Zeolites are porous aluminosilicate minerals that are used in everything from animal feed and detergents to water filtration and nuclear remediation. Now, a team of Swiss researchers have made a surprising new discovery about zeolites by applying the supercomputing power at the Swiss National Supercomputing Centre (CSCS).
The researchers – led by Sergey Churakov of the University of Bern – researched the stellerite group of zeolites, a subsection of the 93 minerals in the zeolite family. Within this group, they found an interesting effect when the cations in a stellerite-group zeolite were replaced with lead (Pb).
One important thing to know about zeolites: their generally useful crystalline structure degrades at high temperatures. But not so with the lead-exchanged stellerites: while their structures contracted under heat, they expanded again at temperatures over 125° Celsius. That behavior had not been observed in zeolites before this research.
“We first speculated that there are chemical reactions in the system, that basically the speciation of the cations is changing with temperature,” Churakov said in an interview with CSCS’ Simone Ulmer. “Speciation determines the chemical composition of lead complexes and thus their size. Normally one would expect that hydrated [lead] complexes will lose water molecules with higher temperature and become smaller in size, but there could be some dissociation of water and the oxidation of lead[.]”
The researchers turned to supercomputing to understand why these lead-exchanged zeolites were behaving differently – and, specifically, to CSCS’ Intel- and Nvidia-powered Piz Daint supercomputer, a 21.2 Linpack petaflops HPE Cray-built system that ranked 26th on the most recent Top500 list. Using a series of simulations on Piz Daint, the researchers were able to discover that in the lead-exchanged zeolites, the water that usually escapes zeolites when heated instead clustered with the lead molecules that remained trapped in the porous zeolite structure.
“Further research is aimed to reveal if other transition metals with rich redox chemistry can extend the thermal stability of zeolites and thus broaden the range of their industrial applications,” Churakov said. But, for now, the researchers are excited at the prospect of zeolites that can be used in higher-temperature environments.
To learn more about this research, read the reporting from CSCS’ Simone Ulmer here. You can also read the research paper, “Pbx(OH)y cluster formation and anomalous thermal behaviour in STI framework-type zeolites,” which was published in the September 2022 issue of Scientific Reports, at this link.