KR102187039B1 - Method and Apparatus for Removing Air Pollutants Using Photocatalyst Based upon Stainless Steel Nanotubes - Google Patents

Abstract

In the present disclosure, a technique for removing organic pollutants from the atmosphere in the presence of a photocatalyst in which metal nanoparticles are supported or attached in a plurality of nanopores formed on a stainless steel nanotube support (or substrate) having a porous surface is described.

Description

[Method and Apparatus for Removing Air Pollutants Using Photocatalyst Based upon Stainless Steel Nanotubes}

The present disclosure relates to a method and apparatus for removing air pollutants using a photocatalyst based on stainless steel nanotubes (SSNTs). More specifically, the present disclosure provides for oxidizing and removing organic pollutants from the atmosphere in the presence of a photocatalyst in which metal nanoparticles are attached or supported in a plurality of nanopores formed on a stainless steel nanotube support (or substrate) having a porous surface. It relates to a method and apparatus.

Effective control of environmental pollution has emerged as a serious problem in urbanized and industrialized societies due to the rise of environmental rights that require a pleasant environment in human life and the strengthening of policies or institutional regulations to support it. The formation of large-scale industrial areas and large cities due to urbanization and industrialization can result in various air pollutants such as nitrogen oxides (NOx), sulfur oxides (SOx), hydrocarbons (e.g., monocyclic or polycyclic aromatic hydrocarbons), It is causing an increase in air pollutants such as volatile organic compounds (VOCs).

VOCs, which are the causative agent of air pollution and generated in various industrial and service facilities, are known to have strong mobility in the atmosphere and cause odor, and have strong anesthetic properties, and act as toxic substances to the nervous system. In addition, pollutants such as benzene and poly aromatic hydrocarbons (PAHs) have carcinogenic properties. In addition, VOC acts as a factor that accelerates global warming by destroying the ozone layer in the stratosphere.

As such, VOCs are not only harmful by themselves, but also harmful secondary air pollutants such as ozone, aldehyde, and PAN (p-oxyacethlnitrate) by acting as a precursor for secondary pollution by generating a photochemical oxidant through a photochemical reaction in the atmosphere. Because of the generation of VOCs, the control of VOCs has become an important research field in the preservation of the atmosphere, and countries around the world are adding reinforced policy measures to reduce VOC emissions. For example, the U.S. Environmental Protection Agency (EPA) designates 189 compounds as hazardous air pollutants, of which 97 are in the VOC family. Even when these air pollutants are present in low concentrations, they act as a factor of dissatisfaction with the indoor environment for people who live most of the time indoors, and have a direct harmful effect on health. In addition, civil complaints in neighboring regions are also on the rise due to odor gases generated from various industries, sewage, agricultural and livestock wastewater, and manure treatment plants, including VOC. Therefore, various studies to remove pollutants from the air are actively being conducted.

Currently, various methods such as heat incineration, adsorption, catalytic combustion, biofilter, adsorption, and absorption have been developed as technologies for controlling pollutants in the atmosphere such as VOC.

In this regard, the thermal incineration method has a large load fluctuation, is low concentration, is uneconomical under a low flow rate condition, and causes a problem in that deadly harmful substances such as NOx and dioxin are generated. In the case of the adsorption method, when ketones, aldehydes, esters, etc. are included, the adsorption capacity of the adsorbent decreases and the generation of waste products of the adsorbent increases.

The catalytic combustion method is a method of combusting combustible substances contained in exhaust gas in the presence of a catalyst. Chemically, it is an oxidation reaction similar to general combustion. If the combustible substance is a hydrocarbon, it is completely combusted to cause harmless and odorless CO ₂ and H ₂ O. Convert to The catalytic combustion method exhibits excellent characteristics in removing air pollutants such as VOC, but may cause various problems depending on the type of pollutant. For example, when other types of VOC are contained when removing hydrocarbons, the treatment efficiency tends to decrease rapidly, and for amines, the endothelial toxicity of the catalyst to sulfur is low, and the selectivity to N ₂ is low. There is a problem that occurs. In particular, in the case of halogen-containing VOCs, toxic substances such as PhClx or volatile CrClxOy complexes are generated, so that treatment efficiency is low, and in the case of mercaptans, the oxidation ability to other VOCs is relatively low. Moreover, it is difficult to secure economic feasibility due to excessive initial investment, high operating costs, and catalyst prices.

As a representative method for overcoming the problems of the conventional treatment method described above, a VOC removal method using a UV/TiO ₂ photocatalyst is in the spotlight. The UV/TiO ₂ photocatalyst system not only can treat low or medium concentration VOCs at low or room temperature, but also has the advantage of low initial investment and operation costs. TiO ₂ catalysts currently applied show good performance in decomposing halogen-containing hydrocarbons (TCE, etc.), but have a problem that the activity of the catalyst decreases with respect to toluene, amine-based or sulfur-containing VOCs. In addition, WO ₃ , SrTiO ₃ , α-Fe ₂ O, ZnO, etc. are known as photocatalysts, and ZnS is used as a metal sulfide system, but it is difficult to be widely applied due to the aforementioned technical limitations.

In the present disclosure, by using a photocatalyst that is economical and has good oxidation removal ability compared to the conventional photocatalyst for removing air pollutants, it is also effectively removed by catalytic oxidation method (especially advanced oxidation process) for various air pollutants including VOCs. We would like to provide a method and apparatus that can be done.

According to the first aspect of this disclosure,

As a method of removing contaminants in gas,

Providing a photo catalyst; And

Including the step of oxidizing and removing contaminants in the gas by contacting a gas containing contaminants in a form of at least one of a gas phase, particles, and fine droplets selected with the photocatalyst under UV irradiation,

Here, the photocatalyst is,

A stainless steel nanotube support having a plurality of nanopores formed on the surface thereof; And

There is provided a method comprising metal nanoparticles supported on nanopores of the stainless steel nanotube support.

According to the second aspect of this disclosure,

Reactor;

At least one port for introducing into the reactor a gas containing contaminants in a form in which at least one of a gas phase, particles and fine droplets is selected;

A fan member for mixing gases in the reactor;

At least one photocatalyst arranged to contact the gas containing the pollutant in the reactor; And

An ultraviolet lamp provided in the reactor to irradiate ultraviolet light to the photocatalyst;

Including,

The photocatalyst,

A stainless steel nanotube support having a plurality of nanopores formed on the surface thereof; And

An apparatus for removing contaminants contained in a gas including metal nanoparticles supported on nanopores of the stainless steel nanotube support is provided.

According to the third aspect of this disclosure,

A stainless steel nanotube support having a plurality of nanopores formed on the surface thereof;

An electron transfer medium doped on the surface of the stainless steel nanotube support; And

A photocatalyst for oxidizing and removing contaminants in a gas is provided, including metal nanoparticles supported on nanopores of a stainless steel nanotube support doped with the electron transport medium.

According to the fourth aspect of this disclosure,

a) providing a stainless steel nanotube support having a plurality of nanopores formed on the surface;

b) separately from this, providing an aqueous solution or aqueous dispersion containing an electron transport medium;

c) doping an electron transport medium onto the surface of the stainless steel nanotube support by immersing the stainless steel nanotube support in an aqueous solution or dispersion containing the electron transport medium;

d) supporting metal nanoparticles in the nanopores of the stainless steel nanotube support doped with the electron transport medium;

Including,

The step b) includes converting the precursor of the electron transport medium into an electron transport medium by thermally decomposing the precursor at a temperature of 200 to 300°C,

The electron transport medium is graphene, graphene oxide, or a combination thereof, and a method of preparing a photocatalyst for removing contaminants contained in a gas is provided.

A method and apparatus for removing contaminants in a gas according to an embodiment of the present disclosure is not a conventional photocatalyst such as TiO ₂ , but a metal nanoparticle on a stainless steel nanotube-based support having a plurality of nanopores formed on the surface thereof, In particular, in the presence of a photocatalyst carrying the reduced metal nanoparticles, a variety of indoor and/or outdoor air pollutants can be effectively oxidized and removed within a shorter time, thereby increasing the treatment capacity, and in particular, a catalyst that can be manufactured at low cost. It has the advantage of dramatically improving the economics by using it. In addition, it is possible to further improve the ability to remove pollutants from the atmosphere by further including an electron transport medium in the catalyst.

Furthermore, the above-described photocatalyst can be applied immediately in the field by replacing or adding only the photocatalyst without requiring any special changes to the existing facility to which ultraviolet rays are applied, and repeated use (or reuse) even after use without a special stabilization process. Also, unlike other pollutant removal methods, it does not require high temperature heat or an additional process for secondary pollutant treatment. Therefore, widespread commercialization is expected in the future.

1 is a diagram showing a mechanism of oxidation and removal reaction of pollutants in a gas by a photocatalyst (OX: oxidizing agent, Red: reducing agent);
2 is a diagram showing a schematic configuration of an apparatus for removing pollutants from the atmosphere according to an embodiment;
3 is a field emission scanning electron microscope (FE-SEM) photograph of the surface of a substrate subjected to anodization treatment in Example 1;
4A and 4B are energy-dispersive X-ray spectroscopy (EDX) analysis results for two types of stainless steel nanotube-based photocatalysts (photocatalyst-1 and photocatalyst-2) prepared in Example 1 Is a graph showing;
5 is a photograph showing the appearance of a polyester aluminum bag containing an aldehyde mixed gas as a pollutant in Example 1;
6 is a photograph showing the appearance of an apparatus for heating benzene and toluene as pollutants in a gas phase in Example 1;
7A and 7B are photographs showing the external and internal structures of the photocatalytic reactor used in Example 1, respectively;
8A to 8D are graphs showing decomposition results of pollutants according to the presence or absence of a photocatalyst (photocatalyst-1) according to Example 1 (FIG. 8A: benzene, FIG. 8B: styrene, FIG. 8C: aldehyde mixed gas) , And FIG. 8D: benzene, styrene and aldehyde mixed gas);
9 is a graph showing the removal efficiency of oil mist according to the presence or absence of a metal nanoparticle-stainless steel nanotube based photocatalyst according to Example 2; And
10 is a graph showing the results of evaluating the reusability of a photocatalyst based on a metal nanoparticle-stainless steel nanotube according to Example 2. FIG.

The present invention can all be achieved by the following description. The following description should be understood as describing preferred embodiments of the present invention, and the present invention is not necessarily limited thereto. In addition, the accompanying drawings are provided to aid understanding, and the present invention is not limited thereto, and details of individual configurations may be appropriately understood by the specific purpose of the related description to be described later.

“Volatile organic compound (VOC)” can be defined as an organic compound having a boiling point of about 50 to 260°C, typically under conditions of ambient temperature and pressure.

"Photocatalyst" promotes a reaction in the presence of light, but may refer to a heterogeneous catalyst that is not consumed in the entire reaction, specifically a solid catalyst. Typically, the photocatalyst is (i) has photoactivity, (ii) uses near-UV light, (iii) is biologically and chemically inert, (iv) exhibits photo-stability, and (v) It may have non-toxic properties.

"Substrate" may mean a structure or structure that provides a surface that can be attached (fixed) or coated (applied) thereon, and may have a one-dimensional, two-dimensional, or three-dimensional shape.

"Advanced oxidation process (AOP)" is a process that promotes non-selective oxidation and uses chemical and/or other forms of energy to generate in-situ transitional species, mainly hydroxy radicals. It can be understood as being based on a physicochemical process. AOP generally involves a two-stage oxidation step. First, a relatively strong oxidizing agent (e.g., hydroxy radical (OH)) is formed, and the oxidizing agent is reacted with a contaminant. Has high oxidation ability.

"Anodization" refers to a reaction of forming a porous film (coating) on the surface of the substrate by oxygen generated from the anode by immersing a substrate such as a metal in an electrolyte, and then attaching an anode to it and allowing current to flow. can do.

“Nanopores” may mean pores having a dimension or size of nanoscale (eg, about 0.1 to 1000 nm, specifically about 1 to 500 nm, more specifically about 10 to 100 nm).

The expressions "on" and "on" may be understood as being used to refer to the concept of relative position. Therefore, not only the case in which another component or layer is directly present in the mentioned layer, but also another layer (intermediate layer) or component may be interposed or present therebetween. Similarly, the expressions “below”, “below” and “below” and the expressions “between” may also be understood as relative concepts of location. In addition, the expression "sequentially" may also be understood as a concept of a relative position.

In the present specification, when a certain component is "included", it means that other components and/or steps may be further included unless otherwise stated.

A. Preparation of photocatalyst for removing pollutants from gas (atmosphere)

1 shows a mechanism of oxidation and removal of pollutants in a gas by a photocatalyst.

Referring to the drawing, the most important step in the photocatalytic oxidation reaction is the step of forming a hole-electron pair that requires energy to overcome a band gap between a valence band and a conduction band. When the light energy equals or exceeds the band gap energy, a hole-electron pair is formed in the catalyst, and is decomposed into photoelectrons in the conduction band, and optical holes in the home appliance band. At the same time, photo-oxidation and reduction reactions occur in the presence of air, oxygen, and pollutants, and the oxidation of moisture in the atmosphere adsorbed in the reaction process or the reactivity of hydroxy radicals derived from OH ⁻ is high. In addition, molecular oxygen is induced to be reduced to superoxide (O ^{2 -} ) due to the electron reducing ability. These highly reactive species, hydroxy groups and superoxides, provide strong decomposition for contaminants (specifically, organic and/or inorganic contaminants, further microbial contaminants).

According to one embodiment, a photocatalyst for removing pollutants, in particular VOCs in a gas, includes: (i) a stainless steel nanotube (SSNT) support having a plurality of nanopores formed on the surface thereof; And (ii) metal nanoparticles supported on nanopores of the support.

-Manufacturing of stainless steel nanotube substrate (support)

According to an exemplary embodiment, the stainless steel nanotube support may be manufactured by an anodization method, which is an electrochemical process. In this case, the anodization system may largely include an electrolyte solution, an anode and a cathode made of a stainless steel substrate. The anodization method is a technology suitable for forming nanotubes and nanoporous structures on various types of metals, and has advantages of easy control and low cost required for mass production.

In this regard, the shape of the stainless steel substrate is not particularly limited, and may have various two-dimensional or three-dimensional shapes such as a plate (or sheet), a hexahedron, and a sphere. Further, according to an exemplary embodiment, the electrolyte solution may be an aqueous solution containing an acid or an organic solvent such as ethylene glycol, and as the acid, hydrogen fluoride, sulfuric acid, phosphoric acid, perchloric acid, etc. may be used alone or in combination. , More specifically, an aqueous solution containing hydrogen fluoride that provides better reactivity, an ethylene glycol organic solvent containing perchloric acid, or the like can be used.

Illustratively, the concentration of the electrolyte solution may range from, for example, about 3 to 10% by volume, specifically about 4 to 8% by volume, and more specifically about 5 to 6% by volume. The electrolyte concentration in the electrolyte solution affects the anodic oxidation reaction conditions (e.g., applied voltage), and can affect the properties of the oxide layer formed on the surface of the stainless steel substrate. It may be desirable to choose. However, the above range should be understood in an exemplary sense.

On the other hand, in the anodic oxidation system, the material of the negative electrode is not particularly limited, but for example, a material having a standard reduction potential larger than that of a stainless steel substrate can be used, and more specifically, it exhibits an appropriate standard reduction potential difference from stainless steel and is available. Easy and chemically stable materials can be used. As the material of such a negative electrode, for example, platinum, copper, carbon, a combination thereof, or the like can be used.

In this way, after immersing the positive electrode and the negative electrode of the stainless steel substrate in the electrolyte solution, a voltage is applied to form a plurality of nanopores while the surface of the stainless steel substrate is oxidized by an oxidation reaction. As the anodic oxidation conditions affect the three-dimensional structure of the nanopores formed on the surface of the stainless steel substrate, it is necessary to appropriately set the reaction conditions according to the desired porosity characteristics. According to an exemplary embodiment, the anodic oxidation temperature for porosity formation may be selected within a range of, for example, about 0 to 20°C, specifically about 2 to 10°C, and more specifically about 3 to 7°C. In addition, each of the applied voltage and current is, for example, about 30 to 70 V (specifically about 35 to 60 V, more specifically about 40 to 55 V), and about 2.0 to 5.2 A (specifically, about 2.5 to 4.5 A , More specifically, it may be selected within the range of about 3.0 to 4.0 A).

In addition, the reaction in the electrolyte solution may be performed under stirring or non-half conditions, and specifically, may be performed under stirring conditions (eg, about 100 to 300 rpm, specifically about 150 to 200 rpm).

As described above, the stainless steel substrate having porosity formed by anodization may optionally undergo a conventional evacuation treatment step, for example, a washing or washing step, for the purpose of removing foreign substances on the surface. Examples of such cleaning or washing include a degreasing treatment, and various treatment methods such as steam degreasing, solvent or alkaline cleaning, as well as conventional detergents, may be applied.

Meanwhile, in this embodiment, the morphology, arrangement, density, specific surface area, pore volume, etc. of the nanopores formed on the surface of the stainless steel nanotube (SSNT) adsorb contaminants in the gas medium to be described later. , It is a factor that affects oxidation and removal of it.

In view of the above, each of the size (average diameter) and depth of the nanopores is a size suitable for processing a gaseous medium, for example, about 10 to 100 nm (specifically, about 15 to 60 nm, more specifically about 20 to 40 nm), and about 40 to 200 nm (specifically about 70 to 150 nm, more specifically about 75 to 100 nm). According to an exemplary embodiment, it may be advantageous to select the size and depth of the nanopores within a range in which metal nanoparticles to be described later can be firmly and easily attached. For example, the ratio of the size of the nanopores to the depth of the nanopores may range from, for example, about 0.05 to 1:1, specifically about 0.2 to 0.8:1, and more specifically about 0.5 to 0.6:1.

In addition, the density of the nanopores formed on the porous SSNT substrate is, for example, about 100 to 500 / μm ² , specifically about 150 to 400 / μm ² , more specifically about 200 to 300 / μm ² I can.

In this regard, when the size and/or depth of the nanopores is too small or large, it is difficult to attach metal nanoparticles to be described later, or mechanical strength may be reduced. In addition, when the density of the nanopores is too low, the efficiency of adsorption/oxidation removal of pollutants in the air may decrease. Therefore, it may be advantageous to select an appropriate level within the above-described range.

In addition, according to an exemplary embodiment, each of the specific surface area (BET specific surface area) and pore volume of the porous SSNT substrate is, for example, about 100 to 400 m 2 /g (specifically about 200 to 350 m 2 /g, more specifically About 250 to 300 m 2 /g) and for example about 0.5 to 2 cc/g (specifically about 1 to 1.8 cc/g, more specifically about 1.3 to 1.5 cc/g). However, the numerical range is not necessarily limited to this as it is affected by the size and density of the aforementioned nanopores.

Attachment (support) of metal nanoparticles on stainless steel nanotube support

According to one embodiment, as described above, the porous SSNT-based substrate having a plurality of nanopores can be used as a support for a photocatalyst, and a photocatalyst is prepared by attaching (supporting) metal nanoparticles to the nanopores. can do.

According to an exemplary embodiment, the size (average diameter) of the metal nanoparticles attached within the nanopores of the SSNT support is, for example, about 5 to 60 nm, specifically about 10 to 40 nm, more specifically about 20 to It can be in the range of 30 nm. In addition, the metal nanoparticles may have, for example, a shape such as a spherical shape, an egg shape, a dish shape, a rod shape, etc., but a spherical shape may be preferable in order to maximize adhesion (or robustness) and activity of the photocatalyst. .

According to one embodiment, in order for the metal nanoparticles to adhere to the nanopores of the SSNT substrate, the size of the metal nanoparticles needs to be selected to be smaller than the size of the nanopores. Illustratively, the ratio of the size of the nanopores: the size of the metal nanoparticles may range from, for example, about 1 to 10: 1, specifically about 1.5 to 5: 1, and more specifically about 1.5 to 2: 1 . If the relative size of the metal nanoparticles is too small, the ability to adhere to the nanopores in the SSNT substrate may be reduced, whereas if the metal nanoparticles are too large, the degree of improvement of the photocatalytic effect according to the support may be reduced. Therefore, it may be advantageous to control the size of the metal nanoparticles within the above-described ratio range.

According to an exemplary embodiment, the amount of metal nanoparticles supported or attached to the SSNT support is, for example, about 1 to 1000 μg/cm2, specifically about 10 to 100 μg/cm2, more specifically about 20 to 50 μg. /Cm2 range.

In this embodiment, the metal nanoparticles attached to the nanopores of the SSNT support perform a function of lowering the band gap in the process of excitation of the photoelectrons to the conduction band after formation of a hole-electron pair by ultraviolet light irradiation energy. As such, the photocatalyst operates even under a small amount of UV irradiation, and as a result, the generation rate of oxidizing agents for oxidation and removal of pollutants in gases such as hydroxy radicals and superoxide radicals is increased in the advanced oxidation process. Can increase the decomposition effect of

According to an exemplary embodiment, the metal nanoparticle may be selected from a type having an easy electron mobility property, and illustratively may be selected from the group consisting of silver (Ag), titanium (Ti), mixtures and alloys thereof. . More specifically, it may be titanium.

At this time, it should be noted that the metal nanoparticles attached (supported) to the nanopores of the SSNT support are in a reduced state rather than an oxidized state. To this end, a reduction method known in the art, for example, a chemical reduction method. Metal nanoparticles in a reduced state (elemental form) may be attached to the nanopores through a photochemical reduction method (Radiation-Assisted Reduction) or the like.

-Chemical reduction method

The chemical reduction method is a method in which a metal in an oxidized state containing a salt (precursor) of a metal is reduced by a reducing agent and grown in the form of particles. According to an exemplary embodiment, the SSNT substrate is immersed in a precursor aqueous solution to which a metal salt (water-soluble metal salt) is added, and then a reducing agent is added to attach the metal nanoparticles in a reduced (element) state into the pores (nanopores) of the SSNT. It can be (supported).

According to an exemplary embodiment, as a precursor of metal nanoparticles, a water-soluble anionic salt of the metal may be used. Illustratively, when the metal is silver (Ag), silver acetate (AgC ₂ H ₃ O ₂ ), silver nitrate (AgNO ₃ ), silver sulfate (AgSO ₄ ), silver phosphate (Ag ₃ PO ₄ ), silver iodide ( AgI), silver chloride (AgCl), silver fluoride (AgF), silver bromide (AgBr), etc., known in the art may be used, and these may be used alone or in combination. In addition, when the metal is titanium, titanium trichloride (TiCl ₃ ), titanium tetrachloride (TiCl ₄ ), titanium isopropoxide (C ₁₂ H ₂₈ O ₄ Ti), titanium butoxide (C ₁₆ H ₃₆ O ₄ Ti) And the like may be used alone or in combination.

According to an exemplary embodiment, the concentration of the metal salt in the aqueous solution may be in the range of, for example, about 0.01 to 1 M, specifically about 0.05 to 0.5 M, more specifically about 0.1 to 0.2 M, and the concentration of the metal salt is generated. It may be advantageous to appropriately control within the above-described range as it affects the uniformity and dimensions of the nanoparticles.

According to an exemplary embodiment, the reducing agent may be a strongly basic reducing agent selected from at least one selected from sodium hydroxide (NaOH), sodium borohydride (NaBH ₄ ), and ammonium hydroxide (NH ₄ OH). At this time, the concentration of the reducing agent added to the aqueous solution may be, for example, about 0.01 to 1 M, specifically about 0.05 to 0.5 M, more specifically about 0.1 to 0.2 M.

As an example, when silver nitrate is used as a silver precursor and sodium borohydride is used as a reducing agent, a reaction mechanism for forming silver particles in a reduced state can be represented as shown in Scheme 1 below.

[Scheme 1]

AgNO ₃ + NaBH ₄ → Ag + ½H ₂ + ½B ₂ H ₆ +NaNO ₃

According to an exemplary embodiment, the reduction reaction temperature may be, for example, about 20 to 60° C., specifically about 25 to 40° C., more specifically about 25 to 35° C., and the reduction reaction time is, for example It may range from about 0.1 to 12 hours, specifically about 0.5 to 6 hours, and more specifically about 1 to 2 hours.

-Photochemical reduction method

According to an alternative embodiment, the metal nanoparticles may be attached (supported) in the nanopores of the SSNT substrate by a photochemical reduction method.

As such, examples of the method of forming metal nanoparticles by the photochemical reduction method are ultraviolet (UV) irradiation after immersing the SSNT substrate in an aqueous solution to which a metal precursor (specifically, a water-soluble metal salt) is added under dark and vacuum conditions. -C investigation) may be involved. UV-C may mean light having a wavelength range of about 200 to 280 nm. In this case, prior to light irradiation, a step of selectively washing with water (specifically distilled water) and/or nitrogen gas may be performed.

In the photochemical reduction method, the type of the metal precursor (specifically, the water-soluble metal salt), the concentration of the metal precursor and the acid component in the aqueous solution, and the like are similar to those in the chemical reduction method described above. During photochemical reduction, the SSNT substrate can be immersed in the aqueous solution for a time during which an appropriate amount of metal nanoparticles can be formed in the nanopores, for example, about 1 to 12 hours, specifically about 3 to 6 hours, more specifically It can be adjusted within the range of about 5 to 6 hours.

According to an exemplary embodiment, the irradiation time of ultraviolet rays (specifically, UV-C light) can be adjusted within an appropriate range in consideration of the reduction efficiency and economy of metal ions, for example, about 1 to 24 hours, Specifically, it may be in the range of about 6 to 18 hours, more specifically about 10 to 12 hours.

According to another embodiment of the present disclosure, in order to facilitate electron transfer between metal nanoparticles supported or attached in the nanopores of the SSNT substrate or the support, the surface of the SSNT substrate (for example, a plurality of nanoparticles formed on the surface of the SSNT substrate The inside of the pore) is first doped with an electron transport medium, and subsequently the metal nanometal is fixed or supported as described above, thereby improving the ability to remove pollutants from the atmosphere.

As an example, the electron transport medium may be an organic material formed based on carbon, for example, graphene, graphene oxide, or a combination thereof. In this regard, "graphene" is a honeycomb-shaped two-dimensional planar carbon allotrope consisting of sp2 bonds of carbon atoms, soccer ball-shaped fullerene (C60) and cylindrical carbon nanotubes, multilayered It may correspond to one of the nanostructured carbon allotropes together with the structured graphite. In addition, "graphene oxide" is graphene functionalized with an oxygen-containing chemical group (eg, epoxy or hydroxy group), specifically, a two-dimensional material derived from graphene by introducing a single layer graphite oxide (CO covalent bond) ), and a carbonyl group and a carboxyl group are positioned at an edge portion of graphene to exhibit polar surface characteristics. Graphene oxide due to the presence of a graphene-based lattice and various oxygen-containing groups, the functional groups on the surface of the graphene oxide can act as anchor sites for fixing various active species, and have adjustable electronic properties.

According to an exemplary embodiment, as an electron transport medium that can be additionally introduced into an SSNT-based photocatalyst, graphene synthesized by thermally decomposing a low-molecular organic acid material to polymerize it may be applied. In this way, the additionally doped electron transport medium can effectively enhance the electron mobility of the previously prepared photocatalyst, thereby providing a function of particularly promoting oxidation removal capability for VOCs.

According to an exemplary embodiment, the electron transport medium may be doped on the SSNT substrate prior to forming the metal nanoparticles, for example, a precursor of an electron transport medium, specifically a precursor of graphene and/or graphene oxide. It may be doped to the SSNT substrate (or its surface) using.

As an example, the precursor of the electron transport medium may be, for example, a carbon-containing compound, specifically an organic acid, and more specifically, citric acid, lactic acid, or the like may be used alone or in combination. As described above, the reason why an organic acid is used as a precursor is that a graphene structure can be synthesized from a low-carbon molecular structure in a bottom-up manner.

According to an exemplary embodiment, a solid precursor may be used to prepare an electron transport medium, and the precursor may be thermally decomposed to liquefy.

According to an exemplary embodiment, the thermal decomposition temperature may range from, for example, about 200 to 300°C, specifically about 220 to 280°C, and more specifically about 230 to 250°C. Further, according to an exemplary embodiment, the thermal decomposition reaction time may range from, for example, about 0.4 to 1 hour, specifically about 0.5 to 0.8 hours, and more specifically about 0.6 to 0.7 hours. These thermal decomposition reaction temperatures and times are described for illustrative purposes, and may vary depending on the type of precursor used and the amount of application.

As described above, the obtained thermal decomposition product can be prepared in the form of an aqueous solution (or aqueous dispersion).According to a specific embodiment, when an organic acid is used as a precursor, an aqueous solution (or aqueous dispersion) of the thermal decomposition product Water) can be acidic. At this time, for the purpose of securing the stability of the aqueous solution (or aqueous dispersion) of the thermal decomposition product, the thermal decomposition product is used as an aqueous base solution (for example, an aqueous solution containing sodium hydroxide, sodium borohydride, ammonium hydroxide, or a combination thereof, Specifically, it can be added to sodium hydroxide aqueous solution). In this regard, the concentration of the aqueous base solution may be, for example, in the range of about 0.01 to 0.5 M, specifically about 0.02 to 0.4 M. In this case, the concentration of the aqueous base solution is exemplary and can be appropriately adjusted according to the amount of the thermal decomposition product added.

According to an exemplary embodiment, the concentration of the electron transport medium (i.e., thermal decomposition product) in the aqueous solution (or aqueous dispersion) is, based on a precursor, for example, about 0.1 to 3 M, specifically about 0.5 to 2 M, more specifically, may be in the range of about 1 to 1.5 M, and it may be advantageous to appropriately control the concentration of the electron transport medium within the above-described range in consideration of the uniformity and dimensions of the doped electron transport medium particles. .

Meanwhile, since the electron transport medium formed by thermal decomposition may exist in the form of an oxide, a subsequent treatment may be performed using a base selectively for its reduction. Illustratively, the base may be, for example, sodium hydroxide (NaOH), sodium borohydride (NaBH ₄ ), ammonium hydroxide (NH ₄ OH), and the like, and may be used alone or in combination. In particular, sodium hydroxide can be used. For this reduction treatment, an aqueous base solution may be added to an aqueous solution containing a thermal decomposition product (ie, an electron transfer medium), and the concentration of the aqueous base solution added at this time is, for example, about 0.1 to 2 M, specifically It is adjustable within the range of about 0.15 to 1 M, more specifically about 0.2 to 0.4 M.

In this way, the pH of the aqueous solution containing the electron transport medium can be adjusted to, for example, about 6.5 to 8, specifically about 7, by the base treatment.

Then, by contacting (depositing) the SSNT substrate or support in an aqueous solution (or aqueous dispersion) containing the electron transport medium, the electron transport medium may be doped (attached) on the SSNT substrate. Illustratively, the concentration of the electron transport medium in the aqueous solution for doping may be adjusted within the range of, for example, about 0.005 to 0.1% by weight, specifically about 0.007 to 0.08% by weight, and more specifically about 0.009 to 0.03% by weight. have. Further, the contact or immersion time may range from, for example, about 0.2 to 2 hours, specifically about 0.5 to 1.5 hours, and more specifically about 0.8 to 1.2 hours. Thereafter, a conventional post-treatment step, for example, a drying step, or the like may be performed. In addition, the contact or immersion temperature is not particularly limited, but may be, for example, about 15 to 30°C, specifically about 20 to 25°C, and more specifically room temperature.

According to an exemplary embodiment, the electron transport medium doped on the SSNT substrate or the support may be, for example, in the form of particles, in which case the particle size is, for example, about 0.5 to 2 nm, specifically about 1 to 1.5 nm, more specifically, may range from about 1.2 to 1.3 nm, and may also exhibit blue luminescence.

The SSNT substrate doped with an electron transport medium may adhere metal nanoparticles according to the same procedure as described above. In this regard, the amount of the electron transport mediator additionally introduced in the photocatalyst is the metal nanoparticles that are subsequently attached or supported: the weight ratio of the electron transport mediator, for example, about 10 to 150:1, specifically about 50 To 100:1, more specifically about 70 to 80:1 may be selected within a range.

Although the present invention is not bound by a specific theory, the selectively introduced electron transport medium improves photocatalytic activity by changing the band gap while improving the electron transfer characteristics between the metal nanoparticles and the SSNT support through doping. I believe it can be done.

B. Removal of air pollutants using photocatalyst

According to one embodiment of the present disclosure, a method and related apparatus for removing contaminants contained in a gas (specifically, indoor or outdoor atmosphere) using an SSNT-based photocatalyst prepared as described above are provided. At this time, the pollutant is not particularly limited as long as it is a kind that can be contained in the atmosphere or indoor/outdoor atmosphere (a gaseous medium).

According to an exemplary embodiment, the pollutant may include at least one selected from the group consisting of reduced sulfur compounds, aldehyde compounds, and VOCs. Exemplary types of such contaminants are shown in Table 1 below.

pollutant Kinds Reduced sulfur compounds Hydrogen sulfide Methyl mercaptan Dimethyl sulfide Dimethyl disulfide Aldehydes Acetaldehyde Propionaldehyde Butylaldehyde Isovarelaldehyde VOCs toluene Styrene benzene Alcohol Ketone

Illustrative contaminants may come from various sources indoors or outdoors, for example various chemicals applied within buildings, fumes or particulate matter in the cooking process, molds or bacteria, and the like.

In this regard, as an example of a pollutant, a reaction mechanism in which acetaldehyde is oxidized by a photocatalyst, specifically, through an advanced oxidation process (AOP), can be represented as shown in Scheme 2 below.

[Scheme 2]

Meanwhile, the concentration of the pollutant in the gas to be treated is not particularly limited, but may be typically about 1 to 200 ppm, more typically about 50 to 100 ppm.

In addition, during an oxidation reaction such as an advanced oxidation process, moisture acts as a source of hydroxy radicals required to remove contaminants. At this time, the humidity (relative humidity) of the gas to be treated is, for example, at least about 15%, specifically about It may range from 15 to 50%, more specifically from about 20 to 30%.

2 shows a schematic configuration of an apparatus for removing pollutants from the atmosphere according to an embodiment.

The apparatus 100 for removing pollutants in the atmosphere (gas) according to the illustrated example is largely spaced apart from the reactor 101, the ultraviolet lamp 102 disposed in the inner space of the reactor, and the ultraviolet lamp 102. At least one (specifically, a pair) of SSNT-based photocatalysts 103 that are spaced apart, at least one port 104 provided in the reactor for introducing the gas to be treated (or atmospheric gas) from the outside of the reactor to the inside. And a fan member 105 for mixing gas components in the reactor.

According to an exemplary embodiment, the reactor 101 may have an arbitrary shape, such as a cylinder (cylindrical) shape, a hexahedral shape, a spherical shape, and the like. However, it may be specifically a cylinder shape.

According to an exemplary embodiment, the pollutant contained in the gas to be treated may be in a form in which at least one of a gas phase, a particle, and a fine droplet is selected. For example, VOCs, hydrocarbons (especially aromatic hydrocarbons such as toluene, hydrocarbons having an unsaturated bond, etc.), aldehydes, etc. may be contained in the gas to be treated as a gas. Meanwhile, contaminants such as oil mist may be contained in the form of oil droplets (eg, oil droplets having a diameter of about 1 to 10 μm, specifically about 2 to 7 μm) in the gas.

The pollutant-containing gas (atmospheric gas) may be introduced into the reactor 101 through at least one port 104, and the introduced gas is driven by the reactor, specifically, the fan member 105 attached to the reactor cover. It may be desirable to make it uniformly mixed (distributed) in the space inside the reactor.

According to an exemplary embodiment, the irradiation intensity of ultraviolet rays emitted from the ultraviolet lamp 102 is, for example, about 0.1 mW/cm 2 to 80 kW/cm 2, specifically about 1 mW/cm 2 to 10 kW/cm 2, more specifically It may be in the range of about 10 mW/cm 2 to 1 kW/cm 2. In this regard, since the irradiation intensity of ultraviolet rays is one of the main factors affecting the photocatalytic efficiency, it may be advantageous to appropriately control it within the above-described range, but this may vary depending on the type and concentration of pollutants in the gas. , Can be understood in an exemplary sense. In addition, the wavelength of the irradiated ultraviolet rays may be, for example, about 100 to 400 nm, specifically about 180 to 320 nm, and more specifically about 230 to 280 nm.

According to an exemplary embodiment, the ultraviolet lamp 102 may be an electrodeless ultraviolet lamp, and the electrodeless ultraviolet lamp does not form an electrode inside the vacuum tube, but the principle that ultraviolet rays are emitted by irradiating high frequency from the outside. It is to use. That is, gaseous molecules, such as mercury or argon, charged in the vacuum tube may be excited to generate discharge to emit ultraviolet rays. Specifically, the ultraviolet lamp may be a UV LED type.

According to an exemplary embodiment, the contact temperature of the pollutant-containing gas and the photocatalyst may range from, for example, about 4 to 40°C, specifically about 10 to 35°C, and more specifically about 15 to 30°C. Bar, since the catalyst reaction temperature can be changed according to the kind of pollutant, the above range can be understood for illustrative purposes.

The photocatalyst 103 may be a structure having various shapes, for example, plates, meshes, tubes, etc., depending on the shape of the aforementioned SSNT substrate or support, and more specifically, may be applied in a plate shape, and in the reactor At least one may be arranged.

According to the illustrated embodiment, in the reactor 101 a plurality, specifically a pair of plate-shaped SSNT-based photocatalysts are disposed. As an example, the plate-shaped photocatalysts 103 may be vertically disposed inside the cylindrical reactor 101 while facing each other.

According to the illustrated embodiment, in order to effectively remove pollutants from the gas introduced into the reactor 101, it may be advantageous to dispose the photocatalyst 102 at a uniform distance from the ultraviolet lamp 102. In the illustrated example, one ultraviolet lamp 102 is disposed, but in some cases, a plurality of ultraviolet lamps may be installed in the reactor. In addition, in order to facilitate the installation of the ultraviolet lamp 102 in the reactor 101, a holder (especially, when it is arranged in a longitudinal direction or vertical direction based on the bottom surface of the reactor; not shown), or A groove structure may be formed on the bottom surface of the reactor to be detachably fixed (especially, in the case of placing it in transverse contact on the bottom surface of the reactor; not shown).

In the example in which a plurality (specifically, a pair) of photocatalytic structures are arranged as shown, when an ultraviolet lamp is disposed on the upper cover of the reactor 101 so that the temperature change inside the reactor is small, the ultraviolet lamp and Catalyst efficiency may decrease due to an increase in the distance between the photocatalysts.

In consideration of the above, according to the illustrated embodiment, a shape having an extended length, for example, a rod or bar-shaped UV lamp 102 is disposed at the central portion of the reactor 101, at this time, the UV lamp ( 102) may be disposed in the longitudinal direction (vertical direction) with respect to the bottom of the reactor. Through the arrangement of the UV lamps 102, the separation distance between the UV lamps 102 and the pair of photocatalysts 103 is maintained uniformly to induce a uniform photocatalytic effect in a plurality of catalysts, and at the same time, the UV lamps 102 ) And the photocatalyst 103 may be kept as close as possible to suppress a decrease in photocatalytic efficiency. Moreover, since the UV lamp in the reactor causes a temperature change in the reactor, this temperature change (specifically, a temperature increase) affects the calculation of the concentration of pollutants in the gas to be treated, which is an obstacle to optimizing the photocatalytic reaction conditions. As much as it can act as, it may be advantageous to arrange the photocatalyst in the manner described above.

In the illustrated embodiment, the reactor 101 is provided with at least one port 104 as described above. The primary function of the port 104 is to introduce a gas to be treated containing contaminants into the reactor.In addition, before, during or after removal of the contaminant by a photocatalyst, It can also function as a sample take-out port to check the degree of contaminant removal (specifically, the concentration). However, in some cases, a separate port may be installed and used as a sample extraction port.

According to another exemplary embodiment, in order to further promote the removal of contaminants from the gas to be treated, a photocatalytic reaction may be selectively performed in the presence of ozone. To this end, ozone may be introduced through a separate ozone inlet (not shown), alternatively, may be introduced into the reactor 101 together with the gas to be treated. In addition, an ozone generator (not shown) may be additionally provided outside the reactor for ozone injection.

By introducing ozone as described above, when a contaminant (eg, benzene, etc.) is present in a relatively high concentration in the gas to be treated, it is possible to provide an additional effect of suppressing the phenomenon of deactivating the catalyst. At this time, the concentration of ozone in the reactor during the photochemical reaction may range from, for example, about 1 to 100 ppm, specifically about 10 to 80 ppm, and more specifically about 30 to 50 ppm.

The present invention may be more clearly understood by the following examples, and the following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

Example 1

Preparation of stainless steel nanotube (SSNT) substrate

A stainless steel nanotube (SSNT) substrate having porosity formed on the surface of a stainless steel (POSCO) substrate was prepared through an anodizing process. The size of the SSNT substrate was 10 cm x 4 cm, and the anodizing process for forming porosity was performed according to the following process conditions.

In order to keep the inside of the anodic oxidation reactor constant at 5°C, an aqueous perchloric acid solution (concentration: 5% by volume) was added as an electrolyte into a reactor (4 L) equipped with a circulating double jacket using a thermostat and a stirrer, and stainless steel The substrate was immersed. Thereafter, a voltage of 50 V was applied using a stainless steel substrate as an anode, and the resultant was kept constant during the anodization reaction. At this time, the anodic oxidation reaction was carried out over 20 minutes under stirring conditions of 150 rpm. In addition, platinum was used as the negative electrode.

The anodized substrate was observed with a field emission scanning electron microscope (FE-SEM), and the results are shown in FIG. 3. From the above drawing, it was confirmed that a porous nanotube structure was formed on the surface of the stainless steel substrate. At this time, the formed nanopores had an average diameter of 20 nm and an average depth of 78 nm, and the density of the nanopores was at the level of 220 pieces/µm ² , and in particular, it was confirmed that it had a pore size suitable for gaseous pollutants. I can.

Preparation of photocatalyst (photocatalyst-1) with Ti nanoparticles attached on SSNT substrate

A metal precursor aqueous solution (0.5 L) to which 0.2 M of titanium isopropoxide was added as a metal precursor was prepared.

Then, after immersing the previously prepared SSNT substrate at room temperature, 0.2 M of ammonium hydroxide (Sigma-Aldrich) was added to the aqueous solution and reacted for 60 minutes. After washing the reduced SSNT substrate with distilled water and ethanol, analysis using energy-dispersive X-ray spectroscopy (EDX) to confirm the attached (supported) state of Ti nanoparticles in the nanopores of the SSNT substrate. And the results are shown in FIG. 4A. From the above drawing, it can be seen that titanium (Ti) nanoparticles are successfully attached to nano-sized pores formed on the surface of the SSNT substrate.

Preparation of photocatalyst (photocatalyst-2) with Ti nanoparticles attached on SSNT substrate doped with electron transport mediator

Citric acid powder (99%; Sigma-Aldrich) was thermally decomposed at 220° C. for 40 minutes to liquefy, and then it was added to 0.25 M NaOH aqueous solution, followed by addition of 1 N NaOH aqueous solution until pH 7 was reached. And it was titrated.

Thereafter, the previously prepared SSNT substrate was immersed (immersed) at room temperature for 1 hour in an aqueous solution (or aqueous dispersion) adjusted to contain 0.01% by weight of the electron transport medium, thereby doping the electron transport medium.

Separately, an aqueous metal precursor solution (0.5 L) to which 0.2 M of titanium isopropoxide was added as a metal precursor was prepared. Then, after immersing the SSNT substrate doped with the electron transport medium at room temperature, 0.2 M ammonium hydroxide (Sigma-Aldrich) was added to the aqueous metal precursor solution, and reacted for 60 minutes. After washing the reduced SSNT substrate with distilled water and ethanol, analysis using energy-dispersive X-ray spectroscopy (EDX) to confirm the attached (supported) state of Ti nanoparticles in the nanopores of the SSNT substrate. And the results are shown in Fig. 4b. From the above drawing, it can be seen that titanium (Ti) nanoparticles and electron transport mediator (C) are successfully attached in nano-sized pores formed on the surface of the SSNT substrate.

Performance test of stainless steel nanotube (SSNT) based photocatalyst against pollutants in gas

-Test materials and devices

(i) Benzene (>99%) and styrene (>99%), respectively, were obtained from Sigma-Aldrich.

(ii) The aldehyde gas mixture was used as it was contained in the polyester aluminum bag shown in FIG. 5. The composition of the aldehyde gas mixture used is shown in Table 2 below.

ingredient Concentration (ppm) Acetaldehyde 99.6 Propionaldehyde 20.1 Butylaldehyde 18.6 Valelaldehyde 15.1 Isovarelaldehyde 19.6

In addition, benzene and styrene were each added to the air blocking container shown in FIG. 6 and heated at 60° C. for 2 hours to obtain vapors of benzene and styrene.

(iii) reactor

The reactor used in this embodiment is a closed chamber type (cylinder-shaped) reactor and has the structure shown in Figs. 7A and 7B. The reactor is a single UV lamp (output: 4W, wavelength: 254 nm), two plate-shaped catalyst structures (catalyst structure size: 10 cm x 4 cm, total surface area: 80 cm2), gas injection and a single for sampling after a predetermined time Included a pot and a single pan for mixing. In addition, the height of the chamber, the chamber diameter, and the reactor volume were 12 cm, 20 cm and 3770 cm 3 (3.77 L), respectively.

-Sample injection

The reactor was sealed using an air tight seal. In the case of benzene and styrene, 120 mL of gas was injected into the reactor through the sample injection port. Since benzene and styrene are prepared as separate mixtures, the initial concentration in the reactor could not be accurately determined. On the other hand, the concentration of the standard aldehyde gas mixture was known, and the initial concentration in the reactor was 165 ppm.

-Sample analysis procedure

A YL-6100 gas chromatography system equipped with a flame ionization detector (FID) was used to analyze the change in the concentration of contaminants in the reactor. For each analysis, 1000 μl of a sample was taken out of the reactor and injected into the GC injection port. Samples were taken at regular time intervals of 1 to 5 hours (T0, T1, T2, T3, T4, and T5). In addition, two experiments were performed for each of the three gas phase samples (with and without UV/SSNT-based catalyst system).

The GC-FID parameters used in the analysis are shown in Table 3 (aldehydes) and Table 4 (benzene and styrene) below.

Component Detail Detector FID column Capillary alumina Column length 50 m Column diameter 0.53 mm Injector temperature 200 ℃ Column temperature 45 ℃ Detector temperature 200 ℃ Carrier gas helium

Component Detail Detector FID column Capillary alumina Column length 50 m Column diameter 0.53 mm Injector temperature 220 ℃ Column temperature 80 ℃ Detector temperature 250 ℃ Carrier gas helium

-Test result

The photocatalytic activity evaluation results for pollutants in gas are shown in FIGS. 8A to 8D.

According to the figure, the concentration of pollutants in the absence of the photocatalyst was not reduced to a significant level. However, when applying the SSNT-based photocatalyst/ultraviolet system, the decomposition rates for benzene, styrene and aldehydes were 43%, 64% and 49%, respectively.

Example 2

Oil mist decomposition performance evaluation

A decomposition test was performed on oil mist generated during cooking indoors as an air pollutant using the SSNT-based photo catalyst (photo catalyst-1) prepared in Example 1. The results are shown in FIG. 9. In addition, the evaluation results for the case where only ultraviolet rays were irradiated (no photocatalyst was used), only the photocatalyst was used (the ultraviolet rays were not irradiated), and both ultraviolet rays and photocatalysts were not applied are shown for comparison purposes. Done.

Referring to the drawing, it can be seen that the removal efficiency of oil mist is highest when UV irradiation to the SSNT-based photocatalyst (photocatalyst-1).

On the other hand, the possibility of repeated use was evaluated by repeatedly applying an SSNT-based photocatalyst to a plurality of oil mist removal reactions, and the results are shown in FIG. 10.

According to the drawing, the photocatalyst exhibited a substantially constant removal efficiency regardless of the number of reuses, which suggests that there is no significant difference in the characteristics of the photocatalyst before and after use, so that semi-permanent use is possible.

Example 3

Decomposition of 5 types of malodorous gases (formaldehyde, ammonia, acetaldehyde, acetic acid and toluene) designated by the Air Purifier Association as air pollutants for the SSNT-based photocatalyst (photocatalyst-2) prepared in Example 1 The test was carried out. The results are shown in Table 5 below.

Referring to the above table, it can be seen that air pollutants are effectively removed by a system using a photocatalyst doped with an electron transport medium and Ti on the SSNT substrate.

All simple modifications to changes of the present invention belong to the scope of the present invention, and the specific scope of protection of the present invention will become apparent by the appended claims.

Claims (20)

As a method of removing contaminants in gas,
Providing a photo catalyst; And
Including the step of oxidizing and removing contaminants in the gas by contacting a gas containing contaminants in a form of at least one of a gas phase, particles, and fine droplets selected with the photocatalyst under UV irradiation,
Here, the photocatalyst is,
A stainless steel nanotube support having a plurality of nanopores formed on the surface thereof;
An electron transport medium having a particle size of 0.5 to 2 nm, doped inside a plurality of nanopores formed on the surface of the stainless steel nanotube support; And
Including metal nanoparticles supported on nanopores of a stainless steel nanotube support doped with the electron transport medium,
The nanopore size is 10 to 60 nm, the nanopore size: the ratio of the depth of the nanopores is 0.05 to 0.8: 1. delete The method of claim 1, wherein the electron transport medium is graphene, graphene oxide, or a combination thereof. The method of claim 3, wherein the weight ratio of the metal nanoparticle: the electron transport medium is in the range of 10 to 150:1. The method of any one of claims 1, 3 and 4, wherein the depth of the nanopores is in the range of 40 to 200 nm. delete The method of claim 1, wherein the density of the nanopores formed on the stainless steel nanotube support is in the range of 100 to 500/µm ² . The method of claim 1, wherein the ratio of the size of the nanopores to the size of the metal nanoparticles is in the range of 1 to 10:1. According to any one of claims 1, 3, and 4, the metal nanoparticles are selected from the group consisting of silver (Ag), titanium (Ti), mixtures and alloys thereof. Methods of removal of substances. The method of any one of claims 1, 3 and 4, wherein the pollutant is at least one selected from the group consisting of reduced sulfur compounds, aldehyde compounds, and VOCs. Way. The method of any one of claims 1, 3, and 4, wherein the irradiation intensity of the ultraviolet rays is in the range of 0.1 mW/cm 2 to 80 kW/cm 2. The method of any one of claims 1, 3 and 4, wherein the contact temperature between the gas containing the pollutant and the photocatalyst is in the range of 4 to 40°C. The method according to any one of claims 1, 3, and 4, wherein the relative humidity of the gas containing the pollutant is at least 15%. The method of any one of claims 1, 3 and 4, wherein the contact of the gas containing the pollutant and the photocatalyst is performed in the presence of ozone. Reactor;
At least one port for introducing into the reactor a gas containing contaminants in a form in which at least one of a gas phase, particles and fine droplets is selected;
A fan member for mixing gases in the reactor;
At least one photocatalyst arranged to contact the gas containing the pollutant in the reactor; And
An ultraviolet lamp provided in the reactor to irradiate ultraviolet light to the photocatalyst;
Including,
The photocatalyst,
A stainless steel nanotube support having a plurality of nanopores formed on the surface thereof;
An electron transport medium having a particle size of 0.5 to 2 nm, doped inside a plurality of nanopores formed on the surface of the stainless steel nanotube support; And
Including metal nanoparticles supported on nanopores of a stainless steel nanotube support doped with the electron transport medium,
The nanopore size is 10 to 60 nm, and the ratio of the nanopore size: the depth of the nanopores is 0.05 to 0.8: 1. An apparatus for removing contaminants contained in a gas. The method of claim 15, wherein the at least one photocatalyst is a pair of photocatalysts arranged to face each other in a plate-like structure in a cylindrical reactor, and
The ultraviolet lamp is a device for removing contaminants contained in gas, characterized in that the ultraviolet lamp is disposed in a longitudinal direction with respect to the bottom of the reactor in a shape having an extended length at the center of the reactor. 18. The apparatus of claim 16, wherein the apparatus further comprises an ozone inlet for introducing ozone into the reactor. A stainless steel nanotube support having a plurality of nanopores formed on the surface thereof;
An electron transport medium having a particle shape of 0.5 to 2 nm, doped inside a plurality of nanopores formed on the surface of the stainless steel nanotube support; And
Including metal nanoparticles supported on nanopores of a stainless steel nanotube support doped with the electron transport medium,
The nanopore size is 10 to 60 nm, the nanopore size: the ratio of the depth of the nanopores is 0.05 to 0.8: 1 Photo catalyst for oxidizing and removing pollutants in the gas. a) providing a stainless steel nanotube support having a plurality of nanopores formed on the surface;
b) separately from this, providing an aqueous solution or aqueous dispersion containing an electron transport medium;
c) doping an electron transport medium onto the surface of the stainless steel nanotube support by immersing the stainless steel nanotube support in an aqueous solution or dispersion containing the electron transport medium;
d) supporting metal nanoparticles in the nanopores of the stainless steel nanotube support doped with the electron transport medium;
Including,
The step b) includes converting the precursor of the electron transport medium into an electron transport medium by thermally decomposing the precursor at a temperature of 200 to 300°C,
The electron transport medium is graphene, graphene oxide, or a combination thereof, a method of manufacturing a photocatalyst for removing contaminants contained in a gas. The method of claim 19, wherein the precursor of the electron transport medium is citric acid, lactic acid, or a combination thereof.

Images