The processes of obtaining colloidal silica and the conversion of sols into gels underlie many modern technologies associated with the production of materials for the most diverse purposes, which have unique properties and a controlled structure. Silicon oxide is the most common substance on Earth; on its basis, a large number of materials have been obtained by the sol-gel method: catalysts and adsorbents, zeolites, coatings and glasses, thermal and sound insulating, porous materials, ceramics, composite and paintwork materials, drilling fluids and reagents, etc. Alkaline silicate suspensions are widely used in the production of building materials. The most effective method for the synthesis of silica nanoparticles is considered to be the sol-gel technology, which is a chemical condensation method of synthesis in the liquid phase. Sol-gel technology allows the process to be carried out under optimal conditions in terms of the efficiency of controlling the properties of the final product, energy costs and process productivity.
The transformation of sols into gels is the basis of the latest nanotechnologies for the production of light guides, ceramic ultrafiltration membranes, optical and anti-corrosion coatings, photographic materials, highly dispersed abrasives and other materials with unique properties and a controlled structure.
Due to its binding properties, colloidal silica is successfully used as an inorganic binder in materials with various fillers: inorganic powders, fibers, polymers, metals, etc. A characteristic feature of such materials is their strength and heat resistance. An example is the production of ceramic molds in investment casting, refractory ceramics, insulating materials, etc.
The chemistry of colloidal silica and the areas of its application are considered in detail in the literature, and primarily in the works of Ayler. Nevertheless, interest in these systems does not weaken, which is manifested in the development of new materials based on silica with unique properties, as well as in a large number of scientific and patent publications, and holding periodic international conferences on silica.
The most common use of silica gels in granular or spherical form is as catalysts, adsorbents and desiccants, for example, in the conservation of power equipment. According to Eiler, the uses of silica powders can be grouped according to their following uses: hardening, thickening, and hardening of organic substances; decrease in adhesion between surfaces of solids: increase in adhesion of adhesives; increase in viscosity and thixotropy in liquids; creating a variety of optical effects. Other general effects: change in surface condition; creation of hydrophobic effects; use as adsorbents; catalyst carriers; to obtain reactive silica; formation of condensation nuclei in clouds; in quantitative analysis as a filler for chromatographic columns.
It should be noted the extremely important use of amorphous nanosized silica as additives in oils and lubricants for internal combustion engines, as well as for any units and mechanisms where there are metal friction pairs, for example, oils and lubricants of the XADO brand. The formation of ceramic films on the surfaces of rubbing pairs leads to the restoration of the geometric dimensions of units and mechanisms to their original state, several times reduces the degree of their subsequent wear. At the same time, fuel consumption is significantly (up to 20%) reduced due to a sharp decrease in the roughness of the metal due to the formation of a silicate film on its surface.
Carbon black was previously used as a reinforcing filler for rubber, but now there is a tendency to partially or completely replace it with fine silica. This allows you to increase the strength of the rubber and give it colors other than black. Rubber tensile strength, tear strength and overall stiffness are markedly increased if the filler particles (silica or esterified silica) are small in size, 5-10 nm in diameter, fully dispersed and in the form of separated, discrete particles within the matrix. For good dispersibility, small particles must be hydrophobic, the presence of polar and hydrophilic surface areas on the filler particles leads to the formation of chains of particles, which stiffens the rubber structure.
Amorphous finely dispersed silica (ATS) is used as a filler for silicone elastomers. ATK further increases the porosity of ion exchange resins. This is achieved by incorporating the silica into the monomer, followed by its dissolution and removal by exposure to dilute hydrofluoric acid HF. Cellulose acetate membranes used for reverse osmosis, when containing 50% silica, acquire 5 times higher throughput compared to cellulose acetate membranes without silica.
ATK is more effective and less visible in preventing sheet and adhesive sticking compared to traditionally used talc and starch. This is made possible by the extremely small size of the ATK particles and the low refractive index. ATK prevents caking of powders or granules that move or do not crystallize during storage, while it is non-toxic and inert. Sticking of the polymer films is prevented by adding silica to the stirred monomers prior to their polymerization. Approximately 0.5% silica reduces adhesion by 50%.
If silica is in the form of dispersed particles in the medium of an adhesive - an adhesive that hardens upon contact with a solid surface, then the adhesion of the system does not decrease, but, on the contrary, increases. For example, the addition of 10% ATK to liquid butyl cyanoacrylate causes an increase in the strength and adhesion of the system to the patient's skin and is used in surgery. Silica is also used as a thickener in epoxy adhesives. Esterified silica is used in engineering as a thickener for greases prepared from petroleum and silicone oils. Lubricants obtained in this way have a markedly higher adhesion to the steel surface in wet conditions, are not subject to abrasive wear, and have a lower oxidizability at elevated temperatures. ATK is used as a thickener, i. viscosity regulator, for paints, primers and inks. In this case, several effects are achieved: matting or gloss reduction, preventing the formation of sediment from the pigment during storage of the product, stabilizing the emulsion and the possibility of applying colorants without droplets.
The transparency of highly porous, high surface area silica has allowed the development of transparent toothpastes that are effective in removing tartar. ATK is added to cosmetic preparations in order to remove fat from the skin, while using the properties of ATK as an adsorbent.
When dispersed ATK is in oil, for example in glycerol monooleate, when a three-phase alternating current of 2000 V is applied, an electroviscous effect appears due to the electrostatic adhesion of two plates, in a narrow gap between which there is oil.
In this case, silica thickens the oil to a gel state, which transfers torque from one plate to another.
Another interesting application of ATK is that large crystals that cannot be grown in water are grown in a silica gel medium. The structure of the gel prevents convection and allows the diffusion process of the components to proceed evenly.
Alkyl nitrates, hydrazine, and other propellants are gelled or lubricated by the introduction of loose, voluminous silica gel. Thickening of acids is achieved, for example, in lead-acid batteries. Silica as foam thickeners enhances their fire-fighting properties.
ATK is widely used for thinning highly colored organic dyes such as phthalocyanine, and for matting and removing gloss effects in paints, plastics and printing inks. ATA particles with both hydrophilic and organophilic surfaces will collect at the interface and thus stabilize emulsions, such as an oil-water system, or paint, where ATK can perform other functions.
Paper and fabrics, as well as other materials, acquire high hydrophobic or water-repellent properties due to the imposition of an invisible adsorption film consisting of hydrophobic colloidal silica particles.
It is interesting to use APA to obtain "dry powdered water", obtained by coating the finely dispersed ice particles obtained by grinding with hydrophobic APA. Similarly, concentrated hydrogen peroxide (20-70%) can be converted into a stable powder by vibrating the liquid with ATK.
Despite many interesting applications, ATK seems to be most widely used as a desiccant for packaged products that can corrode or deteriorate when exposed to moisture.
ATK with alkylsilyl groups deposited on its surface can be used as an adsorbent for enzymes, mitochondria, and other cell organelles while maintaining their activity. This application of ATC has opened up new areas of research in biochemistry. Such organic formations can adhere to the modified ATK surface, giving monolayer coatings at 27°C, but they are able to desorb at 5°C. Apparently, this effect is due to the fact that water displaces these formations from the ATC surface due to the fact that hydrogen bonds become stronger at 5 °C.
The role of silicon compounds in the biochemistry of life is still unclear. Perhaps this is due to the fact that colloidal silica particles are not directly involved in biochemical processes, but play a transport role. According to the latest data, silica particles with a size of up to 5 nm are able to pass through the cell membrane, while transporting nutrients on themselves when entering the cell and removing sorbed toxic substances when leaving it.
The high values of the specific surface area and the dissolution rate of ATS allow the necessary reactions to be carried out at much lower temperatures than is required for powdered fine crystalline silica. For example, transparent fused quartz glass is formed at a pressure of 140 kg/cm2 and a temperature of 1200 °C from ATK with a primary particle size of 15 nm, while a temperature of 2000 °C is required to obtain such a material in the form of mold-blown products. By reacting powdered boron with ATK, oxygen-deficient silica glass is obtained, which is only difficult to devitrify.
ATK is so reactive that it can be used to prepare synthetic clay materials, for example, kaolin is formed under hydrothermal conditions at 200-300 °C.
ATC particles with a size of 30-100 nm, with certain characteristics of their surface, are active for the formation of ice crystallization centers, or the first stage of the formation of raindrops in a cloud. In addition, the use of ATK for these purposes is more economical than the use of silver iodide.
The scale of application of specially designed ATK for use as packing of chromatographic columns and the literature on these issues is so huge that this topic requires a separate consideration.
The addition of amorphous silica to soil or culture solutions has a significant beneficial effect when available phosphorus is deficient.
This is due to the fact that the silicate ion in a weakly alkaline environment is able to displace the phosphate ion from the surface of soil particles or colloidal material, thus, the phosphorus content in the system under consideration increases. This application of APA is especially effective for lateritic soils, on which phosphate ions are adsorbed especially strongly and become inaccessible to plants due to the formation of insoluble iron and aluminum phosphates. As a result, in soils of this type, this method leads to an increase in grain yield by 2-3 times if the environment is alkaline, and increase up to five times if the environment is neutral. In a sandy environment, the beneficial effect of amorphous silica on legume and cruciferous crops is to improve the physical condition of the sandy soil and utilize the available phosphorus by the mechanism described above. The use of ATK, in addition to improving the accumulation and use of phosphorus by plants, has a similar effect on calcium, potassium and magnesium.
Finely dispersed amorphous silica is used as an insecticide against certain insects, interacting with them in a physical way, without being involved in any way in biochemical processes. At the same time, ATK absorbs lipids (oils) from the cuticle of the insect, the body of which is rapidly dehydrated. Hydrophobic silica is stronger in this respect than hydrophilic silica. Silica airgel, partly organophilic due to the method of its preparation, at a concentration of 0.05% inhibits the activity of weevil and grain grinder in granaries, has a longer protective effect compared to chemical insecticides and is non-toxic to animals and humans.
Aqueous silica hydrosol is used to irrigate the hot surfaces of steel pouring molds. Thus, erosion of the surface of the molds is prevented and the separation of the metal ingot is improved. When processing the surface of the rails in the same way, the traction force of the locomotive is improved due to the greater adhesion of the wheels to the rails.
Silica sol is used to produce silicon dioxide, which, in addition to all of the above, is used in the chemical industry for the production of catalysts. Silicon oxide as a carrier has a number of properties that make it very useful in cases where alumina is not applicable, for example, in strongly acidic environments.
In the catalyst synthesis industry, silica sol is specially prepared according to the following method: to a 4% solution of sodium metasilicate, prepared by dissolving a sufficient amount of dry salt in water, nitric, hydrochloric or sulfuric acid is added to change the reaction of the medium, from strongly alkaline to strongly acidic, with the value pH< 2. В этих условиях оксид кремния не образует гель, а будет находиться в виде стабильного золя, который и добавляют к раствору исходных солей катализатора, также имеющему кислую реакцию. Осадитель, которым может быть карбонат или бикарбонат аммония, натрия или калия, прибавляют до тех пор, пока рН не станет равным 6,8-7,5. В этих условиях осаждаются каталитические компоненты, а оксид кремния захватывается осадком и таким образом становится эффективным носителем, действующим как стабилизатор или даже как промотор .
The silicon oxide obtained from the precipitate is much less reactive than the oxide obtained from the sol (acidified silicate) and, therefore, is more resistant to the formation of silicates at higher temperatures (up to 700 °C). At about 700 °C, silicon oxide becomes highly active, sintering, and to a large extent, if not completely, passes into silicates. Thus, a stable silica sol is a high-quality raw material for obtaining a support - silicon dioxide and catalysts based on it with excellent technical characteristics.
Silicon dioxide as a carrier of catalysts is used in the following major large-capacity industrial processes: in the production of sulfuric acid (the catalyst is vanadium oxide promoted with potassium sulfate on silicon dioxide); in the second low-temperature stage of water gas shift (catalyst - a composition of copper and zinc oxide on a carrier - aluminum oxide or silicon oxide); in the production of phthalic anhydride from naphthalene or xylene by air oxidation (catalyst - vanadium oxide on silicon dioxide); the synthesis of vinyl acetate from ethylene and acetic acid with oxygen uses palladium on acid-resistant supports, the best of which is silicon dioxide. In addition, the catalyst for such an important industrial process as oil cracking is a crystalline zeolite on an aluminosilicate matrix. Since zeolites are synthesized under hydrothermal conditions from a gel formed by adding sodium hydroxide to a solution of sodium silicate and sodium aluminate, silicon dioxide is the most important initial component in their industrial production.
The following methods for the synthesis of silicic acid sols have found the greatest application in industry: neutralization of soluble silicates with acids, ion exchange, peptization of freshly formed silicic acid gels, electrodialysis, hydrolysis of alkyl derivatives of silicon, dissolution of elemental silicon, and dispersion of pyrogenic silica. In industry, the most commonly used method is ion exchange, first patented by Byrd. Numerous modifications of this process are known in the literature. The main stages of the synthesis of silica hydrosols with dense particles: obtaining a solution of silicic acid; synthesis of "seed" sol; particle growth; sol concentration; particle surface modification.
The sol-gel technology makes it possible to introduce modifying components at the stage of obtaining the sol. Thus, for example, microporous aluminosilicate gels, optically transparent aluminosilicate gels, silica gels doped with boron, titanium, germanium compounds, as well as sorbents for high performance liquid chromatography, are obtained. The sol-gel technology also makes it possible to obtain xerogels modified with organic and inorganic reagents for use as test tools in the determination of various substances in analytical practice.
Chemically modified silica is of great interest for high performance liquid chromatography and also as a catalyst support. The amorphous structure of silicic acid sols prepared by various methods is preserved for a long time; the onset of crystallization was noted after two years of aging of the system. As a result of the development of stresses, primary amorphous particles decompose into many small crystalline particles, which grow, aggregate, and form structures with further aging of the sol. Amorphous silica is less polymerized. than quartz, and the differences in their structure are not qualitative, but only quantitative. The polymeric nature of silica was also pointed out by Mendeleev.
Crystallization processes, leading to the occurrence of significant stresses and, as a result, to cracking of the product, limit the effective use of a number of materials containing colloidal silica as a binder at temperatures above 1000–1100 °C. Adsorption modification of the surface is one of the ways to control the aggregative stability of sols and the adsorption capacity of the surface of silica particles. The synthesis of modified sols makes it possible to significantly expand the field of application of colloidal silica. The laws governing the adsorption of metal cations on silica at various pH and temperature have been considered in a number of works. The process can be carried out in both acidic and alkaline environments. Fundamental studies of the above processes of sol-gel technologies for the synthesis of materials based on nanosized silica are being carried out at the Russian University of Chemistry and Technology. DI. Mendeleev.
Silicon dioxide, known as a food additive under the number E551, has the form of a crystalline substance that does not have color. This compound has a high degree of strength and hardness. Dioxide is resistant to acids and does not react with water.
In nature, the compound can be found in the form of quartz; ordinary sand consists of tiny quartz grains. Dioxide in this form is used in areas and technologies where there is no requirement for a high degree of purity of the material. Silicon oxide in the form of crystals is represented by jasper, rock crystal, agate, morion, amethyst, chalcedony, topaz. At the bottom of the oceans, amorphous silicon dioxide is formed from dead algae and ciliates.
The synthetic substance is obtained through the oxidation of silicon at a temperature of about 500 degrees Celsius in an oxygen atmosphere.
Food additive E551 is also known as aerosil, amorphous silicon dioxide, silica, white soot, finely dispersed dioxide.
Food silicon dioxide due to its properties is widely used as an emulsifier and a substance that prevents caking and clumping. This supplement can be found in the following product groups:
Silicon dioxide has found its application in the production of toothpastes, enterosorbents, and some types of medicines.
The compound is used during the production of ceramics, glass, abrasives, concrete products, as a filler in the production of rubber, for the production of silicon, during the production of silica refractories, in the field of chromatography, etc. Due to the piezoelectric properties possessed by the crystals of the substance, the use of dioxide silicon found in ultrasonic installations, as well as radio engineering.
Artificially produced oxide films are used as an insulator during the production of microcircuits and other electronic components. Dioxide in its pure fused form, combined with various special ingredients, is used to manufacture fiber optic cables.
Food silicon dioxide, known as an additive under the number E551, is included in a group of chemical compounds that are approved for use in food production processes. But according to the warnings of a number of experts, there is also harm to the human body from silicon dioxide, which manifests itself in the case of interaction with the compound.
However, it is worth noting that silicon dioxide can cause harm if precautions are neglected when working with the substance in its pure form. For example, the dust that is formed during the interaction of dioxide with other chemical reagents can cause serious irritation to the lungs and bronchi of a person.
In the case of the use of the compound inside, it passes through the gastrointestinal tract in an unchanged state, and then naturally leaves the body. Also note that in France for fifteen years there have been studies on this supplement, which showed that in the case of drinking water with a high level of dioxide content, the risk of developing Alzheimer's disease is reduced by as much as 11%.
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Amorphous silica can be classified into three types:
1. Quartz glass made by melting quartz (as well as high-temperature hydrolysis of silicon tetrachloride or its oxidation in a low-temperature plasma).
2. Silica M - amorphous silica obtained by irradiation with fast neutrons of amorphous or crystalline varieties of silica. In this case, the density of the initial amorphous silica increases, while that of the crystalline silica decreases. Silica M is thermally unstable and transforms into quartz at 930C for 16 hours. Its density is 2260 kg / m 3 (for quartz glass - 2200).
3. Miroamorphous silica, including sols, gels, powders and porous glasses, which consist mainly of primary particles with a size of less than one micrometer or with a specific surface area of more than 3 m 2 /g.
Microamorphous silica synthesized under laboratory conditions can be divided into three classes:
I Microscopic varieties obtained by special processes in the form of leaves, ribbons and fibers.
II Conventional amorphous forms consisting of elementary spherical SiO 2 particles smaller than 100 nm in size, the surface of which is formed either from anhydrous SiO 2 or from SiOH groups. Such particles can be separate or connected in a three-dimensional network: a) discrete or isolated (particles, as is the case in sols; b) three-dimensional aggregates connected in chains with a siloxane bond at the points of contact, as in gels; c) bulk three-dimensional particle aggregates, as observed in aerogels, silica of trogenic origin, and some dispersed silica powders (see Fig. 1.13).
III Hydrated amorphous silica in which all or almost all of the silicon atoms are held by one or more hydroxyl groups.
Rice. 1.13. Elementary particles of common forms of colloidal silica. The figure is presented flat, but in fact the aggregation of particles is three-dimensional: a - sol, b - gel, c - silica powder
Microamorphous silica of layered, ribbon and fibrous microforms is obtained:
1. The formation of particles at the gas-liquid interface as a result of the hydrolysis of SiF 4 in the gaseous state at 100 or the hydrolysis of SiCl 4 vapors at 100C. The flakes are thin films of silica gel formed on the contact surface of highly reactive SiF 4 vapors with water droplets. The "fluffy" character of the powder prepared from SiF 4 is manifested in its very low apparent density value of 25 kg/m 3 and also in the "fluidity" of the powder, similar to that of water. Irregular silica gel flakes, about 1 µm in diameter and 1/10 µm thick, contain 92.86% SiO 2 and 7.14% H 2 O.
2. Formation of silica sols by freezing. When a solution of colloidal silica or polysilicic acid is frozen, the growing ice crystals will displace the silica until the latter accumulates between the ice crystals as a concentrated sol. Such silica then polymerizes and forms a dense gel. The subsequent melting of ice produces silica in the form of irregularly shaped flakes formed between the smooth surfaces of ice crystals. Vacuum dried silica powder contains approximately 10% H 2 O.
The most common silica in amorphous form is silica gel and quartz glass. Silica gel is obtained by heating silica gels to temperatures not exceeding 1000C. Ready technical silica gel is solid translucent granules of white or yellowish color. Widely used as a moisture absorbent.
The silica melt is easily supercooled to form quartz glass. Quartz glass used in engineering is a one-component silicate glass. It is obtained by melting natural or artificial varieties of silica of high purity.
With an increase in pressure, modification transformations were also established for non-crystalline silica - quartz glass. When glass is compressed, the Si-O-Si bonds in it are bent. With an increase in pressure to 3100-3300 MPa, a transition is observed, accompanied by a sharp change in density (transformation of the second kind). Glass produced at this pressure is called suprapiezo glass(abbreviated S-P-glass).
With an increase in pressure above 9000 MPa, the density of glassy silica again begins to increase and at 20000 MPa becomes equal to 2.61. 10 3 kg/m 3 , which is close to the density of quartz, but the material remains amorphous. Such glass does not elastically return to its original volume when the pressure is removed, and thin discs of superdense (condensed) quartz glass can be preserved. This compacted quartz glass is called condensed.
Characteristics of polymorphic modifications of SiO 2 are given in table 1.1.
2. Silica M - amorphous silica obtained by irradiation with fast neutrons of amorphous or crystalline varieties of silica. In this case, the density of the original amorphous silica increases, while that of the crystalline silica decreases. Silica M is thermally unstable and transforms into quartz when kept at 930°C for 16 hours. Its density is 2.26 compared to 2.20 for quartz glass or microamorphous silicas. In fact, silica M obtained from some crystalline forms may vary slightly.
3. Microamorphous silica, including sols, gels, powders and porous glasses, which consist mainly of primary particles with a size of less than one micron or with a specific surface area of more than ~3 m2/g. (A detailed discussion of microamorphous silica is given in chapters 4 and 5.)
There is an opinion that, in reality, amorphous silica is not amorphous, but consists of ordered microregions or crystals of extremely small sizes, which, when carefully examined by X-ray diffraction, apparently show the structure of cristobalite. Nevertheless, when studied by conventional diffraction methods, for such a material, in contrast to macroscopic crystals, only a wide band is obtained in the absence of multiplet peaks. Therefore, in this monograph, such silica will be referred to as "amorphous".
Under natural conditions, microamorphous types of silica are formed either in the process of condensation from the vapor phase ejected during volcanic eruptions, or by precipitation from supersaturated silica solutions in natural waters and in living organisms. With the exception of silica,
precipitated in plants or diatoms, naturally occurring microamorphous silica is usually too contaminated to be suitable for solubility studies. (The formation and properties of natural opal are discussed in Chapter 4.)
Microamorphous silica synthesized under laboratory conditions can be divided into three classes:
1. Microscopic varieties obtained by special processes in the form of leaflets, ribbons and fibers.
2. Ordinary amorphous forms, consisting of elementary spherical SiO2 particles, smaller than 1000 A in size, the surface of which is formed either from anhydrous SiO2 or from SiOH groups. Such particles can be separate or connected in a three-dimensional grid, as shown in Fig. 1.2: a) discrete or isolated particles, as is the case in sols; b) three-dimensional aggregates connected in chains with a siloxane bond at the points of contact, as in gels; c) bulk three-dimensional particle aggregates, as observed in aerogels, pyrogenic silica, and some dispersed silica powders.
3. Hydrated amorphous silica, in the structure of which all or almost all of the silicon atoms are held by one or more hydroxyl groups. This type of polymer structure is formed when monosilicic acid or oligosilicic acids are concentrated and polymerized in water under the condition of slightly acidifying the solution and at normal or reduced temperature. It is currently claimed that under such conditions, silica polymerizes to extremely small spherical particles, less than 20-30 Å in diameter. Upon concentration, such particles bind together into a three-dimensional mass of gel, retaining water in the spaces between the particles. The dimensions of such gaps are close to molecular, and therefore they are able to retain water up to a temperature of 60 °C, above which water can be desorbed.
Under normal conditions, such structures are not preserved due to the fact that during the preparation of sols and gels, the pH value does not remain sufficiently low until the final state of the system, and the temperature is not maintained below 60 °C.
The high specific surface area and dissolution rate of amorphous silica allows the necessary reactions to be carried out at much lower temperatures than is required for powdered crystalline silica. Increased chemical reaction ...
For some applications, it is desirable that the surface of the silica or glass be wetted with water. But at the same time, there should be no various characteristic ionic, hydrophobic or hydrogen bonds that arise during the adsorption of organic ...
Undoubtedly, the most ancient fossil remains of living organisms are blue-green algae, found as inclusions in shert (microcrystalline silica), discovered by Barghorn and Tyler and subsequently studied by many researchers ...
The article describes a food additive (anti-caking agent and anti-caking agent) amorphous silicon dioxide (E551), its use, effects on the body, harm and benefits, composition, consumer reviews
Functions performed
anti-caking agent and anti-caking agent
Legality of use
Ukraine
EU
Russia
Silicon dioxide is an inorganic compound with little activity under normal conditions. At room temperature, it does not dissolve in water, does not interact with it and with other substances. This oxide is acidic and under certain conditions can form salts of silicic acid, which are called silicates.
Silicon dioxide is widely distributed in nature, it is part of many rocks and minerals. In everyday life, it is known to everyone as ordinary (quartz) sand. There are several types of crystalline modifications of this substance.
The amorphous form of silicon dioxide is used in pharmaceuticals as an auxiliary and basic substance. Amorphous silicon dioxide is a food additive E551, which is used in the food industry to prevent caking and clumping of dry powder products.
In industry, silicon dioxide is used in the production of building materials, ceramic products, abrasives, fiber optic cables. For technical purposes, a product from natural sources is used. In the food and pharmaceutical industries, silicon dioxide synthesized by oxidation of silicon at a very high temperature is used as an additive E551.
Additive E551 is one of the safest compounds for health. This substance is absolutely insoluble in the esophagus and is excreted from the body unchanged. In addition to a positive effect on food quality, the E551 supplement can have a cleansing effect on the intestines. It is no coincidence that silicon dioxide is used in practical medicine as an enterosorbent. This substance is present in many toothpastes and contributes to the mechanical and microbiological cleaning of the oral cavity.
Given the insolubility of silicon dioxide, people who have problems with the excretory system should not abuse food products with the addition of E551. When large amounts of this substance enter the body, its accumulation in the ducts of the urinary system cannot be completely excluded, especially in cases where they are deformed or spasmodic.
Additive E551 prevents caking of dry food products, the formation of lumps in them. It is used for packing spices and other mixtures. The addition of amorphous silica is especially relevant when dry food products are wrapped in foil. The maximum concentration of E551 in one kilogram of food mixtures should not exceed 30 grams. Silicon dioxide is approved for use as a food additive in all countries.
