Floating type defective molybdenum oxide photocatalyst and preparation method and algae control application thereof

Abstract

The invention discloses a floating type defect molybdenum oxide photocatalyst and a preparation method and algae control application thereof. Natural loofah sponge is modified, a hydrothermal method is utilized, an ammonium molybdate solution and nitric acid are mixed for reaction, molybdenum oxide MoO3 is obtained, blue MoO3-x with o vacancy defects is obtained through annealing, reactants are subjected to vacuum drying, and the powder photocatalyst MoO3 / MoO3-x is obtained; preparing a powder photocatalyst suspension from a powder photocatalyst MoO3 / MoO3-x, adding the modified loofah sponge into the powder photocatalyst suspension, carrying out ultrasonic treatment on the pulse-like structure of the loofah sponge to fully and uniformly load the catalyst, and aging, washing and drying to obtain the floating type photocatalyst. When the floating type photocatalyst is added into an algae bloom water body, algae cells are properly damaged and are greatly adsorbed and gathered on loofah sponge, so that the effect of removing algae by photocatalysis and adsorption is realized.

Description

Technical Field

[0001] The present invention relates to the field of photocatalytic technology for algae killing, and specifically relates to a preparation method and application of a floating defective molybdenum oxide photocatalyst. Background Art

[0002] Cyanobacterial blooms are an ecological anomaly that occurs in water bodies. Under suitable environmental conditions, cyanobacteria multiply rapidly and form a blue-green floating foam on the water surface. With the intensification of human activities and environmental changes, the problem of cyanobacterial blooms has become increasingly prominent. The discharge of a large amount of industrial wastewater, domestic sewage, and agricultural non-point source pollution has increased the content of nutrients such as nitrogen and phosphorus in water bodies, providing sufficient nutrients for the growth of cyanobacteria. The occurrence of cyanobacterial blooms not only disrupts the ecological balance of water bodies but also causes serious harm to aquatic organisms. It consumes a large amount of oxygen in the water, leading to the death of aquatic animals such as fish due to hypoxia. At the same time, cyanobacteria also release toxins, posing a threat to the health of humans and other organisms. Controlling cyanobacterial blooms has long been one of the important tasks of global environmental protection.

[0003] There are mainly three common algal bloom prevention and control technologies: physical methods (mechanical collection, membrane separation), chemical methods (chemical algicides, coagulation and flocculation), and biological methods (algae-eating organisms, allelochemicals). However, each has its limitations, such as high cost and low efficiency, large ecological risks, and unstable effects. As a highly potential environmental purification technology, photocatalytic technology has been practically applied in some fields and regions due to its advantages such as being green and using solar energy. Many researchers have also applied it to the research of algae removal due to its advantages such as high efficiency, low cost, and environmental sustainability.

[0004] Certain progress has been made in the research of photocatalytic technology in algae treatment, mainly focusing on TiO2 and its composites. Most photocatalysts are represented by TiO2. Although the cost is low, the light response region of TiO2 is concentrated in ultraviolet light, and the utilization rate of visible light is low, resulting in insufficient photocatalyst efficiency and limiting the actual algae removal efficiency under natural light conditions. Most of the photocatalytic algicides developed at home and abroad are powder nano-photocatalysts, and mainly binary or ternary composites. By constructing heterojunctions and introducing various metal elements, valence bands are regulated to generate free radicals to achieve the algae-killing effect. Most studies mainly introduce noble metals to improve the light absorption ability of the catalyst, but its preparation process is complex, the yield is low, the cost is high, and there are resource limitation problems. The nano-photocatalysts themselves agglomerate seriously and cannot combine with the characteristics of algae growing and gathering towards light on the water surface, thus affecting the algae removal effect and being inconvenient for subsequent collection, causing secondary pollution and being difficult to promote for practical application. Self-doped oxygen vacancy-regulated MoO 3-xThe photocatalyst utilizes its local surface plasmon resonance effect (LSPR), significantly enhancing the light absorption ability of the photocatalyst, accelerating the generation of free radicals, and effectively expanding the light response region of the catalyst.

[0005] Therefore, it is particularly urgent to develop a highly efficient, environmentally friendly and easily industrialized floating photocatalyst. Most of the floating carriers used in current such research are materials with certain mechanical strength, such as glass microspheres, perlite, polyurethane sponge, melamine sponge, ceramsite, and some solid wastes such as rice husks and loofahs. These materials show certain algae removal effects in different studies, but there are still some problems: ① Poor load stability of the carrier: Although floating carriers such as glass microspheres and polyurethane sponge have certain mechanical strength and floating performance, the binding force with the photocatalyst is insufficient, which easily causes the catalyst to fall off or be lost, reducing the catalytic efficiency and increasing the risk of secondary pollution. ② Poor environmental friendliness: Most carrier materials such as polymer sponges are non-degradable and may cause secondary hazards to the water source environment in practical applications. ③ Limitations in industrial application: Currently, most floating photocatalysts are in the laboratory research stage, with complex preparation processes, high costs of floating carrier materials, and a lack of technical paths for large-scale production. ④ High secondary hazard: Such photocatalysts mainly achieve the purpose of algae removal by completely destroying algal cells. To achieve high-efficiency algae removal, various metals are often introduced, with a high risk of metal ion precipitation, and toxic substances such as microcystins may be released after the cells are completely ruptured, resulting in subsequent ecological risks. Summary of the Invention

[0006] To solve the above-mentioned defects in the prior art, the purpose of the present invention is to provide a preparation method of a floating photocatalyst MoO3 / MoO3-x with loofah as the carrier. Using loofah as the floating carrier, MoO 3-x The photocatalyst is loaded thereon for visible light inactivation of Microcystis aeruginosa, making up for the application defects of powder photocatalysts that are difficult to recover and easily cause secondary pollution. The present invention modifies the surface of loofah by regulating temperature, time and solvent ratio, and uses the impregnation method to fix the powder catalyst on the floating carrier, solving the problems of difficult recovery of existing photocatalysts and existing secondary ecological risks. The present invention uses MoO3 / MoO 3-x @LF to treat the algae on the water surface and strengthen the algae removal application treatment.

[0007] The present invention is realized through the following technical solutions.

[0008] One aspect of the present invention provides a preparation method of a floating defective molybdenum oxide photocatalyst, including the following steps:

[0009] a. Modify the natural loofah, and sequentially place it in deionized water, inorganic base solution, and ionic surfactant for ultrasonic treatment, and then dry to obtain modified loofah;

[0010] b. Prepare an ammonium molybdate solution using the hydrothermal method. Mix the ammonium molybdate solution with nitric acid according to a molar ratio of ammonium molybdate to nitric acid of (2 - 4):1, adjust the pH value, raise the temperature for reaction, cool to room temperature to obtain molybdenum trioxide MoO₃, dry it, and calcine it to obtain MoO with o-vacancy defects. 3-x Centrifuge and alternately wash the reactants, and dry them under vacuum to obtain the powdered photocatalyst MoO₃ / MoO. 3-x ;

[0011] c. Add the powdered photocatalyst MoO₃ / MoO₃₋ₓ to ultrapure water to obtain a suspension of the powdered photocatalyst. According to a mass ratio of modified loofah sponge to powdered photocatalyst of 1:(2 - 5), add the modified loofah sponge to the suspension of the powdered photocatalyst, ultrasonicate, heat in a water bath, and allow the veined structure of the loofah sponge to uniformly load the catalyst. After aging, washing, and drying, obtain the floating photocatalyst MoO₃ / MoO. 3-x @LF 5 / 6 / 7 / 6.5 / 8 。

[0012] Preferably, the modification treatment of natural loofah sponge is to soak the natural loofah sponge in deionized water for 1 - 4 h, then soak it in an inorganic base solution, dry it, place it in an ionic surfactant, oscillate it in a shaker, wash it, ultrasonically treat it for 30 - 90 min, and dry it at 40 - 80 °C for 3 - 12 h.

[0013] Preferably, the inorganic base in the inorganic base solution is sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, or potassium bicarbonate; the ionic surfactant is cetyltrimethylammonium bromide solution, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetyl dimethylammonium chloride, polyethylene glycol, or saponin.

[0014] Preferably, in step b, prepare the ammonium molybdate solution by mixing ammonium molybdate with distilled water according to a solid-liquid ratio of 1:15 - 1:25.

[0015] Preferably, in step b, adjust the pH to 0.5 - 1.5, raise the temperature to 150 - 160 °C, and react for 10 - 12 h.

[0016] Preferably, the molybdenum trioxide MoO₃ is calcined at 250 - 650 °C for 2 - 8 h at a heating rate of 5 - 10 °C / min; after centrifuging and alternately washing the reactants, dry them under vacuum at 80 - 90 °C for 10 - 12 h.

[0017] Preferably, in step c, add the powdered photocatalyst MoO₃ / MoO₃₋ₓ to ultrapure water to obtain a suspension of the powdered photocatalyst with a concentration of 5 - 8 g / L.

[0018] Preferably, in step c, the modified loofah sponge and the powder photocatalyst suspension are ultrasonically treated for 10 - 15 min, heated in a water bath at 30 - 70 °C for 1 - 8 h; aged for 1 - 2 h, washed 3 - 5 times with distilled water, and dried at 60 - 70 °C for 8 - 10 h.

[0019] Another aspect of the present invention provides a floating defective molybdenum oxide photocatalyst prepared by the above method.

[0020] Due to the above technical solutions adopted by the present invention, it has the following beneficial effects:

[0021] Based on the natural fibrous material with a veined multi - level grid structure of natural loofah sponge, combined with the oxygen - vacancy - defective MoO3 photocatalyst, the present invention proposes a floating photocatalyst with excellent performance. The self - doped MoO3 / MoO formed during the preparation process 3-x composed of plasma MoO 3-x and non - plasma MoO3 improves the solar light utilization rate of the photocatalyst. Moreover, the oxygen vacancies introduced on the material surface significantly broaden the light response range (from visible light to near - infrared), accelerating the generation of free radicals. Applying this floating defective molybdenum oxide photocatalyst to the treatment of algal blooms can achieve the effect of photocatalytic and synergistic adsorption for algae removal, showing a more significant algae - removal effect.

[0022] The floating photocatalyst with natural loofah sponge as the carrier evenly loads the powder catalyst by using the three - dimensional network structure of the loofah sponge, overcomes the defect that the powder catalyst is prone to agglomeration and sedimentation, combines its floating characteristics with the growth law of the algae surface layer, improves the solar light utilization rate, realizes the "photocatalysis - adsorption synergy" effect, efficiently controls algal cells and enriches them in situ, and avoids the large - scale release of algal toxins. Moreover, the light - weight cellulose / lignin components of the loofah sponge have the characteristics of biodegradability, low cost, and high stability, and also solve the problem of secondary pollution of traditional carriers, being more suitable for the actual water - body algal bloom treatment scenario.

[0023] Using a single molybdenum salt as the precursor, a self - doped MoO3 / MoO 3-x photocatalyst can be prepared by controlling the temperature during calcination in a system without adding additional organic solvents. The three - dimensional network structure can evenly load the powder - loaded catalyst, thereby fully absorbing visible light and infrared light. Moreover, the main components of the loofah sponge are composed of light - weight cellulose and lignin, which are biodegradable and have good stability. Using this as the carrier of the powder photocatalyst to make a floating photocatalyst, after loading and adding it to the algal - bloom water body, after being irradiated by natural sunlight, the algal cells are moderately damaged and can be adsorbed and aggregated on the loofah sponge in large quantities, achieving the purpose of algae removal without completely destroying the released substances of the algal cells, and the loofah sponge can be recycled to reduce the impact on the environmental water body. It has a lower cost, is more environmentally friendly, has a lower secondary risk, and is more convenient for actual dosing operation compared with conventional floating photocatalysts.

[0024] Combining the environmental protection advantages of natural materials and the high efficiency of photocatalysis technology, the present invention can not only significantly improve the treatment efficiency of cyanobacterial blooms, but also reduce the risk of secondary pollution, optimize the dosing and recovery operations in the actual application process, and has good industrial potential and economy. Compared with the prior art, the present invention has achieved technological breakthroughs in terms of raw material acquisition, catalytic efficiency, carrier stability and environmental friendliness, providing a new solution for the treatment of cyanobacterial blooms. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 is a scanning electron microscope image of a loofah floating carrier;

[0027] Figure 2 is a scanning electron microscope image of the prepared floating photocatalyst MoO3 / MoO 3-x @LF;

[0028] Figure 3 is the algae removal efficiency of the floating photocatalyst MoO3 / MoO 3-x @LF 5 / 6 / 7 / 6.5 / 8 against Microcystis aeruginosa;

[0029] Figure 4 is the effect of the control group, the blank loofah experimental group, the powdered photocatalyst MoO3 / MoO 3-x and the floating photocatalyst on the chlorophyll a content of Microcystis aeruginosa;

[0030] Figure 5 is a schematic diagram of the application scenario of the floating photocatalyst dosing. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be described in detail below in conjunction with the drawings and specific embodiments. Here, the schematic embodiments and descriptions of the present invention are used to explain the present invention, but do not limit the present invention.

[0032] The embodiment of the present invention provides a preparation method of a floating defective molybdenum oxide photocatalyst, comprising the following steps:

[0033] Step 1: Modify natural loofah sponges. Soak them in deionized water for 1 - 4 h, then soak in an inorganic base solution (sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, or potassium bicarbonate). After drying, place them in an ionic surfactant (cetyltrimethylammonium bromide solution, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetyl dimethyl ammonium chloride, polyethylene glycol, or saponin) and shake in a shaker. Then wash and ultrasonically treat for 30 - 90 min, and dry at 40 - 80 °C for 3 - 12 h to obtain modified loofah sponges. The scanning electron micrograph of the loofah sponge carrier is shown in Figure 1 as follows.

[0034] Step 2: Using the hydrothermal method, prepare an ammonium molybdate solution by mixing ammonium molybdate and distilled water at a solid-liquid ratio of 1:15 - 1:25. Mix the ammonium molybdate solution with nitric acid according to an ammonium molybdate:nitric acid molar ratio of (2 - 4):1, adjust the pH value to 0.5 - 1.5, raise the temperature to 120 - 160 °C and react for 10 - 12 h. After drying and cooling to room temperature, obtain molybdenum trioxide MoO3.

[0035] Step 3: Place MoO3 in a quartz boat of a tube furnace. Calcinate in an air atmosphere at a heating rate of 5 - 10 °C / min and at 250 - 650 °C for 2 - 8 h to obtain blue MoO with o-vacancy defects 3-x , centrifuge and wash the reactants alternately, and vacuum dry at 80 - 90 °C for 10 - 12 h to obtain the powdered photocatalyst MoO3 / MoO 3-x .

[0036] Step 4: Add the powdered photocatalyst MoO3 / MoO3-x to ultrapure water to obtain a powdered photocatalyst suspension with a concentration of 5 - 8 g / L. According to a modified loofah sponge:powdered photocatalyst mass ratio of 1:(2 - 5), add the modified loofah sponge to the powdered photocatalyst suspension, ultrasonically treat for 10 - 15 min, and heat in a water bath at 30 - 70 °C for 1 - 8 h. The veined structure of the loofah sponge is fully and evenly loaded with the catalyst. Age for 1 - 2 h, take out with tweezers and wash 3 - 5 times with distilled water to wash off the loosely loaded catalyst, and dry in an oven at 60 - 70 °C for 8 - 10 h, turning over regularly in the middle to obtain the floating photocatalyst MoO3 / MoO 3-x @LF 5 / 6 / 7 / 6.5 / 8 . The scanning electron micrograph of the floating photocatalyst MoO3 / MoO 3-x @LF is shown in Figure 2 .

[0037] The present invention will be further illustrated by different embodiments below.

[0038] Example 1

[0039] (1) Preparation of modified loofah sponges

[0040] After removing the inner core, natural loofah sponge was soaked in hot water for 2 h to fully soften it, then soaked in 0.1 mol / L NaOH solution, dried and placed in 0.1 mol / L cetyltrimethylammonium bromide (CTAB) solution, and shaken in a shaker to ensure full contact. The excess CTAB on the loofah sponge was rinsed off with deionized water, followed by ultrasonic treatment for 30 min and drying at 60 °C for 7 h to obtain modified loofah sponge.

[0041] (2) Preparation of MoO3

[0042] (NH4)6Mo7O was prepared by hydrothermal method 24 ·4H2O was dissolved in distilled water at a solid-liquid ratio of 1:15. Then, while stirring, nitric acid with a concentration of 68% was titrated into the ammonium molybdate solution according to the molar ratio of ammonium molybdate to nitric acid of 3.57:1, and the pH value of the solution was adjusted to 0.8 to produce a white precipitate, and stirring was continued for 30 min. Finally, the solution was transferred to a stainless steel autoclave and maintained at 120 °C for 12 h. After cooling to room temperature, the obtained white MoO3 was filtered with distilled water and dried at 40 °C for 12 h. Finally, the prepared sample was ground in an agate mortar to obtain MoO3 powder.

[0043] (3) Preparation of MoO3 / MoO 3-x

[0044] The MoO3 prepared in step (2) above was spread out in a quartz boat and placed in a tubular furnace. In an air atmosphere, with a heating rate of 10 °C / min, the MoO3 powder was calcined at 250 °C for 8 h. After cooling to room temperature, the brown sample was taken out, centrifugally washed several times alternately with deionized water and absolute ethanol, and vacuum dried at 80 °C for 12 h to obtain the powdered photocatalyst MoO3 / MoO 3-x

[0045] (4) Preparation of floating photocatalytic loofah sponge

[0046] The powdered photocatalyst MoO3 / MoO 3-x was added to ultrapure water to obtain a suspension of powdered photocatalyst with a concentration of 5 g / L. Subsequently, the dried loofah sponge was added to the photocatalyst suspension according to the mass ratio of modified loofah sponge to powdered photocatalyst of 1:5, and ultrasonic treatment was carried out for 10 min. The beaker was placed in a water bath at 30 °C and stirred and heated for 8 h, aged at room temperature for 1 h, washed several times with distilled water, and dried at 60 °C for 10 h to obtain a floating photocatalyst MoO3 / MoO 3-x @LF5.

[0047] Example 2

[0048] (1) Preparation of modified loofah sponge

[0049] After removing the inner core, natural loofah sponge was soaked in hot water for 3 h to fully soften it, then soaked in 0.1 mol / L lithium hydroxide solution, dried and placed in 0.1 mol / L sodium dodecyl sulfate solution, and shaken in a shaker to ensure full contact. Excess CTAB on the loofah sponge was rinsed off with deionized water, followed by ultrasonic treatment for 60 min and drying at 40 °C for 12 h to obtain modified loofah sponge.

[0050] (2) Preparation method of MoO3

[0051] By hydrothermal method, (NH4)6Mo7O 24 ·4H2O was dissolved in distilled water at a solid-liquid ratio of 1:18. Then, while stirring, nitric acid with a concentration of 68% was titrated into the ammonium molybdate solution according to the molar ratio of ammonium molybdate to nitric acid of 3:1, and the pH value of the solution was adjusted to 1.5 to produce a white precipitate, which was continuously stirred for 1 h. Finally, the solution was transferred to a 100 mL stainless steel autoclave and maintained at 130 °C for 12 h. After cooling to room temperature, the obtained white MoO3 was filtered with distilled water and dried at 50 °C for 10 h. Finally, the prepared sample was ground in an agate mortar to obtain MoO3 powder.

[0052] (3) Preparation method of MoO3 / MoO 3-x

[0053] The MoO3 prepared in step (2) above was spread out in a quartz boat and placed in a tubular furnace. In an air atmosphere, with a heating rate of 10 °C / min, the MoO3 powder was calcined at 350 °C for 6 h. After cooling to room temperature, the brown sample was taken out, centrifugally washed several times with deionized water and absolute ethanol alternately, and dried in vacuum at 85 °C for 10 h to obtain the powdered photocatalyst MoO3 / MoO 3-x .

[0054] (4) Preparation of floating photocatalytic loofah sponge

[0055] The powdered photocatalyst MoO3 / MoO 3-x was added to ultrapure water to obtain a suspension of powdered photocatalyst with a concentration of 6 g / L. Subsequently, the dried loofah sponge was added to the photocatalyst suspension according to the mass ratio of modified loofah sponge to powdered photocatalyst of 1:2, and ultrasonic treatment was carried out for 10 min. The beaker was placed in a water bath at 40 °C and stirred and heated sufficiently for 6 h, aged at room temperature for 1 h, washed several times with distilled water, and dried at 65 °C for 9 h to obtain a floating photocatalyst MoO3 / MoO 3-x @LF6.

[0056] Example 3

[0057] (1) Preparation of modified loofah sponge

[0058] After removing the inner core of natural loofah sponge, it was soaked in hot water at 80 °C for 1 h to fully soften it, then soaked in 0.1 mol / L calcium hydroxide solution, dried and placed in 0.1 mol / L sodium dodecylbenzenesulfonate solution, and placed in a shaker to oscillate for sufficient contact. The excess CTAB on the loofah sponge was rinsed off with deionized water, ultrasonicated for 90 min, and dried at 50 °C for 10 h to obtain modified loofah sponge.

[0059] (2) Preparation method of MoO3

[0060] By hydrothermal method, (NH4)6Mo7O 24 ·4H2O was dissolved in distilled water at a solid-liquid ratio of 1:20. Then, while stirring, nitric acid with a concentration of 68% was titrated into the ammonium molybdate solution according to the molar ratio of ammonium molybdate to nitric acid of 2.5:1, and the pH value of the solution was adjusted to 0.5 to produce a white precipitate, and stirring was continued for 1.5 h; finally, the solution was transferred to a 100 mL stainless steel autoclave and maintained at 150 °C for 12 h; after cooling to room temperature, the obtained white MoO3 was filtered with distilled water and dried at 60 °C for 9 h, and finally the prepared sample was ground in an agate mortar to obtain MoO3 powder.

[0061] (3) Preparation method of MoO3 / MoO 3-x

[0062] The MoO3 prepared in the above step (2) was spread out in a quartz boat and placed in a tube furnace. In an air atmosphere, with a heating rate of 8 °C / min, the MoO3 powder was calcined at 450 °C for 5 h. After cooling to room temperature, the brown sample was taken out, centrifugally washed several times alternately with deionized water and absolute ethanol, and vacuum dried at 90 °C for 10 h to obtain the powdered photocatalyst MoO3 / MoO 3-x

[0063] (4) Preparation of floating photocatalytic loofah sponge

[0064] Take the powdered photocatalyst MoO3 / MoO 3-x and add it to ultrapure water to obtain a powdered photocatalyst suspension with a concentration of 7 g / L. Subsequently, according to the mass ratio of modified loofah sponge to powdered photocatalyst of 1:3, an appropriate amount of dried loofah sponge was added to the photocatalyst suspension, ultrasonicated for 15 min, the beaker was placed in a water bath at 50 °C and stirred and heated sufficiently for 4 h, aged at room temperature for 1.5 h, washed several times with distilled water, and dried at 60 °C for 10 h to obtain a floating photocatalyst MoO3 / MoO 3-x @LF7.

[0065] Example 4

[0066] (1) Preparation of modified loofah sponge

[0067] After removing the inner core of the natural loofah, it was soaked in hot water for 4 hours to fully soften it, then soaked in 0.1 mol / L ammonium hydroxide solution, dried and placed in 0.1 mol / L hexadecyl dimethyl ammonium chloride solution, and placed in a shaker for 2 hours to allow full contact, and the excess CTAB on the loofah was rinsed off with deionized water, ultrasonically treated for 40 minutes, and dried at 80°C for 3 hours to obtain a modified loofah.

[0068] (2) Preparation method of MoO3

[0069] Hydrothermal method to convert (NH4)6Mo7O 24 4H2O was dissolved in distilled water at a solid-liquid ratio of 1:22. Then, while stirring, nitric acid with a concentration of 68% was titrated into the ammonium molybdate solution according to a molar ratio of ammonium molybdate to nitric acid of 2:1, and the pH value of the solution was adjusted to 1 to produce a white precipitate, and the stirring was continued for 1.5 hours; finally, the solution was transferred to a 100mL stainless steel autoclave and kept at 160°C for 10 hours; after cooling to room temperature, the white MoO3 obtained was filtered with distilled water and dried at 70°C for 8 hours, and finally the obtained sample was ground in an agate mortar to obtain MoO3 powder.

[0070] (3)MoO3 / MoO 3-x Preparation method

[0071] The MoO3 prepared in the above step (2) was spread in a quartz boat and placed in a tube furnace. The MoO3 powder was calcined at 550°C for 4 h in an air atmosphere at a heating rate of 5°C / min. After cooling to room temperature, a dark brown sample was taken out and washed alternately by centrifugation with deionized water and anhydrous ethanol for several times. The powdered photocatalyst MoO3 / MoO was obtained by vacuum drying at 80°C for 12 h. 3-x .

[0072] (4) Preparation of floating photocatalytic loofah

[0073] Take powder photocatalyst MoO3 / MoO 3-x Ultrapure water was added to obtain a powder photocatalyst suspension with a concentration of 6.5 g / L. Then, an appropriate amount of dried loofah was added to the photocatalyst suspension according to the mass ratio of modified loofah to powder photocatalyst of 1:4. Ultrasonication was performed for 15 min. The beaker was placed in a 60 °C water bath and stirred and heated for 3 h. It was aged at room temperature for 2 h, washed several times with distilled water, and dried at 70 °C for 8 h to obtain a floating photocatalyst MoO3 / MoO 3-x @LF 6.5 .

[0074] Example 5

[0075] (1) Preparation of modified loofah

[0076] After removing the inner core, the loofah sponge was soaked in hot water for 2 h to make it fully softened, soaked in 0.1 mol / L sodium carbonate solution, dried, and then placed in 0.1 mol / L polyethylene glycol or saponin solution, and shaken in a shaker for 2 h to make it fully contact. The excess CTAB on the loofah sponge was rinsed off with deionized water, ultrasonically treated for 80 min, and dried at 70 °C for 5 h to obtain modified loofah sponge.

[0077] (2) Preparation method of MoO3

[0078] (NH4)6Mo7O was prepared by hydrothermal method 24 ·4H2O was dissolved in distilled water at a solid-liquid ratio of 1:25. Then, while stirring, nitric acid with a concentration of 68% was titrated into the ammonium molybdate solution according to the molar ratio of ammonium molybdate to nitric acid of 4:1, and the pH value of the solution was adjusted to 1.2 to produce a white precipitate, and stirring was continued for 2 h; finally, the solution was transferred to a 100 mL stainless steel autoclave and maintained at 140 °C for 11 h; after cooling to room temperature, the white MoO3 obtained was filtered with distilled water, dried at 80 °C for 7 h, and finally the prepared sample was ground in an agate mortar to obtain MoO3 powder.

[0079] (3) Preparation method of MoO3 / MoO 3-x

[0080] The MoO3 prepared in the above step (1) was spread out in a quartz boat and placed in a tube furnace. In an air atmosphere, the heating rate was 6 °C / min, and the MoO3 powder was calcined at 650 °C for 2 h. After cooling to room temperature, the dark brown sample was taken out, and alternately centrifuged and washed several times with deionized water and absolute ethanol, and vacuum dried at 90 °C for 11 h to obtain the powdered photocatalyst MoO3 / MoO 3-x

[0081] (4) Preparation of floating photocatalytic loofah sponge

[0082] Take the powdered photocatalyst MoO3 / MoO 3-x and add it to ultrapure water to obtain a powdered photocatalyst suspension with a concentration of 8 g / L. Subsequently, according to the mass ratio of modified loofah sponge to powdered photocatalyst of 1:2.5, an appropriate amount of dried loofah sponge was added to the photocatalyst suspension, ultrasonically treated for 15 min, the beaker was placed in a 70 °C water bath and stirred and heated for 1 h, aged at room temperature for 1 h, washed several times with distilled water, and dried at 60 °C for 9 h, and turned over regularly in the middle to obtain a floating photocatalyst MoO3 / MoO 3-x @LF8.

[0083] The following is a further illustration of the application of the floating defective molybdenum oxide photocatalyst prepared by the method of the present invention in algae hydration treatment through algae removal tests.

[0084] The experimental algal species was Microcystis aeruginosa, and the initial algal density was 2.0×10 6 cells / mL (OD≈0.2). It was placed in a photocatalytic reactor (the cut-off filter removed ultraviolet light with a wavelength less than 400 nm). One piece of the photocatalytic loofah prepared in Examples 1-5 was added to 80 mL of algal solution, and the reaction time was 6 h. Samples were taken every 1 h to measure the number of algal cells and the content of chlorophyll a.

[0085] After testing, the removal efficiency of the floating photocatalyst MoO3 / MoO 3-x @LF2 for algal cells and their chlorophyll a was 74.31% (the concentration of the photocatalyst suspension was 5 g / L). The removal efficiency of the floating photocatalyst MoO3 / MoO 3-x @LF4 for algal cells and their chlorophyll a was 98.18% (the concentration of the photocatalyst suspension was 6 g / L). Solid The floating photocatalyst MoO3 / Mo prepared in Example 3 3-x The removal efficiency of @LF7 for algal cells and their chlorophyll a is 95.67 % (the concentration of the photocatalyst suspension was 7 g / L). The floating photocatalyst MoO3 / MoO prepared in Example 4 3-x @LF 6.5 had a removal efficiency of 96.42% for algal cells and their chlorophyll a (the concentration of the photocatalyst suspension was 6.5 g / L). The floating photocatalyst MoO3 / MoO prepared in Example 5 3-x @LF8 had a removal efficiency of 97.65% for algal cells and their chlorophyll a (the concentration of the photocatalyst suspension was 8 g / L).

[0086] As shown in the appendix Figure 3 the removal effects of MoO3 / MoO 3-x @LF with different loadings on algal cells were quite different. Among them, the algae removal rate of the floating photocatalyst MoO3 / MoO 3-x @LF5 was about 74%, while the photocatalytic loofah algae removal effects of the floating photocatalysts MoO3 / MoO 3-x @LF6 and MoO3 / MoO 3-x @LF8 were similar, being 98.18% and 97.65% respectively. This was because the excessive loading of the photocatalyst caused the blockage of the pore structure inside the sponge, most of the adsorption sites could not function, and some of the catalysts were blocked inside the sponge and could not contact the external environment, resulting in the reduction of the photocatalytic ability and the removal efficiency of algal cells. Considering the cost and effect, MoO3 / MoO 3-x @LF6 was selected for subsequent further index detection.

[0087] As shown in the appendix Figure 4As shown, the chlorophyll a content of the control group first increased and then slightly decreased within 6 h of reaction time, indicating that under this condition, the light source and magnetic stirring had little effect on algal cells. The removal effect of the blank loofah group on algal cells was poor, with a removal rate of 4.32% compared with the control group. This was mainly because the vein-like structure of the loofah itself had a certain adsorption effect on algal cells. After 6 h of illumination, the chlorophyll content of MoO3 / Mo 3-x @LF6 decreased from the initial 592.51 mg / L to 48.35 mg / L, which was 10.4 mg / L lower than the content after treatment with the powdered photocatalyst, and was significantly different from the control group and the blank loofah group.

[0088] As shown in the appendix Figure 5 is the application diagram of the floating photocatalyst in the actual algal bloom water body. The prepared floating photocatalyst MoO3 / Mo 3-x @LF6 was put into the algal bloom water body. It could float on the water surface and after receiving sunlight irradiation, the algal cells aggregated and shrank on the floating carrier loofah, and the catalyst and the attached algal cells and cell debris could be directly salvaged.

[0089] The floating photocatalyst MoO3 / Mo 3-x @LF prepared by the above method of the present invention had a scanning electron micrograph of a three-dimensional network structure of rough vein-like filaments on the surface. During the loading process, the powdered catalyst was in close contact with it and adhered to the surface and pores of the carrier, and had a good algae removal effect. The algae removal rate could reach 98.18% within 6 h.

[0090] The floating defective molybdenum oxide photocatalyst prepared by the present invention is suitable for the removal of cyanobacteria. Without the additional use of toxic and harmful solvents for regulation, the self-doped MoO3 / Mo 3-x composite photocatalyst can be prepared by using a simple method with a single molybdenum salt precursor, which simplifies the process and greatly reduces the raw material cost, and is suitable for industrial promotion.

[0091] The present invention is not limited to the above embodiments. Based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and deformations of some technical features without creative labor according to the disclosed technical content, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A preparation method of a floating defective molybdenum oxide photocatalyst, characterized in that, It includes the following steps: a. Modify natural loofah sponge, and ultrasonically treat it in deionized water, inorganic base solution, and ionic surfactant in sequence, then dry to obtain modified loofah sponge. b. Prepare an ammonium molybdate solution using the hydrothermal method. Mix the ammonium molybdate solution with nitric acid according to a molar ratio of ammonium molybdate to nitric acid of (2 - 4):1, adjust the pH value, raise the temperature for reaction, cool to room temperature to obtain molybdenum trioxide MoO₃, dry it, and calcine it to obtain MoO with o-vacancy defects. 3-x Centrifuge and wash the reactants alternately, and dry them under vacuum to obtain the powdered photocatalyst MoO₃ / MoO. 3-x ; c. Add the powdered photocatalyst MoO3 / MoO3-x to ultrapure water to obtain a suspension of the powdered photocatalyst. According to the mass ratio of modified loofah sponge to powdered photocatalyst of 1:(2-5), add the modified loofah sponge to the suspension of the powdered photocatalyst, sonicate, and heat in a water bath. The vein-like structure of the loofah sponge is fully and evenly loaded with the catalyst. After aging, washing, and drying, the floating photocatalyst MoO3 / MoO 3-x @LF F 5 / 6 / 7 / 6.5 / 8 .

2. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 1, characterized in that, The modification treatment of natural loofah sponge is to soak natural loofah sponge in deionized water for 1 - 4 h, then soak it in inorganic base solution, dry it, place it in an ionic surfactant, oscillate it in a shaker, wash it, ultrasonically treat it for 30 - 90 min, and dry it at 40 - 80 °C for 3 - 12 h.

3. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 2, characterized in that, The inorganic base in the inorganic base solution is sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate or potassium bicarbonate. The ionic surfactant is cetyltrimethylammonium bromide solution, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetyl dimethylammonium chloride, polyethylene glycol or saponin.

4. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 1, characterized in that, In step b, prepare ammonium molybdate solution by mixing ammonium molybdate and distilled water at a solid-liquid ratio of 1:15 - 1:

25.

5. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 1, characterized in that, In step b, adjust the pH to 0.5 - 1.5, raise the temperature to 150 - 160 °C and react for 10 - 12 h.

6. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 1, characterized in that, Molybdenum trioxide MoO3 is calcined at 250 - 650 °C for 2 - 8 h with a heating rate of 5 - 10 °C / min; after the reactants are centrifuged and washed alternately, they are vacuum dried at 80 - 90 °C for 10 - 12 h.

7. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 1, characterized in that, In step c, add the powdered photocatalyst MoO3 / MoO3-x to ultrapure water to obtain a powdered photocatalyst suspension with a concentration of 5 - 8 g / L.

8. The preparation method of a floating defective molybdenum oxide photocatalyst according to claim 1, characterized in that, In step c, ultrasonically treat the modified loofah sponge and the powdered photocatalyst suspension for 10 - 15 min, heat them in a water bath at 30 - 70 °C for 1 - 8 h; age for 1 - 2 h, wash with distilled water 3 - 5 times, and dry at 60 - 70 °C for 8 - 10 h.

9. A floating defective molybdenum trioxide photocatalyst prepared by the method according to any one of claims 1 - 7.

10. Application of the floating defective molybdenum trioxide photocatalyst according to claim 9 in the treatment of algal blooms.

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