The mounting threats posed by climate change and pollution jeopardize global access to clean water, making desalination and other processes critical to humanity’s ability to survive and tackling various crises.
The new membrane could help mitigate such issues.
“The membrane can be used in purification of drinking water, desalination of brackish water, and the treatment of wastewater,” co-author Lin Zhang, a researcher at China’s Zhejiang University of Technology, said in an email. “In other words, the membrane can be applied in all fields where common nanofiltration membrane can be used.”
Nanofiltration is a fairly recent membrane filtration process typically used with surface water and fresh groundwater to soften and remove disinfection by-product precursors.
By controlling the evolution of the structures of the membrane, the team was able to raise the system’s water flux – the quantity that passes through a substance or surface – by 400 percent.
The team’s breakthrough also verifies one of British scientist Alan Turing’s greatest accomplishments. In 1952, Turing published his only chemistry paper, which contained his theory that by incorporating chemicals that both activate and inhibit a reaction, diffusion during the reaction process – under certain conditions – will produce molecular structures at specifically spaced distances from one another.
More than 60 years later, the team put Turing’s theory into practice by creating spotted and striped Turing structure to make permeable membranes that significantly boost water purification.
Tests showed that the system is very effective at separating water and salt, outperforming traditional nanofiltration membranes.
While the use of standard polymer membranes leads to a tradeoff where increased water permeability typically leads to less effective filtration of salts, the new system does not sacrifice one for the other.
“Microscopic characterization of the Turing-type membranes reveals that the spatial distribution of relatively higher water permeability sites agrees well with the corresponding Turing structures at the nanoscale,” the authors write.
“These unusual nanostructures, which are generated by diffusion-driven instability, enable outstanding transport properties in both water permeability and water-salt selectivity.”
Zhang credits Turing for the team’s achievement.
“Turing,” he said. “Turing gave us a great prediction, and we just apply it.”