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Öğe Environmental exposure to asbestos in eastern Turkey(Heldref Publications, 2003) Hasanoglu, HC; Gokirmak, M; Baysal, T; Yildirim, Z; Koksal, N; Onal, YIn this study, the authors investigated the prevalence of asbestos-related disorders among the inhabitants of Guzelyurt, a town in Malatya, located in eastern Turkey. The authors examined river bed, white soil, and stucco samples taken from various locales in Guzelyurt, and they confirmed the presence of tremolite and chrysotile asbestos fibers. Subjects (N = 920; 449 males and 471 females) were examined by photofluoroscopy. Eighty-five patients (9.2%) had asbestos-related radiological findings; risk increased with age. Calcified pleural plaques were seen more frequently in individuals greater than or equal to 50 yr of age, compared with younger subjects (p < 0.01). Asbestos-related disorders were prevalent in the inhabitants of Guzelyurt, the population of which is exposed environmentally to asbestos-primarily the result of the stuccoing and whitewashing of houses with soil that contains asbestos.Öğe Low temperature extractability and solvent swelling of Turkish lignites(Elsevier Science Bv, 1997) Onal, Y; Ceylan, KSix Turkish lignites have been pretreated with the solutions of HCl or sodium ethanolate at room temperature or at 150 degrees C. The volumetric swelling of the raw or pretreated lignites have been investigated by using 13 solvents at room temperature. These lignites have been subjected to Soxhlet extractions in the same solvents and in the linear alkylamines. The solubility of the samples in toluene under supercritical conditions were also tested. The effect of solvent on swelling ratio and on the extraction yields of the raw or pretreated lignites have been examined. The results have indicated that both swelling and extraction yields generally increased after the pretreatments and the increments are higher with hydrogen bonding solvents. Especially, sodium ethanolate pretreatment increases the solubility in toluene under supercritical conditions, The results suggest that solvent solubility parameter and electron donor number are effective in both swelling and solubility. A qualitative information regarding the structural characteristics of extracts was obtained by UV and NMR analysis. (C) 1997 Elsevier Science B.V.Öğe Preparation and characterization of a clay-polyvinylpyridinium matrix for the removal of bacterial cells from water(Chapman Hall Ltd, 1997) Seckin, T; Onal, Y; Yesilada, O; Gultek, APolyvinylpyridinium salts were immobilized onto a clay matrix and were then tested for their antibacterial properties. The clay-polyvinylpyridinium matrix was prepared by the copolymerization of gamma-methacryloxypropyltriethoxy silane bonded covalently to clay and 4-vinylpyridine and subsequent quaternization with benzyl halides. Suspension tests for antibacterial properties of the immobilized bactericide against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa demonstrated the high activity of the pyridinium salts that are bonded to the polyacrylate spacer. Advantageously, these insoluble clay-polymer bactericides could be applied without any contamination by the substrate.Öğe Preparation and phenol captivating properties of polyvinylpyrrolidone-montmorillonite hybrid materials(Wiley, 2001) Gultek, A; Seckin, T; Onal, Y; Icduygu, MGMontmorillonite minerals were modified in two distinct steps in order to remove hydroxlated toxicants from the aqueous environment. At first, the montmorillonite minerals were acrylated with the silylating agent gamma -methcaryloxypropyl trimethoxysilane to give a product denoted as TAY-10. In the second step these materials readily reacted with vinylpyrrolidone to form copolymers covalently bonded to the clay. All hybrid materials were characterized by FTIR spectroscopy, thermogravimetry, X-ray diffractometry, SEM, and differential thermal analysis. The original montmorillonite structure was maintained for the copolymer modified surfaces. Different loadings of polyvinylpyrrolidone (PVP) were examined to arrive at the optimal conditions for the removal of toxicants from the aqueous environment. The presence of the PVP enhanced the adsorption capacity of the clay toward phenolic compounds from solution as evidenced by the retention percent that was as high as 98.9%. These results demonstrated the feasibility of utilizing a PVP modified clay as a thermally recyclable adsorbent for environmental pollutants. (C) 2001 John Wiley & Sons, Inc.Öğe Synthesis and characterization of asbestos-silane hybrid materials(Elsevier, 2005) Onal, Y; Yakinci, ME; Seçkin, T; Içduygu, MGIn this study, interaction of the silane coupling agent 3-(trimethoxysilyl)propylmethacrylate (A-174) and asbestos was investigated. A-174 grafted onto the surface of the asbestos was polymerized by radical initiator. FT-IR, thermogravimetric analysis (TGA), X-ray diffractometer (XRD), differential thermal analyzer (DTA) and scanning electron microscopy (SEM) were used to characterize modified particles. The effects of temperature on modified particles and were evaluated by differential thermal analysis. After modification with A-174, the effects of grafting on asbestos were discussed in terms of structural change and thermal stability. These results lead us to conclude that the silane coupling agent in asbestos serve as polymeric precursor to form polymer onto asbestos matrix resulting the hybrid materials in which the harmful effect of asbestos was prevented by covering the asbestos particles with polymer. (c) 2004 Elsevier B.V. All rights reserved.Öğe Synthesis and characterization of novel polyacrylate-clay sol-gel materials(Chapman Hall Ltd, 1996) Seckin, T; Onal, Y; Aksoy, I; Yakinci, MEOrgano-functional silanes which were able to form chemical bonds with kaolinite and could also have an affinity to the materials of concern here, were studied by the sol-gel process. Polymethacrylate with trialkoxy silyl functional groups were prepared, hydrolysed and co-condensed with kaolinite. The progress of the hydrolysis, which proceeded very slowly, was followed by Karl-Fischer titration. Thermal behavior was investigated by differential thermal analysis. The extent of the reaction leading to network formation was qualitatively followed by Fourier transform-infrared spectroscopy and X-ray diffraction. Free-radical polymerization was carried out ultrasonically in the presence of a catalyst. Trimethoxy silane end-capped silane was found to be covalently bonded to kaolinite. The copolymers, with various amounts of kaolinite, were then hydrolysed and co-condensed in the presence of a catalyst to yield sol-gel materials which have a controllable combination of properties of both the polymer and kaolinite.Öğe Synthesis, characterization and thermal properties of bentonite-polyacrylate sol-gel materials(Royal Soc Chemistry, 1997) Seckin, T; Gultek, A; Onal, Y; Yakinci, ME; Aksoy, IA new type of material incorporating bentonite with an alkoxide, H2C=C(CH3)COO(CH2)(3)Si(OCH3)(3), has been prepared successfully using a sol-gel process. The structures and structural changes upon heating, of the bentonite and the sol-gel material. were investigated by FTIR, XRD and DSC. Using the metal alkoxide and the corresponding clay mineral as precursors, the additive reaction followed by free radical polymerization resulted in a novel material in which polymer was attached covalently to, silicate sheets of bentonite via hydroxy bonding.
