Remember the following words: Carbon nanotube (CNT) membranes. Researchers at the University of Malaya say these small tubes could play a big role in solving the world’s water crisis.
A report published in the journal Desalination, titled “Carbon Nanotube Membranes for Water Purification: A Bright Future in Water Desalination,” suggests nanotubes could potentially be used to treat sea and brackish water on a massive scale.
Water Crisis
According to the United States Geological Survey, freshwater accounts for only 2.5 percent of Earth’s water supply. Of that percentage, a good chunk is snow or located beneath the ground.
“The available supplies of water are decreasing due to increased population growth, low precipitation, competing demands from industry and more stringent health based regulations for agricultural and urban development,” says Nidal Hilal, the Editor-in-Chief of Desalination.
Nidal adds it’s crucial to find alternative water sources, which could including seawater, wastewater and even industrial water.
“Currently, about 400 million people are using desalinated water and it has been projected that by 2025, 14 percent of the global population will be forced to use sea water,” says Eaqub Ali, a researcher at the University of Malaya’s Nanotechnology and Catalysis Research Center located in Kuala Lumpur. He adds that engineered CNT membranes could help both current and future water purification needs.
This technology isn’t new per se; countries such as Israel and Australia already use desalination plants to provide water to their citizens. But as evaporation and rising seas continue to restrict freshwater, Ali and his team say demand for this technology will undoubtedly increase.
So what’s the issue with current desalination methods? A majority of the existing distillation plants count on reverse osmosis and vacuum distillation (or in some cases both methods). The problem is that these methods come with high price tags and emit greenhouse gasses.
What are nanotubes?
This is where nanotubes come into play. Nanotubes, which require very little energy, are essentially extremely small tubes. Author Rasel Das says the process of making nanotubes involves rolling sheets of graphene. The advantage of using nanotubes is they can be engineered to reject or remove salt, along with other common pollutants.
Nanotubes are frictionless, which boost their ability to purify water using a relatively small amount of energy. CNTs have cytotoxic properties, allowing them to self-clean. The membranes in CNTs have the ability to eliminate microbes that might compromise water, which is one of the reasons why they’re so unique.
“The hollow pores of the CNTs are extremely, extremely tiny,” Ali said. “However, 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.”
Tweaking the CNT membrane
The battle to use CNTs in the fight against water shortage isn’t over just yet; there are still a number of challenges that need to be addressed before these tiny tubes can be used on a massive scale. For starters, CNTs are quite costly to create at the moment. Additionally, the current membranes need to be tweaked so that their pores are more evenly distributed.
The researchers need to figure out a way that fiber cloth composites or thin films can be used to produce the CNT membranes, so that they can be developed on a larger scale.
“Most progress in desalination research is focused on demonstrating [the capability of CNT membranes] at a small scale,” said research paper co-author Sharifah Bee Abd Hamid.
Hamid said it will be “a dream come true for many” if these membranes could potentially be used to filter water bottles and pitchers.