Microstructure and self-solidification/stabilization (S/S) of heavy metals of nano-modified CFA–MSWIFA composite geopolymers

• Effects of nano-SiO2 and nano-γ-Al2O3 on geopolymers from MSWIFA and CFA.
• The optimum contents of nano-SiO2 and nano-γ-Al2O3 are 1.5% and 2.0%.
• Nanomaterials improve structure, and immovability of heavy metals of geopolymer.

Nano-modified composite geopolymers were successfully prepared from municipal solid waste incineration fly ash (MSWIFA) and class C fly ash (CFA). The results indicate that both nano-SiO2 and nano-γ-Al2O3 have a good modification effect on geopolymer, of which nano-SiO2 has a better performance than nano-γ-Al2O3. The optimum content of nano-SiO2 and nano-γ-Al2O3 are 1.5% and 2.0%, respectively. XRD shows that there is no new phase emerging after adding a small amount of nanomaterials. By FT-IR and SEM, it means that nanomaterials facilitate the reaction of geopolymer, making the modified geopolymer more compact. BET shows nano-SiO2 especially modifies the pore distribution and pore structure of geopolymers. Additionally, nanomaterials have an improvement to the solidification/stabilization (S/S) of heavy metals.