Highly selective removal of Technetium-99 using imidazolium-based macroporous anion exchange resins

Technetium-99 (99Tc), as a β-emitting radionuclide, is one of the main components of nuclear waste. The fast environmental mobility of 99TcO4- makes it a great threat to the environment and human beings. Although some adsorption materials have been developed to remove 99TcO4- from the nuclear wastewater, the low selectivity and poor stability under acid and radiation conditions limit their actual application. In this work, an N-methylimidazolium modified macroporous anion exchange resin (PMiMCl) was developed for the highly selective removal of 99TcO4-. Batch adsorption experiments demonstrated that the PMiMCl resin exhibited high adsorption capacity (Re(VII), 677.21 mg g−1) in a wide pH range (3–7). The resin showed high stability after acid (5 mol L-1 HCl), alkali (5 mol L-1 NaOH) and radiation (1000 KGy 60Co γ) treatment and the remove ability was little influenced. More importantly, in the presence of high concentration of competing anions, the removal efficiency of 99TcO4- with PMiMCl resin can also reach to 97.64%, which was much higher than those treated by commercial resins (93.02% for ZGANR170 and 93.10% for IRN78), demonstrating its good selectivity. The density functional theory calculations revealed that the high selectivity was attributed to the strongest interaction of imidazole cation in PMiMCl resin with 99TcO4- anion compared with NO3−, SO42− and Cl− anions. These superior features coupled with low cost and feasible for large scale production and application make PMiMCl resin great potential for 99Tc removal in nuclear wastewater.