CO2 Sequestration by Boron Mineral: Colemanite at Supercritical CO2 Conditions

Abstract

In this study, sequestration of carbon dioxide (CO₂) with colemanite mineral was investigated at supercritical conditions. Instead of mineral acids in leaching of boric acid from boron minerals, carbonic acid formed in aqueous phase was used. Carbonic acid has extracted boric acid and ultimately it was converted into stable calcium carbonate. Temperature range of 35°C to 60°C, reaction time of 1 to 3 h, particle size range of +20-40 µm to +106 µm were used in experiments. Rising the reaction temperature has increased the sequestration rate of CO₂. Decreasing the particle size has increased surface area and higher conversion value (98.28%) was obtained. For commercial colemanite mineral having 106 m particle size, maximum conversion value of 91.98% was obtained for 3 hours of reaction time. According to FTIR, XRD, TGA and SEM analyses, majority of the solid formed at the end reaction was calcium carbonate. Supercritical CO₂ conditions (T>31.1^oC; P>7.3 MPa) have enhanced the reaction conditions to reach higher CO₂ capture. The amount of CO₂ sequestrated was calculated in the range of (0.130-0.182) kg CO₂/1kg colemanite mineral in our experiments. CO₂ gas causing global warming in the world was utilized as green chemical to extract boric acid and it was converted into calcium carbonate.