A SEMIEMPRICAL KINETICS MODEL FOR DISSOLUTION OF COLEMANITE IN AMMONIUM CHLORIDE SOLUTIONS

Authors: Aycan GÜR*

Yuzuncu Yıl University Science and Art Faculty Department of Chemistry 65100, Van-Turkey; E-mail: aycangurbor@yahoo.com

At the industrial area, it is very important that boron compounds are produced from boron ores. In this study, the dissolution of colemanite in aqueous ammonium chloride solutions was investigated in a batch reactor employing the parameters of stirring speed, particle size, reaction temperature, solid-to-liquid ratio and solution concentration. It was found that the dissolution rate increased with increasing temperature, increasing solution concentration and decreasing particle size, decreasing solid-to-liquid ratio. And it was determined that there was no important effect of stirring speed on dissolution rate. Colemanite could be dissolved up to 100 percent in aqueous ammonium chloride solutions.The dissolution kinetics of colemanite was examined according to heterogeneous and homogeneous reaction models; the analysis of the experimental data, the fact that activation energy is very high, indicate that the dissolution rate based on homogeneous reaction models, can be expressed as:(1-X)^-1-1 = 7.73 10¹³ (Rp)^-3,1142.[C_NH4Cl]^1,5124.(S/L)^-1,2592.e^-4622/T. T. The activation energy of the process was determined to be 38,427 kj. mol⁻¹. The experimental data were tested by graphical and statistical methods and it was found that the above model best fit the experimental data.

Keywords : Colemanite, Dissolution kinetics, Ammonium chloride