Browsing by Author "Mona Abu Elgasim Hassan"

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    Adsorption of phenolic compounds from dilute aqueous solutions
    (2008) Mona Abu Elgasim Hassan
    ABSTRACT Adsorption isotherms of four phenolic compounds have been studied onto carbon and clay treated by acid. The results indicated that the adsorption isotherms were complying with Langmuir and Freundlich models. The effect of temperature on adsorption on carbon was also studied and the results of the adsorption on active carbon showed that the adsorption increases with decreasing temperature, exothermic process, for all compounds and it is directly in accordance with Gibbs equation for equilibrium conditions. In the case of clay the increases of temperature showed that there is no a definite mechanism followed by the adsorption due the unequality between adsorption and desorption. Studies on the adsorption at different pH values on carbon showed that the adsorption increases with decreasing pH value. Adsorption on three different particle sizes of activated carbon showed that the adsorption increases with decreasing particle size
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    Preconcentration and Determination of Heavy Metals in Environmental Samples by Cloud Point Extraction and Flame Atomic Absorption
    (Al Neelain University, 2013) Mona Abu Elgasim Hassan
    This work is concerned with the aspects of the preconcentration and separation methods of cloud point extraction(CPE) approach. The proposed CPE procedure is applied for the preconcentration and extraction of trace metals in various water samples and other environmental samples containing Cu(II) and Pb(II). The CPE is based on the property of most non-ionic surfactants in aqueous solutions to form micelles and become turbid when heated to a temperature known as the cloud point temperature (CPT). Above this temperature, the micellar solution separates into surfactant rich phase of a small volume and a dilute aqueous phase. Triton X-100 is of relatively low-cost and low toxicity has been used as non- ionic surfactant. Derivatives of thiosemicarbazide have been used as complexing agents. The surfactant-rich phase has been introduced directly into the nebulizer of a flame atomic absorption spectrometer by dilution with acidified ethanol. The influence of different factors on the preconcentration and recoveries of Cu(II) and Pb(II) by the CPE procedure was evaluated. The study showed that the pH of the solution is the most important factor that influences the optimization of the extraction. Most of the chelates were quantitatively extracted at pH values between 6 and 7. Another critical factor was the concentration of diphenylthiosemicarbazide (DPTC). The extraction was studied at different concentrations of DPTC and the results showed that 0.08% and 0.8% of DPTC result in the complete extraction for Cu(II) and Pb(II) respectively . Other important factors evaluated were the temperature, the concentration of surfactant and the stoichiometry of the chelates. Efficient recovery has been achieved in the range of 92 % - 108 % for copper(II), and 80% -— 112.5 % for lead(II) using DPTC and the method provided a preconcentration factor of l0 for both metal ions. The results of this study has illustrated the importance of the CPE method as well as the application of thiosemicarbazide derivatives as chelating agents.