Synthesis of precipitated calcium carbonate from LD-slag using CO2

The waste Linz-Donawitz (LD) slag produced in the steel industries is known to have high calcium oxide (CaO) content along with other inorganic salts. There is an untapped potential for the valorization of the waste LD-slag, where the constituent calcium oxide can be converted to valuable calcium carbonate and subsequently contributes to the sequestration of carbon dioxide. In this study, table sugar was introduced as a promoter to enhance the conversion of CaO to CaCO3. The valorization of the LD-slag process was conducted in a CO2 atmosphere by varying the temperature over 25–55 °C. The highest calcium oxide conversion was found at 55 °C. Various techniques were employed in order to assess the crystal growth, textural properties, and thermal behavior of the synthetic CaCO3 formed. The calcite phase is dominated in a temperature range of 25–55 °C, whereas unstable vaterite was identified at 45 °C. Further, at higher temperature ∼55 °C, the needle-like aragonite phase was found to dominate. The reaction kinetic data are well-fitted with the pseudo-second-order model (R2 = 0.99) as compared to other models. The whiteness of the obtained samples was measured via UV-spectrometer and the PCC sample achieved at 55 °C showed significant whiteness characteristics among others. The CO2 sequestration efficiency in this study was found to be ∼17%. It was estimated that 500 g of CO2 could sequestrate by 1 kg of LD-slag. Moreover, the “t” value obtained from the hypothesis test is 49.92, which reveals that the presence of table sugar in the reaction, leads to a higher Ca(OH)2 concentration.