Chemistry / Kimya

Permanent URI for this collectionhttps://hdl.handle.net/11147/4072

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1996 - 199942000 - 200919

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Author: search.filters.author.Eroğlu, Ahmet EminEnd date: 2009

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Now showing 1 - 10 of 23
  • Research Project
    Bazı toksik metal iyonlarının kalsit ve aragonit mineralleri ile etkileşimi sonucu oluşan karbonatların oluşum kinetikleri ve morfolojik karakteristiklerinin spektroskopik ve mikroskobik tekniklerle incelenmesi
    (TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2006) Shahwan, Talal; Eroğlu, Ahmet Emin; Tunusoğlu, Gözde; Altay, Özge; Yılmaz, Sinan
    [No Abstract Available]
  • Article
    Citation - WoS: 8
    Hydrogen Sulfide Determination by Solid Surface Luminescence
    (Springer Verlag, 1996) Eroğlu, Ahmet Emin; Volkan, Mürvet; Bayramlı, Erdal; Ataman, O. Yavuz; Mark, Harry B.
    In the analytical system suggested, atmospheric hydrogen sulfide reacts with the surface of a filter paper treated with aqueous cadmium chloride and yields a luminescent species whose intensity can be correlated with the analyte concentration in ambient air. It was shown that the luminescent species are CdS solid particles which were formed in a well defined size. The paper luminescence was also tried on polymeric surfaces; polyethyleneoxide, polyvinyl alcohol, ethylcellulose and carboxymethylcellulose were found to give a similar luminescence signal. The system can be used on the tip of an optical fiber for an irreversible, cumulative type of analytical device for hydrogen sulfide determination. The 3s detection limit for the paper luminescence detection system was 7.8 ppb H2S.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    Evaluation of Dissolution Methods in the Presence of High Chloride Content for the Determination of Germanium in Geological Matrices by Hydride Generation Atomic Absorption Spectrometry
    (Japan Society for Analytical Chemistry, 2001) Abbasi, Husam U.; Eroğlu, Ahmet Emin; Anwari, Mohammad A.; Volkan, Mürvet
    The sample dissolution is probably the most crucial step in the determination of germanium in geological and metallurgical samples due to formation of volatile germanium compounds during the course of dissolution. It has been stated that this is especially true for the samples having high sulfide and/or chloride content.
  • Article
    Citation - WoS: 82
    Citation - Scopus: 92
    Metal Ion Release From Nitrogen Ion Implanted Cocrmo Orthopedic Implant Material
    (Elsevier Ltd., 2006) Öztürk, Orhan; Türkan, Uğur; Eroğlu, Ahmet Emin
    CoCrMo alloys are used as orthopedic implant materials because of their excellent mechanical and corrosion properties. However, when placed in vivo, these alloys release Co, Cr, Mo ions to host tissues, which may give rise to significant health concerns over time. Nitrogen ion implantation can be used to form protective layers on the surface of CoCrMo orthopedic alloys by modifying the near surface layers of these materials. In this study, medical grade CoCrMo alloy (IS0 5832-12) was ion implanted with 60 keV nitrogen ions to a high dose of 1.9 × 10 18 ions/cm 2 at substrate temperatures of 100, 200 and 400 °C. The N implanted layer microstructures, implanted layer phases, and thicknesses were studied by a combination of Bragg-Brentano (θ/2θ) and grazing incidence (Seeman-Bohlin) X-ray diffraction (XRD and GIXRD) and cross-sectional scanning electron microscopy (SEM). Atomic force microscopy (AFM) was used for roughness analysis of N implanted as well as as-polished surfaces. Static immersion tests were performed to investigate metal ion release into simulated body fluid (SBF) by electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). XRD and SEM analyses indicated that the N implanted layers were ∼ 150-450 nm thick and composed of the (Co,Cr,Mo) 2+xN nitride phase and a high N concentration Co-based FCC phase, γ N depending on the substrate temperature. ETAAS analysis results showed that in vitro exposure of the N implanted surfaces resulted in higher levels of cobalt ion release into the simulated body fluid compared to the untreated, polished alloy. The higher Co release from the N implanted specimens is attributed to the nature of the implanted layer phases as well as to the rougher surfaces associated with the N implanted specimens compared to the relatively smooth surface of the untreated material. SEM analysis of N implanted and untreated specimens after immersion tests clearly indicated calcium phosphate formation on the as-polished CoCrMo alloy, indicating a degree of bioactivity of the untreated metal surface which is absent in the N implanted specimens.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 21
    Retention of Aqueous Ba2+ Ions by Calcite and Aragonite Over a Wide Range of Concentrations: Characterization of the Uptake Capacity, and Kinetics of Sorption and Precipitate Formation
    (The Geochemical Society of Japan, 2007) Tunusoğlu, Özge; Shahwan, Talal; Eroğlu, Ahmet Emin
    The uptake of aqueous Ba2+, ions by abiogenic calcite and aragonite was studied over a wide range of concentration; 1.0 × 101, 5.0 × 101, 1.0 × 102 5.0 × 102, 1.0 × 103, 5.0 × 104, and 1.0 × 104 mg/L. The uptake process was characterized using ICP-AES, XRPD, SEM/EDS, and FTIR techniques. Up to the initial concentration of 5.0 × 102 mg/L, the uptake of Ba2+ ions was fast and obeyed Lagergren's kinetic model. The equilibrium data were adequately described using Freundlich isotherm model. The overgrowth of BaCO3 (witherite) took place at higher concentrations, in a kinetically slow process and enhanced the uptake of Ba2+ ions. Quantitative XRPD was used to evaluate the fractions of precipitated BaCO3 on calcite and aragonite minerals and monitor their variation with time. At all the studied concentrations, aragonite showed higher removal capacity of Ba2+ and faster uptake kinetics than did calcite. The precipitated crystals appeared to predominantly possess olivary-like morphology with an average particle size of 1-2 μm. EDS was used to reveal the elemental quantities of Ba and Ca after BaCO3 formation on calcite and aragonite surfaces. FTIR spectroscopy was employed to analyze the vibrational modes in carbonate mixtures upon incorporation of Ba2+ by sorption and precipitation mechanisms.
  • Article
    Citation - WoS: 19
    Citation - Scopus: 21
    Kinetic and Thermodynamic Investigations of Strontium Ions Retention by Natural Kaolinite and Clinoptilolite Minerals
    (Walter De Gruyter Gmbh, 2005) Akar, Dilek; Shahwan, Talal; Eroğlu, Ahmet Emin
    The current study was devoted to the determination of various thermodynamic and kinetic parameters resulting from the fixation of Sr2+ by natural samples of kaolinite and clinoptilolite minerals. The sorption process followed pseudo second order kinetics, with faster sorption on kaolinite compared to clinoptilolite, where the uptake is affected by intraparticle diffusion. Freundlich and Dubinin-Radushkevich isotherm models described the data more adequately than Langmuir model, and clinoptilolite showed a higher strontium sorption capacity than kaolinite. Thermodynamically, the activation energy of Sr2+ sorption by kaolinite and clinoptilolite were respectively, -8.5 and -18.4 kJ/mol. The sorption process on both minerals was spontaneous and endothermic at all the studied concentrations, with ΔH° being 11.3 and 9.8 kJ/mol, for sorption on kaolinite and clinoptilolite, respectively. The findings of this study were compared with those of an earlier study on the uptake of Cs+ by the same minerals.
  • Article
    Citation - WoS: 28
    Citation - Scopus: 28
    Speciation and Preconcentration of Inorganic Antimony in Waters by Duolite Gt-73 Microcolumn and Determination by Segmented Flow Injection-Hydride Generation Atomic Absorption Spectrometry (sfi-Hgaas)
    (Elsevier Ltd., 2005) Erdem, Aslı; Eroğlu, Ahmet Emin
    A selective matrix removal/separation/enrichment method, utilizing a microcolumn of a chelating resin with SH functional groups (Duolite GT-73), was proposed for the determination of Sb(III) in waters by segmented flow injection-hydride generation atomic absorption spectrometry (SFI-HGAAS). The resin was selective to Sb(III) at almost all pH and acidity values employed, whereas Sb(V) was not retained at all and could be determined after a pre-reduction step with l-cysteine. Spike recoveries were tested at various concentration levels in different water types and were found to vary between 85 and 118%. Accuracy of the proposed methodology was checked by analyzing a standard reference material and a good correlation was found between the determined (13.3 ± 1.1 μg l-1) and the certified value (13.79 ± 0.42 μg l-1). The method was applied to several bottled drinking water samples for antimony determination with and without preconcentration and none of the samples were found to contain antimony above the permissible level (5 μg l-1). The characteristic concentration (the concentration of the analyte corresponding to an absorbance of 0.0044) was 0.55 μg l-1 and the 3 s limit of detection (LOD) based on five times preconcentration was 0.06 μg l-1. The applicability of the microcolumn separation/preconcentration/matrix removal method for flow injection systems was also demonstrated.
  • Article
    Citation - WoS: 47
    Determination of Technetium in Sea-Water Using Ion Exchange and Inductively Coupled Plasma Mass Spectrometry With Ultrasonic Nebulisation
    (Royal Society of Chemistry, 1998) Eroğlu, Ahmet Emin; McLeod, Cameron W.; Leonard, Kinson S.; McCubbin, David
    An enrichment–separation scheme employing a strong-base type anion-exchange resin was developed for the determination of99Tc in sea-water by inductively coupled plasma mass spectrometry utilising ultrasonic nebulisation with membrane desolvation. Samples were processed through an anion-exchange column to enrich Tc and to eliminate sea-water matrix ions. The limit of detection for 99Tc in sea-water based on processing a 14 ml sample was 0.03 ng l–1. Accuracy was verified with spike recovery experiments. The potential for rapid on-line sample processing via a microcolumn–flow injection system was demonstrated.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 17
    Separation of Trace Antimony and Arsenic Prior To Hydride Generation Atomic Absorption Spectrometric Determination
    (Elsevier Ltd., 2005) Ural, Müşerref Yersel; Erdem, Aslı; Eroğlu, Ahmet Emin; Shahwan, Talal
    A separation method utilizing a synthetic zeolite (mordenite) was developed in order to eliminate the gas phase interference of Sb(III) on As(III) during quartz furnace hydride generation atomic absorption spectrometric (HGAAS) determination. The efficiency of the proposed separation method in the reduction of suppression effects of transition metal ions on As(III) signal was also investigated. Among the volatile hydride-forming elements and their different oxidation states tested (Sb(III), Sb(V), Se(IV), Se(VI), Te(IV), and Te(VI)), only Sb(III) was found to have a signal depression effect even at low (μg l−1) concentrations under the experimental conditions employed. It has been shown that mordenite adsorbs Sb(III) quantitatively, even at a concentration of 1000 μg l−1, at pHs greater than two, and also, it reduces the initial concentrations of the transition metal ions to lower levels which can be tolerated in many studies. The adsorption of Sb(III) on mordenite follows the Freundlich isotherm and is endothermic in nature.
  • Article
    Citation - WoS: 119
    Citation - Scopus: 151
    Batch Removal of Aqueous Cu2+ Ions Using Nanoparticles of Zero-Valent Iron: a Study of the Capacity and Mechanism of Uptake
    (American Chemical Society, 2008) Karabelli, Duygu; Üzüm, Çağrı; Shahwan, Talal; Eroğlu, Ahmet Emin; Scott, Tom B.; Hallam, Keith R.; Lieberwirth, Ingo
    In this study, nZVI prepared by borohydride reduction was applied for the removal of Cu2+ ions under a variety of experimental conditions. The uptake experiments investigated the effects of initial concentration, contact time, pH, and repetitive loading on the extent of retardation of Cu2+ ions. Within the applied conditions, the sorbent demonstrated fast uptake kinetics and outstanding fixation abilities up to an initial Cu2+ concentration of 200.0 mg/L. Partitioning of Cu2+ ions between liquid and solid phases demonstrated an isotherm of L-type. Within the studied conditions, the capacity of uptake was found to be 250 mg of Cu2+ per g of nZVI. According to X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results, Cu2+ ions were sorbed primarily via a redox mechanism that resulted in the formation of Cu2O and Cu0. The contact of iron nanoparticles with aqueous media caused extensive formation of iron oxide. However, the material did not completely lose its removal capacity and was repeatedly applied at low concentrations for further uptake trials.