Iodine Capture Research Articles

Constructing quinazolinone-anchored electron-rich covalent organic frameworks by photocatalytic reductive cyclization for idealizing iodine capture

Constructing ideal adsorbent for the capture of radioactive iodine often requires both high adsorption capacity and fast adsorption kinetics. However, this remains a challenging issue. Herein, we present an effective method to idealize iodine capture with both ultrahigh adsorption capacity and fast adsorption rate through the construction of quinazolinone-anchored covalent organic frameworks (COFs). Post-synthesis modification was employed to functionalize two vinyl free-standing COFs with quinazolinone units through in-situ photocatalytic reductive cyclization between vinyl and 2-aminobenzamide units. The developed material, ECUT-COF-13, exhibits not only I2 uptake capacity as high as 10.81 g g−1, exceeding all established adsorbents for such use, but also very fast adsorption rate of 1.4 gh−1, surpassing all previously reported two-dimensional COFs. The outstanding I2 capture performance mainly results from an electron-rich mechanism, since anchoring quinazolinone units in COFs will lead to enhanced π-conjugated net and ultrahigh nitrogen content. The results demonstrate not only a new avenue for functionalizing COFs, but also a general electron-rich strategy for COFs.

Cu-loaded MOF-303 for iodine adsorption: The roles of Cu species and pyrazole ligands

The capture of toxic radioiodine is an increasingly important priority for the safe development of nuclear energy. Copper is a promising alternative for expensive silver to capture iodine. To develop novel copper-based adsorbents and determine the effect of copper species on iodine adsorption, the metal–organic framework with dual-pyrazole ligands (MOF-303) is employed as the scaffold to bind Cu2+ species. Cu0 nanoparticles were formed after the reduction by NaBH4. The obtained Cu2+-MOF-303 and Cu0-MOF-303 show high iodine uptake capacities at 353 K, 747 mg·g−1 and 837 mg·g−1, respectively. They also show high iodine uptake capacities of more than 300 mg·g−1 at a high temperature (423 K), which are better than other Cu-based adsorbents. Besides, the loading of Cu can enhance the iodine selectivity under humid vapor, and iodine adsorption rate in iodine-cyclohexane solutions. The Cu0 on Cu0-MOF-303 can react with iodine directly via the redox mechanism. For Cu2+-MOF-303, the adjacent pyrazole ligands can chelate with Cu2+ ions strongly and transfer charges to trapped iodine to form polyiodide anions, and thus stable CuI species could also be generated. The strategy of anchoring Cu species using MOF-303 provides large channels for iodine diffusion, and highly-dispersed Cu and N sites for iodine capture.

Iodine Capture by Ag-Loaded Solid Sorbents Followed by Ag Recycling and Iodine Immobilization: An End-to-End Process

The article demonstrates the complete process of I2(g) capture using Ag-exchanged faujasite (AgX) and Ag-exchanged mordenite (AgZ) zeolite sorbents, the recovery of Ag for recyclability of iodine capture, and the immobilization of iodide (from the elution process) into an iodosodalite waste form, which is chemically and environmentally stable. The gaseous iodine, I2(g), was captured in the AgX via chemisorption by Ag and converted to AgI within the aluminosilicate zeolite frameworks. The elution reaction in Na2S resulted in the precipitation of Ag2S and dissolution of I– and Na+ into the aqueous solution, where powdered sorbent showed higher conversion efficiency than the granular form, which is attributed to Na2S-solution diffusion limitations in the granules. The Ag2S-containing aluminosilicate precipitates were filtered out of the solution, and the filtrate (aqueous solution) was used to synthesize iodosodalite to immobilize iodide. The iodine capture using the recovered Ag2S-containing sorbents shows equivalent iodine loadings to the AgX starting material of Qe = 0.355 g/g for powdered material and 0.255 g/g for granular material, demonstrating the potential recycling of Ag for iodine capture as Ag2S-based sorbents.

Calix[4]arene Derivative for Iodine Capture and Effect on Leaching of Iodine through Packaging

A hydrophobic calix[4]arene derivative was investigated for its iodine (I2) capture efficiency from gaseous and liquid phase. The iodine uptake was followed by UV-vis spectroscopy. Additionally, the influence of the calix[4]arene derivative-polyolefin system on the leaching of iodine through packaging from a povidone-iodine-based (PVP-I) formulation was evaluated. In fact, iodine is a low-cost, multi-target, and broad-spectrum antiseptic. However, it is volatile, and the extended storage of I2-based formulations is challenging in plastic packaging. Here, we investigated the possibility of reducing the loss of I2 from an iodophor formulation by incorporating 4-tert-butylcalix [4]arene-tetraacetic acid tetraethyl ester (CX) and its iodine complex in high-density polyethylene (HDPE) or polypropylene (PP) via a swelling procedure. Surface and bulk changes were monitored by contact angle, thermogravimetric analysis (TGA), and UV-vis diffuse reflectance spectra. The barrier effect of the different polymeric systems (embedded with CX, iodine-CX complex, or I2) was evaluated by monitoring the I2 retention in a buffered PVP-I solution by UV-vis spectroscopy. Overall, experimental data showed the capability of the calix[4]arene derivative to complex iodine in solution and the solid state and a significant reduction in the iodine leaching by the PP-CX systems.

Linkage Design in Two-Dimensional Covalent Organic Frameworks for High Iodine Uptake.

Radioactive iodine waste in the nuclear field is harmful to the environment and human health. Covalent organic frameworks (COFs) are a novel kind of porous organic material with a well-fine and unformal structure, which is an excellent candidate as a solid adsorbent for iodine adsorption. Herein, a linkage design is proposed for effective iodine adsorption. Imine-linkage COF (I-COF) and hydrazone-linked COF (H-COF) are constructed under solvothermal conditions. The Brunauer-Emmett-Teller surface area of H-COF is as high as 1747 m2 g-1 . Furthermore, the H-COF shows high porosity, stability, and rich atoms in the linkage. As a result, the work outperforms most of the previous reports in iodine capture with a high capture value at 5.72gg-1 .

A robust sp2 carbon-conjugated COF for efficient iodine uptake

Synthesis of fully sp2-carbon conjugated covalent organic frameworks (COFs) is generally considered extremely challenging due to the low reversibility of the CC bond. Herein, a novel sp2-carbon conjugated COF material, named sp2c-TFPA-pXD, was prepared by Knoevenagel reaction employing tris(4-formylphenyl)amine with triangular geometry as the knot and p-xylylene dicyanide with symmetric structure as the linker unit. The CC linkages topologically connect the two precursors to a fully sp2-carbon conjugated 2D lattice and develop an eclipsed layer framework, giving sp2c-TFPA-pXD outstanding stability. The prepared sp2c-TFPA-pXD does not decompose in nitrogen atmosphere up to 323 °C, and can be stably present in boiling water, acids, bases and common organic solvents. The excellent chemical and thermal stability of sp2c-TFPA-pXD makes it suitable for the harsh environment of radioiodine treatment. In fact, sp2c-TFPA-pXD shows moderate iodine capture capacity in iodine vapor (1.22 g/g), and also shows acceptable iodine capture performance under real industrial conditions of high temperatures and low iodine concentrations. The iodide capture properties of sp2c-TFPA-pXD can be attributed to its regular channels and sp2-carbon conjugate structure. In addition, sp2c-TFPA-pXD can be reused by simple ethanol soaking treatment, and can almost maintain its original iodine capture performance after five cycles. In addition, sp2c-TFPA-pXD also displays noteworthy capability as adsorbent for iodine in cyclohexane solution. Our study confirms that sp2c-TFPA-pXD is an excellent candidate material for capturing iodine from air and solutions in harsh environments. We hope that the report of sp2c-TFPA-pXD for iodine capture could open up new avenues for sp2-carbon conjugated COFs applications and encourage more research to explore the radioiodine capture potential of other stable COFs.

Highly efficient iodine capture by hydrophobic bismuth-based chrysotile membrane from humid gas streams

Because of their non-toxicity and low cost, bismuth-based materials have received considerable attention for the capture of gaseous iodine, especially for the removal of radioactive iodine in nuclear post-processing plants. In the actual operation conditions of reprocessing plant, the presence of water vapor must be considered as an important factor because it will significantly affect the iodine capturing efficiency for most iodine-capturing materials. To address this problem, we successfully synthesized a hydrophobic bismuth-based chrysotile membrane, which was modified by the silane coupling agent KH570. The chrysotile fiber was chosen to provide rich reactive sites for bismuth loading, and the bismuth was chosen due to its high affinity to iodine. The hydrophobic surface endowed by KH570 acts as a ‘protecting layer’ when water vapor exists during iodine adsorption. The maximum of iodine capture efficiency of the prepared membrane reached 483.37 mg/g in air, and 443.04 mg/g under 75 % relative humidity. Comparing hydrophobic membrane with one that non-modified by KH570, the hydrophobic membrane increases about 54 % iodine adsorption capacity in humid condition. This study provides a certain reference value for the application of bismuth-based materials in iodine removal under humid conditions.

Exploiting a Multi-Responsive Oxadiazole Moiety in One Three-Dimensional Metal-Organic Framework for Remedies to Three Environmental Issues.

Multifunctional metal-organic frameworks (MOFs) rely on the properties of metal centers (nodes) and/or linkers (struts) for their diverse applications in the emerging field of research. Currently, there is a huge demand for MOF materials in the field of capture/fixation/sensing of air pollutants, harmful chemical effluents, and nuclear waste. However, it is a challenging task to utilize one MOF for providing remedies to all these issues. On the basis of our current research activities, we have identified that an oxadiazole moiety-a five-membered ring with two different heteroatoms (O and N)-in a carboxylate linker can be the key to generating such MOF materials for its (a) inherent polarizable nature and molecular docking ability and (b) photoluminescence properties. In this work, we report a 3D MOF {[Co2(oxdz)2(tpbn)(H2O)2]·4H2O}n (1), self-assembled at room temperature from a three-component reaction, with an oxadiazole moiety (where H2oxdz = 4,4'-(1,3,4-oxadiazole-2,5-diyl)dibenzoic acid and tpbn = N,N',N,"N″'-tetrakis(2-pyridylmethyl)-1,4-diaminobutane). The inherent polarizable nature of the oxadiazole moiety in 1 has been efficiently exploited for (i) multimedia iodine capture and (ii) fixation of CO2 under solvent-free and ambient conditions. On the other hand, the luminescent nature of the framework is found to be an efficient, highly preferred turn-on sensor for the ultra-fast detection of ketones with a limit as low as parts-per-trillion (mesitylene oxide: 447 ppt; cycloheptanone: 4.7 ppb; cyclohexanone: 17.2 ppb; acetylacetone: 18 ppb).

In situ growth of UiO-66-NH2 in wood-derived cellulose for iodine adsorption.

The capture of radioactive iodine is an inevitable requirement in nuclear industry for environmental protection. Metal-organic frameworks (MOFs) are a new generation of sorbents that have wide applications for iodine adsorption and recovery. Although the loading of MOFs on wood can avoid the drawbacks of the powder form of MOFs in implementation, the dense structure of wood results in the lower loading, even after delignification, which limits the adsorption capacity. Herein, a hierarchically porous UiO-66-NH2 @WCA composite was fabricated by in-situ synthesis of UiO-66-NH2 in wood-derived cellulose aerogel (WCA) that was further removed hemicellulose from delignified wood. UiO-66-NH2 @WCA exhibited a high loading (36wt%) of UiO-66-NH2 crystals and a high adsorption capacity of 704mg/g for iodine vapor and 248mg/g for iodine aqueous solution. The adsorption behavior in iodine aqueous solution was well predicted by the Freundlich isotherm and pseudo-second-order kinetic model. The adsorption capacity of UiO-66-NH2 @WCA was highest in solution when the pH was 6, while the ionic strength had little effect. The hydroxyl groups on the WCA matrix had a charge transfer effect with iodine, providing additional sites for iodine capture. Furthermore, a packed column system was applied to demonstrate the excellent recyclability and potential for practical application.

Superfast Capture of Iodine from Air, Water, and Organic Solvent by Potential Dithiocarbamate-Based Organic Polymer.

Organic polymers are widely explored due to their high stability, scalability, and more facile modification properties. We developed cost-effective dithiocarbamate-based organic polymers synthesized using diamides, carbon disulfide, and diamines to apply for environmental remediation. The sequestration of radioiodine is a serious concern to tackle when dealing with nuclear power for energy requirements. However, many of the current sorbents have the problem of slower adsorption for removing iodine. In this report, we discuss the utilization of an electron-rich dithiocarbamate-based organic polymer for the removal of iodine in a very short time and with high uptake. Our material showed 2.8 g/g uptake of vapor iodine in 1 h, 915.19 mg/g uptake of iodine from cyclohexane within 5 s, 93% removal of saturated iodine from water in 1 min, and 1250 mg/g uptake of triiodide ions from water within 30 s. To the best of our knowledge, the iodine capture was faster than previously observed for any existing material. The material was fully recyclable when applied for up to four cycles. Hence, this dithiocarbamate-based polymer can be a promising system for the fast removal of various forms of iodine and, thus, enhance environmental security.

Vinyl-functionalized covalent organic frameworks for effective radioactive iodine capture in aqueous solution

131I radioisotopes have been widely employed in diagnostic and therapeutic medicine processes, particularly for thyroid cancer. The radiation hazard of 131I offers a potential threat to environmental safety or human health, so the wastewater generated from the production of 131I drugs must be effluent disposed of on time. In this study, we developed novel vinyl-functionalized covalent organic frameworks (COFs) with large pore volume and internal surface area for highly effective radioactive iodine ions adsorption in water. The as-produced spherical COFs (COF-V) exhibited a rapid adsorption rate (0.318 g g−1 min−1) and exceptionally high adsorption capacity of up to 437.8 mg g−1 for iodine ions in water. Furthermore, it demonstrated more than 90% removal of Na131I in water with radiation doses ranging from 181.3 MBq (4.9 mCi) to 1017.5 MBq (27.5 mCi). Additional characterizations and density functional theory (DFT) calculations revealed that the vinyl groups were linked with a benzene ring and imine to form a large and complete π-π conjugate system with 1D open channels. These channels provided sufficient sites for the effective adsorption of I ions on vinyl groups and benzene rings through hydrogen bonding. The excellent adsorption performance and radiation stability make the developed spherical COF-V a promising candidate for efficient radioactive iodine removal in wastewater.

Abatement of radioiodine in aqueous reprocessing off-gas.

The reprocessing used nuclear fuel (UNF) releases volatile fission and activation products, including 129I, into the off-gas of a processing plant. Mitigation of the release of vapor phase radionuclides is necessary for meeting regulatory requirements in the United States and other countries. In an aqueous reprocessing plant, volatile radioiodine could be present in several forms, depending on the chemistry of the process used. Inorganic iodine will be the predominate species in any shearing or voloxidation pretreatment off-gas and dissolver off-gas (DOG). Organic iodides such as CH3I, C4H9I, and C12H25I have been proposed to be generated during solvent extraction; thus, these species must be captured from the vessel off-gas (VOG). The abatement of inorganic and organic iodide species to meet United States regulatory requirements has been demonstrated in laboratory experiments using Ag-based solid sorbents. The data presented in this paper includes the effect of gas composition (e.g., the presence of water vapor and NO x ), iodine speciation (I2, CH3I, C4H9I, C12H25I), and sorbent bed parameters (e.g., temperature, sorbent age) on complete iodine capture on Ag-mordenite in an aqueous reprocessing plant.

Frontispiece: Cluster‐Based Crystalline Materials for Iodine Capture

Clusters is a group of the same or different elements that aggregate closely together. Cluster-based crystalline materials, including molecular clusters and cluster-based metal-organic frameworks, are emerging candidates for iodine capture due to their aggregative binding sites, precise structural information, tunable pores/packing patterns, and abundant modifications. The contributions of these cluster-based crystalline materials to the host-guest chemistry of iodine are summarized in the Review by W.-H. Fang and colleagues (DOI: 10.1002/chem.202202638).

Highly efficient iodine capture and ultrafast fluorescent detection of heavy metals using PANI/LDH@CNT nanocomposite

Here, the hybrid material of polyaniline/layered double hydroxide@carbonnanotubes (PANI/LDH@CNT) is considered a multifunctional material. Instrumental methods, including FTIR, XRD, TEM, SEM, and TGA/DTA were utilized to characterize PANI/LDH@CNT. The polymerization method created PANI/LDH@CNT as an adsorbent to remove toxic iodine in hexane solution with a capture capacity of 303.20 mg g−1 during 9 h. It is 900 mg g−1 in the vapor phase within 24 h. After three cycles, the PANI/LDH@CNT could be regenerated while maintaining 91.90 % iodine adsorption efficiency. Due to the presence of free amine (-N) groups, OH−, CO2H, and π-π conjugated structures in the PANI/LDH@CNT, it is also explored for efficient iodine uptake. It was demonstrated that the pseudo-first-order (PFO) and Langmuir model had the optimum correlation with the kinetic and isotherm data, respectively. Moreover, the use of PANI/LDH@CNT is not only limited to iodine capture; it can also be utilized as a sensitive sensor that displays a fluorescence “turn-off” response for Mn7+ and Cr6+ ions and a fluorescence “turn-on” response in the case of Al3+ ions. The fluorescence intensity of the PANI/LDH@CNT was turned off in the presence of Mn7+ and Cr6+ because of the fluorescence inner filter effect (IFE) mechanism. In contrast, the fluorescence intensity was turned on in the case of Al3+, relying on the chelation-enhanced fluorescence (CHEF) effect mechanism. Under optimal conditions, the limit of detection (LOD) of 51, 59, and 81 nM for Mn7+, Cr6+, and Al3+, respectively. According to the literature, this is probably the first example based on PANI/LDH@CNT as a multifunctional hybrid material employed as an adsorbent for capturing radioactive iodine and as a chemosensor for detecting heavy metal ions in aqueous solutions.

Polymorphic Covalent Organic Frameworks: Molecularly Defined Pore Structures and Iodine Adsorption Property.

Radioactive iodine-capturing materials are urgently needed for the emerging challenges in nuclear waste disposal. The various pore structures of covalent organic frameworks (COFs) render them promising candidates for efficient iodine adsorption. However, the detailed structure-property relationship of COFs in iodine adsorption remains elusive. Herein, two polymorphic COFs with significantly different crystalline structures are obtained based on the same building blocks with varied molecular ratios. The two COFs both have high crystallinity, high specific surface area, and excellent chemical and thermal stability. Compared with the [C4+C4] topology (PyT-2) with an AA stacking form, the [C4+C2] topology (PyT-1) with an AB stacking form has more twisted pore channels and complex ink-bottle pores. At ambient conditions, PyT-1 and PyT-2 both exhibit good adsorption properties for iodine capture either in a gaseous or liquid medium. Remarkably, PyT-1 presents an excellent maximum adsorption capacity (0.635 g g-1), and the adsorption limit of PyT-2 is 0.445 g g-1 in an n-hexane solution with an iodine concentration of 400 mg L-1, which is highly comparable to the state-of-the-art iodine absorption performance. This study provides a guide for the future molecular design strategy toward novel iodine adsorbents.

Encapsulating covalent organic frameworks (COFs) in cellulose aerogels for efficient iodine uptake

Efficient capture and storage of radioiodine are of great importance for developing nuclear energy and tackling nuclear waste, which however remain challenging due to the scarcity of powerful materials. In this work, we rationally design and fabricate a hybrid material by encapsulating covalent organic frameworks (COFs) into ultralight cellulose aerogels for efficient iodine (I2) capture. Two kinds of functionalized cellulose precursors that can be covalently cross-linked are synthesized. Solvothermally synthesized COF particles with a uniform diameter of ∼ 500 nm are then introduced into the precursors followed by freeze drying to produce hybrid aerogels. With the presence of rich and ordered micropores afforded by COFs, these highly porous aerogels exhibit excellent organic solvent absorption performances and high uptake capacities toward solvent-dissolved and vaporized I2. More importantly, in view of the processable and robust structure, we realize the shaping of hybrid aerogels into aerogel columns to effectively capture I2 vapor and I2 solute in continuous operations. Therefore, this work not only provides a new way to shape COF materials but also could inspire the design of viable platforms for high-performance I2 capture.

Correction: Ln-MOFs with window-shaped channels based on triazine tricarboxylic acid as a linker for the highly efficient capture of cationic dyes and iodine

Correction for ‘Ln-MOFs with window-shaped channels based on triazine tricarboxylic acid as a linker for the highly efficient capture of cationic dyes and iodine’ by Yue Zhao et al., Inorg. Chem. Front., 2021, 8, 1736–1746, https://doi.org/10.1039/d0qi01279c.

Rich nitrogen atoms in an azine covalent organic framework for gas uptake

An azine-linked COF (Ns-COF) exhibited high porosity and rich N-atoms on the walls, suggesting good carbon dioxide and iodine capture.

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture.

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

Covalent organic frameworks with triazine units for iodine capture via weak molecular interactions

Triazine unit functionalized covalent organic frameworks were predesigned for exceptional iodine capture through weak molecular interactions.