Filter aid

Abstract

The present disclosure is concerned with providing a filter aid, wherein the filter aid comprises a first composition comprising an inorganic particulate comprising silicon; and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. Methods of preparation and filtering are also described.

Description

[0001]FILTER AID TECHNICAL FIELD The present disclosure concerns filter aids, wherein the filter aid comprises a first composition including an inorganic particulate which comprises silicon and a second composition including a dicarboxylic acid or a dicarboxylic acid polymer. The present disclosure also concerns methods of filtering liquids, methods of preparing a filter aid and method of preventing or reducing silicon leaching from a filter aid. BACKGROUND Filter aids are used in methods of filtering liquids, where the removal of fine particles or contaminants is required. Such filter aids are either added to the suspension to be filtered or placed on the filter as a layer through which the liquid must pass. Filter aids are usually comprised of inorganic particulates such as diatomaceous earth or perlite which are advantageously lightweight, inert, and are virtually insoluble in mineral and organic acids at all temperatures. However, it is known that unwanted elemental impurities, such as silicon, may leach from filter aids. The leaching of elemental impurities, such as silicon, is also undesirable in methods of filtering, e.g., in method of filtering beverages or in other types of methods of filtering impurities from liquids such as aqueous solutions or hydrocarbons. The aqueous solutions, and the hydrocarbons can include oils, including biofuels. The extraction of unwanted impurities from metal-containing aqueous solutions, such as metal brines, can also be achieved by using filter aid products. An example of this is when extracting lithium from mined sources or lithium-rich brines. Lithium is highly desirable for the production of high-performance lithium-ion batteries. The extraction of other metals is also highly desirable. The use of filter aid products may be undesirable because they leach minerals, such as silicon, into the lithium brine which can be problematic and may decrease the value of the brine. Accordingly, it would be desirable to produce a filter aid with improved impurity leaching. SUMMARY According to some embodiments, there is provided a filter aid, wherein the filter aid comprises: a first composition comprising an inorganic particulate comprising silicon; and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. According to some embodiments, there is provided a method of filtering a liquid, or a use of the filter aid to filter a liquid, the method or use comprising contacting the filter aid according to the present disclosure with the liquid to filter the unwanted particulates from the liquid to form a filtered liquid. According to some embodiments, there is provided a method of filtering a liquid, or a use of the filter aid to filter a liquid, the method or use comprising contacting the filter aid according to the present disclosure with the liquid to filter the unwanted particulates from the liquid to form a filtered liquid, wherein the first and second compositions can be added to the liquid either: i) simultaneously to the liquid (either separately, or as a dry mixture or as a wet mixture or as a coated substrate wherein the first composition is a substrate and the second composition is a coating on the substrate) or ii) sequentially to the liquid in any order of addition. According to some embodiments, there is provided a method of preventing or reducing silicon leaching from a filter aid into a liquid during filtration, or use of a filter aid to prevent or reduce silicon leaching into a liquid during filtration, the method or use comprising: mixing a first composition with a second composition to form the filter aid and filtering the liquid with the filter aid to form a filtered liquid, wherein the first composition comprises an inorganic particulate comprising silicon, and wherein the second composition comprises a dicarboxylic acid or a dicarboxylic acid polymer. According to some embodiments, there is provided a method of preparing a filter aid comprising: mixing a first composition comprising an inorganic particulate comprising silicon with a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. According to some embodiments, there is provided a filter aid, wherein the filter aid comprises: an inorganic particulate which comprises silicon; and a coating selected from: a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). According to some embodiments, there is provided a method of preventing or reducing silicon leaching from a filter aid into a liquid during filtration, the method comprising: coating an inorganic particulate with a coating to form the filter aid and filtering the liquid with the filter aid to form a filtered liquid, wherein the inorganic particulate comprises silicon; and wherein the coating is selected from: a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). According to some embodiments, there is provided a method of preparing a filter aid comprising: coating an inorganic particulate with a coating, wherein the inorganic particulate comprises silicon; and wherein the coating is selected from: a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). The skilled person will appreciate that, except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive, any feature described herein may be applied to any aspect and / or combined with any other feature described herein. DETAILED DESCRIPTION It has surprisingly been found that the leaching of silicon from a filter aid which comprises an inorganic particulate comprising silicon can be reduced or prevented by providing a coating on the inorganic particulate. The coating is selected from a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). It has also surprisingly been found that the leaching of silicon from a filter aid which comprises a first composition comprising an inorganic particulate comprising silicon and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer can be reduced or prevented. The filter aid may comprise a mixture of the first composition and the second composition. The filter aid may be a dry mixture or a wet mixture of the first composition and the second composition. The first composition of the filter aid may be a substrate and the second composition of the filter aid may be a coating on the first composition. Inorganic particulate The inorganic particulate comprises or consists of diatomaceous earth, perlite, expanded perlite, expanded milled perlite, sand, bentonite, silica gel, kaolinite, zeolite, silicoaluminophosphate molecular sieves, or a mixture thereof. All of these inorganic particulates comprise silicon. Diatomaceous earth (DE) is derived from the remains of microscopic fossilized sea or freshwater algae. DE is typically employed as a filter aid. DE is known for having an intricate and porous structure which is effective for entrapping particles in filtration processes. The DE starting material may be DE in its crude form or may have been subjected to one or more processing steps such as physical or chemical modification. Physical modification processes include, but are not limited to, milling, drying and air classifying. Chemical modification processes include, but are not limited to, silanization. Such a modification process is used to render the surfaces of DE either more hydrophobic or hydrophilic using the methods such as those described in US 3,915,735 and US 4,260,498, the contents of which are incorporated herein by reference in their entireties. DE typically comprises about 80 to 90% silica, with 2 to 4% alumina (attributed mostly to clay minerals), and 0.5–2% iron oxide. The types of DE available are well-known to the person skilled in the art. Unless otherwise specified, the particle size properties referred to herein for all the described inorganic particulates herein are as measured by the method employed in the art of laser light scattering, using a CILAS 1064L particle size analyser, as supplied by CILAS (or by other methods which give essentially the same result). In the laser light scattering technique, the size of particles in powders, suspensions and emulsions may be measured using the diffraction of a laser beam, based on an application of Fraunhofer and Mie theory. Such a machine provides measurements and a plot of the cumulative percentage by volume of particles having a size, referred to in the art as the ‘equivalent spherical diameter’ (e.s.d), less than given e.s.d values. The mean particle size D50 is the value determined in this way of the particle e.s.d at which there are 50% by volume of the particles which have an equivalent spherical diameter less than that D50 value. According to the present disclosure, the DE particles have a D50from about 5 to about 60 microns, such as from about 15 to about 45 microns, or from about 20 to about 40 microns, or from about 25 to about 35 microns. In certain embodiments, the DE particles have a D50of about 35 microns. In certain embodiments, the DE particles have a bulk density from about 0.05 g / cm3to about 0.20 g / cm3, such as from about 0.06 g / cm3to about 0.19 g / cm3, such as from about 0.07 g / cm3to about 0.18 g / cm3, such as from about 0.08 g / cm3to about 0.17 g / cm3, such as from about 0.09 g / cm3to about 0.16 g / cm3, such as such as from about 0.10 g / cm3to about 0.15 g / cm3, such as from about 0.11 g / cm3to about 0.14 g / cm3, such as from about 0.12 g / cm3to about 0.13 g / cm3. The DE particles of the present disclosure may be calcined. By calcined, we mean that the DE particles are heated to a high temperature (typically in excess of 1300 °C) in a kiln, such as a rotary kiln. In certain embodiments, the DE particles are flux calcined. Flux calcined inorganic particles are processed and purified in a kiln in the same manner as calcined DE with the addition of a natural fluxing agent to further increase agglomeration. Due to its higher permeabilities, it can be used to remove impurities at very high filtration flow rates. Calcined and flux calcined materials are well-known and understood to the person skilled in the art. The other inorganic particulates described herein may also be calcined and flux calcined. The DE particles may be a commercially available diatomaceous earth product. For example, the at least one natural diatomaceous earth particles is Standard Super Cel®, Hyflo Super Cel® or Diactiv 11® material available from Imerys Performance Materials. Perlite typically contains the following components: silicon dioxide, aluminium oxide, sodium oxide, potassium oxide, iron oxide, magnesium oxide, calcium oxide, water and small amounts of other metallic elements. The perlite particles of the present disclosure may be in the form of expanded perlite. Typically, expanded perlite includes one or more cells, or parts of cells, in which a cell is a void space partially or entirely surrounded by walls of glass, usually formed from expansion of gases when the glass is in the softened state. Processes for expanding perlite may include heating perlite in air to a temperature of least about 700 °C, typically between 800 °C and 1100 °C, in an expansion furnace. Exemplary processes for producing expanded perlite are described in US 2006 / 0075930, the entire contents of which is hereby incorporated by reference. Expanded perlite typically has a bulk volume up to 20 times that of the unexpanded material. The perlite may also be milled after it has been expanded in the expansion furnace. According to the present disclosure, the milled expanded perlite particles have a D50 from about 10 to about 60 microns, such as from about 15 to about 45 microns, or from about 20 to about 40 microns, or from about 25 to about 35 microns. In certain embodiments, the milled expanded perlite particles have a D50 of about 15 microns. In particular, the milled expanded perlite particles have a bulk density from about 0.05 g / cm3to about 0.20 g / cm3, such as from about 0.06 g / cm3to about 0.19 g / cm3, such as from about 0.07 g / cm3to about 0.18 g / cm3, such as from about 0.08 g / cm3to about 0.17 g / cm3, such as from about 0.09 g / cm3to about 0.16 g / cm3, such as such as from about 0.10 g / cm3to about 0.15 g / cm3, such as from about 0.11 g / cm3to about 0.14 g / cm3, such as from about 0.12 g / cm3to about 0.13 g / cm3. In particular, the perlite product is obtained from a commercially available perlite product. In another embodiment, the at least one perlite product is a Harborlite® material available from Imerys Performance Materials or Europerl® available from Europerl GmbH. Kaolinite is a clay mineral derived from kaolin with the chemical composition Al2Si2O5(OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica ( SiO4) linked through oxygen atoms to one octahedral sheet of alumina (AlO6) octahedra. Rocks that are rich in kaolinite, and halloysite, are known as kaolin. Kaolin, or “china clay” as it is commonly called, is a hydrated aluminum silicate crystalline mineral formed over many millions of years by the hydrothermal decomposition of granite rocks. Hydrous kaolin is characterized by its fine particle size, plate-like or lamellar particle shape, and chemical inertness. Calcined Kaolin is an anhydrous aluminum silicate produced by heating ultrafine natural kaolin to high temperatures in a kiln. The calcination process increases whiteness and hardness and alters the size and shape of the kaolin particles. The kaolin D50 of the present disclosure may range from about 0.2 to about 5 micron. Bentonite is a very soft plastic clay consisting predominantly of montmorillonite, a fine particle-sized hydrous aluminum silicate and member of the smectite group. Most bentonites are formed by the alteration of volcanic ash and rocks after intense contact with water. The bentonite used for the present disclosure may have a D50 of from 2µm to 50µm. Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type, i.e., a soil containing more than 85 percent sand-sized particles by mass. The composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. Sand is often used to filter particulates from filtration solutions. The sand particles used for the present disclosure may have a D50 of from 50µm to 900µm. Silicoaluminophosphate molecular sieves (also knowns as SAPO’s) are inorganic particulates comprised of tetrahedron units of PO2+, AlO2- and SiO2arranged in a three- dimensional, microporous, molecular sieve. Such inorganic particulates are mainly composed of silicon, aluminium, phosphorus. SAPO’s are a special class of zeolites that, due to their acidic and shape-selective properties, play a major role in ion exchange and separation processes. The SAPO’s used for the present disclosure may have a D50 of from 0.5µm to 10µm. The above silicon-containing particulates are well-known to the skilled person. Therefore, the skilled person is aware of the various types of filter aid inorganic particulates and may select the type and size as appropriate for the filtration method of choice. For all of the inorganic particulates described herein, each material has a D100 no greater than 1000µm. Filter aid According to the present disclosure, there is provided a filter aid, wherein the filter aid comprises: a first composition comprising an inorganic particulate comprising silicon; and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. In some embodiments, the filter aid comprises a mixture of the first composition and the second composition. In some embodiments, the filter aid comprises a dry mixture or a wet mixture of the first composition and the second composition. In some embodiments, the first composition and the second composition are separate (e.g., not mixed). In some embodiments, the first composition is a substrate and the second composition is a coating on the substrate. In some embodiments, there is provided a filter aid, wherein the filter aid comprises: an inorganic particulate which comprises silicon; and a coating selected from: a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer or copolymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). In some embodiments, there is provided a filter aid which comprises an inorganic particulate which comprises silicon, and an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer. In some embodiments, there is provided a filter aid which comprises an inorganic particulate which comprises silicon, and an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer. In certain embodiments, the filter aid consists of an inorganic particulate which comprises silicon and a polymer coating as described herein. The filter aids of the present disclosure have a measured permeability greater than 300 millidarcy such as from greater than 300 to 1500 millidarcy. Permeability is a measure of rate of liquid flowing through a porous medium or a particulate filter cake. The following method of how to measure permeability is incorporated herein by reference: Tiller, F. M., and W. Li, Theory and Practice of Solid / Liquid Separation, Fourth Edition, 2002, University of Houston Tiller, F. M., Tutorial: Interpretation of Filtration Data, I, Fluid / Particle Separation Journal, Vol.3, 85- 94, 1990. This measurement technique is well-known to the skilled person. The filter aid composition may be formed into sheets, pads, cartridges, or other products which are used to perform the function of filtration. The filter aids of the present disclosure may be used in a variety of processes and compositions as well as in a variety of filtering methods. In certain embodiments, the filter aid material is applied to a filter septum to protect it and / or improve the clarity of the liquid to be filtered in a filtration process. The filter aid material of the disclosure may also be used in a variety of filtering methods. The filtering method may comprise pre-coating at least one filter element with the composition of the disclosure, and contacting at least one liquid to be filtered with the at least one coated filter element. In such an embodiment, the contacting may comprise passing the liquid through the filter aid material or a filter element comprising the filter aid material. The filtering method may further comprise suspending the filter aid material in at least one liquid containing particles to be removed from the liquid, and then separating the filter aid material from the filtered liquid. Filter aid materials comprising compositions of the present disclosure may also be employed to filter various types of liquids. The skilled person is readily aware of liquids that may be desirably filtered. In some embodiments, the liquid is a beverage. Exemplary beverages include, but are not limited to, vegetable-based juices, fruit juices, distilled spirits, and malt-based liquids. Exemplary malt-based liquids include, but are not limited to, beer and wine. In some embodiments, the liquid is one that tends to form haze upon chilling. In some embodiments, the liquid is a beverage that tends to form haze upon chilling. In some embodiments, the liquid is a beer. In some embodiments, the liquid is a hydrocarbon, including an oil. In some embodiments, the liquid is an edible oil. In some embodiments, the liquid is a fuel oil, such as biofuels. In some embodiments, the liquid is water, including but not limited to waste water. In some embodiments, the liquid is blood. In some embodiments, the liquid is a sake. In some embodiments, the liquid is a sweetener, such as for example corn syrup or molasses. In certain embodiments, the filter aid of the present disclosure is used in the extraction of unwanted particulates from a metal-containing solution such as a metal-containing brine, and the method of filtering removes unwanted particulates from the brine. The metal may be an alkaline earth metal such as lithium. The unwanted particulates may be salts such as calcium carbonate and magnesium carbonate. Polymer In some embodiments of the present disclosure, the filter aid comprises a substrate including a coating. The coating may partially or completely coat the inorganic particulate described herein. In some embodiments, the filter aid comprises a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. The organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer. The term “dicarboxylic acid” is used to describe an organic compound containing two carbonyl groups. The formula is HO2C-R-CO2H, where R can be aliphatic (saturated or unsaturated) or aromatic. Examples of suitable dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, 1,4- cyclohexanedicarboxylic acid, azelaic acid, decanedoic acid, undecanedoic acid and dodecanedioic acid. In particular, the dicarboxylic acid may be selected from itaconic acid, malonic acid, maleic acid, succinic acid, glutaric acid or adipic acid, or salts thereof. The dicarboxylic acid polymer may also comprise a copolymer. The co-polymer may comprise at least one of: a sulfonate group (SO3- · X+); or a phosphate group (PO3H - · X+); or a phosphonate group (PO3-2· X+); or a hydroxyl group (OH), or an ester linkage wherein X comprises NH4, Li, H, Na, Ca, K, or Mg. In some embodiments, an ester linkage may be included in an acetate, an acrylate, polymers of an acetate or an acrylate, or a combination thereof. In particular, the organic coating or the second composition comprises an itaconic acid monomer or is a polymer such as polyitaconic acid, or salt thereof (formed as shown in the diagram below). In particular, the organic coating or the second composition may comprise a co-polymer comprising itaconic acid and sulfonic acid. In particular, the sulfonic acid may be selected from styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid, or salts thereof (see the diagrams of formation below, respectively). In certain embodiments, the organic coating or the second composition comprises a polyitaconic acid copolymer such as those commercially available from the company Itaconix®. Examples of polyitaconic acid copolymers which may be used for the present disclosure include, but are not limited to: • Itaconix® CHT™ 121 (poly (itaconic co-styrene sulfonic acid, sodium salt) - referred to herein as Itaconix 121; • Itaconix® CHT™ 122 (poly(itaconic acid-co-2-acrylamido-2-methyl-1- propanesulfonic acid, sodium salt) – referred to herein as Itaconix 122; • Itaconix ® DSP 2K G (sodium polyitaconic acid, sodium salt) – referred to herein as Itaconix DSP 2K G. • Itaconix TSI 322 G (poly(itaconic acid-co-2-acrylamido-2-methyl-1- propanesulfonic acid, sodium salt) – referred to herein as Itaconix 322 G; Advantageously, the Itaconix® range is bio-based and environmentally safe. The organic coating or the second composition may be in the form of a powder or an aqueous solution. In certain embodiments, the polymer coating is an inorganic polymer coating which comprises a halogenated metallic polymer. The halogenated metallic polymer has a formula of either: Aln(OH)mCl(3n-m), wherein n ranges from 2 – 20; and m ranges from 4 – 20; OR Fen(OH)mCl(3n-m), wherein n ranges from 2 – 20; and m ranges from 4 – 20. The inorganic polymer may comprise polyaluminium chloride, polyiron chloride and mixtures thereof. Polyiron chloride is also known as polyferric chloride. In certain embodiments, the first composition comprises an inorganic particulate, which comprises or consists of DE (which may be calcined of flux calcined) or perlite (which may be expanded perlite and may be milled). In some embodiments, the filter aid comprises a mixture of the first composition and the second composition. In some embodiments, the filter aid comprises a dry mixture of the first composition and the second composition. In some embodiments, the filter aid comprises a wet mixture of the first composition and the second composition. In some embodiments, the first composition is a substrate, and the second composition is a coating on the first composition. In some embodiments, the inorganic particulate is coated with an organic polymer which comprises a polyitaconic acid copolymer. In certain embodiments, the inorganic particulate comprises or consists of DE (which may be calcined of flux calcined) or perlite (which may be expanded perlite) and the inorganic particulate is coated with an inorganic polymer which comprises a polyaluminium chloride or polyiron chloride. The present inventors have surprisingly found that the filter aid of the present disclosure comprising a first composition comprising an inorganic particulate comprising silicon and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer advantageously attenuates silicon solubility of the inorganic particulate when exposed to an aqueous solution. As one example, inorganic particulates which comprise silicon may leach silicon when they are present in an aqueous solution, such as a salt solution within a specific pH range of 2 to 12. Additionally, the present inventors have surprisingly found that the organic and inorganic coatings according to the present disclosure have an attenuating effect on silicon solubility from the inorganic particulate, which comprises silicon. Without being bound by theory, the inventors have found that the coating or polymer of the filter aids prepared according to the present disclosure may also chelate with the unwanted particulates (impurities present in the liquid to be filtered). The inorganic particulate itself may also additionally absorb further unwanted particulates. A method of preparing a filter aid comprising: In some embodiments of the present disclosure, there is provided a method of preparing a filter aid comprising: mixing a first composition comprising an inorganic particulate comprising silicon with a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. The first composition and the second composition may be mixed with or without water. Mixing the first composition and the second composition without water results in a “dry mixture” and mixing the first composition and the second composition with water results in a “wet mixture.” In some embodiments, there is provided a method of preparing a filter aid comprising coating an inorganic particulate with a coating, wherein the inorganic particulate comprises silicon; and wherein the coating is selected from: a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). To coat the inorganic particulate with the coating either a wet addition coating process or a dry addition coating process may be used. In the dry addition process, the dry components of the inorganic particulate and the coating as added together, water is added, and the components are mixed. Subsequent to the coating step, the coated product is dried in an oven at a temperature of from 70 to 100 °C. The dry product is then dispersed and sieved to restore the particle size distribution of the resulting filter aid. In the Examples prepared according to the present disclosure and described below, dry DE or dry perlite is combined with a dry Itaconix® product. Deionised water was then added to the dry mixture (in a ratio of from 0.5:1 or 1:1), and the wet mixture now thoroughly mixed to combine and to coat the inorganic particulate with the polymer coating. The sample was then dried in the oven at 90 °C for several hours. In the wet addition coating process, the dry inorganic particulate selected is blended in a container with a polymer coating already prepared in solution. The same method for the dry mixture as described above is followed, except that the Itaconix® product was provided as a solution and therefore the addition of water step is not required. A method of According to the present disclosure there is provided a method comprising contacting the first and second compositions as described herein with the desired liquid to be filtered (as described earlier) to filter unwanted particulates from the liquid to form a filtered liquid. In some embodiments, the first and second compositions can be added to the liquid either: i) simultaneously in the form of the filter aid as prepared and described herein (as a dry mixture or as a wet mixture or as a coated substrate wherein the first composition is a substrate and the second composition is a coating on the substrate) or ii) simultaneously and / or sequentially in any order of addition. The unwanted particulates may be fine particles or impurities. Unwanted particulates may include, but are not limited to salts, metals, oils and fatty acid esters. The filter aid, or the first composition itself, may also act as an absorbent and may absorb unwanted particulates. In certain embodiments, the liquid has a pH at or below 12, or at or below 11.5, or at or below 11, or at or below 10, or from 2 to about 12, or from 2 to about 11.5, or from 2 to about 11, or from 2 to about 10, or at or below 9.8 or at or below 9.7 or at or below 9.5; and wherein the contacting is at a temperature of from 50°C to 100°C or at least 50°C or at least 60°C or at least 65°C or at least 70°C. A method of preventing or reducing silicon leaching from a filter aid into an aqueous solution during filtration In some embodiments of the present disclosure, there is provided a method of preventing or reducing silicon leaching from a filter aid into a liquid during filtration, the method comprising: mixing a first composition with a second composition to form the filter aid and filtering the liquid with the filter aid to form a filtered liquid, wherein the first composition comprises an inorganic particulate comprising silicon, and wherein the second composition comprises a dicarboxyliac acid or a dicarboxylic acid polymer. In some embodiments of the present disclosure, there is provided a method of preventing or reducing silicon leaching from a filter aid into a liquid during filtration, the method comprising: contacting the first and second compositions as described herein with the liquid to be filtered to filter unwanted particulates from the liquid to form a filtered liquid. In some embodiments, the first and second compositions can be added to the liquid either: i) simultaneously in the form of the filter aid as prepared and described herein (as a dry mixture or as a wet mixture or as a coated substrate wherein the first composition is a substrate and the second composition is a coating on the substrate) or ii) simultaneously and / or sequentially in any order of addition. The unwanted particulates may be fine particles or impurities. Unwanted particulates may include, but are not limited to salts, metals, oils and fatty acid esters. The filter aid, or the first composition itself, may also act as an absorbent and may absorb unwanted particulates. In some embodiments, there is provided a method comprising coating an inorganic particulate with a coating to form the filter aid and filtering the liquid with the filter aid to form a filtered liquid, wherein the inorganic particulate comprises silicon; and wherein the coating is selected from: a) an organic coating, wherein the organic coating comprises (i) a dicarboxylic acid; or (ii) a dicarboxylic acid polymer; b) an inorganic polymer coating, wherein the inorganic polymer coating comprises a halogenated metallic polymer; and c) combinations of (a) and (b). In certain embodiments, the liquid is an aqueous solution. In other embodiments, the liquid is an oil. The skilled person is readily aware of liquids that may be desirably filtered with a process comprising the filter aids and may include, but is not limited to, beverages, oils, fuel oils such a biofuels, water, or blood. In some embodiments, the aqueous solution is a metal-containing solution such as an alkaline earth metal brine. Conventional mining for metal practices utilise ancient volcanic systems, where magmatic activity has long since ceased and brines have deposited their metal load as solid ores. These ore bodies can be extracted in giant open or underground pits. An alternative method involves directly mining brines from hot magmatic rocks, such as those beneath dormant volcanic systems or above young granite intrusions. So-called “brine mining” extracts metals from a concentrated solution, rather than solid rock. Typical hydrometallurgy and chemical processing is used to extract the metals from the rocks or brine. Often, salts such as magnesium carbonate and calcium carbonate are used in precipitation and ion exchange reactions to force the metal to crystalise in a desirable form. An example of this is in lithium mining in which magnesium carbonate and calcium carbonate salts are added to the lithium brine to precipitate the desired salt, but then are subsequently removed by filtration using filter aids. In certain embodiments, the filter aids according to the present disclosure are used in such metal extractions methods to filter the unwanted particulates such as the salts described above. After filtering using the filter aids of the present disclosure, the resulting alkaline earth metal brine was found to have a concentration of less than 10 ppm silicon, for example, less than 5 ppm silicon. In certain embodiments, the alkaline earth metal brine is lithium brine. It will be understood that the present disclosure is not limited to the embodiments described above and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein. EXAMPLES The following examples describe the preparation of filter aids which comprise inorganic particulates which are coated with various coatings or filter aids which comprise a first composition of an inorganic particulate and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer. Various combinations of inorganic particulate and polymer coating and the first composition and the second composition were prepared and tested according to the procedures set out below. Filter aid preparation method 1: 100 g of each dry inorganic particulate (Inorganic Particulate Materials 1-4) from Table 1 was blended with the dry polymers in Table 2, in dry form. In the examples below, the polymer (coating) is described as being present in amounts from 0.5% to 3% wt%. This indicates that the coating was present in an amount of from 0.5 to 3 g of coating per 100g of the inorganic particulate. Deionised water was added in 0.5:1 ratio to the dry blend and mixed. The sample was dried in the oven at 90°C for 3 hours and screened through a 60M sieve. Resulting coated filter aid products (“Coated Products”) are listed in Table 5. Filter aid preparation method 2: 100g of each dry inorganic particulate (Inorganic Particulate Materials 1-4) from Table 1 was blended with various polymers from Table 2 (0.5 to 3g per 100 g of inorganic particulate) prepared as an aqueous solution. The sample was then dried in the oven at 90°C for 3 hours and screened through a 60M sieve. Resulting Products are listed in Table 5. Filter aid preparation method 3: 100g of each dry inorganic particulate (Inorganic Particulate Materials 1-4) from Table 1 was blended with various polymers (Itaconix materials) from Table 2 (0.5 to 3g per 100g of inorganic particulate). The blend was prepared as a dry blend or a wet blend. For the dry blend or the wet blend, the sample was mechanically blended for 15 minutes in an appropriate blending receptacle (e.g., plastic jar or kitchen aid). Resulting filter aid products (“Dry or Wet Products”) are listed in Table 6. Filter aid preparation method 4: Dry inorganic particulates (Inorganic Particulate Materials 1-4) from Table 1 and various polymers (Itaconix materials) from Table 2 are measured separately to a total of 100g of powder. The inorganic particulates and Itaconix materials are not blended and added either simultaneously or sequentially, as described below. Table 1: Inorganic Particulate Material Table 2: Chemistry of the inventive and comparative polymers NaCl medium 3g of each type of prepared filter aid products as described above was stirred in 100mL of 1M NaCl (Medium 5, as described in Table 3) at 65 °C for 1 hour and then filtered using disposable plastic 0.45-micron Fisher brand units. Filtrates were diluted 50:1 with high purity water, acidified and analyzed for soluble Si on Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). 3g of Products A, F, and GG were each tested as above at varying pH values. Results of such tests are shown in Tables 4 and 7 below. Additionally, 3g of Products A, GG, HH, JJ, and KK were each tested as above in Medium 5 but at a neutral pH and also separately as above in Medium 5 but at a pH of 9.8. Results for such tests are shown in Tables 8 and 9 below. For Product HH, the inorganic particulate material and Itaconix material were not blended, measured separately, and simultaneously added to Medium 5. For Product JJ, the inorganic particulate material and Itaconix material were measured separately and not blended. The inorganic particulate material was added to Medium 5 first, stirred for one minute, and then the Itaconix material was added to Medium 5. For Product KK, the inorganic particulate material and Itaconix material were measured separately and not blended. The Itaconix material was added to Medium 5 first, stirred for one minute, and then the inorganic particulate material was added to Medium 5. For Product LL, the inorganic particulate material was mechanically blended with a copolymer solution of acrylic acid and itaconic acid to form a wet mixture. Product LL was added to Medium 5 and tested as described above. Results for such test are shown in Table 10 below. Lithium brine surrogate / Potassium hydrogen phthalate medium 3g of each type of prepared filter aid products as described above was stirred in 100 mL of Li brine surrogate salts (Mediums 1-4 and 7, as described in Table 3) at 65°C for 1 hour and then filtered using disposable plastic 0.45-micron Fisher brand units. Filtrates were diluted 50:1 with high purity water, acidified and analyzed for soluble Si on ICP- OES.5g of various Products prepared as described above was stirred in 200 mL of 1% potassium hydrogen phthalate (Medium 6 described in Table 3) for 2 hours at room temperature. Extracts were filtered using disposable plastic 0.45-micron Fisher brand units. Filtrates were analyzed for soluble Si on ICP-OES. Results of such tests are shown in Table 11 below. Table 3 *variable = pH values are given in the Table 4 “Solubility of silicon in 1 M NaCl at different pH” below Table 4: Solubility of silicon in Medium 5 (1 M NaCl ) at different pH Table 5: List of Coated Products Table 6: List of Dry and Wet Products (blended or separately added) Table 7: Solubility of silicon in Medium 5 (2M NaCl ) at different pH Table 8: Solubility of silicon in Medium 5 (2M NaCl ) at neutral pH Table 10: Solubility of silicon in Medium 5 (2M NaCl) at neutral pH TABLE 11: Results for Medium 1 to 4, 6, and 7. Solid bars indicate product below is a comparative example. The results in the Table 11 demonstrate that the filter aids prepared in accordance with the present disclosure showed a significant reduction in the percentage of soluble silicon, compared to the comparative examples (e.g., Products A, S, U, and X).

Claims

CLAIMS 1. A filter aid, comprising: a first composition comprising an inorganic particulate comprising silicon; and a second composition comprising a dicarboxylic acid or a dicarboxylic acid polymer.

2. The filter aid of claim 1, wherein the dicarboxylic acid is selected from itaconic acid, malonic acid, maleic acid, succinic acid, glutaric acid, or adipic acid.

3. The filter aid of claim 1 or 2, wherein the dicarboxylic acid polymer comprises a copolymer.

4. The filter aid of claim 3, wherein the copolymer comprises at least one of: asulfonate group (SO3-· X+); ora phosphate group (PO3H- · X+); or a phosphonate group (PO3-2· X+); or a hydroxyl group (OH); or an ester linkage; wherein X comprises NH4, Li, H, Na, Ca, K, or Mg.

5. The filter aid of any one of claims 1 to 4, wherein the second composition comprises itaconic acid, itaconic acid polymer, or itaconic acid copolymer.

6. The filter aid of any one of claims 1 to 5, wherein the second composition comprises a copolymer comprising itaconic acid and sulfonic acid.

7. The filter aid of claim 6, wherein the sulfonic acid is selected from 2- acrylamido-2-methylpropane sulfonic acid and styrene sulfonic acid.

8. The filter aid of any one of claims 1 to 7, wherein the inorganic particulate comprises diatomaceous earth, perlite, expanded perlite, expanded milled perlite, sand, bentonite, silica gel, kaolinite, zeolite, silicoaluminophosphate molecular sieves, or a mixture thereof.

9. The filter aid of claim 8, wherein the inorganic particulate is a calcined diatomaceous earth or flux calcined diatomaceous earth.

10. The filter aid of any one of claims 1 to 9, wherein the filter aid comprises a mixture of the first composition and the second composition.

11. The filter aid of claim 10, wherein the mixture of the first composition and the second composition is a dry mixture.

12. The filter aid of claim 10, wherein the mixture of the first composition and the second composition is a wet mixture.

13. The filter aid of any one of claims 1 to 9, wherein the first composition is a substrate, and the second composition is a coating on the first composition.

14. The filter aid of any one of claims 1 to 13, wherein the permeability of the filter aid, as measured as set out in the description, is greater than 300 millidarcy.

15. A use of the filter aid to filter a liquid, the use comprising: contacting the filter aid of any one of claims 1-14 with the liquid to filter unwanted particulates from the liquid to form a filtered liquid.

16. The use of claim 15, wherein the first and second compositions of the filter aid are added to the liquid either: i) simultaneously in the form of a mixture of the first and second compositions, or ii) simultaneously and / or sequentially in any order of addition 17. The use of claim 15, wherein the first and second compositions are added to the liquid in the form of the filter aid comprising a dry mixture or a wet mixture of the first and second compositions.

18. The use of claim 15, wherein the filter aid is a coated substrate wherein the first composition is a substrate and the second composition is a coating on the substrate.

19. The use of any one of claims 15 to 18, wherein the aqueous solution has a pH at or below 12, or at or below 11.5, or at or below 11, or at or below 10, or from 2 to about 12, or from 2 to about 11.5, or from 2 to about 11, or from 2 to about 10, or at or below 9.8 or at or below 9.7 or at or below 9.5; and wherein the liquid is at a temperature from 50°C to 100°C, at least 50°C, at least 60°C, at least 65°C, or at least 70°C.

20. The use of any one of claims 15 to 19, wherein the liquid is a metal-containing brine and the method of filtering removes unwanted particulates from the brine.

21. The use of claim 20, wherein the metal-containing brine is lithium brine.

22. A use of a filter aid to prevent or reduce silicon leaching into a liquid during filtration, the use comprising: mixing a first composition with a second composition to form the filter aid and filtering the liquid with the filter aid to form a filtered liquid, wherein the first composition comprises an inorganic particulate comprising silicon, and wherein the second composition comprises a dicarboxylic acid or a dicarboxylic acid polymer.

23. The use of claim 22, wherein the filtered liquid has a concentration of less than 10 ppm silicon, for example, less than 5 ppm silicon.

24. A use of a first composition a second composition comprising to prepare a filter aid, the use comprising: mixing the first composition with the second composition, wherein the first composition comprises an inorganic particulate comprising silicon and the second composition comprises a dicarboxylic acid or a dicarboxylic acid polymer.

25. A method of filtering a liquid, the method comprising: contacting the filter aid of claims 1 - 14 with the liquid to filter unwanted particulates from the liquid to form a filtered liquid.

26. The method of claim 25, wherein the first and second compositions of the filter aid are added to the liquid either: i) simultaneously in the form of a mixture of thefirst and second compositions, or ii) simultaneously and / or sequentially in any order of addition 27. The method of claim 25, wherein the first and second compositions are added to the liquid in the form of the filter aid comprising a dry mixture or a wet mixture of the first and second compositions.

28. The method of claim 25, wherein the filter aid is a coated substrate wherein the first composition is a substrate, and the second composition is a coating on the substrate.

29. The method of any one of claims 25 to 28, wherein the aqueous solution has a pH at or below 12, or at or below 11.5, or at or below 11, or at or below 10, or from 2 to about 12, or from 2 to about 11.5, or from 2 to about 11, or from 2 to about 10, or at or below 9.8 or at or below 9.7 or at or below 9.5; and wherein the liquid is at a temperature from 50°C to 100°C, at least 50°C, at least 60°C, at least 65°C, or at least 70°C.

30. The method of any one of claims 25 to 29, wherein the liquid is a metal- containing brine, and the method of filtering removes unwanted particulates from the brine.

31. The method of any one of claims 25 to 30, wherein the metal-containing brine is lithium brine.

32. A method of preventing or reducing silicon leaching from a filter aid into a liquid during filtration, the method comprising: mixing a first composition with a second composition to form the filter aid and filtering the liquid with the filter aid to form a filtered liquid, wherein the first composition comprises an inorganic particulate comprising silicon, and wherein the second composition comprises a dicarboxylic acid or a dicarboxylic acid polymer.

33. The method of claim 32, wherein the filtered liquid has a concentration of less than 10 ppm silicon.

34. A method of preparing a filter aid comprising: mixing a first composition comprising an inorganic particulate comprising silicon with a second composition, wherein the second composition comprises a dicarboxylic acid or a dicarboxylic acid polymer.

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