Removal of chloride from municipal solid waste incineration fly ash by wet milling and hydrothermal extraction

• Published in: Desalination Vol. 601; p. 118584
• Main Authors: Liu, Yanqing, Wang, Haifeng, Duan, Chenlong, Dai, Guofu, Hao, Juan, Li, Peng, Wang, Chengxu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2025
• Subjects: Chloride removal; Hydrothermal extraction; Municipal solid waste incineration fly ash (MSWI-FA); Wet milling; Hydrothermal extraction; Municipal solid waste incineration fly ash (MSWI-FA); Wet milling; Chloride removal
• ISSN: 0011-9164
• DOI: 10.1016/j.desal.2025.118584

Municipal solid waste incineration fly ash (MSWI-FA) is a hazardous solid waste that poses significant environmental risks. The resource utilization of MSWI-FA has become a mainstream approach, yet the high chloride content limits the quality of recovered products. To address this issue, this study proposes a combined wet milling and hydrothermal extraction process to remove the chlorine salt from MSWI-FA. Wet milling effectively reduces the particle size of the fly ash and promotes chloride release, leading to a chlorine removal rate of 86.56 % under optimal conditions: 20 min milling time, a 6 mL/g liquid-to-solid ratio, 150 r/min rotation speed, and a 14.5 ball-to-mass ratio. The effects of extraction temperature, extraction time, and liquid-to-solid ratio on chlorine salt removal through hydrothermal extraction were investigated by using a response surface methodology. The results indicate that there are significant interactions among these factors, and the removal efficiency of 85.4 % is obtained under optimal conditions with 6.32 mL/g liquid-to-solid ratio and 12.49 min extraction time, and 63.38 °C temperature. Building upon these findings, the combined process experiments were conducted, demonstrating that the combined approach could further increase chloride ion removal to 93.72 % and have a slight leaching effect on heavy metals. Compared to the traditional three-stage washing process, this method reduces treatment stages, simplifies the process, and decreases the generation of high-chloride wastewater. This study presents an economical and environmentally friendly method for the safe treatment of MSWI-FA, with promising industrial application prospects. •A combined process of wet grinding-hydrothermal extraction was proposed.•Wet grinding can increase the soluble chlorine salt liberation in water extraction.•There is interaction between the L-S ratio, temperature and time during extraction.•The removal rate of Cl can reach 93.72 % by wet grinding-hydrothermal extraction.