Highly efficient uptake of TcO4 −/ReO4 − by functionalized PAFs

Abstract

Abstract Selective removal of 99TcO4 − from complex radioactive wastewater is a challenging but meaningful task since it is important for both spent fuel reprocessing and 99TcO4 − leakage handling. Here, we synthesized a series of functionalized PAF-1 framework materials, PAF-1-C-N2, PAF-1-N2-C4, PAF-1-IM and PAF-1-PY, by grafting quaternary ammonium, imidazolium and pyridinium onto the PAF framework as active sites, respectively, which purpose is to screen functional groups with high affinity for TcO4 −. The structures and morphological characteristics of the four adsorbents were characterized by N2 adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM). These materials exhibit high selectivity for TcO4 −/ReO4 −, rapid adsorption kinetics (reaching equilibrium within 30 s), and a wide pH range (pH 3–11) for ReO4 −/TcO4 −adsorption. Among them, PAF-1-IM had the best adsorption performance, and the partition coefficient K d reached 1.27 × 106 mL/g. 97.1 % and 96.9 % of ReO4 − could be removed by PAF-1-IM even when the concentrations of PO4 3− and SO4 2− are 1000 times the concentration of ReO4 −, respectively. When the solid-liquid ratio is 10 g/L, 93.7 % of TcO4 − can be removed from the simulated Low Active Wastewater (LAW), which is higher than most other TcO4 − adsorbents. X-ray energy dispersive spectroscopy (EDS) and FT-IR suggest the adsorption process was anion exchange.