The Bentonite Barrier - Swelling Properties, Redox Chemistry and Mineral Evolution
Author
Summary, in English
assessment is performed for very long periods (100-1000 ka). This thesis focuses on the swelling of smectites in liquid
water, and analysis of bentonite from field experiments at Äspö Hard Rock Laboratory, Sweden. Four field experiments
were analyzed (Alternative Buffer Material experiment, ABM1, ABM2; Temperature Buffer Test, TBT; and Prototype)
with focus on Fe- redox chemistry and formation of trioctahedral smectite. The techniques used were mainly synchrotron
X-ray diffraction and X-ray absorption spectroscopy. In ABM1 and Prototype the Fe(II)/Fe-total ratio had increased. In
TBT no significant increase in Fe(II) was found; instead the corrosion products were dominated by Fe(III). Formation of
trioctahedral clays was found in the iron-bentonite experiments (ABM1, ABM2, TBT), but not in Prototype where the
heater instead was of copper. In swelling experiments, Ca-Wyoming montmorillonite was shown to expand and partly
form a four-water-layer hydrate at lower temperatures in water. This was studied in more detail, and the influence of
divalent interlayer cation, temperature, layer charge, salt and irradiation was investigated. Among the investigated
smectites, decreased temperature increased the crystalline swelling until ice was formed. Lower smectite layer charge
increased the crystalline swelling. Increasing the Gibbs hydration energy of the divalent interlayer cation increased the
crystalline swelling. Introduction of salt in the water partly dehydrated the montmorillonite at 20°C, but minimized the
dehydration of montmorillonite upon ice formation at low temperatures (-50, -100°C), especially with CaCl2. It was
found that in a gradient of ethylene glycol and water a 21 Å basal distance was formed in the montmorillonite, which was
higher than in the pure liquids.
Department/s
Publishing year
2015
Language
English
Full text
- Available as PDF - 10 MB
- Download statistics
Document type
Dissertation
Publisher
Centre for Analysis and Synthesis
Topic
- Chemical Sciences
Keywords
- montmorillonite
- bentonite
- smectite
- freezing
- thawing
- hydration
- intercalation
- four-water-layer
- ethylene glycol
- X-ray diffraction
- time-resolved
- spatial-resolution
- XANES
- Fe
- redox
- iron
- ABM
- TBT
- Äspö
Status
Published
Supervisor
ISBN/ISSN/Other
- ISBN: 978-91-7422-385-9
Defence date
9 March 2015
Defence time
13:15
Defence place
Lecture hall C, Kemicentrum, Lund University, Faculty of Engineering (LTH), Getingevägen 60, Lund
Opponent
- Jon Otto Fossum (Professor)