A high-performance KOH-modified steel slag adsorbent for efficient simultaneous desulfurization and denitrification: Mechanism and performance

To address the dual challenges of industrial steel slag disposal and flue gas pollution, a novel high-performance KOH-modified steel slag (KOH-SS) adsorbent was developed for the simultaneous removal of SO 2 and NOx. The adsorbent was synthesized via a thermal activation process, with the optimal performance achieved at a calcination temperature of 700 °C for 2 h with a 10% KOH loading. Under microwave-assisted adsorption conditions at 200 °C, the KOH-SS adsorbent exhibited exceptional efficiency, with breakthrough times (T 80% and T 50% ) of 31.88 min and 74.36 min for desulfurization and 16.88 min and 86.01 min for denitrification, respectively, significantly outperforming traditional calcium-based materials. Mechanistic analysis revealed that superior performance is rooted in a unique “destruction–reconstruction” process during preparation. The molten K 2 O derived from KOH dehydration aggressively erodes the inert silicate matrix, triggering the depolymerization of mineral phases and the subsequent regeneration of highly reactive “newborn” CaO active sites within a robust crystalline K 2 CaSiO 4 and amorphous gel framework. This structural metamorphosis creates a hierarchically porous architecture that facilitates strong synergy between rapid physical diffusion and intense chemisorption via acid–base neutralization and catalytic–oxidative pathways. This research demonstrates a sustainable “waste-to-wealth” strategy, providing a low-cost and highly efficient solution for the synergistic control of multiple pollutants in industrial flue gas.