核廢料處理的新技術－超臨界流體萃取

A New Technology for Nuclear Waste Management-Supercritical Fluid Extraction

王少芬(Joanna Shaofen Wang) ； 魏建謨(Chien M. Wai)

《化學》 61卷1期 (2003/03) Pp. 1-9

https://doi.org/10.6623/chem.2003001

摘要

在適當的螯合劑的存在下，超臨界二氧化碳流體可將金屬離子從固體樣品中直接分離而不需要酸堿溶解和有機溶劑萃取等步驟。錒系元素的氧化物如UO_2及U_3O_8亦可利用此方法直接溶解於超臨界二氧化碳流體中而分離。超臨界流體萃取放射性元素可大量減少二次廢料的產生並且比傳統的酸堿和有機溶濟萃取方法更為經濟和有效。本文綜述了近期超臨界流體萃取技術在核廢料處理和核工業方面的研究及發展。

關鍵字

超臨界流體萃取 ； 核廢料處理 ； 二氧化碳

並列摘要

Supercritical fluid extraction (SFE) is a new technology for removing organic contamination and metal species from solid materials. Carbon dioxide is widely used in SFE because of its moderate critical constants, non-flammable nature and low cost. The new SFE technology appears attractive with the conventional acid digestion and solvent extraction methods. In highly acidic solutions (3-6 M HNO_3), TBP or TBPO dissolved in SC-CO_2 can extract UO_2^(2+) and Th^(4+) effectively. A new CO_2-soluble TBP/HNO_3/H_2O complex can oxidize U(IV) in Uo_2 into U(VI) in the form of UO_2^(2+), forming soluble UO_2(NO_3)_2．2TBP complex. This new technology of dissolving solid UO_2 in SC-CO_2 without water and organic solvents has important applications for the nuclear fuel reprocess and nuclear waste management. Using sequential SFE process, organic contamination, toxic metals and radioactive elements can be removed separately from solid mixed waste without using acids and organic solvents. Information on SFE of lanthanide, actinides, strontium and cesium available in the literature is summarized in this paper. The possibility of utilizing the SFE techniques for treating mixed wastes and for reprocessing spent nuclear fuels is also discussed.

並列關鍵字

supercritical fluid extraction ； nuclear waste management ； carbon dioxide