Synthetic kitty litter ingredient could have many other applications
By Ben Coxworth
July 13, 2011
Cat litter might not seem like a particularly exotic substance, but it contains a mineral known as sepiolite, which is actually rather remarkable. Mined from only a few sources worldwide, sepiolite is a type of clay that absorbs 2.5 times its weight in water - that's more absorbent than any other known mineral, or any manmade material. This is made possible by its crystalline structure, that maximizes the amount of internal surface area available for soaking up liquids ... such as cat pee. Recently, an international team of scientists have obtained X-ray diffraction microscope images of sepiolite for the first time. Using the information provided by those images, a cheaper, easier-to-source synthetic version of the mineral could be created, and used in everything from batteries to food.
The images were obtained at the European Synchrotron Radiation Facility (ESRF) in France, using an X-ray beam that measured just 2 by 5 micrometers across. The data was not easy to interpret, however, and needed to be run through computer simulations, where it was cross-referenced with data gathered in electron diffraction experiments conducted at the University Complutense of Madrid.
What the team discovered was that sepiolite is composed of elongated, needle-like crystals, that are packed together quite loosely. Tunnels within those crystals, along with the space between the crystals, serve as a capillary network that draws in liquid. Based on the two sepiolite fibers that were imaged, the total internal surface area of the mineral was found to range between 75 and 400 square meters per gram (90 and 478 squares yards per 0.3 oz). In practical terms, that equals out to 20 grams (0.64 oz) having a total internal surface area equivalent to that of a football field.
"Today, no synthetic clay surpasses natural sepiolite," said Mercedes Suárez from Spain's University of Salamanca. "This is about to change as our understanding of their atomic structure will guide the synthesis of sepiolites from other, more abundant clay minerals and the design of completely new materials for use in catalysis and batteries."
"The future of sepiolites in the household is outside the litterbox," added ESRF's Manuel Sanchez del Rio. "Already today, they absorb liquid spillages and odors and stabilize aqueous products like paints, resins and inks. In synthetic form, they could bind food products and stabilize drugs, extending their shelf life and making sepiolite an edible product."
Also participating in the study was France's Institut Laue-Langevin.
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