Sulfide doped biomass-derived carbon for heavy metal stabilization in municipal solid waste incineration fly ash and health risk assessment

Fly ash generated from municipal solid waste incineration power plants contains a variety of harmful heavy metals, and biochar is used to stabilize the heavy metals in incineration fly ash. The results indicated that biochar prepared from corn straw pyrolyzed at 600 °C and modified with hydrogen sulfide gas achieved the best stabilization effect when added at a mass fraction of 5%. After stabilization, leaching concentration of As, Se, Cd, Cr, Ni, Cu and Zn decreased, the residual fraction(F5) of Hg, Se, Pb, Cd, Cr, Cu and Zn increased, whereas As and Ni exhibited an increase in their oxidizable fraction (F4). This is attributed to the introduction of sulfur functional group during the sulfur modification process of biochar. In terms of carcinogenic risk, the risk levels of all elements were reduced to the safe range, with the exception of Cr. Nonetheless, the health risk posed by Cr still exhibited a substantial decrease of approximately 30%. Regarding non-carcinogenic risk, all elements were below the hazardous level. However, that the indices for Cr and Cd were significantly higher than those for the other elements. The stabilization treatment effectively reduced the hazard indices of Cr and Cd by 18.8% to 29.6%.