Comprehensive utilization of MSWI residues metal recovery via bioleaching integrated with mineral residues upcycling as cementitious binders

Research works on developing methods for an efficient recovery of critical metals from MSWI residues have been intensively conducted. Nevertheless, utilization potential of residual solids from incinerated residues after metal leaching has still lacked in-depth studies. Herein, a study on the utilization of mineral residues after bioleaching of municipal solid waste incineration (MSWI) ashes in cementitious materials application is carried out. With roughly 70–90% of Zn, Cu, Cd, or Co recovered, the Acidithiobacillus microorganisms exhibited a good metal extraction yield from fly ash (FA). However, air pollution control (APC) residues with high alkalinity and chlorinated organic compounds may severely hinder leaching capacity of microorganisms, resulting in a lower leaching efficiency than FA. The mineral phases in MSWI residues were reformed into sulfur (S) and jarosite K0.73(H3O)0.27Fe2.65(SO4)2(OH)4.95(H2O)1.05, respectively, with At. ferrooxidans and At. thiooxidans bioleaching. The postleaching residues from FA by At. ferrooxidans were chosen for recycling as cementitious binder according to the major mineral and metal recovery efficacy. When cement was replaced by bioleached FA, the compressive strength of cement mortar was significantly higher than that of washed FA and on par with the CEM II. This different performance as cementitious material was revealed by the study of their hydration products and kinetics. Washed FA led the creation of additional Al-ettringite while the replacement with FA residue following bioleaching resulted in the synthesis of Fe substituted ettringite. Bioleaching process transformed raw FA – a hazardous waste into non-hazardous and potential construction materials.