Optimization by Using the Taguchi Method of Boric Acid Production by Dissolving Flash Calcined Colemanite in Water Saturated with SO2

Turkey has the largest boron reserves in the world with a rate of approximately 72%. The most common commercial boron reserves in Turkey are colemanite, tincal, and ulexite. Boric acid, which is the most commonly used boron compound in Turkey, is obtained from the dissolution of colemanite with sulfuric acid. In the present study, an aqueous medium saturated with sulfur dioxide instead of sulfuric acid was used in order to obtain boric acid.  Colemanite ore was flash calcined at various temperatures and optimum dissolution conditions of the ore obtained in water saturated with SO2 were examined via the “Taguchi Method”. In the trials, flash calcination temperature (500, 600, 700, 800 °C), reaction temperature (50, 60, 70, 80 °C), solid-liquid ratio (0.15, 0.20, 0.25 and 0.30 g/mL), grain size (-500+355, -355+212, -212+150, and -150 µm), and reaction time (15, 30, 45, and 60 minutes) were selected as the parameters and velocity of gas flow and mixing speed were considered as constant in all the experiments. In addition, experiments were carried out at atmospheric pressure. Accordingly, optimum conditions were found as flash calcination temperature of 500oC, reaction temperature of 50oC, grain size of -212+150 µm, solid-liquid ratio of 0.30 g/m, and reaction time of 60 minutes. The estimated dissolution under these conditions was 99.47% and dissolution of 100% was obtained in the experiments conducted. The aim of the study was to obtain more economical and high-purity boric acid compared to sulfuric acid via an environmentally friendly process without any waste.