Preparation method and application of composite modified heavy medium for sewage treatment

Abstract

The present invention provides a preparation method and application of a composite modified heavy medium for sewage treatment, wherein the preparation method comprises: soaking, rinsing and drying the heavy medium with acidic and alkaline solutions respectively; etching the surface of the treated heavy medium with an acid solution; placing the heavy medium in a polydopamine solution for stirring and drying twice; placing the dried heavy medium in a metal cation solution for stirring and drying for the third time; rinsing the obtained heavy medium with deionized water for multiple times and drying for the fourth time, and finally obtaining a composite modified heavy medium. The preparation method provided by the present invention is simple, easy to operate, and has low production cost. The obtained product simultaneously realizes effective sedimentation of suspended matter with positive and negative charges, and has excellent sewage treatment effect.

Description

Technical Field

[0001] The invention belongs to the field of sewage (waste) water treatment, and specifically relates to a preparation method and application of a composite modified heavy medium for sewage treatment that can accelerate the rapid sedimentation of suspended matter in a sedimentation tank. Background Art

[0002] In the process of sewage (waste) water treatment, the sedimentation rate of suspended matter in ordinary sedimentation tanks is slow. The industry can selectively add heavy medium to the sedimentation tank to accelerate the suspended sedimentation rate of the sedimentation tank, thereby enhancing the sewage treatment effect. However, traditional heavy medium filter materials have defects such as few surface voids, small specific surface area, and small porosity.

[0003] There have been studies on modified filter materials in the prior art. For example, Chinese patent CN 114380343 A discloses a method for preparing an iron oxide modified quartz sand filter material. The quartz sand raw material is screened for particle size through a sieve with a specific mesh size, and pickled with hydrochloric acid to remove organic impurities on the surface; after adding ferric chloride solution, it is baked in an oven and then placed in a muffle furnace for high-temperature calcination to obtain a modified quartz sand filter material with iron oxide attached. The modified quartz sand filter material has a good removal effect on negatively charged pollutants such as microplastics and Escherichia coli in water. However, the filter material has technical defects such as being modified with a single substance, having a small surface area, and being applicable to a small amount of water quality. Summary of the invention

[0004] In view of the defects of the prior art, the present invention proposes a preparation method and application of a composite modified heavy medium for sewage treatment. The composite modified heavy medium filter material obtained by the preparation method provided by the present invention has metal cations and anions on the surface of organic functional groups, which is more conducive to the removal of various pollutants and suspended solids in the sedimentation tank, can improve the treatment efficiency, and improve the effluent water quality. At the same time, it has the advantages of convenient acquisition and low price.

[0005] To achieve the above effects, the first aspect of the present invention provides a method for preparing a composite modified heavy medium for sewage treatment, comprising the following specific steps: S1: using an acidic solution and an alkaline solution to soak, rinse and dry the heavy medium, wherein the heavy medium is a non-magnetic heavy medium; S2: using an acid solution to etch the surface of the heavy medium treated by S1; specifically: placing the heavy medium in 1wt% to 50wt% hydrofluoric acid, controlling the reaction temperature to 30 to 70°C, and performing an etching reaction for 15 min to 90 min to obtain a heavy medium after surface etching, so as to increase the contact area between the heavy medium and the reaction solvent and / or the sewage to be treated; S3: placing the heavy medium after surface etching obtained in S2 in a 1.g·L -1The first stirring is performed in the polydopamine solution of S3, and the first drying is performed at the first temperature to obtain a modified heavy medium having an etched surface preliminarily coated with polydopamine nanoparticles; wherein the first stirring time is 4 hours, the first temperature is 40° C., and the first drying time is 24 hours; S4: the surface modified heavy medium preliminarily coated with polydopamine nanoparticles obtained in S3 is again placed in a 1 g·L -1 The polydopamine solution is stirred for a second time, and dried for a second time at a second temperature higher than the fixed value of the first temperature to form a surface-modified heavy medium having a polydopamine nanoparticle layer uniformly coated on the etched surface; wherein the polydopamine nanoparticle layer uniformly coated on the etched surface; the second stirring time is 2 hours, the second temperature is 60°C, and the second drying time is 12 hours. S5: The heavy medium obtained in S4 after the second drying is placed in a metal cation solution, stirred for a third time, and dried for a third time at a third temperature; S6: The heavy medium obtained in S5 after the third drying is rinsed multiple times with deionized water, and dried for a fourth time at a fixed fourth temperature to obtain a composite modified heavy medium.

[0006] Optionally, step S1 specifically includes: S11: soaking the heavy medium in an alkaline solution with a pH value of 8 to 9 for 1 to 2 hours, taking it out and rinsing it with deionized water, and drying it in an oven at 110°C to 116°C; S12: soaking the heavy medium dried in S11 again in an acidic solution with a pH value of 5 to 6 for 1 to 2 hours, taking it out and rinsing it with deionized water, and drying it in an oven at 110°C to 116°C; obtaining the treated heavy medium.

[0007] Optionally, the solute in the metal cation solution in step S5 can be selected from at least one of nano copper oxide, nano iron oxide, and nano zinc oxide.

[0008] Preferably, the metal cation solution is formed by mixing nano copper oxide and water in a molar mass ratio of 1-9:9-1, the third stirring time is 8 hours, the third temperature is 60° C., and the third drying time is 12 hours.

[0009] Optionally, the fourth temperature in step S6 is 100° C., the fourth drying time is 2 hours, and the composite modified heavy medium is polydopamine-metal cation nanoparticle heavy medium.

[0010] The second aspect of the present invention provides an application of a composite modified heavy medium for sewage treatment in the field of sewage treatment, wherein the composite modified heavy medium is prepared by the composite modified heavy medium preparation method.

[0011] Optionally, the application may include adding a certain amount of the prepared composite modified heavy medium into primary sedimentation tank sludge (physical and chemical sludge) and / or secondary sedimentation tank sludge (biochemical sludge), and testing the suspended sedimentation performance by observing the sedimentation rate of the suspended matter.

[0012] The present invention has at least the following beneficial effects:

[0013] (1) The surface of the composite modified heavy medium prepared by the present invention simultaneously introduces functional groups of organic molecules with "negative charge" and nanoparticles with "positive charge", thereby achieving effective sedimentation of suspended matter with both positive and negative charges, and having an excellent sewage treatment effect.

[0014] (2) The present invention introduces a heavy medium surface "etching" process, which increases the contact area between heavy medium particles and suspended matter in sewage per unit mass, and further improves the performance of the composite modified heavy medium.

[0015] (3) The preparation method provided by the present invention has mild reaction conditions and a simple process flow, does not require the use of complex production processes, and is easy to control the stirring temperature and separate to obtain pure products. The obtained products can be reused and the dosage is controllable. The operating cost is low and the safety is high, and it is easy to achieve industrial production of composite modified heavy media.

[0016] In addition, additional advantages, objects, and features of the present invention will be described in part in the following description, and will become apparent to those skilled in the art after studying the following, or may be learned from the practice of the present invention. The objects and other advantages of the present invention may be realized and obtained by the structures and method steps specifically pointed out in the written description and claims and the accompanying drawings.

[0017] Those skilled in the art will appreciate that the objectives and advantages that can be achieved with the present invention are not limited to the above specific description, and the above and other objectives that can be achieved by the present invention will be more clearly understood from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute a limitation of the present invention.

[0019] Figure 1 The figure is a schematic flow chart of a method for preparing a composite modified heavy medium according to an embodiment of the present invention;

[0020] Figure 2 The figures are microscope images of the heavy medium carrier before and after modification, wherein A is the morphology of the unmodified heavy medium under microscope observation, and B is the morphology of the composite modified heavy medium carrier prepared by the method of the present invention under microscope observation. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and the accompanying drawings. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should also be noted that, in order to avoid blurring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0022] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, elements, steps or components, but does not exclude the presence or addition of one or more other features, elements, steps or components.

[0023] Combined with Figure 1 As shown, the first aspect of the embodiment of the present invention provides a preparation method of a composite modified heavy medium for sewage treatment, comprising the following specific steps: S1: soaking, rinsing and drying the heavy medium using acidic and alkaline solutions respectively; S2: etching the surface of the heavy medium treated by S1 using an acid solution; S3: placing the heavy medium obtained by S2 after surface etching in a polydopamine (PDA) solution for a first stirring, and drying it for a first time at a first fixed temperature; S4: placing the heavy medium obtained by S3 in a polydopamine solution again for a second stirring, and drying it for a second time at a second temperature higher than the first fixed temperature; S5: placing the heavy medium obtained by S4 after the second drying in a metal cation solution, stirring it for a third time, and drying it for a third time at a third temperature; S6: rinsing the heavy medium obtained by S5 after the third drying for multiple times using deionized water, and drying it for a fourth time at a fixed fourth temperature to obtain a composite modified heavy medium.

[0024] Optionally, step S1 specifically includes: S11: soaking the heavy medium in an alkaline solution with a pH value of 8 to 9 for 1 to 2 hours, taking it out and rinsing it with deionized water, and drying it in an oven at 110°C to 116°C; S12: soaking the dried heavy medium in S11 again in an acidic solution with a pH value of 5 to 6 for 1 to 2 hours, taking it out and rinsing it with deionized water, and drying it in an oven at 110°C to 116°C; obtaining the treated heavy medium; specifically, the heavy medium usually referred to generally refers to a solid heavy medium powder with a density greater than 1g / ml, which can be divided into magnetic heavy medium powder and non-magnetic heavy medium powder; unless otherwise specified, the heavy medium mentioned in the present invention can specifically refer to a heavy medium used for sewage (waste) water treatment, which is used to be added in a sewage sedimentation tank or a biochemical tank to improve the separation degree of suspended matter, such as magnetic powder, quartz sand, anthracite, glass balls, etc.

[0025] Optionally, the acid solution in step S2 can be selected from at least one of sulfuric acid, nitric acid or hydrofluoric acid. Specifically, the acid solution in S2 is 1wt% to 60wt% hydrofluoric acid; the reaction temperature of the etching process is 20 to 90°C; and the etching reaction time is controlled to be 10 to 100 minutes.

[0026] Preferably, step S2 specifically includes placing the heavy medium in 1wt% to 50wt% hydrofluoric acid, controlling the reaction temperature to 30 to 70°C, and performing an etching reaction for 15 to 90 minutes to obtain a heavy medium after surface etching. The etching referred to in the present invention is applicable to a limited class of heavy medium powders realized based on the specific concept of the present invention, including but not limited to magnetic powder, quartz sand, anthracite, glass balls, etc.

[0027] Optionally, step S3 specifically includes: placing the heavy medium obtained in step S2 after surface etching into a solution having a concentration of 1 g·L -1 The first stirring is carried out in a polydopamine solution, and the first drying is carried out at a first temperature to obtain a modified heavy medium having an etched surface preliminarily coated with polydopamine nanoparticles. The first stirring time is 4 hours, the first temperature is 40°C, and the first drying time is 24 hours. It should be noted that the present invention only provides the use of polydopamine solution to participate in the surface modification of the heavy medium. In fact, the polydopamine solution can be replaced by other organic solutions that can provide the required functional groups on the surface of the heavy medium. At the same time, the embodiments of the present invention do not clearly limit the solvent used for the polydopamine solution, which means that common organic solvents that can dissolve polydopamine, such as DCM, DMF, DMSO, THF, etc., can be selectively used.

[0028] Optionally, step S4 specifically includes: placing the surface-modified heavy medium preliminarily coated with polydopamine nanoparticles obtained in step S3 into a medium having a concentration of 1 g·L -1 The polydopamine solution is stirred for a second time, and dried for a second time at a second temperature higher than the first fixed temperature to form a surface-modified heavy medium having a polydopamine nanoparticle layer uniformly coated on the etched surface. The second stirring time is 2 hours, the second temperature is 60°C, and the second drying time is 12 hours. It is worth noting that steps S3 and S4 can reveal another creative concept proposed by the present invention, that is, by placing the heavy medium into the organic solvent twice in succession, and adjusting the reaction conditions of the two reactions (such as time, temperature, etc.) to ensure the modification effect; this is conducive to the formation of a uniformly attached coating layer on the surface of the heavy medium by the organic matter, so as to ensure that the surface area of ​​the heavy medium is greatly increased after etching.

[0029] Optionally, the solute in the metal cation solution in step S5 can be selected from at least one of nano copper oxide, nano iron oxide, and nano zinc oxide. Preferably, the metal cation solution is formed by nano copper oxide (solute) and water (solvent) in a molar mass ratio of 1 to 9: 9 to 1, the third stirring time is 8 hours, the third temperature is 60°C, and the third drying time is 12 hours. It should be noted that the metal cations here can also be provided by metal compound solvents in other forms, the purpose of which is to form "positively charged" nanoparticles on the surface of the heavy medium that coexist (or couple) with the organic nanoparticle coating layer.

[0030] Optionally, the fourth temperature in step S6 is 100°C, and the fourth drying time is 2 hours, to obtain a pure composite modified heavy medium. Specifically, the composite modified heavy medium generated in this embodiment is a polydopamine-metal cation nanoparticle heavy medium; the metal cation is at least one of copper ions, iron ions or zinc ions. Figure 2 As shown, the morphology of the unmodified heavy medium (A) and the composite modified heavy medium carrier prepared by the method of the present invention under microscope observation (B).

[0031] A second aspect of an embodiment of the present invention provides an application of a composite modified heavy medium for sewage treatment in the field of sewage treatment, wherein the composite modified heavy medium is prepared by a preparation method of the composite modified heavy medium.

[0032] Optionally, the application of the composite modified heavy medium in the field of sewage treatment may include adding a certain amount of the prepared composite modified heavy medium to the primary sedimentation tank sludge (physical and chemical sludge) and / or the secondary sedimentation tank sludge (biochemical sludge), and testing the suspended sedimentation performance by observing the sedimentation rate of the suspended matter.

[0033] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0034] Example 1

[0035] The heavy medium was soaked, rinsed and dried with acidic and alkaline solutions, and the treated heavy medium was placed in 20wt% hydrofluoric acid, and the reaction temperature was controlled to be 30℃. After 15min of etching reaction, the heavy medium after surface etching was obtained. The heavy medium after surface etching was placed in a 1g·L -1 The first stirring was carried out in the polydopamine solution of 4g·L and the first drying was carried out at 40°C for 24h. The surface modified heavy medium obtained after the first stirring was again placed in a 1g·L -1The surface-modified heavy medium after the second stirring is added to a metal cation solution formed by nano-copper oxide and water in a ratio of 5:5 and stirred for a third time for 8 hours, and dried for a third time at 60°C for 12 hours to obtain a composite modified heavy medium; the composite modified heavy medium obtained after the third drying is rinsed with deionized water for multiple times, and dried for a fourth time at 100°C for 2 hours to obtain a pure polydopamine-metal cation nanoparticle composite modified heavy medium.

[0036] Example 2

[0037] The heavy medium was soaked, rinsed and dried with acidic and alkaline solutions, and the treated heavy medium was placed in 25wt% hydrofluoric acid, and the reaction temperature was controlled to be 35°C. After 50 minutes of etching reaction, the heavy medium after surface etching was obtained. The heavy medium after surface etching was placed in a 1g·L -1 The first stirring was carried out in the polydopamine solution of 4g·L and the first drying was carried out at 40°C for 24h. The surface modified heavy medium obtained after the first stirring was again placed in a 1g·L -1 The surface-modified heavy medium after the second stirring is added to a metal cation solution formed by nano-copper oxide and water in a ratio of 4:6 and stirred for a third time for 8 hours, and dried for a third time at 60°C for 12 hours to obtain a composite modified heavy medium; the composite modified heavy medium obtained after the third drying is rinsed several times with deionized water, and dried for a fourth time at 100°C for 2 hours to obtain a pure polydopamine-metal cation nanoparticle composite modified heavy medium.

[0038] Example 3

[0039] The heavy medium was soaked, rinsed and dried with acidic and alkaline solutions, and the treated heavy medium was placed in 50wt% hydrofluoric acid, and the reaction temperature was controlled to be 35°C. After 30 minutes of etching reaction, the heavy medium after surface etching was obtained. The heavy medium after surface etching was placed in a 1g·L -1 The first stirring was carried out in the polydopamine solution of 4g·L and the first drying was carried out at 40°C for 24h. The surface modified heavy medium obtained after the first stirring was again placed in a 1g·L -1The surface-modified heavy medium after the second stirring is added to a metal cation solution formed by nano-copper oxide and water in a ratio of 3:7 and stirred for a third time for 8 hours, and dried for a third time at 60°C for 12 hours to obtain a composite modified heavy medium; the composite modified heavy medium obtained after the third drying is rinsed with deionized water for multiple times, and dried for a fourth time at 100°C for 2 hours to obtain a pure polydopamine-metal cation nanoparticle composite modified heavy medium.

[0040] The polydopamine-metal cation nanoparticle composite modified heavy medium obtained in Example 1 of the present invention was selected as a test sample. The polydopamine-metal cation nanoparticle composite modified heavy medium obtained in Example 1 was added to the primary sedimentation tank sludge (physicochemical sludge) and / or the secondary sedimentation tank sludge (biochemical sludge) under different conditions, and the sedimentation performance between the polydopamine-metal cation nanoparticle composite modified heavy medium obtained in Example 1 of the present invention and ordinary heavy medium under different conditions was compared.

[0041] Example 4

[0042] Take 1 L of sewage (containing physicochemical sludge) before the primary sedimentation tank of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 50-150 mg / L, the water temperature is 20°C, and the pH is 7.5-7.8. 50 mg of the composite modified heavy medium obtained in Example 1 is added, and the suspended matter sedimentation time takes 50-60 s.

[0043] Example 5

[0044] Take 1 L of sewage (containing physicochemical sludge) before the primary sedimentation tank of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 50-150 mg / L, the water temperature is 20°C, and the pH is 6.5-6.8. 50 mg of the composite modified heavy medium obtained in Example 1 is added, and the suspended matter sedimentation time takes 55-65 s.

[0045] Example 6

[0046] Take 1 L of sewage (containing physicochemical sludge) before the primary sedimentation tank of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 50-150 mg / L, the water temperature is 20°C, and the pH is 7.5-7.8. Add 100 mg of the composite modified heavy medium obtained in Example 1, and the suspended matter sedimentation time takes 45-55 s.

[0047] Example 7

[0048] Take 1 L of sewage (containing physicochemical sludge) before the primary sedimentation tank of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 50-150 mg / L, the water temperature is 20°C, and the pH is 7.5-7.8. Add 200 mg of the composite modified heavy medium obtained in Example 1, and the suspended matter sedimentation time takes 35-45 s.

[0049] Example 8

[0050] Take 1 L of sewage (including biochemical sludge) from a biochemical pool of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 3000-5000 mg / L, the water temperature is 20°C, and the pH is 7.0-7.5. 5 g of the composite modified heavy medium obtained in Example 1 is added, and the suspended matter sedimentation time takes 400-600 s.

[0051] Example 9

[0052] Take 1 L of sewage (including biochemical sludge) from a biochemical pool of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 3000-5000 mg / L, the water temperature is 20°C, and the pH is 6.0-6.5. 5 g of the composite modified heavy medium obtained in Example 1 is added, and the sedimentation time of the suspended matter is 450-700 s.

[0053] Example 10

[0054] Take 1 L of sewage (including biochemical sludge) from a biochemical pool of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 3000-5000 mg / L, the water temperature is 20°C, and the pH is 7.0-7.5. Add 10 g of the composite modified heavy medium obtained in Example 1, and the sedimentation time of the suspended matter takes 300-450 s.

[0055] Embodiment 11

[0056] Take 1 L of sewage (including biochemical sludge) from a biochemical pool of a sewage treatment plant into a 1 L measuring cylinder. The concentration of suspended matter in the sewage is about 3000-5000 mg / L, the water temperature is 20°C, and the pH is 7.0-7.5. Add 20 g of the composite modified heavy medium obtained in Example 1, and the sedimentation time of the suspended matter takes 100-300 s.

[0057] Comparative Example 1

[0058] Take the sewage (containing physicochemical sludge) before the primary sedimentation tank with the same dosage, container, suspended matter concentration, water temperature and pH value as Example 4, add 50 mg of the same unmodified heavy medium as in Example 1, and the suspended matter sedimentation time takes 240 to 360 seconds.

[0059] Comparative Example 2

[0060] Take the sewage (including biochemical sludge) from the biochemical pool with the same dosage, container, suspended matter concentration, water temperature and pH value as in Example 11, add 20 g of the same unmodified heavy medium as in Example 1, and the suspended matter sedimentation time takes 480 to 1200 seconds.

[0061] Table 1. Comparative table of purification effect verification of composite modified heavy media based on embodiments of the present invention

[0062]

[0063] As can be seen from Table 1, the case comparison of the composite modified heavy medium prepared by Example 1 of the present invention in sedimentation tank sludge (physical and chemical sludge) and secondary sedimentation tank sludge (biochemical sludge) can significantly illustrate that the composite modified heavy medium material prepared by the embodiment of the present invention can significantly improve the existing heavy medium water purification technology in accelerating the sedimentation effect of suspended matter in sewage.

[0064] First, considering that the basic principle of heavy medium accelerated sewage treatment is electrical neutralization, the present invention simultaneously introduces particles carrying positive and negative charges on the surface of the heavy medium to simultaneously achieve accelerated precipitation of suspended solids of different polarities. Specifically, the first step is to effectively remove suspended solids with positive charges (for example, primary sedimentation tank sludge, sludge containing barium ions, etc.) by introducing "negatively charged" organic molecules (polydopamine) functional groups on the surface of the heavy medium; the second step is to introduce "positively charged" metal nanoparticles (such as nano copper oxide) on the surface of the heavy medium on the basis of the formed polydopamine coating, thereby effectively removing suspended solids with negative charges (for example, secondary sedimentation tank sludge, sludge containing hydroxyl functional groups, etc.).

[0065] Secondly, the present invention forms "grooves" on the surface of the heavy medium by "etching" the original surface of the heavy medium with an acidic solution, thereby greatly increasing the contact area between the heavy medium and the corresponding reaction solvent. Without increasing the amount of original heavy medium raw materials, the heavy medium modification effect and the contact area with the corresponding suspended matter in the sewage are greatly increased, so that the purification performance of the heavy medium filter material after composite modification is greatly improved.

[0066] Finally, when the composite modified heavy medium prepared by the present invention is neutralized with the charged particles, the diffuse double electric layer on the surface of the charged colloid particles is compressed, the electrostatic repulsion is reduced, and the repulsive potential energy between each other is correspondingly reduced, so that they are easily aggregated together and settled when colliding with each other; at the same time, under the action of electrostatic attraction, van der Waals force and hydrogen bond force, the heavy medium undergoes an adsorption and bridging process with the colloid particles or fine suspended matter through active sites; when too much heavy medium is added, it will also form a precipitate with the colloid particles on the surface to form a netting effect, which further accelerates the filtration effect of suspended matter in sewage.

[0067] At present, pollution from combined sewer overflows (CSOs) has become one of the main limiting factors in my country's water ecological environment governance capabilities. Among the pollutants carried by CSOs, pollutants such as COD, BOD5, TOC, TN, TP, etc. can be treated by increasing the amount of sludge in the biochemical system, and suspended solids (SS) are related to the treatment effect. By adding the composite modified heavy medium prepared by the present invention to the sedimentation tank, the treatment load and efficiency of the sedimentation tank for SS can be significantly improved. The specific reason is that SS carrying "positive" and "negative" charges may exist in the sewage to be treated at the same time. The method of accelerating SS sedimentation in the prior art can only remove suspended solids with a single charge, while the present invention can achieve the simultaneous removal of sludge carrying "positive" and "negative" charges, which better solves the pollution problem of CSOs.

[0068] In addition, according to the national sewage treatment standard upgrade, the previous Class B emission standard has been gradually raised to Class A emission standard, and more stringent emission standards have been formulated for areas with fragile ecological environment. Due to the limitations of site and cost, sewage treatment plants will inevitably increase the amount of sludge treated by the system to improve treatment performance, which will cause the sedimentation tank SS connected to the biochemical system to overload and cause the "sludge running" phenomenon. The heavy medium of the present invention can increase the treatment load of the sedimentation tank SS, thereby realizing the expansion of the biochemical system of the sewage treatment plant, and well solving the problem of overload operation of the sewage treatment plant.

[0069] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite modified heavy medium for sewage treatment, characterized in that: The specific steps include: S1: using an acidic solution and an alkaline solution to soak, rinse and dry the heavy medium, wherein the heavy medium is a non-magnetic heavy medium; S2: using an acid solution to etch the surface of the heavy medium treated in S1, specifically: placing the heavy medium in 1wt% to 50wt% hydrofluoric acid, controlling the reaction temperature to be 30 to 70°C, and performing an etching reaction for 15 min to 90 min to obtain a heavy medium after surface etching, so as to increase the contact area between the heavy medium and the reaction solvent and / or the sewage to be treated; S3: Place the surface-etched heavy medium obtained in S2 into a 1.g·L -1 A first stirring is performed in a polydopamine solution, and a first drying is performed at a first temperature to obtain a modified heavy medium having an etched surface preliminarily coated with polydopamine nanoparticles; The first stirring time is 4 hours, the first temperature is 40° C., and the first drying time is 24 hours; S4: The surface-modified heavy medium preliminarily coated with polydopamine nanoparticles obtained in S3 is again placed in a 1 g·L -1 The polydopamine solution is stirred for a second time, and dried for a second time at a second temperature higher than the first fixed temperature to form a surface-modified heavy medium having a polydopamine nanoparticle layer uniformly coated on the etched surface; wherein the polydopamine nanoparticle layer uniformly coated on the etched surface; the second stirring time is 2 hours, the second temperature is 60° C., and the second drying time is 12 hours; S5: placing the heavy medium obtained in S4 after the second drying into the metal cation solution, stirring for the third time, and drying for the third time at a third temperature, wherein the solute in the metal cation solution is at least one of nano copper oxide, nano iron oxide, and nano zinc oxide; S6: The heavy medium obtained in S5 and dried for the third time is rinsed multiple times with deionized water, and dried for the fourth time at a fixed fourth temperature to obtain a composite modified heavy medium.

2. The preparation method according to claim 1, characterized in that: Step S1 specifically includes: S11: soak the heavy medium in an alkaline solution with a pH value of 8 to 9 for 1 to 2 hours, take it out and rinse it with deionized water, and dry it in an oven at 110°C to 116°C; S12: soaking the dried heavy medium in S11 again for 1-2 hours in an acidic solution with a pH of 5-6, taking it out and rinsing it with deionized water, and drying it in an oven at 110° C.-116° C. to obtain the treated heavy medium.

3. The preparation method according to claim 1, characterized in that: The metal cation solution is formed by mixing nano copper oxide and water in a molar mass ratio of 1-9:9-1; The third stirring time is 8 hours, the third temperature is 60° C., and the third drying time is 12 hours.

4. The preparation method according to claim 1, characterized in that: The fourth temperature in step S6 is 100° C., the fourth drying time is 2 hours, and the composite modified heavy medium is a polydopamine-metal cation nanoparticle composite modified heavy medium.

5. Application of a composite modified heavy medium for sewage treatment in the field of sewage treatment, wherein the composite modified heavy medium is prepared by the preparation method of the composite modified heavy medium according to any one of claims 1 to 4.

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