Experimental study of the transformation of smectite at 80 and 300 degrees C in the presence of Fe oxides
Experimental study of the transformation of smectite at 80 and 300 degrees C in the presence of Fe oxides
Clay Minerals (March 2004) 39 (1): 17-34
- bentonite
- clastic rocks
- clay mineralogy
- clay minerals
- experimental studies
- framework silicates
- hematite
- iron oxides
- magnetite
- montmorillonite
- Mossbauer spectra
- oxides
- saponite
- sedimentary rocks
- sheet silicates
- silicates
- smectite
- spectra
- synthesis
- TEM data
- transformations
- United States
- Wyoming
- X-ray diffraction data
- zeolite group
The alteration and transformation behaviour of montmorillonite (Wyoming bentonite) was studied experimentally to simulate the mineralogical and chemical reaction of clays in contact with steel in a nuclear waste repository. Batch experiments were conducted at 80 and 300 degrees C, in low-salinity solutions (NaCl, CaCl (sub 2) ) and in the presence or otherwise of magnetite and hematite, over a period of 9 months. The mineralogical and chemical evolution of the clays was studied by XRD, SEM, transmission Mossbauer spectroscopy and EDS-TEM. Experimental solutions were characterized by ICP-AES and ICP-MS. The main results are that no significant change in the crystal chemistry of the montmorillonite occurred at 80 degrees C, while at 300 degrees C, the presence of Fe oxides leads to a partial replacement of montmorillonite by high-charge trioctahedral Fe (super 2+) -rich smectite (saponite-like) together with the formation of feldspars, quartz and zeolites.
