Immersion grinding and in-situ polymerization synthesis of poly(ionic liquid)s incorporation into MOF composites as radioactive TcO4- scavenger.

ABSTRACT

Imidazolium-based ionic liquids (ILs) are a promising candidate for efficient separation of radioactive pertechnetate (TcO4-) from nuclear waste. However, their effective fixation, availability of active sites and slow adsorption kinetics remain challenges. Here, we incorporated the bisimidazolium-based ILs into porous metal-organic frameworks (MOFs) via a combination of immersion grinding and in-situ polymerization. 3,3'-divinyl-1,1'(1,4-butanediyl) diimidazolium dichloride is tightly bound inside and outside the porous MOFs matrix by uniform immersion grinding, which facilitates the exposure of more adsorption sites and provides channels for the anions to travel through quickly. Solvent-free polymerization reduces environmental pollution and energy consumption. Notably, the composite P[C4(VIM)2]Cl2@MIL-101 possesses an admirable removal efficiency (673 mg g-1) compared with the pristine poly(ionic liquid)s (215 mg g-1). Meanwhile, it exhibits fast sorption kinetics (92% in 2 min), good ß and γ radiation-resistance, excellent regeneration and eminent removal efficiency in high alkaline conditions (83%). These superior traits endow that P[C4(VIM)2]Cl2@MIL-101 effectively separated TcO4- from simulated Hanford Low-activity Waste (LAW) Melter off-gas scrubber solution tested in this work. DFT density functional theory confirms that the strong electrostatic attraction and minimum Gibbs free energy (-6.2 kcal mol-1) achieve high selective adsorption for TcO4-. P[C4(VIM)2]Cl2@MIL-101 demonstrates the considerable potential to remove TcO4- from radioactive contaminants.