RU2362733C1 - Method for processing of carbon mesoporous hemosorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to the technology of preparation of carbon sorbents used for hemosorption in the treatment of the diseases accompanied by the accumulation in human organism of certain toxic substances. The method for processing of carbon hemosorbent includes the processing of the porous carbon material with air by the way of contacting with air-water mixture in boiling bed and additional hemosorbent treatment in fixed bed with 4-6% solution of nitric acid fed to the reaction zone in definite time intervals following with air input with volume rate 8 m³/hr for sorbent mixing. The said acid treatment is carried out during 7 hrs, acid/sorbent ratio is 1:(29-32). The obtained sorbent is dried at 200°C up to residual residual moisture content 0.2%.

EFFECT: preparation of sorbent with high adsorbent activity in relation to nitrogen-containing nonprotein toxic substances such as bilirubin, creatinine, urea.

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Description

The invention relates to a technology for producing carbon sorbents used for hemosorption in the treatment of diseases associated with the accumulation of toxic substances of a certain nature in the human body.

A known method of producing a sorbent for medicine, including keeping activated carbon in boiling distilled water for 45 minutes, cooling the resulting suspension and then passing carbon dioxide through it to lower the pH of activated carbon to 7.0-8.7 (RF patent No. 2036139, C. IPC С01В 31/08).

The disadvantages of this method are: a low degree of removal of carbon dust from the surface and pores of coal, low productivity of the process.

Known methods for producing carbon hemosorbents based on natural carbon-containing raw materials: peat (SKT-6A), a mixture of coal with tar residues of wood hydrolysis (AR-3) by thermal decomposition without air and subsequent activation with water vapor or using chemical reagents (Lopukhin Yu.M., Molodenkov M.N. Hemosorption, 1985. - M .: Medicine. - P.23).

The carbon hemosorbents obtained by this technology have several disadvantages: a high content of mineral impurities, requiring additional processing in order to reduce their amount (up to 2%); low mechanical strength of granules; predominantly microporous structure and "aggressiveness" in relation to the formed elements of the blood.

Known methods for producing carbon hemosorbents based on polymeric materials by pyrolysis and subsequent activation by steam of granules of spherical feedstock of a spherical shape and a certain size (FAS). These sorbents are characterized by high strength granules having a smooth surface topography; low content of mineral impurities (0.1%) (RF patent No. 2026813).

The disadvantage of synthetic sorbents of the FAS type, non-specific in the nature of the interaction and capable of removing a wide range of substances, is the low selectivity of sorption of compounds of a certain nature, in particular, low adsorption activity with respect to bilirubin and creatinine, inertness with respect to urea.

A known method of increasing the adsorption activity of carbon adsorbents with respect to nitrogen-containing compounds: bilirubin, creatinine, urea, by modifying the chemical nature of their surface. Coating the surface of the GS-01 sorbent with a polymer film, which reduces the amount of cationogenic carboxyl groups by 2 times, increases its adsorption activity with respect to bilirubin in comparison with SKN-K and SKT-6A sorbents, which have a more developed mesoporous structure (Gorchakov V.D., Sergienko V.I., Vladimirov V.G. Selective sorbents. - M .: Medicine, 1989. - 224 p.).

However, the polymer coating changes the porous structure of the surface of the sorbents and the kinetics of the sorption process, reduces the effectiveness of the use of sorbents in emergency cases.

There is a method of increasing sorption activity in relation to creatinine, albumin, urea of carbon sorbents SKN-1K, SKN-4M, SKN _o , SKT-6A, actylene A by polarizing the surface (cathode, anode), changing the magnitude and sign of its potential (L. C. Tikhonova, M.V. Belotserkovsky, A.U. Dubikaitis, et al. Effect of activated carbon polarization on the adsorption of urea, creatinine and albumin // Journal of Applied Chemistry. 1992. - T.65. - No. 9. - S.2050-2052). However, the complexity of the procedure and the effect of polarization of the sorbent on the properties of the biological fluid significantly limited the application of this method.

Closest to the proposed is a method of processing carbon hemosorbent, comprising contacting an aqueous suspension of granules of a carbon porous material with an air-water mixture in a fluidized bed by feeding jets of the air-water mixture into the reactor from the bottom up under the material layer. The carbon material is processed until a pH of 6.0-7.0 is reached and its surface is practically dust free. Next, the resulting product is dried at a temperature of 200 ° C (RF patent No. 2211727, prototype). The obtained carbon mesoporous hemosorbent VNIITU-1 fully complies with the medical requirements for sorption materials that are in contact with blood and other biological fluids of a living organism. The hemosorbent is characterized by high chemical purity (carbon content of not less than 99.5%), a minimum content of mineral impurities (not more than 0.15%), the practical absence of carbon dust on the surface and in the pores of round-shaped granules 0.5-1.0 mm ; smooth surface relief, allowing a possible decrease in the content of blood cells after contact with it no more than 10-15%, a specific adsorption surface of 300-400 m ² / g, the presence of oxygen-containing acid groups in the amount of 0.060-0.070 meq / g, of which the content carboxyl groups 0.051-0.058 meq / g; phenolic groups 0.009-0.012 meq / g. In addition, the VNIITU-1 hemosorbent is characterized by high thermal and chemical resistance, ease of sterilization (Surovikin V.F., Pyanova L.G., Luzyanina L.S. New hemo- and enterosorbents based on nanodispersed carbon-carbon materials // Russian Chemical Journal. 2007. - T. LI. - No. 5. - Pages 159-165).

The disadvantage of this method in the context of the present invention should include the receipt of a product with insufficient adsorption activity with respect to nitrogen-containing compounds of non-protein nature.

The aim of the invention is to obtain a carbon hemosorbent with high adsorption activity to nitrogen-containing toxic compounds of non-protein nature: bilirubin, creatinine, urea.

The proposed method of treating carbon hemosorbent includes treating the porous carbon material with air by contact with the air-water mixture in a fluidized bed, then treating the hemosorbent in a stationary layer with a 4-6% nitric acid solution, supplied to the reaction zone in portions at regular intervals, followed by air supply at a flow rate of 8 m ³ / h for mixing the sorbent in the solution, and duration of the acid treatment is 7 hours, and the ratio of acid component to the sorbent 1: (29-32).

Distinctive features of this invention are:

- treatment of hemosorbent in a stationary layer with a 4-6% solution of nitric acid supplied to the reaction zone in portions at certain intervals of time, followed by air supply with a space velocity of 8 m ³ / h to mix the sorbent in the solution;

- processing for 7 hours at room temperature to a pH value of the sorbent 4-5;

- the ratio of acid to sorbent is 1: (29-32).

The set of essential features proposed by the application has made it possible to increase the adsorption activity of hemosorbent to nitrogen-containing toxic compounds of non-protein nature: bilirubin, creatinine, urea.

When the hemosorbent comes in contact with the biological fluid of the body (blood, plasma, lymph, cerebrospinal fluid and others), redistribution of the components dissolved in it between the two phases occurs. The process is largely determined by the structure and chemical nature (the presence of oxygen and the chemical structure of the groups formed by it) of the surface of the sorbent, the chemical nature of the adsorbed component.

A change in the chemical nature of the surface of the sorbent — the total content of oxygen groups and their distribution among groups of different chemical nature — significantly changes the adsorption properties of the sorbent with respect to substances of a certain nature. Oxygen groups of an acidic nature (carboxyl, phenolic), which are specific adsorption centers of the carbon surface, complement the adsorption of compounds by the main mechanism - molecular, adsorption due to ion exchange, hydrogen bonding, complex formation, electrostatic interaction.

By chemical and spectral methods for analyzing the chemical structure of the surface of the obtained carbon mesoporous hemosorbent, the presence of oxygen-containing groups in the amount of 0.040-0.050 meq / g and phenolic 0.0125-0.030 meq / g and phenolic 0.015-0.020 meq / g was found on the surface.

The main physicochemical characteristics of carbon sorbents were determined by standard methods used in the study of porous materials: adsorption surface, porous surface structure - from adsorption-desorption isotherms of a standard inert nitrogen gas, which were experimentally measured using a Sorptomatic-1900 volumetric vacuum static automated installation. The calculation of the adsorption surface of the hemosorbent is made according to the BET equation. The quantitative content of oxygen-containing groups was determined by the chemical method (Bohemian method) from their interaction with chemical reagents of various nature, the qualitative composition was determined by IR spectroscopy.

The surface treatment of the granules of carbon sorbent with a solution of nitric acid is carried out in a stationary layer in the reactor described previously in patent No. 2211727 "Method for processing granules of carbon material for hemo- and enterosorption and the reactor for its implementation." Carbon hemosorbent after treatment in a fluidized bed with an air-water mixture is washed in the reactor with distilled water at a ratio of water to sorbent 2: 1, passing from bottom to top through its layer. Part of the water is removed from the reactor, leaving a layer 20–25 cm high above the surface of the sorbent. Pour into the reactor a 4–6% solution of nitric acid in portions at regular intervals, each time mixing the sorbent in the solution with air at a volume velocity of 8 m ³ / h . The ratio of acid to sorbent is 1: (29-32). The treatment is carried out for 7 hours at room temperature until the sorbent pH is 4-5.

The following examples are provided to illustrate the invention.

Example 1 (prototype)

50 kg of carbon mesoporous material are poured through the charging device into the reactor and an air-water mixture is created from the bottom up under the material layer, creating a fluidized bed. The material is processed until the ultrafine carbon particles (dust) are completely removed from the surface and pores of the material, and its pH is reduced to 6.0-7.0. The resulting product is washed with distilled water with a pH of 5.3-5.6, passing it from the bottom up through a layer of sorbent in the reactor in a ratio with the sorbent 2: 1. The sorbent is discharged from the reactor, dried at a temperature of 200 ° C to a residual moisture content of 0.2%. The obtained carbon mesoporous hemosorbent VNIITU-1 contains on the surface oxygen groups of an acidic nature in the amount of 0.066 meq / g, including carboxylic 0.056 meq / g, phenolic 0.010 meq / g.

Example 2

Analogously to example 1, the carbon porous material is treated in a fluidized bed reactor with an air-water mixture until a pH of 6.0-7.0 is reached and the surface is almost completely de-dusted. The sorbent in the reactor is washed with distilled water in a ratio with the sorbent 2: 1, passing it through the sorbent layer from the bottom up. The bulk of the water is removed from the reactor, leaving a 25 cm high layer of water on the surface of the sorbent. 1.3 L of 5% nitric acid is poured into the reaction zone, the sorbent is mixed in the solution with air at a space velocity of 8 m ³ / h. The treatment is carried out for 4 hours, stirring the sorbent in an acid solution with air every hour. After 4 hours, 0.2 l of acid is poured into the reaction zone, and after 1 h, another 0.2 l of acid is added, stirring the sorbent in the solution with air every hour. The sorbent is washed with distilled water and dried at a temperature of 200 ° C to a residual moisture of 0.2% and the absence of a qualitative reaction to the presence of nitrates. The obtained carbon mesoporous hemosorbent contains on the surface oxygen groups of an acidic nature in an amount of 0.043 meq / g, including carboxylic 0.025 meq / g, phenolic 0.018 meq / g.

To study the effect of changes in the chemical structure of the surface of the hemosorbent on its adsorption activity with respect to toxic nitrogen-containing substances of non-protein nature - bilirubin, creatinine, urea, bench tests of the developed sorbent were conducted at the Central Research Laboratory of the Omsk State Medical Academy. Tests were conducted on the plasma of patients with peritonitis, the test results are presented in the table.

Biochemical parameters of blood plasma of patients with peritonitis during tests of the adsorption activity of carbon hemosorbents Indicator The content of toxic substances in the blood plasma of patients In the initial plasma (n * = 14) After plasma contact with hemosorbent hemosorbent before treatment with an acid solution hemosorbent after treatment with an acid solution The fraction of molecules with an average mass, units 0.632 ± 0.077 0.519 ± 0.068 0.465 ± 0.054 Bilirubin total, μmol / l 30.39 ± 4.98 29.12 ± 4.58 21.63 ± 1.35 Urea, mmol / L 4.58 ± 0.760 4.31 ± 0.821 3.18 ± 0.488 Creatinine, μmol / L 72.72 ± 5.901 64.44 ± 7.740 36.71 ± 7.690 Ammonia, μmol / L 22.33 ± 2.102 13.89 ± 0.949 13.62 ± 1.068 n * is the number of plasma samples

As follows from the table, the proposed hemosorbent in contact with the blood plasma of patients with peritonitis reduces the amount of creatinine by 2 times in relation to the initial value, reduces the content of bilirubin and urea by about 30%, both ammonia are removed from the blood plasma in the same way.

The experimental data presented in the table allow us to conclude that increased (compared with the prototype) adsorption activity of the proposed carbon hemosorbent in relation to nitrogen-containing compounds of non-protein nature - bilirubin, creatinine, urea, which will lead to a significant increase in the efficiency of the hemosorption process and the entire detoxification process of the human body during treatment of acute and chronic endotoxicosis observed with peritonitis.

Claims (1)

A method of treating a carbon hemosorbent, including treating a porous carbon material with air by contact with an air-water mixture in a fluidized bed and then drying the target product, characterized in that the hemosorbent is further treated in a stationary layer with a 4-6% nitric acid solution supplied to portions of the reaction zone at regular intervals, followed by air feed at a flow rate of 8 m ³ / h for mixing the sorbent, wherein the acid treatment time was 7 is h, and the ratio of sorbent to acid is 1: (29-32).