Radiation Controllable Synthesis of Robust Covalent Organic Framework Conjugates for Efficient Dynamic Column Extraction of 99TcO4−

Radiation synthesis of ionic liquid-functionalized silica-based adsorbents: a preliminary investigation on its application for removal of ReO4- as an analog for TcO4. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2021;28:17752-17762. [PMID: 33400123 DOI: 10.1007/s11356-020-12078-z]

The decontamination of radioactive TcO₄^- from nuclear wastes is becoming increasingly crucial for spent nuclear fuel reprocessing and environmental remediation. In this work, a series of ionic liquid-immobilized silica-based adsorbents (SVIL-Cn, n = 1, 4, 8) were newly synthesized using the radiation-induced grafting of 4-vinylbenzyl chloride onto silanized silica and subsequent functionalization with 1-methylimidazole, 1-butylimidazole, or 1-octylimidazole. The synthesis conditions such as the solvent, absorbed dose, and monomer concentration were investigated in detail, and the resulting adsorbents were characterized by elemental analysis, FT-IR, SEM, and TGA. In batch experiments, the adsorbents exhibited a high ReO₄^- (a nonradioactive surrogate of TcO₄^-) removal efficiency over a wide pH range (3 ~ 8), and SVIL-C1 showed a maximum adsorption capacity of 70.62 mg g^-1 towards ReO₄^-. In addition, their adsorption performance barely changed after 800 kGy radiation. The column experiments for treating simulated radioactive wastewater showed that the SVIL-Cn adsorbents could selectively separate TcO₄^-/ReO₄^- from a variety of fission products, and they could be recycled four times with negligible capacity loss. Lastly, XPS and FT-IR analysis confirmed that the adsorption proceeded via an ion-exchange mechanism. The results showed that these adsorbents are suitable for the efficient removal of TcO₄^-/ReO₄^- from radioactive wastewater with complex compositions.

Unveiling the Uncommon Fluorescent Recognition Mechanism towards Pertechnetate Using a Cationic Metal-Organic Framework Bearing N-Heterocyclic AIE Molecules

As one of most problematic radionuclides, technetium-99, mainly in the form of anionic pertechnetate (TcO₄ ^- ), exhibits high environmental mobility, long half-life, and radioactive hazard. Due to low charge density and high hydrophobicity for this tetrahedral anion, it is extremely difficult to recognize it in water. Seeking efficient and selective recognition method for TcO₄ ^- is still a big challenge. Herein, a new water-stable cationic metal-organic framework (ZJU-X8) was reported, bearing tetraphenylethylene pyrimidine-based aggregation-induced emission (AIE) ligands and attainable silver sites for TcO₄ ^- detection. ZJU-X8 underwent an obvious spectroscopic change from brilliant blue to flavovirens and exhibited splendid selectivity towards TcO₄ ^- . This uncommon fluorescent recognition mechanism was well elucidated by batch sorption experiments and DFT calculations. It was found that only TcO₄ ^- could enter into the body of ZJU-X8 through anion exchange whereas other competing anions were excluded outside. Subsequently, after interaction between TcO₄ ^- and silver ions, the electron polarizations from pyrimidine rings to Ag⁺ cations significantly lowered the energy level of the π* orbital and thus reduced the π-π* energy gap, resulting in a red-shift in the fluorescent spectra.

Robust covalent organic frameworks with tailor-made chelating sites for synergistic capture of U(vi) ions from highly acidic radioactive waste

A synergistic strategy for enhancing U(vi) capture under highly acidic conditions (2 M HNO₃) by radiation resistant phosphonate-functionalized two-dimensional covalent organic frameworks with tailor-made binding sites bearing a strong affinity was described. The combination of the radiation resistant characteristic with a strong acid-resistant property endows COFs with practical capabilities for actinide capture from real radioactive liquid waste.

Radiation synthesis of imidazolium-based ionic liquid modified silica adsorbents for ReO4− adsorption

A series of ionic liquid functionalized silica-based adsorbents were synthesized and used to remove ReO₄⁻ from simulated radioactive wastewater.