Browsing by Author "Erten, H. N."

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Open Access
Characterization of Sr2+ uptake on natural minerals of kaolinite and magnesite using XRPD, SEM/EDS, XPS, and DRIFT
(De Gruyter Oldenbourg, 2005) Shahwan, T.; Erten, H. N.
The sorption behavior of Sr2+ ions on natural minerals rich in kaolinite and magnesite was studied using SEM/EDS, XPS, XRPD, AAS/AES and DRIFT techniques. Quantitative analysis of the XPS data shows that magnesite is more effective in Sr2+ uptake than kaolinite. DRIFT spectra and XRPD patterns indicate that the structures of both minerals were not affected upon Sr2+ sorption. Intercalation of DMSO in kaolinite lamellae aiming at increasing the interlayer space did not significantly enhance the sorption capacity of the clay towards Sr2+ probably due to the lack of a negative charge on the accessible sites. EDS mapping indicated that while the sorbed Sr is equally distributed on surface of natural kaolinite, it was associated - to a larger extent - with the regions richer in Mg in the case of natural magnesite. Comparing the uptake mechanisms of natural magnesite with that of pure MgCO3, it was seen that while natural magnesite sorbed Sr2+ mainly through an ion exchange type mechanism, the formation of SrCO3 coprecipitate was detected on the surface of the MgCO 3 at higher loadings. © by Oldenbourg Wissenschaftsverlag, München.
Open Access
A characterization study of some aspects of the adsorption of aqueous Co2+ ions on a natural bentonite clay
(Academic Press, 2006-06-13) Shahwan, T.; Erten, H. N.; Unugur, S.
The natural bentonite used in this study contained montmorillonite in addition to low cristobalite. The uptake of aqueous Co2+ ions was investigated as a function of time, concentration, and temperature. In addition, the change in the interlayer space of montmorillonite was analyzed using XRPD, and the distribution of fixed Co2+ ions on the heterogeneous clay surface was recorded using EDS mapping. The sorbed amount of Co2+ appeared to closely follow Freundlich isotherm, with the sorption process showing apparent endothermic behavior. The relevance of the apparent _Ho values is briefly discussed. Analysis of the Co-sorbed bentonite samples using SEM/EDS showed that the montmorillonite fraction in the mineral was more effective in Co2+ fixation than the cristobalite fraction. XRPD analysis demonstrated that the interlayer space of montmorillonite was slightly modified at the end of sorption.
Open Access
Dating of Black sea sediments from Romanian coast using natural 210Pb and fallout 137CS
(Akademiai Kiado Rt., 2004) Ayçık, G. A.; Çetaku, D.; Erten, H. N.; Salihoǧlu, İ.
The sediment samples collected near the shore from Romania were used for the determination of levels of natural 210Pb, 226Ra and fallout 137Cs radionuclides. The sediment samples were dried and ground to a fine powder. Airtight sealed samples were counted by gamma-spectrometer with 110 cm3 well-type HPGe detector for one week each. By using the isotopic analysis results, sediment accumulation rate was determined. A sedimentation rate of 0.20±0.01 cm·y-1 was determined using 210Pb method and 0.15±0.03 cm·y-1 using 137Cs isotope. Fallout peak from Chernobyl reactor accident, as well as the peaks due to nuclear tests, act as time markers.
Open Access
Dating the sea of Marmara sediments by a uniform mixing model
(Elsevier, 1996) Gökmen, A.; Yıldız, M.; Erten, H. N.; Salihoğlu, İ.
The sedimentation rates and ‘t”Pb fluxes on sediment surfaces were measured in the north, northwestern and southwestern parts of the Sea of Marmara. Each core had varying thickness of constant 2’0Pb activity regions followed by a decreasing part with sediment depth. The sedimentation rates of the samples collected from the Bosporus and the Dardanelles could not be analysed due to the homogenization of activity in the strong currents of these straits. A untform mixing model is proposed for the simultaneous analysis of sedimentation rates, “‘Pb fluxes and mixing depths from the experimental data. In this model, the parameters were obtained by minimizing the multi-dimensional parameter space using a grid search algorithm. The 2’0Pbfluxes were found to be about 0.048 Bqcm-’ year-t for all sampling sites. The mass sedimentation rates were 0.19 and 0.073gcm-2 year-’ at the shelves of the Bosporus and the Dardanelles and 0.055 and 0.064 g cm-’ year -’ in the northwestern and middle northern basins, respectively, of the Sea of Marmara.
Open Access
Determination of trace element levels in human scalp hair in occupationally exposed subjects by XRF
(Akademiai Kiado Rt., 2001) Dede, Y.; Erten, H. N.; Zararsiz, A.; Efe, N.
Trace element levels in hair of individuals living in urban areas were determined by energy dispersive XRF. Two groups of subjects were investigated, the first group was assumed to be from a healthy environment, the other one was exposed to a high level of contamination due to working conditions. The results were compared to data reported in the literature. The concentrations of Ca, Fe, Cu, Zn and Pb in the scalp hair were determined and the correlation between hair trace element levels and environmental effects was discussed. The results given by the second group show that environmental exposure effects hair trace element levels which are related to body trace element concentrations.
Open Access
Efficiency calibration and summation effects in gamma-ray spectrometry
(Kluwer Academic Publishers, 1988) Erten, H. N.; Aksoyoğlu, S.; Göktürk, H.
Precise, absolute γ-ray efficiences (∈γ) and total efficiences (∈T), have been measured at various distances from the detector, using a set of standards. The observed linear variation of ∈γ and ∈T as well as ∈γ/∈T with Eγ and {Mathematical expression} provides a simple means of interpolation and extrapolation. Experimental coincidence summation effects were determined for various nuclides and compared with calculated values. The results are found to be in good agreement with each other. © 1988 Akadémiai Kiadó.
Open Access
Fine structure of mass and charge distribution in low energy fission
(Akademiai Kiado Rt., 1992) Erten, H. N.; Aras, N. K.
Studies of finer details in mass and charge distribution fission leads to a better understanding of the fission process. Experimental determination of independent and cumulative yields using radiochemical techniques as well as mass spectrometers and fission product recoil separators form the basis of such studies. It has been established that closed shells as well as an even number of nucleons influence both mass and charge distributions. The magnitudes of these effects may be estimated from existing experimental yield data and various fission models. Using our measurements of several fission yields and those existing in the literature we have calculated even-odd proton and neutron effects for various low energy fissioning systems. Where enough data existed, direct calculations were made, whereas for other cases the Zp-model of WAHL has been used. It is found that the even-odd proton effect is well established and pronounced in thermal neutron fission of235U and233U. Lesser effects were found for reactor neutron induced fission of232Th, thermal neutron fission of239Pu and spontaneous fission of245Cm and249Cf. No effect seems to exist in the thermal neutron fission of241Pu and the spontaneous fission of252Cf. The even-odd neutron effect is found to be much lower than the corresponding proton effect in235U and233U fissions and is nonexistent in the rest of the fissioning systems.
Open Access
Influence of even nucleon numbers and closed shells on mass and charge distribution in low energy fission
(Kluwer Academic Publishers, 1994) Buyukmumcu, Z.; Erten, H. N.; Aras, N. K.
Extensive experimental and evaluated yield data are now available for the fragments in low energy nuclear fission. Using these data we re-examined the influence of even nuclear numbers and closed shells on the mass and charge distribution in low energy fission. We used WAHL's Zp model and Ap model. We also examined the effects of Z=50, N=82 and possibly N=88 shells. A new method was developed based on two Gaussian curves for the even and odd products. The EOZ and EON values calculated are based on these different methods and are seen to be consistent with each other in spite of the somewhat different definitions of the even-odd effect. The even-odd effect decreases with an increasing fissility parameter. The EON values are substantially lower than the corresponding EOZ values, probably due to the effect of washing out the neutron pairing effect by prompt neutron emission. The magnitude of the even-odd effect varies with different mass regions. The EOZ and EON values decrease as they go from asymmetric to symmetric regions in mass distributions. © 1994 Akadémiai Kiadó.
Open Access
Instrumental neutron activation analysis of blood serum
(Kluwer Academic Publishers, 1995) Tadjiki, S.; Erten, H. N.; Erten, J.
Instrumental neutron activation analysis has been used to determine 15 trace elements in twelve blood serum samples taken from healthy students at Bilkent University in Ankara. The method allowed the determination of Sc, Cr, Mn, Fe, Co, Zn, Se, Rb, Cs, Ce, Eu, Tb, Hf, Ta and Hg, which occur at the μg.ml-1 to ng.ml-1 levels. There are no values reported for Tb, Hf, Ce, Eu and Ta before. The other results are compared with the values reported in the literature. Most are in the range of the reported values except for Fe, Zn, Se and Cs. © 1995 Akadémiai Kiadó.
Open Access
Isomeric yields of130Sb, 132Sb, 134I, and 136I in the thermal neutron fission of235U
(Kluwer Academic Publishers, 1992) Erten, H. N.
Isomer yield ratios of130Sb,132Sb,134I and136I isomers formed in the thermal neutron fission of235U have been calculated from our previous experimental studies that led to the identification of these species. In those studies the iodine and antimony fractions formed in fission were rapidly separated and the decay of γ-rays belonging to each isomer pair were followed using Ge(Li) detectors and a multichannel analyzer. The isomer ratios were calculated from growth and decay considerations of these γ-rays. The results are compared with the recently published values obtained with an on-line isotope separator, those from LOHENGRIN, and those from model calculations. Angular momenta of fission fragments corresponding to the measured isomer yields have also been calculated.
Open Access
Migration behaviour of Barium and Strontium in Granite
(De Gruyter Oldenbourg, 1994-12-01) Hatipoğlu, S.; Göktürk, H.; Erten, H. N.
The sorption behaviour of Ba2+ and Sr2+ cations on granite have been studied under flowing and static conditions in column and batch experiments. 133Ba, 90Sr and 3H were used as radio tracers. The retardation factors, R1, and distribution ratios, Rd, of barium and strontium in column experiments were found to be smaller than those from batch experiments. In both techniques barium was sorbed more strongly on granite than strontium. Sorption energies were found to be in good agreement with literature val-ues.
Open Access
Migration behaviour of barium and strontium through colemanite
(De Gruyter Oldenbourg, 1996) Hatipoǧlu, S.; Göktürk, H.; Erten, H. N.
Column and batch experiments were performed to study the migration behaviour of Ba and Sr in colemanite matrix. 133Ba. 90Sr and 3H were used as tracers. The retardation factors and the distribution ratios of Ba and Sr in column experiments were found to be smaller than those obtained in batch experiments. Sorption Ra values of Ba were higher than those of Sr determined by both techniques. Sorption energies calculated from batch experiments are in good agreement with the literature values.
Open Access
Possible exit channel effect on isomer yield ratios
(Kluwer Academic Publishers, 1997) Kildir, M.; Morel, Z.; Büyükmumcu, Z.; Erten, H. N.
Isomer yield ratio measurements in fission are important in understanding the fission process. With the development of new instrumental techniques, a large number of yield data are now available. The experimental data on isomer yield ratios in the thermal neutron induced fission of235U are compared with those calculated from the simple statistical model by Madland and England. The method of calculation has been extended to the isotopes having more than one isomeric state. The results may be explained according to the multi-exit-channel model of fission. © 1997 Akadémiai Kiadó.
Open Access
Radiochemical studies of the sorption behavior of strontium and barium
(Kluwer Academic Publishers, 1995) Göktürk, H.; Eylem, C.; Hatipoĝlu, S.; Erten, H. N.
The sorption behavior of strontium and barium on kaolinite, bentonite and chlorite-illite mixed clay was studied by radioanalytical techniques using the batch method.90Sr (29.1 y) and133Ba (10.5 y) were used as radiotracers. Characterization of the solid matrices was done by FTIR and XRD spectrometries and specific surface area measurements. Synthetic groundwater was used as the aqueous phase. The variation of the distribution ratio Rd, as a function of metal ion loading was examined. The sorption isotherms were fitted to various isotherm models. The sorption energies were calculated to be in the range of 8-10 kJ/mol suggesting an ion exchange type of sorption mechanism. In detailed experiments, chlorite-illite mixed clay was first presaturated with K+, Sr2+, Ca2+ and Al3+ ions, respectively, prior to sorption studies with Ba2+ ions. The results of Ca2+ pretreated chlorite-illite were very similar to those of natural chlorite-illite, suggesting that the Ba2+ ion exchanges primarily with the Ca2+ ion on the clay minerals. © 1995 Akadémiai Kiadó.
Open Access
Radiochemical study of Co2+ sorption on chlorite and kaolinite
(Akademiai Kiado Rt., 1999) Shahwan, T.; Erten, H. N.
In this work, the sorption behavior of Co(II) ions on natural chlorite and kaolinite as a function of time, concentration and temperature was studied. 60Co radiotracer method and the batch technique were used. The kinetic results indicated that about one day of contact time was enough to achieve equilibrium. The sorption process was described by Freundlich type isotherms. Sorption of Co(II) ions on both clays was found to be endothermic with ΔH(o) (kJ/mol) and ΔS(o) (kJ/mol·K) being 33 and 0.14 for kaolinite and 17 and 0.102 for chlorite, respectively. The magnitudes of the corresponding ΔG(o) values suggest that sorption occur mainly via an ion exchange mechanism on both clays.
Open Access
Radiochronology of lake sediments
(Walter de Gruyter GmbH, 1997) Erten, H. N.
Sediment cores from Lakes Zurich, Constance, from the Sea of Marmara and from southern Turkey, northern Cyprus and eastern Spain were dated using natural 210Pb, fallout 137Cs and cosmic-ray produced 7Be radionuclides. Constant activity regions in the uppermost sections of sediments from Lake Zurich and the Sea of Marmara were attributed to post-depositional mobility of 210Pb in the former case and to bioturbation in the latter. A serious discrepancy exists between the 210Pb dating of Sea of Marmara sediments and those obtained by organic carbon based methods. The elements Zn, Cu, P and Pb were enriched in the upper sections of the sediment cores corresponding to the last 200 years. The increased metallurgical activities as a result of reforms in the Ottoman Army during the 18 th century could be the most likely cause.
Open Access
Radiochronology of sediments from the Mediterranean sea using natural 210Pb and fallout 137Cs
(Kluwer Academic Publishers, 1994) Tadjiki, S.; Erten, H. N.
The210Pb and137Cs profiles of sediment cores from two locations in southern Spain, three locations in southern Turkey and two locations in northern Cyprus were determined by direct γ-ray spectroscopy. Sedimentation rates were derived for all locations using the210Pb data. The rates range from 1.39±0.12 cm · y-1 (0.50±0.04 g · cm-2 · y-1) to 0.08±0.01 cm · y-1 (0.039±0.003 g · cm-2 · y-1). Except for one core, the137Cs profiles were also used to compute sedimentation rates. The results are in good agreement with those of210Pb values. The results of the Constant Initial Concenration and Constant Rate of Supply dating models are in good agreement with each other. The flux of unsupported210Pb varies between 0.11±0.03 to 0.74±0.01 pCi · cm-2. The average depositional flux was found to be considerably lower for cores from the Eastern Mediterranean. © 1994 Akadémiai Kiadó.
Open Access
Sedimentation rates in the central lake constance determined with210Pb and137Cs
(Birkhäuser-Verlag, 1987) von Gunten, H. R.; Sturm, M.; Erten, H. N.; Rössler, E.; Wegmüller, F.
Sediment cores from central Lake Constance were dated with210Pb and137Cs. A sedimentation rate of (0.11±0.02) g·cm-2·y-1 was determined with the210Pb method.137Cs measurements revealed sedimentation rates of (0.11±0.01) g·cm-2·y-1 and (0.08±0.01) g·cm-2·y-1 respectively for two different cores sampled at the same location. The lower Cs-dated value indicates incomplete core recovery and demonstrates the sensitivity of this simple dating method to small losses of material at the water/sediment interface. An unambiguous application of the137Cs method is, therefore, only possible if complete core recovery is ensured. Sedimentation rates based on particulate matter, collected in sediment traps at various water depths, agree with the results of the radioisotope methods. Estimates of 30-125 days residence times for suspended particulate matter were calculated from7Be measurements. © 1987 Birkhäuser Verlag.
Open Access
Sorption behavior of Co2+, Zn2+ and Ba2+ ions on alumina, kaolinite and magnesite
(Kluwer Academic Publishers, 1994) Erten, H. N.; Gokmenoglu, Z.
The sorption behavior of Ba2+, Co2+ and Zn2+ ions on alumina, kaolinite and magnesite have been investigated using the batch method.60Co,65Zn and133Ba were used as radiotracers. The mineral samples were separated into different particle size fractions using an Andreasen Pipette. The particle sizes used in the sorption experiments were all less than 38 μm. Synthetic groundwaters were used which had compositions similar to those from the regions where the minerals were recovered. The samples were shaken with a lateral shaker at 190 rpm, the phases were separated by centrifuging and adioactivity counted using a NaI(Tl) detector. Kinetic studies indicated that sorption onto the minerals took place in two stages with the slower process dominating. The highest sorption was observed on alumina. Both Freundlich and Dubinin-Radushkevich type isotherms were found to describe the sorption process well. The distribution ratio, Rd was found to be a function of the liquid volume to solid mass ratio. The Rd's for sorption on binary mixtures of minerals were experimentally determined and compared with those predicted from Rd values of each individual mineral. © 1994 Akadémiai Kiadó.
Open Access
The sorption behavior of CS + ion on clay minerals and zeolite in radioactive waste management: sorption kinetics and thermodynamics
(Springer, 2011) Yildiz, B.; Erten, H. N.; Kış, M.
In this work, Cs+ ion sorption on some clays and zeolite were investigated. 137Cs was used as a tracer. Activities were measured with a NaI crystal gamma counter. The particle size distribution was determined by a laser sizer. Surface area of the particles were determined by BET (Brunauer, Emmett and Teller method). Structure analysis was made by using X-ray diffraction. The chemical compositions of the solid samples were determined using a ICAP-OE spectrometer. Kinetic and thermodynamic parameters were determined. Due to very high uptake results; clay and zeolite can be proposed as a good sorbents in waste management considerations.