The colloidal fraction is the vital part of a soil. These extremely minute particles determine the nature of the soil and are mainly responsible for its many and varied functions. The most important of these functions is perhaps the ability of the colloids to adsorb and exchange cations, the elements so essential to all organisms as building materials. When pure water is passed through a non-saline. soil, the leachate will contain very few dissolved cations. If, on the other hand, an electrolyte such as a weak solution of sodiun chloride, is passed through the same soil, the leachate will contain considerable quantities of calcium, magnesium and potassiun chlorides as well as much of the original sodium chloride. The number of equivalents of the cations collected will be approximately the same as the number of equivalents of sodium ions added. Sodium ions have displaced some of the calcian, magnesium and potassium ions from the soil. This phenomenon is known as cation exchange. Intro., p. 1.

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

In order to increase the current efficiency in copper electrowinning tankhouses, iron can be removed from the electrolyte using ion exchange. While this is a proven technology, very little data is available for the application of this technology to copper electrowinning electrolytes containing antimony and bismuth. The feasibility of utilizing iron ion exchange for the removal of iron from copper electrowinning electrolytes containing antimony and bismuth was studied in the laboratory. A picolylamine, a sulphonated diphosphonic, an aminophosphonic and three sulphonated monophosphonic resins were tested. The picolylamine resin was found to be completely impractical as it loaded high levels of copper. All the phosphonic resins tested loaded an appreciable amount of antimony, however, only the aminophosponic resin loaded an appreciable amount of bismuth. Tests to determine whether or not the sulphonated monophosphonic Purolite 5957 resin would continue to load antimony with time and, hence, reduce the resin's ability to remove iron gave inconclusive results. In the event that the resin's ability to remove iron is hampered due to antimony loading, testing has shown that the resin performance may be restored via a regeneration with a solution containing sulphuric acid and sodium chloride. A case study for the application of this technology to the CVRD Inco CRED plant has shown that, while iron removal by ion exchange is technically feasible, it will upset the plant's acid balance in electrolyte. Therefore, an acid removal process would need to be implemented in tandem with an iron ion exchange system. Additionally, preliminary calculations suggest that a system with a single ion exchange column may have difficulty removing sufficient iron for the CRED design conditions. Therefore, consideration should be given to the possibility of utilizing a two column system (one column loading, one column stripping). / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The aim of this study was to establish whether samples of South African-mined clinoptilolite could be used to remove selected metal cations from aqueous solution. The clinoptilolite samples supplied, (by Pratley SA) were in four different particle sizes. Batch study results revealed a decrease in the initial metal concentration in samples that were in contact with clinoptilolite. The finer particle size clinoptilolite had a greater capacity to remove metal cations from aqueous solution. However, ion-exchange results from atomic absorption analysis showed that the larger particle sizes, removed more magnesium ions. Magnesium was the only ion investigated in this study that was present as an exchangeable ion in the Pratley clinoptilolite chemical formula, (MgCaNa2K2)2.5(AlO2)7(SiO2)30.21H2O. Results from the ion-exchange studies showed that the decreasing order of percentage metal removal at pH 3.00 was as follows: Pb > Ni > Cu > Fe > Mg. The mass of metal ions that accumulated on one gram of clinoptilolite as determined from the isotherms was calculated to be 6.16 mg/g for lead and 0.74 mg/g for copper. Data from the lead equilibrium studies were fitted into Langmuir and Freundlich equations and linear regression was used to calculate linearity coefficients for the isotherms. The results showed that the removal of lead ions by clinoptilolite is complex as both monolayer and multilayer adsorption occurs on a heterogeneous surface.

No description available.

The potential use of 6,7,8-trimethyllumazine (6,7,8-trimethyl-2,4-dioxopteridine) and Its dihydro derivative as a redox couple for the pteridine and flavin systems is investigated. The syntheses of the above compounds and related lumazine derivatives are described and their spectroscopic and chromatographic properties are tabulated. While examining the p.m.r. spectra of 6,7,8-trimethyllumazine (TML) and 7,8-dihydro-6,7,8-trimethyl-lumazine (DHTML) in deuterium oxide media, the hydrogens of the C-7 methyl group and of the C-6 methyl group in the former and latter compounds respectively were observed to undergo exchange. In the pH range -0.4 to 8.0, the exchange of TML is subject to general acid-base catalysis. The pseudo first-order exchange rate constant (k₁) was found to be the sum of several catalytic terms. Prom measurements of the exchange rate-buffer dependency at various pH values, the following values of the specific catalytic constants (in l.mole⁻¹min⁻¹) have been calculated: K[subscript H]+= 1.2, k[subscript H3PO4] = 0.41, k[subscript H2PO4]- = 0.14, k[subscript HPO4]-2 = 52.9 The mechanism of the acid- and base-catalyzed exchange of TML is outlined. The relatively facile exchange is explained in terms of the formation of neutral and ionic intermediates which have long conjugated bonding arrangements. Pseudo first-order rate constants have been tabulated for the general acid-catalyzed exchange of DHTML in the pH range -0.4 to 8.2 leading to an unusual pH-rate profile. The marked decrease in exchange rates and anomalous rate plots in the more acidic pH regions is attributed to acid-catalyzed covalent hydration across the C(6)-N(5) double bond and equilibration of hydrated and unhydrated cations. Evidence for hydration is presented and the exchange mechanism is discussed. The ferricyanide oxidation of DHTML was investigated in the pH range 5 to 12.5 by spectrophotometry and potentiometric techniques. The second-order reaction proceeds in a complicated sequence of steps, some of which are dependent upon the ionization of the reaction intermediate, trimethyl-lumazine. Beyond pH 11, the oxidation rate is directly proportional to the hydroxide ion concentration. At pH 12, the absence of a primary isotope effect and the inhibitory effect of added ferrocyanide indicate that the oxidation proceeds via an initial rapid and reversible one-electron abstraction from the anionic form of DHTML. The resulting mesoroeric radical can undergo further reactions with ferricyanide ion or with hydroxide ion. A very negative ΔS‡ value was obtained for the reaction at pH 12, consistent with a reaction between ions of the same charge. A study of the effects of potassium ion on the oxidation rate indicates the partial participation of the associated species KFe(CN)₆⁻² in the reaction. A limited study of the reaction between trimethyl-lumazine and ferricyanide was undertaken. The hydroxylated anion of TML reacts via a highly coloured intermediate to produce 7-oxo-6,8-dimethyllumazine. Further investigation into the reaction is required. / Science, Faculty of / Chemistry, Department of / Graduate

The immune response of chickens immunized with β-N-acetylglucosaminidase was monitored in the egg yolks of the birds using an enzyme-linked immunosorbent assay. Significantly higher levels of specific antibodies were detected in the yolks of the birds immunized with the enzyme when compared with the yolks of a control bird collected over the same period significant differences also were found in the response within the immunized group of birds, indicating individual variability to the injections. Immunoglobulins were isolated from egg yolk after a preliminary purification using alginate to precipitate lipoproteins. A ten millilitre DEAE-Sephacel ion exchange chromatography column resulted in a final product containing 16 mg of IgG with a purity of 60% when 50 mL of an egg yolk supernatant was applied. Specific antibody activity toward the antigens β-lactoglobulin and E. coli lipopolysaccharide was higher in both cases in the isolated immunoglobulin fractions which contained lower purity (40%). Lower antibody activity was observed in the 60% purified fractions. Separation of specific antibodies from non-specific antibodies appeared to occur, possibly due to the given characteristics of the specific antibodies, or due to the differences exhibited by chicken IgG subpopulations. Using metal chelate interaction chromatography, a 10 mL copper-loaded column was able to yield 104 mg of IgG with a purity of 75% when 200 mL egg yolk supernatant was applied. Again, the heterogeneous nature of chicken IgG was illustrated. A comparison of the two chromatographic techniques indicated the advantages of metal chelate interaction chromatography over ion exchange chromatography under the conditions examined. Applications of the chicken IgG isolated by metal chelate interaction chromatography to an enzyme-linked immunosorbent assay for the detection of β-N-acetylglucosaminidase was attempted. Linear relationships were obtained when standard solutions of the enzyme were used in the assay. The results indicate that MCIC-isolated chicken immunoglobulins have excellent potential for use in analytical tests. / Land and Food Systems, Faculty of / Graduate

The purpose of the investigation described herein was to investigate the degree of delocalization of the unpaired electron in ion radicals formed in the oxidation process of compounds with aromatic rings connected by means of various groups and atoms not entering the ring; then, to establish the relationship of coupling constants in radical cations with substituent σ values. The parent cation radical, in which the co-planar ion was derived from N,N-dimethylaniline, was selected in order to maximize the substituent effects on coupling constants and to obtain couplings at several positions (specifically, CH3, N, and ring protons).

Orientador: Graciliano de Oliveira Neto / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-07-20T17:04:53Z (GMT). No. of bitstreams: 1 Marques_MargarethRitadeCassia_D.pdf: 2606900 bytes, checksum: 07e992cee414e439a7b580c89d45bb79 (MD5) Previous issue date: 1995 / Doutorado

This thesis has contributed to the achievement of in-beam PET as a promising clinical monitoring technique. In response to a pressing medical demand, this work has provided a tool for quantification of local dose deviations in case of observed discrepancies between the measured and expected PET images. The implemented interactive approach described in chapter 3 is in clinical use since 2001. It provides the radio-oncologist with a valuable feedback which may allow a prompt reaction in the strategy of the therapy prior to the delivery of the successive treatment fraction in case of significant deviations between planned and actually applied dose. ...