Browsing by Author "Turkozu, D. Alkim"

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Adsorption and Thermodynamic Behaviour of U(Vi) on the Tendurek Volcanic Tuff
(Springer, 2010) Yusan, Sabriye; Aslani, Mahmoud A. A.; Turkozu, D. Alkim; Aycan, Hasan A.; Aytas, Sule; Akyil, Sema
In this work, sorption of uranium ions on volcanic tuff collected from the deposits located at the Tendurek of Eastern Turkey was investigated in batch technique. The effect of different parameters such as pH of the medium, contact time, uranium concentration and temperature were investigated. The maximum removal of U(VI) was found to be 68% at pH 5.0, initial U(VI) concentration of 75 mg L(-1) and 30 degrees C. Thermodynamic parameters, such as enthalpy of adsorption Delta H degrees, free energy change Delta G degrees and entropy change Delta S degrees have been also calculated and interpreted. The suitability of the Langmuir, Freundlich and Dubinin-Radushkhevic adsorption models to the equilibrium data was investigated for uranium-volcanic tuff system. The results suggest that volcanic tuff can be used as efficient and cost effective adsorbents for uranium ion removal.
Biosorption of Uranium(Vi) by Bi-Functionalized Low Cost Biocomposite Adsorbent
(Elsevier, 2011) Aytas, Sule; Turkozu, D. Alkim; Gok, Cem
This paper presents biosorption properties of U(VI) by bi-functionalized biocomposite adsorbent consists of macro marine algae (Jania rubens) and yeast (Saccharomyces cerevisiae) immobilized on silica gel. Removal of U(VI) from aqueous solution by biosorption on biocomposite in a single component system with pH, initial concentration of U(VI), various contact time and temperature was investigated. Experimental equilibrium biosorption data was analyzed by five two-parameter equations, namely; Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin and Flory-liuggins isotherms. Among these isotherm models, the Temkin model fits better with the experimental data compared to others. Thermodynamic parameters, such as the enthalpy (Delta H degrees), entropy (Delta S degrees) and Gibbs free energy (Delta G degrees) were calculated from the slope and intercept of logK(d) vs. 1/T plot. Results suggested that the bi-functionalized low cost biocomposite adsorbent is a suitable biosorbent material to remove uranium ions from diluted aqueous solutions. On the other hand, immobilization of algae and yeast on silica gel was found to improve their interaction properties with uranium ions in biosorption process. (C) 2011 Elsevier B.V. All rights reserved.
Determination and Evaluation of Natural Radioactivity and Heavy Metal Levels in the Aquatic Environment of Trans-Boundary Rivers: Maritza, Tundja and Arda
(Springer, 2014) Aytas, Sule; Erenturk, Sema; Aslani, Mahmut A. A.; Yusan, Sabriye; Turkozu, D. Alkim; Gok, Cem; Oguz, K. Firat
The main problem in the trans-boundary river system is that heavy metal and radioactive pollution can cause long-term effects on ecosystems. Therefore the natural radioactivity and heavy metal levels in the Maritza, Tundja and Arda Rivers, common for Bulgaria and Turkey, were determined for 3 years period (2007-2010). Gross alpha, gross beta and total radium isotopes activities, uranium and heavy metal concentrations of the surface water of the rivers were investigated and also terrestrial gamma and gamma dose rate were measured. The results were compared with reported data from other countries of the world and the recommended international standards. The results gathered in this study may provide background data on the natural radioactive and heavy metal levels of these trans-boundary rivers.
Natural Radioactivity of Riverbank Sediments of the Maritza and Tundja Rivers in Turkey
(Taylor & Francis inc, 2012) Aytas, Sule; Yusan, Sabriye; Aslani, Mahmoud A. A.; Karali, Turgay; Turkozu, D. Alkim; Gok, Cem; Oguz, K. Firat
This article represents the first results of the natural radionuclides in the Maritza and Tundja river sediments, in the vicinity of Edirne city, Turkey. The aim of the article is to describe the natural radioactivity concentrations as a baseline for further studies and to obtain the distribution patterns of radioactivity in trans-boundary river sediments of the Maritza and Tundja, which are shared by Turkey, Bulgaria and Greece. Sediment samples were collected during the period of August 2007-April 2010. The riverbank sediment samples were analyzed firstly for their pH, organic matter content and soil texture. The gross alpha/beta and U-238, Th-232 and K-40 activity concentrations were then investigated in the collected sediment samples. The mean and standard error of mean values of gross alpha and gross beta activity concentrations were found as 91 +/- 11, 410 +/- 69 Bq/kg and 86 +/- 11, 583 +/- 109 Bq/kg for the Maritza and Tundja river sediments, respectively. Moreover, the mean and standard error of mean values of U-238, Th-232 and K-40 activity concentrations were determined as 219 +/- 68, 128 +/- 55, 298 +/- 13 and as 186 +/- 98, 121 +/- 68, 222 +/- 30 Bq/kg for the Maritza and Tundja River, respectively. Absorbed dose rates (D) and annual effective dose equivalents have been calculated for each sampling point. The average value of adsorbed dose rate and effective dose equivalent were found as 191 and 169 nGy/h; 2 and 2 mSv/y for the Maritza and the Tundja river sediments, respectively.
Spatial Distribution and Risk Assessment of Radioactivity and Heavy Metal Levels of Sediment, Surface Water and Fish Samples From Lake Van, Turkey
(Springer, 2014) Erenturk, Sema; Yusan, Sabriye; Turkozu, D. Alkim; Camtakan, Zeyneb; Olgen, M. Kirami; Aslani, Mahmut A. A.; Isik, M. Akif
In this study, radioactivity levels of 228 lake water samples, 63 upper and depth sediment samples and 12 fish samples from Lake Van were investigated from 2005 to 2008 and the distribution patterns of the radionuclides were presented. Analysis included gross alpha-beta and total radium isotopes activities and uranium concentrations of the water, and gross alpha and gross beta activities and relevant U-238, Th-232 and K-40 activity of the sediment and fish samples of the lake. Mean gross alpha, gross beta and radium isotopes activities of lake water were found 0.74 +/- A 0.46, 0.02 +/- A 0.01 and 0.06 +/- A 0.04 Bq/L, respectively. Mean gross alpha and beta activities in upper and depth sediments were found to be 41 +/- A 6 and 1,514 +/- A 74 Bq/kg; 77 +/- A 5 and 394 +/- A 24 Bq/kg at a 95 % confidence level, respectively. Mean activities of U-238, Th-232 and K-40 activity concentrations in upper and depth sediments were determined to be 225 +/- A 22, 70 +/- A 7 and 486 +/- A 39 Bq/kg; 174 +/- A 4, 63 +/- A 3 and 263 +/- A 25 Bq/kg, respectively. The mean gross alpha and beta, U-238, Th-232 and K-40 aktivities in fish samples were established as 47 +/- A 18, 470 +/- A 12, 0.57 +/- A 0.220, 0.022 +/- A 0.006, 319 +/- A 11 Bq/kg, respectively. The transfer factor from lake water to fish tissues, annual intake by humans consuming fish, and annual committed effective doses were estimated and evaluated.