CN116615276A

CN116615276A - Filter medium

Info

Publication number: CN116615276A
Application number: CN202180085471.5A
Authority: CN
Inventors: 克里斯汀·勒马森; 克里斯托弗·塞隆; 拉尔·西蒙
Original assignee: Ahlstrom Corp
Current assignee: Ahlstrom Corp
Priority date: 2020-12-18
Filing date: 2021-12-17
Publication date: 2023-08-18

Abstract

Filter media suitable for filtering fluids are provided. The filter medium comprises filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ The content is as follows.

Description

Filter medium

Technical Field

The present invention relates to a filter medium, and more particularly to a filter medium useful for filtering contaminants such as heavy metals from a fluid such as water.

Introduction to the invention

Heavy metals are naturally occurring metallic elements that have relatively high atomic weights and densities compared to water. Heavy metals have been widely distributed in the environment and thus pose a health threat to humans due to their industrial, domestic, agricultural, medical and technical uses. The toxicity of heavy metals depends on many factors, including the level of contact, the nature of the metal species, and the manner of contact. Metals that pose the greatest risk to public health due to their toxicity are lead, arsenic, cadmium, chromium and mercury.

The presence of heavy metals in drinking water is strictly controlled due to their adverse effects on human health. For example, the maximum allowable concentration of lead in drinking water is 5. Mu.g/L, arsenic is 10. Mu.g/L, cadmium is 5. Mu.g/L, and mercury is 2. Mu.g/L.

Lead is one of the most common heavy metal contaminants in drinking water. The lead pollution source comprises a lead water pipe, a water tank, a pipeline device and a pipe fitting. Exposure to lead can have many negative effects on health, affecting the nervous, reproductive and renal systems, leading to hypertension and anemia, and at very high concentrations leading to death.

Heavy metal impurities are present in both soluble and particulate form in fluids such as water. Most current fluid filtration systems are designed to retain only particulates because they have only a mechanical retention mechanism. However, removal of soluble heavy metals requires that the filter media chemically or electrostatically interact with the dissolved metal particles to retain them.

Current filtration schemes capable of trapping soluble heavy metals such as lead typically include a bulk absorbent material. However, the large amount of absorbent material required in these systems can make them expensive. These systems also have reduced flow rates because the fluid must pass through large volumes of filter material and are generally unable to remove soluble heavy metals to levels recommended by regulatory bodies such as National Sanitation Foundation (NSF) and water quality institute (WQA). Furthermore, current filtration systems are unable to retain particulate and soluble heavy metals within regulatory limits.

Thus, there is a need for new filter media capable of removing particulate and dissolved heavy metal contaminants such as lead from fluids such as water.

Disclosure of Invention

According to a first aspect of the present invention there is provided a filter medium comprising filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ The content is as follows.

According to another aspect of the present invention, there is provided a filter medium comprising filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ Content, wherein the filter particles comprise at least 5 wt% Na ₂ O。

Filtering particulate Al ₂ O ₃ The content may be 20 to 45 wt%, preferably 30 to 40 wt%.

Filtering the SiO of the particles ₂ The content may be less than 60 wt%, preferably less than 50 wt%.

The filter particles may comprise at least 5 wt%, preferably at least 10 wt%, most preferably at least 15 wt% Na ₂ O。

The silica-alumina mass ratio (Si/Al) of the filter particles may be 0.6 to 4, preferably 0.7 to 3.5, more preferably 0.8 to 1.5.

The sodium to silicon mass ratio (Na/Si) of the filter particles may be 0.1 to 0.9, preferably 0.4 to 0.7, more preferably 0.5 to 0.6.

The sodium to aluminium mass ratio (Na/Al) of the filter particles may be from 0.1 to 2, preferably from 0.3 to 1.5, more preferably from 0.5 to 1.2.

The filter particles may be alkali treated filter particles.

The filter particles may comprise pores having a diameter of 0.1 to 1.0nm, preferably 0.3 to 0.7 nm.

The filter particles may also comprise one or more additional components selected from titanium-containing components (such as TiO ₂ ) A phosphorus-containing component (such as P ₂ O ₅ ) Sulfur-containing components (such as SO ₃ ) Potassium-containing components (such as K ₂ O), calcium-containing components (such as CaO), iron-containing components (such as FeO, feO ₂ Or Fe (Fe) ₂ O ₃ ) A strontium-containing component (such as SrO), an yttrium-containing component (such as Y) ₂ O ₃ ) And zirconium-containing components (such as ZrO ₂ ). The additional components may be located within the zeolite framework, in which case they are not in the oxide form. For example, a titanosilicate zeolite is a zeolite having a titanium-containing component located within the zeolite framework.

The filter particles may comprise 5 to 70 wt%, preferably 10 to 50 wt%, most preferably 20 to 40 wt%, of the total weight of the filter medium.

The filter media may further comprise matrix fibers selected from one or more of cellulose fibers, polymer fibers, glass fibers and fibrillated fibers, preferably cellulose fibers and/or glass fibers.

Fibrillated fibers are generally synthetic or cellulosic fibers that have been mechanically treated to produce fibrils. When present, fibrillated cellulose fibers are counted as cellulose fibers, whereas fibrillated synthetic fibers are counted as synthetic fibers.

The cellulose fibers may be selected from one or more of softwood fibers, hardwood fibers, plant fibers, and regenerated cellulose fibers (also known as man-made cellulose fibers, such as Lyocell fibers or viscose (Rayon) fibers). The cellulose fibers may be present in an amount of 5 to 100% by weight, more preferably 10 to 70%. For example, in some embodiments 7 to 20 wt% or in other embodiments 50 to 70 wt% based on the total weight of the matrix fibers. The cellulose fibers may preferably be regenerated cellulose fibers.

The glass fibers may be present in an amount of 5 to 100 wt%, more preferably 10 to 70 wt%. For example, in some embodiments 7 to 20 wt% or in other embodiments 50 to 70 wt% based on the total weight of the matrix fibers.

The polymer fibers may be polyester fibers and may be present in an amount of 1 to 30 wt%, preferably 5 to 30 wt%, based on the total weight of the filter medium. The polyester fibers may be bio-polyester fibers, which may be biodegradable or even compostable according to EN1334 standard.

The filter media may comprise a mixture of cellulosic fibers and synthetic fibers. The synthetic fibers may be oil-based (such as polyolefin) or vegetable-based synthetic fibers.

The matrix fibers may be at least partially coated with nano-alumina and the filter particles may be substantially uncoated with nano-alumina.

The filter media may be a nonwoven filter media. The nonwoven filter media can be corrugated, cut, folded, pleated, and assembled into a final filtration product for use.

The filter media may further comprise one or more additives selected from the group consisting of a resin component, preferably a polyamide epichlorohydrin (PAE) resin, a binder, preferably comprising latex, activated carbon and/or silver particles.

The filter media may be configured for home fluid filtration.

The filter media may be configured for industrial fluid filtration.

The filter medium may be a water filter medium. The pH of the water may be 5 to 9, preferably 6.5 to 8.

The filter media may conform to NSF/ANSI53 (version 2019): drinking water treatment device-health impact standard.

In some embodiments, a glass-free medium may be desired. In such embodiments, the filter media may comprise less than 1% by weight glass fibers, preferably less than 0.1% by weight glass fibers.

The filter media may be configured to act as a prefilter for the second filter media. The second filter media may comprise fibers coated with nano-alumina.

According to a second aspect of the present invention there is provided a method of manufacturing a filter medium as defined above, the method comprising:

(a) Contacting the filter particles with an alkaline solution, the filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ The content is as follows;

(b) Forming a wet laid sheet from a fibrous slurry comprising filter particles; and

(c) The sheet is dried to obtain a filter medium.

According to another aspect of the present invention there is provided a method of manufacturing a filter medium as defined above, the method comprising:

(a) Contacting the filter particles with an alkaline solution, the filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ And comprises at least 5% by weight of Na ₂ O；

(c) The sheet is dried to obtain a filter medium.

The contact step can reduce SiO of the filtered particles ₂ The content is preferably reduced to below 70% by weight.

Step (a) and step (b) may be performed simultaneously.

Step (a) may be performed before step (b).

The pH of the alkaline solution may be between 8 and 14, preferably between 9 and 11, most preferably 10.

The fiber slurry may comprise matrix fibers and/or one or more additives as defined above.

The method may include at least partially coating the filter particles and the matrix fibers with nano-alumina. The method may include:

(a1) Contacting the matrix fibers and/or binder fibers with nano-alumina to at least partially coat the matrix fibers and/or binder fibers; and

(a2) The at least partially coated fibers are combined with filter particles and an alkaline solution to form a fiber slurry.

According to a third aspect of the present invention there is provided a method of filtering a fluid, the method comprising passing the fluid through a filter medium as defined above.

The fluid may be water, preferably potable water.

According to a fourth aspect of the present invention there is provided a method of removing heavy metals from a fluid, the method comprising passing the fluid through a filter medium as defined above.

The heavy metal may be selected from arsenic, antimony, cadmium, cobalt, copper, iron, lead and lead oxide, mercury, nickel, palladium, selenium, silver, thallium, tin and organotin, and zinc, preferably lead. The heavy metals may be in soluble and/or particulate form.

The invention will be better understood from the following examples, given by way of illustration and not to be interpreted in a limiting manner, and the accompanying drawings.

Drawings

In the drawings:

FIG. 1 is a graph illustrating the effect of pH on lead retention during formation of a filter medium;

FIG. 2 is a graph illustrating the relative ability of a nano-alumina coated glass fiber filter media ("4603") to filter lead from a fluid with the filter media of the present disclosure ("19P 64");

FIG. 3 is a graph illustrating the lead filtration capacity of two filter media prepared according to the present disclosure, wherein each filter media comprises a different aluminosilicate zeolite ("SZT" or "SZP") as the filter particles; and

fig. 4 is a graph illustrating the lead filtration capacity of two filter media prepared according to the present disclosure, wherein each filter media comprises a different aluminosilicate zeolite ("SZT" or "Alusil") as the filter particles.

Detailed Description

As used herein and in the appended claims, the following terms are intended to have the following definitions unless the content requires otherwise.

Variations such as "comprises" or "comprising" are to be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

"nanometer alumina" refers to aluminum hydroxide oxide [ AlO (OH) ]And aluminum hydroxide [ Al (OH) ₃ ]Obtained by reacting aluminum metal with an aqueous alkaline solution such as NaOH, KOH or ammonium hydroxide.

"fiber" is a high aspect ratio fiber or filament structure having a length to diameter.

The "mass ratio" of the two components a and B relative to each other can be expressed in the form: component a/component B. This refers to the ratio of the weight of component a to the weight of component B. Component a and component B may be elemental (such as Al, si, na, etc.) or chemical species (such as Al ₂ O ₃ 、SiO ₂ 、Na ₂ O, etc.). The mass ratio can be converted to a molar ratio by dividing the mass of the components by the molecular weight of the components.

Similarly, the "molar ratio" of the two components a and B relative to each other can be expressed in the form: component a/component B. This refers to the ratio of the number of moles of component a to the number of moles of component B. Component a and component B may be elemental (such as Al, si, na, etc.) or chemical species (such as Al ₂ O ₃ 、SiO ₂ 、Na ₂ O, etc.). The molar ratio can be converted to a mass ratio by multiplying the molecular weight of the components by the number of moles of the components.

The prior art rarely explains whether the reported ratio is a mass ratio of a substance (e.g., a mass ratio of alumina to silica) or a molar ratio of a specific element in a substance (e.g., a molar ratio of aluminum atoms to silicon atoms). The lack of a specific explanation presents the ratio in an ambiguous and ambiguous manner, making it difficult for a skilled artisan to certainly appreciate the teachings of the prior art. As used throughout this disclosure, the mass and molar ratios of the two components of the filter particles or filter media, as the case may be, will be understood in light of the above definitions.

"staple fibers" refers to fibers that naturally have or have been cut or further processed into definite, relatively short segments or individual lengths.

"fibrous" refers to a material consisting essentially of fibers and/or staple fibers.

The term "nonwoven" or "web" refers to a collection of fibers and/or staple fibers in the form of a web or mat that are randomly interlocked, entangled, and/or bonded to one another to form a self-supporting structural element.

"synthetic fibers" refers to fibers made from fiber forming materials including polymers synthesized from chemical compounds, modified or converted natural polymers, and siliceous (glass) materials. Such fibers may be produced by conventional melt spinning, solution spinning, solvent spinning, and similar filament production techniques.

The present disclosure provides filter media suitable for use in a variety of industrial and domestic fluid purification applications. The filter media are particularly useful for removing impurities such as heavy metals (e.g., arsenic, antimony, cadmium, cobalt, copper, iron, lead and lead oxides, mercury, nickel, palladium, selenium, silver, thallium, tin and organotin, and zinc), dyes, oils, biological materials (e.g., bacteria, viruses, natural organic substances, vesicles and cell debris), and trace amounts of drugs from fluids such as water.

The filter medium comprises filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ The content is as follows. Filtering particulate Al ₂ O ₃ The amount may be 20 wt% to 65 wt%, 20 wt% to 60 wt%, 20 wt% to 55 wt%, 20 wt% to 50 wt%, 20 wt% to 45 wt%, 20 wt% to 40 wt%, 25 wt% to 65 wt%, 25 wt% to 60 wt%, 25 wt% to 55 wt%, 25 wt% to 50 wt%, 25 wt% to 45 wt%, 25 wt% to 40 wt%, 30 wt% to 65 wt%, 30 wt% to 60 wt%, 30 wt% to 55 wt%, 30 wt% to 50 wt%, 30 wt% to 45 wt%, 30 wt% to 40 wt%, 35 wt% to 65 wt%, 35 wt% to 60 wt%, 35 wt% to 55 wt%, 35 wt% to 50 wt%, 35 wt% to 45 wt%, or 35 wt% to 40 wt%. Filtering the SiO of the particles ₂ The content may be less than 70 wt%, 65 wt%, 60 wt%, 55 wt%, 50 wt%, 45 wt%, 40 wt% or 35 wt%, preferably less than 50 wt%. Filtering the SiO of the particles ₂ The content may be 10 to 65 wt%, 10 to 60 wt%, 10 to 55 wt%, 10 to 50 wt%, 10 to 45 wt%, 10 to 40 wt%, 10 to 35 wtFrom 10% to 30%, from 10% to 25%, from 10% to 20%, from 15% to 65%, from 15% to 60%, from 15% to 55%, from 15% to 50%, from 15% to 45%, from 15% to 40%, from 15% to 35%, from 15% to 30%, from 15% to 25%, from 15% to 20%, from 20% to 65%, from 20% to 60%, from 20% to 55%, from 20% to 50%, from 20% to 45%, from 20% to 40%, from 20% to 35%, from 25% to 65%, from 25% to 60%, from 25% to 55%, from 15% to 25%, from 15% to 20%, from 20% to 65%, from 20% to 40%, from 20% to 35%, from 25% to 65%, from 25% to 55%, from 25 to 50 wt%, 25 to 45 wt%, 25 to 40 wt%, 25 to 35 wt%, 25 to 30 wt%, 30 to 65 wt%, 30 to 60 wt%, 30 to 55 wt%, 30 to 50 wt%, 30 to 45 wt%, 30 to 40 wt%, 30 to 35 wt%, 35 to 65 wt%, 35 to 60 wt%, 35 to 55 wt%, 35 to 50 wt%, 35 to 45 wt%, 40 to 65 wt%, 40 to 60 wt%, or 40 to 45% by weight. The mass ratio of silicon to aluminum (Si/Al) in the filter particles may be 0.7 to 4.0, 0.7 to 3.5, 0.7 to 3.0, 0.7 to 2.5, 0.7 to 2.0, 0.7 to 1.5, 0.8 to 4.0, 0.8 to 3.5, 0.8 to 3.0, 0.8 to 2.5, 0.8 to 2.0, 0.8 to 1.5, 0.9 to 4.0, 0.9 to 3.5, 0.9 to 3.0, 0.9 to 2.5, 0.9 to 2.0, or 0.9 to 1.5.

The filter particles are capable of binding soluble heavy metal cations in a fluid such as water and entrap particulate metal particles when the filter particles are incorporated into the filter medium. It has been found that the above amounts of Al ₂ O ₃ And SiO ₂ The performance of the filter particles is enhanced by optimizing the degree of electrostatic attraction between the filter particles and impurities (such as heavy metals) in a fluid such as water during filtration. Without wishing to be bound by theory, it is believed that filtering the particular Si/Al in the particlesThe mass ratio produces a more concentrated negative charge concentration within the filter particles than particles with a higher Si content. This is because the aluminum sites in the filter particles are negatively charged, while the silicon sites remain neutral. By having a higher proportion of negatively charged sites, the negative charge concentration is higher, which results in a greater number of exchangeable cations (such as Na ⁺ Ions) and enhances the ability to bind positively charged soluble heavy metal cations, such as lead cations.

The filter particles may comprise at least 5 wt%, 10 wt%, 15 wt% or 20 wt%, preferably at least 15 wt% Na ₂ O. The filter particles may comprise 5 to 40 wt% Na ₂ O, preferably 10 to 30 wt% Na ₂ O, more preferably 15 to 25% by weight of Na ₂ O. The mass ratio of Na/Si in the filter particles may be 0.1 to 0.9, 0.2 to 0.8, 0.3 to 0.8, 0.4 to 0.7 or 0.5 to 0.6. The mass ratio of sodium to aluminum (Na/Al) of the filter particles may be 0.1 to 2.0, 0.2 to 1.5, 0.3 to 1.5, 0.4 to 1.5, 0.5 to 1.2, more preferably 0.6 to 0.9. These ratios provide for the exchange of Na in the filter particles ⁺ Indication of the proportion of cations.

The filter particles may be alkali treated filter particles. The base may be selected from NaOH, KOH, ba (OH) ₂ 、Ca(OH) ₂ LiOH and NH ₄ One or more of OH. The filter particles may be treated with an alkaline solution having a pH of 8 to 14, preferably 9 to 11, or more preferably about pH 10. The alkaline solution may, for example, alter at least the outer surface of the filter particles by altering the Si, al or Na content of the filter particles. In some embodiments, the alkaline solution may reduce the silicon content of the outer surface of the filter particles.

The filter particles may also comprise one or more additional components selected from titanium-containing components (such as TiO ₂ ) A phosphorus-containing component (such as P ₂ O ₅ ) Sulfur-containing components (such as SO ₃ ) Potassium-containing components (such as K ₂ O), calcium-containing components (such as CaO), iron-containing components (such as FeO, feO ₂ Or Fe (Fe) ₂ O ₃ ) A strontium-containing component (such as SrO), an yttrium-containing component (such as Y) ₂ O ₃ ) And zirconium-containing components (such as ZrO ₂ ). Additional components may beLocated within the zeolite framework, in which case they are not in the oxide form. For example, a titanosilicate zeolite is a zeolite having a titanium-containing component located within the zeolite framework.

The filter media may include pores through which fluid may pass during filtration. The pores may have a diameter of 0.5 to 10 μm, 0.6 to 5 μm or 0.7 to 4 μm. The average pore size of the pores may be 0.8 to 3 μm, preferably 1.2 to 2.0 μm. Pore size is measured in accordance with American Society for Testing and Materials (ASTM) standard 316-03 (2011) using capillary flow porosimetry techniques.

The average flow pore size (mean flow pore size) of the filter media can be less than 3 μm, preferably less than 2.5 μm, more preferably equal to or less than 2 μm.

The gravity flow of the filter media may be less than 200s/500mL and preferably less than 150s/500mL.

The filter media may have a wet MD tensile strength of at least 3lb/in, preferably at least 5lb/in and most preferably at least 10lb/in.

According to NSF/ANSI53 standard (2019), for at least 2000L/m ² When challenged with water containing 150ppb lead, the filter media can maintain soluble lead levels in the effluent at no more than 10ppb.

According to NSF/ANSI53 standard (2019), for at least 2000L/m ² Or even 5000L/m ² When challenged with water containing 150ppb lead, the filter media can maintain soluble lead levels in the effluent at no more than 5ppb.

The filter particles may have pores or channels in which exchangeable cations may be located. In some embodiments, the pores or channels may have a diameter of 0.1 to 1.0nm, preferably 0.3 to 0.7nm. The pores may act as molecular sieves to selectively screen molecules or atoms according to size and exchangeable cations. The pores may have negative internal polarity and high cation exchange affinity for dissolved heavy metals such as arsenic, antimony, cadmium, cobalt, copper, iron, lead and lead oxides, mercury, nickel, palladium, selenium, silver, thallium, tin and organotin, or zinc.

The surface area of the filter particles, as determined by the Brunauer-Emmett-Teller (BET) method, may be 300 to 900m ² /g, preferably 400 to 700m ² /g, most preferably about 600m ² And/g. This may provide sufficient surface for ion exchange and may increase the efficiency of the filter particles in trapping heavy metals.

The Cation Exchange Capacity (CEC) of the filter particles for heavy metal cations, especially lead cations, may be at least 2meq/g, preferably 3meq/g, when measured at a pH value between 6 and 8.

The filter particles may have a uniform isotherm at pH 5 and pH 8.5 (+/-0.5) so as to have a point of zero charge (PZC or isoelectric point) outside the pH range of 5 to 8.5.

In some embodiments, the filter particles may be powdered aluminosilicates (such as zeolites). In some embodiments, the filter particles may be in the form of aluminosilicate fibers (e.g., ceramic fibers). For clarity, it should be noted that in such embodiments where the filter particles are in fibrous form, the matrix fibers (if present) are different from the filter particles.

Similar to other naming conventions for polyatomic species in organic chemistry, the components of a composition of zeolites can be represented in their monomeric form as their common oxides. However, it should be appreciated that this is a routine aimed at simplifying and standardizing analysis and communication. For example, an aluminosilicate skeleton is a multi-atom skeleton structure comprising a substantial proportion of repeating units [ -SiO ] ₄ -] ^4- And [ -AlO ₄ -] ^5- 。

In describing the components of the zeolite, the base species are considered alone, so that the base units are not described in the form of coordination tetrahedra, but rather are represented in the form of common mineral oxides. In other words, the proportion of elemental species can be expressed in the usual form of oxides of the base unit, e.g. SiO ₂ Or Al ₂ O ₃ 。

The filter particles may have an average diameter of 0.1 to 50 μm. The average diameter may be 1 to 30 μm when the filter particles are in the form of powder particles, and 1 to 5 μm when the filter particles are in the form of fibers.

The filter media may also comprise matrix fibers for structural support. The matrix fibers may be present in an amount of 10 to 90 wt%, preferably 20 to 80 wt%, preferably 30 to 80 wt%, based on the total weight of the filter medium. In some embodiments, the matrix fibers may be present in an amount of 30 to 50 wt%, preferably 35 to 45 wt%, based on the total weight of the filter medium. In some embodiments, the matrix fibers may be present in an amount of 50 to 70 wt%, preferably 55 to 65 wt%, based on the total weight of the filter medium. The matrix fibers may be selected from one or more of cellulose fibers, synthetic fibers, polymer fibers, glass fibers, and fibrillated fibers. The cellulosic fibers may be present in an amount of 5 to 100 wt%, preferably 7 to 20 wt%, or more preferably 50 to 70 wt%, based on the total weight of the matrix fibers. The cellulose fibers may be selected from one or more of softwood fibers, hardwood fibers, plant fibers, and regenerated cellulose fibers (such as lyocell or Rayon fibers), and may preferably be regenerated cellulose fibers.

The glass fibers may be present in an amount of 5 to 100 wt%, preferably 10 to 70 wt%, more preferably 7 to 20 wt%, or in some other embodiments preferably 50 to 70 wt%, based on the total weight of the matrix fibers.

The filter media may comprise at least 80 wt%, preferably at least 90 wt%, or more preferably at least 95 wt% synthetic matrix fibers, based on the total weight of the matrix fibers. The synthetic matrix fibers may be oil-based or vegetable-based synthetic fibers and may be selected from one or more of synthetic polymer fibers, modified or converted natural polymer fibers, or silicon-containing (glass) fibers. Exemplary fibers include polyesters (e.g., polyethylene terephthalate, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.), polyolefins (e.g., polyethylene, polypropylene, etc.), polyacrylonitrile (PAN), etc.), and polyamides (nylons, e.g., nylon 6, nylon 6,12, etc.).

The polymer fibers may be polyester fibers and may be present in an amount of 1 to 30 wt%, preferably 5 to 30 wt%, based on the total weight of the matrix fibers. The polyester fibers may be bio-polyester fibers, which may be biodegradable or even compostable according to the EN1334 standard.

According to another alternative, the matrix fibers may comprise a mixture of cellulosic fibers and synthetic fibers. The synthetic fibers may be present in the filter medium in an amount up to 50 wt%, preferably 10 wt% to 30 wt% of the total weight of matrix fibers in the filter medium.

To enhance the bond between the filter particles and the matrix fibers, the filter media may include binder fibers, such as those made fromFabricated->T256PET microfiber. If binder fibers are present, the binder fibers are counted as matrix fibers when calculating the weight percent. The binder fibers include thermoplastic portions that may soften or melt during processing of the filter media (e.g., during the calendaring step). The binder fibers may be monocomponent or bicomponent. The bicomponent thermoplastic fiber may comprise a polymeric core fiber surrounded by a fusible sheath of a thermoplastic polymer having a melting point lower than the melting point of the core.

The filter media may include a polymeric binder that may be added to enhance the overall cohesiveness of the components of the filter media. The filter media may include polymeric binders such as styrene acrylic acid, acrylic acid copolymers, polyethylene vinyl chloride, styrene butadiene rubber, polystyrene acrylate, polyacrylate, polyvinyl chloride, polynitrile, polyvinyl acetate, polyvinyl alcohol derivatives, starch polymers, phenolic resins, and combinations thereof, including aqueous and solvent borne. In some cases, the polymeric binder may be in the form of a latex (e.g 26450 Such as a water-based latex emulsion. The filter media may comprise less than 15 wt%, preferably less than 10 wt%, of the polymeric binder in latex form, based on the total weight of the filter media.

The filter medium may also includeOne or more additive components. The additive component may be selected from: activated carbon (which may be suitable for chlorine removal and improving the taste and odor of water), wet strength resins such as polyamide epichlorohydrin (PAE) resins (e.gGHP resin) that may be added to enhance the wet strength of the filter media; a colorant that may be required to impart a good appearance to the filter media; a fibrous retention aid; separation aids (e.g., silicone additives and associated catalysts); hydrophilic or hydrophobic agents; a wetting agent; an antistatic agent; or an antibacterial agent (such as silver particles). If present, these additives may be added in an amount greater than 0 wt%, 0.01 wt%, 0.1 wt%, 1 wt%, 5 wt%, 10 wt%, and/or less than about 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, or any combination thereof, including for example between 0.01 wt% and 1 wt%, based on the total weight of the filter medium.

In some embodiments, the filter media may be at least partially coated with nano-alumina. The matrix fibers and/or binder fibers may be at least partially, preferably substantially completely, coated with nano-alumina, and the filter particles may be substantially uncoated with nano-alumina. In some embodiments, the filter particles may be at least partially coated with nano-alumina.

The nano-alumina may be present in the filter medium in an amount of 1 to 70 wt%, preferably 10 to 50 wt%, 15 to 40 wt%, or 25 to 35 wt%, based on the total weight of the filter medium.

In use, the nano alumina coating will be positively charged when immersed in water (such as when water is passed through the filter medium). The pH of the water may be 5 to 9, preferably 6.5 to 8. The positive charge may be used to electrostatically attract and entrap negatively charged impurities in the water, thereby allowing the water to be purified by the filter medium.

The filter particles may be mixed with matrix fibers, binder fibers, polymeric binders, and/or additive components to produce a nonwoven filter medium.

In some embodiments, the filter media may comprise less than 1% by weight glass fibers, preferably less than 0.1% by weight glass fibers.

The filter medium may be configured to act as a prefilter, meaning that it may be used in conjunction with a second filter medium. The pre-filter may be connected to a filtration system comprising a second filter medium, or may be arranged to pass the effluent through the pre-filter before passing through the second filter medium. In some embodiments, the second filter media may include fibers coated with nano-alumina. In use, the pre-filter may be positioned upstream of the filtration system and may be arranged to replenish the second filter medium by filtering out impurities of a different nature. For example, the pre-filter may be arranged to remove positively charged impurities such as heavy metal cations from the fluid prior to the fluid entering the filtration system comprising the second filter medium, and the second filter medium may be configured to remove negatively charged contaminants such as particulate matter, organic acids, viruses, bacteria, capsules, cell debris, or micro-pharmaceuticals. The porosity of the filter media in the prefilter may be large enough to have a negligible effect on the flow rate through the second filter media. This arrangement may be more cost effective than incorporating a complete second layer of filter media into the filtration system to remove heavy metal impurities from the fluid to be filtered.

The filter media used as a prefilter or stand-alone filter media may be protected or supported by additional layers that have a limited effect on the porosity of the filter media.

The present disclosure extends to a method of manufacturing a filter medium as defined herein, the method comprising:

(c) The sheet is dried to obtain a filter medium.

Filtering the particulate Al in step (a) ₂ O ₃ The content may be 20 to 65 wt%, 20 to 60 wt%, 20 to 55 wt%, 20 to 50 wt%, 20 to 45 wt%, 20 to 40 wt%, 25 to 65 wt%, 25 to 60 wt%, 25 to 55 wt%, 25 to 50 wt%, 25 to 45 wt%, 25 to 40 wt%, 30 to 65 wt%, 30 to 60 wt%, 30 to 55 wt%, 30 to 50 wt%, 30 to 45 wt%, 30 to 40 wt%, 35 to 65 wt%, 35 to 60 wt%, 35 to 50 wt%, 35 to 45 wt%, or 35 to 40 wt%, and SiO ₂ The amount may be less than 65 wt%, 60 wt%, 55 wt%, 50 wt%, 45 wt%, 40 wt% or 35 wt%, preferably less than 50 wt%, or 10 to 65 wt%, 10 to 60 wt%, 10 to 55 wt%, 10 to 50 wt%, 10 to 45 wt%, 10 to 40 wt%, 10 to 35 wt%, 10 to 30 wt%, 10 to 25 wt%, 10 to 20 wt%, 15 to 65 wt%, 15 to 60 wt%, 15 to 55 wt%, 15 to 50 wt%, 15 to 45 wt%, 15 to 40 wt%, 15 to 35 wt%, 15 to 30 wt%, 15 to 25 wt%, 15 to 20 wt%, 20 to 65 wt%, 20 to 60 wt%, 20 to 55 wt%, 20 to 50 wt%, 20 to 45 wt%, 20 to 40 wt%, 20 to 35 wt%, 25 to 65 wt%, 25 to 60 wt%, 25 to 55 wt%, 25 to 50 wt%, 25 to 45 wt%, 25 to 40 wt%, 25 to 35 wt%, 25 to 30 wt%, 30 to 65 wt%, 30 to 60 wt%, 30 to 55 wt%, 30 to 30 wt% From 30 to 45 wt%, from 30 to 40 wt%, from 30 to 35 wt%, from 35 to 65 wt%, from 35 to 60 wt%, from 35 to 55 wt%, from 35 to 50 wt%, from 35 to 45 wt%, from 35 to 40 wt%, from 40 to 65 wt%, from 40 to 60 wt%, from 40 to 55 wt%, from 40 to 50 wt%, or from 40 to 45 wt%.

Step (a) and step (b) may be performed simultaneously. Alternatively, step (a) may be performed before step (b).

The pH of the alkaline solution may be between 8 and 14, preferably between 9 and 11, or preferably about 10.

The fiber slurry may include matrix fibers, binder fibers, polymeric binders, and/or additive components. The method may include the step of mixing the filter particles with matrix fibers, binder fibers, polymeric binders, and/or additive components to form a fiber slurry. The fiber slurry may also comprise an alkaline solution. In some embodiments, the filter particles may be separated from the alkaline solution prior to forming the fiber slurry.

The filter media produced according to the method may be a nonwoven filter media.

By contacting the filter particles with an alkaline solution, neutral charged SiO in the filter particles ₂ The amount of (2) can be mainly determined by SiO ₂ Is reduced by dissolution of negatively charged Al ₂ O ₃ The amount of (c) can remain largely unaffected. This may serve to increase the negative charge density on the filter particles and thus increase the ability of the filter particles to entrap positively charged heavy metal ions such as lead ions. The treated filter particles can be incorporated into a filter medium to provide a prolonged and higher degree of soluble metal ion entrapment than can be achieved with an equivalent amount of untreated filter particle material. Furthermore, filter media comprising treated filter particles may be capable of removing heavy metals from fluids such as water to within regulatory limits. However, although in some embodiments this effect may be further enhanced by alkali treatment, even without alkali treatment, including having a particle-based15 to 70 wt% of Al by weight of the pellet ₂ O ₃ Content of SiO less than 70 wt% ₂ Content and at least 5 wt% Na ₂ The filter media of the filter particles with O content can provide effective heavy metal removal, in particular lead removal.

The method may include the step of at least partially coating the matrix fibers and/or the binder fibers with nano-alumina. The coating may be applied to the matrix fibers and/or binder fibers prior to combining the coated fibers with the filter particles to form a fiber slurry. Accordingly, the method may further comprise:

(a2) The at least partially coated fibers are combined with the filter particles and an alkaline solution to form a fiber slurry.

The nano-alumina may be formed in situ by reacting aluminum metal (typically in powder or flake form) under heat (60 to 80 ℃, preferably about 70 ℃) in an alkaline solution (such as an aqueous solution of NaOH, KOH or ammonium hydroxide) having a pH of 8 to 14, preferably 9 to 11, more preferably about pH 10. After the reaction is complete, the pH of the solution may be selectively adjusted (e.g., reduced or neutralized).

Once the dried filter media has been formed, it can be corrugated, cut, folded, pleated, and assembled into the final filter product for use.

The present disclosure extends to a method of filtering a fluid, the method comprising passing the fluid through a filter medium as defined above. The fluid may be water, preferably potable water. The fluid may be forced through the filter media by application of externally applied pressure or by hydrostatic pressure. During filtration, impurities in the fluid bind to the filter media (e.g., by electrostatic adhesion to the filter particles and/or nano alumina coating) and/or are trapped by physical occlusion, thereby producing a purified fluid exiting the filter media.

The present disclosure further extends to a method of removing heavy metals from a fluid, the method comprising passing the fluid through a filter medium as defined above. The fluid may be water, preferably potable water. The heavy metals may be selected from arsenic, antimony, cadmium, cobalt, copper, iron, lead and lead oxide, mercury, nickel, palladium, selenium, silver, thallium, tin and organotin, and zinc, preferably lead or preferably arsenic. The heavy metal may be in soluble form, in particulate form, or in both soluble and particulate form.

The filter media may be suitable for filtering fluids in industrial applications, such as removing contaminants from municipal drinking water or wastewater, treating industrial wastewater containing chemical or pharmaceutical contaminants, improving mine wastewater, or treating water contaminated by oil and gas drilling or processing operations.

The filter media may also be suitable for filtering fluids in household applications, such as purifying water for drinking or cooking purposes.

The filter medium may be incorporated into a device for filtering a fluid such as water. The device may comprise a dispensing unit for dispensing the fluid and a filter unit for filtering the fluid dispensed by the dispensing unit. The filter unit may comprise a filter medium as defined above.

Examples

Example 1

The NSF/ANSI-53 industry standard describes a protocol for testing the efficacy of a water filter for filtering lead in two different types of water. The first is low alkalinity water having a pH of 6.5 and having 10 to 30mg/L CaCO ₃ . The second is water with higher mineralization, pH 8.5 and 100mg/L CaCO ₃ . Both solutions contained 150. Mu.g/L Pb, of which 30.+ -. 10% of Pb was particulate lead.

One prior art filter medium as described in US 2019/0218111 A1 uses a three layer structure to remove lead. The first and third layers are cellulosic fibrous materials with ceramic particles coated with iron disposed therebetween. Although the product can retain soluble lead, the product is saturated quickly and is not suitable for long-term use. The results of NSF/ANSI-53 (version 2019) testing on this filter media are shown in Table 1 below.

Table 1: test data indicating lead reduction at pH 6.5

As shown in the above data, the lead level in the output water exceeded the 5 μg/L level of NSF throughout the test.

Example 2: influence of pH on lead entrapment

Preparation of the Filter media

The filter media were prepared with the components shown in table 2 below. The amounts are in weight% on a dry basis.

Table 2: components and amounts for preparing the filter media tested

Preparation and testing of the Filter media

Six filter media were prepared by a wet-laid process at pH 5, 7, 8, 9, 10 and 11, respectively. The lead retention performance of each filter media was tested using a solution containing 150ppb of soluble lead. The lead-containing solution was passed through the filter medium and the amount of lead ions in the effluent was measured. After such a preliminary screening of the filter media, it was concluded that the filter media prepared at pH 10 exhibited the highest performance. The results are shown in FIG. 1.

Example 3

Using the data of example 2, filter media were prepared on an industrial scale according to the components and amounts thereof shown in table 3 below.

Table 3: components and amounts used in the filter media tested

Component (A)	Weight percent
		Aluminosilicate zeolite filter particles (surfats SZT)	30.9％
Fiber 1 Lyocell L-040-6 (fibrillated fiber)	8.9％
		Fiber 2 Trevira T256 (synthetic PET fiber)	17.8％
Fiber 3 Lauscha B-06-F (glass fiber)	26.6％
		Fiber 4 Lauscha C-04-F (glass fiber)	12.4％
Kymene 557H (1% wet flow additive)	0.5％
		Lubrizol (Hycar) 26450Latex (10% for general cohesiveness)	2.9％

The components were added to the pulper in the following order:

50% Lauscha B-06-F was added and dispersed for 5 minutes at 850 to 950 rpm. The remaining Lauscha was added and dispersed at 850 to 950rpm for 5 minutes.

Lauscha C-04-F was added and dispersed at 850 to 950rpm for 5 minutes.

Lyocell L-040-6, trevira T256 and filter particles (Surfatas SZT powder) were added and dispersed for 5 minutes at 850 to 950 rpm.

Sodium hydroxide solution is added until a pH of 10 is reached.

Kymene 557H was added and dispersed for 1 min.

Lubrizol (Hycar) 26450Latex was added and dispersed for 1 minute.

Preparation and testing of the Filter media

Using this solution, the filter media was prepared by a wet-laid process. The filter media had the following characteristics:

table 4: physical Properties of the prepared Filter media

Physical Properties	Unit (B)
			Basis weight	g/m2	223.5
Basis weight	lbs/1389ft2	63.7
			Thickness of (L)	μm	796.6
Thickness of (L)	mils	31.4
			Ash content	％	62.4
MFP (average flow aperture)	μm	1.9
			Gravity flow	s/500mL	93
Dry MD tensile Strength	lbs/in	16
			Wet MD tensile Strength	lbs/in	11.7

Average flow pore sizeIs the pore size at which the flow rate through the wetting medium is 50% of the flow rate through the drying medium at the same pressure drop using capillary flow porosimetry techniques.

Pore size is determined by American Society for Testing and Materials (ASTM) standard 316-03 (2011), which is incorporated herein by reference in its entirety. In capillary flow porosimetry, the sample is first wetted with a wetting fluid such that all pores in the sample are filled. The non-reactive gas with increased pressure is applied to one side of the wet sample to displace the liquid from the pores. A graph of gas pressure and gas flow rate downstream of the sample was measured and plotted for the wet sample. After the sample was dried, the test was repeated to plot the airflow against the applied pressure for the dried sample. Using this capillary porosimetry technique, the "maximum pore size", "minimum pore size" and "average flow pore size" can be determined.

Pore size and average flow pore size were measured using a porosimeter 3G zh full-scale capillary flow porosimeter.

Gravity flow is used to assess the ability of a filter medium to pass liquid through the filter medium without external pressurization devices such as pumps. Gravity flow can also be used to indirectly evaluate the pressure drop during filtration.

To measure gravity flow of the filter media, the following method was used:

the filter media was cut into 13.3mm disks and firmly secured to the bottom of a 2L water column contained in a graduated measuring cylinder. The diameter of the water column is approximately the same as the filter media disc.

The cylinder was placed on top of the beaker placed on the balance, but the cylinder did not apply weight to the balance. The amount of water that was dropped from the water column into the beaker was measured at various time intervals by means of a balance. Gravity flow can be determined by measuring the time required to hold 500mL of water in a beaker.

Wet MD tensile strength was measured according to ISO1924-2, but in which the test piece was immersed in water for 5 seconds and placed between two pieces of absorbent paper to absorb excess water. The tensile strength of the test pieces was then measured in accordance with ISO 1924-2.

The filter media was tested to meet NSF/ANSI-53 standard. The results are provided in table 5 below.

Table 5: test data showing filtration of lead by filter media at pH 6.5

The results demonstrate that the filter media of the present disclosure is capable of reducing soluble and particulate lead in the effluent stream to less than 5.0 μg/L according to the maximum allowable levels specified in the NSF/ANSI-53 standard.

Example 4

The filter media from example 3 (labeled "19P 64") was disposed as a prefilter upstream of the fibrous nano alumina coated filter media ("4603") and tested for NSF/ANSI-53 compliance. The nano-alumina coated filter media includes nano-alumina coated glass fibers. The results are provided in table 6 below, which shows that both the levels of particulate and soluble lead remained below the maximum allowable levels specified in the NSF/ANSI-53 standard throughout the experiment.

Table 6: results of lead entrapment experiments using the prepared filter media

To demonstrate the lead removal effect of pre-filters, rather than fibrous nano alumina filter media, each filter media was independently tested for lead removal performance using a solution containing 150ppb of soluble lead in accordance with the NSF/ANSI-53 protocol. The results are shown in fig. 2, which shows that the nano alumina filter media ("4603") becomes saturated rapidly, while the filter media of example 2 ("19P 64") consistently filters and entraps lead throughout the experiment.

Example 5

A filter medium coated with nano alumina was prepared according to the components and amounts indicated in table 7 below.

Table 7: components and amounts used in the filter media tested

Component (A)	Weight percent
		Aluminosilicate zeolite filter particles (surfats SZT)	30.9％
Fiber 1 Lyocell L-040-6 (fibrillated fiber)	4.8％
		Fiber 2 Trevira T256 (synthetic PET fiber)	9.7％
Fiber 3 Lauscha B-06-F (glass fiber)	14.5％
		Fiber 4 Lauscha C-04-F (glass fiber)	6.8％
Nanometer alumina	30.0％
		Kymene 557H (1% wet flow additive)	0.5
Lubrizol (Hycar) 26450Latex (10% for general cohesiveness)	2.9

After the fiber component and nano alumina reagents (aluminum powder and NaOH solution) were added to the pulper, the mixture was heated at 71 ℃ for about 15 to 20 minutes with stirring. Heating was stopped and stirring was maintained for 20 minutes to complete the nano alumina forming reaction (hydrolysis of aluminum powder in NaOH solution). The nano alumina coated fibers are combined with filter particles and additives and the filter media is prepared by a wet laid process. The filter media was tested to meet NSF/ANSI-53 standard. The results are provided in table 8 below.

Table 8: results of lead entrapment experiments using the prepared nano alumina coated filter media

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Example 6

Various aluminosilicate zeolites were used to prepare filter media to determine whether treatment with an alkaline solution enhanced their ability to entrap lead impurities in water. The filter media was prepared according to the protocol described in example 3. The results are shown in fig. 3 and 4.

The results show that both SZT and SZP aluminosilicate zeolites exhibit high levels of lead retention after treatment with alkaline solutions, whereas Alusil becomes saturated after about 3600mL and thereafter exhibits poor lead retention. Bauxaline and Zeochem did not exhibit any appreciable lead removal effect and no attempt was made to make pH changes. The chemical composition of the zeolite tested is provided in table 9 below.

Table 9: chemical composition of the zeolite tested (values expressed in wt.%)

	SZT	SZP	Alusil	Zeochem	Bauxaline
						Na ₂ O	19.068	22.591	6.642	2.723	1.991
MgO	1.791		2.577	13.125	2.519
						Al ₂ O ₃	32.720	35.989	19.730	76.051	12.246
SiO ₂	37.593	41.272	67.251	3.428	6.881
						P ₂ O ₅	0.012			2.980	8.152
SO ₃	0.038			0.182	9.038
						K ₂ O	0.014		0.341	1.458	0.245
CaO	0.022		3.377	0.005	0.401
						TiO ₂	8.716	0.132	0.022	0.006	0.097
Fe ₂ O ₃	0.026	0.017	0.034	0.015	58.078
						SrO			0.026	0.027	0.019
Y ₂ O ₃					0.021
						ZrO ₂					0.288
PbO					0.023

The results further illustrate Na in the filtered particles ₂ The presence of O enhances the removal of heavy metals from the fluid. Specifically, na ₂ The presence of O improves lead retention, typically when the filter particles contain at least 5 wt.%, preferably at least 10 wt.% Na ₂ O.

The invention may be further understood in conjunction with the following clauses.

1. A filter medium comprising filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ The content is as follows.

2. The filter medium of clause 1, wherein the Al of the filter particles ₂ O ₃ The content is 20 to 45% by weight, preferably 30 to 40% by weight.

3. The filter medium of clause 1 or 2, wherein the SiO of the filter particles is ₂ The content is less than 60% by weight, preferably less than 50% by weight.

4. The filter medium of any of clauses 1-3, wherein the filter particles comprise at least 5 wt.% Na, preferably at least 10 wt.%, most preferably at least 15 wt.% ₂ O。

5. The filter media of any of clauses 1 to 4, wherein the filter particles have a silicon to aluminum mass ratio (Si/Al) of 0.6 to 4, preferably 0.7 to 3.5, more preferably 0.8 to 1.5.

6. The filter media of any of clauses 1 to 5, wherein the sodium to silicon mass ratio (Na/Si) of the filter particles is 0.1 to 0.9, preferably 0.4 to 0.7, more preferably 0.5 to 0.6.

7. The filter media of any of clauses 1-6, wherein the sodium to aluminum mass ratio (Na/Al) of the filter particles is 0.1 to 2.0, preferably 0.3 to 1.5, more preferably 0.5 to 1.2.

8. The filter media of any preceding clause, wherein the filter particles are alkali treated filter particles.

9. The filter media of any preceding clause, further comprising matrix fibers, preferably selected from one or more of cellulose fibers, polymer fibers, glass fibers, and fibrillated fibers.

10. The filter media of clause 9, wherein the cellulose fibers are selected from one or more of softwood fibers, hardwood fibers, plant fibers, and regenerated cellulose fibers.

11. The filter medium of any of clauses 9 or 10, wherein the cellulose fibers are present in an amount of 5 to 100 weight percent, more preferably 10 to 70 weight percent, or 7 to 20 weight percent or 50 to 70 weight percent, based on the total weight of the matrix fibers.

12. The filter media of any of clauses 9 to 11, wherein the cellulose fibers are regenerated cellulose fibers.

13. The filter media of any of clauses 9 to 12, wherein at least a portion of the cellulose fibers are fibrillated.

14. The filter media of clause 9, wherein the glass fibers are present in an amount of 5 to 100 weight percent, more preferably 10 to 70 weight percent, or 7 to 20 weight percent or 50 to 70 weight percent, based on the total weight of the matrix fibers.

15. The filter media of clause 9, wherein the polymer fibers are polyester fibers, and the polymer fibers are present in an amount of 1 to 30 weight percent, preferably 5 to 30 weight percent, based on the total weight of the filter media.

16. The filter media of any preceding clause, wherein the filter particles have 20 to 45 wt%, preferably 30 to 40 wt% Al, based on the weight of the particles ₂ O ₃ Content and less than 60% by weight, preferably less than 50% by weight, of SiO ₂ Content, wherein the filter particles comprise at least 10 wt%, most preferably at least 15 wt% Na ₂ O, wherein the silica-alumina mass ratio (Si/Al) of the filter particles is 0.6 to 4, preferablyFrom 0.7 to 3.5, more preferably from 0.8 to 1.5.

17. The filter medium of clause 8, wherein the filter particles have 20 to 45 wt%, preferably 30 to 40 wt% Al, based on the weight of the particles ₂ O ₃ Content and less than 60% by weight, preferably less than 50% by weight, of SiO ₂ Content, wherein the filter particles comprise at least 10 wt%, most preferably at least 15 wt% Na ₂ O, wherein the silica-alumina mass ratio (Si/Al) of the filter particles is 0.6 to 4, preferably 0.7 to 3.5, more preferably 0.8 to 1.5, and wherein the filter particles are alkali-treated filter particles.

18. The filter media of clause 9, wherein the matrix fibers are at least partially coated with nano-alumina.

19. The filter media of any preceding clause, wherein the filter media is configured to function as a prefilter for a second filter media.

20. The filter media of clause 18, wherein the filter particles have 20 to 45 wt%, preferably 30 to 40 wt% Al, based on the weight of the particles ₂ O ₃ Content and less than 60% by weight, preferably less than 50% by weight, of SiO ₂ Content, wherein the filter particles comprise at least 10 wt%, most preferably at least 15 wt% Na ₂ O, wherein the silica to alumina mass ratio (Si/Al) of the filter particles is from 0.6 to 4, preferably from 0.7 to 3.5, more preferably from 0.8 to 1.5, wherein the filter particles are alkali treated filter particles, wherein the filter medium comprises matrix fibers selected from glass fibers and cellulose fibers, and wherein the glass fibers and/or cellulose fibers are at least partially coated with nano alumina.

21. The filter media of clause 20, configured to function as a prefilter for a second filter media.

22. The filter media of any preceding clause, wherein the filter particles comprise one or more additional components selected from titanium-containing components (such as TiO ₂ ) A phosphorus-containing component (such as P ₂ O ₅ ) Sulfur-containing components (such as SO ₃ ) Potassium-containing components (such as K ₂ O), calcium-containing component (such as CaO), iron-containing components (such as FeO, feO ₂ Or Fe (Fe) ₂ O ₃ ) A strontium-containing component (such as SrO), an yttrium-containing component (such as Y) ₂ O ₃ ) And zirconium-containing components (such as ZrO ₂ )。

23. The filter medium of clauses 9-16 or 18, wherein the filter particles have 20 to 45 wt%, preferably 30 to 40 wt% Al ₂ O ₃ Content and less than 60% by weight, preferably less than 50% by weight, of SiO ₂ Content, and wherein the matrix fibers are at least partially coated with nano-alumina.

24. The filter media of any preceding clause, wherein the filter particles may comprise 5 to 70 weight percent, preferably 10 to 50 weight percent, most preferably 20 to 40 weight percent of the total weight of the filter media.

25. A method of manufacturing the filter media of any one of clauses 1 to 24, the method comprising:

(b) Forming a wet laid (wet laid) sheet from a fibrous slurry comprising filter particles; and

(c) The sheet is dried to obtain a filter medium.

26. The method of clause 25, wherein the fiber slurry comprises matrix fibers, binder fibers, a polymer binder, and/or an additive component.

27. The method of clause 25 or 26, wherein step (a) and step (b) are performed simultaneously.

28. The method of clause 25 or 26, wherein step (a) is performed before step (b).

29. The method of any one of clauses 26 to 28, further comprising at least partially coating the matrix fibers and/or the binder fibers with nano-alumina.

30. The method of clause 25 or 28, comprising:

(a) The filter particles are contacted with an alkaline solution,the filter particles have 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ The content is as follows;

(c) The sheet is dried to obtain a filter medium,

wherein step (a) is performed before step (b).

31. The method of clause 26 or 29, further comprising:

(a2) The at least partially coated fibers are combined with the filter particles and the alkaline solution to form a fiber slurry.

32. A method of removing heavy metals from a fluid, the method comprising passing the fluid through the filter medium of any one of clauses 1-24.

33. The method of clause 32, wherein the heavy metal is lead and the fluid is water.

Claims

1. A filter medium comprising filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ Content, wherein the filter particles comprise at least 5 wt% Na ₂ O。

2. The filter media of claim 1, wherein the filter particles are Al ₂ O ₃ The content is 20 to 45% by weight, preferably 30 to 40% by weight.

3. The filter medium of claim 1 or 2, wherein the filter particles are of SiO ₂ The content is less than 60% by weight, preferably less than 50% by weight.

4. According to claimThe filter medium of any one of claims 1 to 3, wherein the filter particles comprise at least 10 wt%, most preferably at least 15 wt% Na ₂ O。

5. The filter medium according to any one of claims 1 to 4, wherein the filter particles have a silicon to aluminum mass ratio Si/Al of 0.6 to 4, preferably 0.7 to 3.5, more preferably 0.8 to 1.5.

6. The filter media of any one of claims 1 to 5, wherein the filter particles are alkali treated filter particles.

7. The filter media of any one of claims 1 to 6, further comprising matrix fibers, preferably selected from one or more of cellulose fibers, polymer fibers, glass fibers, and fibrillated fibers.

8. The filter media of claim 7, wherein the matrix fibers are at least partially coated with nano-alumina.

9. A filter medium according to any preceding claim, configured to act as a prefilter for a second filter medium.

10. A filter medium according to any preceding claim having an average flow pore size of less than 3 μm, preferably less than 2.5 μm.

11. A filter medium according to any preceding claim, which has a gravity flow of less than 200s/500mL, preferably less than 150s/500mL.

12. The filter media of any one of the preceding claims, having a wet MD tensile strength of at least 3lb/in, preferably at least 5lb/in, and most preferably at least 10lb/in.

13. A filter medium according to any preceding claim, wherein the filter medium is NSF/ANSI 53 compliant.

14. A method of manufacturing the filter media of any one of claims 1 to 13, the method comprising:

(a) Contacting filter particles with an alkaline solution, the filter particles having 15 to 70 wt% Al based on the weight of the particles ₂ O ₃ Content and less than 70 wt% SiO ₂ And comprises at least 5% by weight of Na ₂ O；

(b) Forming a wet laid sheet from a fibrous slurry comprising the filter particles; and

(c) Drying the sheet to obtain the filter medium.

15. The method of claim 14, wherein the fiber slurry comprises matrix fibers and/or binder fibers.

16. The method of claim 14 or 15, wherein step (a) and step (b) are performed simultaneously.

17. The method of claim 14 or 15, wherein step (a) is performed before step (b).

18. The method of any of claims 15 to 17, further comprising:

(a1) Contacting the matrix fibers and/or the binder fibers with nano-alumina to at least partially coat the matrix fibers and/or the binder fibers; and

(a2) Combining the at least partially coated fibers with the filter particles and an alkaline solution to form the fiber slurry.

19. A method of removing heavy metals from a fluid, the method comprising passing the fluid through the filter medium of any one of claims 1 to 13.

20. Use of a filter medium according to any one of claims 1 to 13 for removing heavy metals from a fluid.

21. Use according to claim 20, wherein the filter medium is used as a prefilter for a second filter medium.