The future of cat litter lies ‘outside the litterbox’, according to a new study by a team of European scientists to be published in American Mineralogist in October. Sarah Day has the story.
Geoscientist Online, 19 July 2011
It might not look like much, but cat litter is composed of one of nature’s most useful and sought-after minerals – a clay known as sepiolite, or Meerschaum. At present, sepiolite is not particularly abundant in the Earth’s crust, and is only found in a few mines worldwide, most of which are clustered around Madrid – making Spain the world’s biggest exporter of the ‘wonder mineral’.
That could all change, thanks to the first ever atomic scale images of sepiolite, showing its crystalline structure in detail.
Well known for its lightweight porous structure, which is capable of absorbing two and a half times its own weight in water, sepiolite has been used since Roman times, when it was employed in the filtration and purification of wine. Since then its uses have been widespread, including industrial absorbents, an ingredient in drilling mud, odour removal in fridges and, of course, pet litter.
But until now, our understanding of how sepiolite’s tiny crystals are so good at absorbing liquids has been incomplete. As the crystals are only a few micrometres in length and a dozen or so atoms across, resolving their three dimensional structure has proved extremely difficult.
The team, including scientists from the Universities of Madrid and Salamanca in Spain, the Institut Laue-Langevin (ILL), the European Synchrotron Radiation Facility (ESRF) and the Spanish CRG Beamline at the ESRF, used single-crystal X-ray diffraction to obtain the images, using samples of sepiolite fibres from twenty different deposits around the world.
‘To study very small crystals’ explains Manuel Sanchez del Rio from the ESRF, ‘we use an X-ray beam with just 2 by 5 micrometres cross section. In the end, we collected X-ray diffraction data for two fibres’.
Even then, the results were hard to interpret. ‘We needed extensive computer simulations to confirm and refine the information gathered by electron diffraction experiments done in parallel at the University Complutense of Madrid’.