Thesis (Ph. D.)--University of Wisconsin, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (MTech(Chemical engineering))--Cape Technikon, Cape Town,1996 / Metal cyanide complexes are a toxic pollutant in waslewater originating from various industrial and mining activities. The removal/retrieval ofcyanide and metal cyanide complexes has been studiedby researches for many years, leading to the establishment of a variety of patents. The mechanisms used by these patents vary from purely chemical techniques to those using ion exchange Iesins. In this thesis, ,the feasIbility ofthe recovery ofmetal cyanide complexes by using a strong base macroreticular resin, in a fluidized bed configuration, has been investigated. The resin in question is presently used in the sugar indnstry where its main application is the recovery oflarge organic molecules similar in nature to metal cyanides. The selected resin was contacted with synthetic solntions of various metal cyanide complexes. for the purposes of evaluating performance in the adsorption th..."feOf. It was found that polyvalent metal cyanide molecules were adsOlbed efficiently, while divalent metal cyanide molecules were adsorbed satisfactorily. The loaded resin was also evalnated for the ease with which the metal cyanides conId be removed. It was discovered that a brine solntion ofpH 7, conId effectively remove all metal cyanide complexes. This test-work was of particular importance as it is well !moon that the removal ofmetal cyanides from strong base metals is not easily achieved. To distingnish the fluidization characteristics of the selected resin (or any resin for that matter), a method of modelling the expansion of a flnidized resin bed was proposed, that takes into account the diflicnIties associated with the byclrod:)nantic charncteristics of a macroporous resin of this nature. The technique is based on the Serial Afadel which is a discretised application of the Z3ki and Richardson equation. From the interpretation of the resnIts of a matrix of fluidization tests, it was fonnd that the algorithm proposed conId effectively model the expansion of a fluidized bed of ion exchange resin, independently of the dimensions ofthe accomodatiog receptical. Finally. it was shown that the change in the fluidization characteristics of the selected resin, between its chloride and metal cyanide states, could clearly be modelled by the technique referred to above.

The object of this research is to further investigate the possiblitiy of resolving racemic bases on an optically active cation exchange resin. Any success in this direction would help to explain the reason for Bunnett and Mark's failure, since the general assumption that selective adsorption of one enantimorph of a racemic compound on an active exchanger should occur has been verified by Grubhofer and Schleith. The work can be conveniently divided into two sections. a) The preparation of optically active cation exchange resins and, b) the use of these as resolving agents. P. 8

Ion exchange resins have been used for retrieving radiocaesium from aqueous waste streams since the earliest days of the nuclear power industry. The physical and chemical properties of Lewatit DN ion exchange resins encapsulated in silica fume (SF)-blended cement were investigated with the aim of producing a stable solid wasteform for possible future disposal in an underground repository. Expansive reactions involving resin swelling in the high pH pore fluid and Ca(OH)2 formation around the resin particles can be suppressed by the addition of 50-75% SF at w/c ratios of 1.400-1.71. The basis of this suppression is the pozzolanic reaction between Ca(OH)2 and SF which consumes Ca(OH)2 and lowers the pH of the pore fluid to less than 10. The total heat evolution of blended cements is similar to that of a neat Portland cement, demonstrating the exothermic nature of the pozzolanic reaction. The use of high w/c ratios in cements containing 50% SF increases the permeability of the matrix. Porosity measurements indicate that this is due to the high free water content of the paste and the relatively high porosity of SF agglomerates. Elevated curing temperatures (up to 85oC) also increase the permeability as a result of coarsening of the microstructure. Despite the inferior physical immobilisation of caesium in high SF-content cements, leach tests, sorption measurements and pore fluid analysis show that chemical retention of caesium is enhanced by blending, more so in blends containing a permanent excess of SF, due to the formation of highly sorptive silica gel and low ratio C-S-H (Ca/Si as low as 0.80). On the other hand, SF-blended cements are more susceptible to physiochemical degradation in simulated groundwater's containing MgSO4. Chemical attack by MgSO4 converts C-S-H gel and silica gel to a non-cementitious magnesium silicate hydrate (identified as sepiolite) in 50-75% SF pastes, resulting in extensive deterioration of the attacked zone.

No description available.

Thesis (M.S.)--University of Michigan, 1985. / Project completed May 1984. Degree awarded August 1985.

A Thesis presented in the University of the Witwatersrand, Johannesburg for the degree of Doctor of Philosophy, 1953 / Investigations have been carried out into the life of various Anion Exchange Resins employed on the Rand for the extraction of uranium from the uranium Leach Liquors. It was found that in the case of the leach liquors produced at the western Reefs pilot plant and at the West Rand Consolidated Uranium plant, the major factor causing a decrease in the efficiency of the Ion exchange resins was the presence of certain chemical poisons in these pregnant solutions. [No abstract provided. Information taken from General Summary] / AC2017

Ion exchange equilibria are presented for [ ]??? ??? Au(CN)2 / Cl , [ ]??? ??? Au(CN)2 / SCN and SCN??? / Cl??? in aqueous solution, and in various mixed solvents, at 303K using Purolite A500 as the ion-exchanger. The mixed solvents investigated include water-acetone, water-dimethylsulfoxide (DMSO) and water-N-methyl-2-pyrrolidone (NMP). In aqueous solution, the selectivity of Purolite A500 for a given anion increases in the order: [ ]??? ??? &lt ??? &lt Cl SCN Au(CN)2 . This selectivity sequence confirms the high affinity of the ion exchange resin for the [ ]??? Au(CN)2 species. In mixed solvents, however, the selectivity of Purolite A500 for [ ]??? Au(CN)2 decreases with an increase in the composition of the organic solvent in the external solution. Mixed solvents containing greater than 60 mol% organic solvent are preferred for the displacement of [ ]??? Au(CN)2 from the resin. The effectiveness of a given type of mixed solvent generally increases in the following order: DMSO &it acetone &it NMP. The ion exchange equilibria are correlated using the Law of Mass Action, modified with activity coefficients, to determine the equilibrium constant for each binary system. The fitted values of the equilibrium constants are consistent with the trends observed in the ion exchange isotherms. The accuracy of the correlation results in the mixed solvent systems range from 1 to 10% and this is similar to the level of accuracy obtained for the ion exchange equilibria in aqueous solution. From these results it can be concluded that the Law of Mass Action is equally valid in mixed solvent systems. The variation in the equilibrium constant with mixed solvent composition, for a given binary system, correlates well with the dielectric constant of the mixed solvent. For a given value of the dielectric constant, however, the equilibrium constant, however, the equilibrium constant is dependent on the type of mixed solvent. A fundamental relationship is derived between the equilibrium constants and the Gibbs energies of transfer associated with the solvation of the ions in the mixed solvents. Based on this relationship, the redistribution of ions between the pore solution and the bulk mixed solvent, appears to be the most significant factor that governs the selectivity of the resin in mixed solvent systems.

This thesis explores the behaviour of metal cyanide complexes under oxidative acid conditions in ion exchange systems, with the objective of developing an ion exchange based process for the treatment of gold cyanidation tailings. The novel cyanide detoxification process developed from this study employs strong base ion exchange resins to extract cyanide from tailings. Variations in the stability of cyanide complexes are exploited to concentrate, recover, or destroy cyanide species loaded on the resin, through the use of an oxidative acid eluent containing H2O2 and H2SO4. This eluent removes all base metal cyanide complexes from strong base resins, while regenerating the resin. The spent eluent, containing the base metals recovered from the tailings, can be used as a source of such base metals. Copper can be recovered separately from other base metals if necessary. Low levels of precious metals present in the tailings are accumulated on the resin as the ion exchange bed is cycled between loading and elution stages. They can be recovered economically, so as to offset the cost of the tailings detoxification. Cyanide is initially concentrated as an alkaline solution, which can be detoxified within the process or recovered for recycling. This process was successfully tested at pilot scale by treating approximately 14,000 m3 of cyanide contaminated tailings solution, over 14 loading/elution cycles on a standard strong base ion exchange resin bed. This treatment reduced the total cyanide concentration of the contaminated solution from approximately 50 mg/L to an average of 1.5 mg/L. The reagent cost was approximately ADD 0.50 per m3 of treated liquor. When the resin was repeatedly loaded with mixed metal cyanide species and eluted with the oxidative acid eluent, a gradual deterioration of the ion exchange resin performance was noted. The reduction of net operating capacity of the columns due to resin deterioration was in the order of 1-3% per loading/elution cycle. The oxidation of resin catalysed by copper, the precipitation of metal hexacyanoferrates on the resin and the oxidation of Au(CN)2- to Au(CN)4- were identified as possible factors giving rise to the reduction of resin loading capacity.

Ion exchange equilibria are presented for [ ]??? ??? Au(CN)2 / Cl , [ ]??? ??? Au(CN)2 / SCN and SCN??? / Cl??? in aqueous solution, and in various mixed solvents, at 303K using Purolite A500 as the ion-exchanger. The mixed solvents investigated include water-acetone, water-dimethylsulfoxide (DMSO) and water-N-methyl-2-pyrrolidone (NMP). In aqueous solution, the selectivity of Purolite A500 for a given anion increases in the order: [ ]??? ??? &lt ??? &lt Cl SCN Au(CN)2 . This selectivity sequence confirms the high affinity of the ion exchange resin for the [ ]??? Au(CN)2 species. In mixed solvents, however, the selectivity of Purolite A500 for [ ]??? Au(CN)2 decreases with an increase in the composition of the organic solvent in the external solution. Mixed solvents containing greater than 60 mol% organic solvent are preferred for the displacement of [ ]??? Au(CN)2 from the resin. The effectiveness of a given type of mixed solvent generally increases in the following order: DMSO &it acetone &it NMP. The ion exchange equilibria are correlated using the Law of Mass Action, modified with activity coefficients, to determine the equilibrium constant for each binary system. The fitted values of the equilibrium constants are consistent with the trends observed in the ion exchange isotherms. The accuracy of the correlation results in the mixed solvent systems range from 1 to 10% and this is similar to the level of accuracy obtained for the ion exchange equilibria in aqueous solution. From these results it can be concluded that the Law of Mass Action is equally valid in mixed solvent systems. The variation in the equilibrium constant with mixed solvent composition, for a given binary system, correlates well with the dielectric constant of the mixed solvent. For a given value of the dielectric constant, however, the equilibrium constant, however, the equilibrium constant is dependent on the type of mixed solvent. A fundamental relationship is derived between the equilibrium constants and the Gibbs energies of transfer associated with the solvation of the ions in the mixed solvents. Based on this relationship, the redistribution of ions between the pore solution and the bulk mixed solvent, appears to be the most significant factor that governs the selectivity of the resin in mixed solvent systems.