Dechlorination behavior and kinetic characteristics of municipal solid waste incineration fly ash-based artificial aggregates

To address the low-cost removal of soluble chloride salts during the preparation of artificial aggregates derived from municipal solid waste incineration (MSWI) fly ash, a particle-based static soaking dechlorination process was proposed. This method enables reduced equipment investment, simplified operation, and controllable dechlorination efficiency. Artificial aggregates were prepared by pelletizing fly ash with stabilizing agents, followed by thermal treatment at 650 °C. Static soaking experiments were subsequently conducted under different liquid-to-solid ratios and particle size conditions. Soluble chloride removal efficiency and dechlorination kinetics were systematically evaluated. The results indicate that granulation significantly improves solid–liquid separation conditions, thereby reducing separation difficulty and enhancing process efficiency. During static soaking, the leaching of soluble chloride salts is governed by diffusion under concentration polarization. A decrease in particle size increases the solid–liquid interfacial area, leading to an enhanced dechlorination rate. Kinetic analysis based on the Weibull model reveals that the dechlorination behavior is strongly dependent on particle size. Under non-agitated conditions, after 11 cycles of static soaking, the soluble chloride content decreased from 16.5% in raw fly ash to 1.9%. Meanwhile, the leaching concentrations of heavy metals such as Zn and Pb were significantly reduced, meeting the requirements of the HJ 1134 standard. This study provides experimental evidence supporting aggregate-based static soaking treatment for MSWI fly ash dechlorination and detoxification. The findings contribute to understanding chloride migration behavior and dechlorination characteristics during artificial aggregate production.