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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
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    The future of recycling could one day mean dissolving plastic with   
   electricity    
      
     Date:   
         July 5, 2023   
     Source:   
         University of Colorado at Boulder   
     Summary:   
         Every year, consumers in the United States produce millions of   
         tons of plastic waste, and most of it winds up in landfills. New   
         research from chemists takes a first step toward making all that   
         trash vanish.   
      
      
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   Chemists at the University of Colorado Boulder have developed a new   
   way to recycle a common type of plastic found in soda bottles and other   
   packaging. The team's method relies on electricity and some nifty chemical   
   reactions, and it's simple enough that you can watch the plastic break   
   apart in front of your eyes.   
      
   The researchers described their new approach to chemical recycling July   
   3 in the journal Chem Catalysis.   
      
   The study tackles the mounting problem of plastic trash around the world.   
      
   According to the Environmental Protection Agency, the United States alone   
   produced nearly 36 million tons of plastic products in 2018. A majority   
   of the waste winds up in landfills, said study co-author Oana Luca.   
      
   "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 Luca, assistant professor in the Department of Chemistry. "We   
   wanted to find out how we could recover molecular materials, the building   
   blocks of plastics, so that we can use them again."  In the new research,   
   she and her colleagues got one step closer to doing just that.   
      
   The group focused on a type of plastic called polyethylene terephthalate   
   (PET), which consumers encounter every day in water bottles, blister   
   packs and even some polyester fabrics. In small-scale lab experiments,   
   the researchers mixed bits of that plastic with a special kind of molecule   
   then applied a small electric voltage. Within minutes, the PET began   
   to disintegrate.   
      
   The team has a lot more work to do before its recycling tool can take   
   a realistic bite out of the world's plastic trash problem. But it was   
   still fun to watch the waste, which can stick around in garbage piles   
   for centuries, disappear in a matter of hours or days, said study lead   
   author Phuc Pham.   
      
   "It was awesome to actually observe the reaction progress in real time,"   
   said Pham, a doctoral student in chemistry. "The solution first turns   
   a deep pink color, then becomes clear as the polymer breaks apart."   
   One person's trash Luca said it's a whole new way of thinking about the   
   possibilities of trash.   
      
   Recycling bins, she noted, may look like a good solution to the world's   
   plastics problem. But most municipalities around the world have struggled   
   to collect and sort the small mountain of rubbish that people produce   
   every day.   
      
   The result: Less than one-third of all PET plastic in the U.S. comes close   
   to being recycled (other types of plastic lag even farther behind). Even   
   then, methods like melting plastic waste or dissolving it in acid can   
   alter the material properties in the process.   
      
   "You end up changing the materials mechanically," Luca said. "Using   
   current methods of recycling, if you melt a plastic bottle, you can   
   produce, for example, one of those disposable plastic bags that we   
   now have to pay money for at the grocery store."  She and her team,   
   in contrast, want to find a way to use the basic ingredients from old   
   plastic bottles to make new plastic bottles. It's like smashing your Lego   
   castle so that you can retrieve the blocks to create a whole new building.   
      
   Another's treasure To achieve that feat, the group turned to a   
   process called electrolysis -- or using electricity to break apart   
   molecules. Chemists, for example, have long known that they can apply   
   a voltage to beakers filled with water and salts to split those water   
   molecules into hydrogen and oxygen gas.   
      
   But PET plastic is a lot harder to divide than water. In the new   
   study, Pham ground up plastic bottles then mixed the powder into a   
   solution. Next, he and his colleagues added an extra ingredient, a   
   molecule known as [N-DMBI]+ salt, to the solution. Pham explained that in   
   the presence of electricity, this molecule forms a "reactive mediator"   
   that can donate its extra electron to the PET, causing the grains of   
   plastic to come undone. Think of it like the chemistry equivalent of   
   delivering a karate chop to a wooden board.   
      
   The researchers are still trying to understand how exactly these   
   reactions take place, but they were able to break down the PET into   
   its basic building blocks -- which the group could then recover and,   
   potentially, use to make something new.   
      
   Deploying only tabletop equipment in their lab, the researchers reported   
   that they could break down about 40 milligrams (a small pinch) of PET   
   over several hours.   
      
   "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.   
      
   Luca, at least, has some big-picture ideas for the technology.   
      
   "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 said.   
      
   "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."   
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   Source: Materials provided by University_of_Colorado_at_Boulder. Original   
   written by Daniel Strain. Note: Content may be edited for style and   
   length.   
      
      
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   Journal Reference:   
      1. Phuc H. Pham, Stephen Barlow, Seth R. Marder, Oana   
      R. Luca. Electricity-   
         driven recycling of ester plastics using one-electron electro-   
         organocatalysis. Chem Catalysis, 2023; 100675 DOI: 10.1016/   
         j.checat.2023.100675   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/07/230705105825.htm   
      
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