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    Boric Acid Extraction from Calcined Colemanite with Ammonium Carbonate Solutions
    (Amer Chemical Soc, 2012) Kunkul, Asim; Aslan, Nezahat Ezgi; Ekmekyapar, Ahmet; Demirkiran, Nizamettin
    Colemanite, a calcium-borate hydrate, is found in significant amounts in Turkey. Colemanite is used as a raw material in the production of boric acid. In this study, the leaching kinetics of calcined colemanite in ammonium carbonate solutions was investigated in a batch reactor. The effects of calcination temperature, solution concentration, solid-to-liquid ratio, stirring speed, and reaction temperature on the dissolution rate were determined and evaluated. It was found that the dissolution rate of calcined samples was higher than that of the uncalcined sample. It was observed that the leaching rate of calcined colemanite enhanced with increasing calcination temperature up to 450 degrees C, and did not change above this temperature. Thus, it was found that the applied calcination temperature had a significant effect on the leaching of colemanite. It was determined that the leaching rate raised with an increasing ammonium carbonate concentration, increasing reaction temperature, and decreasing solid/liquid ratio. It was detected that calcium carbonate was not formed on the particle surface. The dissolution kinetics of calcined colemanite was examined using both heterogeneous and homogeneous reaction models, and it was determined that the reaction rate can be described by a first-order pseudohomogeneous reaction model. The activation energy for this process was calculated to be 59.03 kJ/mol.