‘Water water everywhere but not a drop to drink’. That particular phrase might have to be rewritten after a team of researchers produced a sieve out of graphene oxide with holes that are so small they can remove salt from seawater. It is yet another potential wonder product made out of the wonder material that is graphene which is known for its incredible strength and electrical conductivity. The key is having a membrane with holes small enough to trap the salt. Previous work has already proven that graphene oxide membranes can sieve out small nanoparticles, organic molecules and large salts. The smaller common salts required smaller sieves but during testing the membranes expanded when immersed in water, which allowed small salts to pass through the holes along with the water. The team of scientists from the University of Manchester led by Dr Rahul Nair appear to have a solution: attaching epoxy resin walls on either side of the membrane stops the swelling, allowing common salt to be trapped. Dr Nair explains “Water molecules can go through individually, but sodium chloride cannot. It always needs the help of the water molecules. The size of the shell of water around the salt is larger than the channel size, so it cannot go through”. Water on the other hand is able to quickly flow through the membrane, offering the tantalising prospect that the discovery could have major implications for desalination. “This is our first demonstration that we can control the spacing [of pores in the membrane] and that we can do desalination, which was not possible before. The next step is to compare this with the state-of-the-art material available on the market,” said Dr Nair. With the UN predicting 14% of the world’s population will face water scarcity by 2025, the stakes are high for Dr Nair and his team. Keep up the good work doctor, sounds like you are Nairly there.
April 17, 2017