A method for preparing a high-efficiency photocatalyst and a method for enhancing Fenton flue gas denitrification using a photocatalyst.

Abstract

This invention discloses a method for preparing a high-efficiency photocatalyst and a method for enhancing Fenton flue gas denitrification using a photocatalyst, belonging to the field of photocatalytic-oxidative wet denitrification technology. First, tetrabutyl titanate is used as a Ti source, and hydrofluoric acid solution is used as a crystal facet modifier. Through a solvothermal reaction, F-TiO2 with a high (001) crystal facet is obtained. Then, sodium iodate is used as an electron sacrificial agent, cobalt salt is used as a Co precursor, and the F-TiO2 with the high (001) crystal facet is used as a support. After uniform mixing, cobalt oxide selectively loaded on the (001) crystal facet of high (001) crystal facet titanium dioxide is generated under ultraviolet light, yielding CoO. x @F-TiO2 photocatalyst. And F-TiO2 and CoO x @F-TiO2 photocatalyst is used for Fenton denitrification of flue gas. It solves the problem of excessive Fe(III) accumulation in Fenton denitrification, accelerates the iron cycle in the reaction, and improves the denitrification capacity of the Fenton reaction.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic-oxidative wet denitrification technology, and in particular to a method for preparing a high-efficiency photocatalyst and a method for enhancing Fenton flue gas denitrification using a photocatalyst. Background Technology

[0002] With rapid economic development, energy demand has been rising continuously, and the consumption of fossil fuels such as coal, oil, and natural gas has been increasing year by year. Meanwhile, the production capacity of the ceramics and non-ferrous metal smelting and processing industries has been expanding, leading to increased emissions of nitrogen oxides (NOx). x NO increased sharply x NO (the main component, accounting for 95%) is one of the major air pollutants, contributing to acid rain, smog, and photochemical smog, severely impacting human health and the natural environment. Currently, flue gas denitrification technologies can be broadly categorized into dry and wet methods. Dry denitrification primarily includes selective catalytic reduction (SCR) and selective non-catalytic reduction (SCNR) technologies. However, this technology has significant limitations. The chemical reaction requires high temperatures, but for small and medium-sized boilers and industrial boilers, the flue gas temperature is far below the required high temperatures. Furthermore, dust in the flue gas can easily poison and deactivate the precious metal catalysts in SCR technology, resulting in high investment and maintenance costs. Compared to dry denitrification, wet Fenton denitrification (Fe(II) / H2O2 and Fe(III) / H2O2) has received widespread attention due to its simple system, environmental friendliness, and lack of secondary pollution. However, during the denitrification process, the reaction rate of Fe(III) with H2O2 to generate Fe(II) is very slow, leading to a large accumulation of Fe(III). Moreover, Fe(III) readily forms iron oxide deposits, hindering the reaction.

[0003] Therefore, Fenton denitrification is often combined with other methods, such as UV Fenton denitrification. Ultraviolet light can accelerate the Fe(III) / Fe(II) cycle by photoreducing Fe(III) to Fe(II), thereby generating more ·OH and enhancing the Fenton denitrification process. However, the effective penetration distance of ultraviolet light in the liquid phase is often quite limited. In real-world industrial waste gases, the presence of particulate matter and various impurities is common, leading to incomplete absorption and utilization of ultraviolet light by the denitrification absorbent. Therefore, it is necessary to use photocatalysts to enhance the effect of ultraviolet light.

[0004] TiO2 photocatalysts are considered the best choice among heterogeneous ultraviolet catalysts due to their non-toxicity and wide applicability. Their photocatalytic activity mainly depends on the electron-hole separation capability of the photoinduced catalyst. However, existing TiO2 photocatalysts have relatively weak catalytic activity and still cannot meet the application requirements of photocatalytic wet Fenton denitrification technology. Therefore, it is essential to develop high-performance photocatalysts suitable for photocatalytic wet Fenton denitrification. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high-efficiency photocatalyst and a method for enhancing Fenton flue gas denitrification using a photocatalyst, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of the present invention is a method for preparing a high (001) crystal surface titanium dioxide photocatalyst, which uses tetrabutyl titanate (Ti(OC4H9)4) as Ti source and hydrofluoric acid (HF) solution as crystal surface modifier, and obtains F-TiO2 through solvothermal reaction, which is the high (001) crystal surface titanium dioxide photocatalyst.

[0008] This invention prepares a high (001) crystal plane F-TiO2 photocatalyst through a simple one-step solvothermal method. Compared with synthesis methods such as sol-gel method and liquid phase hydrolysis-precipitation method, it has the advantages of simple process and high synthesis efficiency. The reagents used in the preparation process are inexpensive and more suitable for large-scale production.

[0009] Furthermore, the high (001) crystal plane titanium dioxide photocatalyst has a nanosheet structure.

[0010] Furthermore, the preparation method of the high (001) crystal plane titanium dioxide photocatalyst specifically includes the following steps:

[0011] Tetrabutyl titanate and hydrofluoric acid solution are mixed to obtain a precursor solution; the precursor solution is heated to carry out a solvothermal reaction to obtain the high (001) crystal plane titanium dioxide photocatalyst.

[0012] Furthermore, the concentration of the hydrofluoric acid solution is 40 wt%; the volume ratio of the tetrabutyl titanate to the hydrofluoric acid solution is 80:12.8; and the temperature of the solvothermal reaction is 200°C, and the time is 12-24 h.

[0013] Furthermore, the preparation method of the high (001) crystal plane titanium dioxide photocatalyst includes the following more specific steps:

[0014] Under magnetic stirring, 12.8 mL of 40 wt% HF solution was added dropwise to 80 mL of Ti(OC4H9)4, and the mixture was stirred continuously until the solution was homogeneous to obtain the precursor solution.

[0015] The precursor solution was poured into a 220 mL polytetrafluoroethylene reactor, the reactor was sealed and placed in an oven, and the reaction was carried out at 200 °C for 12-24 h using a solvothermal method.

[0016] After the solvothermal reaction was completed, the reaction product was cleaned with deionized water and ethanol, dried at 60°C for 12 h to obtain the high (001) crystal surface titanium dioxide photocatalyst (F-TiO2), which was then ground into powder and collected for storage.

[0017] The second technical solution of the present invention: a high (001) crystal plane titanium dioxide photocatalyst prepared by the above preparation method.

[0018] The third technical solution of the present invention: A method for preparing a high-efficiency photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide, using sodium iodate (NaIO3) as an electron sacrificial agent, cobalt salt as a Co precursor, and the above-mentioned high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) as a support. After uniform mixing, cobalt oxide selectively loaded onto the (001) crystal plane of high (001) crystal plane titanium dioxide is generated under ultraviolet light, thus obtaining CoO. x @F-TiO2 photocatalyst is the highly efficient photocatalyst.

[0019] Furthermore, the method for preparing a high-efficiency photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide specifically includes the following steps:

[0020] Sodium iodate solution, cobalt salt, and high (001) crystal plane titanium dioxide photocatalyst were mixed evenly, nitrogen gas was introduced, and the mixture was sealed. The sealed mixture was placed in the dark and stirred continuously for 50 min. Then, it was irradiated with ultraviolet light for 1-5 h to carry out a selective photodeposition reaction (a reaction that generates cobalt oxide selectively loaded on the (001) crystal plane of high (001) crystal plane titanium dioxide) to obtain CoO. x @F-TiO2 photocatalyst is the highly efficient photocatalyst.

[0021] Further, the concentration of the sodium iodate solution is 0.1 mol / L; the cobalt salt is CoCl2·2H2O; and the ratio of the sodium iodate solution, cobalt salt, and high (001) crystal surface titanium dioxide photocatalyst is 500 mL: 0.016-0.800 g: 1.0-5.0 g.

[0022] Furthermore, the nitrogen gas is introduced for 10 minutes.

[0023] Furthermore, the wavelength of the ultraviolet light is 254nm and the intensity is 30W.

[0024] Furthermore, the method for preparing a high-efficiency photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide includes the following more specific steps:

[0025] Take 500 mL of 0.1 mol / L NaIO3 solution and place it in a quartz photocatalytic reaction flask. Add 0.016-0.800 g of CoCl2·2H2O under magnetic stirring. After mixing evenly, add 1.0-5.0 g of the above-mentioned high (001) crystal facet titanium dioxide photocatalyst (F-TiO2). Stir and purge with nitrogen gas for 10 min. Seal and maintain an oxygen-free condition.

[0026] After sealing the mixture, place it in the dark and stir continuously for 50 minutes (to allow the ion adsorption on the catalyst surface to reach equilibrium). Then, irradiate it with a 30W 254nm wavelength ultraviolet lamp for 1-5 hours while stirring to carry out a selective photodeposition reaction (to generate cobalt oxide selectively loaded on the (001) crystal plane of high (001) crystal plane titanium dioxide).

[0027] After the selective photodeposition reaction was completed, the mixture was allowed to stand for 30 min, the bottom precipitate was collected, washed with ethanol and deionized water, and dried under vacuum at 60 °C for 10 h to obtain CoO. x @F-TiO2 photocatalyst, and the dried product was ground into powder and collected for storage.

[0028] The fourth technical solution of the present invention: a high-efficiency photocatalyst prepared according to the above method.

[0029] Fifth technical solution of the present invention: the above-mentioned high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) or the above-mentioned high efficiency photocatalyst (CoO2) x Application of @F-TiO2 in photocatalytic enhancement of Fenton flue gas denitrification.

[0030] The sixth technical solution of the present invention: a method for enhancing Fenton flue gas denitrification using a photocatalyst, comprising the following steps:

[0031] The photocatalyst was dispersed in a Fenton solution and then introduced into the flue gas containing nitric oxide. Flue gas denitrification was then completed under ultraviolet light irradiation. The photocatalyst was either the aforementioned high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) or the aforementioned high-efficiency photocatalyst (CoO2). x @F-TiO2).

[0032] Further, the Fenton solution is a mixed solution of Fe(III) and hydrogen peroxide, wherein the concentration of Fe(III) in the Fenton solution is 5-7 mmol / L and the concentration of hydrogen peroxide is 5-6 wt%; the concentration of NO in the flue gas is 500-700 ppm and the concentration of oxygen is 2-4 wt%; and the dispersion concentration of the photocatalyst in the Fenton solution is 0.05-0.15 g / 50 mL.

[0033] More preferably, the concentration of Fe(III) in the Fenton solution is 6 mmol / L, and the concentration of hydrogen peroxide is 5.5 wt%; the concentration of NO in the flue gas is 600 ppm, and the concentration of oxygen is 3 wt%; the dispersion concentration of the photocatalyst in the Fenton solution is 0.1 g / 50 mL.

[0034] Furthermore, the pH of the Fenton solution is 3.0, and the temperature is 25°C (i.e., the temperature of the flue gas denitrification reaction is 25°C).

[0035] Furthermore, the airflow rate of the flue gas is 0.3 L / min.

[0036] Furthermore, the ultraviolet lamp has an irradiation power of 30W and an irradiation wavelength of 254nm.

[0037] To address the slow Fe(III) / Fe(II) cycle during Fenton flue gas denitrification, this invention synthesizes a high (001) crystal surface titanium dioxide photocatalyst (F-TiO2) and a high-efficiency photocatalyst (CoO2) through crystal plane engineering and selective photodeposition. x @F-TiO2) and combined with Fenton are applied to wet flue gas denitrification. Specifically, this invention first uses crystal plane engineering to expose more (001) crystal planes in TiO2, causing electrons and holes to migrate to the (101) and (001) planes respectively, thereby improving the electron and hole separation efficiency and obtaining a high (001) crystal plane titanium dioxide photocatalyst F-TiO2 with improved photocatalytic activity. Then, cobalt oxide is selectively photodeposited onto the (001) crystal plane of the high (001) crystal plane titanium dioxide to form a heterojunction, further promoting the separation of photoinduced charge carriers and increasing the catalyst active sites, thereby improving the photocatalytic activity and obtaining a highly efficient photocatalyst CoO with further improved photocatalytic activity. x @F-TiO2. This invention involves preparing high (001) crystal plane titanium dioxide F-TiO2, and then selectively depositing cobalt oxide on the (001) surface of F-TiO2 to synthesize the photocatalyst CoO. x @F-TiO2 improves the separation efficiency of photoinduced charge carriers and enhances its UV-catalyzed Fenton activity. This strategy can effectively solve the problem of slow Fe(III) / Fe(II) cycling in Fenton wet denitrification.

[0038] The present invention discloses the following technical effects:

[0039] (1) This invention achieves crystal plane separation by fluorination regulation of TiO2 photocatalyst and selectively increases the proportion of (001) crystal plane, promotes the separation and transfer of photogenerated electrons and holes, and enhances photocatalytic activity, thus obtaining high (001) crystal plane titanium dioxide photocatalyst F-TiO2 with improved photocatalytic activity.

[0040] (2) This invention selectively photodeposits cobalt oxide onto the (001) crystal plane of high (001) crystal titanium dioxide to form a heterojunction, further achieving electron-hole separation and increasing the active sites of the catalyst, thereby improving photocatalytic activity and obtaining a highly efficient photocatalyst CoO with further improved photocatalytic activity. x @F-TiO2.

[0041] (3) This invention provides a method for enhancing Fenton denitrification using a photocatalyst, wherein the photocatalyst is F-TiO2 or CoO2. x @F-TiO2 can accelerate the Fe(III) / Fe(II) cycle, improve Fenton efficiency, and enhance NO capture capacity to achieve efficient denitrification. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 CoO prepared in Example 2 of the present invention x A schematic diagram of the synthesis route for preparing the F-TiO2 photocatalyst in Example 1;

[0044] Figure 2 CoO prepared in Example 2 x The morphology characterization results of the @F-TiO2 photocatalyst are shown in (a) SEM image, (b) HR-TEM image, and (c) and (d) EDS images.

[0045] Figure 3 CoO prepared in Example 2 x X-ray diffraction pattern (a) and Raman spectrum (b) of F-TiO2 photocatalyst, F-TiO2 photocatalyst prepared in Example 1 and TiO2 photocatalyst prepared in Comparative Example 1;

[0046] Figure 4 CoO prepared in Example 2 x XPS full spectrum of F-TiO2 photocatalyst and F-TiO2 photocatalyst prepared in Example 1;

[0047] Figure 5 CoO prepared in Example 2 x@Comparison of photocurrent response (a), photoluminescence spectrum (b), and AC impedance (c) of F-TiO2 photocatalyst, F-TiO2 photocatalyst prepared in Example 1, and TiO2 photocatalyst prepared in Comparative Example 1;

[0048] Figure 6 This diagram shows the process equipment used in the flue gas denitrification experiment. 1-NO cylinder; 2-N2 (or Ar) cylinder; 3-O2 cylinder; 4-Gas valve; 5-Mass flow meter; 6-Gas mixing tank; 7-Glass rotor flow meter; 8-Reaction flask; 9-Ultraviolet lamp; 10-Water bath; 11-Tail gas absorption device; 12-Flue gas analyzer.

[0049] Figure 7 The reactions are: Fe(III) + H₂O₂, UV + Fe(III) + H₂O₂, UV + TiO₂ photocatalyst prepared in Comparative Example 1 + Fe(III) + H₂O₂, UV + F-TiO₂ photocatalyst prepared in Example 1 + Fe(III) + H₂O₂, UV + CoO₂ prepared in Example 2. x Denitrification effect under five modes: @F-TiO2 photocatalyst + Fe(III) + H2O2. Detailed Implementation

[0050] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0051] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0052] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0053] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] This invention provides a method for preparing a high (001) crystal facet titanium dioxide photocatalyst. Tetrabutyl titanate (Ti(OC4H9)4) is used as the Ti source, and hydrofluoric acid (HF) solution is used as the crystal facet modifier. Through a solvothermal reaction, F-TiO2 is obtained, which is the high (001) crystal facet titanium dioxide photocatalyst. The preparation method modifies the TiO2 photocatalyst by fluorination, changing its crystal structure to anatase, and controlling the coexistence of (001) and (010) crystal faces, with the (001) crystal facet ratio controlled at approximately 80%. These methods promote the separation and transfer of photogenerated electrons and holes, enhance photocatalytic activity, improve the iron cycle efficiency in the Fenton process, and thus enhance the Fenton denitrification effect.

[0056] This invention prepares a high (001) crystal plane F-TiO2 photocatalyst through a simple one-step solvothermal method. Compared with synthesis methods such as sol-gel method and liquid phase hydrolysis-precipitation method, it has the advantages of simple process and high synthesis efficiency. The reagents used in the preparation process are inexpensive and more suitable for large-scale production.

[0057] As a specific embodiment of the present invention, the preparation method of the high (001) crystal plane titanium dioxide photocatalyst specifically includes the following steps:

[0058] Tetrabutyl titanate and hydrofluoric acid solution are mixed to obtain a precursor solution; the precursor solution is heated to carry out a solvothermal reaction to obtain the high (001) crystal plane titanium dioxide photocatalyst.

[0059] In a preferred embodiment of the present invention, the concentration of the hydrofluoric acid solution is 40 wt%; the volume ratio of the tetrabutyl titanate to the hydrofluoric acid solution is 80:12.8.

[0060] In a preferred embodiment of the present invention, the solvothermal reaction is carried out at a temperature of 200°C for 12-24 hours. The reaction temperature plays a crucial role in controlling the thickness and size of the TiO2 nanosheets. If the reaction temperature is too high, the TiO2 nanosheets become larger and thicker; if the reaction temperature is too low, the TiO2 nanosheets become small and thin, resulting in insufficient exposure of the (001) crystal facets, both of which reduce photocatalytic performance. The optimal reaction condition for obtaining the maximum percentage of (001) crystal facets is 200°C, with the prepared nanosheets having an 80% (001) crystal facet ratio.

[0061] As a preferred embodiment of the present invention, the preparation method of the high (001) crystal plane titanium dioxide photocatalyst includes the following more specific steps:

[0062] Under magnetic stirring, 12.8 mL of 40 wt% HF solution was added dropwise to 80 mL of Ti(OC4H9)4, and the mixture was stirred continuously until the solution was homogeneous to obtain the precursor solution.

[0063] The precursor solution was poured into a 220 mL polytetrafluoroethylene reactor, the reactor was sealed and placed in an oven, and the reaction was carried out at 200 °C for 12-24 h using a solvothermal method.

[0064] After the solvothermal reaction was completed, the reaction product was cleaned with deionized water and ethanol, dried at 60°C for 12 h to obtain the high (001) crystal surface titanium dioxide photocatalyst (F-TiO2), which was then ground into powder and collected for storage.

[0065] The present invention also provides a high (001) crystal plane titanium dioxide photocatalyst prepared by the above preparation method.

[0066] This invention also provides a method for preparing a highly efficient photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide. Sodium iodate (NaIO3) is used as an electron sacrificial agent, cobalt salt as a Co precursor, and the aforementioned high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) is used as a support. After uniform mixing, cobalt oxide is selectively loaded onto the (001) crystal plane of high (001) crystal plane titanium dioxide under ultraviolet light, yielding CoO. x @F-TiO2 photocatalyst is the highly efficient photocatalyst.

[0067] As a specific embodiment of the present invention, the method for preparing a high-efficiency photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide specifically includes the following steps:

[0068] Sodium iodate solution, cobalt salt, and high (001) crystal plane titanium dioxide photocatalyst were mixed evenly, nitrogen gas was introduced, and the mixture was sealed. The sealed mixture was placed in the dark and stirred continuously for 50 min. Then, it was irradiated with ultraviolet light for 1-5 h to carry out a selective photodeposition reaction (a reaction that generates cobalt oxide selectively loaded on the (001) crystal plane of high (001) crystal plane titanium dioxide) to obtain CoO. x @F-TiO2 photocatalyst is the highly efficient photocatalyst.

[0069] Loading cobalt oxide onto the (001) crystal plane utilizes the high entropy function of cobalt, which provides excellent catalytic performance. Simultaneously, the introduction of cobalt oxide forms a heterojunction on the (001) crystal plane, allowing photogenerated holes to further accumulate near the cobalt oxide, thus enhancing the catalytic performance of the active sites. This also improves the separation performance of photogenerated electrons and holes and inhibits electron-hole recombination.

[0070] In a preferred embodiment of the present invention, the concentration of the sodium iodate solution is 0.1 mol / L; the cobalt salt is CoCl2·2H2O; and the ratio of the sodium iodate solution, cobalt salt and high (001) crystal surface titanium dioxide photocatalyst is 500 mL: 0.016-0.800 g: 1.0-5.0 g.

[0071] In a preferred embodiment of the present invention, the nitrogen gas is introduced for 10 minutes.

[0072] In a preferred embodiment of the present invention, the wavelength of the ultraviolet light is 254nm and the intensity is 30W.

[0073] As a preferred embodiment of the present invention, the method for preparing a high-efficiency photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide comprises the following steps:

[0074] Take 500 mL of 0.1 mol / L NaIO3 solution and place it in a quartz photocatalytic reaction flask. Add 0.016-0.800 g of CoCl2·2H2O under magnetic stirring. After mixing evenly, add 1.0-5.0 g of the above-mentioned high (001) crystal facet titanium dioxide photocatalyst (F-TiO2). Stir and purge with nitrogen gas for 10 min. Seal and maintain an oxygen-free condition.

[0075] After sealing the mixture, place it in the dark and stir continuously for 50 minutes (to allow the ion adsorption on the catalyst surface to reach equilibrium). Then, irradiate it with a 30W 254nm wavelength ultraviolet lamp for 1-5 hours while stirring to carry out a selective photodeposition reaction (to generate cobalt oxide selectively loaded on the (001) crystal plane of high (001) crystal plane titanium dioxide).

[0076] After the selective photodeposition reaction was completed, the mixture was allowed to stand for 30 min, the bottom precipitate was collected, washed with ethanol and deionized water, and dried under vacuum at 60 °C for 10 h to obtain CoO. x @F-TiO2 photocatalyst, and the dried product was ground into powder and collected for storage.

[0077] The present invention also provides a highly efficient photocatalyst prepared according to the above method.

[0078] This invention also provides the above-mentioned high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) or the above-mentioned high efficiency photocatalyst (CoO2). x Application of @F-TiO2 in photocatalytic enhancement of Fenton flue gas denitrification.

[0079] The present invention also provides a method for enhancing Fenton flue gas denitrification using a photocatalyst, comprising the following steps:

[0080] The photocatalyst was dispersed in a Fenton solution and then introduced into the flue gas containing nitric oxide. Flue gas denitrification was then completed under ultraviolet light irradiation. The photocatalyst was either the aforementioned high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) or the aforementioned high-efficiency photocatalyst (CoO2). x @F-TiO2).

[0081] In a preferred embodiment of the present invention, the Fenton solution is a mixed solution of Fe(III) and hydrogen peroxide, wherein the concentration of Fe(III) in the Fenton solution is 5-7 mmol / L and the concentration of hydrogen peroxide is 5-6 wt%; the concentration of NO in the flue gas is 500-700 ppm and the concentration of oxygen is 2-4 wt%; and the dispersion concentration of the photocatalyst in the Fenton solution is 0.05-0.15 g / 50 mL.

[0082] In a more preferred embodiment of the present invention, the concentration of Fe(III) in the Fenton solution is 6 mmol / L and the concentration of hydrogen peroxide is 5.5 wt%; the concentration of NO in the flue gas is 600 ppm and the concentration of oxygen is 3 wt%; and the dispersion concentration of the photocatalyst in the Fenton solution is 0.1 g / 50 mL.

[0083] In a preferred embodiment of the present invention, the pH of the Fenton solution is 3.0 and the temperature is 25°C (i.e., the temperature of the flue gas denitrification reaction is 25°C).

[0084] In a preferred embodiment of the present invention, the flue gas flow rate is 0.3 L / min.

[0085] In a preferred embodiment of the present invention, the ultraviolet lamp has an irradiation power of 30W and an irradiation wavelength of 254nm.

[0086] The technical solution of the present invention will be further described below through specific embodiments.

[0087] Unless otherwise specified, the experimental methods used in the specific embodiments of this invention are conventional methods. Unless otherwise specified, the materials, reagents, and instruments used are all conventional materials, reagents, and instruments in the art, and can be purchased commercially by those skilled in the art.

[0088] Example 1

[0089] The preparation steps of a high (001) crystal plane titanium dioxide photocatalyst (F-TiO2) are as follows (synthetic route schematic diagram is shown in the figure). Figure 1 As shown):

[0090] Under magnetic stirring, 12.8 mL of 40 wt% HF solution was added dropwise to 80 mL of Ti(OC4H9)4, and the mixture was stirred continuously until the solution was homogeneous (stirring time was 15 min) to obtain the precursor solution.

[0091] The precursor solution was poured into a 220 mL polytetrafluoroethylene reactor, the reactor was sealed and placed in an oven, and the reaction was carried out at 200 °C for 24 h in a solvothermal manner.

[0092] After the solvothermal reaction was completed, the reaction product was cleaned with deionized water and ethanol, dried at 60°C for 12 h to obtain high (001) crystal surface titanium dioxide photocatalyst (F-TiO2), which was then ground into powder and collected for storage.

[0093] Comparative Example 1

[0094] Preparation of ordinary TiO2:

[0095] Same as Example 1, except that the amount of 40wt% HF solution used is 0 mL, that is, TiO2 is not modified with fluorine. The specific preparation method is as follows:

[0096] Under magnetic stirring, 12.8 mL of deionized water was added dropwise to 80 mL of Ti(OC4H9)4 and stirred continuously until the solution was homogeneous to obtain the precursor solution.

[0097] The precursor solution was poured into a 220 mL polytetrafluoroethylene reactor, the reactor was sealed and placed in an oven, and the reaction was carried out at 200 °C for 24 h in a solvothermal manner.

[0098] After the solvothermal reaction was completed, the reaction product was washed with deionized water and ethanol, dried at 60°C for 12 hours to obtain TiO2 photocatalyst, which was then ground into powder and collected for storage.

[0099] Example 2

[0100] Highly efficient photocatalyst (CoO) xThe preparation of @F-TiO2 is as follows (synthetic route diagram is shown in the figure). Figure 1 As shown):

[0101] Take 500 mL of 0.1 mol / L NaIO3 solution and place it in a quartz photocatalytic reaction flask. Add 0.016 g of CoCl2·2H2O under magnetic stirring. After mixing evenly, add 2.0 g of F-TiO2 prepared in Example 1. Stir and purge with nitrogen gas for 10 min. Seal and maintain an oxygen-free condition.

[0102] The sealed mixture was placed in the dark and stirred continuously for 50 minutes to allow the ion adsorption on the F-TiO2 surface to reach equilibrium. Then, it was irradiated with a 30W 254nm wavelength ultraviolet lamp for 3 hours while stirring to carry out a selective photodeposition reaction (a reaction that generates cobalt oxide selectively loaded on the (001) crystal plane of high (001) crystal plane titanium dioxide).

[0103] After the selective photodeposition reaction was completed, the mixture was allowed to stand for 30 min, the bottom precipitate was collected, washed with ethanol and deionized water, and dried under vacuum at 60 °C for 10 h to obtain CoO. x @F-TiO2 photocatalyst, and the dried product was ground into powder and collected for storage.

[0104] Performance testing

[0105] I. Catalyst Characterization Tests

[0106] 1. Morphological characteristics

[0107] Figure 2 CoO prepared in Example 2 x The morphology characterization results of the @F-TiO2 photocatalyst are as follows: First, the CoO2 prepared in Example 2... x @F-TiO2 was subjected to SEM testing, and the SEM images are shown below. Figure 2 (a) indicates that the synthesized catalyst has a top-removed octahedral structure with a diameter of approximately 100 nm and a thickness of approximately 10 nm. It was then subjected to TEM testing, and high-resolution TEM (HR-TEM) images were obtained. Figure 2 (b) Directly shown, the lattice spacing parallel to the top and bottom facets is approximately 0.232 nm, corresponding to the (001) plane of anatase TiO2. Based on the above structural information, the CoO... x The (001) crystal plane of @F-TiO2 accounts for approximately 80%. Furthermore, EDS mapping was used to investigate the CoO... x Elemental composition and distribution of @F-TiO2 photocatalyst, EDS image ( Figure 2Figures (c) and (d) show the presence of Ti, Co, O, and F signals in the samples, indicating that cobalt oxide has been successfully loaded onto the TiO2 surface. Moreover, as shown in Figures (c) and (d), the Co element bright spots are not uniformly distributed on the TiO2 nanosheet surface, but rather exhibit distinct sparse and dense distributions, mostly in a linear pattern. This indirectly suggests that cobalt oxide tends to selectively deposit on the (001) crystal plane of the TiO2 nanosheets.

[0108] 2. Crystal structure

[0109] CoO prepared in Example 2 x XRD and Raman tests were performed on F-TiO2, F-TiO2 prepared in Example 1, and TiO2 prepared in Comparative Example 1. The results are as follows: Figure 3 As shown, (a) is the XRD image and (b) is the Raman image. As the XRD image shows, strong diffraction peaks 2θ appear at 25.29°, 37.81°, 40.05°, 53.89°, 55.06°, and 62.69°, corresponding to the (101), (004), (200), (105), (211), and (204) crystal planes of tetragonal anatase TiO2 (JCPDS No. 21-1272), respectively. Furthermore, compared to pure TiO2, F-TiO2 and CoO... x The intensity of the (004) diffraction peak of @F-TiO2 decreased, and its full width at half maximum (FWHM) broadened, indicating that the thickness of the TiO2 nanosheets along the (001) crystal axis decreased. Furthermore, the intensity of the (200) peak of both nanosheets increased, and their FWHM narrowed, indicating that the edge length of the TiO2 nanosheets along the (100) crystal axis increased. Therefore, based on the XRD characterization results, it can be concluded that F-TiO2 and CoO2... x @F-TiO2 exposes more (001) crystal planes. Raman images show that, compared to pure TiO2, F-TiO2 and CoO2... x @F-TiO2's 144 and 636cm -1 E at the location g The peak intensity decreased, while at 394 cm⁻¹ -1 B 1g Peak and 514cm -1 Location A 1g The higher the peak intensity, the higher the percentage of (001) crystal plane exposure, and the higher the E value in the Raman spectrum. g The peak intensity decreases, A 1g and B 1g The peak intensity increases. Therefore, the Raman spectroscopy results further illustrate the effects of F-TiO2 and CoO2. x @F-TiO2 is rich in a high proportion of (001) crystal planes.

[0110] 3. Surface characteristics

[0111] XPS analysis was performed on the CoO prepared in Example 2. x The surface electronic states of F-TiO2 and F-TiO2 prepared in Example 1 are shown in the following results. Figure 4 As shown. Figure 4 The peaks at 779.9 eV and 796.5 eV belong to Co 2p, respectively. 3 / 2 and Co 2p 1 / 2 Characteristic peaks. The spin-orbit splitting value of Co2p is 16.6 eV, indicating that the oxidation state of Co in the photocatalyst is +2 or +3. The selectively deposited cobalt oxide can be labeled as CoO. x The characteristic peaks at 458.08 eV and 463.96 eV correspond to CoO. x Ti 2p in the @F-TiO2 structure 3 / 2 and Ti 2p 1 / 2 The peaks are typical Ti-O peaks in TiO2; and compared to undeposited F-TiO2, the CoO... x The shift of the @F-TiO2Ti 2p peak to the high binding energy region is attributed to CoO. x @F-TiO2 during the preparation process, TiO2 and CoO x A heterojunction effect is formed between them. The peaks at 529.1 eV and 529.5 eV are related to lattice oxygen (Co-O) and surface adsorbed -OH (Co-OH), respectively.

[0112] 4. Photoelectric performance testing

[0113] The CoO2 prepared in Example 2 was tested using an electrochemical workstation. x The photocurrent responses of @F-TiO2, F-TiO2 prepared in Example 1, and TiO2 prepared in Comparative Example 1 are as follows: Figure 5 As shown in (a), it can be seen that compared to pure TiO2 and F-TiO2 with high (001) crystal plane constructed by crystal plane engineering, CoO x @F-TiO2 exhibits higher photocurrent density, demonstrating better electron-hole separation efficiency; the CoO2 prepared in Example 2 was tested using a fluorescence spectrophotometer. x The photoluminescence (PL) properties of F-TiO2, F-TiO2 prepared in Example 1, and TiO2 prepared in Comparative Example 1 are shown in the following results. Figure 5 As shown in (b), it can be seen that CoO x The photoluminescence intensity (PL) of @F-TiO2 is much weaker than that of F-TiO2 and TiO2, indicating that crystal plane engineering and surface heterostructure construction can effectively suppress photoinduced electron-hole recombination. The CoO2 prepared in Example 2 was tested using an electrochemical workstation. xThe electrochemical impedance spectroscopy (EIS) spectra of F-TiO2, F-TiO2 prepared in Example 1, and TiO2 prepared in Comparative Example 1 are shown below. Figure 5 As shown in (c), it can be seen that compared to pure TiO2 and F-TiO2 with high (001) crystal plane constructed by crystal plane engineering, CoO x The @F-TiO2 catalyst surface exhibits a higher electron migration rate, which can demonstrate better hole and electron separation efficiency.

[0114] II. Flue Gas Denitrification Experiment

[0115] The process diagram of the equipment used in the flue gas denitrification experiment is shown below. Figure 6 The system comprises: 1-NO cylinder; 2-N2 (or Ar) cylinder; 3-Air cylinder; 4-Gas valve; 5-Mass flow meter; 6-Gas mixing tank; 7-Glass rotor flow meter; 8-Reaction flask; 9-UV lamp; 10-Water bath; 11-Tail gas absorption device; 12-Flue gas analyzer. The absorption device mainly consists of three parts: a waste simulation device, a photocatalytic reactor, and a gas absorption and detection device. The gas device includes N2 (or Ar), air, and NO gas cylinders. The photocatalytic reactor mainly consists of a 500mL quartz absorption bottle immersed in a water bath, with a fully submersible UV lamp inserted into the bottle. The temperature of the entire system is controlled by the water bath. The gas detection device is primarily a Testo 330-2 flue gas analyzer.

[0116] (1) UV (ultraviolet light) + CoO prepared in Example 2 x @F-TiO2 photocatalyst + Fe(III) + H2O2

[0117] First, 208 mL of deionized water and 0.725 g of ferric ammonium sulfate dodecahydrate (NH4Fe(SO4)2·12H2O) were added to a quartz reaction flask to obtain a Fe(III) solution. Then, under magnetic stirring, 0.5 g of CoO prepared in Example 2 was added. x@F-TiO2 photocatalyst, uniformly dispersed. Then, simulated flue gas was introduced at a flow rate of 0.3 L / min and a NO concentration of 500 ppm. Air was introduced to mix with the NO (i.e., air was used as the equilibrium gas) to prepare a mixed gas with an O2 concentration of 3 wt% and a NO concentration of 500 ppm as the simulated flue gas (by adjusting the ratio of NO to air flow rate, simulated flue gas with different concentrations of NO and O2 was obtained; if the reaction under anaerobic conditions is to be compared, N2 (or Ar) was introduced to create an anaerobic environment). At the start of the reaction, 42 mL of 30 wt% H2O2 (208 mL deionized water + 0.725 g ferric ammonium sulfate dodecahydrate + 42 mL 30 wt% H2O2 constituted Fenton solution, with the pH of Fenton solution adjusted to 3.0) was added to the Fe(III) solution. Simultaneously, the quartz reaction flask was immersed in a 25°C water bath, and a fully submersible UV lamp (wavelength 254 nm, power 30 W) was inserted into the quartz glass reaction flask and turned on. The temperature of the entire system was controlled by the water bath (±0.1°C). The NO concentration in the outlet gas was measured every 3 minutes using a flue gas analyzer, and the NO removal efficiency η was calculated according to formula (1).

[0118]

[0119] Where η is the NO removal efficiency, % and C in NO inlet concentration, ppm; C out NO outlet concentration, ppm.

[0120] CoO x The denitrification effect of @F-TiO2 photocatalyst enhanced by photo-Fenton denitrification is shown in [link to documentation]. Figure 7 .

[0121] (2) UV + F-TiO2 photocatalyst prepared in Example 1 + Fe(III) + H2O2

[0122] The experimental procedure was the same as in (1), except that 0.5g of the CoO prepared in Example 2 was used. x The F-TiO2 photocatalyst was replaced with 0.5g of the F-TiO2 photocatalyst prepared in Example 1.

[0123] The denitrification effect of F-TiO2 photocatalyst enhanced by Fenton denitrification is shown in [reference needed]. Figure 7 .

[0124] (3) UV + TiO2 photocatalyst prepared in Comparative Example 1 + Fe(III) + H2O2

[0125] The experimental procedure was the same as in (1), except that 0.5g of the CoO prepared in Example 2 was used. xThe @F-TiO2 photocatalyst was replaced with 0.5g of the TiO2 photocatalyst prepared in Comparative Example 1.

[0126] The denitrification effect of TiO2 photocatalyst enhanced by Fenton denitrification is shown in [reference needed]. Figure 7 .

[0127] (4) UV + Fe(III) + H2O2

[0128] The experimental procedure is the same as (1), except that no photocatalyst is added.

[0129] The denitrification effect of Guangfenton denitrification is shown in the figure. Figure 7 .

[0130] (5) Fe(III) + H₂O₂

[0131] The experimental procedure is the same as (1), except that no photocatalyst is added and no UV light is applied.

[0132] The denitrification effect of Fenton denitrification is shown in the figure. Figure 7 .

[0133] Depend on Figure 7 It can be seen that Fe(III) + H2O2, UV + Fe(III) + H2O2, UV + TiO2 photocatalyst prepared in Comparative Example 1 + Fe(III) + H2O2, UV + F-TiO2 photocatalyst prepared in Example 1 + Fe(III) + H2O2, UV + CoO2 prepared in Example 2 x The NO absorption rates after 30 min under the five modes of @F-TiO2 photocatalyst + Fe(III) + H2O2 were 48.71%, 56.1%, 60.40%, 75.79%, and 81.23%, respectively. This result demonstrates that the introduction of ultraviolet light can significantly improve the Fenton denitrification effect. Furthermore, the addition of the photocatalyst can further enhance the denitrification effect of Fe(III) / H2O2 photo-Fenton, and the addition of CoO2 prepared in Example 2 further improves the effect. x @F-TiO2 photocatalyst provides the best enhancement effect, therefore, CoO x @F-TiO2 photocatalyst can be used as a photocatalyst with good catalytic Fenton denitrification effect.

[0134] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a high-efficiency photocatalyst by selectively photodepositing cobalt oxide onto high (001) crystal plane titanium dioxide, characterized in that, Using sodium iodate as an electron sacrificial agent, cobalt salt as a Co precursor, and high (001) crystal plane titanium dioxide photocatalyst as a support, after uniform mixing, cobalt oxide selectively supported on the (001) crystal plane of high (001) crystal plane titanium dioxide is generated under ultraviolet light, yielding CoO. x @F-TiO2 photocatalyst, which is the aforementioned high-efficiency photocatalyst; The method specifically includes the following steps: Sodium iodate solution, cobalt salt, and high (001) crystal plane titanium dioxide photocatalyst were mixed thoroughly, nitrogen gas was introduced, and the mixture was sealed. The sealed mixture was placed in the dark and stirred continuously for 50 min. Then, it was irradiated with ultraviolet light for 1-5 h to perform a selective photodeposition reaction, yielding CoO. x @F-TiO2 photocatalyst, which is the aforementioned high-efficiency photocatalyst; The concentration of the sodium iodate solution is 0.1 mol / L; the cobalt salt is CoCl2·2H2O; the ratio of sodium iodate solution, cobalt salt and high (001) crystal surface titanium dioxide photocatalyst is 500 mL:0.016-0.800 g:2.00 g, and the amount of cobalt salt is not 0. The preparation steps of the high (001) crystal plane titanium dioxide photocatalyst include: Using tetrabutyl titanate as the Ti source and hydrofluoric acid solution as the crystal surface modifier, F-TiO2 was obtained through a solvothermal reaction, which is the high (001) crystal surface titanium dioxide photocatalyst. The concentration of the hydrofluoric acid solution is 40 wt%; the volume ratio of the tetrabutyl titanate to the hydrofluoric acid solution is 80:12.8; the temperature of the solvothermal reaction is 200 °C, and the time is 12-24 h.

2. A highly efficient photocatalyst prepared according to the method of claim 1.

3. The application of the high-efficiency photocatalyst as described in claim 2 in photocatalytically enhanced Fenton flue gas denitrification.

4. A method for enhancing Fenton flue gas denitrification using a photocatalyst, characterized in that, Includes the following steps: The photocatalyst is dispersed in a Fenton solution and then introduced into flue gas containing nitric oxide. The flue gas denitrification is completed under ultraviolet light irradiation. The photocatalyst is the high-efficiency photocatalyst described in claim 2.

5. The method as described in claim 4, characterized in that, The Fenton solution is a mixed solution of Fe(III) and hydrogen peroxide, wherein the concentration of Fe(III) in the Fenton solution is 5-7 mmol / L and the concentration of hydrogen peroxide is 5-6 wt%; the concentration of NO in the flue gas is 500-700 ppm and the concentration of oxygen is 2-4 wt%; and the dispersion concentration of the photocatalyst in the Fenton solution is 0.05-0.15 g / 50 mL.

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