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Making Potable Water with Carbon Nanotubes

Close up pouring purified fresh drink water from the bottle on table in living room
 

There are genuine concerns in Florida that the underground aquifer that supplies most of the state’s fresh drinking water is running dry. Similar concerns about a lack of potable water are found in California, Arizona, and a number of other states. The good news is that science may have the solution by way of carbon nanotubes and desalinization.

More than 95% of the water on planet Earth is salt water. Across the globe, the world’s oceans represent a nearly inexhaustible supply of water if we could just find a cost-effective and efficient way to desalinate it. Potable water flows freely where desalinization is already being used, so we know desalinization is a workable strategy. Now we just have to find a way to do it better.

In Japan, researchers are already on the job looking for ways to make desalinization more lucrative. One particular research project recently reported by the Asian Scientist involves a reverse osmosis process involving membranes made from carbon nanotube composites. The research has gone well enough to this point to continue pressing forward with it.

How Reverse Osmosis Works

Reverse osmosis as a water purification method is a process by which water is passed through a semi permeable membrane in order to remove impurities. The key to making the process work is pressure. Applied pressure is used to overcome osmotic pressure, thereby leaving purified water on one side of the membrane and impurities on the other. In this case, the number one impurity is salt.

Reverse osmosis has proven to be a very effective way to desalinate seawater. But like any complicated scientific process, desalinization via reverse osmosis is expensive. A big part of the cost are the membranes used to filter the water. The membranes do not stand up well to the harsh operating conditions and cleaning treatments they are subjected to.

Japanese researchers believe they can make desalinization less costly by improving the strength and robustness of semi permeable membranes. This is where carbon nanotubes come into play. Carbon nanotubes are essentially carbon molecules that are joined into long strings and then rolled into tubes.

Carbon nanotubes are very strong and yet still fairly flexible. As such, the Japanese researchers believe they can be useful for creating semi permeable membranes by combining them with other nanocomposites. The carbon nanotubes would not do any filtering in and of themselves. Rather, they would strengthen and stabilize reverse osmosis membranes so that they last longer and perform better.

Carbon Nanotubes Have Proven Themselves

Asked why they chose to investigate carbon nanotubes for their project, the researchers explained that the nanotubes have already proven themselves in other fields. As reinforcing molecules, carbon nanotubes have been used to strengthen semi permeable concrete, for example. The researchers figured there is no reason to reinvent the wheel if there’s already a composite material they can use to create a better semi permeable membrane.

Assuming the Japanese researchers succeed, they could end up creating a whole new market for composite materials. It is easy to envision a scenario in which one manufacturer produces the carbon nanotubes while another combines those nanotubes with additional composites to create the semi permeable membranes necessary for desalinization. Just creating those membranes alone could be quite a big business venture.

Stateside, that could mean good things. A company like Utah-based Rock West Composites could seize the opportunity to expand by selling composite semi permeable membranes to desalinization plants in California and Florida, for example. At the same time, those states could finally get serious about addressing their ongoing concerns over running out of potable water.

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