Synthesis of composite zirconosilicate sorbents based on fly ash cenospheres and their sorption properties for Cs+, Pb2+ and Cd2+ cations for immobilisation in ceramic form
E. A. KUTIKHINA1, T. A. VERESHCHAGINA1,2, A. A. BELOV3, O. O. SHICHALIN3
1Krasnoyarsk Scientific Centre SB RAS, Institute of Chemistry and Chemical Technology SB RAS, Krasnoyarsk, Russia
2Siberian Federal University, Krasnoyarsk, Russia
3Far Eastern Federal University, Vladivostok, Russia
Keywords: cenospheres, zirconosilicates, sorbents, spark plasma sintering, mineral-like ceramics
Abstract
Hollow aluminosilicate microspheres (cenospheres) of stabilised composition (glass phase - 95.4 wt%; (SiO2/Al2O3)glass - 3.1) isolated from coal fly ashes from coal combustion were used to prepare composite sorbents containing a sorption-active component based on zirconosilicates of framework structure. The synthesis products were characterised by X-ray diffraction analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and their sorption properties for Cs+, Pb2+ and Cd2+ cations were studied. The zirconosilicate material shows a high distribution coefficient in the process of sorption of Cs+, Pb2+ and Cd2+ from aqueous solutions (103-105 mL/g). For Pb2+ as an example, it is shown that as a result of high-temperature phase transformation of the Pb2+-form of zirconosilicate, Pb2+ cations are stabilised in the crystalline phase of lead zirconate PbZrO3. The possibility to use spark plasma sintering for obtaining mineral-like ceramics based on zirconosilicate sorbent for immobilisation of radionuclide Cs-137 has been investigated. For ceramics sintered at different temperatures (800-1000 °C) the cesium leaching rate was studied, which is a criterion of hydrolytic stability of radioactive ceramics intended for disposal in rocks. The obtained values of leaching rate (~10-5 g/(cm2⋅day)) meet the requirements of Federal Norms and Rules in the area of atomic energy use NP-019-2000 “Collection, processing, storage and conditioning of liquid radioactive wastes. Safety requirements”.
|
