CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Patent Application Ser. No. 62/448,462 entitled “ALUMINOSILICATE NANORODS” and filed on Jan. 20, 2017, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention relates to nanostructured aluminosilicates including aluminosilicate nanorods, as well as materials that include the nanostructured aluminosilicates, the aluminosilicate nanorods, and materials that contain the aluminosilicate nanorods, aggregates thereof, or both.

BACKGROUND

Nanorods are a type of one-dimensional nanostructured materials. Nanorods are nanostructures shaped like sticks or dowels with a nanoscale diameter and a length that exceeds the diameter. Nanorods are alternatively called elongated nanoparticles, acicular particles, high aspect ratio particles, and nanowhiskers. Nanorods are suitable for a broad range of applications including sensors and composites.

Alkali-activated aluminosilicates are a type of geopolymer. Geopolymers are also commonly referred to by a variety of terms, including low-temperature aluminosilicate glass, alkali-activated cement, geocement, alkali-bonded ceramic, inorganic polymer concrete, and hydroceramic. Geopolymers are prepared by curing geopolymer resins. In some cases, geopolymer resins are prepared by coupled alkali-mediated dissolution and precipitation reactions of silicate or aluminosilicate precursors in an aqueous media. Geopolymers are nanomaterials that exhibit a dense gel-like structure with 5 nm- to 60 nm-sized “isotropic” amorphous aluminosilicate particles. Their chemical structure typically includes an amorphous, three-dimensional network of corner-sharing aluminate and silicate tetrahedra, with the negative charge due to Al³⁺ ions in the tetrahedral sites balanced typically by the alkali metal ions.

SUMMARY

In a first general aspect, a nanostructured aluminosilicate includes aluminosilicate nanorods. The aluminosilicate nanorods have an average width between about 5 nm and about 100 nm, and a majority of the aluminosilicate nanorods have an aspect ratio between about 2 and about 100.

In a second general aspect, an aqueous medium, organic medium, colloidal medium, latex colloidal medium, dispersion medium, suspension medium, polymeric medium, or elastomeric medium includes the nanostructured aluminosilicates or modified nanostructured aluminosilicates of the first general aspect.

In a third general aspect, an article includes the nanostructured aluminosilicates or modified nanostructured aluminosilicates of the first general aspect.

In a fourth general aspect, a material includes the nanostructured aluminosilicates or modified nanostructured aluminosilicates of the first general aspect.

In a fifth general aspect, forming aluminosilicate nanorods includes heating a geopolymer resin containing up to about 90 mol % water (e.g., between about 70 mol % and about 90 mol %) in a closed container at a temperature between about 70° C. and about 200° C. for a length of time up to about one week to yield a first material including nanostructured aluminosilicates. The nanostructured aluminosilicates include aluminosilicate nanorods.

Implementations of the first through fifth general aspects may include one or more of the following features.

In some cases, the aluminosilicate nanorods have an average width between about 5 nm and about 60 nm, or between about 5 nm and about 30 nm. In certain cases, at least 50% of the aluminosilicate nanorods have an aspect ratio of at least 2, at least 3, at least 4, at least 5, or at least 10. In certain cases, a majority of the aluminosilicate nanorods are not chemically or covalently bonded to another one of the aluminosilicate nanorods.

The mesopore volume of the nanostructured aluminosilicates may be at least about 0.05 cc/g, at least about 0.1 cc/g, at least about 0.2 cc/g, or at least about 0.3 cc/g on the Barrett-Joyner-Halenda (BJH) cumulative pore volume from the desorption branch of the N₂sorption isotherm, where the mesopore volume is the total pore volume of the pores having a pore width between about 2 nm and about 50 nm.

In some implementations, the aluminosilicate nanorods have a majority of aluminum and silicon atoms in a tetrahedral coordination environment. The aluminosilicate nanorods may have a crystallinity with a CAN-type framework structure. In some cases, the aluminosilicate nanorods include a zeolite containing anions in the zeolite cages.

The specific external surface area of the nanostructured aluminosilicates may be between 50 m²/g and 400 m²/g. As used herein, “specific external surface area” generally refers to the total specific surface area minus the specific micropore surface area. In some cases, the specific micropore surface area of the nanostructured aluminosilicates is between 1 m²/g and 60 m²/g or between 60 m²/g and 700 m²/g.

In some implementations, the aluminosilicate nanorods are formed in a geopolymerization process. In one example, a geopolymerization process includes providing a geopolymer resin containing up to about 90 mol % water (e.g., between about 70 mol % and about 90 mol %), optionally keeping the geopolymer resin at a temperature up to about 60° C. for up to about a week, and heating the geopolymer resin in a closed container at a temperature between about 70° C. and about 200° C. for up to about a week to yield a first material including the nanostructured aluminosilicates. In some cases, the process includes treating first material to produce a second material. In some cases, the process includes concentrating a solid component or collecting a solid product from the first or second material, where the solid component or solid product includes nanostructured aluminosilicates, and the nanostructured aluminosilicates include aluminosilicate nanorods or modified nanostructured aluminosilicates comprising modified aluminosilicate nanorods.

In some cases, treating the first material may include reducing the concentration of hydroxide of the first material to about 1 M or reducing the pH of the first material from about 14. In certain cases, treating the first material includes diluting the first material or mixing the first material with an acidic solution. In certain cases, treating the first material includes combining the first material with a solution of a metal ion that forms an oxide, hydroxide, hydrous oxide, or combination thereof in contact with hydroxide ions.

In some implementations, the absolute value of the zeta potential of the nanostructured aluminosilicates or the modified nanostructured aluminosilicates is at least about 30 mV, at least about 40 mV, at least about 50 mV, or at least about 60 mV in a pH range between about 3 and about 14, between about 3 and about 13, between about 3 and about 12, between about 4 and about 14, between about 4 and about 13, between about 4 and about 12, between about 5 and about 14, between about 5 and about 13, or between about 5 and about 12.

In some cases, a surface of the aluminosilicate nanorods is covered partially or completely with one or more organic molecules, surfactants, or polymers or a combination thereof. In some cases, a surface of the aluminosilicate nanorods is covered partially or completely with inorganic molecules or nanoparticles. In some cases, a surface of the aluminosilicate nanorods is covered partially or completely with molecules of a biological origin. In some cases, the alkali ions in the aluminosilicate nanorods are exchanged partially or completely with other metal ions or protons.

In some implementations of the second general aspect, the nanostructured aluminosilicates or modified nanostructured aluminosilicates provide a thixotropic property to the aqueous medium, organic medium, suspension medium, polymeric medium, or elastomeric medium of the second general aspect.

In some implementations of the third general aspect, the article is a tire, a rubber belt, a rubber seal, a rubber tube, footwear, a polystyrene foam, a polyurethane foam, a plastic, a fire extinguisher, a tooth paste, a drug tablet, a membrane, a dehumidifier, fertilizer or a heat exchanger.

In some implementations of the fourth general aspect, the material is an adhesive, a sealant, a colorant, an ink, an ink for ink-jet printers, a toner, a paint, a coating, a defoamer, a grease, a paper, a cement, a thermal insulating material, a sound proofing material, a rubber, a silicone rubber, a plastic, an animal feed, an animal nutrient, an antibiotic, an antimicrobial agent, a fertilizer, a pesticide, a gel, an antacid, a food item, a fire retardant, a cosmetic, a cream, a lotion, a sealing agent, an adsorbent, a gas adsorbent, a carbon dioxide adsorbent or separator, a gas purifier, a deodorant, a detergent, a cat litter, a catalyst, an oxygen concentrator, an ion exchanger, a sulfur scavenger, an acid scavenger, a radionuclide sorbent, or a desiccant. In certain implementations of the fourth general aspect, the material is in the form of a liquid, a semi-liquid, a paste, a semi-solid, powder, granules, beads, pellets, film, coating, fibers, hollow fibers, wires, strings, tubing, foams, or monoliths.

Implementations of the fifth general aspect may include one or more of the following features.

In one implementation, the fifth general aspect includes heating the geopolymer resin at a temperature up to about 60° C. for a length of time up to about one week before heating the geopolymer resin at the temperature between about 70° C. and about 200° C. for the length of time up to about one week. The first material may be treated to yield a second material. In some cases, a solid product from the first or second material is collected. Collecting the solid product from the first or second material may include removing water partially or completely from the first or second material.

The details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing a process for forming geopolymeric aluminosilicate particles.

FIG. 2 shows the dynamic light scattering particle size distribution of the wet product in Example 1.

FIG. 3 shows a transmission electron micrograph of the dried product in Example 1.

FIG. 4 shows the powder X-ray diffraction pattern of the oven-dried sample in Example 1.

FIG. 5 shows N₂sorption isotherms of the oven-dried sample in Example 1.

FIG. 6 shows Barrett-Joyner-Halenda (BJH) pore size distributions of the oven-dried sample in Example 1.

FIG. 7 shows Barrett-Joyner-Halenda (BJH) cumulative pore volume as a function of the pore width of the oven-dried sample in Example 1.

FIG. 8 shows the dynamic light scattering particle size distribution of the wet product in Example 2.

FIG. 9 shows a transmission electron micrograph of the dried product in Example 2.

FIG. 10 shows the powder X-ray diffraction pattern of the oven-dried sample in Example 2.

FIG. 11 shows N₂sorption isotherms of the oven-dried sample in Example 2.

FIG. 12 shows Barrett-Joyner-Halenda (BJH) pore size distributions of the oven-dried sample in Example 2.

FIG. 13 shows Barrett-Joyner-Halenda (BJH) cumulative pore volume as a function of the pore width of the oven-dried sample in Example 2.

FIG. 14 shows the dynamic light scattering particle size distribution of the wet product in Example 3.

FIG. 15 shows a transmission electron micrograph of the dried product in Example 3.

FIG. 16 shows the powder X-ray diffraction pattern of the oven-dried sample in Example 3.

FIG. 17 shows N₂sorption isotherms of the oven-dried sample in Example 3.

FIG. 18 shows Barrett-Joyner-Halenda (BJH) pore size distributions of the oven-dried sample in Example 3.

FIG. 19 shows Barrett-Joyner-Halenda (BJH) cumulative pore volume as a function of the pore width of the oven-dried sample in Example 3.

FIG. 20 shows the dynamic light scattering particle size distribution of the wet product in Example 4.

FIG. 21 shows a transmission electron micrograph of the dried product in Example 4.

FIG. 22 shows the powder X-ray diffraction pattern of the oven-dried sample in Example 4.

FIG. 23 shows N₂sorption isotherms of the oven-dried sample in Example 4.

FIG. 24 shows Barrett-Joyner-Halenda (BJH) pore size distributions of the oven-dried sample in Example 4.

FIG. 25 shows Barrett-Joyner-Halenda (BJH) cumulative pore volume as a function of the pore width of the oven-dried sample in Example 4.

FIG. 26 shows the dynamic light scattering particle size distribution of the wet product in Example 5.

FIG. 27 shows a transmission electron micrograph of the dried product in Example 5.

FIG. 28 shows the powder X-ray diffraction pattern of the oven-dried sample in Example 5.

FIG. 29 shows N₂sorption isotherms of the oven-dried sample in Example 5.

FIG. 30 shows Barrett-Joyner-Halenda (BJH) pore size distributions of the oven-dried sample in Example 5.

FIG. 31 shows Barrett-Joyner-Halenda (BJH) cumulative pore volume as a function of the pore width of the oven-dried sample in Example 5.

FIG. 32 shows the dynamic light scattering particle size distribution of the wet product in Example 6.

FIG. 33 shows the powder X-ray diffraction pattern of the oven-dried sample in Example 6.

FIG. 34 shows N₂sorption isotherms of the oven-dried sample in Example 6.

FIG. 35 shows Barrett-Joyner-Halenda (BJH) pore size distributions of the oven-dried sample in Example 6.

FIG. 36 shows Barrett-Joyner-Halenda (BJH) cumulative pore volume as a function of the pore width of the oven-dried sample in Example 6.

FIG. 37 shows the powder X-ray diffraction pattern of the final product in Example 7.

FIG. 38 shows Fourier transform infrared spectrum of the final product in Example 7 (Top) together with those of the product in Example 6 (Middle) and stearic acid (Bottom) for comparison.

DETAILED DESCRIPTION

A process for synthesizing aluminosilicate nanorods from a geopolymer resin is described. As used herein, “aluminosilicate” generally refers to a composition of matter including aluminium, silicon, and oxygen, plus countercations. Typical counterions include sodium, potassium, cesium, barium, and calcium. As used herein, “nanorod” generally refers to a solid or porous nanostructure having a generally cylindrical shape, with its diameter (width) in a range between about 1 nm and about 100 nm. As used herein, a geopolymer resin typically includes water and dissolved, dispersed, or suspended inorganic species (e.g., selected metal precursors), and may appear to be homogeneous upon visual inspection. Geopolymer resins can be prepared in various ways. In one example, geopolymer resins are prepared by coupled alkali-mediated dissolution and precipitation reactions of silicate or aluminosilicate precursors in an aqueous media. Geopolymer resins can be formed by reacting a clay material with an alkaline or acidic solution. In some examples, metakaolin and metakaolinite are reacted with an alkaline solution to form a geopolymer resin. Geopolymer resins are described in U.S. Pat. No. 9,242,900 which is incorporated herein by reference in its entirety.

Synthesizing aluminosilicate nanorods from a geopolymer resin includes a geopolymerization process in which a geopolymer is formed from a geopolymer resin by curing the geopolymer resin. In some embodiments, synthesizing aluminosilicate nanorods from a geopolymer resin includes heating a geopolymer resin including water from about 70 mol % to about 90 mol % in a closed container at a temperature between about 70° C. and about 200° C. for a length of time from about 30 minutes up to about one week to yield a nanostructured aluminosilicate comprising aluminosilicate nanorods. The water mol % is estimated from the molar amounts (“mole#”) of the elements of alkali metals (“A”), alkaline earth metals (“AE”), aluminum and silicon in their corresponding anhydrous oxide forms (A₂O, AEO, Al₂O₃and SiO₂, respectively) and the mole# of water in the geopolymer resin, using the following formula:

water



mol



%

=

100
×
mole



#


(
water
)

2
×
mole



#


(

A
2

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O

)

+

mole
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
#


(
AEO
)

+

2
×
mole



#


(

Al
2



O
3

)

+

mole



#


(

SiO
2

)

+

mole



#


(
water
)

.

The closed container prevents any significant loss of water from the geopolymer resin during heating. An average width of the aluminosilicate nanorods formed via the described process is between about 5 nm and about 100 nm, between about 5 nm and about 60 nm, or between about 5 nm and about 30 nm. In some embodiments, a majority (e.g., over 50%, over 60%, over 70%, over 80%, over 90%, over 95%, or over 99%) of the nanorods have an aspect ratio in a range between about 2 and about 100. As used herein, an “aspect ratio” of a nanorod refers to a length of the nanorod divided by a width of the nanorod. In some embodiments, a majority of the aluminosilicate nanorods have an aspect ratio of at least 2, at least 3, at least 4, at least 5, or at least 10. In some embodiments, a majority of the aluminosilicate nanorods are unbound. As used herein, “unbound” aluminosilicate nanorods are not chemically or covalently bonded to one or more other aluminosilicate nanorods.

In some embodiments, a majority of aluminum and silicon atoms in the aluminosilicate nanorods are in a tetrahedral coordination environment. In some embodiments, the aluminosilicate nanorods are microporous. In certain embodiments, the specific micropore surface area of the nanostructured aluminosilicates, which is usually estimated from t-plot obtained from gas sorption analysis, is between about 1 m²/g and about 60 m²/g or between about 60 m²/g and about 700 m²/g. In some embodiments, the aluminosilicate nanorods comprise a zeolite. In some embodiments, the aluminosilicate nanorods comprise a zeolite having crystallinity with a cancrinite (CAN)-type framework structure. As used herein, “zeolite” generally refers to minerals including hydrated aluminosilicates of sodium, potassium, cesium, calcium, and barium. In certain embodiments, the zeolite contains an anion in the zeolite cage.

In some embodiments, the nanostructured aluminosilicate includes unbound aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes aggregates of aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes an agglomerate of aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes an aggregate and an agglomerate of aluminosilicate nanorods. In some embodiments, the specific external surface area of the nanostructured aluminosilicates is between about 50 m²/g and about 400 m²/g. As used herein, “specific external surface area” refers to the total specific surface area, or total surface area per unit of mass, minus the specific micropore surface area.

In some embodiments, the nanostructured aluminosilicates exhibit mesopores, with pore sizes in a range between about 2 nm and about 50 nm. In certain embodiments, a mesopore volume of the nanostructured aluminosilicates is at least about 0.05 cc/g, at least about 0.1 cc/g, at least about 0.2 cc/g, or at least about 0.3 cc/g on the Barrett-Joyner-Halenda (BJH) cumulative pore volume from the desorption branch of the N₂sorption isotherm, where the mesopore volume is the total pore volume of the pores having a pore diameter between about 2 nm and about 50 nm.

The absolute value of the zeta potential of the nanostructured aluminosilicates is at least about 30 mV, at least about 40 mV, at least about 50 mV, or at least about 60 mV in a pH range between about 3 and about 14, between about 3 and about 13, between about 3 and about 12, between about 4 and about 14, between about 4 and about 13, between about 4 and about 12, between about 5 and about 14, between about 5 and about 13, or between about 5 and about 12.

FIG. 1 depicts a flow chart of process 100 for synthesizing aluminosilicate nanorods from a geopolymer resin including water from about 70 mol % to about 90 mol % including optional operations 102, 106, and 108. In 102, a geopolymer resin is optionally heated at a temperature from about 25° C. to less than about 60° C. for a length of time from 30 minutes up to about one week. In 104, the geopolymer resin is heated in a closed container at a temperature between about 70° C. and about 200° C. for a length of time from about 30 minutes up to about one week to yield a first material. In some embodiments, the first material is a semisolid, a semiliquid, or a paste. The first material includes nanostructured aluminosilicate. In some embodiments, the nanostructured aluminosilicate includes unbound aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes an aggregate of aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes an agglomerate of aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes an aggregate and an agglomerate of aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate includes an agglomerate of aggregates of aluminosilicate nanorods.

In 106, the first material from 104 is optionally treated to yield a second material. In some embodiments, the second material is a semisolid, a semiliquid, a paste, or a dispersion. In some embodiments, the second material includes nanostructured aluminosilicates or modified nanostructured aluminosilicates. In some embodiments, the nanostructured aluminosilicates or modified nanostructured aluminosilicates include unbound aluminosilicate nanorods or unbound modified aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicates or modified nanostructured aluminosilicates include an aggregate of aluminosilicate nanorods or modified aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate or modified nanostructured aluminosilicates include an agglomerate of aluminosilicate nanorods or modified aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate or modified nanostructured aluminosilicates includes an aggregate and an agglomerate of aluminosilicate nanorods or modified aluminosilicate nanorods. In some embodiments, the nanostructured aluminosilicate or modified nanostructured aluminosilicate includes an agglomerate of aggregates of aluminosilicate nanorods or modified aluminosilicate nanorods. In some embodiments, modified nanostructured aluminosilicates or modified aluminosilicate nanorods are obtained when treating the first material. In some embodiments, treating the first material includes reducing the concentration of hydroxide of the first material to about 1 M. In some embodiments, treating the first material includes reducing the pH of the first material from about 14. In certain embodiments, treating the first material includes diluting the first material with water or combining the first material with an acidic solution comprising mineral acid, sulfuric acid, hydrochloric acid, nitric acid, organic acid or a combination thereof. In other embodiments, treating the first material includes combining the first material with a solution of a metal ion that forms an oxide, hydroxide, hydrous oxide, or combination thereof in contact with hydroxide ions. In some embodiments, the metal ion is a main group metal (e.g., antimony), a transition metal (e.g., silver, zinc, copper, iron, molybdenum), a lanthanide metal (e.g., cerium), or a combination thereof.

In 108, a solid product is optionally collected from the first material, the second material, or both. The solid products include the nanostructured aluminosilicates comprising aluminosilicate nanorods or modified aluminosilicate nanorods. In some embodiments, collecting the solid product includes removing water partially or completely from the first or second material to concentrate the solid product. In some embodiments, collecting the solid product is aided by addition of a flocculant or a surfactant.

In some embodiments, process 100 includes only operation 104. In other embodiments, process 100 includes one or more of optional operations 102, 106, and 108. In still other embodiments, process 100 includes one or more additional operations in addition to operation 104, together with or in the absence of one or more of optional operations 102, 106, and 108.

In some embodiments, process 100 yields modified aluminosilicate nanorods, in which a surface of the aluminosilicate nanorods is at least partially covered with one or more organic molecules such as organic dyes and urea, carboxylic acids such as stearic acid, surfactants such as quaternary ammonium and quaternary phosphonium, or polymers such as polyethylene glycol, elastic polymers and PVC or a combination thereof. In some embodiments, process 100 yields modified aluminosilicate nanorods in which a surface of the aluminosilicate nanorods is at least partially covered with inorganic molecules such as silanes and ferrocene or nanoparticles such as zinc oxide, copper oxide, titanium oxide, and cerium oxide. In certain embodiments, process 100 yields modified aluminosilicate nanorods in which a surface of the aluminosilicate nanorods is at least partially covered with molecules of a biological origin such as proteins, DNAs, RNAs, and biogenic polymers. In other embodiments, alkali ions in the aluminosilicate nanorods are at least partially exchanged with protons or other metal ions such as silver, zinc, copper, alkaline earth metals, transition metals, and lanthanide metals.

In some embodiments, the nanostructured aluminosilicate, the modified nanostructured aluminosilicate, the aluminosilicate nanorods or the modified aluminosilicate nanorods are combined with an aqueous medium, an organic medium, a colloidal medium, a latex colloidal medium, a dispersion medium, a suspension medium, a polymeric medium, or an elastomeric medium, and provides a thixotropic property to the selected medium.

Articles, such as tires, rubber belts, rubber seals, rubber tubes, footwear, polystyrene foams, polyurethane foams, plastics, fire extinguishers, tooth pastes, drug tablets, membranes, dehumidifiers, fertilizers, or heat exchangers may be fabricated to include the nanostructured aluminosilicate, the modified nanostructured aluminosilicate, the aluminosilicate nanorods or the modified aluminosilicate nanorods. In comparison to isotropic particles, nanorods can provide a lower viscosity mixture, easy mixing of the components and/or provide an anisotropic physical property to the composite in which the nanorods are incorporated. In some embodiments, the nanostructured aluminosilicate, the modified nanostructured aluminosilicate, the aluminosilicate nanorods or the modified aluminosilicate nanorods are included in materials such as adhesives, sealants, colorants, inks (including inks for ink-jet printers), toners, paints, coatings, defoamers, greases, papers, cements, thermal insulating materials, sound proofing materials, rubbers (such as silicone rubbers), plastics, animal feeds, animal nutrients, antibacterial agents, antimicrobial agents, fertilizers, pesticides, gels, antacids, food items, fire retardants, cosmetics, creams, lotions, sealing agents, adsorbents (such as gas adsorbents), carbon dioxide adsorbents or separators, gas purifiers, deodorants, detergents, cat litters, catalysts, oxygen concentrators, ion exchangers, sulfur scavengers, acid scavengers, radionuclide sorbents, or desiccants. These materials may be liquids, semiliquids, pastes, semisolids, powders, granules, beads, pellets, films, coatings, fibers, hollow fibers, wires, strings, tubing, foams, or monoliths.

EXAMPLES
Example 1

6.37 g of NaOH was dissolved in 6.28 g of deionized water in an ice bath. 11.01 g of sodium silicate (˜10.6% Na₂O, ˜26.5% SiO₂) was added subsequently into the NaOH solution and stirred in a water bath with a laboratory mixer at 800 rpm, until the solution became homogeneous by visual inspection. Into the solution, 5.50 g of metakaolin (MetaMax®) was added and stirring was continued at 800 rpm for about 40 min, which yielded a geopolymer resin having approximate nominal Na:Al:Si atomic ratios of 4:1:2. This geopolymer resin was poured into a polypropylene tube, sealed airtight, and heated at 120° C. for 24 hours in a lab oven to give a paste-like geopolymer resin material with a pH value of about 14. The paste was taken out of the container, mixed with a copious amount of deionized water, and subjected to centrifugation at 5000 rpm for 10 min. The resulting clear supernatant solution (pH about 14) was decanted to obtain a wet off-white paste. The mixing with deionized water, centrifugation and decanting steps were repeated until the supernatant liquid attained near neutral pH. The supernatant was decanted to give a wet off-white paste. The dynamic light scattering experiments indicated an average particle size of about 191 nm. FIG. 2 shows the particle size distribution from the dynamic light scattering experiment. It is noted that the paste was thixotropic. FIG. 3 shows a TEM image of the product. After drying at 90° C., the product showed a CAN structure from the powder X-ray diffraction studies (FIG. 4). FIG. 5 shows the N₂sorption isotherms of the oven-dried sample. FIG. 6 shows the corresponding the BJH pore distributions of the oven-dried sample. FIG. 7 shows the corresponding BJH cumulative pore volume as a function of the pore width of the oven-dried sample. The product showed a mesopore volume of 0.5 cm³/g and a surface area of 103 m²/g. The calculated micropore volume and surface area were 0.006 cm³/g and 15.6 m²/g, respectively.

Example 2

6.37 g of NaOH was dissolved in 6.28 g of deionized water in an ice bath. 11.01 g of sodium silicate (˜10.6% Na₂O, ˜26.5% SiO₂) was added subsequently into the NaOH solution and stirred in a water bath with a laboratory mixer at 800 rpm, until the solution became homogeneous by visual inspection. Into the solution, 5.50 g of metakaolin (MetaMax®) was added and stirring was continued at 800 rpm for about 40 min, which yielded a geopolymer resin having approximate nominal Na:Al:Si atomic ratios of 4:1:2. This geopolymer resin was poured into a polypropylene tube, sealed airtight, and heated at 120° C. for 6 hours in a lab oven to give a paste-like geopolymer resin material with a pH value of about 14. The paste was taken out of the container, mixed with a copious amount of deionized water, and subjected to centrifugation at 5000 rpm for 10 min. The resulting clear supernatant solution (pH about 14) was decanted to obtain a wet off-white paste. The mixing with deionized water, centrifugation and decanting steps were repeated until the supernatant liquid attained near neutral pH. The supernatant was decanted to give a wet off-white paste. The dynamic light scattering experiments indicated an average particle size of about 308 nm. FIG. 8 shows the particle size distribution from the dynamic light scattering experiment. It is noted that the paste was thixotropic. FIG. 9 shows a TEM image of the product. After drying at 90° C., the product showed a CAN structure from the powder X-ray diffraction studies (FIG. 10). FIG. 11 shows the N₂sorption isotherms of the oven-dried sample. FIG. 12 shows the corresponding the BJH pore distributions of the oven-dried sample. FIG. 13 shows the corresponding BJH cumulative pore volume as a function of the pore width of the oven-dried sample. The product showed a mesopore volume of 0.9 cm³/g and a surface area of 143 m²/g. The calculated micropore volume and surface area were 0.009 cm³/g and 22.8 m²/g, respectively.

Example 3

6.37 g of NaOH was dissolved in 6.28 g of deionized water in an ice bath. 11.01 g of sodium silicate (˜10.6% Na₂O, ˜26.5% SiO₂) was added subsequently into the NaOH solution and stirred in a water bath with a laboratory mixer at 800 rpm, until the solution became homogeneous by visual inspection. Into the solution, 5.50 g of metakaolin (MetaMax®) was added and stirring was continued at 800 rpm for about 40 min, which yielded a geopolymer resin having approximate nominal Na:Al:Si atomic ratios of 4:1:2. This geopolymer resin was poured into a polypropylene tube, sealed airtight, and heated at 90° C. for 24 hours in a lab oven to give a paste-like geopolymer resin material with a pH value of about 14. The paste was taken out of the container, mixed with a copious amount of deionized water, and subjected to centrifugation at 5000 rpm for 10 min. The resulting clear supernatant solution (pH about 14) was decanted to obtain a wet off-white paste. The mixing with deionized water, centrifugation and decanting steps were repeated until the supernatant liquid attained near neutral pH. The supernatant was decanted to give a wet off-white paste. The dynamic light scattering experiments indicated an average particle size of about 260 nm. FIG. 14 shows the particle size distribution from the dynamic light scattering experiment. It is noted that the paste was thixotropic. FIG. 15 shows a TEM image of the product. After drying at 90° C., the product showed a CAN structure from the powder X-ray diffraction studies (FIG. 16). FIG. 17 shows the N₂sorption isotherms of the oven-dried sample. FIG. 18 shows the corresponding the BJH pore distributions of the oven-dried sample. FIG. 19 shows the corresponding BJH cumulative pore volume as a function of the pore width of the oven-dried sample. The product showed a mesopore volume of 1.00 cm³/g and a surface area of 141 m²/g. The calculated micropore volume and surface area were 0.008 cm³/g and 19.9 m²/g, respectively.

Example 4

6.37 g of NaOH was dissolved in 6.28 g of deionized water in an ice bath. 11.01 g of sodium silicate (˜10.6% Na₂O, ˜26.5% SiO₂) was added subsequently into the NaOH solution and stirred in a water bath with a laboratory mixer at 800 rpm, until the solution became homogeneous by visual inspection. Into the solution, 5.50 g of metakaolin (MetaMax®) was added and stirring was continued at 800 rpm for about 40 min, which yielded a geopolymer resin having approximate nominal Na:Al:Si atomic ratios of 4:1:2. This geopolymer resin was poured into a polypropylene tube, sealed airtight, and heated at 90° C. for 6 hours in a lab oven to give a paste-like geopolymer resin material with a pH value of about 14. The paste was taken out of the container, mixed with a copious amount of deionized water, and subjected to centrifugation at 5000 rpm for 10 min. The resulting clear supernatant solution (pH about 14) was decanted to obtain a wet off-white paste. The mixing with deionized water, centrifugation and decanting steps were repeated until the supernatant liquid attained near neutral pH. The supernatant was decanted to give a wet off-white paste. The dynamic light scattering experiments indicated an average particle size of about 188 nm. FIG. 20 shows the particle size distribution from the dynamic light scattering experiment. It is noted that the paste was thixotropic. FIG. 21 shows a TEM image of the product. After drying at 90° C., the product showed a CAN structure from the powder X-ray diffraction studies (FIG. 22). FIG. 23 shows the N₂sorption isotherms of the oven-dried sample. FIG. 24 shows the corresponding the BJH pore distributions of the oven-dried sample. FIG. 25 shows the corresponding BJH cumulative pore volume as a function of the pore width of the oven-dried sample. The product showed a mesopore volume of 0.85 cm³/g and a surface area of 168 m²/g. The calculated micropore volume and surface area were 0.008 cm³/g and 21.2 m²/g, respectively.

Example 5

12.74 g of NaOH was dissolved in 12.56 g of deionized water in an ice bath. 22.02 g of sodium silicate (˜10.6% Na₂O, ˜26.5% SiO₂) was added subsequently into the NaOH solution and stirred in a water bath with a laboratory mixer at 800 rpm, until the solution became homogeneous by visual inspection. Into the solution, 11.0 g of metakaolin (MetaMax®) was added and stirring was continued at 800 rpm for about 40 min, which yielded a geopolymer resin having approximate nominal Na:Al:Si atomic ratios of 4:1:2. This geopolymer resin was poured into a polypropylene tube, sealed airtight, and heated at 120° C. for 144 hours in a lab oven to give a paste-like geopolymer resin material with a pH value of about 14. The paste was taken out of the container, mixed with a copious amount of deionized water, and subjected to centrifugation at 6000 rpm for 10 min. The resulting clear supernatant solution (pH about 14) was decanted to obtain a wet off-white paste. The mixing with deionized water, centrifugation and decanting steps were repeated until the supernatant liquid attained near neutral pH. The supernatant was decanted to give a wet off-white paste. The dynamic light scattering experiments indicated an average particle size of about 254 nm. FIG. 26 shows the particle size distribution from the dynamic light scattering experiment. It is noted that the paste was thixotropic. FIG. 27 shows a TEM image of the product. After drying at 90° C., the product showed a CAN structure from the powder X-ray diffraction studies (FIG. 28). FIG. 29 shows the N₂sorption isotherms of the oven-dried sample. FIG. 30 shows the corresponding the BJH pore distributions of the oven-dried sample. FIG. 31 shows the corresponding BJH cumulative pore volume as a function of the pore width of the oven-dried sample. The product showed a mesopore volume of 0.27 cm³/g and a surface area of 54.9 m²/g. The calculated micropore volume and surface area were 0.003 cm³/g and 7.1 m²/g, respectively.

Example 6

12.74 g of NaOH was dissolved in 12.56 g of deionized water in an ice bath. 22.02 g of sodium silicate (˜10.6% Na₂O, ˜26.5% SiO₂) was added subsequently into the NaOH solution and stirred in a water bath with a laboratory mixer at 800 rpm, until the solution became homogeneous by visual inspection. Into the solution, 11.0 g of metakaolin (MetaMax®) was added and stirring was continued at 800 rpm for about 40 min, which yielded a geopolymer resin having approximate nominal Na:Al:Si atomic ratios of 4:1:2. This geopolymer resin was poured into a polypropylene tube, sealed airtight, and heated at 120° C. for 48 hours in a lab oven to give a paste-like geopolymer resin material with a pH value of about 14. The paste was taken out of the container, mixed with a copious amount of deionized water, and subjected to centrifugation at 6000 rpm for 10 min. The resulting clear supernatant solution (pH about 14) was decanted to obtain a wet off-white paste. The mixing with deionized water, centrifugation and decanting steps were repeated until the supernatant liquid attained near neutral pH. The supernatant was decanted to give a wet off-white paste. The dynamic light scattering experiments indicated an average particle size of about 217 nm. FIG. 32 shows the particle size distribution from the dynamic light scattering experiment. It is noted that the paste was thixotropic. After drying at 90° C., the product showed a CAN structure from the powder X-ray diffraction studies (FIG. 33). FIG. 34 shows the N₂sorption isotherms of the oven-dried sample. FIG. 35 shows the corresponding the BJH pore distributions of the oven-dried sample. FIG. 36 shows the corresponding BJH cumulative pore volume as a function of the pore width of the oven-dried sample. The product showed a mesopore volume of 0.59 cm³/g and a surface area of 90.1 m²/g. The calculated micropore volume and surface area were 0.006 cm³/g and 14.5 m²/g, respectively.

Example 7

Surface functionalization of the product particles in Example 6 was carried out with stearic acid by following the process disclosed by Sakthivel et al. (“Hydrophobic High Surface Area Zeolites Derived from Fly Ash for Oil Spill Remediation” Environmental Science & Technology 2013, 47, 5843-5850), which is incorporated herein by reference. 0.16 g of stearic acid was dissolved in 25.0 ml of sodium hydroxide solution (˜0.60 M) in 100° C. water bath and an opaque solution was obtained after magnetically stirred for 20 minutes. 1.0 g of the product in Example 6 was subsequently added to the solution. After stirring for another 10 minutes, then the mixture was stirred while slowly cooling to room temperature, which caused precipitation of stearic acid mixed with the product of Example 6. The precipitate was filtered and washed several times with water to remove residual sodium hydroxide. The powder was then dried and placed in a lab oven at 160° C. for 4 h to induce chemical bonding of the stearic acid to the surfaces of the particles. Then the particles were washed several times with hot toluene and room-temperature water to remove excess stearic acid and dried in a lab oven at 90° C. The final product showed a CAN structure from the powder X-ray diffraction studies (FIG. 37). FIG. 38 shows Fourier transform infrared spectrum of the final product (Top) together with those of the product in Example 6 (Middle) and stearic acid (Bottom) for comparison. The presence of absorption peaks in 2800-3000 cm⁻¹in the spectrum of the final product indicates the presence of stearic acid in the final product. The CHN analysis on the final product with triplicates indicated a carbon content of 1.78±0.07 wt %, while the carbon content in the product in Example 6 (before the surface functionalization) was 0.48±0.02 wt %.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of disclosure. Accordingly, other embodiments are within the scope of the following claims.