion Coefficients In Alcohol - Water, Frank Gustav Meier

Theses

Diffusion coefficients of potassium, calcium and magnesium ions in ethanol-water solutions have been determined at 20°C. by means of Dowex 50W-X8 under experimental conditions that indicate that the transfer rate is controlled by film diffusion.

This investigation presents, for the first time, diffusion coefficients for these ions in ethanol solutions at concentrations below 0.01N.

The combined effect of viscosity and dielectric Constant of the solvent on the diffusion coefficient of Ions is demonstrated.

Application Of Radioactive Tracers In The Study Of Diffusional Phenomena, Rodolfo Cilento

Theses

The study of mass transfer of a solute through a solvent can be greatly facilitated by the use of radioactive tracers.

This experiment was developed to demonstrate that by using radioactive tracers very small quantities of matter that would be very difficult to test chemically, can not only be tested but easily followed without disturbing the apparatus in which the diffusion is taking place.

Oleic Acid tagged with radioactive iodine (I¹³¹) was diffused through hexane at constant temperature in a glass column, one inch in diameter and thirty-six inches long.

The diffusion of Oleic Acid was followed by …

Diffusion Of Single And Multicomponent Solutes From Capillaries, Oleh S. Sklepkowycz

Theses

The purpose of this investigation was to determine the diffusion coefficients of several single and multi-component solutes, and to establish the relations between the diffusivity, the solute composition) and the diffusion rate. Such information pertinent to the extraction and leaching operations, can not be found in literature.

The procedure developed by Piret, Wbel, and Armstrong (25), involving observation of the extraction rate of two-phase mixtures from straight capillaries, was adopted and verified on a known sodium chloride-water system.

In the course of the experimental work diffusion coefficients more determined for ursolic acid, palmitic acid, and tripalmitin in methyl isobutyl ketone. …

Interphase Gas-Liquid Mass Transfer Study In A Horizontal Channel, Bruce R. Marx

Theses

The rate of transfer of hydrogen sulfide and of carbon dioxide from an atmosphere of the gas saturated with water to a flowing stream of water in a horizontal channel was investigated over a range of water flow velocities and absolute pressures.

Mathematical models describing the system in terms of the penetration and boundary layer theories were inadequate when used to calculate the diffusivity of each gas in water at various conditions. The results of the hydrogen sulfide-water system study shows a relationship between the diffusivity, the interfacial concentration and the liquid flow rate. The calculated diffusivity of the carbon …

Mass Transfer Into Cylindrical Liquid Films Measurement Of Liquid Diffusivities, Ronald Francis Lovenguth

Theses

This thesis was undertaken to augment and validate the previous work of Ratcliff and Reid⁽⁷⁾ in the area of diffusion of immiscible liquids. Their novel approach to this particular problem of liquid diffusion led the author to consider an experimental technique that has been used in gas-liquid studies. A short vetted-wall column was used to determine the rate of mass transfer of benzene and toluene into thin cylindrical films of water. A general analytical solution for the rate of mass transfer has been derived and is given below. This solution was checked using the system benzene-water.

G=3.63(Π(ρ_ω-ρ …

A Simplified Procedure For Diffusion Coefficients From Cation Exchange Studies, Robert Peter Lanyon

Theses

The purpose of this investigation was to extend the data and to improve the procedures of previous investigators (1), (2), and (3), in the study of diffusion coefficients in aqueous media.

The main contribution of this investigation is the elimination of the tedious work of size grading, drying, weighing, and rehumidification of the Dowex 50 W - X8 resin, which is used to determine the ion exchange rates for the cations under consideration, The simplified procedure measures the resin volume by displacing a known volume of water. The method of calculating diffusion coefficients follows the procedure of (1), (2), (3), …

Diffusion Coefficient From Hydrogen Ion Exchange Studies, Michael Maxwell Kahn, Norman A. Martin

Theses

The study of monovalent and bivalent ion diffusion coefficients was undertaken to determine the practicability of using the Reichen berg equation to calculate a film thickness from a single diffusion coefficient and through the use of this film thickness to predict the diffusion coefficient of any monovalent or bivalent ion.

Experimentation employed the use of a mixing vessel with a two bladed propellor into which a solution of known ion concentration was kept at a constant temperature and mixing speed. Dowex 50 x -8 hydrogen ion type resin was added to the solution and by means of a pH meter …

Exploratory Study High Purity Colbalt Using An Anion Exchange Resin, Charles Edward Hoffman

Theses

This investigation accounts for the exploratory phase of a program to develop a commercial or semi-commercial process for producing high purity cobalt; in effect, a separation of cobalt and nickel.

An extensive review of all published literature, patents, etc. from 1900 to 1958 of all known commercial, semi-commercial and analytical methods of separating cobalt and nickel was completed. Qualitative evaluation of these methods to determine the possibility of one being practically extended and/or developed to produce high purity cobalt yielded one potential commercial method. Developed for analytical purposes by Moore and Kraus (1), use is made of the fact that …

A Study In Diffusion, Nicholas James Driscoll

Theses

The object of this thesis was to build an experimental apparatus and to study the diffusion of crystal violet in ethanol-water mixtures and diacetone alcohol-water mixtures. In order to validate experimental technique and to check the work of Mouquin Cathcart(1) who postulated compouhd formation in ethanol-water based on diffusion studies, experiments were conducted on the ethanol-water system in the area where compound formation was predicted.

In order to check the proposal of Konrad(2), based on studies of the heats of mixing that compound formation occurs between diacetone alcohol and water, studies were made on the diffusion of crystal violet in …

Effect Of Concentration On The Mass Transfer Coefficient In The Liquid Film, Marvin Baker Schaffer, Philip Major Pomerantz

Theses

The effect of liquid concentration on the resistance to mass transfer across the liquid film is studied for an acetone-methyl isobutyl ketone-air system in a packed tower. The liquid film resistance is computed by measuring the overall resistance for various concentrations and subtracting the gas film resistance. The gas film resistance is determined at the same liquid and gas rates by measurements on the pure components.

In the theory developed to handle the calculations, it is assumed that the interface temperatures are the wet-bulb temperatures based on a dynamic equilibrium. This supposition is supported experimentally at a liquid rate of …