Reutilization of washed MSWI fly ash into sustainable alkali-activated materials: Leaching behaviors and ecological...

Integrating water washing with alkali activation is a promising strategy for the safe reutilization of municipal solid waste incineration fly ash (MSWIFA); however, the environmental and ecological safety levels of the resulting materials remain poorly understood. In this study, high-performance alkali-activated materials (WFA-AAMs) were synthesized from water-washed MSWIFA (WFA), coal fly ash, silica fume, and sodium silicate, achieving a 28-day compressive strength of 32.17 MPa through the optimization of the C-(A)-S-H/N-A-S-H gel network. Their environmental safety levels were systematically evaluated using short-term, long-term static, and semi-dynamic leaching tests combined with ecological risk assessments and ecotoxicity bioassays across four trophic levels. The results revealed that compared with WFA, WFA-AAMs reduced Pb and Zn leaching by more than 99%, with acute hazard quotients (HQs) consistently being less than 1. Ecotoxicity tests on bacteria, algae, crustaceans, and fish confirmed negligible toxicity from WFA-AAM leachates, whereas WFA leachates caused substantial adverse effects. Principal component analysis revealed Pb as the dominant toxicity driver, with Cl⁻ exerting synergistic effects. Through this study, the first comprehensive chemical-ecological-toxicological framework for evaluating the safety of WFA-AAMs was established, providing scientific guidance for their sustainable application.