DBU-based CO2 absorption–mineralization system: Reaction process, feasibility and process intensification

Amine-based carbon dioxide (CO2) capture is still limited by high desorption energy consumption. Fixing CO2 into carbonate is a safer and more permanent method. In this work, calcium oxide (CaO) is introduced to perform chemical desorption instead of thermal desorption on 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) aqueous solution after CO2 absorption. The X-ray diffraction (XRD) patterns of solid products show the formation of calcite calcium carbonate (CaCO3), which prove the feasibility of this method. The effects of reaction temperature, reaction time and Ca2+/CO32− molar ratios on the related reactions in CO2 absorption–mineralization process and CaCO3 precipitation are discussed, and purer CaCO3 is obtained by ultrasonic treatment. The CaCO3 content can be increased to 95.8% and the CO2 desorption ratio can achieve 80% by 30 min ultrasonic dispersion treatment under the conditions (40 °C, 180 min, Ca2+/CO32− molar ratio = 1.0). After five cycles, DBU aqueous solution shows stable CO2 absorption and mineralization ability. Fourier transform infrared spectroscopy (FT-IR) spectra of the reaction process also indicate the regeneration of the solvent. Compared with thermal desorption, this process is exothermic, almost without no additional heat.