Preparation of Nano-CaCO3 from Phosphogypsum by Gas–Liquid–Solid Reaction for CO2 Sorption

Nano-CaCO 3 was prepared from phosphogypsum (PG) through reactive crystallization in the gas (CO 2 )–liquid (NH 3 ·H 2 O)–solid (PG) three-phase system. The effects of temperature, CO 2 flow rate, and reaction time on the CaCO 3 particle size distribution (PSD) were investigated. The results show that PG-derived nano-CaCO 3 with an average particle diameter of 86–104 nm can be obtained under a 251–138 mL/min CO 2 flow rate at a corresponding temperature of 30–40 °C. Research indicates that the CaCO 3 particle size is subjected to the mutual influences of temperature, CO 2 flow rate, and reaction time. A relatively low CO 2 flow rate with increasing temperature and a strictly controlled reaction time are advantageous to the formation of nanosized CaCO 3 grains. Additionally, PG-derived nano-CaO maintains a CO 2 sorption capacity of 0.27 g of CO 2 /g of CaO after 10 calcination–carbonation cycles, which is the same as for commercial nano-CaO.