Treating waste with waste: Facile KHCO3-modified calcium carbide slag for simultaneous removal of NO and SO2

The simultaneous removal of nitric oxide (NO) and sulfur dioxide (SO2) in a cost-effective and environmentally friendly method is a major challenge in the field of industrial tail gas purification. In this study, the solid waste calcium carbide slag (CS) was modified by potassium bicarbonate (KHCO3) to achieve simultaneous removal of NO and SO2 under low temperature conditions. Experimental results confirmed that this low-cost KHCO3-modified calcium carbide slag (KCS) has excellent simultaneous removal of NO and SO2 activity, which is attributed to its unique morphology and abundant surface adsorbed oxygen species (Oads). Interestingly, the presence of SO2 improved the capacity of KCS for NO removal. In-situ diffuse reflectance infrared Fourier-transform spectroscopy results demonstrate that the addition of SO2 promote the formation of oxygen-containing functional groups. Further studies indicated that increasing the Oads could effectively facilitate oxidation of NO and SO2 to nitrate (NO3–) and sulfate (SO42-), while the SO42- formed on the KCS surface continuously provided Oads for the oxidation reaction. Over all, the study proposes a strategy for typical solid waste (CS) resource utilization, to attain simultaneous removal of NO and SO2 under low temperature conditions, thus achieving the goal of “treating waste with waste”.