New Zealand Science Teacher

Graphene Membranes offer hope for the future

10/05/2017

We live on an ocean planet!  While this may be a revelation for some, it should be no surprise.  Nearly 71% of the surface of our world is covered by oceans, rivers, lakes and ice. Yet, despite this vast amount of water, only about 1% of this water is accessible as fresh water.  

Population growth, climate change, and economic growth will all put pressure on the availability of fresh water for future generations.  This is a major concern that will affect our children and the sustainability of our civilisation.  The United Nations predicts that by 2030 the world will face a 40% water deficit, if we continue with business as usual.

While there is a significant amount of research that continues to look for solutions to these issues through sustainable practices, political influence and new technologies, the issue of water availability has still been touted as the challenge of the century for humanity.  Now it seems some of the hard work and investment in scientific enquiry is about to offer one solution toward the problem.  

The vast majority of water on the planet is held as salty water in the oceans.  However, we can’t drink salty water!  Worse still, the ions that make up the salt in salty water (like sodium, chloride, potassium, magnesium, calcium and sulphate) are too small to be removed by even the best micro-filters.  This has made desalination a difficult technology to develop.  So far, the main options for removing the salts have been to treat the water chemically and to use distillation.  Chemical treatment essentially sticks the ions to bigger molecules that can be filtered out, and distillation evaporates the water and condenses it as fresh water, leaving behind a salty sludge.

Both of these processes are expensive, energy intensive and relatively slow.

 

Enter Nanotechnology.  New materials are being rapidly discovered and developed around the world by combining atoms in novel arrangements at an atomic level.  One such material is an allotrope of carbon.  With a structure similar to a fishing net made of carbon atoms with picoscopic (that’s 1,000,000,000 times smaller than microscopic!) holes it.  This material is called Graphene (Graff-een).  Recently, a team at the University of Manchester has developed a technique that could allow for affordable mass production of Graphene Oxide membranes, which could be used in desalination filters that could cope with removing the salt from sea water.  

 

The joint-lead authors of the paper published in Nature Nanotechnology, Mr. Jijo Abraham and Dr. Vasu Siddeswara Kalangi believe their technique is a breakthrough that could be applied to commercial production of membranes for separation of dissolved particles and gases.

 

“The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes.” said Mr. Abraham.

 

Although this new technology may indeed lead to efficient desalination plants, there will still be economic and political hurdles to overcome before the United Nations vision for water sustainability into the future is realised; but we are a step closer.