How Leaching of Heavy Metals Changes. Long-Term Environmental Safety of Incineration Fly Ash Solidified by Cement

The cement industry has achieved the harmless and resourceful disposal of incineration fly ash, but the environmental safety of heavy metals during its service life is still unknown. Therefore, the evolution of heavy metal leaching during the wet-dry cycle of the incineration of fly ash after different solidification treatments has been studied. We provide a theoretical basis for the long-term safe use of incineration fly ash after resource utilization. The results showed that when incineration fly ash underwent 90 dry-wet cycles, the leaching of Cd exceeded 19.40% of Chinese standard GB 18598-2019. Upon addition of 10% and 30% cement to incineration fly ash, the trend of increasing leaching of heavy metals slowed, with a higher cement content enhancing the solidification capability for heavy metals. When incineration fly ash mixed with 10% cement underwent 180 dry-wet cycles, the leaching of Cd exceeded 40.75% of Chinese standard GB 18598-2019, while that of samples with 30% cement content did not exceed the limit, with Cd leaching at 84.45% of Chinese standard GB 18598-2019. As an admixture, the compressive strength increased with the number of dry-wet cycles. When the incineration fly ash dosage was 20%, the maximum leaching of heavy metals after 180 dry-wet cycles was only 5.19% of Chinese standard GB 18598-2019. The toxicity index of heavy metals also showed a decreasing trend compared with that of incineration fly ash. Therefore, cement admixture with incineration fly ash ensured the safety of heavy metals during its service life.