Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Page 145 left intentionally blank. Includes bibliographical references (leaves 123-125). Also available on the World Wide Web.

This work has included a review of the most relevant aspects of measurement techniques and mathematical models proposed in the literature to assess the equilibrium and mass transfer data of metal extraction by the use of chelating agents. The limitations of these techniques and models have been highlighted. Three chelating extractants diluted in EscaidllO were used to study the extraction equilibrium of copper. The extractants are 5-nonylacetophenone oxime (LIX84®), 5- dodeylsalicylaldoxime (LIX860®) and 50/50 v/v mixture of both oximes (LIX984®). The copper concentration changes in the aqueous and the organic phases were monitored by using atomic absorption spectrophotometer. Two mathematical models (a chemical model and a semi-empirical model) have been developed in this study to predict the equilibrium data of copper sulfate/hydroxyoxime system. The chemical model was found to fit all the three equilibrium systems (CuSO4/LIX84®, LIX860®and LIX984®) equally. The semi-empirical model based on Freundlich's adsorption equation was also found to fit the three systems but with less accuracy. The mass transfer characteristics and properties of copper extraction and recovery from an aqueous solution using LIX984® were studied using dispersion-based (rising drops) and dispersion-free techniques. In the dispersion-based technique the organic phase was dispersed in form of drops at the tip of hypodermic needle while the aqueous solution was used as a continuous phase. The extraction process was carried out in four different height columns under wide range of conditions. The effects of the columns' height, the dispersed and the continuous phases concentrations on the metal rate of mass transfer were investigated. It has been found in that the metal's rate of mass transfer and system's overall mass transfer coefficient have remained constant in all four columns. A model utilising the two-film theory, some of the dimensionless groups and the experimental results has been proposed in this work to calculate the local mass transfer coefficients in the dispersed phase and the continuous phase. The overall mass transfer coefficient and the calculated local coefficients were used to account for the reaction rate constant at the interface from the sum of the individual resistances to mass transfer. A dispersion-free technique consisting of a microporous hollow fibre module was used in this study to examine the mass transfer properties of the extraction and stripping processes of copper across an immobilised interface system. The extraction and re-extraction (stripping) processes in this system were conducted under a wide range of operating conditions and produced satisfactory results. In general it has been found that counter current flow arrangement gave higher concentration driving forces which were reflected in form higher metal concentrations at the extract phase. A generalised mathematical model was developed in this study which utilised Wilson's method, the experimental data, some dimensionless groups and the two-film theory to account for local resistances and predict the system's overall mass transfer coefficient. A correlation was established first to calculate mass transfer coefficients using a form of Leveque's equation which relates the two phase's physical properties and the system's parameters. The membrane mass transfer coefficient was calculated from the structural properties of the membrane material. While the resistance at the reaction interface was calculated under set of experimental conditions. The individual coefficients were then used to predict the overall mass transfer coefficient under any set of conditions by using the aditivity approach of the individual resistances to mass transfer. However, further checks and investigations are necessary to validate this model over variety of extraction systems and membrane configurations.

No description available.

C. acetobutylicum is an anaerobic bacterium that produces acetic and butyric acids, hydrogen gas, and carbon dioxide during the exponential phase of growth. When the culture pH is allowed to remain near 4.5, the metabolism switches to the production of the neutral compounds (solvents) - acetone, n-butanol, and ethanol. The two metabolic phases are known as the acidogenic and solventogenic phases. The enzyme hydrogenase plays an important role in this bacterium because it converts excess reducing power into hydrogen gas to maintain a balance in the oxidation-reduction state in the cell. During solventogenesis, additional reducing power is used in the production of n-butanol and ethanol, which leaves excess reducing power to be vented as hydrogen gas. There are conflicting reports about the level of hydrogenase in acidogenic and solventogenic cells. There is also evidence that hydrogenase may consume too much reducing power during solventogenensis that it actually decreases the cell's capacity to produce solvents. The purpose of this study was to examine the level of hydrogenase in acidogenic and solventogenic cells and to search for clues that may indicate the presence of multiple forms of hydrogenase in C. acetobutylicum. Both the hydrogen-oxidation (uptake) and the hydrogen-production (evolution) activities were measured in this study. The level of hydrogenase was found higher in acidogenic cells than in solventogenic cells, but there was no difference in the molecular weight of hydrogenase from these two types of cells. A significant increase in the ratio of the hydrogen-uptake over the hydrogen-evolution activity was observed in oxygen or heat-treated cell extracts and in hydrogenase partially purified on a DEAE-cellulose column. The results suggest the presence of more than one type of hydrogenase in this species or hydrogenase activities in the two directions may be differentially altered. These possibilities will be investigated in a future study. / Master of Science

<p> Several types of apparatus have been previously developed to give a constant and measurable interfacial area for solvent extraction. In this work, a new and relatively simple device for this purpose has been tested. The organic phase is allowed to rise or fall freely through the aqueous phase in a tube as a cylindrical "slug". In the mass transfer operation, the "slug" of sparingly-soluble organic liquid is held stationary by the downflow of water. The shrinkage rate of the slug can be measured easily and it gives the experimental mass transfer rate. In order to apply the Higbie penetration theory to the experimental conditions, the interfacial velocity and radius ratio of the slug must be known; these factors can be calculated from the hydrodynamics of the system, using the measured value of slug superficial velocity. Finally, a comparison between experimental and theoretical mass transfer results can be made. 1-butanol shows a good agreement (to within 1%) while 1-pentanol and methyl iso-butyl ketone show less satisfactory agreement due to lack of precise data on their molecular diffusivities in water.</p> / Thesis / Master of Engineering (MEngr)

The equilibrium and the kinetics of the reaction of Mo (VI) with 8-hydroxyquinoline; 8-hydroxyquinaldine; KELEX 100; LIX63; and LIX65N were studied by solvent extraction. From the equilibrium studies it was concluded that in weakly acidic solution (pH 5 to 6) the overall extraction reaction is (UNFORMATTED TABLE FOLLOWS) MoO₄²⁻ + 2H⁺ + 2HL(o) ↔ (K(ex)) MoO₂L ₂(o) + 2H₂O (TABLE ENDS) where HL is the monoprotic bidentate ligand, "(o)" refers to the organic phase, and K(,ex) is the extraction constant. It was concluded that the complexation reaction requires four protons to convert molybdate into molybdenyl. The extractions constants for LIX63 and 8-hydroxyquinaldine, corrected for the side reaction of the ligand and metal, are 10¹⁶·⁴³ and 10¹⁴·⁴⁰, respectively. In the case of LIX65N, the plot of log(D) vs pH has a maximum at pH 1.0, which was explained qualitatively in terms of protonation of the ligand and molybdic acid at low pH. The extraction constant for the reaction of molybdic acid and the neutral ligand was estimated to be 100,000. The kinetics of extraction Mo (VI) with LIX63, 8-hydroxyquinoline, 8-hydroxyquinaldine, and Kelex 100 were studied in this work. In all cases, except 8-hydroxyquinoline, the rate-determining step of the reaction involves the formation of a 1:1 complex between the neutral ligand and several Mo(VI) species differing in the degree of protonation. The rate-determining step for the reaction of Mo(VI) with 8-hydroxyquinoline involves the formation of a 1:2 complex. The rate constant for the reaction of HMoO₄ with 8-hydroxyquinaldine is four orders of magnitude smaller than the corresponding value reported in the literature for 8-hydroxyquinoline. The slower reaction with 8-hydroxyquinaldine was attributed to the presence of the methyl group next to the nitrogen atom of the ligand which hinders its binding with molybdenum in the rate determining step of the reaction.

Interfacially active reagents are utilized in metal solvent extraction processes and it is therefore important to understand the role of the liquid-liquid interface in the study of the kinetics and equilibria of extraction. The diffusion problems encountered in the traditional apparatus were overcome by using a high speed stirring apparatus. The microporous teflon membrane phase separator permitted more accurate measurements of interfacial areas, characterization of extraction kinetics of metal chelates, and a greater understanding of the phase separation mechanism. In contrast to the neutral ligands, the anionic ligand of dithizones and substituted dithizones showed significant interfacial adsorption at the chloroform/water interface as monitored spectro-photometrically. Equilibrium studies on p-halodithizones indicated that the adsorption constant increased as the substituent was altered from chloro to bromo to iodo, and with the distribution ratio of the ligand. Kinetic studies on dithizone and p-iododithizone with Ni(II) and Zn(II) indicated that the extent of participation of the interface in solvent extraction kinetics of these metal ions is dictated by the interfacial activity of the extractant and the mechanisms of the rate limiting step in the bulk aqueous and interfacial regions.

No description available.

Fundamental solvent extraction studies on the separation of the lanthanides were carried out by investigating both the hydroxamic acid and phosphinic acid reagent families. In general, the lanthanides were found to extract as self-adducts. It was found that the separation of the individual lanthanides with both of these reagent families was adversely affected by steric hindrance.