Porous Crystalline Silica (Gubka) as a Inorganic Support Matrix for Novel Sorbents

Abstract

ABSTRACTInorganic ion exchange media typically exist as fine powders, making large-scale use impractical, unless the media can be affixed to an appropriate matrix. Likewise, organic chelating agents are typically dissolved in a solvent and absorbed into porous matrices for use in extraction chromatography. The most common matrices utilized in both cases are organic materials, that are not compatible with high radiation fields or acceptable as final waste forms. Recent investigations have shown that ion exchange sorbents can be effectively loaded within a porous crystalline silica (Gubka) matrix. This approach allows for target radionuclides to be adsorbed into a porous micro-crystalline glass matrix which encapsulates the contaminant and becomes the final waste form. Subsequent to adsorption of the radionuclides, the Gubka matrix can be compressed in a hot uniaxial press, resulting in an even greater volume reduction. The porous glass matrix is produced in Russia using fly ash residue from coal combustion power generating plants. It consists of consolidated arrays of hollow glass cenospheres and is termed Gubka which is the Russian word for sponge. This paper describes results of a collaborative research program between the Khlopin Radium Institute, St.Petersburg, Russia, the Institute of Chemistry and Chemical Technologies, Krasnoyarsk, Russia, the Mining and Chemical Combine, Zheleznogorsk, Russia, and the Idaho National Engineering and Environmental Laboratory. Ammonium molybdophosphate (AMP) for the removal of cesium from acidic liquid waste has been successfully incorporated into Gubka matrices. Test results for cesium removal, using AMP-Gubka, are discussed.