Plastic waste is returned to black as virgin graphene, thanks to ACDC.
The laboratory’s research appeared in the Journal of the American Chemical Society ACS Nano.
Simply, instead of raising the temperature of the DC carbon source as in the original process, the laboratory first exposes the plastic waste to about eight seconds of high-intensity AC, followed by DC.
The products are high quality turbostratic graphene, a valuable and soluble substance that can be used to improve electronics, composites, concrete and other materials, as well as carbon oligomers, molecules that can be removed from graphene for use in other applications.
“We produce a significant amount of hydrogen, which is pure fuel, in our flashing process,” said student Rice and lead author Wala Algozeeb.
Tour estimated that on an industrial scale, the ACDC process could produce graphene for about $ 125 in electricity costs per tonne of plastic waste.
“We showed in the original paper that the plastic could be converted, but the quality of the graphene was not as good as we wanted it to be,” Tour said. “Now, using a different sequence of electrical impulses, we can see a big difference.”
He noted that most of the world’s plastic recycling technologies are inefficient and that only about 9% of the plastic produced is recycled. The most famous, Tour said, is an island the size of Texas-sized plastic waste that formed in the Pacific Ocean.
“We have to deal with this,” he said. “And there’s another problem: The microbes in the ocean that convert carbon dioxide into oxygen are hindered by the breakdown products of plastics, and they reverse the process by absorbing oxygen and converting it to carbon dioxide. It’s going to be really bad for people.”
Tour notes that converting lightning joules eliminates much of the cost of recycling plastics, including sorting and cleaning, which requires energy and water. “Instead of recycling plastic into pellets, which sell for $ 2,000 a ton, you could recycle to graphene, which has a much higher value,” he said. “There is both economic and environmental incentive.”
Despite the huge amount of plastic raw materials, too much graphene will not be a problem, Tour said. “Whatever you do with carbon, once you take it out of the ground with oil, gas or coal, it falls into the carbon 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 introduce the carbon cycle for hundreds of years.”
He noted that researchers are working to improve the process of flash graphene for other materials, especially food waste. “We are working to generate a good pulse sequence to turn food waste into very high quality graphene with as few emissions as possible,” he said. “We use machine learning programs to know where to go.”
The new study follows another recent article that features flash graphene produced from soot by heating with direct current joules. This paper, also in ACS Nano, combines microscopy and simulations to show two different morphologies: turbostratic graphene and wrinkled graphene sheets. The study describes how and why rearranged carbon atoms would take one form or another, and that the ratio can be controlled by adjusting the flash duration.
The lab instantly turns garbage into valuable graphene
Wala A. Algozeeb et al, Flash Graphene from plastic waste, ACS Nano (2020). DOI: 10.1021 / acsnano.0c06328
Provided by Rice University
Quote: Flash strategy for graphene scales for plastic waste (2020, October 30) downloaded on October 30, 2020 from https://phys.org/news/2020-10-graphene-strategy-plastic.html
This document is subject to copyright. Except for any fair transaction for the purpose of private examination or research, no part may be reproduced without written permission. The content is provided for informational purposes only.