Browsing by Author "Velikova N."

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    Silica-based organic-inorganic hybrid materials as potential adsorbents for Hg(II) ions
    (2013-12-17) Velikova N.; Vueva Y.; Ivanova Y.; Salvado I.; Fernandes M.; Vassileva P.; Georgieva R.; Detcheva A.
    In the present study four functionalized mesoporous silica materials denoted as BIS-1, BIS-2, BIS-3 and BIS-4 have been synthesized through a simple co-condensation of bis-[3-(trimethoxyosilyl)propyl] amine (BTPA) and tetraethyl orthosilicate (TEOS). The influence of the BTPA amount on the structural and adsorption properties of the resultant materials was investigated. The novel hybrid materials have been characterized by FT-IR, BET, 13C CP MAS NMR and elemental analysis. The adsorption properties of mesoporous organic-inorganic materials containing amine functional groups, regarding Hg(II) ions were studied by the batch method. Experiments were carried out in acidic media. The material BIS-3 exhibits highest adsorption capacity for mercury ions. Kinetics of Hg (II) adsorption on BIS-3 was investigated. Equilibrium experimental data for BIS-3 were fitted to linear Langmuir and Freundlich models. All studied hybrid materials could be successfully used for effective removal of mercury ions from acidic aqueous solutions.
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    Thioether functionalized hybrid materials
    (2013-12-17) Abdallah M.; Velikova N.; Ivanova Y.; Dimitriev Y.
    Thioether-functionalized materials were synthesized by co-condensations of bis[3-(triethoxysilyl)propyl]tetra sulfide (BTPTS) and tetraethoxylsilane (TEOS) in the presence of the nonionic surfactant triblock copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (EO20PO70EO20), Pluronic P123. The surfactant was used as a template for improving the porosity of the hybrid gels. In this work we synthesized samples with different amounts of BTPTS in acidic media. The final materials were soaked for 24 hours in ethanol and HCl for removing P123. In this work we investigate structure of the materials and the functional group amount incorporated in the silica frame work after extraction of the surfactant. For this purpose we used thermo gravimetric analysis (DTA/TG), Fourier-transform infrared spectroscopy (FT-IR), 29Si MAS NMR and element analysis. On the bais of these results it was confirmed that the materials were organic inorganic hybrid materials and they are thermally stable to 900°C, which was the result of the incorporation of a hydrophobic thioester group in the silicate frame work.