Preparation of calcium carbonate nanoparticles from waste carbide slag based on CO2 mineralization.

This study proposes a novel method for simultaneously dealing with the waste carbide slag (WCS) and CO 2 mitigation. In addition, the ultrafine vaterite CaCO 3 with high economic value was produced under mild conditions of 25 °C and 0.1 MPa. Ammonium sulfate ((NH 4) 2 SO 4) was employed to efficiently extract calcium from WCS into the solid phase calcium sulfate dehydrate (CaSO 4 ·2H 2 O). Subsequently, it was subjected to "dropwise carbonation" leading to the formation of a calcium carbonate with controllable particle size between 100 nm–1 μm through multiple crystalline phase transformations. The results showed that nano-sized CaCO 3 with nearly 90% purity and whiteness was prepared at 25 °C, CO 2 -500 mL/min, and NH 4 +/Ca2+ = 2.4 conditions. Results of TG and FTIR analyses confirmed that CaCO 3 polymorphs with vaterite and metastable were formed. Based on the calcium conversion ratio of the entire process, treatment with 1 ton of WSC captured ∼0.5 tons of CO 2 and yields about 1.15 tons of nano-sized CaCO 3 per each cycle operation. This study provides a valuable method for identifying potential application for scale preparation of vaterite nanoparticles from low cost but abundant calcium resource such as WCS and gypsum. [Display omitted] • Simultaneously deal with the waste carbide slag (WCS) and CO 2 mitigation. • A stepwise mild method for preparation of nano-sized CaCO 3 from WCS based on CO 2 mineralization is proposed. • Multiple crystal phase transformations of calcium component contribute to control vaterite particle size. • Treatment of 1 ton of WSC captures ∼0.5 tons of CO 2 and yields about 1.15 tons of nano-sized CaCO 3. [ABSTRACT FROM AUTHOR]