On the application of calcium carbide slag as CO2 absorbent

Calcium carbide slag, generated in the hydrolysis process of calcium carbide, is an potential carbon capture reagent because its main ingredient is Ca（OH）2. Calcium carbide slag, a by-product of a resin factory was used as carbon capture reagent. The change of pH and electrical conductivity （EC） of the calcium carbide slag slurry with different solid-to-liquid ratios, as well as the capture efficiency and dynamics under different temperatures and flow rates of CO2 were studied. The properties of solid were characterized with XRD, TG-DTA, SEM and FT-IR before and after capturing carbon. The results show that the change of pH and EC were greater with low solid-to-liquid ratio than that with high solid-to-liquid ratio. The analysis of XRD and SEM show that the content of CaCO3 increased significantly, which improved that Ca（OH）2 and free CaO were reacted with CO2. The results of TG-DTA and FT-IR show that the physicochemical properties and microstructure of the slag changed after capturing CO2 because of the increase of CaCO3 content. All the results mentioned above improve the feasibility of utilizing calcium carbide slag to capture CO2 and offer a practical way for carbon emission reduction and disposal of wasted calcium carbide slag.