Nature inspired technique to help turn seawater into freshwater
Efforts to develop more efficient desalination techniques for converting seawater to freshwater are expected to gain a significant boost as researchers gain new insights into the molecular functioning of aquaporins, the water channels found in human cell membranes.
Growing population and climate change will pose a significant global challenge in terms of water availability in the coming years. Scientific communities all over the world are working to find better ways to convert saline water in seas and oceans into freshwater for domestic and industrial use. Despite the fact that various desalination technologies are available on the market today, their high energy consumption limits their widespread use.
To address the issues, a team of researchers at the Indian Institute of Technology (IIT) - Madras has been investigating the use of carbon nanotubes and graphene nanopores. Although studies have shown that graphitic carbon materials have a higher water permeation capability than conventional reverse osmosis membranes, the hydrodynamic resistance at their entrance reduces the rate of permeation. To solve this problem, the team looked to nature for inspiration.
They noticed that the hourglass shape of aquaporins aids in the simultaneous passage of water and the exclusion of ions/salts from it, so they decided to see if the same structure could improve the desalination efficiency of carbon nanomaterial-based membranes. The researchers discovered how and why the introduction of a conical or hourglass-shaped inlet improves water conduction in carbon nanotubes.
Prof. Sarith P Sathian, team leader, stated, "Our study reveals the mechanisms responsible for enhanced water permeation inside hourglass-shaped nanopores." It is possible that the same mechanisms can be replicated in a different system of nanopores, resulting in greater desalination efficiency. Second, when it comes to desalination via nanoporous membranes, ion rejection of the membrane is critical. According to our findings, the ion rejection is primarily determined by the size of the CNTs. As a result, it may be possible to design a nanopore geometry with a very high permeation capacity while maintaining ion rejection."
The research was carried out in collaboration with Swinburne University of Technology in Australia and Delft University of Technology in the Netherlands. It was a project sponsored by the Government of India's Department of Science and Technology as part of its Water Technology Initiative (WTI).
Mr. Vishnu Prasad Kurupath of IIT Madras, Dr. Sridhar Kumar Kannam of Swinburne University of Technology in Australia, and Dr. Remco Hartkamp of Delft University of Technology in the Netherlands comprised the team. The study's findings were published in the journal Desalination.