Dissolution of Kestelek's colemanite containing clay minerals in water saturated with sulfur dioxide

Colemanite is one of the most important underground riches of Turkey, having approximately 60% of the world boron deposits, and it has a large portion in the deposits. When colemanite having a 2CaO.3B(2)O(3).5H(2)O formula is mined naturally, it contains various clay minerals. During boric acid production by a sulfuric acid process, some kinds of clay minerals cause difficulties in the filtration process. In this study, the dissolution of Kestelek colemanite has been investigated in SO2-saturated water as an alternative method to the sulfuric acid process to remove the difficulties faced in filtration. The particle size, solid-to-liquid ratio, stirring speed, and reaction temperature have been chosen as parameters in the experiments. It was determined that the dissolution rate of colemanite increased with decreasing particle size and solid-to-liquid ratio and increasing reaction temperature but was unaffected by the stirring speed. The activation energy of the dissolution process was estimated to be 39.53 kJ.mol(-1). A semiempirical model was found by using experimental data and package programs, as follows: 1 - (1 - X)(1/3) = 3.423 x 10(4)D(-0.70)(S/L)-(0.65)e(-4754/T)t. Evaluation of the experimental data and semiempirical model shows that the dissolution process is controlled by a chemical reaction.