• • The lead-zinc molten slag slurry achieved >90% SO2 removal efficiency sustained for approximately 70 hours, demonstrating its viability as a low-cost desulfurizing agent for smelting flue gas.
• • NaClO2 was the most effective oxidant among tested (KMnO4, H2O2, K2Cr2O7, NaClO2), yielding up to 94.76% NOx removal when combined with the desulfurization slurry.
• • Under optimized conditions (NaClO2 0.025 mol·L−1, 45 °C, 200 mL·min−1, 10% O2, 0.03% NOx, pH 6), NOx removal reached 97.24%, highlighting the process's high efficiency.
• • Fe3+ ions leached from the slag significantly enhanced NOx removal by promoting NaClO2 decomposition into ClO2 and other reactive species, enabling a cyclic catalytic mechanism that boosts oxidation performance.