CO2 sequestration technology through mineral carbonation: An extraction and carbonation of blast slag

Abstract Mineral carbonation refers to a CO 2 sequestration technology which is used to produce carbonate from minerals containing calcium and magnesium which are then reacted with CO 2 . It has been assessed as technology that disposes of CO 2 in a thermodynamically stable state. In this study, calcium ion was extracted from blast furnace slag, granulated slag and air-cooled slag and calcium carbonate was then synthesized from the extracted calcium, which was reacted with CO 2 . Based on the results, the feasibility of reducing CO 2 emissions in this manner is demonstrated. The chemical composition of blast furnace slag as a raw material was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES), and the characterization of the crystal phase of the slag were calculated by the Rietveld method. Calcium extraction was conducted using ammonium salts (NH 4 NO 3 , NH 4 Cl, CH 3 COONH 4 with (NH 4 ) 2 SO 4 ) as an extraction solvent under ambient conditions (30 °C, 1 bar). The calcium extraction efficiency was compared according to the solvent type and the optimal extraction conditions were examined according to the experimental variables of the solvent concentration, reaction temperature, reaction time and solid-to-liquid ratio. The calcium concentration in the extraction solution was measured by ICP-OES. The calcium extraction efficiency was proportional to the solvent concentration, the reaction temperature and the reaction time, whereas it was not proportional to the solid-to-liquid ratio. The calcium extraction efficiency of NH 4 NO 3 , NH 4 Cl and CH 3 COONH 4 was approximately 52.0 wt.% on average and the Ca extraction efficiency of (NH 4 ) 2 SO 4 showed a low value (37.7 wt.%) compared to those of other solvents. A field-emission scanning electron microscope (FE-SEM) equipped with an energy dispersive spectrometer (EDS) was employed to assess the surface morphology and for an elemental analysis of the calcium carbonate synthesized from the carbonation test. The economic assessment to reduce CO 2 was conducted based on this information along with the calcium extraction efficiency, and processing costs of the solvents, CO 2 , and other materials.