Controllable crystallization of pure vaterite using CO2-storage material and different Ca2+ sources

The controllable synthesis of pure vaterite with the good properties and broad application prospects is considered as an important, yet a challenging task because the product properties are greatly affected by reaction conditions. In the present work, the controllable synthesis of pure vaterite crystals was explored with four different Ca 2+ sources including CaCl 2 , Ca(NO 3 ) 2 , CaBr 2 and Ca(Ac) 2 using an CO 2 -storage material (CO 2 SM) prepared by an indirect CO 2 utilization approach as the CO 3 2− source. The effects of five major reaction conditions including reaction medium, hydrothermal reaction temperature, hydrothermal reaction time, Ca 2+ concentration and sources, and pH and conductivity on the crystallization of CaCO 3 were systemically investigated. It is found that the amounts of CO 2 SM required for the formation of pure vaterite phase are in the order of CaBr 2 (20 g/L CO 2 SM) > Ca(NO 3 ) 2 (16 g/L CO 2 SM) > Ca(Ac) 2 (8 g/L CO 2 SM) due to the effects of ethylenediamine (EDA), diethylene glycol (DEG) and their anions. Especially, vaterite was not found in CaCl 2 system. The effects of Ca 2+ sources on the crystal phase composition of CaCO 3 are revealed for the controllable synthesis of CaCO 3 crystals. Our work not only provides a controllable synthesis method of pure vaterite, but also an indirect CO 2 utilization strategy.