Princeton Engineers have created a material that can remove salt and microplastics from seawater using breakfast foods at a low cost.

An aerogel, a versatile material known for its light weight and porosity, was created by the researchers using egg whites. Water filtration, energy storage, and sound and thermal insulation are just a few of its many applications. The Susan Dod Brown Professor of Mechanical and Aerospace Engineering and vice dean of innovation at Princeton, Craig Arnold, directs a lab that works on engineering-related new materials like aerogels.

He had an idea one day while sitting in a faculty meeting.

Arnold stated, “I was sitting there, staring at the bread in my sandwich,” remarked Arnold, “And I thought to myself, this is exactly the kind of structure that we need.” Therefore, in order to determine whether they could replicate the aerogel structure he was seeking, he asked his lab team to prepare various bread recipes containing carbon. Since none of them worked well at first, the team kept testing and removing ingredients until only egg whites remained.

“We started with a more complex system,” Arnold stated, “and we just kept reducing, reducing, reducing, until we got down to the core of what it was. It was the proteins in the egg whites that were leading to the structures that we needed.”

When egg whites are freeze-dried and heated to 900 degrees Celsius in an atmosphere devoid of oxygen, they form a structure of carbon fiber strands and graphene sheets that are interconnected. Egg whites are a complex system made almost entirely of protein. Arnold and his coauthors demonstrated in a paper that was published on August 24 in Materials Today that the resulting material is capable of removing salt and microplastics from seawater with an efficiency of 98% and 99%, respectively.

Sehmus Ozden, the paper’s first author, stated, “The egg whites even worked if they were fried on the stove first, or whipped,” Ozden is a scientist at Aramco Research Center and previously worked as a postdoctoral research associate at the Princeton Center for Complex Materials. Ozden said that other proteins that are comparable and can be purchased commercially produced the same results as the regular egg whites used in the initial tests.

Arnold stated, “Eggs are cool because we can all connect to them and they are easy to get, but you want to be careful about competing against the food cycle.” The material may be able to be produced in large quantities at a low cost without affecting the supply of food because other proteins also function. Ozden mentioned that one of the researchers’ next steps would be to improve the fabrication procedure so that it could be used for water purification on a larger scale.

The material has significant advantages because it is inexpensive to produce, energy-efficient to use, and highly effective if this problem can be resolved. Ozden stated, “Activated carbon is one of the cheapest materials used for water purification. We compared our results with activated carbon, and it’s much better.” This filtration method uses only gravity to operate and does not waste any water, in contrast to reverse osmosis, which requires a significant amount of energy and excess water for operation.

Although Arnold regards the purity of the water as a “major grand challenge,” this material could also be used in other ways. He is also looking into other applications for insulation and energy storage.

The chemical and biological engineering and geosciences departments at Princeton and elsewhere contributed to the research. “It’s one thing to make something in the lab,” Arnold said, “and it’s another thing to understand why and how.” Professors Rodney Priestley and A. James Link from chemical and biological engineering, who identified the molecular transformation mechanism of the egg white proteins, were among the collaborators who assisted in answering the why and how questions. Water filtration measurements were made with the assistance of geosciences colleagues from Princeton.

The aerogel’s formation from egg white proteins was simulated theoretically by Susanna Monti of the Institute for Chemistry of Organometallic Compounds and Valentina Tozzi of the Instituto Nanoscienze and NEST-Scuola Normale Superiore.

The Princeton Center for Complex Materials and the National Science Foundation provided funding for the study.

Reference:  “Egg protein derived ultralightweight hybrid monolithic aerogel for water purification” by Sehmus Ozden, Susanna Monti, Valentina Tozzini, Nikita S. Dutta, Stefania Gili, Nick Caggiano, A. James Link, Nicola M. Pugno, John Higgins, Rodney D. Priestley and Craig B. Arnold, 24 August 2022, Materials Today.
DOI: 10.1016/j.mattod.2022.08.001


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