Ümran Hiçsönmez

Adsorption of thorium from aqueous solutions by perlite.

The use of expanded perlite for the adsorption of thorium from aqueous solution by batch technique is presented. The effects of particle size, pH of the solution, initial thorium concentration, shaking time, V/m ratio and temperature were determined. It was found that the adsorption capacity increases by the increase in the pH of the suspensions. The rate of thorium adsorption on expanded perlite was observed to be fast in the first hour of the reaction time. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models and the adsorption experiments conducted at 30 +/- 1 degrees C showed that the adsorption isotherms correlated well with the Langmuir model. From the adsorption data, thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated as a function of temperature.

Use of extraction chromatography for thorium purification from Eskişehir-Beylikahir thorium-REEs ore deposit

The extraction chromatography method was used to separate thorium from acidic leach solution. The separation of thorium was realized on silica gel column coated with tri-octlyphosphine oxide (TOPO). The extraction yield of thorium on this column from nitric acid leach solution is 91.9%. Then thorium was eluted by using 0.5 M H2SO4 solution, and elution yield was determined as 96.5%. The chemical analysis of H2SO4 fractions indicated that thorium was concentrated and purified succesfully by this method. As a result, thorium was recovered in dilute leach solution with a yield of 81.0±6.8%.

Leaching of Celestite in Sodium Hydroxide Solutions and Kinetic Modelling

Abstract 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. GRAPHICAL ABSTRACT