At Virginia Tech, through an innovative technique, researchers convert Polyethylene into soap through upcycling. This discovery is based on the unexpected similarity between polyethylene and fatty acids, which are used to make soap. The team successfully created short-chain polyethylene molecules by breaking down polyethylene chains using a new temperature-gradient thermolysis process. This can now be used to make soap.
Researchers from Virginia Tech have successfully developed an innovative technique, and they are making soap from polyethylene. The process involves transforming plastics into valuable surfactants. These chemicals are widely employed in the production of essential everyday products such as soap and detergent.
Plastics and soaps are vastly different in terms of their texture, appearance, and, more importantly, their practical applications. There is a surprising molecular connection between the two. Polyethylene, one of the most frequently employed plastics worldwide, exhibits a remarkably close resemblance to the chemical structure of a fatty acid. This fatty acid is used as a chemical precursor for the production of soap. Even though both materials are made from long chains of carbons, towards the end of the chain in fatty acids there is an extra group of atoms.
The similarities between polyethylene and fatty acids led Guoliang “Greg” Liu, an associate professor of chemistry at Virginia Tech College of Science, to believe that it was possible to convert polyethylene into fatty acids. With a few extra steps, this could be used to make soap. He needed to find a way to break a long polyethylene chain into shorter chains, but not too short.
Efficiency was also important. Liu firmly believed that there existed an immense opportunity to revolutionize the process of upcycling, by transforming the seemingly insignificant plastic waste into a valuable and practical commodity.
Source of Inspiration
While enjoying a cozy winter evening by the fireplace, Liu had a moment of inspiration. He observed the smoke rising from the fire and realized that it consisted of small particles created when the wood burned. While it is important to avoid burning plastics in fireplaces due to safety and environmental concerns, Liu’s curiosity was piqued as he contemplated the potential outcome of safely burning polyethylene in a laboratory.
The Blackwood Junior Faculty Fellowship holder in Life Sciences in the Department of Chemistry, Liu said, “Firewood is mostly made of polymers such as cellulose. The combustion of firewood breaks these polymers into short chains, and then into small gaseous molecules before full oxidation to carbon dioxide.”
“If we similarly break down the synthetic polyethylene molecules but stop the process before they break all the way down to small gaseous molecules, then we should obtain short-chain, polyethylene-like molecules,” Professor Liu added.
Liu collaborated with Zhen Xu and Eric Munyaneza, two Ph.D. chemistry students in his lab, to construct a compact and efficient reactor resembling an oven. This innovative design facilitated the application of temperature-gradient thermolysis to heat polyethylene, yielding extraordinary results.
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The Process
The oven reaches a temperature at the bottom that is sufficiently high to rupture the polymer chains, while at the top, it is cooled down to a low enough temperature to prevent any further breakdown. Following the thermolysis process, they collected the remaining substance, resembling the removal of soot from a chimney. To their delight, Liu’s intuition had proven correct as it consisted of short-chain polyethylene, specifically, in the form of waxes.
According to professor Liu, “This was the first step in developing a method for upcycling plastics into soap.”
The researchers convert polyethylene into soap through upcycling, which is the world’s first soap out of plastics. The team then added a few more steps, like saponification, a process involved in soap making. In order to advance the process further, the team sought the assistance of computational modeling experts, economic analysts, and other professionals.
A number of these experts were brought on board thanks to their connections with the Macromolecules Innovation Institute at Virginia Tech. The group worked collaboratively to carefully document and enhances the upcycling process, reaching a point where it is now prepared to be shared with the scientific community.
Zhen Xu, the lead author of the paper said, “Our research demonstrates a new route for plastic upcycling without using novel catalysts or complex procedures. In this work, we have shown the potential of a tandem strategy for plastic recycling. This will enlighten people to develop more creative designs of upcycling procedures in the future.”
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Applicable on Other Plastics
Polyethylene was the initial plastic that motivated this project. However, the upcycling method can also be applied to another plastic called polypropylene. From product packaging to food containers to fabrics, these two materials form a significant portion of the plastics that consumers come across on a daily basis.
Advantages of the Upcycling Technique
Liu’s innovative upcycling method is advantageous in the following ways.
- In comparison to certain recycling techniques currently in use, it eliminates the need for particular plastic sorting to prevent contamination.
- It can seamlessly process both types of plastics simultaneously, eliminating the need for laborious separation.
- Not only does this contribute to the cost-effectiveness of the method, but it also minimizes its environmental footprint.
- This upcycling technique only requires plastic and heat to begin with. While the subsequent stages of the process do call for some extra ingredients to convert the wax molecules into fatty acids and soap, the initial conversion of the plastic is a simple and direct reaction.
Requirements to Make Upcycling Effective
In order for upcycling to have a significant impact, the end product must possess enough value to not only offset the expenses of the process but also render it more economically attractive than the available recycling alternatives. Soap and related products are in high demand, similar to the demand for plastics.
Professor Liu said, “This research lays the groundwork for a new way to reduce waste by channeling used plastics into the production of other useful materials.”
He hopes that recycling facilities worldwide will gradually adopt this technique. Consumers may eventually be able to purchase innovative and sustainable soap products that help reduce plastic waste in landfills.
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“For this reason, turning plastics into soaps can be demonstrated to be economically viable,†added Professor Liu.
Lead author Zhen Xu said, “It should be realized that plastic pollution is a global challenge rather than a problem of a few mainstream countries. Compared to a sophisticated process and complex catalyst or reagent, a simple process may be more accessible to many other countries worldwide. I hope this can be a good start for the war fighting plastic pollution.”
Professor Liu holds membership in the nanoscience program, a prestigious part of the College of Science’s esteemed Academy of Integrated Science. Moreover, he is also affiliated with the Department of Materials Science and Engineering within the renowned Virginia Tech College of Engineering. The researchers convert polyethylene into soap through upcycling and the project involved collaboration with researchers from the Department of Chemical Engineering. The collaboration played a vital role in contributing to the research paper’s development.
Source Chemical upcycling of polyethylene, polypropylene, and mixtures to high-value surfactants
