Investigating the migration mechanisms of heavy metals under silicate polymerization in gasification slag from landfilled municipal solid waste with rice husk additionOA

Slag gasification represents one of the key technologies for the clean and resource‑oriented treatment of organic solid wastes with high heavy‑metal content, such as landfilled municipal solid waste. Using rice husk as a silicon source, this work investigated the effect of rice‑husk addition on the vitrification of landfilled‑waste slag and the solidification behavior of heavy metals. The results demonstrated that the incorporation of rice husk(5%10%) lowered the flow temperature of the slag and effectively suppressed heavy‑metal leaching. Specifically, the leaching concentrations of Cr and Zn decreased from 41.60 and 108.00mg/L to 5.89 and 7.10mg/L, respectively. The active SiO_(2) introduced by rice husk promoted the formation of highly polymerized siloxane networks(Q3, Q4), which inhibited gasification‑induced migration of heavy metals and enhanced physical encapsulation of them. Concurrently, it facilitated the incorporation of Zn^(2+), Cr^(3+) and Cu^(2+) via substitution or solid‑solution mechanisms into stable mineral phases such as Zn_(2)SiO_(4) and CuFe_(2)O_(4), immobilizing them in garnet and spinel structures. This process increased the residual fraction and reduced the bioavailability of the heavy metals. The present study elucidates the mechanistic role of rice husk in modulating slag structure and heavy‑metal immobilization, thereby provides a theoretical basis for the clean and efficient co‑treatment of landfilled waste and biomass through a “treating waste with waste” strategy.