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Öğe Dissolution kinetics of ulexite in ammonia solutions saturated with CO2(Elsevier Science Bv, 1997) Kunkul, A; Yapici, S; Kocakerim, MM; Copur, MThe dissolution kinetics of ulexite in ammonia solutions saturated with carbon dioxide were investigated, Experiments investigating the following parameters: concentration of ammonia; particle size; stirring speed; solid to liquid ratio; reaction temperature; and carbon dioxide flow rate; showed that ulexite can be dissolved completely in solutions of carbonic acid at atmospheric conditions, It was found that the dissolution rate increased with increasing ammonia concentration, reaction temperature and calcination temperature, and with decreasing particle size and solid to liquid ratio, It was observed that the flow rate of carbon dioxide and stirring speed have almost no effect on the dissolution rate, It was determined that the dissolution rate of ulexite can be described by a first-order pseudo-homogeneous reaction model and an empirical equation for the process was developed: -ln(1-X) = 1.0X10(5)(C-A)(0.22)(d)(-0.92)(S/L)(-0.54)exp(-6600/T). t where C-A is the ammonia concentration, d the initial particle size and (S/L) the solid to liquid ratio. The activation energy for the process was found to be approximately 55 kJ mol(-1)Öğe Dissolution of thermally dehydrated ulexite in sulfuric acid solution(Amer Chemical Soc, 1997) Kunkul, A; Tunc, M; Yapici, S; Ersahan, H; Kocakerim, MMThe present study concerns a work on the investigation of the effect of the dehydration temperature on the dissolution process of a boron mineral, ulexite, in sulfuric acid solution. In the experiments, the dehydration temperature and dissolution temperature were chosen as the parameters. First, the dehydration of ulexite was performed isothermally in an oven, and DTA and X-ray analysis were carried out to observe the structural changes in the mineral. The effect of the dehydration temperature on the dissolution rate of ulexite in sulfuric acid solutions was then investigated, using a batch reactor made of glass. The kinetic parameters of the dissolution process, frequency factor and activation energy, were evaluated using dissolution data.Öğe Nonisothermal decomposition kinetics of trona(Amer Chemical Soc, 1996) Ekmekyapar, A; Ersahan, H; Yapici, SIn the present work, experiments on the nonisothermal decomposition of trona in thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) devices were carried out, and kinetic analysis of the process was performed by employing four different approaches. It was determined that the process fits a first-order reaction kinetic model and that the value of the activation energy changes, to some degree, depending upon the method used in the analysis, with a maximum deviation of 8.9% from the average value. The activation energy was found to be approximately 112 kJ mol(-1), which is in good agreement with the data from similar studies in the literature.
