Plastic waste turns black again like pristine graphene, thanks to the ACDC.
That is what the Rice University scientists call the process they have taken to efficiently use waste plastic that would otherwise cause additional environmental disaster on the planet. In this case, Rice chemist James Tour̵7;s lab modified its method for generating graphene flash in order to augment it for recycling plastic into graphene.
The laboratory research appeared in the journal American Chemical Society ACS Nano.
Simply put, instead of increasing the temperature of the carbon source with direct current, as in the initial process, the lab first exposes the plastic waste to a high-intensity alternating current for about 8 seconds, and then DC.
The products are high-quality turbine graphene, a valuable and soluble substance that can be used to strengthen electronics, composites, concrete and other materials, and carbon oligomers, The molecule can escape graphene for use in other applications.
“We generate a considerable amount of hydrogen, which is a clean fuel, in our flashing process,” said graduate student Rice and lead author Wala Algozeeb.
Tour estimates that on an industrial scale, the ACDC process can produce graphene at an electrical cost of about $ 125 per ton of plastic waste.
“We showed in the original paper that plastic can be converted, but the quality of graphene is not as good as we wanted it to be,” says Tour. “Now, using a series of different electrical impulses, we can see a big difference.”
He notes that most of the plastic recycling technologies in the world are ineffective and that only about 9% of the plastic produced is recycled. The most famous, Tour says, is an island of plastic trash the size of Texas that formed in the Pacific.
“We have to deal with this,” he said. “And there’s another problem: Microbes in the ocean that convert carbon dioxide to oxygen are being hampered by plastic decomposition products and they’re reversing the process, taking oxygen and converting it to carbon dioxide. That would be really harmful to humans. “
The tour notes that the joule flash conversion eliminates most of the costs associated with plastic recycling, including sorting and cleaning that requires energy and water. “Instead of recycling plastic into small pellets that sell for $ 2,000 a ton, you can use graphene, which has a much higher value,” he said. “There’s an economic drive as well as the environment.”
Despite the huge amount of plastic material available, having too much graphene should not be a problem, Tour said. “Whatever you do with carbon, once you’ve taken it off the ground from oil and gas or coal, it ends in the carbon dioxide cycle,” he said. “The good thing about graphene is that its biodegradation under many conditions is very slow, so in most cases it doesn’t go back to the carbon cycle for hundreds of years.”
He notes that the researchers are working to refine the graphene flash process for other materials, especially food waste. “We are working on creating a good pulse chain that turns food waste into high quality graphene with the least amount of emissions possible,” he said. “We are using machine learning programs to help us know where to go.”
The new study follows another recent paper that describes flash graphene is produced from black carbon via direct current joule heating. That paper, also in the ACS Nano, combined microscopy and simulation to show two distinct morphologies: turbine graphene and wrinkled graphene sheets. The study has described how and why the carbon atoms are rearranged to take one form or another, and this ratio can be controlled by adjusting the timing of the flash.
Lab turns trash into valuable graphene in the blink of an eye
Wala A. Algozeeb et al, Flash Graphene from plastic waste, ACS Nano (Year 2020). DOI: 10.1021 / acsnano.0c06328
Provided by Rice University
Quote: Graphene flash strategy for plastic waste (2020, October 30) retrieved October 30, 2020 from https://phys.org/news/2020-10-graphene-strategy-plastic.html
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