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Engineers Use Graphene Oxide Sheets to Convert Dirty Water Into Clean Water

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Graphene oxide when incorporated into nanocellulose foam, scientists created a light, strong and highly flexible material that is capable of conducting heat and electricity faster and more efficient.

A team of engineers at the Washington University in St. Louis discovered a possible global game-changing way of utilizing graphene oxide sheets. Scientists used graphene sheets to change dirty water into potable water.

Srikanth Singamaneni, associate professor of Mechanical Engineering and Materials Science at the School of Engineering & Applied Science said that they are hoping that this discovery could help other countries especially those with ample sunlight, like India, collect dirty water and evaporate it using their material, and eventually turn it to potable water.

This new technique combines bacteria-produced cellulose and graphene oxide which then form a bi-layered biofoam. The research is fully detailed in an online magazine, Advance Materials (“Bilayered Biofoam for Highly Efficient Solar Steam Generation”).  Singamaneni added that the process of changing dirty water into drinkable water using their material is relatively simple. He said that the nanoscale fiber network that was produced by the bacteria has a great ability to move the water from the bulk to the evaporative surface while minimizing the heat coming down, and the whole thing is produced in just one shot. The professor also said that the design of the material is novel.

“You have a bi-layered structure with light-absorbing graphene oxide filled nanocellulose at the top and pristine nanocellulose at the bottom. When you suspend this entire thing on water, the water is actually able to reach the top surface where evaporation happens.”

Singamaneni further explained that when light radiates on top of it, the graphene oxide converts it into heat, but the heat dissipation to the bulk water below it is minimized mainly due to the presence of the nanocellulose layer.  Singamaneni also added  “You don’t want to waste the heat; you want to confine the heat to the top layer where the evaporation is actually happening.”

Acting as a sponge, the cellulose which is found at the bottom of the bi-layered biofoam draws water up to the graphene oxide where a very fast evaporation takes place. The fresh water obtained from this process can then be collected easily from the top of the sheet.

Aside from the design, the process in which the bi-layered biofoam is form is also novel. Akin to the way an oyster makes pearl, the bacteria forms layers of nanocellulose fibers in which the graphene oxide flakes gets implanted.

Qisheng Jiang, lead author of the research and a graduate student in the Singameni Laboratory said that they are culturing the bacteria for the cellulose, and flakes made from graphene oxide are added into the medium. And the graphene oxide becomes embedded due to the cellulose produced by the bacteria. After which, they stop the process, remove the medium with the graphene oxide and reintroduce another medium, creating another layer of the foam. Jiang also added that the interface is quite strong and robust.

“The new biofoam is also extremely light and inexpensive to make, making it a viable tool for water purification and desalination.”Cellulose can be produced on a massive scale,” Singamaneni further said, “and graphene oxide is extremely cheap — people can produce tons, truly tons, of it. Both materials going into this are highly scalable. So one can imagine making huge sheets of the biofoam.”

Lucy and Stanley Lopata Professor, Pratim Biswas said that the properties of the foam that they have synthesized have the capability to enhance solar energy harvesting, making it a really effective way to clean up water.

Biswas, who is also the chair of the Department of Energy, Environmental and Chemical Engineering, said “The synthesis process also allows addition of other nanostructured materials to the foam that will increase the rate of destruction of the bacteria and other contaminants, and make it safe to drink. We will also explore other applications for these novel structures.”

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