Modified wollastonite sequestrating CO2 and exploratory application of the carbonation products

The feasibility of wollastonite carbonation for CO2 sequestration was systematically investigated, and the recovery of the by-products (SiO2, NH4Cl) in the carbonation process, the controllable preparation of carbonation product (CaCO3) with different polymorph and morphology during the carbonation process, and the application of the carbonation product were evaluated. The ammonia dosage and volume of the Ca2+ leaching solution showed a prominent effect on the wollastonite carbonation ratio. The synthesis of the carbonation product (CaCO3) with different polymorphs and morphologies was successfully realized by controlling the temperature and ammonia dosage during the carbonation process. A reaction mechanism of wollastonite carbonation was also proposed by thermodynamic research of the gas-liquid-solid reaction. The carbonation ratio could reach up to 93%, and 1 ton wollastonite could sequester 350 kg of CO2 under optimized conditions. The crystalline phase of the as-obtained CaCO3 was spherical vaterite and cubic calcite, which could meet the relevant standards for the industrial precipitated calcium carbonate CaCO3 (HG/T 2226-2010). The physical properties of the corresponding PP/CaCO3 composites were very close. The cost of wollastonite carbonation was estimated to be 120 $ per t without industrial scale experiment. The wollastonite carbonation strategy showed potential application for CO2 sequestration.