RU2559506C1 - Method of production of photocatalytic sorbing fabric material - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: invention relates to the field of production of self-cleaning fabric material having the photocatalytic activity under the action of ultraviolet and visible radiation and intended for the photocatalytic destruction of hazardous organic and inorganic substances and macromolecules. The method of production of the material comprises impregnating of the washed and dried fabric base with aqueous sol of silicon dioxide, air drying, washing with distilled water and redrying. Then the fabric impregnation is carried out with the coated silicon dioxide of titanyl sulphate solution and the immersion is carried out into the aqueous suspension of the photocatalyst based on nanocrystalline titanium dioxide with ultrasound treatment. The resulting material is air dried, washed with water and finally dried.

EFFECT: invention provides obtaining the material effective for adsorption cleaning of gas and water environments polluted by organic and inorganic substances, followed by self-cleaning by photocatalytic degradation.

10 cl, 1 dwg, 3 tbl, 10 ex

Description

The invention relates to the field of development of a method for producing self-cleaning tissue material having photocatalytic activity under the influence of ultraviolet or visible radiation and intended for photocatalytic destruction of hazardous organic and inorganic substances and macromolecules.

It is known that for the purification of water and indoor air, methods based on the phenomena of sorption and concentration on the surface or in the bulk of substances called sorbents are mainly used. Moreover, in many cases, the accumulation of the pollutant on the sorbent occurs without changing its chemical structure. Therefore, over time, the efficiency of sorption treatment decreases, the regeneration of the sorbent is required, and the problem of further disposal of the pollutants accumulated as a result of treatment remains.

On the other hand, it is known that titanium dioxide, mainly in anatase modification, when irradiated with ultraviolet light, has a high oxidative activity and is able to oxidize most compounds adsorbed on its surface, including volatile organic and inorganic compounds. In this regard, photocatalytic technologies based on the use of titanium dioxide as a photocatalyst are a promising purification method, since in most cases they provide complete oxidation of pollutants to carbon dioxide, water and mineral acids.

The development of a method for producing highly active photocatalysts with a large specific surface area was the subject of a number of inventions. The preparation methods can be divided into two large groups: the sol-gel method and the sulfate method.

A known method of producing titanium dioxide (US 5718878, C01B 37/00, 02.17.1998) by sol-gel method from titanium alkoxide in an aqueous-organic solution using a stabilizing agent such as alkylamine with the number of carbon atoms in the alkyl group from 6 to 18. The specified method allows to obtain titanium dioxide with a surface area of more than 300 m ² / g and a pore size of not more than 100 Å, which has photocatalytic activity.

A known method for producing a photocatalyst based on anatase titanium dioxide (RU 2494045, C01G 23/053, 09/27/2013) by preparing an aqueous solution of titanyl sulfate and sulfuric acid and its subsequent hydrolysis in hydrothermal conditions with simultaneous treatment of the solution with microwave radiation. The specified method allows to obtain a photocatalyst with a high yield and a specific surface area of more than 300 m ² / g, which has a high photocatalytic activity.

It is also known that the deposition of noble metals such as silver, gold, platinum and palladium on titanium dioxide allows photocatalytic oxidation to be carried out not only under the influence of ultraviolet radiation, but also under visible light. For example, in (Á. Veres, T. Rica, L. Janovák, M. Dömök, N. Buzás, V. Zöllmer, T. Seemann, A. Richardt, I. Dékány, Silver and gold modified plasmonic TiO ₂ hybrid films for photocatalytic decomposition of ethanol under visible light, Catalysis Today, 181 (2012) 156-162), particles of gold or silver were applied to the surface of titanium dioxide TiO ₂ Degusssa P25 by photoreduction from their respective precursors to achieve their content of 0.5 wt.%. It was shown that the deposition of metals significantly increases the rate of oxidation of ethanol vapor under the action of visible light with a wavelength of more than 435 nm compared with unmodified titanium dioxide.

An additional advantage of platinum supported titanium dioxide photocatalysts is that, unlike unmodified TiO _2, they are capable of oxidizing carbon monoxide to CO ₂ at a fairly high rate. For example, in (Sangman Hwang, Myung Churl Lee, Wonyong Choi, Highly enhanced photocatalytic oxidation of CO on titania deposited with Pt nanoparticles: kinetics and mechanism, Applied Catalysis B: Environmental, 46 (2003) 49-63), platinum was deposited on the surface of three samples of titanium dioxide with a different specific surface by the method of photoreduction from platinum hydrochloric acid. On platinized photocatalysts, oxidation of 30 ppm CO occurred in 4-6 minutes of exposure to ultraviolet radiation, while on unmodified titanium dioxide, the oxidation rate of CO was negligible.

The main disadvantage of the above methods is that the resulting photocatalysts are presented in the form of fine powders. In this case, a serious problem is the need to separate the photocatalyst from the cleaned water or air environment after the process, which significantly increases the cost of energy and the cost of the process. Therefore, for practical use in water and air purification systems and for creating photocatalytically active materials, it is necessary to fix the photocatalyst on some medium. The carrier must provide high adhesion of the photocatalyst, have a large specific surface area, the availability of this surface for illumination with UV lamps, sufficient mechanical strength and chemical stability.

The development of methods for producing photocatalytically active materials based on woven and non-woven inorganic and organic canvases coated with a photocatalyst was the subject of a number of inventions.

A known method of producing material (JP 2000199173, B01D 53/86, 07/18/2000) by immersing fiberglass in a colloidal solution of titanium dioxide and then calcining the material at temperatures of 450-650 ° C. The specified material has photocatalytic activity in the oxidation of organic substances. The main disadvantage of this material is the low adhesion of TiO ₂ particles to fiberglass due to the fact that its fibers are non-porous. This leads to the fact that the photocatalyst is easily blown away. Due to the low content of the photocatalyst and its small specific surface area, such a material has a low adsorption capacity. Moreover, it cannot be used to create self-cleaning protective clothing.

Various adhesives are used to increase the adhesion of titanium dioxide particles and create a strongly bonded photocatalyst layer on the surface of the carrier. Known material (JP 11290700, B01J 31/06, 10.26.1999), which is a photocatalytically active fabric based on fiberglass impregnated with a suspension of anatase titanium dioxide in a tetrafluoroethylene polymer. The specified material has a high adhesion of the photocatalyst to the tissue base. A known method of producing tissue (US 2005/0227557, B32B 5/02, 04/09/2004 US), which has the functions of sterilization, deodorization, self-cleaning and protection against mold formation when exposed to light, by impregnating the washed fabric base with an aqueous suspension containing from 0.1 up to 10 wt.% titanium dioxide powder and from 1 to 5 wt.% acetone and from 2 to 10 wt.% resin. The specified material has a high adhesion of the photocatalyst to the tissue base.

The main disadvantage of the above methods is that the use of the adhesive method degrades the porous structure of the photocatalyst, since part of the surface of the photocatalyst is blocked by glue. This leads to low photocatalytic activity and sorption ability of such a material. Also, this leads to the fact that when the material is irradiated, the organic glue will be oxidized by the photocatalyst with the possible release of hazardous chemicals, such as, for example, formaldehyde, and its performance deterioration.

A known method of preparing material (Tung, WS Understanding photocatalytic behavior on biomaterials: Insights from TiO ₂ concentration / WS Tung, WA Daoud, SK Leung // J. Colloid Interface Sci. - 2009. - Vol. 339. - P. 424-433 ) based on activated carbon fibers obtained from viscose yarns and having a specific surface area of 934 m ² / g, onto which titanium dioxide is deposited by hydrolysis of titanium tetrachloride vapor. To increase the crystallinity of titanium dioxide, the material is calcined at a temperature of 600-1000 ° C in an argon flow to prevent burnout of the carrier. This material exhibits photocatalytic activity in the oxidation of dye methylene blue in aqueous solution and has a high adsorption capacity. The disadvantage of this method of producing photocatalytically active material is that the material has low mechanical properties and cannot be used for the manufacture of protective clothing. In addition, the carbon base partially absorbs ultraviolet radiation and enhances electron-hole recombination on the particles of the photocatalyst due to its conductive properties, which as a result leads to a decrease in the photocatalytic activity of the material as a whole.

Closest to this invention is a method of obtaining a filtering and sorbing material with photocatalytic properties (RU 2482912, B01J 20/02, 05.27.2013), which consists in the fact that the textile base, which is used as a cotton or cotton polyester fabric with a cotton content of at least 35%, impregnated with a titanium-silicate complex, including silicon dioxide freed from sodium oxide, and anatase photocatalytically active titanium dioxide with a mass ratio of titanium dioxide and silicon dioxide (1-3): 5. The material obtained in this way has high photocatalytic activity under the action of ultraviolet radiation in the oxidation of volatile compounds such as ammonia, acetone, benzene, xylene and ethyl acetate.

A significant disadvantage of this method is that the resulting material is structurally disorganized, since particles of titanium dioxide are randomly distributed in the titanium-silicate layer on the surface of the fabric. Therefore, part of the particles of titanium dioxide has close contact with the surface of tissue fibers and oxidizes them, which as a result leads to strong self-destruction of the material and its complete destruction upon prolonged exposure to ultraviolet radiation. Due to the fact that titanium dioxide particles are embedded in silicon dioxide resulting from the sol-gel process, partial blocking of the surface is observed and the transport of oxidized substrate molecules to the surface of the photocatalyst is impaired and, as a result, a decrease in photocatalytic activity is observed. The specified material exhibits photocatalytic activity only under the influence of ultraviolet radiation and cannot conduct oxidation under the influence of visible light. In addition, it does not have photocatalytic activity in the oxidation of carbon monoxide.

It can be seen from the above examples that, despite the many known methods for producing a photocatalytic sorbent tissue material, it is not possible to ensure that the resulting material simultaneously satisfies several requirements, namely: 1) it is a photocatalytically active tissue material based on textile fabrics for use in creating protective clothes with self-cleaning function; 2) had a high sorption ability due to the high content of fine particles; 3) possessed high stability to self-destruction under prolonged exposure to ultraviolet radiation; 4) had photocatalytic activity under the influence of visible light; 5) possessed photocatalytic activity in the oxidation of carbon monoxide.

The present invention aims to develop a method for producing tissue material that meets the above criteria.

The problem is solved by a method for producing a photocatalytic sorbent fabric material, which is a structurally organized system, which consists in applying to the fabric base from a cotton-containing fabric, first, an intermediate insulating layer of silicon dioxide and then an outer layer of photocatalytically active nanocrystalline titanium dioxide with a specific surface area of more than 300 m ² / d, on which additionally deposited particles of precious metals, mainly gold and platinum

In more detail, the problem is solved by a method for producing a photocatalytic sorbent fabric material for photocatalytic and adsorption purification of gas and aqueous media, which includes impregnation of the washed and dried fabric base with SiO ₂ silica sol, subsequent drying of the treated fabric base in air, washing with distilled water and final drying; impregnation of a fabric coated with silicon dioxide with a solution of titanyl sulfate and subsequent immersion in an aqueous suspension of a photocatalyst based on nanocrystalline titanium dioxide at a constant temperature of 70-90 ° C and vigorous stirring and sonication, drying of the material in air, washing with water and final drying.

Impregnation of the washed and dried fabric base with an aqueous sol of silicon dioxide SiO ₂ , as a result of which the condensation of the SiO ₂ sol on the surface of the fabric base into a gel takes place, is carried out in a sealed container for at least 10 hours

Final drying is carried out at a temperature not exceeding 90 ° C.

A solution of titanyl sulfate with a concentration of 4-10 wt.% Is used.

Use an aqueous suspension of a photocatalyst based on nanocrystalline titanium dioxide with a concentration of 0.5-20 g / L.

As the fabric base, use cotton or mixed cotton polyester fabric with a cotton content of at least 60%.

Use freshly prepared silica sol obtained by hydrolysis of tetraethylorthosilicate in an aqueous solution of isopropanol, or a silica hydrosol with a particle size of 6.0-10.5 nm, purified from stabilizing sodium ions by treatment with cation exchanger in acid form.

As the photocatalyst, nanocrystalline titanium dioxide in anatase modification with a specific surface area of more than 300 m ² / g is used or nanocrystalline titanium dioxide in anatase modification with the addition of noble metals such as platinum, gold or mixtures thereof in an amount of 0.1-2 wt.% Is used .

An important feature of the use of the photocatalyst in fabric materials is that as a result of exposure to UV light, powerful oxidizing agents are formed on the surface of the photocatalyst, capable of destroying the organic compounds in contact with it, and hence the fabric base itself. The application of silicon oxide to the fabric base allows one to increase the sorption capacity of the fabric and form an intermediate insulating layer between the surface of the fabric fibers and the surface of the photocatalyst, thereby preventing their direct contact in order to prevent self-destruction of the fabric base.

The application of an anatase modification of a photocatalyst based on nanocrystalline titanium dioxide with a specific surface area of more than 300 m ² / g allows the fabric to give high oxidative ability under the influence of ultraviolet light and high sorption ability. The additional use of a binder based on amorphous titanium dioxide obtained by hydrolysis of titanyl sulfate, allows you to firmly bind particles of nanocrystalline titanium dioxide with the surface of the fabric and thereby increase their adhesion.

The application of nanocrystalline titanium dioxide to a photocatalyst fabric on the surface of which noble metal particles are deposited, mainly gold, the content of which is 0.1-2% of the mass of titanium dioxide, allows the fabric to give photocatalytic activity under the influence of visible radiation. The application of nanocrystalline titanium dioxide to a photocatalyst fabric on the surface of which noble metal particles are deposited, mainly platinum, the content of which is 0.1-2% by weight of titanium dioxide, allows the fabric to give photocatalytic activity in the oxidation of carbon monoxide by ultraviolet radiation.

The technical result consists in obtaining a structurally organized tissue material having high photocatalytic activity under the influence of ultraviolet or visible radiation and high sorption ability, showing high stability to self-destruction during prolonged irradiation. The technical result is achieved by sequentially applying to the fabric base an intermediate insulating layer of silicon dioxide and an outer photocatalytically active layer. Obtained by the claimed method, the material is intended to create self-cleaning coatings and surfaces, personal protective equipment with the function of self-cleaning, self-degassing suits and use in water and air purification systems as a replaceable fabric filter.

The essence of the production method is that the washed fabric base is first impregnated with a SiO ₂ sol, while the sol particles are adsorbed on the surface of the fabric fibers and completely cover them. Next, the impregnated fabric is placed in a sealed chamber for a period of at least 10 hours for the process of sol condensation to occur in a SiO ₂ gel. As a result, a uniform layer of porous silicon dioxide forms on the surface of the fabric fibers. After that, the treated tissue is dried in air, washed with distilled water and finally dried at a temperature of not more than 90 ° C. Next, the fabric is impregnated with a solution of titanyl sulfate and placed for 1 h in an aqueous suspension of nanocrystalline titanium dioxide, the temperature of which is maintained constant in the range of 70-90 ° C. Preferably, the concentration of titanyl sulfate is 4-10 wt.%. The suspension is stirred with a magnetic stirrer and sonicated (20 kHz) to increase the dispersion of TiO ₂ particles and their uniform distribution throughout the volume of the suspension. As the concentration of titanium dioxide particles in the suspension increases, the content of TiO ₂ in the material increases. Preferably, the concentration of TiO ₂ in the suspension is 0.5-20 g / L. When a tissue impregnated with a solution of titanyl sulfate is immersed in a hot aqueous suspension, thermal hydrolysis of TiOSO ₄ molecules adsorbed on the surface of the fabric takes place with the formation of amorphous titanium dioxide, which traps crystalline TiO ₂ particles in water and binds them strongly with aging the surface of the fabric material. As a result, an external tightly bound photocatalytic layer of porous titanium dioxide is formed on the surface of the fabric material. After that, the treated tissue is dried in air, washed with distilled water and finally dried at a temperature of not more than 90 ° C.

The invention is illustrated by the following examples.

In the examples, 100% cotton “Panacea Cotton 350” (Tchaikovsky Textile Group of Companies) with a surface density of 350 g / m ² , pre-washed using anionic detergent “7X” and non-ionic detergent “Triton X-100 ”(Helikon Company LLC) and distilled water. The prepared tissue is cut into pieces of size 85 × 85 mm.

To apply a protective layer of silicon oxide, tetraethylorthosilicate Si (OC ₂ H ₅ ) ₄ (Soyuzkhimprom CJSC, ChDA) or commercial silica sol Kremnezol KZ-L (KazKhimNII OJSC), consisting of SiO ₂ particles with a content of 10 wt. % and a size of 6.0-10.5 nm, stabilized by sodium cation.

For the deposition of the photocatalytically active layer, TiOSO ₄ titanyl sulfate (Reachim CJSC) is used, from which an aqueous solution with a concentration of 10 wt% is prepared, and nanocrystalline titanium dioxide TiO ₂ Hombifine N (Sachtleben Chemie GmbH), which is 100% anatase with specific surface area 350 m ² / g and crystallite size 10-15 nm.

Example 1

183 ml of isopropanol are added to 194 ml of tetraethylorthosilicate (TEOS) and the resulting solution is cooled to a temperature of 0-4 ° C. Sulfuric acid is then added dropwise to 100 ml of distilled water until a pH of 2.0 is reached, which is monitored using a pH meter. Acidified water is slowly added dropwise to a solution of TEOS and isopropanol. After that, the solution is heated to a temperature of 60 ° C and maintained at this temperature for 3 hours with constant stirring. The result is a silica sol.

The washed fabric is impregnated with freshly prepared SiO ₂ sol and placed in a sealed chamber for 10-12 hours for the process of sol condensation in the SiO ₂ gel. After that, the treated tissue is dried in air, washed with distilled water and finally dried at a temperature of not more than 90 ° C.

Next, 1 g of nanocrystalline TiO ₂ is added to 1 liter of distilled water. The resulting suspension is constantly mixed with a mechanical stirrer and further treated with ultrasound (20 kHz) to increase the dispersion of TiO ₂ particles and their uniform distribution throughout the volume. The suspension is maintained at a constant temperature of 70-90 ° C. The fabric is impregnated with an aqueous solution of titanyl sulfate with a content of 10 wt.% And placed for 1 h in a prepared aqueous suspension of titanium dioxide. After that, the treated tissue is dried in air, washed with distilled water and finally dried at a temperature of not more than 90 ° C.

The sample was marked as 2TiO ₂ + CT / SiO ₂ -T / T.

Example 2

Similar to example 1 with the exception that the concentration of titanium dioxide in the aqueous suspension is 20 g / L.

The sample is labeled as 20TiO ₂ + CT / SiO ₂ -T / T.

Example 3

Similar to example 1 with the exception that they use not a freshly prepared silica sol, but a commercial silica sol “Silica sol KZ-L” with a SiO ₂ content of 10 wt.%.

To do this, silica sol is passed through a column filled with KU-2-8 ion-exchange resin in protonated form to remove the stabilizing sodium ions present. The pH of silica sol after purification is 2.00-2.09. Then proceed analogously to example 1.

The sample is labeled as 2TiO ₂ + CT / SiO ₂ -K / T.

Example 4

Similar to example 3 with the exception that the concentration of titanium dioxide in the aqueous suspension is 20 g / L.

The sample is labeled as 20TiO ₂ + CT / SiO ₂ -K / T.

Example 5

Similar to example 3 with the exception that before being placed in an aqueous suspension of titanium dioxide, the fabric is not impregnated with titanyl sulfate.

A sample was labeled as 2TiO ₂ / SiO ₂ —K / T.

Example 6

Similar to example 3 with the exception that before being placed in an aqueous suspension of titanium dioxide, the concentration of which is 20 g / l, the fabric is not impregnated with titanyl sulfate.

The sample is labeled as 20TiO ₂ / SiO ₂ -K / T.

Example 7 (comparative).

A comparative sample is prepared by applying titanium dioxide alone without silica.

To 1 liter of distilled water, 2 g of nanocrystalline titanium dioxide was added. The resulting suspension is constantly stirred with a mechanical stirrer and further treated with ultrasound (20 kHz). The suspension is maintained at a constant temperature of 70-90 ° C. The initial washed tissue (without silica) is placed for 1 hour in a prepared aqueous suspension of titanium dioxide. After that, the treated tissue is dried in air, washed with distilled water and finally dried at a temperature of not more than 90 ° C.

The sample is labeled as 2TiO ₂ / T.

Example 8 (comparative).

Similar to example 7 with the exception that the concentration of titanium dioxide in the aqueous suspension is 20 g / L.

The sample is labeled as 20TiO ₂ / T.

Testing the photocatalytic activity of the obtained materials under the influence of ultraviolet radiation is carried out in the oxidation reaction of acetone vapor in a flow-circulation installation. The study of the kinetics of oxidation is carried out at 40 ° C and values of the volumetric flow rate of 63-65 cm ³ / min. The source of UV radiation is an LED (Nichia, Japan) with a light intensity in the wavelength range of 320-400 nm, equal to 9.7 mW / cm ² .

The concentration of reagents and products is analyzed by changing the area of the absorption bands corresponding to a particular substance on the IR spectra recorded using an FT-801 FT-IR spectrometer (Simeke NPF LLC, Russia) equipped with a long-pass cell (Infrared Analysis, USA) with the length of the optical path equal to 2.4 m. The concentration of acetone in the final reaction mixture is 15-25 μmol / L. A measure of the photocatalytic activity of materials is the rate of CO ₂ formation during the oxidation of acetone, which is calculated by the following formula

, где $$\Delta C_{C{O}_2}$$

- разность концентраций CO₂ в конечной и исходной реакционных смесях (мкмоль/л), U - объемная скорость (л/мин). $$W_{C{O}_2}=\Delta C_{C{O}_2}\cdot U$$

where $$\Delta C_{C{O}_2}$$

- the difference in the concentrations of CO ₂ in the final and initial reaction mixtures (μmol / l), U is the space velocity (l / min).

The test results for determining the photocatalytic activity of the obtained materials, as well as the content of the applied modifiers, are presented in table 1.

The test results show that the application of nanocrystalline titanium dioxide on a fabric base gives it a high photocatalytic activity under the influence of ultraviolet radiation. Complete oxidation of acetone vapor to carbon dioxide and water is observed without the formation of intermediate products. The rate of photocatalytic oxidation depends on the content of titanium dioxide on the tissue. An increase in the concentration of titanium dioxide in the impregnation suspension leads to an increase in the content of TiO ₂ fixed on the surface of the tissue, and the photocatalytic activity of the material increases.

The application of only one titanium dioxide (samples 2TiO ₂ / T and 20TiO ₂ / T) leads to a high content of TiO ₂ in the material and its high photocatalytic activity. However, TiO ₂ particles have low adhesion to the tissue base, as evidenced by a strong decrease in photocatalytic activity after long-term washing of the samples.

The impregnation of the fabric with a silica sol leads to a high content of SiO ₂ particles in the fabric material and, due to this, to its high sorption ability. For samples with an intermediate layer of silicon oxide, the TiO ₂ content is lower, but the photocatalytic activity of such materials is greater and decreases only slightly after a long wash, which indicates strong adhesion. The additional use of titanyl sulfate when applying the photocatalytic layer allows to increase the number of particles of nanocrystalline TiO ₂ fixed on the surface of the fabric base, and their adhesion. The highest photocatalytic activity is demonstrated by the 20TiO ₂ + CT / SiO ₂ -T / T sample.

Titanium dioxide in the composition of materials can cause destruction of the fabric base. A study of the stability of materials and analysis of gaseous products formed during their self-destruction during prolonged irradiation with powerful ultraviolet radiation is carried out in a thermostatic static reactor with a volume of 300 ml at a temperature of 25 ° C, which is built into the cuvette compartment of the Nicolet 380 IR-Fourier spectrometer (Thermo, USA), so that the optical path passes through the gas phase in the reactor. A sample of 7 cm ² material is placed in a reactor and illuminated with a UV LED (Nichia, Japan) with a light intensity in the wavelength range of 320-400 nm equal to 10.2 mW / cm ² , monitoring the concentration of gaseous products using recorded IR spectra. The main product in the self-destruction of materials is CO ₂ , so the stability of the material is evaluated by the rate of CO ₂ formation - the lower the rate of CO ₂ formation, the higher the stability of the material.

The test results of the materials obtained in examples 1-8 are presented in table 2.

From the data presented in Table 2 (column 4), it can be seen that for 2TiO ₂ / T and 20TiO ₂ / T samples containing only titanium dioxide, a high rate of self-destruction of materials is observed. The application of an intermediate layer of SiO ₂ can significantly reduce the rate of self-destruction of materials due to the fact that it prevents direct contact of the particles of the photocatalyst with the surface of the fabric fibers and prevents them from oxidizing. Partial self-destruction of materials with an intermediate layer of SiO ₂ can occur due to the fact that highly reactive particles, such as, for example, OH radicals formed on the surface of the photocatalyst upon irradiation, can migrate along the surface and reach tissue fibers, gradually oxidizing them. The optimal ratio of activity and stability is a sample of 20TiO ₂ + CT / SiO ₂ -T / T.

Thus, it can be seen from the data presented in Tables 1 and 2 that the synthesis method by sequentially depositing layers of SiO ₂ and a photocatalyst allows one to obtain fabric materials with high sorption ability due to the high content of fine particles (TiO ₂ , SiO ₂ ), high photocatalytic activity in the decomposition of volatile organic substances under the influence of ultraviolet radiation to harmless components (CO ₂ , H ₂ O) due to the presence of photocatalytically active titanium dioxide and high stability to self-destruction during prolonged exposure due to the presence of an intermediate insulating layer of silicon oxide.

Example 9

Similar to example 2 with the exception that they use a modified photocatalyst based on titanium dioxide, on the surface of which platinum particles are deposited.

The surface of the photocatalyst is modified by impregnating TiO ₂ powder with an aqueous solution of H ₂ PtCl ₆ acidified with HCl with a given concentration to obtain the desired platinum content, followed by ultrasonic treatment (20 kHz) for 30 minutes. The resulting catalyst was dried at 120 ° C for 2 hours and calcined in air at 650 ° C for 3 hours, or a three-fold excess of NaBH _{4 was} reduced. The platinum content varies in the range of 0.1-2 wt.%. Finally, the catalyst is washed and subsequently dried at 120 ° C for 2 hours.

The sample is labeled as wPt / 20TiO ₂ + CT / SiO ₂ -T / X, where w is the calculated Pt content, expressed in% by weight of dry TiO ₂ . For example, 1Pt / 20TiO ₂ + CT / SiO ₂ -T / X means that Pt with a calculated content of 1% by weight is deposited on titanium dioxide.

Example 10

Similar to example 2 with the exception that they use a modified photocatalyst based on titanium dioxide, on the surface of which gold particles are deposited.

The surface modification of the photocatalyst is carried out by adding to an aqueous suspension of TiO _{2 an} aqueous solution of HAuCl ₄ acidified with HCl, followed by sonication (20 kHz) for 30 minutes. Then, a three-fold excess of NaBH _{4 is} reduced. At the end, the catalyst is washed by repeated centrifugation until pH ≈ 5 is reached and subsequent drying at 120 ° C for 2 hours. The gold content varies in the range of 0.1–2 wt%.

The sample is labeled as wAu / 20TiO ₂ + CT / SiO ₂ -T / X, where w is the calculated Pt content, expressed in% by weight of dry TiO ₂ . For example, 1Au / 20TiO ₂ + CT / SiO ₂ -T / X means that Au is deposited on titanium dioxide with a calculated content of 1 wt.%.

The photocatalytic activity of the samples under the action of visible light is carried out in the oxidation reaction of ethanol vapor. The main difficulty in determining the activity of photocatalysts sensitive to visible light is that, as a rule, the rate of release of the final CO ₂ product is low. Therefore, the rate of formation of an intermediate product, acetaldehyde, is used as a measure of photocatalytic activity. The study of the kinetics of the oxidation of ethanol vapor is carried out in the above static reactor. A spectral laboratory illuminator (LOS-2) with a DXL-1000 Xe lamp using a ZhS-11 light filter (λ> 420 nm) is used as a radiation source. The radiation intensity in the wavelength range of 420-800 nm is 90 mW / cm ² with a maximum at 436 nm. The reaction temperature is 25 ° C.

The initial formation rate of acetaldehyde during the photocatalytic oxidation of ethanol vapor on the samples obtained in examples 1, 9 and 10, under visible light are presented in table 3.

The test results show that the material 20TiO ₂ + CT / SiO ₂ -T / X, obtained using unmodified titanium dioxide, is not able to oxidize ethanol under the influence of visible light. On the other hand, the use of titanium dioxide with supported particles of noble metals makes it possible to obtain tissue material exhibiting photocatalytic activity under visible light. From the data presented in table 3, it can be seen that the most active material is 1Au / 20TiO ₂ + CT / SiO ₂ -T / X. Less active are materials containing platinum. The optimum in all series is a noble metal content of 1 wt.%. The degree of conversion of ethanol to acetaldehyde on the most active material 1Au / 20TiO ₂ + CT / SiO ₂ -T / X is 22% in the first 180 minutes of the photoprocess.

Thus, the deposition of noble metals, mainly gold and platinum, allows one to obtain fabric materials with photocatalytic activity under visible light.

In addition to volatile organic substances, one of the main air pollutants is CO. In addition, the formation of CO, as an undesirable by-product, can occur during the photocatalytic oxidation of complex organic molecules, for example dimethyl methylphosphonate. To determine the photocatalytic activity of the obtained materials in CO oxidation, a comparison is made of the kinetics of CO accumulation and consumption generated during the photocatalytic oxidation of dimethylmethylphosphonate vapor in the static reactor described above.

The kinetic curves of CO during photocatalytic oxidation of 0.4 μl of dimethyl methylphosphonate under the action of ultraviolet radiation on tissue materials are shown in FIG. It can be seen that for the 20TiO ₂ + CT / SiO ₂ / T material, the kinetic curve of CO represents a saturation curve, i.e., CO consumption is not observed during the process, which indicates the absence of photocatalytic activity in CO oxidation in this sample. While for materials containing platinum or gold, the kinetic curves pass through a maximum, that is, the CO, formed during the oxidation of dimethylmethylphosphonate, is gradually consumed by its oxidation to carbon dioxide. The most active material is 1Pt / 20TiO ₂ + CT / SiO ₂ -T / X, obtained by chemical reduction.

Thus, the application of noble metals, mainly gold and platinum, allows fabricated materials to be photocatalytically active with respect to CO oxidation.

The material obtained by the proposed method allows efficient adsorption treatment of gas and water environments contaminated with organic and inorganic substances, and subsequent self-cleaning by photocatalytic destruction of accumulated pollutants under the action of ultraviolet or visible radiation to harmless components.

Claims (10)

1. A method of producing a photocatalytic sorbent tissue material for photocatalytic and adsorption purification of gas and aqueous media, characterized in that the material is prepared by impregnation of the washed and dried fabric base with SiO ₂ silica water followed by drying of the treated fabric base in air, washing with distilled water and final drying, impregnating a fabric coated with silicon dioxide with a solution of titanyl sulfate and then immersing in an aqueous suspension of a nanocrystal-based photocatalyst -crystal titanium dioxide at a constant temperature of 70-90 ° C, vigorous stirring and sonication, drying the material in air, washing with water and final drying. 2. The method according to p. 1, characterized in that the impregnation of the washed and dried fabric base with an aqueous sol of silicon dioxide SiO ₂ , as a result of which the condensation of the SiO ₂ sol on the surface of the fabric base into a gel takes place, is carried out in a sealed container for at least 10 hours . 3. The method according to p. 1, characterized in that the final drying is carried out at a temperature of not more than 90 ° C 4. The method according to p. 1, characterized in that use a solution of titanyl sulfate with a concentration of 4-10 wt.% 5. The method according to p. 1, characterized in that the use of an aqueous suspension of a photocatalyst based on nanocrystalline titanium dioxide with a concentration of 0.5-20 g / L. 6. The method according to p. 1, characterized in that the textile base is a cotton or mixed cotton polyester fabric with a cotton content of at least 60%. 7. The method according to p. 1, characterized in that they use a freshly prepared sol of silicon dioxide obtained by hydrolysis of tetraethylorthosilicate in an aqueous solution of isopropanol. 8. The method according to p. 1, characterized in that they use a silica hydrosol with a particle size of 6.0-10.5 nm, purified from stabilizing sodium ions by treatment with cateonite in acid form. 9. The method according to p. 1, characterized in that as the photocatalyst use nanocrystalline titanium dioxide in anatase modification with a specific surface area of more than 300 m ² / g 10. The method according to p. 1, characterized in that as the photocatalyst use nanocrystalline titanium dioxide in anatase modification with the addition of noble metals such as platinum, gold or mixtures thereof in an amount of 0.1-2 wt.%.

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