Tuning crystal polymorphisms and structural investigation of precipitated calcium carbonates for CO2 mineralization

Abstract

Mineral carbonation, which involves spontaneous reactions of CO2 with alkaline earth metals such as calcium or magnesium, is considered one of the most attractive options to sequester CO2 because CO2 can be permanently stored in an inert solid forming stable inorganic carbonate. Moreover, the precipitated CaCO3 has various potential applications in industrial areas, including adhesives, sealants, food, pharmaceuticals, paints, coating, paper, cement, construction materials, etc. In particular, it is expected that the total cost of the carbon capture and storage process could be partly offset by producing value-added CaCO3 materials. In order to add value to the precipitated CaCO3 produced in the ex-situ mineral carbonation process, CaCO3's polymorphs, as well as other properties such as particle size, shape, density, color, and brightness, must be finely tuned. Among CaCO3's polymorphs, calcite, aragonite, and vaterite, calcite is considered to be the most thermodynamically favorable structure at ambient temperatures. However, kinematic constraints in the crystallization induced by synthetic factors are known to significantly affect the formation of polymorphs as well. Here, we revisited the effects of the synthetic factors such as pH, temperature, feeding order, and concentration and molar ratio of Ca2+ and CO3 2- on the formation of CaCO3's polymorphs to provide fundamental insight into how to control the polymorphism of CaCO3 with the ultimate goal of creating value-added mineral carbonation products. ATR FT-IR spectroscopy and a powder X-ray diffraction analysis were performed on the precipitated CaCO3 using model chemicals, K2CO3 and CaCl2, and CaCO3's thermal stability was also investigated. © 2016 American Chemical Society.