To optimize membranes used to separate industrial gases, scientists typically incorporate structures which attract the gas they want to obtain effectively enhancing the membranes permeability and improving target gas isolation. New research, however, has demonstrated the opposite can occur, where the membrane could bind too strongly to the target gas, slowing the permeability.
"It's very counterintuitive, and it challenges traditional thinking in gas separation science," said Haiqing Lin, professor of chemical and biological engineering at the University at Buffalo School of Engineering and Applied Sciences.
The study, recently published in the journal Science Advances, demonstrates this in a membrane constructed of crosslinked polyamines, a CO2 attracting polymer. Their experiments and simulations show that the crosslinked polyamines slow CO2’s passage through the membrane.
Based on those findings the team of researchers wondered if the membrane so effectively slows CO2’s movement, could it excel at separation hydrogen in a gas mixture? To test the theory the team conducted a set of experiments, ultimately revealing that the membrane achieved record setting selectively allowing hydrogen to pass through 1,800 times more easily than the CO2.
"Before this work, the best selectivity rates were around 100. So this really sets new benchmark in terms of performance," added Leiqing Hu, a former postdoctoral researcher at UB who is now an assistant professor at Zhejiang University in China.
"Industrial chemical separations presently require a tremendous amount of energy, up to 15% of global energy consumption," concluded Kaihang Shi, assistant professor of chemical and biological engineering at UB. "That's why membranes like this, due to their energy efficiency and absence of chemical wastes, are critically important to reducing carbon emissions and supporting cleaner industrial processes."