Visible-light sensitive magnetic photocatalyst and manufacturing method thereof

Abstract

One embodiment of the present invention provides a visible-light sensitive magnetic photocatalyst and a manufacturing method thereof, in which nitrogen, which is a non-metal, and cobalt or nickel, which is a metal element providing magnetic properties, are doped on a titanium dioxide photocatalyst, enabling activation by visible light and allowing recovery of the photocatalyst after use through electromagnets or permanent magnets due to magnetic properties thereof.

Description

Visible light-sensitive magnetic photocatalyst and method for producing the same

[0001] The present invention relates to a titanium dioxide photocatalyst, and more particularly, to a titanium dioxide-based photocatalyst having improved reactivity to visible light and magnetic properties by doping titanium dioxide with a metal element providing nitrogen and magnetic properties.

[0002] A photocatalyst is a material that has a band gap corresponding to photon energy and can remove pollutants by causing a catalytic effect when exposed to light of a wavelength corresponding to the band gap energy. Titanium dioxide (TiO2) is a representative and widely used material, but zinc oxide (ZnO) is also known to have photocatalytic action. In particular, titanium dioxide has a wider range of applications than zinc oxide due to its excellent acid and alkali resistance.

[0003] These photocatalysts have antibacterial and sterilizing effects, as well as the property of breaking down organic matter into carbon dioxide and water, so they can be applied to air pollution treatment, wastewater treatment, etc. Recently, the UN World Water Development Report pointed out sewage and wastewater treatment water as a reliable alternative water resource, and as the importance of wastewater treatment increases, research on sterilization and organic matter decomposition methods using photocatalysts for eco-friendly wastewater treatment is steadily increasing.

[0004] However, the conventionally used photocatalyst is titanium dioxide (TiO2) in the form of nanoparticles. In the case of anatase TiO2, the band gap is approximately 3.22 eV, so it can only function as a photocatalyst when irradiated with ultraviolet rays (200-400 nm). This has the problem that it does not react in the visible light range because most of the sunlight is in the visible light range and the ultraviolet range accounts for less than 5%, so solar energy cannot be effectively utilized.

[0005] In addition, in order to repeatedly reuse the photocatalyst after the wastewater treatment reaction, the photocatalyst, which is a nanoparticle, must be easily recovered. Although recovery is possible using existing separation membrane technologies such as nanofiltration or reverse osmosis, this is not economically efficient, and there is a problem of secondary pollution occurring if the used photocatalyst is not recovered and is discarded with the wastewater.

[0006] Therefore, there is a need to develop a photocatalyst that can not only decompose pollutants by activating the photocatalyst in the visible light range without an additional high-energy heat source, but also easily recover the used photocatalyst.

[0007] [Prior art literature]

[0008] Korean Patent No. 10-2504656

[0009] The technical problem to be achieved by the present invention is to provide a titanium dioxide photocatalyst that reacts to visible light and a photocatalyst and a manufacturing method that can be easily recovered by utilizing the magnetic properties of the photocatalyst after use.

[0010] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0011] To achieve the above technical task, one embodiment of the present invention provides a visible light-sensitive magnetic photocatalyst.

[0012] In one embodiment of the present invention, the visible light-sensitive magnetic photocatalyst may include titanium dioxide doped with nitrogen and a metal element providing magnetic properties.

[0013] Additionally, in one embodiment of the present invention, the metal element providing the magnetic properties may include cobalt or nickel.

[0014] Additionally, in one embodiment of the present invention, the nitrogen may be 1 to 6 mol% relative to the total mole.

[0015] Additionally, in one embodiment of the present invention, the metal element providing the magnetic properties may be 2 to 5 mol% based on the total mole.

[0016] Additionally, in one embodiment of the present invention, it may be a nanocomposite further including iron oxide.

[0017] In order to achieve the above technical task, another embodiment of the present invention provides a method for manufacturing a visible light-sensitive magnetic photocatalyst.

[0018] In one embodiment of the present invention, the method for manufacturing the visible light-sensitive magnetic photocatalyst may include a step of forming titanium dioxide doped with a metal element providing magnetic properties; and a step of doping nitrogen into the titanium dioxide doped with the metal element providing magnetic properties.

[0019] In addition, in one embodiment of the present invention, the step of forming titanium dioxide doped with a metal element providing magnetic properties may include the steps of preparing a titanium oxide solution and a metal element precursor solution providing magnetic properties; mixing the titanium oxide solution, the metal element precursor solution providing magnetic properties, an acidic aqueous solution, and a solvent by stirring; and drying the mixture and then heating and cooling it to obtain titanium dioxide doped with a metal element providing magnetic properties.

[0020] Additionally, in one embodiment of the present invention, the titanium oxide solution may include at least one selected from the group consisting of titanium butoxide, titanium propoxide, and titanium tetraisopropoxide.

[0021] Additionally, in one embodiment of the present invention, the metal element precursor solution providing the magnetic properties may include cobalt nitrate hexahydrate or nickel nitrate hexahydrate.

[0022] Additionally, in one embodiment of the present invention, the acidic aqueous solution may include at least one selected from the group consisting of glacial acetic acid, hydrochloric acid, nitric acid, and sulfuric acid.

[0023] In addition, in one embodiment of the present invention, in the step of doping nitrogen into titanium dioxide doped with a metal element providing the magnetic properties, nitrogen can be doped using an impregnation method.

[0024] In addition, in one embodiment of the present invention, a step of manufacturing a nanocomposite further including iron oxide using an impregnation method may be included after the step of doping nitrogen into titanium dioxide doped with a metal element providing the magnetic properties.

[0025] According to an embodiment of the present invention, by doping a titanium dioxide photocatalyst with a metal element that provides nitrogen and magnetic properties, the photocatalyst is activated in the visible light region to improve the decomposition efficiency of organic matter, and the magnetic properties of the photocatalyst enable easy recovery after use using an electromagnet or permanent magnet.

[0026] While the present invention focuses on wastewater treatment, the visible light-sensitive magnetic photocatalyst can be applied to a variety of fields, including sterilization, antibacterial applications, air pollution purification, and water-splitting hydrogen production. Therefore, the visible light-sensitive magnetic photocatalyst of the present invention is a material that can contribute to the development of sustainable environmental technologies and water-splitting hydrogen production.

[0027] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0028] FIG. 1 is a diagram illustrating the movement of 3d electrons in cobalt-doped titanium dioxide according to one embodiment of the present invention.

[0029] FIG. 2 shows a) a spectrum in the wavelength range of 200 to 1500 nm and b) a band gap measured using a Tauc plot of a nitrogen and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention.

[0030] FIG. 3 is a drawing comparing the band gaps of a) a conventional titanium dioxide photocatalyst and b) a nitrogen- and cobalt-doped visible light-sensitive magnetic photocatalyst according to an embodiment of the present invention.

[0031] Figure 4 is a graph showing the results of X-ray diffraction analysis of a conventional titanium dioxide photocatalyst and a nitrogen and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention.

[0032] FIG. 5 is a graph of a magnetic hysteresis curve of a nitrogen- and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention, measured using a vibrating sample magnetometer (SQUID).

[0033] Figure 6 is a graph showing the comparative results of dyeing wastewater treatment using a conventional titanium dioxide photocatalyst and a visible light-sensitive magnetic photocatalyst according to an embodiment of the present invention.

[0034] FIG. 7 is an electron microscope photograph of a nanocomposite composed of a titanium dioxide photocatalyst doped with nitrogen and cobalt and iron oxide according to one embodiment of the present invention.

[0035] Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention can be implemented in various different forms and is therefore not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar parts have been designated with similar reference numerals throughout the specification.

[0036] Throughout the specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another part in between. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that it may include other components, unless otherwise specifically stated.

[0037] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0039]

[0040] A visible light sensitive magnetic photocatalyst according to one embodiment of the present invention is described.

[0041] A visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention may include titanium dioxide doped with nitrogen and a metal element providing magnetic properties.

[0042] At this time, when the above nitrogen is doped into the titanium dioxide photocatalyst, a 2p orbital is added to the valence band, which provides the effect of reducing the band gap of the photocatalyst.

[0043] In addition, doping with a metal element that provides the above magnetic properties provides a d-orbital below the conduction band, which results in a reduction in the overall band gap.

[0044] At this time, as the metal element that provides magnetic properties is doped into titanium dioxide, the electrons (e-) of the 3d orbitals move and align the spins of the metal atoms that provide magnetic properties, so that all atoms point in the same direction, resulting in the effect of magnetic properties.

[0045] Meanwhile, the nitrogen may be 1 mol% to 6 mol% of the total mole.

[0046] At this time, if the nitrogen is less than 1 mol% based on the total mole, there may be a problem that the band gap reduction effect is weak, and if it exceeds 6 mol%, there is a problem that the performance of the TiO2 photocatalyst deteriorates. Therefore, preferably, the nitrogen may include 1 mol% to 6 mol% based on the total mole.

[0047] Meanwhile, the metal element providing the above magnetic properties may include cobalt or nickel.

[0048] At this time, the metal element providing the magnetic properties may be 2 mol% to 5 mol% based on the total mole.

[0049] At this time, if the metal element providing the magnetic properties is less than 2 mol% with respect to the total mole, not only is the band gap reduction effect not significant, but there may be a problem of poor magnetic properties, and if it exceeds 5 mol%, there is a problem of weakening the photocatalytic action of TiO2. Therefore, preferably, the metal element providing the magnetic properties may include 2 mol% to 5 mol% with respect to the total mole.

[0050] Meanwhile, titanium dioxide doped with the above-described nitrogen and metal elements providing magnetic properties has many active sites and defects that can induce dispersion of metal atoms and increase electrical conductivity, and titanium dioxide becomes magnetic due to alignment of magnetic moments caused by the presence of oxygen vacancies or other defects that can create unpaired electrons.

[0051] In addition, the presence of a metal element that provides magnetic properties as an electron donor and nitrogen as an electron acceptor induces a charge compensation effect, which significantly increases the activity of the titanium dioxide photocatalyst.

[0052] At this time, titanium dioxide doped with the metal element providing the above nitrogen and magnetic properties can be activated in the visible light range and can be used under sunlight, and has the effect of enabling the photocatalyst to be recovered after use using a permanent magnet or electromagnet by utilizing the magnetic properties of the photocatalyst.

[0053] Meanwhile, the visible light-sensitive magnetic photocatalyst may be a nanocomposite further comprising iron oxide.

[0054] At this time, since iron oxide is further included, the magnetic properties of the nanocomposite are further increased, which has the effect of making recovery using a magnet easier.

[0055]

[0056] A method for manufacturing a visible light-sensitive magnetic photocatalyst according to another embodiment of the present invention is described.

[0057] A method for manufacturing a visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention may include a step of forming titanium dioxide doped with a metal element providing magnetic properties; and a step of doping nitrogen into the titanium dioxide doped with the metal element providing magnetic properties.

[0058] At this time, the step of forming titanium dioxide doped with a metal element providing magnetic properties may include the steps of preparing a titanium oxide solution and a metal element precursor solution providing magnetic properties; mixing the titanium oxide solution, the metal element precursor solution providing magnetic properties, an acidic aqueous solution, and a solvent by stirring; and drying the mixture and then heating and cooling it to obtain titanium dioxide doped with a metal element providing magnetic properties.

[0059] The first step may include preparing a titanium oxide solution and a metal element precursor solution providing magnetic properties.

[0060] At this time, the titanium oxide solution may be prepared, for example, by adding titanium oxide to alcohol and stirring.

[0061] At this time, the titanium oxide solution may include at least one selected from the group consisting of titanium butoxide, titanium propoxide, and titanium tetraisopropoxide.

[0062] At this time, the metal element precursor solution providing the magnetic properties can be prepared by, for example, dissolving the metal element precursor providing the magnetic properties in alcohol.

[0063] At this time, the metal element precursor solution providing the magnetic properties may include cobalt nitrate hexahydrate or nickel nitrate hexahydrate.

[0064] The second step may include a step of mixing the titanium oxide solution, the metal element precursor solution providing the magnetic properties, the acidic aqueous solution, and the solvent by stirring.

[0065] At this time, the acidic aqueous solution may include at least one selected from the group consisting of glacial acetic acid, hydrochloric acid, nitric acid, and sulfuric acid.

[0066] The third step may include a step of drying the mixture and then heating and cooling it to obtain a visible light-sensitive magnetic photocatalyst.

[0067] At this time, for example, the drying temperature can be 85°C, the heating temperature can be 500°C, and the cooling temperature can be room temperature. However, the present invention discloses the above temperature as an example and is not limited thereto.

[0068] In addition, a step of nitrogen-doping the visible light-sensitive magnetic photocatalyst obtained after the cooling may be further included using an impregnation method.

[0069] At this time, as an example, the impregnation method may be a method of suspending in a urea solution, adjusting the pH using nitric acid, stirring the mixed solution, drying at high temperature, crushing the obtained product again, and then calcining it.

[0070] Meanwhile, the step of doping nitrogen into titanium dioxide doped with a metal element providing the above magnetic properties may include doping nitrogen using an impregnation method.

[0071] FIG. 1 is a diagram illustrating the movement of 3d electrons in cobalt-doped titanium dioxide according to one embodiment of the present invention.

[0072] At this time, referring to the above-described Figure 1, the cobalt-doped titanium dioxide aligns the spins of the cobalt atoms as the electrons (e-) of the 3d orbitals move, causing all the cobalt atoms to point in the same direction, thereby obtaining magnetic properties.

[0073] According to one embodiment of the present invention, a visible light-sensitive magnetic photocatalyst has magnetic properties, and thus, by developing a photocatalyst that is convenient to recover after use using a permanent magnet or electromagnet, there is no need to incur additional costs using separation membrane technology, etc., and thus, economic efficiency can be greatly increased.

[0074] Meanwhile, the method may include a step of manufacturing a nanocomposite further including iron oxide using an impregnation method after the step of doping nitrogen into titanium dioxide doped with a metal element providing the above magnetic properties.

[0075] At this time, for example, the visible light-sensitive magnetic photocatalyst and the iron oxide of the same mass can be mixed and dispersed in ethanol to produce a photocatalyst and iron oxide nanocomposite.

[0076]

[0077] Hereinafter, the present invention will be described in more detail through manufacturing examples and experimental examples. These manufacturing examples and experimental examples are intended solely to illustrate the present invention, and the scope of the present invention is not limited by these manufacturing examples and experimental examples.

[0078]

[0079] Manufacturing Example 1

[0080] A nitrogen- and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention was manufactured. First, 30 g of titanium butoxide (Ti(C4H9O]4) is added to 90 g of ethanol (99%) and stirred to mix thoroughly. Next, 0.96 g of cobalt nitrate hexahydrate (Co(NO)3·6H2O) is dissolved in 12.2 g of ethanol (99%). Next, while mixing the titanium butoxide solution and the cobalt nitrate hexahydrate solution, 6 mL of glacial acetic acid, 3 mL of 68% nitric acid, and 5 mL of deionized water are added, and the mixture is stirred for 5 hours at room temperature and pressure and then left as is for 3 days. Next, it is dried overnight in a drying oven set to 85°C, and finally, the sample is placed in a furnace and heat-treated in an air atmosphere at a temperature of 500°C for 2 hours. After that, the temperature of the furnace is cooled to room temperature, and the sample is taken out and pulverized to obtain 3 mol% of cobalt. A doped nano-sized photocatalyst is obtained.

[0081] Next, an impregnation method is used to dope the cobalt-doped nano-sized photocatalyst with nitrogen. First, 1 g of the prepared powder is suspended in a urea solution, and the pH is adjusted to 2 using nitric acid. The mixed solution is stirred for 1 hour and then dried at 100°C for 12 hours. The resulting product is then crushed again and calcined at 450°C for 3 hours. The resulting product is a visible-light-sensitive magnetic photocatalyst doped with nitrogen and cobalt, with a significantly reduced bandgap and magnetic properties.

[0082]

[0083] Manufacturing Example 2

[0084] According to one embodiment of the present invention, a visible light-sensitive magnetic photocatalyst doped with nitrogen and cobalt was prepared. 13.3 mL of titanium tetraisopropoxide was dissolved in 100 mL of propanol, and 4 mL of glacial acetic acid was added and stirred at 70 o Heat to C. Then, add 4 mL of ethylene glycol as a coolant (named as solution A).

[0085] Solution B for nitrogen doping is prepared as follows. Dissolve urea in 20 mL of deionized water to prepare a 4.7 mol% solution, and adjust the pH to 2 using 0.5 M nitric acid (solution B).

[0086] Solution C for doping cobalt is prepared by dissolving 3 mol% cobalt nitrate hexahydrate in 4 mL of deionized water and 20 mL of propanol with thorough stirring. The prepared solution C is heated in an oven at 100 o Dry overnight in C to obtain powder, and wash this powder several times with ethanol and deionized water at 450 o C for 4 hours. The obtained product is a visible light-sensitive magnetic photocatalyst with a significantly reduced band gap and magnetism, doped with nitrogen and cobalt, identical to that obtained in Manufacturing Example 1.

[0087]

[0088] Manufacturing Example 3

[0089] A nitrogen- and nickel-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention was manufactured.

[0090] First, 30 g of titanium butoxide (Ti(C4H9O]4) is added to 90 g of ethanol (99%) and stirred to mix thoroughly. Next, 0.96 g of nickel nitrate hexahydrate (Co(NO)3·6H2O) is dissolved in 12.2 g of ethanol (99%). Next, 6 mL of glacial acetic acid, 3 mL of 68% nitric acid, and 5 mL of deionized water are added while mixing the titanium butoxide solution and the nickel nitrate hexahydrate solution, and the mixture is stirred for 5 hours at room temperature and pressure and then left as is for 3 days. Next, it is dried overnight in a drying oven set to 85°C, and finally, the sample is placed in a furnace and heat-treated in an air atmosphere at a temperature of 500°C for 2 hours. After that, the furnace temperature is cooled to room temperature, and the sample is taken out and pulverized to obtain nano-sized particles doped with 3 mol% nickel. A photocatalyst of the size is obtained.

[0091] Next, an impregnation method is used to dope the nickel-doped nano-sized photocatalyst with nitrogen. First, 1 g of the prepared powder is suspended in a urea solution, and the pH is adjusted to 2 using nitric acid. The mixed solution is stirred for 1 hour and then dried at 100°C for 12 hours. The resulting product is then crushed again and calcined at 450°C for 3 hours. The resulting product is a visible-light-sensitive magnetic photocatalyst doped with nitrogen and nickel, exhibiting a reduced bandgap and magnetic properties.

[0092]

[0093] Manufacturing Example 4

[0094] A photocatalyst and iron oxide nanocomposite were prepared according to one embodiment of the present invention. Iron oxide (Fe3O4) was prepared by a chemical coprecipitation method. A mixed solution of iron trichloride hexahydrate (FeCl36H2O) and iron dichloride tetrahydrate (FeCl24H2O) was prepared and stirred at 100°C for 1 hour. o Maintain at C, then add ammonium hydroxide (NH4OH), a precipitant, to precipitate. Collect the precipitate using a centrifuge and dry it overnight.

[0095] A wet impregnation method was used to manufacture a nanocomposite composed of a visible light-sensitive magnetic photocatalyst and iron oxide according to one embodiment of the present invention manufactured in Manufacturing Examples 1 to 3. The same mass of the visible light-sensitive magnetic photocatalyst and the iron oxide were mixed and dispersed in ethanol, and then 80 o The photocatalyst and iron oxide nanocomposite were prepared by heating to C to evaporate all ethanol.

[0096] FIG. 7 is an electron microscope photograph of a nanocomposite composed of a titanium dioxide photocatalyst doped with nitrogen and cobalt and iron oxide according to one embodiment of the present invention.

[0097] Referring to the above Figure 7, it can be confirmed that the photocatalyst and iron oxide nanocomposite have a size of about 500 nm when observed with an electron microscope.

[0098]

[0099] Comparative Example 1

[0100] Titanium dioxide photocatalyst was used.

[0101]

[0102] Experimental Example 1

[0103] The characteristics of the nitrogen- and cobalt-doped visible-light-sensitive magnetic photocatalysts manufactured in Manufacturing Examples 1 and 2, the nitrogen- and nickel-doped visible-light-sensitive magnetic photocatalysts manufactured in Manufacturing Example 3, and the titanium dioxide photocatalyst of Comparative Example 1 were measured.

[0104]

[0105] FIG. 2 shows a) a spectrum in the wavelength range of 200 to 1500 nm and b) a band gap measured using a Tauc plot of a nitrogen and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention.

[0106] Referring to FIG. 2, the band gap of a visible light-sensitive magnetic photocatalyst doped with nitrogen and cobalt according to one embodiment of the present invention is measured at 5 nm intervals in a wavelength range of 200 to 1500 nm using a spectrophotometer, and when confirmed using a Tauc plot, it can be seen that the band gap of the visible light-sensitive magnetic photocatalyst doped with nitrogen and cobalt is 2.61 eV.

[0107] FIG. 3 is a drawing comparing the band gaps of a) a conventional titanium dioxide photocatalyst and b) a nitrogen- and cobalt-doped visible light-sensitive magnetic photocatalyst according to an embodiment of the present invention.

[0108] Referring to the above Figure 3, it can be seen that a) the conventional titanium dioxide photocatalyst has 3.22 eV, and b) the nitrogen and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention has 2.61 eV.

[0109] Through this, it can be seen that the band gap of titanium dioxide doped with nitrogen and cobalt is reduced by approximately 0.61 eV.

[0110] Accordingly, it can be seen that the visible light-sensitive magnetic photocatalysts doped with nitrogen and cobalt prepared in Preparation Examples 1 to 3 have better reactivity under visible light than the conventional titanium dioxide photocatalyst under sunlight.

[0111]

[0112] Figure 4 is a graph showing the results of X-ray diffraction analysis of a conventional titanium dioxide photocatalyst and a nitrogen and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention.

[0113] Referring to the above Figure 4, it can be confirmed that there is no change in the structure of titanium dioxide due to doping with nitrogen and cobalt, as the diffraction peaks unique to titanium dioxide before and after doping are the same.

[0114]

[0115] FIG. 5 is a graph of a magnetic hysteresis curve of a nitrogen- and cobalt-doped visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention, measured using a vibrating sample magnetometer (SQUID).

[0116] Referring to the above Figure 5, it can be seen that the magnetic flux density initially increases rapidly depending on the strength of the external magnetic field, then gradually increases and becomes saturated, showing a typical hysteresis curve of a ferromagnetic material.

[0117] Through this, it can be seen that the visible light-sensitive magnetic photocatalyst doped with nitrogen and cobalt according to one embodiment of the present invention has excellent magnetic properties.

[0118]

[0119] Experimental Example 2

[0120] The organic matter removal rate of wastewater was measured using the nitrogen and cobalt-doped visible light-sensitive magnetic photocatalysts manufactured in Manufacturing Examples 1 and 2, the nitrogen and nickel-doped visible light-sensitive magnetic photocatalysts manufactured in Manufacturing Example 3, and the conventional titanium dioxide photocatalyst manufactured in Comparative Example 1.

[0121] The organic matter removal reaction of the photocatalyst can be explained by the following equation.

[0122] [Chemical Formula 1]

[0123] Photocatalyst + light ->e- + h+

[0124] In the above chemical formula 1, e- and h+ represent electrons and holes, respectively.

[0125] [Chemical Formula 2]

[0126] h+ + H2O -> OH + H+

[0127] [Chemical Formula 3]

[0128] e- + O2 -> O2-

[0129] [Chemical Formula 4]

[0130] Dyemolecule + OH, O2- ->Oxidation products

[0131] As shown in the chemical formulas 2 to 4 above, electrons and holes react with water or dissolved oxygen to generate highly oxidizing hydroxyl radicals (OH) and oxygen ions, thereby removing organic matter in wastewater.

[0132] Figure 6 is a graph showing the comparative results of dyeing wastewater treatment using a conventional titanium dioxide photocatalyst and a visible light-sensitive magnetic photocatalyst according to an embodiment of the present invention.

[0133] Referring to the above Figure 6, a solution of Acid Red 4, a type of dye, was used to simulate organic matter in wastewater (concentration 20 ppm), the concentration of the photocatalyst was 0.25 g / L, the volume of the simulated wastewater was 500 mL, and the simulated wastewater was stirred by a magnetic stirrer and exposed to natural light.

[0134] C / C0 on the vertical axis of the above graph is the ratio of the arbitrary time concentration (C) and the initial concentration (C0), and can be used to check the removal rate over time.

[0135] In the graph above, it can be seen that in the case of the titanium dioxide photocatalyst doped with nitrogen and cobalt (N&Co doped) manufactured in Manufacturing Examples 1 and 2 according to one embodiment of the present invention, it took about 50 minutes for the Acid Red 4 solution to be decolored by more than 95%, and that more than 99% of the decolorization was achieved after 60 minutes.

[0136] In the graph above, it can be confirmed that in the case of the titanium dioxide photocatalyst doped with nitrogen and nickel (N&Ni doped) manufactured in Manufacturing Example 3 according to one embodiment of the present invention, the Acid Red 4 solution was decolorized by approximately 69% after 60 minutes.

[0137] In the graph above, in the case of the conventional titanium dioxide photocatalyst as a comparative example, it can be confirmed that the Acid Red 4 solution was decolorized by approximately 66% after 60 minutes.

[0138] As a result, it can be confirmed that both the nitrogen and cobalt doped titanium dioxide photocatalyst and the nitrogen and nickel doped titanium dioxide photocatalyst are more effective than the conventional titanium dioxide photocatalyst.

[0139] In addition, through Experimental Example 1, it can be confirmed that the visible light-sensitive magnetic photocatalyst, which is an example of the present invention, is activated under visible light, that is, sunlight.

[0140] Therefore, it can be seen that the visible light-sensitive magnetic photocatalyst according to one embodiment of the present invention manufactured according to Manufacturing Examples 1 to 3 is activated under sunlight, which is visible light, without additional supply of ultraviolet energy, compared to a conventional titanium dioxide photocatalyst, and exhibits high efficiency in decomposing organic matter, and has magnetic properties through doping with cobalt or nickel, which is a metal that provides magnetic properties, so that it can be easily recovered using an electromagnet or a permanent magnet.

[0141] In addition, in the case of the photocatalyst and iron oxide nanocomposite according to one embodiment of the present invention of Manufacturing Example 4, the magnetic properties are improved by adding iron oxide, so that the photocatalyst can be more easily recovered by a permanent magnet or an electromagnet.

[0142]

[0143] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0144] The scope of the present invention is indicated by the claims described below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. A visible light-sensitive magnetic photocatalyst characterized by comprising titanium dioxide doped with nitrogen and a metal element providing magnetic properties.

2. In paragraph 1, A visible light-sensitive magnetic photocatalyst characterized in that the metal element providing the above magnetic properties includes cobalt or nickel.

3. In paragraph 1, A visible light-sensitive magnetic photocatalyst characterized in that the nitrogen is 1 mol% to 6 mol% of the total mole.

4. In paragraph 1, A visible light-sensitive magnetic photocatalyst characterized in that the metal element providing the above magnetic properties is 2 mol% to 5 mol% based on the total mole.

5. In paragraph 1, A visible light-sensitive magnetic photocatalyst characterized by being a nanocomposite further containing iron oxide.

6. A method for producing a visible light-sensitive magnetic photocatalyst, characterized by comprising the steps of: forming titanium dioxide doped with a metal element providing magnetic properties; and doping nitrogen into the titanium dioxide doped with the metal element providing magnetic properties.

7. In paragraph 6, The step of forming titanium dioxide doped with a metal element providing the above magnetic properties is: A step of preparing a titanium oxide solution and a metal element precursor solution providing magnetic properties; A step of mixing the titanium oxide solution, the metal element precursor solution providing the magnetic properties, the acidic aqueous solution, and the solvent by stirring; and A method for producing a visible light-sensitive magnetic photocatalyst, characterized by comprising a step of drying the mixture and then heating and cooling the mixture to obtain titanium dioxide doped with a metal element providing magnetic properties.

8. In paragraph 7, A method for producing a visible light-sensitive magnetic photocatalyst, characterized in that the titanium oxide solution comprises at least one selected from the group consisting of titanium butoxide, titanium propoxide, and titanium tetraisopropoxide.

9. In paragraph 7, A method for producing a visible light-sensitive magnetic photocatalyst, characterized in that the metal element precursor solution providing the above magnetic properties includes cobalt nitrate hexahydrate or nickel nitrate hexahydrate.

10. In paragraph 7, A method for producing a visible light-sensitive magnetic photocatalyst, characterized in that the above acidic aqueous solution comprises at least one selected from the group consisting of glacial acetic acid, hydrochloric acid, nitric acid, and sulfuric acid.

11. In paragraph 6, A method for manufacturing a visible light-sensitive magnetic photocatalyst, characterized in that nitrogen is doped into titanium dioxide doped with a metal element providing the above magnetic properties using an impregnation method.

12. In paragraph 6, A method for producing a visible light-sensitive magnetic photocatalyst, characterized in that it comprises a step of producing a nanocomposite further including iron oxide using an impregnation method after a step of doping nitrogen into titanium dioxide doped with a metal element providing the above magnetic properties.

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