Simultaneous removal of SO2 and NOx by potassium-modified carbide slag

Abstract

The treatment of solid waste carbide slag (CS) poses an urgent challenge in terms of its resolution. This study presented an efficient and cost-effective method for simultaneous desulfurization and denitrification at low temperatures using different modified potassium compounds (KOH, K2CO3, and KHCO3) as adsorbents. The experimental results revealed the significant impact of potassium modification on the performance of the CS, leading to a significant improvement in its denitrification activity while maintaining the same desulfurization effect. The denitrification rates of the modified CS demonstrated increases by 30 % (KOH), 25 % (K2CO3), and 40 % (KHCO3), respectively, compared to the unmodified CS at 200 ℃. The NO adsorption capacities were 2.48 (KOH), 2.24 (K2CO3), and 3.05 (KHCO3) times that of CS, respectively. Subsequent investigations suggested that the potassium modification process induced changes in the microstructure of CS, augmenting the abundance of oxygen vacancies, KOx, C = O, and Oads, thereby enhancing the intensity and quantity of basic sites. This reduced the activation energy of the CS during simultaneous desulfurization and denitrification. In addition, it was observed that certain byproducts formed during the desulfurization and denitrification processes, such as sulfate, sulfite, and nitrate, accumulated on the surface and within the inner pores of the adsorbents, ultimately resulting in a decline in catalytic activity. This study aims to embrace the “treat waste with waste” approach and is expected to provide guidance for the advancement of simultaneous desulfurization and denitrification technologies targeting solid waste CS.