RU2761627C1 - Adsorbent polymethylsiloxane polyhydrate and method for its preparation - Google Patents

Abstract

FIELD: pharmaceutical industry.

SUBSTANCE: invention relates to the pharmaceutical industry and can be used in medicine or veterinary medicine to produce an organosilicon adsorbent based on a hydrogel of methyl silicic acid (polymethylsiloxane polyhydrate). The resulting sorbent can be used as an enterosorbent and detoxifying agent. A method for obtaining an adsorbent by polycondensation of 5 parts by weight of an aqueous-alkaline solution of sodium methyl silicate (density 1.20-1.30 g/cm³) with 3 parts by weight of an aqueous solution of hydrochloric acid with a concentration of 12.0-14.0, wt. %, is proposed. The components cooled to a temperature of +2° + 5°C are mixed, further maturation of the target product is carried out at room temperature from 30 to 90 minutes without stirring. The resulting hydrogel is crushed, washed by decantation with purified water and 0.3-0.8 M hydrochloric acid solution to the pH of the washing water 5.0-7.0, after which the adsorbent is dried. An adsorbent obtained by the claimed method with an adsorption activity of 6.65-7.30 mmol/g is also proposed.

EFFECT: proposed method makes it possible to increase the adsorbent yield by 2%, increase the adsorption activity of the resulting adsorbent by 36% and reduce the volume of washing water 10 times, while the technology does not involve the use of ethyl alcohol and synthesis is carried out at a temperature no higher than +20°C.

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Description

The technical field to which the invention relates

The invention relates to the pharmaceutical industry and can be used in medicine or veterinary medicine to obtain an organosilicon adsorbent based on methylsilicic acid hydrogel (polymethylsiloxane polyhydrate). The resulting sorbent can be used as an enterosorbent and detoxifying agent.

State of the art

Polymethylsiloxane polyhydrate (PMSPG) is a hydrogel of methylsilicic acid with a porous structure (“molecular sponge”), which has a selective sorption effect by the mechanism of molecular adsorption to medium molecular weight toxic metabolites and by the mechanism of coprecipitation in the gel absorbs high molecular weight toxins. Physicochemical properties determined the use of polymethylsiloxane polyhydrate as a drug - enterosorbent, which is used to bind and remove toxic substances from the gastrointestinal tract.

Polymethylsiloxane polyhydrate is a polymeric organosilicon compound in the form of a gel, which is dispersed in water to particles (less than 300 microns). Electron microscopic studies have shown the globular structure of the gel-forming matrix, which consists of an ensemble of intergrown globules connected by siloxane bonds, forming pores. The pores are the spaces between the globules, they are filled with water, and the pore sizes are limited. The presence of methyl groups on the surface of the sorbent determines its hydrophobic properties. Usually, polymethylsiloxane polyhydrate particles form a continuous network in solution to reduce the intergroup interaction of hydrophobic SiCH ₃ groups with water, they are like two-dimensional sheets rather than three-dimensional solid particles. Polymethylsiloxane polyhydrate solutions have high viscosity.

The industrial production of the drug began in the early 1990s, and for the first time polymethylsiloxane polyhydrate was synthesized in the 1970-1980s by employees of the L.V. Pisarzhevsky Institute of Physical Chemistry.

Let us consider the methods known from the prior art for producing organosilicon adsorbents.

Patent RU2111979 (publ. 27.05.1998) discloses a method for producing polymethylsiloxane polyhydrate, including the process of polycondensation of a solution of sodium or potassium methylsiliconate with a concentration of 1.75 - 2.30 mol / l by adding a strong acid solution to it until the formation of a hydrogel, which after holding for 30 - 90 minutes break and activate the action of a dilute solution of a strong acid concentration of 0.04 - 0.15 mol / l, followed by washing with water until neutral. The disadvantage of this method is the low adsorption activity of the resulting product (no more than 2.5 μmol / g), the yield of the target product is no more than 36.7%.

Adsorption activity (in the scientific literature synonyms are used - adsorption capacity, sorption capacity, adsorption capacity, sorption pore volume) is a specific quality indicator for drugs of the enterosorbent group and is used to characterize the absorption capacity of the sorbent, which determines the amount of adsorbate (reagent) that the sorbent can absorb per unit of its mass.

A slightly different method for producing polymethylsiloxane polyhydrate is described in patent EA012985 (priority date 10/30/2006). According to this method, a solution of a strong acid is added to a solution of sodium methylsiliconate or potassium until the product is formed, followed by holding, grinding, activating the product by adding a dilute solution of a strong acid and washing the product until neutral, characterized in that a solution of sodium or potassium methylsiliconate is used in a concentration 2.35-2.95 mol / L. This method involves a long process, while the resulting product has insufficient adsorption activity.

The patent EA020108 (priority date: 12/16/2009) describes a method for preparing a hydrogel of methylsilicic acid, including the preparation of a working mixture of methyltriethoxysilane and an organic solvent, preparation of a hydrolysis mixture from hydrochloric acid and purified water, preparation of an alkaline solution, hydrolysis of methyltriethoxysilane in the presence of acid catalyst followed by alkaline treatment, holding the reaction mass, grinding the obtained methylsilicic acid alkoxel, its further washing with water purified to form methylsilicic acid hydrogel, characterized in that when preparing the working mixture as an organic solvent, an aqueous solution of ethanol is used with a volume fraction of ethyl alcohol from 60 to 96.5%, and the quantitative volumetric ratio of methyltriethoxysilane and an organic solvent in the form of an aqueous solution of ethanol is 1-1.2: 2-2.7, respectively, while methyltriethoxysilane is used with a mass fraction of the basic th substance is not less than 98%, and the hydrolysis of methyltriethoxysilane is carried out at a volume ratio of the working mixture and the hydrolyzing mixture of 3-3.5: 0.7-1.5, respectively, while the time for introducing the hydrolyzing mixture into the reaction mass is 30-40 minutes, and the holding of the resulting reaction mass is carried out for 3-3.5 hours at a pH value of not less than 3, and after the hydrolysis of methyltriethoxysilane is completed, an alkaline solution is introduced into the resulting reaction mass, having a temperature of 16-30 ° C, after which the obtained methylsilicic acid alcoholhydrogel is kept for aging for at least 7.5 hours, while the process of maturation of the methylsilicic acid alcohol hydrogel is carried out until a colorless intermediate product with a slight opalescence is obtained, and the crushed methylmetasilicic acid alcoholhydrogel is washed out by introducing purified water into it at a rate of 2-4 l / h. This method also involves the use of a flammable reagent - ethyl alcohol, which makes the production process fire hazardous.

Obtaining an adsorbent is also known from patent UA72402 U (priority date: 03.03.2010). A method of obtaining a sorbent based on a hydrogel of methylsilicic acid of the general formula {(CH ₃ SiO _1.5) mH ₂ O} n, where m is the number of water molecules in the link {(CH ₃ SiO _1.5) ⋅mH ₂ O}, n - the number of units {(CH ₃ SiO _1,5) ⋅mH ₂ O} in a hydrogel, in which a hydrogel is obtained from the starting material in the presence of a strong acid in an alcohol medium by hydrolysis followed by polycondensation in an alkaline medium, which is kept and ground and washed the resulting product until neutral. A strong acid is used at a concentration of 0.5% to 1.2%, and an alkaline reagent for carrying out the polycondensation reaction is used at a concentration of 20% to 27%. The disadvantage of this method is the use of a flammable reagent (ethanol), which leads to an increased hazard in production and a decrease in environmental safety.

Patent application EA202000102 (priority date: 08/30/2017) discloses a method for producing a methylsilicic acid hydrogel with properties of supramolecular structures, according to which a solution of sodium methylsiliconate is used, characterized in that a gaseous acidic agent is passed through the sodium methylsiliconate solution loaded into the reactor to carry out bubbling, the resulting product is floated in the throat of the reactor, after the end of the process, the product is unloaded from the reactor, evacuated to remove residual gas and washed with water purified to pH 6.5-7.0 and without residual amounts of anions, obtaining a methylsilicic acid hydrogel with properties of supramolecular structures. The disadvantage is that when implementing this method, it is necessary to ensure the tightness of the equipment used, as well as the use of toxic gaseous reagents (hydrogen sulfide, sulfuric and sulfurous anhydrides, hydrogen chloride).

There is also known a method for producing polymethylsiloxane polyhydrate from patent RU2714728 (priority date: 03/29/2019), which consists in the hydrolysis of methyltriethoxysilane in ethanol in the presence of a catalyst, followed by maturation and washing of the hydrogel, characterized in that an alkaline catalyst is used and the hydrolysis is carried out in an alkaline medium, the components are taken in the following molar ratio methyltriethoxysilane: ethanol: alkaline catalyst - 1: [1.7-3]: [0.3-0.7] and the alkaline catalyst is introduced in the form of an aqueous solution, the water of which is used for the hydrolysis reaction, the molar ratio of methyltriethoxysilane and water for hydrolysis is 1: 7.8-13.6. This method also involves the use of a flammable reagent - ethyl alcohol, which greatly complicates the production process, makes it fire hazardous and reduces environmental safety, and the resulting product has a low adsorption activity.

The prototype of the proposed technical solution is a method for producing an organosilicon adsorbent disclosed in patent RU2293744 (priority date: 22.12.2005). To obtain, 19-20 hours of an alkaline solution of sodium dioxymethylsiliconate (DOMKN) with a density of 1.16-1.19 g / cm ³ with 6 hours of sulfuric acid with a density of 1.195-1.205 g / cm ³ with stirring at a temperature of 0 ° From to + 5 ° C until the target product ripens, water is added to the resulting mixture, the resulting product is stirred and ground, after which water is added to the resulting suspension and defended to precipitate the product to the bottom, the supernatant liquid is removed by decantation, the addition of water is repeated, settling and decantation for complete removal of DOMKN, after which the resulting product is washed with a solution of sulfuric acid until the pH of the wash water is 4.0, and then with water until the pH of the wash water is from 5.0 to 7.0, followed by drying.

The disadvantages of the prototype method are:

- the impossibility of using monosubstituted sodium methylsiliconate for the synthesis of the adsorbent. The patent RU2293744 uses sodium dioxymethylsilicate CH ₃ Si (OH) ₂ ONa (the trivial name for sodium methylsiliconate), the formula of which is presented as a monosubstituted compound with a molecular weight of 116 g / mol, but methylsiliconate is a mixture of oligomers in an alkaline solution and 100% monosubstituted methylsiliconate sodium cannot exist in an aqueous solution (K.A.Andrianov, L.M.Khananashvili Technology of organoelement monomers and polymers / Moscow, 1973).

- low adsorption activity of the resulting product - no more than 4.9 ± 0.7 μmol / g;

- the product yield is no more than 96 ± 1%.

Thus, the technical problem, the solution of which is provided in the implementation or use of the invention, and which could not be solved in the implementation or use of analogs of the invention, is to obtain polymethylsiloxane polyhydrate with low adsorption activity according to the methods known from the prior art and use for the synthesis of flammable reagents and unstable raw materials in aqueous solution.

Disclosure of the essence of the invention

The technical result of the claimed invention is to obtain an adsorbent polymethylsiloxane polyhydrate with high yield and high adsorption activity without the use of flammable substances from a stable in an aqueous solution of raw materials, reducing the amount of wash water.

Also, according to the invention, an adsorbent obtained according to the described method is obtained. The resulting adsorbent differs in that it has a higher adsorption activity and is obtained using an improved technology without the use of organic solvents and flammable substances.

Table 1. Comparison of the characteristics of adsorbents obtained by the prototype method and the claimed method

Prototype The claimed invention Improving performance Product yield,% 96 ± 1 98 ± 1 increase by 2% Adsorption activity, μmol / g 4.9 ± 0.7 6.7 ± 0.6 an increase of 36% The ratio of the target product to the volume of wash water 1: 100 1:10 decrease by 10 times

The technical result is achieved due to the implementation of the process of synthesis of the adsorbent as follows: use 5 parts of an aqueous-alkaline solution of sodium methylsiliconate (density 1.20-1.30 g / cm ³ ) with 3 parts of an aqueous solution of hydrochloric acid with a concentration of 12.0-14, 0 wt%. The components cooled to a temperature of + 2 ... + 5 ° C are mixed with stirring, further maturation of the target product is carried out at a temperature not higher than + 20 ° C without stirring for 30 to 90 minutes, followed by grinding and washing the final product first with purified water, then 0.3 -0.8 M hydrochloric acid to pH of wash water 5.0-7.0.

The chemical scheme of the polycondensation reaction of sodium methylsiliconate is presented below:

where, [xNa] - corresponds to the amount of sodium (in terms of sodium hydroxide) in an aqueous solution of sodium methylsiliconate with a density of 1.20-1.30 g / cm ³ , at x = 1; y = 0.1-0.2; z = 0.001-0.02; n = 52 - 94.

As a result of the study, it was found that it is possible to increase the yield of polymethylsiloxane polyhydrate and its adsorption activity if the preparation is carried out by a method including the stages:

1.activation of the polycondensation process due to the introduction of hydrochloric acid;

2. polycondensation of the polymer due to the intermolecular interaction of sodium methylsiliconate;

3. the formation of the structure of the polymer and its purification.

The initial commercial reagent "sodium methylsiliconate" is a strongly alkaline aqueous solution, its spontaneous polycondensation is impossible. To start the polycondensation process, it is necessary to partially neutralize the alkali with a solution of hydrochloric acid. By shifting the equilibrium in the system, the process of polymer formation starts. When mixing the reagents for the synthesis, the change in the acidity of the medium is monitored from pH 13-14 to pH 10-11.

The final product according to the claimed method is an adsorbent having the structure of polymethylsiloxane polyhydrate, which is confirmed by taking IR and NMR spectra from the resulting product.

Obtaining an adsorbent having the structure of polymethylsiloxane polyhydrate is determined by controlling the ^{amount of sodium and silicon in the reagent solution (density 1.20-1.30 g / cm 3} ) by calculating the mass fraction of alkali and silicon in the solution.

The sodium content in terms of sodium hydroxide in the finished solution should be in the range of 7.5-8.6 wt.% And the silicon content should be at least 5.2% (the determination of silicon is carried out by the gravimetric method). These indicators are necessary and sufficient conditions for the synthesis of the adsorbent. If these parameters do not match, it is not possible to synthesize polymethylsiloxane polyhydrate.

The indicators "mass fraction of silicon" and "mass fraction of alkali" were introduced to control the ratio of reagents in the reaction mixture, since if the ratios of the reagents are different, then the composition and structure of the polymer will be different.

The ratio of the starting components 5: 3 by weight was found experimentally, so that polycondensation took place with the formation of an adsorbent with the structure of polymethylsiloxane polyhydrate, without impurities of other products.

For the polycondensation process, one of the strong acids was chosen - hydrochloric acid; it is hydrochloric acid that ensures the achievement of the technical result. For the synthesis, it is the hydrochloric acid solution with a concentration of 12.0-14.0 wt. %. This range is selected as a result of a series of experiments, which provides partial neutralization of sodium hydroxide in a solution of sodium methylsiliconate, to start the polycondensation process. For the polycondensation process, it is important to cool the reagents to a temperature of + 2 ... + 5 ° C, since this action compensates for the temperature jump that occurs during the partial neutralization of sodium hydroxide.

The components are mixed at the time of mixing to quickly and evenly distribute hydrochloric acid throughout the entire volume of sodium methylsiliconate solution.

When maturing the adsorbent under synthesis conditions, the temperature is maintained at a level not higher than +20 ° C, since at temperatures above + 20 ° C the sorption capacity of the sorbent decreases.

A time interval of 30-90 minutes allows you to obtain an adsorbent polymethylsiloxane polyhydrate with the declared properties.

The separation of the solid phase of the resulting adsorbent from the mother liquor is carried out by decantation.

The resulting adsorbent is washed first with purified water, then with a 0.3-0.8 M solution of hydrochloric acid (to pH = 3.0-4.5) to completely remove sodium hydroxide from the pores of the adsorbent and to save wash water by neutralizing NaOH in the solution sodium methylsiliconate. Then the adsorbent is subjected to final washing with purified water to pH = 5.0-7.0. The change in the acidity of the wash water is controlled by the potentiometric method. The ratio of the target product to the volume of the wash water is 1:10. The use of 0.3-0.8M hydrochloric acid saves a significant amount of wash water.

After washing, the adsorbent is subjected to vacuum drying, moisture control is carried out on a moisture analyzer.

Brief Description of Drawings

FIG. 1 shows the IR spectrum of the sample taken in a disk with potassium bromide (about 3 mg of dry residue triturated with 300 mg of potassium bromide) in the region from 4000 to 400 cm ^-1 according to the position of the absorption bands corresponds to the pattern of the spectrum of polymethylsiloxane polyhydrate.

FIG. 2 shows the ²⁹ Si NMR spectra obtained by the direct polarization method ( ²⁹ Si DP / MAS)

FIG. 3 shows the VMU NMR spectra on ²⁹ Si nuclei obtained by the method of polarization transfer from protons to silicon-29 nuclei ( ²⁹ Si СP / MAS)

Implementation of the invention

To carry out the synthesis of the adsorbent take the following reagents.

Sodium methylsiliconate - a colorless or light yellow transparent aqueous solution with a density of 1.20-1.30 g / cm ³ has a strongly alkaline reaction. Fire and explosion proof. In the used aqueous-alkaline solution of sodium methylsiliconate, the density, mass fraction of alkali and silicon are controlled. It can be stored for 2 years in packaging according to the manufacturer's specifications.

Hydrochloric acid (hydrochloric acid, hydrochloric acid, hydrogen chloride) is a strong monobasic acid. Colorless, transparent, caustic liquid, "fuming" in air. The maximum concentration at 20 ° C is 38 wt. %, the density of such a solution is 1.19 g / cm³.

Hydrochloric acid solutions are prepared from a concentrated solution by diluting it, since the process is exothermic, then during the preparation process heat is removed by supplying cooled water to the jacket. A freshly prepared solution is used for synthesis.

Purified water is water obtained from drinking water by distillation, ion exchange, reverse osmosis, a combination of these methods or in another way, and intended for the production or manufacture of medicines, obtaining water for injection, as well as for testing medicines.

Below are examples of adsorbent synthesis:

Example 1

To 90 g of an aqueous-alkaline solution of sodium methylsiliconate (t = + 2.0 ° C) with stirring, add aqueous 12.5 wt. % hydrochloric acid solution in an amount of 54 g (t = + 2.0 ° C). The solutions are loaded into the reactor by weight, controlled by strain gauges. The ripening of the reaction mass is carried out for 30 minutes at a temperature not higher than + 20 ° C. The freshly precipitated gel is ground to a particle size of 200 µm using an overhead frame mixer with scrapers and a bottom homogenizer. Particle size control is carried out by a microscopic method. After grinding, they are washed with purified water and a 0.5 M solution of hydrochloric acid by decantation until the pH of the wash water is 5.0-7.0. The appearance of the obtained polymethylsiloxane polyhydrate was monitored visually, a wet mass of white or almost white color was obtained, consisting of jelly-like lumps of various sizes, odorless. The moisture content in the product is analyzed using a moisture analyzer by the gravimetric method and is at least 90%. The adsorption activity of this sample was 6.65 μmol / g. The product yield is 97%.

Example 2

To 120 g of an aqueous alkaline solution of sodium methylsiliconate (t = + 3.0 ° C) with stirring add an aqueous 13.0 wt.% Hydrochloric acid solution in the amount of 72 g (t = + 3.0 ° C). The solutions are loaded into the reactor by weight, controlled by strain gauges. The ripening of the reaction mass is carried out for 60 minutes at a temperature not higher than + 20 ° C. The freshly precipitated gel is ground to a particle size of 200 µm using an overhead frame mixer with scrapers and a bottom homogenizer. Particle size control is carried out by a microscopic method. After grinding, they are washed with purified water and a 0.3 M solution of hydrochloric acid by decantation until the pH of the wash water is 5.0-7.0. The appearance of the obtained polymethylsiloxane polyhydrate was monitored visually, a wet mass of white or almost white color was obtained, consisting of jelly-like lumps of various sizes, odorless. The moisture content in the product is analyzed using a moisture analyzer by the gravimetric method and is at least 90%. The adsorption activity of this sample was 7.30 μmol / g. The product yield is 99%.

Example 3

To 200 g of an aqueous alkaline solution of sodium methylsiliconate (t = + 5.0 ° C) with stirring, add an aqueous 13.5% solution of hydrochloric acid in an amount of 120 g (t = + 5.0 ° C). The solutions are loaded into the reactor by weight, controlled by strain gauges. The ripening of the reaction mass is carried out for 90 minutes at a temperature not exceeding 20 ° C. The freshly precipitated gel is ground to a particle size of 200 µm using an overhead frame mixer with scrapers and a bottom homogenizer. Particle size control is carried out by a microscopic method. After grinding, they are washed with purified water and a 0.8 M hydrochloric acid solution by decantation until the pH of the wash water is 5.0-7.0. The appearance of the obtained polymethylsiloxane polyhydrate was monitored visually, a wet mass of white or almost white color was obtained, consisting of jelly-like lumps of various sizes, odorless. The moisture content in the product is analyzed using a moisture analyzer by the gravimetric method and is at least 90%. The adsorption activity of this sample was 6.70 μmol / g. The product yield is 98%.

Samples of polymethylsiloxane polyhydrate obtained according to examples 1, 2, 3 were examined according to the following indicators: appearance; authenticity; adsorption activity.

Methods for determining the adsorption activity have been developed in accordance with the Russian Federation GF OFS.1.2.3.0021.15 "Determination of the adsorption activity of enterosorbents". For this type of sorbent, the OFS recommends determining the adsorption activity by a spectrophotometric method using dyes such as Congo red, methylene blue, and methyl orange. To exclude electrostatic interactions of the sorbent, two anionic dyes of different molecular weights were selected: Congo red (molecular weight 696.7 g / mol) and methyl orange (molecular weight 327.0 g / mol). Since methylene blue belongs to cationic dyes, it was excluded from the method for determining the sorption capacity of the adsorbent.

Example 4

Samples of polymethylsiloxane polyhydrate, obtained according to examples 1, 2, 3, had a gel-like form of almost white color, were practically insoluble in water and 95% ethanol (study by the method of the State Pharmacopoeia of the Russian Federation).

Example 5

The adsorption activity was determined spectrophotometrically (using a Congo red solution).

0.02 M sodium chloride solution. Place 1.170 g of sodium chloride in a volumetric flask with a capacity of 1000 ml, add 950 ml of purified water, adjust the pH of the resulting solution with 0.1 M sodium hydroxide solution or 0.1 M hydrochloric acid solution to 6.2 ± 0.1, dilute the volume of the solution with water cleaned to the mark and mix.

Congo red stock solution. About 0.381 g (accurately weighed) of Congo red is placed in a volumetric flask with a capacity of 1000 ml, dissolved in 700 ml of 0.02 M sodium chloride solution with constant stirring and weak heating, cooled and the volume of the solution is brought to the mark with the same solvent and stirred again.

Congo red solution. 2.0 ml of the original solution of Congo red is quantitatively transferred into a volumetric flask with a capacity of 50 ml, the volume of the solution is brought up to the mark with 0.02 M sodium chloride solution and stirred.

Test solution. About 1.00 g (accurately weighed) of the substance is placed in a conical flask with a ground-in stopper with a capacity of 100 ml, add 50.0 ml of a stock solution of Congo red, shake vigorously for 1 hour on a shaker at a speed of 500 rpm, then filter the resulting the solution through the "Blue Ribbon" filter discarding the first portions of the filtrate.

2.0 ml of the filtrate is quantitatively transferred into a volumetric flask with a capacity of 50 ml, the volume of the solution is brought up to the mark with 0.02 M sodium chloride solution and stirred.

Measure the optical density of the Congo red solution and the test solution at the maximum absorption at a wavelength of 489 nm in a cuvette with a layer thickness of 10 mm, using 0.02 M sodium chloride solution as a reference solution.

The adsorption activity (A _to ) of the drug, in micromoles per gram, is calculated by the formula:

where A the optical density of the test solution; A ₀ - the optical density of the Congo red solution; a ₀ - weight of Congo red, g; a - weight of substance, g; M - molecular weight of Congo red (696.7), g / mol; 50, 50.50 - the dilution factor of the test solution and the Congo red solution; 1,000,000 - recalculation of moles to micromoles.

Example 6

The adsorption activity was determined spectrophotometrically (using a methyl orange solution).

0.02 M sodium chloride solution. In a volumetric flask with a capacity of 1000 ml, place 1.170 g of sodium chloride, add 950 ml of purified water, adjust the pH of the resulting solution with 0.1M sodium hydroxide solution or 0.1M hydrochloric acid solution to 6.2 ± 0.1, dilute the volume of the solution with purified water to the mark and mix.

Methyl orange stock solution. About 0.180 g (accurately weighed) of methyl orange is placed in a volumetric flask with a capacity of 1000 ml, dissolved in 700 ml of 0.02 M sodium chloride solution with constant stirring and weak heating (40-50 ° C), cooled and the volume of the solution is adjusted with the same solvent to the mark and mix again.

Methyl orange solution. 5.0 ml of the stock solution of methyl orange is quantitatively transferred into a volumetric flask with a capacity of 100 ml, the volume of the solution is brought to the mark with 0.2 M sodium chloride solution and stirred.

Test solution. About 1.00 g (accurately weighed) of the adsorbent is placed in a conical flask with a ground-in stopper with a capacity of 100 ml, add 50.0 ml of a stock solution of methyl orange, shake vigorously for 1 hour on a shaker at a speed of 500 rpm, then filter the resulting the solution through the "Blue Ribbon" filter discarding the first portions of the filtrate.

5.0 ml of the filtrate is quantitatively transferred into a volumetric flask with a capacity of 100 ml, the volume of the solution is brought to the mark with 0.02 M sodium chloride solution and stirred.

Measure the optical density of the methyl orange solution and the test solution at the maximum absorption at a wavelength of 464 nm in a cuvette with a layer thickness of 10 mm, using a 0.02 M sodium chloride solution as a reference solution.

The adsorption activity (A _m ) of the drug, in micromoles per gram, is calculated by the formula:

where A - the optical density of the test solution; A ₀ - the optical density of the methyl orange solution; a ₀ - weighed amount of methyl orange, g; a - weight of substance, g; M - molecular weight of methyl orange (327.0), g / mol; 50.50.50 - the dilution factor of the test solution and the Congo red solution; 1,000,000 recalculation of moles to micromoles.

Example 7

The authenticity of the obtained adsorbent was determined by taking the IR spectrum (see Fig. 1). The IR spectrum of the adsorbent according to the position of the absorption bands should correspond to the pattern of the spectrum of polymethylsiloxane polyhydrate.

The IR spectrum of the sample, recorded in a disk with potassium bromide (about 3 mg of dry residue triturated with 300 mg of potassium bromide) in the region from 4000 to 400 cm ^-1 according to the position of the absorption bands, corresponds to the pattern of the spectrum of polymethylsiloxane polyhydrate shown in Fig. 1. (GF RF, OFS.1.2.1.1.0002.15 "Spectrometry in the infrared region").

Table 2. Characteristic absorption bands in the region of the main vibration frequencies

Wavelength, cm ^-1 Characteristic stripes 3340 - 3250 stretching vibration bands O-H 2975 - 2845 stretching vibration bands C-H 1250 - 800 bending vibration bands C-H 1100 - 1000 O-Si stretching vibration bands 850 - 650 stretching vibration bands of C-Si

Example 8

The authenticity of the obtained adsorbent was also determined by taking NMR spectra of 29Si (see Fig. 2), which should contain singlets R-Si (OH) 2 (OSi), R-Si (OH) (OSi) 2, R-Si (OSi ) 3.

_{Si (CH 3} ) ₄ - 0 ppm was used as an external standard for determining the chemical shift. The spectra were processed using the Bruker Topspin 2.1 software.

The spectra were recorded using two spectral techniques.

The first, the direct polarization method (90-degree pulse + full relaxation) (abbreviated DP / MAS), provides quantitative data and allows, under the condition of complete magnetic relaxation, to detect all possible states of silicon atoms, including silicon in dense proton-free phases ... The disadvantage of this technique is its low sensitivity. This technique was used to determine the quantitative composition of the test material.

The second technique is ¹ H- ²⁹ Si cross-polarization (CP / MAS), a semi-quantitative method that allows you to register signals from silicon atoms, which are surrounded by hydrogen atoms. Has a high sensitivity. CP / MAS spectra are not quantitative without prior direct polarization transfer calibration. Also, this method does not allow registering silicon, in the environment of which there are no hydrogen atoms. At the same time, with certain, specially selected for specific types, spectrum registration parameters and using calibration procedures, the CP / MAS method allows obtaining quantitative spectra with a high signal-to-noise ratio. This technique was used to refine the quantitative data obtained by the DP / MAS method.

The recorded spectra of the solid-phase NMR sample on ²⁹ Si nuclei (Figs. 2 and 3) show the signals in (ppm) for the local environment of silicon atoms: at -46 ppm. (singlet, R-Si (OH) ₂ (OSi)), -56 ppm (singlet, R-Si (OH) (OSi) ₂ ), -66 (singlet, R-Si (OSi) ₃ ), where R is an organic radical, in this case it is a methyl group (CH ₃ -).

Table 3. Fraction of detected types of silicon atoms in different chemical environments.

Sample Group / Chem. Signal shift R-Si (OSi) ₃ / -66 ppm R-Si (OH) (OSi) ₂ / -56 ppm R-Si (OH) ₂ (OSi) / - 46 ppm Polymethylsiloxane polyhydrate 85.9 ± 0.4% 13.6 ± 0.3% 0.5 ± 0.2%

The presence of registered signals confirms that the analyzed adsorbent samples have the structure of an organosilicon adsorbent - "Polymethylsiloxane polyhydrate".

Thus, the proposed method, combining optimally selected conditions and reagents, makes it possible to achieve an increase in the yield of polymethylsiloxane polyhydrate by 2%, the adsorption activity of the resulting adsorbent by 36%, and a decrease in the volume of wash water by a factor of 10, while the technology does not imply the use of ethyl alcohol and the synthesis is carried out at a temperature not higher than +20 ° С.

Claims (2)

1. A method of obtaining an adsorbent, which consists in the interaction of solutions of sodium methylsiliconate and acid cooled to a temperature of + 2 ... + 5 ° C with stirring, maturation of the target product, water is added to the resulting mixture of the target product, stirred and crushed, the supernatant liquid is removed by decantation, washed with water purified and acid solution to pH of wash water from 5.0 to 7.0, followed by drying, characterized in that the ratio of an aqueous-alkaline solution of sodium methylsiliconate with a density of 1.20-1.30 g / cm ³ and an aqueous solution of hydrochloric acid with concentration of 12-14 wt. % is 5: 3 by weight, maturation is carried out at a temperature not higher than +20 ° C without stirring for 30-90 minutes, the resulting product is washed with 0.3-0.8 M hydrochloric acid. 2. The adsorbent obtained according to the method according to claim 1 and having an adsorption activity of 6.65-7.30 μmol / g.

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