Highly efficient capture of TcO4-/ReO4- by imidazolium ionic liquid supported silica materials prepared by radiation induced RAFT-mediated graft polymerization technology

Abstract

Technetium (⁹⁹Tc) is a main long-lived radionuclide of nuclear waste, which poses a great threat to the environment and human health. The reasonable disposal of ⁹⁹Tc is vital important. In this paper, a series of novel materials (SMILR_m, m = 0, 1/500, 1/200, m is the molar ratio of IL to RAFT reagent) was synthesized by radiation-induced grafting combined with reversible addition-fragmentation chain transfer (RAFT) polymerization. The adsorption performance of SMILR_m to ⁹⁹Tc were investigated. The graft polymerization process is controlled by the RAFT reagent, resulting in a restricted dispersion of SMILR_m molecular weight. With the increase of RAFT reagent content, the grafting yield (GY) decreased. The addition of RAFT reagent increases the specific surface area of the adsorbent, accelerates the adsorption rate, increases the adsorption capacity, but reduces the adsorption selectivity. Especially, the adsorption of SMILR₀ was a single step adsorption and obeyed Langmuir adsorption model, while SMILR_m (1/500, 1/200) showed a stepwise adsorption isotherm model. SMILR_m exhibited excellent recyclability and could efficiently capture $\text{Re}{\text{O}}_{\text{4}}^{-}$ from a simulated Beishan groundwater in dynamic experiments. Finally, XPS and FT-IR analysis confirmed that the adsorption was an ion exchange mechanism. The results showed that SMILR_m are suitable for the effective removal of $\text{Re}{\text{O}}_{\text{4}}^{-}/Tc{O}_4^{-}$ from radioactive wastewater with complex composition.