Using pressure to swell pores, not crush them

July 16, 2013 by Steven Powell
Using pressure to swell pores, not crush them

More than a decade ago, Thomas Vogt and Yongjae Lee, then colleagues at Brookhaven National Laboratory, uncovered a counter-intuitive property of zeolites. When they put these porous minerals in water, and then put the water under high pressure, the tiny cavities within the zeolites actually grew in size.

Pressure failed to crush, and even caused expansion. In the years since, Vogt and Lee, now at the University of South Carolina and Yonsei University (Seoul), respectively, have followed up with cation exchange experiments, placing a series of alkali into the pores of the aluminosilicate , particularly focusing on natrolite. X-ray diffraction studies, in collaboration with Chi-Chang Kao at Stanford University, have revealed the interior geometry of the cavities and the arrangement of the cations and water molecules held within, before and after pressurization.

The team has just published a detailed characterization of Li+, Na+, K+, Rb+ and Cs+ natrolites, the first four of which, when treated under pressure in water, become "super-hydrated" with water molecules – that is, the process inserts more water molecules into the zeolites than are present under .

The and ions together adjust the surrounding aluminosilicate framework. The team likens the shift in structure under pressure to what you see when you shift a "chatterbox," the children's fortune teller constructed from paper. The pressure-induced hydration can cause dramatic unit cell volume increases: more than a 20 percent expansion in Li-natrolite, for example.

The phenomenon is more than just an academic curiosity. The team is pursuing a number of applications in which a "tuned" cavity size that is triggered by pressure could be useful. Selectively – and irreversibly – trapping radioactive cations in a nuclear , for example, is just one area in which they've already demonstrated progress.

Explore further: Clays can expand under pressure

More information: dx.doi.org/10.1002/chem.201300591

Related Stories

Clays can expand under pressure

March 27, 2013

It was always believed that water is "squeezed" out of the clay structure under pressure but physicists at Umea University in Sweden together with German colleagues show that this appear to be not always true if excess of ...

Zeolite synthesis made easy

December 12, 2011

Zeolites are porous materials with perfectly regular pores and high surface area that can act as molecular sieves. This property has led to important applications including the purification of air or water such as the contaminated ...

Working backward: Computer-aided design of zeolite templates

June 18, 2013

(Phys.org) —Taking a page from computer-aided drug designers, Rice University researchers have developed a computational method that chemists can use to tailor the properties of zeolites, one of the world's most-used industrial ...

Recommended for you

Scientific advances can make it easier to recycle plastics

November 17, 2017

Most of the 150 million tons of plastics produced around the world every year end up in landfills, the oceans and elsewhere. Less than 9 percent of plastics are recycled in the United States, rising to about 30 percent in ...

The spliceosome—now available in high definition

November 17, 2017

UCLA researchers have solved the high-resolution structure of a massive cellular machine, the spliceosome, filling the last major gap in our understanding of the RNA splicing process that was previously unclear.

Ionic 'solar cell' could provide on-demand water desalination

November 15, 2017

Modern solar cells, which use energy from light to generate electrons and holes that are then transported out of semiconducting materials and into external circuits for human use, have existed in one form or another for over ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Doug_Huffman
not rated yet Jul 16, 2013
Zeolites are now used to polish reactor coolant water.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.