Abstract
In this study, utilizing the minute gas-liquid interfaces around CO2 microbubbles as novel reaction fields where the crystal nucleation proceeds predominantly, a crystallization technique that enables the synthesis of dolomite(CaMg(CO3)2)fine particles with a Mg/Ca ratio of 1.0 was developed. In the regions around the gas-liquid interfaces of CO2 microbubbles, the local increase in the concentrations of Ca2+, Mg2+, and CO32- because of the electric charge on microbubble surface and the acceleration of CO2 mass transfer are caused by minimizing the bubble size. CO2 microbubbles with an average bubble size of 40 μm were continuously supplied to the concentrated brine coming from salt manufacture discharge in Japan using a self-supporting bubble generator, and CaMg(CO3)2 was crystallized within a reaction time of 120 min. The CO2 flow rate varied in the range between 1.49 and 23.8 mmol/(l・min). For comparison, the reactive crystallization with the injection of CO2 bubbles at dbbl of 200, 300, 800 or 2000 μm was performed using a dispersing bubble generator. The results indicated that minimizing the bubble formation and increasing the CO2 flow rate can achieve the high-yield crystallization of CaMg(CO3)2 fine particles with a higher Mg/Ca ratio.