ABSTRACT Heavy metals in municipal waste incineration fly ash are potentially harmful to the ecological environment and human health. To mitigate the hazards of fly ash, this study attempts to detoxify fly ash through organic acid washing pretreatment coupled with cement/sodium diethyldithiocarbamate (DDTC) solidification. The results indicate that increasing the concentration of organic acids enhances the leaching of Fe, Al, K, Na, and Ca; reduces the alkalinity of the fly ash; and weakens its acid buffering capacity. Regarding the impact on heavy metals, higher acid concentrations promote the migration of Cd, Cu, Ni, and Pb into the liquid phase and increase the proportion of unstable forms of heavy metals remaining in the fly ash. Among them, citric acid (CA) exhibits a stronger affinity for K, Na, Ca, Pb, and Cu compared to oxalic acid (OA). Furthermore, the analysis of cement combined with DDTC for stabilizing heavy metals in acid‐washed fly ash reveals that, compared to cement stabilization alone, the combination of cement and DDTC significantly improves the stability of heavy metals in the solidified matrix. The leaching concentrations of Cd, Pb, and Cu initially increase and then decrease with the number of leaching cycles, while Ni shows an opposite trend. The morphology and crystalline phase analysis of the fly ash before and after stabilization elucidate the mechanisms of heavy metal immobilization. This study provides valuable insights for the practical industrial disposal of fly ash concerning the control of heavy metals and alkalinity.
Pang et al. (Wed,) studied this question.
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