Compositions with shell and core for removing ionic impurities

Abstract

A composition for selectively removing a first ionic impurity substance from a wastewater stream. The composition is formed into particles. The composition includes a core formed from a material inactive against the first ionic impurity substance and a shell formed from a material active against the first ionic impurity substance, the active material comprising 10-50% by weight of the particle. The shell may also include a binder material that may be inactive against the first ionic impurity substance but active against a second ionic impurity substance. The core may be formed from a glass forming material such that a vitrification process can be used for consumed solid waste.

Description

[Technical field]

[0001] (Statement of priority) This application claims priority to U.S. Provisional Patent Application No. 63 / 195,074, filed May 31, 2021, which is incorporated by reference in its entirety.

[0002] FIELD OF THEINVENTION The present invention relates generally to compositions for nuclear decontamination, and more particularly to such compositions with better utilization of active adsorbent materials. [Background technology]

[0003] Ion exchange compositions are well known and include molecular sieves, clays, and non-porous inorganic oxides. These compositions are usually synthesized as powders and formed into shaped articles such as beads, extrudates, pellets, pills, etc., to be commercially useful. These articles, when formed into their final shape, must have sufficient physical strength to withstand wear or abrasion and destruction during use, packing, and transportation.

[0004] These compositions can be used to remove selected ionic species from wastewater by providing particles with the active material and flowing the wastewater (containing the impurity material) through the particles such that the impurity material can come into contact with the particles. In many conventional applications, the compositions are packed into ion exchange columns and treated waste is passed through the column. The usefulness of such materials is measured by the amount of impurity material removed and the distribution of the impurity material migration area through the adsorbent bed. Distribution is governed to a large extent by the selectivity of the active phase and the diffusivity through the particles.

[0005] There is an increasing need to utilize more efficient sorbents in the decontamination of liquid nuclear waste, driven by the need to reduce costs and minimize radioactive solid waste. The sorbents should maintain high selectivity to allow for narrow mass transfer zones while at the same time maintaining a controllable ability to prevent overloading of ion exchange columns and shift to higher classification as solid waste. Solid nuclear waste is required by many laws to be vitrified via several high risk steps. Materials with unique properties that are less hazardous and allow for smaller volumes of vitrified waste to be formed would provide the advantages of a safer process, lower costs, and long term storage.

[0006] The structural and chemical stability of some of the existing inorganic adsorbents has been a concern in the past, leading to operational problems and failures. Increasing the strength of their components or methods to minimize leaching into solution can address these concerns.

[0007] Thus, there remains a need for compositions that effectively and efficiently remove contaminant substances from wastewater streams. Summary of the Invention

[0008] A novel composition has been invented for selectively removing contaminant substances from wastewater streams. The novel composition allows for increased efficiency and improved selectivity compared to existing commercial adsorbents based on the same active phase. The result is reduced overall treatment costs compared to currently used products.

[0009] The new compositions rely on the use of a core-shell based approach, where the active phase is present in the outer layer. The layer thickness and level of the active component do not correlate linearly with performance, so adjustments to these two attributes may be selected based on the desired use.

[0010] The shape and type of the core may be adjusted and selected based on the desired use. For example, it has been found that in some cases, the use of irregular or non-spherical shapes provides additional accessible surface area compared to spheres. The core may be a material that can be a glass former. This allows the composition, once loaded, to be transformed by a vitrification process. The core may be an active phase that adsorbs secondary impurity materials at higher concentrations. For example, a granular shaped chabazite core coated with a shell containing titanates or titanium silicates, such as monosodium titanate (MST), may be a useful material for wastes that are high in cesium and also contain strontium.

[0011] The core material can be selected to have a narrow particle size (compared to conventional particles with similar amounts of active material) and distribution before the shell is added, so that the final product has an equivalent distribution and good flow properties. At the same time, losses associated with the formation of small (~0.5 mm) beads are reduced, resulting in further cost savings both in terms of raw materials and production time. Binders can be included in the shell; for example, oxides can be used, allowing the use of as-synthesized crystalline silicotitanate (CST) powders, which provide the shell with further selectivity to impurity materials.

[0012] Thus, the present invention, in at least one aspect, can feature a composition for selectively removing a first ionic impurity species from a wastewater stream. The composition is formed into a particle and includes a core of a non-active material for the first ionic impurity species and a shell formed from an active material for the first ionic impurity species. The active material constitutes 10-50% by weight of the particle. The shell may further include a binder. The shell may have 0.1-40% by weight of the binder. The particles may have a median diameter size of 2.1-0.4 mm. The particles may have a spherical or non-spherical shape. The shell may have a thickness of 20-100 μm. The first ionic impurity species may be selected from the group consisting of cesium, strontium, mercury, silver, lead, transition metals, iodine, lanthanide and actinide metal ions. The core or the binder, or both, may be active against ionic impurity substances in the wastewater stream, which may be the same or different from the first ionic impurity substance. The ionic impurity substance may be selected from the group consisting of cesium, strontium, mercury, silver, lead, transition metals, iodine, lanthanide metals and actinide metal ions. The core may include or be formed from a material configured to undergo a vitrification process without releasing the first and / or second ionic impurity substances. The shell may include a material selected from the group consisting of metal titanates, metal germanates, pillared clays, metal phosphonates and combinations thereof. The binder may be a hydroxyl metal oxide. The core may be a material selected from the group consisting of ceramics, silica, alumina, titania, zirconia, silicates, titanates, zeolites and combinations thereof.

[0013] In a second aspect, the invention can be broadly characterized as providing a composition for selectively removing a first ionic impurity substance from a wastewater stream. The composition may be formed into particles and includes a core of a material inactive against the first ionic impurity substance and a shell formed from a material active against the first ionic impurity substance and a binder. The shell may include 0.1-40% by weight of the binder, and the active material may comprise 10-50% by weight of the particle. The shell may be 10-30% by weight of the binder. The binder may be active against an ionic impurity substance in the wastewater stream, the ionic impurity substance may be different from or the same as the first ionic impurity substance. The core may be a material configured to be subjected to a vitrification process without releasing the first and / or second ionic impurity substances. The particles may have a median diameter size of 2.1-0.4 mm. The shell may have a thickness of 20-100 μm.

[0014] Further aspects, embodiments and details of the invention, all of which may be combined in any manner, are set out in the following detailed description of the invention. [Brief description of the drawings]

[0015] One or more exemplary embodiments of the invention are described below in conjunction with the following drawing figures. [Figure 1] 1 is a partial cross-sectional view of a particle according to one or more embodiments of the present invention. [Diagram 2] 1 is a cross-sectional image of a spherical particle according to one or more embodiments of the present invention. [Diagram 3] 1 is a cross-sectional image of a non-spherical particle according to one or more embodiments of the present invention. [Figure 4] 1 is a graph showing the size of the final composition compared to the core size for a particular target layer thickness. [Diagram 5] FIG. 1 shows two different sized particles with the same amount of active phase material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] As mentioned above, novel compositions have been invented that utilize the engineering of core-shell particles to increase the utilization of the active phase. In addition to the core-shell, the particle shape and size allow for tuning of the external surface area and thus performance. The novel compositions also allow for the selection of binders with desired properties, such as selectivity to secondary contaminant contamination. Compared to conventional materials, the novel compositions are believed to have better wear and leaching characteristics, thus realizing improved performance and safety benefits. Additionally, the compositions of the present invention may use cores formed with glass-forming precursors to facilitate vitrification. Finally, the compositions of the present invention use less active material (without compromising performance) compared to conventional designs, thus limiting and controlling nuclear waste classification of consumed materials while maintaining dynamic properties.

[0017] With these general principles in mind, one or more embodiments of the invention are described, with the understanding that the following description is not intended to be limiting.

[0018] As shown in Figures 1-3, the present invention provides compositions in the form of particles 10. Particle 10 has a core 12 and a shell 14 surrounding core 12.

[0019] 2 and 3 show examples of core 12 selections that have not only specific sizes and shapes, but also porosity, and that also have different chemistries that target different additional roles played by the core 12 material.

[0020] The shell 14 is formed from an active material against a selected or specific ionic impurity material and may further include a binder or binder material. The core 12 and binder may be inactive materials against a specific impurity material. As used herein, "active material" refers to a composition capable of selectively exchanging ions present in the structure of the composition with one species in a feed stream contacting the composition of the present invention. "Inactive material" refers to a material that does not selectively exchange ions present in the structure of the composition with the same target ionic species. Thus, one material may be "inactive" against a particular species but "active" against another species. It should therefore be understood that the core 12 and binder may be active materials against different impurity materials. In this manner, the particle 10 may be used to remove both a first and a second impurity material.

[0021] The active material in shell 14 comprises 10-50% by weight of particle 10. Alternatively, the amount can be 20-50% by weight of particle 10, 20-40% by weight of particle 10, or 25-35% by weight of particle 10, or 28-33% by weight of particle 10. If a binder is present in shell 14, it is contemplated that the binder comprises 0.1-40% by weight of shell 14, preferably 10-30% by weight of shell 14.

[0022] The thickness of the shell 14 can vary from 10 to 200 μm. The thickness of the shell 14 can be more specifically in the range of 20 to 100 μm. Expressed as a percentage of the radius of the core 12, the thickness of the shell 14 can be anywhere in the range of 5 to 50% of the radius of the core 12. FIG. 4 shows a core 12 having two different shells 14 grown on its surface. Starting with an average core diameter of 480 μm, material 2709 was prepared with a shell 14 having a thickness of 31 μm, which is equal to 13% of the radius of the core 12. Alternatively, material 2700 using the same core 12 was prepared with a shell 14 having a thickness of 98 μm or 41% of the radius of the core 12. The size of the core 12 can be selected to provide a particular desired thickness of the shell 14.

[0023] Additionally, the thickness of the shell 14 may vary, as shown in Figure 5, where it is believed that a smaller particle 10 with the same amount of active material will be able to remove more impurity material than a larger particle 10. Thus, the size of the particle 10, the thickness of the shell 14, and the amount of active material can be adjusted to obtain a particle 10 with a desired level of selectivity.

[0024] The shape of the particle 10 may be spherical (FIG. 2) or non-spherical (FIG. 3). Non-spherical shapes include cylinders, oblongs, ellipsoids, cones, disks, irregularly shaped particles, spherocylinders, ellipsoids, spherocylinders, spherocylinders, and spherocylinders, to name a few.

[0025] Impurity substances which it is contemplated that the compositions of the present invention are useful for removing from liquid streams include cesium, strontium, mercury, silver, lead, ions of transition metals, iodine, and lanthanide and actinide metal ions.

[0026] Shell active substances Exemplary active materials for shell 14 include, but are not limited to, metal titanates, metal germanates, pillared clays, and / or metal phosphonates. Examples of metal titanates include silicotitanates and substituted silicotitanates. For example, the material for shell 14 may be crystalline silicotitanates (CSTs) or derivatives or modifications thereof, such as substituted crystalline silicotitanates (sCSTs). Another class of example active materials is alkali metal titanates or their protonated / mixed forms, such as sodium or potassium monotitanates, hexatitanates, octatitanates, and nanotitanates, to name a few. Ion exchange compositions may also be formed from pillared clays, which are expandable clays containing pillars between the clay layers. Examples of clays that have ion exchange capacity and may be pillared include montmorillonite, sauconite, nonthorinite, saponite, and hectorite. The pillars may include aluminum chlorohydroxide with rare earth elements or zirconium.

[0027] Binder Exemplary materials for the binder include hydroxyl metal oxides such as zirconium oxide, titanium oxide, etc. "Hydroxy metal oxide" refers to an oxide having an empirical formula MO2.xH2O, where x ranges from 2 to 4, and M is zirconium, titanium, or a mixture thereof.

[0028] As noted above, it is contemplated that the binder may be made from a material that also has selectivity for the same impurity substance, or is active against a second impurity substance. Thus, the binder may contribute to the activity of the active phase or may contribute to the co-adsorption of a secondary impurity substance.

[0029] core Core 12 may be formed from ceramic materials, silica, alumina, titania, zirconia, silicates, zeolites, such as chabazite, clinoptilolite, mordenite, or other potential ion exchangers. For example, if removal of strontium ions is desired in the composition of the present invention, core 12 may be zeolite 4A. Zeolite 4A has the following formula: Na2O:[AlO2] 12 :[SiO2] 12 :[H2O] 27 Alternatively, the compositions of the present invention may be desirable for the removal of cesium ions. For the removal of cesium ions, an exemplary composition of the present invention may include a chabazite-type or chabazite-eronite-type zeolite as the core 12. An exemplary chabazite-type zeolite is (K2O,Na2O,MgO,CaO)[(Al2O3)(SiO2) 4-6 ].zH2O.

[0030] It is contemplated that the core 12 may be made from a material that is active against the second impurity substance. Thus, the shell 14 may remove the first impurity substance by ion exchange and adsorbing the first impurity substance, while the core 12 may also remove the second impurity substance, for example, by ion exchange.

[0031] It is also further contemplated that core 12 may be formed from a material that is configured to undergo a vitrification process without releasing the first and / or second ionic impurity substances. Thus, core 12 may be made from a glass-forming material.

[0032] The materials can be made by adhesion of a shell 14 consisting of a binder and an active phase to the core 12. Alternatively, the active phases can be epitaxially grown on the outer surface of the core 12. Finally, the upper layer of the core 12 can be converted to a reactive phase by reaction control, in which case the size of the particle 10 does not change. Examples are the conversion of the outer layer of an alumina core 12 to a zeolite, or the conversion of the outer layer of a titania core 12 to a titanate, by controlled synthetic conversion.

[0033] The particles 10 are useful as selective ion exchangers. In particular, the novel compositions are useful as selective ion exchangers for various metal ion impurities from a liquid stream, such as a water stream, thereby removing these metal ions from the liquid stream. In general, these metal ions can be removed from a liquid stream by contacting the particles 10 with the liquid stream for a time sufficient to remove the metal ions and capture them on the surface of the particles 10. For example, the particles 10 can be placed in a column, and the stream to be treated can be passed through the column, usually downward, until the impurity metal ions are detected in the column outlet stream. The metal ion-containing article can be discarded in any case. If the core 12 is made of a suitable material, the entrained particles 10 can be subjected to a vitrification process.

[0034] The compositions of the present invention and particles 10 described herein can perform ion exchange in highly acidic, neutral, and highly basic aqueous solutions, depending on the selection of their components. Furthermore, the compositions of the present invention and particles 10 described herein can be formed with selective activity toward desired ions. In other words, the compositions and particles 10 of the present invention can be fine-tuned or adjusted to achieve any practical level of activity toward exchangeable ions, such as strontium and / or cesium ions.

[0035] Specific Embodiments While the following will be described in conjunction with specific embodiments, it will be understood that this description is illustrative and is not intended to limit the scope of the foregoing description and appended claims.

[0036] A first embodiment of the invention is a composition formed into particles for selectively removing a first ionic impurity species from a wastewater stream, the composition comprising a core of a non-active material against the first ionic impurity species and a shell formed from an active material against the first ionic impurity species, the active material making up 20-50% by weight of the particle. An embodiment of the invention is one, any or all of the first embodiment of this paragraph through the previous embodiment of this paragraph, where the shell further comprises a binder. An embodiment of the invention is one, any or all of the first embodiment of this paragraph through the previous embodiment of this paragraph, where the shell comprises 0-40% by weight of binder. An embodiment of the invention is one, any or all of the first embodiment of this paragraph through the previous embodiment of this paragraph, where the particles have a median diameter size of 2.1-0.4 mm. An embodiment of the invention is one, any or all of the first embodiment of this paragraph through the previous embodiment of this paragraph, where the particles have a spherical shape. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, in which the particles have a non-spherical shape. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, in which the shell has a thickness of 20 to 100 μm. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, in which the first ionic impurity species is selected from the group consisting of cesium, strontium, mercury, silver, lead, transition metals, iodine, lanthanide and actinide metal ions. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, in which the core or the binder, or both, are active against a second ionic impurity species in the wastewater stream, the second ionic impurity species being different from the first ionic impurity species. An embodiment of the invention is one, any or all of the first embodiment of this paragraph through the previous embodiment of this paragraph, wherein the second ionic impurity material is selected from the group consisting of cesium, strontium, mercury, silver, lead, transition metal, iodine, lanthanide metal and actinide metal ions.An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, where the core comprises a material configured to undergo a vitrification process without releasing the first and / or second ionic impurity material. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, where the shell comprises a material selected from the group consisting of metal titanates, metal germanates, pillared clays, metal phosphonates, and combinations thereof. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, where the binder comprises a hydroxyl metal oxide. An embodiment of the invention is any one, any or all of the first embodiment to the previous embodiment of this paragraph, where the core comprises a material selected from the group consisting of ceramics, silica, alumina, titania, zirconia, silicates, titanates, zeolites, and combinations thereof.

[0037] A second embodiment of the invention is a composition formed into particles for selectively removing a first ionic impurity species from a wastewater stream, the composition comprising a core of a material inactive against the first ionic impurity species, a shell formed from a material active against the first ionic impurity species, and a binder, the shell comprising 0-40% by weight of the binder, and the active material making up 20-50% by weight of the particle. An embodiment of the invention is one, any or all of the second embodiment of this paragraph through the previous embodiment of this paragraph, where the shell comprises 10-30% by weight of the binder. An embodiment of the invention is one, any or all of the second embodiment of this paragraph through the previous embodiment of this paragraph, where the binder is active against a second ionic impurity species in the wastewater stream, the second ionic impurity species being different from the first ionic impurity species. An embodiment of the invention is any one, any or all of the second embodiment of this paragraph through the previous embodiment of this paragraph, where the core comprises a material configured to undergo a vitrification process without releasing the first and / or second ionic impurity material. An embodiment of the invention is any one, any or all of the second embodiment of this paragraph through the previous embodiment of this paragraph, where the particles have a median diameter size of 2.1 to 0.4 mm. An embodiment of the invention is any one, any or all of the second embodiment of this paragraph through the previous embodiment of this paragraph, where the shell has a thickness of 20 to 100 μm.

[0038] Without further elaboration, it is believed that, using the preceding description, one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of the present invention, and can make various changes and modifications to the present invention to adapt it to various uses and conditions, without departing from the spirit and scope of the present invention. The preceding preferred specific embodiments are therefore to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way, but are intended to cover various modifications and equivalent arrangements falling within the scope of the appended claims.

[0039] Above, all temperatures are listed in degrees Celsius and all parts and percentages are by weight unless otherwise stated.

[0040] In the above detailed description of the present invention, at least one exemplary embodiment has been presented, but it should be understood that a vast number of variations exist. It should also be understood that the exemplary embodiment(s) are merely examples, and are in no way intended to limit the scope, applicability, or configuration of the present invention. Rather, the above detailed description provides those skilled in the art with a convenient guide for implementing the exemplary embodiments of the present invention, and it should be understood that various changes may be made in the functions and arrangement of elements described in the exemplary embodiments without departing from the scope of the present invention as set forth in the appended claims and their legal equivalents.

Claims

1. A composition formed into particles (10) for selectively removing a first ionic impurity substance from a wastewater stream, comprising: a core (12) of inactive material with respect to said first ionic impurity material, said core (12) being formed of silica, alumina, titania, zirconia, a silicate, or a zeolite; a shell (14) formed from an active material for the first ionic impurity material, the active material constituting 10-50% by weight of the particle; A composition comprising:

2. The composition of claim 1 , wherein the shell (14) further comprises a binder.

3. The composition of claim 2, wherein the shell (14) comprises 0.1 to 40 weight percent of the binder.

4. The composition of any one of claims 1 to 3, wherein the core (12) is formed from chabazite, clinoptilolite, or mordenite.

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