Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology & Toxicology Student: Monika Moravcová Supervisor: Assoc. Prof. Přemysl Mladěnka, Pharm.D., Ph.D. Title of thesis: Preparation of a Novel Method for Screening of Cobalt Chelators Cobalt as a structural part of the vitamin B12 is an essential microelement for living organisms including humans. However, its excess is associated with pathological conditions. Cobalt poisoning can be caused for example by exposure to cobalt metal dust during the production of hard metals or follow the corrosion of metal hip prosthesis. Patients intoxicated by cobalt can develop different manifestations including neurological impairment, hypothyroidism or cardiomyopathy. The aim of this work is to prepare a standardized, rapid, cheap but precise method for the screening of cobalt chelators. For this purpose, spectrophotometric detection using 1-nitroso-2-nafphhol-3,6-disulfonic acid disodium salt as the indicator was used. Firstly, it was found that the addition of cobalt ions led to a clear bathochromic shift of the maximum absorbance of the indicator. The relationship between the absorbance and cobalt concentration was highly linear from 470 to 560 nm at all 4 tested pH conditions (4.5, 5.5, 6.8 and 7.5). The sensitivity of the method...

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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of the degree of Master of Science. November 1995. / The preparation of supported cobalt and gold catalysts by the technique of electroless plating, and the establishment of the influence of synthesis variables on the physical properties of the supported catalyst, forms the basis of this dissertation. In both the cases of cobalt and gold supported on extruded cylindrical alumina pellets, the penetration profile of the metal into the support showed dependence on the pH of the activation solution, while the metal loading onto the same support showed no dependence on pH of the activation solution at all. The variables involved in the plating process of the activated pellets, namely: i) the concentration of the activation solution, ii) pH and temperature of the plating bath, iii) plating time, and Iv) variation of the concentrations of components of the plating bath all influenced the mass of metal loaded onto the support, but not the penetration characteristics. It is therefore possible to prepare a supported catalyst with very specific , properties using the above information. Under similar conditions, with extruded alumina pellets as support and with the specific plating formulations used, gold showed higher metal loadings at lower gold concentrations than cobalt.

Several self-supported and metal oxide supported cobalt Fisher-Tropsch (FT) catalysts were prepared applying incipient wetness impregnation method. The catalysts were characterized by TPR, adsorption-desorption, XRD, TEM and SEM. The gas products were characterized by GC. The effect of support was investigated. The selfsupported 3D ordered macro-porous (3DOM) Fe-Co and self-supported 2D ordered mesoporous catalyst showed low or no activity under typical F-T reaction conditions. The 3DOM Al2O3 supported cobalt catalyst showed much higher CO conversion and C4+ selectivity than conventional Co/Gamma-Al2O3 catalyst. However, the 3DOM Co/Al2O3 prepared by incorporated method showed no activity. The supported Co/SBA-15 performed better CO conversion than the conventional Co/SiO2. The effects of temperature and time on 3DOM Co/Al2O3 and Co/SBA-15 system were coherent with traditional catalysts. The well-defined structure of 3DOM Al2O3 and SBA-15 may favor to the selectivity of C4+ hydrocarbons product.

<p> The diffusion coefficient of Co has been measured as a function of temperature in the body-centered-cubic phase of 99.99% zirconium. The diffusion rates are extraordinarily large, and follow the relation D = [3.26 ± 2.77] x 10^(-3) exp -(21,820 ± 960/RT) cm^2 /sec over the range 900 to 1600°C. </p> <p> The Arrhenius plot has a positive curvature above 1600°C. The influence of cobalt additions on the diffusion of 95 ZR and 60 Co in dilute Zr-Co alloys was studied from 0 -2 at.% cobalt at 933°C. A theoretical model was developed to relate the effect to the solute correlation factor. It is established that diffusion in these systems cannot be accounted for in terms of a vacancy mechanism alone. Other models are discussed. </p> / Thesis / Doctor of Philosophy (PhD)

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