Modified phosphogypsum sequestrating CO2 and characteristics of the carbonation product

A method of PG carbonation to produce polymorphs of high-purity CaCO3 was proposed. The effect of experimental conditions on transformation process from PG to calcium carbonate was systematically discussed. PG transformed into granular portlandite and fibrous quartz under the action of caustic soda at room temperature for 10 min. The carbonation ratio (eta) was 98.57%, and 1000 kg of PG could produce 519 kg of high-purity CaCO3 and sequestrated 228 kg of CO2. The spherical vaterite carbonation product met the relevant standards for the industrial precipitated calcium carbonate. A reaction mechanism of PG carbonation was also proposed by thermodynamic research of the gas-liquid-solid reaction. The products with a single vaterite structure, or a vaterite and calcite mixing structure or a vaterite, aragonite and calcite mixing structure were all successfully prepared. All of these indicated that the whole procedure setup of PG carbonation showed potential application for PG utilization and CO2 sequestration. (C) 2019 Elsevier Ltd. All rights reserved.