Integrated multi-scale study of dioxin degradation in municipal solid waste incineration fly ash (MSWIFA) by...

The significant toxicity of dioxins in municipal solid waste incineration fly ash (MSWIFA), coupled with their persistence and bioaccumulation, necessitates robust detoxification strategies. This study elucidates the degradation mechanisms of dioxins during low-temperature thermal treatment through an integrated multi-scale approach. In this approach, molecular-level insights from density functional theory (DFT) guided parameter optimization in experimental simulations. These simulations were subsequently validated through industrial-scale trials. DFT showed that reactive hydroxyl groups (-OH) on CaO preferentially attacked class B chlorine adjacent to oxygen, with a lower energy barrier (-4.27 eV) than class A sites (-4.20 eV), initiating stepwise dechlorination and Cl₂ release. Experimental simulations identified that under 400 ℃, 90 min, and 1 % O₂, a 96.98 % solid-phase detoxification was achieved, stabilizing toxicity below 50 ng I-TEQ/kg. However, gaseous toxicity increased by 127 % compared with N₂, highlighting oxygen's critical role in promoting gaseous emissions. Industrial validation identified oxygen content (<1 %) and temperature (380 °C-420 °C) as critical for efficiency, achieving > 95 % TEQ removal with compliant flue gas emissions (<0.5 ng I-TEQ/Nm³) after catalytic ceramic filtration. These findings provide molecular-level mechanistic insights and industrial process frameworks for low-temperature thermal treatment technology, offering significant guidance for the safe disposal and environmental risk control of MSWIFA.