Egg whites used to produce a cheap, effective, water-purifying filter
As microplastics pollution and potable water scarcity both worsen, it's becoming increasingly important to find efficient ways of filtering and desalinating seawater. A new aerogel definitely holds some promise, and it's made from egg whites.
Princeton University's Prof. Craig Arnold first got the idea at a faculty meeting, when he was contemplating the bread in his sandwich. He thought that the bread's internal structure would work well if incorporated into a water-filtration aerogel, so he got his lab group to develop different bread recipes with added carbon.
Initially, none of the bread aerogels reproduced the structure well enough, so the team kept eliminating ingredients until they were left with nothing but egg whites and a small amount of carbon. "It was the proteins in the egg whites that were leading to the structures that we needed," said Arnold.
The current version of the aerogel reportedly removes salt and microplastic particles from seawater with 98% and 99% efficiency, respectively. And it's made simply by freeze-drying the egg protein/carbon mixture, then heating it to 900 ºC (1,652 ºF) in an oxygen-free environment. What results is a material with a bread-like structure, made up of interconnected carbon fiber strands and sheets of graphene.
The aerogel is claimed to work much better than activated carbon filters, and unlike reverse osmosis systems, it requires no electricity – instead, it just uses gravity to pull the seawater through. There's currently no word on the rate at which it filters water.
It should be noted that although eggs are reasonably cheap and plentiful, utilizing them to produce the aerogel would take away from the supply that could be used as food. That shouldn't be a problem, however, as it was discovered that similar commercially available proteins work just as well.
Arnold and colleagues are now working at scaling up the production process. It is hoped that the aerogel could ultimately be used not just for water filtration, but also in applications such as energy storage, soundproofing, and thermal insulation.
The research is described in a paper that was recently published in the journal Materials Today.
Source: Princeton University