A novel hydrothermal method to convert incineration ash into pollucite for the immobilization of a simulant radioactive cesium

Zhenzi Jing, Wenbo Hao, Xiaojun He, Junjie Fan, Yi Zhang, Jiajun Miao, Fangming Jin

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

The Fukushima nuclear accident in Japan on March 11, 2011 produced huge amounts of Cs-polluted incineration ashes; conventional solidification methods seem unsuitable for the treatment of large amounts of Cs-polluted ashes. A novel hydrothermal method was developed to directly convert Cs-polluted incineration ash (rice husk ash) into pollucite to immobilize Cs in its crystal structure in situ. Results revealed that pollucite could be synthesized readily over a wide range of added Cs (Cs/Si = 0.2-0.6); the addition of more Cs (Cs/Si ≥ 0.5) caused the formation of a small amount of cesium aluminosilicate (CsAlSiO4), which exhibits poor immobilization behavior for Cs. Pollucite could be formed even for a short curing time (1h) or at a low curing temperature (150°C). However, a high curing temperature or a long curing time favored the formation of a pure pollucite. With the added calcium hydroxide, a tough specimen with a flexural strength of approximately 22 MPa could be obtained, which suggested that this technology may be applied directly to the solidification of Cs-polluted incineration ashes. Hydrogarnet and tobermorite formations enhanced the strength of the solidified specimens, and meanwhile the formed pollucite was present in a matrix steadily. Leaching test demonstrated that the amount of Cs that leached from the synthesized specimens was very low (0.49×10-5-2.31×10-5) and even lower than that from the reference hollandite-rich synroc (2.0×10-2), although a higher content of Cs was found in the synthesized pollucite specimens (6.0-31.7%) than in the reference (3.7%). Therefore, the hydrothermal conversion of Cs-polluted incineration ash into pollucite can be applied to immobilize Cs directly.

Original languageEnglish
Pages (from-to)220-229
Number of pages10
JournalJournal of Hazardous Materials
Volume306
DOIs
Publication statusPublished - 2016 Apr 5

Keywords

  • Hydrothermal synthesis
  • Immobilization
  • Incineration ash
  • Pollucite
  • Radioactive cesium

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis

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