Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, ChemistrySubject: search.filters.subject.Selenium

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  • Master Thesis
    Development of Novel Sorbents for Speciation of Inorganic and Organik Selenium Prior To Determination by Atomic Spectrometric Techniques
    (Izmir Institute of Technology, 2011) Demirkurt, Merve; Eroğlu, Ahmet Emin; Eroğlu, Ahmet Emin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Selenium is an essential trace element forplants, animals and the human body. Hovewer, its possible toxicity at high concentrations necessitates the development of analytical methods for theseparation and determination of the several forms of the element in environmental andbiological systems.In the first part of the study, commercially available and newly synthesized ceria (CeO2) and zirconia (ZrO2) were used for the sorption and speciation of inorganic selenium. Sorption parameterswere investigated for both sorbents for selenite (Se(IV)) and selenate (Se(VI))and the optimized parameters were determined to be 25°C for sorption temperature, 50.0 mg for sorbent amount, 30 min for shaking time for 20.0 mLof 100.0 μgL-1of both species. Therelease of Se(IV) and Se(VI) from the sorbents was realizedusing two eluents, 0.10 M NaOH and 0.10 NH4Cl, respectively. The accuracy of the proposedmethodology was verified with spike recovery tests for various water types spiked with 10.0 μgL-1and 100.0 μgL-1Se(IV) and Se(VI). Spike recovery values were determinedto range between 91% and 97% at 10.0 μgL-1level, and between 97% and 113% at100.0 μgL-1level, for ceria and zirconia, respectively. Moreover, the sorption efficiencies of the newly synthesized sorbentswere compared with those of the commercial sorbents.Ceria and zirconia were shown to be applied in the speciation of inorganic selenium. Sorption studies with nZVI-modified zirconia have demonstrated that the sorbent can be utilized for the speciation of inorganic and organoselenium; namely, Se(IV), Se(VI), Seleno-L-cystine and Seleno-DL-methionine. In the final part of the study, it was shown by column-type equilibration studies that alginate beads modified/immobilized with CeO2 or ZrO2through three different synthesis routes can be used for the sorption and speciation of inorganic selenium.
  • Master Thesis
    Use of Amine-And Mercapto-Modified Silica as Soild Phase Extraction Sorbent for Speciation of Inorganic Selenium Prior To Determination by Atomic Spectrometric Techniques
    (İzmir Institute of Technology, 2010) Dönertaş, Esen; Eroğlu, Ahmet Emin; Eroğlu, Ahmet Emin; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Silica-based sorbents containing amino-, mercapto-, and both functional groups (bifunctional) were prepared and used for the sorption of inorganic Se(IV) and Se(VI) species from waters prior to their determination by atomic spectrometric techniques, namely, inductively coupled plasma mass spectrometry (ICP-MS) and hydride generation atomic absorption spectrometry (HGAAS). The presence of the functional groups on the surface of the silica was demonstrated by using several characterization techniques such as scanning electron microscopy (SEM), solid-state NMR spectroscopy, thermo gravimetric analysis (TGA), elemental analysis and Brunauer-Emmett-Teller (BET) surface area analysis. Amine-modified silica was found to be selective towards Se(VI) at pHs 2.0 and 3.0 whereas mercapto-modified silica retains Se(IV) over a wide range from acidic regions to pH 4.0. Bifunctional silica, on the other hand, possesses the good features of the two sorbents; it can be used in the separate sorption of Se(IV) or of both Se(IV) and Se(VI) species. Acidic pHs (<1.0) are convenient for the sorption of Se(IV) alone where no sorption is observed for Se(VI). Alternatively, pH can be adjusted to 2.0 or 3.0 and Se(IV) and Se(VI) can be retained simultaneously. Desorption of selenium species from the sorbents was realized with two different eluents; 0.2% (m/v) KIO3 in 1 M HCl was used for Se(IV) and 2.0 M HCl for Se(VI). The efficiency of the proposed sorbents was demonstrated through spike recovery tests carried out with bottled drinking and tap water samples and the percentage recoveries were found to change between 82.2 ± 7.1 and 109.4 ± 3.6 for Se(IV). For Se(VI), mechanically mixed amino- and mercapto-modified (MIX) silicas in (1:1) ratio has shown the best performance with percentage recoveries of 87.1 ± 3.6 and 74.5 ± 6.6 for the spiked bottled drinking and tap water samples, respectively.