Modified manganese sand as well as preparation method and application thereof in sewage treatment

Abstract

The invention relates to the technical field of sewage treatment, in particular to modified manganese sand and a preparation method and application thereof in sewage treatment. The preparation method comprises the following steps: preparing g-C3N4 powder by taking urea as a precursor; the preparation method comprises the following steps: adding g-C3N4 into pure water, and carrying out ultrasonic treatment to obtain a g-C3N4 suspension; manganese sand is added into the g-C3N4 turbid liquid, magnetic stirring and heating are carried out, and a mixture containing modified manganese sand is obtained; and washing, drying and grinding the mixture to obtain the modified manganese sand. The preparation method disclosed by the invention is simple, mild in reaction condition and free of environmental pollution. The composite material prepared by the method can be simultaneously subjected to adsorption treatment and photocatalysis treatment in the water treatment process. MnO2 in the manganese sand promotes transfer and separation of free charges of g-C3N4, so that the light conversion efficiency of g-C3N4 is improved, the treatment effect on sulfonamide compounds is improved, and the purpose of removing pollution in water more efficiently is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to modified manganese sand and a preparation method thereof and application thereof in sewage treatment. Background Art

[0002] Manganese sand is a natural mineral with manganese dioxide as its main component, usually gray-black or brown-red. It has a high specific surface area and porosity, which enables manganese sand to effectively adsorb and remove impurities in water during the filtration process. In addition, manganese sand has good chemical stability and mechanical strength. In addition, it has the characteristics of low price, wide availability, and easy operation. In recent years, it has gradually been used in the deep treatment process of water, and its application has become more and more extensive. It plays an irreplaceable role in the fields of drinking water purification and industrial wastewater treatment. Manganese sand filter material can effectively remove pollutants such as heavy metal ions, some organic matter and chromaticity in wastewater, and reduce the impact of wastewater on the environment.

[0003] Although manganese sand has good adsorption properties in water treatment, its application scenarios as an adsorbent for water treatment are limited by its limited specific surface area, small adsorption capacity, and negative surface charge under neutral pH conditions. Especially when treating certain specific pollutants, such as sulfonamide compounds, the limited effect is more prominent. Sulfonamide compounds are a class of chemical substances widely used in medicine, agriculture and other fields, with high toxicity and biodegradability. In the water environment, sulfonamide compounds may pose a potential threat to the ecosystem and human health. Given that the current treatment effect of manganese sand on sulfonamide compounds is not ideal, it is often necessary to perform multiple adsorptions, or to assist with other more expensive means to improve the treatment effect on sulfonamide compounds, resulting in longer water treatment cycles and high costs. Summary of the invention

[0004] In order to solve or partially solve the problems existing in the related art, the present invention provides a modified manganese sand and a preparation method thereof and application in sewage treatment.

[0005] The present invention provides a method for preparing modified manganese sand, which comprises: Step a), using urea as a precursor to prepare g-C3N4 powder; Step b), adding the g-C3N4 into pure water and performing ultrasonic treatment to obtain a g-C3N4 suspension; Step c), adding manganese sand to the g-C3N4 suspension, performing magnetic stirring and heating to obtain a mixture containing modified manganese sand; Step d), washing, drying and grinding the mixture to obtain modified manganese sand.

[0006] Furthermore, the step a) is specifically as follows: The urea is calcined at a high temperature of 500-600°C, the time of 1.5-2.5h, and the heating rate of 3-7°C / min to obtain g-C3N4 powder.

[0007] Furthermore, in the step b), the ultrasonic frequency is 40W-60W, and the ultrasonic time is 0.5-2h.

[0008] Furthermore, in the step c), the mixing ratio of g-C3N4 and manganese sand is (8~12):1.

[0009] Furthermore, in the step c), the magnetic stirring and heating are performed for 10 to 14 hours at a temperature of 70 to 90°C.

[0010] Furthermore, before step c), the step of pre-treating the manganese sand is also included, which is specifically as follows: Place manganese sand in pure water for ultrasonic treatment and then filter; The filtered manganese sand is subjected to magnetic stirring; The manganese sand after magnetic stirring was washed alternately with water and ethanol; The washed manganese sand is dried and then ground into powder.

[0011] Furthermore, in the step d), the drying temperature is 60-85° C. and the time is 10-15 hours.

[0012] The present invention also provides a modified manganese sand, which is prepared according to any one of the methods described above.

[0013] The present invention also provides an application of the modified manganese sand in sewage treatment.

[0014] Further, it comprises the steps of: The modified manganese sand is added into sewage containing sulfonamide compounds, dispersed evenly, and allowed to stand under normal lighting conditions.

[0015] The preparation method of modified manganese sand provided by the present invention and the preparation method thereof can include the following beneficial effects: 1. The preparation method is to mix g-C3N4 powder prepared by using urea as a precursor with manganese sand after ultrasonic dispersion, and finally prepare a g-C3N4 / manganese sand composite material. The preparation method of the present invention is simple, the reaction conditions are mild, and there is no pollution to the environment.

[0016] 2. The composite material prepared by this method can be subjected to adsorption treatment and photocatalytic treatment at the same time during water treatment. MnO2 in manganese sand promotes the transfer and separation of free charges of g-C3N4, thereby improving the photoconversion efficiency of g-C3N4. Compared with traditional manganese sand filter materials, it can not only achieve the effect of adsorption, but also use daytime light under natural conditions to perform photocatalytic decomposition, thereby improving the treatment effect of sulfonamide compounds and achieving the purpose of removing water pollution more efficiently.

[0017] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0019] Figure 1 is a scanning electron microscope image of the modified manganese sand prepared in Example 1 of the present invention; Figure 2 is a scanning electron microscope image of g-C3N4 prepared in Example 1 of the present invention; Figure 3 is a scanning electron microscope image of the pretreated manganese sand obtained in Example 1 of the present invention; Figure 4 This is the removal rate curve of 2 ppm sulfadiazine by the modified manganese sand prepared in Example 1 of the present invention.

[0020] Figure 5 The present invention is the removal rate curve of 2ppm sulfadiazine by the modified manganese sand, g-C3N4 and pretreated manganese sand prepared in Example 1; Figure 6 The modified manganese sand, g-C3N4 and pretreated manganese sand prepared in Example 1 of the present invention, and the modified manganese sand, g-C3N4 and pollutant residual rate curves for 2 ppm sulfadiazine prepared in Comparative Example 1; Figure 7 It is the removal rate curve of 2 ppm sulfadiazine by the modified manganese sand, g-C3N4 and pretreated manganese sand prepared in Example 2; Figure 8 It is the removal rate curve of 2ppm sulfadiazine by the modified manganese sand, g-C3N4 and pretreated manganese sand prepared in Example 3; Figures 4 to 8 The medium gray area simulates the night environment. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0023] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0024] As a non-metallic semiconductor material, graphite carbon nitride (g-C3N4) has the activity of catalytic removal of pollutants under visible light at the non-nanoscale. In addition, its chemical properties are relatively stable in acidic and alkaline environments, with high thermal stability, wide and easy-to-obtain raw material sources, easy preparation, non-toxicity and good biocompatibility. Therefore, it has been widely used in photocatalytic degradation of pollutants. However, g-C3N4 has relatively weak absorption of visible light, and due to its own electronic structure and band structure characteristics, the separation efficiency of photogenerated charges is relatively low. This may lead to the recombination and loss of photogenerated charges, reducing the photocatalytic activity and efficiency. At present, in order to improve the photocatalytic performance of g-C3N4, most of them are mainly doped with various elements (metal elements such as Na, Fe or non-metal elements such as P, S, etc.) or semiconductor composites such as TiO2 and ZnO. Improve the absorption capacity of g-C3N4 to visible light and enhance the separation efficiency of photogenerated charges, thereby improving its photocatalytic activity and efficiency, such as the Chinese patent document with publication number CN114210355A. However, such methods have relatively harsh reaction conditions and high costs.

[0025] The inventor of the present application considered using g-C3N4 to perform composite modification on manganese sand. Since the bandgap width of g-C3N4 is 2.7eV (valence band is -1.3 eV, conduction band is 1.4 eV), it can absorb and utilize light energy in the visible light range, and manganese sand is rich in MnO2. After g-C3N4 is modified and composited with manganese sand, MnO2 in manganese sand promotes the transfer and separation of free charges, thereby improving the light conversion efficiency of g-C3N4. Compared with traditional manganese sand filter materials, it can better utilize daylight under natural conditions, achieving the purpose of removing water pollution with higher efficiency.

[0026] Therefore, the embodiment of the present invention provides a method for preparing modified manganese sand, which comprises: Step a), using urea as a precursor to prepare g-C3N4 powder; Step b), adding the g-C3N4 into pure water and performing ultrasonic treatment to obtain a g-C3N4 suspension; Step c), adding manganese sand to the g-C3N4 suspension, performing magnetic stirring and heating to obtain a mixture containing modified manganese sand; Step d), washing, drying and grinding the mixture to obtain modified manganese sand.

[0027] In the above-mentioned preparation method, step a) is the step of preparing g-C3N4 powder, and the obtained g-C3N4 powder is subsequently used to load on the surface of manganese sand. In this step, urea is used as a precursor to prepare g-C3N4 powder. The inventors of the present application have found that the selection of g-C3N4 precursor has an impact on the performance of the final modified manganese sand filter material. Relative to other precursors such as melamine, urea is used as a precursor to prepare g-C3N4 powder, and the modified filter material finally obtained has a stronger processing ability for sulfonamide compounds, so the present application uses urea as a precursor to prepare g-C3N4 powder.

[0028] Step a) is preferably as follows: The urea is calcined at a high temperature of 500-600°C, a time of 1.5-2.5 hours, and a heating rate of 3-7°C / min to obtain g-C3N4 powder. More preferably, the calcination temperature is 550°C, the time is 2 hours, and the heating rate is 5°C / min.

[0029] The inventors of the present application further found that after the prepared g-C3N4 powder was directly compounded with manganese sand, the obtained manganese sand had an unsatisfactory removal effect on sulfonamide compounds. The inventors of the present application found that by pre-dispersing the g-C3N4 into a uniform suspension, the problem of agglomeration in the subsequent compounding process can be effectively avoided. Therefore, in order to improve the processing capacity of the modified manganese sand filter material, the present application adds a step of ultrasonically dispersing the g-C3N4 powder before compounding, that is, the above-mentioned step b). In this step, g-C3N4 is added to pure water for ultrasonic treatment to obtain a uniformly dispersed suspension of g-C3N4. As a preferred embodiment of this step, the ultrasonic frequency is 40W~60W, and the ultrasonic time is 0.5~2h. More preferably, the ultrasonic frequency is 50W and the ultrasonic time is 1h. The mixing ratio of g-C3N4 and pure water is preferably 1g: (400~600) ml, and more preferably 1g: 500ml.

[0030] Above-mentioned step c) is the step of compounding g-C3N4 and manganese sand, and this step is to add manganese sand to g-C3N4 suspension, then carry out magnetic stirring and heating, finally obtain the mixture containing modified manganese sand, and the modified manganese sand obtained is g-C3N4 / manganese sand composite material. This composite material can be subjected to adsorption treatment and photocatalytic treatment simultaneously during water treatment. MnO2 in manganese sand promotes the transfer and separation of free charge of g-C3N4, so that the light conversion efficiency of g-C3N4 is improved. Compared with traditional manganese sand filter material, it can not only play the effect of adsorption, but also can utilize daytime illumination under natural conditions, carry out photocatalytic decomposition, improve the treatment effect of sulfonamide compounds, and achieve the purpose of removing pollution in water more efficiently.

[0031] Heating helps to accelerate the rate of compounding. Stirring helps to further refine the manganese sand particles and increase the contact area between manganese sand and g-C3N4. On the other hand, it helps the uniformity of g-C3N4 and manganese sand compounding. In this step, the time of magnetic stirring and heating is preferably 10-14 hours, and the temperature is 70-90°C. More preferably, the time of magnetic stirring and heating is 12 hours, and the temperature is 80°C. The mixing ratio of g-C3N4 and manganese sand is preferably (8-12):1, and more preferably 10:1.

[0032] The inventors of the present application also found that the stability of the treatment effect of the manganese sand filter material obtained after compounding on sulfonamide compounds needs to be improved. The inventors of the present application found through research that the source of manganese sand has an impact on the performance of the compounded product. This may be because the impurities and contents of manganese sand from different sources are different, which affects the adsorption of g-C3N4, thereby causing the difference in the treatment effect of the final product on sulfonamide compounds. In order to improve the stability of the performance of the final product, the present application preferably includes a step of pre-treating the manganese sand before step c), as follows: Place manganese sand in pure water for ultrasonic treatment and then filter; The filtered manganese sand is subjected to magnetic stirring; The manganese sand after magnetic stirring was washed alternately with water and ethanol; The washed manganese sand is dried and then ground into powder.

[0033] In the above-mentioned pretreatment process, placing manganese sand in pure water for ultrasonic treatment can effectively remove impurities and pollutants on the surface of manganese sand and improve the purity of manganese sand. The ultrasonic time is preferably 40-90min, and the most preferred is 1h. Magnetic stirring after filtration helps to break up manganese sand into finer particles, increase the surface area of ​​manganese sand, and enhance the impurity removal effect of subsequent washing. Preferably, the time of magnetic stirring is 5-7h, and the most preferred is 6h. Using water and ethanol to alternately wash the manganese sand after magnetic stirring and ethanol to alternately wash can more effectively remove organic and inorganic impurities on the surface and inside of manganese sand, further improve the purity of manganese sand, and reduce the influence of impurities on subsequent compounding. It can be understood by those skilled in the art that centrifugation is required after each washing, the supernatant is removed, and the next washing or subsequent drying is performed. The effect of drying and grinding after alternating washing is: drying is used to remove moisture and residual ethanol in manganese sand; grinding can refine manganese sand particles, increase its specific surface area, and facilitate subsequent adsorption and reaction. The drying temperature is preferably 60-85°C, the drying time is preferably 10-15 hours, and the grinding time is preferably 10-15 minutes. Most preferably, the drying temperature is 80°C, the drying time is 12 hours, and the grinding time is 12 minutes.

[0034] After compounding according to step c), the post-treatment step can be performed according to step d). This step is to wash, dry and grind the mixture containing modified manganese sand obtained in step c) to obtain modified manganese sand. The drying temperature is preferably 60-85°C, and the time is preferably 10-15h. More preferably, the drying temperature is 60°C and the time is 12h. Washing is used to clean up the impurities remaining in the g-C3N4 / manganese sand composite material. It can be understood by those skilled in the art that after washing, centrifugation is performed, and the washing process is completed after removing the supernatant, and the subsequent drying and grinding processes can be performed. Drying removes the residual moisture in the g-C3N4 / manganese sand composite material, and grinding can refine the composite material and increase its specific surface area, which is beneficial to the adsorption and photocatalytic effect in the subsequent water treatment process.

[0035] Another embodiment of the present invention also provides a modified manganese sand, which is prepared according to the above method. The modified manganese sand is a g-C3N4 / manganese sand composite material, which can be subjected to adsorption treatment and photocatalytic treatment simultaneously during water treatment. The MnO2 in the manganese sand promotes the transfer and separation of the free charge of g-C3N4, thereby improving the photoconversion efficiency of g-C3N4. Compared with traditional manganese sand filter materials, it can not only achieve the effect of adsorption, but also use daytime illumination under natural conditions to perform photocatalytic decomposition, thereby improving the treatment effect of sulfonamide compounds and achieving the purpose of removing pollution in water more efficiently.

[0036] From the above content, it can be seen that the preparation method of modified manganese sand provided by the embodiments of the present invention and the preparation method thereof have the following advantages: 1. The preparation method is to mix g-C3N4 powder prepared by using urea as a precursor with manganese sand after ultrasonic dispersion, and finally prepare a g-C3N4 / manganese sand composite material. The preparation method of the present invention is simple, the reaction conditions are mild, and there is no pollution to the environment.

[0037] 2. The composite material prepared by this method can be subjected to adsorption treatment and photocatalytic treatment at the same time during water treatment. MnO2 in manganese sand promotes the transfer and separation of free charges of g-C3N4, thereby improving the photoconversion efficiency of g-C3N4. Compared with traditional manganese sand filter materials, it can not only achieve the effect of adsorption, but also use daytime light under natural conditions to perform photocatalytic decomposition, thereby improving the treatment effect of sulfonamide compounds and achieving the purpose of removing water pollution more efficiently.

[0038] Another embodiment of the present invention further provides an application of the modified manganese sand in sewage treatment. Specifically, the application may include the following steps: The modified manganese sand is added into sewage containing sulfonamide compounds, dispersed evenly, and allowed to stand under normal lighting conditions.

[0039] This method can achieve efficient removal of sulfonamide compounds in sewage under daily lighting conditions.

[0040] The technical solution of the present invention is further described below in conjunction with specific embodiments: Example 1 (1) Grind 10 g of urea and transfer it to a 50 ml alumina crucible. Place it in a muffle furnace and heat it at 550 °C for 120 min at a rate of 5 °C / min to obtain powdered g-C3N4.

[0041] (2) The manganese sand was soaked in pure water and ultrasonically treated for 1 hour. After filtering, the manganese sand was magnetically stirred for 6 hours. The manganese sand was transferred to a centrifuge tube and washed and centrifuged alternately with water and ethanol. The sand was dried at 80°C for 12 hours and ground into powder to obtain pretreated manganese sand.

[0042] (3) Place 100 mg of g-C3N4 in a 100 mL beaker, add 50 mL of pure water and ultrasonicate for 1 h to obtain a suspension. Add 1 g of pretreated manganese sand to the suspension and stir on a magnetic stirrer at 80 °C for 12 h to obtain a slurry mixture.

[0043] (4) The mixture is washed alternately with water and ethanol, centrifuged, placed in a forced air drying oven at 60° C. for 24 h, and then ground into powder to obtain modified manganese sand.

[0044] In this embodiment, the scanning electron microscope image of the modified manganese sand obtained in step (4) is as follows: Figure 1 The scanning electron microscope image of g-C3N4 prepared in step (1) is shown in Figure 2 As shown, the scanning electron microscope image of the pretreated manganese sand obtained in step (2) is as follows Figure 3 As shown. Figures 1 to 3 It can be seen that g-C3N4 is successfully composited onto manganese sand.

[0045] The modified manganese sand prepared in Example 1 was tested for the time required to reach the upper limit of removal of 2 ppm sulfonamide compounds according to the following method: Take 55mg of modified manganese sand filter material and add it to 50mL of 2mg / L sulfadiazine solution. Ultrasonicate for 5min to disperse evenly, put it in a shaker at 170rpm and 30℃, use a low-voltage 12V8mm wide white light strip to simulate daytime light, and alternate light and dark every 12h. The sampling time nodes are 0, 12, 24, 36, 48, 60, 72, 84, 96, 108 and 120h. After sampling, the sample is filtered through a 0.22μm water filter membrane, and the filtered sample is analyzed by liquid chromatography. The test results are as follows: Figure 4 As shown by Figure 4 It can be seen that the removal trend of 2ppm sulfadiazine by modified manganese sand tends to be stable after 48h. Considering the time cost, the experiment uniformly adopts 48h as a cycle.

[0046] Comparative Example 1 (1) Take 10 g of melamine, grind it and transfer it to a 50 ml alumina crucible. Place it in a muffle furnace and heat it at 550 °C for 120 min at a rate of 5 °C / min to obtain powdered g-C3N4.

[0047] Steps (2) to (4) are the same as those in Example 1.

[0048] The modified manganese sand, g-C3N4 and pretreated manganese sand in Example 1 are respectively denoted as A, A1 and A2. The modified manganese sand and g-C3N4 in Comparative Example 1 are respectively denoted as B and B1. The treatment capacity of five filter materials A, A1, A2, B and B1 for sulfonamide compounds in sewage was tested according to the feed ratio.

[0049] The test method is as follows: Take 55mg of modified manganese sand filter material, 5mg of g-C3N4 and 50mg of pretreated manganese sand and add them to 50mL of 2mg / L sulfadiazine solution, ultrasonicate for 5min to disperse evenly, put it in a shaker at 170rpm and 30℃, use a low-voltage 12V8mm wide white light strip to simulate daytime light, and alternate light and dark every 12h. The sampling time nodes are selected as 0, 2, 5, 8, 12, 24, 36, and 48h. After sampling, the samples are filtered through a 0.22-micron water filter membrane, and the filtered samples are analyzed by liquid chromatography. The analysis results are as follows Figure 5 and Figure 6 As shown by Figure 5 and Figure 6 It can be seen that: The treatment capacity of modified manganese sand for sulfonamide compounds is improved compared with that of manganese sand and g-C3N4; The modified manganese sand obtained by using urea as a precursor of g-C3N4 has a stronger ability to treat sulfonamide compounds than the modified manganese sand obtained by using urea as a precursor of g-C3N4; The modified manganese sand obtained in Example 1 can achieve a 65-70% removal rate of 2 mg / L sulfadiazine within 24 hours; and a 80-85% removal rate of 2 mg / L sulfadiazine within 48 hours.

[0050] Example 2 On the basis of Example 1, the ratio of g-C3N4 to pretreated manganese sand in step (3) was changed to 1:5, and the modified manganese sand prepared in this example was recorded as A 1-5 . Test A according to feed ratio 1-5 , the treatment capacity of A1 (g-C3N4) and A2 (pretreated manganese sand) for sulfonamide compounds in sewage.

[0051] The test method is as follows: Take 55mg of modified manganese sand filter material, 9.2mg of g-C3N4 and 45.8mg of pretreated manganese sand and add them to 50mL of 2mg / L sulfadiazine solution, ultrasonicate for 5min to disperse evenly, put it in a shaker at 170rpm and 30℃, use a low-voltage 12V8mm wide white light strip to simulate daytime light, and alternate light and dark every 12h. The sampling time nodes are selected as 0, 2, 5, 8, 12, 24, 36, and 48h. After sampling, the samples are filtered through a 0.22-micron water filter membrane, and the filtered samples are analyzed by liquid chromatography. The analysis results are as follows Figure 7 shown.

[0052] Example 3 On the basis of Example 1, the ratio of g-C3N4 to pretreated manganese sand in step (3) was changed to 1:20, and the modified manganese sand prepared in this example was recorded as A 1-20 . Test A according to feed ratio 1-5 , the treatment capacity of A1 and A2 for sulfonamide compounds in sewage.

[0053] The test method is as follows: Take 55 mg of modified manganese sand filter material, 2.6 mg of g-C3N4 and 52.4 mg of pretreated manganese sand and add them to 50 mL of 2 mg / L sulfadiazine solution, ultrasonicate for 5 minutes to disperse evenly, put it in a shaker at 170 rpm and 30 ° C, use a low-voltage 12V8mm wide white light strip to simulate daytime light, and alternate light and dark every 12 hours. The sampling time nodes are selected as 0, 2, 5, 8, 12, 24, 36, and 48 hours. After sampling, the samples are filtered through a 0.22-micron water filter membrane, and the filtered samples are analyzed by liquid chromatography. The analysis results are as follows Figure 8 shown.

[0054] By comparing Figure 5 and Figure 7 and Figure 8 It can be seen that: The mixing ratio of g-C3N4 and pretreated manganese sand has an impact on the sewage treatment capacity of modified manganese sand. When the ratio of g-C3N4 and pretreated manganese sand is 1:5, the water treatment effect of sulfonamide compounds of modified manganese sand is not significantly improved compared with the ratio of 1:10, but the cost increases; when the ratio of g-C3N4 is 1:20, the water treatment effect of sulfonamide compounds of modified manganese sand is significantly reduced compared with the ratio of 1:10. Considering the treatment effect and preparation cost, it is best to use a ratio of g-C3N4 and pretreated manganese sand of 1:10 to prepare modified manganese sand.

[0055] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing modified manganese sand, characterized in that: include: Step a), using urea as a precursor to prepare g-C3N4 powder; Step b), adding the g-C3N4 into pure water and performing ultrasonic treatment to obtain a g-C3N4 suspension; Step c), adding manganese sand to the g-C3N4 suspension, performing magnetic stirring and heating to obtain a mixture containing modified manganese sand; Step d), washing, drying and grinding the mixture to obtain modified manganese sand.

2. The preparation method according to claim 1, characterized in that: The step a) is specifically as follows: The urea is calcined at a high temperature of 500-600°C for 1.5-2.5h at a heating rate of 3-7°C / min to obtain g-C3N4 powder.

3. The preparation method according to claim 1, characterized in that: In the step b), the ultrasonic frequency is 40W-60W, and the ultrasonic time is 0.5-2h.

4. The preparation method according to claim 1, characterized in that: In the step c), the mixing ratio of g-C3N4 and manganese sand is (8-12):

1.

5. The preparation method according to claim 1, characterized in that: In the step c), the magnetic stirring and heating time is 10-14 hours, and the temperature is 70-90°C.

6. The preparation method according to claim 1, characterized in that: The step of pre-treating the manganese sand is also included before step c), which is specifically as follows: Place manganese sand in pure water for ultrasonic treatment and then filter; The filtered manganese sand is subjected to magnetic stirring; The manganese sand after magnetic stirring was washed alternately with water and ethanol; The washed manganese sand is dried and then ground into powder.

7. The preparation method according to claim 1, characterized in that: In the step d), the drying temperature is 60-85° C. and the drying time is 10-15 hours.

8. A modified manganese sand, characterized in that: It is prepared according to the method according to any one of claims 1 to 7.

9. Use of the modified manganese sand according to claim 8 in sewage treatment.

10. The use according to claim 9, characterized in that: Includes steps: The modified manganese sand is added into sewage containing sulfonamide compounds, dispersed evenly, and allowed to stand under normal lighting conditions.

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