Modified wollastonite sequestrating CO2 and exploratory application of the carbonation products

Abstract

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.