Carbon nanotube membranes to 'take over' water purification

CNT membrane technology could reduce the costs of desalination as people around the world might be forced to use sea water in day to day life, a study says.

About 400 million of the global population are already using desalinated water especially in Israel, Saudi Arabia, and Australia, and estimates show that in a decade 14 per cent of people will have to resort to sea water to address the freshwater supply shortage.

However, according to researchers from the University of Malaya in Kuala Lumpur, CNT membranes can be a cost-effective solution for water purification.

Carbon nanotubes are tiny hexagonal tubes, made by rolling sheets of graphene, said Rasel Das, one of the authors of the paper published in the journal Desalination.

“They require little energy and can be designed to specifically reject or remove not only salt, but also common pollutants,” he added.

Current methods to desalinate water such as reverse osmosis, vacuum distillation, or a combination of the two, come at a very high cost in terms of energy, which, the paper said, means more greenhouse gases and more global warming.

Speaking about the properties of CNT membranes Eaqub Ali, co-author, said: "Because of their amazing chemical and physical properties, they allow frictionless passes of water through the pores, but reject most salts, ions, and pollutants, giving us purified water, probably in its best form."

"What makes CNTs special is that they have cytotoxic properties," he said. That means that the membranes naturally kill microbes that might otherwise foul up their surfaces. As a result, carbon nanotube membranes have the potential to last longer and may be reusable.

It’s not all good news, Sharifah Bee Abd Hamid, co-author, added. The pitfall at the moment is that CNT membranes are costly to produce, especially for large-scale uses.

For larger scale operations, CNT membranes need to be produced on thin films or fibre cloth composites and getting the membranes ready will need more research into material design.

Nonetheless, once these hurdles are overcome, membranes can be put to use in water-filtering pitchers or bottles, "to directly treat salty water at point of use," Hamid says, "it is a dream come true for many."

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