⁹⁹TcO₄^– Separation through Selective Crystallization Assisted by Polydentate Benzene-Aminoguanidinium Ligands

Abstract

99 Tc is one of the most abundant radiotoxic isotopes in used nuclear fuel with a high fission yield and a long half-life. Effective removal of pertechnetate (TcO 4 − ) from an aqueous solution is important for nuclear waste separation and remediation. Herein, we report a series of facilely obtained benzene-linked guanidiniums that could precipitate TcO 4 − and its nonradioactive surrogate ReO 4 − from a high-concentration acidic solution through self-assembly crystallization. The resulting perrhenate and pertechnetate solids exhibit exceptionally low aqueous solubility. The benzene-linked guanidiniums hold one of the highest TcO 4 − removal capacities (1279 mg g −1 ) among previously reported materials and possess a removal percentage of 59% for ReO 4 − in the presence of Cl − over 50 times. The crystallization mechanism was clearly illustrated by the single-crystal structures and density functional theory calculations, indicating that TcO 4− is captured through a charge-assisted hydrogen bonding interaction and stabilized by π−π stacking layers. In addition, the removal process is easily recycled and no toxic organic reagents are introduced. This work provides a green approach to preliminarily separate TcO 4− from high-level nuclear wastes.

Thiourea as a Stabilizer of Reduced Forms of Technetium─Tc(III) and Tc(IV): Experimental and Theoretical Studies of Complexes

“…Weak intermolecular interactions are of particular interest from a theoretical point of view; the study of such interactions in pertechnetates and perrhenates of purines led to the discovery of a new type of chemical bond. , New methods of separating perrhenates and pertechnetates are based on nonvalent interactions. − The study of the contribution of the nonvalent interactions for various technetium compounds will allow a deeper understanding of the impact of radiopharmaceuticals on living organisms and of the formation of nontrivial technetium complex compounds, similar to those described in refs , − . Information about weak interactions can also be useful for predicting the behavior of Tc-containing intermediates in catalytic and sorption processes on complex organic sorbents like those described …”

Modulating Anion Nanotraps via Halogenation for High-Efficiency 99TcO4–/ReO4– Removal under Wide-Ranging pH Conditions

“…This approach offers easy operation and high efficiency. Commonly used ion exchange materials include resins, , molecular compounds, silica, − metal borates, , layered double hydroxide (LDH), , metal–organic frameworks (MOFs), − ionic polymers, − cationic covalent organic nanosheets (iCONs), and covalent organic frameworks (COFs), − among others . Resins, molecular compounds, and LDH-based adsorbents all have limitations due to their relatively low 99 TcO 4 – adsorption capacity and poor selectivity.…”

A Promising 1,3,5-Triazine-Based Anion Exchanger for Perrhenate Binding: Crystal Structures of Its Chloride, Nitrate and Perrhenate Salts

“…The precipitation of TcO 4 − from aqueous solutions in the form of insoluble salts is one of the most efficient and cost-effective isolation methods, which does not require the use of organic solvents. Quaternary phosphonium and arsonium salts [ 11 , 12 , 13 , 14 ], guanidinium salts [ 15 ] and cationic 1,2,4-selenodiazoles [ 16 ] have been used as precipitants. The most promising results have been obtained using polycations [ 17 ].…”