Tech Briefs Magazine - August 2021 - 45

Using Wood Byproducts to Produce Sustainable Bioplastics
The high-quality bioplastics can be molded into a film that can be used in plastic bags
and packaging.
Yale University, New Haven, Connecticut
fforts to shift from petrochemical
plastics to renewable and biodegradable
plastics have proven tricky - the
production process can require toxic
chemicals and is expensive, and the
mechanical strength and water stability is
often insufficient. Now, researchers have
used wood byproducts to produce more
durable and sustainable bioplastics.
The process deconstructs the porous
matrix of natural wood into a slurry. The
resulting material shows a high mechanical
strength, stability when holding liquids,
and UV-light resistance. It can also
be recycled or safely biodegraded in the
natural environment and has a lower life -
cycle environmental impact when compared
with petroleum-based plastics and
other biodegradable plastics.
E
To create the slurry mixture, the re -
searchers used a wood powder - a processing
residue usually discarded as
waste in lumber mills - and deconstructed
the loose, porous structure of
the powder with a biodegradable and
recyclable deep eutectic solvent (DES).
The resulting mixture - which features
nanoscale entanglement and hydrogen
bonding between the regenerated lignin
and cellulose micro/nanofibrils - has a
high solid content and high viscosity
that can be casted and rolled without
breaking.
A comprehensive lifecycle assessment
tested the environmental impacts of the
bioplastic against common plastics. Sheets
of the bioplastic were buried in soil, fracturing
after two weeks and completely
degrading after three months; additionally,
researchers say the bioplastic can be
broken back down into the slurry by
mechanical stirring, which also allows for
the DES to be recovered and reused.
The bioplastic can be molded into a
film that can be used in plastic bags and
packaging - one of the major uses of
plastic and causes of waste production.
Because the bioplastic can be molded
into different shapes, it has potential for
use in automobile manufacturing as
well. The team has begun working with
a forest ecologist to create forest simulation
models, linking the growth cycle of
forests with the manufacturing process.
For more information, contact Josh
Anusewicz at joshua.anusewicz@yale.edu;
203-436-8994.
Method Recovers Metals from Electronic Waste
The technology recovers pure and precious metals from alloys in cellphones and other
electrical waste.
Iowa State University, Ames
nspired by nature's work to build spiky
structures in caves, engineers have de -
veloped a method to recover precious
metals from electronic waste. Using controlled
applications of oxygen and relatively
low temperatures, the engineers
say they can de-alloy a metal by slowly
moving the most reactive components to
the surface, where they form stalagmitelike
spikes of metal oxides. That leaves
the least-reactive components in a purified,
liquid core surrounded by brittle
metal-oxide spikes.
I
The structure formed when the metal
is molten is analogous to filled cave structures
such as stalactites or stalagmites.
Instead of water, the team used oxidation
to create the structures. The work demon -
strates the controlled be havior of surface
oxidation in metals and its potential in
design of new particle structures or
purification/de-alloying. By tuning oxidation
via temperature, oxidant partial
pressure, time, and composition, a balance
between reactivity and thermal
deformation enables un precedented mor -
phologies that could be useful in recoverTech
Briefs, August 2021
Cov
New technology uses heat and oxidation to recover pure and precious metals from electronic
waste. It works in two ways: it can bring the most reactive components to the surface, forming stalagmite-like
spikes (left), and it can leave the least reactive components in the core surrounded by
metal-oxide spikes, creating a " ship-in-a-bottle " structure (right). (Photo courtesy of Martin Thuo)
ing precious metals from e-waste or
mixed-metal materials.
The team demonstrated that traditional
electrochemical or high-temperature
methods (above 1,832 °F) may not be
necessary in metal purification, as the
metal's reactivity can be used to drive separation.
The oxidation technology works
well at temperatures of 500 to 700 °F.
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ToC
Besides metal purification and recovery,
the method could also be applied to
metal speciation - the ability to dictate
creation and distribution of certain
metal components. One use could be
production of complex catalysts to drive
multi-stage reactions.
For more information, contact Martin
Thuo at mthuo@iastate.edu; 515-294-8581.
45

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Tech Briefs Magazine - August 2021

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