Study On The Stability Of The Solidified Products Of Municipal Solid Waste Incineration Fly Ash With Geopolymer

Fly ash, which is produced in the waste incineration process, is hazardous waste. Currently, solidification technology is applied to the disposal of the heavy metals contained in fly ash. Geopolymer have the advantages of corrosion resistance, high temperature resistance, cheap and easily available. The previous studies indicated that geopolymer were good solidification materials for incineration fly ash due to lower leaching concentrations of heavy metals and better compressive strength after the solidified process.It will be an attractive solution not only from the treatment for waste but also from the recovery of valuable materials in case of the resource utilization of solidified fly ash. Consequently, the study on fly ash solidified geopolymer used for building is an important subject.In this study, the probability of fly ash solidified geopolymer used for building is discussed, and the optimal formulation is determined. Studies on the stability of solidification MSWI fly ash with geopolymer, including solidified time, leaching concentration of heavy metals, acid-base resistance, sulphates resistance, biological stability and corrosion resistance with seawaterare, are conducted. In addition, both the economic benefit and environmental benefit for geopolymer solidified fly ash are analyzed.Conclusion: （ 1 ） The optimal formulation: oxide proportion is confirmed as n（SiO₂）/n（Al₂O₃）=5.1, n（Na₂O）/n（SiO₂）=0.3, When 40% MSWI fly ash was added.（2） Fly ash solidified geopolymer has the advantage of high early strength. The compression strength is up to 20 MPa only when solidified time was 1 d.（3） There is little difference on leaching concentration of heavy metals which leaching in different pH solution.（4） The appearance of fly ash solidified geopolymer is not changed after immersed in thiobacillus thiooxidans solution （pH 1.9） for 28 d, and the compression strength is still up to 21.88 MPa.（5） The stability of fly ash solidified geopolymer immersed in low concentration basic solution were better. However, the structure of fly ash solidified geopolymer suffered serious damage from high concentration basic.（6） The results indicated that fly ash solidified geopolymer is a good sulfate resistance material due to the high corrosion resistance coefficient is still up to 1.06 in 28 d immersion time. The effects of different leaching time on leaching concentration of heavy metals are almost negligible.（7） The appearance of fly ash solidified geopolymer and normal weight loss rates are not changed after immersed in artificial seawater. With the increasing of leaching time, the pressive strength is fluctuant and keeps above 30 MPa.（8） Compared with solidified with portland cement, fly ash solidified geopolymer slightly higher cost, based on the same compression strength and leaching concentration of heavy metals. However, the process of portland cement produces large amounts of CO₂ emissions, and which is far beyond that geopolymer produces.Consequently, fly ash solidified geopolymer used for building provides a new environmentally-friendly method for the disposal of MSWI. It has a good prospect, and it will effectively treat hazardous waste and realize the resource utilization.