The noble gases krypton and xenon are on the far right of the periodic table and have practical and important uses. For example, both are used for lighting. Xenon is the more useful of the two, having more applications in medicine and nuclear technology.
Unlike natural gas, which is plentiful underground, krypton and xenon make up only a small fraction of the earth’s atmosphere. To collect them, the gases must go through several cycles of an energy-intensive process called cryogenic distillation, in which air is captured and cooled down to about -300 degrees Fahrenheit. This extreme cooling separates the gases according to their boiling point.
A new krypton and xenon collection technology that saves energy and money is highly desirable. The researchers now believe they have found such a technique, and their method is detailed in the Journal of the American Chemical Society.
The team synthesized silicoaluminophosphate (SAPO), a crystal containing very small pores. Sometimes the pore size is between the size of a krypton atom and a xenon atom. Smaller krypton atoms can easily pass through the pores while larger xenon atoms get stuck. Thus, SAPO acts like a molecular sieve. (See picture.)
Using their new instrument, the authors showed that krypton diffuses 45 times faster than xenon, demonstrating its efficiency in noble gas separation at room temperature. Further experiments showed that not only did the xenon struggle to squeeze through these tiny pores, but it also tended to adsorb onto the SAPO crystals.
In an interview with ACSH, the authors said their previous analysis showed that their method could reduce the energy needed to collect krypton and xenon by about 30 percent. If this is true, then industrial scientists and fluorescent light enthusiasts will have much to be proud of.
Source: Xuhui Feng, Zhaowang Zong, Sameh K. Elsaidi, Jacek B. Jasinski, Rajamani Krishna, Praveen K. Tallapally, and Moises A. Carreon. “Kr/Xe separation on chabazite zeolite membranes”, J. Am. Chemical. Publication date (Internet): July 27, 2016 Article as soon as possible DOI: 10.1021/jacs.6b06515
Dr. Alex Berezov is a PhD microbiologist, science writer and speaker who specializes in debunking pseudoscience for the American Council on Science and Health. He is also a USA TODAY writers board member and a guest speaker at The Insight Bureau. Previously, he was the founding editor of RealClearScience.
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Post time: Jun-15-2023
