RU2562485C1 - Photocatalytic sorbing fabric material - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: material is a structurally organised system which consists of a fabric base coated with an intermediate silicon dioxide layer and an outer layer of photocatalytically active nanocrystalline titanium dioxide of an anatase modification.

EFFECT: efficient adsorption cleaning of gaseous and aqueous media while enabling subsequent self-cleaning by breaking down accumulated contaminants under the effect of ultraviolet and visible radiation to safe components.

2 cl, 2 dwg, 3 tbl, 10 ex

Description

The invention relates to the field of development of 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. 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.

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 there remains the problem of further disposal of pollutants accumulated as a result of treatment.

On the other hand, it is known that titanium dioxide predominantly 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 highly active photocatalysts based on titanium dioxide with a large specific surface area has been the subject of a number of inventions.

A known method of producing titanium dioxide (US 5718878, C01B 37/00, 02.17.1998) sol-gel method from titanium alkoxide in an aqueous-organic solution using a stabilizing agent such as an alkyl amine 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 Angstroms, 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 use of titanium dioxide modified with noble metals such as silver, gold, platinum and palladium 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, Μ. 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) applied gold or silver particles to the surface of titanium dioxide TiO ₂ Degusssa P25 by photoreduction from their respective precursors to achieve a metal particle content of 0.5 wt. % It was shown that for photocatalysts modified with noble metals, the rate of oxidation of ethanol vapor under the influence of visible light with a wavelength of more than 435 nm is significantly increased compared to 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 platinum photocatalysts, the oxidation of 30 ppm CO took place within 4–6 min of illumination with ultraviolet radiation, while on unmodified titanium dioxide the rate of CO oxidation was significantly lower.

The main disadvantage of the above inventions 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 its cost and energy costs. Therefore, for practical use in water and air purification systems and for the creation of photocatalytic filters and materials, it is necessary to mount 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 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.

Known material (JP 2000199173, B01D 53/86, 07/18/2000) obtained by immersing fiberglass in a colloidal solution of titanium dioxide and subsequent calcination of 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 the fiberglass fibers are non-porous. This leads to the fact that the photocatalyst is easily blown away from the material. 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), having the functions of sterilization, deodorization, self-cleaning and protection against mold formation when irradiated with light, by impregnating the washed tissue base with an aqueous suspension containing from 0.1 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 materials 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. And also to the fact that during the operation of the material, the organic glue will be oxidized by the photocatalyst with the possible release of hazardous chemicals such as formaldehyde and a deterioration in the performance of the material.

Known 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 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 an aqueous solution and has a high adsorption capacity. The disadvantage of this material is that it has low strength characteristics 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 ions, 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, a significant proportion of titanium dioxide particles has close contact with the surface of tissue fibers and oxidizes them, which results in 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 silica resulting from the sol-gel process, a partial blocking of the surface is observed and the transport of oxidized substrate molecules to the surface of the photocatalyst is impaired, and therefore, a decrease in photocatalytic activity is observed. Also, this material exhibits photocatalytic activity only under the influence of ultraviolet radiation and cannot oxidize 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 inventions created, it is not possible to ensure that the resulting material simultaneously satisfies several requirements, namely: 1) it is a photocatalytically active fabric material based on textile fabrics for use in creating protective clothing with a 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 fabric material that meets the above criteria.

The problem is solved by the proposed material for photocatalytic and adsorption purification of gas and aqueous media, which is a structurally organized system consisting of a textile fabric base, an intermediate insulating layer of porous silicon dioxide and an outer photocatalytically active layer.

The outer photocatalytically active layer contains a photocatalyst sensitive to ultraviolet light, consisting of nanocrystalline titanium dioxide anatase modification, or sensitive to ultraviolet and visible light, consisting of nanocrystalline titanium dioxide anatase modification further modified by particles of noble metals such as gold or platinum or their , in an amount of 0.1-2% by weight of the deposited titanium dioxide.

The fiber structure model of the material being developed is shown in FIG. one.

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

The anatase-based photocatalyst based on nanocrystalline titanium dioxide with a specific surface area of more than 300 m ² / g allows the tissue to give high oxidative power under the influence of ultraviolet light and high sorption ability. A photocatalyst based on nanocrystalline titanium dioxide in anatase modification, on the surface of which additionally deposited particles of noble metals, mainly gold, whose content is 0.1-2% by weight of titanium dioxide, allows photocatalytic activity to be imparted to the tissue under the influence of visible radiation. An anatase-based photocatalyst based on nanocrystalline titanium dioxide, on the surface of which particles of noble metals are deposited, mainly platinum, the content of which is 0.1-2% by weight of titanium dioxide, which allows the tissue to give photocatalytic activity in the oxidation of carbon monoxide by ultraviolet radiation.

The technical result consists in a fabric 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. 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 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, freshly prepared silica sol is used, obtained by hydrolysis of Si tetraethylorthosilicate (OC ₂ H ₅ ) ₄ (ZAO Soyuzkhimprom, ChDA) in a solution of isopropanol with water acidified with sulfuric acid, with an appropriate molar ratio of components equal to 1: 3.8: 6.4: 0.085, or use commercial silica hydrosol “Kremnezol KZ-L” (OJSC “KazKhimNII”) with a particle size of 6.0-10.5 nm, purified from stabilizing sodium ions by treatment with cation exchange resin in acid form. The washed fabric base is first impregnated with SiO ₂ sol and placed in a sealed chamber for a period of at least 10 hours to allow the sol to condense into the 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.

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. %, and nanocrystalline titanium dioxide TiO ₂ Hombifine N (Sachtleben Chemie GmbH), which is 100% anatase with a specific surface area of 350 m ² / g and a crystallite size of 10-15 nm. The fabric coated with silicon dioxide is impregnated with a solution of titanyl sulfate and placed for 1 h in an aqueous suspension of nanocrystalline titanium dioxide with a concentration of 0.5-20 g / l, the temperature of which is maintained constant in the range of 70-90 ° C. The suspension is intensively mixed and further treated with ultrasound (20 kHz) to evenly distribute TiO ₂ particles throughout the volume of the suspension. 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.

To give the material photocatalytic activity under the action of visible light, titanium dioxide modified with gold or platinum is used. Modification of the surface of the photocatalyst with gold is carried out by adding to an aqueous suspension of TiO _{2 an} aqueous solution of HAuCl ₄ acidified with HCl, followed by reduction with a three-fold excess of NaBH ₄ . Finally, the catalyst is washed by centrifugation repeatedly until the pH of the washings reaches 5 and then dried at 120 ° C for 2 hours. The surface of the photocatalyst is modified with platinum by impregnating the TiO ₂ powder with an aqueous solution of H ₂ PtCl ₆ acidified with HCl, s predetermined concentration to obtain the desired platinum content, followed by sonication (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. Finally, the catalyst is washed and subsequently dried at 120 ° C for 2 hours.

Example 1

A sample of material is prepared consisting of a fabric base onto which an intermediate insulating layer of silicon dioxide is applied by impregnation with freshly prepared SiO ₂ sol and then a photocatalytically active layer by impregnation with a solution of titanyl sulfate and a suspension of nanocrystalline titanium dioxide. The concentration of titanium dioxide in the impregnation suspension is 2 g / L.

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

Example 2

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

The sample is labeled as 20TiO ₂ / 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”, purified from stabilizing sodium ions by treatment with cation exchange resin in acid form.

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

Example 5 (comparative).

A comparative material sample is prepared containing only the photocatalytic layer of titanium dioxide without an intermediate insulating layer of silicon dioxide. The concentration of titanium dioxide in the impregnation suspension is 2 g / L.

The sample is labeled as 2TiO ₂ / T.

Example 6 (comparative).

Similar to example 5 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.

Example 7 (comparative).

A comparative sample is prepared of a material consisting of a fabric base onto which silicon dioxide and photocatalytically active titanium dioxide are applied from a joint suspension. The sample is prepared by impregnating the fabric base with a suspension of nanocrystalline titanium dioxide in the silica hydrosol “Silica sol KZ-L”, purified from stabilizing sodium ions by treatment with cation exchange resin in acid form. The concentration of titanium dioxide in the impregnation suspension is 2 g / L.

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

Example 8 (comparative).

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

The sample is labeled as 20TiO ₂ + SiO ₂ —K / 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 a volumetric flow rate of 0.063-0.065 l / min. The source of UV radiation is a LED (Nichia, Japan), the light intensity in the wavelength range of 320-400 nm for this experimental formulation was 9.7 mW / cm ² .

The concentration of reagents and products is analyzed by changing the area of the absorption bands corresponding to a specific substance on IR spectra recorded using an FT-801 FT-IR spectrometer (NPF Simeks, Russia) equipped with a long-pass cell (Infrared Analysis, USA) with a length 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:

, $$W_{C{O}_2}=\Delta C_{C{O}_2}\cdot U$$

,

- разность концентраций CO₂ в конечной и исходной реакционных смесях (мкмоль/л), U - объемная скорость (л/мин).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).

Test data to determine the photocatalytic activity of the obtained materials, as well as the content of the applied modifiers are presented in table 1.

Table 1 No. p / p Sample Name The content of SiO ₂ , g / m ² The content of TiO ₂ , g / m ² The rate of formation of CO ₂ μmol / min source sample after washing * one 2TiO ₂ / SiO ₂ -T / T 96.5 2.13 0.92 0.87 2 20TiO ₂ / SiO ₂ -T / T 94.7 7.17 1.41 1.30 3 2TiO ₂ / SiO ₂ -K / T 81.8 1.99 0.79 0.72 four 20TiO ₂ / SiO ₂ -K / T 77.9 6.47 1.33 1.24 5 2TiO ₂ / T - 7.46 0.99 0.22 6 20TiO ₂ / T - 12.15 1.22 0.36 7 2TiO ₂ + SiO ₂ -K / T 85,4 1.40 0.51 0.22 8 20TiO ₂ + SiO ₂ -K / T 90.0 9.76 1.35 0.48 * the sample was subjected to three cycles of automatic rinsing in water for 30 minutes and spin at a drum speed of 800 rpm

The test results show that the use of nanocrystalline titanium dioxide in the composition of the fabric material gives it 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 in the material. 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 (examples 5-6) 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.

Samples containing silicon dioxide (examples 1-4 and 7-8) have a high sorption capacity due to its high content. For these samples, a decrease in the titanium dioxide content is observed in comparison with samples containing only one photocatalyst, but the photocatalytic activity of such materials is greater and decreases to a lesser extent after long-term washing.

If we compare the samples of materials obtained by sequentially applying a protective layer of SiO ₂ and a photocatalytic layer of TiO ₂ (examples 1-4) and by simultaneously applying SiO ₂ and TiO ₂ (examples 7-8), the former have greater photocatalytic activity, which is ensured by the formation structurally organized system with an intermediate layer of SiO ₂ and the outer layer of the photocatalyst, in which screening and blocking of the particles of the photocatalyst do not occur. In addition, for materials obtained by sequential application, the photocatalytic activity after long-term washing decreases significantly less, which indicates strong adhesion of the photocatalyst particles in these materials. The highest photocatalytic activity is demonstrated by the 20TiO ₂ / 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 light 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 a Nicolet 380 IR-Fourier spectrometer (Thermo, USA), so that the optical path of the sensor passed through the pelvic phase in the reactor. A sample of 7 cm ² material was placed in a reactor and illuminated with a UV LED (Nichia, Japan). The light intensity in the wavelength range of 320-400 nm for this experimental formulation was 10.2 mW / cm ² . The concentration of gaseous products was measured 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.

table 2 No. p / p Sample Name The content of SiO ₂ , g / m ² The content of TiO ₂ , g / m ² The rate of formation of CO ₂ during self-destruction, µmol / min one 2TiO ₂ / SiO ₂ -T / T 96.5 2.13 0.91 2 20TiO ₂ / SiO ₂ -T / T 94.7 7.17 1,03 3 2TiO ₂ / SiO ₂ -K / T 81.8 1.99 1.32 four 20TiO ₂ / SiO ₂ -K / T 77.9 6.47 1.46 5 2TiO ₂ / T - 7.46 2,30 6 20TiO ₂ / T - 12.15 3,59 7 2TiO ₂ + SiO ₂ -K / T 85,4 1.40 1,64 8 20TiO ₂ + SiO ₂ -K / T 90.0 9.76 2.06

From the data presented in table 2 (column 4), it is seen that for samples of 2TiO ₂ / T and 20TiO ₂ / T (examples 5 and 6) containing only titanium dioxide without an insulating layer, a high rate of self-destruction of materials is observed. For samples of 2TiO ₂ + SiO ₂ -K / T and 20TiO ₂ + SiO ₂ -K / T (examples 7 and 8) obtained by the combined deposition of SiO ₂ and TiO ₂ , the self-destruction rate decreases, but still remains very high. The best option is materials with an intermediate layer of SiO ₂ (examples 1-4). The 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 OH radicals formed on the surface of the photocatalyst during 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 / SiO ₂ -T / T.

Thus, from the data presented in tables 1 and 2, it can be seen that fabric materials consisting of textile fabric and sequentially deposited layers of SiO ₂ and a photocatalyst have a 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 action of ultraviolet radiation to harmless components (CO ₂ , H ₂ O) due to the presence of photocatalytically active titanium dioxide and high stability self-destruction during prolonged exposure due to the presence of an intermediate insulating layer of silicon dioxide.

Example 9

Similar to example 2 with the exception that platinum modified titanium dioxide is used as the photocatalyst in the outer layer. The platinum content varies in the range of 0.1-2 wt. %

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

Example 10

Similar to example 2, with the exception that titanium dioxide modified with gold is used as the photocatalyst in the outer layer. The gold content varies in the range of 0.1-2 wt. %

The sample is labeled as wAu / 20TiO ₂ / SiO ₂ -T / T, where w is the calculated Pt content, expressed in% by weight of dry TiO ₂ . For example, 1Au / 20TiO ₂ / SiO ₂ -T / T means that titanium dioxide is used, on which Au is deposited 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 the acetaldehyde intermediate is used as a measure of photocatalytic activity. The study of the kinetics of ethanol vapor is carried out in the static reactor described above. 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 9 and 10, under visible light are presented in table 3.

Table 3 Sample Name The method of applying metal The initial rate of formation of acetaldehyde, million d / min 20TiO ₂ / SiO ₂ -T / T 0,039 0.1Pt / 20TiO ₂ / SiO ₂ -T / T high temperature synthesis 0.103 0.3Pt / 20TiO ₂ / SiO ₂ -T / T 0.229 0.5Pt / 20TiO ₂ / SiO ₂ -T / T 0.221 1Pt / 20TiO ₂ / SiO ₂ -T / T 0.395 2Pt / 20TiO ₂ / SiO ₂ -T / T 0.277 1Pt / 20TiO ₂ / SiO ₂ -T / T chemical reduction of NaBH ₄ 0.264 0.1Au / 20TiO ₂ / SiO ₂ -T / T chemical reduction of NaBH ₄ 0,055 0.3Au / 20TiO ₂ / SiO ₂ -T / T 0.170 0.5Au / 20TiO ₂ / SiO ₂ -T / T 0.196 1Au / 20TiO ₂ / SiO ₂ -T / T 0,500 2Au / 20TiO ₂ / SiO ₂ -T / T 0.217

The test results show that the material 20TiO ₂ / SiO ₂ -T / T 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 allows photocatalytic activity to be manifested to the fabric material under visible light. From the data presented in table 3 it is seen that the most active is the material 1 Au / 20TiO ₂ / SiO ₂ -T / T. Less active are materials containing platinum. The optimum in each series is the content of noble metal, equal to 1 wt. % The degree of conversion of ethanol to acetaldehyde on the most active material 1Au / 20TiO ₂ / SiO ₂ -T / T is 22% in the first 180 minutes of the photoprocess.

Thus, the use of photocatalysts modified with noble metals, mainly gold and platinum, allows one to obtain fabric materials that are photocatalytically active 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.

Kinetic curves for CO during photocatalytic oxidation of 0.4 μl of dimethylmethylphosphonate under the action of ultraviolet radiation on tissue materials are shown in FIG. 2.

It can be seen that for the 20TiO ₂ / SiO ₂ -T / 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 / SiO ₂ -T / T, obtained by chemical reduction.

Thus, the use of photocatalysts modified with noble metals, mainly platinum and gold, makes it possible to obtain fabric materials photocatalytically active with respect to CO oxidation.

Claims (2)

1. Photocatalytic sorbent tissue material for photocatalytic and adsorption purification of gas and aqueous media, characterized in that it is a structurally organized system consisting of a textile fabric base, an intermediate insulating layer of porous silicon dioxide and an outer photocatalytically active layer, while the outer photocatalytic the active layer contains a photocatalyst sensitive to ultraviolet light, consisting of nanocrystalline anatase titanium dioxide katsii. 2. The photocatalytic sorbent tissue material according to claim 1, characterized in that the outer photocatalytically active layer contains a photocatalyst sensitive to ultraviolet and visible light, consisting of anatase-modified nanocrystalline titanium dioxide modified with noble metal particles such as gold or platinum or mixtures thereof , in an amount of 0.1-2% by weight of titanium dioxide.

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