Porous Materials Based on Cenospheres of Coal Fly Ash for Fixation of Cs-137 and Sr-90 in Mineral-like Aluminosilicates

摘要

Among the crystalline matrices being developed for immobilization of ~(137)Cs and ~(90)Sr are framework aluminosilicates like feldspars and feldspathoids.A novel approach to obtain mineral-like aluminosilicate forms of ~(137)Cs and ~(90)Sr with using porous materials based on hollow aluminosilicate microspheres of coal fly ash (cenospheres) has been demonstrated.Two modifications of microspherical porous materials have been developed,(i) moulded porous matrices based on consolidated cenospheres and (ii) zeolite sorbents obtained by hydrothermal zeolitization of cenospheres.The first includes impregnation of Cs-or Sr-containing solutions into porous matrices,drying and calcining at temperatures (700-900 deg C) lower than the softening point of the porous matrix material,at which solid phase crystallization takes place with formation of framework aluminosilicates,such as Cs-nepheline,pollucite or Sr-anorthite.Using zeolite sorbents,immobilization of Cs~+and Sr~(2+) proceeds through the step of trapping ions from the solution followed by drying and thermochemical solid-phase transformation of saturated zeolites into pollucite or Sr-anorthite over the same temperature range.Cenosphere-derived porous matrices and zeolite sorbents were tested in fixation of ~(137)Cs using spiked simulants of actual radioactive waste.The durability of crystalline aluminosilicate ~(137)Cs-forms obtained was shown to satisfy Russian (GOST P 50926-96) and international standards.