Abstract: We used fluidized bed incineration (800 ℃) cyclone ash to assess the feasibility of recovering metal(loid)s in the incineration ash of the hyperaccumulator Sedum plumbizincicola. We examined the factors affecting the leaching characteristics of metal(loid)s in fly ash, namely extractant type (hydrochloric acid, nitric acid or ammonium chloride) and concentration, liquid/solid ratio and leaching time. Furthermore, we evaluated the safety of the leaching residues. The type, concentration, and liquid-solid ratio of the extractant were important parameters influencing metal leaching performance, whereas leaching time had minor influence. Acids (hydrochloric acid, HCl; or nitric acid, HNO₃) showed higher leaching efficiency than ammonium chloride. The leaching characteristics of cadmium (Cd), zinc (Zn), and lead (Pb) in fly ash can bedescribedby the cationic leaching mode. The leaching efficiency of Cd, Zn, and Pb increased with increasing concentration and liquid/solid ratio of extractants, with the maximum leaching rates reaching 94.9%, 90.2%, and 92.4%, respectively. The environmental risk from leaching residues was effectively reduced by increasing the liquid/solid ratio of the extractant. An optimum leaching procedure with 1 mol·L^-1 HCl at a liquid/solid ratio of 16:1 for 30 minutes is suggested for the routine treatment of fly ash of S. plumbizincicola, which may meet the requirement for landfill. The leachates may be further used for the recovery of high-value metals.

Key words: incineration fly ash, heavy metal, leaching, Sedum plumbizincicola.