Porous Zr2SC-carbon composite microspheres: Possible radiation tolerant sorbents and transmutation hosts for technetium-99

Abstract

The preparation, characteristics and adsorption properties of novel porous carbon-ceramic composite microspheres are presented. The composites were synthesised by a simple ion exchange process involving the cationic Zr tetramer and commonly-available macroporous sulphonated polystyrenedivinylbenzene cation exchange resins, with subsequent carbothermal reduction at 1350 °C. The materials were extensively characterised with respect to composition, chemical structure and porosity. Carbothermal reduction of the Zr-loaded templates resulted in formation of crystallites of the MAX phase zirconium sulphide carbide (Zr 2 SC) embedded within a highly microporous carbon framework with a macroporous secondary structure inherited from the resin template. Despite the high BET surface areas of the Zr 2 SC-carbon composite microspheres (in some cases, greater than 600 m 2 g −1), they are extremely mechanically robust. The microspheres displayed high adsorption selectivity for oxoanions relative to cationic solution species, including perrhenate (ReO 4 −), a pertechnetate (TcO 4 −) surrogate. Accumulation of ReO 4 − on the Zr 2 SC particles was unequivocally demonstrated by elemental mapping. Such materials are potential candidates as combined 99 Tc sorbents and reusable transmutation hosts.

High surface area of carbonaceous Cr2GaC composite microspheres synthesized by sol–gel chemistry

“…For example, Zr 2 SC carbon composite spheres exhibited a BET specific surface area of 626 m 2 g −1 . 37 These Zr 2 SC composites were prepared by loading ZrOCl 2 solutions into macroporous sulphonated polystyrene-divinylbenzene strong cation exchange resins, which were then heat treated at 1350 °C under a mixed H 2 /Ar atmosphere. This differs from the use of the polymer type II complex technique that provides higher levels of atomistic homogeneity of the precursors and slightly lower temperatures at 1050 °C that are utilized for Cr 2 GaC composite spheres.…”

Efficient Capture of Perrhenate and Pertechnetate by a Mesoporous Zr Metal–Organic Framework and Examination of Anion Binding Motifs

“…The maximum adsorption capacity of NU-1000 for perrhenate was determined to be 210 mg/g using the Langmuir eq (Figure S1 and Table S3) making NU-1000 among the best sorbents reported to date (Table S4). ,,− …”