Photocatalytic material for removing algae in eutrophic water body and preparation method and application thereof

Abstract

The application discloses a kind of photocatalytic material for removing eutrophication water body algae and its preparation method and application, in the present application, anhydrous ethanol containing polytetrafluoroethylene is used to adhere powdered Ag3VO4 / WO3 catalyst on graphite felt, realizing the recovery of catalyst and avoiding secondary pollution, and when reused, the removal rate of algal cells by the photocatalytic material is still close to 90%. In addition, heterojunction can be formed between WO3 and Ag3VO4 in the photocatalytic material, effectively inhibiting the recombination of photo-generated hole-electron pairs, thereby improving the photocatalytic activity of the photocatalytic material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a photocatalytic material for removing algae in eutrophic water bodies and a preparation method and application thereof. BACKGROUND

[0002] Global warming and water eutrophication create favorable conditions for uncontrollable growth of Microcystis aeruginosa, which is one of the most common harmful algal blooms. The outbreak of red tide algae forms a dense barrier in shallow water bodies, blocking sunlight and air from entering, leading to continuous consumption of dissolved oxygen in the water body, further leading to the death of aquatic plants and animals. At the same time, these algae also release toxic metabolites such as malodorous gas and algal toxins into the water body, causing nerve damage, liver and kidney failure in humans. Therefore, harmful algal blooms have caused serious threats to the aquatic ecological environment and public health, and need to be solved urgently.

[0003] So far, there have been several methods for controlling red mold, such as physical methods of mechanical rescue and ultrasonic treatment, chemical methods of adding algicides such as KMnO4, H2O2, peroxoacetic acid, ClO2, and biological methods of plant allelopathy. However, due to poor removal effect, or high operating cost, or secondary pollution, these traditional methods cannot be practically applied.

[0004] Therefore, there is an urgent need for an algae removal agent that is relatively stable in operation, low in cost and environmentally friendly. SUMMARY

[0005] In order to solve the problems of poor effect, high cost and easy secondary pollution of existing algicides, one of the purposes of the present application is to provide a preparation method of a photocatalytic material for removing algae in eutrophic water bodies.

[0006] The technical solution of the present application to solve the above technical problems is as follows:

[0007] A preparation method of a photocatalytic material for removing algae in eutrophic water bodies, comprising the following steps:

[0008] Step 1, calcining tungstate to obtain WO3;

[0009] Step 2, dispersing WO3 in a solvent and then adding AgNO3 to obtain a mixed solution; slowly dropping Na3VO4·12H2O solution into the mixed solution under dark conditions, and stirring at room temperature in the dark for 5-8h to obtain Ag3VO4 / WO3 photocatalyst;

[0010] Step 3, after grinding Ag3VO4 / WO3, the mixture is prepared by mixing with polytetrafluoroethylene, the colloidal mixture is drop-coated on the pretreated graphite felt, and the photocatalytic material for removing algae in eutrophic water body is prepared by flattening, compacting and drying. Preferably, the solvent in step 2 is deionized water; in addition, in order to mix the ground Ag3VO4 / WO3 with polytetrafluoroethylene, anhydrous ethanol is added to the polytetrafluoroethylene during the preparation of the colloidal mixture.

[0011] Further, the tungstate is selected from ammonium paratungstate or ammonium tungstate.

[0012] Further, the tungstate in step 1 is calcined at a temperature of 500-650℃ for 3-5h to prepare WO3.

[0013] Further, the mass ratio of WO3, AgNO3 and Na3VO4·12H2O in step 2 is 0.5:0.581:0.210-0.5:0.6:0.230.

[0014] Further, the pretreated graphite felt is prepared by sequentially ultrasonic cleaning the graphite felt with acetone, ethanol and deionized water, and drying to obtain the pretreated graphite felt.

[0015] The second object of the present application is to provide a photocatalytic material for removing algae in eutrophic water body.

[0016] Further, the photocatalytic material comprises graphite felt and Ag3VO4 / WO3 photocatalyst adhered to the graphite felt.

[0017] The third object of the present application is to use the photocatalytic material for removing algae in eutrophic water body.

[0018] The present application has the following advantages:

[0019] 1. In the present application, anhydrous ethanol containing polytetrafluoroethylene is used to adhere the powdered Ag3VO4 / WO3 catalyst to the graphite felt, so that the powdered catalyst can be completely recovered after use, avoiding secondary pollution to the water environment.

[0020] 2. In the present application, the electron conduction rule of Ag3VO4 / WO3 catalyst is Z-type electron conduction path. The conduction band potential of Ag3VO4 is 0.145eV, and the valence band potential is 2.145eV; the conduction band potential of WO3 is 0.64eV, and the valence band potential is 3.34eV. In the present application, the electrons on the conduction band of WO3 can combine with the holes on the valence band of Ag3VO4, so that the holes on the valence band of WO3 can oxidize H2O / OH- into ·OH, and the main active substances ·OH and H+ The algae cells will be continuously attacked, thereby inactivating the algae cells and achieving removal of the algae.

[0021] In addition, Ag in the Ag3VO4 / WO3 catalyst can be reduced to Ag 0 which has natural antibacterial toxicity to algae. At the same time, Ag can also have localized surface plasmon resonance (LSPR) as a noble metal, which has higher light absorption capacity than ordinary atoms, promotes photo-induced charge separation and transfer, and increases the production of photo-induced electrons. Therefore, the construction of a heterojunction using a silver-based material can accelerate the migration of photo-induced electrons, effectively separate electron-hole pairs, reduce the photo-corrosion of the silver-based material, and also specifically attack algae cells, thereby improving the removal efficiency of algae to a certain extent.

[0022] 3. Subsequent tests show that the removal rate of the algae cells by the prepared photocatalytic material is still close to 90% after repeated use, that is, the prepared photocatalytic material has strong photocatalytic performance and stability, and also has the characteristics of strong visible light absorption capacity, high separation efficiency of photo-induced charges, etc. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a SEM image of graphite felt;

[0024] Figure 2 is a SEM image of the prepared photocatalytic material;

[0025] Figure 3 is an algae removal effect diagram;

[0026] Figure 4 is a recycling performance comparison diagram of the prepared photocatalytic material. DETAILED DESCRIPTION

[0027] The principles and characteristics of the present application are described below in conjunction with the accompanying drawings, and the examples are only used to explain the present application and are not used to limit the scope of the present application. If no specific conditions are specified in the examples, conventional conditions or manufacturer recommended conditions are used. If no manufacturer of the reagents or instruments is specified, it is a conventional product that can be purchased on the market.

[0028] Example 1

[0029] A preparation method of a photocatalytic material for removing algae in eutrophic water bodies, comprising the following steps:

[0030] Step 1, 5g of ammonium paratungstate was weighed into a crucible, which was placed in a muffle furnace, and heated to 550℃ at a heating rate of 5℃ / min, and calcined at this temperature for 4h, then ultrasonic dispersed for 30min, and washed several times by centrifugation with water and ethanol, and dried in an oven at 60℃. After being ground thoroughly in an agate mortar, a light yellow WO3 powder was obtained.

[0031] Step 2, 0.5g of WO3 was added to 50mL of deionized water and ultrasonic dispersed for 30min, and mixed thoroughly. Subsequently, 0.581g of AgNO3 was added to the WO3 dispersion, and magnetically stirred for 30min, then 0.210g of Na3VO4·12H2O dissolved in 30mL of deionized water was added slowly dropwise to the above solution under dark conditions, and finally stirred for 6h at room temperature in the dark to prepare an Ag3VO4 / WO3 catalyst. The obtained catalyst was washed by centrifugation with water and ethanol, and dried in an oven at 60℃, and ground thoroughly in an agate mortar to obtain a yellow Ag3VO4 / WO3 catalyst in powder form.

[0032] Step 3, commercially available graphite felt was cut into a size of 2cm×2cm, and sequentially ultrasonic cleaned with acetone, ethanol and deionized water for 30min, and then dried in an oven to obtain a pretreated graphite felt.

[0033] Then 30mg of Ag3VO4 / WO3 catalyst, 2mL of anhydrous ethanol and 300μL of a polytetrafluoroethylene dispersion were mixed, and then ultrasonic dispersed for 30min to obtain a colloidal mixture. The obtained mixture was drop-coated on the pretreated graphite felt, and flattened and compacted using a medicine spoon, and finally dried in an oven to obtain an Ag3VO4 / WO3 / PTEE / GF photocatalytic material.

[0034] Example 2

[0035] A preparation method of a photocatalytic material for removing algae in eutrophic water bodies, comprising the following steps:

[0036] Step 1, 5g of ammonium paratungstate was weighed into a crucible, which was placed in a muffle furnace, and heated to 550℃ at a heating rate of 5℃ / min, and calcined at this temperature for 4h, then ultrasonic dispersed for 30min, and washed several times by centrifugation with water and ethanol, and dried in an oven at 60℃. After being ground thoroughly in an agate mortar, a light yellow WO3 powder was obtained.

[0037] Step 2, 0.5 g of WO3 was added into 50 mL of deionized water and ultrasonically dispersed for 30 min to make it fully mixed. Then, 0.592 g of AgNO3 was added into the WO3 dispersion, magnetically stirred for 30 min, and then 0.220 g of Na3VO4·12H2O dissolved in 30 mL of deionized water was slowly added dropwise into the above solution under dark condition, and finally stirred for 5 h at room temperature in the dark to prepare the Ag3VO4 / WO3 catalyst. The obtained catalyst was washed by centrifugation with water and ethanol, dried in an oven at 60 °C, and then ground by agate mortar to obtain a yellow Ag3VO4 / WO3 catalyst in powder form.

[0038] Step 3, commercially available graphite felt was cut into a size of 2 cm x 2 cm, and then sequentially ultrasonically cleaned with acetone, ethanol and deionized water for 30 min, and finally dried in an oven to obtain a pretreated graphite felt.

[0039] Then 30 mg of Ag3VO4 / WO3 catalyst, 2 mL of anhydrous ethanol and 300 μL of polytetrafluoroethylene dispersion were mixed, and then ultrasonically dispersed for 30 min to obtain a colloidal mixture. The obtained mixture was drop-coated on the pretreated graphite felt, and then flattened and compacted by using a medicine spoon, and finally dried in an oven to obtain an Ag3VO4 / WO3 / PTEE / GF photocatalytic material.

[0040] Example 3

[0041] A preparation method of a photocatalytic material for removing algae in eutrophic water bodies, comprising the following steps:

[0042] Step 1, 5 g of ammonium paratungstate was weighed into a crucible, and then placed in a muffle furnace, and heated to 650 °C at a heating rate of 5 °C / min, and calcined at this temperature for 5 h, and then ultrasonically dispersed for 30 min, and washed by centrifugation with water and ethanol for several times, and then dried in an oven at 60 °C. After being fully ground by an agate mortar, a yellowish WO3 powder was obtained.

[0043] Step 2, 0.5 g of WO3 was added into 50 mL of deionized water and ultrasonically dispersed for 30 min to make it fully mixed. Then, 0.6 g of AgNO3 was added into the WO3 dispersion, magnetically stirred for 30 min, and then 0.230 g of Na3VO4·12H2O dissolved in 30 mL of deionized water was slowly added dropwise into the above solution under dark condition, and finally stirred for 8 h at room temperature in the dark to prepare the Ag3VO4 / WO3 catalyst. The obtained catalyst was washed by centrifugation with water and ethanol, dried in an oven at 60 °C, and then ground by an agate mortar to obtain a yellow Ag3VO4 / WO3 catalyst in powder form.

[0044] Step 3, cut the commercially available graphite felt into 2 cm x 2 cm size, and sequentially clean with acetone, ethanol and deionized water for 30 min, and then dry in an oven to obtain the pretreated graphite felt.

[0045] Then mix 30 mg of Ag3VO4 / WO3 catalyst, 2 mL of anhydrous ethanol and 300 μL of polytetrafluoroethylene dispersion, and then ultrasonic for 30 min to obtain a colloidal mixture. The obtained mixture is drop-coated on the pretreated graphite felt, and then flattened and compacted with a medicine spoon, and finally dried in an oven to obtain the Ag3VO4 / WO3 / PTEE / GF photocatalytic material.

[0046] Comparative Example 1

[0047] A preparation method of a photocatalytic material for removing algae in eutrophic water bodies, comprising the following steps:

[0048] Step 1, weigh 5 g of ammonium paratungstate into a crucible, and place it in a muffle furnace, and heat it to 550℃ at a heating rate of 5℃ / min, and then calcine it at this temperature for 4 h, and then ultrasonic for 30 min, and then centrifugal washing with water and ethanol several times, and then dry in a 60℃ oven; and then fully grind with a agate mortar to obtain a light yellow WO3 powder.

[0049] Step 2, cut the commercially available graphite felt into 2 cm x 2 cm size, and sequentially clean with acetone, ethanol and deionized water for 30 min, and then dry in an oven to obtain the pretreated graphite felt.

[0050] Then mix 30 mg of WO3 catalyst, 2 mL of anhydrous ethanol and 300 μL of polytetrafluoroethylene dispersion, and then ultrasonic for 30 min to obtain a colloidal mixture. The obtained mixture is drop-coated on the pretreated graphite felt, and then flattened and compacted with a medicine spoon, and finally dried in an oven to obtain the WO3 / PTEE / GF photocatalytic material.

[0051] Comparative Example 2

[0052] A preparation method of a photocatalytic material for removing algae in eutrophic water bodies, comprising the following steps:

[0053] Step 1, disperse 0.581 g of AgNO3 in deionized water, and magnetically stir for 30 min, and then slowly drop 0.210 g of Na3VO4·12H2O dissolved in 30 mL of deionized water into the above solution under dark conditions, and finally stir at room temperature for 6 h in the dark to obtain Ag3VO4 catalyst. The obtained catalyst is washed with water and ethanol, and then dried in a 60℃ oven, and then fully ground with an agate mortar to obtain a yellow Ag3VO4 catalyst powder.

[0054] Step 2, cut the commercially available graphite felt into 2 cm x 2 cm size, sequentially clean with acetone, ethanol and deionized water for 30 min, and then dry in an oven to obtain pretreated graphite felt.

[0055] Then mix 30 mg of Ag3VO4 catalyst, 2 mL of anhydrous ethanol and 300 μL of polytetrafluoroethylene dispersion, and then ultrasonic for 30 min to obtain a colloidal mixture. Drop the mixture on the pretreated graphite felt, and then flatten and compact with a spoon, and finally dry in an oven to obtain the Ag3VO4 / PTEE / GF photocatalytic material.

[0056] Test analysis:

[0057] 1. SEM test analysis

[0058] The pretreated graphite felt and the photocatalytic material prepared in Example 1 were analyzed by SEM, and the analysis results are shown in Figure 1 and Figure 2 , combined with Figure 1 and Figure 2 It can be seen that the Ag3VO4 / WO3 photocatalyst in the application is firmly adhered to the graphite felt, realizing the recovery of the powdered Ag3VO4 / WO3 photocatalyst, and at the same time avoiding the secondary pollution of the powdered Ag3VO4 / WO3 photocatalyst to the system.

[0059] 2. Algae removal performance test

[0060] (1) The pretreated graphite felt (GF), the photocatalytic material prepared in Example 1 (Ag3VO4 / WO3 / PTEE / GF), the photocatalytic material prepared in Comparative Example 1 (WO3 / PTEE / GF), and the photocatalytic material prepared in Comparative Example 2 (Ag3VO4 / PTEE / GF) were tested for algae removal performance under visible light irradiation. The specific test conditions are as follows: a 500W xenon lamp is used as the light source, the initial algae density is 4.6 x 10 6 cells / mL (OD 680 ≈0.800), and the sample is taken every 30 min for chlorophyll a determination. After 240 min of treatment, the test results are shown in Figure 3 . From Figure 3 , it can be seen that under visible light, the removal rates of the graphite felt (GF) alone, the graphite felt loaded with WO3 (WO3 / PTEE / GF), and the graphite felt loaded with Ag3VO4 (Ag3VO4 / PTEE / GF) on algae cells are 14.4%, 19.1% and 27.2% respectively, and the photocatalytic material prepared in the application has a significant removal effect on algae cells, and the removal rate on algae cells is 100% at 210 min.

[0061] (2) The algae removal performance of the photocatalytic material prepared in Example 1 was tested under both dark and light conditions. Specific test conditions: a 500W xenon lamp was used as the light source, and the initial algae density was 4.6 × 10⁻⁶. 6 cells / mL (OD) 680 (≈0.800), samples were taken every 30 minutes to determine chlorophyll a. See details of the test results. Figure 3 The formulas represent algae removal performance under dark conditions (Drak+Ag3VO4 / WO3 / PTEE / GF) and algae removal performance under light conditions (Light+Ag3VO4 / WO3 / PTEE / GF). Figure 3 As can be seen, under light conditions, the algae removal performance of the photocatalytic material in this invention is significantly higher than its algae removal performance in the dark.

[0062] 3. Stability Test

[0063] The photocatalytic material prepared in Example 1 was reused, and its algal cell removal rate was tested during each use. Specific test conditions: a 500W xenon lamp was used as the light source, and the initial algal density was 4.6 × 10⁻⁶. 6 cells / mL (OD) 680 (≈0.800), samples were taken every 30 minutes to determine chlorophyll a. Specifically, the photocatalytic material in Example 1 was reused three times in this test, and the removal rate of algal cells by the photocatalytic material during each use was tested. The test results are detailed in [link to test results]. Figure 4 .

[0064] from Figure 4 As can be seen, the photocatalytic material prepared in this invention still maintains a removal rate of nearly 90% for algal cells during repeated use, demonstrating good stability. In other words, the photocatalytic material in this invention can be repeatedly recycled and reused in practical applications, possessing high practical value.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a photocatalytic material for removing algae from eutrophicated water bodies, characterized in that, The method comprises the following steps: Step 1, calcining tungstate to obtain WO3; Step 2, dispersing WO3 in a solvent, then adding AgNO3 to obtain a mixed solution; slowly dropping Na3VO4·12H2O solution into the mixed solution under dark condition, and stirring at room temperature for 5-8 hours to obtain Ag3VO4 / WO3 photocatalyst; Grinding Ag3VO4 / WO3, mixing with polytetrafluoroethylene to obtain a colloidal mixture, dropping the colloidal mixture on pretreated graphite felt, and then flattening, compacting and drying to obtain a photocatalytic material for removing algae in eutrophic water body; The mass ratio of WO3, AgNO3 and Na3VO4·12H2O in step 2 is 0.5:0.581:0.210-0.5:0.6:0.

230.

2. The production method according to claim 1, characterized by, The tungstate is selected from ammonium paratungstate or ammonium tungstate.

3. The production method according to claim 2, characterized by, The tungstate in step 1 is calcined at a temperature of 500-650°C for 3-5 hours to obtain WO3.

4. The method of claim 1, wherein, The pretreated graphite felt is prepared by sequentially ultrasonic cleaning graphite felt with acetone, ethanol and deionized water, and then drying to obtain the pretreated graphite felt.

5. The photocatalytic material for removing algae in eutrophic water body prepared by the method of any one of claims 1-4.

6. The photocatalytic material according to claim 5, characterized in that, The photocatalytic material comprises graphite felt and Ag3VO4 / WO3 photocatalyst adhered on the graphite felt.

7. The photocatalytic material of claim 5 or 6 for removing algae in eutrophic water body.

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