1 research outputs found
Water Radiolysis in Exchanged-Montmorillonites: The H<sub>2</sub> Production Mechanisms
The
radiolysis of water confined in montmorillonites is studied
as a function of the composition of the montmorillonite, the nature
of the exchangeable cation, and the relative humidity by following
the H<sub>2</sub> production under electron irradiation. It is shown
that the main factor influencing this H<sub>2</sub> production is
the water amount in the interlayer space. The effect of the exchangeable
cation is linked to its hydration enthalpy. When the water amount
is high enough to get a basal distance higher than 1.3 nm, then a
total energy transfer from the montmorillonite sheets to the interlayer
space occurs, and the H<sub>2</sub> production measured is very similar
to the one obtained in bulk water. For a basal distance smaller than
1.3 nm, the H<sub>2</sub> production increases with the relative humidity
and thus with the water amount. Lastly, electron paramagnetic resonance
measurements evidence the formation of a new defect induced by ionizing
radiation. It consists of a hydrogen radical (H<sub>2</sub> precursor)
trapped in the structure. This implies that structural hydroxyl bonds
can be broken under irradiation, potentially accounting for the observed
H<sub>2</sub> production