Effect of TiO2 on the properties of microwave-sintered ceramics derived from coal fly ash for Nd-contaminated soil immobilization

Coal fly ash (hereinafter CFA) was employed to rapidly immobilise Nd-contaminated soil with the addition of TiO2 via microwave sintering technology. The effect of TiO2 doping on the phase composition, microstructure, elemental distribution, density, and chemical durability of the solidified samples was systemically investigated. The results indicated that the Nd element can be incorporated in the matrix with oxyapatite and pyrochlore as TiO2 content increased at 1200°C. Moreover, the sintered sample with the high bulk density and low open porosity was fabricated at a TiO2-doping amount of 7 wt.%. Meanwhile, the as-prepared samples doping with TiO2 exhibited excellent chemical durability. Especially, the sintered sample doping with 3 wt.% TiO2 had the lowest leaching rate (7.97×10−6 g·m−2·d−1 at 28 d). Our investigation reflects that CFA is suitable for Nd-contaminated soil immobilisation via microwave sintering technology and the introduction of TiO2 is conducive to the improvement of densification and chemical durability.