Nanoscale Carbon Called Graphene Could Solve Water Scarcity

By Quinn Fucile | Mar 26, 2015 06:21 PM EDT

Carbon is arguably one of the greatest elements known to man. Not only is it the foundation of all organic molecules, and therefore life, but it also fueled the Industrial Revolution and its crystals are how we propose marriage. Okay so those last two might be a bit of a mixed bag, but carbon isn't done helping us yet.

Carbon nanotubes and graphene are essentially the rock stars in the world of nanotechnology and material science. They have applications in medicine, electronics, industry, and much much more. Now some researchers from the Oak Ridge National Laboratory are using carbon, in the form of graphene, to tackle humanity's water issue. (via Eureka Alert)

Only about 1% of the water on earth is naturally drinkable. Beyond that we also need a lot of fresh water for agriculture, hygiene, and industry. As the human population grows and more of that population is used to a modern lifestyle, we're going to need a lot more water. Saltwater is extremely abundant but the problem is converting it into fresh water.

One option for completing this task is distillation, boiling and collecting water vapor. A less energy intensive option is reverse osmosis, which involves pressing salt waters through a specialized membrane. That is where these researchers come in.

Right now, reverse osmosis systems rely on polymer membranes to filter out salt ions. These membranes require a lot water pressure, and therefore a lot of power to actually work. What these researchers are attempting to do is replace the polymer membranes with a single layer of carbon in the form of graphene.

To do that they first expose methane to 1000°C on a piece of copper foil. This catalyzes the reaction to deposit the single layer of carbon in a honeycomb pattern. Then they actually have to create pores in this sheet of carbon, since neither water molecules or salt ions pass through unmodified graphene. Currently the best method for doing this is exposing the graphene to an oxygen-based plasma.

Using a scanning transmission electron microscope, they were able to analyze different versions of the membrane at a single atom scale. The more pores they had the faster water was able to flow through the membrane, but too much and the material would lose structural integrity. Eventually they were able to create a membrane that allowed a rapid flow of water with nearly complete rejection of salt ions.

There are still some issues to work out but the hope is that a graphene membrane will be able to greatly outperform current polymer membranes. Making a reverse osmosis a more energy-efficient and convenient way of producing freshwater. 

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