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montmorillonite

Montmorillonite is a clay mineral in the smectite group, characterized by a 2:1 layered silicate structure. It consists of two tetrahedral sheets of silicon-oxygen around a central octahedral sheet of aluminum or magnesium. Isomorphous substitution within the layers imparts a negative charge, which is balanced by exchangeable cations such as sodium or calcium in the interlayer spaces. The interlayer region can hold water, giving rise to strong swelling when hydrated.

Structurally, montmorillonite belongs to the montmorillonite–beidellite–nontronite subgroup and is the most common member of the montmorillonite

Occurrence and naming: montmorillonite was first described from Montmorillon in France and is a major component

Uses and applications: due to its swelling, plasticity, and sorption properties, montmorillonite is used in drilling

family.
Its
chemical
formula
is
often
represented
as
(Na,Ca)0.33(Al,Mg)2Si4O10(OH)2·nH2O,
reflecting
variable
cation
content
and
hydration.
The
mineral
has
a
high
surface
area
and
a
high
cation
exchange
capacity
(CEC),
typically
in
the
range
of
60–150
cmol(+)/kg,
making
it
highly
reactive
with
water
and
organic
molecules.
Swelling
behavior
is
pronounced
and
depends
on
the
interlayer
cations
and
hydration
state.
of
bentonite,
formed
from
alteration
of
volcanic
ash.
It
is
widespread
in
soils
and
sedimentary
rocks
and
is
a
key
swelling
clay
in
many
environmental
and
engineering
contexts.
fluids,
barrier
liners
for
landfills
and
containment,
absorbents
for
oils
and
chemicals,
cosmetics
and
pharmaceuticals
as
excipients,
and
as
a
reinforcing
phase
in
polymer
nanocomposites.
Health
and
safety
considerations
focus
on
inhalation
of
fine
powders
and
exposure
control
during
processing.