Co-disposal of MSWI fly ash and electrolytic manganese residue based on geopolymeric system

•MSWI fly ash and EMR were successfully co-disposed based on geopolymeric system.•Alkaline products of MSWI together with NaOH activated geopolymeric system.•The S/S mechanism includes alkaline surroundings and geopolymeric encapsulation.•The S/S effects for heavy metals show the following order: Pb > Cu > Cr > Zn > Mn. MSWI fly ash (MSWI FA) and electrolytic manganese residue (EMR) were successfully co-disposed by use of a geopolymeric system. Alkaline products of MSWI FA and NaOH were used to elicit chemical reactions to promote solidification. The best performing formulation of EMR-based geopolymer for immobilization of heavy metals was composed of 75 wt% MSWI FA and 25 wt% EMR with NaOH solution (7.5 M)/solid of 0.5. Solidification was most effective for the heavy metals: Pb > Cu > Cr > Zn > Mn, respectively. The EMR-based geopolymer had high structural stability likely due to the high ratio of SiO2/Al2O3. The Solidification/Stabilization (S/S) mechanism for heavy metals of geopolymers is likely due to alkaline conditions and geopolymeric encapsulation, highlighting the utility and feasibility of this approach.