Mechanochemically enhanced synthesis of isomorphously substituted kaolinites
A mechanochemical method for the rapid bulk synthesis of kaolinte has been developed. Metalhydroxides and silicic acid are mechanically ground and hydrothermally treated for as little as a day at 250C to produce X-ray pure crystalline materials. This approach has been expanced to allow the synthesis of kaolinites with a portion of the aluminium sites isomorphously substituted with other trivalent metals. The synthetic parameters, such as length of mechanical and hydrothermal treatment, were studied. Products were analyzed by powder X=ray diffraction, attenuated total reflectance infrared spectrometry, scanning electron microscopy, and transmission electron microscopy. The samples exhibited strong order along the c axis and less order along the a and b axes. Trivalent transition and rare earth metals were used to replace aluminum in the structure. These metals included Cr, La, Ce, Pr, Nd, Eu Gd, Ho, and Er. Cerium (III) substituted kaolinite was sucessfully synthesized using air-free conditions. This approach allows bulk quantities of substituted kaolinites to be prepared in a relatively short amount of time and offers a new route to synthesize pure and substituted kaolinites that may have novel catalytic properties.
Published in: Applied Clay Science, Volume 52, Issue 4, June 1, 2011, pages 386-391. Copyright © 2011 Elsevier. The final published version is available at: http://www.sciencedirect.com/science/article/pii/S0169131711001347