Leaching kinetics of calcined ulexite in ammonium nitrate solutions

Among boron minerals, ulexite is one of the most common substances and is found in great amount in Turkey. Ulexite, sodium-calcium-borate hydrate, has a chemical formula of Na2O center dot 2CaO center dot 5B(2)O(3)center dot 16H(2)O. In this study, the leaching kinetics of calcined ulexite in ammonium nitrate solutions was investigated in a batch reactor employing the parameters of calcination temperature, concentration, particle size, stirring speed and reaction temperature. It was found that the dissolution rate increased with increasing concentration and reaction temperature and with decreasing particle size. No effect of stirring speed was observed on the conversion. It was determined that the dissolution rate fit the chemical reaction control model. An empirical equation for the process was derived as 1 - (1 - x)(1/3) = 3.5 x 10 (4)C(0.31)D(-0.80)exp(-46.5/ RT)t. The activation energy of this dissolution process was found to be 46.5 kJ mol(-1).