Global Water Shortage? Problem Solved Forever

Two materials scientists from MIT have shown in simulations that nanoporous graphene can filter salt from water at a rate that is 100 to 1000 times faster than today’s best commercial desalination technology, reverse osmosis (RO).

The researchers predict that graphene’s superior water permeability could lead to desalination techniques that require less energy and use smaller modules than RO technology, at a cost that will depend on future improvements in graphene fabrication methods.

Water Desalination across Nanoporous Graphene
David Cohen-Tanugi and Jeffrey C. Grossman*
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States

We show that nanometer-scale pores in single-layer freestanding graphene can effectively filter NaCl salt from water. Using classical molecular dynamics, we report the desalination performance of such membranes as a function of pore size, chemical functionalization, and applied pressure. Our results indicate that the membrane’s ability to prevent the salt passage depends critically on pore diameter with adequately sized pores allowing for water flow while blocking ions. Further, an investigation into the role of chemical functional groups bonded to the edges of graphene pores suggests that commonly occurring hydroxyl groups can roughly double the water flux thanks to their hydrophilic character. The increase in water flux comes at the expense of less consistent salt rejection performance, which we attribute to the ability of hydroxyl functional groups to substitute for water molecules in the hydration shell of the ions. Overall, our results indicate that the water permeability of this material is several orders of magnitude higher than conventional reverse osmosis membranes, and that nanoporous graphene may have a valuable role to play for water purification.

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3 responses to “Global Water Shortage? Problem Solved Forever

  1. Single-layer freestanding graphene is one atom thick.

    While interesting, this is a very long way from commercial application.

  2. Good news on junkScience.com, what a pleasant surprise.

  3. The problem can be solved even easier and much cheaper. It just requires overcoming attitudes. Given that water is probably the most common multi-atomic molecule in the universe, the earth has probably been gathering or “picking up” water from space since day 1. So, we probably have more on earth than we ever had. The issue is not the amount of water, but our attitudes about reusing water. In the early 1980s, I was told by the lead water quality chemist for Orange County, CA, that the best quality water in the entire county was discharged from the outlet of the wastewater treatment plant, but legally they couldn’t drink it, it had to be injected into the earth via a well, or discharged to a river. Nearly every molecule of water in a glassful has been reused millions of times. Someone pissed in your glass multiple times. So, stop wasting perfectly good water, and reuse it! Sure, we want to have adequate and reasonable safeties built in, but stop wasting resources. Another case of emotion ruling over science.

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