Stable solidification of silica-based ammonium molybdophosphate by allophane: Application to treatment of radioactive cesium in secondary solid wastes generated from fukushima

Yan Wu; Chuan-Pin Lee; Hitoshi Mimura; Xiaoxia Zhang; Yuezhou Wei

doi:10.1016/j.jhazmat.2017.07.044

Stable solidification of silica-based ammonium molybdophosphate by allophane: Application to treatment of radioactive cesium in secondary solid wastes generated from fukushima

J Hazard Mater. 2018 Jan 5:341:46-54. doi: 10.1016/j.jhazmat.2017.07.044. Epub 2017 Jul 21.

Authors

Yan Wu¹, Chuan-Pin Lee², Hitoshi Mimura³, Xiaoxia Zhang¹, Yuezhou Wei⁴

Affiliations

¹ School of Nuclear Science and Engineering, Shanghai Jiaotong University, Shanghai, 200240, PR China.
² Department of Earth Sciences, National Cheng Kung University, Tainan City, 70101.
³ Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan.
⁴ School of Nuclear Science and Engineering, Shanghai Jiaotong University, Shanghai, 200240, PR China. Electronic address: yzwei@sjtu.edu.cn.

PMID: 28768220
DOI: 10.1016/j.jhazmat.2017.07.044

Abstract

Silica-based ammonium molybdophosphate (AMP/SiO₂) is an absorbent material that can effectively remove Cs from radioactive-contaminated wastewater (RCW) generated by Fukushima nuclide accident. Pressing/sintering method was used for final disposal of secondary waste (spent absorbent) to achieve the volume reduction of AMP-Cs/SiO₂ (AMP/SiO₂ saturation adsorption of Cs) and stable solidification of Cs by adding natural allophane. The structure of AMP-Cs completely collapsed at approximately 700°C, and most Mo and P species in AMP sublimed. The optimal sintering temperature was estimated as 900°C. The stable crystalline phase of Cs₄Al₄Si₂₀O₄₈ was recrystallized by the reaction of Cs₂O, Al₂O₃, and SiO₂, and the immobilization ratio of Cs was approximately 100%. The leachability of Cs from the sintered product in distilled water was approximately 0.41%. The high immobilization and low leachability of Cs were attributed to the excellent solidification properties of the sintered products of AMP-Cs/SiO₂-allophane.

Keywords: Allophane; Ammonium molybdophosphate cesium; Cs(4)Al(4)Si(20)O(48); Fukushima NPP-1; Porous silica; Stable solidification.