Yunus Önal

Removal of lead ions by acid activated and manganese oxide-coated bentonite

This paper presents the adsorption of Pb(II) from aqua solutions onto Unye (Turkey) bentonite in raw (RB), acid activated (AAB) and manganese oxide-coated (MCB) forms. Adsorption of Pb(II) by RB, AAB and MCB sample was investigated as a function of the initial Pb(II) concentration, solution pH, ionic strength, temperature and inorganic ligand (Cl(-)). Changes in the surfaces and structure were characterized by means of XRD, IR and potentiometric titration. The Langmuir monolayer adsorption capacities of RB, AAB and MCB in 0.1M KNO(3) solution were estimated as 16.70, 8.92 and 58.88 mg/g, respectively. The spontaneity of the adsorption process is established by decrease in DeltaG which varied from -21.60 to -28.60 kJ/mol (RB), -22.63 to -29.98 kJ/mol (AAB) and -19.57 to -26.22 (MCB) in temperature range 303-338 K.

Effects of treatments on the mineral matter and acidic functional group contents of Turkish lignites

Six Turkish lignites were treated with solutions of HCl or EtONa at ambient temperature or at 150°C. The proximate analysis, forms of sulfur, acidic functional groups and calcium contents of the raw and treated lignites were determined. The solutions after treatment were analysed for calcium. The effects of the treatment on certain structural components of the lignites varied from one lignitie to another. HCl treatment was effective in ash reduction and in the transformation of carboxylate species to carboxylic acids, but not in desulfurization. The ash reduction was accompanied by an increase in combustible sulfur. EtONa treatment was effective in desulfurization but not in ash reduction or in the removal of chelate- or salt-forming cations. The results suggested that this treatment promoted selective cleavage of certain chemical bonds, such as ester, ether or carbon-sulfur bonds, resulting in an increase in acidic functional groups of the lignites, desulfurization and partial dissolution. FT-i.r. spectroscopy and X-ray diffractometry provided some additional evidence regarding the changes in lignite structure due to the treatments.

Demineralisation of lignites by single and successive pretreatment

In this study, two Turkish lignites (Bolu-Mengen, Kutahya-Tuncbilek) were treated under atmospheric and reflux conditions with 10–30% NaOH, 10% HCl and 10% H2SO4 solutions, singly and/or successive treatments to determine the effects of this treatment on the mineral matter and acidic functional groups. Characterisation of the treated and untreated samples was by Fourier transform infrared spectroscopy. The process of successive pretreatment was found to be more effective than single steps in terms of demineralisation and removal of carboxylate structures. During NaOH treatment, the first of successive steps, salts soluble in acid but not in water were determined. In successive demineralisation steps with 30% NaOH and 10% HCl, a low level of 3.3% ash was obtained for the Tuncbilek lignite. In addition, during the pretreatment, most of the Ca and K were exchanged with Na.

Preparation and characterization of a clay-polyvinylpyridinium matrix for the removal of bacterial cells from water

Polyvinylpyridinium 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 γ-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.

Error Anlaysis Studies of Dye Adsorption onto Activated Carbon from Aqueous Solutions

Adsorption of tartrazine and methylene blue from aqueous solution onto activated carbon has been investigated. Experimental datas obtained from dye adsorption have been studied by five two-parameter (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, and Frumkin), five three-parameter (Redlich-Peterson, Sips, Toth, Radke-Prausnitz, Koble-Corrigan) isotherm models. In this study, eight nonlinear error functions (sum squares errors, hybrid fractional error function, Marquardts percent standard deviation, average relative error, sum of absolute error, the coefficient of determination, nonlinear chi-square test, and standard deviation of relative errors) were examined for isotherm equations. In order to clarify the adsorption kinetics fit of pseudo-first order and pseudo-second order kinetic models were used. The best fitting isotherm model was the Radke-Prausnitz and kinetics model was pseudo-second order for two dyes. Adsorption experiment showed that the maximum capacity of activated carbons for methylene blue and tartrazine were 28.571 and 18.182 mg.g−1, respectively.

How safe is the use of herbal weight-loss products sold over the Internet?

Background: In recent years, the use of herbal weight-loss products sold over the Internet has rapidly increased; however, the safety of these products has not been well documented yet. More importantly, the declared ingredients in these products could be different than the marketed contents. Methods: Nine different herbal weight-loss products sold over the Internet were obtained. The ingredients of each product were analyzed in the Laboratory of Forensic Medicine and the Scientific and Technological Research Laboratory of Inonu University. Results: Although all studied weight-loss products were presented as pure herbal, three of them contain sibutramine, three contain caffeine, and three contain caffeine + temazepam. The amount of sibutramine in each capsule was found to be over 10 mg. We analyzed toxic and trace element levels of nine herbal products and found that these herbal products, even in low amounts, contain Pb, Al, Ni, and Ba. Conclusions: Our results indicate that herbal weight-loss products available without prescription and claimed to be purely herbal may contain pharmaceutical substances like sibutramine or temazepam in high doses. Moreover, they also may become contaminated with toxic metals. Since people commonly use these products unaware of its real constituents and without the suggestion or control of a physician, they might cause various health problems some of which might be harmful. Strict legal rules and control mechanisms must be established to minimize their possible harmful effects.

Synthesis and characterization of novel polyacrylate-clay sol-gel materials

Organo-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.

Environmental exposure to asbestos in eastern Turkey.

In this study, the authors investigated the prevalence of asbestos-related disorders among the inhabitants of Güzelyurt, a town in Malatya, located in eastern Turkey. The authors examined river bed, white soil, and stucco samples taken from various locales in Güzelyurt, 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 ≥ 50 yr of age, compared with younger subjects (p < 0.01). Asbestos-related disorders were prevalent in the inhabitants of Güzelyurt, the population of which is exposed environmentally to asbestos—primarily the result of the stuccoing and whitewashing of houses with soil that contains asbestos.

Low temperature extractability and solvent swelling of Turkish lignites

Abstract Six Turkish lignites have been pretreated with the solutions of HCl or sodium ethanolate at room temperature or at 150°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.

Synthesis, characterization and thermal properties ofbentonite-polyacrylate sol–gel materials

A new type of material incorporating bentonite with an alkoxide, H 2 CC(CH 3 )COO(CH 2 ) 3 Si(OCH 3 ) 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.