Researchers from the University of Colorado Boulder have developed a new way to break down and recycle one of the most widely used forms of plastic for food packaging, consumer electronics, and clothing.
In a process called electrochemical plastic dissolution, the scientists utilized chemical reactions and electrolysis — which separates water into hydrogen and oxygen gas through electric currents — to disintegrate polyethylene terephthalate (PET) plastic in just a few hours.
"We pat ourselves on the back when we toss something into the recycling bin, but most of that recyclable plastic never winds up being recycled," said Oana Luca, an assistant professor at UC Boulder's Department of Chemistry and study co-author. "We wanted to find out how we could recover molecular materials, the building blocks of plastics, so that we can use them again."
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As detailed in the study published in the journal Chem Catalysis last July, the chemists ground the PET into a powder and mixed it into a solution with [N-DMBI]+ salt. The molecule is a "reactive mediator" that donates its spare electron to the PET particles when activated by a low electric voltage, causing the plastic to break down.
The researchers found that the electricity-driven recycling process could reduce about 40 milligrams of PET to its basic building blocks — which can then be recycled to create new products — over a few hours.
"It was awesome to actually observe the reaction progress in real time," Phuc Pham, a doctoral student in chemistry and lead author of the study, said. "The solution first turns a deep pink color, then becomes clear as the polymer breaks apart."
According to the National Renewable Energy Lab, the world produces about 90.4 million tons of PET annually to create single-use beverage bottles, jars, textiles, and packaging, making it one of the largest contributors to plastic waste.
Per the latest data from the EPA, just 29.1% of all PET bottles and jars in the U.S. were recycled in 2018. It's a higher rate than most other plastic types, as less than 9% of the 36 million tons of plastic waste that year was recycled, while over 75% ended up in landfills.
It's a concerning statistic since plastic pollution releases planet-warming gases as it decays, breaks down into harmful microplastics that can enter the food chain, and endangers the well-being of wildlife.
That makes this research, while not yet ready for large-scale operations, all the more crucial.
"If I were to have my way as a mad scientist, I would use these electrochemical methods to break down many different kinds of plastic at once," Luca added. "That way, you could, for example, go to these massive garbage patches in the ocean, pull all of that waste into a reactor, and get a lot of useful molecules back."
"Although this is a great start, we believe that lots of work needs to be done to optimize the process as well as scale it up so it can eventually be applied on an industrial scale," Pham said.
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