Ball-milled red mud photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a ball-milled red mud photocatalyst and a preparation method and application thereof, and belongs to the technical field of solid waste resource utilization, the ball-milled red mud is subjected to ball milling to obtain a red mud aqueous solution, a saturated Na2CO3 solution is added into the red mud aqueous solution, heating reaction is performed to obtain a red mud mixed solution, the red mud mixed solution is washed to be neutral, and the red mud photocatalyst is obtained. And centrifuging the neutral red mud mixed solution, and drying the obtained red mud precipitate to prepare the ball-milled red mud photocatalyst. Rich metal oxides in the red mud are activated after ball milling, active sites are enhanced, the effect of purifying the antibiotic wastewater is achieved, meanwhile, pollution of the red mud to the environment can be reduced, the environment treatment cost is reduced, and resource utilization of the red mud is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and in particular relates to a ball-milled red mud photocatalyst and a preparation method and application thereof. Background Art

[0002] Red mud is the main by-product of bauxite refining and contains rich metal oxides such as Fe 2 O 3 、Al 2 O 3 、TiO 2 Etc., has the effective potential to treat water pollutants. Different from the quality and processing technology of alumina, red mud can be classified into three types: Bayer red mud, sintering red mud and combined red mud. According to data from 2022, the total domestic alumina production exceeded 80 million tons, while the output of red mud reached more than 100 million tons, of which only 8 million tons were used, an increase of nearly 40% compared with 2021. According to the report, by 2025, the new comprehensive utilization rate of bulk solid waste should reach the target of 60%. However, as one of the difficult-to-treat solid wastes, the comprehensive utilization rate of red mud is only 7-8%, which is much lower than the utilization rate of other bulk industrial solid wastes. Due to the low effective recycling of red mud, a large amount of red mud can only be piled up by occupying a large amount of ground, resulting in a great waste of land resources. If the comprehensive utilization rate of red mud cannot be significantly improved, it will have a huge impact on industrial production and make normal production difficult. In addition, improper treatment of red mud may also cause serious pollution problems to soil, water resources and atmospheric environment. Therefore, the key is to improve the comprehensive utilization rate of red mud and thus solve the problem of large-scale accumulation of red mud.

[0003] Antibiotics are key drugs for treating bacterial infections and are widely used around the world. Today, their continued accumulation in the natural environment has turned into a long-term pollution problem, which poses a serious threat to human health. Using advanced oxidation technology to decompose antibiotics and other persistent toxic substances in water plays a very important role in solving water pollution.

[0004] Advanced oxidation technology involves the degradation of organic pollutants in water by generating free radicals with high oxidative capacity. Currently, the most widely used technology is the Fenton reaction. In recent years, researchers are exploring the use of sulfate free radicals (·SO 4-) is a new advanced oxidation technology. Sulfate radicals have a very strong standard redox potential (2.5-3.1eV), which means that they can theoretically oxidize most organic matter. Therefore, this advanced oxidation technology based on sulfate radicals shows great potential and application value. However, the catalytic effects of various metal-free materials vary and there are certain limitations. Therefore, finding an environmentally friendly catalyst with high catalytic efficiency is the key to implementing this technology. Summary of the invention

[0005] The present invention aims at the deficiencies in the prior art for degrading tetracycline pollutants, and provides a ball-milled red mud photocatalyst and its preparation method and application. The rich metal oxides in the red mud are activated after ball milling to enhance the active sites, thereby achieving the effect of purifying antibiotic wastewater, and at the same time reducing the pollution of the red mud to the environment, reducing the cost of environmental governance, and realizing the resource utilization of the red mud.

[0006] One of the technical solutions provided by the present invention:

[0007] A method for preparing a ball-milled red mud photocatalyst comprises the following steps: ball-milling red mud to obtain a red mud aqueous solution, adding saturated Na 2 CO 3 The solution is heated for reaction to obtain a red mud mixed solution, the red mud mixed solution is washed with water until it is neutral, the neutral red mud mixed solution is centrifuged, and the obtained red mud precipitate is dried to prepare the ball-milled red mud photocatalyst.

[0008] Preferably, the ball milling method is: mixing red mud and zirconium oxide balls, dry-milling for 1.5-6 hours at room temperature, adding water, and wet-milling for 1-3 hours.

[0009] If the dry grinding time is too long, the surface structure of the red mud will be destroyed, while if it is too short, less active sites on the red mud surface will be exposed. The main purpose of wet grinding is to make the grinding effect more uniform and the particle size more consistent.

[0010] Preferably, the mass ratio of the red mud to the zirconium oxide balls is 2:(40-60).

[0011] Too few zirconia balls will result in insufficient contact area with the red mud, resulting in insufficient grinding of the red mud, while too many zirconia balls will increase the capacity pressure of the reactor.

[0012] Preferably, the rotation speed of the ball mill is 250 rpm.

[0013] Preferably, the ratio of red mud to water is (1-3) g: (1-3) mL.

[0014] Preferably, the saturated Na 2 CO 3The volume ratio of the solution to the red mud aqueous solution is (40-60):(1-5).

[0015] By adding saturated Na 2 CO 3 The solution can remove impurities in red mud, expose more active sites on the surface of red mud, and saturate Na 2 CO 3 Adding too little solution will result in incomplete removal of impurities.

[0016] Preferably, the heating reaction is carried out at a temperature of 30-100°C and for a time of 1-2 hours.

[0017] The second technical solution provided by the present invention is:

[0018] A ball-milled red mud photocatalyst is prepared by the above-mentioned preparation method.

[0019] The third technical solution provided by the present invention is:

[0020] An application of the ball-milled red mud photocatalyst in degrading tetracycline in wastewater is to mix the ball-milled red mud photocatalyst with wastewater containing tetracycline, stir for 5-30 minutes in the dark, then add a monopersulfate solution, and carry out a photocatalytic reaction for 60-120 minutes.

[0021] Preferably, the added amount of the ball-milled red mud photocatalyst is 0.4-0.6 g per liter of tetracycline-containing wastewater, and the volume ratio of the tetracycline-containing wastewater to the monopersulfate solution is 15:(0.1-0.5).

[0022] Preferably, the tetracycline concentration in the tetracycline-containing wastewater is 20-60 mg / mL, and the concentration of the monopersulfate solution is 0.1 mol / L.

[0023] Preferably, stirring is carried out in the dark for 30 minutes, and then the monopersulfate solution is added and the photocatalytic reaction is carried out for 120 minutes.

[0024] The technical principle of the present invention for degrading tetracycline is:

[0025] The present invention utilizes ball-milled red mud photocatalyst to activate persulfate to generate sulfate free radicals (·SO 4 - ), Fe(II)+HSO 5 - →Fe(III)+SO 4 · - +OH -

[0026] Fe(III)+HSO 5 -→Fe(II)+SO 5 · - +H +

[0027] 2HSO 5 - +(Vo)¨→2HSO - 4 +O 2

[0028] O 2 +(Vo)¨+e - →O ·- 2

[0029] O ·- 2 +HSO 5 - →SO 4 · - +O 2 +OH -

[0030] Fe(III)+O ·- 2 →Fe(II)+O 2

[0031] 2Fe(III)+O 2- →2Fe(II)+O × o

[0032] O × o +HSO 5 - →HSO - 4 + 1 O 2

[0033] 2SO 5 · - +H 2 O→2HSO - 4 +1.5 1 O 2

[0034] 2SO 5 · - +O 2 - →2SO 4 .- +2O 2

[0035] 1 O 2 +SO 4 - +TC→Degraded products

[0036] Sulfate radicals have a high redox potential (2.5-3.1 eV), which allows them to react rapidly with most organic matter at a rate close to diffusion control. This method can effectively oxidize and decompose most organic pollutants. Considering that persulfates are mostly solid, easy to store and transport, and have good stability in the environment and good water solubility, they have shown significant advantages over other oxidants in practice. Commonly used persulfates include monopersulfate (SO 5- , PMS) and peroxydisulfate (S 2 O 8 2- , PS, also commonly known as persulfate), are common sources of sulfate radicals. The peroxydisulfate used in the present invention is potassium hydrogen persulfate (chemical formula: KHSO 5 ).

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] The present invention utilizes ball-milled red mud photocatalyst to treat tetracycline in antibiotic wastewater. Compared with red mud that has not been ball-milled, the present invention has better pore structure and selectivity, and the specific surface area is 1 times larger than that of the red mud that has not been ball-milled. The removal rate of tetracycline can be improved, providing a new method for the resource utilization of red mud. The ball milling operation has no strict technical requirements and can be mass-produced.

[0039] Compared with the traditional technology of using ultrasound and microwave to activate persulfate, the method of the present invention activates persulfate by ball-milling red mud photocatalyst to produce sulfate radicals and decompose organic matter. It does not require high temperature and high pressure or other complex equipment, and therefore has high operability.

[0040] Compared with the traditional Fenton catalytic method, the present invention has a wide pH application range and can also achieve good results under alkaline conditions. The present invention uses the method of "using waste to treat waste", which not only improves the utilization rate of red mud, but also reduces the production cost of photocatalysts and reduces the pollution to the environment.

[0041] The ball-milled red mud photocatalyst provided by the present invention uses a small amount of catalyst for catalyzing difficult-to-degrade organic matter. Compared with the prior art, the reagents used are green and non-toxic, can react at room temperature, the method is simple, low-cost and environmentally friendly, and persulfate can be efficiently activated at room temperature without high temperature and high pressure conditions, thereby reducing the cost of sewage treatment. After the reaction, the catalyst is easier to recover and reuse from the solution without causing secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 This is the XRD pattern of the ball-milled red mud photocatalyst prepared in Example 1;

[0044] Figure 2 TEM image of the ball-milled red mud photocatalyst prepared in Example 1 (magnification 500X);

[0045] Figure 3 This is a TEM image of the ball-milled red mud photocatalyst prepared in Example 1 (magnification is 200KX);

[0046] Figure 4 TEM image of the ball-milled red mud photocatalyst prepared in Example 1 (magnification 1000X);

[0047] Figure 5 The degradation curve of tetracycline catalytically oxidized and degraded by different dosages of monopersulfate solution in the presence of the ball-milled red mud catalyst prepared in Example 1;

[0048] Figure 6 is the first-order kinetic constant k for the catalytic oxidation degradation of tetracycline by different potassium persulfate dosages in the presence of the ball-milled red mud catalyst prepared in Example 1 app Value graph;

[0049] Figure 7 This is a degradation curve diagram of tetracycline catalytic oxidation degradation by the ball-milled red mud catalyst prepared in Example 1 of Application Example 6;

[0050] Figure 8 is a degradation curve diagram of tetracycline degradation by catalytic oxidation in Application Example 7;

[0051] Fig. 9 This is a graph showing the relationship between the reuse of ball-milled red mud photocatalyst and the degradation rate of tetracycline. DETAILED DESCRIPTION

[0052] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0053] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0054] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0055] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0056] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0057] The room temperature in the present invention refers to 25±2°C.

[0058] The monopersulfate (PMS) added in the embodiment of the present invention is potassium persulfate, and the concentration is 0.1 mol / L.

[0059] Example 1 A method for preparing ball-milled red mud photocatalyst

[0060] (1) Accurately weigh 2 g of pure red mud in a ball mill, add 50 g of zirconium oxide balls, and then dry grind at room temperature for 6 h. Then, add 2 mL of pure water to the mill and wet grind for 2 h to prepare a red mud aqueous solution;

[0061] (2) adding 50 mL of saturated sodium carbonate solution (saturated sodium carbonate can be obtained by adding 1.423 g of anhydrous sodium carbonate to 100 mL of pure water) to the red mud aqueous solution obtained in step (1), and then placing the ball mill in an oven (60° C., 1 h) to obtain a red mud mixed solution;

[0062] (3) washing the red mud mixed solution obtained in step (2) with water, wherein the water washing comprises centrifuging the red mud mixed solution (8000 r / min, 5 min) and removing the supernatant, adding 5 mL of pure water, ultrasonicating for 3 min, mixing the red mud precipitate obtained after centrifugation (8000 r / min, 5 min) with the pure water, centrifuging again, removing the supernatant, adding 5 mL of pure water to the obtained red mud precipitate, ultrasonicating for 3 min, mixing the red mud precipitate obtained after centrifugation with the pure water, centrifuging again, and repeating the above operation until the red mud and pure water mixed solution is neutral;

[0063] (4) The neutralized red mud mixed liquid is centrifuged (8000 r / min, 5 min), and the obtained red mud precipitate is dried (60° C., 8 h). The obtained ultrafine red mud is a ball-milled product of block red mud, i.e., a ball-milled red mud photocatalyst.

[0064] Figure 1 The XRD pattern of the ball-milled red mud photocatalyst prepared in Example 1 is shown in FIG. Figure 1 It can be clearly seen that the ball milling product is a composite of the simulated standard card Fe 2 O 3 and match, indicating that Fe from red mud 2 O 3 It is still the active component of ball-milled red mud. In addition, the crystal phase of red mud did not change significantly after ball milling, indicating that red mud has good mechanical strength.

[0065] Figure 2 TEM image of the ball-milled red mud photocatalyst prepared in Example 1 (magnification 500X); Figure 3 This is a TEM image of the ball-milled red mud photocatalyst prepared in Example 1 (magnification is 200KX); Figure 4 TEM image of the ball-milled red mud photocatalyst prepared in Example 1 (magnification 1000X); Figure 2-4 It can be seen that the morphology of the ball-milled red mud becomes relatively rough and loose, and some small particles appear, which will reduce the mass transfer resistance and expose more active sites.

[0066] Example 2 A method for preparing ball-milled red mud photocatalyst

[0067] (1) Accurately weigh 2 g of pure red mud in a ball mill, add 40 g of zirconium oxide balls, and then dry grind (room temperature, ball mill speed of 250 rpm, 6 h), then add 2 mL of pure water to the kettle and wet grind (room temperature, ball mill speed of 250 rpm, 2 h) to prepare a red mud aqueous solution;

[0068] (2) adding 50 mL of saturated sodium carbonate solution (saturated sodium carbonate can be obtained by adding 1.423 g of anhydrous sodium carbonate to 100 mL of pure water) to the red mud aqueous solution obtained in step (1), and then placing the ball mill in an oven (60° C., 1 h) to obtain a red mud mixed solution;

[0069] (3) washing the red mud mixed solution obtained in step (2) with water, wherein the water washing comprises centrifuging the red mud mixed solution (8000 r / min, 5 min) and removing the supernatant, adding 5 mL of pure water, ultrasonicating for 3 min, mixing the red mud precipitate obtained after centrifugation (8000 r / min, 5 min) with the pure water, centrifuging again, removing the supernatant, adding 5 mL of pure water to the obtained red mud precipitate, ultrasonicating for 3 min, mixing the red mud precipitate obtained after centrifugation with the pure water, centrifuging again, and repeating the above operation until the red mud and pure water mixed solution is neutral;

[0070] (4) The neutralized red mud mixture is centrifuged (8000 r / min, 5 min) to obtain the red mud precipitate, which is then dried (60° C., 8 h) to obtain the ball-milled red mud photocatalyst.

[0071] Example 3

[0072] (1) Accurately weigh 2 g of pure red mud in a ball mill, add 60 g of zirconium oxide balls, and then dry grind (room temperature, ball mill speed of 250 rpm, 6 h), then add 2 mL of pure water to the kettle and wet grind (room temperature, ball mill speed of 250 rpm, 2 h) to prepare a red mud aqueous solution;

[0073] (2) adding 50 mL of saturated sodium carbonate solution (saturated sodium carbonate can be obtained by adding 1.423 g of anhydrous sodium carbonate to 100 mL of pure water) to the red mud aqueous solution obtained in step (1), and then placing the ball mill in an oven (60° C., 1 h) to obtain a red mud mixed solution;

[0074] (3) washing the red mud mixed solution obtained in step (2) with water, wherein the water washing comprises centrifuging the red mud mixed solution (8000 r / min, 5 min) and removing the supernatant, adding 5 mL of pure water, ultrasonicating for 3 min, mixing the red mud precipitate obtained after centrifugation (8000 r / min, 5 min) with the pure water, centrifuging again, removing the supernatant, adding 5 mL of pure water to the obtained red mud precipitate, ultrasonicating for 3 min, mixing the red mud precipitate obtained after centrifugation with the pure water, centrifuging again, and repeating the above operation until the red mud and pure water mixed solution is neutral;

[0075] (4) The neutralized red mud mixture is centrifuged (8000 r / min, 5 min) to obtain the red mud precipitate, which is then dried (60° C., 8 h) to obtain the ball-milled red mud photocatalyst.

[0076] Application Example 1

[0077] The ball-milled red mud photocatalyst prepared in Example 1 was used to catalyze persulfate to produce sulfate radicals to degrade tetracycline (TC) under visible light:

[0078] (1) A TC degradation experiment was conducted on a photocatalytic reactor equipped with a filter (>420 nm) light source: 7.5 mg of the ball-milled red mud photocatalyst prepared in Example 1 was placed in three test tubes, 15 mL of tetracycline solution (concentration 20 mg / L) was added to each test tube (equivalent to adding 0.5 g of ball-milled red mud photocatalyst per liter of tetracycline solution), and then stirred in the dark for 30 min to ensure uniform dispersion of the ball-milled red mud photocatalyst in the suspension and achieve adsorption-desorption equilibrium of TC on the catalyst surface;

[0079] (2) adding 100 μL of monopersulfate solution to the solution stirred in step (1), and then immediately turning on the xenon lamp to carry out a photocatalytic reaction; starting from the time of adding the monopersulfate solution, sampling 1 mL at 0 min, 1 min, 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, and 60 min, respectively.

[0080] (3) The sample was filtered through a 0.22 μm membrane filter to remove the ball-milled red mud photocatalyst from the solution, and the absorbance of the TC solution at a wavelength of 356 nm before and after degradation was measured using an ultraviolet spectrophotometer.

[0081] Application Example 2

[0082] Same as Application Example 1, except that 500 μL of monopersulfate solution is added in step (2).

[0083] Application Example 3

[0084] Same as Application Example 1, except that 100 μL of pure water is added in step (2).

[0085] The calculation formula of TC degradation degree is: η(%) = (C0-Ct) / C0×100%.

[0086] Figure 5 The degradation curve of tetracycline catalytically oxidized and degraded by different monopersulfate solution dosages in the presence of the ball-milled red mud catalyst prepared in Example 1 is shown; Figure 5It can be seen that due to the addition of monopersulfate, the catalytic oxidation degradation of tetracycline in Application Example 1 (ball-milled red mud + 100 μL PMS) and Application Example 2 (ball-milled red mud + 500 μL PMS) has obvious effect. Application Example 3 (ball-milled red mud) shows that ball-milled red mud is an effective catalyst that can activate PMS to degrade tetracycline. It can be seen that by adding 7.5 mg of ball-milled red mud catalyst and 100 μL of PMS to 15 mL of tetracycline solution (concentration of 20 mg / L), the combined reaction for 60 minutes can degrade nearly 87% of tetracycline.

[0087] Figure 6 is the first-order kinetic constant k for the catalytic oxidation degradation of tetracycline by different potassium persulfate dosages in the presence of the ball-milled red mud catalyst prepared in Example 1 app Value graph, from Figure 6 It can be seen that the degradation performance of the ball-milled red mud + PMS system is significantly better than that of the ball-milled red mud system, and the degradation rate constant (k) is 42 times that of the ball-milled red mud.

[0088] Application Example 4

[0089] (1) A TC degradation experiment was conducted on a photocatalytic reactor equipped with a filter (>420 nm) light source: 6 mg of the ball-milled red mud photocatalyst prepared in Example 1 was placed in three test tubes, 15 mL of tetracycline solution (20 mg / L) was added to each test tube (equivalent to adding 0.4 g of ball-milled red mud photocatalyst per liter of tetracycline solution), and then stirred in the dark for 30 min;

[0090] (2) adding 100 μL of monopersulfate solution to the solution stirred in step (1), and then immediately turning on the xenon lamp to carry out a photocatalytic reaction; starting from the time of adding the monopersulfate solution, sampling 1 mL every 60 minutes.

[0091] (3) The sample was filtered through a 0.22 μm membrane filter to remove the ball-milled red mud photocatalyst from the solution. The absorbance of the TC solution before and after degradation at a wavelength of 356 nm was measured using an ultraviolet spectrophotometer. The degradation rate of tetracycline was determined to be 89%.

[0092] Application Example 5

[0093] (1) A TC degradation experiment was conducted on a photocatalytic reactor equipped with a filter (>420 nm) and a light source: 9 mg of the ball-milled red mud photocatalyst prepared in Example 1 was placed in three test tubes, 15 mL of tetracycline solution (20 mg / L) was added to each test tube (equivalent to 0.6 g of ball-milled red mud photocatalyst per liter of tetracycline solution), and then stirred in the dark for 30 min;

[0094] (2) adding 100 μL of monopersulfate solution to the solution stirred in step (1), and then immediately turning on the xenon lamp to carry out a photocatalytic reaction; starting from the time of adding the monopersulfate solution, sampling 1 mL every 60 minutes.

[0095] (3) The sample was filtered through a 0.22 μm membrane filter to remove the ball-milled red mud photocatalyst from the solution. The absorbance of the TC solution before and after degradation at a wavelength of 356 nm was measured using an ultraviolet spectrophotometer. The degradation rate of tetracycline was determined to be 90.7%.

[0096] Application Example 6

[0097] 7.5 mg of ball-milled red mud photocatalyst prepared in Example 1 was directly placed on a photocatalytic reactor, equipped with a filter (>420 nm) and a light source to catalytically degrade 15 mL of tetracycline solution (20 mg / L). 1 mL of samples were taken at 0 min, 1 min, 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, and 60 min after the photocatalyst was added. The samples were filtered through a 0.22 μm membrane to remove the photocatalyst from the solution. The absorbance of the TC solution at a wavelength of 356 nm before and after degradation was measured using an ultraviolet spectrophotometer. Figure 7 The degradation curve of tetracycline catalytic oxidation degradation by the ball-milled red mud catalyst prepared in Example 1 of Application Example 6 is shown in FIG. Figure 7 It can be seen that the ball-milled red mud catalyst alone degraded only 17% of the TC solution in 60 min.

[0098] Application Example 7

[0099] 100 μL of persulfate solution was directly added to 15 mL of tetracycline solution (20 mg / L) for catalytic degradation. 1 mL of samples were taken at 0 min, 10 min, 20 min, 30 min, 40 min and 60 min after the addition of the persulfate solution. The samples were passed through a 0.22 μm membrane filter and the absorbance of the TC solution at a wavelength of 356 nm before and after degradation was measured using an ultraviolet spectrophotometer. Figure 8 The degradation curve of tetracycline catalytic oxidation degradation in Application Example 7 is shown in FIG. Figure 8 It can be seen that PMS alone degraded 72% of the TC solution in 60 min, which is due to the slow generation of 1 O 2 (One of the main active substances).

[0100] Application Example 8

[0101] (1) A TC degradation experiment was conducted on a photocatalytic reactor equipped with a filter (>420 nm) light source: 7.5 mg of the ball-milled red mud photocatalyst prepared in Example 1 was placed in three test tubes, 15 mL of tetracycline solution (40 mg / L) was added to each test tube (equivalent to adding 0.5 g of ball-milled red mud photocatalyst per liter of tetracycline solution), and then stirred in the dark for 30 min;

[0102] (2) adding 100 μL of monopersulfate solution to the solution stirred in step (1), and then immediately turning on the xenon lamp to carry out a photocatalytic reaction; starting from the time of adding the monopersulfate solution, sampling 1 mL every 60 minutes.

[0103] (3) The sample was filtered through a 0.22 μm membrane filter to remove the ball-milled red mud photocatalyst from the solution. The absorbance of the TC solution before and after degradation at a wavelength of 356 nm was measured using an ultraviolet spectrophotometer. The degradation rate of tetracycline was determined to be 88%.

[0104] Application Example 9

[0105] (1) A TC degradation experiment was conducted on a photocatalytic reactor equipped with a filter (>420 nm) and a light source: 7.5 mg of the ball-milled red mud photocatalyst prepared in Example 1 was placed in three test tubes, 15 mL of tetracycline solution (60 mg / L) was added to each test tube (equivalent to adding 0.5 g of ball-milled red mud photocatalyst per liter of tetracycline solution), and then stirred in the dark for 30 min;

[0106] (2) adding 500 μL of monopersulfate solution to the solution stirred in step (1), and then immediately turning on the xenon lamp to carry out a photocatalytic reaction; starting from the time of adding the monopersulfate solution, sampling 1 mL every 60 minutes.

[0107] (3) The sample was filtered through a 0.22 μm membrane filter to remove the ball-milled red mud photocatalyst from the solution. The absorbance of the TC solution before and after degradation at a wavelength of 356 nm was measured using an ultraviolet spectrophotometer. The degradation rate of tetracycline was determined to be 99.52%.

[0108] Cyclic stability test of ball-milled red mud photocatalyst

[0109] In order to study the reusability of ball-milled red mud in the presence of PMS, TC-HCl degradation experiments were carried out five times in succession under the same conditions. The specific steps are as follows:

[0110] (1) A TC degradation experiment was conducted on a photocatalytic reactor equipped with a filter (>420 nm) light source: 7.5 mg of the ball-milled red mud photocatalyst prepared in Example 1 was placed in three test tubes, 15 mL of tetracycline solution (concentration 20 mg / L) was added to the test tubes, and then stirred in the dark for 30 min to ensure uniform dispersion of the ball-milled red mud photocatalyst in the suspension and achieve adsorption-desorption equilibrium of TC on the catalyst surface;

[0111] (2) adding 100 μL of monopersulfate solution to the solution stirred in step (1), and then immediately turning on the xenon lamp to carry out a photocatalytic reaction; starting from the time of adding the monopersulfate solution, sampling 1 mL at 0 min, 1 min, 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 40 min, and 60 min, respectively.

[0112] (3) The sample was filtered through a 0.22 μm membrane filter to remove the ball-milled red mud photocatalyst from the solution, and the absorbance of the TC solution at a wavelength of 356 nm before and after degradation was measured using an ultraviolet spectrophotometer.

[0113] (4) After the material is recovered, steps (1) to (3) are repeated 4 times.

[0114] Fig. 9 The relationship between the reuse of the ball-milled red mud photocatalyst prepared in Example 1 and the degradation rate of tetracycline is shown in FIG. Fig. 9 It can be seen that in the ball-milled red mud / PMS system, the degradation rate of TC solution in the 5th cycle only decreased by 7%, indicating that the ball-milled red mud has good reusability.

[0115] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a ball-milled red mud photocatalyst, characterized in that: The following steps are involved: The red mud is ball-milled to obtain a red mud aqueous solution, a saturated Na2CO3 solution is added to the red mud aqueous solution, and the mixture is heated for reaction to obtain a red mud mixed solution, the red mud mixed solution is washed with water until it is neutral, the neutral red mud mixed solution is centrifuged, and the obtained red mud precipitate is dried to prepare the ball-milled red mud photocatalyst.

2. The method for preparing ball-milled red mud photocatalyst according to claim 1, characterized in that: The ball milling method is: mixing red mud and zirconium oxide balls, dry milling for 1.5-6 hours at room temperature, adding water, and wet milling for 1-3 hours.

3. The method for preparing ball-milled red mud photocatalyst according to claim 2, characterized in that: The mass ratio of the red mud to the zirconium oxide balls is 2:(40-60).

4. The method for preparing ball-milled red mud photocatalyst according to claim 2, characterized in that: The dosage ratio of the red mud to water is (1-3) g: (1-3) mL.

5. The method for preparing ball-milled red mud photocatalyst according to claim 1, characterized in that: The volume ratio of the saturated Na2CO3 solution to the red mud aqueous solution is (40-60): (1-5).

6. The method for preparing ball-milled red mud photocatalyst according to claim 1, characterized in that: The temperature of the heating reaction is 30-100° C. and the time is 1-2 hours.

7. A ball-milled red mud photocatalyst, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the ball-milled red mud photocatalyst according to claim 7 in degrading tetracycline in wastewater, characterized in that: The ball-milled red mud photocatalyst is mixed with the wastewater containing tetracycline, stirred in the dark for 5-30 minutes, and then the monopersulfate solution is added to carry out the photocatalytic reaction for 60-120 minutes.

9. The use according to claim 8, characterized in that: The amount of the ball-milled red mud photocatalyst added is 0.4-0.6 g per liter of tetracycline-containing wastewater, and the volume ratio of the tetracycline-containing wastewater to the monopersulfate solution is 15:(0.1-0.5).

10. The use according to claim 8, characterized in that: The concentration of tetracycline in the tetracycline-containing wastewater is 20-60 mg / mL, and the concentration of the monopersulfate solution is 0.1 mol / L.

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