CN116688779B

CN116688779B - Super-smooth multi-mechanism anti-pollution anti-scaling separation membrane and preparation method and application thereof

Info

Publication number: CN116688779B
Application number: CN202310505593.6A
Authority: CN
Inventors: 赵姗姗; 刘桂梅; 孟凡刚; 劳晓敏; 张文天; 韩木侨
Original assignee: Sun Yat Sen University
Current assignee: Sun Yat Sen University
Priority date: 2023-05-06
Filing date: 2023-05-06
Publication date: 2024-01-05
Anticipated expiration: 2043-05-06
Also published as: CN116688779A

Abstract

The invention discloses a preparation method of a super-smooth multi-mechanism anti-pollution and anti-scaling separation membrane. The method comprises the steps of activating a basal membrane with carboxyl on the surface, and then mixing the basal membrane with an amine compound, wherein the amine compound is grafted and crosslinked on the basal membrane to form a positively charged hydration layer; and then the positively charged hydration layer is covalently connected with polydimethylsiloxane to form a super-smooth layer, and the super-smooth multi-mechanism anti-pollution anti-scaling separation membrane is prepared and obtained. The method sequentially builds the positively charged hydration layer and the superparamagnetic layer on the surface of the separation membrane, ensures the advantages of high flux and high interception of the separation membrane, and greatly improves the capability of the separation membrane for resisting organic pollution and inorganic salt scaling.

Description

Super-smooth multi-mechanism anti-pollution anti-scaling separation membrane and preparation method and application thereof

Technical Field

The invention belongs to the technical field of separation membranes, and particularly relates to a super-smooth multi-mechanism anti-pollution anti-scaling separation membrane, and a preparation method and application thereof.

Background

Population growth and resource shortages have had an increasing impact on global economy, social stability and ecological environment, and sustainable recovery of effective resources from wastewater is expected to alleviate this problem. At present, the membrane separation technology is widely applied to the field of high-salt and high-organic matter wastewater treatment and is used for resource recovery and utilization.

However, most commercial membranes (loose nanofiltration membrane, nanofiltration membrane and reverse osmosis membrane) are polyamide separation membranes, the hydrophilicity is poor, the membrane surface is rough, the electronegativity is strong, and the membrane surface is provided with unreacted complete carboxyl residues. In the process of treating high-salt and high-organic wastewater, as the recovery rate of a system is increased, the concentration of organic matters and inorganic salts (calcium and magnesium ions, carbonate ions, sulfate ions and the like) in the feed liquid is greatly increased, the organic matters are easy to deposit on the surface of the membrane in a large amount due to the hydrophobic effect and the bridging effect of carboxyl groups and metal ions, and the inorganic salts form heterogeneous nucleation crystallization on the surface of the membrane due to electrostatic adsorption and the complexing effect of carboxyl groups, so that serious organic matter pollution and inorganic salt scaling are formed on the surface of the membrane, membrane holes are blocked, the water yield of the membrane is reduced, the water quality of produced water is poor, and the service life of the membrane is prolonged.

The current method for controlling membrane pollution in high-salt and high-organic wastewater treatment comprises pretreatment of feed liquid, such as adding scale inhibitor, membrane cleaning, membrane modification and the like. However, pretreatment of feed streams and addition of scale inhibitors can result in more complex, more difficult to handle membrane concentrates, which is detrimental to sustainable zero-emission treatment and increases treatment costs. In contrast, the modification of the anti-pollution and anti-salt scaling on the surface of the membrane can effectively improve the durability of the membrane, relieve the membrane pollution, improve the production efficiency and reduce the maintenance cost.

The surface modification technology is widely used for preparing an anti-pollution film because of simple operation, mild condition and easy operation, so as to weaken the interaction between pollutant and the film surface. The surface hydrophilic modification is commonly used for preparing nanofiltration/reverse osmosis membranes with high water flux and organic pollution resistance, and a hydration layer is formed on the membrane surface through hydration of hydrophilic substances (such as polyvinyl alcohol PVA and polyethylene glycol PEG) so as to block complexation of organic pollutants and carboxyl residues on the membrane surface and resist blocking of holes caused by adhesion of the pollutants on the membrane surface. For example, lin et al, 9, 2021, report on the preparation of hydrophilic porous nanofiltration membranes based on metal-organic complexation of tannic acid-iron ions, which are effective against hydrophobic humus organic contamination. The authors used the anti-pollution membrane in the separation and concentration treatment of landfill leachate reverse osmosis concentrate containing a large amount of humus. However, as the recovery rate of the system is improved, the flux of the modified membrane of the hydrophilic loose nanofiltration membrane is continuously reduced, and the single hydrophilic modified surface has limitations and an anti-pollution threshold in the actual water treatment process, is easily covered by high-concentration pollutants to lose the anti-pollution capability, and the hydrophilic loose nanofiltration membrane cannot realize the effect of resisting inorganic scaling at the same time, namely, the single hydrophilic modification of the membrane surface cannot achieve the excellent effect of resisting organic pollution and resisting inorganic scaling at the same time in treating complex high-salt high-organic wastewater.

At present, the nanofiltration reverse osmosis process mainly carries out inorganic scaling resistance through pretreatment steps such as acidification or adding a scale inhibitor, and the like, and compared with the research and development of an organic pollution resistance membrane, the research on the inorganic scaling resistance nanofiltration membrane/reverse osmosis membrane is limited. Anti-scaling on the surface of materials is often surface modified with hydrophobic substances, which reduce nucleation sites by imparting low surface energy to the surface of the material, inhibit heterogeneous scaling, and simultaneously prevent deposition of homogeneous crystals on the surface of the material. However, the commonly used perfluorinated modifiers have serious environmental hazards, especially the current worldwide limited use of perfluorinated and polyfluoroalkyl products, making the anti-fouling modification of membrane material surfaces a need for fluorine-free material replacement. In addition, a great deal of research is focused on only a single hydrophilic membrane resistant to organic contamination or a hydrophobic surface resistant to inorganic scaling, and few documents report separation membranes having both properties of resistance to organic contamination and inorganic scaling.

Disclosure of Invention

Aiming at the prior art problems, the primary aim of the invention is to provide a green preparation method of a super-smooth multi-mechanism anti-pollution anti-scaling separation membrane, which sequentially constructs a positively charged hydration layer (pollution resisting layer) and a super-smooth layer (pollution releasing layer) on the surface of the separation membrane, thereby greatly improving the capability of the separation membrane for resisting organic pollution and inorganic scaling while ensuring the advantages of high flux and high interception of the separation membrane.

The second aim of the invention is to provide the ultra-smooth multi-mechanism anti-pollution and anti-scaling separation membrane prepared by the preparation method.

The third object of the invention is to provide the application of the ultra-smooth multi-mechanism anti-pollution and anti-scaling separating membrane in the treatment of high-salt and high-organic wastewater.

In order to achieve the above object, the present invention is realized by the following technical scheme:

a preparation method of a super-smooth multi-mechanism anti-pollution and anti-scaling separation membrane comprises the steps of activating a basal membrane with carboxyl on the surface, and then mixing the basal membrane with an amine compound, wherein the amine compound is grafted and crosslinked on the basal membrane to form a positively charged hydration layer; and then the positively charged hydration layer is covalently connected with polydimethylsiloxane to form a super-smooth layer, and the super-smooth multi-mechanism anti-pollution anti-scaling separation membrane is prepared and obtained.

The single hydrophilic modified surface has limitation and anti-pollution threshold in the actual water treatment process (especially in high-salt high-organic matter wastewater), the inventor finds that the single hydrophilic layer has low anti-pollution load because the concentration of pollutants in the high-salt high-organic matter wastewater is extremely high and the organic-inorganic ions are in strong interaction, the hydration layer can be used as a protective layer to resist the complexation and pore blocking of the pollutants and the membrane substrate, however, the high-concentration organic-inorganic composite pollutants are easy to deposit and cover the hydration layer to form a pollution layer, the organic-inorganic pollutants accumulated on the surface of the hydration layer are easy to nucleate at an interface to form heterogeneous scaling, and the heterogeneous scaling is further aggravated after the homogeneous scaling formed in the supersaturated solution is deposited in the concentration process.

The acting force of the membrane surface on the pollutant is reduced, so that the deposited surface pollutant can be promoted to slide on the membrane surface, and therefore, the hydrophobic modification with low surface energy has pollutant release capability, heterogeneous scaling of the membrane surface and serious membrane pollution caused by homogeneous scaling deposition in solution can be effectively relieved, and the hydrophobic modification with low surface energy has surface scaling resistance. The Polydimethylsiloxane (PDMS) molecular brush is a fluorine-free low-surface-energy hydrophobic substance, has high fluidity at room temperature and can dynamically and freely rotate due to the extremely low glass transition temperature, so that the modified surface has the dynamic characteristic of super-smooth similar liquid, the dynamic flow of pollutants on the surface of a film is promoted, and the scaling precursor and inorganic scaling on the surface of the film can be effectively released. However, organic contaminants in wastewater often exhibit high hydrophobicity, and a single hydrophobic surface tends to attract hydrophobic organics and promote their sliding into the membrane pores of the membrane substrate resulting in membrane pore blockage and ultimately irreversible severe organic contamination. It is further noted that the typical smooth surface is currently a lubricant silicone oil injection surface (lubricant-injected surface), which is suitable for modification of a non-porous surface with a micro-nano structure or a micro-filtration membrane with a larger pore diameter, and the injection of silicone oil can seriously block membrane pores. If a single silicone oil injection method is adopted to modify the nanofiltration membrane to construct an ultra-smooth surface, PDMS silicone oil is easy to enter the nanofiltration membrane holes to cause serious blockage. Meanwhile, the affinity of a single hydrophobic surface to water molecules is extremely low, the contact area of a solution and the surface is reduced, the membrane flux is greatly reduced, and the method is not suitable for preparing a high-flux separation membrane (loose nanofiltration/reverse osmosis membrane) and efficiently treating high-salt and high-organic wastewater. I.e. a single hydrophobic surface modification is detrimental for the preparation of separation membranes resistant to complex organic contamination and inorganic scaling.

The inventor discovers through long-term research that a basal membrane with carboxyl on the surface and a branched amine compound are grafted on the basal membrane through an acylation reaction to form a tightly crosslinked positively charged hydration layer with an amino group, and then the amino group on the positively charged hydration layer and an epoxy group on PDMS undergo a nucleophilic ring-opening reaction to enable the PDMS chain molecular sieve to be grafted on the surface of the positively charged hydration layer. By the method, a positively charged hydration layer (pollution resisting layer) and a super smooth layer (pollution releasing layer) are gradually constructed on the surface of the active layer of the base film. In the invention, on one hand, the compact cross-linked network layer rich in amino consumes carboxyl groups on the surface of the base film through acylation reaction, and positively charged amino groups have electrostatic repulsive force on organic matter-divalent metal ion composite pollutants, and meanwhile, good hydrophilicity of the amino groups is favorable for forming a compact hydration protective layer with a certain thickness on the surface of the film, so that serious organic pollution caused by complexation between carboxyl residues on the surface of the organic matter-metal ion-polyamide film is resisted, and the anti-pollution performance of the surface of the film is further improved. On the other hand, the flexible dynamic chain PDMS molecular brush constructs a lubrication surface (super smooth layer) with low surface energy, so that crystal nuclei and massive crystals deposited on the surface of the membrane are easy to release under the condition of hydraulic flushing, and the anti-scaling performance of the surface of the membrane is further improved.

In addition, due to the existence of the compact cross-linked network hydration layer, on one hand, the hydrophobic influence of the hydrophobic PDMS is counteracted by enhancing the hydration, and on the other hand, PDMS silicone oil is not easy to enter the base membrane through the compact cross-linked network and block membrane holes during modification, so that the great attenuation of flux is avoided, namely, the separation membrane provided by the invention still maintains the characteristics of high flux and interception of high-molecular organic matters after the PDMS is subjected to hydrophobic modification, and the problem of serious decline of the flux of the membrane after the traditional hydrophobic modification is solved. The preparation method provided by the invention has the advantages of ensuring high flux and high interception, and simultaneously has the separation membrane with excellent organic pollution resistance and inorganic salt scaling resistance, and can effectively resist complex organic-inorganic composite pollution in high-salt and high-organic wastewater. The separation membrane prepared by the invention ensures the efficient separation, concentration and recovery of organic matters and inorganic salts in the wastewater, and has important application value in the field of high-salt and high-organic matter wastewater recycling treatment.

In some embodiments, the base film is selected from one or more of a polyamide film, a carboxylated cellulose acetate film, a Polyacrylonitrile (PAN) hydrolyzed film.

In some embodiments, the membrane pore size of the base membrane ranges from 200 to 10000Da. When the base film is a polyamide film, the pore diameter of the polyamide film is in the range of 200 Da to 2000Da. More specifically, the polyamide membrane may have a membrane pore size of 400, 600, 800, 1000, 1200, 1400, 1600, 1800Da, etc., to which the present application is not limited.

In some embodiments, the amine compound is selected from one or more of polyethylenimine, triethanolamine, polyacrylamide, ethylenediamine, polyvinylamine.

Preferably, the amine compound is polyethylenimine. More specifically, the polyethyleneimine may be a linear polyethyleneimine or a branched polyethyleneimine.

In some embodiments, the polyethyleneimine has a molecular weight of 600 to 750000Da. Further preferably, the molecular weight of the polyethyleneimine is 600-10000 Da; more preferably, the molecular weight of the polyethyleneimine is 600-1000 Da; most preferably, the molecular weight of the polyethyleneimine is 600Da. The molecular weight of the polyethyleneimine is increased, the number of amine groups is increased, the electropositivity is increased, however, the thickness of a hydration layer is increased, the water resistance is increased, the membrane flux is reduced, and the crosslinking degree and the diffusion capacity of the polyethyleneimine with high molecular weight on the membrane surface are reduced due to the large steric hindrance of the polyethyleneimine with high molecular weight, so that the hydration layer is defective, and the pollution resistance is reduced.

In some embodiments, the polydimethylsiloxane is selected from monoglycidyl ether terminated polydimethylsiloxanes; the molecular weight is 800-10000 Da. The inventor finds that adopting the structure that the single glycidyl ether is used for blocking PDMS, one end of the structure can be fixed on the surface of the membrane, and the other end of the structure can freely rotate at the interface, so that the prepared separation membrane surface has stronger pollution release capability. The flexibility and fluidity of the double glycidyl ether terminated PDMS are weakened because both ends of the molecular brush are fixed on the surface of the membrane, and the pollution release capability of the double glycidyl ether terminated PDMS on the surface of the membrane is damaged, so that the single glycidyl ether is preferably used for terminated PDMS.

The molecular weight of the polydimethylsiloxane may be 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, etc., and the present application is not limited thereto. Further preferably, the molecular weight of the polydimethylsiloxane is 4000-6000 Da; most preferably, the molecular weight of the polydimethylsiloxane is 5000Da. The inventors found that the size of the molecular weight of PDMS can affect the grafting density of the PDMS molecular brush on the membrane surface, and thus the morphology of the PDMS molecular brush on the membrane surface, and ultimately the anti-fouling ability of the separation membrane. The inventor finds that the separation membrane prepared by PDMS with the preferable molecular weight range has higher release resisting effect on organic pollutants and stronger anti-pollution capability.

In some embodiments, the amine compound is used in an excess amount.

In some embodiments, the mass to volume ratio of the amine compound to the polydimethylsiloxane is from 0.7 to 2.2:1g/mL. More specifically, the mass-volume ratio of the amine compound to the polydimethylsiloxane is 2.0-2.2: 1g/mL.

In some embodiments, the activation includes the step of mixing a base film having carboxyl groups on the surface with an activation solution. The activated carboxyl can react with amine groups in the polyethyleneimine in the environment of simple operation, i.e. room temperature aqueous solution, so that the polyethyleneimine cross-linked network is covalently connected on the surface of the polyamide membrane.

In some embodiments, the activation solution includes an activation reagent including, but not limited to, 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide (EDC), N-hydroxysuccinimide (NHS), and the like.

In some embodiments, the activation solution may also be a mixed solution of an activation reagent and a buffer solution including, but not limited to, 2- (N-morpholino) ethanesulfonic acid (MES), phosphate Buffered Saline (PBS), and the like.

In some embodiments, the activating solution has a molar concentration of 0.01 to 1mol/L; further preferably, the molar concentration of the activation solution is 0.1 to 0.2mol/L; most preferably, the molar concentration of the activation solution is 0.1mol/L.

In some embodiments, the time of the activation mixing is from 10 to 360 minutes; further preferably, the time of the activation mixing is 90 to 240 minutes; most preferably, the time for activating the mixing is 180 minutes.

In some embodiments, the temperature of the activation mixing is 15 to 60 ℃; further preferably, the temperature of the activation mixing is 15-35 ℃; most preferably, the temperature of the activation mix is 25 ℃.

In some embodiments, the positively-charged hydration layer is reacted with polydimethylsiloxane for a time period of 60 to 1440 minutes; further preferably, the reaction time is 180 to 360 minutes; most preferably, the reaction time is 300min.

In some embodiments, the positively-charged hydration layer is reacted with polydimethylsiloxane at a temperature of 15 to 90 ℃; further preferably, the reaction temperature is 50 to 70 ℃; most preferably, the reaction temperature is 60 ℃.

Furthermore, the invention also claims a super-smooth multi-mechanism anti-pollution anti-scaling separation membrane prepared by the preparation method.

Furthermore, the invention also claims the application of the ultra-smooth multi-mechanism anti-pollution anti-scaling separation membrane in the treatment of high-salt high-organic wastewater.

In some embodiments, the high-salt high-organic wastewater has a conductivity of 10mS/cm or more and a Total Organic Carbon (TOC) of 100mg/L or more.

Compared with the prior art, the invention has the following beneficial effects: the invention provides a super-smooth multi-mechanism anti-pollution and anti-scaling separating membrane, wherein a positively charged hydration layer and a super-smooth layer are sequentially constructed on the surface of the separating membrane, so that the separating membrane has high flux and high interception, simultaneously, the capability of the separating membrane for resisting organic pollution and inorganic salt scaling is greatly improved, the efficient separation, concentration and recovery of organic matters and inorganic salts in wastewater are ensured, and the super-smooth multi-mechanism anti-pollution and anti-scaling separating membrane has important application value in the field of high-salt and high-organic matter wastewater recycling treatment. The preparation method provided by the invention is that the membrane surface is contacted with the reaction solution under mild conditions, the preparation process is simple, the preparation conditions are mild, the preparation method is suitable for surface modification of various separation membranes, can be used for preparing anti-pollution and anti-scaling ultrafiltration membranes, loose nanofiltration membranes, reverse osmosis membranes and the like, and has wide application range and easy amplification and popularization.

Drawings

FIG. 1 is an atomic force microscope (AFM, fatscan, brookfield (Beijing) technology Co., ltd.) view of the ultra-smooth multi-mechanism anti-fouling separation membrane prepared in examples 1 to 2 and comparative example 1.

FIG. 2 is a schematic view showing the surface properties of the separation membranes in examples 1 to 2 and comparative examples 1 to 3; fig. 2 (a) shows the surface water contact angle of the separation membrane, fig. 2 (b) shows the surface energy of the separation membrane, and fig. 2 (c) shows the surface charge of the separation membrane.

FIG. 3 is a graph showing separation performance of the separation membranes in examples 1 to 2 and comparative examples 1 to 3; wherein, FIG. 3 (a) is the membrane molecular weight cut-off (MWCO) of the separation membrane, FIG. 3 (b) is the membrane pore size distribution of the separation membrane, FIG. 3 (c) is the water flux of the separation membrane, and FIG. 3 (d) is the divalent salt cut-off performance of the separation membrane.

FIG. 4 shows the retention performance of examples 1 to 2 and comparative examples 1 to 3 on organic and inorganic salts in effluent of a landfill leachate Membrane Bioreactor (MBR).

Fig. 5 is a graph showing the variation of membrane flux of the ultra-smooth multi-mechanism anti-pollution and anti-scaling separation membranes prepared in examples 1-2 and comparative examples 1-3 applied to the wastewater depth treatment of the high-salt high-organic garbage leachate MBR.

FIG. 6 is a scanning electron microscope (SEM, JSM-6330F, japanese electronic Co., ltd.) diagram of the ultra-smooth multi-mechanism anti-fouling separation membrane prepared in examples 1 to 2 and comparative examples 1 to 3 after fouling and after cleaning. Fig. 6 (a) to (d) are SEM images of the surface contamination layer after separation membrane contamination; fig. 6 (e) to (h) are SEM electron microscope images of the surfaces of the separation membranes after the contamination by pure water.

FIG. 7 shows the retention rate of organic and inorganic salts in the MBR effluent depth treatment process of the high-salt and high-organic garbage leachate according to examples 1-2.

Detailed Description

The invention is further illustrated in the following drawings and specific examples, which are not intended to limit the invention in any way. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art.

Example 1 preparation of ultra-smooth Multi-mechanism anti-fouling separation Membrane

(1) Rinsing a commercial polyamide membrane (UF 0011, national science and technology (Xiamen) Co., ltd.) with deionized water for multiple times to remove a preservative and a membrane pore retention agent to obtain a pretreated base membrane, wherein the surface of the pretreated base membrane contains carboxyl groups, and soaking the pretreated base membrane in deionized water for later use, and marking the pretreated base membrane as Uncoated-PA;

(2) 100mL of 0.1mol/L MES (Macklin) buffer solution with pH of 5.5 was prepared, and 1- (3-dimethylaminopropyl) -3-Ethylcarbodiimide (EDC) (Aladin Co.) and N-hydroxysuccinimide (NHS) (Aladin Co.) were dissolved in the MES buffer solution successively (the preparation concentrations of EDC and NHS were 0.1 mol/L), to obtain an activated solution;

(3) 6.6g of Polyethylenimine (PEI) with a molecular weight of 600Da (Aladin Co., ltd., product No. E107077) were dissolved in water and the pH of the solution was adjusted to 7.5 with hydrochloric acid; the adjusted PEI concentration was 3wt% and the amount of solution was 100mL.

(4) Fixing the base film in a surface modification device so that a selective layer of the base film faces upwards; pouring the activation solution prepared in the step (2) into a surface modification device, placing the surface modification device on a shaking table, activating one side of a selection layer of a base film for 3 hours at room temperature at a rotating speed of 50rpm, pouring the activation solution after the activation is finished, and fully rinsing the surface modification device by deionized water;

(5) Mixing the activated base film in the step (4) with the amine compound configured in the step (3) at room temperature, reacting for 2 hours, forming a positively charged hydration layer on the surface of the base film selection layer, and washing off excessive reactants by using deionized water;

(6) Uniformly and thinly coating a layer of mono glycidyl ether-terminated polydimethylsiloxane (PDMS, pure silicone oil) (Sigma-Aldrich company, product number 480290) with the molecular weight of 5000Da on the surface of the hydrophilically modified film in the step (5), standing in an oven at 60 ℃ for reaction for 5 hours, washing off the residual reactant by deionized water after the reaction is finished, and storing the modified film in the deionized water to obtain the ultra-smooth multi-mechanism anti-pollution anti-scaling separation film (marked as P5000-PEI-PA).

Example 2 preparation of ultra-smooth Multi-mechanism anti-fouling separation Membrane

This embodiment differs from embodiment 1 in that: the molecular weight of the monoglycidyl ether terminated Polydimethylsiloxane (PDMS) employed in step (6) was 1000Da. The ultra-smooth multi-mechanism anti-pollution and anti-scaling separation membrane is marked as P1000-PEI-PA.

Comparative example 1

The difference between this comparative example and example 1 is that: in this comparative example, only the steps (1) to (5) were carried out, and the operation of step (6) was not carried out, and the obtained modified film was labeled PEI-PA. That is, this comparative example was subjected to only hydrophilic modification and was not subjected to hydrophobic and smooth layer modification.

Comparative example 2

The difference between this comparative example and example 1 is that: the comparative example was conducted only with steps (1), (2), (4) and (6), and the obtained modified film was labeled PDMS-PA; that is, the base film in this comparative example was not hydrophilically modified after activation, and was directly modified with a hydrophobic smooth layer.

Comparative example 3

This comparative example employs a commercial polyamide separation membrane (SynderNFW, stardard Membrane technologies Co., USA) labeled SynderPA having similar separation properties to the separation membranes prepared in examples 1-2.

Synder PA is a commercial loose nanofiltration membrane, the separation layer of which is a polyamide film, the surface of the membrane contains exposed carboxyl functional groups, and the membrane has similar surface properties as a blank membrane Uncoated-PA. SynderPA pore size was smaller than Uncoated-PA, and similar to the separation membranes prepared in examples 1-2, membrane pore size, organic rejection, inorganic salt rejection, and membrane flux. When the MBR effluent is filtered, the interception of organic matters in the wastewater by the Synder PA membrane is far higher than that of Uncoated-PA, and the interception of organic matters and inorganic salts in the wastewater is similar to that in examples 1-2. Therefore, when the modified membrane is used for treating the pollution resistance of the high-salt high-organic matter landfill leachate MBR effluent, the similar membrane separation performance enables Synder PA to be more suitable for being used as a representative of a polyamide commercial membrane, and when the modified membrane is compared with the separation membrane prepared in the embodiment 1-2, the interference caused by different filtration performances of the membrane can be better eliminated.

Test example 1 characterization of the surface topography of a ultra-smooth Multi-mechanism anti-fouling separation Membrane

AFM characterization was performed on the ultra-smooth multi-mechanism anti-pollution and anti-scaling separation membranes prepared in examples 1-2 and comparative example 1, and FIG. 1 is an AFM characterization diagram of examples and comparative examples.

As is clear from FIG. 1, the PEI modification of the film surface improved the film surface roughness to a roughness of 14.2nm. After the surface coating of the PDMS is carried out in the examples 1 and 2, the roughness of the film surface is obviously reduced, and the roughness is about 5.6nm and 7.5nm respectively, which shows that after the PDMS is modified, the super-smooth film surface is successfully constructed on the film surface, and in a certain molecular weight range, the higher the molecular weight of the PDMS is, the more the film surface is lubricated.

Test example 2 flux and rejection test of ultra-smooth multi-mechanism anti-fouling separation membrane

The separation membranes of examples 1 to 2 and comparative examples 1 to 3 were subjected to the test for pure water flux, retention rate and water contact angle as follows:

pure water flux measurement: the effective area of the membrane was 16cm as measured using a cross-flow filtration device (CF 016D, sterlitech Co., U.S.A.) ² The filtration temperature was controlled at 25℃and the test pressure was 6bar, and the membrane flow rate was controlled at 0.1m/s. And pre-pressing the membrane by pure water, and recording the water permeability J of the membrane after the flux is stable. The calculation formula is as follows:

Wherein V represents the volume of the percolate (L), A represents the effective membrane area (m ² ) Δt represents the filtering time period (h).

Measurement of membrane rejection: determination of separation Membrane pair 1000mg/L NaCl, mgCl ₂ 、Na ₂ SO ₄ And MgSO ₄ Retention of salt in solution. The rejection rate of the membrane is calculated according to the following formula:

wherein C is _F And C _P The conductivities of the concentrate and the percolate are shown respectively.

Determination of average molecular cut-off: the rejection rate of 200mg/L of 200, 300, 400, 600, 800Da polyethylene glycol (PEG) molecular solution by the separation membrane is measured, and the concentration of PEG in the concentrated solution and the rejection solution is measured by a total organic carbon analyzer (TOC), wherein the rejection rate (R) is calculated as follows:

in TOC _P And TOC _R Representing the concentration of PEG in the permeate and concentrate, respectively.

The water contact angles of the separation membranes in examples 1 to 2 and comparative examples 1 to 3 were measured. The air media Contact Angle (CA) measurements were performed using a drop shape analyzer (DSA 25E, kruss, germany). Specifically, after a2 μl droplet was dropped on the surface of the sample and stopped for 5s, the droplet profile was recorded with a droplet shape contactor, and the water contact angle at which the gas-liquid-solid three-phase angle was the sample was calculated. Each patch was tested more than eight times and averaged.

As can be seen from FIG. 2 (a), the water contact angles of SynderPA, uncoated-PA and PEI-PA are 26.5 degrees, 26.1 degrees and 35.5 degrees respectively, and the water contact angles of PEI-PA are slightly increased compared with Uncoated-PA, and the water flow on the surface of the membrane is blocked mainly due to the rough cross-linked network structure of PEI. The water contact angles of the P1000-PEI-PA and the P5000-PEI-PA are greatly increased and are 86.4 degrees and 91.6 degrees respectively, which shows that the hydrophobic PDMS molecular brush is successfully grafted on the surface of the separation membrane.

Fig. 2 (b) shows that the surface energy of the separation membrane with a hydrophilic surface is high, and the surface energy of the separation membrane is remarkably reduced after PDMS modification, so that the PDMS modified membrane can remarkably reduce the interaction force between the membrane surface and the contaminants, and helps to release the contaminants deposited on the membrane surface. In addition, P5000-PEI-PA has higher hydrophobicity and lower surface energy than P1000-PEI-PA, which shows that the molecular weight of the PDMS molecular brush has an influence on the pollution release capacity, and in a certain molecular weight range, the higher the molecular weight is, the more beneficial to release of pollutants on the surface of the film is.

FIG. 2 (c) shows that the isoelectric point of the separation membrane is in the order of magnitude of Uncoated-PA < SynderPA < PEI-PA < P1000-PEI-PA < P5000-PEI-PA. The electronegativity of the PEI-PA film surface is obviously reduced, because the positively charged amine groups of PEI can effectively consume negatively charged carboxyl residues on the polyamide film surface, and a positively charged hydration layer is successfully constructed on the film surface, thereby being beneficial to resisting film pollution mainly caused by organic pollution caused by complexation between organic matters, metal ions and the carboxyl residues on the polyamide surface, and further improving the anti-pollution performance of the film surface. The negative charge of the PDMS modified membrane was further reduced, possibly due to the dilution effect of the charge neutrality of the PDMS long chain. Finally, in wastewater containing high-concentration organic-divalent cation composite dirt, compared with PEI-PA and commercial polyamide membranes, the P1000-PEI-PA and P5000-PEI-PA membranes have smaller electrostatic attraction to the composite pollutant with divalent metal ions, and are more beneficial to resisting organic-inorganic composite pollution.

As is clear from fig. 2 (a) - (c), examples 1-2 (P1000-PEI-PA and P5000-PEI-PA) have both positively charged hydration contamination prevention layer and low surface energy super-smooth contamination release layer by constructing the PEI positively charged hydration layer and PDMS hydrophobic layer in sequence, and the higher the molecular weight of PDMS, the lower the surface energy, the smaller the interaction force to the contaminants, which is helpful for realizing the contamination and scale resistance. In addition, as commercial polyamide membranes, synderPA and Uncoated-PA have similar surface chemistry, including similar hydrophilicity, surface energy and chargeability, and the surface chemistry of the two commercial polyamide membranes differs significantly from that of the modified membrane.

As can be seen from FIGS. 3 (a) and 3 (b), the MWCO of Synder PA, uncoated-PA, PEI-PA, P1000-PEI-PA, P5000-PEI-PA are respectively: 540 The pore diameters of the surface films are 0.56,0.65,0.55,0.51 and 0.47nm respectively, and the PEI and PDMS grafting modification can effectively reduce the pore diameters and narrow the pore diameter distribution, and the larger the molecular weight of the PDMS is, the more obvious the pore shrinking effect is. In addition, it is known that the organic matter retention performance and the membrane pore diameter of Uncoated-PA and PEI-PA, P1000-PEI-PA and P5000-PEI-PA are greatly different, and compared with Synder PA, the Synder PA has more similar performance.

As can be seen from FIG. 3 (c), the membrane fluxes of SynderPA, uncoated-PA, PEI-PA, P1000-PEI-PA, P5000-PEI-PA, PDMS-PA are respectively: 12.0 16.2, 11.0, 10.0, 11.3,6.0L.m ^-2 ·h ^-1 ·bar ^-1 (LMH bar ^-1 ). After single hydrophobic modification of PDMS alone, the hydrophobic PDMS is compatible with water moleculesThe force is low, and PDMS silicone oil permeates into the membrane pores in the modification process and seriously blocks the membrane pores, so that the membrane flux is 16.2LMH bar ^-1 Greatly reduced to 6.0LMH bar ^-1 。

When hydrophilic modification (PEI-PA) is adopted, the PEI endows the surface of the membrane substrate with a compact hydration layer, so that the membrane passing resistance is increased, and the membrane flux is reduced. However, after the PDMS hydrophobic modification is continuously carried out on the basis of PEI, the membrane flux can be kept unchanged basically, on one hand, because the existence of a compact PEI interlayer prevents the PDMS from penetrating into and blocking membrane holes, and on the other hand, the low-surface-energy highly flexible PDMS molecular brush is not easy to adhere to water molecules, can promote the water molecules to flow transversely and longitudinally on the surface of the membrane, promotes more water molecules to enter a hydrophilic PEI layer to pass through the membrane, and counteracts the membrane passing resistance brought by the PDMS layer.

FIG. 3 (d) shows that polyamide SynderPA and Uncoated-PA are resistant to divalent anions SO ₄ ^2- High retention of divalent cations Mg ²⁺ The interception results of inorganic salts of PEI-PA, P1000-PEI-PA and P5000-PEI-PA are opposite, and the inorganic salts have low interception results, and the positive amine groups on the surface of the modified membrane have electrostatic repulsive force on divalent cations after PEI modification, so that the interception rate of the divalent cations is improved. This result is consistent with the film surface charging result in fig. 2 c.

As can be seen from the results of FIG. 3, the hydrophilic-super smooth low surface energy bilayer structure of examples 1-2 (P1000-PEI-PA and P5000-PEI-PA) helps to alleviate the trade-off effect of flux-entrapment in the conventional surface modification process, solves the problem of serious decrease of membrane flux after conventional hydrophobic modification, builds a separation membrane with high flux and high organic entrapment, and realizes smaller membrane pore diameter and higher organic entrapment on the premise of keeping the flux unchanged as the PDMS molecular weight is higher. Furthermore, the results also show that the Uncoated-PA has a significant difference in separation performance (organics retention, membrane pore size distribution, water flux) from examples 1-2, whereas syncer PA has similar separation performance to examples 1-2.

Test example 3 test of ultra-smooth Multi-mechanism anti-fouling separation Membrane for advanced treatment of high-salt high-organic landfill leachate

The separation membranes prepared in examples 1-2 and comparative examples 1-3 are used in the advanced treatment process of the MBR effluent of the actual high-salt high-organic garbage leachate to examine the separation performance of organic matters/inorganic salts and the anti-pollution and anti-scaling performance.

From FIGS. 2 to 3, it is understood that commercial polyamide membranes Uncoated-PA are similar to SynderPA in terms of surface chemistry, and that Uncoated-PA differs significantly in separation performance from the separation membranes of examples 1 to 2, whereas SynderPA has similar membrane pore size, molecular weight cut-off, and water flux as examples 1 to 2. As can be seen from fig. 2c, under the environment of the landfill leachate MBR effluent (ph=8.4), the syncer PA has similar surface potential to the PEI-PA, P1000-PEI-PA and P5000-PEI-PA, and thus has similar inorganic salt retention performance.

FIG. 4 shows the retention performance of organic and inorganic salts in the effluent of the landfill leachate MBR in the examples and the comparative examples. As can be seen from fig. 4, in the process of treating the effluent of the landfill leachate MBR, the organic matter retention rates of syncer PA, uncoated-PA, PEI-PA, P1000-PEI-PA and P5000-PEI-PA are respectively: 93.8%,77.9%,94.6%,94.9%,97.0%, and inorganic salt rejection rates of 21.8%,7.7%,14.4%,15.2%, and 17.9%, respectively.

It can be seen that the separation performance of the Uncoated-PA is significantly different from that of examples 1-2 in the effluent process of treating the landfill leachate MBR, because the interception effect of the Uncoated-PA on organic matters is too low, and the Uncoated-PA is not suitable for recycling the organic matters in the effluent treatment process of the landfill leachate MBR. To exclude the effect of separation, the effect of membrane surface chemistry on anti-fouling and anti-fouling properties was better compared, so a subsequent comparison was made using SynderPA with similar separation properties as the representative of a commercial polyamide membrane.

The test method is as follows:

taking the MBR effluent of garbage leachate of a garbage incineration plant in Guangzhou city of Guangdong as raw material liquid (the component content is shown in table 1), placing the separation membranes prepared in examples 1-2 and comparative examples 1-3 in an effective area of 16cm ² In a cross-flow filtration test apparatus (CF 016D, sterlitech Co., U.S.A.), the prepared separation membrane was tested for landfill leachate MBR effluentIs a processing performance of the (c).

TABLE 1

Index (I)	Content of	Index (I)	Content of
				pH	8.2±0.2	Fe(mg L ^-1 )	0.39±0.04
Conductivity (mS cm) ^-1 )	12.8±0.2	Cr(mg L ^-1 )	0.06±0.10
				Total soluble solids (g L) ^-1 )	7.1±0.1	Zn(mg L ^-1 )	ND ^a
Total organic carbon (mg L) ^-1 )	98.2±0.5	Ni(mg L ^-1 )	ND ^a
				NH ₄ ⁺ -N(mg L ^-1 )	0.5±0.1	Cu(mg L ^-1 )	ND ^a
NO ₃ ^- (mg L ^-1 )	ND ^a	Pb(mg L ^-1 )	ND ^a
				Cl ^- (mg L ^-1 )	2479.3±85.2	Co(mg L ^-1 )	ND ^a
SO ₄ ^2- (mg L ^-1 )	735.8±5.6	Ba(mg L ^-1 )	ND ^a
				CO ₃ ^2- /HCO ₃ ^- (mg L ^-1 )	531.8±3.6	Cd(mg L ^-1 )	ND ^a
Na(mg L ^-1 )	1401.16±88.43	As(mg L ^-1 )	ND ^a
				K(mg L ^-1 )	872.45±37.66	/	/
Ca(mg L ^-1 )	51.27±4.43	/	/
				Mg(mg L ^-1 )	192.89±3.30	/	/

^a ND represents not detected

Each test procedure included four steps: pure water pre-pressing, sodium chloride salt blank sample testing, MBR effluent concentration treatment and physical cleaning. In the first step, the prepared separation membrane is pre-pressed with pure water for 2 hours until the membrane flux reaches constant, the test pressure is 6bar, and the temperature is 25 ℃. And secondly, adopting NaCl solution with the same conductivity as that of MBR effluent water as raw material liquid, and filtering for at least 2 hours until the membrane flux is constant so as to eliminate the influence of concentration polarization on the membrane flux. The membrane flux was recorded at this time as baseline J ₁ . Step three, taking 800mL of landfill leachate MBR effluent as raw material liquid to carry out filtration and concentration, collecting loose nanofiltration leachate in a filtrate tank, and filtering the flux J _t Recording by means of a computer-monitored balance. The concentration process was stopped until the feed solution was concentrated to 185mL (minimum required feed solution volume in the nanofiltration device tank), at which point the Concentration Factor (CF) was 4.3. Samples were taken from the concentrate and the percolate, respectively, at intervals. The test conditions were adjusted to an initial membrane flux of 60LMH, a membrane surface flow rate of 0.12m/s and a temperature of 25 ℃. Fourthly, adopting pure water to physically clean the polluted membrane, and scouring the surface of the separation membrane for 30min in a cross-flow way under the condition of no pressure, wherein the method comprises the following steps ofPure water was changed every 10min and repeated 3 times to remove the removable contaminants from the membrane surface. Then, the membrane flux after physical cleaning was measured under the same test conditions as in step two using the NaCl solution in step two as the raw material liquid, and recorded as a baseline J ₂ . And (3) performing normalized treatment on membrane flux change in the MBR water outlet process of the deep treatment landfill leachate, and comparing. SEM and energy dispersive X-ray spectroscopy (EDS) characterization are carried out on the membrane polluted by the landfill leachate MBR effluent and the membrane cleaned by pure water.

Normalized flux (Normalized flux) can be calculated by the following formula:

wherein J is ₁ And J _t The initial flux in the MBR effluent concentration process and the membrane flux at time t are respectively.

The concentration factor (Concentration factor, CF) can be calculated by the following formula:

wherein V is ₀ And V _t The initial volume of the raw material liquid is MBR effluent, and the concentrated liquid volume (L) after a period of time t is concentrated.

Fig. 5 is a graph showing the variation of membrane flux of the ultra-smooth multi-mechanism anti-pollution and anti-scaling separation membranes prepared in examples 1-2 and comparative examples 1-3 applied to the wastewater depth treatment of the high-salt high-organic garbage leachate MBR. FIG. 6 is an SEM image of the ultra-smooth multi-mechanism anti-fouling separation membranes prepared in examples 1-2 and comparative examples 1-3 after fouling and after cleaning. Fig. 6 (a) to (d) are SEM images of the surface contamination layer after separation membrane contamination; fig. 6 (e) to (h) are SEM electron microscope images of the surfaces of the separation membranes after the contamination by pure water.

As can be seen from FIG. 5, the commercial polyamide bulk nanofiltration membrane SynderPA of comparative example 3 shows a sudden drop in membrane flux immediately after exposure to MBR effluent (inAt the beginning of the MBR effluent contact, if flux is not lost, at this time, normal fluoride=1, syncer PA immediately drops to about 0.6 after MBR effluent contact, and a phenomenon of dip appears, which indicates that a large amount of contaminants are adsorbed on the membrane surface, and after MBR effluent is concentrated 1.5 times (Permeate volume=280 mL), cliff dip appears in membrane flux. Figure 6a shows that serious membrane fouling occurs at the membrane surface and a large amount of contaminants accumulate on the membrane surface. As can be seen from Table 2, the oxygen content of the membrane surface pollution layer is far greater than that of the carbon element, which indicates that the membrane surface has a large amount of organic pollutants (such as humus, etc.), and the high content of calcium and magnesium elements indicates that the membrane surface has a large amount of inorganic salt scale (such as CaCO) ₃ ，MgCO ₃ ). In the concentration and filtration process, organic-inorganic composite pollutants complexed on the surface of the membrane and penetrating into the membrane pores provide divalent cations as crystal nuclei, heterogeneous nucleation and crystallization gradually form inorganic scaling of larger particles, which leads to the blocking of the membrane pores and the great reduction of flux. Meanwhile, the organic matters in the organic-inorganic composite pollution layer deposited on the surface of the membrane provide a large number of carboxyl sites to complex with homogeneous crystals formed in the solution, so that the massive crystals are tightly adhered to the surface of the membrane and are not easy to clean, and heterogeneous scaling on the surface of the membrane is further deteriorated by taking the massive crystals as crystal nuclei (fig. 6 (a) and 6 (e)). It has been found that commercial polyamide membranes with carboxyl residues are prone to organic enhanced inorganic scale contamination when filtering high salt organic wastewater.

A single hydrophilic modification was performed on the surface of the base film to obtain comparative example 1 (PEI-PA). In fig. 5, the flux of the single-layer hydrophilically modified PEI-PA of comparative example 1 is not greatly reduced in the initial stage, which indicates that the positively charged hydration layer on the surface of the PEI-PA has a certain resistance to organic pollutants in the initial stage, however, after the membrane is concentrated 1.8 times (Permeate volume=340 mL) from the MBR effluent, the membrane flux is still greatly reduced, and as shown in fig. 6 (b) and table 2, a large amount of organic-inorganic composite pollutants are deposited on the surface of the membrane during the concentration process, and serious organic enhanced inorganic scaling is caused by the positively charged hydration layer as crystal nucleus. However, due to the existence of the positively charged PEI hydration protective layer, the tight complexation between pollutants and the surface of the membrane is resisted, so that most of organic-inorganic composite pollution on the surface of the membrane is easy to clean after the pure water is cleaned.

TABLE 2

A single hydrophobic modification of the surface of the base film gave comparative example 2 (PDMS-PA). In fig. 5, the flux decrease amplitude of the monolayer hydrophobically modified PDMS-PA of comparative example 2 was lower at the initial stage compared to the polyamide membrane syncer PA, since the lubrication characteristics of PDMS caused part of the contaminants to be released with transverse shear force, alleviating the deposition of the initial contaminants. However, after 1.3-fold concentration of MBR effluent (Permeate volume=173 mL), PDMS-PA showed a rapid flux cliff dip compared to syncer PA. This is because the low surface energy and lubricating properties of PDMS also have the effect of promoting the longitudinal sliding of contaminants. With the continuous improvement of concentration factors, the pollutants longitudinally pushed into the membrane holes by the PDMS are increased, and due to the lack of a PEI hydration defense layer, the PDMS promotes the contact complexation of organic-inorganic composite pollutants and exposed carboxyl groups on the surface of the membrane substrate, so that the membrane pollution and membrane scaling are accelerated and worsened.

From the above results, it is clear that both single hydrophilic modification and single hydrophobic modification cannot achieve the effects of simultaneously resisting organic pollution and inorganic scaling when treating complex high-salt high-organic wastewater, and single hydrophobic super-lubrication modification generates even more serious membrane pollution.

In the embodiment 2, after 1000Da PDMS is adopted for modification (P1000-PEI-PA), the hydrophilic PEI layer has remarkable pollution resistance effect on organic pollutants in the early stage of pollution, and after inorganic scaling occurs in concentration, the chain-shaped soft molecular brush of the macromolecules has stronger dirt removal and release effects, and meanwhile, the smooth membrane surface ensures that the inorganic pollutants are not easy to adhere to the nucleation scaling, so that the decrease of the membrane flux is further relieved. As can be seen from Table 2, the contents of the contaminants O, ca and Mg on the surface of the film are remarkably reduced, and the organic pollution and inorganic scaling are greatly relieved.

In example 1, after PDMS of 5000Da is adopted (P5000-PEI-PA), the membrane flux is reduced to the minimum extent, the pollution condition of the membrane surface in FIG. 6 is obviously relieved, meanwhile, the content of O, ca and Mg elements of the formed P5000-PEI-PA in Table 2 is the minimum, and the macromolecular PDMS molecular brush can release inorganic crystals deposited on the surface and scaling precursors (organic-inorganic composite pollutants and inorganic metal ions) more effectively so as to relieve the organic pollution and inorganic scaling on the membrane surface. After the pure water is Cleaned, the O content of the Cleaned P5000-PEI-PA surface is greatly reduced, the Ca and Mg contents are cleared, and the PDMS molecular brush with a long chain has stronger pollution release capability than the PDMS molecular brush with a short chain. This is because the PDMS molecular brush arrangement of small molecular chains is relatively tightly biased to take on a linear structure, while shorter molecular chains make the PDMS molecular brush more rigid. The chain length (molecular weight) of the chain-shaped molecular brush is increased, so that the grafting density of the chain-shaped molecular brush on the surface of the membrane can be reduced, the morphology of the PDMS molecular chain on the surface of the membrane is biased to be mushroom-shaped, more membrane area can be covered to enable the PDMS molecular brush to be in a lubrication state, and in addition, the long-chain PDMS molecular brush has higher flexibility and flexibility, so that pollutants on the surface of the membrane can be resisted and released more efficiently.

Fig. 6 (e) to (h) are SEM images of the surfaces of the separation membranes after the contamination of examples 1 to 2, comparative example 1 and comparative example 3, after the pure water washing. For Synder PA membranes, due to the complexation between carboxyl and organic-inorganic composite pollutants, the pollutants are tightly combined with the membrane surface, so that a large amount of organic matters and inorganic scaling residues remain on the Synder PA membrane surface after pure water is cleaned. After PEI modification, carboxyl on the surface of the membrane is covered by amino on PEI, and the PEI hydration layer is used as a pollution prevention layer, so that most pollutants are not easy to be firmly adsorbed on the surface of the membrane. However, due to the high concentration of pollutants in the wastewater, the pollutants are easy to accumulate on the surface of the membrane and are not easy to be released under the hydraulic drive, so that a small amount of pollutants remain on the surface of the PEI-PA membrane. After the low molecular weight PDMS molecular brush is grafted on the surface of the membrane, the P1000 molecular brush has lower flexibility and higher rigidity and has weaker release function on pollutants, so that a small amount of pollutants remain on the surface of the P1000-PEI-PA membrane after pure water is used for cleaning. After grafting the high molecular weight P5000 molecular brush, the P5000 molecular brush has high flexible rotation capability and a more lubricated surface, and has a strong release effect on pollutants deposited on the surface of the film, so that most of pollutants on the surface of the super-smooth P5000-PEI-PA film in the figure 6 (h) can be cleaned.

The results show that the construction of the positively charged hydration layer-super-smooth hydrophobic molecular brush layer 'double layer' enables the membrane surface to have the capability of 'pollution resistance' and 'pollution release', the positively charged hydration protective layer can effectively block the close complexation of organic-inorganic composite pollutants and the membrane surface, and the super-smooth layer constructed by the highly flexible long-chain PDMS molecular brush can effectively relieve the deposition of inorganic scale and has stronger pollution release capability.

FIG. 7 shows the retention rate of organic and inorganic salts in the MBR effluent depth treatment process of the high-salt and high-organic garbage leachate according to examples 1-2. The results show that in the advanced treatment process, as the membrane pollution is obviously relieved, the separation membrane has no obvious difference on interception of organic matters and inorganic salts, has excellent high interception characteristics on organic matters Humus (HS) in MBR effluent (the interception of HS is 97.2 percent for a P1000-PEI-PA membrane and 98.1 percent for a P5000-PEI-PA membrane), and has high permeability on inorganic salts in MBR effluent (the interception of inorganic salts is 20.8 percent for a P1000-PEI-PA membrane and 22.2 percent for a P5000-PEI-PA membrane). The result shows that the separation membrane prepared by the invention can effectively separate organic matters and inorganic salts in the effluent of the landfill leachate MBR, can realize concentration and recovery of the organic matters, and is suitable for recycling treatment of high-salt and high-organic wastewater.

From the results, the separation membrane prepared by the preparation method has the advantages of large permeation flux, good separation performance and small membrane aperture, and solves the technical problem of membrane flux reduction after the traditional hydrophobic modification. In addition, in the actual advanced treatment process of the high-salt high-organic wastewater, the wastewater treatment device has excellent anti-pollution and anti-scaling performances, is suitable for recycling treatment of the high-salt high-organic wastewater, and has important application value.

The foregoing examples are illustrative only and serve to explain some features of the method of the invention. The claims that follow are intended to claim the broadest possible scope as conceivable and the embodiments presented herein are demonstrated for the applicant's true test results. It is, therefore, not the intention of the applicant that the appended claims be limited by the choice of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within which variations in these ranges should also be construed as being covered by the appended claims where possible.

Claims

1. A preparation method of a super-smooth multi-mechanism anti-pollution and anti-scaling separation membrane is characterized by comprising the steps of activating a basal membrane with carboxyl on the surface, mixing the basal membrane with an amine compound, and grafting and crosslinking the amine compound on the basal membrane to form a positively charged hydration layer; then the positively charged hydration layer is covalently connected with polydimethylsiloxane to form a super-smooth layer, and the super-smooth multi-mechanism anti-pollution anti-scaling separation membrane is prepared;

The base film is selected from one or more of polyamide film, carboxylated cellulose acetate film and polyacrylonitrile hydrolysis film;

the amine compound is selected from one or more of polyethylenimine, triethanolamine, polyacrylamide, ethylenediamine and polyvinylamine;

the polydimethylsiloxane is selected from monoglycidyl ether terminated polydimethylsiloxanes.

2. The preparation method according to claim 1, wherein the amine compound is polyethyleneimine, and the molecular weight of the polyethyleneimine is 600-750000 Da.

3. The preparation method according to claim 1 or 2, wherein the molecular weight of the polydimethylsiloxane is 800-10000 Da.

4. The preparation method according to claim 1, wherein the mass-to-volume ratio of the amine compound to the polydimethylsiloxane is 0.7-2.2: 1g/mL.

5. The method according to claim 1, wherein the positively-charged hydration layer is reacted with polydimethylsiloxane for 60 to 1440 minutes at a reaction temperature of 15 to 90 ℃.

6. The ultra-smooth multi-mechanism anti-pollution and anti-scaling separation membrane prepared by the preparation method of any one of claims 1 to 5.

7. The use of the ultra-smooth multi-mechanism anti-pollution anti-scaling separation membrane of claim 6 for treating high-salt and high-organic wastewater.

8. The use according to claim 7, wherein the high-salt and high-organic wastewater has a conductivity of not less than 10mS/cm and a total organic carbon of not less than 100mg/L.