Double Benefits Achieved in the Cosintering of Incineration Fly Ash and Heavy-Metals-Enriched Wastes: Valuable Metals Recovery and Calcium Aluminate (Chloro-Sulfur) Phases-Dominant High Cementitious Byproduct

The cosintering of incineration fly ash (IFA) with multisource heavy-metal-containing solid wastes offers a promising strategy for simultaneous valuable metal recovery and ceramsite production as inert aggregates. However, the feasibility of high-concentration heavy-metal-bearing wastes remains uncertain, particularly regarding the cementitious performance and long-term leaching stability of byproducts with elevated residual metals. This study explores the potentials of cosintering Si–Al–S-based heavy-metals-enriched wastes with IFA to synthesize chemically stable cementitious materials while simultaneously recovering valuable metals. Resource attribute conversion efficiency (RACE) and strength active index (SAI) are used to quantify this double benefit performance. Results show that the new paths, designated as IFA-SZn and IFA-SPb, exhibit significant RACE values of 83.06% Zn and 91.49% Pb, respectively, with metal concentrates obtained comparable to natural-source minerals. Cosintered ceramsite dominated by calcium aluminate (chloro-sulfur), dicalcium silicate, and calcium aluminosilicate phases exhibited SAI values at 3 and 28 days 1.30–1.38 and 1.03–1.10 times those of coal fly ash. Low heavy metal leaching and soluble chlorine levels, due to the binding effect from calcium aluminate (chloro-sulfur) phases, further demonstrate its potential as an alternative cementitious material. These findings provide new insights for synergistically managing IFA and multisource heavy-metal-enriched wastes through integrated stabilization-resource recovery.