Dissolution kinetics of colemanite ore in propionic acid solutions and optimization

Colemanite is one of the commercially important boron minerals and is often used in industry for the production of boric acid. In the present method, boric acid is obtained from the reaction of colemanite with sulfuric acid and sulfate ions pass into crystallized boric acid as impurities. In this study, the kinetics and optimization of the dissolution of sulfuric acid-derived colemanite in propionic acid solutions were investigated. Thus, it was tried to determine whether dissolving in propionic acid could be an alternative to sulfuric acid. In the first phase of this three-stage study, propionic acid The dissolution kinetics of colemanite in solutions were investigated. As dissolution parameters, reaction temperature(T) 293-333 K, solid/liquid ratio (S/L) 20-80 g/L, propionic acid (CH3CH2COOH) concentration (C) 4.05-8.1 M, stirring speed 300-500 (KH) dev/dk and particle size (D) were chosen as 100-600 µm. In the dissolution of colemanite in propionic acid solutions, the increase in temperature increased the dissolution rate, while the increase in the solid/liquid ratio, acid concentration, and grain size decreased the dissolution rate. No significant effect of mixing speed on dissolution rate was observed. The dissolution and Ca+2 impurity kinetics of colemanite ore in propionic acid solutions, homogeneous and heterogeneous reaction models were correlated with linear regression of the experiment results using the Statistica 10.0 package program. It has been determined that the dissolution and impurity kinetic reaction rates comply with the 'ash film diffusion-controlled sphere for fixed-size grains' model, and kinetic equations representing the process are derived respectively, taking into account the effects of the parameters. The activation energies (A.E.) of the dissolution and Ca+2 impurity kinetics of the process were determined as 37.54 and 36.56 kj/mol, and the Arrhenius constants (A) were determined as 8,06*105 and 2,82*105 respectively. 1 - 3(1-X_(B_2 O_3 ))2/3 + 2(1-X_(B_2 O_3 )) = 8,06*105 (KS)-1.10. (C)-1.40.(TB)1.351. e (-37.54)/(R*T) *t 1 - 3(1-X_(〖Ca〗^(+2) ))2/3 + 2(1-X_(〖Ca〗^(+2) )) = 2,82*105 (KS)-1.573. (C)-0.185.(TB)-0.9033. e (-36.56)/(R*T) *t In the second step, the optimization of dissolution of colemanite ores in the presence of propionic acid was investigated by the Topsis-based Taguchi method. With this method, optimum reaction conditions were determined where the Ca+2 and Mg+2 impurities in the solution were the least and the %B2O3 dissolution was the highest. These conditions were found to be an acid concentration 60%, a reaction temperature 90°C, the reaction time 120 min and a particle size -90 µm. In the determined optimum conditions and verification, experiments are provided close to dissolution 100%B2O3. In the last stage, serial (cyclic) experiments consisting of 6 experiments were carried out under the optimum operating conditions determined in the second stage. SEM, FTIR and XRD analyzes of boric acid crystals produced were proven to be boric acid (H3BO3). It was compared with the impurity values of boric acid produced by Eti Maden enterprises and it was determined that the impurity rate was low. In this way, it is aimed to develop an alternative process for the production of boric acid with high impurity.