Designing super-compatibility all-solid-waste binders for stabilization/solidification of Cr-contaminated soil

Chromium (Cr) contamination in soils represents a critical environmental and public health challenge globally, necessitating efficient and sustainable remediation strategies. This study proposes a “waste control by waste” concept by developing municipal solid waste incineration fly ash (MSWIFA)-activated all-solid-waste binders for the stabilization/solidification (S/S) of Cr-contaminated soil. Experimental results revealed that a binder system composed of MSWIFA and ground granulated blast-furnace slag exhibited superior performance due to the formation of calcium silicate hydrate (C-S-H), ettringite, and Friedel's salt. While the binder system composed of MSWIFA and incineration sewage sludge ash (ISSA) initially demonstrated limited reactivity owing to their low amorphous aluminosilicate content, however, the MSWIFA-ISSA system was unexpectedly activated by Cr-contaminated soil. CrO₄²^- ions triggered a dissolution-reaction cascade, driving the formation of abundant hydration products stable monochromate (3CaO·Al₂O₃·CaCrO₄·nH₂O) phases. Notably, MSWIFA-ISSA systems with 50% soil dosage obtained a 28-day compressive strength of 42.6 MPa and Cr immobilization efficiency of 96.9%. Overall, this study provides valuable insights into the development of sustainable all-solid-waste binders for waste utilization and hazardous waste treatment.