WC137 JulyAug 2024 - Magazine - Page 19
Additionally, the production of activated carbon often involves the
use of highly polluting materials like coal or petroleum products.
Depending on what the activated carbon is made from, the
properties that make activated carbon useful for water filtration,
namely surface area and surface charge, can vary. That means not
all activated carbon is equal when treating pollutants.
Fortunately, the approach to generating activated carbon by
way of soft plastic proved successful in the application of removing dyes. With this success, Mekonnen decided to take this same
approach with epoxy resin.
Epoxy resin is a thermoset plastic, or hard plastic, used for
things like wind turbines, ship parts, or circuit boards. These
plastics are more difficult to work with than their soft plastic
counterparts used for water bottles due to the nature of their
chemistry.
“Think of spaghetti. You cook it, you can freeze it, and the
next day when you try to eat it, you see that it’s all attached
together. But if you warm it up and pour some warm water on
it, it regains its flexibility,” said Mekonnen. “But, imagine the
spaghetti chains are welded together. There’s no way to soften it.
Thermosets are like that.”
After much experimentation, the team found a way to turn
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what is otherwise seen as a non-recyclable plastic due to the inability to use thermo-mechanical processes into activated carbon.
“What we found out is it’s highly porous, but it doesn’t have
any charge, so we thought we could use this to capture very tiny
particles. And what’s a major problem in the environment? We
thought of nanoplastics,” said Mekonnen.
Highly porous might mean different things to different
people. To put it in perspective, the surface area of the activated
carbon generated from epoxy resin is 1,700 square metres per
gram, which is equivalent to four basketball courts.
In the case of nanoplastics, the high porosity or surface area
and low charge is all that was proven needed in lab studies. The
charge isn’t an issue because the capture of nanoplastics happens
via physical adsorption. As water flows through the activated carbon, the nanoplastics become lodged within the pore structures.
At this point, there are a few ways the nanoplastics can be
dealt with. The first is to remove the activated carbon with the
trapped nanoplastics into a controlled landfill. Simple. The second could be to wash out the nanoplastics and separate them so
the activated carbon can be reused several times.
The third option is to reactivate it, a process Mekonnen and
his lab are looking into.
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WAT E R C A N A D A . N E T
WATER C AN ADA • JULY/AUGUS T 2024
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