Hierarchical multifunctional sewage purification material and preparation method and application thereof

Abstract

The present application relates to a kind of hierarchical multifunctional sewage purification material and its preparation method and application, belong to sewage purification material technical field.The present application discloses a kind of hierarchical multifunctional sewage purification material, the hierarchical multifunctional sewage purification material includes isolation layer and functional layer;Wherein isolation layer is dense structure, the surface potential of isolation layer is negative potential;Functional layer is porous structure, the surface potential of functional layer is positive potential, the specific surface area of functional layer is 220-240m 2 / g, porosity is 25-32%.The present application also discloses a kind of preparation method of hierarchical multifunctional sewage purification material and the application of hierarchical multifunctional sewage purification material in water purification treatment.

Description

Technical Field

[0001] This invention belongs to the field of wastewater purification materials technology, and relates to a graded multifunctional wastewater purification material, its preparation method and application. Background Technology

[0002] my country is a country with scarce water resources, and surface water and groundwater provide the vast majority of our drinking water. The development of industry and agriculture, and the rapid pace of society, easily lead to serious pollution of water resources, such as heavy metal pollution, organic chemical pollution, particulate matter pollution, and biological pollution. These pollutants, once ingested through drinking water, can harm human organs, trigger acute or chronic diseases, and seriously threaten public health and safety. Given the complexity and diversity of pollutants, the key to obtaining clean and safe freshwater from polluted water resources lies in using a holistic strategy to remove complex pollutants. This is both our direction of effort and a formidable challenge.

[0003] Filtration, with its advantages of high-efficiency separation and simple operation, is considered the most advantageous water purification technology. However, simple filtration can only remove particulate pollutants from water and cannot remove dissolved heavy metals, bacteria, or other pollutants, thus failing to purify complex wastewater into safe and reliable drinking water in one step. Currently, source water mainly undergoes processes such as coagulation, sedimentation, filtration, and post-filtration disinfection before being transported to urban pipe networks to become household drinking water. This purification process is complex, energy-intensive, and has high requirements for water sources; in remote mountainous areas and other regions, tap water access is not yet widespread. Therefore, a simple device equipped with multifunctional wastewater purification materials is needed to ensure safe drinking water.

[0004] Chinese patent application (publication number: CN106552519A) discloses a method for preparing and applying a superhydrophilic and underwater superoleophobic calcium carbonate hybrid membrane. The method includes the following steps: adding a calcium ion solution to an alginate solution to prepare a calcium alginate gel, followed by stirring to form flocculation and precipitation; then adding a carbonate solution to obtain calcium carbonate-calcium alginate hybrid particles; finally, filtration and drying to obtain the superhydrophilic and underwater superoleophobic calcium carbonate hybrid membrane. The membrane prepared by this method is mainly used for oil-water separation, but it does not mention its ability to filter and purify other pollutants in water. Wastewater contains complex pollutants; therefore, there is an urgent need to develop a material that can simultaneously achieve comprehensive purification of complex pollutants and can be applied to simple devices. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a graded multifunctional wastewater purification material that simultaneously achieves oil-water separation and the removal of negatively charged micro-nano-sized particulate pollutants and heavy metal ions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A graded multifunctional wastewater purification material includes an isolation layer and a functional layer; wherein the isolation layer has a dense structure and a negative surface potential; the functional layer has a porous structure, a positive surface potential, and a specific surface area of ​​220-240 m². 2 / g, with a porosity of 25-32%.

[0008] The functional layer first contacts the wastewater, preventing the low-toxicity modifier from directly contacting the purified water. Simultaneously, it further removes pollutants and regulates water flux to achieve highly efficient water purification. The functional layer possesses a large specific surface area and high porosity. The presence of numerous carboxyl, hydroxyl, and amino groups on its surface and within the material endows the multifunctional wastewater purification material with superhydrophilicity and underwater superoleophobicity, thus enabling oil-water separation. Furthermore, the surface of the functional layer is strongly positively charged, allowing it to adsorb negatively charged micro- and nano-particle pollutants and heavy metal ions from the water, and to adhere to and inhibit the activity of pathogenic microorganisms such as bacteria.

[0009] Preferably, the surface pore size of the isolation layer is 1-5 nm; the surface pore size of the functional layer is 40-55 μm.

[0010] Preferably, the total thickness of the graded multifunctional wastewater purification material is 100-500 μm.

[0011] Further preferably, the thickness of the isolation layer is 20-40 μm; the thickness of the functional layer is 100-400 μm.

[0012] More preferably, the thickness ratio of the isolation layer to the functional layer is 1:(11-18).

[0013] The thickness of a membrane affects its permeate flux and purification efficiency. Generally, thicker membranes have higher purification efficiency but lower water flux. Thinner membranes have higher water flux but lower purification efficiency. Choosing an appropriate membrane thickness can balance purification efficiency with water flux.

[0014] This invention also provides a method for preparing a graded multifunctional wastewater purification material. The preparation method includes the following steps: dissolving alginate in deionized water to prepare an alginate sol, dividing it into two portions, taking one portion and sequentially adding a carboxyl activator, a modifier, and a pore-forming agent to stir to obtain a modified sol, and using a first round of spraying to solidify the modified sol on the surface of a crosslinking agent ice block to form a crude functional layer; covering the surface of the crude functional layer with the other portion of alginate sol through a second round of spraying, and then immersing it in a crosslinking agent solution to obtain a crude graded multifunctional wastewater purification material, and then using a vacuum freeze-drying method to obtain a graded multifunctional wastewater purification material including an isolation layer and a functional layer.

[0015] Preferably, the mass ratio of alginate, carboxyl activator, modifier, and pore-forming agent in the modified sol is 1:(0.1-2):(0.1-3):(0.3-3).

[0016] Further preferably, the mass ratio of the alginate to the pore-forming agent is 1:(0.5-2).

[0017] Preferably, the mass ratio of the modified alginate sol in the first round of spraying to the alginate sol in the second round of spraying is 1:(0.5-2).

[0018] Preferably, after adding the carboxyl activator and modifier, an activation reaction is carried out first, and the activation time is 0.5-5h.

[0019] Preferably, the stirring time after adding the pore-forming agent is 1-10 hours.

[0020] Further preferably, the stirring time is 2-5 hours.

[0021] Preferably, the alginate is one or more of sodium alginate, potassium alginate, and ammonium alginate.

[0022] More preferably, the concentration of the alginate sol is 0.5-5 wt.%.

[0023] Preferably, the carboxyl activator is one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

[0024] Adding a carboxyl activator to alginate sol activates the carboxyl groups in the alginate. However, adding too much carboxyl activator will cause the modifier to react too quickly with the alginate, resulting in premature gelation of the sol; adding too little will cause the reaction to be too slow or not to proceed at all, resulting in a modified gel with poor performance.

[0025] Preferably, the modifier is one or more of the following: polycarboxylated amine, chitosan, polyaniline, penicillamine, and polyethyleneimine.

[0026] More preferably, the modifier is one or more of polyaniline, penicillamine, and polyethyleneimine.

[0027] Adding too much modifier will lead to material waste, while adding too little modifier will result in insufficient purification and antibacterial capabilities of the finished membrane.

[0028] Preferably, the pore-forming agent is waterborne polyurethane.

[0029] In this invention, waterborne polyurethane is used as a pore-forming agent. It does not participate in chemical reactions and is added to form a porous structure in the material, thereby improving water flux and purification efficiency. However, adding too little pore-forming agent will result in a dense functional layer, reducing water flux; adding too much pore-forming agent will make the functional layer too porous, resulting in excessive water flux and thus reducing purification efficiency.

[0030] Preferably, the crosslinking agent includes one or more of copper sulfate, ferric sulfate, magnesium chloride, copper chloride, and calcium chloride.

[0031] More preferably, the crosslinking agent is one or more of copper chloride and calcium chloride.

[0032] Preferably, the concentration of the crosslinking agent is 0.1-10 wt.%.

[0033] More preferably, the concentration of the crosslinking agent is 0.5-5 wt.%.

[0034] Within the above-mentioned crosslinking agent concentration range, the crosslinking is sufficient and uniform, resulting in a membrane with few defects and high quality.

[0035] Preferably, the crosslinking agent ice cubes are made by freezing a crosslinking agent solution at (-10)-(-30)°C.

[0036] Preferably, the temperature of the crosslinking agent solution is 0-5°C.

[0037] Low-temperature crosslinking can prevent defects such as uneven crosslinking and wrinkles caused by excessively rapid crosslinking. In this invention, the obtained solid sol is immersed in a low-temperature crosslinking agent solution. The upper surface of the solid sol is slowly and uniformly crosslinked under the action of metal ions from the crosslinking agent, while the lower surface of the solid sol is simultaneously crosslinked under the action of metal ions released from the melting ice surface of the same type of crosslinking agent. After the ice surface has completely melted, a uniformly crosslinked, graded, multifunctional wastewater purification material is obtained.

[0038] Preferably, the number of spraying passes in the first round is 10-80.

[0039] Further preferred, the number of spraying passes in the first round is 40-60.

[0040] Preferably, the second round of spraying involves 40-60 sprays.

[0041] Controlling the number of spray coats can correspondingly control the film thickness, ensuring the water purification effect.

[0042] Preferably, the vacuum freeze-drying temperature is (-60)-(-90)℃ and the drying time is 12-36h.

[0043] This invention also provides an application of a graded multifunctional wastewater purification material in water treatment.

[0044] As a preferred option, a multi-functional wastewater purification material is combined with a rigid material with a porous structure to create a water purification tool.

[0045] Further preferred, the rigid material with a porous structure includes, but is not limited to, one or more of copper mesh, plastic mesh, and stainless steel mesh, or other rigid materials with a porous structure. It can not only support the graded multifunctional sewage purification material, but also allow sewage to pass through and be treated.

[0046] Preferably, when a graded multifunctional wastewater purification material is combined with a rigid material with a porous structure to form a water cup, and the water cup is placed in wastewater, the functional layer on the outside of the water cup comes into contact with the wastewater first. Through the cup wall and / or the bottom of the cup, clean water is obtained inside the cup. And because the water diffuses slowly from the dense layer to the porous layer, the water inside does not undergo back osmosis. Alternatively, when a graded multifunctional wastewater purification material is combined with a rigid material with a porous structure, a water cup with the functional layer on the inside can also be made. When wastewater is poured into the cup, clean water is obtained through the filtration of the cup.

[0047] Preferably, the water purification tool can be used alone or in combination with other devices, including but not limited to water cups, kettles, and buckets, and may also include disposable water purification devices, simple outdoor water purification devices, and emergency water treatment devices.

[0048] As a preferred option, graded multifunctional wastewater purification materials can also be directly applied to other water purification devices.

[0049] The graded multifunctional wastewater purification material obtained by this invention is combined with a rigid material with a porous structure to create a water purification tool, facilitating wastewater purification. The wastewater can include oily wastewater, heavy metal ion wastewater, biological wastewater, and wastewater containing micro-nano particles. Oily wastewater can include liquid paraffin, chloroform, diesel, gasoline, cyclohexane, n-hexane, edible oil, etc.; heavy metal ion wastewater includes wastewater from electroplating plants, leather factories, etc., containing lead ions, copper ions, cobalt ions, cadmium ions, etc.; biological wastewater includes wastewater containing Gram-positive bacteria, Gram-negative bacteria, and pathogenic microorganisms; wastewater containing micro-nano particles includes wastewater containing insoluble natural particles and negatively charged microplastics.

[0050] The graded multifunctional wastewater purification material prepared by this invention has abundant nitrogen atoms and hydroxyl oxygen atoms on the carboxyl groups, both of which can provide lone pairs of electrons and empty orbitals that can enter the central atom, thereby forming stable complexes with heavy metal ions and achieving efficient adsorption of heavy metal ions.

[0051] The graded multifunctional wastewater purification material prepared by this invention has an oil-water separation efficiency of over 99.5%, a heavy metal ion removal efficiency of over 99%, and a micro-nano particle removal efficiency of over 99%. Furthermore, the graded multifunctional wastewater purification material has good antibacterial properties and can effectively inhibit bacteria in water bodies.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. This invention achieves oil-water separation, filtration of micro- and nano-sized particulate pollutants and heavy metals, and antibacterial properties simultaneously through a graded, multi-functional wastewater purification material with an isolation layer and a functional layer.

[0054] 2. The functional layer of the graded multifunctional wastewater purification material in this invention has ultra-low underwater oil adhesion and roll-off angle, so that when it comes into contact with wastewater, the oil remains outside the aerogel membrane.

[0055] 3. The functional layer of the graded multifunctional wastewater purification material in this invention enables negatively charged micro- and nano-sized particulate pollutants and heavy metals to remain on the membrane surface or inside the membrane when wastewater passes through, and can also inhibit bacterial activity.

[0056] 4. The wastewater purification process of the present invention does not require the application of other pressures; complex pollutants can be purified in one step under the action of gravity.

[0057] 5. The preparation method of the present invention is simple, the raw material cost is low, and it can be mass-produced.

[0058] 6. The graded multifunctional sewage purification material obtained by this invention is combined with a rigid material with a porous structure and then made into a water purification tool, which can easily obtain clean water resources. Attached Figure Description

[0059] Figure 1 This is a scanning electron microscope image of the cross-section of the graded multifunctional wastewater purification material prepared in Example 1 of the present invention.

[0060] Figure 2 This is a scanning electron microscope image of the isolation layer of the graded multifunctional wastewater purification material prepared in Example 1 of the present invention.

[0061] Figure 3 This is a diagram showing the experimental results of designing inhibition zones using Gram-negative Escherichia coli as a model in Example 1 of the present invention.

[0062] Figure 4 This is a diagram showing the experimental results of designing inhibition zones using Gram-positive Staphylococcus aureus as a model in Example 1 of the present invention. Detailed Implementation

[0063] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0064] Example 1

[0065] 3g of sodium alginate was dissolved in 200ml of deionized water to prepare an alginate sol. This sol was divided into two portions. 120ml of one portion was mixed with 1g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1g of chitosan, and stirred for 2.5h. Then, 1g of aqueous polyurethane was added and stirring continued for 2h to obtain a modified sol. The modified sol was then sprayed 40 times to solidify it on the surface of ice blocks prepared by freezing a 2wt.% calcium chloride crosslinking agent solution at -20℃. A second round of spraying 40 times was then applied to cover the solid sol surface with the other portion of alginate sol. The solid sol was then immersed in a 2.5wt.% calcium chloride solution at 4℃. After film formation, immersion for 1h was continued to obtain a gel. Finally, the gel was freeze-dried at -80℃ for 24h to obtain a graded multifunctional wastewater purification material. The scanning electron microscope image of the material cross-section is shown below. Figure 1 As shown, the scanning electron microscope image of the isolation layer is as follows: Figure 2 As shown; the thickness of the isolation layer is 22 μm; the thickness of the functional layer is 370 μm. From Figure 1 , 2 The results show that the isolation layer has a dense structure with ultra-low underwater oil adhesion and roll-off angle, which can effectively achieve oil-water separation; while the functional layer has a porous structure with a large specific surface area and high porosity, which can filter and adsorb particulate pollutants, heavy metal ions, bacteria and other pollutants in sewage.

[0066] Antibacterial test:

[0067] An inhibition zone experiment was designed using Gram-negative Escherichia coli as a model. The graded multifunctional wastewater purification material prepared in Example 1 was placed in a co-culture environment and cultured at 37°C for 24 hours. The experimental results are shown in the figure below. Figure 3 As shown, a distinct antibacterial zone can be observed around the graded multifunctional wastewater purification material, indicating that it has a good antibacterial effect.

[0068] An inhibition zone experiment was designed using Gram-positive Staphylococcus aureus as a model. The graded multifunctional wastewater purification material prepared in Example 1 was placed in a co-culture environment and incubated at 37°C for 24 hours. The experimental results are shown in the figure below. Figure 4 As shown, a distinct antibacterial zone can be observed around the graded multifunctional wastewater purification material, indicating that it has a good antibacterial effect.

[0069] Example 2

[0070] Alginate sol was prepared by dissolving 2g of potassium alginate in 200ml of deionized water. The sol was divided into two equal portions. One portion was mixed with 0.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 3g of polyethyleneimine, and stirred for 2.5h. Then, 2g of aqueous polyurethane was added and stirring was continued for 3.5h to obtain a modified sol. The modified sol was then sprayed 10 times to solidify it on the surface of ice blocks prepared by freezing a 3wt.% calcium chloride crosslinking agent solution at -20℃. A second round of spraying 50 times was then applied to cover the solid sol surface with the other portion of alginate sol. The solid sol was then immersed in a 3wt.% calcium chloride solution at 4℃, and after film formation, it was immersed for another 1h to obtain a gel. Finally, it was freeze-dried at -80℃ for 24h to obtain a graded multifunctional wastewater purification material. The thickness of the isolation layer was 25μm, and the thickness of the functional layer was 360μm.

[0071] Example 3

[0072] 3g of ammonium alginate was dissolved in 200ml of deionized water to prepare an alginate sol. This sol was divided into two portions. 80ml of one portion was mixed with 1.5g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.5g of penicillamine, and stirred for 1 hour. Then, 2g of aqueous polyurethane was added and stirring was continued for another hour to obtain a modified sol. The modified sol was sprayed 40 times in a first round to solidify it on the surface of ice blocks prepared by freezing a 3wt.% calcium chloride crosslinking agent solution at -20℃. A second round of spraying 60 times was then applied to cover the solid sol surface with the other portion of alginate sol. The solid sol was then immersed in a 2.5wt.% calcium chloride solution at 4℃. After film formation, immersion for another hour yielded a gel. Finally, the gel was freeze-dried at -80℃ for 24 hours to obtain a graded multifunctional wastewater purification material. The thickness of the isolation layer was 32μm, and the thickness of the functional layer was 370μm.

[0073] Example 4

[0074] 3g of ammonium alginate was dissolved in 200ml of deionized water to prepare an alginate sol, which was divided into two equal parts. One part was mixed with 0.1g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 3g of polyaniline, and stirred for 5 hours. Then, 2g of aqueous polyurethane was added and stirred for another 2 hours to obtain a modified sol. The modified sol was sprayed 50 times to solidify it on the surface of ice blocks made by freezing a 3wt.% calcium chloride crosslinking agent solution at -20℃. Then, the other part of the alginate sol was sprayed 60 times to cover the surface of the solid sol. The mixture was then immersed in a 2wt.% calcium chloride solution at 1℃. After film formation, it was immersed for another hour to obtain a gel. Finally, it was freeze-dried at -80℃ for 24 hours to obtain a graded multifunctional wastewater purification material. The thickness of the isolation layer was 34μm, and the thickness of the functional layer was 375μm.

[0075] Example 5

[0076] 3g of sodium alginate was dissolved in 200ml of deionized water to prepare an alginate sol. This sol was divided into two portions. 110ml of one portion was mixed with 2g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1g of polyethyleneimine, and stirred for 5 hours. Then, 5g of aqueous polyurethane was added and stirring continued for 2 hours to obtain a modified sol. The modified sol was sprayed 50 times to solidify it on the surface of ice blocks prepared by freezing a 3wt.% calcium chloride crosslinking agent solution at -20℃. A second round of spraying 50 times was then applied to cover the solid sol surface with the other portion of alginate sol. The solid sol was then immersed in a 2.5wt.% magnesium chloride solution at 5℃. After film formation, immersion for 1 hour yielded a gel. Finally, the gel was freeze-dried at -80℃ for 24 hours to obtain a graded multifunctional wastewater purification material. The thickness of the isolation layer was 26μm, and the thickness of the functional layer was 390μm.

[0077] Example 6

[0078] 3g of sodium alginate was dissolved in 200ml of deionized water to prepare an alginate sol, which was divided into two equal parts. One part was mixed with 2g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1g of polyethyleneimine, and stirred for 5 hours. Then, 0.5g of aqueous polyurethane was added and stirred for another 2 hours to obtain a modified sol. The modified sol was sprayed 40 times to solidify it on the surface of ice blocks made by freezing 2.5wt.% calcium chloride crosslinking agent solution at -30℃. Then, the other part of the alginate sol was sprayed 50 times to cover the surface of the solid sol. The mixture was then immersed in 2.5wt.% magnesium chloride solution at 5℃. After film formation, it was immersed for another hour to obtain a gel. Finally, it was freeze-dried at -80℃ for 24 hours to obtain a graded multifunctional wastewater purification material. The thickness of the isolation layer was 25μm, and the thickness of the functional layer was 320μm.

[0079] Example 7

[0080] Alginate sol was prepared by dissolving 6g of sodium alginate in 200ml of deionized water. The sol was divided into two portions. 180ml of one portion was mixed with 1g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1g of polyaniline, and stirred for 2.5h. Then, 2.5g of aqueous polyurethane was added and stirring continued for 3.5h to obtain a modified sol. The modified sol was then sprayed 60 times to solidify it on the surface of ice blocks prepared by freezing a 5wt.% calcium chloride crosslinking agent solution at -20℃. A second round of spraying 30 times was then applied to cover the solid sol surface with the other portion of alginate sol. The solid sol was then immersed in a 2.5wt.% calcium chloride solution at 4℃. After film formation, immersion for 1h was continued to obtain a gel. Finally, the gel was freeze-dried at -80℃ for 24h to obtain a graded multifunctional wastewater purification material. The thickness of the isolation layer was 15μm, and the thickness of the functional layer was 380μm.

[0081] Application Examples 8-14

[0082] The graded multifunctional wastewater purification materials prepared in Examples 1-7 were combined with copper mesh and then made into water cups with the functional layer on the inside.

[0083] Wastewater preparation:

[0084] Preparation of Class I wastewater: Add 5g of chloroform to 100ml of ultrapure water and stir vigorously with a magnetic force to obtain a chloroform-oil-water mixture. Preparation of Class II wastewater: Add 5g of chloroform and 1g of nonionic surfactant to 100ml of ultrapure water and stir vigorously with a magnetic force to obtain a chloroform-mixed oil-water mixture. Preparation of Class III wastewater: Prepare 5mg / L Pb solutions separately. 2+ Cr 3+ Cd 2+ Cu 2+ 40 ml of aqueous solution. For preparing Class IV wastewater: Prepare 100 mg / L solutions of polystyrene (PS) and polyvinyl chloride (PVC) nanoparticles respectively.

[0085] Pour the above four types of wastewater into the water cups prepared in Application Examples 8-14.

[0086] The separation efficiency R1 of oil-water mixture, the separation efficiency R2 of oil-water emulsion, the removal efficiency AE of heavy metal ions, and the removal efficiency RP of micro-nano particles were calculated according to the following formulas. The specific data are shown in Table 1.

[0087] Formula for calculating oil-water separation efficiency (R, %):

[0088]

[0089] In the formula, C f and C o These represent the oil concentrations in the filtrate and the oil-water mixture, respectively.

[0090] Formula for calculating heavy metal removal efficiency (AE, %):

[0091]

[0092] In the formula C a C b The values ​​represent the concentrations of heavy metal ions before and after adsorption.

[0093] Micro / nano particle removal efficiency (RP, %):

[0094]

[0095] In the formula C a C b The values ​​represent the concentrations of micro- and nano-particles before and after filtration, respectively.

[0096] Comparative Example 1

[0097] Compared to Example 1, the difference lies in that the wastewater purification material does not have an isolation layer and is combined with a copper mesh before being made into a water cup. The prepared wastewater was passed through the water cup of this comparative example, and the oil-water separation efficiency R, heavy metal ion removal efficiency AE, and micro-nano particle removal efficiency RP were calculated according to the following formulas. Specific data are shown in Table 1.

[0098] Table 1. Test results of the purification efficiency of wastewater purification materials

[0099]

[0100] According to the test results in the table above, it can be seen that: in Comparative Example 1, due to the lack of an isolation layer, its oil-water separation efficiency, heavy metal removal efficiency, and micro-nano particle removal efficiency are all lower than those of the purification material provided by the present invention. In Example 4 (11), the amount of hydroxyl activator added was too small, resulting in insufficient activation reaction and poor functional layer effect; in Example 5 (12), the amount of pore-forming agent added was too large, making the functional layer too porous and reducing the purification efficiency; in Example 6 (13), the amount of pore-forming agent added was too small, resulting in a dense functional layer and reduced water flux. Although it did not affect the purification efficiency, the filtration speed was slow and the water treatment efficiency was low; in Example 7 (14), the amount of alginate sol remaining in the second round of spraying was too small, resulting in insufficient number of second rounds of spraying, and the isolation layer was too thin and could not play a good role.

[0101] In summary, this invention achieves simultaneous oil-water separation, filtration of micro- and nano-sized particulate contaminants and heavy metals, and antibacterial properties through a graded, multi-functional wastewater purification material with an isolation layer and a functional layer; moreover, the preparation method is simple and safe. Combining the prepared graded, multi-functional wastewater purification material with a water purification device allows for the easy acquisition of clean water resources.

[0102] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A graded, multifunctional wastewater purification material, characterized in that, The graded multifunctional wastewater purification material includes an isolation layer and a functional layer; wherein the isolation layer has a dense structure and a negative surface potential. The functional layer has a porous structure, a positive surface potential, and a specific surface area of ​​220-240 m². 2 / g, porosity 25-32%; The preparation method of the graded multifunctional wastewater purification material includes the following steps: dissolving alginate in deionized water to prepare alginate sol, dividing it into two portions, taking one portion and adding carboxyl activator, modifier, and pore-forming agent in sequence and stirring to obtain a modified sol, and using a first round of spraying to solidify the modified sol on the surface of crosslinking agent ice to form a crude functional layer; covering the surface of the crude functional layer with the other portion of alginate sol through a second round of spraying, and then immersing it in a crosslinking agent solution to obtain a crude graded multifunctional wastewater purification material, and then using vacuum freeze-drying to obtain a graded multifunctional wastewater purification material including an isolation layer and a functional layer.

2. The graded multifunctional wastewater purification material according to claim 1, characterized in that, The surface pore size of the isolation layer is 1-5 nm; the surface pore size of the functional layer is 40-55 μm.

3. The graded multifunctional wastewater purification material according to claim 1, characterized in that, The thickness of the isolation layer is 20-40 μm; the thickness of the functional layer is 100-400 μm.

4. The graded multifunctional wastewater purification material according to claim 1, characterized in that, The graded multifunctional wastewater purification material has a gradient pore structure in the cross-sectional direction, and the pore size in the cross-sectional direction is 15-25μm.

5. The graded multifunctional wastewater purification material according to claim 1, characterized in that, The total thickness of the graded multifunctional wastewater purification material is 100-500μm.

6. A method for preparing the graded multifunctional wastewater purification material as described in claim 1, characterized in that, The preparation method includes the following steps: dissolving alginate in deionized water to prepare alginate sol, dividing it into two portions, taking one portion and adding carboxyl activator, modifier, and pore-forming agent in sequence and stirring to obtain a modified sol, and using a first round of spraying to solidify the modified sol on the surface of crosslinking agent ice to form a functional layer crude product; covering the surface of the functional layer crude product with the other portion of alginate sol through a second round of spraying, and then immersing it in a crosslinking agent solution to obtain a graded multifunctional wastewater purification material crude product, and then using vacuum freeze-drying to obtain a graded multifunctional wastewater purification material including an isolation layer and a functional layer.

7. The preparation method according to claim 6, characterized in that, The mass ratio of alginate, carboxyl activator, modifier, and pore-forming agent in the modified sol is 1:(0.1-2):(0.3-3):(0.5-3).

8. The preparation method according to claim 6, characterized in that, The mass ratio of alginate sol in the first round of spraying to alginate sol in the second round of spraying is 1:(0.5-4).

9. The preparation method according to claim 6, characterized in that, The carboxyl activator is one or more of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide.

10. The preparation method according to claim 6, characterized in that, The modifier is one or more of the following: polycarboxyamine, chitosan, polyaniline, penicillamine, and polyethyleneimine.

11. The preparation method according to claim 6, characterized in that, The pore-forming agent is waterborne polyurethane.

12. The preparation method according to claim 6, characterized in that, The crosslinking agent includes one or more of copper sulfate, ferric sulfate, magnesium chloride, copper chloride, and calcium chloride.

13. The preparation method according to claim 6, characterized in that, The first round of spraying consists of 10-80 sprays; the second round of spraying consists of 40-60 sprays.

14. The application of the graded multifunctional wastewater purification material as described in claim 1 in water treatment.

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