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

ABSTRACT

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.

KEYWORDS:

• Microwave sintering
• ceramics immobilisation
• chemical durability
• coal fly ash
• tiO₂

Acknowledgements

The authors sincerely appreciate the financial support from the Research and Development Program in key areas of Hunan Province (No. 2019SK2011), Hunan Provincial Innovation Foundation for Postgraduate (No. CX20210915), the National Natural Science Foundation of China (No. 11875164), and the Natural Science Foundation of Hunan Province (No. 2019JJ50497).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Education Department of Hunan Province: [Grant Number CX20210915]; National Natural Science Foundation of China: [Grant Number 11875164]; Yunnan Provincial Science and Technology Department: [Grant Number 2019JJ50497,2019SK2011].