Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
Browse
Search Results
Article Citation - WoS: 19Citation - Scopus: 21Kinetic and Thermodynamic Investigations of Strontium Ions Retention by Natural Kaolinite and Clinoptilolite Minerals(Walter De Gruyter Gmbh, 2005) Akar, Dilek; Shahwan, Talal; Eroğlu, Ahmet EminThe 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: 36Citation - Scopus: 40The Kinetics of Citral Hydrogenation Over Pd Supported on Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Yılmaz, Selahattin; Uçar, Şule; Artok, Levent; Güleç, HilalThe liquid phase hydrogenation of citral has been investigated over Pd (2.42%) supported on clinoptilolite rich natural zeolite catalyst for different reaction conditions. The zeolite support did not affect the active metal properties. This was attributed to the large size of Pd particles on the support. High selectivity (90%) to citronellal was obtained at complete conversion of citral. The catalytic activity increased with reaction temperature (80, 100, 120°C) following an Arrhenius behaviour, while selectivity remained constant for a given conversion. Selectivity to citronellal increased from 78 to 90% with increase in the amount of catalyst in the reaction solution (Citral/Pd mole ratio 293, 176 and 105). The spent catalyst regained its fresh activity and selectivity upon regeneration.Article Citation - WoS: 50Citation - Scopus: 53Physicochemical Characterization of the Retardation of Aqueous Cs+ Ions by Natural Kaolinite and Clinoptilolite Minerals(Elsevier Ltd., 2005) Shahwan, Talal; Akar, Dilek; Eroğlu, Ahmet EminThe aim of this study was to carry out kinetic, thermodynamic, and surface characterization of the sorption of Cs+ ions on natural minerals of kaolinite and clinoptilolite. The results showed that sorption followed pseudo-second-order kinetics. The activation energies were 9.5 and 13.9 kJ/mol for Cs+ sorption on kaolinite and clinoptilolite, respectively. Experiments performed at four different initial concentrations of the ion revealed that the percentage sorption of Cs+ on clinoptilolite ranged from 90 to 95, compared to 28 to 40 for the kaolinite case. At the end of a 1 week period, the percentage of Cs+ desorption from clinoptilolite did not exceed 7%, while it amounted to more than 30% in kaolinite, indicating more stable fixation by clinoptilolite. The sorption data were best described using Freundlich and D–R isotherm models. Sorption showed spontaneous and exothermic behavior on both minerals, with ΔH0 being −6.3 and −11.4 kJ/mol for Cs+ uptake by kaolinite and clinoptilolite, respectively. Expanding the kaolinite interlayer space from 0.71 to 1.12 nm using DMSO intercalation, did not yield a significant enhancement in the sorption capacity of kaolinite, indicating that the surface and edge sites of the clay are more energetically favored. EDS mapping and elemental analysis of the surface of kaolinite and clinoptilolite revealed more intense signals on the surface of the latter with an even distribution of sorbed Cs+ onto the surfaces of both minerals.Article Citation - WoS: 62Citation - Scopus: 60Preconcentration and Atomic Spectrometric Determination of Rare Earth Elements (rees) in Natural Water Samples by Inductively Coupled Plasma Atomic Emission Spectrometry(Elsevier Ltd., 2005) Pasinli, Türker; Eroğlu, Ahmet Emin; Shahwan, TalalThe usage of a variety of sorbents has been shown as promising matrix removal/preconcentration strategies for the determination of rare earth elements (REEs) in various natural water samples by inductively coupled plasma atomic emission spectrometry (ICP-AES). The sorption efficiency of various zeolites (clinoptilolite, mordenite, zeolite Y, zeolite Beta), ion-exchangers (Amberlite CG-120, Amberlite IR-120, Rexyn 101, Dowex 50W X18) and chelating resins (Muromac, Chelex 100, Amberlite IRC-718) towards REEs was investigated in terms of solution pH, shaking time and sorbent amount. The results have shown that most of the materials can take up REEs at a wide pH range. The experiments were continued with clinoptilolite, zeolite Y and Chelex 100 and it was demonstrated that all three materials displayed very fast kinetics for REE sorption (higher than 96% in 1 min). Desorption from the sorbents was realized with 2.0 M HNO3 for clinoptilolite and 0.1 M HNO3 for zeolite Y and Chelex 100. Only the lower concentration range (0.01–2.0 mg l−1) of matrix-matched standards were used in quantitation although the calibration graphs were linear at least up to 10.0 mg l−1 for all REEs studied. The limit of detection (3 s) without preconcentration was 0.1, 1.0, and 0.2 μg l−1 for Eu, La, and Yb, respectively. The validity of the method with the selected sorbents was checked through spike recovery experiments.Article Citation - WoS: 43Citation - Scopus: 47Aas, Xrpd, Sem/Eds, and Ftir Characterization of Zn2+ Retention by Calcite, Calcite–kaolinite, and Calcite–clinoptilolite Minerals(Elsevier Ltd., 2005) Shahwan, Talal; Zünbül, Banu; Tunusoğlu, Özge; Eroğlu, Ahmet EminIn this study, the sorption behavior of Zn2+ on calcite, kaolinite, and clinoptilolite, in addition to mixtures of calcite with kaolinite and clinoptilolite, was investigated at various loadings and mixture compositions using atomic absorption spectroscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray powder diffraction, and Fourier transform infrared techniques. According to the obtained results, within the experimental operating conditions, the sorption capacity was enhanced with increasing amount of calcite in both types of mixtures. Under neutral–alkaline pH conditions and high loadings, the order of Zn2+ retention was observed as calcite > clinoptilolite > kaolinite. The experiments on the retention of Zn2+ by pure calcite under conditions of oversaturation showed that the uptake process proceeds via an initial adsorption mechanism (possibly ion-exchange type) followed by a slower mechanism that leads to the overgrowth of the hydrozincite phase, Zn5(OH)6(CO3)2.Article Citation - WoS: 17Citation - Scopus: 18Effect of Magnesium Carbonate on the Uptake of Aqueous Zinc and Lead Ions by Natural Kaolinite and Clinoptilolite(Elsevier Ltd., 2005) Shahwan, Talal; Zünbül, Banu; Eroğlu, Ahmet Emin; Yılmaz, SinanAdsorption behavior of Zn2+ and Pb2+ ions on kaolinite and clinoptilolite, originating from natural resources, was studied as a function of contact time and concentration. Zn2+ and Pb2+ ions are quickly adsorbed on both minerals and the uptake of the latter is more favored. The uptake of both ions was then examined on kaolinite–MgCO3 and clinoptilolite–MgCO3 mixtures over a metal ions range from 1 to 10 000 mg/L. The sorption behavior of Zn2+ and Pb2+ on pure MgCO3 was also studied. MgCO3 is much more effective in the retention of Zn2+ and Pb2+ ions, in particular at higher concentrations. The large increase in the retarded amounts of both ions was associated with formation of the hydroxy-carbonate phases; namely hydrozincite for Zn2+, and cerussite and hydrocerussite in the case of Pb2+.