RU2375112C1 - Photocatalyst-adsorbent (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a photocatalyst composition based on carbon material with large specific surface area with a deposited photocatalyst based on titanium dioxide or titanium dioxide which is modified with noble metals, mainly used for photocatalytic purification of air and water, contaminated with molecular impurities of organic or inorganic nature. A photocatalyst-adsorbent is described, which is characterised by that, it consists of an inorganic fabric on a woven or non-woven base, soaked with a composition which contains an inorganic binder, adsorbent and photocatalytically active titanium dioxide. Surface area of the adsorbent is at least twice larger than the surface area of the photocatalytically active titanium dioxide. A photocatalyst-adsorbent is also described, which is characterised by that, it consists of an inorganic fabric on a woven or non-woven base, soaked with a composition which contains an inorganic binder and adsorbent, on which photocatalytically active titanium dioxide is deposited. Surface area of the adsorbent is at least twice larger than surface area of photocatalytically active titanium dioxide.

EFFECT: above described catalysts-adsorbents combine sorbent and photocatalyst properties, have low hydrodynamic resistance, sufficient hardness and have value of photocatalytic activity with respect to decomposition of organic and inorganic substances in water and air.

12 cl, 1 tbl, 2 dwg, 10 ex

Description

The invention relates to a composition of a photocatalyst based on carbon material with a large specific surface area coated with a photocatalyst based on titanium dioxide or titanium dioxide modified with noble metals, used primarily for the photocatalytic purification of air and water contaminated with molecular impurities of organic and inorganic origin.

In connection with the restoration of the industrial potential of Russia, an increase in the number of cars and office buildings located near roads, the emergence of new requirements for the quality of water and air in medical institutions and residential areas, the task of adapting the photocatalytic method to clean water and air from toxic compounds in small concentrations .

Therefore, the main characteristics of the photocatalyst that can ensure their effective application are:

- the composition of photocatalysts - the content of metal additives that affect the rate and completeness of decomposition of toxic substances, such as CO, NO _x and organic substances;

- the ability of the photocatalyst components to additionally reversibly adsorb pollutants from the external environment, acting as a buffer and preventing the deactivation of the active components of the photocatalyst (TiO ₂ ) by volley emissions of pollutants;

- low aerodynamic drag;

- ability to self-purify (regenerate).

The development of adsorbents and photocatalysts has been the subject of a number of inventions.

Known sorption-filtering material containing a carrier in the form of a woven shell of mineral or glass fibers, filled with a mixture of expanded perlite and activated carbon impregnated with chlorophyll (RU 2150996, B01J 20/00, 11/04/1999). The specified carrier adsorbent has a fairly low hydrodynamic resistance and is intended for use in kitchen hoods. This material has the disadvantage that it lacks photocatalytic activity, as a result of which the material is not capable of self-cleaning. Thus, its sorption activity will decrease during operation, deactivation will occur and the material will require periodic replacement.

Known material based on a woven fiberglass cloth onto which titanium dioxide is deposited by spraying an aqueous suspension of titanium dioxide (JP 2000199173, 07/18/2000) or by coprecipitation of vapors of titanium tetrachloride (TiCl ₄ ) and water on the surface of a glass fabric with their simultaneous hydrolysis and the formation of a TiO ₂ phase (JP 2004057912, 02.26.2004). This treatment gives the fabric photocatalytic properties, and it becomes capable of oxidizing organic impurities under the influence of UV radiation. In addition, the hydrodynamic resistance of such a canvas is small. A significant drawback of such a material is the very small sorption capacity of the material, which will lead to its rapid deactivation, for example, when exposed to a volley of pollutants. Further reactivation may be difficult due to the blockage of the surface by contaminant molecules, and the material will have to be replaced. In addition, the resulting material does not have sufficient rigidity and requires the use of an additional frame-forming element to give the desired shape.

Known inventions: borosilicate fiber reinforced drainage material (RU 2123549, D04B 21/14, B01D 39/08, 12/20/1998); a catalyst carrier based on fiberglass (JP 10015397 and JP 10015396, 01.20.1998), in which it is proposed to give the carriers additional rigidity by impregnating them with binders containing organic components. The disadvantage of these inventions is the low adsorption capacity due to the absence of a sorbent in the composition of the carrier, as well as the low photocatalytic activity of titanium dioxide, which, when applied to said carrier, will be deactivated by the organic components of the binder.

Closest to this invention is a photocatalytic fabric (JP 11290700, B01J 31/06, 10.26.1999) based on inorganic glass fiber reinforced with metal threads and impregnated with a suspension of anatase titanium dioxide in a solution of rubber in tetrafluoroethylene, followed by drying. The specified material has sufficient mechanical strength and also photocatalytic activity.

Its disadvantages include the use of organic substances, which will undergo photocatalytic destruction with the destruction of the material itself. Also, this material does not have sufficient sorption capacity due to the fact that the specific surface of the components used in its creation is small.

It can be seen from the above examples that, despite the variety of methods and compositions for preparing sorption and photocatalytically active materials based on canvases, not one combines the properties of both a sorbent and a photocatalyst, which would have a low hydrodynamic resistance, possess sufficient rigidity, and have high photocatalytic values activity in relation to the destruction of organic and inorganic substances in water and air.

The present invention aims at creating such a material.

First option.

The photocatalyst adsorbent consists of an inorganic fabric on a woven or non-woven base, impregnated with a composition containing an inorganic binder, an adsorbent and photocatalytically active titanium dioxide, the surface area of the adsorbent is at least two times the surface area of photocatalytically active titanium dioxide.

The composition of the inorganic binder may include compounds of silicon, and / or aluminum, and / or magnesium, as well as phosphoric and / or nitric acid, and / or their salts.

As an adsorbent, it may contain either compounds based on coal, or based on silicon dioxide SiO ₂ , or a mixture thereof.

The adsorbent content in percent of the dry weight of the impregnating composition is 0.1-95.0 wt.%.

The content of photocatalytically active titanium dioxide as a percentage of the dry weight of the impregnating composition is 0.001-4.0 wt.%.

The photocatalyst adsorbent may contain additives of noble metals such as silver, gold, platinum, palladium in an amount of not more than 1.0 wt.% Of the dry weight of the impregnating composition.

Since the binder consists of either coal-based or silicon dioxide-based SiO ₂ compounds, or a mixture with a high specific surface area and photocatalytically active titanium dioxide, the finished material, after impregnating with such a composite binder and subsequent drying, acquires both the properties of the photocatalyst and adsorbent .

In order for the obtained material to exhibit adsorption properties, the total surface area of coal or silica gel contained in the binder must be at least two times the total surface of photocatalytically active titanium dioxide.

The second option.

The photocatalyst adsorbent consists of an inorganic cloth on a woven or non-woven base, impregnated with a composition containing an inorganic binder and an adsorbent on which photocatalytically active titanium dioxide is deposited, the surface area of the adsorbent is at least two times the surface area of photocatalytically active titanium dioxide.

The composition of the inorganic binder may include compounds of silicon, and / or aluminum, and / or magnesium, as well as phosphoric and / or nitric acid, and / or their salts.

As the adsorbent can be used either compounds based on coal, or based on silicon dioxide SiO ₂ , or a mixture thereof.

The adsorbent content in percent of the dry weight of the impregnating composition is 0.1-99.0 wt.%.

The content of photocatalytically active titanium dioxide as a percentage of the mass of the photocatalyst adsorbent is 0.001-20.0 wt.%.

The photocatalyst adsorbent may contain additives of noble metals such as silver, gold, platinum, palladium in an amount of not more than 1.0 wt.% By weight of photocatalytically active titanium dioxide.

The binder consists of coal or silicon dioxide with a high specific surface, so that the finished material after impregnation with such a composite binder and subsequent drying acquires the properties of an adsorbent. Photocatalytically active titanium dioxide is deposited on the adsorbent carrier thus formed.

In order for the obtained material to exhibit additional adsorption properties, the total surface area of the adsorbent carrier must be at least two times higher than the surface area of the deposited photocatalytically active titanium dioxide.

The photocatalyst adsorbent of the present invention has a rigidity sufficient for its self-maintenance in the design of cleaners, has a sufficient adsorption capacity to quickly absorb organic impurities, and, moreover, has a self-regenerating ability under the influence of UV light.

To increase the photocatalytic activity of the photocatalyst adsorbent or to give it the ability to decompose specific impurities, additives of noble metals such as silver, gold, platinum, palladium in an amount of not more than 1 wt% can be introduced into the photocatalyst composition.

The invention is illustrated by the following examples.

In all examples, a glass fiber grid with the number of threads in the weft 22 by 10 cm and the number of threads in the warp 26 by 10 cm, annealed in air in a muffle furnace at a temperature of 400 ° C for 2 hours, is used as an inorganic web. × 3 cm.

Example 1 (comparative).

A grid of 3 × 3 cm in size is impregnated with an aluminophosphate binder and dried at a temperature of 100 ° C for 12 hours. Then, an aqueous suspension of photocatalytically active TiO ₂ (anatase, specific surface area of 350 m ² / g) is applied to the grid and dried at 120 ° C for 2 hours. The amount of TiO ₂ applied, measured by weighing, was 0.03 g.

The resulting sample was called O1.

Example 2

A grid of 3 × 3 cm and a weight of 0.5 g is impregnated with a composition containing 1.5 g of aluminophosphate binder mixed with 1.5 g of activated carbon of the OU-A grade (specific surface of 1200 m ² / g), and dried at a temperature of 100 ° C for 12 hours. Then, an aqueous suspension of photocatalytically active TiO ₂ (anatase, specific surface area 350 m ² / g) is applied to the grid and dried at 120 ° C for 2 hours. The amount of TiO ₂ deposited, measured by weighing, is 0 , 03 g. The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the applied TiO ₂ , which is equal to 10.5 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3) · 100% = 50%.

The content of photocatalytically active titanium dioxide as a percentage of the mass of the photocatalyst adsorbent is (0.03 / 3.53) · 100% = 0.85%

The resulting sample was called O2.

Example 3

Similar to example 2 with the exception that the photocatalytically active TiO ₂ (anatase, specific surface area 350 m ² / g) in an amount of 0.1 g is introduced into the composition of 3 g of an impregnating composition consisting of an aluminophosphate binder mixed with activated charcoal OU-A (specific surface area 1200 m ² / g) in a ratio of 1: 1 by weight.

The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the deposited TiO ₂ , which is equal to 35.0 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3.1) · 100% = 48.4%.

The content of photocatalytically active titanium dioxide as a percentage of the dry weight of the impregnating composition is (0.1 / 3.1) · 100% = 3.2%

The resulting sample was called O3.

Example 4

Similar to example 3 with the exception that the photocatalytically active TiO ₂ contains finely divided metallic silver. The silver content in TiO ₂ is 1 wt.%.

The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the deposited TiO ₂ , which is equal to 35.0 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3.1) · 100% = 48.4%.

The content of photocatalytically active titanium dioxide as a percentage of the dry weight of the impregnating composition is (0.099 / 3.1) · 100% = 3.2%

The content of silver addition by weight of photocatalytically active titanium dioxide is - (0.001 / 0.1) · 100% = 1%.

The resulting sample was called O4.

Example 5

Similar to example 2, with the exception that instead of the aluminophosphate binder, the impregnating solution contains an inorganic binder with a total dry mass of 1.5 g, consisting of alumina Al ₂ O ₃ , pseudoboehmite AlO (OH) and nitric acid HNO ₃ , and drying is finished Photocatalyst adsorbent is carried out in two stages. First, at a temperature of 100 ° C for 2 hours and then at a temperature of 500 ° C for 3 hours.

The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the deposited TiO ₂ , which is 10.5 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3) · 100% = 50%.

The content of photocatalytically active titanium dioxide as a percentage of the mass of the photocatalyst adsorbent is (0.03 / 3.53) · 100% = 0.85%

The resulting sample was called O5.

Example 6

Similar to example 2, with the exception that instead of the aluminophosphate binder, the impregnating solution included an inorganic binder with a total dry mass of 1.5 g, consisting of alumina Al ₂ O ₃ , pseudoboehmite AlO (OH) and nitric acid HNO ₃ , and photocatalytically active TiO ₂ (anatase, specific surface area 350 m ² / g) in an amount of 0.1 g. Drying of the finished photocatalyst adsorbent is carried out in two stages. First, at a temperature of 100 ° C for 2 hours and then at a temperature of 500 ° C for 3 hours.

The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the deposited TiO ₂ , which is equal to 35.0 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3.1) · 100% = 48.4%.

The content of photocatalytically active titanium dioxide as a percentage of the dry weight of the impregnating composition is (0.1 / 3.1) · 100% = 3.2%

The resulting sample was called O6.

Example 7

Similar to example 6 with the exception that the photocatalytically active TiO ₂ contains finely divided metallic gold. The gold content in TiO ₂ - 1 wt.%.

The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the deposited TiO ₂ , which is equal to 35.0 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3.1) · 100% = 48.4%.

The content of photocatalytically active titanium dioxide as a percentage of the dry weight of the impregnating composition is (0.099 / 3.1) · 100% = 3.2%

The content of gold additive by weight of photocatalytically active titanium dioxide is - (0.001 / 0.1) · 100% = 1%.

The resulting sample was called O7.

Example 8

Similar to example 2, with the exception that, instead of the aluminophosphate binder, the impregnating solution contains a magnesium phosphate binder, and the drying of the finished photocatalyst adsorbent is carried out by smooth heating to a temperature of 210 ° C for 1 h and then keeping it at this temperature for 3 h .

The surface area of coal is 1800 m ² , which is more than 2 times greater than the surface area of the deposited TiO ₂ , which is 10.5 m ² .

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (1.5 / 3) · 100% = 50%.

The content of photocatalytically active titanium dioxide as a percentage of the mass of the photocatalyst adsorbent is (0.03 / 3.53) · 100% = 0.85%.

The resulting sample was called O8.

Testing.

Testing the activity and adsorption capacity of the synthesized photocatalyst adsorbents is carried out in the photocatalytic oxidation reaction of acetone vapor:

CH ₃ COCH ₃ + 4O ₂ = 2CO ₂ + 3H ₂ O

A test sample is placed in a static reactor with a volume of 450 cm ³ , acetone vapor is injected and the concentration of acetone and carbon dioxide vapor is monitored using a gas chromatograph. The shape of the curves determines the effectiveness of the sample.

For example, figure 1 presents graphs of the decrease in the concentration of acetone, and figure 2 - graphs of the accumulation of the concentration of CO ₂ for samples O1 and O2. Figure 1 shows that at the initial moment 42% of acetone vapor is adsorbed on the O2 sample, while the O1 sample does not adsorb acetone at the initial moment. The time for the decrease in the acetone concentration to 10% of the initial amount introduced is 45 min for sample O2 and 150 min for sample O1. According to Figure 2, the final degree of conversion of acetone is the same for both cases and corresponds to 100%.

Similar graphical dependences were obtained for the remaining samples, and the obtained parameters are given in the Table.

Table Sample The proportion of acetone adsorbed at the initial moment,% The time the acetone concentration decreased to 10% of the initial amount administered, min O1 (comparative) 0 150 O2 42 45 O3 41 43 O4 45 48 O5 39 fifty O6 44 44 O7 41 45 O8 35 55

Samples O3, O4 and O7 are tested in the photocatalytic oxidation of hydrocyanic acid vapors. The tests are carried out in the same reactor and under the same conditions as the oxidation of acetone vapor. The initial concentration of HCN vapor is 100 ppm. The rate of decrease in HCN vapor concentration measured over the first 60 minutes of the photooxidation reaction is 0.015 ppm / min, 1.09 ppm / min and 0.96 ppm / min for samples O3, O4 and O7, respectively.

Thus, O2-O8 samples remove organic impurities from polluted air more than 3 times faster than O1 sample, which does not have adsorption activity, and the degree of air purification when using them is also 100%. In addition, all samples containing an adsorbent at the initial moment are capable of adsorbing up to 40% or more of organic impurities.

The introduction of silver and gold additives in the composition leads to an increase in photocatalytic activity in the oxidation of hydrocyanic acid vapors by 72 and 64 times, respectively.

Example 9

A grid of 3 × 3 cm in weight of 0.5 grams is impregnated with a mixture of the following composition: 5 ml of 0.1 M Hcl and 25 ml of tetraethylorthosilicate (TEOS) and 0.5 g of activated carbon of the OU-A grade are added to 8 ml of H ₂ O (specific surface 1200 m ² / g). The resulting mixture was stirred at room temperature for 10 minutes. The impregnated carrier is dried for 1 h at a temperature of 100 ° C and then calcined for 2 hours at a temperature of 400 ° C. The mass of deposited coal and silicon dioxide SiO ₂ , determined by weighing, is 0.05 grams, and the mass fraction of coal, determined by x-ray data, is 20%. Next, the carrier is impregnated with photocatalytically active TiO ₂ (anatase, specific surface area 350 m ² / g). 0.1 g of catalyst is applied to the mesh.

The total surface area of silica gel and coal formed as a result of the hydrolysis of TEOS is 160 m ² , which is more than 2 times the surface area of the deposited TiO ₂ , which is 35.5 m ² .

Since in this case the specific surface area of coal is only 12 m ² , which is much less than 160 m ² , the adsorbent is SiO ₂ , which also carries the function of a binder, and coal has an auxiliary function.

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (0.04 / 0.05) · 100% = 80%.

The content of photocatalytically active titanium dioxide as a percentage of the mass of the photocatalyst adsorbent is (0.1 / 0.65) · 100% = 15.4%

The resulting sample was called O9.

Example 10

Similar to example 9 with the exception that the photocatalytically active TiO ₂ (anatase, specific surface area 350 m ² / g) is introduced into the composition of the impregnation solution in an amount of 0.02 g. The weight of the deposited coal and SiO ₂ determined by weighing is 0.05 gram, and the mass fraction of coal, determined by x-ray data, is 20%. The amount of TiO ₂ deposited, calculated by taking away the mass of TiO ₂ remaining in the solution after application, is 0.002 g.

The surface area of coal and silica gel formed as a result of the hydrolysis of TEOS is 160 m ² , which is more than 2 times the surface area of the deposited TiO ₂ , which is 35.5 m ² .

Since in this case the specific surface area of coal is only 12 m ² , which is much less than 160 m ² , the adsorbent is SiO ₂ , which also carries the function of a binder, and coal has an auxiliary function.

The adsorbent content as a percentage of the dry weight of the impregnating composition is - (0.04 / 0.05) · 100% = 80%.

The content of photocatalytically active titanium dioxide as a percentage of the dry weight of the impregnating composition is (0.002 / 0.05) · 100% = 4%

The resulting sample was called O10.

Testing.

A comparison was made of the rates of photocatalytic oxidation of dimethyl methylphosphonate (DMMF) in an aqueous suspension of a Degussa P25 photocatalyst (TiO ₂ : 80% rutile and 20% anatase, specific surface area 50 m ² / g) and in the same reactor with 3 nets arranged one after another, representing either sample O9 or sample O10. The volume of the reactor V = 150 ml. The initial concentration of DMMF With ₀ = 0.75 mm. The concentration of the catalyst Degussa P25 in a suspension of 333 mg / L.

The initial oxidation rate of DMMF in a suspension of W ₀ is 0.70 ± 0.10 μM DMMF / min. The initial oxidation rate W ₉ with grids representing an O9 sample varies from 1.55 to 1.75 μM DMMF / min and varies within the measurement error for 10 experiments. The initial oxidation rate W ₁₀ with grids representing an O10 sample varies from 1.45 to 1.55 μM DMMF / min and varies within the measurement error for 10 experiments.

Thus, samples O9 and O10 demonstrate a more than twofold increase in the rate of photocatalytic oxidation due to the use of an adsorbent in the form of silica gel SiO ₂ in the composition of the photocatalyst. In addition, the initial concentration of DMMF in the case of samples O9 and O10 with adsorption properties was 48% lower, which is important from a practical point of view for the rapid removal of pollutants from water.

From the above examples it is seen that the proposed adsorbent catalyst combines the properties of both a sorbent and a photocatalyst, has a low hydrodynamic resistance, sufficient rigidity, and has high photocatalytic activity in relation to the destruction of organic and inorganic substances in water and air.

Claims (12)

1. Photocatalyst adsorbent, characterized in that it consists of an inorganic fabric on a woven or non-woven base, impregnated with a composition containing an inorganic binder, an adsorbent and photocatalytically active titanium dioxide, the surface area of the adsorbent is at least two times the surface area of the photocatalytic active titanium dioxide. 2. The photocatalyst adsorbent according to claim 1, characterized in that the inorganic binder includes compounds of silicon and / or aluminum and / or magnesium, as well as phosphoric and / or nitric acid and / or their salts. 3. The photocatalyst adsorbent according to claim 1, characterized in that as the adsorbent it contains either compounds based on coal or based on silicon dioxide SiO ₂ or a mixture thereof. 4. Photocatalyst adsorbent according to claim 1, characterized in that the adsorbent content is 0.1-95.0% of the dry weight of the impregnating composition. 5. The photocatalyst adsorbent according to claim 1, characterized in that the content of photocatalytically active titanium dioxide is 0.001-4.0% of the dry weight of the impregnating composition. 6. The photocatalyst adsorbent according to claim 1, characterized in that it may contain additives of noble metals, such as silver, gold, platinum, palladium, in an amount of not more than 1.0% of the dry weight of the impregnating composition. 7. Photocatalyst adsorbent, characterized in that it consists of an inorganic cloth on a woven or nonwoven base, impregnated with a composition containing an inorganic binder and an adsorbent on which photocatalytically active titanium dioxide is deposited, the surface area of the adsorbent is at least two times the surface area photocatalytically active titanium dioxide. 8. The photocatalyst adsorbent according to claim 7, characterized in that the inorganic binder includes compounds of silicon, and / or aluminum, and / or magnesium, as well as phosphoric and / or nitric acid and / or their salts. 9. The photocatalyst adsorbent according to claim 7, characterized in that either carbon-based compounds or silicon dioxide-based SiO ₂ compounds or a mixture thereof can be used as adsorbent. 10. The photocatalyst adsorbent according to claim 7, characterized in that the adsorbent content is 0.1-99.0% of the dry weight of the impregnating composition. 11. The photocatalyst adsorbent according to claim 7, characterized in that the content of photocatalytically active titanium dioxide is 0.001-20.0% by weight of the photocatalyst adsorbent. 12. The photocatalyst adsorbent according to claim 7, characterized in that it may contain additives of noble metals, such as silver, gold, platinum, palladium, in an amount of not more than 1.0% by weight of photocatalytically active titanium dioxide.

Images