Metal-organic structure for removing iodine oxyanion

Abstract

The present invention provides the use of metal-organic frameworks (MOFs) in the removal of certain chemical species or compounds, particularly iodate oxyanions, from liquids or liquid streams. In some embodiments, the MOF is a Zr-based MOF (such as NU-1000 or MOF-808). Zr-based MOFs, including NU-1000 or MOF-808, can be used to remove these oxyanions from various liquid streams or liquids in industrial processes, such as nuclear and fossil fuel power plants.

Description

Technical Field

[0001] Background of the Invention Field of the Invention The present invention and its embodiments relate to the removal of a given chemical species from a liquid. Specifically, the present invention and its embodiments relate to the use of metal-organic frameworks having specific properties suitable for the removal of oxyanions such as iodine oxyanions from a liquid stream.

Background Art

[0002] Description of Related Art Nuclear facilities struggle with the removal of several impurities that are significantly involved in or drive issues such as dose, radioactive waste generation, concerns about environmental drainage, and material degradation. Similarly, fossil fuel power plants struggle with regulatory waste requirements related to flue gas desulfurization and wastewater from scrubbers, fireside cleaning, and boiler cleaning operations, and similarly, with the obligation for groundwater purification resulting from coal mine outflows and ash pond leaching. Current technologies (e.g., ion exchange) lack the ability to remove these impurities to the extent required due to factors related to the capture of other impurities and competing mechanisms.

[0003] Recently developed separation media provide organometallic ligands decorated on a resin backbone (where it would normally be possible to hold cation exchange groups) that are significantly improved removal media for analytes that are cations such as cobalt. Unfortunately, such ligands cannot accommodate the larger geometries of oxyanions of species such as selenium found in the target water stream. For example, ion exchange and adsorption technologies are typically used to capture chemical impurities in a water stream. However, these technologies are exposed to several significant drawbacks. They are non-specific (i.e., capture many different species to some extent), subject to competition (i.e., the higher concentration species dominates), and reversible (i.e., the captured species is released when it undergoes a change in the aqueous state).

[0004] The removal of selenium from water streams is of particular interest. Selenium is a naturally occurring element that is essential for human health at low concentrations. However, among all essential elements, selenium has the most limited range between dietary deficiency (<40 μg / day) and toxicity (>400 μg / day). Selenium enters our waterways through several different sources such as agricultural runoff, mining, industrial production, and flue gas desulfurization processes. As a result of the narrow range between deficiency and toxicity, it is very important to monitor and manage the amount of biologically available selenium in our drinking water. The U.S. Environmental Protection Agency recognizes the risks of selenium and has mandated a maximum allowable level of 50 ppb for selenium in drinking water. However, in more recent proposals, regulatory agencies plan to reduce selenium discharge requirements to 14 ppb and then further reduce them to about 10 ppb, and without methods beyond typical ion exchange or adsorption engineering unit operations that are typical in the current operation of many flue gas desulfurization wastewater treatment facilities, it will be impossible to achieve such purity.

[0005] Selenium can occur in both organic and inorganic forms, but has high solubility and thus selenite (SeO3 2- ) and selenate (SeO4 2-) Due to the biological availability of inorganic species such as these, these anions have become a major focus of purification techniques. Many techniques for removing selenite and selenate from water, including the use of vertical flow wetland zones and bioreactors, have been investigated, but high start-up costs and size requirements have limited the application of these techniques. Alternative approaches that have been investigated include the use of adsorption media to absorb and remove unwanted inorganic selenium. Iron oxides (hematite, goethite, and ferrihydrite) have been extensively studied as potential adsorbents for selenite and selenate in aqueous solutions. These iron-based materials have a very low surface area, meaning that many materials are discarded due to the lack of available adsorption sites. Iron oxides also tend to be effective for the removal of selenite due to the formation of inner-sphere complexes between the selenite anions and the iron oxide surface, while the removal of selenate is not sufficient as only weak outer-sphere interactions occur.

[0006] Furthermore, the removal of other oxyanions from water or water streams, such as waste liquid streams or contaminated liquids, for example liquids having radioactive oxyanions, may also be required in certain situations related to nuclear power plants. Such other oxyanions, including oxyanions of antimony, lead, and iodate from water associated with nuclear fuel plants, may also be problematic in some situations.

[0007] Accordingly, there is a need for a novel technology that effectively and efficiently removes specific impurities such as selenate, antimonate, lead, iodate, and other oxyanions including oxyanions containing selenium, antimony, lead, iodate, and other oxyanions from water and other liquid streams such as other industrial water-based streams or large quantities of liquids held in storage for treatment. Such a technology is sought to remove these impurities in the presence of other competing species or chemical species that may compete for removal, thereby effectively reducing the removal efficiency of the species targeted for removal. Also sought is such a technology that specifically targets the capture of these impurities and in a manner that minimizes any reversibility or release from the capture, thereby being held with a very high binding energy. In particular, different types of structural media are required to specifically address the removal of specific species such as aqueous oxyanions of selenium at low levels that have a binding energy high enough to maintain a substantially irreversible uptake, since the analyte concentration decreases while the competing concentration simultaneously increases. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0008] BRIEF SUMMARY OF THE INVENTION The present invention provides for the use of metal-organic frameworks (MOFs) in the removal of specific species or compounds, particularly oxyanions, from liquids or liquid streams. In some embodiments, the oxyanions to be removed include, for example, oxyanions of selenium including selenite (SeO3 2- ) and selenate (SeO4 2- ); oxyanions of antimony including oxyanions in either the redox state of Sb[III] (antimonite) or Sb[V] (antimonate); oxyanions of lead including oxyanions in either the redox state of Pb[II] or Pb[IV] such as Pb(OH)6 2- , Pb(OH)6 4- , PbO3 2- and PbO2 2- ; and IO3 -(iodate) and other iodine oxyanions are included.

[0009] In one embodiment, the present invention provides the use of a metal-organic framework for removing oxyanions, such as those described above, from a liquid stream, such as an industrial process liquid stream containing wastewater, or from a given quantity of liquid held for treatment. In particular, the present invention provides a method for reducing the concentration of an oxyanion in a liquid stream or liquid, the method comprising contacting a liquid stream or liquid containing the oxyanion with a structure comprising a metal-organic framework (MOF) having the molecular formula Zr6(μ3-O)4(μ3OH)4(OH)4(H2O)4(TBAPy)2, where TBAPy is 1,3,6,8-tetrakis(p-benzoic acid)pyrene (known as NU-1000), and complexing at least a portion of the oxyanion on the metal-organic framework by binding to zirconium-derived node forms of the MOF structure or by binding to specialized ligands linked to the nodes of the MOF, and providing ligands selective for oxyanion uptake, or both, thereby reducing the concentration of the oxyanion in the liquid stream or liquid. The ability of NU-1000 to reduce the concentration of oxyanions in water provides a more environmentally acceptable water stream. In other embodiments, prior to activation, MOF-808 having the molecular formula Zr6O5(OH)3(BTC)2(HCOO)5(H2O)2, where BTC is 1,3,5-benzenetricarboxylate, may be used in a similar manner, and after activation, MOF-808 having the molecular formula Zr6(μ3-O)4(μ3-OH)4(BTC)2(OH)6(H2O)6, where BTC = 1,3,5-benzenetricarboxylate, may be used in a similar manner.

[0010] The present invention also features the further possibility of reducing the concentration of an oxyanion in an aqueous liquid stream or in a liquid to ultra-low levels when the stream contains competing species such as oxyanions of sulfur or boron, and when sodium cations are present in the local liquid near the node uptake point for charge balance purposes, where the competing species compete for the node adsorption sites of the MOF. However, in some embodiments, depending on the factors to be considered, even when the concentration of such competing species exceeds the effluent concentration of the oxyanion initially targeted for removal, the effluent oxyanion concentration can be maintained at a low level. The present invention further achieves the required effluent oxyanion concentration even when the temperature is raised to the treatment temperature of condensate cooling water in a typical power plant where temperatures from room temperature are more frequently encountered. The present invention also includes potential embodiments where one of ordinary skill in the art can apply known regeneration procedures to MOF-based media such as NU-1000 or MOF-808 previously exposed to oxyanions, or apply known metallization chemistries to substitute less costly metal components such as hafnium (Hf) or zirconium (Zr) or both in the MOF, and should be able to apply known methodologies for reducing the commercial cost of using NU-1000 or MOF-808 for water treatment applications.

[0011] MOFs are relatively costly to manufacture and, in some cases, may incur exorbitant costs for their use. Accordingly, the present invention also describes a method for binding certain MOFs to a substrate to form MOF-containing products that can be used in a number of ways depending on the particular MOF bound to the substrate. Thus, it should be understood that a particular MOF having particular properties, such as an affinity for a particular chemical species to be removed from a given fluid, can be selected for binding to the substrate. The substrate can be any substrate to which a given MOF can be bound, and the form and shape of the substrate may be selected based on its end use. For example, the configuration or shape of the substrate can enable the use of the selected MOF in a given environment, such as a given industrial process or a given piece of equipment, and can provide for proper exposure of the MOF to the fluid in that environment, such as exposure of the MOF to a given fluid in a given process or piece of equipment.

[0012] It should be understood that the MOF can be any one of the MOFs described herein. For example, in one embodiment, the MOF can be an MOF capable of removing a particular chemical species from a given fluid. For example, the MOF can be an MOF configured to remove or capable of removing a particular liquid-phase species from a given liquid or liquid stream. In some embodiments, the MOF is a Zr-based MOF (such as NU-1000 or MOF-808) for removing a particular anion, such as an oxyanion containing an oxyanion of iodine, such as iodate, from a liquid or liquid stream. In some embodiments, the liquid or liquid stream can be an industrial liquid or liquid stream, such as a waste liquid stream or a liquid stream associated with a nuclear power plant containing a contaminated liquid containing a particular liquid-phase species to be removed, such as a liquid containing an oxyanion containing an oxyanion of iodine, such as iodate.

[0013] In one embodiment, the substrate may be any inert substrate to which the MOF can be bound. For example, the substrate may be inert polypropylene polymer resin beads, a macroscopic fabric such as a mesh material or a mesh filter, a molecular fabric, or any other three-dimensional shaped substrate.

[0014] In one embodiment, a MOF comprising any of the MOFs described herein, such as a Zr-based MOF (such as NU-1000 or MOF-808), may be bound to an inert substrate such as polypropylene polymer resin beads, a macroscopic fabric such as a mesh material or a mesh filter, or a molecular fabric. In one embodiment for binding the MOF, the substrate is first subjected to atomic layer deposition of a metal oxide such as aluminum oxide, titanium oxide, or zinc oxide on the surface of the substrate. Alternatively, the MOF may be bound to CTAB in solution and then combined with a substrate having a metal oxide. As a result, the MOF is bound to the substrate, producing a product consisting of the substrate having the bound MOF. In another embodiment for binding the MOF to the substrate, the MOF may be bound to beta-CD in solution and then combined with the substrate. As a result, the MOF is bound to the substrate via beta-CD, producing a product consisting of the substrate having the bound MOF.

[0015] It should be understood that the MOF-containing substrate, which may be a commodity, may be used in a number of ways depending on the MOF selected to bind to a given substrate. As described above, in some embodiments, the MOF may be a MOF capable of removing certain chemical species from a given fluid. For example, the MOF may be a Zr-based MOF (such as NU-1000 or MOF-808) configured to remove certain anions and certain cations, such as certain oxyanions, from a liquid or liquid stream. In particular, NU-1000 is based on zirconium (Zr) and has the molecular formula Zr6(μ3-O)4(μ3OH)4(OH)4(H2O)4(TBAPy)2 [where TBAPy is 1,3,6,8-tetrakis(p-benzoic acid)pyrene]. MOF-808 has the molecular formula Zr6O5(OH)3(BTC)2(HCOO)5(H2O)2 (where BTC is 1,3,5-benzenetricarboxylate (before activation)) and the formula Zr6(μ3-O)4(μ3-OH)4(BTC)2(OH)6(H2O)6 (where BTC = 1,3,5-benzenetricarboxylate (after activation with hydrochloric acid)), but other linkers that can bind via carboxylate may also be used. NU-1000 or MOF-808 is selenite (SeO3 2- ) and selenate (SeO4 2- ) oxyanions of selenium; antimony oxyanions containing oxyanions in either the redox state of Sb[III] (antimonite) or Sb[V] (antimonate); lead oxyanions containing oxyanions in either the redox state of Pb[II] or Pb[IV], such as Pb(OH)6 2- , Pb(OH)6 4- , PbO3 2- and PbO2 2- ; and IO3 -It can be used on a substrate to remove iodine oxyanions such as (iodate). Thus, such a MOF can provide the ability to remove anionic species from a given liquid or liquid stream, such as a coolant or waste stream of a power plant, including contaminated liquids held for the liquid flow or treatment of a nuclear power plant. In an embodiment of the present invention, for example, the following items are provided. (Item 1) A method for reducing the concentration of an iodine oxyanion from a liquid stream, the method comprising: contacting a liquid stream containing an iodine oxyanion with a zirconium-based metal-organic framework; and complexing the iodine oxyanion with the zirconium-based metal-organic framework, thereby reducing the concentration of the iodine oxyanion in the liquid stream . (Item 2) The method according to item 1, wherein the liquid stream includes a liquid stream from a nuclear power plant. (Item 3) The method according to item 2, wherein the contacting step is carried out using a desalination device. (Item 4) The method according to item 2, wherein the zirconium-based metal-organic framework is disposed on a substrate. (Item 5) The method according to item 4, wherein the substrate includes a plurality of polypropylene beads. (Item 6) The method according to item 4, wherein the substrate includes a macroscopic fabric. (Item 7) The method according to item 4, wherein the substrate includes a molecular fabric including organic strands. (Item 8) The method according to item 2, wherein the zirconium-based metal-organic framework includes MOF-808. (Item 9) The method according to item 2, wherein the zirconium-based metal-organic framework includes MOF-808 before activation. (Item 10) The method according to item 2, wherein the zirconium-based metal-organic framework includes MOF-808 after activation. (Item 11) The method according to item 1, wherein the oxyanion includes iodate. (Item 12) The method according to item 1, wherein the complexing step includes an η2μ2 bond.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0041] Detailed Description of the Invention The present invention will be described in more detail below with reference to the accompanying drawings. Although the present invention is described in connection with specific embodiments, the present invention can be widely applied to various applications, and it should be understood that the description herein is intended to include alternatives, modifications, and equivalents within the spirit and scope of the present invention and the scope of the claims. Accordingly, the following description is exemplary in view of the fact that several embodiments are described (e.g., by the use of terms such as "preferably", "for example", or "in one embodiment"), but this description should not be seen as limiting or describing only those embodiments of the present invention, as it includes other embodiments not specifically listed herein. Further, the use of the terms "invention", "the present invention", "embodiment", and similar terms throughout this description is used broadly and is not meant to imply that the present invention requires or is limited to any particular aspect described, nor that such description is the only way to practice or use the present invention.

[0042] Generally, the present invention is directed to metal-organic frameworks (MOFs) for use in the removal of specific compounds, particularly oxyanions, from liquids or liquid streams. In some embodiments, the MOF is a Zr-based MOF (such as NU-1000 or MOF-808), and the oxyanions to be removed include, for example, selenite (SeO3 2- ) and selenate (SeO4 2- ) oxyanions of selenium; oxyanions of antimony including those in either the Sb[III] (antimonite) or Sb[V] (antimonate) redox state; Pb(OH)6 2- , Pb(OH)6 4- , PbO3 2- and PbO2 2- oxyanions of lead including those in either the Pb[II] or Pb[IV] redox state, such as; and oxyanions of iodine such as IO3 - (iodate). It should be understood that the preferred mechanism for the adsorption of oxyanions is node uptake via the oxidized / hydroxylated zirconium node morphology of the MOF. In some embodiments, iodate is removed using MOF-808. It should be understood that reference to a liquid stream includes a given quantity of liquid held in a tank, which may not be flowing as a stream. In this case, the held liquid can be treated in the same manner as described for a given liquid stream and, in some embodiments, may be made into a flowing liquid stream for treatment.

[0043] In one embodiment, the present invention provides the use of a metal-organic framework for removing an oxyanion, such as those described above, from a liquid stream, such as an industrial process liquid stream including a wastewater stream. In particular, the present invention is a method for reducing the concentration of an oxyanion in a liquid stream, the method comprising contacting a liquid stream containing the oxyanion with a structure comprising a metal-organic framework (MOF) having the molecular formula Zr6(μ3O)4(μ3OH)4(OH)4(H2O)4(TBAPy)2, where TBAPy is 1,3,6,8-tetrakis(p-benzoic acid)pyrene (known as NU-1000), and complexing at least a portion of the oxyanion on the metal-organic framework by binding to the zirconium-derived node forms of the MOF structure, or by binding to specialized ligands attached to the nodes of the MOF, providing ligands selective for oxyanion uptake, or both, thereby reducing the concentration of the oxyanion in the liquid stream. The ability of NU-1000 to reduce the concentration of oxyanions in water provides a more environmentally acceptable water stream. In other embodiments, prior to activation, MOF-808 having the molecular formula Zr6O5(OH)3(BTC)2(HCOO)5(H2O)2, where BTC is 1,3,5-benzenetricarboxylate, may be used in a similar manner, and after activation, MOF-808 having the molecular formula Zr6(μ3-O)4(μ3-OH)4(BTC)2(OH)6(H2O)6, where BTC = 1,3,5-benzenetricarboxylate, may be used in a similar manner.

[0044] Figure 1 shows a MOF according to an embodiment of the present invention. A MOF is a structurally diverse porous material composed of metal nodes bridged by organic linkers. A MOF is composed of multifunctional organic linkers and metal-based nodes interconnected by coordination bonds of moderate strength. With regard to the adsorption or complexation of analyte molecules from aqueous solutions, MOFs containing zirconium metal nodes are of interest due to their inherent stability over a wide pH range in water. This stability results from strong Zr(IV)-O bonds and can also make these structures mechanically and thermally robust up to temperatures exceeding 500 °C. MOFs in aqueous solutions are suitable candidate materials for applications such as precoatable filter / desalination devices or examples of independent packed column separations and are not incompatible with use within vessels already existing in a given plant, such as in a flue gas desulfurization wastewater treatment facility of an e - power plant (e.g., vessels already used for ion exchange) or a fossil fuel power plant.

[0045] MOFs may be usable in such liquid flow applications in their native structure, but the amount of pressure required to permeate a packed bed of such small particles (typical sizes are 5 micron crystallites formed from MOF particles, ranging from 75 to 1200 nanometers) may exceed the available fluid for operating the equipment, meaning that the MOF particles may need to be transferred to some other larger particle carriers (larger than the resin particle level, typically 50 to 850 microns in diameter in powder or bead form) so that the fluid can more easily permeate the agglomerates of carrier particles. One skilled in the art should be able to configure multiple methods for contacting MOF particles onto some suitable carrier particles such that the water permeability of such carrier particle agglomerates is high enough to obtain the required fluid volume throughput in either column flow through a bed of such carrier particles or flow through a filter providing a porous surface coated with such carrier particles. Thus, the adsorption properties of the MOF are still revealed because the MOF itself is exposed to the analyte in the water stream as the MOF medium flows around the carrier particles to which it is bound on the surface.

[0046] Figure 2 shows a particular MOF, NU-1000. NU-1000 is a Zr-based MOF with the molecular formula Zr6(μ3-O)4(μ3OH)4(OH)4(H2O)4(TBAPy)2 [where TBAPy is 1,3,6,8-tetrakis(p-benzoic acid)pyrene which can be used as an MOF in the present invention]. The parent structural node of this MOF consists of an octahedral Zr6 cluster capped by four μ3-OH and four μ3-O ligands. Eight of the twelve octahedral edges are connected to TBAPy units, while the remaining Zr coordination sites (after activation) are occupied by four terminal -OH and four terminal -OH2 ligands. The 3D structure is a 2D connected by TBAPy ligands It can be described as a Kagome sheet. Two of the four terminal -OH groups point to mesoporous channels, while the remaining terminal hydroxyls are within the smaller apertures between the Kagome sheets.

[0047] Figure 3 shows the structural features of the MOF, NU - 1000, of Figure 2. Further features of this MOF and its synthetic techniques are described in Mondloch, JE, W Bury, D Fairen - Jimenez, S Kwon, EJ DeMarco, MH Weston, AA Sarjeant, ST, which is incorporated herein by reference in its entirety. Nguyen, PC Stair, RQ Smurr, OK Farha and JT Hupp, ”Vapor - Phase Metalation by Atomic Layer Deposition in a Metal - Organic It is described in “Framework”, J. Am. Chem. Soc. (2013) 135, 10294-10297. For example, the synthesis of the organic linker of NU-1000 involves two steps: Suzuki coupling between 1,3,6,8-tetrabromopyrene and 4-(ethoxycarbonyl)phenyl)boronic acid, followed by hydrolysis of the resulting tetraester compound, resulting in the tetracarboxylic acid linker, 1,3,6,8-tetrakis(p-benzoic acid)-pyrene. To synthesize NU-1000, Zr6-cluster nodes are first formed by reacting zirconyl chloride octahydrate with an excess of benzoic acid modulator in N,N-dimethylformamide at 80 °C for 1 hour. After cooling the reaction mixture to room temperature, 0.2 equivalent of 1,3,6,8-tetrakis(p-benzoic acid)-pyrene linker is added and the mixture is heated at 100 °C for 24 hours to obtain benzoic acid-capped NU-1000. The MOF is activated with 8M HCl for 24 hours to remove the benzoic acid ligand and expose the terminal -OH and -OH2 on the nodes. It should also be understood that starting materials with low purity of ZrOCl2·8H2O and HfOCl2·xH2O reduce the cost of manufacturing NU-1000. For example, 99.99% pure ZrOCl2·8H2O and HfOCl2·xH2O cost approximately 400% more than 98% pure precursors. Also, the structural features of this MOF are described in Planas, N.; Mondloch, J. E.; Tussupbayev, S.; Borycz, J.; Gagliardi, L.; Hupp, J. T.; Farha, O. K.; Cramer, C. J. Defining the Proton Topology of the Zr6-Based Metal-Organic Framework NU-1000. J. Phys. Chem. Lett. 2014, 5, 3716-3723, which is hereby incorporated by reference in its entirety.

[0048] Naked NU-1000, unexpectedly, in an aqueous solution, selenite (SeO3 2-) and selenate (SeO4 2- ) have been found to complex with oxyanions of selenium. The results have shown that the oxyanions of selenium bind with such strength that they remove their anions to levels of 20 ppb in a simple continuous stirred tank environment within reasonable and relatively short times, and in other embodiments to even lower levels, for example 10 ppb and lower, 6 ppb and lower, and 2 ppb and lower. The binding with respect to selenate and selenite is shown to be directly to the zirconium nodes of the MOF without concern for ligand interactions with the MOF cavities. The ability of NU-1000 to complex with selenite and selenate has been realized without the need to modify the structure of NU-1000, for example by metallization using atomic layer deposition (ALD), by solvent-assisted linker exchange (SALE), or by solvent-assisted ligand incorporation (SALI).

[0049] In particular, a series of zirconium-based MOFs were tested with respect to their ability to adsorb and remove selenate and selenite anions from aqueous solutions. The MOFs were tested with respect to adsorption capacity and uptake time at various concentrations (Figure 7 is a flowchart outlining the screening process for selenate and selenite adsorption in Zr-based MOFs). NU-1000 was shown to have the highest adsorption capacity and the fastest uptake rate with respect to both selenate and selenite among all zirconium-based MOFs in this test.

[0050] Adsorbent: Various ratios of adsorbent to adsorbate were tested to understand how this ratio affects uptake. Samples of 2, 4, 6, and 8 mg of NU-1000 were exposed to 10 mL of a solution containing 1000 ppb of Se as either 2- or SeO3 2- . At all adsorbent:adsorbate ratios tested, 98.3% or more of the SeO3 2-is adsorbed, leaving on average 10 - 17 ppb in solution. Similarly, for all adsorbent:adsorbate ratios tested, 97.7% or more of the SeO4 2- is adsorbed, leaving on average 20 - 23 ppb in solution. Generally these experiments show that varying the adsorbent:adsorbate ratio by a factor of 4 at these concentration levels has no significant effect on the total Se adsorbed from solution. Throughout the NU-1000 tests on Se uptake, for example through studies conducted at pH 6 and similar batch studies conducted using a starting Se concentration of 100 ppb instead of 1000 ppb, it should be noted that residual Se concentrations of less than 10 ppb (down to 6 ppb and 2 ppb) were observed when 2 mg of NU-1000 was exposed to 1000 ppb and 100 ppb of Se respectively. In such embodiments, the present invention may be used to reduce the total selenium concentration (i.e., the sum of all selenium species) to less than 10 ppb or to an amount set in accordance with appropriate drinking water standards. Thus, the present invention can reduce the total Se concentration in a given liquid or liquid stream by more than 90%, more than 94%, and more than 98% in some embodiments.

[0051] Figure 4A shows the structure of NU-1000, highlighting the hexagonal pore size and structure of the Zr6 nodes. Figure 4B shows the structure of UiO-66, highlighting the octahedral pores and structure of the Zr6 nodes. Metal-organic frameworks from the NU-1000 (Figure 4A), UiO-66 (Figure 4B), and UiO-67 families were screened with respect to their selenate and selenite uptake capabilities. In the initial screening, two samples of each MOF were separately exposed to an aqueous solution of either selenate (100 ppm Se) or selenite (100 ppm Se). After 72 h of exposure, UiO-66 adsorbed 54% and 34% of the selenite and selenate, respectively, present in each solution, suggesting that anion exchange occurred both on the surface and inside of the MOF. This demonstrates that the Zr-bonded hydroxides in the MOF are useful for the adsorption of selenoanions, despite the strongly cross-linking nature of the OH groups at the nodes of UiO-66. Furthermore, anion exchange appears to be enhanced by the presence of Lewis / Bronsted basic amine groups on the terephthalic acid linker, and UiO-66-(NH2)2 and UiO-66-NH2 exhibit some of the highest selenate and selenite adsorption per Zr6-node among the MOFs studied (Figure 5). Without being bound by theory, this appears to be the result of hydrogen-bonding interactions between the amine groups and the selenate and selenite anions, similar to the hydrogen-bonding motifs in amine-containing macrocyclic structures that have a high affinity for sulfate and selenate anions.

[0052] Figure 5 is a bar graph showing the number of adsorbed selenate or selenite molecules per node in a series of Zr-based MOFs. Figure 5 shows that among the seven MOFs tested, NU-1000 achieves the highest uptake of selenate and selenite both gravimetrically and on a node basis. The most complete removal of these ions from a 100 ppm Se test solution was also achieved, i.e., 88% (SeO4 2- ) and 90% (SeO3 2-) This is the case. These results emphasize the value and importance of MOFs with unstructured ligand instability in achieving anion uptake.

[0053] Again, without being bound by theory, alternative forms of uptake could, to the extent possible, be, for example, the adsorption of sodium salts of selenate / selenite through oxy-selenium-anion / node-aqua (hydroxy) hydrogen bonds. ICP-OES (Inductively Coupled Plasma - Optical Emission Spectroscopy) measurements revealed no sodium adsorption in the MOF, indicating that the adsorbate is unlikely to be a salt, and suggesting that each adsorbed oxy-selenium dianion must be charge-balanced by the loss of two anionic ligands (presumably hydroxides) from the MOF. The ICP-OES measurements further established that no zirconium was lost into the solution.

[0054] Figure 6 is a graph showing the kinetics of selenate and selenite uptake in NU-1000, UiO66-NH2, and UiO66-(NH2)2. Assuming high capacities of UiO-66-NH2, UiO-66-(NH2)2, and NU-1000 for selenate and selenite, SeO x 2-The dynamics of uptake were also evaluated. As shown in Figure 6, to limit high-capacity uptake from a 100 ppm solution, it took about 70 hours or longer for UiO-66-(NH2)2, about 27 hours for UiO-66-NH2, and less than 3 hours for NU-1000. The fast uptake by NU-1000 compared to UiO-66 and its derivatives seems to be related to the aperture and pore size. NU-1000 has triangular and hexagonal pores with diameters of 12 Å and 30 Å respectively and the same aperture size (Figure 4A), while UiO-66 contains tetrahedral and octahedral pores with apertures of 7 Å and diameters of 8 Å and 11 Å respectively (Figure 4B shows the octahedral pores). The apertures of UiO-66-NH2 and UiO-66-(NH2)2 are expected to be even smaller. Selenate and selenite anions have radii of 2.4 Å and 2.6 Å respectively. Therefore, based only on the pore size vs. analyte size, it is possible to predict that the diffusion of selenate and selenite through the pores of NU-1000 will be faster than that in the UiO-66 derivatives.

[0055] A notable feature for both NU-1000 and UiO-66-NH2 is their ability to take up selenate and selenite, which have essentially equal efficacy - equal efficacy both kinetically and with respect to uptake capacity. The ability to adsorb both forms of inorganic selenium is an important feature for selenium purification. The high adsorption capacity combined with the fast uptake time using NU-1000 suggests that both the aperture size on the Zr6 nodes and the presence of replaceable ligands (aqua and hydroxy groups) may be important in achieving high uptake capacity and fast uptake kinetics.

[0056] Examination of the periodic table of elements suggests that the oxyanions of the following elements may also be incorporated by such MOFs, such as NU-1000 or MOF-808, in a manner similar to selenium, namely aluminum (i.e., water-soluble aluminum oxide / hydroxide), silicon (i.e., silicate and hydrosilicate), phosphorus (such as phosphate and hydrogen phosphate), sulfur (i.e., sulfate), chlorine (such as chlorate and perchlorate), germanium (i.e., water-soluble oxide / hydroxide of germanium), arsenic (such as arsenate), tin (i.e., stannate), antimony (such as antimonate and antimonite), iodine (such as iodate, periodate, and iodite), and lead (i.e., water-soluble oxide / hydroxide of lead).

[0057] To gain insights into the mechanism(s) of selenate and selenite adsorption on NU-1000, the maximum adsorption capacity per Zr6 node was determined. When exposed to aqueous solutions containing various concentrations of selenate and selenite anions ranging from 2 to 7 per node, the maximum adsorption capacity of NU-1000 was found to be two anions per node (Table S1). Furthermore, the affinity of NU-1000 for selenate and selenite is similar under these conditions, suggesting that the two analytes are likely bound in a similar manner. At initial concentrations corresponding to more than 6 per node (>90 ppm Se, with respect to the volume of solution examined and the amount of sorbent), NU-1000 is shown to incorporate more anions per node than two, accompanied by the adsorption of sodium cations. This sodium adsorption indicates that when more than two anions are adsorbed per node, NU-1000 can no longer essentially achieve charge balance. Na +In the absence of co - incorporation, for each of the adsorbed doubly - charged selenate or selenite anions, two negative charges must be relinquished by the MOF to maintain charge balance. One approach for NU - 1000 to accommodate two selenate or selenite anions (-4 charge) per node is thought to be to replace all four terminal hydroxyl groups (OH - ) from the Zr6 node; as detailed below, replacement of water molecules also appears to be the same (Figure 4A).

[0058]

Table 1

[0059] Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to gain insights into the location of two analyte molecules per node of NU - 1000. Figure 8A shows the DRIFTS spectra of NU - 1000 as - synthesized (lower trace), and after adsorption of two molecules of selenite (middle trace) and selenate (upper trace). Figure 8B shows an expanded DRIFTS spectrum from 4000 - 2000 cm -1 . Figure 8C shows the potential binding modes between selenate (or selenite) and the nodes of NU - 1000. Before analyte adsorption, the IR spectrum of NU - 1000 contains a sharp peak at 3670 cm -1 (Figure 8A / B, bottom - most trace), which corresponds to the stretching of the terminal - OH groups of the nodes (Figure 4a). The spectrum also contains a small peak at 2745 cm -1 (lower trace in Figure 8A / B), which corresponds to the O - H stretching from hydrogen bonding between aqua and hydroxyl ligands in the Zr6 - node (Figure 4A). After adsorption of approximately two molecules of selenate or selenite per node, the O - H stretching at 3670 cm -1 is significantly attenuated, and the hydrogen - bond - based O - H stretching at 2745 cm -1 completely disappears (Figure 8A / B, middle and upper traces respectively). Based on this information, for each SeO4 2- or SeO32- It is reasonable to suggest that the anions replace the two terminal hydroxyl groups on the Zr6-nodes. Thus, if two analyte molecules are bound per node, all four terminal hydroxyl groups are replaced, and analyte binding can occur as η2μ2 or μ2 (Figure 8C).

[0060] X-ray total scattering data pair distribution function (PDF) analysis was used to evaluate the structural changes associated with the binding of selenate and selenite anions. Figure 9A shows the differential pair distribution function (PDF) calculated for NU-1000 loaded with selenite and selenate. Figure 9B shows the experimental differential PDF for NU-1000 loaded with selenite and selenate, which only shows peaks at distances consistent with η2μ2 binding. The simulated PDFs show Se-Zr distances of 3.41 Å and 2.72 Å for η2μ2 and μ2 binding, respectively (Figure 9A). The results of the experimental PDF were evaluated from the difference data to isolate the interatomic distances unique to the adsorbent / adsorbate combination and showed features at ~3.4 Å (3.36 Å for selenite and 3.37 Å for selenate), but not at 2.7 Å, clearly indicating that these anions bind exclusively in the η2μ2 mode (the curve for selenite starts from the higher position on the left in Figure 9B). Both differential PDFs show peaks at ~1.7 Å assignable to the Se-O distance within the anion, and the features at 2.0 - 2.3 Å are consistent with a slight contraction of the average Zr-O distance.

[0061] Figure 10 shows the uptake of selenate and selenite in NU-1000 (2 mg) at low concentrations and with an initial concentration of 1000 ppb as Se over time. To test whether the current EPA standards for selenium in water can be met by using NU-1000 as an adsorbent, the uptake of selenate and selenite at low concentrations was also investigated. When exposed to 5 mL of an aqueous solution of selenium as 1000 ppb sodium selenite or sodium selenate, 2 mg of NU-1000 adsorbed 98% of the selenite or selenate in the solution in less than 5 minutes. After 3 hours, the adsorbed amount remained constant, meaning that the anions adsorbed after 5 minutes did not leach from the adsorbent thereafter. With a residual solution concentration of only about 20 ppb of selenium, the test samples treated with NU-1000 meet the EPA standards for drinking water with less than 50 ppb of selenium. Those skilled in the art of engineering fluid purification equipment and similar fields would predict that these results can be optimized such that the NU-1000 MOF is contacted with a continuous flow of an aqueous solution of selenate and selenite, and after an appropriate contact time, a wastewater stream containing these ions at concentrations on the order of parts per billion as selenium is produced.

[0062] The adsorption of selenate and selenite by NU-1000 at low concentrations was also tested at 40 °C (Figure 11) and pH 6 (Figure 12) to simulate the state of recirculating cooling water from a flue gas desulfurization process in a power plant where the purification of selenate and selenite is of concern. Figure 11 shows the uptake of selenate and selenite in NU-1000 (2 mg) at low concentrations and 40 °C, and with an initial concentration of 1000 ppb as Se over time. Figure 12 shows the uptake of selenate and selenite in NU-1000 (2 mg) at low concentrations and pH 6, and with an initial concentration of 1000 ppb as Se over time. The well-conducted tests showed that NU-1000 is a promising candidate for removing selenite or selenate under power plant operating conditions.

[0063] Figures 13A - E show the adsorbed amount (q) versus time at various concentrations of selenite and selenate per node of NU - 1000. The adsorbed amount is presented as the weight of total oxyanion in milligrams normalized by the weight of the bare NU - 1000 MOF in grams. Figures 14A - C show Langmuir plots (linear, type I) for the adsorption of selenite and selenate on NU - 1000, where the adsorbed amount is shown as the weight of total oxyanion. The amounts of selenite and selenate adsorbed per gram of NU - 1000 were investigated by exposing the MOF to various concentrations of selenite or selenate and monitoring the adsorbed amount (q) in units of mg of analyte / g of adsorbent over time (Figures 13A - E). The adsorption isotherm data were fitted using the Langmuir model, and high correlation coefficients were obtained (Figures 14A - C). Using the Langmuir equation, the maximum adsorption capacity (Q) of selenite on NU - 1000 is 95 mg / g, and for selenate it is 85 mg / g. These data are approximately equivalent to millimolar levels of analyte per gram of uptake medium. At amounts (i.e., concentrations and volumes) corresponding to 1.00 to 3.00 selenite or selenate anions per node, NU - 1000 was found to reach its maximum adsorption within 1 minute of exposure (Figure 13). The adsorption capacity of NU - 1000 is among the highest - capacity selenite and selenate adsorption materials described to date; these oxyanion analytes are much larger in size than typical sulfate or chloride anions, and it is more difficult to reach full uptake capacity with many typical commercially available adsorption or ion - exchange media. The uptake time of less than 1 minute particularly distinguishes NU - 1000 from other materials such as aluminum and iron oxide derivatives and ion - exchange and polymer resins, each of which requires 30 minutes or more to reach maximum adsorption capacity under equivalent conditions.This feature appears to demonstrate a significantly improved binding capacity of the MOF for oxyanions compared to other available sorbent media, along with the low equilibrium final Se concentration observed for NU-1000.

[0064] The adsorption capacity as a function of time at various concentrations (q) is given in Figure 14, where q = (C i - C f ) × V / m, with C i = the initial concentration of selenate or selenite, C f = the final concentration at a given time, V = the volume of the selenate or selenite solution used, and m = the mass of NU-1000. In the illustrated Langmuir plot, a type I linear equation (Figure 14) is used, where C e = the equilibrium concentration of selenate or selenite in the solution, q e = the equilibrium adsorption capacity, Q = the maximum adsorption capacity of NU-1000, and K L = the Langmuir adsorption constant. q e and C e are obtained as the average values of q and C f respectively, from the analysis performed in Figure 13 and described above.

[0065]

Table 2

[0066] Figure 15A shows the powder X-ray diffraction pattern of as-synthesized NU-1000 compared to NU-1000 after adsorption of selenite or selenate. Figure 15B shows the nitrogen adsorption isotherm of as-synthesized NU-1000 compared to NU-1000 after adsorption of selenite or selenate. The characterization of NU-1000 before and after adsorption of selenate and selenite suggests that the structure remains intact. The powder X-ray diffraction pattern does not change before and after adsorption. The Brunauer - Emmett - Teller (BET) volumetric surface area of NU-1000 before adsorption is 1035 ± 5 m 2 / cm3 (Specific surface area: 2130 ± 5 m 2 / g), and after the adsorption of selenate and selenite, the volumetric surface area is 682 ± 10 m 2 / cm 3 and 705 ± 10 m 2 / cm 3 respectively, showing a slight decrease to (gravimetric surface area: 1240 ± 10 and 1300 ± 10 m 2 / g) (Figure 15B). Similarly, a moderate decrease was reported after the introduction of Al(III) on the nodes of NU-1000 via atomic layer deposition.

[0067] Figures 16A - C show the uptake of selenate and selenite as a function of time using 2 mg of NU-1000 and 10 mL of an aqueous solution containing 100 ppb of Se and (a) 100 ppb of sulfur S, (b) 500 ppb of S, and (c) 1000 ppb of S as sulfate. In particular, Figures 16A - C show the performance of the NU-1000 MOF using the node uptake of selenate and selenite in the presence of competing sulfate anions.

[0068] Batch adsorption studies were first conducted on the uptake of both selenate and selenite in the presence of sulfate after exposing the bare MOF, and as a "knock-off study", the MOF already adsorbed with selenoanions was exposed to sulfate. For competitive adsorption, 2 mg of NU-1000 was investigated by exposing it to 10 mL of an aqueous solution containing 100 ppb of Se as either SeO4 2- or SeO3 2- and 100, 500, or 1000 ppb of S as SO4 2- . In all cases, more than 95% of the Se in the solution was adsorbed (Figures 16A - C), and the presence of SO4 2- (at concentrations up to 10 times higher, in ppb) did not affect the uptake of SeO4 2- or SeO3 2- at these concentrations. Furthermore, SeO3 2-or SeO4 2- The residual Se concentration as such was found to be between 2 - 7 and 4 - 9 ppb for Se, respectively.

[0069] The "knock - off" study was first carried out by exposing 2 mg of NU - 1000 to 10 mL of an aqueous solution containing 24 ppm of Se as SeO4 2- and SeO3 2- This is equivalent to an exposure level of 3.3 Se / nodes and was used to ensure that NU - 1000 was saturated with SeO4 2- and SeO3 2- Then NU - 1000 - 2SeO4 2- and NU - 1000 - 2SeO3 2- were exposed to an aqueous solution containing 25 ppm of SO4 2- (equal to 3S / nodes), and the leaching of SeO4 2- and SeO3 2- was investigated as a function of time. In the presence of SO4 2- there was minimal leaching (3%) of SeO3 2- from NU - 1000 - 2SeO3 2- However, the leaching of SeO4 2- from NU - 1000 - 2SeO4 2- was more pronounced (20%) in the presence of SO4 2- but still low compared to many other types of adsorption media where it is difficult to obtain adsorption of both selenate anions even without sulfate and much less using a knock - off challenge.

[0070] The general methods used in the above analysis are described below. UiO-66, UiO-66-NH2, UiO-66-(NH2)2, UiO-66-(OH)2, and UiO-67 were prepared according to the procedure described in Katz, M. J.; Brown, Z. J.; Colon, Y. J.; Siu, P. W.; Scheidt, K. A.; Snurr, R. Q.; Hupp, J. T.; Farha, O. K. A facile synthesis of UiO-66, UiO-67 and their derivatives. Chem. Commun. 2013, 49, 9449-9451, which is incorporated herein by reference in its entirety. NU-1000 was prepared according to the procedure described in Planas, N.; Mondloch, J. E.; Tussupbayev, S.; Borycz, J.; Gagliardi, L.; Hupp, J. T.; Farha, O. K.; Cramer, C. J. Defining the Proton Topology of the Zr6-Based Metal-Organic Framework NU-1000. J. Phys. Chem. Lett. 2014, 5, 3716-3723, which is incorporated herein by reference in its entirety. Powder X-ray diffraction measurements were obtained using a Bruker MX IμS microsource and an Apex II CCD detector with Cu-Kα radiation. The measurements were carried out over the range 2° < 2θ < 37°. N2 adsorption and desorption isotherm measurements were performed at 77 K on a Micromeritics Tristar II. The samples were activated by heating at 120 °C for 12 h in high vacuum on a Micromeritics Smart VacPrep. All gases used were of ultra-high purity grade 5 as received from Airgas Specialty Gases. DRIFTS was recorded on a Nicolet 6700 FTIR spectrometer equipped with an MCT detector cooled to 77 K. Spectra were collected in a KBr mixture under argon purge (samples were prepared in air). Pure KBr was measured as a background and subtracted from the sample spectra.ICP-OES data was collected on a Varian Vista MPX ICP spectrometer. ICP-MS data was collected on a ThermoFisher X Series II instrument equipped with Collision Cell Technology (CCT) to reduce interference from doublet lines for accurate detection of Se. ICP standards were purchased from Fluka Analytical. As-purchased Na and Se ICP standards were 1000 mg / L in 2% nitric acid, and TRACERT® and Zr standards were 10000 μg / mL in 4 wt% HCl. Standards for ICP-OES measurements (0.25 - 10 ppm) were prepared via serial dilution in 3% H2SO4, and standards for ICP-MS measurements (4 - 1000 ppb) were prepared via serial dilution in 3% HNO3. Scattering data for PDF analysis was collected at the Advanced Photon Source (APS) of Argonne National Laboratory (ANL) on beamline 11-ID-B. High energy X-rays (58.66 keV, λ = 0.2114 Å) were used in combination with a Perkin Elmer amorphous silicon-based area detector. Samples were loaded into Kapton capillaries for PDF measurements under ambient conditions. PDF measurements were collected for NU-1000 samples containing selenate or selenite by obtaining 60 frames of 2-second exposures each. 2-D scattering images were integrated using the software Fit2D to obtain 1-D scattering intensity data. The structure function S(Q) was obtained using the software PDFgetX3. The direct Fourier transform of the reduced structure function F(Q) = Q[S(Q) - 1] gave the reduced pair distribution function, G(r), Q. max = 23 Å -1 resulted. The contribution from the initial state MOF was measured under exactly the same conditions and subtracted to obtain the differential PDF (dPDF). The dPDF data shows the new contribution obtained from Se atom correlations. Models (η2μ2 or μ2) for the Se coordination mode to the MOF Zr-cluster were constructed in CrystalMaker. PDFs for both models were simulated using PDFGui 32 and compared to the experimental ones.

[0071] Initial selenite / selenate uptake studies were performed by exposing 10 mg of MOF in a 15 mL polypropylene centrifuge tube to 5 mL of an aqueous 100 ppm solution of selenium as sodium selenite or sodium selenate. 100 ppm control solutions of sodium selenite and sodium selenate were also prepared. The solutions were centrifuged for 1 minute to sediment the MOF to the bottom of the tube. After 72 hours, 0.5 mL of the supernatant was removed and diluted to 10 mL in 3% H2SO4 for ICP-OES measurement. ICP-OES was used to determine the concentrations of Se, Zr, and Na in each solution. Comparison between the control solutions and those containing MOF was used to determine the amount of selenate or selenite adsorbed by the MOF.

[0072] Kinetic studies were performed by exposing 10 mg of UiO-66-(NH2)2, UiO-66-NH2, and NU-1000 in a 15 mL polypropylene centrifuge tube to 5 mL of an aqueous 100 ppm solution of selenium as sodium selenite or sodium selenate. The solutions were centrifuged for 1 minute to sediment the MOF to the bottom of the tube. 0.5 mL aliquots of the supernatant were removed at 3, 27, and 72 hours and diluted to 10 mL in 3% H2SO4 for analysis by ICP-OES. ICP-OES was used to determine the concentrations of Se, Zr, and Na in each solution. Comparison between the control solutions and those containing MOF was used to determine the amount of selenate or selenite adsorbed by the MOF at each time.

[0073] The maximum uptake per node of NU-1000 was determined by exposing 2 mg of NU-1000 to 5 mL of an aqueous solution of sodium selenite or sodium selenate in 15 mL polypropylene centrifuge tubes at selenite concentrations of 30, 45, 60, 75, 90, and 105 ppm. These concentrations correspond to exposure levels of 2 - 7 analyte molecules per MOF node (i.e., Zr6 clusters). The solutions were centrifuged for 1 minute to sediment the MOF to the bottom of the tube. Aliquots of the supernatant were removed, diluted to 10 mL in 3% H2SO4, and analyzed by ICP - OES. ICP - OES was used to determine the concentrations of Se, Zr, and Na in each solution. Comparison of the control solution with those containing the MOF was used to determine the number of adsorbed selenate or selenite anions per node of NU-1000.

[0074] The low - concentration kinetic studies were performed by exposing six 2 mg samples of NU-1000 to 5 mL of an aqueous 1 ppm solution of selenium as sodium selenite or sodium selenate in 15 mL polypropylene centrifuge tubes. The solutions were centrifuged for 1 minute to sediment the MOF to the bottom of the tube. 2895 μL aliquots of the supernatant were removed from each solution at various times (5, 10, 15, 30, 60, and 180 minutes), diluted to 3 mL in 3% HNO3, and analyzed by ICP - MS. ICP - MS was used to determine the concentrations of Se, Zr, and Na in each solution. Comparison of the control solution with those containing the MOF was used to determine the amount of selenate or selenite adsorbed by the MOF at each time. Studies at 40 °C and pH 6 were performed in the same manner. To conduct the tests at 40 °C, the selenate and selenite solutions were heated in a beaker filled with Lab ARMOR BEADS, and to conduct the tests at pH 6, the selenate and selenite solutions were prepared in HCl at pH 6.

[0075] The amount of selenate or selenite adsorbed per gram of NU-1000 was determined by exposing 5 mg of NU-1000 to 10 mL of an aqueous solution of selenium as sodium selenite or sodium selenate in 15 mL polypropylene centrifuge tubes at concentrations of about 18, 27, 36, 45, and 55 ppm. These concentrations correspond to exposure levels of 1.00, 1.50, 2.00, 2.50, and 3.00 analyte molecules per Zr6-node of NU-1000. The solutions were centrifuged for 30 seconds to sediment the MOF to the bottom of the tube. Aliquots of the supernatant were removed and diluted to 10 mL in 3% H2SO4 at 1, 2, 3, 4, 5, 10, 15, 30, 60, 90, 120, and 180 minutes and analyzed by ICP-OES. The concentrations of Se, Zr, and Na in each solution were determined using ICP-OES. The amount of adsorbed selenate or selenite on NU-1000 (q) in mg / g was determined using a comparison of the control solution and that containing the MOF, where q = (Ci - Cf) × V / m, Ci = initial concentration, Cf = final concentration, V = volume of solution exposed to NU-1000, and m = mass of NU-1000 in g.

[0076] As described above, Zr-based MOFs, such as NU-1000 and MOF-808, may remove oxyanions of other elements, such as aluminum (i.e., water-soluble aluminum oxide / hydroxide), silicon (i.e., silicate and hydrosilicate), phosphorus (such as phosphate and hydrogen phosphate), sulfur (i.e., sulfate), chlorine (chlorate and perchlorate), geranium (i.e., water-soluble oxide / hydroxide of geranium), arsenic (such as arsenate), tin (i.e., stannate), antimony (such as antimonate and antimonite), iodine (such as iodate, periodate, and iodite), and lead (i.e., water-soluble oxide / hydroxide of lead).

[0077] In some embodiments, a Zr-based MOF containing NU-1000 is used to adsorb antimony oxyanions containing oxyanions in either the redox state of Sb[III] (antimonite) or Sb[V] (antimonate). Antimony is used in pressurized water reactors as a neutron source (paired with beryllium), and thus antimony is a constituent in the wastewater generated from nuclear power plants. Antimony is also released from the fuel oxide layer into the primary coolant water during the shutdown of nuclear power plants, resulting in a large amount of radiation dose to personnel and the surrounding environment. The common forms of antimony present in aqueous solutions under oxidizing conditions are Sb(OH)6 - , HSbO2, Sb(OH)3, and Sb(OH) 4+ . Therefore, the Zr-based MOF containing NU-1000 can be used to remove antimony oxyanions including those listed above from these sources.

[0078] NU-1000 was exposed to Sb(OH)6 - at a concentration corresponding to 2 - 7 Sb / nodes. Aliquots were taken from the supernatant at 24 hours and 48 hours. Table S3 shows the amount of Sb(OH)6 - adsorbed by NU-1000 per node. Antimony adsorption in NU-1000 per node after 24 hours and 48 hours using Sb(OH)6 - as the antimony source.

[0079]

Table 3

[0080] Figures 17A - B show the uptake of Sb(OH)6 - over time with respect to the uptake per node. The tests were conducted with Sb(OH)6 - at concentrations corresponding to 1.00, 1.50, 2.00, 2.50, and 3.00 Sb / Zr6 nodes over time for Sb(OH)6 -was performed to determine the uptake. Aliquots from each solution were taken at 1, 5, 10, 15, 30, 60, 90, 120, 180, 240, 300, 360, 420, 1440, 1800, and 2880 minutes. These show that the adsorption kinetics for Sb(OH)6 in NU-1000 - reach a rate that exceeds 60% of the total volume in less than 1 minute. Figure 18 shows the Langmuir fitting from the Sb adsorption isotherms of Figures 17A - B. Figure 18 shows the maximum adsorption capacity for Sb(OH)6 - on NU-1000 at 260 mg / g (or only 142 mg / g of Sb).

[0081] Figure 19 shows the powder X-ray diffraction patterns for NU-1000 and NU-1000 containing Sb(OH)6 - . This shows the stability of NU-1000 after the adsorption of Sb(OH)6 - . PXRD, nitrogen adsorption - desorption isotherms, and ICP - OES measurements were performed to determine the bulk crystallinity, porosity, and Zr leaching, respectively. The PXRD pattern shows that the bulk crystallinity of NU-1000 is not impaired after adsorption. Figure 20 shows the nitrogen isotherms for NU-1000 and NU-1000 containing Sb(OH)6 - . This shows that the surface area of the material decreases to a value that can be approximately predicted if mass is added to the structure. Finally, Zr leaching from the structure is not observed by ICP - OES.

[0082] Similar to the adsorption of selenium oxyanions, the adsorption of lead oxyanions is thought to be predictable using Zr - based MOFs including NU-1000 and MOF-808. Lead in the caustic solution in which its oxyanions are formed, as already clarified above, is thought to be involved in intergranular attack / stress corrosion cracking of steam generator tubes in nuclear power plants. Therefore, from the relevant liquid streams, Pb(OH)6 2- , Pb(OH)6 4- , PbO3 2- , and PbO2 2-The removal of these oxyanions, which are in either the Pb[II] or Pb[IV] redox state, such as, is considered beneficial. It should also be understood that the adsorption of iodine oxyanions, similar to the adsorption of selenium oxyanions, is expected to occur using Zr-based MOFs including NU-1000 and MOF-808.

[0083] In some embodiments, it should be understood that the MOFs of the present invention result in the adsorption of oxyanions even in the presence of other chemical species that can compete at the adsorption sites on the MOF. In particular, in some liquid streams, such as those in flue gas desulfurization systems, oxyanions of boron and sulfur in the liquid phase can compete at the adsorption sites on the MOF. However, it has been found that the MOFs of the present invention still result in the adsorption of oxyanions even in the presence of these chemical species. Those skilled in the art will understand that the concentrations of the various chemical species, including the oxyanions to be adsorbed and any competing species, should be taken into account when determining the concentration of the MOF to be used in the liquid stream in question.

[0084] Tables S4, S5, and S6 show the test results regarding the use of NU-1000 in flue gas desulfurization liquid stream samples both before and after the addition of NU-1000 (with respect to Table S4, it should be understood that the Stage 1 FGD wastewater may contain a much higher amount of particulate selenate / selenite than soluble oxyanions, which may explain the relatively low adsorption amount after exposure to the MOF).

[0085] [Table 4]

[0086] [Table 5]

[0087] [Table 6]

[0088] Regarding Tables S4 and S5, 10 mg of NU-1000 was added to 10 mL of wastewater, which is equivalent to exposure levels of 15B / Zr6 nodes, 26S / Zr6 nodes, and only 0.007 Se / Zr6 nodes, which are very difficult competing conditions. Table S4 shows the levels of B, Se, and S in the wastewater after treatment with NU-1000, and that only 100 ppb of B, 43 ppb of Se, and 160 ppb of S were taken up by the MOF. If the exposure levels of B and S are 2100× and 3700× that of Se, NU-1000 can still adsorb Se. Thus, in some embodiments, the adsorption of selenoxyanions still occurs in the presence of ions present in the range of 100 - 10,000× the selenoxyanion concentration.

[0089] Regarding Table S6, various amounts of NU-1000 (50 mg, 25 mg, 10 mg, 5 mg) were tested for the removal of SeOx 2- from stage 3 FGD water, and data points were obtained in shorter times (5 minutes, 10 minutes, 30 minutes). This shows the minimum amount of MOF and the shortest time possible to obtain the desired results. As is clear from Table S6, as the amount of MOF and the exposure time increase, the effluent concentration of the oxyanion remaining in the plant water sample decreases. The improvement in MOF exposure time and MOF loading appears to be equivalent in their ability to improve the uptake of the oxyanion.

[0090] The Zr-based MOF of the present invention may extend in crystalline size and may still result in the adsorption of the above-described oxyanions. In some embodiments, the crystalline size of NU-1000 may extend to approximately 75 to 5000 nm. In some embodiments, the crystalline size of NU-1000 may extend to approximately 75 to 1200 nm or approximately 300 to 5000 nm. In some embodiments, NU-1000 may extend to 75 to 1200 nm. In some embodiments, the MOF of the present invention may have a relatively large aperture, e.g., up to approximately 30 Å or larger, which promotes the diffusion of the analyte and improves the uptake kinetics. It should be understood that MOFs with larger apertures enable access by diffusion of the oxyanions to the available nodes in order to be taken up more readily than smaller geometries.

[0091] In use and according to one embodiment of the present invention, the MOF of the present invention can be used to selectively remove specific chemical species from a liquid stream. Generally, it should be understood that the amount of MOF required depends on several factors. For example, the Langmuir adsorption capacity (moles of ions per unit weight of MOF) can be obtained for a particular analyte to be removed (e.g., iodine containing the iodate oxyanion), for example in a desalination unit bed, in conjunction with the stream being treated, or the influent concentration of the analyte, the liquid stream or the amount of MOF required to contact the influent stream. Other factors are thought to depend on the corresponding apparatus geometry or design used for contact between the liquid stream and the MOF, sufficient contact between the liquid stream and the MOF on the substrate, and loss of MOF during loading or unloading of the substrate such as loading or unloading of beads of the desalination unit or other apparatus used. In the case of a desalination unit, it should be understood that the desalination unit beads may be a mixture of beads or a mixed bed of beads containing beads for both cation removal (e.g., by ion exchange) and anion removal (by MOF). In this case, the amount of contact between the liquid stream and the MOF beads needs to be accounted for, particularly in the determination of the amount of MOF beads used.

[0092] Certain MOFs can be attached to any structure used to facilitate contact between a liquid stream having a particular chemical species to be removed and the MOF. For example, the MOF can be attached to a pre - coatable filter / desalination device or an independent packed column, including such devices already used in a given facility or plant (e.g., existing vessels used in ion exchange). For example, the MOF can be pre - coated onto the filter fabric of an existing filter desalination device or a similar filter system. Thereafter, the structure can be appropriately installed to allow contact between the liquid stream and the MOF on the structure. For example, using a desalination device or a similar filter coated with MOF, the liquid or water to be treated is thought to flow through the filter fabric, for example, from the outside of a cylindrical filter, through the filter fibers into the lumen, enabling contact between the MOF and the water. When contacted with the liquid stream, the particular chemical species to be removed is adsorbed onto the MOF, thereby reducing the concentration of that chemical species in the liquid stream.

[0093] Since chemistries established for changing the metal component of MOFs exist in the literature, those with sufficient expertise in the art should be able to produce MOFs related to NU - 1000 containing less expensive metal components, such as using a zirconium metal precursor that is 90% pure and contains hafnium. In fact, in the present invention, one embodiment tested an NU - 1000 MOF analog containing Zr:Hf in a 9:1 ratio within the node component. In an experiment similar to that defined above for NU - 1000 itself, the 90%Zr / 10%Hf MOF was found to exhibit similar excellent node uptake of selenium - derived oxyanions (i.e., uptake that is about 90% to 95% higher than that seen in the pure Zr NU - 1000 MOF), suggesting that commercial cost reduction should be possible by using less pure zirconium starting materials for making NU - 1000.

[0094] Similarly, since chemistries have been established in the literature for modifying the linker portions of MOFs such as SALE (solvent-assisted linker exchange) and SALI (solvent-assisted ligand incorporation: see, for example, P. Deria, W. Bury, J.T. Hupp and O.K. Farha, ”Versatile Functionalization of the NU-1000 Platform by Solvent-Assisted Ligand Incorporation,” Chem. Commun. 2014, 50, 1965-1068; and P. Deria, J.E. Mondloch, O. Karagiardi, W. Bury, J.T. Hupp and O.K. Farha, ”Beyond Post-Synthesis Modification: Evolution of Metal-Organic Frameworks via Building Block Replacement,” Chem. Soc. Rev., 2014, 43, 5896-5912), one of ordinary skill in the art should be able to envision an algorithm suitable for introducing appropriate ligand functional groups into the NU-1000 or MOF-808 cavities that apply such chemistries to further attract oxyanions such as selenate and selenite, enhancing the overall binding ability of the material for these analyte species, and thus improving the engineering operations using these media for water treatment functions. In the specific case of selenate or selenite, one linker chemistry predicted by one of ordinary skill in the field of theoretical binding calculations is a functionalized urea chemistry such as pyridylurea that holds a pendant on a carbon or ether oxygen straight chain of sufficient length (e.g., 6 to 12 elemental carbon or oxygen atom lengths) that allows the selenooxyanion permeating the MOF cavity to contact an appropriate end group and bind to the ligand on the components forming the MOF cavity and aperture.

[0095] Finally, it is known to those of ordinary skill in the art that acid treatment, such as, but not limited to, hydrochloric acid, sulfuric acid, or nitric acid washing, should be able to lead to a regeneration procedure for the anion removal medium so that the removal medium previously used for reuse is recovered for the overall purpose of reducing operating costs. Thus, those of ordinary skill in the art should be able to subject the MOF to a similar acid washing technique to regenerate NU-1000 or MOF-808 for continuous reuse after saturation with oxyanion impurities, and thus the overall cost of the water treatment operation using the MOF is reduced to the point of economic viability.

[0096] As described, the present invention also describes a method for forming a MOF-containing product by binding a MOF to a substrate to form a MOF-containing product that can be used in a number of ways depending on the particular MOF bound to the substrate. It is to be understood that the substrate may be any substrate suitable for use in the environment or process in which a given MOF is bound and used to remove a particular species or compound from a liquid or liquid stream. In some embodiments, the substrate may be an inert substrate that avoids any chemical interaction with the liquid or liquid stream being treated. In some embodiments, the substrate has a physical shape that enables its deployment and use in a given process or in a particular piece of processing equipment for removing a particular species from a given liquid stream. In some embodiments, the substrate may be one bead or a plurality of beads. In some embodiments, the beads may be inert polypropylene polymer resin beads. In some embodiments, the substrate may be a macroscopic fabric such as a mesh material or a mesh filter. In some embodiments, the substrate may be a molecular fabric made of organic strands that consists essentially of a two-dimensional copolymer structure or an organic woven material.

[0097] The following description of methods for binding a given MOF to a substrate, as well as the description of methods for using a substrate having a bound MOF, should be understood to refer to MOFs generally. However, it should be understood that in all embodiments described herein, the specific MOFs described above may be used. Thus, some of the specific MOFs are capable of removing or are configured to remove specific liquid-phase anionic species, but it should be understood that other MOFs capable of removing other liquid-phase species from a liquid or liquid stream may likewise be used and may be bound to a given substrate. Further, while the following methods are described with respect to specific substrates, it should be understood that other substrates having different chemical compositions or different geometries may be used in any suitable combination with any MOF.

[0098] Generally, the method for binding a given MOF particle to a substrate may depend on the specific substrate being used. Thus, the following describes methods for binding a given MOF, including any applicable MOF, including NU-1000 and MOF-808, to a substrate that is a bead or beads including a plurality of beads, a macroscopic fabric such as a mesh fabric or a mesh filter, and a molecular fabric made from organic strands that consists essentially of a two-dimensional copolymer structure or an organic woven material.

[0099] In some embodiments, a given MOF may be bound to a substrate that is one bead or a plurality of beads. In some embodiments, the beads may be inert polypropylene polymer resin beads. In some embodiments, the beads contain oxyanions of selenium including selenite (SeO3 2- ) and selenate (SeO4 2- ); oxyanions of antimony including oxyanions in either the redox state of Sb[III] (antimonite) or Sb[V] (antimonate); Pb(OH)6 2- , Pb(OH)6 4- , PbO3 2- and PbO2 2-Lead oxyanions, including oxyanions in any redox state of Pb[II] or Pb[IV], such as; and IO3 - It is used in the removal of anions, including oxyanions of iodine such as (iodate).

[0100] Generally, the method for binding the MOF is performed using a buffer modifier that adheres the MOF to the surface of the beads. In some embodiments, the buffer modifier may be a buffer modifier typically used in capillary electrophoresis, such as an osmotic flow modifier including cetyl-trimethylammonium bromide (CTAB) and beta-cyclodextrin (beta-CD). Both CTAB and beta-CD are compounds that bind well to MOF particles at room temperature and chemisorb the MOF onto the surface of the beads.

[0101] In one embodiment, CTAB may be used to bind the MOF to the bead surface. In this case, atomic layer deposition (ALD) is used to sprinkle the beads with a metal oxide that provides surface hydroxyl groups capable of forming a chemical bond with the MOF particles via CTAB. In some embodiments, the metal oxide chemisorbs onto the bead surface in water, thereby making the hydroxyl groups available for binding to CTAB, for example via the cationic head groups of CTAB. These metal oxides include, but are not limited to, aluminum oxide, titanium oxide, zinc oxide, and combinations thereof. When exposed to water, the deposited metal oxide appears to be similar to silicon dioxide / surface oxide in the application of CTAB capillary electrophoresis osmotic flow reversal. Thus, the MOF is then bound to the CTAB through hydrogen bonding, electrostatic interactions, and van der Waals forces. Without being limited by theory, the non-polar surface of the MOF, such as the organic linker of the MOF, is thought to bind to the trimethyl "arms" of the CTAB.

[0102] In one embodiment using CTAB, the beads may first be subjected to ALD to chemisorb a metal oxide on the surface of the beads. Alternatively, CTAB and MOF may be combined at room temperature to bind the MOF to the CTAB, forming a solution of CTAB to which the MOF is bound. Then the beads with the metal oxide bound thereto may be contacted with the solution or combined with the CTAB having the bound MOF to obtain CTAB bound to the bead surface via the metal oxide, and in this case also, it can be carried out at room temperature in an aqueous solution, and in some embodiments, it can be carried out in a basic aqueous solution. Alternatively, the beads after being subjected to ALD so as to bind a metal oxide may be mixed in an aqueous solution containing MOF, and in some embodiments, may be mixed in a basic aqueous solution containing MOF. Then, CTAB may be added to the solution to bind to both the MOF and the metal oxide, obtaining binding of the MOF to the bead surface. Then, the beads can be washed and dried. Thus, at this point, MOF-adsorbing beads such as a plurality of MOF-adsorbing polypropylene beads are produced, which can constitute a product that can be used as further described below.

[0103] In another embodiment, beta-CD may be used to bind the MOF to the bead surface. In this case, it is not necessary to subject the substrate to ALD. Rather, the nonpolar region of beta-CD binds to the corresponding nonpolar portion of the polypropylene beads via hydrogen bonding, electrostatic interaction, and van der Waals forces. Then the MOF can be bound to the beta-CD via interaction between one or more polar portions on the surface of the MOF by the negative charge on the beta-CD. In some embodiments, the MOF can be bound to the beads in an aqueous solution containing beta-CD. In some embodiments, a solvent that is not very polar, such as alcohol, may be used. Then, the beads can be washed and dried. Thus, at this point, MOF-adsorbing beads such as a plurality of MOF-adsorbing polypropylene beads are produced, which can constitute a product that can be used as further described below.

[0104] In some embodiments, it should be understood that both beta-CD and CTAB may be used in combination. In this case, the substrate or beads are considered to be subjected to ALD, and then a solution containing both MOF and both CTAB and beta-CD is considered to be added.

[0105] In some embodiments, it should also be understood that the surface of the beads for functionalizing CTAB and beta-CD may be silicon dioxide. In some cases, the polymer beads may be functionalized using the chemistry of hydroxysilane to accept the silicon adduct, and then the hydroxide may be accepted to provide the chemistry necessary to bind CTAB or beta-CD.

[0106] In some embodiments, it should be understood that the ion exchange resin beads are polystyrene divinylbenzene cross-linked (2 - 12%) copolymer beads functionalized in the pores by chemical bonding to the pendant benzyl rings from the polymer backbone of the exchange ligand. In such cases, the substrate beads coated with MOF need to have the same density as the anion exchange resin beads in order to achieve sufficient water sluicing of the anion beads from the mixed bed replaced by the substrate beads coated with MOF. Further, there are several choices of polypropylene that depend on the local stereochemistry of the propylene adduct in the free radical polymerization process.

[0107] Thus, in some embodiments, for example, a process for preparing a plurality of beads suitable for use in the deep layer of a plant desalination device may include determining the MOF specific gravity capacity for the target analyte / oxyanion, calculating the amount of MOF required to associate with each bead, thereby enabling evaluation of the number concentration of beads coated with MOF in water that must be flushed through the existing deep layer of the desalination device already present in the process stream, testing the density to equilibrate with the existing anion exchange beads within the deep layer of the plant desalination device, testing the possibility of exchange between those beads and the beads coated with MOF via a typical plant flushing method, and adjusting the number concentration of beads coated with MOF to account for loss beads in the preceding steps.

[0108] In another embodiment, the present invention includes a method for binding MOF to a macroscopic fabric for subsequent use. In some embodiments, the macroscopic fabric may be any fabric that includes a man-made fiber-based material to which a given MOF can be bound. In some embodiments, the macroscopic fabric is a mesh material or a mesh filter, including an inert polypropylene-based mesh material or filter. Thus, it should be understood that the fabric may have any dimensions, such as any area or surface area, as desired or determined by the end use of the fabric. The MOF particles may be bound to the fibers of the fabric in the same manner as previously described for the binding of beads. Thus, it should be understood that buffering modifiers such as beta-CD and CTAB may be used as described above in combination with ALD treatment of the fabric to bind MOF to the fabric. After binding the MOF to the macroscopic fabric, a MOF-adsorbing macroscopic fabric is produced and can constitute a product that can be used as further described below. The term "macroscopic" is used to distinguish this fabric as something visible to the naked eye or physically handleable by hand, as opposed to the molecular fabrics described below.

[0109] In another embodiment, the present invention includes a method for binding a MOF to a molecular fabric for subsequent use. In some embodiments, the molecular fabric is made from organic strands that essentially form a two-dimensional copolymer structure or an organic woven material to which a given MOF can be bound. The MOF particles may be bound to the strands of the fabric in the same manner as previously described for binding to beads. Thus, it should be understood that buffer modifiers such as beta-CD and CTAB may be used as described above to bind the MOF to the fabric in combination with ALD treatment of the fabric. After binding the MOF to the molecular fabric, a MOF-adsorbing molecular fabric is produced and can constitute a product that can be used as further described below. It should be understood that a molecular fabric is a fabric formed at the molecular level and is thus, for example, much smaller in size than the macroscopic fabrics described above.

[0110] Once bound, a substrate having the bound MOF can be used to remove certain chemical species from a liquid or liquid stream, such as an industrial liquid stream (e.g., a coolant stream in a power plant, such as a nuclear power plant) or a wastewater stream. Generally, a substrate having the bound MOF is considered to be positioned such that it can come into contact with a liquid containing one or more liquid species to be removed from the liquid and the MOF. After contact, the liquid species to be removed binds to the MOF and is thus considered to be removed from the liquid. In this regard, the manner in which a substrate having the bound MOF is considered to be used depends on the particular MOF that is bound and the liquid phase species that it can remove, and also on the physical configuration of the inert substrate used (e.g., beads or fabric).

[0111] In the case of beads, they can be used in the same way as traditional resin beads for removing certain chemical species from a liquid, for example, by placing the beads in a resin bed within a given container and considering that the liquid to be treated passes therethrough. It should be understood that existing equipment designed to manage the resin bed can be adapted to manage the use of beads coated with MOF particles, if necessary. In one embodiment, a cylindrical container containing a bed of beads coated with MOF particles can be used. In this case, the bed of beads is considered to be stationary within the container, and the liquid flow is considered to pass through the container, thereby bringing about contact between the liquid containing the liquid species to be removed passing through the bed of beads and the MOF particles. After contact, the liquid species to be removed binds to the MOF and is thereby considered to be removed from the liquid passing through the container.

[0112] In some embodiments, resin beads used to remove certain liquid phase species are contained within a vessel, and it should be understood that such resin beads can be replaced with beads coated with a given MOF according to the present invention. In one embodiment, if resin beads require replacement, they can be easily replaced within the same apparatus with beads coated with a given MOF according to the present invention. Alternatively, the resin beads can be replaced with inert polypropylene beads, and the attachment of the selected MOF can be performed in-situ. In this case, the beads can be pretreated with ALD to attach a given metal oxide and then placed within the vessel, or such treatment by ALD to attach the metal oxide can also be performed in-situ. In the latter case, the beads are placed within the vessel and then treated using ALD to attach the metal oxide. Thereafter, a solution containing CTAB and the selected MOF can be added to the vessel to bind CTAB and the MOF to the beads, or a solution of CTAB can be added to the vessel and then a solution of the selected MOF can be added. As a result, the original resin beads are considered to be replaceable with beads coated with the selected MOF without the need to modify or change any of the existing apparatus used with respect to the original resin beads.

[0113] Alternatively, the beads can be placed within the vessel, and thereafter, a solution containing beta-CD and the selected MOF can be added to the vessel to bind beta-CD and the MOF to the beads, or a solution of beta-CD can be added to the vessel and then a solution of the selected MOF can be added. As a result, the original resin beads are considered to be replaceable with beads coated with the selected MOF without the need to modify or change any of the existing apparatus used with respect to the original resin beads.

[0114] In the case of a macroscopic fabric coated with a selected MOF, such a fabric can be positioned or arranged so that a liquid flow can pass through the fabric, thereby bringing into contact a liquid containing the liquid species to be removed with the MOF particles bound to the fibers of the fabric. After contact, the liquid species to be removed is thought to bind to the MOF and is thereby removed from the liquid passing through the fabric. It should be understood that the fabric may be disposed inside a container or a pipe or any one piece of equipment such that the liquid can pass through the fabric.

[0115] In one embodiment, a desalination device through which a liquid flow passes internally may be used. In this case, the macroscopic fabric may be a mesh filter that can be wound in a spiral, thereby creating a lumen in the center. The liquid may enter the interior of the desalination device and pass along the outside of the wound mesh filter. The liquid is then thought to pass through the wound mesh filter, enter the lumen or center of the desalination device, and exit out through the center of the desalination device. It should be understood that in some embodiments, an existing mesh filter may be coated with a selected MOF. In this case, the MOF can be bound in-situ to the existing mesh filter in the same manner as previously described for in-situ coating of beads in an existing container.

[0116] It should also be understood that the fabric coated with MOF may be used in many different situations. In one embodiment, the fabric coated with MOF may be used at the top of the resin bed to facilitate the removal of liquid phase species, resulting in the removal of other liquid phase species or further removal of the same or similar chemical species from what has been removed by the resin bed. Further, in embodiments where the bed of beads is coated in-situ with the selected MOF, it should be understood that the use of the macroscopic fabric at the top of the bed may be coated in-situ with the selected MOF and may be done simultaneously with the coating of the bed of beads. Thus, the MOF used for the beads and the fabric may be the same or different, and if different, it should also be noted that either the beads or the fabric need to be coated before placing both in a given container.

[0117] In the case of a molecular fabric coated with the selected MOF, such a fabric can be positioned or arranged so that a liquid stream can pass through the fabric, thereby bringing into contact the liquid containing the liquid species to be removed with the MOF particles bound to the fibers of the fabric. After contact, the liquid species to be removed is thought to bind to the MOF and is thereby removed from the liquid passing through the fabric. It should be understood that the fabric can be placed inside a container or a pipe or any one piece of equipment such that the liquid can pass through the fabric. It should also be understood that the molecular fabric can be generated in-situ and then bind the selected MOF particles. In some embodiments, the molecular fabric can be configured to be positioned at the outlet of a container, such as a container containing resin beads within a bed or a desalination device.

[0118] However, regardless of the substrate used, with respect to a given liquid stream and the concentrations of the various liquid-phase components to be removed, the capacity of the selected MOF for removing those liquid-phase components generally becomes even greater, and thus it should be understood that there is no limit to the saturation of the MOF. Therefore, the use of a substrate coated with MOF particles, rather than, for example, using a bed filled with MOF particles, still provides the essential surface area required to obtain the desired removal of a given liquid-phase species.

[0119] Various embodiments of the present invention have been described heretofore. However, it should be understood that alternative embodiments are possible and that the present invention is not limited to the specific embodiments described above. For example, in some embodiments, the adsorption of aqueous selenate and selenite can be obtained by a series of highly porous, water-stable, Zr-based MOFs. Among the seven MOFs tested, NU-1000 was found to exhibit both the highest gravimetric adsorption capacity and the fastest uptake. This result indicates the importance of both large MOF apertures and a significant number of node-based adsorption sites, i.e., substantially labile Zr(IV) coordination sites, where rapid and efficient selenate and selenite adsorption and removal occur. Both anions are shown to bind to the nodes in a bridging (η2μ2) fashion where one dianion bridges two zirconium metal centers. In contrast to many materials that are only validly effective for selenite and related technologies for the purification of selenium, NU-1000 shows strong affinity for both selenate and selenite. In some embodiments, oxyanions of antimony containing an oxyanion in either the Sb[III] (antimonite) or Sb[V] (antimonate) redox state; Pb(OH)6 2- , Pb(OH)6 4- , PbO3 2- and PbO2 2- oxyanions of lead containing an oxyanion in either the Pb[II] or Pb[IV] redox state such as; and IO3 -The adsorption of iodine oxyanions such as (iodate) can be obtained by a series of highly porous, water-stable, Zr-based MOFs. Furthermore, the adsorption of these species can be obtained even in the presence of competing species.

Claims

1. A method for reducing the concentration of iodine oxyanion from a liquid stream, said method comprising: contacting a liquid stream containing iodine oxyanion with a zirconium-based metal-organic framework, wherein said zirconium-based metal-organic framework comprises MOF-808, and complexing said iodine oxyanion with said zirconium-based metal-organic framework, thereby reducing the concentration of said iodine oxyanion in said liquid stream A method comprising.

2. The method according to claim 1, wherein said liquid stream comprises a liquid stream from a nuclear power plant.

3. The method according to claim 2, wherein said contacting step is carried out using a desalination device.

4. The method according to claim 2, wherein said zirconium-based metal-organic framework is disposed on a substrate.

5. The method according to claim 4, wherein said substrate comprises a plurality of polypropylene beads.

6. The method according to claim 4, wherein said substrate comprises a macroscopic fabric.

7. The method according to claim 4, wherein said substrate comprises a molecular fabric comprising organic strands.

8. The method according to claim 2, wherein said zirconium-based metal-organic framework comprises MOF-808 before activation.

9. The method according to claim 2, wherein said zirconium-based metal-organic framework comprises MOF-808 after activation.

10. The method according to claim 1, wherein said oxyanion comprises iodate.

11. The method of claim 1, wherein the step of misincorporating comprises η2μ2 binding.

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