Browsing by Author "Erten, Hasan N."
Now showing 1 - 5 of 5
- Results Per Page
- Sort Options
Item Open Access Adsorption behavior of radionuclides, 137Cs and 140Ba, onto solid humic acid(Springer, 2011) Çelebi, O.; Erten, Hasan N.In this research, the adsorption behaviors of two important fission product radionuclides (137Cs and 133Ba) onto sodium form of insolubilized humic acid (INaA) were investigated as a function of time, cation concentration and temperature, utilizing radiotracer method. The resulting data was fitted well to the Freundlich and Dubinin-Radushkevich (D-R) isotherms. Thermodynamic constants such as; free energy (ΔGads), enthalpy (ΔHads), entropy (ΔSads) of adsorption were determined. Temperature change didn't effect sorption processes significantly. Best fitting kinetic models were found for a better understanding of adsorption mechanisms. It was found that Ba2+ was adsorbed five times more than Cs+ onto structurally modified humic acid and kinetic studies indicated that adsorption behaviors of both ions obey the pseudo second order rate law. The effect of pH changes on adsorption was also examined and optimum pH range was found in the range of pH 6-8. FTIR and solid state carbon nmr (13CNMR) spectroscopic techniques were used to understand the structural changes during insolubilization process. Quantitative determination of adsorption sites was carried out using potentiometric titration method and the resulting data was treated by using appropriate Gran functions.Item Open Access Photoelectron spectroscopy: a tool in sorption studies(TÜBİTAK, 1997) Süzer, Şefik; Erten, Hasan N.Photoelectron spectroscopy using AlK α (h ν =1486.3 eV) has been applied to study the sorption of Cs+ , Sr2+ , Ba2+ , Zn2+ and Co2+ on magnesite kaolinite, smectite and chlorite. From the observed intensities of photoelectron peaks it was determined that in magnesite the sorption affinity of the above ions follow the order: Ba2+ > Co2+ ≅Sr2+ ≅Zn2+ > Cs+ . The order for the sorption of Ba2+ and Cs+ are also determined as chlorite > magnesite > smectite > kaolinite and smectite > chlorite ≅ kaolinite > magnesite, respectively.Item Open Access Radiochronological methods as tools to study environmental pollution(Springer, 2011) Erten, Hasan N.The study of the environmental impact of natural and anthropogenic events forms the essence of environmental pollution considerations. The nature of the polluting species as well as their time distributions are of primary importance with respect to identifying the polluting sources. Sediments are the most frequently used materials in such studies. Sediments act as the ecological memories of the environments of their formation. Besides classical chronological methods, radiochronological methods developed recently gave a big impetus to environmental pollution studies. One of the key radioisotopic technique is to utilize 210Pb, a product of the 235U radioactive series to date the last 200 years of the sediments. A number of supporting indicators are also utilized. One of them being anthropogenic 137Cs which is used as a time-marker. Large amounts of 137Cs radioactivity was released to the environment during 1954-1963, in time of the most intense atmospheric nuclear arms testing and again in 1986 during the Chernobyl nuclear accident. These intense 137s activities form time-markers throughout sediment cores corresponding to their release years. During our studies extending over several years we have used radiochronological methods in dating several sediment cores from Zurich and Constance Lakes in Switzerland from east coast of Spain, Sea of Marmara, from the Black Sea region, Southern coast of Turkey and from North Cyprus. The distribution of several elemental concentrations of importance in pollution considerations along sediment cores were also determined. These studies allowes proposing time frames to pollution events and help inqueries in tracing possible sources of pollution.Item Open Access Sedimentlerde radyoizotopik yöntemlerle yaş tayini(Scientific and Technical Research Council of Turkey - TUBITAK, 2001) Erten, Hasan N.Sedimentlerde yaş tayini, sediment boyunca kimyasal element dağılımı ile birlikte ele alınınca doğal ve kültürel olayların çevresel etkilerinin belirlenmesinde çok önemli rol oynamaktadır. Doğal 238U radyoaktif serisinin bir ürünü olan 210Pb (t1/2= 22.3y) kullanılarak sedimentlerde son 200 yılı kapsayan bir süre içinde yaş tayini yapmak mümkün olmaktadır. Diğer yandan çevrede yapay olarak bulunan 137Cs (t1/2= 30.1y) izotopunun sediment boyunca dağılımı incelemelerinden 1954-1963 yıllarındaki yeryüzünde yapılan nükleer silah denemelerinin sonucunda ve 1986 yılındaki Çernobil kazasında çevreye yayılan 137Cs’nin dağılım profillerinden söz konusu tarihleri belirlemek mümkün olmaktadır. Bu yöntem 210Pb ile birlikte kullanıldığı zaman güvenilir sediment çökelme hızı tayinleri yapılabilmektedir. Diğer yandan bir kozmik ışın ürünü olan 7Be(t1/2=53.3g) izotopunun incelenmesi ise sediment örneklerinin kayıpsız elde edilişlerini belirlemektedir. Radyoizotopik yöntemler klasik yöntem olarak kullanılan katman sayma yöntemi ile karşılaştırılabilir. ˙Item Open Access Sorption of Cs+ and Ba2+ on magnesite(Cambridge University Press, 1998) Shahwan, Talal; Süzer, Şefik; Erten, Hasan N.Sorption behavior of Cs and Ba ions on magnesite was studied using the radiotracer method complemented by X-ray photoelectron spectroscopy. Cs and Ba were used as radiotracers. The sorption of Cs is seen to be temperature dependent, whereas Ba sorption is not much affected by temperature changes. It was found that Freundlich type isotherms provide an adequate description of the sorption process. The magnitude of the free energy of sorption are seen to be within the 8-16 kj/mol range. It can be remarked that the sorption of Cs and Ba on magnesite is a fast process suggesting an ion exchange type mechanism, mainly taking place at the surface of mineral particles.