The structure of the aerogel is formed by graphene sheets stretched across carbon fiber networks.

Egg whites used to whisk away microplastics from water

Image credit: Shaharyar Wani

Princeton Engineering researchers have turned egg whites into a new material that can cheaply remove salt and microplastics from seawater.

The scientists used egg whites to create an aerogel, a lightweight and porous material that can be used in many types of applications, including water filtration, energy storage, and sound and thermal insulation.

The idea came to Craig Arnold, vice dean of innovation at Princeton, who was working on developing new materials for engineering applications, during a faculty meeting.

“I was sitting there, staring at the bread in my sandwich,” he said. “And I thought to myself, this is exactly the kind of structure that we need.”

Arnold asked his lab group to make different bread recipes mixed with carbon to see if they could recreate the aerogel structure he was looking for. None of them worked quite right initially, so the team kept eliminating ingredients until only egg whites remained.

“We started with a more complex system,” Arnold said, “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.”

Egg whites are a complex system of almost pure protein that, when freeze-dried and heated to 900°C in an environment without oxygen, create a structure of interconnected strands of carbon fibres and sheets of graphene.

In a paper published in Materials Today, Arnold and his coauthors showed that the resulting material can remove salt and microplastics from seawater with 98 per cent and 99 per cent efficiency, respectively.

“The egg whites even worked if they were fried on the stove first, or whipped,” said Sehmus Ozden, first author on the paper. 

“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,” said Arnold.

Because other proteins also worked, the material can potentially be produced in large quantities relatively cheaply and without impacting the food supply. One next step for the researchers, Ozden noted, is refining the fabrication process so it can be used in water purification on a larger scale.

If this challenge can be solved, the material could have significant benefits because it is inexpensive to produce, energy-efficient to use and highly effective.

“Activated carbon is one of the cheapest materials used for water purification. We compared our results with activated carbon and it’s much better,” said Ozden. 

However, while Arnold sees water purity as a “major grand challenge,” he is also exploring other uses related to energy storage and insulation.

In July 2022, a University of Portsmouth study revealed that the UK’s wastewater infrastructure is increasingly vulnerable to “pollution events” due to climate change. That same month, the UK’s Environment Agency’s annual assessment found an increase in polluting activities from most of England’s water and sewage companies, with performance on pollution falling to its lowest level since 2013. 

In light of the “appalling” situation, the regulator called for the organisations’ executives to face prison time if they oversee serious and repeated pollution incidents. 

Earlier this month, Rice University researchers reprogrammed cells in Escherichia coli – a type of bacteria found in the environment, foods, and intestines of people and animals – to release an electrical current that can sense pollutants quicker than traditional methods.

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