http://bura.brunel.ac.uk/handle/2438/4327 2013-05-24T14:59:34Z 2013-05-24T14:59:34Z Ahmad, Abid Rafiq http://bura.brunel.ac.uk/handle/2438/7130 2013-01-18T09:26:46Z 1994-01-01T00:00:00Z

Title: Studies of novel diazanaphthoquinones and ion-responsive fluorescent quinoxaline derivatives Authors: Ahmad, Abid Rafiq Abstract: The work reported is divided into two parts: fIrstly a section dealing with the preparation of some novel diazanaphthoquinones and their reactions, especially the Diels-Alder reaction, and secondly an account of some quinoxaline derivatives and their fluorescence properties. Quinoxaline quinones containing electron-donating groups at both the 2- and 3- position have shown a difference in their stability and their behaviour in the Diels-Alder reaction compared to the stability and the reactions of quinoxaline quinone. Symmetrical dienes in the Diels-Alder reaction yielded the initial addition products, which were resistant to oxidation, whereas unsymmetrical dienes produced fully aromatized products. Crown ether derivatives of 5,8-dimethoxyquinoxaline and the corresponding quinoxaline quinones were prepared. An improved method for the preparation of a fluorescent derivatising reagent is described. This compound was then used to prepare ion-responsive fluoroionophores containing monoazacrown ethers of different cavity sizes. The complexation of these fluoroionophores, in dichloromethane, was achieved by using perchlorates of alkali and alkaline earth metals. A strong correlation between the size of the metal ion and the cavity size of the crown ether was seen in the fluorescence quantum yields of the complex, and a fluoroionophore containing a diazacrown ether gave particularly noteworthy results. A bathochromic shift with a strong hyperchromic effect was the most important feature caused by complexation with metal ions for these fluoroionophores. Fluorescent open chain ethers (podands) were also prepared and their complexation with metal ions was studied. A strong bathochromic shift and a hypochromic effect was observed especially in their excitation spectra. A further novel fluorescent derivatising reagent was prepared by extending the conjugated system. This gave the expected improved results upon the preparation of the derivatives including fluoroionophores having crown ethers of different cavity sizes. However, the changes in fluorescence did not correlate with the relationship between the sizes of the metals ion and the cavity of the crown ether. Nevertheless, a large bathochromic shift was observed on complexation with metal ions. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

1994-01-01T00:00:00Z Tadesse, Behailu http://bura.brunel.ac.uk/handle/2438/6624 2012-09-19T14:58:29Z 1997-01-01T00:00:00Z

Title: Iron and manganese oxides in the soil-water environment Authors: Tadesse, Behailu Abstract: The importance of iron and manganese oxides in soil-water environments and their roles in controlling the availability and mobility of contaminants and nutrients are determined. Sorption is simulated using the synthetic iron and manganese oxides: goethite (a-FeOOH), birnessite (Na4Mn14O27.9H20a) nd magnetite (Fe304) which are analogous to natural soil components. Goethite is investigated in the three possible modes of occurrences in soil: colloidal, aggregate, and as coatings on inert materials. The adsorption of cadmium and cobalt onto goethite occurs in a narrow pH range between 6.5 and 7.5. Metal retention increased with both temperature and contact time. A tenfold decrease in ionic strength has no effect on the adsorption pH. Goethite pellets have a different pattern of adsorption due to reduction in surface area and granulation. The sorbing capacity of goethite coated sand is lower than that of the colloidal goethite but has a similar adsorption curve. The coated material is shown to have potential in industrial applications and notably in effluent treatment. Cobalt and cadmium uptake on to hydrated suspensions of birnessite occur in a pH range (3.0-8.0) with sigmoidal shapes for the percent of adsorption curves. Birnessite uptake capacity increases with increasing pH with a maximum at about 6.4 pH. The pH, contact time and the surface area of the oxide are the main factors that control the uptake. The adsorption of coloured species and organic colloids on magnetite was investigated in which magnetite is used both as an adsorbent and as magnetic material. Colour species and organic colloids adsorbed in acid pH and the adsorption decreases with increasing alkalinity. Dissolutions of the magnetite itself increases in low and high pH conditions. The results of investigations of sorption of contaminants and nutrients onto iron and manganese oxides have been applied to shed light upon the behaviour of contaminants and nutrients in soil in the light of soil resource management. The importance of a detailed understanding of contaminant and nutrient transport behaviour in soil-water systems to achieve effective environmental management is demonstrated. Although soil pollution is of major environmental concern, it is probably the least understood source of pollution in terms of both transport of contaminants and remediation. The studies carried out in this work have indicate the types of information required to permit the development of soil management and remediation protocols that will assist in technical management of issues related to soil resources. Detailed knowledge from experimental work must form the scientific basis for the development of contaminated soil assessment and management in an integrated approach. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

1997-01-01T00:00:00Z Furlong, Donald Neil http://bura.brunel.ac.uk/handle/2438/6372 2013-04-30T11:33:12Z 1975-01-01T00:00:00Z

Title: The deposition of silica on titanium dioxide surfaces Authors: Furlong, Donald Neil Abstract: The deposition of amorphous silica from aqueous solution on to rutile particles has been studied with the aim of elucidating the nature of the silica-titania interactions occurring and of following the progressive build up of the silica coating. The coating process, which involves the addition of an aqueous sodium silicate solution to an aqueous dispersion of titanium dioxide, has been investigated by performing a series of controlled preparations and using the technique of microelectrophoresis. Prepared silica-coated rutile samples ranging from partial to full silica coatings have been characterized using transmission electron microscopy, microelectrophoresis and nitrogen, argon and water sorption. Nitrogen and argon adsorption isotherms have been analysed using the equation of Brunauer, Emmett and Teller (BET). Differential energies of adsorption of nitrogen and argon have been determined calorimetrically. Water sorption isotherms have been analysed using the BET equation and the Frenkel - Halsey - Hill (FHH) equation. It has been shown that uniform silica coatings can be produced if adsorption of monomeric silica is followed by polymerization of silica at the solid/liquid interface. Surface cations on rutile may be hydroxylated or co-ordinately bound to water molecules and it appears that monomeric silica adsorbs preferentially by replacing ligand water molecules. Rutile particles with silica coatings thicker than approximately 2.5nm exhibit characteristics typical of silica and not of the base rutile. Silica coatings deposited at pH 10 contain narrow channels which are accessible to water molecules but not to nitrogen or argon. Neutralization to pH 7 reduces the volume in the coating accessible to water molecules. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

1975-01-01T00:00:00Z Omidian, Hossein http://bura.brunel.ac.uk/handle/2438/5792 2012-11-26T15:26:24Z 1997-01-01T00:00:00Z

Title: Improved superabsorbent polymers Authors: Omidian, Hossein Abstract: This work is devoted to the synthesis, characterization and modification of a class of acrylic-based superabsorbent polymers. The techniques of inverse suspension and solution polymerisations were used for synthesis. Each absorbent was mainly characterised by its equilibrium capacity of water absorption and by the rate of absorption. The swelling characteristics of the polymers were evaluated in terms of change in polymerisation variables which include, type and amount of crosslinker, monomer composition, process of polymerisation, temperature, initiator concentration, monomer concentration and particle size of the product. The swelling dependency on salinity was also examined. In some cases, the base polymer was blended with certain polymers in order to upgrade the swelling properties. A swelling model was devised based on a simple viscoelastic model, i. e. Voigt model, to obtain a better understanding of the effect of the above-mentioned variables on the swelling behaviour. Finally, our materials of choice were compared with some commercial analogues and some further comments have been made for continuing the work. Description: This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.

1997-01-01T00:00:00Z