Synthesis of geopolymers using municipal solid waste incineration fly ash and construction and demolition waste: Mechanical and thermal activation

The safe disposal and utilization of MSWI FA, enriching with high amounts of heavy metals, chlorides and organic pollutants, has turned into a critical problem that restricts MSWI development. In this study, the resource utilization feasibility of MSWI FA with CDW and GGFBs by geopolymers was analyzed, and the performance of geopolymers with the different MSWI FA dose and activation method was investigated. With the increase of MSWI FA addition, the compressive strength of geopolymer showed a trend of first increasing and then decreasing. Mechanical and thermal activation had a significant effect on the properties of geopolymers through improving the reactivity of raw materials and promoting hydration reaction. Various characterization methods indicated hydration products such as CSH, CASH and NASH gel were generated in geopolymers. In terms of S/S of pollutants, geopolymers exhibited excellent capability. Compared with MSWI FA, the concentration of heavy metals, especially Pb, in the leachate from geopolymers was significantly reduced due to the transformation of heavy metals into more stable forms. Moreover, mechanical and thermal activation could promote the S/S of heavy metals, except Pb and Zn. After geopolymerization, the total TEQ of PCDD/Fs decreased from 42.8 to 4.7 ng TEQ/kg with the IE of 45.09%. This article provides a new method for the collaborative resource utilization of MSWI FA, CDW and GGFBs.

Automated summary

This study analyzed the feasibility of utilizing geopolymers to recycle MSWI FA and found that geopolymers can improve their properties by enhancing the reactivity of raw materials and promoting hydration reactions. Geopolymers also exhibit excellent capability in solidification/stabilization of pollutants.