Durable plastic pollution – such as fishing nets – can be easily degraded without leaving harmful by-products thanks to a new high-tech process.
Disturbing images of wildlife – including sea turtles, dolphins and seals – tangled in abandoned fishing nets have become all too common.
Scientists explained that the main issue with Nylon-6 – the plastic inside fishing nets, carpet and clothing – is that it’s too strong and durable to break down on its own.
So, once it’s in the environment, it lingers for years, littering waterways, breaking corals and strangling birds and sea life.
Now, chemists at Northwestern University have developed a new catalyst that “quickly, cleanly and completely” breaks down Nylon-6 in a matter of minutes — without generating harmful by-products.
They say that the new process doesn’t require toxic solvents, expensive materials or extreme conditions, making it “practical” for everyday applications.
The research team, whose findings were published in the journal Chem. believe it could even perform the first step in upcycling Nylon-6 wastes into higher-value products.
Study senior author Professor Tobin Marks said: “The whole world is aware of the plastic problem.
“Plastic is a part of our society; we use so much of it.
“But the problem is: What do we do when we’re finished with it? Ideally, we wouldn’t burn it or put it into landfills. We would recycle it.
“We’re developing catalysts that deconstruct these polymers, returning them to their original form, so they can be reused.”
Up to one million pounds (453,000 kilos) of fishing gear is abandoned in the ocean each year – with fishing nets composed of Nylon-6 making up at least 46 percent of the notorious Great Pacific Garbage Patch, according to the World Wildlife Federation.
Lead first author Dr. Liwei Ye said: “Fishing nets lose quality after a couple years of use.
“They become so water-logged that it’s difficult to pull them out of the ocean.
“And they are so cheap to replace that people just leave them in the water and buy new ones.”
Marks said: “There is a lot of garbage in the ocean.
“Cardboard and food waste biodegrades. Metals sink to the bottom. Then we are left with the plastics.”
The team explained that current methods for disposing of Nylon-6 are limited to simply burying it in landfills.
When Nylon-6 is burned, it emits toxic pollutants, such as nitrogen oxides, which are linked to several health complications including premature death, or carbon dioxide, a potent greenhouse gas.
Although other labs have explored catalysts to degrade Nylon-6, those catalysts require extreme conditions – such as temperatures as high as 350 degrees Celsius, and high-pressure steam – which is energetically expensive and inefficient) or toxic solvents that only contribute to more pollution.
Marks said: “You can dissolve plastics in acid, but then you are left with dirty water.
“What do you do with that? The goal is always to use a green solvent. And what type of solvent is greener than no solvent at all?”
To bypass the issues, the researchers looked to a novel catalyst already developed in Marks’ lab.
The catalyst harnesses yttrium – an inexpensive Earth-abundant metal – and lanthanide ions.
When the researchers heated Nylon-6 samples to melting temperatures and applied the catalyst without a solvent, the plastic fell apart, reverting to its original building blocks without leaving by-products behind.
Marks said: “You can think of a polymer like a necklace or a string of pearls. In this analogy, each pearl is a monomer. These monomers are the building blocks.
“We devised a way to break down the necklace but recover those pearls.”
In experiments, Marks and his team were able to recover 99 percent of plastics’ original monomers.
He said, in principle, those monomers then could be upcycled into higher-value products, which are currently in demand for their strength and durability.
Marks said: “Recycled nylon is actually worth more money than regular nylon. Many high-end fashion brands use recycled nylon in clothes.”
He says the catalyst is “highly selective” – acting only on the Nylon-6 polymers without disrupting surrounding materials.
Marks said that means the industry could apply the catalyst to large volumes of unsorted waste and selectively target Nylon-6.
He added: “If you don’t have a catalyst that’s selective, then how do you separate the nylon from the rest of waste?”
“You would need to hire humans to sort through all the waste to remove the nylon. That’s enormously expensive and inefficient.
“But if the catalyst only degrades the nylon and leaves everything else behind, that’s incredibly efficient.”
Recycling the monomers also avoids the need to produce more plastics from scratch, according to the researchers.
Dr. Ye said: “These monomers are produced from crude oil, so they have a huge carbon footprint.
“That’s just not sustainable.”
After filing a patent for the new process, Marks and his team have already received interest from potential industrial partners.
They hope others can use their catalysts on a large scale to help solve the global plastic problem.
Dr. Ye said: “Our research represents a significant step forward in the field of polymer recycling and sustainable materials management.
“The innovative approach addresses a critical gap in current recycling technologies, offering a practical and efficient solution for the nylon waste problem.”
Dr. Ye added: “We believe it has implications for reducing the environmental footprint of plastics and contributing to a circular economy.”
Produced in association with SWNS Talker