Application of hybrid MOF composite in extraction of f-block elements: Experimental and computational investigation

Unlocking a radioactive pertechnetate (TcO4 -) treatment process with functionalized metal-organic frameworks (MOFs)

Technetium-99 (99Tc), a troublesome radioisotope prevalent in nuclear liquid waste, poses significant environmental and human health hazards due to its long half-life, high fission yield, and fast environmental mobility. The successful mitigation of 99Tc is imperative for nuclear waste management; however, it continues to present a significant obstacle. In this comprehensive review, we explore the state-of-the-art developments in separating TcO4 - ions using functionalized metal-organic framework (MOF) materials, spanning from 2010 to the present. We delve into the intricate separation mechanisms of TcO4 - ions, shedding light on advanced research avenues in this field. Furthermore, we aim to provide a comprehensive understanding of the underlying receptor chemistry that is necessary for the specific targeting of pertechnetate anion-based materials. This will provide valuable insights into the molecular characteristics that are crucial for the separation of TcO4 - ions from solutions containing nuclear waste. The review outlines perspectives and conclusions that pave a promising path for the comprehensive investigation of materials poised to revolutionize TcO4 - separation. Finally, we provide forward-looking recommendations for future research directions, opportunities, and associated challenges, to encourage more researchers to leverage TcO4 - selective materials for better management of environmental pollution.

Mechanism unravelling for highly efficient and selective 99TcO4 - sequestration utilising crown ether based solvent system from nuclear liquid waste: experimental and computational investigations

Selective and efficient separation of pertechnetate (TcO4 -) from nuclear waste is desirable for the safe and secure management of radioactive waste. Here, we have projected dibenzo-18-crown-6 ether (DB18C6) in a highly polar nitrobenzene medium for enhancing the removal efficiency of 99Tc from reprocessing plant low level waste (LLW). An effort was made to determine the stoichiometry of metal-ligand complex by slope ratio method, revealing that one ligand (DB18C6) binds with one TcO4 - moiety. Optimum ligand concentration for 99Tc extraction was evaluated. Relevant interference of the anions was studied systematically. The effect of solution pH was analysed on the extraction efficiency of 99Tc. A kinetic study was carried out for maximum extraction of metal ions. A quantitative stripping study was also achieved for metal ions with a suitable stripping solution. After evaluation of all essential parameters, selectivity and feasibility studies were finally carried out with actual low level reprocessing plant waste to demonstrate a laboratory scale process for effective separation of TcO4 - ions. Density functional theory (DFT) calculations were carried out to understand the nature of the complexation of TcO4 - ion with DB18C6 in different solvents systems and to elucidate the key aspect behind ionic selectivity and enhanced the 99Tc extraction efficiency of DB18C6 in the studied diluent systems. The ΔE and ΔG values for different modeled complexation reactions were evaluated systematically. From the calculated free energy of complexation of TcO4 - with DB18C6, it was observed that the consideration of explicit solvent plays a vital role in predicting the experimental selectivity.