Engineers at the Washington University in St. Louis (WUSTL) have developed graphene-based biofoam sheets that can be laid on dirty or salty dams and ponds to produce clean drinking water, using the power of the sun. This new technique could be a cheap and simple way to help provide fresh water in countries where large areas of water are contaminated with suspended particles of dirt and other floating matter.
The reason behind of using graphene oxide sheets is that it is a good conductor of heat and electricity which can work wonders in treating contaminated water.
"We hope that for countries where there is ample sunlight, such as India, you'll be able to take some dirty water, evaporate it using our material, and collect fresh water," said Srikanth Singamaneni, associate professor of mechanical engineering and materials science at the School of Engineering & Applied Science.
"The process is extremely simple," said Srikanth. "The beauty is that the nanoscale cellulose fiber network produced by bacteria has excellent ability to move the water from the bulk to the evaporative surface while minimizing the heat coming down and the entire thing is produced in one shot."
"The design of the material is novel here," Singamaneni said. "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.
"Light radiates on top of it, and it converts into heat because of the graphene oxide -- but the heat dissipation to the bulk water underneath is minimized by the pristine nanocellulose layer. You don't want to waste the heat; you want to confine the heat to the top layer where the evaporation is actually happening."
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 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."