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

Abstract

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 Ca2+ sources including CaCl2, Ca(NO3)2, CaBr2 and Ca(Ac)2 using an CO2-storage material (CO2SM) prepared by an indirect CO2 utilization approach as the CO32− source. The effects of five major reaction conditions including reaction medium, hydrothermal reaction temperature, hydrothermal reaction time, Ca2+ concentration and sources, and pH and conductivity on the crystallization of CaCO3 were systemically investigated. It is found that the amounts of CO2SM required for the formation of pure vaterite phase are in the order of CaBr2 (20 g/L CO2SM) > Ca(NO3)2 (16 g/L CO2SM) > Ca(Ac)2 (8 g/L CO2SM) due to the effects of ethylenediamine (EDA), diethylene glycol (DEG) and their anions. Especially, vaterite was not found in CaCl2 system. The effects of Ca2+ sources on the crystal phase composition of CaCO3 are revealed for the controllable synthesis of CaCO3 crystals. Our work not only provides a controllable synthesis method of pure vaterite, but also an indirect CO2 utilization strategy.