Browsing by Author "Sahan, T."

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238u and 222rn Activity Concentrations and Total Radioactivity Levels in Lake Waters
(Springer, 2013) Zorer, O. Selcuk; Sahan, T.; Ceylan, H.; Dogru, M.; Sahin, S.
The concentrations and distributions of natural radioactivity, uranium and radon in lake waters from around Van, Turkey were investigated with an aim of evaluating the environmental radioactivity. Fourteen lake waters were collected from different six lakes around Van (Turkey) to determine U-238, Rn-222 and total alpha and total beta distributions in 2009. The total alpha and total beta activities were counted by using alpha/beta counter of the multi-detector low background system (PIC-MPC-9604) and the U-238 concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2) and radon concentrations were measured with the solid state nuclear track detector technique. The activity concentrations ranging from ND to 0.039 Bq L-1 and from 0.026 to 3.728 Bq L-1 for total alpha and beta, respectively, and uranium concentrations ranging from 0.083 to 3.078 mu g L-1, and radon concentrations varying between 47.80 and 354.86 Bq m(-3) were observed in the lake waters.
Removal of Cu(Ii), Zn(Ii) and Co(Ii) Ions From Aqueous Solutions by Adsorption Onto Natural Bentonite
(Springer, 2007) Kubilay, S.; Gurkan, R.; Savran, A.; Sahan, T.
In this study, the removal of Cu(II), Zn(II) and Co(II) ions from aqueous solutions using the adsorption process onto natural bentonite has been investigated as a function of initial metal concentration, pH and temperature. In order to find out the effect of temperature on adsorption, the experiments were conducted at 20, 50, 75 and 90 degrees C. For all the metal cations studied, the maximum adsorption was observed at 20 degrees C. The batch method has been employed using initial metal concentrations in solution ranging from 15 to 70 mL(-1) at pH 3.0, 5.0, 7.0 and 9.0. A flame atomic absorption spectrometer was used for measuring the heavy metal concentrations before and after adsorption. The percentage adsorption and distribution coefficients (K-d) were determined for the adsorption system as a function of adsorbate concentration. In the ion exchange evaluation part of the study, it is determined that in every concentration range, adsorption ratios of bentonitic clay-heavy metal cations match to Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich (DKR) adsorption isotherm data, adding to that every cation exchange capacity of metals has been calculated. It is shown that the bentonite is sensitive to pH changes, so that the amounts of heavy metal cations adsorbed increase as pH increase in adsorbent-adsorbate system. It is evident that the adsorption phenomena depend on the surface charge density of adsorbent and hydrated ion diameter depending upon the solution pH. According to the adsorption equilibrium studies, the selectivity order can be given as Zn2+ > Cu2+ > Co2+. These results show that bentonitic clay hold great potential to remove the relevant heavy metal cations from industrial wastewater. Also, from the results of the thermodynamic analysis, standard free energy Delta G(0), standard enthalpy Delta H-0 and standard entropy Delta S-0 of the absorption process were calculated.