Radiation Controllable Synthesis of Robust Covalent Organic Framework Conjugates for Efficient Dynamic Column Extraction of 99TcO4−

Abstract

Anion-scavenging materials tailored for 99 TcO 4 À trapping are urgently needed for both nuclear-related environmental remediation and management of spent nuclear fuel. For the first time, we report here an ultra-robust imidazolium-decorated covalent organic framework (COF) conjugate fabricated by an ionizing radiation strategy, for efficient capture of 99 TcO 4À . The charged imidazolium moieties are controllably anchored into the channel of the COF by simply adjusting the g-ray dose, thereby leading to tunable ReO 4 À uptake up to 952 mg g À1 with high selectivity and fast kinetics. More importantly, the high porosity and ultra-robust nanofiber structure of the COFs make them ideal packing materials for dynamic column experiments. >99.98% ReO 4 À /TcO 4 À can be efficiently separated and re-collected, even after four adsorptiondesorption cycles, ranking a new record of the elimination rate for ReO 4 À adsorption. The performance of these materials suggests attractive opportunities in practical applications for TcO 4 À removal from the environment and nuclear waste.

Porous Cationic Electrospun Fibers with Sufficient Adsorption Sites for Effective and Continuous 99TcO4− Uptake

“…The removal of ReO 4 − under different pH values were tested to show the fibers' adsorption ability in acidic and alkaline conditions (Figure S18, Supporting Information). At selected pH range (2)(3)(4)(5)(6)(7)(8)(9)(10)(11), the removal efficiencies were high up to 90%. In certain types of nuclear waste streams, the pH values are either highly acidic or alkaline.…”

“…− uptake capability exceeding PCE fibers, such as TbDa-COF (952 mg g -1 ), [6] SCU-CPN-1 (999 mg g -1 ), [7] ImCOP (1162 mg g -1 ), [31] and SCU-CPN-2 (1467 mg g -1 ). [18] However, compared with powdery cationic organic networks, PCE fibers with membranous engineering form is more suitable for practical application, which is favorable to recycling and can be − equilibrium adsorption time and maximum adsorption capacity of various reported adsorbents and their corresponding references are given in Table S3 (Supporting Information).…”

“…[31,45] Additionally, compared with that of KReO 4 salts, the binding energy of Re 4f2/7 had a red shift from 45.4 to 45.0 eV because of the increase in electron density from the interaction between ReO 4 − ions and quaternary ammonium groups. [6,32] EXAFS data were collected to further illustrate the local structure around Re atoms. Raw and Fourier transforms of Re L3 edge k3-weighted spectra of ReO 4…”

“…[12] Thus, a series of new adsorbents have been explored to replace traditional resin beads. For example, inorganic cationic materials with easy preparation and low costs such as layered double hydroxide (LDH), Yb 3 O(OH) 6 Cl, and thorium borates (NDTB-1) exhibited 99 TcO 4 − /ReO 4 − adsorption ability, but their relatively low uptake capacity and poor selectivity limited the practical applications. [13][14][15] Recently, advanced porous materials such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and cationic polymer networks (CPNs) with cationic adsorptive sites have been designed and investigated for 99 TcO 4 − /ReO 4 − removal, which showed high uptake capacity, fast kinetics, and excellent selectivity.…”

“…Moreover, 99 Tc also disturbs the extraction of uranium, neptunium, and plutonium through its catalytic redox activity, and the volatile tendency of 99 TcO 4 − to 99 Tc 2 O 7 during nuclear waste vitrification process leads to a risk of leakage. [ 6–9 ] Therefore, the capture of 99 TcO 4 − is critical and significant for nuclear fuel retreatment and environmental remediation.…”