RU2482912C1 - Method of producing filtering-sorbing material with photo catalytic properties - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to filtration materials intended for cleaning air of vapors and gases of an healthy substances. Proposed invention covers filtering sorbent comprising cloth base, silicon dioxide and photo catalytically active titanium dioxide in the anatase form. Titanium dioxide-to-silicon dioxide weight ratio makes (1-3):5. Proposed method comprises preparing titanium dioxide dispersion in silicon dioxide hydrosol, impregnating fabric base with said dispersion, ageing said sorbent in darkness, thermal treatment and washing.

EFFECT: higher efficiency of air cleaning in closed rooms.

5 cl, 2 tbl, 7 ex

Description

The invention relates to the production of filter-type protective materials intended for use in the manufacture of protective clothing for the purification of air from vapors and gases of harmful chemicals in enclosed spaces, including in collective protection facilities providing vital activity in autonomous conditions. A method is proposed for producing a filtering and sorbing material containing a fabric base, silicon dioxide and photocatalytically active anatase titanium dioxide having adsorption and photocatalytic properties, high efficiency of air purification from harmful chemical compounds and the ability to self-degassing. The proposed method allows to obtain filtering sorbing material that combines high filtering and sorbing properties with photocatalytic activity, which ensures the decomposition of organic compounds.

The use of titanium dioxide as a photocatalyst is the subject of a number of inventions.

A known method for producing material with antibacterial activity by impregnating cotton knit with a titanium dioxide sol obtained by hydrolysis of a titanium dioxide precursor (titanium alkoxide, titanium nitrate or titanium chloride) with absolute alcohol (ethyl, propyl or butyl) or in an aqueous medium at pH 1-2 (US Pat. US 2005/0260455 A1). Sol formation occurs at room temperature. The material is not only cleaned of gram-negative bacteria Klebsiella pneumonia when irradiated with ultraviolet light, but also destroys bacterial cells. A disadvantage of the known invention is the absence in the impregnating composition of the sorbent, the functions of photocatalytic decomposition of harmful chemicals, the use as a basis for impregnating cotton knitwear, which is not used for the manufacture of protective clothing.

Known film coatings on the surfaces of various materials to remove nitrogen oxides and volatile organic compounds based on compositions that include titanium dioxide, mainly anatase form, which gives the materials photocatalytic activity, particles that are active with respect to nitric acid (calcium, magnesium carbonates or their mixture), a silicon-containing compound (polysiloxane) and an organic binder (polyvinyl acryl or methacrylic acid esters) (US 2008/0003367, C08K 3/22, B05D 3/00, 09/14/2004 and US 2010/0009085, B05D 3/02, C09D 183 / 04). A thin coating film under the influence of ultraviolet radiation provides the decomposition of nitrogen oxides and volatile organic compounds, as well as from surface contamination of the material by atmospheric precipitation. The disadvantage of these inventions is the low adsorption ability of the coating due to the absence of a sorbent in the composition, as well as the introduction of organic components that reduce the photocatalytic activity of titanium dioxide into the composition.

A known method of obtaining tissue with the properties of self-degassing, deodorization, sterilization, as well as anti-mold properties after exposure to light, by applying an aqueous dispersion, including titanium dioxide, acetone and resin, on a previously prepared fabric (washed with water and detergent that does not contain phosphates and heavy Metals) (US 2005/0227557, B32B 5/02). A significant disadvantage of the material obtained by the known method is the low sorption ability.

Known object coated with a photocatalyst, which includes a substrate and a layer of photocatalyst located on the substrate. The photocatalyst layer includes particles of metal oxides, preferably particles of anatase titanium oxide, particles of silicon oxide, aluminum, zirconium, cerium and other metals, preferably particles of silicon oxide in an aqueous colloidal form or in the form of an organosol in a hydrophilic solvent, hydrolyzable silicone and a nonionic surfactant substance as optional components. The photocatalyst layer is applied to the substrate with a brush, roller, spray, inkjet, immersion in a liquid coating, screen printing and the like. After application to the substrate, the liquid coating is dried at room temperature or by heating. The substrates onto which the photocatalyst layer is applied include building materials, window frames and glass, structural elements, vehicle coatings, etc. (RU 2434691, B05 D7 / 24). Known photocatalyst cannot be used to obtain filtering and sorbing material for the manufacture of protective clothing.

The closest technical solution to the present invention is a photocatalyst adsorbent obtained by impregnating an inorganic cloth on a woven or non-woven base with a composition containing an inorganic binder, adsorbent and photocatalytically active titanium dioxide, or impregnated with a composition containing an inorganic binder and adsorbent, followed by the application of photocatalytically active titanium dioxide (RU 2375112, B01J 21/06, B01J 21/08, B01J 21/18, B01J 23/38, B01J 27/18, B01J 32/00, C02F 1/30, B01D 53/86, 12/18/2008). The adsorbent catalyst obtained in a single or two-way method combines the properties of a photocatalyst and a sorbent and is used as a structural material mainly for the photocatalytic purification of air and water contaminated with molecular impurities of organic and inorganic origin. As an inorganic binder, compounds of silicon and / or aluminum and / or magnesium are used, as well as phosphoric and / or nitric acids and / or their salts. Activated carbon or silica gel, or a mixture thereof, is included in the impregnating composition as an adsorbent. As an inorganic web, a glass fiber mesh is used. Photocatalyst adsorbent may contain additives of noble metals - silver, gold, platinum, palladium. Photocatalyst adsorbent has sufficient sorption capacity and self-regenerating ability under the influence of ultraviolet light.

The disadvantages of this photocatalyst adsorbent include low hydrodynamic resistance, the rigidity of the material sufficient for its self-maintenance in the design of cleaners, the use of glass fiber mesh as the basis, which makes the photocatalyst adsorbent unsuitable for use in the manufacture of protective clothing.

The technical task of the invention is a method for producing filtering and sorbing material with photocatalytic properties, providing a high level of protection due to sorption of toxic chemicals and decomposition of these substances when irradiated with ultraviolet light at room temperature.

The technical result is achieved by the fact that the titanium-silicate complex, including silicon dioxide, freed from sodium oxide, and photocatalytically active anatase titanium dioxide with a mass ratio of titanium dioxide and silicon dioxide (1-3): 5 is applied to a textile base, as which a cotton fabric is used, for example C514-TI flannel, or a blended cotton-polyester fabric with a cotton content of at least 35%, for example, fabric art.81428 (35% cotton, 65% polyester).

The object of the invention is a method for producing a filtering and sorbing material with photocatalytic properties, based on the sol-gel method, which consists in impregnating cotton or cotton-polyester fabric with sol - a colloidal solution containing silicon dioxide hydrosol freed from sodium oxide and photocatalytically active titanium dioxide anatase forms, followed by maintaining the impregnated fabric at a temperature of (55 ± 5) ° C for 4 hours to form a titanium-silicate complex - gel, heat treatment, etc. washing and drying the finished material.

Silica hydrosol “Kremnesol KZ-L” TU 6-00-0209604-019-89 (empirical formula (SiO ₂ ) _x · (Na ₂ O) _y ,) used as a binder, is a dispersed system consisting of nanoscale particles (particle size 6.0-10.5 nm, the pH of the colloidal solution is 8.0-10.5), stabilized by an alkaline cation. The removal of sodium cations from the hydrosol of silicon dioxide promotes the transition of the sol into a gel. The formation of gels is preceded by an induction period during which the properties of the system do not noticeably change.

Titanium dioxide is characterized by the following indicators:

- phase composition - anatase;

- region of coherent scattering (according to the XRD data) - 10-15 nm;

- specific surface area S _BET - 250-265 m ² / year

Before adding anatase titanium dioxide to the silica hydrosol, the latter is treated with cation exchange resin in the H ⁺ form. The content of sodium oxide after deionization is 0.01-0.03%.

Powdered anatase titanium dioxide is added in small portions to the silica hydrosol freed from sodium cations with vigorous stirring at room temperature. Samples of cotton or mixed cotton-polyester fabric are impregnated with the obtained aqueous dispersion on a two-shaft pad and kept at a temperature of (55 ± 5) ° С to form a titanium-silicate complex, then subjected to heat treatment. The formation of a titanium-silicate complex on a tissue goes through the following stages: sol → gel → silica with a photocatalyst incorporated into it.

Preferably, the silica hydrosol is treated with a cation exchanger, for example KU-2-8 cation exchanger in the H ⁺ form, in order to release sodium cations.

Preferably, the titanium dioxide has a crystalline anatase structure and the coherent scattering region is 10-15 nm.

Preferably, the mass ratio of titanium dioxide and silicon dioxide is (1-3): 5.

Preferably, the duration of the dispersion of titanium dioxide in the silica sol is at least 3 hours.

Preferably, a cotton or mixed cotton-polyester fabric with a cotton content of at least 35% is used for impregnation and the fabric is dried at a temperature of (100 ± 5) ° С before impregnation.

Preferably, the fabric after impregnation was kept in a closed container without exposure to light for at least 4 hours at a temperature of (55 ± 5) ° C to form a titanium-silicate complex.

Preferably, the fabric is then subjected to heat treatment at a temperature of (120 ± 5) ° C for 15 minutes.

After heat treatment, the fabric is preferably washed with demineralized water until the washings are neutral and dried at a temperature of (100 ± 5) ° С.

Obtained by the claimed method, the material has high photocatalytic activity - the ability to decompose most of the organic impurities present in the air when irradiated with ultraviolet light to harmless components - carbon dioxide and water. The invention is demonstrated by the following examples.

Example 1. 200 ml of a hydrosol of silicon dioxide with a concentration of SiO _{2 of} 10% (pH 10.5) is passed through a column filled with KU-2-8 cation exchanger in the H ⁺ form. To a deionized silica hydrosol (pH 3.6) was added portionwise with vigorous stirring 4 g of titanium dioxide powder. Stirring is continued for 3 hours at room temperature. The obtained aqueous dispersion (pH 4.06) is impregnated with a sample of the C514-TI flannel previously dried at a temperature of (100 ± 5) ° С, twice immersing the fabric in an impregnating solution and squeezing twice between the shafts of the plus. The impregnated tissue sample is maintained at a temperature of (55 ± 5) ° C for 4 hours, then subjected to heat treatment at a temperature of (120 ± 5) ° C for 15 minutes, washed with demineralized water to a neutral reaction of washing water and dried at a temperature of (100 ± 5) ° С. The sample is labeled as C514-TI-4. The content of titanium-silicate complex (TC complex) in the sample is 12.5%.

Example 2. Similar to example 1 with the exception that as the basis for impregnation using a mixed fabric art.81428. The sample is marked as art.81428-4. The content of the TC complex in the sample is 6.4%.

Example 3. To 200 ml of deionized hydrosol of silicon dioxide (SiO ₂ concentration _of 10%, pH 3.8), 8 g of titanium dioxide powder are added in portions with vigorous stirring. Stirring is continued for 3 hours at room temperature. The pre-dried C514-TI flannel sample is impregnated with the resulting dispersion (pH 5.1). The sample is labeled as C514-TI-8. The content of the TC complex in the sample is 14.1%.

Example 4. Similar to example 3 with the exception that as the basis for impregnation using a mixed fabric art.81428. The sample is marked as art.81428-8. The content of the TC complex in the sample is 7.6%.

Example 5. To 200 ml of deionized hydrosol of silicon dioxide (SiO ₂ concentration _of 10%, pH 2.8), 12 g of titanium dioxide powder are added in portions with vigorous stirring. Stirring is continued for 3 hours at room temperature. The pre-dried C514-TI flannel sample is impregnated with the resulting dispersion (pH 5.21). The sample is labeled as C514-TI-12. The content of the TC complex in the sample is 15.4%.

Example 6. Similar to example 5 with the exception that as the basis for impregnation using a mixed fabric art.81428. The sample is marked as art.81428-12. The content of the TC complex in the sample is 8.5%.

Example 7 (comparative). An aqueous suspension of a commercial Hombifine N photocatalyst (Sachtleben Chemie) (S _BET = 350 m ² / g) in a deionized water concentration of 14 mg TiO ₂ per 1 ml of suspension was prepared and sonicated for 15 minutes. Then, 0.5 ml of the suspension is taken with a micropipette and evenly distributed over the surface of a defatted glass substrate with a size of (2.4 × 2.9) cm. It is dried at room temperature for 24 hours, and then at 100 ° C for two hours. The density of the applied TiO ₂ powder is 1 mg / cm ² . A sample is labeled as TiO ₂ —HF.

The photocatalytic activity of the samples under the influence of UV light is measured in the oxidation reaction of acetone vapor in a flow-circulation installation, as well as in the oxidation reaction of a mixture of organic substances in a sealed chamber.

When testing in a flow-circulation installation, a sample of material (2.4 × 2.9) cm ² in size was placed in a steel reactor and Philips lamps, 365 nm, 9 W were illuminated with UV light. Acetone with a concentration of 16-22 μmol / L is fed to the reactor inlet and the concentration of the acetone oxidation product — carbon dioxide at the outlet of the reactor — is determined within 6 hours by changing the area of the absorption bands of the corresponding substances in the IR spectra.

, мкмоль/мин, вычисляют по формуле:Carbon dioxide emission rate

, mmol / min, calculated by the formula:

,

,

- разность концентраций СО₂ в конечной реакционной смеси (КРС) и исходной реакционной смеси (ИРС), мкмоль/л;Where

- the difference in the concentrations of CO ₂ in the final reaction mixture (cattle) and the initial reaction mixture (IRS), µmol / l;

U is the volumetric flow rate, l / min.

The volumetric flow rate is 30 l / min.

The results of measuring the rate of CO ₂ formation during the photocatalytic oxidation of acetone vapors in a flow-circulation installation are presented in Table 1.

Table 1 Sample Name The rate of emission of CO ₂ , µmol / min C514-TI-4 (TiO ₂ : SiO ₂ = 1: 5, the content of the TC complex is 12.5%) 0.28 art.81428-4 (TiO ₂ : SiO ₂ = 1: 5, the content of the TC complex is 6.4%) 0.17 C514-TI-8 (TiO ₂ : SiO ₂ = 2: 5, the content of the TC complex is 14.1%) 0.34 art.81428-8 (TiO ₂ : SiO ₂ = 2: 5, the content of the TC complex is 7.6%) 0.26 C514-TI-12 (TiO ₂ : SiO ₂ = 3: 5, the content of the TC complex is 15.4%) 0.41 art.81428-12 (TiQ ₂ : SiO ₂ = 3: 5, the content of the TC complex is 8.5%) 0.30 TiO ₂ -HF 0.42

Comparison of the presented data shows that samples of filtering and sorbing material with an embedded photocatalyst have photocatalytic activity. The rate of oxidation of acetone vapor and the release of CO ₂ upon irradiation of samples of filtering and sorbing material with UV light increases with an increase in the content of the titanium-silicate complex on the fabric and the content of titanium dioxide in the complex. The rate of CO ₂ emission during irradiation of sample C514-TI-12 is practically equal to the rate of CO ₂ emission during irradiation of a commercial Hombifine N photocatalyst (Sachtleben Chemie).

When conducting tests in a sealed chamber, the photocatalytic activity of the filter-sorbing material is evaluated by changing the concentration of ammonia, acetone, benzene, xylene and ethyl acetate under the influence of UV radiation. The sample is fixed in a box with a volume of 150 dm ³ on a support ring with a diameter of 120 mm around a UV lamp with an incident radiation power of 15 mW / cm ² . The exposure time is from 60 to 180 minutes. The concentration of harmful impurities in a sealed chamber is determined by the chromatographic method on a Crystal 2000M gas chromatograph TU 9443-001-12908609 with a flame ionization detector and Chromatek Analytic software.

The catalytic activity of a filtering and sorbing material with an embedded photocatalyst is maintained after prolonged exposure to ultraviolet light.

The photocatalytic activity of samples of filtering and sorbing material (FSM) with embedded titanium dioxide (examples 1-6) illustrate the test results presented in table 2.

table 2 Photocatalytic activity of samples of filtering and sorbing material with embedded titanium dioxide The name of the substance. Initial concentration Time from the beginning of the experiment, min The change in the concentration of substances in the chamber upon irradiation of FSM samples, mg / m ³ S514-TI-4 Art.81428-4 S514-TI-8 Art.81428-8 S514-TI-12 Art.81428-12 Ammonia 60 27.71 34.82 19.82 24.70 11.05 18.66 120 14.62 17.85 10.23 17.50 3.37 12.28 50.0 mg / m ³ 180 7.45 11.33 4.00 11.00 8.48 Acetone 60 263.95 282.33 238.60 265.71 208.24 226.30 120 230.71 245.90 213.95 258.23 138.20 195.00 300.0 mg / m ³ 180 181.34 201.95 168.19 182.24 129.58 154.30 Benzene 60 97.51 89.40 76.93 80.62 60.78 70.81 120 88.80 85,20 51.74 65.49 35.79 55.56 120.0 mg / m ³ 180 66.40 74.50 35.79 58.32 12.11 49.78 m-xylene 60 73.93 81.25 61.78 74.77 35.39 51.36 120 35.09 50.14 30.28 33.49 20,23 27.48 120.0 mg / m ³ 180 22.56 28.30 10.54 21.92 4,50 20.43 Ethyl acetate 60 63.79 68.12 55.85 58.81 44.21 47.45 120 35.29 49.26 32.28 43.82 12.11 36.48 120.0 mg / m ³ 180 10.12 33.23 9.27 27.79 1.82 24.85

From the data presented in table 2, it can be seen that the filtering and sorbing material with an embedded photocatalyst obtained by the method of the invention with high efficiency destroys harmful chemical compounds in the air of a sealed chamber when irradiated with UV light. With an increase in titanium dioxide content on the fabric, catalytic activity increases.

Claims (5)

1. A method of obtaining a filtering and sorbing material with photocatalytic properties, including the preparation of a dispersion by introducing anatase photocatalytically active titanium dioxide into a silica hydrosol, previously deionized by treatment with cation exchange resin in H ⁺ form, with a ratio of titanium dioxide to silicon dioxide (1-3): 5 (parts by weight), with vigorous stirring for 3 hours, impregnation of a previously dried textile base on a two-shaft plus, maturation of the sorbent on an impregnated textile base in a closed container in the absence of light at a temperature of (55 ± 5) ° C for 4 h, heat treatment of the material at a temperature of (120 ± 5) ° C for 15 min, washing with demineralized water and drying at a temperature of (100 ± 5) ° FROM. 2. The method according to claim 1, characterized in that the cotton or mixed cotton-polyester fabric with a cotton fiber content of at least 35% is used as the textile base. 3. The method according to claim 1, characterized in that photocatalytically active anatase titanium dioxide with a coherent scattering region of 10-15 nm and a specific surface area S _{BET of} 250-265 m ² / g are used to impart photocatalytic properties to the material. 4. The method according to claim 1, characterized in that for the formation of a tissue-based complex of titanium dioxide anatase form with silicon dioxide using a silica hydrosol with a particle size of 6.0-10.5 nm, previously deionized by treatment with cation exchange resin in H ⁺ form. 5. Filtering and sorbing material with photocatalytic properties, obtained by the method described in claims 1-4, and containing a fabric base with an anatase titanium dioxide complex with silicon dioxide attached to it with a mass ratio of titanium dioxide to silicon dioxide equal to (1- 3): 5.