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

• • Rice husk addition of 5–10% reduces slag flow temperature to a minimum of 1213 °C, enabling energy-efficient vitrification and slag tapping in entrained-flow gasifiers. • • Leaching concentrations of Cr and Zn drop from 41.60 and 108.00 mg/L to 5.89 and 7.10 mg/L, respectively, with 10–15% rice husk, meeting stringent environmental discharge limits and reducing landfill aftercare costs. • • At temperatures >1400 °C, Cu and Zn residual rates fall to 33–60% and 31–55%, respectively, while Cr maintains 70–123%, indicating the need for temperature control to minimize volatile heavy metal emissions. • • Rice husk promotes transformation of heavy metals from acid-soluble and reducible fractions to the residual fraction, enhancing environmental stability and reducing bioavailability, as confirmed by sequential extraction.