Browsing by Author "Hicsonmez, U"

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Removal of 209Po from aquatic environment and its equilibrium and thermodynamic parameters
    Hicsonmez, U; Erenturk, SA; Gorgun, AU; Aslani, MAA
    In this study, removal of Po-209 from aqueous media using a natural zeolite as an adsorbent material was investigated. The adsorption experiments were performed by batch technique. The influence of specific process parameters such as initial concentration, pH of solution, contact time and temperature was studied to predict the optimum conditions for effective removing of Po-210. Initial and equilibrium activity concentration of Po-209 in solutions was counted by a ZnS(Ag) alpha scintillation counter. Adsorption yield of Po-209 onto the zeolite was determined as 90 +/- 2% at pH: <3 and 25 degrees C for 40 min of contact time. The applications of the isotherm models such as Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms were studied to evaluate adsorption characteristics of Po-209 onto natural zeolite. Results indicated that the Dubinin-Radushkevich and Freundlich models gave a better fit to the experimental data than Langmuir isotherm models. The thermodynamic parameters such as Gibbs free energy COG-1, enthalpy (Delta H degrees) and entropy (Delta S degrees) of adsorption process were calculated. The change in entropy (Delta S degrees) and enthalpy (Delta H degrees) were estimated to be -0.0003 J nmol(-1) K-1 and 0.1008 kJ nmol(-1), respectively.
  • No Thumbnail Available
    Item
    Leaching of Celestite in Sodium Hydroxide Solutions and Kinetic Modelling
    Kocan, F; Hicsonmez, U
    In this study, the dissolution kinetics of celestite in solutions of sodium hydroxide was investigated by batch process. The results showed that the parameters which had the greatest effect on the dissolution of celestite in sodium hydroxide solutions were reaction temperature, the concentration of sodium hydroxide and stirring speed. It was determined that the dissolution rate increased with increased stirring speed, sodium hydroxide concentration, reaction time and temperature and decreased with increasing particle size and solid-liquid ratio. The leaching process fitted the shrinking core model with diffusion through the product layer model as the rate-determining step. The activation energy of the dissolution of celestite was calculated as 62.24 kJ/mol. A semi-empirical kinetic model was obtained for dissolution of celestite in sodium hydroxide solution.
  • No Thumbnail Available
    Item
    Leaching kinetics of celestite in nitric acid solutions
    Kocan, F; Hicsonmez, U
    In this study, strontium nitrate extraction from celestite in nitric acid solutions was investigated using the leaching method. The influences of acid concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the leaching of strontium from celestite concentrate were studied. The results showed that the leaching rate increased with increasing acid concentration, stirring speed, and temperature and decreased with increasing solid-to-liquid ratio. The particle size was fixed in all of the dissolution experiments. The results showed that the stirring speed and the temperature were the most influential parameters with respect to the leaching process. The kinetic model best fit control by diffusion through the product layer. The activation energy of the dissolution celestite in nitric acid solutions was calculated to be 42.22 kJ/mol.
  • No Thumbnail Available
    Item
    Low-temperature synthesis of SrCrO4 nanorod particles from strontium sulfate
    Kocan, F; Hicsonmez, U
    Strontium chromate (SrCrO4) nanorod particles were successfully prepared at low temperature using the chemical precipitation method. In this synthesis process, sodium dichromate and celestite mineral, which is a water-insoluble mineral, were used as starting materials. The morphology and size of the particles obtained were determined by SEM-EDAX analysis. XRD analysis of the synthesized particles revealed an SrCrO4 phase and other phases. The effects of different molar ratios on SrCrO4 formation were investigated. The addition of NaCl has been found to play a significant role in the formation of strontium chromate nanorods, in particle size, particle shape and product composition. [GRAPHICS] .
  • No Thumbnail Available
    Item
    Use of zeolite in reducing environmental risk of polonium: kinetic models
    Hicsonmez, U; Erenturk, SA; Gorgun, AU; Aslani, MAA
    A study was conducted to understand the mechanism of adsorption kinetic that is effective in removal of Po-209 by clinoptilolite, a natural zeolite, from aquatic environments. Studies of the adsorption kinetics of Po-209 were carried out by interacting zeolite with Po-209 at different time intervals. Experimental polonium adsorption data obtained in our previous article were applied to some known kinetic models such as pseudo-first order, pseudo-second order, Elowich, Bangham, Homogeneous particle diffusion and Shell step models. The data obtained from the models revealed that the rate-limiting step is more compatible with the pseudo-second order model, which is based on the assumption that chemical sorption. According to the results obtained, the calculated the amount of Po-209 adsorbed at equilibrium (q(e)) and the equilibrium rate constant of pseudo-second-order sorption (k(2)) were found to be 0.3302 ng g(-1), - 4.4 x 10(-5) ng g(-1) min(-1), respectively.