Exploring the variations in the properties of municipal solid waste incineration fly ash in CO2 sequestration in ammonium salt solutions assisted by ball milling and ultrasonic treatment.

Municipal solid waste incineration fly ash (MSWI FA) has been used for CO2 sequestration, but the synergistic effects of mechanical and ammonium salt treatment on both sequestration efficiency and treatment safety require further study. This study proposed an integrated approach that combined ball milling, ultrasound, and ammonium salt treatment to enhance CO2 sequestration efficiency in FA while significantly reducing heavy metal content, thereby ensuring its safe recycling and utilization. The results demonstrated that optimal CO2 sequestration efficiency and minimal heavy metal leaching were achieved when using (NH4)2HPO4 (40 g/L), (NH4)3PO4 (60 g/L), and CH3COONH4 (40 g/L). After 6 h of wet ball milling and 2 h of ultrasound, the treated FA exhibited the best performance. However, if ammonium salt treatment was not applied, heavy metal leaching still failed to meet safety standards. When mechanical treatment was combined with CH3COONH4 solution, the CO2 sequestration capacity of FA reached 0.161 g CO2/g FA, while compliance with safety standards was ensured. Furthermore, the recycling potential and application prospects of the treated FA were evaluated, indicating its broader utilization potential. This study successfully achieved the dual objectives of carbon sequestration and FA detoxification, providing an effective strategy for waste treatment.