Sorbents for atmospheric water harvesting devices based on precipitated, fumed, sol-GEL, and templated oxides and hygroscopic salts

Abstract

An exemplary embodiment of the present disclosure provides a method of making a sorbent, comprising: dissolving a hygroscopic salt in a solvent to form a first solution; impregnating a plurality of supports with the first solution, each of the plurality of supports having a plurality of mesopores; and evaporating the solvent from the solution to form a dry sorbent, such that at least a portion of the hydroscopic salt is impregnated within the plurality of mesopores of each of the supports to form composite sorbents. Another exemplary embodiment of the present disclosure provides a composite sorbent, comprising a hygroscopic salt; a plurality of mesoporous supports; a binder; and a crosslinker, wherein the hygroscopic salt is impregnated within the plurality of mesoporous supports.

Description

SORBENTS FOR ATMOSPHERIC WATER HARVESTING DEVICES BASED ON PRECIPITATED, FUMED, SOL-GEL, AND TEMPLATED OXIDES AND HYGROSCOPIC SALTS AND THEIR INTEGRATION WITH SUBSTRATES OF INTEREST TO ATMOSPHERIC WATER GENERATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 604,915, filed on December 1, 2024, which is incorporated herein by reference in its entirety as if fully set forth below.GOVERNMENT LICENSE RIGHTS

[0002] This invention was made with government support under Agreement No. HR001120S0014-AWE-PA-035, awarded by DARPA. The government has certain rights in the invention.FIELD OF THE DISCLOSURE

[0003] The various embodiments of the present disclosure relate generally to sorbents for atmospheric water harvesting and methods of making the same.BACKGROUND

[0004] An increasing number of people around the world face water scarcity, as access to surface and underground freshwater vary seasonally and geographically. With the number of remaining options dwindling for accessing freshwater, more nations have turned towards desalination as a source for potable water. In some remote arid regions where there is no easy access to saltwater sources, desalination can be difficult to implement and can cause major negative natural impacts. As such, there is a need to develop an additional technology that can add to existing capabilities for water production in remote areas around the world: atmospheric water harvesting (AWH).BRIEF SUMMARY

[0005] An exemplary embodiment of the present disclosure provides a method of making a sorbent, comprising: dissolving a hydroscopic salt in a solvent to form a first solution; impregnating a plurality of supports with the first solution, each of the plurality of supportshaving a plurality of mesopores; and evaporating the solvent from the solution to form a dry sorbent, such that at least a portion of the hydroscopic salt is impregnated within the plurality of mesopores of each of the supports to form composite sorbents.

[0006] In any of the embodiments disclosed herein, the method can further comprise mixing the composite sorbents with a binder to form a slurry.

[0007] In any of the embodiments disclosed herein, the binder can comprise a waterborne resin.

[0008] In any of the embodiments disclosed herein, the waterborne resin can be based on an epoxide polymer that is suspended in water without an organic solvent.

[0009] In any of the embodiments disclosed herein, the binder can be present in a ratio of 10:90 to 30:70 binder to composite sorbent.

[0010] In any of the embodiments disclosed herein, the slurry can further comprise a crosslinker.

[0011] In any of the embodiments disclosed herein, the method can further comprise coating a substrate with the slurry.

[0012] In any of the embodiments disclosed herein, coating can comprise dip coating, drop coating, and / or spray coating.

[0013] In any of the embodiments disclosed herein, the method can further comprise crosslinking the slurry.

[0014] In any of the embodiments disclosed herein, the crosslinker can comprise an amide crosslinker.

[0015] In any of the embodiments disclosed herein, the plurality of supports can be silica supports, inorganic oxide supports, mixed oxide supports, carbon supports, or combinations thereof.

[0016] In any of the embodiments disclosed herein, the composite sorbents can have a water adsorption capacity that remains substantially constant are relative humidity set points between 10 and 80 %RH.

[0017] In any of the embodiments disclosed herein, the hygroscopic salt can be selected from the group consisting of LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KC1, KBr, K2CO3, MgCh, MgSCh, CaCh, CaFz, VF2, C0F3, SrCh.bfhO, SrBi'3.61 HO, and combinations thereof.

[0018] In any of the embodiments disclosed herein, impregnating can comprise an incipient wetness impregnation method.

[0019] In any of the embodiments disclosed herein, impregnating can comprise mixing the plurality of supports in the first solution.

[0020] In any of the embodiments disclosed herein, impregnating can comprise ultrasonicating the plurality of supports in the first solution.

[0021] In any of the embodiments disclosed herein, evaporating can comprise evaporating a first portion of the solvent at a temperature less than a boiling point of the solvent.

[0022] In any of the embodiments disclosed herein, the first portion of solvent can comprise at least 50% of the solvent.

[0023] In any of the embodiments disclosed herein, evaporating can further comprise evaporating a second portion of the solvent at a temperature greater than a boiling point of the solvent.

[0024] In any of the embodiments disclosed herein, the solvent can be a volatile solvent.

[0025] In any of the embodiments disclosed herein, the mesopores can have a mean pore width of between 2nm and 50nm.

[0026] In any of the embodiments disclosed herein, the plurality of supports can have specific surface areas greater than 200 m2 / g.

[0027] In any of the embodiments disclosed herein, the mesopores can have volumes of at least 0.4 cm3 / g.

[0028] Another embodiment of the present disclosure provides a composite sorbent comprising a hygroscopic salt, a plurality of mesoporous supports, a binder, and a crosslinker, wherein the hygroscopic salt is impregnated within the plurality of mesoporous supports.

[0029] In any of the embodiments disclosed herein, the binder can comprise a waterborne resin.

[0030] In any of the embodiments disclosed herein, the waterborne resin can be based on an epoxide polymer that is suspended in water without an organic solvent.

[0031] In any of the embodiments disclosed herein, the crosslinker comprises an amide crosslinker.

[0032] In any of the embodiments disclosed herein, the plurality of mesoporous supports comprise a plurality of silica supports, inorganic oxide supports, mixed oxide supports, carbon supports, or combinations thereof.

[0033] In any of the embodiments disclosed herein, the composite sorbent can have a water adsorption capacity that remains substantially constant at relative humidity set points between 10 and 80 %RH.

[0034] In any of the embodiments disclosed herein, the hygroscopic salt can be selected from the group consisting of LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KC1, KBr, K2CO3, MgCh, MgSCh, CaCh, CaFz, VF2, C0F3, SrCh.bfhO, SrBi'3.61 HO, and mixtures thereof.

[0035] In any of the embodiments disclosed herein, the plurality of mesoporous supports can comprise pores with a mean pore width of between 2nm and 50nm.

[0036] In any of the embodiments disclosed herein, the plurality of mesoporous supports can have a specific surface area greater than 200 m2 / g.

[0037] In any of the embodiments disclosed herein, the plurality of mesoporous supports can comprise pores having volumes of at least 0.4 cm3 / g.

[0038] In any of the embodiments disclosed herein, the composite sorbent can further comprise a carbon additive.

[0039] In any of the embodiments disclosed herein, the carbon additive can be selected from the group consisting of carbon black, onion-like carbons, graphite, graphite platelets, graphene, carbon nanotubes, carbon nanohoms, carbon fibers, bamboo-like carbon fibers, and chevronlike carbon fibers.

[0040] These and other aspects of the present disclosure are described in the Detailed Description below and the accompanying drawings. Other aspects and features of embodiments will become apparent to those of ordinary skill in the art upon reviewing the following description of specific, exemplary embodiments in concert with the drawings. While features of the present disclosure may be discussed relative to certain embodiments and figures, all embodiments of the present disclosure can include one or more of the features discussed herein. Further, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used with the various embodiments discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments, it is to be understood that such exemplary embodiments can be implemented in various devices, systems, and methods of the present disclosureBRIEF DESCRIPTION OF THE DRAWINGS

[0041] The following detailed description of specific embodiments of the disclosure will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, specific embodiments are shown in the drawings. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities of the embodiments shown in the drawings.

[0042] FIG. 1 provides a schematic illustrating different types of sorbents materials prepared by sol-gel method, and by modified sol-gel method yielding precipitated and templatedmaterials, in accordance with some embodiments of the present disclosure. Fumed materials are prepared by flame oxidation method and have comparable structure to precipitated oxides, but with lower internal particle porosity.

[0043] FIGS. 2A-2C provide example adsorption properties of the sorbent supports (FIG. 2A), N2 at 77K isotherms and corresponding pore size distribution (FIG. 2B) and cumulative pore volume curves of bare silica supports, H2O sorption isotherms (FIG. 2C) at 300K for bare silica supports, in accordance with some embodiments of the present disclosure.

[0044] FIGs. 3A-3F provide adsorption isotherms (FIGs. 3A, 3C, 3E) and calculated pore size distributions (FIGs. 3B, 3D, 3F) of bare silicas and of LiCl-silica composites at various LiCl loadings, in accordance with some embodiments of the present disclosure. FIGs. 3A-3B show adsorption isotherms and pore size distributions, respectively, for small mesopore silica gel. FIGs. 3C-3D show adsorption isotherms and pore size distributions, respectively, for large mesopore silica gel. FIGs. 3E-3F show adsorption isotherms and pore size distributions, respectively, for small mesopore silica gel. FIGs. 3G-3H show adsorption isotherms and pore size distributions, respectively, for small and large mesopore alumina, silica-alumina and alumina-silica supports in comparison to precipitated silicas.

[0045] FIGs. 4A-4E provide representative volumetric water vapor adsorption isotherms (FIGs. 4A-4C) at 300K and dynamic water vapor breakthrough curves (FIG. 4D-4F) for salt- loaded commercial silica materials, in accordance with some embodiments of the present disclosure. The salt loaded silica supports are LiCl loaded small mesopore precipitated silica (FIG. 4A), LiCl loaded large mesopore precipitated silica (FIG. 4B), and LiCl loaded small mesopore silica gel (FIG. 4C). FIG. 4D shows large mesopore precipitated silica support impregnated with different loads and ratios of LiCl to CaCh. FIG. 4E shows water isotherms for alumina, silica-alumina, and alumina-silica mesoporous supports containing LiCl. FIG. 4F shows dynamic water vapor breakthrough experiments for salt-loaded templated silica.

[0046] FIGs. 5A-5B provide optical photograph of dip-coated Copper metal foam candidate for fins in AWG devices (FIG. 5A), and the normalized water adsorption isotherm (FIG. 5B) of the fin per estimated weight of composite LiCl@SiO2-35wt% sorbent prepared by dropcoating (SiCh: HS-PEG from two different batches, NB and SB), in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0047] To facilitate an understanding of the principles and features of the present disclosure, various illustrative embodiments are explained below. The components, steps, and materials described hereinafter as making up various elements of the embodiments disclosed herein are intended to be illustrative and not restrictive. Many suitable components, steps, and materials that would perform the same or similar functions as the components, steps, and materials described herein are intended to be embraced within the scope of the disclosure. Such other components, steps, and materials not described herein can include, but are not limited to, similar components or steps that are developed after development of the embodiments disclosed herein.

[0048] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0049] Also, in describing the preferred exemplary embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

[0050] Ranges can be expressed herein as from “about” or “approximately” one particular value and / or to “about” or “approximately” another particular value. When such a range is expressed, another exemplary embodiment includes from the one particular value and / or to the other particular value.

[0051] By ‘ ‘comprising” or “containing” or “including” is meant that at least the named compound, member, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0052] Mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0053] The materials described as making up the various members of the invention are intended to be illustrative and not restrictive. Many suitable materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of the invention. Such other materials not described herein can include, but are notlimited to, for example, materials that are developed after the time of the development of the invention.

[0054] Atmospheric water generation (AWG) is a promising new technology to extract water from air on demand and at different size scales. Potential uses include defense, first responders, civilian use, agriculture, and industry. Existing and developing AWG devices are based on either based on sorbent, or on condenser / heat exchanger technologies.

[0055] Other technologies that will benefit from the sorbents, sorbent preparation, and integration disclosed herein are Thermal Energy Storage (TES) systems that use salts or composite sorbents for using the energy in of the chemical bonds formed between water and the salts. When anhydrous salts absorb water, these can release heat that can be used for work, or environment heating (commercial, residential buildings). Heat from the environment or other thermal source is added to the salt or sorbent compartment to remove the water.

[0056] Sorbent-based devices can theoretically outperform condenser / heat exchanger type devices at extreme temperature and humidity conditions. Best sorbent performance is expected for materials that can uptake water at every relative humidity prior to liquid water precipitation. Sorbents to perform in this fashion can be based on porous sorbents (MOFs, ZIFs, Zeolites, silicas, inorganic oxides, and composites) supporting inorganic hygroscopic salts (i.e., LiF, LiCl, NaF, NaCl, KF, KC1, K2CO3, MgCh, MgSO4, CaCl2, CaF2, VF2, C0F3, SrCl3.6H2O, SrBr3.6H2O). The best supports can have mesopores in the range of 2nm to 50nm in size [mean pore width, Barrett-Joyner-Halenda (BJH), Density Functional Theory (DFT)], have specific surface areas [from Brunauer-Emmett-Teller (BET), DFT, or comparative plot]greater than 200m2 / g, and mesopore volumes of at least 0.4cm3 / g.

[0057] The present disclosure builds on the sorbents disclosed in PCT Publication No. WO2023 / 201223, entitled “Porous Silica Materials and Methods of Making the Same,” which is incorporated herein in its entirety as if fully set forth below.

[0058] The present disclosure reports on the properties of oxide supports having these adsorption properties and supporting hygroscopic salts at various loading ratios. These sorbents can be impregnated using the minimum possible amount of a volatile organic solvent by a modified incipient wetness impregnation method developed for accommodating very low to very high salt concentrations. The composite sorbents obtained can retain part of the original mesopore volume and possess high surface areas, both of which facilitate water vapor diffusion and accessibility to the supported salts. The obtained composites can be stable during water adsorption-desorption cycling in the range of 10-80% RH (%Relative Humidity), meaning thatthese can retain their original performance in terms of water capacity and kinetics. The present method further includes a method for binding the solid powders by using a waterborne epoxide resin and that is crosslinked using an amide compound. The sorbent-resin composites can be suitable for integrating the sorbent to different surfaces, as coatings.

[0059] An exemplary embodiment of the present disclosure provides a method of making a sorbent, comprising: dissolving a hydroscopic salt in a solvent to form a first solution; impregnating a plurality of supports with the first solution, each of the plurality of supports having a plurality of mesopores; and evaporating the solvent from the solution to form a dry sorbent, such that at least a portion of the hydroscopic salt is impregnated within the plurality of mesopores of each of the supports to form composite sorbents.

[0060] In any of the embodiments disclosed herein, the plurality of supports can be silica supports, inorganic oxide supports, mixed oxide supports, carbon supports, or combinations thereof. Suitable supports include, without limitation, SiCh, SiCh-AhCh, AhCh-SiCh, AI2O3, carbons, zeolites, and metal organic frameworks (MOFs).

[0061] In any of the embodiments disclosed herein, the composite sorbents can have a water adsorption capacity that remains substantially constant at relative humidity set points between 10 and 80 %RH. For example, the composite sorbents can have a water adsorption capacity that remains substantially constant at relative humidity set points between 10 and 20 %RH, 10 and 30 %RH, 10 and 40 %RH, 10 and 50 %RH, 10 and 60 %RH, 10 and 70 %RH, 20 and 30 %RH, 20 and 40 %RH, 20 and 50 %RH, 20 and 60 %RH, 20 and 70 %RH, 20 and 80 %RH, 30 and 40 %RH, 30 and 50 %RH, 30 and 60 %RH, 30 and 70 %RH, 30 and 80 %RH, 40 and 50 %RH, 40 and 60 %RH, 40 and 70 %RH, 40 and 80 %RH, 50 and 60 %RH, 50 and 70 %RH, 50 and 80 %RH, 60 and 70 %RH, 60 and 80 %RH, or 70 and 80 %RH.

[0062] In any of the embodiments disclosed herein, the hygroscopic salt can be, without limitation, LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KC1, KBr, K2CO3, MgCl2, MgSO4, CaCl2, CaF2, VF2, C0F3, SrC13.6H2O, Si i'3.61 FC), and mixtures thereof.

[0063] In any of the embodiments disclosed herein, the solvent that dissolves the hygroscopic salt can be, without limitation, an alcohol, water, acetone, ethers, and combinations thereof. In some embodiments, the solvent is methanol. In some embodiments, water can be added as a cosolvent.

[0064] In any of the embodiments disclosed herein, evaporating can comprise evaporating a first portion of the solvent at a temperature less than the boiling point of the solvent. In some embodiments, the first portion of the solvent comprises at least 50% of the solvent. Forexample, in some embodiments, the first portion of the solvent comprises 50%, 60%, 70%, 80%, 90%, or 95% of the solvent. In some embodiments, evaporating can further comprise evaporating a second portion of the solvent at a temperature greater than the boiling point of the solvent. In any of the embodiments disclosed herein, the solvent can be volatile.

[0065] In any of the embodiments disclosed herein, the method can further comprise mixing the composite sorbents with a binder to form a slurry. The binder can comprise a waterborne resin. In some embodiments, the waterborne resin can be based on an epoxide polymer that is suspended in water without an organic solvent. An exemplary resin is EPI-REZ Resin 6006- W-68 provided by Hexion. Other waterborne or water-solvent mixed systems include, without limitation, polyurethane polymer, acrylic resins, phenolic resins, lattices (latex), and hybrid resins (i.e., polyurethane hybridized with acrylic resins).

[0066] In any of the embodiments disclosed herein, the binder can be present in a ratio of 10:90 to 30:70 binder to composite sorbent. For example, in some embodiments, the binder can be present in a ratio of 10:90 to 15:85, 10:90 to 20:80, 10:90 to 25:75, 15:85 to 20:80, 15:85 to 25:75, 15:85 to 30:70, 20:80 to 25:75, 20:80 to 30:70, or 25:75 to 30:70 binder to composite sorbent.

[0067] In any of the embodiments disclosed herein, the slurry can further comprise a crosslinker. In some embodiments, the crosslinker can be an amide crosslinker. An exemplary amide crosslinker is dicyandiamide (DICY). Additional crosslinkers include, without limitation, those under the classes of compounds classified as amines, isocyanates, aziridines, melamines, polycarbodiimides, and combinations thereof. Crosslinking may be initiated by heat, pressure, or pH changes, or non-covalent interactions (Van der Waals, hydrogen bonding).

[0068] In some embodiments, the crosslinker is dissolved in a solvent to form a solution, and a plasticizer is optionally added to the solution. Suitable solvents include methanol, ethanol, isopropyl alcohol, butanol, tertbutyl alcohol, any other solvents in which the salts have low solubility, or mixtures thereof. The binder can then be added to the solution to form a suspension, which can then be sonicated. The composite sorbent of the present disclosure can then be added to the suspension, which can be sonicated to form a slurry. In some embodiments, the slurry can be used to coat a target substrate, which can be done by dip coating, drop coating, or spray coating. The coated substrates can then be heated in an oven to thermally crosslink the slurry. Heating can take place at a temperature between 150 and 190°C for 6 to 12 hours. For example, in some embodiments, heating takes place at a temperature between 150 and 160°C,150 and 170°C, 150 and 180°C, 160 and 170°C, 160 and 180°C, 160 and 190°C, 170 and 180°C, or 170 and 190°C. In some embodiments, heating takes place for 6 to 7 hours, 6 to 8 hours, 6 to 9 hours, 6 to 10 hours, 6 to 11 hours, 8 to 9 hours, 8 to 10 hours, 8 to 11 hours, 8 to 12 hours, 10 to 11 hours, or 10 to 12 hours.

[0069] In any of the embodiments disclosed herein, the impregnating can comprise an incipient wetness impregnation method. Incipient Wetness Impregnation is a method where an impregnation solution containing an active precursor is added to a support material containing the same pore volume as the volume of solution added. The impregnation solution is drawn into the pores of the support via capillary action. The material can then be dried to remove the volatile solvent, depositing the precursor within the pores of the support material. This technique allows for the loading of a specific amount of active precursor based on its solubility in the chosen solvent. In some embodiments of the present disclosure, a modified Incipient Wetness Impregnation can be used, where the volume of solvent is greater than the pore volume of the support material. The excess is determined to facilitate the dissolution of the salt, and subsequently the mixing of the salt solution and selected support.

[0070] In any of the embodiments disclosed herein, impregnating can comprise mixing the plurality of supports in the first solution. In some embodiments, impregnating can comprise ultrasonicating the plurality of supports in the first solution. In some embodiments, impregnating can comprise mechanically mixing the plurality of supports in the first solution.

[0071] In any of the embodiments disclosed herein, the mesopores have a mean pore width of between 2nm and 50nm. For example, in some embodiments, the mesopores have a mean pore width of between 2nm and lOnm, between 2nm and 20nm, between 2nm and 30nm, between 2nm and 40nm, , between 1 Onm and 20nm, between 1 Onm and 30nm, between 1 Onm and 40nm, between lOnm and 50nm, between 20nm and 30nm, between 20nm and 40nm, between 20nm and 50nm, between 30nm and 40nm, between 30nm and 50nm, or between 40nm and 50nm.

[0072] In any of the embodiments disclosed herein, the plurality of supports have specific surface areas greater than 200 m2 / g. In any of the embodiments disclosed herein, the mesopores have volumes of at least 0.4 cm3 / g.

[0073] Another exemplary embodiment of the present disclosure is a composite sorbent comprising a hygroscopic salt, a plurality of mesoporous supports, a binder, and a crosslinker, wherein the hygroscopic salt is impregnated within the plurality of mesoporous supports.

[0074] The hygroscopic salt, plurality of mesoporous supports, binder, and crosslinker are those of the present disclosure as described herein.

[0075] In any of the embodiments disclosed herein, the composite sorbent can further comprise a carbon additive. The carbon additive can be a conductive material for improving the thermal conductivity of the composite sorbents. Suitable carbon additives include, without limitation, carbon black, onion-like carbons, graphite, graphite platelets, graphene (monolayer or multilayer, powder, turbostratic), carbon nanotubes, carbon nanohoms, carbon fibers, bamboolike and chevron-like carbon fibers, and any other type of carbon nanomaterial having similar structural properties to the listed examples.

[0076] The composite sorbent can be produced by any of the methods described herein and can be used in an atmospheric water generation system.

[0077] It is to be understood that the embodiments and claims disclosed herein are not limited in their application to the details of construction and arrangement of the components set forth in the description and illustrated in the drawings. Rather, the description and the drawings provide examples of the embodiments envisioned. The embodiments and claims disclosed herein are further capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting the claims.

[0078] Accordingly, those skilled in the art will appreciate that the conception upon which the application and claims are based may be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the embodiments and claims presented in this application. It is important, therefore, that the claims be regarded as including such equivalent constructions.

[0079] Furthermore, the purpose of the foregoing Abstract is to enable the United States Patent and Trademark Office and the public generally, and especially including the practitioners in the art who are not familiar with patent and legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the claims of the application, nor is it intended to be limiting to the scope of the claims in any way.EXAMPLES

[0080] The following Examples are presented to illustrate various aspects of the present application, but are not intended to limit the scope of the claimed application.

[0081] Commercial oxide supports were obtained from different vendors. The examples here provided are for three representative amorphous precipitated and sol-gel silicas (SiCh)supported Lithium Chloride (LiCl). The present results can be extended to other mixed silica- alumina, alumina- silica, and to high surface area alumina precipitated, fumed or sol-gel based oxides (hydrogels, xerogels, cryogels, aerogels), and templated materials of commercial origin. Representative scheme of the possible structure of these supports is presented in FIG. 1.

[0082] The summary of possible / representative adsorption properties of the sorbent supports is given in FIG. 2A. These have isotherms of type IV. Materials having mesopores smaller than 4nm do not exhibit N2 sorption hysteresis. The sorbent supports having larger than 4nm mesopores have hysteresis loops with positions depending on the mesopores width. Multimodal mesopore structures are possible, with one or more hysteresis loops being observed in the N2 isotherms. The steepness and height of each condensation step change according to the width of the distribution of pore sizes, and with total pore volume. The corresponding pore size distribution (PSD) curves in Fig.2B further corroborate that. For most commercial supports, broad distributions of mesopores are expected. Templated materials can have narrow PSDs. The representative water vapor sorption isotherms at 300K for the sample supports are also given in FIG. 2C. These are type V for materials having small mesopores. These results from the stronger interactions between water molecules than with the supports surfaces, but with capillary condensation taking place at a relative humidity range proportional to the mesopore size. The step height and steepness also depend on the total pore volume and adsorbed phase density, and the width of the PSD, respectively. The isotherm of materials having larger than 1 Onm mesopores may not exhibit condensation within the investigated vapor relative humidity range. Condensation can be expected to take place above the condensation pressure for water under these conditions. Consequently, the isotherms are classified as type III rather than type II.

[0083] LiCl can be used as the representative hygroscopic salt, but the hygroscopic salt candidates, include, but are not limited to, any inorganic salt, or salt mixtures, having high affinity for water. These can be based on small cationic metal ions (Na, K, Mg, Ca), and transition metals. Some examples include: LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KC1, KBr, K2CO3, MgCl2, MgSO4, CaCl2, CaF2, VF2, C0F3, SrCl3.6H2O, SrBr3.6H2O.

[0084] The impregnation procedure can be based on a modified incipient wetness impregnation method (IWI). The IWI can be used for depositing small amounts of catalysts onto the surfaces of a catalyst support. The present modification (MIWI) was developed to introduce high loadings of hygroscopic salt onto the surface of any type of support. First the hygroscopic salt can be dissolved in a volatile solvent, and ensures high solubility of salts. Here, as an example,LiCl was dissolved in methanol as the solvent. Other suitable solvents include, without limitation, alcohols, water, acetone, and ethers. The amount of LiCl is specified for the target weight ratio to the support, i.e., to prepare 1g of LiCl@Support (Support: SiOz, SiOi-AhOs, ALOs-SiOz, AI2O3, carbons, MOFs) with composition of 50wt%, 0.5g of LiCl are dissolved in 1 to 5ml of methanol using the help of ultrasound at room temperature. The obtained solution can then be used to impregnate 0.5g of support (powder, pellet, film, etc.). The support can be placed in a container so that all particles are fully covered by the LiCl solution. The system can be ultrasonicated for 5 minutes for outgassing of the silica supports and for facilitating the transport of the LiCl solution into the pores of the support. Alternatively, the system can be mechanically mixed for up to Ih. The system can be kept undisturbed from a minimum of Ih, and up to 12h at room temperature. The solvent can be evaporated initially below the boiling point of methanol, or of any other selected solvent, with stirring. Vacuum in addition to heating and stirring is optional based on the volatility of the solvent and the size of the system. Once the volume of solvent is reduced to 50% or less, the temperature can be increased to above the boiling point of the solvent, and the temperature can be maintained until the composite is dry. Salts with limited solubility in methanol can be dissolved using the same procedure, except that water can be added as a cosolvent, or as the single solvent. The amount of water can be adjusted for each individual salt.

[0085] The salts can deposit primarily within the mesopores. The total salt loaded within mesopores can depend on the total mesopore volume. This capacity can change given the nature of the mesopores. Smaller mesopores can retain most of the salt within its volume. Large mesopores can allow for aggregation and crystallization of salt crystals on external surfaces. Very large mesopores, >10nm can tend to be interpreted as interparticle (or external) pores when these are formed by a mechanism different than a templating method. The representative N2 isotherms and corresponding PSD curves, respectively, for salt loaded supports and in comparison, to the bare supports are shown in FIGs. 3A-3B for small mesopore precipitated silica, FIGs. 3C-3D for large mesopore precipitated silica, FIGs. 3E-3F for small mesopore silica gel, and FIGs. 3G-3H for small and large mesopore alumina, silica-alumina and alumina- silica supports in comparison to precipitated silicas from FIGs. 3A and 3C. The decrease in the total amount of gas adsorbed, and the absence of new condensation steps, both can indicate that most salt is loaded within the mesopores of the support and without formation of additional pores. Higher salt loadings may lead to additional steps due to particle aggregation and new external mesopore formation. The calculated PSD curves confirm that only the original poresof the support decrease in volume, that no additional pores are created, and that the mechanism of salt loading takes place within the open and accessible mesopores. The decrease in pore volume and in specific surface area can be proportional to the total amount of salt loaded in these supports. Higher loadings can lead to lower remaining pore volumes. Materials having broad PSDs, can exhibit uneven decrease in the PSD peaks, given the heterogeneity of these systems.

[0086] Water vapor adsorption isotherms of salt loaded silica supports are given for LiCl loaded small mesopore precipitated silica in FIG. 4A, large mesopore precipitated silica in FIG. 4B, for small mesopore silica gel in FIG. 4C. These isotherms indicate the increase of water uptake at every relative humidity is proportional to the amount of salt loaded. The water uptake is also dependent on the salt type on the support. For the same salt load, LiCl@SiO2 has higher gravimetric water uptake than CaC12@SiO2. The uptake of LiCl blends with other salts, as exemplified for LiCl-CaCh can be adjusted in small increments by having slight increases in LiCl in the blend as exemplified for large mesopore precipitated silica support impregnated with different loads and ratios of LiCl to CaCh in FIG. 4D. Most pure salts deliquesce at low relative humidity ranges. The dispersion and stability of the salt on the support prevents deliquescence via a pore confinement effect. Bulk salt present in these composites would deliquesce and reduce the overall composite stability as seen for LiCl in FIGs. 4A and 4B in comparison to supported LiCl. For the same salt, such as LiCl, the water uptake is dependent only on the salt load and its dispersion on the support. The water isotherms exemplified in FIG. 4E verify that for different alumina, silica-alumina, and alumina-silica mesoporous supports containing the salt LiCl load in comparison to a large mesopore precipitated silica with the same LiCl load. The stability of these composite sorbents is further verified by dynamic water vapor breakthrough experiments, as exemplified by the curves for a salt-loaded templated silica in FIG. 4F, at various relative humidity set points and cycles over a specific amount of time required for the vapor concentration to remain constant. This indicates when the sorbents are completely saturated. The water adsorption capacity of these materials remains the same for numerous cycles investigated at relative humidity set points between 10 and 80%RH, as also verified by gravimetric water vapor sorption analysis.

[0087] Binders are commonly used for depositing solids onto different surfaces. Most AWG devices can use sorbent fins having high thermal conductivity. The composite sorbents can then be mixed with a binder that is stable under the conditions for the operation of the AWG device, it can be inert, and it may not release harmful byproducts form eventual decomposition.The binder can be a waterborne resin based on an epoxide polymer that is suspended in water and without any organic solvent. The binder solution can be weighted to reach any ratio between 10wt% to 30wt% with respect to the composite sorbent. The slurries can then be crosslinked with an amide crosslinker.

[0088] Here, a resin can be provided by Hexion (Westlake Epoxy, a Westlake Company) and identified as EPI-REZ Resin 6006-W-68. The resin suspension contained 62-65wt% solids. The average molecular weight of the resin was estimated to be approximately 250g / equivalent. For 50g of suspension, approximately 32.5g corresponded to solids, thus yielding 0.13equivalents. The crosslinker used was dicyandiamide (DICY) and of molecular weight 84.08g / mol. The EPI-REZ to DICY ratio was leq: lmol. Hence, the same number of equivalents was used for DICY, meaning 0.13eq. x 84.08g / mol and yielding 10.93g. The use of a plasticizer such as hydroquinone bis(2-hydroxyethyl) ether (HBHE) of molecular weight 198.22g / mol is optional. The HBHE can assist with sorbent particle stabilization during mixing and crosslinking with the EPI-REZ / DICY. The HBHE can be used at the Imol / lmol of DICY. The DICY and HBHE can be dissolved in methanol, acetone, or in mixtures of methanolacetone. Other suitable solvents include, without limitation, ethanol, isopropyl alcohol, butanol, tertbutyl alcohol, or any other solvents in which the salts have low solubility. Once dissolved, EPI-REZ can be added, and the suspension sonicated. The composite sorbent can be added, the suspension sonicated, and the slurry used for coating the target substrates. The coating can be done by dip coating, drop coating, spray coating, or the like. The spray coating can be done by forming an aerosol of the suspension using a spray gun for ceramic coatings. Electrospray can be a suitable alternative to the latter method. The coating procedure can be done until the surface of the target substrate is visibly saturated. Caking of composite sorbent onto substrate may take place but it may not be desired for its decreased stability. The coated substrates can then be thermally crosslinked upon heating in oven at temperatures between 150 to 190°C for 6 to 12h. Images of di-coated Cu foams are shown in FIG. 5A for a templated silica containing LiCl salt. The pores of the foam are partially filled with composite coating. Alternative heating methods include, but are not limited to, lasers, infrared radiation, microwave, ultraviolet. Besides Cu, other metal surfaces can be coated using this method, including Al, Al-alloys, Ni and its alloys, bronzes and Zn alloys, and any grades of stainless steel.

[0089] The estimated final loading of binder mixture was 16.6wt.% based on weight of reactants added, and changes in weight after drying and crosslinking of mounted binder-sorbenton multiple Cu foams. For drop-coated samples, the sorbent loading increased. The loading of LiCl@SiO2 in the example by drop-coating was estimated to be 48wt.%. The normalized water adsorption isotherm for sorbent-Cu foam system is shown in FIG. 5B for two different batches of salt-loaded templated silica and the same composite mixed with EPI-REZ / DICY after crosslinking, indicate similar water uptake to the composite sorbent powders without the binder components.

[0090] Fluctuations can be expected based on increasing heterogeneity of resin suspensions and polydispersity of waterborne epoxy resins, and on the repeatability of the coating method used.

[0091] Spray coating methods can be expected to yield most repeatable coatings for easiness of controlling solvent evaporation, preventing particle sedimentation, and forming uniform aerosol particles. This method can be best applied to composite sorbents having mean particle sizes of 50pm or less. Smaller particles can yield more stable suspensions and allow for finer substrate coating.

[0092] For improving the thermal conductivity of these bound sorbents, conductive materials such as carbon black, onion-like carbons, graphite, graphite platelets, graphene (monolayer or multilayer, powder, turbostratic), carbon nanotubes, carbon nanohoms, carbon fibers, bamboolike and chevron-like carbon fibers, and any other type of carbon nanomaterial having similar structural properties to these listed as examples.

Claims

CLAIMSWhat is claimed is:

1. A method of making a sorbent, comprising: dissolving a hygroscopic salt in a solvent to form a first solution; impregnating a plurality of supports with the first solution, each of the plurality of supports having a plurality of mesopores; and evaporating the solvent from the solution to form a dry sorbent, such that at least a portion of the hygroscopic salt is impregnated within the plurality of mesopores of each of the supports to form composite sorbents.

2. The method of claim 1, further comprising mixing the composite sorbents with a binder to form a slurry.

3. The method of claim 2, wherein the binder comprises a waterborne resin.

4. The method of claim 3, wherein the waterborne resin is based on a material selected from the group consisting of an epoxide polymer, a polyurethane polymer, an acrylic resin, a phenolic resin, a latex, and a hybrid resin, wherein the material is suspended in water without an organic solvent.

5. The method of any of claims 2-4, wherein the binder is present in a ratio of 10:90 to 30:70 binder to composite sorbent.

6. The method of any of claims 2-4, wherein the slurry further comprises a crosslinker.

7. The method of claim 6, further comprising coating a substrate with the slurry.

8. The method of claim 7, wherein coating comprises dip coating, drop coating, and / or spray coating.

9. The method of claim 7, further comprising crosslinking the slurry.

10. The method of any of claims 6-8, wherein the crosslinker is selected from the group consisting of amides, amines, isocyanates, aziridines, melamines, and polycarbodiimides.

11. The method of any of claims 1-10, wherein the plurality of supports are silica supports, inorganic oxide supports, mixed oxide supports, carbon supports, or combinations thereof.

12. The method of any of claims 1-11, wherein the composite sorbents have a water adsorption capacity that remains substantially constant at relative humidity set points between 10 and 80 %RH.

13. The method of any of claims 1-12, wherein the hygroscopic salt is selected from the group consisting of LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KC1, KBr, K2CO3, MgCh, MgSCU, CaCh, CaFz, VF2, C0F3, SrCh.bFbO, SrBn.61 FC), and mixtures thereof.

14. The method of any of claims 1-13, wherein impregnating comprises an incipient wetness impregnation method.

15. The method of any of claims 1-14, wherein impregnating comprises mixing the plurality of supports in the first solution.

16. The method of any of claims 1-14, wherein impregnating comprises ultrasonicating the plurality of supports in the first solution.

17. The method of any of claims 1-4, wherein evaporating comprises evaporating a first portion of the solvent at a temperature less than a boiling point of the solvent.

18. The method of any of claim 17, wherein the first portion of solvent comprises at least 50% of the solvent.

19. The method of claim 17 or claim 18, wherein evaporating further comprises evaporating a second portion of the solvent at a temperature greater than a boiling point of the solvent.

20. The method of any of claims 1-19, wherein the solvent is a volatile solvent.

21. The method of any of claims 1-20, wherein the mesopores have a mean pore width of between 2nm and 50nm.

22. The method of any of claims 1-21, wherein the plurality of supports have specific surface areas greater than 200 m2 / g.

23. The method of any of claims 1-22, wherein the mesopores have volumes of at least 0.4 cm3 / g.

24. A composite sorbent, comprising: a hygroscopic salt; a plurality of mesoporous supports; a binder; and a crosslinker, wherein the hygroscopic salt is impregnated within the plurality of mesoporous supports.

25. The composite sorbent of claim 24, wherein the binder comprises a waterborne resin.

26. The composite sorbent of claim 25, wherein the waterborne resin is based on an epoxide polymer that is suspended in water without an organic solvent.

27. The composite sorbent of any of claims 24-26, wherein the crosslinker comprises an amide crosslinker.

28. The composite sorbent of any of claims 24-27, wherein the plurality of mesoporous supports comprise a plurality of silica supports, inorganic oxide supports, mixed oxide supports, carbon supports, or combinations thereof.

29. The composite sorbent of any of claims 24-28 having a water adsorption capacity that remains substantially constant at relative humidity set points between 10 and 80 %RH.

30. The composite sorbent of any of claims 24-29, wherein the hygroscopic salt is selected from the group consisting of LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, KC1, KBr, K2CO3, MgCh, MgSCfi, CaCh, CaFz, VF2, C0F3, SrCh.bfhO, SrBi'3.6112O, and mixtures thereof.

31. The composite sorbent of any of claims 24-30, wherein the plurality of mesoporous supports comprise pores with a mean pore width of between 2nm and 50nm.

32. The composite sorbent of any of claims 24-31, wherein the plurality of mesoporous supports have a specific surface area greater than 200 m2 / g.

33. The composite sorbent of any of claims 24-32, wherein the plurality of mesoporous supports comprise pores having volumes of at least 0.4 cm3 / g.

34. The composite sorbent of any of claims 24-33, further comprising a carbon additive.

35. The composite sorbent of claim 34, wherein the carbon additive is selected from the group consisting of carbon black, onion-like carbons, graphite, graphite platelets, graphene, carbon nanotubes, carbon nanohoms, carbon fibers, bamboo-like carbon fibers, and chevronlike carbon fibers.

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