Mechanical Optimization of Diatomite Monoliths fromFreeze Casting for High-Throughput Applications
2020
The silica cell walls of diatoms,
the abundant microalga 1–100
μm in size, show a highly ordered hierarchical porosity and
are widely available through their fossilized form known as diatomite.
The goal of this research was to use this cost-effective source of
porous silica in a unidirectional freezing process called ice-templating,
or freeze casting, to create a ceramic membrane with unidirectional
lamellar walls of ∼15 μm channels, which allows for an
efficient mass transport of fluids (i.e., low pressure drop), while
maintaining the optimal mechanical properties. Control over the monoliths
was explored by varying the mass ratio of diatomite and sodium carbonate
and the solid ratio in the initial slurry before freeze casting. The
resultant monolith properties were assessed using scanning electron
microscopy, mercury intrusion porosimetry, and mechanical testing.
The membranes then underwent an in-line vacuum filtration of methylene
blue dye and monodisperse latex beads to quantify the membrane filtration
performance through chemical adsorption and depth filtration capabilities,
respectively. Control over the material properties of the biosourced
ceramic monoliths allows for a cost-efficient and hierarchically porous
ceramic template with efficient mass transfer capabilities that can
be potentially functionalized with a variety of sophisticated nanomaterials
for various adsorbent, filter, catalysis, and sensor applications.
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