Self-assembled composite coating film for removing antibiotics in wastewater and preparation method of self-assembled composite coating film

Abstract

The invention discloses a self-assembled composite coating membrane for removing antibiotics in wastewater and a preparation method thereof, and the preparation method comprises the following steps: S1, pretreating the surface of a membrane assembly by using a persulfate aqueous solution under an alkaline condition to prepare an activated membrane; s2, an iron ion solution is introduced into the activated membrane through suction filtration and makes contact with the surface of the activated membrane, and an iron ion loaded membrane surface is formed; s3, a tannic acid solution is introduced into the iron ion loaded membrane through suction filtration and makes contact with the surface of the iron ion loaded membrane, and an iron-tannic acid coating membrane is formed; s4, a polyethyleneimine solution is introduced into the iron-tannic acid coating film through suction filtration and makes contact with the surface of the iron-tannic acid coating film, and the tannic acid-iron-polyethyleneimine self-assembled composite coating film is formed. The disassembly liquid is introduced into the adsorption-saturated self-assembled composite coating membrane assembly, the composite coating is disassembled, then the coating is recycled, and the self-assembled composite coating membrane is used for removing antibiotics in wastewater and has the characteristics of detachability and cyclic utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water treatment, in particular to a self-assembled composite coating membrane for removing antibiotics in wastewater and a preparation method thereof. BACKGROUND

[0002] Antibiotics are widely used in human life, medical treatment, aquaculture and livestock production, resulting in a large amount of antibiotics detected in domestic wastewater, hospital wastewater, and wastewater from aquaculture and livestock production. These wastewaters entering the environment will cause serious harm to the ecological environment and human health. Especially the antibiotic pollution in drinking water, even at a low concentration level, but if long-term drinking, will increase the probability of producing drug-resistant bacteria, leading to adverse reactions such as allergic reactions, liver and kidney damage, and high health risks. Therefore, there is an urgent need for new technologies to efficiently remove trace amounts of antibiotics in wastewater and drinking water.

[0003] Membrane separation technology is widely used in drinking water purification and wastewater treatment due to its energy saving, environmental protection, simple operation and high separation efficiency. Compared with other water treatment technologies, membrane separation technology has higher treatment efficiency, better effluent water quality, and is more stable, and has obvious advantages in removing high-risk trace pollutants. However, there is still a lack of membrane materials or technologies for deep removal of antibiotic pollution. Although some studies have reported that membrane structure and membrane surface modification can effectively improve the removal efficiency of antibiotics by membrane separation, there are still key challenges in practical application: 1) it is difficult to achieve efficient removal in the presence of mixed antibiotics of different types; 2) the modification method of the membrane is complex and difficult to be used sustainably in practical application. Therefore, there is a great demand for the development of efficient and sustainable membrane technology that can cope with mixed antibiotic pollution of different types. SUMMARY

[0004] In view of the problems in the prior art that the current membrane technology cannot efficiently remove trace amounts of antibiotics in wastewater, and the existing membrane modification method still cannot achieve simultaneous efficient removal of different types of antibiotics, and the modified membrane faces the problems of stability and sustainability in practical application, the present application provides a self-assembled composite coating membrane for removing antibiotics in wastewater and a preparation method thereof.

[0005] The technical scheme of the present application is as follows:

[0006] The first object of the present application is to provide a preparation method of a self-assembled composite coating membrane for removing antibiotics in wastewater, comprising the following steps:

[0007] S1, pretreating the surface of the membrane module with a persulfate aqueous solution under alkaline conditions to obtain an activated membrane;

[0008] S2, passing an iron ion solution into the activated membrane through suction filtration to contact the surface of the activated membrane, and forming an iron ion loaded membrane surface;

[0009] S3. The tannic acid solution is filtered through a vacuum filter and introduced into an iron ion supported membrane to contact the surface of the iron ion supported membrane and form an iron-tannic acid coating membrane.

[0010] S4. The polyethyleneimine solution is passed through a vacuum filter into the iron-tannic acid coated membrane, and comes into contact with the surface of the iron-tannic acid coated membrane to form a tannic acid-iron-polyethyleneimine self-assembled composite coating membrane.

[0011] In one embodiment of the present invention, in step S1, the membrane module is a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, or a reverse osmosis membrane; the persulfate is one of sodium persulfate, potassium persulfate, or ammonium persulfate, and the concentration of the persulfate aqueous solution is 0.01-0.05M; the solution pH is 9-10.

[0012] In one embodiment of the present invention, in step S1, the pH is adjusted using a 5-15mM NaOH aqueous solution.

[0013] In one embodiment of the present invention, in step S1, the pretreatment method is as follows: an aqueous solution of persulfate is passed into the membrane module, the pressure of the filtration is 0.1-1 bar, the temperature is 20-40°C, and the filtration time is 30-60 min.

[0014] In one embodiment of the present invention, in step S2, the concentration of ferric ions in the ferric ion solution is 0.5-1.5 mM, the filtration pressure is 0.1-1 bar, the temperature is 20-40°C, and the filtration time is 10-30 min.

[0015] In one embodiment of the present invention, in step S3, the concentration of the tannic acid solution is 0.1-1.0 mM, the filtration pressure is 0.1-1 bar, the temperature is 20-40°C, and the filtration time is 10-30 min.

[0016] In one embodiment of the present invention, in step S4, the concentration of the polyethyleneimine solution is 1-10 mg / mL, the filtration pressure is 0.1-1 bar, the temperature is 20-40°C, and the filtration time is 10-30 min.

[0017] A second objective of this invention is to provide a self-assembled composite coating membrane for antibiotic removal in wastewater prepared by the above-described method.

[0018] In one embodiment of the present invention, the antibiotic is one or more of norfloxacin, oxytetracycline, azithromycin, and sulfadiazine.

[0019] A third objective of this invention is to provide an application of the above-described self-assembled composite coating membrane for wastewater treatment.

[0020] In an embodiment of the present application, the self-assembled composite coating film has the characteristics of being detachable and recyclable;

[0021] The self-assembled composite coating film is used for treating wastewater containing antibiotics, and after reaching adsorption saturation, a dismounting liquid is introduced in situ to dismount the composite coating; the dismounting liquid is introduced at a suction filtration pressure of 0.5-1 bar and a temperature of 20-40℃ for 30-90 min;

[0022] The dismounting liquid is prepared by mixing hydrochloric acid, sulfuric acid or nitric acid with citric acid; the molar ratio of hydrochloric acid, sulfuric acid or nitric acid to citric acid is 1:1-3:1, the concentration of hydrochloric acid, sulfuric acid or nitric acid is 0.01-0.1 M, and the concentration of citric acid is 0.01-0.1 M; the pH of the dismounting liquid is 1-3.

[0023] In an embodiment of the present application, the pH of the dismounting liquid is adjusted by adjusting the amount of hydrochloric acid and citric acid.

[0024] In an embodiment of the present application, the loading and dismounting of the composite coating are cyclically performed with the self-assembled composite coating film reaching adsorption saturation of antibiotics as the critical point, so that the film of the coating can be used sustainably.

[0025] The adsorption coating technology is an effective way to simply and efficiently improve the removal capacity of a film for specific pollutants. Tannic acid molecules and polyvalent metal ions can easily form stable complexes through coordination complexation, and the complexes have strong adhesion and can form uniform and stable coatings on various materials. The coatings are rich in negative charges and have good adsorption and removal capacity for heavy metal ions and some positively charged antibiotics, but have poor removal capacity for negatively charged antibiotics (such as sulfonamides). On this basis, the positively charged PEI polymer is combined with the tannic acid-metal ion coating through layer-by-layer self-assembly to form a self-assembled composite coating. The positively charged PEI polymer is in the surface layer and removes negatively charged antibiotics through adsorption, while the negatively charged tannic acid coating is in the middle layer and removes positively charged and electrically neutral antibiotics, thereby realizing the simultaneous removal of different kinds of antibiotics. In addition, the tannic acid-metal ion coating at the bottom is sensitive to pH and can be quickly disassembled when the pH is lower than 3. Therefore, when the coating reaches adsorption saturation, the coating can be disassembled through a specific cleaning and dismounting method, and a new composite coating can be obtained by reloading the coating, so that the purpose of sustainable application can be achieved through the recycling of the process. The entire coating process is efficient and simple, and the materials used are all natural and low-cost environmentally friendly materials, which has significant application potential.

[0026] The present application has the beneficial technical effects of:

[0027] The application establishes a kind of iron-tannic acid-polyethyleneimine layer-by-layer self-assembly coating method, which can greatly improve the removal efficiency of different types of antibiotics by membrane materials, and realize efficient control of antibiotic pollution in wastewater.

[0028] The self-assembled composite coating film provided by the application is simple and fast to apply, does not require special environmental conditions, is clean and non-polluting in process, and can be applied to various membrane materials such as PVDF, PES, PTFE, PP and PFS, and has high practicability.

[0029] The self-assembled composite coating film has two characteristics of simple loading and controllable disassembly, can completely remove the adsorbed protective coating through simple membrane chemical cleaning, and can restore the adsorption performance after coating loading, and has the advantages of sustainability and recycling.

[0030] The self-assembled composite coating film uses non-toxic, harmless and inexpensive common chemicals as materials, has low application cost and simple process without toxic and harmful risks.

[0031] The self-assembled composite coating film can not only be applied to wastewater treatment, but also be applied to drinking water guarantee, can achieve the purpose of controlling antibiotic risk in drinking water, and has important practical value and social and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Schematic diagram for removing antibiotics by recycling the composite coating

[0033] Figure 2 Flux level of the composite coating film of Example 1 and each commercial membrane material;

[0034] Figure 3 Multi-cycle removal effect of the composite coating film of Example 1 after recycling on antibiotics;

[0035] Figure 4 Multi-cycle removal effect of the composite coating film of Example 1 without disassembly on antibiotics. DETAILED DESCRIPTION

[0036] The application will be specifically described below in combination with the drawings and examples.

[0037] Antibiotic removal rate test method:

[0038] A dead-end filtration system was used to evaluate the performance of the coated membrane in removing different types of antibiotics. The concentrations of norfloxacin, oxytetracycline, azithromycin and sulfadiazine were all set to 100 ppb. The pH value of the solution was adjusted by HCl and NaOH. The concentrations of antibiotics in the raw material liquid and the permeate were determined by ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry, and the removal rate (R) of the antibiotics was calculated by the following formula.

[0039]

[0040] In the formula, C f represents the concentration of antibiotics in the feed liquid, ppb; C p represents the concentration of antibiotics in the permeate, ppb.

[0041] The ferric chloride hexahydrate, tannic acid, polyethyleneimine and the four types of antibiotics involved in the following examples are all analytical pure and purchased from the National Pharmaceutical Group.

[0042] Example 1

[0043] A preparation method of a self-assembled composite coated membrane for removing antibiotics in wastewater, comprising the steps of:

[0044] S1, under alkaline conditions, using sodium persulfate to pretreat the membrane module to obtain an activated membrane;

[0045] The membrane module is a polyether sulfone (PES) ultrafiltration membrane with a molecular weight cut-off of 150 kDa, purchased from Microdyn-nadir;

[0046] The concentration of the sodium persulfate aqueous solution is 0.01 M, and the pH is adjusted to 10 with NaOH; the sodium persulfate aqueous solution is introduced into the membrane module by suction filtration, the control pressure is 0.1 bar, the temperature is 25℃, and the introduction time is 30 min.

[0047] S2, the trivalent iron ion solution is contacted with the activated membrane surface by suction filtration to form an iron ion loaded membrane surface;

[0048] The concentration of the trivalent iron ion solution in the ferric chloride hexahydrate solution is 1.0 mM; the trivalent iron ion solution is introduced into the membrane module by suction filtration, the control pressure is 0.1 bar, the temperature is 25℃, and the introduction time is 10 min.

[0049] S3, the tannic acid solution is contacted with the iron ion loaded membrane surface by suction filtration to form an iron-tannic acid coated membrane (Fe-TA composite coating);

[0050] The concentration of the tannic acid solution is 1.0 mM; the tannic acid solution is introduced into the membrane module by suction filtration, the control pressure is 0.1 bar, the temperature is 25℃, and the introduction time is 10 min.

[0051] S4, the polyethyleneimine solution is contacted with the surface of the iron-tannic acid coating membrane by suction filtration to form a tannic acid-iron-polyethyleneimine self-assembled composite coating membrane (Fe-TA-PEI composite coating);

[0052] The concentration of the polyethyleneimine solution is 5 mg / mL; the polyethyleneimine solution is introduced into the membrane module by suction filtration, the control pressure is 0.1 bar, the temperature is 25°C, and the introduction time is 30 min.

[0053] The self-assembled composite coating membrane is used for treatment of wastewater containing antibiotics, and the treatment method is as follows:

[0054] Mixed antibiotic wastewater is configured, in which the concentrations of norfloxacin, oxytetracycline, azithromycin and sulfadiazine are all set to 100 ppb; the self-assembled composite coating membrane is fixed in a membrane cell, the coating membrane is operated under a pressure of 2 bar, and the content of antibiotics in the effluent of the coating membrane and the raw water is tested to evaluate the removal performance of the coating membrane on antibiotics, and the results are shown in Table 1.

[0055] The dismounting liquid is introduced into the self-assembled composite coating membrane module saturated with adsorption to dismount the composite coating.

[0056] The dismounting liquid is a mixed aqueous solution of hydrochloric acid and citric acid, the concentration of citric acid in the dismounting liquid is 0.04 M, and the amount of hydrochloric acid is adjusted to make the pH of the dismounting liquid 2.5;

[0057] The suction filtration pressure of the introduction of the dismounting liquid is 1 bar, the temperature is 25°C, and the introduction time is 60 min.

[0058] Deionized water is introduced again for cleaning to load the coating again, the suction filtration cleaning pressure is 1 bar, the temperature is 25°C, and the introduction time is 30 min, and the cleaning is for loading the composite coating again.

[0059] Table 1

[0060] Norfloxacin Oxytetracycline Azithromycin Sulfadiazine Raw water (ppb) 98.9 99.5 100.2 101.3 Polyethersulfone ultrafiltration membrane raw membrane effluent (ppb) 91.0 88.56 85.17 96.24 Polyethersulfone ultrafiltration membrane removal rate (%) 8 11 13 5 Self-assembled composite coating membrane effluent (ppb) 2.97 4.98 3.01 6.08 Self-assembled composite coating membrane removal rate (%) 97.2 95.1 97.4 94.2

[0061] The removal rates of the original membrane on the four antibiotics are all poor, because the pore size of the ultrafiltration membrane used in the experiment is generally much larger than that of the four antibiotics, so the rejection rate of the antibiotics is very limited; the self-assembled composite coating membrane of the present application shows excellent removal efficiency on the four antibiotics, and the removal rates of norfloxacin, oxytetracycline, azithromycin and sulfadiazine are 97.2%, 95.1%, 97.4% and 94.2% respectively, which indicates that the presence of the composite coating greatly improves the removal capacity of the membrane on antibiotics.

[0062] Comparative Example 1:

[0063] With reference to Example 1, the only difference is that step S4 is omitted, i.e. no loading of PEI coating, to obtain a Fe-TA composite coating; and its effect of intercepting different antibiotics is investigated under the same experimental conditions. The results are shown in Table 2 below.

[0064] Table 2

[0065] Norfloxacin Oxytetracycline Azithromycin Sulfadiazine Raw water (ppb) 98.9 99.5 100.2 101.3 Fe-TA coating membrane effluent (ppb) 3.96 1.99 5.01 75.98 Fe-TA coating membrane removal rate (%) 96 98 95 25

[0066] As can be seen from Table 2, the Fe-TA coating film exhibits good intercepting effect on norfloxacin, oxytetracycline and azithromycin, with the intercepting rates reaching 96%, 98% and 95% respectively; but its intercepting efficiency on sulfadiazine is not high, only 25%. Under neutral conditions (pH = 7), norfloxacin and azithromycin mainly exist in the form of cations, and the Fe-TA coating with rich negative charges can adsorb the two antibiotics through electrostatic attraction force, thereby achieving efficient removal; in addition, although oxytetracycline mainly exists in the form of neutral ions, there may be hydrogen bond interaction or coordination interaction between it and the rich hydroxyl groups and iron ions in the Fe-TA coating, so it can also be efficiently adsorbed and removed. However, sulfadiazine mainly presents negative charge under neutral conditions, so the removal efficiency of Fe-TA coating thereon is low.

[0067] Compared with the above, the Fe-TA-PEI composite coating not only has high removal efficiency for negatively charged norfloxacin and azithromycin and electrically neutral oxytetracycline, but also exhibits high removal capacity for negatively charged sulfadiazine. This is because PEI is a polymer with rich positive charges, which has strong electrostatic adsorption removal effect on negatively charged sulfadiazine. The Fe-TA-PEI composite coating combines the strong electrostatic interaction of Fe-TA coating and PEI coating on different charged antibiotics, and also has coordination complexation of Fe ions and hydrogen bond interaction of TA, so it has the ability to simultaneously remove different types of antibiotics.

[0068] Comparative Example 2:

[0069] With reference to Example 1, the only difference is that steps S2 and S3 are omitted, i.e. no loading of Fe-TA coating, to obtain a coating only with PEI; and its effect of intercepting different antibiotics is investigated under the same experimental conditions. The results are shown in Table 3 below.

[0070] Table 3

[0071] Norfloxacin Oxytetracycline Azithromycin Sulfadiazine Raw water (ppb) 98.9 99.5 100.2 101.3 PEI coating membrane effluent (ppb) 77.14 81.59 66.13 9.39 PEI coating membrane removal rate (%) 22 18 34 91

[0072] Table 3 shows that the PEI coating still achieves a removal rate of 91% for sulfadiazine, but its removal efficiencies for norfloxacin, oxytetracycline, and azithromycin are only 22%, 18%, and 34%, respectively. This indicates that the PEI coating only has a good removal capacity for negatively charged antibiotics. The comparative results further demonstrate that the Fe-TA-PEI composite coating membrane combines the characteristics and functions of multiple materials, achieving simultaneous removal of antibiotics with different properties through different adsorption mechanisms.

[0073] Comparative Example 3:

[0074] Commercial ultrafiltration and nanofiltration membranes were used for antibiotic removal. Under identical conditions, the antibiotic removal and flux levels of different membranes were compared and evaluated. Figure 2 As shown, commercial ultrafiltration membranes can achieve a flux of 687 LMH at 1 bar. After loading the commercial ultrafiltration membrane with the composite coating, the flux decreased to 565 LMH at the same pressure. The removal rates of norfloxacin, oxytetracycline, azithromycin, and sulfadiazine by the commercial ultrafiltration membrane were only 8%, 11%, 13%, and 5%, respectively, while the removal rates of norfloxacin, oxytetracycline, azithromycin, and sulfadiazine by the composite-coated ultrafiltration membrane reached 97.2%, 95.1%, 97.4%, and 94.2%, respectively. The results indicate that loading the composite-coated membrane significantly improves its antibiotic removal efficiency while maintaining high membrane flux performance.

[0075] Compared to nanofiltration membranes, as shown in Table 4, among the three common commercial nanofiltration membranes, only NF90 exhibited antibiotic removal performance comparable to that of composite-coated ultrafiltration membranes. NF270 and DL membranes showed inferior removal performance for various antibiotics compared to composite-coated ultrafiltration membranes. Furthermore, the flux levels of NF270, NF90, and DL membranes at the same pressure were only 32, 15, and 28 LMH, respectively, significantly lower than that of composite-coated ultrafiltration membranes. These results indicate that the composite coating strategy can achieve antibiotic removal comparable to or better than nanofiltration membranes while maintaining higher flux levels. This is mainly due to the specific adsorption and removal of antibiotics by the composite coating. This advantage is particularly suitable for water treatment scenarios with large treatment volumes and high removal limits, such as the control of antibiotic contamination in drinking water.

[0076] Table 4

[0077] Norfloxacin Oxytetracycline Azithromycin Sulfadiazine NF270 (%) 85.9 83.6 90.5 82.5 NF90 (%) 95.8 92.5 93.5 92.2 DL (%) 83.5 80.2 81.5 81.4 Fe-TA-PEI coating membrane removal rate (%) 97.2 95.1 97.4 94.2

[0078] Comparative Example 4:

[0079] To compare the performance of cross-flow deposition and filtration deposition in antibiotic removal from composite coated membranes, cross-flow deposition involved the coating solution flowing parallel to the membrane surface, while filtration deposition involved the solution flowing perpendicular to the membrane surface. Under identical conditions, Fe was sequentially loaded onto the original membrane surface using cross-flow deposition.3+ The composite coating membrane was prepared by cross-flow deposition with a cross-flow rate of 0.5 m / s. The effect of the composite coating membrane on the retention of antibiotics was investigated under the same experimental conditions. The results are shown in Table 5.

[0080] Table 5

[0081] Norfloxacin Oxytetracycline Azithromycin Sulfadiazine Coating membrane prepared in a cross-flow mode 90.2 91.2 92.6 89.7 Coating membrane prepared in a suction filtration mode 97.2 95.1 97.4 94.2

[0082] The removal rates of the composite coating membrane prepared by cross-flow deposition for norfloxacin, terramycin, azithromycin and sulfadiazine were only 90.2%, 89.2%, 91.6% and 89.7%, respectively, which were lower than those of the composite coating membrane prepared by suction filtration deposition. This is because the coating deposited by cross-flow is mainly concentrated on the membrane surface, while the coating deposited by suction filtration is not only on the membrane surface but also in the internal pores of the membrane, thereby increasing the contact adsorption surface of the coating and improving the removal capacity of the coating membrane for antibiotics.

[0083] Example 2:

[0084] The same as Example 1, except that in step S1, the aqueous persulfate solution is an aqueous potassium persulfate solution with a concentration of 0.05 M.

[0085] Example 3:

[0086] The same as Example 1, except that in step S2, the concentration of ferric ions is 1.5 mM.

[0087] Example 4:

[0088] The same as Example 1, except that in step S3, the concentration of tannin acid solution is 0.5 mM; the tannin acid solution is introduced into the membrane module by suction filtration, the control pressure is 0.5 bar, the temperature is 30°C, and the introduction time is 20 min.

[0089] Example 5:

[0090] The same as Example 1, except that in step S4, the concentration of polyethyleneimine solution is 10 mg / mL, the suction filtration pressure is 0.1 bar, the temperature is 30°C, and the introduction time is 20 min.

[0091] The self-assembled composite coating membranes obtained in Examples 2-5 were used to investigate the effect of retaining different antibiotics under the same experimental conditions. The removal rates of the four antibiotics were all above 90%.

[0092] Test Example:

[0093] The self-assembled composite coating membrane prepared in Example 1 was used for the treatment of wastewater containing antibiotics, and after reaching adsorption saturation, the composite coating was disassembled by introducing the disassembly liquid in situ;

[0094] The filter pressure of the disassembly liquid is 1 bar, the temperature is 25 DEG C, and the time of the disassembly liquid is 30 min; the disassembly liquid is prepared by mixing hydrochloric acid and citric acid; the concentration of citric acid in the disassembly liquid is 0.04 M, and the amount of hydrochloric acid is adjusted to make the pH of the disassembly liquid 2.5. After disassembly, the antibiotic treatment and disassembly are repeated.

[0095] The stability and sustainability of the removal effect of the recycled and regenerated composite coating membrane on antibiotics are investigated through multi-cycle experiments, and the results are shown in Table 2. Figure 3 As shown in Table 2, the recycled and regenerated composite coating maintains high and stable removal efficiency for four different antibiotics under multiple cycle operation conditions, and the removal rate is stable at more than 95%. The removal of antibiotics by the composite coating is mainly realized by multiple adsorption, so regular coating regeneration can ensure the sustainability and stability of the removal performance of the coating membrane.

[0096] The self-assembled composite coating membrane prepared in Example 1 is used for antibiotic-containing wastewater treatment, and after reaching adsorption saturation, subsequent multi-cycle operation does not disassemble and regenerate the coating, and other conditions remain the same as those of the recycled and regenerated multi-cycle experiment of the test example. The results are shown in Table 3. Figure 4 As shown in Table 3, the removal efficiency of the coating membrane without regular disassembly and loading of the coating decreases significantly with the extension of the cycle operation, especially after the fourth cycle, the removal rate of the composite coating membrane for the four antibiotics is less than 40%. This is because, with the extension of the operation, the adsorption of the coating membrane to the antibiotics reaches saturation, and then the effective adsorption sites are lost, resulting in rapid decrease of the adsorption removal rate.

[0097] The above results show that the recycled and regenerated coating is crucial for the composite coating membrane to maintain high efficiency in removing antibiotics. The composite coating method proposed in the present application can not only simply and quickly load the coating to improve the removal efficiency of the membrane for multiple antibiotics, but also can disassemble the coating in a simple and efficient way to realize the recycling and regeneration of the coating membrane, so as to realize sustainable and efficient removal of antibiotics.

[0098] The above provided examples are not intended to limit the scope covered by the present application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the present application in combination with existing common knowledge, which also falls within the protection scope defined by the claims of the present application.

Claims

1. A method for preparing a self-assembled composite coating film for antibiotic removal in wastewater, characterized by, The method comprises the steps of: S1, pretreating the surface of the membrane module with an aqueous solution of persulfate under alkaline conditions to obtain an activated membrane; S2, introducing an iron ion solution into the activated membrane by suction filtration to form an iron ion-loaded membrane surface; S3, introducing a tannic acid solution into the iron ion-loaded membrane by suction filtration to form an iron-tannic acid coated membrane; S4, introducing a polyethyleneimine solution into the iron-tannic acid coated membrane by suction filtration to form a tannic acid-iron-polyethyleneimine self-assembled composite coating membrane.

2. The production method according to claim 1, characterized by, In step S1, the membrane module is a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane or a reverse osmosis membrane; the persulfate is one of sodium persulfate, potassium persulfate and ammonium persulfate; the concentration of the aqueous solution of persulfate is 0.01-0.05M; and the pH of the solution is 9-10.

3. The preparation method according to claim 1, characterized in that, In step S1, the pretreatment method is as follows: introducing the aqueous solution of persulfate into the membrane module; the suction filtration pressure is 0.1-1bar; the temperature is 20-40℃; and the introduction time is 30-60min.

4. The method of claim 1, wherein, In step S2, the concentration of trivalent iron ions in the iron ion solution is 0.5-1.5mM; the suction filtration pressure is 0.1-1bar; the temperature is 20-40℃; and the introduction time is 10-30min.

5. The preparation method according to claim 1, characterized in that, In step S3, the concentration of the tannic acid solution is 0.1-1.0mM; the suction filtration pressure is 0.1-1bar; the temperature is 20-40℃; and the introduction time is 10-30min.

6. The method of claim 1, wherein, In step S4, the concentration of the polyethyleneimine solution is 1-10mg / mL; the suction filtration pressure is 0.1-1bar; the temperature is 20-40℃; and the introduction time is 10-30min.

7. A self-assembled composite coating membrane for removing antibiotics from wastewater, prepared by the method of any one of claims 1-6.

8. The self-assembled composite coating film according to claim 7, wherein The antibiotics are one or more of norfloxacin, terramycin, azithromycin and sulfadiazine.

9. Use of the self-assembled composite coating film according to claim 7, characterized in that, The self-assembled composite coating membrane is used for wastewater treatment.

10. Use according to claim 9, characterized in that, The self-assembled composite coating membrane has the characteristics of being detachable and recyclable. When the self-assembled composite coating membrane is used for treating wastewater containing antibiotics, a dismounting solution is introduced into the composite coating in situ after the adsorption saturation to remove the composite coating; the suction filtration pressure of the dismounting solution is 0.5-1bar; the temperature is 20-40℃; and the introduction time is 30-90min. The dismounting solution is prepared by mixing hydrochloric acid, sulfuric acid or nitric acid with citric acid; the molar ratio of hydrochloric acid, sulfuric acid or nitric acid to citric acid is 1:1-3:1; the concentration of hydrochloric acid, sulfuric acid or nitric acid is 0.01-0.1M; and the concentration of citric acid is 0.01-0.1M; and the pH of the dismounting solution is 1-3.

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