Desulfurization of Lead-Zinc Molten Slag and Synergistic Oxidation of NOx with NaClO2
The emission of sulfur dioxide (SO2) and nitrogen oxides (NOx) from fossil fuel combustion and metal smelting industries poses severe risks to environmental and human health. This study utilized depleted lead-zinc molten slag as a desulfurizer for wet flue gas desulfurization, and the resulting desulfurization slurry was further employed for NOx removal, achieving resource utilization. The desulfurization efficiency of the slag was determined, and NaClO2 was identified as the most effective oxidant when combined with the slag slurry for NOx removal. The effects of NaClO2 concentration, reaction temperature, flue gas flow rate, oxygen concentration, NOx concentration, and pH on removal efficiency were investigated. Optimal conditions were found at NaClO2 concentration of 2.5 mmol·L−1, temperature 45 °C, flue gas flow 200 mL·min−1, O2 volume fraction 10%, NOx volume fraction 0.03%, and pH 6, achieving a NOx removal efficiency of 97.24%. Metal ion experiments revealed that Fe3+, Zn2+, Mn2+, and K+ exhibited synergistic effects with NaClO2, with Fe3+ showing the most significant enhancement. Fe3+ promoted the decomposition of NaClO2 to generate stronger oxidants such as ClO2, thereby enhancing NOx oxidation and absorption. This approach offers a cost-effective and environmentally friendly alternative to traditional selective catalytic reduction, avoiding ammonia slip and secondary pollution.