RU2173576C2 - High-purity biogenic silicon dioxide product - Google Patents

Abstract

FIELD: biologically active materials. SUBSTANCE: high-purity biogenic silicon dioxide product is prepared from diatomite. Invention also relates to high-purity non-calcined , calcined, and alloyed calcined diatomite products characterized by porous and complex silicon dioxide structure only characteristic of diatomite and which show unusually high silicon dioxide content and low density, which cause high specific volume of silicon dioxide. These products are also often characterized by exclusively low content of soluble metals and/or extremely high brightness. EFFECT: extended choice biologically acceptable materials. 20 cl, 1 tbl, 3 ex

Description

The present invention relates to a high-purity biogenic silicon dioxide product obtained from diatomite, and to methods for its preparation. In particular, the present invention relates to a high-purity biogenic silicon dioxide product that has a characteristic porous and complex silica structure characteristic only of diatomite, and which is characterized by an unusually high content of silicon dioxide (i.e. SiO ₂ ) and low density, which leads to a high specific volume silica. The present invention also relates to modified highly pure biogenic silicon dioxide products having an extremely low soluble metal content and / or extremely high brightness.

BACKGROUND OF THE INVENTION
A full list of identifying references to various publications, patents and published patent applications found throughout the text of the present description can be found at the end of the description immediately before the claims. The contents of these referenced publications, patents, and published patent descriptions are incorporated herein by reference in order to more fully represent the current state of the art to which the present invention relates.

 The present invention relates to purified diatomite products, which not only retain the complex and porous structure inherent only to diatomite (i.e., which are characterized by the complex and porous structure of diatom silicon dioxide), but also have a unique combination of special physical and chemical properties (for example, such as high purity, low density, low soluble impurities, low total impurities and high brightness). The unique combination of the special properties demonstrated by these high-purity diatom products of the present invention (which contribute, among other things, to increase the efficiency and economy) are not manifested by any other known diatomaceous products.

 Currently, diatomite products are used in a wide variety of technical fields, including, but not limited to, separation, adsorption, preparation of carriers and functional fillers. Recently published reviews (Breese, 1994; Engh, 1994) provide a particularly valuable insight into the properties and applications of diatomite. The purified diatomite products of the present invention are characterized by both a complex and porous structure, characteristic only of diatomaceous silicon dioxide, and exceptional purity, therefore they can achieve significantly higher efficiency in many of these applications.

 Diatomaceous products are obtained from diatomaceous earth (also known as kieselguhr), which is sludge enriched with biogenic silicon dioxide (i.e. silicon dioxide produced or produced by organisms) in the form of silicon-containing shells (i.e. shells or skeletons) diatoms. Diatoms include many different microscopic unicellular golden brown algae of the Bacillariophyceae class, which have an ornamented silicon-containing skeleton (i.e., carapace) of a diverse and complex structure consisting of two folds that, in living diatoms, are interconnected and resemble a box in shape for pills. The morphology of the shells of various species differs in a wide variety and serves as the basis for taxonomic classification: at least over 2000 different species are known. On the surface of each sash there are a number of holes that form a complex thin structure of the sash and create a pattern by which to distinguish individual species. The size of a typical leaf is 0.75-1000 microns, although in most it is 10-150 microns. These flaps are strong enough to maintain a substantial part of their porous and complex structure virtually intact for long geological periods during storage under conditions in which chemical equilibrium is maintained.

 Given the nature of the chemical composition in combination with the complex and porous structure of the shell of diatoms, the unique technical value and versatility of diatomite, which has no analogues among other natural varieties of silicon dioxide, for example, in the field of technology such as filtering and preparation of filters. The fine structure of the skeleton of diatoms in the form of particles explains the low density and large specific surface area, as well as high porosity and permeability.

 Diatomaceous products can be obtained by various methods and from many sources, causing a variety of both physical and chemical properties.

 In the field of filtration, many methods for separating powdered substances from liquids are carried out using diatomite products as auxiliary filter substances. The complex and porous structure, characteristic only of diatomaceous silicon dioxide, is especially effective for the physical capture of particles in filtering processes. In accordance with conventional practice, diatomaceous products are used to increase the transparency of liquids that contain suspended particles or a powdery material and are characterized by turbidity.

 To increase transparency and increase flow rate during filtration processes, at the stage, which is sometimes referred to as "applying a layer of filter material", diatomite products are often applied to the membrane. Diatomite is often also added directly to the liquid when it is filtered, in order to reduce the load of the undesirable powdery material on the membrane while maintaining the estimated flow rate of the liquid in the stage, often referred to as “thickener replenishment”. Depending on the specific separation process, diatomite products can be used to apply a layer of filter material, replenish thickener, or both. The basics of diatomite filtration are presented in a review (Kiefer, 1991).

 When used in some filtering processes with the aim of further modifying or optimizing the filtering mode, various diatomite products are mixed together. In addition, diatomite products are sometimes combined with other substances. In some cases, such combinations may include simple mixtures, for example, with cellulose, activated charcoal, clay or other materials. In other cases, these combinations are composite materials in which diatomite products are homogeneously compounded with other components in the form of sheets, gaskets or sleeves. However, even more complex modifications of any such diatomite products are used for filtration or separation, including, for example, surface treatment and the addition of chemicals to diatomaceous products, mixtures or their composite materials.

In some circumstances, diatomite products can also exhibit unique adsorption properties during filtration, which can greatly enhance clarification or purification of the liquid. These adsorption properties are highly specific and depend on the weak attractive forces of adsorbed materials under the influence of weak electric charges on the surface of diatomite or on the reactivity of silanol (i.e., ≡Si-OH) functional groups, which are often located on the diatomite surface. For example, an ionized silanol group (i.e., iSi-O ^- ) is able to interact with a hydroxonium ion (i.e., H ₃ O ⁺ ), which is facilitated by an acidic substance, e.g., citric acid (i.e., C ₆ H ₈ O ₇ ), adsorbing the released H ⁺ ion on the surface during the process.

 The complex and porous structure of silicon dioxide, characteristic only of diatomite products, also determines the possibility of their industrial application to give polymers such a property as non-stickiness. Diatomite products are often used to change the appearance or properties of paints, enamels, varnishes and related materials for coating and finishing materials. In addition to their use in paper products or cellulose-containing filter media, diatomaceous products find industrial application in papermaking processes and are essential in the manufacturing technology of some industrial catalysts. Diatomaceous products are also used as chromatographic solid carriers, and they are particularly suitable for gas-liquid chromatographic methods.

 Regardless of the method in which a diatomite product is used to separate particles from liquids, the diatomite product must come into contact with a liquid from which particles are removed. As a component in polymers, plastics, paints, coating materials and other compositions, the diatomite product also contacts most of the other components of the composition. For this reason, high purity of silicon dioxide and low solubility of impurities in the diatomite product are often very necessary properties. In addition, the effectiveness and feasibility of using a diatomite product as an auxiliary filter medium is also related to its density when it is in contact with the liquid during the filtering process. In most cases, there is an urgent need for a low-density diatomaceous product.

 The high-purity diatomite products of the present invention and their further modifications may find application in numerous other technical fields. Since the effectiveness of diatomite in its application is usually associated with the presence of pores and the complex structure of silicon dioxide, which is characteristic only of diatomite, in combination with a high degree of purity of silicon dioxide, these distinctive qualities exhibit to a greater extent than was possible to date, highly pure diatomite products with the present invention.

Description of the invention
In one embodiment of the present invention, there is provided a high-purity diatomite product having a complex and porous structure of diatom silica, this product being selected from the group consisting of a non-calcined product with a specific volume of silica of more than 3.5; a calcined product with a specific volume of silica of more than 3.6; and a fluxed calcined product with a specific volume of silica of more than 3.3. In a preferred embodiment, the total content of silicon dioxide (SiO ₂ ) in the non-calcined product is more than 95 wt.% In terms of the amount after calcination; the total content of silicon dioxide (SiO ₂ ) in the calcined product is more than 98 wt.% in terms of the amount after calcination; and the total content of silicon dioxide (SiO ₂ ) in the fluxed calcined product is more than 92 wt.% in terms of the amount after calcination. In a preferred embodiment, the content of beer-soluble aluminum in the product is less than 10 mg Al / kg of product. In another preferred embodiment, the content of beer-soluble iron in the product is less than 7 mg Fe / kg of product.

According to another embodiment of the present invention, there is provided a high-purity non-calcined diatomite product having a complex and porous structure of diatom silica, the specific volume of silica of this product being more than 3.5. In a preferred embodiment, the total content of silicon dioxide (SiO ₂ ) in the non-calcined product is more than 95 wt.% In terms of the amount after calcination. In another preferred embodiment, the content of beer-soluble aluminum in the non-calcined product is less than 10 mg Al / kg of product. In a further preferred embodiment, the content of beer-soluble iron in the non-calcined product is less than 7 mg Fe / kg of product. In another preferred embodiment, the specific resistance of the product is more than 50 kOhm · cm.

In another embodiment of the present invention, there is provided a high purity calcined diatomaceous product having a complex and porous structure of diatom silica, wherein the specific volume of silica of this product is more than 3.6. In a preferred embodiment, the total content of silicon dioxide (SiO ₂ ) in the calcined product is more than 98 wt. % in terms of the amount after calcination. In another preferred embodiment, the content of beer-soluble aluminum in the calcined product is less than 10 mg Al / kg of product. In another preferred embodiment, the content of beer-soluble iron in the calcined product is less than 7 mg Fe / kg of product. In another preferred embodiment, the specific resistance of the calcined product is more than 80 kOhm · cm. According to another preferred embodiment, the brightness of the reflected blue light of the calcined product is more than 96%.

In yet another embodiment of the present invention, there is provided a high purity fluxed calcined diatomaceous product having a complex and porous structure of diatom silica, wherein the specific volume of silica of this product is more than 3.3. In a preferred embodiment, the total content of silicon dioxide (SiO ₂ ) in the fluxed calcined product is more than 92 wt.% In terms of the amount after calcination. In another preferred embodiment, the content of beer-soluble aluminum in the fluxed calcined product is less than 10 mg Al / kg of product. In a further preferred embodiment, the content of beer-soluble iron in the fluxed calcined product is less than 7 mg Fe / kg of product. According to another preferred embodiment, the luminance according to the reflected blue light of the fluxed calcined product is more than 95%. In another preferred embodiment, the total total content of sodium (Na ₂ O) and the total content of silicon dioxide (SiO ₂ ) in the fluxed calcined product is more than 98 wt.% In terms of the amount after calcination.

 Further, according to another embodiment of the present invention, there is provided a high-purity diatomite product having a complex and porous structure of diatom silica, the brightness of the reflected blue light of this product being more than 99%.

Brief Description of the Drawings
In FIG. 1 is a bar chart illustrating data for the specific volume of silica in various silicon dioxide products, as presented in Table 1, Part B.

 In FIG. Figure 2 shows a photographic image of a calcined high-purity diatomite product from Example 2 made using a scanning electron microscope.

Embodiments of the invention
A. High Purity Biogenic Silicon Dioxide Product
The high-purity diatomite products of the present invention are characterized by an unusually high silica content. In addition to the high content of silicon dioxide, these products also retain a complex and porous structure, which is a distinctive feature of diatomite (i.e., products have a complex and porous structure of diatom silicon dioxide), which is essential for the effective use of a diatomite product in many areas of technology. This unique combination of properties determines, among other things, the target low density in the wet state after centrifugation, the additional result of which is a large specific volume of silicon dioxide in excess of the specific volume of any previously known diatomite product.

 The purified diatomite product of the present invention has a low density in combination with a low content of soluble impurities, which leads to increased throughput, flow rate, transparency or occupancy per unit mass when used in a confined space while at the same time significantly less undesirable aluminum, iron and other elements, passing from the diatomaceous product into the material in contact with it. Thus, in many areas of technology, the use of the proposed high-purity diatomite products can improve purity, as well as increase the efficiency of material consumption, the level of which is significantly lower than that which is currently achievable.

 The high-purity diatomite products of the present invention, depending on the manner in which these products were prepared, can accordingly be described as non-calcined, calcined or fluxed calcined. These broad classes reflect the production methods used that allow you to control the permeability of the product by adjusting the degree to which agglomeration and sintering of the product occur and which is fundamental to the effectiveness of these high-purity diatomite products.

 As used herein, the term "non-calcined product" refers to a product that has not been calcined or calcined in a fluxed state. As used herein, the term “calcined product” refers to a product that has been calcined. Typical methods of calcination and its parameters are presented below in the description of the methods. As used herein, the term “fluxed calcined product” refers to a product that has been subjected to fluxed calcination (ie, calcination in the presence of flux). Typical fluxes are presented below in the description of the methods.

 The composition and properties of the high-purity diatomite products of the present invention, as well as known diatomite products are described in detail below.

1. Permeability
For use in filtration, diatomite products are usually processed to provide a range of filtration rates that are closely related to their permeability. The permeability, expressed in units of darcy, which is usually denoted by "D", is easy to determine (European Brewery Convention, 1987) using a specially designed device that serves to form a filter cake on a membrane from a suspension of diatomite in water, then measure time , which is required for a certain volume of water to pass through a filter cake set by measuring thickness with a known cross-sectional area. Earlier, Darcy's law (Bear, 1972) derived principles for a porous medium, due to which there are a number of alternative instruments and methods that correlate well with permeability. Diatomite filter aid, which is currently technically available, includes materials in a wide range of permeability from about 0.001 to about 30 D. The choice of filter aid with a specific permeability, suitable for use in a particular filtering process, depends on the flow rate and the degree of clarification of the liquid that are required for a specific application.

 The high-purity diatomite products of the present invention are characterized by a permeability spectrum that is comparable to the range exhibited by diatomaceous filter excipients that are currently technically available. The permeability of non-calcined, high-purity diatomite products of the present invention is less than about 0.1 D (typically in the range of from about 0.001 to about 0.1 D). The permeability of the calcined high purity diatomite products of the present invention is in the range of from about 0.05 to about 1.5 D. The permeability of the fluxed calcined high purity diatomite products of the present invention is more than about 1 D (typically in the range of from about 1 to about 50 D).

2. Solubility of iron / aluminum
Known diatomite products are used in large volumes for filtering liquids, such as beer. The main problem is the contamination of filtered beer with metals, such as iron (i.e., Fe in the form of Fe ²⁺ and / or Fe ³⁺ ions) or aluminum (i.e., Al in the form of Al ³⁺ ions). Thus, the content in the diatomite product of iron or aluminum, which is soluble in beer (for example, beer-soluble iron or beer-soluble aluminum) is an effective indicator of the degree to which contamination with these impurities can reach. So, for example, depending on the particular filter aid selected, the content of beer-soluble iron in the bulk of the known diatomaceous filter aid is from about 7 to about 50 mg Fe / kg of product.

Reliable analytical methods have been developed in industry for determining the solubility of iron in diatomite products in beer (American Society of Brewing Chemists, 1987). A preferred analytical method for high purity diatomite products is the calibrated calorimetry method using 1,10-phenanthroline (i.e., o-phenanthroline, C ₁₂ H ₈ N ₂ ). If the test sample is a non-calcined product, then this sample must be dried in air at 110 ^o C to constant weight, and then left to cool in air to room temperature (i.e., dried product). If the test sample is a calcined or fluxed calcined product, then this sample must be dried to constant weight in air at room temperature. A 5 g sample is introduced at room temperature in 200 ml of decarbonated beer (in this case, BUDWEISER, registered trademark of Anheuser-Busch) and the mixture is intermittently mixed in a vortex mode for a duration of 5 minutes and 50 seconds. Immediately after this, the mixture is transferred to a funnel containing filter paper with a diameter of 25 cm, after passing through which the filtrate collected during the first 30 s is discarded. Over the next 150 s, the filtrate is collected and a portion of 25 ml is treated with approximately 25 ml of ascorbic acid (i.e., C ₆ H ₈ O ₆ ) to recover dissolved iron ions to divalent iron ions (i.e. Fe ²⁺ ) (obtaining thus "sample extract"). When 1 ml of 0.3% (weight / volume) 1,10-phenanthroline is added, color appears and after 30 minutes the optical density of the obtained sample solution is compared with a reference calibration curve. This calibration curve is constructed using standard solutions of iron in beer of known concentration. The crude filtrate is used as a control to adjust for turbidity and color. The optical density is measured at 505 nm using a spectrophotometer, in this case, the company Milton & Bradley Spectronic.

 The content of beer-soluble iron in the high-purity diatomite products of the present invention is less than about 7 mg Fe / kg of product (usually in the range from about the lower limit to about 7 mg Fe / kg of product), more preferably less than about 5 mg Fe / kg of product (usually in the range from about the lower detectable limit to about 5 mg Fe / kg of product). The lower detectable limit (i.e., the detection limit) is approximately 2 mg Fe / kg of product.

 In a preferred method for determining the solubility of aluminum contained in diatomite products in beer, spectrophotometry using inducible argon plasma emission (IAP) is used. Extracts from the samples are prepared according to the method developed by the American Society of Brewing Chemists for beer (as described above for iron) and diluted with a solution of nitric acid in deionized water at a concentration of 2 vol.% To a beer content of 20 vol.%. This dilution is necessary to optimize sensitivity while maintaining plasma stability. The data for the analysis of dilute extract solutions presented in the description were collected using a Baird PSX model sequential IAP spectrophotometer, which can operate in a variety of spectroscopic sequences from 160 to 800 nm. This device is equipped with a thermostatically controlled 0.75-meter modified Czerny-Turner monochromator (models L-507 of Acton Research Corporation), in which a residual pressure of 8.5 Pa (≈65 mTorr) is created, a crystal oscillator is used, which generates high frequency of 40.68 MHz and creates a plasma using a coaxial flare device made of fused silica using a direct wave power of 700 watts (for the analysis results described in the description) at a reflected power of less than 0.5 watts. Welding grade liquid argon was used for the primary plasma, which was supplied through a mass flow controller (model 5876 from Emerson Electric Company, Brooks Instrument Division) in a mode of approximately 46 relative units. Interfacial optics were blown with argon at a flow rate of 4.0 relative units, as determined using a Mateson rotameter. The wavelengths were selected using a sine-wave mechanism, with absolute reference wavelengths being generated at the lattice edge of 160,000 nm, and with primary standard argon emission, the wavelength is 415.859 nm. Aluminum was determined at a first-order spectral line of 396.152 nm. For this line, the spectral interference from calcium, vanadium, and manganese was preliminarily evaluated and it was determined to be insignificant. The intensity for the sample solutions was compared with the intensity for a number of standards prepared in beer using industrial aluminum standard reference solutions (Spex Industries, Inc.).

 The content of beer-soluble aluminum in the high-purity diatomite products of the present invention is less than about 10 mg Al / kg of product (usually in the range from about the lower limit to about 10 mg Al / kg of product), more preferably less than about 8 mg Al / kg of product (usually in the range from about the lower detectable limit to about 8 mg Al / kg of product). The lower detectable limit (i.e., the detection limit) is approximately 2 mg Al / kg of product.

3. Resistivity
Since diatomite products are in close contact with the filtered fluid or come in tight contact with other components of the compounded products, when measuring the resistivity (i.e. electrical resistivity) of a 10% (mass / volume) suspension of the diatomite product in deionized water, a result that corresponds to a more general concentration of soluble ions. Deionized water is a very poor conductor of electric current, as a result of which the introduction of soluble ions (i.e. from a diatomaceous product) reduces the high resistivity of pure water. Diatomaceous products, which when suspended in deionized water exhibit a low resistivity, contribute to the addition of unwanted soluble ions to the suspension. In many cases, the presence of certain soluble monovalent alkali metal ions of group IA of the Periodic Table of the Elements (for example, potassium K ⁺ , and in particular sodium Na ⁺ ) has a weak effect on the suitability for use of a high-purity diatomite product. However, other ions, especially polyvalent ones (for example, iron Fe ²⁺ and / or Fe ³⁺ and aluminum Al ³⁺ ), have a stronger effect on the suitability for using a high-purity diatomite product.

Specific resistivity data for the high purity diatomite products of the present invention can be obtained using a cell to measure the electrical conductivity of the solution. If the test sample is a non-calcined product, this sample must be dried in air at 110 ^o C to constant weight, and then left to cool in air to room temperature (i.e., to dry the product). If the test sample is a calcined or fluxed calcined product, then this sample must be dried to constant weight in air at room temperature. A 10 g sample is introduced into a 250 ml funnel containing 100 ml of distilled or deionized water with a minimum resistivity of 1 MΩ • cm [i.e. 10% (w / v)]. The mixture is vortexed for 15 s to completely suspend the sludge, and then the suspension is allowed to settle. The mixture is again subjected to vortex mixing after 15 minutes and the suspension is allowed to settle for at least 1 hour. The liquid of the upper layer is decanted into the cell tube and the cell is immersed in the liquid to measure the electrical conductivity of the solution (EC Meter from Cole Farmer model 1481-61). To remove all trapped air bubbles from the cell, the cell is raised and lowered several times using the bridge for measuring low resistances, which is provided in the device, and the conductivity is measured. The cells for measuring the electrical conductivity of the solution are calibrated (to obtain a calibration constant) using solutions with a known resistivity. Using the results of measuring the resistivity and the calibration constant, the corrected resistivity is determined.

 The resistivity of the non-calcined, high-purity diatomite products of the present invention is greater than about 50 kΩ · cm (typically in the range of about 50 to about 250 kΩ · cm), more preferably in excess of about 60 kΩ · cm (usually in the range of about 60 to about 250 kΩ •cm). The resistivity of the calcined high-purity diatomite products of the present invention is more than about 80 kΩ · cm (usually in the range of about 80 to about 500 kΩ · cm), more preferably in excess of about 130 kΩ · cm (usually in the range of about 130 to about 500 kΩ •cm).

4. Brightness in reflected light
In many cases, especially when used as fillers, diatomaceous products are more effective if they exhibit high reflected brightness. A preferred method for determining the reflected brightness includes determining the amount of blue light reflected from the smooth surface of the product, which is carried out using a special device that is equipped with a light source, a blue filter and a detector (Photovolt Brightness Meter, model 575). After turning on the lamp and stabilizing its emitting power, this device is calibrated using standard plates with known reflectivity for blue light. If the test sample is a non-calcined product, this sample must be dried in air at 110 ^o C to constant weight, and then left to cool in air to room temperature (i.e., to dry the product). If the test sample is a calcined or fluxed calcined product, then this sample must be dried to constant weight in air at room temperature. The recess in the plastic plate, which is made mechanically, is somewhat overfilled with a sample, which is then pressed using a plate with a smooth front side, using circular motions during pressing. A plate with a smooth face is carefully removed due to a sliding movement, which allows you to get a flat, undamaged surface. Next, the sample is placed in the sample hole in the device with a blue filter in place. After that, the measurement results of reflectivity are read directly from the indicator of the device. The ability to reflect blue light can also be calculated according to the brightness measurements carried out using other devices, for example, those supplied by Hunter or provided by the International Space Lighting Commission (ISS).

 The reflected brightness of the calcined highly pure diatomite products of the present invention is in excess of about 96% (usually in the range of about 96 to 100%), more preferably in excess of about 98% (usually in the range of about 98 to 100%), even more preferably in excess of about 99 % (usually in the range of from about 99 to 100%). The reflected brightness of the fluxed, calcined, high purity diatomite products of the present invention is in excess of about 95% (typically in the range of about 95 to 100%), more preferably in excess of about 97% (usually in the range of about 97 to 100%), even more preferably in excess of about 99% (usually in the range of about 99 to 100%).

5. The total content of silicon dioxide / iron / aluminum / sodium
Although silica in diatomaceous earth is a predominantly amorphous type of material that resembles the opal mineral, sometimes it contains crystalline quartz dust or sand, which although it consists of silicon dioxide, is not able to compete with diatomaceous earth or diatomite products that are complex and porous structure. During calcination or fluxed calcination, products can be obtained in which particles of diatomaceous earth are sintered with each other with the formation of large agglomerated particles, which leads to the modification of some properties of diatomaceous products. Even after intensive calcination, most of the diatomite products to a large extent retain their complex and porous structure, although the result of this treatment may be the conversion of amorphous hydrated silicon dioxide to amorphous anhydrous silicon dioxide, cryptocrystalline cristobalite or cryptocrystalline quartz.

 High-precision determination of the total silica content can be carried out using x-ray fluorescence spectrometry. This method can also be used to determine the total content of other elements, such as aluminum, iron and sodium.

In a preferred fused tetraborate matrix X-ray fluorescence method used to determine the total content of elements in the high purity products of the present invention, a 2 g sample of diatomite (after calcining at 950 ^° C. in air for 1 h) is melted together with 7.7 g of lithium tetraborate (i.e., Li ₂ B ₄ O ₇ ) and a rod 40 mm long is cast from the melt. Such a rod is analyzed in a Philips PW1600 simultaneous X-ray fluorescence spectrometry instrument. This system is calibrated using more than 40 reference materials, most of which are presented in the table in Covindaraju (1989). The estimated time for basic elements such as silicon, aluminum, iron or sodium is 60 s, each element being determined by its own fixed channel. The decrease in data is due to the calcination mentioned. In order to coordinate the natural losses of hydration in the structure of silicon dioxide, the total content of silicon, aluminum, iron and sodium in all examples is given in terms of the amount after calcination for their corresponding higher oxides (i.e., SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ and Na ₂ O). Used in the present description, the term "in terms of the amount after calcination" reflects the preliminary processing of the sample before analysis by calcination at 950 ^o C in air for 1 hour

In another “pressed binder matrix” X-ray fluorescence method used to determine the total content of elements, a 3 g sample of diatomite (after calcining at 950 ^° C. in air for 1 h) is added to 0.75 g of SPECTROBLEND binder product (registered trademark Chemplex mark). The mixture is ground by shaking for 5 minutes in a tungsten carbide mixing container with shock balls. The finished mixture is then pressed into a 31 mm mold under a load of 24,000 psi (165 MPa) to form a tablet. Next, the chemical composition is determined using an Spectrace 6000 X-ray fluorescence spectrometer, which operates in the basic parameters mode and is calibrated using diatomite standards prepared in the same way as samples. This spectrometer employs an electronically cooled detector Li (Si) and an X-ray source with a rhodium anode at a voltage of 50 kV; its design allows the sample to be excited with an approximately 50% delay time. The intensity of the bands in the spectrum is analyzed by linear analytical comparison with the spectrum for a single reference element. The intensity of the K _alpha bands, used specifically for determining silicon, aluminum, and iron, is consistent with energy values of 1.740, 1.487, and 6.403 keV, respectively. The intensity of the bands for diatomite standards is then converted into calculated coefficients for pure elements, which are used to determine the content of elements in the samples according to the intensity of the bands and the correspondence of the data. Using this method, results are obtained that are compatible with the results of the method mentioned above for all elements except sodium, in which case the relative error is much larger than in the method with fused tetraborate matrix.

The total silica content of the non-calcined high purity diatomite products of the present invention is more than about 95 wt.% (SiO ₂ ) [usually in the range of from about 95 to about 99.9 wt. % (SiO ₂ )]; more preferably in excess of about 97 wt.% (SiO ₂ ) [usually in the range of from about 97 to about 99.9 wt.% (SiO ₂ )]; even more preferably in excess of about 98 wt.% (SiO ₂ ) [usually in the range of from about 98 to about 99.9 wt.% (SiO ₂ )]; most preferably in excess of about 99 wt.% (SiO ₂ ) [usually in the range of from about 99 to about 99.9 wt.% (SiO ₂ )], calculated on the amount after calcination.

The total content of silicon dioxide in the calcined high-purity diatomite products of the present invention is more than about 98 wt. % (SiO ₂ ) [usually in the range of from about 98 to about 99.9 wt.% (SiO ₂ )]; more preferably in excess of about 99 wt.% (SiO ₂ ) [usually in the range of from about 99 to about 99.9 wt.% (SiO ₂ )], calculated on the amount after calcination.

The total silica content of the fluxed, calcined, high-purity diatomite products of the present invention is more than about 92 wt. % (SiO ₂ ) [usually in the range of from about 92 to about 99.9 wt.% (SiO ₂ )]; more preferably in excess of about 94 wt. % (SiO ₂ ) [usually in the range of from about 94 to about 99.9 wt.% (SiO ₂ )]; most preferably in excess of about 96 wt.% (SiO ₂ ) [usually in the range of from about 96 to about 99.9 wt.% (SiO ₂ )], calculated on the amount after calcination.

The total iron content of the non-calcined, calcined and fluxed calcined high purity diatomite products of the present invention is less than about 0.3 wt.% In terms of Fe ₂ O ₃ [usually in the range of from about 0.005 to about 0.3 wt.% (Fe ₂ O ₃ )]; more preferably less than about 0.2 wt.% (Fe ₂ O ₃ ) [typically in the range of about 0.005 to about 0.2 wt.% (Fe ₂ O ₃ )] of the amount after calcination.

The total aluminum content of non-calcined, calcined and fluxed calcined highly pure diatomite products of the present invention is less than about 0.5 wt.% In terms of Al ₂ O ₃ [usually in the range of from about 0.01 to about 0.5 wt.% ( Al ₂ O ₃ )]; more preferably less than about 0.4 wt.% (Al ₂ O ₃ ) [typically in the range of from about 0.01 to about 0.4 wt.% (Al ₂ O ₃ )] of the amount after calcination.

6. Density in the wet state
The extent to which a diatomite product retains a porous and complex structure characteristic only of diatomite can be determined by measuring its density in the wet state after centrifugation or density in the wet state after settling, or by equivalent measurement of bulk density, since the density value is limited by the placement in the mass, which can to be achieved. Density in the wet state is crucial because it reflects the pore volume suitable for trapping particles of the material during the filtering process, and it is the most important criterion for determining filtering efficiency. Diatomite products with a lower density in the wet state are characterized by a larger pore volume and, therefore, higher filtering efficiency.

Acceptable methods for measuring the bulk density of diatomaceous powders in a liquid medium give more reproducible results than in gases. A preferred method for determining the bulk density of the high purity products of the present invention is to measure the bulk density in the wet state after centrifugation. If the test sample is a non-calcined product, then this product must be dried in air at 110 ^o C to constant weight, and then left to cool in air to room temperature (i.e., to dry the product). If the test sample is a calcined or fluxed calcined product, then this sample must be dried to constant weight in air at room temperature. A sample of known mass in the range of 0.50-1.00 g is placed in a 14 ml calibrated centrifuge tube into which deionized water is added to bring the volume to about 10 ml. The mixture is thoroughly shaken until the entire sample is wetted and a dry powder remains. An additional amount of deionized water is added, washing the upper part of the tube in order to wash off the part of the mixture that adheres to the side wall of the tube after shaking. In the case of calcined or fluxed calcined products, the tube is centrifuged (in a Beckman AccuSpin instrument) for 3 minutes at a speed of 2700 rpm; in the case of non-calcined (e.g. dried) products, the tube is centrifuged for an additional 6 minutes at a speed of 2700 rpm. After centrifugation, the tube is carefully removed so as not to disturb the rest of the solid particles, and the level (i.e. volume) of the settled material is measured to the nearest half of the 0.05-milliliter graduation on the tube. The wet density after centrifugation of a known mass of powder is easily calculated by dividing the mass of the sample by the volume obtained by measurement. Typically, wet density after centrifugation is expressed in pounds / ft ³ or g / cm ³ ; the conversion factor for these units is 1 lb / ft ³ ~ 0.01602 g / cm ³ .

The wet density after centrifugation of non-calcined, high-purity diatomite products of the present invention is less than about 0.28 g / cm ³ (usually in the range of about 0.15 to about 0.28 g / cm ³ ); more preferably less than about 0.27 g / cm ³ (usually in the range of from about 0.15 to about 0.27 g / cm ³ ).

The wet density after centrifugation of the calcined highly pure diatomite products of the present invention is less than about 0.28 g / cm ³ (usually in the range of about 0.10 to about 0.28 g / cm ³ ); more preferably less than about 0.25 g / cm ³ (usually in the range of from about 0.10 to about 0.25 g / cm ³ ); even more preferably less than about 0.23 g / cm ³ (usually in the range of from about 0.10 to about 0.23 g / cm ³ ); most preferably less than about 0.21 g / cm ³ (usually in the range of from about 0.10 to about 0.21 g / cm ³ ).

The wet density after centrifugation of the fluxed, calcined, high-purity diatomite products of the present invention is less than about 0.29 g / cm ³ (usually in the range of about 0.10 to about 0.29 g / cm ³ ); more preferably less than about 0.25 g / cm ³ (usually in the range of from about 0.10 to about 0.25 g / cm ³ ); even more preferably less than about 0.23 g / cm ³ (usually in the range of from about 0.10 to about 0.23 g / cm ³ ); most preferably less than about 0.21 g / cm ³ (usually in the range of from about 0.10 to about 0.21 g / cm ³ ).

где долю кремнийдиоксидного компонента рассчитывают делением массового процентного содержания SiO₂ в пересчете на количество после прокаливания на 100, а плотность в мокром состоянии после центрифугирования выражают в граммах на кубический сантиметр (т.е. г/см³). Так, например, для образца с установленным общим содержанием диоксида кремния 99,1 мас.% (SiO₂) и плотностью в мокром состоянии после центрифугирования 0,27 г/см³ удельный объем диоксида кремния составляет 0,991/0,27 ~ 3,7. Как совершенно очевидно из этого уравнения, чем больше удельный объем диоксида кремния, тем обычно выше степень чистоты диатомитного продукта.7. Specific volume of silicon dioxide
It is believed that under ideal environmental conditions, the highest-purity diatomite product is characterized by both a high total silica content and a low wet density after centrifugation. This combination of properties often serves as a criterion for the effectiveness of a refined product compared to less pure diatomite products. It is believed that unclean diatomite has a higher density in the wet state after centrifugation due to the fact that its porous complex structure is occupied by pollutants. To quantify these properties, the specific volume occupied by silicon dioxide is determined by the following equation:

where the proportion of the silicon dioxide component is calculated by dividing the mass percentage of SiO ₂ in terms of the amount after calcination by 100, and the density in the wet state after centrifugation is expressed in grams per cubic centimeter (i.e. g / cm ³ ). So, for example, for a sample with a total silica content of 99.1 wt.% (SiO ₂ ) and a density in the wet state after centrifugation of 0.27 g / cm ^{3, the} specific volume of silica is 0.991 / 0.27 ~ 3.7 . As is perfectly obvious from this equation, the larger the specific volume of silicon dioxide, the usually higher the degree of purity of the diatomite product.

 This simple expression explains the effect of both total silica and bulk density. Even small changes in the total silica content or density in the wet state after centrifugation cause significant changes in the specific volume of silicon dioxide, therefore the specific volume of silicon dioxide is an exceptionally indicative sign of the purity of the diatomite product.

 The specific volume of silica of non-calcined, high-purity diatomite products of the present invention is more than about 3.5 (usually in the range of about 3.5 to about 7); preferably more than about 3.6 (usually in the range of from about 3.6 to about 7); more preferably above about 3.7 (typically in the range of from about 3.7 to about 7).

 The specific volume of silica in the calcined high purity diatomite products of the present invention is more than about 3.6 (usually in the range of about 3.6 to about 10); preferably more than about 3.8 (usually in the range of from about 3.8 to about 10); more preferably greater than about 4.0 (typically in the range of about 4.0 to about 10), most preferably greater than about 4.5 (usually in the range of about 4.5 to about 10) and preferably more than about 4.7 (usually in the range of from about 4.7 to about 10).

 The specific volume of silica of the fluxed, calcined, high-purity diatomite products of the present invention is more than about 3.3 (typically in the range of about 3.3 to about 10); preferably more than about 3.5 (usually in the range of from about 3.5 to about 10); more preferably greater than about 3.6 (typically in the range of about 3.6 to about 10), most preferably greater than about 4.0 (usually in the range of about 4.0 to about 10), preferably more than about 5.0 (usually in the range of about 5.0 to about 10), particularly preferably more than about 6.0 (typically in the range of about 6.0 to about 10).

8. High purity diatomaceous products of the present invention
The specific volume of silica of the non-calcined, high-purity diatomite product of the present invention is more than about 3.5 (typically in the range of about 3.5 to about 7). More preferably, the total silica content of this product is more than about 95 wt.% (SiO ₂ ), calculated on the amount after calcination [usually in the range of about 95 to about 99.9 wt.% (SiO ₂ )], due to wherein the wet density after centrifugation is less than about 0.28 g / cm ³ (usually in the range of about 0.15 to about 0.28 g / cm ³ ). This product retains a complex and porous structure inherent only to diatomite and a permeability that is typically less than 0.1 D (usually in the range of about 0.001 to about 0.1 D). In an even more preferred embodiment, the total iron content of this product is less than about 0.3 wt.% Based on Fe ₂ O ₃ of the amount after calcination [typically in the range of about 0.005 to about 0.3 wt.% (Fe ₂ O ₃ )]; and the total aluminum content is less than 0.5 wt.% in terms of Al ₂ O ₃ [usually in the range from about 0.01 to about 0.5 wt. % (Al ₂ O ₃ )] of the amount after calcination. Regarding solubility, it can be noted that the resistivity of the preferred product is more than about 50 kΩ · cm (usually in the range of about 50 to about 250 kΩ · cm); the content of beer-soluble iron is less than 7 mg Fe / kg of product (usually in the range from about the lower detectable limit to about 7 mg Fe / kg of product); and the content of beer-soluble aluminum is less than 10 mg Al / kg of product (usually in the range from about the lower detectable limit to about 10 mg Al / kg of product).

The specific volume of silica of the calcined high purity diatomite product of the present invention is more than about 3.6 (typically in the range of about 3.6 to about 10). In a more preferred embodiment, the total silica content of this product is more than about 98 wt.% (SiO ₂ ), calculated on the amount after calcination [usually in the range of about 98 to about 99.9 wt.% (SiO ₂ )], due to wherein the wet density after centrifugation is less than about 0.27 g / cm ³ (typically in the range of from about 0.10 to about 0.27 g / cm ³ ). This product retains the complex and porous structure inherent only to diatomite, and permeability, which is usually in the range from about 0.05 to about 1.5 D. In an even more preferred embodiment, the total iron content in this product is less than about 0.3 wt. . % in terms of Fe ₂ O ₃ of the amount after calcination [usually in the range from about 0.005 to about 0.3 wt.% (Fe ₂ O ₃ )]; and the total aluminum content is less than 0.5 wt.% in terms of Al ₂ O ₃ [usually in the range of from about 0.01 to about 0.5 wt.% (Al ₂ O ₃ ] of the amount after calcination. Concerning solubility, note that the resistivity of the preferred product is more than about 80 kOhm · cm (typically in the range of about 80 to about 250 kOhm · cm); the content of beer-soluble iron is less than 7 mg Fe / kg of product (usually in the range of about the lower detectable limit to approximately 7 mg Fe / kg product), and the beer content soluble aluminum is less than 10 mg Al / kg product (usually in the range from about a lower limit determined to about 10 mg Al / kg product). The brightness of such a preferred product of the reflected blue light is more than 96%.

The specific volume of silica of the fluxed, calcined, high-purity diatomite product of the present invention is more than about 3.3 (typically in the range of about 3.3 to about 10). In a more preferred embodiment, the total silica content of this product is more than about 92 wt.% (SiO ₂ ), calculated on the amount after calcination [typically in the range of from about 92 to about 98 wt. % (SiO ₂ )], whereby the density in the wet state after centrifugation is less than about 0.29 g / cm ³ (usually in the range from about 0.10 to about 0.29 g / cm ³ ). This product retains the complex and porous structure inherent only to diatomite, and a permeability that is more than about 1 D (usually in the range of from about 1 to about 50 D). In an even more preferred embodiment, the total iron content of this product is less than about 0.3 wt.% Based on Fe ₂ O ₃ of the amount after calcination [typically in the range of about 0.005 to about 0.3 wt.% (Fe ₂ O ₃ )]; and the total aluminum content is less than 0.5 wt.% in terms of Al ₂ O ₃ [usually in the range from about 0.01 to about 0.5 wt.% (Al ₂ O ₃ )] of the amount after calcination. Regarding solubility, it should be noted that the content of beer-soluble iron in the preferred product is less than 7 mg Fe / kg of product (usually in the range from about the lower limit to about 7 mg Fe / kg of product), and the content of beer-soluble aluminum is less than 10 mg Al / kg product (usually in the range from about the lower detectable limit to about 10 mg Al / kg of product). The brightness of the blue light reflected by such a preferred product is more than 95%.

9. Comparison of the high purity diatomite products of the present invention with known diatomite products
Significant efforts aimed at turning low-grade diatomaceous lands into higher-grade minerals led to the production of diatomaceous products, which in their qualities are essentially equivalent to technical products obtained from naturally improved minerals. Examples include Norman and Ralston (1940), Bartuska and Kalina (1968a, 1968b), Vistman and Picard (1972), Tarhanic and Kortisova (1979), Xiao (1987), Li (1989), Liang (1990) Zhong et al. (1991), Brozek et al. (1992), Wang (1992), Cai et al. (1992) and Videnov et al. (1993). By a unique combination of properties, none of these products resulting from these developments reaches the level of the high-purity diatomite products of the present invention.

 It is more appropriate in this connection to mention several diatomaceous products, which are obtained with the improvement of a single target property, since these products are designed to achieve unique properties. For example, Thompson and Barr (1907), Barr (1907), Vereinigte (1913, 1928), Koech (1927), Swallen (1950), Suzuki and Tomizawa (1971), Bradley and McAdam (1979), Nielsen and Vogelsang (1979), Heyse and Feigl (1980) and Mitsui et al. (1989) focused their efforts on producing products with only a reduced total iron or soluble iron content and only a slight improvement, reported other important properties, if possible . The diatomite product obtained by Baly (1939) was characterized by a low content of organic substances, Codolini (1953), Pesce (1955, 1959), Martin and Goodbue (1968) and Munn (1970) received diatomite products with relatively high brightness, but the effect on other important properties not reported.

 In some cases, it was reported that diatomite products were obtained in which more than one property was improved. The diatomite product obtained by Enzinger (1901) at the same time had a reduced normal solubility. Diatomite products obtained by Bregar (1955), Cruder and vy et al. (1958) and Nishamura (1958) showed a higher brightness in combination with a reduced total iron content. The fluxed calcined diatomite product obtained by Smith (1991a, b, c; 1992a, b, c; 1993; 1994a, b) had an improved content of soluble polyvalent cations. In all these cases, there were no reports of effects on other important properties.

The product obtained by Schuetz (1935) was characterized by a relatively high total silica content [94.6% (SiO ₂ )] and a total iron content of 0.5% (Fe ₂ O ₃ ), but the total aluminum content in the product was still 2 5% (Al ₂ O ₃ ). Although Filho and Mariz da Veiga (1980) obtained a product with a low total aluminum content (0.28% Al ₂ O ₃ ) and a total iron content of 0.31% (Fe ₂ O ₃ ), the total silicon content was only 92.6% (SiO ₂ ), and a residual loss on ignition of 1.3% indicated that the diatomite product was still unclean.

From the starting materials, the silicon dioxide component of which was a mixture of approximately 65% diatomite, 30% quartz and a total of 5% silicates, Marcus and Creanga (1965) and again Marcus (1967) obtained products with interesting properties, including the total content of silicon dioxide up to 98.5% (SiO ₂ ), a low total iron content of 0.06% (Fe ₂ O ₃ ) and a total aluminum content of only 0.36% (Al ₂ O ₃ ). The actual concentration of crystalline quartz remaining in the products was not reported, but all the residual crystalline quartz was probably covered by the total content of silicon dioxide, thus partially depriving the products of all the advantages achieved due to the complex and porous structure of diatomite. The reported high wet density of the products (at least 0.43 g / cm ³ ) confirms that a notable portion of the total silica reported was accounted for non-diatom silica. The highest value of the specific volume of silicon dioxide obtained by calculation for the mentioned products is 2.3, which clearly indicates diatomite with low efficiency and quality. In fact, these products are characterized by a density that is significantly higher than the density of technical diatomaceous products, as a result of which they are unattractive or generally unsuitable for the main areas of application of diatomite products. In addition, Marcus and Creanga (1965) and again Marcus (1967) do not provide data on the residual soluble aluminum and iron content, which are crucial for many applications of diatomaceous products.

B. Methods for the production of high purity biogenic silicon dioxide products
1. Methods of obtaining non-calcined product
The high-purity diatomite products of the present invention can be obtained using a specific sequence of technological steps, carried out in the following order: (I) grinding in a friction mill, (II) processing in a hydrocyclone, (III) flotation and optionally (IV) leaching. Subsequent process steps, such as calcining or fluxing, can also be carried out.

 In a typical method, diatomaceous earth in the form of a raw mineral is crushed to a size that can be further reduced by grinding to such an extent that the material passes through a coarse, with large mesh sieve. Water is added to the mineral and the mixture is wet milled in a friction mill to obtain a uniform slurry of particles that pass through a fine, fine-mesh sieve. This slurry is introduced into a hydrocyclone, the design of which is designed to form an overhead product that includes particles of a much smaller average size, with the effective separation of heavier mineral impurities (in the lower hydrocyclone product) from diatomite (in the upper hydrocyclone product). The upper product of the hydrocyclone is sent to the reverse flotation process, during which, under the chosen conditions (for example, pH, concentration of solid particles, etc.), impurities are concentrated in a foam, into which a collector (for example, greasy) is added to increase the concentration and remove impurities amine), while the enriched diatomite fraction is separated and recovered. To improve the purification, the enriched diatomite fraction is leached in an appropriate medium and under special conditions (for example, acid treatment), which allows additional residual impurities to be removed, then washed thoroughly with deionized water. At this stage, high-purity diatomaceous earth is dehydrated, compacted and dried.

 A preferred method for preparing a non-calcined, high-purity diatomite product of the present invention and the properties of the finished product are illustrated in Example 1 below.

2. Methods for producing calcined products
Uncalcified high-purity diatomite product can then be purified by calcination to obtain a calcined product. Calcination conditions and methods are usually chosen so that the degree of sintering and agglomeration of diatomaceous particles is achieved, which are necessary to ensure a specific flow rate of the product. Calcination can be carried out in a temperature range that definitely exceeds ~ 110 ^o C required for drying under atmospheric pressure, and usually from more than about 300 to about 1300 ^o C, with an acceptable exposure time, usually depending on the equipment used for calcination, within 2 -120 min. Calcination is usually carried out in air or in air enriched with oxygen (i.e., O ₂ ) or in air enriched in combustible gases, for example carbon monoxide (i.e. CO), or carbon dioxide (i.e. CO ₂ ) although calcination is possible in a different atmosphere. Calcination can be carried out using static means, for example, using a muffle furnace, a tunnel furnace or a hearth furnace, or dynamic means, for example, using a rotary furnace or in a fluidized bed apparatus. Calcination is a very flexible method for producing diatomaceous filter aids with permeability for various flow rates, usually in the range of 0.05-1.5 D.

 A preferred method for producing a calcined high purity diatomite product of the present invention and the properties of the finished product are illustrated in Example 2 below.

3. Methods for producing fluxed calcined products
An uncalcified high-purity diatomite product can then be purified and agglomerated by calcination in the presence of flux to obtain a fluxed calcined product. The calcination conditions and methods described above can also be used for fluxed calcination. Typically, the presence of flux during calcination reduces the temperature at which sintering and agglomeration of diatomaceous particles occur, thereby allowing larger agglomerates to form and expanding the permeability range of filter aids to approximately 50 D. Suitable fluxes include alkali metal salts of group IA of the Periodic Table of Elements , primarily those that are formed with the participation of sodium (i.e., Na). Examples of the most effective fluxes used in practice are sodium carbonate (i.e., soda ash, Na ₂ CO ₃ ), sodium hydroxide (i.e., NaOH) and sodium chloride (i.e., NaCl).

 A preferred method for preparing the fluxed, calcined, high-purity diatomite product of the present invention and the properties of the finished product are illustrated in Example 3 below.

4. Further product modifications
Further modifications of highly pure diatomite products are also possible. So, for example, the purified product can be further processed to improve one or more specific properties of this highly pure product (for example, soluble impurities, total content
silica, density in the wet state after centrifugation or brightness) or to obtain a new product for a particular purpose of use.

a. Acid wash
Another class of products from non-calcined, calcined or fluxed calcined, high-purity diatomite products described above can be obtained by washing with an acidic substance, followed by washing with deionized water to remove residual acid, and then drying. Suitable acids include mineral acids, e.g., sulfuric acid (i.e., H ₂ SO ₄ ), hydrochloric acid (i.e., HCl), phosphoric acid (i.e., H ₃ PO ₄ ), or nitric acid (i.e. HNO ₃ ), as well as organic acids, for example citric acid (i.e., C ₆ H ₈ O ₇ ) or acetic acid (i.e., CH ₃ COOH).

b. Surface treatment
Another class of products can be obtained by surface treatment of non-calcined, calcined or fluxed calcined highly pure diatomite products described above. So, for example, the surface of the products can be modified, in particular by silanization, in order to make this surface either more hydrophobic or more hydrophilic.

Thus, in particular, a high-purity diatomite product can be placed in a plastic vessel and dimethyldichlorosilane [i. SiCl ₂ (CH ₃ ) ₂ or hexamethyldisilazane (CH ₃ ) ₃ Si-NH-Si (CH ₃ ) ₃ ]. The reaction is carried out on the surface in the vapor phase for 24 hours, resulting in the formation of more hydrophobic products. Such products find application in the compositions used in chromatography, as well as when they are combined with other hydrophobic materials, to improve mechanical operational means, for example, in those technical fields where the participation of hydrocarbons and oils is provided.

Similarly, a high-purity diatomite product can be reacted, for example, by suspending it in a solution containing 10% (w / v) aminopropyltriethoxysilane (i.e., C ₉ H ₂₃ NO ₃ Si) in water, refluxing at 70 ^o C for 3 hours, filtering the mixture and drying the remaining solid particles to obtain more hydrophilic products. Such products find application in the compositions used in chromatography when they are combined with aqueous systems to achieve improved mechanical performance and to further derivatize a product containing converted terminal hydroxyl (i.e., -OH) functional groups on the surface of this highly pure diatomite product into aminopropyl groups [i.e. - (CH ₂ ) ₃ NH ₂ ].

in. Derivatization with Organic Compounds
Hydrophilic (eg, silanized) modified high-purity diatomite products can then be reacted to bind organic compounds, for example protein; due to this, the diatomite product serves as a substrate for immobilization of the organic compound. Modified in this way, the product finds application in areas of technology such as affinity chromatography and biochemical purification.

 A series of other reactions related to the derivatization of diatomite products have been previously described (Hermanson, 1992). However, as a result of the derivatization of the high-purity diatomite products of the present invention, which exhibit a unique combination of properties, such as high purity and low density, modified products with significantly higher efficiency are obtained.

 It is obvious that, similarly to the above, many other modifications and embodiments of the invention can be made without departing from its scope and essence, as a result of which it is necessary to take into account only those restrictions that are given in the attached claims.

B. Methods for the use of high purity biogenic silicon dioxide products
The high-purity diatomite products of the present invention and their further modifications can be used in the processing, processing or preparation of other materials.

 When filtering, the high-purity diatomite products of the present invention and their further modifications can be applied to the membrane in order to increase transparency and increase the flow rate in the filtering processes or added directly to the filtered liquid in order to reduce the load of undesirable particles on the membrane. During filtration, these products can be used in combination with other media, such as cellulose, activated charcoal, clay or other materials. Such products can also be used in the preparation of composite materials in which they are homogeneously compounded with other components, in the form of sheets, gaskets or sleeves. The appropriate choice of the modification that is preferred for high-purity diatomite products is determined by the specific purpose of the application. For example, in a filtering process that requires exceptionally high transparency, but a reduced flow rate of the filtered material is acceptable, a highly pure diatomite product of a non-calcined or calcined class may be preferred. Alternatively, in a filtration process that requires a large flow rate but does not require extremely high transparency, a highly pure diatomaceous product of a fluxed, calcined class may be preferred. Similar considerations apply to highly pure diatomite products when they are used in combination with other materials or in the preparation of composite materials containing these products. Similarly, the amount of product that is used is determined by the specific process carried out with its participation.

 The use of these high-purity diatomite products as functional fillers, for example, in paints and coating materials or in polymers, is usually carried out by direct incorporation into the composition at a concentration necessary for the desired effect. The matting property of such products both in paints and coating materials, as well as the ability of such products to provide non-sticking properties to polymers are achieved by surface heterogeneity due to the porous, complex structure of diatomite.

 Silanized hydrophobic or hydrophilic products are necessary when their properties further improve the filtering or performance characteristics of functional fillers due to their higher compatibility with other materials or components when used for a specific purpose. The change in surface characteristics due to silanization is crucial for use in chromatography, since these characteristics have a strong influence on the efficiency of chromatographic separation in the case of special systems. For example, the hydrophobic surfaces of a chromatographic carrier decrease the surface activity of the carrier and significantly reduce the formation of “tails” when it is used for the analytical determination of many organic compounds, such as pesticides.

 These products are also necessary for further derivatization with organic substances, such as the combination of a protein with an aminosilanized support. For example, protein A, a polypeptide obtained from a bacterial source, is combined with an aminosilanized diatomite-based support for use in the clinical treatment of immunological diseases (Jones, 1992).

 The high-purity products of the present invention and their further modifications may find application in many other areas of technology.

D. Examples
Some highly pure diatomite products of the present invention and methods for their preparation are described in the following examples, which are presented for illustrative and not restrictive purposes only.

Example 1
High purity biogenic silicon dioxide product (non-calcined)
The diatomaceous earth in the form of a raw mineral was crushed and ground in a hammer mill so that the material was sieved through a 12 mesh sieve (i.e., with a hole size of approximately 1.82 mm), suspended in water to achieve a suspension density of 20-23% solids and then crushed in a friction mill so that the material passes through a 100 mesh sieve (with a hole size of approximately 174 μm). The sludge was diluted with water to a solids content of 8-10% and introduced into a 1-inch (2.5 cm) hydrocyclone, which operated at a pressure of 50-60 psi (345-414 kPa). The top product included particles of average size 10-12 microns. Before addition, the collector was prepared by dissolving trypentylamine [i.e. N (C ₅ H ₁₁ ) ₃ ] in acetic acid (ie, CH ₃ COOH) in equal volumes. In the pretreatment step with sulfuric acid (i.e., H ₂ SO ₄ ), the pH of the diatomaceous top product was adjusted so that it was in the range of 3-5, and a tripentylamine solution was added in an amount sufficient to 1000 kg of dry matter accounted for 360-390 g of added tripentylamine. Next, mechanical flotation was carried out in two stages: the stage of roughing and the stage of removal of impurities. The diatomite flotation product from the second stage, the impurity removal stage, was returned to the process in combination with the hydrocyclone overhead product to the first flotation stage, the roughing stage, with the supply of trypentylamine solution directly to the flotation chambers in an amount sufficient to add 240-260 g of additional tryptylamine per 1000 kg of dry matter. The flotation process was generally regulated in such a way as to provide a 60-65% yield of flotation product. This flotation product was then thickened to a suspension density of 10% solid particles using 600 g of SuperFloc 127 Plus {Cytec, polyacrylamide [t. e. CH-CH (CONH ₂ ) _n ] flocculating agent} per 1000 kg of dry matter, and then leached for 2 hours 2n. sulfuric acid (i.e., H ₂ SO ₄ ), the temperature of which was maintained at 90-95 ^o C. The suspension was dehydrated with a pressure filter, the filter cake was washed with deionized water until the minimum specific resistance of the wash water was 250 kOhm · cm, and then at 110 ^° C., air dried in an oven to constant weight.

Subsequent analysis determined that the total silica content of the non-calcined product of the present invention from this example was 99.1 wt.% (SiO ₂ ) of the amount after calcination, as determined by fluorescence X-ray diffraction using the fused tetraborate matrix method. Further, the total aluminum content in this product was 0.31 wt.% (In terms of Al ₂ O ₃ ), and the total iron content was 0.15 wt.% (In terms of Fe ₂ O ₃ ), as determined by fluorescence radiograph using the fused tetraborate matrix method. Its density in the wet state after centrifugation was 0.27 g / cm ³ . Calculations using this information showed that the specific volume of silicon dioxide in this product was 3.7 and that this indicator exceeded any product in the class of non-calcined diatomite products (see, for example, table, example 1).

 The content of beer-soluble iron in the product of this example was less than 5 mg Fe / kg of product, the content of beer-soluble aluminum was less than 8 mg Al / kg of product, and the specific resistance was 62 kOhm · cm, which further indicated its purity.

Example 2
High purity biogenic silicon dioxide product (calcined)
The product from Example 1 above was further ground to reduce the average particle size by 1 μm and calcined in air at 2150 ^° F (≈ 1175 ^° C) for a residence time of 40 minutes. Further, this material was dispersed in air, allowed to cool to room temperature in a humid environment and classified by sorting so that the permeability was in the range of the known calcined product, amounting to approximately 0.3 D.

In a subsequent analysis, it was found that the total silica content of the calcined product of the present invention from this example was 99.6 wt.% (SiO ₂ ) with a negligible loss of quantity as a result of calcination, as determined by fluorescence X-ray diffraction using the fused tetraborate method matrix. The total aluminum content in this product was 0.31 wt.% In terms of Al ₂ O ₃ , and the total iron content was 0.09 wt.% In terms of Fe ₂ O ₃ , as determined by fluorescence X-ray using the method with fused tetraborate matrix. Its density in the wet state after centrifugation was 0.21 g / cm ² . Calculations using this information showed that the specific volume of silicon dioxide in this product was 4.7 and that this indicator exceeded any product in the class of calcined diatomite products (see, for example, table, example 2).

 The content of beer-soluble iron in the product of this example was less than 5 mg Fe / kg of product, the content of beer-soluble aluminum was less than 8 mg Al / kg of product, and the specific resistance was 140 kOhm · cm, which further indicated its purity. In addition, the brightness of this product, measured by blue light reflection, was 100%.

Example 3
Highly pure biogenic silicon dioxide product (fluxed, calcined)
The product from Example 1 above was further calcined in air at a temperature of 2150 ^° F (≈1175 ^° C) with a residence time of 40 minutes in the presence of approximately 3 wt. % of powdered anhydrous sodium carbonate (i.e., Na ₂ CO ₃ ), which was added as a flux. This material was then allowed to cool to room temperature in a humid environment, then it was dispersed in air and classified by sorting so that the permeability was in the range of the known fluxed calcined product, amounting to approximately 1.2 D.

In a subsequent analysis, it was found that the total silica content of the fluxed calcined product of the present invention from this example was 96.8 wt.% (SiO ₂ ) with a negligible loss of quantity as a result of calcination, and the total sodium content was 1.50 wt. % in terms of Na ₂ O, as determined by fluorescence X-ray diffraction using the method with fused tetraborate matrix. The total aluminum content in this product was 0.40 wt.% In terms of Al ₂ O ₃ and the total iron content was 0.11 wt.% In terms of Fe ₂ O ₃ , as was also determined by fluorescence X-ray using fused tetraborate matrix method. Its density in the wet state after centrifugation was 0.16 g / cm ^3. Calculations using this information showed that the specific volume of silicon dioxide in this product was 6.1 and that this indicator exceeded any product in the fluxed class calcined diatomaceous products (see, for example, table, example 3).

 The content of beer-soluble iron in the product of this example was less than 5 mg Fe / kg of product, the content of beer-soluble aluminum was less than 8 mg Al / kg of product, which further testified to its purity. In addition, the brightness of this product, measured by reflection of blue light, was equal to 99%.

 The properties of diatomite products that are technically public are listed in the table according to information provided by CR Minerals Corporation (not dated), CECA S.A. (1988), Celite Corporation (1991a, 1991b), Eagle-Picher Minerals, Inc. (1988), Grefco, Inc. (1990) and Showa Chemical Industry Co., Ltd. (1995). These known products in the table are compared with the high purity products of the present invention described in the above examples.

 The specific volume of silica contained in part B of the table is graphically illustrated in the column diagram in FIG. 1. It is easy to see that the high-purity products from the examples of the present invention in terms of the specific volume of silicon dioxide are superior to the known products for each of the classes of products. In addition, a micrograph of the high purity calcined product of the present invention shown in the attached FIG. 2 shows that the purified diatomite products of the present invention retain the complex and porous structure characteristic of diatomite.

D. Literary references
The contents of publications, patents, and published patent descriptions that are referenced in the present description, is incorporated into this description by reference in order to more fully represent the current state of the art to which the present invention relates.

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Claims (20)

1. High purity diatomite product, which has a complex and porous structure of diatom silicon dioxide and a large specific volume of silicon dioxide and which is selected from the group including
non-calcined product, the specific volume of silicon dioxide, calculated as the ratio of the content of silicon dioxide to the density of the product in the wet state after centrifugation, is more than 3.5, and the total content of silicon dioxide SiO ₂ is more than 95 wt.%, as determined by x-ray fluorescence analysis , in terms of the amount after calcination;
calcined product, the specific volume of silicon dioxide, calculated as the ratio of the content of silicon dioxide to the density of the product in the wet state after centrifugation, is more than 3.6, and the total content of silicon dioxide is more than 98 wt.% SiO ₂ as determined by x-ray fluorescence analysis , in terms of the amount after calcination;
fluxed calcined product, the specific volume of silicon dioxide, calculated as the ratio of the content of silicon dioxide to the density of the product in the wet state after centrifugation, is more than 3.3, and the total content of silicon dioxide is more than 92 wt.% SiO ₂ as determined by x-ray fluorescence analysis, in terms of the amount after calcination. 2. A high-purity diatomite product, which is characterized by the complex and porous structure of diatom silicon dioxide and a large specific volume of silicon dioxide and is a non-calcined product, the specific volume of silicon dioxide in which, calculated as the ratio of the content of silicon dioxide to the density of the product in the wet state after centrifugation, is more than 3.5, and the total content of silica is more than 95 wt.% SiO ₂ as determined by X-ray fluorescence analysis calculated and the number after calcination. 3. A high-purity diatomite product, which is characterized by the complex and porous structure of diatom silicon dioxide and a large specific volume of silicon dioxide and which is a calcined product, the specific volume of silicon dioxide in which, calculated as the ratio of the content of silicon dioxide to the density of the product in the wet state after centrifugation, is more than 3.6, and the total content of silica is more than 98 wt.% SiO ₂ as determined by X-ray fluorescence analysis, in re couple on the amount after calcination. 4. A high-purity diatomite product, which is characterized by the complex and porous structure of diatom silicon dioxide and a large specific volume of silicon dioxide and which is a fluxed calcined product, the specific volume of silicon dioxide in which is calculated as the ratio of the content of silicon dioxide to the density of the product in the wet state after centrifugation is more than 3.3, and the total content of silica is more than 92 wt.% SiO ₂ as determined by X-ray fluorescence ana izom, based on the amount after calcination. 5. High-purity non-calcined diatomite product, which is characterized by a complex and porous structure of diatom silicon dioxide, and the total content of silicon dioxide in it is more than 95 wt.% SiO ₂ , as determined by x-ray fluorescence analysis, in terms of the amount after calcination. 6. High-purity non-calcined diatomite product, which is characterized by a complex and porous structure of diatom silicon dioxide, and the total content of silicon dioxide in it is more than 97 wt.% SiO ₂ , as determined by x-ray fluorescence analysis, in terms of the amount after calcination. 7. High-purity non-calcined diatomite product, which is characterized by a complex and porous structure of diatom silicon dioxide, and the total content of silicon dioxide in it is more than 98 wt.% SiO ₂ , as determined by x-ray fluorescence analysis, in terms of the amount after calcination. 8. High-purity non-calcined diatomite product, which is characterized by a complex and porous structure of diatom silicon dioxide, and the total content of silicon dioxide in it is more than 99 wt.% SiO ₂ , as determined by x-ray fluorescence analysis, in terms of the amount after calcination. 9. High purity calcined diatomite product, which is characterized by a complex and porous structure of diatom silicon dioxide, and the total content of silicon dioxide in it is more than 98 wt.% SiO ₂ , as determined by x-ray fluorescence analysis, in terms of the amount after calcination.  10. The product according to any one of claims 1 to 9, in which the content of beer-soluble aluminum is less than 10 mg Al / kg of product.  11. The product according to any one of claims 1 to 10, in which the content of beer-soluble iron is less than 7 mg Fe / kg of product.  12. The non-calcined product according to any one of claims 1, 2, 5 to 8, 10 and 11, the specific resistance of which is more than 50 kΩ • cm.  13. The calcined product according to any one of claims 1, 3 and 9 to 11, the specific resistance of which is more than 80 kΩ • cm.  14. The calcined product according to any one of claims 1, 3, 9 to 11 and 13, the brightness of the reflected blue light of which is more than 96%.  15. Fluxed calcined product according to any one of claims 1, 4, 10 and 11, the brightness of the reflected blue light of which is more than 95%. 16. Fluxed calcined product according to any one of claims 1, 4, 10, 11 and 15, in which the total total content of sodium (Na ₂ O) and the total content of silicon dioxide (SiO ₂ ) is more than 98 wt.% In terms of quantity after calcination.  17. The product according to any one of claims 1 to 16, the brightness of the reflected blue light of which is more than 99%.  18. The filter in the form of a sheet, gasket or cartridge, comprising the product according to any one of claims 1 to 17.  19. A method of filtering a liquid, comprising adding to this liquid a product according to any one of claims 1 to 17, or passing this liquid through a filter including a product according to any one of claims 1 to 17.  20. High-purity diatomite product having a complex and porous structure of diatom silicon dioxide, and the brightness of the reflected blue light of this product is more than 99%.

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