PHYSICAL, CHEMICAL AND STRUCTURAL EVOLUTIION OF ZEOLITE-CONTAINING WASTE FORMS PRODUCED FROM METAKAOLINITE AND CALCINED SODUIM BEARING WASTE (HLW AND/OR LLW)
Zeolites can adsorb liquids and gases, take part in catalytic reactions and serve as cation exchange media. They are commercially available as finely divided powders. Using zeolites to manage radioactive waste is not new, but a process by which zeolites can be made to act both as a host phase and a cementing agent is. It is notable that zeolites occur in nature as well consolidated/cemented deposits. The Romans used blocks of Neapolitan zeolitized tuff as a building material and some of these buildings are still standing. Zeolites are easy to synthesize from a wide range of both natural and man-made precursor materials. The method of making a ''hydroceramic'' is derived from a process in which metakaolinite (thermally dehydroxylated kaolinite) is slurried with a dilute sodium hydroxide (NaOH) solution and then reacted for hours to days at mildly elevated temperatures (60-200 C). The zeolites that form in solution are finely divided powders containing micrometer sized crystals. However, if the process is changed and only enough concentrated sodium hydroxide solution (e.g. 12 M) is added to the metakaolinite to give the mixture a putty-like consistency and the mixture is then cured under similar conditions, the mixture becomes a very hard ceramic-like material containing distinct tectosilicate crystallites (zeolites and feldspathoids) imbedded in an X-ray amorphous sodium aluminosilicate hydrate matrix. Due to the material's vitreous character, the composite has been called a hydroceramic. Similar to zeolite/feldspathoid powders, a hydroceramic is able to sequester cations and a wide range of salt molecules (e.g., nitrate, nitrite and sulfate) in lattice positions and within structural channels and voids thus rendering them ''insoluble'' and making them an ideal contingency waste form for solidifying radioactive waste. The obvious similarities between a hydroceramic waste form and a waste form based on solidified Portland-cement grout are superficial because their chemistries are entirely different. In addition to being vastly superior to conventional Portland cement grouts with respect to salt retention, standard radwaste leach protocols (PCT, TCLP) have shown that hydroceramics also do a better job of immobilizing the RCRA-toxic and radioactive components of liquid sodium bearing waste (SBW) now in storage at DOE's Hanford, Savannah River and Idaho sites.
- Research Organization:
- Pittsburgh State University, University Park, PA (US)
- Sponsoring Organization:
- USDOE Office of Science (SC) (US)
- DOE Contract Number:
- FG07-98ER45726
- OSTI ID:
- 834996
- Report Number(s):
- EMSP-81963-2003; R&D Project: EMSP 81963; TRN: US0407413
- Resource Relation:
- Other Information: PBD: 15 Jun 2003
- Country of Publication:
- United States
- Language:
- English
Similar Records
Physical, Chemical and Structural Evolution of Zeolite-Containing Waste Forms Produced from Metakaolinite and Calcined Sodium Bearing Waste (HLW and/or LLW)
Physical, Chemical and Structural Evolution of Zeolite-Containing Waste Forms Produced from Metakaolinite and Calcined HLW
Related Subjects
54 ENVIRONMENTAL SCIENCES
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BEARINGS
BUILDING MATERIALS
CATIONS
GROUTING
HYDRATES
KAOLINITE
MIXTURES
NITRITES
PORTLAND CEMENT
RADIOACTIVE WASTES
SAVANNAH RIVER
SODIUM HYDROXIDES
WASTE FORMS
WASTES
ZEOLITES