Polyfunctional microspherical materials for long-term disposal of liquid radioactive wastes

Abstract

The possibility of immobilizing liquid radioactive wastes into polyfunctional microspherical materials of the block and powdered types is demonstrated. These materials are intended for reprocessing radioactive wastes of different compositions and make it possible to perform a multistage process of conditioning radioactive wastes under relatively mild conditions (at temperatures below 1000 ° C) with the conversion of water-soluble cesium and strontium compounds into water-insoluble mineral forms in the course of solid-phase transformations. Owing to the aluminosilicate composition of microspherical components of energy ashes (cenospheres), the cenospheres can serve as precursors of aluminosilicate granitoid minerals. Different techniques are proposed and conditions are experimentally determined for transforming precursors into final mineral-like materials of the predicted structure types chosen in the framework of the geoecological approach. The framework structures of aluminosilicates and phosphates thus formed can fix cesium and strontium in the crystal lattice and ensure the geochemical equilibrium between the matrix and incorporating granitoid rocks under conditions of long-term disposal.

Synthesis and structure of analcime and analcime-zirconia composite derived from coal fly ash cenospheres

“…The advantage of this approach is possibility to use CFAC of required chemical and phase composition provided by separation of a CFAC concentrate on the basis of differences of individual globules in size, density, and magnetic properties [27e29]. In most cases the direct transformation of the CFAC material, in dependence on reaction parameters (temperature, duration, alkaline concentration, solid-toliquid ratio), results in zeolitic phases of different structural types, such as NaX (FAU, JCPDS 12e0228), NaA (LTA, JCPDS 43e0142), NaP1 (GIS, JCPDS 40e1464), chabazite (CHA, JCPDS 12e0194), analcime (ANA, JCPDS 19e1180), and/or hydroxysodalite (JCPDS 11e401) [25]. Among them, only zeolite NaP1 was shown to crystallize as an individual phase under certain conditions (T ¼ 100e120 C, 1.5e2.5 M NaOH) [25,26].…”

“…In most cases the direct transformation of the CFAC material, in dependence on reaction parameters (temperature, duration, alkaline concentration, solid-toliquid ratio), results in zeolitic phases of different structural types, such as NaX (FAU, JCPDS 12e0228), NaA (LTA, JCPDS 43e0142), NaP1 (GIS, JCPDS 40e1464), chabazite (CHA, JCPDS 12e0194), analcime (ANA, JCPDS 19e1180), and/or hydroxysodalite (JCPDS 11e401) [25]. Among them, only zeolite NaP1 was shown to crystallize as an individual phase under certain conditions (T ¼ 100e120 C, 1.5e2.5 M NaOH) [25,26]. As it has been noted by Vereshchagin et al [25], analcime crystallized at elevated temperatures (T > 150 C) but detailed results on zeolite formation from CFAC under temperatures higher than 120 C were not reported anywhere.…”

Synthesis and Catalytic Application of Zeolite-Based Hollow Materials

“…Coal fly ash cenospheres, the by-products of powdered coal combustion, 43 44 were reported as a suitable starting material for the syntheses of hollow sphere-shaped zeolites. 45 46 Wang et al 47 48 proposed a seed-induced in-situ hydrothermal conversion technique to prepare novel hollow microspheres with zeolite/mullite composite shells from fly ash cenosphere (FAC). Two groups of hollow microspheres were prepared, one with zeolite FAU/mullite composite shells and the other with zeolite LTA/mullite composite shells.…”

Magnetic Composite Sorbents for Trapping Heavy Metals from Liquid Waste and Their Immobilization in a Mineral-Like Matrix

“…Другим вариантом получения инженерной формы магнитного сорбента может быть агломерация ферросфер с использованием цирконосиликатного связующего, выполняющего также функцию сорбционно-активного компонента и прекурсора фазы циркона. Микросферические сорбенты такого типа были получены в работах [18,19] путем консолидации алюмосиликатных микросфер с силикатным связующим.…”