https://www.sciencenews.org/article/tiny-magnetic-coils-could-help-break-down-microplastic-pollution
[links and images in online article]
Tiny magnetic coils could help break down microplastic pollution
In the lab, carbon nanotubes release chemicals that erode the durable trash
By Maria Temming
July 31, 2019
A new way to decompose microplastics could help clear waterways of these
tiny bits of trash, which may pose health risks to people and other animals.
Water treatment plants typically aren’t equipped to filter out
microplastics, such as exfoliating beads or flakes broken off larger
pieces of garbage, like water bottles (SN: 8/9/14, p. 9). Those pesky
particles can take decades to break down naturally, but new
nanomaterials that produce plastic-degrading chemicals could break down
this detritus much more quickly. In preliminary tests, the nanomaterials
cleansed some water samples of about half their microplastic content in
mere hours, researchers report online July 31 in Matter.
In the future, water treatment facilities that employ these
nanomaterials may not only help prevent new microplastic pollutants from
entering the environment, but also potentially remove the particles from
polluted waterways.
This water purification method uses nitrogen-coated carbon nanotubes.
When mixed with a compound called peroxymonosulfate, the nanotubes
generate chemicals known as reactive oxygen species, which crumble
microplastics into smaller chemical components. Heating the water speeds
up this process. Manganese embedded within each nanotube made the tubes
magnetic, allowing them to be fished out of water using magnets for reuse.
Jian Kang, a chemical engineer at Curtin University in Perth, Australia
and colleagues tested their technique on 80-milliliter water samples
contaminated with microplastic particles. Carbon nanotube treatment in
water warmed to 120° Celsius for eight hours reduced the amount of
microplastic in the water by about 30 to 50 percent.
Chemical by-products of this microplastic decomposition, such as
aldehydes and carboxylic acids, aren’t major environmental hazards, says
Long Chen, an environmental engineer at Northeastern University in
Boston not involved in the work. Kang’s team, for example, found that
exposing green algae to water containing the microplastic by-products
for two weeks didn’t harm the algae’s growth.
“There is a whole battery of tests” that could further gauge the
environmental risks of this technique, says Bart Koelmans, an
environmental scientist at Wageningen University & Research in the
Netherlands not involved in the work. Future experiments could
investigate effects on other major players in water ecosystems,
including phytoplankton, zooplankton and fish.
Using heat to facilitate microplastic breakdown may not be feasible for
purification plants that need to process lots of water quickly, Chen
says. But Kang and colleagues are now working to refine their nanotubes
to break down microplastics more efficiently without the help of high
temperatures.
“It’s great to have this option as a tool in a toolbox” to curb
microplastic pollution, Koelmans says. “It’s innovative, [and] it’s
great chemistry.” But devising new plastic cleanup strategies “should
not dismiss us from thinking about what the real problem is, and that’s
the [release] of plastic into places where it does not belong,” he says.
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