Dissolution Kinetics of Colemanite in Sulphuric Acid Solutions for High Solid to Liquid Ratios

Aycan Gur*, Hasan Ceylan, Ahmet Sel

Department of Chemistry, Faculty of Science and Literature, Yuzuncu Yil University, 650 80 Van-Turkey.

Production of boron compounds from boron ores are very important for the industrial area. In this study, the dissolution of colemanite at high solid-to-liquid ratios in aqueous sulphuric acid solutions was investigated in a batch reactor employing the parameters of stirring speed, particle size, temperature, solid-to-liquid ratio and acid concentration. It was found that the dissolution rate increased with increasing temperature, decreasing solution concentration, decreasing particle size and decreasing solid-to-liquid ratio, while no important effect of stirring speed was observed on dissolution rate. Colemanite could not be dissolved completely in aqueous sulphuric acid solutions. Because it was determined that solid products such as CaSO4 (anhydrite), CaSO4.2H2O (gypsum) formed on mineral surface. Dissolution kinetics of colemanite was examined according to heterogeneous and homogeneous reaction models; the analysis of the experimental data indicate that the dissolution phenomenon is controlled by diffusion from ash film and according to the experimental data tested by graphical and statistical methods, the mathematical model to represent the kinetics of this process can be expressed as: t = t*[1-3.(1-X)-2/3 + 2.(1-X)].

Colemanite; boric acid; boron; dissolution kinetics; sulphuric acid