Mechanochemical Treatment of Municipal Waste Incineration Fly Ash for Simultaneous Dioxins Degradation, Heavy Metals Immobilization and Chloride Removal – A Pilot-Scale Study

Municipal solid waste incineration fly ash (MSWI-FA) contains carcinogenic PCDD/Fs, leachable heavy metals, and soluble chlorides. Although mechanochemical (MC) treatment is a promising method for FA detoxification, pilot-scale validation and simultaneous multi-pollutant removal are lacking. This study reports the construction and operation of a 5 t/d pilot-scale MC plant designed to co-remove PCDD/Fs, heavy metals, and chlorides from MSWI-FA. Key results demonstrate PCDD/Fs degradation efficiencies of 94.3% for low-contamination FA1 (from 4050.8ng/kg to 229.4ng/kg) and 91.0% for high-contamination FA2 (from 33458.9ng/kg to 2999ng/kg). This degradation is attributed to charge-transfer-induced cleavage of C-Cl bonds via O2- release from activated CaO-additive systems. MC treatment effectively immobilized heavy metals (Hg, Cu, Zn, Ba, As, Cr) in FA to levels compliant with the GB 8978 standard by converting soluble compounds into stable crystalline phases, although Pb leaching remained elevated (3-4mg/L). Dechlorination efficiency reached 60%, achieved through the release of encapsulated chlorides via lattice distortion and the subsequent physical separation of volatile species by the pilot plant airflow classification system. Finally, a combined washing-mechanochemical process is proposed for FA treatment, enabling the production of building materials from the treated FA and salt recovery from washing residues. This study validates the scalability of MC technology for MSWI-FA processing and management, providing a technical foundation for industrial applications.