An Inorganic Microsphere Composite for the Selective Removal of¹³⁷Cesium from Acidic Nuclear Waste Solutions. 1: Equilibrium Capacity and Kinetic Properties of the Sorbent

Abstract

A new inorganic ion exchange composite consisting of ammonium molybdophosphate, (NH 4 ) 3 P(Mo 3 O 10 ) 4 ?3H 2 O (AMP), synthesized within hollow aluminosilicate microspheres (AMP-C) has been developed. Two different batches of the sorbent were produced resulting in 20% and 25% AMP loading for two and three loading cycles, respectively. The selective cesium exchange capacity of this inorganic composite was evaluated using simulated sodium bearing waste solution as a surrogate for the acidic tank waste currently stored at the Idaho National Laboratory (INL). Equilibrium isotherms obtained from these experiments were very favorable for cesium uptake and indicated maximum cesium loading of approximately 9% by weight of dry AMP. Batch kinetic experiments were also performed to obtain the necessary data to estimate the effective diffusion coefficient for cesium in the sorbent particle. These experiments resulted in effective intraparticle cesium diffusivity coefficients of 4.99 6 10 28 cm 2 /min and 4.72 6 10 28 cm 2 /min for the 20% and 25% AMP-C material, respectively.

Immobilization of metal hexacyanoferrates in chitin beads for cesium sorption: synthesis and characterization

“…This could be explained by the contribution of other diffusion mechanisms and/or by the partial heterogeneity of the material (external layers vs. core material with different diffusion characteristics). These values are signicantly higher than those cited for Cs(I) diffusion into AMP-aluminosilicate microspheres (AMP: ammonium molybdophosphate; around 4.8 Â 10 À12 m 2 min À1 ), 45 and comparable to those found for Cs(I) sorption on nickel-potassium hexacyanoferrate/PAN composite beads (1.6-4.5 Â 10 À10 m 2 min À1 ). 22 The tests performed on 137 Cs solutions are reported in Table 6.…”

The Effect of Gamma Irradiation on the Physiochemical Properties of Caesium-Selective Ammonium Phosphomolybdate–Polyacrylonitrile (AMP–PAN) Composites

“…Due to the environmental mobility of Cs + isotopes [5][6][7], even potentially from vitrified wasteforms [50], questions as to the best disposal route for radiocaesium-bearing materials have abounded for many years [51,52]. The vitrification of AMP as a route to Cs disposal has received very limited attention to date [34], and as such, further research will be required to assess the best disposal route of AMP-PAN composites for appropriate waste management.…”

Composition and Morphology of Fly Ash Cenospheres Produced from the Combustion of Kuznetsk Coal

“…21 The stabilization of composition and, correspondingly, properties of cenospheres, owing to the differences in physical characteristics of individual globules (size, density, and magnetic properties), makes it possible to use them instead of expensive synthetic microspheres in the fabrication of new functional materials. In particular, narrow fractions of cenospheres have been used in the fabrication of microspherical sorbents with zeolite/mullite composite shells, 22 sensitizers of commercial emulsion explosives, 23 multifunctional porous materials for liquid radioactive waste treatment, 24 sorbents, 25 pH-sensitive spin probes of molecular systems, 26 microspherical membranes for selective separation of helium, 27,28 metal-matrix syntactic foams, 29 and composite sorbents with a deposited magnetic component and a functionalized surface for extraction of phenolic compounds from aqueous media. 30 In each case where cenospheres are used for the production of functional materials with predictable properties, it is necessary to know the chemical and phase compositions of their narrow fractions.…”