Utilization of Phosphogypsum to Prepare High-Purity CaCO 3 in the NH 4 Cl–NH 4 OH–CO 2 System

High-purity CaCO 3 via a facile two-step dissolution–carbonation coprecipitation procedure using NH 4 Cl, NH 4 OH, and CO 2 with phosphogypsum (PG) as the raw material was successfully produced in the present work. The impact of different experimental parameters on dissolution and carbonation processes was discussed herein. The optimum amount of dissolved CaSO 4 ·2H 2 O in PG was found to be 18.7 g/L, and the optimum carbonation ratio was found to be 98.22%. The carbonation filtrate could be used up to nine times. Meanwhile, the corresponding reaction efficiency would remain above 50%. Products composed of vaterite and calcite and those composed of pure vaterite and pure calcite were successfully produced. The purity of the product was measured to be 99.8%, and its whiteness was 95.8%. The prepared products met the specifications in the HG/T 2226-2010 Chinese standard. The suggested CaCO 3 preparation and PG utilization scheme show promising prospect for applications.