KR101891512B1 - Photocatalytic element for purification and disinfection of air and water and method for the production thereof - Google Patents

Abstract

The present invention relates to the field of air and water disinfection. The photocatalytic element is composed of sintered glass beads having a pore volume fraction of 20% to 40% and a pore size of 0.1 to 0.5 mm, the surface of which is coated with titanium dioxide having a specific surface area of 150-400 m < 2 > / g And titanium dioxide is used at 0.5 - 2% of the total mass of the photocatalytic element. Also, the glass beads have a cup shape with a cup-shaped concave portion of 0.5 to 10 microns. The method of making the photocatalytic element comprises sintering the glass beads at a temperature greater than the glass softening point by 5-20 ° C, modifying the bead surface with a chemical etchant, And coating the bead surface with titanium powder. The present invention provides the production of a photocatalytic element, characterized in that it strongly bonds and retains the titanium dioxide powder on the surface of the carrier in the flow of the medium to be purified, and has a high photocatalytic activity.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalytic element for air and water purification and disinfecting, and a method for manufacturing the same. BACKGROUND ART < RTI ID = 0.0 > Photocatalytic < / RTI >

The present invention relates to the field of purification and disinfection of air and water, and more particularly, to a method of manufacturing and designing a photocatalytic element that can be used as a primary functional part in a molecular and integrated processing apparatus using photocatalyst.

Photoactive, catalytic oxidative destruction of organic contaminants using titanium dioxide and under the action of ultraviolet radiation is an advanced method for air and water purification and disinfection. This method is efficient, cost effective, and environmentally friendly, thereby eliminating almost all organic contaminants by mineralizing them with water and carbon dioxide. The primary function of the photocatalytic treatment device is to ensure the efficacy and durability is a photocatalytic element in the form of a combination of a nanocrystalline catalyst and a certain type of carrier mounted in a UV receiving zone.

The photocatalytic element can be used as part of air purification and disinfection used in health care facilities, day care centers, schools, offices, theaters, living rooms, etc. for effective control of respiratory infections, toxic contaminants, and unpleasant odor removal.

(U.S. Patent No. 5,919,726, filed July 6, 1999), the first step of which includes the silica gel with an approximate particle size of 20 to 50 microns Application of any material on a substrate made of any material (metal, cement, mud, sand, gravel, ceramic, plastic, wood, stone, glass, etc.) of the sublayer with a thickness of 0,05 to 2 microns Spraying, brushing, etc.), and then the sub-layer is fixed by heat treatment at 100 to 900 占 폚 for 3 to 30 minutes. In a second step, the sub-layer is treated with liquid or vaporous titanium tetrachloride (water vapor may be added. In a third step, the obtained material is heat treated at 150 to 500 DEG C for 1 to 10 minutes in the presence of oxygen As a result of this, an anatase titanium dioxide layer is formed on the surface. Due to the presence of the silica sublayer, the resultant titanium dioxide is fixed on the substrate and has its photocatalytic properties. It is primarily recommended for the production of building materials (ceramic tiles, wall panels, etc.) with purification and disinfection effects.

The sterilization test included applying the cell suspension (0.5 ml) on the resulting ceramic tile. The tiles were placed in a petri dish and covered with a quartz glass cover. And incubated in a sterilization chamber at < RTI ID = 0.0 > 25 C < / RTI > for 3 hours under 1200 lux fluorescence light. The results are shown in Table 2. For reference, tiles without a titanium dioxide layer were also tested. The best test showed that the concentration of Stirylococcus aureus cells decreased from 3100 to 135 and the concentration of Krebsiella nuumonia decreased from 1725 to 400.

A major disadvantage of the photocatalytic material manufacturing method is that it is an environmentally dangerous manufacturing method due to the use of complex, highly volatile and toxic titanium tetrachloride. Also, during application of the titanium dioxide layer, toxic and corrosive hydrogen chloride is produced as a result of TiCl ₄ hydrolysis.

The bactericidal activity of the resulting material test specimens is not sufficient for application to air purification and disinfection equipment.

Photocatalytic air treatment filters are known (U.S. Patent No. 6,491,883 B2; issued on Dec. 10, 2002). The filter comprising:

Particles (such as glass particles or fibers) that permit passage of ultraviolet light, in an amount of from 5 to 60% by weight, having a micro size of from 0.2 to 50 microns;

- photocatalytic TiO ₂ particles having an average size of from 0.001 microns to 0.02 microns and in an amount of from 20 to 80% by weight;

Silicon dioxide particles having an average size of from 0.002 to 0.2 microns and in an amount of from 10 to 60% by weight;

- conditionally consisting of a substrate having a coating of 5 to 60 microns thick, comprising clay minerals in an amount of from 2 to 20% by weight.

The coating is characterized by good adhesion to the substrate material and allows the passage of ultraviolet light, but the use of finely divided components, especially those with clay binders, is advantageous for the coating to pass through the gas well, It does not guarantee the effective action of the stannic TiO ₂ particles. In order to create a photocatalytic element of the air and the water disinfection device, it is necessary to ensure that the highly porous material does not interfere with the diffusion of the medium treated with the photocatalyst.

An air purification system for a transport carrier is known (U.S. Patent Application Publication No. US 2012/0128539 A1, published on May 24, 2012). The system consists of an air inlet, an air outlet and a space for air flow therebetween. One or more elements having a reaction surface and one or more ultraviolet sources are mounted in the space. The reaction surface contains catalytic material and occupies at least 50% of the internal surface of the device. Titanium dioxide or a material containing it is used as the catalytic material. Emitting tube or light-emitting diodes are used as the ultraviolet ray source. The air is forced into the space of the device by the fan. To increase the surface area and time of the air contact with the reaction surface, various elements of various shapes such as, for example, waves, spirals, stars, fingers, etc., fixed in the filter case, It is proposed to use elements in the form of non-existent materials (eg, short glass and plastic tubes, balls, etc.). In order to further improve the air purification efficiency, the reaction surface of the element may comprise nano-zeolite and / or nanosilver. The use of untouched elements coated with catalysts increases the reaction surface in contact with the air to be treated, but the mechanical wear and tear of the catalyst bed due to friction, as the unfixed elements can move relative to each other, and Dust may be discharged from the apparatus, and the catalytic service life may be shortened. In order for the device to perform efficiently, there is a need for an integrated photocatalytic element with high internal porosity and gas permeability. The catalyst should be applied to the entire surface of the support, including the inner pore surface.

The most similar combination of essential features of the present invention relates to a photocatalytic element and a method of manufacturing the same (Russian Federation Patent No. 2151632, October 20, 1998), a certain shape of porous structure made of 5 to 10 layers of sintered glass beads (Preferably in the form of a tube or a plate) and anatase titanium dioxide powder having a specific surface area of from 100 to 150 m < 2 > / g, applied on the surface of the carrier. Such photocatalytic element manufacturing methods include:

Glass beads having a diameter of 0.1 to 1.5 mm are sintered in a shell made of metal, graphite or fragile material at a temperature below the softening point of the glass, cooled, and the carrier is taken out of the shell, Activating the surface, applying an aqueous suspension of titanium dioxide to the surface of the carrier, and air drying the carrier to produce a carrier in a certain form.

The photocatalytic element and its manufacturing method have the following disadvantages:

Due to the fact that the glass beads are sintered at temperatures below the glass softening point, the resultant photocatalytic elements do not have sufficient mechanical strength, and thus there is a significant proportion of photocatalytic element destruction during transport, assembly and operation of the photocatalytic device ;

- The insufficient high specific surface area (100 to 150 m < 2 > / g) of the titanium dioxide powder used limits the maximum achievable activity of the photocatalytic element during air and water purification;

- Carrier surface activation (treatment with hydrofluoric acid vapor or 1-2% solution) by the above method is suitable for enhancing the strength of the titanium dioxide powder, especially the photocatalytic element used in the water purifier, It is not efficient. A part of the titanium dioxide powder is removed from the surface of the carrier during the operation of the photocatalytic element in the water stream, resulting in a reduction in the activity of the photocatalytic element and a shortening of its life;

During the application of the titanium dioxide, the control over the aqueous suspension pH is lost so that it can not continuously produce the maximum active photocatalytic element.

It is an object of the present invention to provide novel photocatalytic elements having improved mechanical strength, increased catalytic activity, and extended operating life.

This object is achieved by providing a photocatalytic air and a water disinfection element having the following:

A sintered glass bead having a constant shape and a pore size of 0.1 mm to 0.5 mm, a pore volume fraction of 20% to 40%, a surface relief depth of 0.5 to 5 microns, A porous carrier composed of a titanium dioxide powder having a specific surface area of 150 to 400 m < 2 > / g, applied in an amount of 0.5 to 2% of the total photocatalytic element weight.

This object is also achieved by providing a photocatalytic element comprising:

Preparing a carrier by sintering the glass beads in a shell giving a shape and size required for the carrier at a temperature higher by 5 to 20 캜 than the glass softening point;

Cooling the carrier and removing it from the shell;

Treating the carrier with concentrated hydrofluoric acid for 1 to 5 minutes and treating the carrier with concentrated sulfuric acid for 1 to 5 minutes to form a glass surface of the carrier at a depth of 0.5 to 5 microns;

Washing the carrier and drying in a drying oven at a temperature of 80 to 120 캜;

By applying an aqueous suspension of titanium dioxide having a specific surface area of 150 to 400 m < 2 > / g to the carrier, wherein the titanium dioxide is present in an amount of 0.5 to 2% of the total photocatalytic element weight, To the glass surface.

Drying the resultant photocatalytic element in a drying oven at a temperature of from 150 to 200 < 0 > C.

Sintering the glass beads at a temperature 5 to 20 ° C above the glass softening point can provide a high mechanical strength to the carrier while having a high open porosity (20% to 40% of 0.1 to 0.5 mm pores).

The present invention provides a novel photocatalytic element having improved mechanical strength, increased catalytic activity, and extended operating life.

Fig. 1 shows the carrier surface before (1) and after (2) the acidic reforming.
Figure 2 shows the photocatalytic activity of titanium dioxide as a function of the pH value of the suspension.

By modifying the surface of the glass bead sintered with the concentrated hydrofluoric acid and sulfuric acid solution, it is possible to provide a glass surface wetting depth of 0.5 to 5 microns which is maintained on the carrier surface in the stream of air or water to be bound and cleaned by strong titanium dioxide powder . The following figures are photomicrographs showing the surfaces of sintered beads before (1) and after (2) acid treatment. Such a reduction is not achieved with conventional surface activation by steam or dilute hydrofluoric acid solution.

Fig. 1 shows the carrier surface before (1) and after (2) the acidic reforming.

When applying the TiO2 powder to the surface of the carrier, the most important factor determining the final activity of the photocatalytic element is the pH value of the aqueous suspension to which the powder is applied. The maximum activity is obtained at pH = 2.9 ± 0.1. In view of the extreme dependence of the photocatalytic activity on the pH value of the medium (Figure 2), the specific acidity of the suspension (pH = 2.9 ± 0.1) must be observed during the application of the titanium dioxide powder. This technique, combined with the use of titanium dioxide powder with a high specific surface area (150 to 400 m < 2 > / g), produces the most active photocatalytic element.

Figure 2 shows the photocatalytic activity of titanium dioxide as a function of the pH value of the suspension.

The essence of the present invention will be described in the following embodiments.

Specific Example 1

Glass beads (0.8 to 1 mm fraction) were poured into a detachable cylindrical stainless steel shell having an outer diameter of 86 mm, a width of 6 mm and a height of 420 mm. The shells are placed in an oven where the beads are sintered at a temperature 15 DEG C higher than the glass softening point (about 690 DEG C) for 1 hour and 20 minutes. After cooling to room temperature, the shell is disassembled and the carrier in the form of a porous glass tube is removed.

Next, the precipitate was first precipitated in concentrated hydrofluoric acid for 1 minute, washed with water, treated with concentrated sulfuric acid for 3 minutes, washed with water and dried in a drying oven at 100 DEG C until completely dehydrated to modify the carrier surface Respectively.

The aqueous suspension is made from distilled water and anatase titanium dioxide having a surface area of 350 m < 2 > / g and a titanium dioxide content of 10% by weight. By adding dropwise sulfuric acid, the pH value of the suspension was adjusted to pH = 2.9 ± 0.1. The dried carrier was precipitated in the suspension, removed and dried in a drying oven at 150 ° C.

Completed photocatalytic elements include:

A porous tubular carrier composed of sintered glass beads having a modified surface, a length of 420 mm, a diameter of 86 mm and a wall of 6 mm thickness;

12 g of anatase titanium dioxide powder per urea with a specific surface area of 350 m 2 / g.

One additional photocatalytic element was prepared as a reference sample. The manufacturing process of these samples is different only in that the surface modification operation is not carried out. No appreciable amount was observed on the bead surface. The titanium dioxide content in the finished photocatalytic element was 10 g.

Samples (primary sample no. 1 and reference no. 2) produced according to this embodiment were tested for the purification process of water containing cultures of colibacillus (Escherichia coli). According to the test pattern, water containing E. coli was circulated through the walls of the vertically mounted photocatalytic element at a flow rate of 2 L / min. An ultraviolet lamp was placed inside the tube and ultraviolet light having a wavelength of 320 to 405 nanometers was irradiated to the inner surface of the photocatalytic element at a power of 9 W in the infrared region. Water samples were taken at specific time intervals and applied to culture media in Petri dishes. The number of colonies grown in the culture medium after 48 hours was calculated. Also, the titanium dioxide entrainment by the water flow was calculated by measuring the weight of the dried photocatalytic element after 10 hours of continuous water flow. The measurement results are shown in Table 1.

Processing time (min) CFU concentration Weight reduction (g) Sample 1 Sample 2 Sample 1 Sample 2 0 10000 10000 0 0 5 5950 7250 - - 10 90 750 - - 30 0 50 - - 60 0 0 - 600 0 0 0.3 2.1

The results show that modifying the carrier by imparting a profiled shape to the glass surface increases the titanium dioxide powder capture when applied from the suspension and provides for the catalyst to bind more strongly to the carrier, Lt; RTI ID = 0.0 > photocatalytic < / RTI >

Specific Example 2

Glass beads (0.8 to 1 mm fraction) were poured into a detachable cylindrical stainless steel shell having a length of 60 mm, a width of 5 mm and a height of 400 mm. The sintering, the carrier surface modification, and the catalyst application operation were carried out in the same manner as in Example 1.

These finished photocatalytic elements include the following:

A porous carrier comprised of sintered glass beads having a modified surface and in the form of a rectangular parallelepiped having a size of 400 x 60 x 5 mm;

2 g of anatase titanium dioxide powder per urea with a specific surface area of 350 m 2 / g.

A reference test sample was produced in the same manner, except that the titanium dioxide powder was applied to the carrier from a suspension with pH = 4.5.

Processing time (min)
CFU concentration Weight reduction (g) Sample 1 Sample 2 Sample 1 Sample 2 0 10000 10000 0 0 5 5950 7250 - - 10 90 750 - - 30 0 50 - - 60 0 0 - 600 0 0 0.3 2.1

Samples (Primary Sample No. 3 and Reference No. 4) produced according to this embodiment were tested under the reaction of photocatalytic oxidation of acetone vapor in air. The test was performed in a 300 l volume sealed box equipped with a reaction vessel with the sample to be tested, an ultraviolet lamp similar to that used in Example 1, and a fan to move the air. The initial vapor concentration was generated by evaporating the required amount of liquid acetone, reaching 100 ppm. After turning on the UV lamp, the concentration of acetone and its concentration of oxidation end product (CO ₂ ) were measured over time by a gas sensor. The test results are shown in Table 2.

The results demonstrate that Sample 1, which is laminated from a suspension of titanium dioxide having a pH of 2.9 ± 0.1, has greater catalytic activity.

Claims (3)

A photocatalytic element for air and water disinfection comprising sintered glass beads having titanium dioxide applied thereto, wherein the sintered glass beads have a constant shape, a pore size of 0.1 mm to 0.5 mm, a porosity of 20% to 40% Having open porosity with a volume fraction; Wherein the surface of the sintered glass beads has a convex shape with a surface wear depth of 0.5 to 10 microns; Wherein the titanium dioxide powder has a specific surface area of 150 to 400 m < 2 > / g, and the titanium dioxide powder applied to the glass surface is 0.5 to 2 wt% of the weight of the photocatalytic element. A method of manufacturing a photocatalytic element, comprising: sintering glass beads, modifying the surface of sintered glass beads, and applying titanium dioxide powder on the modified surface of the sintered glass beads. Wherein the glass beads are sintered at a temperature 5 to 20 占 폚 above the glass softening point and before the application of the titanium dioxide powder the surface of the sintered glass beads is modified with an etching chemistry and the titanium dioxide powder Is applied on the surface of the sintered glass beads from a titanium dioxide powder aqueous suspension having a pH value of 2.9 ± 0.1. 3. The method according to claim 2, wherein the modification of the surface of the sintered glass beads with an etching chemical comprises treating with hydrogen fluoride for 1 to 5 minutes and sulfuric acid for 1 to 5 minutes continuously .

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