Ultra-low surface charge bio-based silica filtration medium

Abstract

The diatomaceous earth filtration product comprises flux-calcined diatomaceous earth, wherein the diatomaceous earth filtration product has (1) a complex pore structure of diatomaceous earth, (2) a zeta potential in the range of about -1.0 to about -6.0 mV within a pH range of about 3.0 to about 8.0, and (3) a centrifugal wet density in the range of about 0.176 to about 0.256 g / mL.

Description

[Technical Field]

[0001] This application claims the benefits of U.S. Patent Application No. 17 / 142,416, filed on 6 January 2021, which is incorporated in its entirety by reference.

[0002] This disclosure generally relates to silica filtration products obtained from the flux-calcination of diatomaceous earth. More specifically, this disclosure relates to ultra-low surface charge bio-derived silica filtration products applicable to fields of life sciences and electrochemistry where low surface charge filtration aids are desired in the filtration and separation of fluids and liquids. [Background technology]

[0003] Diatoms belong to one of the classes of algae (Bacillariophyceae) and comprise approximately 12,000 different species found in sediments of lake (lumiscent) and ocean (marine) habitats. Diatom cells have a unique characteristic: they are enclosed within a cell wall of amorphous hydrated biosilicon dioxide (silica) called a husk. These husks are thought to belong to the opal A phase of silica mineralogy and exhibit a wide range of morphological diversity, but are usually nearly bilaterally symmetrical. Because diatom husks are composed of the inert substance silica, they are well preserved in geological sediments over long periods of time.

[0004] Furthermore, during the formation of diatom fossils, organic pollutants, as well as other minerals such as clay, volcanic ash, calcite, dolomite, and feldspar, are deposited together. Even if the diatomaceous earth crust itself does not contain crystalline silica, silica sand in the form of quartz, a type of crystalline silica, may also be deposited during its formation. While quartz is commonly found in marine diatomaceous earth sediments, lacustrine diatomaceous earth sediments may not contain quartz, or they may contain quartz grains that are easily freed by crushing, drying, and then mechanical air classification. Quartz grains can also form over time as a result of a phase transition from opal-A silica. That is, after the death of the diatoms, the opal-A phase is partially dehydrated and, through a series of steps, can be converted from the opal-A phase to other forms of opal with shorter molecular order and lower hydration water content, such as the opal-CT phase and opal-C phase. Under very long periods of time and suitable conditions, opal-CT can transform into quartz.

[0005] The amorphous silica in diatomaceous earth exists in the form of an opaline diatom skeleton and may also contain alumina, iron, alkali metals, and alkaline earth metals. Typical commercially available diatomaceous earth ore, when measured on an organic-free basis, may show chemical analysis results of approximately 80–90 wt% silica, approximately 0.6–8 wt% alumina (Al₂O₃), approximately 0.2–3.5 wt% iron oxide (Fe₂O₃), less than approximately 1 wt% of alkali metal oxides such as Na₂O and MgO, approximately 0.3–3 wt% of CaO, and small amounts of other impurities such as P₂O₅ and TiO₂. However, in selected sediments, the silica concentration can be as high as approximately 97 wt% SiO₂.

[0006] In commercial-grade ore, the unique fine porosity of the crust of diatomaceous earth, a mineral composed of fossil diatoms, results in specific product characteristics such as high surface area, low bulk density, and high absorption capacity. The complex porous structure of diatomaceous earth ore, consisting of macropores, mesopores, and micropores, provides the wettability and high absorption capacity required for certain formulations involving the use of diatomaceous earth products.

[0007] For example, the combination of chemical stability derived from its inert silica composition and the high porosity of its shell makes diatomaceous earth useful for commercial filtration applications. Diatomaceous earth products have long been used for solid-liquid separation (filtration) in a variety of industries, including beverages (beer, wine, spirits, and juices), oils (fat, petroleum), water (swimming pools, drinking water), chemicals (dry cleaning fluids, TiO2 additives), ingestible pharmaceuticals (antibiotics), metallurgy (coolants), agricultural food intermediates (amino acids, gelatin, yeast), and sugars.

[0008] Processing of commercial-grade diatomaceous earth ore As mentioned earlier, diatomaceous earth products are obtained from the processing of diatomaceous earth ore. Diatomaceous earth ore can contain up to approximately 70% free water and various organic and inorganic substances. Therefore, before using diatomaceous earth in a filtration process, the feed material is subjected to a conditioning process that may include some or all of the following unit operations: crushing, grinding, drying, heavy mineral separation, calcination, and abrasive separation. For example, diatomaceous earth ore can be crushed, ground, flash-dried to remove water and heavy mineral waste, and a natural filter aid can be produced (if the feed does not contain large amounts of organic compounds and extractable metals). In other examples, diatomaceous earth feed can be ground, flash-dried to remove water, and calcined to remove organic contaminants and convert soluble inorganic substances into more inert oxides, silicates, or aluminosilicates.

[0009] Figure 1 shows a flow chart of process 100 used in a typical diatomaceous earth production facility that uses low-purity diatomaceous earth ore as feed to produce a high-flow filtration medium (and optionally a functional filler by-product). This process begins with selecting high-grade, low-impurity diatomaceous earth ore from a mine (block 102), which typically has a water content ranging from approximately 30% to 60% by weight.

[0010] Next, the manufacturing process 100 in the manufacturing plant includes crushing the feed ore to prepare it for drying. The most economical and practical means of drying natural diatomaceous earth ore is to crush and flash dry (block 104) the feed material simultaneously, as a result of deagglomeration of the solidified material and removal of moisture to approximately 2 to 10% by weight. Flash drying can be a one-stage or two-stage process. In a one-stage flash drying process, a portion of the dried material is reused in the moist feed material to reduce the moisture content of the feed entering the dryer, ensuring that the moisture target of the product is achieved in a single pass. Alternatively, a static cone classifier can be incorporated into the one-stage flash dryer, which classifies the partially dried particles from the material discharged from the dryer and returns them to the feed material entering the dryer. Two-stage flash drying involves either crushing and drying the feed material simultaneously in two stages, or crushing and drying simultaneously in the first stage followed by drying by pneumatic hot air conveying in the second stage. Using an in-line static classifier results in dried products with minimal particle degradation, producing materials with lower density than those obtained with two-stage flash drying or one-stage recycling systems.

[0011] Next, physical beneficiation of the feed (block 106) to remove heavy minerals and other waste impurities is carried out by employing different forms of mechanical air classifiers. Crystalline silica minerals such as quartz can be removed at this stage of process 100. Heavy minerals such as sand, chert, and other particles are also separated. Beneficiation block 106 helps remove sand grains (grits) from the feed ore but does not significantly affect the chemical properties and density of the feed material.

[0012] Next, a fluxing agent (often soda ash (sodium carbonate)) is mixed with the beneficiated powder under air pressure (block 150), and then collected in a feed bin to maintain a constant feed rate of the material to the rotary kiln for heat sintering (also called flux firing) of the powder (block 108). This heat treatment burns and removes organic matter in the ore, promotes the aggregation of finer and coarser particles, reduces the surface area of ​​the product due to some loss of porosity, and consequently increases the permeability of the material. Flux firing block 108 is carried out in a temperature range of approximately 870°C to approximately 1250°C, partially or completely dehydrating the naturally occurring hydrated amorphous silica structure of the diatomaceous earth. Firing is performed by heat-treating the diatomaceous earth ore in a rotary kiln or rotary firing machine.

[0013] The kiln discharge of the fused calcined material is usually agglomerated and must be passed through a dispersion fan to produce a fine diatomaceous earth powder that typically exhibits a very broad particle size distribution. Thus, to produce a filter aid product acceptable for filtration applications, process 100 involves subjecting the powder to mechanical or air classification (block 110), removing approximately 10–30% by weight of fine particles as a functional filler product in a baghouse (block 112), and collecting the coarser particles in a cyclone as a filter aid (block 114) to significantly improve permeability. If necessary, very coarse particles may be further dispersed and classified to control the particle size requirements of the filter aid particles.

[0014] Conventional diatomaceous earth filtration aids Conventional diatomaceous earth filter aids are inorganic powders that distinguish them from all other fine natural granular silica by their low bulk density, high brightness, and the complex porous structure of the diatom husk, which gives diatomaceous earth products unique commercial value in filtration applications. Diatomaceous earth products are manufactured to meet a certain permeability, measured in Darcy units, which is a measure of the flow of liquid through a standard amount of filter cake under standard conditions. This is achieved by thermal sintering of natural diatomaceous earth powder using a flux (flux firing), typically soda ash (sodium carbonate), to a surface area of ​​approximately 30 m². 2From / g to approximately 3m 2 Reducing the amount to less than / g significantly increases the permeability of the filter medium. Flux-fired commercially available diatomaceous earth products have permeability ranging from approximately 500 millidarcy to approximately 10,000 millidarcy, and the density of a typical centrifuged wet cake ranges from approximately 0.29 g / ml to approximately 0.45 g / ml. Table 1 below lists typical flux-fired diatomaceous earth filter products / filter media from various commercial manufacturers, showing the permeability and corresponding silica to soda (Na2O) stoichiometric ratios for three of the world's leading diatomaceous earth manufacturers: EP Minerals LLC, Imerys Filtration Minerals, and Showa Chemical Company. The calculated soda-to-silica stoichiometric ratio is the ratio of moles of silica oxide (weight %SiO2 / MWSiO2) to moles of soda oxide (weight %Na2O / MWNa2O). [Table 1]

[0015] The silica content of all these flux-fired products of exemplary conventional diatomaceous earth filtration media ranges from approximately 89.0% by weight to approximately 93.0% by weight SiO2, and the sodium oxide concentration ranges from approximately 2.8% by weight for low-permeability products to approximately 4.0% by weight for high-flow products. In general, the stoichiometric ratio of sodium oxide to silica ranges from approximately 2.9% to approximately 4.0%, with the exception of Radiolite 1100, which has a stoichiometric ratio of approximately 4.5%.

[0016] The chemical inertness of diatomaceous earth silica and its resulting complex porous structure give diatomaceous earth products unique commercial value in quality-sensitive filtration applications. Diatomaceous earth filtration products / media have long been used for liquid / solid separation in the food, beverage, and chemical industries. Conventional diatomaceous earth filtration media are used in the processing of a wide range of fluids, including beverages, petroleum products and their derivatives, chemicals, ingestible pharmaceuticals, agricultural food intermediates, and sweeteners.

[0017] Diatomaceous earth can be used in filtration processes as a pre-coat, a body feed, or a combination of both, depending on the properties of the material being filtered and the type of filter used. The principle of body feed filtration (BFF), an established process used in plasma fractionation and fluid-solid separation in the beverage industry, is being tested as an alternative cell culture harvesting solution. In pre-coat-only systems, a layer of filter aid is created on the filter septum by recirculating a slurry of filter aids, preventing clogging by particles in the medium. In body feed-only systems, small amounts of filter aid are periodically added to the liquid being filtered along with the suspended particles to be removed. This continuously forms a new filter surface that is useful for capturing suspended particles and simultaneously ensuring a constant flow rate of the liquid. In rotary vacuum filtration, large quantities of filter medium are used in pre-coat-only form, while in pressure filtration systems, large quantities of filter medium are used in both pre-coat and body feed forms. In some special pressure filtration applications, such as sake filtration, the pre-coat-only method is used.

[0018] In both pre-coat filtration and body-feed filtration applications, diatomaceous earth filter aids or filtration media come into contact with the fluid being filtered. One drawback of using diatomaceous earth filtration media for solid-liquid separation is the release of extractable metals from the filtration media into the fluid. In such applications, the presence of high levels of soluble metals introduced by diatomaceous earth filtration media can affect the purity of the liquid product, as well as the stability and taste of the filtered fluid. Therefore, conventional filtration aids, when used in food and beverage processing, must meet government purity requirements, such as those specified in the U.S. Food Chemicals Codex.

[0019] The control of soluble heavy metals such as lead, arsenic, iron, and aluminum is important in life science separation processes where diatomaceous earth filtration media are used for the treatment of premium fluids such as plasma fractions. As a result, in these applications, diatomaceous earth filtration media that contribute to reducing the impurity levels of the filtered liquid are preferred and used. Several purified diatomaceous earth filtration media products have been developed and used for these applications, but the applications and requirements for higher purity liquids continue to increase, and there is a demand for diatomaceous earth filtration products / media with improved purity.

[0020] Similar to the need to control the involvement of extractable heavy metals in biological fluids, the surface charge of the particles of diatomaceous earth filtration media in contact with biological fluids has also been found to be important in limiting the generation of unwanted contaminants in the fluid. One such contaminant is prekallikrein activator (PKA), which is found in human albumin solutions and immunoglobulin solutions prepared from fractionated plasma using diatomaceous earth filtration media. It is known that albumin solutions contaminated with significant levels of PKA can cause adverse events such as vasodilation and hypotension when injected into patients. This is of particular concern because albumin may be administered as a plasma volume expander to counteract blood volume reduction, and its treatment may exacerbate existing problems. When PKA is present at a sufficiently high concentration, kallikrein is released, and the patient may enter a shock state. Therefore, since PKA usually needs to be removed and verified by chromatography after fractionation, all regulatory authorities for blood products require manufacturers to measure the PKA level for each batch of the final product before it is released for patient care. For example, the guidelines of the European Pharmacopoeia limit the PKA content in plasma preparations to a level of less than 35 IU / ml.

Prior Art Documents

Patent Documents

[0021]

Patent Document 1

[0022] Therefore, it is desirable to provide a high-performance diatomaceous earth filtration medium with an ultra-low surface charge, having a combination of a very low surface charge, very low extractable impurities per unit mass, a very low centrifugal wet density, and very high flux rates relative to density. Furthermore, other desirable features and properties of specific compositions and related analytical methods will become apparent from the following detailed description and the attached claims, in conjunction with the attached drawings and the aforementioned background. [Means for solving the problem]

[0023] overview This specification discloses exemplary embodiments of ultra-low surface charge bio-based silica filtration products obtained from the flux calcination of diatomaceous earth. The ultra-low surface charge filtration products of this disclosure function as filtration aids for the filtration and separation of various fluids and liquids. Accordingly, according to one exemplary embodiment, the diatomaceous earth filtration product comprises flux calcined diatomaceous earth, wherein the diatomaceous earth filtration product has (1) a complex porous structure of diatomaceous earth, (2) a zeta potential in the range of about -1.0 mV to about -6.0 mV within a pH range of about 3.0 to about 8.0, and (3) a centrifuged wet density in the range of about 0.176 g / ml to about 0.256 g / ml.

[0024] According to further embodiments, the filtered product may have a transmittance in the range of about 450 millidarcy to about 20,000 millidarcy. Furthermore, the filtered product may have a stoichiometric ratio of sodium oxide to silicon dioxide in the range of about 5.0% to about 8.0%. The filtered product may also be produced using a flux selected from the group of sodium oxide, sodium carbonate, and sodium bicarbonate. Furthermore, the filtered product may contain less than 1 mg / kg of USP extractable lead (Pb). Furthermore, the filtered product may contain less than 1 mg / kg of USP extractable arsenic (As). Furthermore, the filtered product may contain less than 10 mg / kg of USP extractable iron (Fe).

[0025] This summary is provided to introduce the selection of simplified forms of concepts, which will be further discussed in the detailed description below. This summary is not intended to identify the main or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. [Brief explanation of the drawing]

[0026] The present disclosure will be explained below with reference to the following drawings, where similar numbers represent similar elements. [Figure 1] This is a flowchart of a conventional (prior art) diatomaceous earth manufacturing process for filtration media products. [Figure 2A] This is a flow chart of a diatomaceous earth manufacturing process for an ultra-low surface charge and high-performance filtration medium, in accordance with this disclosure. [Figure 2B] This is a flowchart of the diatomaceous earth production process for purifying an ultra-low surface charge and high-performance filtration medium, prepared according to the process shown in Figure 2A. [Modes for carrying out the invention]

[0027] The following detailed description is essentially illustrative and is not intended to limit the present invention or its application and use. As used herein, the term “exemplary” means “useful as an example, illustration, or explanation.” Therefore, embodiments described herein as “exemplary” should not necessarily be construed as being preferable or advantageous to other embodiments. Furthermore, as used herein, numerical ordinal numbers such as “first,” “second,” “third,” etc., such as “first,” “second,” and “third,” simply indicate different units of a plurality, unless specifically defined by the language of the appended claims. All embodiments and representations described herein are exemplary embodiments provided to enable those skilled in the art to manufacture or use the present invention and are not intended to limit the scope of the present invention as defined by the claims. Furthermore, there is no intention to be bound by the express or implied theories presented in the preceding technical field, background, summary, or the following detailed description.

[0028] This disclosure relates to an ultra-low surface charge biosilica filtration product obtained from the flux calcination of diatomaceous earth. The novel ultra-low surface charge product of this disclosure is of greatest value in the fields of life sciences and electrochemistry where low surface charge filter aids are required for the filtration and separation of high-value fluids and liquids. The novel filtration product of this disclosure has properties that result in high filtration performance associated with reduced filter aid consumption and extended filtration cycle time, with extremely low centrifugal wet density and a wide permeability range. The novel filtration medium has a permeability range of 450 millidarcy to 20,000 millidarcy and a density of 0.160 g / ml (10.0 lb / ft). 3 )~0.256g / ml (16.0lb / ft 3 It has a centrifugal wet density in the range of ).

[0029] Furthermore, this disclosure relates to products / filtration media containing diatomaceous earth, wherein the diatomaceous earth is derived from ore that is specifically selected for its naturally low centrifugal wet density and optionally acid-treated to reduce extractable heavy metal impurities. Selected natural ore with low centrifugal wet density is also treated by calcination methods to produce even lower calcined products and ultra-low surface charge products. These product properties are maintained even after acid purification treatment to reduce the amount of extractable metals. Another aspect of this disclosure relates to a combination of filtration media with higher permeability and lower density, resulting in high particle retention capacity and high flow rate.

[0030] Ultra-low surface charge, high-performance filtration products / media (non-acid washed) One of the two product series in this disclosure is an ultra-low surface charge and high-performance filtration product / filtration medium containing diatomaceous earth, which follows a conventional process for producing flux-fired diatomaceous earth, but with an increased level of soda flux compared to comparable conventional diatomaceous earth products on the market. Unlike conventional flux-fired diatomaceous earth, the use of high levels of soda ash in this disclosure is made possible by introducing 7-15% water into the diatomaceous earth firing feed material to solubilize the soda flux powder and provide uniformly dispersed soda that does not produce glass during the firing process. The high concentration of sodium reacting with diatomaceous earth silica produces a ceramic surface with negligible charge. This product does not undergo the acid washing process commonly used to significantly reduce the extractable metallic properties of diatomaceous earth products. These products / filtration media are characterized by extremely low centrifugal wettance and high filtration performance with long filtration cycle times and high flow rates compared to currently available diatomaceous earth filtration media products.

[0031] These ultra-low surface charge and high electrolytic diatomaceous earth filtration products provide filter aids covering product permeability ranges from approximately 400 millidarcy to approximately 20,000 millidarcy. One aspect of these ultra-low surface charge diatomaceous earth filtration media is that, unlike conventional diatomaceous earth manufacturing, they are produced by direct-run manufacturing, which does not require the removal of fine particles from the product to achieve high permeability. These direct-run product series are achieved by using the Quadro Comil conical screen mill, available from Quadro Engineering, through a combination of mechanical sieving of fine particles and grinding of coarse particles.

[0032] Table 2 below shows a range of some physical and chemical properties of the exemplary ultra-low surface charge and high-performance filtration media of this disclosure. These are all approximately 0.181 g / ml (11.3 lb / ft 3 ) ~ approx. 0.248g / ml (15.5lb / ft 3 These materials exhibit exceptionally low centrifugal wet densities in the range of ). The transmittance of these low-density products ranges from approximately 400 millidarcy to approximately 20,000 millidarcy, which is far higher than that of conventional commercially available products. The surface charges corresponding to these products are shown in Table 3 below. The surface charge is indicated by the zeta potential (ζ) of the filter medium particles at a given pH in the liquid medium, and it is shown that as the amount of soda flux increases to the optimal level, the zeta potential approaches zero charge. In these flux-fired diatomaceous earth filter media, increasing the stoichiometric ratio of sodium oxide to silica to a minimum of 5.1% resulted in a zeta potential of approximately -0.9mV to approximately -5.9mV, which is the lowest compared to prior art. [Table 2] [Table 3]

[0033] Ultra-low surface charge and high-performance filtration products / media (acid washing) The second series of products in this disclosure are refined versions of ultra-low surface charge and high-performance filtration media containing diatomaceous earth, which have undergone the aforementioned flux-fired diatomaceous earth manufacturing process and have a higher level of soda flux compared to comparable conventional diatomaceous earth products on the market. Furthermore, these second series products have undergone an acid treatment purification process, which significantly reduces extractable metals without adversely affecting high permeability and ultra-low density, while maintaining ultra-low surface charge properties.

[0034] Table 4 below shows the physical properties and some related extractable properties of exemplary acid-purified, ultra-low surface charge, and high-performance diatomaceous earth filtration media of the present disclosure. The purified products of the present disclosure provide filtration media covering a product permeability range of about 400 millidarcy to about 7000 millidarcy, with very little extractable chemicals and very low density. The centrifugal wet density of these purified products is about 0.192 g / ml (12.0 lb / ft). 3 ) ~ approx. 0.232g / ml (14.5lb / ft 3 The range is as follows: The amount of extractable heavy metals is very small, with Pb and As being less than approximately 0.1 ppm. The zeta potential also remains very low, even after the acid treatment process, in the pH range of approximately 4 to approximately 8, as shown in Table 5 below. [Table 4] [Table 5]

[0035] Method for preparing an ultra-low surface charge and high-performance diatomaceous earth filtration medium according to the present disclosure The process for preparing the high-performance diatomaceous earth filtration medium of this disclosure begins with selecting an ore with a very low natural centrifugal wet density compared to the natural ore used in the manufacture of typical commercially available filtration aid products.

[0036] An aspect unique to the present disclosure relates to a firing process in which the amount of soda flux incorporated into natural diatomaceous earth kiln feed is significantly greater compared to conventional diatomaceous earth production. Generally, using a large amount of flux in a flux firing process results in the formation of glassy particles. To avoid the formation of this glassy material and improve the efficiency of the flux, the present specification employs a wet kiln feed fluidization technique to solubilize the dry soda ash powder in the feed, ensuring a uniform distribution of the flux on the surface of the diatomaceous earth particles. Solubilization of the soda ash by the wet kiln feed fluidization technique also reduces the bulk density of the ore before heat treatment. The net effect is a flux-fired product having a very high concentration of Na2O, a very low centrifuged wet density, and a higher permeability than can be achieved by other methods, compared to similar conventional products.

[0037] U.S. Patent No. 8,410,017 (Nyamekye et al.) teaches kiln feed pre-agglomeration with water for high-density feed ores containing a large amount of fine particles and having a wet density exceeding about 25 lb / ft 3 and a permeability of less than about 10 millidarcies. However, the present disclosure utilizes wet feed fluidization for ores already having a very low density in the range of about 9 lb / ft 3 to about 15 lb / ft 3 (about 0.144 g / ml to about 0.240 g / ml) and a permeability in the range of about 50 millidarcies to about 200 millidarcies. (Other prior art regarding the addition of water to diatomaceous earth kiln feed to improve the permeability of the fired product is disclosed in U.S. Patent No. 3,013,981 (Riede, R.G.) and U.S. Patent No. 2,693,456 (Fennell, J.E.).

[0038] Another unique aspect of this disclosure relates to the dispersion and sizing of the final product to maintain a low-density product and minimize product degradation, resulting in high filtration media performance. Conventional diatomaceous earth products are dispersed into fine powder using a crushing fan as they exit the kiln. The fine powder generated in this processing step is classified to obtain a filler product, and the coarser particles become the filtration product (see Figure 1). This operation typically increases the density of the final filtration aid product compared to the material exiting the kiln. In this disclosure, the final product is manufactured in a direct-run manner without fine powder removal, by first sieving the kiln discharge through a centrifugal sieve with a predetermined wedge wire screen size opening, and then dispersing the coarser discharge using the aforementioned Quadro Comil sieving device. These two processing steps result in a final product with a centrifugal wet density as close as possible to the kiln discharge material. It is also possible to produce a product with a lower flow rate by directly passing the kiln discharge through the Quadro Comil device and reducing the screen size to lower the transmittance.

[0039] Another unique aspect of this disclosure relates to a high-purity version of this low-surface-charge diatomaceous earth filter medium, which undergoes an acid treatment that results in very little extractable metal, making it suitable for use in premium filtration applications such as pharmaceuticals and electronic devices. The acid treatment is performed to purify the material without affecting the low surface charge generated by the proprietary flux calcination process described above.

[0040] Process flow diagrams for manufacturing the ultra-low surface charge and high-performance filtration media described herein are shown in Figures 2A and 2B. Figure 2A shows the manufacturing process 200 for the ultra-low surface charge, high-performance filtration media, while Figure 2B shows a process flow diagram for purifying the ultra-low surface charge and high-performance filtration media to produce an ultra-low extractable metal filtration product. The product / media obtained from process 200 in Figure 2A may be advantageously used in the filtration of liquids less susceptible to extractable metals, or it may be used as a raw material for manufacturing a high-purity product / media series of ultra-low surface charge high-performance filtration media that can be used for the filtration of pharmaceutical and electronic chemicals from process 300 in Figure 2B.

[0041] Starting from process 200, block 210 includes selecting a suitable low-density diatomaceous earth crude ore based on the results of a centrifugal wet density (CWD) test. To identify a suitable low centrifugal wet density diatomaceous earth crude ore, a representative sample of the crude ore is dried and hammer-ground through an 80-mesh size. Then, a representative sample is taken from the ground powder and centrifugal wet density test is performed to determine if the CWD is 0.256 ml / g (16 lb / ft). 3 It is confirmed that the ore selection criterion is met, such that it does not exceed ). The standard operating procedure for conducting centrifugal separation wet density tests is described later in the section "Method for Characterizing Ultra-Low Surface Charge and High-Performance Diatomaceous Earth Filtration Medium" of this disclosure.

[0042] In block 220, the low-density crude ore identified in block 210 is crushed to obtain an ore size suitable for input to a flash dryer, which includes a hammer mill and a hot jet. The flash drying is performed by simultaneously crushing and heating the wet ore, and the net effect is to produce a dry powder. To avoid over-crushing and maintain the particle integrity of the ore during the flash drying step, the flash dryer is configured to use an in-line double-cone static classifier. In this configuration, the ore is gently crushed during the flash drying operation, and coarse particles that do not meet the particle size specifications are returned to the mill through the coarse discharge of the in-line double-cone classifier.

[0043] In block 230, the resulting dried powder is subjected to a dry heavy mineral impurity waste separator, and quartz, chert, sand, and other heavy impurities in the ore are removed using an air separator or air classifier.

[0044] Following block 230, the dried and separated feed material is mixed with finely ground soda ash flux. Effective mixing of high-density soda ash and light diatomaceous earth powder is carried out by in-line dilute air fluidization. The resulting blend is discharged into a ribbon blender and mixed with atomized fine mist water in amounts of about 0.0 wt% to about 15 wt%, e.g., about 1.0 wt% to about 15 wt%, or about 2.0 wt% to about 15 wt%, or about 3.0 wt% to about 15 wt%, or about 4.0 wt% to about 15 wt%, e.g., about 5.0 wt% to about 15 wt%, to wet the surface of the diatomaceous earth particles, and the net effect is a moist fluidized kiln feed material with a lower, looser weight density. The conditions of the firing process (block 240) are selected so that the kiln discharge has a transmittance within the target transmittance range of the desired filtration medium. The kiln feed can be fired at a temperature ranging from approximately 704°C to approximately 1177°C (approximately 1300°F to approximately 2150°F) for a time ranging from approximately 15 minutes to approximately 100 minutes. The amount of flux (e.g., soda ash) used to produce a product having a permeability of approximately 400 millidarcy to approximately 20,000 millidarcy is generally in the range of approximately 6% to 12% by weight, depending on the appropriate firing temperature. The flux firing process can be carried out in a direct-fired kiln in which the feed is in direct contact with the flame from the kiln burner.

[0045] The cooled product from block 240 is processed in block 250 using a stepwise grinding and separation approach. Centrifugal sieves are used to simultaneously disperse and sieve fine particles at a predetermined screen size opening. The coarser particles discharged from the sieves are introduced into a Quadro Comil grinder, which is equipped with a screen at a predetermined size opening.

[0046] The final product obtained in block 260 is an ultra-low surface charge and high-performance filtration medium with the material properties described above, which is a combination of the sieved product and the pulverized product from Quadro Comil.

[0047] Referring next to Figure 2B, this flow chart illustrates a manufacturing process 300 for a purified product grade of an ultra-low surface charge and high-performance filtration medium taught by this disclosure. This product grade provides low extractability metals that may be important in the filtration of pharmaceutical fluids, for example, when a low surface charge filtration medium is also desired.

[0048] In block 310, the ultra-low surface charge and high-performance filtration medium from block 260 (Figure 2A) is used as the feed for process 300. After the wet processing in manufacturing process 300, the permeability of the purified product may decrease slightly.

[0049] In block 320, the powder product from block 310 is transferred by a diaphragm powder pump to a mixing tank with an agitator that already contains water. The amount of water and powder added to the mixing tank is such that a slurry with a solid content of approximately 10 to 15% by weight is prepared for the subsequent acid treatment step in block 330. To minimize product degradation, the agitator is operated at the minimum speed sufficient to suspend the solids in the tank.

[0050] The slurry in block 320 is pumped in block 330 to a glass reactor (or similar) using a slurry diaphragm pump that tends to minimize solid degradation. An inorganic acid, such as sulfuric acid, is added to the slurry in the reactor to produce an acid concentration of about 0.05 M to about 1.0 M. The polishing leaching process is carried out by heating the slurry in the glass reactor directly by steam injection or by heating the contents through the reactor's steam jacket. At the temperature of the leaching operation, the holding time can be about 20 minutes to about 100 minutes, and the temperature can be in the range of about 90°C to about 100°C under ambient pressure.

[0051] The leaching slurry in block 330 is dewatered in block 340 using a pressure filter. The filtration cake obtained in the pressure filter is thoroughly washed with deionized water until the conductivity of the slurry of approximately 10% by weight of the dry product is less than approximately 20 μS / cm.

[0052] In block 350, the filtration cake undergoes declumping and drying, and in block 360, it is dispersed into a powder to obtain the final purified, ultra-low surface charge, and high-performance diatomaceous earth filtration medium of the present disclosure. To maintain the integrity of the diatom particles and preserve the centrifugal wet density of the dried product, drying of the cake may be carried out in a static dryer, typically a tray dryer, and the dried cake may be dispersed using a centrifugal sieve. Alternatively, a flash drying system may be used to obtain a dried product with minimal product degradation.

[0053] Characterization method for ultra-low surface charge and high-performance diatomaceous earth filtration media -Surface charge measurement- Zeta potential (symbol ζ) All materials spontaneously acquire a surface charge when in contact with a polar medium such as water, and material interfaces can be negatively or positively charged. The charging mechanism commonly observed on all metal oxide surfaces (M-OH), such as diatomaceous earth (Si-OH), is related to the ionization of surface groups. This charging mechanism is also seen in materials with carboxylic acid and amine-type functional groups. The latter category includes proteins, ionic polymers, and polyelectrolytes, many of which are widely used in pharmaceutical formulations. The ionization and / or dissociation of these groups is strongly dependent on the pH of the solution in which they are dispersed.

[0054] Zeta potential is a physical property parameter related to the surface charge that all materials possess or acquire when suspended in a fluid, and can be used to predict interactions with particle surfaces. Zeta potential is the potential difference between the dispersion medium and the fixed layer of fluid attached to the dispersed particles, and is widely used to quantify the magnitude of surface charge.

[0055] Zeta potential measurements were performed using the ZetaCAD streaming potential system. Total length: 12 cm 3 The sample was packed into a PVC tube capped at both ends with mesh to prevent particles from escaping the chamber. Electrolytes (5 mM KCl, 0.1 mM KCO3), with pH adjusted to different pH points using HCl or KOH, were passed through the sample column under increasing pressure conditions to calculate the streaming zeta potential using the Helmholtz-Smoluchowski equation. Three different conditions were used for each sample. -Condition 1: Pressure: 98mBar to 490mBar, in 98mBar increments, 30-second steps -Condition 2: Pressure: 98mBar to 490mBar, in 98mBar increments, 60-second steps -Condition 3: Pressure: 196mBar to 588mBar, in 98mBar increments, 30-second steps. These three conditions evaluate the reproducibility of the measurements, but they do not constitute true repeated measurements.

[0056] The dry powder was gently packed into the cell, and deionized water was added to create a moist paste. This process of adding more dry powder and deionized water was repeated until the cell was completely filled with the moist powder paste. The cell was kept vertical during the measurement.

[0057] -Transmittance The permeability of a filtration cake (including diatomaceous earth filtration products / filtration media) is a measure of the flow rate of a standard liquid passing through a standard volume of the filtration product / filtration media under standard conditions. Filtration using diatomaceous earth filtration cakes is applied to the removal of particulate solids from fluids in industrial processes, and while the permeability of the medium is used to measure the flow rate of liquid passing through the medium, the permeability of the medium often correlates with the medium's particle size exclusion capacity. In other words, generally, a medium with high permeability allows for a high flow rate through the filtration cake, but has low particle size exclusion capacity (a high-permeability medium cannot remove as many fine particles as a coarser permeability medium).

[0058] The permeability measurements of the filtration cake samples described herein were performed using the Celatom Permeameter method disclosed in U.S. Patent No. 5,878,374. The Celatom Permeameter is an automated device that forms a "filtration cake" from a diatomaceous earth sample of known mass and measures all the necessary parameters required for calculating permeability and wet bulk density. Tap water is used as the fluid medium for the measurements. The formulas for calculating wet bulk density (ρ) (unit: g / ml) and permeability (β) (unit: millidarcy) are shown below.

number

[0059] - Bulk chemical composition Diatomaceous earth primarily contains the skeletal remains of diatoms, with silica as its main component and small amounts of impurities such as magnesium, calcium, sodium, aluminum, and iron. The proportions of various elements can vary depending on the source of the diatomaceous earth deposit. The biogenic silica contained in diatomaceous earth is in the form of hydrated amorphous silica minerals and is generally considered to be a type of opal with varying amounts of hydration water. Other minor silica sources in diatomaceous earth may originate from finely dispersed quartz, chert, and sand. However, these minor silica sources do not possess the complex porous structure of biogenic diatom silica species.

[0060] The bulk chemical composition of diatomaceous earth ore and products determines the quality of the material and generally affects the extractable metallic properties of filter aid products. XRF (X-ray fluorescence) spectroscopy is a widely accepted analytical method of choice for determining the bulk chemical composition of diatomaceous earth materials and is a non-destructive analytical technique used to determine the elemental composition of materials. XRF analyzers determine the chemical composition of a sample by generating a series of characteristic fluorescent X-rays specific to certain elements. This is why XRF spectroscopy is an excellent technique for qualitative and quantitative analysis of material composition. In the bulk chemical tests of diatomaceous earth materials reported herein, 5 g of a dry powder sample and 1 g of an X-ray mixed powder binder are finely ground in a Spex® mill and pressed into pellets. To measure the bulk chemical composition, these pellets are loaded into an automated wavelength-dispersive (WD) XRF instrument calibrated beforehand with a reference mean value of diatomaceous earth. To account for the natural loss of hydration within the silica structure, the total mineral content in all examples is reported for each high oxide in terms of loss on ignition (LOI) or on an ignition basis. As used herein, "ignition base" refers to the mineral oxide content measured without the influence of hydration water within the silica structure. The results for the chemical composition of ultra-low surface charge and high-performance diatomaceous earth filtration media and other competing materials are shown in various sections of this disclosure.

[0061] -Centrifugal wet density The wet density of natural diatomaceous earth ore or product is a measure of the void volume available for trapping particulate matter during the filtration process. Wet density often correlates with the unit consumption of the diatomaceous earth filter medium. In other words, diatomaceous earth filter mediums with low centrifugal wet density often result in lower unit consumption of diatomaceous earth product in filtration operations.

[0062] Several methods have been used to characterize the wet density of diatomaceous earth filtration media products. The method used in this disclosure is centrifugal wet density (CWD) and / or wet bulk density (WBD) as described in the transmittance test method. This CWD test method has been frequently used in prior art such as U.S. Patent No. 6,464,770; U.S. Patent No. 5,656,568; and U.S. Patent No. 6,653,255. In this test method, first, 10 ml of deionized water is added to a 15 ml graduated centrifuge glass tube, and 1 g of dry powder sample is loaded into the tube. The sample is completely dispersed in water using a Vortex Jenny 2 shaker. Then, the sides of the tube are rinsed with several milliliters of deionized water to ensure that all particles are suspended, and the contents are brought to the 15 ml mark. After centrifugation using an IEC Centra® MP-4R centrifuge (International Equipment Company; Needham Heights, Massachusetts, USA) equipped with a Model 221 swing rotor, the tube was carefully removed without disturbing the solids, and the contents were centimeters apart. 3 By reading the scale measured in units, the level (volume) of the precipitate can be recorded. The centrifugal wet density of the powder can be calculated by dividing the mass of the sample by the measured volume. The centrifugal wet density is determined by the value obtained by dividing the weight of the sample by the volume (g / ml). Applying the conversion factor 62.428, lb / ft 3 Obtain the centrifugal wet density per unit.

[0063] -Extractable metals Analysis of filtrate sample solutions containing iron (Fe), lead (Pb), and arsenic (As) was performed using inductively coupled plasma (ICP) spectrophotometers or graphite furnace atomic absorption (GFAA). The choice between ICP and GFAA was based on the detection limit (LD) of the element being measured. The ICP instrument used in this analysis was an atomic emission spectrometry (AES) type. This method measures the amount of elements in a sample by utilizing the intensity of light emitted from a flame at specific wavelengths. The wavelength of the atomic spectral line indicates the identification of the element, and the intensity of the emitted light is proportional to the number of atoms of the element. The sample to be analyzed is introduced into the flame as a sprayed solution. The heat from the flame evaporates the solvent, breaking chemical bonds and creating free atoms. This thermal energy also excites atoms, which then emit light. Each element emits light at its characteristic wavelength, and this light is dispersed by a diffraction grating or prism and detected by a spectrometer.

[0064] GFAA, also known as electrothermal atomization (ETA), is a technique for improving the sensitivity and detection limits of atomic absorption spectrometry. In this test, a small amount of filtrate from the sample solution is placed in a hollow graphite tube. This is resistively heated under a temperature program, burning away impurities, atomizing the analyte and forming a plume of free metal vapor, and finally the tube is cleaned. Free atoms absorb light at frequencies or wavelengths characteristic of the element in question (hence the name atomic absorption spectrometry). Within a certain range, the amount of light absorbed can correlate linearly with the concentration of the analyte present.

[0065] Reliable test methods have been established for measuring the amounts of acid-soluble iron, lead, and arsenic in refined siliceous earth, particularly diatomaceous earth products that are further refined after firing as exemplified in this disclosure. An ICP spectrophotometer was used for the analysis of acid-soluble iron, and GFAA spectroscopy was used for the quantification of acid-soluble lead and arsenic.

[0066] In the acid-soluble iron test, 2.0 g of diatomaceous earth product sample was added to 50 ml of 0.1 N hydrochloric acid (HCl) in a 250 ml flask, and soluble iron was extracted. The contents of the flask were stirred for 5 seconds every 10 minutes for a total of 1 hour. This solution was filtered through Whatman #1 filter paper, and a portion of the filtrate was collected in a 15 ml test tube for analysis using an ICP-OES instrument. The iron concentration was calculated as follows: Soluble iron (ppm) = ICP measurement value (ppm) × 25 dilution

[0067] The acid solubility analysis of heavy metals such as lead and arsenic contained in diatomaceous earth products is performed according to the United States Pharmacopeia (USP) and the National Medical Products Collection (NF), specifically "USP40-NF35 Monograph on Purified Siliceous Earth, USP38-NF33" and "USP40-NF35 Monograph on Purified Siliceous Earth." <233> The procedure was carried out according to "Elemental Impurities". In the extraction step, 10.0 g of diatomaceous earth filtration product was added to 50 mL of 0.5 N hydrochloric acid in a 250 mL flask. The flask was covered with a watch glass and placed in a 70°C water bath for 15 minutes. The contents of the flask were filtered through Whatman #1 filter paper and the filtrate was collected in a 100 mL volumetric flask. The solid on the filter paper was washed with 3 volumes of 10 mL of deionized water preheated to 70°C. The total volume of the filtrate was diluted to 100 mL of solution using deionized water.

[0068] In the analysis of lead or arsenic using GFAA, a set of lead and arsenic standards was prepared and used to calibrate the spectrometer. Next, 10 mL of the sample filtrate was analyzed to determine the concentration of extractable metals in the solution. The concentration of Pb or As in the solution was calculated as follows: Soluble metal (ppm) = (Metal from GFAA (ppm)) × Dilution factor × 40.

[0069] Exemplary Examples Next, the present disclosure will be illustrated by the following non-limiting embodiments. Note that various changes and modifications may be applied to the following embodiments and processes without departing from the scope of the invention as defined in the appended claims. Accordingly, note that the following embodiments should be construed as illustrative only and not limiting in any sense.

[0070] Various product examples of the ultra-low surface charge, high-performance bio-based filtration media of this disclosure are shown below, covering transmittances from 600 millidarcy to 20,000 millidarcy. These examples are provided for illustrative purposes only and are not limiting.

[0071] Method for preparing an ultra-low surface charge and high-performance diatomaceous earth filtration medium (non-acid washed grade) The dried crude ore extracted from the mine was crushed in a hammer mill and passed through an 80-mesh size, and a centrifugal separation wet density test was performed, yielding a density of 0.256 g / ml (16.0 lb / ft). 3 The material was confirmed to be less than 0.224 g / ml (14.0 lb / ft) and used for the preparation of the process feed. The standard operating procedure for performing the centrifugal wet density test is described above in the section “Method for Characterizing Ultra-Low Surface Charge and High-Performance Diatomaceous Earth Filtration Media” of this disclosure. The centrifugal wet density of the feed material used to prepare the ultra-high-performance product / media (non-acid washed version) of this disclosure was 0.224 g / ml (14.0 lb / ft). 3) was then used. The crushed material was then classified using a mechanical air separator to separate heavy mineral impurities such as quartz, chert, and sand from the freed low-density diatomaceous earth particles. The product from the separator was thoroughly blended with finely crushed soda ash using a fluidizing shaker, and then water was added with a mist of water, which effectively reduced the loose weight density of the feed in the subsequent calcination process. The material was calcined in a muffle furnace at a predetermined temperature and the product was cooled to room temperature. The final filtration medium was prepared in two ways depending on the permeability of the product in question. For filtration mediums with very high permeability (>5000 millidarcy), the cooled product was first sieved through a 50-mesh Tyler sieve using an alumina ceramic medium to help disperse large aggregates. Then, oversized material was dispersed using a Quadro Comil grinder equipped with a 35-mesh sieve. Then, both the sieved and crushed particles were combined to obtain the final filtration medium product. For low-permeability filtration media (less than 5000 millidarcy), the cooled product was fed into a Quadro Comil grinding apparatus to obtain the final product. The process conditions for calcining various filtration media are shown in Table 6 below. [Table 6]

[0072] -Example 1 Table 7 below shows the properties of exemplary products obtained by blending 8.0–12.0 wt% soda ash into diatomaceous earth feed material and firing it at 999°C to obtain ultra-low surface charge and high-performance filtration media. The zeta potential, which measures the surface charge of the products, is very low for all three product examples. An ideal low surface charge filtration media is zero mV, and the surface charge of the products in Table 7 approaches zero potential in the pH range of 3–8 as the amount of sodium oxide flux increases from 4.7 wt% to 7 wt%. The stoichiometric ratio of sodium oxide to silica for these ultra-low surface charge products is 5.1%–7.8%. The addition of a large amount of flux and water to the fired feed material results in extremely high permeability and extremely low centrifugal wet density. The combination of an extremely low zeta potential of -6.4 to -1.0 mV in the pH range of 3 to 8, a very high transmittance of up to 20,000 mD, and a very low density of filter aids results in a unique filter medium compared to currently available diatomaceous earth filter media products and prior art. [Table 7]

[0073] -Example 2 Table 8 below shows the properties of three examples of ultra-low surface charge and high-performance diatomaceous earth filter media (unacid-washed) with transmittances ranging from 5,000 to 9,700 millidarcy, prepared using 8.0%, 10%, and 12.0% soda ash at a firing temperature of 943°C. Unlike conventional commercially available diatomaceous earth products, the filter products of this disclosure have a much higher sodium oxide concentration. It is believed that the reaction of Na2O and SiO2 during the heat firing process to form sodium silicate suppresses the charge on the silica particle surface, helping to bring the zeta potential of the diatomaceous earth particles closer to zero. The high transmittance of these products is accompanied by a very low centrifugal wet density, lower than any prior art product and any commercially available product in this product category. [Table 8]

[0074] -Example 3 The physical and chemical properties of three exemplary products obtained by thermally reacting Na2O and SiO2 at a firing temperature of 871°C are shown in Table 9 below. In all of these examples, the permeability of the product decreases at this much lower firing temperature, even though the surface charge remains the same. The surface charge is always proportional to the amount of Na2O present in the filter medium. [Table 9]

[0075] -Example 4 The physical and chemical properties of three exemplary filtration media of this disclosure are shown in Table 10 below, using 8.0% by weight, 10% by weight, and 12.0% by weight of soda ash in feed preparation for the subsequent calcination process. [Table 10]

[0076] As demonstrated, despite the very high sodium oxide content, the product's permeability remained very low. The permeability range of 417 millidarcy to 3,203 millidarcy was achieved by employing a dry blend of soda ash and omitting the water addition step, which typically catalyzes the reaction between Na2O and SiO2 to produce high permeability. The surface charge remained very low at both low and high permeability, with a very low product density compared to products of prior art and other commercially available filtration media.

[0077] Method for preparing an ultra-low surface charge and high-performance diatomaceous earth filter medium (acid-washed grade) Examples of the acid-washed grades of the ultra-low surface charge and high-performance diatomaceous earth filtration media of this disclosure were prepared using a non-acid-washed grade of ultra-low surface charge filtration media as the starting feed material. A slurry of the feed material was prepared and leached with sulfuric acid in a glass reactor under the process conditions shown in Table 11 below. [Table 11]

[0078] The feed material can also be leached at high temperature and pressure as needed. At the end of the leaching operation, the slurry was dewatered using a pressure filter, and the resulting cake was thoroughly washed with deionized water in the filter so that the conductivity of the 10 wt% slurry of the dried filtration cake was less than 20 μS / cm. This cake was dried and dispersed to obtain a high-purity filtration medium without altering the surface charge properties of the original diatomaceous earth filter material.

[0079] -Example 5 Table 12 below shows the characteristics of exemplary ultra-low surface charge and high-performance diatomaceous earth filtration media after acid purification. These exemplary products feature extremely low surface charge, with zeta potentials in the range of only -1.2 mV and -2.5 mV in the pH 3 and pH 8 ranges, as the sodium oxide content of the media increases to 7.0 wt%. The concentrations of extractable heavy metals, lead and arsenic, in the media are less than 1 ppm, below the detection limit for analysis. The extractable iron content is also extremely low. These products cover a transmittance range of 7,100 to 4,600 mD and have a very low centrifugal wet density compared to conventional equivalent products of the same type. [Table 12]

[0080] -Example 6 The properties of exemplary ultra-low surface charge filtration media with transmittances in the range of 3000–6000 millidarcy are shown in Table 13 below. These exemplary ultra-low surface charge filtration media have very low centrifugal wet density, which results in high filtration performance. Conductivity is less than 10 μS / cm, and the extractable metal content is very low in all of these products. The range of surface charge of these products is determined by the stoichiometric ratio of sodium oxide to silica, with the zeta potential decreasing as this ratio increases. [Table 13]

[0081] -Example 7 The properties of exemplary purified, ultra-low surface charge high-performance diatomaceous earth filtration media in the transmittance range of 450 millidarcy to 2500 millidarcy are shown in Table 14 below. These exemplary products exhibit very low conductivity, low extractable metals, and ultra-low surface charge. [Table 14]

[0082] Thus, this disclosure provides embodiments of an ultra-low surface charge, high-performance diatomaceous earth filter medium having a unique combination of extremely low surface charge, extremely low extractable impurities per unit mass, extremely low centrifugal wet density, and extremely high flow rate relative to density. Because the centrifugal wet density of this biofilter medium is extremely low, the unit consumption is significantly reduced in terms of the mass consumed per unit of fluid being filtered. The combination of reduced unit consumption and ultra-low surface charge may be beneficial in plasma fractionation processes by providing a combined effect that minimizes the overall charged particles that come into contact with the fluid to generate unwanted PKA contamination. The net effect is a diatomaceous earth filter medium that maintains the PKA content of plasma products below desired levels and provides the performance necessary to eliminate the need for secondary chromatography processes to reduce PKA levels below regulatory limits.

[0083] While the above detailed description presents at least one exemplary embodiment, it should be understood that a vast number of variations exist. Furthermore, it should be understood that the exemplary embodiments are merely illustrative and are not intended to limit the scope, applicability, or configuration of the present invention in any way. Rather, the above detailed description will provide a convenient roadmap for those skilled in the art to carry out exemplary embodiments of the compositions and methods of the present invention. It should be understood that various modifications can be made to the function and arrangement of the elements described in the exemplary embodiments without departing from the scope of the present invention as defined in the appended claims.

Claims

1. A diatomaceous earth filtration product containing diatomaceous earth calcined with a flux, The aforementioned diatomaceous earth filtration product, (1) The complex porous structure of diatomaceous earth, (2) Zeta potential in the range of -1.0 to -6.0 mV within a pH range of 3.0 to 8.0, and (3) Having a centrifugal wet density in the range of 0.176 to 0.256 g / mL, The aforementioned filtration product is produced by blending dry diatomaceous earth with a centrifugal wet density of 0.256 g / ml or less with a flux in an amount of 6% to 12% by weight based on the total weight of the blend, preparing a blend, and then heat-sintering the blend to form a flux-fired diatomaceous earth. The blend has a stoichiometric ratio of the flux to silicon dioxide of at least 5.0%, and 7 to 15% by weight of water is introduced into the blend based on the total weight of the blend to form a dispersion of diatomaceous earth, water, and flux, thereby providing a diatomaceous earth filtration product.

2. The diatomaceous earth filtration product according to Claim 1, having a permeability in the range of 450 millidarcy to 20,000 millidarcy.

3. The diatomaceous earth filtration product according to claim 1 or 2, wherein the stoichiometric ratio of sodium oxide to silicon dioxide is 5.0 to 8.0%.

4. The diatomaceous earth filtration product according to claim 1, wherein the flux is selected from the group consisting of sodium oxide, sodium carbonate, and sodium bicarbonate.

5. The diatomaceous earth filtration product according to claim 1, wherein the filtration product contains less than 1 mg / kg of USP extractable lead (Pb).

6. The diatomaceous earth filtration product according to claim 1, wherein the filtration product contains less than 1 mg / kg of USP extractable arsenic (As).

7. The diatomaceous earth filtration product according to claim 1, wherein the filtration product contains less than 10 mg / kg of USP extractable iron (Fe).

8. The diatomaceous earth filtration product according to claim 1, wherein the dried diatomaceous earth has a centrifugal wet density in the range of 0.144 g / ml to 0.240 g / ml.

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