Browsing by Author "Philip, Joseph Yoeza Naimani"

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    Corrosion inhibiting properties of cashew nut shell liquid in aqueous carbon dioxide solutions
    (University of Dar es Salaam, 2001) Philip, Joseph Yoeza Naimani
    The corrosion inhibiting properties of CNSL was studied using SAE 1008 carbon steel in aqueous C02 saturated NaCI solutions. The NaCI concentration in the electrolyte was varied from 1 - 5 %, pH in a range from 4.0 to 6.0 and temperature of the system between 30 and 80 °C. Measurements were performed in both inhibited and uninhibited solutions in order to deduce the influence of the CNSL inhibition of COZ corrosion of the carbon steel. The corrosion inhibition and the adsorption of the inhibitor molecules were monitored on stationary electrode by electrochemical techniques, gravimetric and UV/VIS. The solution pH was found to influence the performance of the CNSL inhibitor. With the solution pH <_ 4 the inhibitor performance was poor but increased to over 95 % as the pH increases. It was suggested that poor solubility of the CNSL inhibitor in solutions of lower pH could be the reason for the poor performance of the inhibitor. Also, it was observed that the solution temperature affects the corrosion inhibiting properties of CNSL. The addition of the CNSL inhibitor in the test solutions of temperatures between 30 to 45 °C, significantly reduced the corrosion rate of the SAE 1008 carbon steel electrodes, however, above 45 °C the performance of the inhibitor decreased. NaCI concentration was found to influence the corrosion rate and mechanism of the carbon steel in the uninhibited solutions. However, NaCI concentration was found to have no effect on the CNSL corrosion inhibitor performance. The CNSL showed a very strong tendency to inhibit the corrosion process for carbon steel electrodes in C02 - saturated NaCI solutions. It was found to be a mixed type inhibitor with predominant anodic effects. In these range of parameters an efficiency of over 95 % was achieved by just 600 ppm. The adsorption process of the CNSL inhibitor on the carbon steel surface reasonably followed the Langmuir adsorption isotherm. The adsorption mechanism of the CNSL inhibitor was elucidated and found to follow physical adsorption, whereby, a phenoxide ion, (R-Ar-O-) of the inhibitor molecule interacts electrostatically with the positively charged metal surface.
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    Investigation on natural cashew nut shell liquid based imprinted polymers
    (University of Dar es Salaam, 2009) Philip, Joseph Yoeza Naimani
    The objective of this work was to use monomers from cashew (Anacordium Accidentalel) nut shells to develop molelarly imprinted polymers. Cashew nut shell liquid (CNSL) is a cheap and renewable agro byproduct consisting of versalite monomers. Solvent-extracted CNSL contains over 80% anaeardic acid (AnAcr) with more than 90% degree of unsaturation in its C15 side chain. In this study, isolation of AnAc from natural CNSL was achieved via calcium anacardate procedure and through continuous supercritical carbon dioxide (seCO2) extraction. From AnAc monomer, anacardanyI acrylate (AnAcr) and anacardanyL methacrylate (AnMcr) monomers were synthesized and their chemical structures were characterized by Fourier transform IR and NMR. Different imprinted bulk polymers based on AnAc, AnAncr and AnMcr functional monomers have been prepared. Each functional monomers was separately co- polymerized in toluene with ethylene glycol dimethacry and divinybenzene as cross-linkers, using racemic propranolol as a model template. While the AnAc based polymer revealed a meager rebinding ability, the imprinted polymers made from AnMcr displayed highly specific propranolol binding. At a polymer concentration of 2mg/ml, AnAcr and AnMcr based imprinted polymers were able to bind over 50% of race propranolol (initial concentration 1.2nM). under the same condition propranolol uptake by the two non-imprinted control polymers was less than 20%, chiral recognition properties of these polymers were further confirmed using tritium-labeled (s) propranolol as a tracer in displacement experiments suggesting that the apparent affinity of the imprinted chiral sites for the correct enantiomer is at least 10 times that of the mismatched (R ) propranolol. Cross reactivity studies of these polymeter showed that the (S) –propranolol and (R) –timolol. Moreover, the presence of the aliphatic side chain in AnMcr resulted in more uniform imprinted beads. Therefore, these results denote an important advancement towards exploiting renewable source from cashew nut shells to synthesize valuable new polymer product.