Microwave-Enhanced Simultaneous SO₂ and NO Removal: Performance and Mechanism of Highly Efficient Adsorbents...

The simultaneous removal of SO₂ and NO using solid waste-derived materials represents a promising but challenging strategy for complex flue gas purification. Herein, a highly efficient KOH-modified Ti-bearing blast furnace slag (KOH-TS) adsorbent was successfully synthesized via thermal activation at a calcination temperature of 800 °C for 2 h with the addition of 10 wt% KOH. When evaluated at a microwave-assisted adsorption temperature of 200 °C, the KOH-TS adsorbent exhibited exceptional simultaneous desulfurization and denitrification capabilities. Specifically, the T_80% and T_50% values for desulfurization efficiency were 17.85 min and 63.67 min, respectively, and the T_95% and T_90% values for denitrification efficiency were 30.63 min and 68.67 min, respectively. The characterization results reveal that this superior performance stems from dual-pathway structural reconstruction during preparation. Macroscopically, thermochemical etching by KOH results in the formation of a hierarchical porous skeleton, whereas microscopically, the isomorphic substitution of potassium ions (K⁺) into the primary CaTiO₃ perovskite lattice induces abundant oxygen vacancies. Consequently, a robust multifunctional adsorbent integrating catalytic oxidation, chemical fixation, and physical confinement was constructed. Mechanistically, the K-doped defective perovskite acts as a catalytic engine to activate oxygen species, synergistically accelerating the continuous oxidation of SO₂ and NO. The resulting oxidized intermediates are subsequently neutralized by surface basic sites and securely accommodated as stable sulfates and nitrates within the developed mesopores. This work provides a sustainable and highly efficient "waste-to-wealth" paradigm for multipollutant emission control.