Optimization of low-temperature pyrolysis of dioxins in fly ash from municipal solid waste incineration: adding catalysts and inhibitors†

This study simulates the low-temperature heat treatment of municipal solid waste incineration fly ash (MSWIFA, abbreviated as FA) under industrial conditions and investigates the enhancement of the process by inhibitors and catalysts. The results show that compared with the experimental group without catalysts or inhibitors, neither CaO nor CO(NH₂)₂ can play an optimization role. Among the inhibitors, the total concentration and toxicity of dioxins in the 10 wt% CaO experimental group are the lowest, which are 467.01 ± 57.55 ng kg⁻¹ and 48.40 ± 8.40 ng I-TEQ per kg, respectively. Among the two catalysts (MnO and V₂O₅), the experimental group with 1 wt% MnO has the best degradation efficiency. The total concentration and toxicity of dioxins in FA are 371.58 ± 19.92 ng kg⁻¹ and 34.45 ± 2.56 ng I-TEQ per kg, respectively, and the removal rate and detoxification rate are 96.64% and 95.58%. These values meet the requirements of “China's Technical Specification for Pollution Control of Fly Ash from Domestic Waste Incineration” (trial) (HJ 1134-2020, China). XRD and FT-IR analyses indicate that dioxin degradation is likely due to dioxins being adsorbed onto the surface of MnO. Furthermore, the presence of manganese encourages the creation of radicals and oxidative ring opening, leading to carbonate formation. Simultaneously, dechlorination and substitution reactions take place, with Cl substitution on the benzene ring resulting in the production of Cl₂ and HCl. Therefore, promoting the degradation of dioxins is more feasible than inhibiting the synthesis of dioxins. This study provides a new way to realize low-temperature heat treatment of dioxins in domestic waste incineration facilities.