Method for making silica aerogel powder from recycled glass

Abstract

The present invention relates to a method of forming silica aerogel from waste glass, comprising the steps of: providing waste glass; crushing and / or grinding the waste glass to form a glass powder; extracting silica from the glass powder in the presence of a base to form a water glass; adding an acid to the water glass to form a sol-gel; solvent exchange and surface modification of sol-gel; and drying the sol-gel to form the silica aerogel, wherein the waste glass or glass powder is not chemically pre-treated before the extracting step. The present invention also relates to a system of forming silica aerogel from waste glass.

Description

[0001] METHOD FOR MAKING SILICA AEROGEL POWDER FROM RECYCLED GLASS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to the field of materials. Tn particular, the present invention relates to a method of forming a silica acrogel from waste glass, a system of forming silica acrogel from waste glass, the use of waste glass to form a silica acrogel and a silica acrogel obtained by such method.

[0004] BACKGROUND OF THE INVENTION

[0005] Aerogels, in general, may be classified into four subtypes: carbon and carbide, organic, hybrid and inorganic subtypes. Inorganic acrogels mainly consist of metal oxides, which include silica, titania, alumina, zirconia, niobates and metals. Silica acrogel is one of the most common types of acrogels, being studied and widely used worldwide. Silica acrogels are widely established as the world's lightest solid materials and is composed of up to 95 % of air by its volume, with the remnant 5 % consisting of silica nanoparticles which form an amorphous, cross-linked three-dimensional silica network.

[0006] Due to such a high porosity value, silica acrogels are highly unique materials with a spectrum of properties: high specific surface area; low refractive index; low density; ultra-low dielectric constant and low thermal conductivity. Such properties make silica acrogels the optimal material for a multitude of applications and industries. For example, silica acrogels are being applied as thermal insulating materials for refrigeration and construction use, acoustic bamers, absorbents, catalytic supports, or super capacitators. Silica acrogels have also been known to be widely used by the National Aeronautics and Space Administration (NASA) for a variety of applications such as insulating the Mars Rover, use in space suits and cryogenics.

[0007] Current acrogel production methods face significant limitations in terms of cost, efficiency, and sustainability. Conventional processes rely on expensive silica precursors, multiple solvent exchanges, and supercritical drying, making production both time-consuming and costly. In addition, large quantities of solvents are consumed and discarded, resulting in high waste generation and environmental impact. These drawbacks restrict acrogel’s widespread adoption despite its excellent performance as an insulating material.

[0008] The prices of acrogel powder vary’ from supplier to supplier of the product. Moreover, depending on the particle size, or the quality’ of the product, the price may differ as well. As there are rising demands for silica acrogel, and the current methods of fabrication are expensive, in view of the limitations of current methods for preparing silica acrogel, there is a need for development of a method that overcomes or at least ameliorates, one or more of the disadvantages described above.

[0009] SUMMARY

[0010] Tn an aspect, there is provided a method of forming a silica acrogel from waste glass, comprising the steps of:

[0011] (i) providing waste glass;

[0012] (ii) crushing and / or grinding the waste glass to form a glass powder:

[0013] (iii) extracting silica from the glass powder in the presence of a base to form a water glass;

[0014] (iv) adding an acid to the water glass to form a sol-gel;

[0015] (v) solvent exchange and surface modification of sol-gel; and

[0016] (vi) drying the sol-gel to form the silica acrogel, wherein the waste glass or glass powder is not chemically pre-treated before the extracting step.

[0017] Advantageously, the method as defined above utilises waste glass as the raw material for the fabrication of silica acrogel. Further advantageously, waste glass has considerable silica content, and is also a cheap source of raw material. Thus, creating silica acrogel from waste glass would result in a high-value and high- quality product, by recycling waste glass and thus reducing the amount of waste glass disposed of.

[0018] Further advantageously, given that silica acrogel is made from waste glass which is a more cost-effective starting material, there are significant cost-savings, making it more affordable for end-users. By employing the method as defined above, silica acrogel may be advantageously fabricated in a more efficient and cost- effective manner, and this may in turn result in increased applications of silica acrogel in built environment, water treatment, construction, automotive, cryogenic, aeronautic and astronautic applications, which may have previously been not possible due to high costs.

[0019] Advantageously, the silica acrogel fabricated by the method as defined above offers the same physiochemical properties and performance as conventionally available silica acrogel.

[0020] Tn another aspect, there is provided a system of forming silica acrogel from waste glass, comprising the components of:

[0021] (i) a crusher to crush and / or grind waste glass to a glass powder;

[0022] (ii) a silica extractor to extract silica from the glass powder to form a water glass;

[0023] (iii) a reactor to add an acid to the water glass to form a sol-gel, and to perform solvent exchange and surface modification of a sol -gel; and (iv) a dryer to dry the sol -gel to form the silica acrogel, wherein the system does not comprise a component for chemically pre-treating the waste glass or glass powder before extracting the silica.

[0024] Advantageously, the system as defined above may eliminate the need for chemical pre-treatment of waste glass or glass powder before silica extraction, simplifying the process and reducing both time and operational steps. This may result in lower costs by avoiding the use of additional reagents and utilities, while also improving sustainability through reduced solvent use, waste generation, and safety risks. Further advantageously, the system as defined above may be used to directly process waste glass from common waste glass streams such as container and flat glass, enhancing feedstock flexibility and scalability. Further advantageously, by streamlining the workflow and maximizing silica recovery, the method may provide a more cost-effective, scalable, and environmentally sustainable route for producing silica acrogels from waste glass compared to conventional methods.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:

[0027] [Figure 1] refers to a flowchart of a typical process for fabricating silica acrogel from waste glass according to an embodiment of the present disclosure.

[0028] [Figure 2] refers to a schematic diagram showing the components in a pilot scale process for making silica acrogel from waste glass, comprising the components of 1) crusher, wherein waste glass is crushed with a smooth roller crasher (202); 2) siever, wherein an automatic vibrating sieving machine (206) is employed to separate raw glass particles with sizes below 150 to 200 pm, and smaller particles proceed to the next treatment step, while larger particles are returned via a recycling loop (204) to the smooth roller crasher (202) for further size reduction; 3) reactor, wherein silica extraction is conducted in a pressurized reactor (208); 4) filtration press systems, wherein glass powder is dried after treatment using filtration press systems (210); 5) reactor, wherein the sol-gel and surface treatment process can be readily upscaled by employing a large-volume reactor (212); 6) rotary evaporator, wherein solvents arc recycled and the silica acrogel is dried using a rotary evaporator (214); and 7) oven, wherein silica acrogel is obtained through oven drying (216). DEFINITIONS

[0029] The following words and terms used herein shall have the meaning indicated:

[0030] As used herein, the term “waste glass” may refer to any glass article intended to be discarded or recycled, and may include glass bottles, glass jars, glass cups, glass containers, glass vases, glass pots, glass wool, glass window panes, glass panels, glass shields, glass eyewear, glass tiles, glass ceilings, glass doors, glass casings, glass films, glass ampoules, glass tank, glass kitchenware, glass cookware, glass walls, glass boxes, glass frames, glass tanks, glass spheres, glass marbles, glass prisms, glass handle, glass partitions, glass terraria, glass fibers, glass railings, glass dials, glass screens, stained glass, frosted glass, shatterproof glass, tinted glass, mirrored glass, sandblasted glass, ceramic glass, bulletproof glass, wired glass, thermal glass, tempered glass, laminated glass, float glass, double glazed glass or patterned glass.

[0031] “Aging” for the purposes of this disclosure refers to a phenomenon observed in solid solutions or liquid sols that describes the change of an inhomogeneous structure over time, i.c. small crystals or sol particles dissolve, and redeposit onto larger crystals or sol particles by formation of new and longer crosslinks. This includes a process of continued gelling of a sol-gel involving further condensation and polymerization of water glass which may strengthen the gel network, and / or alter pore structure and may lead to shrinkage due to solvent loss. The term “age” and “aged” should be construed accordingly.

[0032] "Alkyl" as a group or part of a group refers to a straight or branched aliphatic hydrocarbon group, preferably a C1-C12alkyl unless otherwise noted. Examples of suitable straight and branched C1-C6alkyl substituents include methyl, ethyl, n-propyl, 2-propyl, n-butyl, sec-butyl, t-butyl, hexyl, heptyl, octyl and the like. The group may be a terminal group or a bndging group.

[0033] The invention illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms "comprising", "including", "containing", etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such tenns and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the inventions embodied therein herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention. The word “substantially’' does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the invention.

[0034] As used in this application, the singular form “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a genetic marker” includes a plurality of genetic markers, including mixtures and combinations thereof.

[0035] As used herein, the term “about”, in the context of concentrations of components of the formulations, typically means + / - 5% of the stated value, more ty pical 1 x + / - 4% of the stated value, more typically + / - 3% of the stated value, more typically, + / - 2% of the stated value, even more typically + / - 1% of the stated value, and even more typically + / - 0.5% of the stated value.

[0036] Throughout this disclosure, certain embodiments may be disclosed in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the disclosed ranges. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub-ranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0037] Certain embodiments may also be described broadly and generically herein. Each of the narrower species and sub-generic groupings falling within the generic disclosure also form part of the disclosure. This includes the generic description of the embodiments with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

[0038] The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

[0039] DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE

[0040] The requirements for improving the thermal insulation of residential and non -residential buildings have led to several developments in the field of building materials for massive outer walls. To improve the energy efficiency of buildings, silica acrogel powder has been used in high strength cement matrix, to develop a high performance acrogel concrete which combines the benefits of conventional concrete such as compressive strength and unlimited moldability, with the properties of a heat insulating material.

[0041] Concrete comprising silica acrogel was conceived as a response to the demand of cooler homes which are green and sustainable. Being that concrete makes up majority of buildings, by applying the thermal - insulating properties of acrogel into the concrete, the coverage of its effects would be larger. With acrogel incorporated into concrete, the thermal-insulating properties of the concrete could be increased drastically while posing minimal effects on the mechanical properties of the existing concrete. This allowed for greater applications in the construction i ndu stry as an enhanced green building material . Being an excellent thermal insulator, silica acrogel may reduce the temperature within homes and buildings, thus lessening the energyconsumption due to air-conditioning. It could also reduce carbon emissions and display multiple advantages while posing minimal effects on the structural integrity of the building.

[0042] Silica acrogel is also effective in acoustic insulation as it exhibits a lower density- than conventional concrete, thus imposing a lower load on the structural load-taking elements in a building. It may save cost in transportation and handling of precast units and cause a reduction in formwork and propping. Using silica acrogel may reduce the amount of sand required to produce concrete and silica acrogel has also been found to be sustainable and eco-friendly, making it an invaluable product.

[0043] Silica acrogel incorporation into paint may also be carried out by adding silica acrogel powders to the paint and mixing till homogenous, giving the paint thermal insulating properties, while not affecting the mechanical properties of the paint. This may result in a product that could insulate heat in any scenario, given that paint could be applied on most surfaces and is even able to be applied on structures with irregular shapes. This makes silica acrogcl-infuscd paint a versatile and useful product, which could be applied to most industries, not only the built environment.

[0044] Silica acrogel is also multifunctional as an absorbent. Due to its three-dimensional netw orks and nanoscale mesoporous structure, it allows for the absorption of inorganic and organic contaminants and is shown to be useful in the absorption of oil. In tests, experiments w ere conducted with methylene blue as an organic contaminant, copper as an inorganic contaminant, and its effectiveness in the removal of oil was also tested. In this regard, silica acrogel has proved to be an effective absorbent and in comparison to activated carbon, which is the most common ty pe of absorbent used in the industry, silica acrogel has proven to be more effective and efficient in the removal of the contaminants. Furthermore, silica acrogel has also proved to be a reusable absorbent, where it could be washed with solvents to remove the contaminants it has absorbed, and subsequently reused for the absorption process again. In general, silica acrogels are materials with a wide spectrum of properties such as high specific surface area (500-1200 m2 / g); low refractive index (1 to 1.08); low density (3 to 100 kg / m3, depending on porosity of the acrogel); ultra-low dielectric constant (k = 1.0 to 2.0) and low thermal conductivity (0.003 to 0.02 W / mK), which enables silica acrogel to be used in a variety of applications.

[0045] In view of the above, as there are rising demands for silica acrogels, there are also corresponding increases in demand for improved methods of producing silica acrogel, which are further described in the disclosure herein.

[0046] There is provided a method of forming a silica acrogel from waste glass, comprising the steps of:

[0047] (i) providing waste glass;

[0048] (ii) crushing and / or grinding the waste glass to form a glass powder;

[0049] (iii) extracting silica from the glass powder in the presence of a base to form a water glass;

[0050] (iv) adding an acid to the water glass to form a sol-gel;

[0051] (v) solvent exchange and surface modification of sol-gel; and

[0052] (vi) drying the sol-gel to form the silica acrogel, wherein the waste glass or glass powder is not chemically pre-treated before the extracting step.

[0053] As part of the step of providing the waste glass, the method may further comprise a step of drying the waste glass before step (ii) at a temperature range of about 50 °C to about 150 °C, about 50 °C to about 70 °C, about 50 °C to about 90 °C, about 50 °C to about 110 °C, about 50 °C to about 130 °C, about 70 °C to about 90 °C, about 70 °C to about 110 °C, about 70 °C to about 130 °C, about 70 °C to about 150 °C, about 90 °C to about 1 10 °C, about 90 °C to about 130 °C, about 90 °C to about 150 °C, about 110 °C to about 130 °C, about 110 °C to about 150 °C, or about 130 °C to about 150 °C.

[0054] The method may comprise the step of crushing and / or grinding the waste glass after step (i) but before step (iii) to form a glass powder of particle size of less than 300 pm, less than 200 pm, less than 150 pm, less than 100 pm or less than 50 pm. The method may comprise the step of crushing and / or grinding the waste glass to form a glass powder of particle size of about 1 pm to about 300 pm, about 1 pm to about 250 pm, about 1 pm to about 200 pm, about 1 pm to about 150 pm, about 1 pm to about 100 pm, about 1 to about 50 pm, about 50 pm to about 100 pm, about 50 pm to about 150 pm, about 50 pm to about 200 pm, about 50 pm to about 250 pm, about 50 pm to about 300 pm, about 100 pm to about 1 0 pm, about 100 pm to about 200 pm, about 100 pm to about 250 pm, about 100 pm to about 300 pm, about 150 pm to about 200 pm, about 150 pm to about 250 pm, about 150 pm to about 300 pm, about 200 pm to about 250 pm, about 200 pm to about 300 pm or about 250 pm to about 300 pm. The crashing step may be performed using a crasher. The crasher may be a mortar and pestle, a mallet, a hammer, a rod, j aw crusher, roller crasher, g ratory crusher, cone crusher, compound crusher, shaft crusher, mineral sizer, hammer crasher, roller crasher, hydraulic press, hydraulic crasher, mechanical press, mechanical crusher, stoner crusher or impact crusher.

[0055] The crashing step may be performed before or after the step of dry ing the waste glass.

[0056] The grinding step may be performed before or after the step of drying the waste glass.

[0057] The grinding step may be performed using a grinder. The grinder may be a ball mill, ring mill, roller mill, bowl mill, attrition mill, hammer mill, roller mill, burr mill or pulverizer. The grinding may be performed in a ball mill containing 7 to 500, 7 to 20, 7 to 50, 7 to 100, 7 to 250, 20 to 50, 20 to 100, 20 to 250, 20 to 500, 50 to 100, 50 to 250, 50 to 500, 100 to 250, 100 to 500, 200 to 500, 7 to 13, 7 to 10, 10 to 13 or 8 to 12 balls. Tire number of balls may depend on the size of the ball mill. Tire balls may have a diameter in the range of about 5 mm to about 10 cm, about 5 mm to about 1cm, about 5 mm to about 2 cm, about 5 mm to about 5 cm, about 1 cm to about 2 cm, about 1 cm to about 5 cm, about 1 cm to about 10 cm, about 2 cm to about 5 cm, about 2 cm to about 10 cm or about 5 cm to about 10 cm. The balls may compnse a metal, zirconia, tungsten carbide, alumina, agate. Teflon or any mixture thereof, or may be an iron-core coated with polyurethane. The ball mill may be operated a rotational speed in the range of about 200 rpm to about 400 rpm, about 200 rpm to about 300 rpm, about 300 rpm to about 400 rpm, or at about 300 rpm. The ball mill may be operated for a duration in the range of about 10 minutes to about 20 minutes, about 10 minutes to about 15 minutes, about 15 minutes to about 20 minutes, or for about 15 minutes.

[0058] As part of the step of crashing and / or grinding the waste glass, the method may further comprise a step of sieving the glass powder through a sieve after step (ii) but before step (iii) . The sieve may have a mesh size of less than 300 pm, less than 250 pm, less than 200 pm, less than 150 pm, less than 100 pm or less than 50 pm. The mesh size may be about 1 pm to about 300 pm, about 1 pm to about 250 pm, about 1 pm to about 200 pm, about 1 pm to about 150 pm, about 1 pm to about 100 pm, about 1 to about 50 pm, about 50 pm to about 100 pm, about 50 pm to about 150 pm, about 50 pm to about 200 pm, about 50 pm to about 250 pm, about 50 pm to about 300 pm, about 100 pm to about 150 pm, about 100 pm to about 200 pm, about 100 pm to about 250 pm, about 100 pm to about 300 pm, about 150 pm to about 200 pm, about 150 pm to about 250 pm, about 150 pm to about 300 pm, about 200 pm to about 250 pm, about 200 pm to about 300 pm, or about 250 pm to about 300 pm.

[0059] The sieving step may be performed using a sieve. The sieve may be an auto-sieve, centrifugal sieve, jet sieve, vibratory' sieve, sonic sieve, sieve shaker, mesh sieve, wire sieve, orbital sieve, sieve, wet washing sieve or microplate sieve. The method may comprise the step of extracting silica from the glass powder in the presence of a base to form water glass.

[0060] The extraction step may comprise the step of reacting glass powder with a base at a temperature in tire range of about 160 °C to about 200 °C, about 160 °C to about 180 °C or about 180 °C to about 200 °C, or at about 180 °C, for a duration in the range of about 30 minutes to about 6 hours, about 30 minutes to about 1 hour, about 30 minutes to 2 hours, about 30 minutes to about 3 hours, about 30 minutes to 4 hours, about 30 minutes to about 5 hours, about 30 minutes to about 6 hours, about 1 hour to about 4 hours, about 1 hour to about 2 hours, about 1 hour to about 3 hours, about 1 hour to about 4 hours, about 1 hour to about 5 hours, about 2 hours to about 6 hours, about 2 hours to about 3 hours, about 2 hours to about 4 hours, about 2 hours to about 5 hours, about 3 hours to about 6 hours, or about 3 hours to about 4 hours, about 3 hours to about 5 hours, about 4 hours to about 6 hours, about 4 hours to about 5 hours, or about 5 hours to about 6 hours.

[0061] The base in the extraction step may be a strong base. The strong base maybe be sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide or any mixture thereof.

[0062] The base may be dissolved in a solvent. The solvent may comprise water, an alcohol, an alkyl having 6 or more carbon atoms, acetone, xylene, toluene, 1,4-dioxane, diethyl ether, tetrahydrofuran, ethyl acetate, chloroform, di chloromethane, acetonitrile, dimethylformamide, dimethyl sulfoxide, nitromethane, or any mixture thereof. The water may be deionised water, distilled water, or any mixture thereof, the alcohol may be methanol, ethanol, isopropyl alcohol, t-butanol, or any mixture thereof and the alkyl having 6 or more carbon atoms may be n-hcxanc, n-hcptanc, n-octanc or any mixture thereof.

[0063] The base may be aqueous.

[0064] The extraction step may be described by the following formula (I): 2M(OH)a+aSiO2= M2(SiO3)a+aH2O (I), where M may be a metal and a may be the ionic charge of the metal . M may be sodium, potassium, barium, calcium or any mixture thereof.

[0065] To perform the extraction step, Y g of waste glass powder having X percentage by weight of silica (0<X< 1) may be provided

[0066] The mass of the base (mi,a,e) to be used in the extraction step may be described by the following equation (la): wherein MWbasemay be the molecular weight of the base and a is the ionic charge of the metal cation of the base.

[0067] The volume of the base dissolved in deionised water to form a solution (Vbase), to be used in the extraction step may be described by the following equation (lb): wherein Mbasemay be the molar concentration of the base, typically about 1 M to about 3 M, and a is the ionic charge of the metal cation of the base .

[0068] The strong base may be contacted with Y g of waste glass powder in a range of Y mL to 10Y mL of the strong base, wherein the concentration of the strong base is in the range of about 1 M to about 3 M, where Y is the mass in grams of the waste glass powder. The base may be sodium hydroxide, and to extract the silica, the sodium hydroxide may be contacted with X g of glass powder in a solution of about of sodium hydroxide in about of deionized water. The concentration of sodium hydroxide may be about

[0069] 1.2 M.

[0070] The extraction step may comprise a step of preventing solvent loss. The extraction step may be conducted by evaporating the solvent and reintroducing it into the water glass simultaneously.

[0071] Prevention of solvent loss may be performed using a liquid condenser, an air condenser, a chiller, a cold plate, a coil condenser, an evaporative condenser or a cold finger.

[0072] The extraction step may be conducted using an autoclave reactor.

[0073] To prevent any reaction between the base and a glass container, the extraction step may be conducted in a Teflon, plastic or stainless-steel container instead of a glass container.

[0074] As part of the extraction step, the method may comprise a step of cooling the water glass after step (iii) but before step (iv) to a temperature of less than 60 °C, less than 55 °C, less than 50°C, less than 45 °C or less than 40 °C. The temperature may be in the range of about 40 °C to about 60 °C, about 40 °C to about 45 °C , about 40 °C to about 50 °C, about 40 °C to about 55 °C, about 45 °C to about 60 °C, about 45 °C to about 50 °C, about 45 °C to about 55 °C, about 50 °C to about 60 °C, about 50 °C to about 55 °C or about 55 °C to about 60 °C.

[0075] Water glass may be a solution of sodium silicate ( Na2SiO3) in water. The method may further comprise a step of filtering the water glass after step (iii).

[0076] The filtration step may be performed after the step of cooling the water glass.

[0077] The filtration may be performed using an about 0.1 pm to about 12 pm, about 0.1 pm to about 0.1 pm to about 0.2 pm , about 0.1 pm to about 0.45 pm, about 0.1 pm to about 1 pm, about 0.1 pm to about 1 1 pm, about 0.2 pm to about 0.45 pm, about 0.2 pm to about 1 pm, about 0.2 pm to about 2 pm, about 0.2 pm to about 11 pm, about 0.2 pm to about 12 pm , about 0.45 pm to about 1 pm, about 0.45 pm to about 2 pm, about 0.45 pm to about 11 pm, about 0.45 pm to about 12 pm, about 1 pm to about 2 pm, about 1 pm to about 11 pm, about 1 pm to about 12 pm, about 2 pm to about 11 pm, about 2 pm to about 12 pm, or about 11 pm to about 12 pm, or a 0.2 pm , 2 pm, 0.45 pm, 1 pm or 11 pm filter membrane.

[0078] The method may further comprise the step of diluting the water glass in deionized water at a ratio in the range of about 1:2 to about 3:4 by volume, preferably at a ratio of about 2:3 by volume.

[0079] The method may comprise a step of adding a first acid to the water glass to form a sol-gel after step (iii) but before step (v).

[0080] The acid may be a strong acid, a weak acid or a mixture thereof. The strong acid maybe be hydrochloric acid, nitric acid, sulfuric acid or any mixture thereof. Tire weak acid may be selected from the group consisting of phosphoric acid, acetic acid, tartaric acid, oxalic acid and any mixture thereof.

[0081] The acid may be of concentration in the range of about 1 M to about 3 M, about 1 M to about 2.5 M, about 1 M to about 2 M, about 1 M to about 1.5 M, about 1.5 M to about 3 M, about 1.5 M to about 2.5 M, about 1.5 M to about 2 M, about 2 M to about 3 M, about 2 M to about 2.5 M or about 2.5 M to about 3 M.

[0082] The method may further comprise a step of stirring after adding the acid to the water glass, at room temperature at a stirring speed in the range of about 200 rpm to about 400 rpm, about 200 rpm to about 300 rpm or about 300 rpm to about 400 rpm, or at about 300 rpm, for a duration in the range of 1 minute to about 30 minutes, about 1 minute to about 10 minutes, about 1 minute to about 20 minutes, about 1 minute to about 30 minutes, about 10 minutes to about 20 minutes, about 10 minutes to about 30 minutes, or about 20 minutes to 30 minutes.

[0083] The method may further comprise a step of adding an additional second acid while stirring, after the addition of the first acid. The second acid may be the same or different to the first acid. The acid may be added to the water glass in one or more portions. When one portion of the acid is used, the one portion may be added before the step of stirring. When more than one portions of the acid are used, the more than one portions may be added before or during the step of stirring.

[0084] The second acid may be a strong acid, a weak acid or a mixture thereof. The strong acid maybe be hydrochloric acid, nitric acid, sulfuric acid or any mixture thereof. The weak acid may be selected from the group consisting of phosphoric acid, acetic acid, tartaric acid, oxalic acid and any mixture thereof

[0085] The concentration of the second acid may be in the range of about 0.5 M to about 5 M, about 0.5 M to about 1 M, about 0.5 M to about 2.5 M, about 0.5 M to about 4 M, about 1 M to about 2.5 M, about 1 M to about

[0086] 4 M, about 1 M to about 5 M, about 2.5 M to about 4 M, about 2.5 M to about 5 M or about 4 M to about

[0087] 5 M.

[0088] The acid may be hydrochloric acid. The method may comprise a step of adding an additional 15 mL of 2 M hydrochloric acid while stirring.

[0089] The method may further comprise the step of purify ing the water glass on a strongly acidic ion exchange resin to collect silicic acid. The strongly acidic ion exchange resin may facilitate removal of contaminant anions such as Na+, Ca2+, Ba2+and Al3+. The strongly acidic cation exchange resin may be Amberlite™ IR-120H, Purolite® C100, Indion 730 or a resin in the Diaion™ series. The method may further comprise the step of adding a pH -adj listing base to the silicic acid until the pH is in the range of about 3 to about 6, about 3 to about 4, about 3 to about 5, about 4 to about 5, about 4 to about 6 or about 5 to about 6, to fonn a sol-gel.

[0090] The strongly acidic cation exchange resin Amberlite ™ 1R-120H may have the structure of:

[0091] The strongly acidic cation exchange resin Purolite® CT 00 may be a gel polystyrene crosslinked with divinylbenzene, with sulfonic acid functional groups.

[0092] The strongly acidic cation exchange resin Indion 730 may have the structure of:

[0093] The strongly acidic cation exchange resin in the Diaion™ series may have the structure of:

[0094] The water glass may begin to form a gel as soon as the pH of the silicic acid is adjusted to be in the range of about 3 to about 6. The sol-gel may refer to the water glass as soon as it begins to form the gel.

[0095] The pH-adjusting base may be a weak base The weak base may be ammonia, ammonium hydroxide, triethylamine, trimethylamine or any mixture thereof The base may have a concentration in the range of about 0.3 M to about 0.7 M, about 0.3 M to about 0.5 M or about 0.5 M to about 0.7 M, or at about 0.5 M.

[0096] The pH adjusting base may be ammonia.

[0097] The method may further comprise a step of aging the sol -gel after step (iv) but before step (v).

[0098] The aging process may increase modulus and viscosity of the sol-gel, but may reduce subsequent shrinkage of the sol-gel during the drying process.

[0099] The step of aging the sol-gel may be for a duration of about 2 hours to about 24 hours, about 2 hours to about 4 hours, about 2 hours to about 6 hours, about 2 hours to about 8 hours, about 2 hours to about 10 hours, about 2 hours to about 12 hours, about 2 hours to about 16 hours, about 2 hours to about 20 hours, about 2 hours to about 24 hours, about 4 hours to about 6 hours, about 4 hours to about 8 hours, about 4 hours to about 10 hours, about 4 hours to about 12 hours, about 4 hours to about 16 hours, about 4 hours to about 20 hours, about 4 hours to about 24 hours, about 6 hours to about 8 hours, about 6 hours to about 10 hours, about 6 hours to about 12 hours, about 6 hours to about 16 hours, about 6 hours to about 20 hours, about 6 hours to about 24 hours, about 8 hours to about 10 hours, about 8 hours to about 12 hours, about 8 hours to about 16 hours, about 8 hours to about 20 hours, about 8 hours to about 24 hours, about 10 hours to about 12 hours, about 10 hours to about 16 hours, about 10 hours to about 20 hours, about 10 hours to about 24 hours, about 12 hours to about 16 hours, about 12 hours to about 20 hours, about 12 hours to about 24 hours, about 16 hours to about 20 hours, about 16 hours to about 24 hours, or about 20 hours to about 24 hours.

[0100] The aging step may be performed in the presence of radiation, preferably UV or IR radiation. The UV radiation may have a wavelength in the range of about 100 nm to about 420 nm, about 100 nm to about 200 nm, about 100 nm to about 300 nm, about 200 nm to about 300 nm, about 200 nm to about 420 nm, or about 300 nm to about 420 nm. The U V radiation may have an intensity in the range of about 5 W / cm2to about 15 W / cm2, 5 W / cm2to about 10 W / cm2, about 10 W / cm2to about 15 W / cm2. The IR radiation maybe in the range of about 720 nm to about 2400 nm, about 720 nm to about 1500 nm, about 720 nm to about 2000 nm, about 1500 nm to about 2000 nm, about 1500 nm to about 2400 nm or about 2000 nm to about 2400 nm. The IR radiation may have an intensity in the range of about 10 W / cm2to about 100 W / cm2, about 10 W / cm2to about 25 W / cm2, about 10 W / cm2to about 50 W / cm2, about 25 W / cm2to about 50 W / cm2, about 25 W / cm2to about 100 W / cm2, about 50 W / cm2to about 100W / cm2.

[0101] Aged sol-gel may refer to sol-gel that has undergone the process of aging and has been substantially completely aged. The aged sol-gel may have a hardness in the range of about 10 kPa to about 500 kPa, about 10 kPa to about 20 kPa, about 10 kPa to about 50 kPa, about 10 kPa to about 100 kPa, about 10 kPa to about 200 kPa, about 20 kPa to about 50 kPa, about 20 kPa to about 100 kPa, about 20 kPa to about 200 kPa, about 20 kPa to about 500 kPa, about 50 kPa to about 100 kPa, about 50 kPa to about 200 kPa, about 50 kPa to about 500 kPa, about 100 kPa to about 200 kPa, about 100 kPa to about 500 kPa or about 200 kPa to about 500 kPa.

[0102] The method may further comprise the step of crushing the aged sol -gel after step (iv) but before step (v). The crushing may be performed by a crusher as defined above.

[0103] The step of crushing the aged sol-gel may result in the formation of a sol-gel powder. The sol-gel powder may have a particle size in the range of about 2 pm to about 1200 pm, about 2 pm to about 10 pm, about 2 pm to about 100 pm, about 2 pm to about 200 pm, about 2 pm to about 500 pm, about 2 pm to about 1200 pm, about 10 pm to about 100 pm, about 10 pm to about 200 pm, about 10 pm to about 500 pm, about 10 pm to about 1200 pm, about 100 pm to about 200 pm, about 100 pm to about 500 pm, about 100 pm to about 1200 pm, about 200 pm to about 500 pm, about 200 pm to about 1200 pm or about 500 pm to about 1200 pm.

[0104] Advantageously, by crushing the aged silica gel into a powder, the surface area of the aged silica gel may be increased, thereby allowing the surface modification step to be performed more efficiently subsequently. Further advantageously, the step of solvent exchange may be accelerated by crushing of the aged silica gel, due to the shorter path of penetration of solvent into the gel structure, making the overall fabrication process of the silica acrogel shorter.

[0105] The method may further comprise the step of solvent exchange and surface modification after step (iv) and after the step of crushing the sol-gel, but before step (v).

[0106] The step of solvent exchange may be for exchanging the water that is present in the aged sol -gel with an organic solvent. The organic solvent may have a low surface tension which may reduce capillary pressure and prevent gel shrinkage and collapse of the pore walls formed in the acrogel. The organic solvent may also facilitate the surface modification step to occur more efficiently. The step of solvent exchange may be performed in an exchange solvent comprising alcohol, an alkyl having 6 or more carbon atoms, acetone, xylene or any mixture thereof. The alcohol may be methanol, ethanol, isopropyl alcohol, t-butanol or any mixture thereof. The alkyl having 6 or more carbon atoms may be n-hexane, n-heptane, n-octane or any mixture thereof.

[0107] The step of solvent exchange may be performed at a temperature in the range of about 40 °C to about 60 °C, or at about 50 °C.

[0108] The step of surface modification may be performed by reacting the aged sol-gel with an organosilicon compound. The organosilicon compound may be trialkylsilyl halide, wherein the alkyl group may be methyl, ethyl or propyl and the halide may be chloride, bromide or iodide. Tire surface modification may be performed by reacting the aged sol-gel with trimethylsilyl chloride (TMCS), hexamethyldislioxane (HMDSO), hexamethyldisilazane (HMDZ), trimethylmethoxysilane (TMMS), phenyltrimethoxysilane (PTMS), phcnyltncthoxysilanc (PTES), vinlytri ethoxy silane (VTMS), mcthyltrimcthoxysilanc (MTMS) or any combination thereof.

[0109] The organosilicon compound may react with hydroxy groups on the surface of the aged sol -gel to functionalise the aged sol-gel with an oganosilicon group such as a trialky lsilyl group. Advantageously, the surface modification may cause the aged sol-gel to become hydrophobic.

[0110] For the surface modification step, the surface modification solvent may comprise an alcohol, an alkyl having 6 or more carbon atoms, acetone, xylene or any mixture thereof. The alcohol may be methanol, ethanol, isopropyl alcohol, t-butanol, or any mixture thereof and the alkyl having 6 or more carbon atoms may be n-hexane, n-heptane, n-octane or any mixture thereof.

[0111] The step of surface modification may comprise the step of adding the aged sol -gel to a mixture of organosilicon compound, an alcohol and an alkyl having 6 or more carbon atoms, wherein: - the molar ratio of organosilicon compound: silica is in the range of about 3: 1 to about 1: 1;

[0112] - the molar ratio of organosilicon compound:alcohol is in the range of about 2: 1 to about 1 :2; and

[0113] - the ratio of alkyl having 6 or more carbon atoms: organosilicon compound by volume is in the range of about 1: 1 to about 10: 1.

[0114] The step of surface modification may comprise the step of adding the aged sol -gel to a mixture of TMCS, ethanol and n-hexane, wherein the molar ratio of TMCS:silica may be in the range of about 3: 1 to about 1: 1, or at a ratio of about 2: 1, the molar ratio of TMCS:cthanol may be in the range of about 2: 1 to about 1 : 2, or at a ratio of about 1: 1, and the ratio of hexane : TMC S by volume may be in the range of about 1 : 1 to about 10: 1, or at a ratio of about 25:2.

[0115] The step of surface modification may comprise the step of the aged sol-gel added to a mixture of organosilicon compound in a surface modification solvent, wherein:

[0116] - the ratio of the surface modification solvent:aged silica gel is about 1 : 1 to about 6: 1 by volume; and

[0117] - the molar ratio of silica: organosilicon compound is in the range of about 1: 10 to about 1:2.

[0118] The step of surface modification may comprise the step of the aged sol-gel added to a mixture of organosilicon compound and a surface modification solvent, wherein the ratio of surface modification solventaged sol-gel may be about 1: 1 to about 6: 1, about 1: 1 to about 2: 1, about 1: 1 to about 3: 1, about 1: 1 to about 4: 1, about 1: 1 to about 5: 1, about 2: 1 to about 3: 1, about 2: 1 to about 4: 1, about 2: 1 to about 5: 1, about 2: 1 to about 6: 1, about 3: 1 to about 4: 1, about 3: 1 to about 5: 1, about 3: 1 to about 6: 1, about 4: 1 to about 5: 1, about 4: 1 to about 6: 1 or about 5: 1 to about 6: 1 by volume.

[0119] The ratio of the alkyl having 6 or more carbon atoms:alcohol:aged sol-gel may be about 10:6:3 by volume.

[0120] The step of surface modification may comprise the step of the aged sol-gel immersed in a mixture of TMCS and a surface modification solvent comprising IPA and n-hexane, wherein the ratio of n-hexane:IPA:aged sol-gel may be about 10:6:3 by volume and the molar ratio of silica:TMCS may be in the range of about l: 10 to about 1: 1, or at a ratio of about 1:4.

[0121] For the surface modification step, the surface modification solvent may comprise an alcohol, an alkyl having 6 or more carbon atoms, acetone, xylene or any mixture thereof. The alcohol may be methanol, ethanol, isopropyl alcohol, t-butanol, or any mixture thereof and the alkyl having 6 or more carbon atoms may be n-hexane, n-heptane, n-octane or any mixture thereof. The step of surface modification may be performed at a temperature in the range of about 30 °C to about 50 °C, about 30 °C to about 40 °C or about 40 °C to about 50 °C, or at about 40 °C, or at about 50 °C for a duration in the range of about 2 hours to about 36 hours, about 2 hours to about 4 hours, about 2 hours to about 3 hours, about 3 hours to about 4 hours, about 2 hours to about 12 hours, about 2 hours to about 18 hours, about 2 hours to about 24 hours, about 12 hours to about 18 hours, about 12 hours to about 24 hours, about 12 hours to about 36 hours, about 18 hours to about 24 hours, about 18 hours to about 36 hours or about 24 hours to about 36 hours, with or without stirring.

[0122] The stirring may be performed at a stirring speed of less than about 400 rpm, less than about 300 rpm, less than about 200 rpm, less than about 100 rpm or less than about 50 rpm. The stirring may be performed at a stirring speed in the range of about 50 rpm to about 200 rpm, about 50 rpm to about 400 rpm or about 200 rpm to about 400 rpm. The surface modified silica gel may be separated from the surface modification solvent and dispersed in IP A, ethanol or n-hexane.

[0123] The silica gel before surface modification may comprise water in its matrix. During the surface modification step, the water that is present in the matrix of the silica gel may be displaced and replaced with the surface modification solvent. As water is displaced from the silica gel matrix, the surface modification solvent that is not in the silica gel matrix may mix with the displaced water to form an aqueous solution. The surface modified silica gel, whereby the water has been displaced with the surface modification solvent, may therefore float on the surface of the aqueous solution, as the surface modified silica gel comprising the surface modification solvent in its matrix may become less dense than tire aqueous solution. Separation of the surface modified silica gel may therefore be performed by removing the aqueous solution by layer separation, evaporation or filtration.

[0124] The surface modified silica gel may be dispersed in IPA, ethanol or hexane at a volume of about 0.5 to about 50 times the volume of the surface modified silica gel.

[0125] Surface modified silica gel may refer to silica gel that has been at least partially or substantially completely surface modified. Surface modified silica gel may be at least about 90%, about 95% or about 98% surface modified. Surface modified silica gel may be about 90% to 100%, about 95% to 100%, or about 98% to 100% surface modified. Surface modified silica gel may have been at least partially or substantially completely surface modified with trialkylsilanol.

[0126] The step of solvent exchange and surface modification may be performed simultaneously. The simultaneous solvent exchange step and surface modification step may be performed by adding a mixed solvent system containing an alcohol, an alkyl having 6 or more carbons, and an organosilicon compound, or any mixture thereof as defined above, to the crushed sol-gel.

[0127] The mixed solvent system for the step of simultaneous solvent exchange and surface modification may comprise in volume about 20% to about 30 % of an alcohol, about 40 % to about 60 % of an alkyl having 6 or more carbons, and about 10 % to about 25% of an organosilicon compound.

[0128] The mixed solvent system for the step of simultaneous solvent exchange and surface modification may be isopropyl alcohol, n-hexane and tnmethylsilyl chloride. The volume ratio of the n-hexane, isopropyl alcohol, trimethylsilyl chloride and sol-gel sample may be 40-60:20-30: 10-25:75. The volume of the mixed solvent system may be about 40 mL to about 60 mL of n-hexane, about 20mL to about 30 mL of isopropyl alcohol, about 10 mL to about 25 mL of trimethylsilyl chloride, and about 75 mL of sol -gel sample.

[0129] The volume ratio of the n-hcxanc, isopropyl alcohol, trimcthylsilyl chloride and sol-gel sample may be 44:22: 15:75.

[0130] The simultaneous solvent exchange step and surface modification step may be performed by adding the sol-gel sample in the mixed solvent system as described above, for a duration of about 3 hours to about 5 hours, about 3 hours to about 4 hours, or about 4 hours to about 5 hours, with stirring speed in the range of about 50 rpm to about 200 rpm, about 50 rpm to about 400 rpm or about 200 rpm to about 400 rpm, until acrogel separation occurs in the upper layer.

[0131] The simultaneous solvent exchange step and surface modification step may be performed in a container, a tank, a vessel, or a flask. The container, tank, vessel, or flask may be sealed. The use of sealed containment may prevent solvent loss and increase ease of transiting to step (vi).

[0132] The simultaneous solvent exchange step and surface modification step (step (v)) may be repeated for about one to five times. Step (v) maybe repeated once, twice, thrice, four times, or five times.

[0133] The simultaneous solvent exchange step and surface modification step may generate elevated pressure to accelerate extraction. The simultaneous solvent exchange step and surface modification step may occur in a scaled reactor, wherein the temperature may be raised from room temperature to a range of about 60 °C to about 80 °C, which may be due to occurrence of an exothermic reaction during the solvent exchange and surface modification process. This increase in temperature may also increase the pressure in the sealed reactor to a range of about 1.1 atm to about 1.2 atm. The elevated temperature and pressure may accelerate the solvent exchange step and the surface modification step by reducing the overall reaction time from about 5 hours to a range of about 3 hours to about 4 hours.

[0134] Without any repeats of step (v), the acrogel obtained may have a density of about 0.15 g / cm3and thermal conductivity of about 0.032 W / mK.

[0135] Advantageously, the simultaneous solvent exchange and surface modification may significantly reduce time, chemical consumption, and cost as compared to conventional methods of silica acrogel production where the solvent exchange and surface modifications steps are performed in two separate steps, which require multiple cycles of reactions and high solvent usage that may lead to longer production time. Accordingly, the method of the present disclosure may result in an improvement in the overall efficiency of silica acrogel production. Further advantageously, the simultaneous solvent exchange and surface modification may also lead to more uniform modification of the gel network, improving the quality of the of silica acrogel produced.

[0136] The method may comprise the step of drying the sol -gel to form the silica acrogel in step (vi). The drying step may comprise two steps, a first drying step and a second drying step.

[0137] The first drying step may be vacuum drying and may be performed using a rotary' evaporator, under the pressure in the range of about 100 mbar to about 500 mbar, about 100 mbar to about 200 mbar, about 100 mbar to about 300 mbar, about 100 mbar to about 400 mbar, about 200 mbar to about 300 mbar, about 200 mbar to about 400 mbar, about 200 mbar to about 500 mbar, about 300 mbar to about 400 mbar, about 300 mbar to about 500 mbar, or about 400 mbar to about 500 mbar, at a temperature in the range of about 40°C to about 60 °C, about 40°C to about 45 °C, about 40°C to about 50 °C, about 40°C to about 55°C, about 45°C to about 50 °C, about 45°C to about 55 °C, about 45°C to about 60 °C, about 50 °C to about 55 °C or about 55 °C to about 60 °C, for a duration of about 5 minutes to 50 minutes, about 5 minutes to about 15 minutes, about 5 minutes to about 30 minutes, about 5 minutes to about 40 minutes, about 10 minutes to about 15 minutes, about 10 minutes to about 30 minutes, about 10 minutes to about 40 minutes, about 10 minutes to about 50 minutes, about 15 minutes to about 30 minutes, about 15 minutes to about 40 minutes, about 15 minutes to about 50 minutes, about 30 minutes to about 40 minutes, about 30 minutes to about 50 minutes, or about 40 minutes to about 50 minutes, at a rotary speed of about 10 rpm to about 300 rpm, about 10 rpm to about 50 rpm, about 10 rpm to about 100 rpm, about 10 rpm to about 160 rpm, about 10 rpm to about 200 rpm, about 10 rpm to about 250 rpm, about 50 rpm to about 100 rpm, about 50 rpm to about 160 rpm, about 50 rpm to about 200 rpm, about 50 rpm to about 250 rpm, about 50 rpm to about 300 rpm, about 100 rpm to about 160 rpm, about 100 rpm to about 200 rpm, about 100 rpm to about 250 rpm, about 100 rpm to about 300 rpm, about 160 rpm to about 200 rpm, about 160 rpm to about 250 rpm, about 160 rpm to about 300 rpm, about 200 rpm to about 250 rpm, about 200 rpm to about 300 rpm, or about 250 rpm to about 300 rpm.

[0138] Advantageously, the reduced temperature and reduced pressure environment in the first drying step may require less energy input, while also leading to faster drying and consequently shorter production times. The reduced temperature may also lower the thermal stress on the silica acrogel formed. Further advantageously, the sealed containment may also facilitate the complete removal of solvents that are entrapped within the microstructure of silica acrogel, which may improve the quality of the silica acrogel in terms of porosity, density, and thermal insulation performance.

[0139] The method may comprise a step of collecting the surface modification solvent added in the surface modification step during the first dry ing step.

[0140] The solvent may be collected from the evaporation flask connected to the condenser, or from a drain port connected to the evaporation flask.

[0141] The second dry ing step may be performed at a temperature in the range of about 100 °C to about 200 °C, about 100 °C to about 125 °C, about 100 °C to about 150 °C, about 100 °C to about 175 °C, about 125 °C to about 150 °C, about 125 °C to about 175 °C, about 125 °C to about 200 °C, about 150 °C to about 175 °C, or about 175 °C to about 200 °C, for a duration in the range of about 30 minutes to about 2 hours, about 30 minutes to about 1 hour, about 30 minutes to about 1.5 hours, about 1 hour to about 1.5 hours, about 1 hour to about 2 hours, or about 1.5 hours to about 2 hours.

[0142] The second drying step may be performed in an oven, on a hotplate, in a heater, in a furnace, in a kiln, on a radiator, or in an incinerator

[0143] As part of the drying step, the method may further comprise a step of recycling the surface modification solvent collected after step (vi). The recycled surface modification solvent may be referred to as a recycled solvent. The recycled solvent may be used for forming additional silica acrogel. The additional silica acrogel may be synthesized using the recycled solvent, along with adding a volume of alkyl having 6 or more carbon atoms, alcohol, and organosilicon compound, or any mixture thereof, in combination with sol- gel.

[0144] Recycling the surface modification solvent may refer to using the mixed solvent collected from the step of drying as defined above, in the step of solvent exchange and surface modification of additional water glass. Additional silica acrogel may be synthesized using about 80 mL to about 100 mL of recy cled solvent, with about 30 mL to about 50 mL of alkyl having 6 or more carbon atoms, about 10 mL to about 30 mL of alcohol, about 20 mL to about 40 mb of organosilicon compound, or any mixture thereof, in combination with about 130 mb to about 170 mb of sol-gel.

[0145] For example, the additional silica acrogel may be synthesized using 87 mb of the recycled solvent, 40 mb of n-hexane, 20 mL of isopropyl alcohol, and 30 mb of trimethylsilyl chloride, or any mixture thereof, in combination with 150 mL of sol-gel.

[0146] Advantageously, the scaled containment may facilitate efficient solvent collection and recycling of surface modification solvents during the drying step, which may allow the solvents to be directly reused in subsequent batches, which may reduce chemical consumption and minimize waste generation. This may also lead to cost-savings and improved sustainability as compared to conventional acrogel drying techniques.

[0147] The method may not further comprise the step of chemically pre-treating the waste glass or glass powder before the extracting step. The pre-treatment step may not be performed before step (li) of extracting silica from waste glass or glass powder. For example, the method may not further comprise the step of chemically pre-treating the waste glass or glass powder using an acid, a water, a detergent, a base, a solvent, a salt, a salt solution, a buffer, an abrasive or any mixture thereof.

[0148] The acid, water, detergent, base, solvent, salt, salt solution, buffer or abrasive may be at a temperature in the range of about 5 °C to about 130 °C, about 5 °C to about 10 °C, about 5 °C to about 20 °C, about 5 °C to about 50 °C, about 5 °C to about 100 °C, about 10 °C to about 20 °C, about 10 °C to about 50 °C, about 10 °C to about 100 °C, about 10 °C to about 130 °C, about 20 °C to about 50 °C, about 20 °C to about 100 °C, about 20 °C to about 130 °C, about 50 °C to about 100 °C, about 50 °C to about 130 °C or about 100 °C to about 130 °C.

[0149] The acid, water, detergent, base, solvent, salt, salt solution, buffer or abrasive may be at a temperature in the range of about 25 °C to about 125 °C or about 50 °C to about 125 °C.

[0150] The method may be performed on waste glass or glass powder directly as sourced, without any washing step.

[0151] The acid in the pre-treatment step may be a strong acid, a weak acid or a mixture thereof. The strong acid maybe be hydrochloric acid, nitric acid, sulfuric acid or any mixture thereof. The weak acid may be selected from the group consisting of phosphoric acid, acetic acid, tartaric acid, oxalic acid and any mixture thereof. The concentration of the acid may be in the range of about 0.01 M to about 18 M, about 0.01 M to about 0.1 M, about 0.01 M to about 1 M, about 0.01 M to about 2 M, about 0.01 M to about 4 M, about 0.01 M to about 5 M, about 0.01 M to about 10 M, about 0.01 M to about 14 M, about 0.1 M to about 18 M, about 0.1 M to about 1 M, about 0.1 M to about 2 M, about 0.1 M to about 4 M, about 0.1 M to about 5 M, about 0.1 M to about 10 M, about 0.1 M to about 14 M, about 1 M to about 18 M, about 1 M to about 2 M, about 1 M to about 4 M. about 1 M to about 5 M, about 1 M to about 10 M, about 1 M to about 14 M, about 2 M to about 18 M, about 2 M to about 4 M, about 2 M to about 5 M, about 2 M to about 10 M, about 2 M to about 14 M, about 4 M to about 18 M, about 4 M to about 5 M, about 4 M to about 10 M, about 4 M to about 14 M, about 5 M to about 18 M, about 5 M to about 10 M, about 5 M to about 14 M, about 10 M to about 18 M, about 10 M to about 12 M, about 10 M to about 14 M, or about 14 M to about 18 M.

[0152] The water in the pre-treatment step may be deionised water, distilled water, steam, or any mixture thereof. The detergent in the pre-treatment step may be a water-based detergent, a solvent-based detergent, a enzymatic detergent, a cationic detergent, an anionic detergent, an acid-based detergent, an alkaline-based detergent, an effervescent based detergent, a chclant-bascd detergent or any mixture thereof. For example, the detergent may be selected from the group consisting of Alconox®, Dural®, M&H®, Lux®, Tide®, Fab®, Glass-Klenz™, LabKlenz™, Ambersil Ultrasonic Cleaner, and Decon 90.

[0153] The base in the pre-treatment step may be a strong base, a weak base or a mixture thereof. The base maybe a strong base. The strong base maybe be sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide or any mixture thereof. The weak base may be ammonia, ammonium hydroxide, triethylamine, trimethylamine or any mixture thereof.

[0154] The solvent in the pre-treatment step may be an organic solvent, inorganic solvent or a mixture thereof. The organic solvent may be an alcohol, an alkyl having 6 or more carbon atoms, acetone, xylene, toluene, 1,4- dioxane, diethyl ether, tetrahydrofuran, ethyl acetate, chloroform, dichloromethane, acetonitrile, dimethylformamide, dimethyl sulfoxide, nitromethane, or any mixture thereof. The alcohol may be methanol, ethanol, isopropyl alcohol, t-butanol, or any mixture thereof and the alkyl having 6 or more carbon atoms may be n-hexane, n-heptane, n-octane or any mixture thereof. The inorganic solvent may be bromine, phosphorus trichloride, phosphorus tribromide, thionyl chloride, thionyl bromide, iodine pentafluoride or any mixture thereof.

[0155] The salt in the pre-treatment step may be an alkali metal salt, an alkaline earth metal salt, or any mixture thereof. The alkali metal salt may include, but not limited to, sodium chloride, sodium carbonate, sodium nitrate, potassium chloride, potassium nitrate, potassium carbonate or any mixture thereof. The alkaline earth metal salt may include, but not limited to, magnesium chloride, magnesium nitrate, calcium chloride, calcium nitrate, or any mixture thereof. The salt solution in the pre-treatment step may be a solution of an alkali metal salt, an alkaline earth metal salt, or any mixture thereof. The alkali metal salt, the alkaline earth metal salt and any mixture thereof, may be as defined above.

[0156] The buffer in the pre-treatment step may be phosphate buffer, phosphate buffered saline (PBS), tris(hydroxymethyl)aminomethane (TRIS), 4-(2-hydroxyethyl)-l -piperazineethanesulfonic acid (HEPES), 3-(N-morpholino)propancsulfonic acid (MOPS), or any mixture thereof.

[0157] The abrasive in the pre-treatment step may be aluminium oxide, silicon carbide, silicon dioxide, carbon dioxide (dry ice), or any mixture thereof.

[0158] There is provided a system of forming silica acrogel from waste glass, comprising the components of:

[0159] (i) a crusher to crush and / or grind waste glass to a glass powder;

[0160] (ii) a silica extractor to extract silica from the glass powder to form a water glass;

[0161] (iii) a reactor to add an acid to the water glass to form a sol-gel, and to perform solvent exchange and surface modification of a sol -gel; and

[0162] (iv) a dryer to dry the sol-gel to form the silica acrogel, wherein the sy stem does not comprise a component for chemically pre-treating the waste glass or glass powder before extracting the silica.

[0163] The system may comprise a crusher to form glass powder of particle size of less than 300 pm, less than 250 pm, less than 200 pm, less than 150 pm, less than 100 pm or less than 50 pm before component (ii). The system may comprise a crusher to form glass powder of particle size of about 1 pm to about 300 pm, about 1 pm to about 250 pm, about 1 pm to about 200 pm, about 1 pm to about 150 pm, about 1 pm to about 100 pm, about 1 to about 50 pm, about 50 pm to about 100 pm, about 50 pm to about 150 pm, about 50 pm to about 200 pm, about 50 pm to about 250 pm, about 50 pm to about 300 pm, about 100 pm to about 150 pm, about 100 pm to about 200 pm, about 100 pm to about 250 pm, about 100 pm to about 300 pm, about 150 pm to about 200 pm, about 150 pm to about 250 pm, about 150 pm to about 300 pm, about 200 pm to about 250 pm, about 200 pm to about 300 pm, or about 250 pm to about 300 pm.

[0164] The crusher may be as defined above, and may be a roller crusher.

[0165] The system may further comprise a siever to sieve the glass powder before component (ii) but after component (i). The siever may have one or more sieves with mesh size of less than 300 pm, less than 250 pm, less than 200 pm, less than 150 pm, less than 100 pm or less than 50 pm. The size may be about 1 pm to about 300 pm, about 1 pm to about 250 pm, about 1 pm to about 200 pm, about 1 pm to about 150 pm, about 1 μm to about 100 μm. about 1 to about 50 μm, about 50 μm to about 100 μm, about 50 μm to about 150 μm, about 50 μm to about 200 μm, about 50 μm to about 250 μm, about 50 μm to about 300 μm, about 100 μm to about 150 μm, about 100 μm to about 200 μm, about 100 μm to about 250 μm, about 100 μm to about 300 μm, about 150 μm to about 200 μm, about 150 μm to about 250 μm, about 150 μm to about 300 μm, about 200 μm to about 250 μm, about 200 μm to about 300 μm, or about 250 μm to about 300 μm.

[0166] The sicvcr may comprise a sieve as defined above, and may be an automatic vibrating machine.

[0167] The system may further comprise a component to return glass powder of particle size greater than 300 μm, greater than 250 μm, greater than 200 μm, greater than 150 gin. greater than 100 μm or greater than 50 μm from the siever to the crusher.

[0168] The component to return glass powder to the crusher may be a tube, a pipe, a lift, a chute, a conveyer, a belt, a pulley, a slide, a spiral, or a wheel.

[0169] The system may comprise a silica extractor to extract silica from the glass powder to form a water glass.

[0170] The silica extractor may be a tank, a container, a drum, a batch reactor, a continuous stirred-tank reactor, or a flow reactor, which contains a base for extracting the silica from the glass powder. The silica extractor may be made of Teflon or stainless-steel. The silica extractor may be a pressurized reactor operating in the pressure range of about 30 bar to about 100 bar, about 30 bar to about 45 bar, about 30 bar to about 60 bar, about 30 bar to about 80 bar, about 45 bar to about 60 bar, about 30 bar to about 80 bar, about 45 bar to about 100 bar, about 60 bar to about 80 bar, about 60 bar to about 100 bar, or about 80 bar to about 100 bar, at a temperature range of about 150 °C to about 250 °C, about 150 °C to about 175 °C, about 150 °C to about 200 °C, about 150 °C to about 225 °C, about 175 °C to about 200 °C, about 175 °C to about 225 °C, about 175 °C to about 250 °C, about 200 °C to about 225 °C, about 200 °C to about 250 °C, or about 225 °C to about 250 °C, for a duration of about 18 hours to about 36 hours, about 18 hours to about 22 hours, about 18 hours to about 26 hours, about 18 hours to about 30 hours, about 22 hours to about 26 hours, about 22 hours to about 30 hours, about 22 hours to about 36 hours, about 26 hours to about 30 hours, about 26 hours to about 36 hours, or about 30 hours to about 36 hours.

[0171] The system may comprise a further filter to separate residual glass powder from water glass after the silica extraction.

[0172] The filter may be a vacuum filter, gravity filter, centrifugal filter, membrane filter, vacuum filter, inline filter, cartridge filter, or basket filter. The filter may be a filter press, operating under vacuum, or under the pressure in the range of about 0.0001 MPa to about 3 MPa, about 0.0001 MPa to about 0.5 MPa, about 0.0001 MPa to about 1 MPa, about 0.0001 MPa to about 1.5 MPa, about 0.0001 MPa to about 2 MPa, about 0.0001 MPa to about 2.5 MPa, about 0.5 MPa to about 1 MPa, about 0.5 MPa to about 1.5 MPa, about 0.5 MPa to about 2 MPa, about 0.5 MPa to about 2.5 MPa, about 0.5 MPa to about 3 MPa, about 1 MPa to about 1.5 MPa, about 1 MPa to about 2 MPa, about 1 MPa to about 2.5 MPa, about 1 MPa to about 3 MPa, about 1 .5 MPa to about 2 MPa, about 1.5 MPa to about 2.5 MPa, about 1.5 MPa to about 3 MPa, about 2 MPa to about 2.5 MPa, about 2 MPa to about 3 MPa, or about 2.5 MPa to about 3 MPa, at a particle size of about 1 pm to about 300 pm, about 1 pm to about 50 pm, about 1 pm to about 100 pm, about 1 pm to about 150 pm, about 1 pm to about 200 pm, about 1 pm to about 250 pm, about 50 pm to about 100 pm, about 50 pm to about 150 pm, about 50 pm to about 200 pm, about 50 pm to about 250 pm, about 50 pm to about 300 pm, about 100 pm to about 150 pm, about 100 pm to about 200 pm, about 100 pm to about 250 pm, about 100 pm to about 300 pm, about 150 pm to about 200 pm, about 150 pm to about 250 pm, about 150 pm to about 300 pm, about 200 pm to about 250 pm, about 200 pm to about 300 pm, or about 250 pm to about 300 pm, at room temperature, or at a temperature range of about 20 °C to about 35 °C, about 20 °C to about 25 °C, about 20 °C to about 30 °C, about 25 °C to about 30 °C, about 25 °C to about 35 °C, or about 30°C to about 35 °C.

[0173] The process of filtration may effectively dry any unreacted glass powder as residue. The residue glass powder may be returned to the silica extractor via a second component. The system may comprise a second component to return the residue glass powder from the filter to silica extractor. The second component maybe a tube, a pipe, a lift, a chute, a conveyer, a belt, a pulley, a slide, a spiral, or a wheel.

[0174] The system may comprise a reactor to first add acid to the water glass to form a sol -gel, and subsequently perform solvent exchange and surface modification. The reactor may have a volume of about 100 L to about 5000 L, about 100 L to about 500 L, about 100 L to about 1000 L, about 100 L to about 2000 L, about 100 L to about 3500 L, about 500 L to about 1000 L, about 500 L to about 2000 L, about 500 L to about 3500 L, about 500 L to about 5000 L, about 1000 L to about 2000 L, about 1000 L to about 3500 L, about 1000 L to about 5000 L, about 2000 L to about 3500 L, about 2000 L to about 5000 L, or about 3500 L to about 5000 L, at a temperature range of about 20 °C to about 60 °C, about 20 °C to about 30 °C, about 20 °C to about 40 °C, about 20 °C to about 50 °C, about 30 °C to about 40 °C, about 30 °C to about 50 °C, about 30 °C to about 60 °C, about 40 °C to about 50 °C, about 40 °C to about 60 °C, or about 50 °C to about 60 °C, for a duration of about 1 hour to about 24 hours, about 1 hour to about 3 hours, about 1 hour to about 6 hours, about 1 hour to about 9 hours, about 1 hour to about 12 hours, about 1 hour to about 15 hours, about 1 hour to about 18 hours, about 1 hour to about 21 hours, about 3 hours to about 6 hours, about 3 hours to about 9 hours, about 3 hours to about 12 hours, about 3 hours to about 15 hours, about 3 hours to about 18 hours, about 3 hours to about 21 hours, about 3 hours to about 24 hours, about 6 hours to about 9 hours. about 6 hours to about 12 hours, about 6 hours to about 15 hours, about 6 hours to about 18 hours, about 6 hours to about 21 hours, about 6 hours to about 24 hours, about 9 hours to about 12 hours, about 9 hours to about 15 hours, about 9 hours to about 18 hours, about 9 hours to about 21 hours, about 9 hours to about 24 hours, about 12 hours to about 15 hours, about 12 hours to about 18 hours, about 12 hours to about 21 hours, about 12 hours to about 24 hours, about 15 hours to about 18 hours, about 15 hours to about 21 hours, about 15 hours to about 24 hours, about 18 hours to about 21 hours, about 18 hours to about 24 hours, or about 21 hours to about 24 hours, at ambient pressure of about 0.101 MPa to about 0.102 MPa, or about 0.101325 MPa to about 0.102 MPa.

[0175] The reactor may comprise stirring blades to crush the sol-gel before performing solvent exchange and surface modification of the sol-gel as defined above. The stirring blades may be stainless steel. Teflon or plastic.

[0176] The stirring blades may be metal with polytetrafluoroethylene (PTFE) coating.

[0177] The reactor may comprise a valve, a switch, a chamber, a dropping funnel or a tap to first add acid to the water glass to form a sol-gel, and subsequently perform solvent exchange and surface modification of the sol-gel as defined above.

[0178] The reactor may be a pressurized reactor, batch reactor, a continuous stirred-tank reactor, or a flow reactor. The system may further comprise a second reactor for the solvent exchange and surface modification of the sol-gel as defined above.

[0179] The system may also compnsc a component to transfer sol-gel from the first reactor to the second reactor. The component to transfer the sol-gel from the first reactor to the second reactor may be a tube, a pipe, a dram, a slide, a spiral, or a wheel.

[0180] The system may comprise a dryer to dry the sol-gel.

[0181] The dryer may be a rotary' evaporator, vacuum dry er, or an oven.

[0182] The rotary evaporator may be operating in the pressure range of about 150 mbar to about 400 mbar, about 150 mbar to about 200 mbar, about 150 mbar to about 250 mbar, about 150 mbar to about 300 mbar, about 150 mbar to about 350 mbar, about 200 mbar to about 250 mbar, about 200 mbar to about 300 mbar, about 200 mbar to about 350 mbar, about 200 mbar to about 400 mbar, about 250 mbar to about 300 mbar, about 250 mbar to about 350 mbar, about 250 mbar to about 400 mbar, about 300 mbar to about 350 mbar, about 300 mbar to about 400 mbar, or about 350 mbar to about 400 mbar, at a temperature range of about 45 °C to about 50 °C, for a duration of about 10 minutes to about 40 minutes, about 10 minutes to about 20 minutes, about 10 minutes to about 30 minutes, about 20 minutes to about 30 minutes, about 20 minutes to about 40 minutes, or about 30 minutes to about 40 minutes.

[0183] The rotary evaporator may be an industrial scale rotary evaporator.

[0184] The oven may be operating at a temperature of about 30 °C to about 80 °C, about 30 °C to about 40 °C, about 30 °C to about 50 °C, about 30 °C to about 60 °C, about 30 °C to about 70 °C, about 40 °C to about 50 °C, about 40 °C to about 60 °C, about 40 °C to about 70 °C,, about 40 °C to about 80 °C, about 50 °C to about 60 °C, about 50 °C to about 70 °C, about 50 °C to about 80 °C, about 60 °C to about 70 °C, about 60 °C to about 80 °C, or about 70 °C to about 80 °C.

[0185] The oven may be equipped with a condensing system to collect a solvent for recycling.

[0186] The oven may be a box oven, glass oven or conveyer oven.

[0187] The system may not comprise a component to chemically pre-treat the waste glass or glass powder before extracting the silica.

[0188] There is provided the use of waste glass to form a silica acrogel. The use may comprise the methods as defined above .

[0189] There is provided a silica acrogel prepared by the method as defined above. The silica acrogel may have a thermal conductivity of about 0.015 W / mK to about 0.045 W / mK, about 0.015 W / mK to about 0.020 W / mK, about 0.015 W / mK to about 0.025 W / mK, about 0.015 W / mK to about 0.030 W / mK, about 0.015 W / mK to about 0.035 W / mK, about 0.015 W / mK to about 0.040 W / mK, about 0.015 W / mK to about 0.020 W / mK, about 0.020 W / mK to about 0.025 W / mK, about 0.020 W / mK to about 0.030 W / mK, about 0.020 W / mK to about 0.035 W / mK, about 0.020 W / mK to about 0.040 W / mK, about 0.020 W / mK to about 0.045 W / mK, about 0.025 W / mK to about 0.030 W / mK, about 0.025 W / mK to about 0.035 W / mK, about 0.025 W / mK to about 0.040 W / mK, about 0.025 W / mK to about 0.045 W / mK, about 0.030 W / mK to about 0.035 W / mK, about 0.030 W / mK to about 0.040 W / mK, about 0.030 W / mK to about 0.045 W / mK, about 0.035 W / mK to about 0.040 W / mK, about 0.035 W / mK to about 0.045 W / mK, or about 0.035 W / mK to about 0.045 W / mK, with a density of about 0.01 g / cm3to about 0.15 g / cm3, about 0.01 g / cm3to about 0.03 g / cm3, about 0.01 g / cm3to about 0.05 g / cm3, about 0.01 g / cm3to about 0.10 g / cm3, about 0.01 g / cm3to about 0.12 g / cm3, about 0.03 g / cm3to about 0.05 g / cm3, about 0.03 g / cm3to about 0.10 g / cm3, about 0.03 g / cm3to about 0.12 g / cm3, about 0.03 g / cm3to about 0.15 g / cm3, about 0.05 g / cm3to about 0.10 g / cm3, about 0.05 g / cm3to about 0.12 g / cm '. about 0.05 g / cm3to about 0.15 g / cm3, about 0.10 g / cm3to about 0.12 g / cm3, about 0.10 g / cm3to about 0.15 g / cm3, or about about 0.12 g / cm3to about 0.15 g / cm3.

[0190] EXAMPLES

[0191] Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

[0192] Materials and Methods

[0193] Raw waste glass was collected from the local waste collector. Hydrochloric acid, 37%, sodium hydroxide, >97%, trimcthylsilyl chloride (TMCS), >98%, n-hcxanc, 95%, isopropyl alcohol, 99.5%, and Amberlite® IRC 120 H, hydrogen fonn, strongly acidic were obtained from Siμma-Aldrich (Merck Pte. Ltd., Singapore).

[0194] Jaw crusher was from Henan Hongji Mine Machinery Co. Ltd (Zhengzhou City, China)., ball mill (PM100) was from Retsch (Haan, Germany), magnetic stirring and heating extraction sleeve (500 mL) were from Xiamen Ollital Technology Co. Ltd. (Xiamen, China), glass reactor (10 L) was from Radleys (Essex, United Kingdom), rotary evaporator (Rotavapor R-100) was from Buchi (Singapore), and oven (FD56) was from Binder (Tuttlingen, Germany).

[0195] Example 1: Preparation of Silica Aerogel from Waste

[0196] As outlined in Figure 1, raw waste glass was collected from the local waste collector and first dried to remove any liquid. Subsequently, the waste glass (102) was crushed (104) in a crusher, resulting in glass cutlets. To further reduce the glass particle size, the glass cutlets were grounded (104) with a ball mill machine at 300 rpm for approximately 15 minutes to reduce the particle size. Once completed, the ground waste glass was sieved through an auto-sieve using a sieve with mesh size of 150 pm to obtain glass powder (106) with a particle size of less than 150 pm.

[0197] Tire silica extraction process (108) was conducted by reacting sodium hydroxide solution (NaOH) with glass powder for 4 hours at 180°C. Tire sodium hydroxide solution was prepared by dissolving grams

[0198] 3X of sodium hydroxide tablets in — litres of deionized water, where X is the mass in grams of the glass powder. The silica extraction process (108) was conducted using a condensing unit and condenser to prevent water loss at high temperatures. The evaporated water was condensed and simultaneously reintroduced into the mixture during the process. Alternatively, the silica extraction process ( 108) could be conducted using an autoclave reactor. A Teflon or stainless-steel container was preferably used to prevent any reaction between the sodium hydroxide and the glass container. The reaction mixture was reacted for a period of 1 to 4 hours, and the mixture was subsequently allowed to cool to a temperature of 50°C or below before attempting filtration. The filtration process was carried out by pouring the mixture through a filtration system equipped with a 2 pm filter membrane to separate the glass residue from the sodium silicate solution (Na2SiO3). commonly known as water glass (110). Next, 35ml of 2M HC1 was added to 100ml of the water glass solution (110), and mixed thoroughly within the container using a stir bar. Another 15ml of 2M HO was subsequently added to the water glass solution. The water glass solution was closely observed while being stirred; and when the mixture became cloudy, the precursor sol-gel (112) began to gel. The sol-gel allowed to age for 4 hours (112) to form silica gel (114), before solvent exchange and surface modification (116) were attempted.

[0199] After the 4 hour period, the silica-gel (114) was crushed before a mixed solvent solution containing IPA (C3H8O), n-Hexane (C6H14), and trimethylsilyl chloride (TMCS) |(CI h),SiCI)| was added. The volume ratio of n- hexane, IPA, TMCS, and sample was 44:22: 15:75. In a sealed container, the samples were submerged in the mixed solvents and stirred for 4 hours until the acrogel separation occurred in the upper layer from the formation of hydrophobic silica gel (118).

[0200] To recycle the solvents (n-Hexane and IPA), a rotary evaporator was first used to dry (120) the hydrophobic silica gel (118), following the settings outlined in Table 1. The solvents were collected after evaporation, and silica acrogel (122) products were obtained by final drying (120) in an oven at 150°C for 1 hour.

[0201] Table 1. The settings for the rotary evaporator for drying and solvent collection.

[0202] Example 2: Recycling of Solvents for preparing new batch of silica aerogel

[0203] The recycled solvents, comprising n-Hexane and IPA, could be reused for the next batch of acrogel fabrication. With 150 ml of sol-gel, 87 ml of recycled solvents was used, and an additional volume of 40 ml of n- Hexane, 20 ml of IP A, and 30 ml of TMCS were added. The remaining steps for preparing silica acrogel as described above in Example 1 were repeated.

[0204] Table 2. The fresh chemical usage for batch fabrication of acrogel from recycle glass.

[0205] Example 3: Properties of Silica Aerogel Prepared

[0206] The thermal conductivity of the acrogel samples was measured using the C-Therm Max-k Module with a Modified Transient Plane Source (MTPS) Sensor. The test was conducted in compliance with the ASTM D7984 standard, which is a Standard Test Method for Measurement of Thermal Effusivity of Fabrics Using a Modified Transient Plane Source (MTPS) Instrument, which is suitable fortesting solids, liquids, powders and pastes.

[0207] Briefly, in the ASTM D7984 standard test, a minimum of five specimens from each sample was tested. Specimens were staggered in such a manner that no two specimens contain the same yams. The specimens were required to be thicker than 1.0 mm so that the heat wave does not penetrate beyond its maximum test penetration of 1.0 mm thickness during the sampling period. This thickness ensured that even if the specimen is on the higher end of the thermal effusivity range, the penetration depth of the heat flux during the measurement time was maintained within the specimen.

[0208] The procedures of the ASTM D7984 standard test were as follows: Firstly, sufficient volume of specimen (2 ml) were placed over the heater surface so that the heater was completely covered and that a total specimen thickness of more than 1.0 mm was achieved. A fixed load of between 10 to 50 kPa was then selected and applied to the specimen on the side opposite to the heater to ensure intimate contact with the heater. The experiment was subsequently initiated by providing a constant momentary power pulse to the heater and guard ring so that a temperature rise of 1 to 3°C occurred at the surface of the test specimen within 1 to 3 seconds and the thermal effusivity was recorded. After which, the test specimen and apparatus was allowed to cool to ambient temperature, and the thermal effusivity measurement was repeated for each specimen for an additional two times. The procedures were repeated until all five specimens were tested.

[0209] The results were shown in Table 3.

[0210] Table 3. The specifications of fabncatcd silica acrogel

[0211] *The data was measured at the machine's lower limit.

[0212] The specifications of SP1 acrogel were comparable to those of commercially available acrogels, such as Krosslinkcr acrogel (Singapore). Similarly, SPO acrogel matched the specifications of leading acrogels on the market, including Cabot acrogel (USA), and Mingyi acrogel (China). The thermal conductivities were measured using the same instrument for accurate comparison. Notably, SPO, with its lower density, matched the quality of the best acrogels on the market and exhibits superior thermal insulation properties, as demonstrated by its lower thermal conductivity compared to SP 1.

[0213] Example 4: Pilot Scale Process of Preparing Silica Aerogel

[0214] The pilot-scale process illustrated in Figure 2 was designed for larger-scale production. The ball mill was substituted with a smooth roller crusher (202). An automatic vibrating sieving machine (206) was employed to separate raw glass particles with sizes below 150 to 200 pm. Smaller particles proceeded to the next treatment step, while larger particles were returned via a recycling loop (204) to the smooth roller crusher (202) for further size reduction. Silica extraction was conducted in a pressunzed reactor (208). Unreacted or residual glass powder was dried after treatment using filtration press systems (210). The collected water glass solution was subsequently utilized in the manufacturing of silica acrogel.

[0215] The sol-gel and surface treatment process could be readily upscaled by employing a large-volume reactor (212). Solvents were recycled and the silica acrogel was dried using an industrial-scale rotary evaporator under vacuum (214). Finally, the silica acrogel was dried through an oven (216) at 150°C for 1 hour.

[0216] Alternatively, the solvents could also be recycled and the silica acrogel could also be dried using an oven (216) equipped with a condensing system. The acrogel could then be obtained through a conveyor oven (216). INDUSTRIALLY APPLICABILITY

[0217] The disclosed method of forming a silica acrogel from waste glass may be useful in facile, versatile and efficient preparation of silica acrogel as defined above. The disclosed system of forming a silica acrogel from waste glass as defined above may be useful for scaling up the production process of silica acrogel from waste glass, leading to more versatile and efficient large-scale production of silica acrogel.

[0218] In the building and construction industries, the silica acrogel produced by the method and system as defined above may be used as thickening agents in paints, to create paint with insulation properties. The silica acrogel may also be a good replacement of partial sand in concrete to increase the compressive strength, reduce energy consumption, weight and cost while maintaining good heat insulating properties.

[0219] In the field of fibre optics, the silica acrogel may act as a mctamatcrial, wherein light sees the silica acrogel as an averaged-out medium that is mainly air, but the glass network makes it rigid like a solid.

[0220] Th silica acrogel may also be useful in air purification where it could realise simultaneous adsorption and photodegradation of organic pollutants which may be more efficient than existing materials used in air purification. The silica acrogel may also be an effective and efficient chemical absorbent for oils and organic liquids clean.

[0221] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.

Claims

CLAIMS1. A method of forming a silica acrogel from waste glass, comprising the steps of:(i) providing waste glass;(ii) crushing and / or grinding the waste glass to fonn a glass powder:(iii) extracting silica from the glass powder in the presence of a base to form a water glass;(iv) adding an acid to the water glass to form a sol-gel;(v) solvent exchange and surface modification of sol-gel; and(vi) drying the sol-gel to form the silica acrogel, wherein the waste glass or glass powder is not chemically pre-treated before the extracting step.

2. The method according to claim 1, further comprising a step of of drying the waste glass before step (ii) at a temperature in the range of 50 °C to 150 °C.

3. The method according to claim 1 or 2, wherein the glass powder is of particle size of less than 300 pm.

4. The method according to any one of claims 1 to 3, wherein the extraction step is performed at a temperature in the range of 160 °C to 200 °C for a duration in the range of 30 minutes to 6 hours, or wherein the extraction step further comprises: a step of preventing solvent loss, comprising: evaporating the solvent; and reintroducing the evaporated solvent into the water glass of step (iii) simultaneously; or a step of cooling the water glass after step (iii) but before step (iv) to a temperature of less than 60 °C; or a step of filtering the water glass after step (iii); or a step of diluting the water glass in deionized water at a ratio in the range of 1:2 to 3:4 by volume.

5. The method according to any one of claims 1 to 4, wherein the step of adding an acid to the water glass to fonn a sol-gel further comprises a step of adding a first acid to the water glass to fonn a sol -gel after step (iii) but before step (v).

6. The method according to claim 5, wherein the step of adding an acid to the water glass to form a sol-gel further comprises a step of stirring after adding the first acid to the water glass, at room temperature at a stirring speed in the range of 200 rpm to 400 rpm, for a duration in the range of 1 minute to 30 minutes.

7. The method according to claims 5 or 6, further comprising a step of adding an additional second acid while stimng, after the addition of the first acid.

8. The method according to any one of claims 1 to 7, further comprising a step of purifying the water glass on a strongly acidic ion exchange resin to collect silicic acid, and a step of adding a pH- adjusting base to the silicic acid until the pH is in the range of 3 to 6, to form the sol-gel.

9. The method according to any one of claims 1 to 8, further comprising a step of aging the sol-gel after step (iv) but before step (v) for a duration of 2 hours to 24 hours.

10. The method according to claim 9, further comprising a step of crushing the aged sol-gel to form a sol-gel powder.

11. The method according to claim 10, further comprising the step of solvent exchange and surface modification of the aged sol-gel after step (iv) and after the step of crushing the aged sol-gel, but before step (v), preferably wherein the step of surface modification is performed by reacting the aged sol-gel with an organosilicon compound at a temperature in the range of 30 °C to 50 °C, for a duration in the range of 2 hours to 36 hours, with or without stirring.

12. The method according to claim 11, wherein: the step of surface modification further comprises a step of adding the aged sol-gel to a mixture of organosilicon compound, an alcohol and an alkyl having 6 or more carbon atoms, wherein:- the molar ratio of organosilicon compound: silica is in the range of 3 : 1 to 1: 1:- the molar ratio of organosilicon compound: alcohol is in the range of 2: 1 to 1 :2; and- the ratio of alkyl having 6 or more carbon atoms: organosilicon compound by volume is in the range of 10: 1 to 15: 1; or the step of surface modification further comprises a step of the adding the aged sol-gel to a mixture of organosilicon compound in a surface modification solvent, wherein:- the ratio of the surface modification solvent aged silica gel is 1 : 1 to 6: 1 by volume; and- the molar ratio of silica: organosilicon compound is in the range of 1 : 10 to 1:2.

13. The method according to any one of claims 1 to 12, where the drying step further comprises two steps, a first drying step and a second drying step, wherein the first drying step is performed at a pressure in the range of 100 mbar to 500 mbar, at a temperature in the range of 40°C to 60 °C, for a duration in the range of 5 minutes to 50 minutes, and at a rotary speed in the range of 10 rpm to 300 rpm.

14. Tire method according to claim 13, further comprising a step of collecting the surface modification solvent added in the surface modification step, during the first drying step.

15. The method according to claim 14, wherein the second dry ing step is performed at a temperature in the range of 100 °C to 200 °C for a duration in the range of 30 minutes to 2 hours.

16. The method according to claim 15, further comprising a step of recy cling the surface modification solvent collected after step (vi).

17. A system of forming silica acrogel from waste glass, comprising the components of:(i) a crusher to crush and / or grind waste glass to a glass powder;(ii) a silica extractor to extract silica from the glass powder to form a water glass;(iii) a reactor to add an acid to the water glass to form a sol-gel, and to perform solvent exchange and surface modification of a sol-gel; and(iv) a dryer to dry the sol -gel to form the silica acrogel, wherein the system does not comprise a component for chemically pre-treating the waste glass or glass powder before extracting the silica.

18. The system according to claim 17, further comprising a siever to sieve the glass powder before component (ii) but after component (i), wherein the siever is one or more sieves with mesh size of less than 300 pm, or a component to return glass powder of particle size greater than 300 pm from the siever to the crusher.

19. The system according to claim 17 or 18, wherein the silica extractor is operated at a pressure in the range of 30 bar to 100 bar, at a temperature in the range of 150 °C to 250 °C, for a duration in the range of 18 hours to 36 hours, or wherein the reactor comprises stirring blades to crush the sol-gel before performing solvent exchange and surface modification of the sol-gel, orwherein the dryer is operated at a pressure in the range of 150 mbar to 400 mbar. at a temperature in the range of 45 °C to 50 °C, for a duration in the range of 10 minutes to 40 minutes.

20. The system according to any one of claims 17 to 19, further comprising a filter to separate residual glass powder from water glass after the silica extraction.

Images