Controllable synthesis of two CaO crystal generations: precursors' synthesis and formation mechanisms†
In this study, novel rod-like and block-like CaO crystals were prepared after calcinating three types of CaCO3 precursors containing dumbbell-like, wheat spike-like and microsphere-like morphologies at 1000 °C for 3 h. The CaCO3 precursors were synthesized via the hydrothermal reaction of a CO2 storage-material (CO2SM) with Ca(OH)2 without additional additives. In the preparation process, CO2SM was not only used as a raw material but it also played the role of a directing agent. Moreover, as the major influence factors, CO2SM dosage, reaction temperature, reaction time and Ca2+ concentration were systemically investigated. Subsequently, the possible formation mechanism of the CaCO3 precursors was proposed. Finally, the as-obtained CaO crystals exhibit the adsorption amounts of 14.67, 16.32 and 7.50 mg g−1 for an 8% CO2/N2 mixture at 25 °C.