HK1072591B - Processes for manufacturing water filters - Google Patents

Description

Method for manufacturing water filter

Technical Field

The present invention relates to a method of manufacturing a water filter, and more particularly, to a method of manufacturing a water filter including activated carbon particles.

Background

Water may contain many different types of contaminants including, for example, particulates, harmful chemicals, and microbiological organisms such as bacteria, parasites, protozoa, and viruses. In many cases, these contaminants must be removed before the water can be used. For example, in many medical applications and in the manufacture of certain electronic devices, it is desirable to use highly purified water. Another more general example is that the water must be freed of any harmful contaminants before it is potable, i.e., potable. Despite modern water purification methods, there are still risks for the average person, especially for infants and persons with compromised immune systems.

In the united states and other developed countries, municipal treated water typically contains one or more of the following impurities: suspended solids, bacteria, parasites, viruses, organic matter, heavy metals and chlorine. Sometimes malfunctions and other problems of the water treatment system can result in the water not being completely cleaned of bacteria and viruses. In other countries, exposure to contaminated water has had fatal consequences due to increasing population density, decreasing water supply, and the absence of water treatment facilities in some regions. Since drinking water sources are commonly located adjacent to human and animal waste, microbial contamination is a major health concern. Contamination by microorganisms in water is estimated to cause the death of six million people each year, half of which are children under the age of 5.

In 1987, the U.S. Environmental Protection Agency (EPA) introduced "test guidelines standards and protocols for microbiological water purification devices". The protocol establishes minimum requirements for the performance of drinking water treatment systems designed to reduce specific contaminants related to human health in public or domestic water supplies. It is required that the effluent water from the supply water has 99.99% (or 4log equivalent) virus clearance and 99.9999% (or 6log equivalent) bacteria clearance. According to the EPA protocol, the concentration of virus in influent water should be 1X 10⁷The bacteria should be present in the influent water at a concentration of 1X 10 per liter⁸Per liter. Coli (e.coli) is a major bacterial subject since it is ubiquitous in water supplies and presents associated hazards when consumed. Similarly, MS-2 bacteriophage (or simply MS-2 bacteriophage) is a representative microorganism typically used for viral clearance because its size and shape (i.e., 26nm in size and icosahedral) are similar to many viruses, and thus the ability of a filter to remove MS-2 bacteriophage is indicative of its ability to remove other viruses.

Due to these demands and public interest in improving the quality of potable water, it is always desirable to provide a method of manufacturing a water filter material that is capable of removing bacteria and/or viruses from a fluid.

Summary of The Invention

The invention provides a method for producing a water filter material. The method comprises the following steps: providing a plurality of carbon particles having a point of zero charge of less than 7, wherein the sum of the mesopore and macropore volumes of the plurality of filter particles is greater than 0.12 mL/g. The plurality of carbon particles are exposed to a converting agent and heated in a furnace after the exposing step.

Brief Description of Drawings

While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a BET nitrogen adsorption isotherm of mesoporous acidic activated carbon particles CA-10 and mesoporous basic activated carbon particles TA 4-CA-10;

FIG. 2 is a mesopore volume distribution of the particles of FIG. 1;

FIG. 3 is a graph of the point of zero charge of the particle of FIG. 1;

FIG. 4 is a cross-sectional side view of an axial flow filter made in accordance with the present invention;

FIG. 5 illustrates the concentration of the E.coli bath of the filter particles of FIG. 1 as a function of time; and

FIG. 6 illustrates the concentration of the MS-2 bath of filter particles of FIG. 1 as a function of time.

Description of The Preferred Embodiment

I. Definition of

The terms "filter" and "filtration" as used herein refer to a structure or mechanism associated with the removal of microorganisms (and/or the removal of other contaminants) by adsorption and/or size exclusion.

The phrase "filter material" as used herein means an aggregate of filter particles. The aggregates of filter particles forming the filter material may be homogeneous or heterogeneous. The filter particles may be uniformly or non-uniformly distributed within the filter material (e.g., layers of different filter particles). The filter particles forming the filter material also need not be of the same shape or size and may be provided in loose or interconnected form. For example, the filter material may comprise mesoporous and basic activated carbon particles bonded to activated carbon fibers, and these filter particles may be provided either in loose association or by a polymeric binder or otherwise partially or fully bonded to form a unitary structure.

The phrase "filter particles" as used herein means a separate member or strip used to form at least a portion of a filter material. For example, a fiber, a particle, a bead, etc. are all considered a filter particle in the present invention. Moreover, the size of the filter particles can vary from non-tactile filter particles (e.g., very fine powders) to tactile filter particles.

As used herein, the terms "microorganism", "microbial organism" and "pathogen" are used interchangeably. These terms refer to a variety of microorganisms that have the characteristics of bacteria, viruses, parasites, protozoa, and germs.

The phrase "bacterial removal index of filter particles (BRI)" as used herein is defined as:

BRI 100 × [1- (E.coli bacteria equilibrium status bath concentration) × [1

(control concentration of E.coli bacteria) ],

wherein the "Escherichia coli bacteria equilibrium state bath concentration" refers to bacteria concentration in equilibrium state in bath containing a large amount of filter particles with a total external surface area of 1400cm²And the Sauter mean diameter is less than 55 μm, as described in more detail below. When the test is carried out at two time points separated by 2 hours, equilibrium is reached when the E.coli concentration variation remains within half an order of magnitude. The phrase "control concentration of E.coli bacteria" refers to the concentration of E.coli bacteria in the control bath, which is equal to 3.7X 10⁹CFU/L. The Sauter mean diameter refers to the diameter of a particle whose area-to-volume ratio is equal to the distribution of the entire particle. Note that the term "CFU/L" means "colony forming units per liter", which is a typical technique for E.coli enumerationThe phrase. The BRI index is measured without the use of chemical agents having a bactericidal effect. An equivalent way to report the removal capacity of filter particles is to use the "bacterial removal log index" (BLRI), which is defined as:

BLRI＝-log[1-(BRI/100)]。

BLRI has units of "log" (where "log" denotes log). For example, a BRI index of the filter particles equal to 99.99%, i.e. equivalent to a BLRI index equal to 4 log. The procedure for determining the BRI and BLRI indices is given below.

The phrase "virus removal index" (VRI) of a filter particle as used herein is defined as:

VRI 100 × [1- (bath concentration of MS-2 phages at equilibrium)

(control concentration of MS-2 phage) ],

wherein "bath concentration of MS-2 phage at equilibrium" means the concentration of phage at equilibrium in a bath containing a large number of filter particles having a total external surface area of 1400cm²And the Sauter mean diameter is less than 55 μm, as described in more detail below. When the test is performed at two time points spaced 2 hours apart, equilibrium is reached when the MS-2 concentration remains constant to within a half order of magnitude. The phrase "MS-2 phage control concentration" refers to the concentration of MS-2 phage in the control bath, which is equal to 2.07X 10⁹PFU/L. Note that the term "PFU/L" means "phagocytic units formed per liter", which is a typical term for MS-2 counting. The VRI index is measured without using a chemical agent having a bactericidal effect. An equivalent way to report the removal capacity of filter particles is to use the "log viral removal index" (VLRI), which is defined as:

VLRI＝-log[100-(VRI/100)]。

the VLRI units are "log" (where "log" denotes log). For example, the VRI of a filter particle is equal to 99.9%, then its VLRI is equal to 3 log. The procedure for determining the VRI and VLRI values is given below.

As used herein, the phrase "total external surface area" means the external geometric surface area of one or more filter particles, as described in more detail below.

The phrase "specific external surface area" as used herein means the total external surface area of the filter particles per unit mass, as described in more detail below.

The term "microporosity" as used herein means pores having a width or diameter of less than 2nm (or equivalent to 20 *).

The term "mesopore" as used herein means a pore having a width or diameter of between 2nm and 50nm (or equivalently between 20 * and 500 *).

The term "macropore" as used herein means a pore having a width or diameter greater than 50nm (or equivalent to 500 *).

The phrase "total pore volume" and its derivatives as used herein means the total volume of all pores, i.e., micropores, mesopores, and macropores. The total pore volume can be calculated as the nitrogen adsorption capacity at a relative pressure of 0.9814 using the BET method (ASTM D4820-99 standard), which is well known in the art.

The phrase "micropore volume" and its derivatives as used herein means the total volume of all micropores. Micropore capacity the nitrogen adsorption capacity can be calculated at a relative pressure of 0.15 using the BET method (ASTM D4820-99 standard), which is a method well known in the art.

As used herein, the phrase "sum of mesopore and macropore volumes" and its derivatives means the total volume of all mesopores and macropores. The sum of the mesopore and macropore volumes is equal to the difference between the total pore volume and the micropore volume, or corresponds to the difference in nitrogen adsorption volume at relative pressures of 0.9814 and 0.15 using the BET method (ASTM D4820-99 standard), which is well known in the art.

The phrase "mesopore range pore size distribution" as used herein means the pore size distribution calculated using the Barrett, Joyner and halenda (BJH) method, which is well known in the art.

As used herein, the term "carbonize" and its derivatives are intended to refer to a process for the reduction of non-carbonaceous materials in a carbonaceous material.

The term "activation" and its derivatives as used herein means a treatment that renders the carbonized substance more porous.

The term "active particle" and its derivatives as used herein means a particle that has been subjected to an activation process.

The phrase "point of zero charge" as used herein means a critical pH above which the total surface of the carbonized particles is negatively charged. Well known measurement procedures for measuring the point of zero charge are set forth below.

The term "basic" as used herein means that the filter particles have a point of zero charge greater than 7.

The term "acidic" as used herein means that the filter particles have a point of zero charge of less than 7.

The phrase "mesoporous and basic activated carbon filter particle" as used herein means an activated carbon filter particle having a plurality of mesopores and having a point of zero charge greater than 7.

The phrase "mesoporous acidic activated carbon filter particle" as used herein means an activated carbon filter particle having a plurality of mesopores and having a point of zero charge of less than 7.

As used herein, the phrase "converting agent" refers to an agent that can reduce the number of oxygen-containing functional groups in a material and/or increase the number of nitrogen-containing functional groups in a material.

Mesoporous and basic activated carbon granules

It has been surprisingly found that mesoporous and basic activated carbon particles adsorb a large number of microorganisms compared to the adsorbed amount of mesoporous and acidic activated carbon particles. While not wishing to be bound by theory, applicants hypothesize that: 1) the large number of mesopores and/or macropores provides more convenient adsorption sites for the pathogens, their fimbriae, and surface polymers (e.g., proteins, lipopolysaccharides, oligosaccharides, and polysaccharides) that make up the outer membrane, capsid, and pathogen envelope, and 2) the basic activated carbon surface contains the necessary types of functional groups to attract a large number of microorganisms compared to the acidic activated carbon surface. This enhanced adsorption capacity on the surface of mesoporous and basic activated carbon can help to make the typical size of fimbriae and surface polymers similar to those of mesopores and macropores, thereby making the basic activated carbon surface attractive to the typically negatively charged microorganisms and functional groups on its surface.

The filter particles can be made in various shapes and sizes. For example, the filter particles may be formed in simple shapes such as particles, fibers, and beads. The filter particles can be formed in spherical, polyhedral, cylindrical, and other symmetrical, asymmetrical, and irregular shapes. Moreover, the filter particles may also be formed into composite forms, such as webs, screens, grids, nonwovens, woven materials, and cohesive blocks, which may or may not be formed from the simple forms described above.

The shape and size of the filter particles may vary and the filter particles used in any single filter need not be uniform in size. In practice, it is also desirable that the filter particles in a single filter have different sizes. Typically, the size of the filter particles is between 0.1 μm and 10mm, preferably between 0.2 μm and 5mm, more preferably between 0.4 μm and 1mm, most preferably between 1 μm and 500 μm. For spherical and cylindrical particles (e.g., fibers and beads, etc.), the above dimensions refer to the diameter of the filter particles. For mesoporous and basic activated carbon particles having distinctly different shapes, the above dimensions refer to the largest dimension (e.g., length, width, or height).

The filter particles may be made from any precursor material that can produce mesopores and macropores during carbonization and activation. For example, but not by way of limitation, the filter particles can be wood-based activated carbon particles, carbon-based activated carbon particles, peat-based activated carbon particles, pitch-based activated carbon particles, tar-based activated carbon particles, and mixtures thereof.

Activated carbon can be rendered acidic or basic. Acidity is associated with oxygen-containing functionalities or functional groups such as, but not limited to, phenol, carboxyl, lactone, hydroquinone, anhydride, and ketone. Basicity is associated with such functionalities as pyrones, benzopyrans, ethers, carbonyls, and the basal plane pi electrons. The acidity or basicity of the activated carbon particles is determined by the point-of-zero-charge method (Newcomb, G., et al, "Colloids and Surfaces A: physical and Engineering assays", 78, 65-71(1993)), which is incorporated herein by reference. This technique is also described in section IV hereinafter. The "point of zero charge" of the filter particles of the present invention is greater than 7, preferably greater than 8, more preferably greater than 9, and most preferably between 9 and 12.

After carbonization and activation, the acidic mesoporous activated carbon particles can be converted to alkaline by furnace treatment. The processing conditions include temperature, time, air, and exposure to the converting agent. The conversion agent may be provided in the form of a liquid or a pre-treatment gas and/or form part of the furnace gas. For example, the converting agent may be a nitrogen-containing liquid such as, but not limited to, urea, methylamine, dimethylamine, triethylamine, pyridine, pyrolidine, ethylenediamine, diethylenetriamine, urea, acetonitrile, and dimethylformamide. The nitrogen-containing liquid may coat or wet the filter particles prior to placing the filter particles in the furnace. The furnace gas may also contain nitrogen, inert gases, reducing gases or the above-mentioned conversion agents.

When the carbon particles do not contain any noble metal catalyst (e.g., platinum, gold, palladium), the treatment temperature may be between 600 ℃ and 1,200 ℃, preferably between 700 ℃ and 1,100 ℃, more preferably between 800 ℃ and 1,050 ℃, and most preferably between 900 ℃ and 1,000 ℃. If the carbon particles comprise a noble metal, the treatment temperature is between 100 ℃ and 800 ℃, preferably between 200 ℃ and 700 ℃, more preferably between 300 ℃ and 600 ℃, most preferably between 350 ℃ and 550 ℃. The treatment time is between 2 minutes and 10 hours, preferably between 5 minutes and 8 hours, more preferably 10Between minutes and 7 hours, most preferably between 20 minutes and 6 hours. The process gas comprises hydrogen, carbon monoxide or ammonia. The air flow rate was 0.25 standard L/h.g (i.e., standard liters per hour per gram of carbon; 0.009 standard ft)³/h.g) and 60 Standard L/h.g (2.1 Standard ft)³/h.g), preferably between 0.5 Standard L/h.g (0.018 Standard ft)³/h.g) and 30 Standard L/h.g (1.06 Standard ft)³/h.g), more preferably 1.0 Standard L/h.g (0.035 Standard ft)³/h.g) and 20 Standard L/h.g (0.7 Standard ft)³/h.g), most preferably 5 Standard L/h.g (0.18 Standard ft)³/h.g) and 10 Standard L/h.g (0.35 Standard ft)³/h.g). It should be appreciated that other methods may be used to make the basic mesoporous activated carbon filter material.

The specific surface area measured using the Brunauer, Emmett and teller (bet) methods and the pore size distribution measured using the Barrett, Joyner and halenda (bjh) methods can be used as characteristics of the pore structure of the mesoporous and basic activated carbon particles. Preferably, the filter particles have a BET specific surface area of 500m²G and 3,000m²Between/g, preferably 600m²G and 2,800m²Between/g, more preferably 800m²G and 2,500m²Between/g, most preferably 1,000m²G and 2,000m²Between/g. Referring to FIG. 1, there is shown a typical isothermal adsorption line for mesoporous basic wood-based activated carbon (TA4-CA-10) and mesoporous acidic activated carbon (CA-10) as measured using the BET method.

The total pore volume of the mesoporous and basic activated carbon particles can be measured in the BET nitrogen adsorption process and calculated as the relative pressure P/P₀A nitrogen adsorption capacity of 0.9814. More specifically, and as is known in the art, the total pore volume is calculated by multiplying the "nitrogen adsorption capacity in mL (STP)/g" at a relative pressure of 0.9814 by the conversion factor of 0.00156, at which time a volume of nitrogen is converted to a liquid under STP (standard temperature and pressure) conditions. The total pore volume of the mesoporous and basic activated carbon particles is greater than 0.4mL/g, or greater than 0.7mL/g, or greater than 1.3mL/g, or greater than 2mL/g, and/or less than 3mL/g, or less than 2.6mL/g, or less than 2mL/g, or less than 1.5 mL/g.

The sum of the mesopore and macropore volumes can be measured during the BET nitrogen adsorption process and calculated as P/P₀The difference between the total pore capacity and the nitrogen adsorption capacity under the condition of 0.15. The sum of the mesopore and macropore volumes of the mesoporous and basic activated carbon particles is greater than 0.12mL/g, or greater than 0.2mL/g, or greater than 0.4mL/g, or greater than 0.6mL/g, or greater than 0.75mL/g, and/or less than 2.2mL/g, or less than 2mL/g, or less than 1.5mL/g, or less than 1.2mL/g, or less than 1 mL/g.

The BJH method pore size distribution can be measured using Barrett, Joyner and Halenda (BJH) methods described in J.Amer.chem.Soc.73, 373-80(1951) in "ADSORPTION, SURFACACE AREA, ANDPOROSITY" (Greg and Sing, second edition, Academic Press, N.Y., 1982), the contents of which are incorporated herein by reference. In one embodiment, the pore volume is at least 0.01mL/g for any pore diameter between 4nm and 6 nm. In an alternative embodiment, the pore volume is between 0.01mL/g and 0.04mL/g for any pore diameter between 4nm and 6 nm. In another embodiment, the pore volume is at least 0.03mL/g, or between 0.03mL/g and 0.06mL/g, for any pore diameter between 4nm and 6 nm. In a preferred embodiment, the pore volume is between 0.015mL/g and 0.06mL/g for any pore diameter between 4nm and 6 nm. FIG. 2 shows a typical mesopore size distribution of mesoporous basic wood-based activated carbon (TA4-CA-10) and mesoporous acidic activated carbon (CA-10) as measured by the BJH method.

The ratio of the sum of the mesopore and macropore volumes to the total pore volume is greater than 0.3, preferably between 0.4 and 0.9, more preferably between 0.5 and 0.8, and most preferably between 0.6 and 0.7.

The total external surface area is calculated by multiplying the specific external surface area by the mass of the filter particles and is based on the size of the filter particles. For example, the specific external surface area of a monodisperse (i.e., of the same diameter) fiber can be obtained by calculating the ratio of the area of the fiber (neglecting the area of 2 cross-sections at the end of the fiber) to the weight of the fiber. Thus, the specific external surface area of the fibres is equal to: 4/Dp, where D is the fiber diameter and p is the fiber density. For monodisperse spherical particles, aThe specific external surface area obtained by a similar calculation is equal to: 6/Dp, where D is the particle diameter and p is the particle density. For polydisperse fibers, spherical or irregularly shaped particles, the specific external surface area is calculated by_3，2Replacing D and calculating by the same method as the formula, wherein D is_3，2Is the Sauter mean diameter, which is the diameter of a particle when the particle area to volume ratio is the same as the ratio of the distribution of the entire particle. A well known method of measuring the Sauter mean diameter in the art is laser diffraction, for example using a Malvern apparatus (manufactured by Malvern Instruments ltd. of Malvern, uk). The specific external surface area of the filter particles is 10cm²G and 100,000cm²Between/g, preferably 50cm²G and 50,000cm²Between/g, more preferably 100cm²G and 10,000cm²Between/g, most preferably 500cm²G and 5,000cm²Between/g.

The BRI of the mesoporous and basic activated carbon particles is greater than 99%, preferably greater than 99.9%, more preferably greater than 99.99%, and most preferably greater than 99.999%, when measured according to the batch test procedure set forth herein. This corresponds to mesoporous and basic activated carbon particles having BLRI greater than 2log, preferably greater than 3log, more preferably greater than 4log, and most preferably greater than 5 log. The VRI value of the mesoporous and basic activated carbon particles is greater than 90%, preferably greater than 95%, more preferably greater than 99%, and most preferably greater than 99.9%, when measured according to the batch test procedure set forth herein. This corresponds to mesoporous and basic activated carbon particles having VLRI values greater than 1log, preferably greater than 1.3log, more preferably greater than 2log, and most preferably greater than 3 log.

In a preferred embodiment of the invention, the filter particles comprise mesoporous and basic activated carbon particles that are wood-based activated carbon particles. The BET specific surface area of these particles was 1,000m²G and 2,000m²Between 0.8 and 2mL/g total pore volume, and the sum of the mesopore and macropore volumes is between 0.4 and 1.5 mL/g.

In another preferred embodiment of the invention, the filter particles comprise a material that is initially acidic but in ammoniaThe active carbon particles are treated to be alkaline mesoporous and alkaline active carbon particles in a gas environment. These particles are wood-based activated carbon particles. The treatment temperature was between 925 ℃ and 1,000 ℃, the ammonia flow was between 1 standard L/h.g and 20 standard L/h.g, and the treatment time was between 10 minutes and 7 hours. The BET specific surface area of these particles is 800m²G and 2,500m²Between 0.7mL/g and 2.5mL/g total pore volume, and the sum of the mesopore and macropore volumes is between 0.21mL/g and 1.7 mL/g. The following are non-limiting examples of the conversion of acidic activated carbon to basic activated carbon.

Example 1

Conversion of mesoporous acidic activated carbon to mesoporous basic activated carbon

A mass of 2kg of CARBOCHEM obtained from Carbochem, Inc. located in Ardmore, Pa^*CA-10 mesoporous acid wood-based activated carbon granules were placed on the conveyor belt of a furnace model BAC-M, made by c.i. hayes inc. The furnace temperature was set at 950 ℃ for 4 hours of treatment, where the gas was separated ammonia and the volumetric flow rate of the gas stream was 12,800 standard L/h (i.e., 450 standard ft. f.)³H, or equivalently 6.4 standard L/h.g). The treated carbon particles are designated TA4-CA-10 and their BET isotherms, mesopore volume distributions, and point of zero charge analyses are shown in FIGS. 1,2, and 3, respectively.

III. Filter according to the invention

Referring to fig. 4, an exemplary filter made in accordance with the present invention is illustrated. The filter 20 includes a housing 22 in the form of a cylinder having an inlet 24 and an outlet 26. The housing 22 may be provided in a variety of forms, shapes, sizes and arrangements, as is known in the art, depending on the desired filter to be used. For example, the filter may employ axial flow filtration in which fluid is caused to flow in the axial direction of the housing by the provision of its inlet and outlet. A radial flow filter may also be used, wherein the inlet and outlet are arranged such that fluid (e.g. liquid, gas or a mixture thereof) flows in the radial direction of the housing. Moreover, the filter may include both axial and radial flow. The housing may also be made as part of another structure without departing from the scope of the invention. Although the filter of the present invention is particularly useful for water, it should be appreciated that it is also useful for other fluids (e.g., air, gas, and mixtures of gas and liquid). In this way, the filter 20 may function as a conventional liquid filter or gas filter. The size, shape, spacing, alignment and positioning of the inlet 24 and outlet 26 may be selected to accommodate the flow rate and desired use of the filter 20, as is known in the art. Preferably, the filter 20 is configured to be applicable to drinking water for residential use or commercial use. Examples of filter configurations, drinking water appliances, water using appliances and other water filtration devices suitable for use in the present invention are disclosed in the following U.S. patents: 5,527,451, respectively; 5,536,394, respectively; 5,709,794, respectively; 5,882,507, respectively; 6,103,114, respectively; 4,969,996, respectively; 5,431,813, respectively; 6,214,224, respectively; 5,957,034, respectively; 6,145,670, respectively; 6,120,685, respectively; and 6,241,899, hereby incorporated by reference. For potable water applications, the filter 20 is preferably configured to provide a flow rate of less than 8L/min, or less than 6L/min, or between 2L/min and 4L/min, and the filter comprises less than 2kg, or less than 1kg, or less than 0.5kg of filter material. Filter 20 also includes a filter material 28, wherein filter material 28 includes one or more filter particles (e.g., fibers, particles, etc.). One or more of the filter particles can be mesoporous and basic activated carbon particles and have the aforementioned characteristics. The filter material may also include particles made from other materials such as activated carbon powder, activated carbon particles, activated carbon fibers, zeolites, and mixtures thereof. As previously mentioned, the filter material may be provided in loose or interconnected form (e.g., as a unitary structure formed by a polymeric binder or otherwise bonded in part or in whole).

IV. testing procedure

The following test procedures were used to calculate the point of zero charge, BET, BRI/BLRI, and VRI/VLRI values described herein. Although the BRI/BLRI and VRI/VLRI values are measured for aqueous media, there is no need to limit the filter material ultimately used in the present invention, and other filter materials as previously described may ultimately be used, although the BRI/BLRI and VRI/VLRI values are calculated for aqueous media. Moreover, the filter materials selected below to illustrate the testing procedure used are not intended to limit the scope of processing and/or filter material composition in the present invention, nor is it intended to limit the type of filter material used in the present invention when evaluated at the testing procedure.

BET test procedure

The BET specific surface area and pore volume distribution are measured using a nitrogen adsorption technique, such as the multipoint nitrogen adsorption method described in ASTM D4820-99 at 77K, using a surface area and pore size determinator of the Coulter SA3100 series, manufactured by Coulter Corp, Miami, FL. The process also allows for micropore, mesopore and macropore volumes. For the TA4-CA-10 filter particles of example 1, the BET region was 1,038m²The micropore volume is 0.43mL/g, and the sum of the mesopore and macropore volumes is 0.48 mL/g. Note that the corresponding values for feed CA-10 are: 1,309m²G, 0.54mL/g, and 0.67 mL/g. Typical BET nitrogen isotherms and mesopore volume distributions of the filter material of example 1 are shown in fig. 1 and fig. 2, respectively. It will be appreciated that BET measurements may be made by other instruments instead, as is known in the art.

Testing procedure of zero charge point

A0.010 m aqueous KCl solution was prepared from reagent grade KCl and water, freshly distilled under argon. The water used for distillation is deionized using continuous reverse osmosis and ion exchange. A 25.0mL volume of aqueous KCl solution was dispensed into six 125mL flasks, each fitted with 24/40 ground glass stoppers. Microliter quantities of standard aqueous HCl or NaOH solution were added to each flask to bring the initial pH range between 2 and 12. The pH of each flask was then recorded using an acid-base meter model 420A manufactured by Orion with a triode combination pH/ATC electrode model 9107BN manufactured by Thermo Orion inc. This pH is referred to as the initial pH. 0.0750. + -. 0.0010g of activated carbon particles were added to each of the six flasks and the aqueous suspension stoppered for 24 hours at room temperature was stirred (speed 150rpm) before the final pH was recorded. FIG. 3 shows the initial and final pH values measured using the CA-10 and TA4-CA-10 activated carbon material tests. The points of zero charge for CA-10 and TA4-CA-10 are 4.7 and 10, respectively. It will be appreciated that other instruments may be substituted for this testing step, as is known in the art.

BRI/BLRI assay procedure

Using Phipps from Richmod, VA&PB-900 manufactured by Bird, Inc^TMProgrammable JarTester test apparatus with 2 or more Pyrex^*Heat resistant glass beakers (determined by the amount of material tested). The beaker had a diameter of 11.4cm (4.5 ") and a height of 15.3cm (6"). Each beaker contained 500mL of municipal supply dechlorinated tap water contaminated with E.coli microorganisms with a rotary agitation at 60 rpm. The paddles were stainless steel paddles 7.6cm (3 ") in length, 2.54cm (1") in width, and 0.24cm (3/32 ") in thickness. The stirring bar was placed 0.5cm (3/16') from the bottom of the beaker. The first beaker did not contain any filter material and served as a control, and the other beakers contained sufficient filter material with a Sauter mean diameter of less than 55 μm, so that the total external geometric surface area of the material in the beakers was 1400cm². The Sauter mean diameter is obtained by the following method: a) screening out samples with a wide size distribution and a high Sauter mean diameter; or b) reducing the size of the filter particles (e.g., if the filter particles are larger than 55 μm, or if the filter material is in an integrated or bonded form) using size reduction techniques known in the art. For example, but not by way of limitation, size reduction techniques include crushing, grinding, and milling. Typical equipment used for size reduction includes jaw crushers, gyratory crushers, roller crushers, heavy impact mills, medium mills, and jet mills such as centrifugal jets, opposed jet jets, or jets with anvils. Size reduction may be used for loose or bound filter particles. The biocidal coating should be removed from any filter particles or filter material prior to testing. Alternatively, uncoated filter particles may be substituted in the test.

After adding the filter particles to the beaker, duplicate samples of water were collected at different times for analysis, every 5mL of capacity water, until equilibrium was reached in the beaker containing the filter particles. Typical sampling times are: 0. after 2, 4 and 6 hours, samples were collected from each beaker for assay. Other devices known in the art may be used instead.

The Escherichia coli used was ATCC # 25922 supplied by American type culture Collection of Rockville, Md. The target E.coli concentration in the control beaker was set at 3.7X 10⁹. Coli can be assayed using membrane filtration technology according to method #9222 in Standard methods for the Examination of Water and Wastewater (Standard methods for the Examination of Water and Wastewater), 20 th edition (published by the American Public Health Association (APHA) in Washington, D.C.). Limit of detection (LOD) of 1X 10³CFU/L。

Exemplary BRI/BLRI results for the filter material of example 1 are shown in FIG. 5. The amount of CA-10 mesoporous and acidic activated carbon material was 0.75g, and the amount of TA40-CA-10 mesoporous and basic activated carbon material was 0.89 g. Both of which correspond to an external surface area of 1,400cm². Coli concentration in control beaker was 3.7X 10⁹CFU/L. The E.coli concentrations in the beakers containing the CA-10 and TA4-CA-10 samples reached equilibrium within 6 hours, with values of 2.1X 10, respectively⁶CFU/L and 1.5X 10⁴CFU/L. Then BRI values are calculated as 99.94% and 99.9996% respectively and BLRI values are calculated as 3.2log and 5.4log respectively.

VRI/VLRI determination procedure

The test equipment and test procedures used were the same as when BRI/BLRI values were determined. The first beaker contained no filter material and, as a control, the other beakers contained sufficient amount of filter material that the Sauter mean diameter of the material was less than 55 μm, so that the total geometric external surface area in the beakers was 1400cm². The biocidal coating should be removed from any filter particles or filter material prior to testing. Alternatively, there may be no coating in the testFilter particles or filter material.

The MS-2 bacteriophage used was ATCC #15597B, supplied by American type Culture Collection of Rockville, Md. The target MS-2 concentration in the control beaker was set at 2.07X 10⁹PFU/L. MS-2 assays can be performed according to the procedures described in c.j.hurst, appl.environ.microbiol., 60(9), 3462 (1994). Other assays known in the art may be used instead. Limit of detection (LOD) of 1X 10³PFU/L。

Exemplary VRI/VLRI results for the filter material of example 1 are shown in FIG. 6. The amount of CA-10 mesoporous and acidic activated carbon material was 0.75g, and the amount of TA40-CA-10 mesoporous and basic activated carbon material was 0.89 g. Both of which correspond to an external surface area of 1,400cm². The MS-2 concentration in the control beaker is 2.07X 10⁹CFU/L. The MS-2 concentrations of the samples containing CA-10 and TA4-CA-10 reached equilibrium within 6 hours, with values of 1.3X 10, respectively⁶PFU/L and 5.7X 10⁴PFU/L. Then their VRI values were calculated as 99.94% and 99.997% respectively, and their VLRI values were calculated as 3.2log and 4.5log respectively.

The embodiments were chosen and described in order to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims (19)

1. A method of making a water filter material, said method comprising the steps of:

providing a plurality of carbon particles having a point of zero charge of less than 7, wherein the sum of the mesopore and macropore volumes of said plurality of filter particles is greater than 0.12 mL/g;

exposing the plurality of carbon particles to a conversion agent; and

after the exposing step, heating the plurality of carbon particles within a furnace.

2. The method of claim 1, further comprising the step of activating the plurality of carbon particles.

3. The method of claim 2, wherein the activating step occurs before the heating step.

4. The method of claim 1, wherein the plurality of particles are selected from the group consisting of wood-based carbon particles, coal-based carbon particles, peat-based carbon particles, pitch-based carbon particles, tar-based carbon particles, and mixtures thereof.

5. The process of claim 1, wherein the conversion agent is selected from the group consisting of urea, triethylamine, and mixtures thereof.

6. The method of claim 1, wherein the process temperature within the furnace is between 600 ℃ and 1,200 ℃.

7. The method of claim 1, wherein the process temperature within the furnace is between 100 ℃ and 800 ℃.

8. The method of claim 1, wherein after the heating step, the plurality of filter particles have a point of zero charge greater than 8.

9. The method of claim 1, wherein after the heating step, the plurality of filter particles have a point of zero charge greater than 9.

10. The method of claim 1, wherein after the heating step, the plurality of filter particles have a point of zero charge between 9 and 12.

11. A method of making a water filter material, said method comprising the steps of:

providing a plurality of carbon particles having a point of zero charge of less than 7, wherein the sum of the mesopore and macropore volumes of said plurality of filter particles is greater than 0.12 mL/g;

exposing the plurality of carbon particles to a conversion agent; and

heating the plurality of carbon particles within a furnace after the exposing step;

activating the plurality of carbon particles; and

placing the plurality of particles into a filter housing having a water inlet and a water outlet.

12. The method of claim 11, wherein the activating step occurs before the exposing step.

13. The method of claim 11, wherein the plurality of particles are selected from the group consisting of wood-based carbon particles, coal-based carbon particles, peat-based carbon particles, pitch-based carbon particles, tar-based carbon particles, and mixtures thereof.

14. The process of claim 11, wherein the conversion agent is selected from the group consisting of urea, triethylamine, and mixtures thereof.

15. The method of claim 11, wherein the process temperature within the furnace is between 600 ℃ and 1,200 ℃.

16. The method of claim 11, wherein the process temperature within the furnace is between 100 ℃ and 800 ℃.

17. The method of claim 11, wherein after the heating step, the plurality of filter particles have a point of zero charge greater than 8.

18. The method of claim 11, wherein after the heating step, the plurality of filter particles have a point of zero charge greater than 9.

19. The method of claim 11, wherein after the heating step, the plurality of filter particles have a point of zero charge between 9 and 12.