Halogen microregulation in metal-organic frameworks for enhanced adsorption performance of ReO4-/TcO4. J Hazard Mater 2023;446:130744. [PMID: 36630874 DOI: 10.1016/j.jhazmat.2023.130744]

Construction of a Porous Zwitterionic Polyimidazole Resin for the Elimination of Technetium in Acidic Environments

Due to the complex type of coexisting ions, remarkable acidity, and high radioactivity, efficient and sustainable methods for the removal of pertechnetate (99TcO4-) from acidic nuclear waste streams have attracted much attention. Herein, a porous highly polymeric zwitterionic resin (PDVBVIM1.5SO3) was synthesized by installing sulfobetaine zwitterionic units in the polymeric imidazole resin to achieve the purpose of balancing the hydrophilicity and hydrophobicity of the resin structure and improving the reaction kinetics and ion selectivity of the resin at the same time for perrhenate (ReO4-)/99TcO4- removal from acidic solutions. The results demonstrate that PDVBVIM1.5SO3 exhibits fast adsorption kinetics, superior adsorption capacity, and excellent selectivity in the presence of a variety of 1000-fold competing anions. The rapid elimination of ReO4- can be achieved even in 1 mol L-1 HNO3. Importantly, when subject to acid soaking, calcination procedure, and high doses of ionizing radiation, PDVBVIM1.5SO3 maintained its structural integrity and outstanding performance. Additionally, PDVBVIM1.5SO3 displayed outstanding adsorption efficiency toward a simulated Hanford low-activity waste stream with ReO4-. This work demonstrates that achieving a balance between hydrophobicity and hydrophilicity in an exchange resin is of great significance for enhancing the selection and removal of TcO4-/ReO4-, and PDVBVIM1.5SO3 resin could be an excellent acid nuclear waste-adsorbing material candidate.

Efficient capture of 99TcO4-/ReO4- via node and linker bifunctional anion exchange covalent organic frameworks

In nuclear wastewater treatment, ion-scavenging materials designed to trap 99TcO4- is urgently needed. However, strong acid/base, high radiation and high salt concentration of nuclear wastewater usually result in inadequate stability and adsorption capacity of the adsorbent. Herein, we report a new class of bifunctional anion-exchange olefin-linked COF (BPDC-MTMP) prepared via Knoevenagel condensation reactions, the first example exploring the synergistic integration of positively charged fragments at both nodes and linkers. Surprisingly, BPDC-MTMP exhibits a record ReO4- (a non-radioactive surrogate of 99TcO4-) adsorption capacity up to 1593.21 mg g-1, its outstanding adsorption capacity can be attributed to the synergistic enhancement of the positively charged fragments of the nodes and linkers leading to a significant increase in the positive charge density and the number of anion exchange sites. BPDC-MTMP's hydrophobicity is enhanced by the highly conjugated bulky alkyl skeleton, the affinity toward ReO4- and chemical stability are therefore significantly improved, ReO4- can be selectively and reversibly extracted even under strong acid/base and high salt concentration solutions. This study illustrates that the node and linker bifunctional anion exchange COF is of great potential for ReO4-/99TcO4- trapping, which provides a new method to design high-performance adsorbents for the treatment of nuclear wastewater.

Unlocking a radioactive pertechnetate (TcO4 -) treatment process with functionalized metal-organic frameworks (MOFs)

Technetium-99 (99Tc), a troublesome radioisotope prevalent in nuclear liquid waste, poses significant environmental and human health hazards due to its long half-life, high fission yield, and fast environmental mobility. The successful mitigation of 99Tc is imperative for nuclear waste management; however, it continues to present a significant obstacle. In this comprehensive review, we explore the state-of-the-art developments in separating TcO4 - ions using functionalized metal-organic framework (MOF) materials, spanning from 2010 to the present. We delve into the intricate separation mechanisms of TcO4 - ions, shedding light on advanced research avenues in this field. Furthermore, we aim to provide a comprehensive understanding of the underlying receptor chemistry that is necessary for the specific targeting of pertechnetate anion-based materials. This will provide valuable insights into the molecular characteristics that are crucial for the separation of TcO4 - ions from solutions containing nuclear waste. The review outlines perspectives and conclusions that pave a promising path for the comprehensive investigation of materials poised to revolutionize TcO4 - separation. Finally, we provide forward-looking recommendations for future research directions, opportunities, and associated challenges, to encourage more researchers to leverage TcO4 - selective materials for better management of environmental pollution.

Fabricating Porous Alkali-Resistant Resin for Segregation of Perrhenate/Pertechnetate Anions from Wastewater

The elimination of the β-emitting pertechnetate ion (99TcO4-) from highly alkaline tank waste poses a daunting challenge that is of great significance for nuclear safety and environmental protection. Herein, we report a strategy to fabricate an alkaline-stable porous resin (PANPEI-MeCl) that features hyperbranched quaternary amine groups grafted on the surface and confined within the pores of a superhydrophobic polymer matrix synthesized by a one-pot method, exhibiting a clear superiority both in adsorption kinetics and efficiency compared with available commercial anion-exchange resins applying to 99TcO4- capture. Notably, the alkaline stability of the resin can be improved by manipulating the length of side chain alkyl groups, and it shows ultrahigh structural integrity and prominent performance toward acid/alkaline soaking, high-temperature calcination procedures, and high doses of ionizing radiation. Encouraged by its excellent peculiarity, PANPEI-MeCl can continuously capture most of the ReO4- from the simulated radioactive waste by using a sequential injection automatic separation system.

DGA-grafting pyridine for ultra-selective and prior extraction of 99TcO4- from simulated spent nuclear fuel

Selective and prior extraction of 99TcO4- ahead of uranium and plutonium separation is a beneficial strategy for the modern nuclear fuel cycle. Herein, a novel DGA-grafting pyridine ligand BisDODGA-DAPy (L1) was tailored for the efficient separation of TcO4- from simulated spent nuclear fuel based on the selectivity of pyridine and synergistic effect of diglycolamide (DGA) group. Compared to the ligands BisDOSCA-DAPy (L2) and BisDODGA-MPDA (L3) with similar structure, BisDODGA-DAPy (L1) demonstrated the better separation performance including good extraction efficiency, reusability, and high loading capacity for TcO4- under high acidic medium. The interactions of the ligands with Tc(VII)/Re(VII) have been investigated in detail using FT-IR, 1H NMR titration, UV-Vis spectrophotometric titration, ESI-HRMS and DFT simulations. The extraction mechanism affected by the protonation of ligand was elucidated under different acidity. BisDODGA-DAPy (L1) demonstrated the ultra-selective extraction ability for TcO4- from simulated spent nuclear fuel. The maximum SFTc/U and SFTc/Pu values were up to 1.29 × 104 and 5.08 × 103, respectively. In the presence of 9 × 104-fold excess of NO3-, the extraction of TcO4- was almost unaffected. Moreover, the good radiolytic stability further highlights the promising potential of this ligand for 99Tc separation. DFT calculation revealed the dominant role of DAPy and DODGA in TcO4- extraction, providing the theoretical evidence for BisDODGA-DAPy (L1) to selectively bind TcO4- over NO3-.

Rapid screening of drugs in environmental water using metal organic framework/Ti3C2Tx composite coated blade spray-mass spectrometry

Simultaneous rapid screening of multiple drugs of abuse in environmental water facilitates effective monitoring and trend assessments. Herein, a novel porphyrin-based metal organic frameworks modified Ti3C2Tx nanosheets (Cu-TCPP/Ti3C2Tx) composite was prepared and utilized as solid-phase microextraction (SPME) coating for the simultaneous analysis of 21 drugs from water samples. The composite was embedded with matrix-compatible polyacrylonitrile binder to prepare a coated blade with thin and uniform coating layer. Ambient mass spectrometry (MS) technique was used to create a coated blade spray-MS (CBS-MS) method for the quantitative determination of drugs in water samples. High throughput and automated sample preparation were achieved with the use of a Concept 96-well plate system, enabling analysis of 21 drugs of abuse within 1 min per sample, while using only 8 µL of organic solvent for desorption and CBS-MS detection. The developed method showed favorable linearity (R2 ≥ 0.9983) in the range of 0.05 to 10 ng mL-1, low limits of detection (1.5-9.0 ng L-1), sufficient recovery (67.6-133.2%), as well as satisfactory precision (RSDs≤13.5%). This study not only delivers a novel and efficient SPME coating composite, but also demonstrates the excellent performance of a high-throughput, efficient, and green analytical method for determination of drugs in environmental water.

Molecular fingerprint and machine learning enhance high-performance MOFs for mustard gas removal

Chemical warfare agents (CWAs), epitomized by the notoriously used mustard gas (HD), represent a class of exceptionally toxic chemicals whose airborne removal is paramount for battlefield safety. This study integrates high-throughput computational screening (HTCS) with advanced machine learning (ML) techniques to investigate the efficacy of metal-organic frameworks (MOFs) in adsorbing and capturing trace amounts of HD present in the air. Our approach commenced with a comprehensive univariate analysis, scrutinizing the impact of six distinct descriptors on the adsorption efficiency of MOFs. This analysis elucidated a pronounced correlation between MOF density and the Henry coefficient in the effective capture of HD. Then, four ML algorithms were employed to train and predict the performance of MOFs. The Random Forest (RF) algorithm demonstrates strong model learning and good generalization, achieving the best prediction result of 98.3%. In a novel exploratory stride, we incorporated a 166-bit MACCS molecular fingerprinting (MF) to identify critical functional groups within adsorbents. From the top 100 MOFs analyzed, 22 optimal functional groups were identified. Leveraging these insights, we designed three innovative substructures, grounded in these key functional groups, to enhance HD adsorption efficiency. In this work, the combination of MF and ML could provide a new direction for efficient screening of MOFs for the capture of HD in the air. The outcomes of this study offer substantial potential to revolutionize the domain of CWA capture. This represents a significant stride toward developing practical solutions that enhance both environmental protection and battlefield security.

Advanced Porous Materials as Designer Platforms for Sequestering Radionuclide Pertechnetate

Technetium-99 (99Tc), predominantly present as pertechnetate (99TcO4 -), is a challenging contaminant in nuclear waste from artificial nuclear fission. The selective removal of 99TcO4 - from nuclear waste and contaminated groundwater is complex due to (i) the acidic and intricate nature of high-level liquid wastes; (ii) the highly alkaline environment in low-activity level tank wastes, such as those at Hanford, and in high-level wastes at locations like Savannah River; and (iii) the potential for 99TcO4 - to leak into groundwater, risking severe water pollution due to its high mobility. This Review focuses on recent developments in advanced porous materials, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and their amorphous counterparts, porous organic polymers (POPs). These materials have demonstrated exceptional effectiveness in adsorbing 99TcO4 - and similar oxyanions. We comprehensively review the adsorption mechanisms of these anions with the adsorbents, employing macroscopic batch/column experiments, microscopic spectroscopic analyses, and theoretical calculations. In conclusion, we present our perspectives on potential future research directions, aiming to overcome current challenges and explore new opportunities in this area. Our goal is to encourage further research into the development of advanced porous materials for efficient 99TcO4 - management.

Ultrafast and selective capture of 99TcO4-/ReO4- from wastewater by hyper-branched quaternary ammonium group-functionalized resin

99Tc primarily exists high mobility in the natural aqueous environment due to its extremely high solubility and non-complexing features, which can easily cause radioactive pollution. We herein report a general strategy for constructing a novel resin (SiPAN-PEI) with multiple positive charges nitrogen, exhibiting ultrafast adsorption kinetics (< 3 min), superior adsorption capacities (463.96 mg g-1), and excellent selectivity in the presence of excess competitive anions, which exceed those of most commercial resins. Moreover, based on impressive structure stability in extreme conditions, SiPAN-PEI can still maintain superior adsorption abilities after suffering irradiation, calcination, and immersion in strong acid. In addition, the separation performance kept excellently after five loading-washing-eluting cycles and the total adsorption ratio can still reach 97 %. Outstandingly, SiPAN-PEI can remove most of ReO4- from simulated nuclear wastewater through a sequential injection automatic separation system and can reduce the concentration of ReO4- to the maximum concentration standard set by the World Health Organization (WHO) in a short time. Leveraging density functional theory calculations and other characteristics clearly elucidated adsorption mechanism of anion-exchange between Cl- and TcO4-/ReO4-. In terms of superior adsorption property, SiPAN-PEI is demonstrated to be a pretty candidate for 99Tc elimination from wastewater.

Synthesis and performance of guanidinium-based cationic organic polymer for the efficient removal of TcO4-/ReO4. JOURNAL OF HAZARDOUS MATERIALS 2024;466:133602. [PMID: 38286051 DOI: 10.1016/j.jhazmat.2024.133602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Cationic organic polymers have found relatively extensive utility for TcO4-/ReO4- removal, but the harsh preparation conditions constrain their practical application. The bifunctional guanidinium-based cationic organic polymer (GBCOP) was successfully and facilely synthesized in benign conditions within 1 h. Batch experiments showed that GBCOP exhibited rapid removal kinetics (1 min, >98.0%) and a substantial removal capacity of 536.8 mg/g for ReO4-. Even in 1000-fold co-existing NO3- anions, the removal efficiency of GBCOP for ReO4- was 74.0%, indicating its good selectivity. Moreover, GBCOP had high removal efficiencies for ReO4- across a wide pH (3.0-10.0) range and presented remarkable stability under the conditions of strong acid and base. GBCOP could be reused four times while removing 80.8% ReO4- from simulated Hanford wastewater. SEM and XPS results revealed that the mechanism of ReO4- removal involved Cl- ion exchange within the channels of GBCOP. Theoretical calculation results supported that existing the strong electrostatic interaction between guanidinium and ReO4-. This dual-function GBCOP material is cost-effective and holds significant potential for large-scale preparation, making it a promising solution for TcO4- removal from nuclear wastewater.

Toward a mechanistic understanding of Rhenium(VII) adsorption behavior onto aminated polymeric adsorbents: Batch experiments, spectroscopic analyses, and theoretical computations

Rhenium, a rare and critical metal, existing in the industrial wastewater has been aroused extensive interests recently, due to its environmental and resource issues. Chitosan, an easily available, low-cost and eco-friendly biopolymer, was prepared and modified by grafting primary, secondary, tertiary and quaternary amino groups, respectively. Adsorption behaviors and interactions between ReO4- and these four types of aminated adsorbents were investigated through batch experiments, spectroscopic analysis, and theoretical computations. Chitosan modified with secondary amines showed an extremely high uptake of ReO4- with 742.0 mg g-1, which was higher than any reported adsorbents so far. Furthermore, a relatively high adsorption selectivity for Re(VII), as well as the stable and facile regeneration of these aminated adsorbents revealed a promising approach for Re(VII) recovery in full-scale applications. The electrostatic attraction was illustrated to be the main adsorption mechanism by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy analyses. Significantly, the sub-steps of the adsorption process, encompassing the transformation of binding sites and the subsequent binding between these sites and the adsorbate, have been thoroughly investigated through the density functional theory (DFT) calculation method. This approach was firstly proposed to clearly demonstrate the differences in Re(VII) adsorption behavior onto four types of aminated adsorbents, resulting the importance of not only strong binding energy but also an appropriate binding spatial environmental for effective Re(VII) adsorption.

CTAB assisted evaporation-induced self-assembly to construct imidazolium-based hierarchical porous covalent organic polymers for ReO4-/TcO4- removal

Evaporation-induced self-assembly method (EISA) was a facile and reliable method to synthesize porous materials. Herein, we report a kind of hierarchical porous ionic liquid covalent organic polymers (HPnDNH₂) under cetyltrimethylammonium bromide (CTAB) assisted by EISA for ReO₄^-/TcO₄^- removal. Unlike covalent organic frameworks (COFs), which usually needed to be prepared in a closed environment or with a long reaction time, HPnDNH₂ in this study was prepared within 1 h in an open environment. It was worth noting that CTAB not only served as a soft template for forming pore, but also induced ordered structure, which was verified by SEM, TEM, and Gas sorption. Benefit from its hierarchical pore structure, HPnDNH₂ exhibited higher adsorption capacity (690.0 mg g^-1 for HP1DNH₂ and 808.7 mg g^-1 for HP1.5DNH₂) and faster kinetics for ReO₄^-/TcO₄^- than 1DNH₂ (without employing CTAB). Additionally, the material used to remove TcO₄^- from alkaline nuclear waste was seldom reported, because combining features of alkali resistance and high uptake selectivity was not easy to achieve. In this study, in the case of HP1DNH₂, it displayed outstanding adsorption efficiency toward aqueous ReO₄^-/TcO₄^- in 1 mol L^-1 NaOH solution (92%) and simulated Savannah River Site High-level waste (SRS HLW) melter recycle stream (98%), which could be a potentially excellent nuclear waste adsorbing material.

Ultra-stable 3D pyridinium salt-based polymeric network nanotrap for selective 99TcO4-/ReO4- capture via hydrophobic and steric engineering

Selective capture of radioactive ⁹⁹TcO₄^- from highly alkaline nuclear waste is highly desirable for environmental remediation and waste disposal. However, the combined features of adsorbents with excellent chemical stability and high capture selectivity for ⁹⁹TcO₄^- have not yet been achieved. Herein, we report an ultra-stable 3D pyridinium salt-based polymeric network (TMP-TBPM) nanotrap with remarkable radiation, acid and base stability for selective capture of ReO₄^- via hydrophobic engineering and steric hindrance, a non-radioactive surrogate of ⁹⁹TcO₄^-. The batch capture experiments show that TMP-TBPM has high capture capacity (918.7 mg g^-1) and fast sorption kinetics (94.3 % removal in 2 min), which can be attributed to the high density of pyridinium salt-based units on the highly accessible pore channels of 3D interconnected low-density skeleton. In addition, the introduction of abundant alkyl and tetraphenylmethane units into the 3D framework not only greatly enhanced the hydrophobicity and stability of TMP-TBPM, but also significantly improved the affinity toward ⁹⁹TcO₄^-/ReO₄^-, enabling reversible and selective capture of ⁹⁹TcO₄^-/ReO₄^- even under highly alkaline conditions. This study exhibits the great potential of 3D pyridinium salt-based polymeric network nanotrap for ⁹⁹TcO₄^-/ReO₄^- capture from highly alkaline nuclear waste, providing a new strategy to construct high-performance cationic polymeric sorbents for radioactive wastewater treatment.