Technetium Encapsulation by A Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7)

Abstract

Technetium (99Tc) is an important long-lived radionuclide released from various activities including nuclear waste processing, nuclear accidents and atmospheric nuclear weapon testing. The removal of 99Tc from the environment is a challenging task, and chemical capture by stable ceramic host systems is an efficient strategy to minimise the hazard. Here we use density functional theory with dispersion correction (DFT+D) to examine the capability of the porous inorganic framework material C12A7 that can be used as a filter material in different places such as industries and nuclear power stations to encapsulate Tc in the form of atoms and dimers. The present study shows that both the stoichiometric and electride forms of C12A7 strongly encapsulate a single Tc atom. The electride form exhibits a significant enhancement in the encapsulation. Although the second Tc encapsulation is also energetically favourable in both forms, the two Tc atoms prefer to aggregate, forming a dimer.

[Ca24Al28O64]4+(4e−) are directly and quickly synthesized by self‐reduction of C12H10Ca3O14 + Al2O3 without any reducing agent

“…[Ca 24 Al 28 O 64 ] 4+ (4e − ) electrides (C12A7:e − ) is a conductive oxide ceramic with high carrier density and low work function 1–3 . Its unit cell structure is shown in Figure 1, its lattice constant is 11.95 Å, 4,5 and it is a simple cubic crystal structure composed of Ca, Al, and O elements 1,6 . The unit cell is composed of a positive electric framework [Ca 24 Al 28 O 64 ] 4+ formed by 12 sub‐nanometer cages and 4e − bounded inside the cage, and these cages are coplanar connected 7–9 .…”

“…[1][2][3] Its unit cell structure is shown in Figure 1, its lattice constant is 11.95 Å, 4,5 and it is a simple cubic crystal structure composed of Ca, Al, and O elements. 1,6 The unit cell is composed of a positive electric framework [Ca 24 Al 28 O 64 ] 4+ formed by 12 sub-nanometer cages and 4e − bounded inside the cage, and these cages are coplanar connected. [7][8][9] This allows free electrons to shuttle freely in the cage cavity to form jumping conduction.…”

Nitric Oxide Decomposition via Selective Catalytic Reduction by Ammonia on a Transition-Metal Cluster of W2TcO6

“…Introducing a metal on the W 2 XO 6 – cluster with a 4d transition metal such as technetium (Tc), which has a similar metallic radius to W so that the effect remains largely electronic keeping the geometry distortion to a minimum, could make a core asymmetric and electronic anisotropy, leading to nucleophilic attack at the metal center for higher efficiency of the catalyst reported by Adhikari and Raghavachari . In addition, Tc has been used to study nanoporous cluster oxides . Tc is a Group 7 transition metal and is the lightest radioelement in the periodic table.…”

Lithium Storage in Nanoporous Complex Oxide 12CaO•7Al2O3 (C12A7)

“…In the electride form of C12A7, the framework is compensated by four electrons and its overall composition is denoted by C12A7:e − . Both forms of C12A7 have been considered for the encapsulation of many metal atoms [25][26][27][28][29] and ions [30][31][32][33][34]. Their surface structures have been investigated as promising catalysts for the activation of small molecules such as CO 2 and N 2 [35][36][37].…”