More Desalination: Carbon nanotube membranes may reduce energy for desalination by 75%

A prior review of the state of desalination

A nanotube membrane on a silicon chip the size of a quarter may offer a cheaper way to remove salt from water.

Researchers at the Lawrence Livermore National Laboratory have created a membrane made of carbon nanotubes and silicon that may offer, among many possible applications, a less expensive desalinization. The team was able to measure flows of liquids and gases by making a membrane on a silicon chip with carbon nanotube pores making up the holes of the membrane. The membrane is created by filling the gaps between aligned carbon nanotubes with a ceramic matrix material. The pores are so small that only six water molecules could fit across their diameter.

“The gas and water flows that we measured are 100 to 10,000 times faster than what classical models predict,” said Olgica Bakajin, the Livermore scientist who led the research. “This is like having a garden hose that can deliver as much water in the same amount of time as fire hose that is 10 times larger.”

Salt removal from water, commonly performed through reverse-osmosis, uses less permeable membranes, requires large amounts of pressure and is quite expensive. However, these more permeable nanotube membranes could reduce the energy costs of desalination by up to 75 percent compared to conventional membranes used in reverse osmosis.

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