Silicon dioxide. Silicon dioxide - properties, application in medicine and cosmetics.
Silica in the food industry - food additive under the code E-551 emulsifier groups. Silica used as an additive that prevents caking and clumping of the main product. In food E-551 most often found in the composition of crackers, chips, some medicines (enterosorbents), toothpastes.
Impact on the body
When using silicon dioxide inside, it passes unchanged through the gastrointestinal tract, and then excreted from the body. According to unverified information, studies conducted in France showed that the use of water with a high content of silicon dioxide reduces the risk of developing Alzheimer's disease by 11%.
Silica occurs naturally in the form of sand, quartz. In general silica - the main component of almost all terrestrial rocks.
Silicon dioxide application
Silica used in the manufacture of glass, ceramics, abrasives, concrete products, for the production of silicon, as a filler in the production of rubber, in the production of silica refractories, in chromatography, etc. Quartz crystals possess piezoelectric properties and therefore are used in radio engineering and ultrasonic installations. Artificially produced silica films are used as an insulator in the manufacture of microchips and other electronic components. Clean fused silica in combination with a number of special ingredients used to produce fiber optic cables.
general information
In nature silica It is found in the form of a quartz mineral; sand. Such dioxide is used in technologies that do not involve a high level of material purity. Synthetic silica obtained by oxidation of silicon in an oxygen atmosphere at a temperature of E-400-500 ° C.
Silica it is a very solid, colorless crystalline substance. Silica does not react with water and is resistant to acids. The molecular formula of the substance: SiO 2. Silicon oxide, a member of the group of acid glass-forming oxides, interacts with increasing temperature with alkalis and basic oxides, soluble in hydrofluoric acid, tends to form a supercooled melt, i.e. glass is an excellent dielectric.
According to the structure of the compound and the properties of the food emulsifier E551, silicon dioxide belongs to the group of substances, which are silicon oxides. In addition to the name fixed in the food industry, there are other names for the E551 food emulsifier, silicon dioxide. For example, amorphous silicon dioxide, aerosil, white carbon black, silica, as well as finely dispersed silicon dioxide. The properties of the food emulsifier E551 Silicon dioxide give all the reasons to classify the chemical compound to the category of acid oxides.
E551 food emulsifier. Silicon dioxide under the influence of temperature begins to enter into a chemical reaction with alkalis, as well as basic oxides. In addition, the organically active compound silica, which is part of the E551 emulsifier, is capable of dissolving in hydrofluoric acid, as well as being used as a dielectric and part of the glass forming oxides. It is worth noting that the food emulsifier E551 Silicon dioxide can be presented in several versions.
The harm of food emulsifier E551 silicon dioxide
It is noteworthy that α-quartz is considered to be the most common natural modification of silicon dioxide on the surface of planet Earth. At present, food emulsifier E551 Silicon dioxide belongs to the group of chemical compounds permitted for use in production processes in the food industry. However, a number of experts warn against the harm of food emulsifier E551 Silica for the human body, which can occur as a result of interaction with food additives.
However, for the sake of justice, it is worth emphasizing that harm to the food emulsifier E551 Silicon dioxide can inflict only in case of non-compliance with precautions when working with a chemical substance in its pure form. For example, dust generated by the interaction of silicon dioxide with other chemical reagents can cause serious irritation of the bronchi and human lungs.
On the other hand, experts have found a link between regular consumption of water enriched with silicon dioxide and a reduction in the risk of severe and resistant to Alzheimer's disease. True, with some benefit, experts still set the standards for the limiting content of the food emulsifier E551 Silicon dioxide in the composition of those food products, in the manufacturing process of which the food additive was used.
The most common food emulsifier E551 Silicon dioxide is found in the following food groups:
- spices, seasonings and various ready-to-eat and dried spices;
- powdered foods, for example, sugar, salt or flour;
- fermented milk products, as a rule, cheeses;
- sweets and pastries;
- various types of snacks, usually chips, nuts in all kinds of glazes, as well as crackers and most other snacks for beer;
- alcohol products.
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Silicon dioxide (chemical formula: SiO2, silica) is a colorless crystalline, glassy or This mineral in the form is widely used in construction, in the manufacture of chemical products and radio engineering, in aircraft construction and many other industries.
Silica spread in nature
Silicon dioxide is found in the crust as mixtures with some other minerals (they are called granites) and, in the form of silicates, is a part of rocks. The most common mineral in nature is quartz; cristobalite, chalcedony, tridymite, opals, and leschelerite (quartz glass) are much less common. Small quartz crystals form the so-called "vein" quartz. With the gradual destruction of rocks, quartz sands are formed, which, compacted, lead to the appearance of quartzite and sandstone.
Rock crystal is the purest quartz, colorless. Its crystals can weigh tens of tons and reach a length of several meters. Also, quartz can be colored with various impurities in the color purple (amethyst), yellow (citrine), black (morion), smoky (rauchtopaz). In nature, cryptocrystalline forms of quartz are also found: red-pink carnelian, green apple chrysoprase, bluish sapphire, finely colored jasper, sandy onyxes and agate, hornfels and flint.
The “noble” opal is unique, which consists of homogeneous colloidal particles with a diameter of about 0.2 microns. These particles are tightly packed into ordered agglomerates; they contain less than one percent of water (in most opals, about seven percent). Natural deposits of silicon dioxide can also form diatomite, tripilla. Skeletons of some sponges are built from this mineral. It is part of the stems of plants - such as reeds, horsetail, bamboo.
How to get silica?
Synthetic SiO2 can be obtained:
By exposure to hydrochloric (HCl) or sulfuric (H2SO4) acids less often - to other soluble silicates (this method is the main in developed countries);
Using colloidal silicon dioxide (by freezing or coagulating it under the action of F-, Na + ions);
By hydrolysis of silicon fluoride SiF4, silicon tetrachloride SiCl4, tetraethoxysilane (C2H5O) 4Si, solid desublimate (NH4) 2SiF6 in gas form, and also in aqueous ammonia and aqueous solutions (sometimes with the addition of organic bases or ethanol).
Amorphous silica is obtained:
From diatomite and tripoli;
Calcinating rice husk;
Milling fused silica sand.
Anhydrous silica powders get:
Using chemical vapor deposition;
By hydrolysis and oxidation of fumed silica and silicon fluoride;
By burning the fumes of silicon tetrachloride SiCl4 in a mixture of O2 and H2.
How to use silica?
Silica natural is used in the manufacture of porcelain, concrete, abrasives, silicate bricks, ceramics, earthenware, dinas, silicate glasses;
Synthetic silica (“white soot”) is used as a filler in the production of rubber;
Quartz single crystals have found application in radio engineering (filters, frequency stabilizers, piezoelectric resonators), in acoustoelectronics and acoustooptics, in jewelry, in optical instrument-making;
Rock crystal and synthetic silicon dioxide are used as raw materials for the production of quartz glass, quartz single crystals, quartz fibers and ceramics. In turn, ceramics and quartz glass are used in the aviation industry, optics, electronics and other industries. Quartz fabric is used as a material that retains heat, and quartz fibers are used to create fiber-optic systems and communication lines.
Physical and chemical properties of aerosil (silica)
Aerosil (from the Latin word - Aerosilum), oxyls (from the Latin word - Oxylum) silicon dioxide, Silica colloidalis anhydrica (Ph. Eur.), Colloidal silicon dioxide (USP), Colloidal anhydrous silica (BP), Silica (CAS No. 7631-86-9) - anhydrous amorphous silica, belongs to the group of synthetic active highly dispersed mineral fillers. In pharmacy, Aerosil (silicon dioxide) is used as an auxiliary substance, a stabilizer, a gelling agent, an adsorbent, improves the fluidity of the tablets, ointment, gel and other mixtures. Sometimes silicon dioxide is used as an active pharmacological ingredient (it has antibacterial properties, detoxifier, sorbent).
Get silica by hydrolysis of silicon tetrachloride vapor in a hydrogen flame at a temperature of\u003e 1000 ° C (1100-1400 ° C). The resulting product is a white, amorphous, non-porous, indifferent powder that is sprayed, contains 99.3% SiO2; has a high dispersion (particle diameter 4-40 microns, have a spherical or almost spherical shape), the specific adsorption surface is 50-450 m2 / g; bulk density of about 50 g / l, density - 2.36 g / cm3; the pH of the aqueous suspension is 4.0; refractive index n20D = 1.46. Aerosil does not dissolve in water, acids and dilute alkalis. At a concentration of Aerosil in water in an amount of 10-12%, a low-viscous fluid suspension is formed, at 17% - a semi-rigid mass, at 20% - a coarse mass, which, when rubbed, turns into a homogeneous ointment-like mass. Due to the high affinity for water, aerosil is referred to as hydrophilic substances. But silicon dioxide (Aerosil) brand R972 has hydrophobic properties.
There are several trademarks of Aerosil (silicon dioxide)which differ mainly in the specific surface area, degree of hydrophilicity or hydrophobicity, as well as the presence of other filler substances. According to the definition of the nomenclature commission, amorphous silicon dioxide is called oxide. In Ukraine, a chemical and metallurgical plant licensed by Degussa produces unmodified standard aerosil of 175 grades; 300 380 with a hydrophilic surface; methylarosyl AM-1/175 and AM-1/300, modified with dimethyldichlorosilane; Aether organosols of the brands ADEG-175 and ADEG-300, modified with ethylene glycol and diethylene glycol, and AM-2, modified with amino alcohols. In the United States, modified aerosil is produced - organosil and kebosil (Cabot), in Russia, butosil, aerosil-K, which is a combination of 85% silica and 15% starch, COK-84 aerosil, which is a coagulant of 85% silica and 14% ammonium oxide. In Germany, the company "Degussa" produces hydrated brands of aerosilcontaining bound water (durosil, vulkasin, sifloks, ultrasil, etc.), which differ in SiO2 content, particle diameter, density and properties), aerosil in the form of suspensions (K-314, contains 14% A., K-328, contains 28% A.). In Japan, microsils are produced and worn, in France - Francil, in England - Manosil. For cosmetics can be made in the form of a paste. Recently, aerosil was introduced into the pharmacopoeia of various countries (Hungary, Denmark, Austria, etc.). In the USA, silicon dioxide (aerosil) is also allowed as an additive to food products in the amount of 2%.
Aerosil attributed to the theory of "pure" substances that release the active ingredients without energy costs. Electron microscopic studies have shown that each basic particle of aerosil consists of four separate layers (figure). The core of this particle is a three-dimensional polymer of SiO2 elements. Having Silane Si-OH and siloxane Si-O-Si groups on the surface of the particles, Aerosil is capable of creating a pattern-like framework due to hydrogen bonds, which allows limiting the thermal expansion of the gelled liquid. Siloxane and silane groups in aerosil are functional, and the silicon-oxygen bond is characterized by high strength (reaches 372.5 J / mol), which is explained by its polarity, due to which the covalent bond approaches the ionic bond.
Table - The main properties of silicon dioxide (Aerosil)
Picture. The structure of the spatial grid of Aerosil in hydrogel
Silanol groups are unevenly distributed. There are surface silane groups, which can be free or connected by hydrogen bridges, and silanol groups within the molecule, which can also be interconnected by hydrogen bridges. As a result, a branched bulk structure is created, with the result that aerosil is referred to as inorganic polymers. Siloxane groups have hydrophobic properties, they are stable (OH silanol groups are split off at a temperature of\u003e 300 ° C), they cause an acid reaction; have hydroxyl groups both on the surface and inside aerosil molecules. With a uniform distribution, every second silicon atom has a hydroxyl group on the surface.
This causes three types of aerosil interaction: physical adsorption, chemical adsorption (the formation of hydrogen bridges by silanol groups with water, alcohols, acids and other substances) and chemical reactions on the surface of the molecule. Thus, silanol groups interact with alcohols to form ethers.
Aerosil (silicon dioxide) has good sorption properties, absorbs from 15 to 60% of various liquids depending on their nature, without changing the appearance and flowability of the powder. The first layer of water is absorbed by aerosil due to the creation of hydrogen bridges (chemical adsorption), and the subsequent layers are due to physical adsorption. Physically adsorbed water is released at a temperature of 25-150 ° С, whereas chemically adsorbed water is released at 800 ° С.
Aerosil, which is used for the production of drugs, must have high purity. Table 1 shows the chemical composition of various trademarks of Aerosil, which may have certain impurities formed during production processes, for example, traces of hydrochloric acid, which causes a pH of 4% of an aqueous suspension of the polymer (3.6-4.3). So, Aerosil (silica) behaves like a weak acid.
Table 1 - The chemical composition of various grades of aerosil (in terms of dry substance, according to MM Astrakhanov)
| Content% | Aerosil brands, composition,% | ||||
| 200; 300; 380 | 0 | SOK84 | R972 | Combined | |
| SiO2 | >99,87 | >99,8 | 82–86 | >98,3 | 85 |
| Al2O2 | 14–18 | – | |||
| Fe2O3 | – | ||||
| TiO2 | – | 0,03 | – | ||
| Na2O | – | – | – | – | |
| As | – | – | – | – | |
| B2O3 | – | – | – | – | |
| Bi2O3 | – | – | – | – | |
| P2O5 | – | – | – | – | |
| HCl | – | 0,05 | |||
| Starch | – | – | – | – | – |
Table 2 shows the most important physicochemical properties of different aerosil brandswhich are widely used in the manufacture of medicines
Table 2. Physical and chemical properties of different brands of aerosil
| Indicator | Stamps of aerosil | |||||
| 200 | 300 | 380 | 0 | SOK-84 | R-972 | |
| Specific surface, m2 / g | 200 ± 25 | 300 ± 30 | 380 ± 30 | 200 ± 25 | 170 ± 30 | 120 ± 30 |
| Losses during ignition,% | 1 | 2 | 2,5 | 1 | 1 | 2 |
| Average particle size | 12 | 7 | 7 | 12 | – | 16 |
| Moisture content,% (dried at 105 ° С) | – | 1,5 | 1,5 | 1,5 | 0,5 | 2,5 |
| Saturated weight, g / l, standard (non-extruded) pressed | ≈60≈120 | |||||
| Porosity | Porous | Non-porous | ||||
| pH 4% water dispersion | 3,6–4,3 | – | – | 3,6–4,3 3.5–4.1 (in methanol) |
||
AT drug manufacturing Aerosil used as a stabilizer for suspension oil liniments. It has a high ability to adsorb various liquids. The addition of aerosil to the composition of oil and water-alcohol-glycerol suspension liniments enhances the sedimentation, aggregation and aggregative stability of these systems, creating a sufficiently strong spatial structure capable of retaining immobilized liquid phase with suspended particles of pharmaceutical substances in cells. In aqueous and aqueous-alcoholic suspensions, the stabilizing effect of aerosil is mainly due to electrostatic forces. The sedimentation of particles of the solid phase in stabilized aqueous-alcoholic suspensions occurs 3 times slower than in unstabilized systems. The stabilizing effect of Aerosil increases in the presence of a small amount of surfactant, for example, Tween-80. The presence of aerosil (at a concentration of 1.0–5.0%) in emulsions and suspensions increases their stability, the ability to better fixate on the skin and the effectiveness of the therapeutic action. With water and alcohol silicon dioxide at a concentration of 3% creates turbid suspensions whose fractions have a negative charge.
One of the properties of Aerosil is its thickening (thickener) ability (Table 3).
Table 3. The thickening effect of Aerosil-200
This property is used to obtain aerosil-containing gels and ointment bases, which include aerosil. As a liquid phase for their compositions, a polyethylsiloxane liquid is used under the name Esilon-5 or Esilon-4, fish oil, PEG-400, castor oil, fatty oils, and the like. Esilon-5 thickened 16% of Aerosil known as Vaseline KV-E / 16, does not irritate the skin, does not prevent the absorption of active substances. As a thickener liquid phase is used aerosil (silicon dioxide) in the amount of 8-16%. The resulting gels have a soft plastic consistency, are well distributed and fixed on the skin. They have good colloidal stability at elevated temperatures (≥40 ° C), retain the necessary consistency, which does not change even at 100 ° C, and therefore aerosil-containing gels and ointments can be used in tropical climates. According to the structural and mechanical properties of the gels, which include aerosil, constitute thixotropic plastic thermostable systems and have antimicrobial stability. The quantitative content of aerosil in the system affects the rheological and biopharmaceutical properties of gels. The increase in silicon dioxide in the composition of the gels leads to an increase in their plastic viscosity and thixotropic properties, while the release of the active pharmacological ingredient is noticeably slowed down.
The use of Aerosil (silicon dioxide) in the medical and veterinary pharmaceutical industry
Aerosil is used in the manufacture of tablets. in a concentration of 0.1-0.5% as a sliding and loosening (0.1-2.0%) substance, which reduces the time of their disintegration, facilitates the process of granulation, improves the fluidity of the tablet mass. The adsorption properties of Aerosil are used in the manufacture of powders, extracts and other pharmaceutical preparations.
Numerous pharmacological, toxicological and biopharmaceutical studies have confirmed that when used internally, aerosil is indifferent, well tolerated by patients, has healing properties for diseases of the gastrointestinal tract and other inflammatory processes, and can be a source of supply of silicon in the body. There is evidence that aerosil (silicon dioxide) can contribute to the reduction of smooth muscles and blood vessels, and also has antibacterial properties.
Aerosil-containing pharmaceutical systems do not exhibit irritating and toxic effects. The same properties are inherent in ointments when using epsilon and aerosil as a basis (composition of epsilon-5, thickened with 15% aerosil in the manufacture of ointments with antibiotics and corticosteroids). Ointments with Aerosil (silica) easily squeezed out of tubes, well fixed on the skin, have a prolonged effect.
Literature
Zhoglo F., Wozniak V., Popovich V., Bogdan J. Auxiliary substances and their use in the technology of medicinal forms. - Lviv, 1996; Pertsev I.M., Kotenko A.M., Chueshov A.V., Khaleeva E.L. Pharmaceutical and biological aspects of ointments: Monograph. - H., 2003; Pechkovskaya K.A. Filling rubber. In: Encyclopedia of Polymers. In 3 t. - M., 1974.
Silicon oxide (IV)
Chemical properties
Silica, what is it? According to Wikipedia, tetravalent silica is a component of almost all rocks. This chemical compound has the form of colorless crystals, with a rather high melting point. Silicon Dioxide Formula: SiO2. The chemical formula of silica coincides with the formula of silica. Melting point - about 1600 degrees Celsius.
The substance belongs to the group of acidic oxides, is a dielectric, and has several polymorphic modifications of crystals. Under the action of high temperatures and pressure, the substance turns into coesite and stishovite, has various modifications and forms, quartzin, opal, authigenic quartz, chalcedony; amorphous silica is a quartz glass.
Silica application
Substance due to the variety of forms, is used in various fields. The mineral is used in the manufacture of glass, abrasives, concrete products and ceramics; as a filler during rubber production, to obtain silicon; in the production of refractory materials; in chromatography. Quartz crystals are used for the production of lighters, ultrasonic installations, in radio engineering. Some algae contribute to the accumulation of silica in the biosphere and perform a biochemical function. The compound is also used as an emulsifier in the food industry ( E551), added to the toothpaste. Used as an insulator in the production of fiber optic cables, used as a heating element in electronic cigarettes; in jewelry and so on. The use of Silicon Dioxide in medicine as an auxiliary substance, a food additive or as an enterosorbent is widespread.
Silicon dioxide: harm and benefits
The substance can not cause special harm to the body, since the penetration into the gastrointestinal tract is not absorbed through the walls of the stomach and excreted unchanged. Food supplement E 551 is present in many foods, in sugar, powdered milk and slava, chips, crackers, alcoholic beverages and confectionery. With proper use of drugs, the harm of silicon dioxide colloid is also absent.
pharmachologic effect
Adsorbing, regenerating.
Pharmacodynamics and pharmacokinetics
Silica has a fairly high absorption capacity. The substance binds and removes various enzymes from the body, angiigens , tissue decay products, microorganisms and food allergens . The substance is actively used for the evacuation of certain drugs, water and poisons. After penetration into the digestive tract, the agent does not undergo systemic absorption and does not accumulate in the body.
When used locally, the substance prevents necrotic changes in tissues and promotes wound healing.