A nanocomposite ultrafiltration membrane loaded with zirconium oxide and its preparation method and application

Abstract

The present invention discloses a nanocomposite ultrafiltration membrane loaded with zirconium oxide, and its preparation method and application, belonging to the field of membrane separation technology. After grafting charged groups onto the ultrafiltration membrane skeleton, a zirconium precursor is introduced into the membrane pores and evenly distributed by circulating through the membrane under a certain pressure. A dopamine alkaline solution is then used to in-situ convert the precursor into functional nanoparticles, and a dopamine coating is simultaneously formed on the membrane surface to enhance the immobilization of the nanoparticles. Thus, a nanocomposite ultrafiltration membrane loaded with functional nanoparticles is obtained. While retaining the high flux and low energy consumption advantages of the ultrafiltration membrane, it can achieve the selective separation of inorganic ionic pollutants such as phosphorus and fluorine in water. Furthermore, the membrane has the advantages of good hydrophilicity, high operating flux, good stability of the immobilized nanoparticles, and resistance to loss.

Description

Technical Field

[0001] The present invention belongs to the field of membrane separation technology, and more specifically relates to a zirconium oxide-loaded nanocomposite ultrafiltration membrane and a preparation method and application thereof. Background Art

[0002] Inorganic ionic pollutants such as heavy metals, arsenic, and fluorine are biotoxic, and phosphorus is a major factor in water eutrophication. Controlling the concentration of these pollutants in water is crucial for ensuring water quality. Adsorption separation technology is highly effective in treating such polluted waters, especially for deep purification of slightly polluted waters. However, due to low pollutant concentrations, complex composition, and high concentrations of competing ions, traditional adsorption separation materials face challenges in terms of selectivity, working capacity, and regeneration performance.

[0003] Membrane separation technology utilizes functional membranes as filtration media to achieve highly precise separation and purification of liquids or gases. It boasts advantages such as high separation efficiency, high selectivity, low energy consumption, no phase change, simple operation, minimal footprint, and zero pollution. It has been widely used in areas such as water resources, the environment, and the transformation of traditional technologies. Membrane materials can be broadly categorized into inorganic membranes and organic polymer membranes. Compared to inorganic membranes, organic polymer membranes are more flexible and can be tailored to specific physical and chemical properties, making them a leading choice in industrial applications.

[0004] Membrane separation technologies such as nanofiltration, reverse osmosis, and electrodialysis can effectively separate inorganic ions from water, but they typically require high operating pressures or electrical drive, resulting in high energy consumption. Ultrafiltration membranes (1-20 nm) have pore sizes between microfiltration (0.2-10 μm) and nanofiltration (~1 nm), and can achieve high operating fluxes at lower operating pressures. However, traditional ultrafiltration membranes primarily separate macromolecular components in water through sieve separation and have little separation effect on inorganic ionic pollutants. Organic-inorganic nanocomposite membranes can be prepared by filling, depositing, adsorbing, or encapsulating inorganic nanoparticles into polymer membrane materials. This allows the properties of polymer membrane materials to be manipulated with greater freedom by varying the properties, composition, structure, and morphology of the nanoparticles. Using polymeric organic membranes as carriers and incorporating specific inorganic nanoparticles into the polymer matrix, membrane materials can be endowed with unique adsorption or degradation properties, thereby creating multifunctional composite membranes.

[0005] The main methods for loading nanoparticles in membrane materials are blending, surface coating, and in-situ synthesis. The blending method is to mix nanoparticles into the casting solution and then make the membrane material; the surface coating method is to coat the nanoparticles on the surface of the membrane; the in-situ synthesis method is to mix the precursor solution of the nanomaterial with the membrane and then synthesize it into nanoparticles in situ on the membrane surface. For example, the invention patent application with application number 201710801507.0 and application date of September 7, 2017 discloses a method for preparing a cellulose / nano-cerium oxide composite membrane. By using the in-situ generation method, the porous structure of the cellulose membrane is used to adsorb Ce 3+ The precursor solution was used to remove the unadsorbed Ce 3+ ions; then immersed in an alkaline solution with a concentration of 5-20 mol / L to react, the cellulose membrane loaded with Ce(OH)3 nanoparticles was washed and the pH adjusted to 6-7; the cellulose membrane was first air-dried at room temperature and then dried at a temperature ≥40°C for ≥6 hours to prepare a cellulose / nanocerium oxide composite membrane. However, composite membranes obtained by blending, surface coating, and in-situ synthesis methods suffer from various problems such as easy agglomeration of nanoparticles, low loading, uneven distribution, and easy loss. Moreover, existing nanocomposite membranes mostly improve the physical and chemical properties of the membrane itself or superimpose functions, failing to achieve synergistic enhancement of the membrane and nanomaterials. Summary of the Invention

[0006] 1. Problem to be solved

[0007] To address the problems of existing nanocomposite ultrafiltration membranes, such as poor separation efficiency for inorganic ionic pollutants, low loading, uneven distribution, and easy loss of loaded nanoparticles, the present invention provides a zirconium oxide-loaded nanocomposite ultrafiltration membrane, its preparation method, and application. After grafting positively charged functional groups onto the ultrafiltration membrane skeleton, a zirconium precursor is introduced into the membrane pores under a certain pressure in a circulating manner, evenly distributed. Subsequently, an alkaline dopamine solution is used to in situ convert the precursor into functional nanoparticles, while simultaneously forming a dopamine coating on the membrane surface. This results in a zirconium oxide-loaded nanocomposite ultrafiltration membrane capable of simultaneously removing both macromolecular and ionic pollutants.

[0008] 2. Technical solution

[0009] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0010] The invention discloses a nano-composite ultrafiltration membrane loaded with zirconium oxide. The ultrafiltration membrane is modified with positively charged groups as a matrix, loaded with hydrated zirconium oxide nanoparticles, and dopamine is coated on the membrane surface.

[0011] Preferably, the ultrafiltration membrane is a polyvinylidene fluoride ultrafiltration membrane, a polyethersulfone ultrafiltration membrane or a polyamide ultrafiltration membrane.

[0012] Preferably, the positively charged group is a quaternary ammonium group.

[0013] Preferably, the loading amount of the zirconium oxide is not less than 1.0 wt%.

[0014] The present invention provides a method for preparing a nano-composite ultrafiltration membrane loaded with zirconium oxide, comprising the steps of grafting positively charged functional groups onto an ultrafiltration membrane skeleton, circulating a hydrated zirconium oxide precursor solution through the membrane under pressure, and then soaking the membrane in a dopamine alkaline solution to convert the precursor into nano-zirconium oxide in situ and load it onto the membrane, while forming a dopamine coating layer on the membrane surface to obtain the nano-composite ultrafiltration membrane loaded with zirconium oxide.

[0015] Preferably, the positively charged functional group is a quaternary ammonium group, and the grafting rate of the quaternary ammonium group is not less than 3%.

[0016] Preferably, the hydrated zirconium oxide precursor solution is passed through the membrane at a pressure of 0.05 to 0.20 mPa, and the cycle is repeated 2 to 20 times.

[0017] Preferably, after the hydrated zirconium oxide precursor solution is circulated through the membrane under pressure, 1-3 g / L dopamine Tris / HCl buffer solution, pH 8.5, is added to the membrane and reacted at 25-35° C. in an aerobic environment for more than 20 hours to form a dopamine coating layer on the membrane surface.

[0018] Preferably, the zirconium ion content in the hydrated zirconium oxide precursor solution is not less than 30 mM.

[0019] The invention discloses an application of a nanocomposite ultrafiltration membrane loaded with zirconium oxide or a nanocomposite ultrafiltration membrane loaded with zirconium oxide prepared according to the above preparation method in wastewater treatment, wherein the adsorption capacity of the nanocomposite ultrafiltration membrane loaded with zirconium oxide for phosphate in water is greater than 1.0 mg / g.

[0020] Preferably, the membrane flux of the nanocomposite ultrafiltration membrane loaded with zirconium oxide of the present invention or the nanocomposite ultrafiltration membrane loaded with zirconium oxide prepared according to the above preparation method is not less than 200 L / (m 2 ·h).

[0021] 3. Beneficial effects

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention provides a method for preparing a nanocomposite ultrafiltration membrane loaded with zirconium oxide. The method adopts a method in which a precursor solution of a nanomaterial is circulated through the membrane under a certain pressure to load the precursor ions onto the charged groups of the membrane carrier. Compared with the traditional immersion method, the method not only overcomes the charge repulsion between the load and the membrane, but also has a higher raw material utilization rate, a higher efficiency in the entry of the precursor into the membrane pores, and a more uniform distribution.

[0024] (2) The present invention provides a method for preparing a nanocomposite ultrafiltration membrane loaded with zirconium oxide, wherein a dopamine alkaline solution is used to form a dopamine coating on the membrane surface to enhance the fixation of the loaded substance; at the same time, the precursor in the membrane is converted into hydrated zirconium oxide nanoparticles in an alkaline environment, eliminating the need for an additional alkaline treatment step; the surface of the formed dopamine coating contains a large number of active groups, which is also beneficial to improving the surface hydrophilicity of the membrane material;

[0025] (3) The nanocomposite ultrafiltration membrane loaded with zirconium oxide of the present invention can achieve a certain enrichment and separation effect on ions in water through ion exchange while retaining the high flux and low energy consumption advantages of the ultrafiltration membrane by grafting charged groups on the ultrafiltration membrane skeleton, thereby enhancing the adsorption effect of the loaded nano-metal oxide on the target ions and achieving the simultaneous removal of large molecular pollutants and ionic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process of preparing a nanocomposite ultrafiltration membrane loaded with zirconium oxide according to the present invention;

[0027] Figure 2 This is a transmission electron microscope image of a nanocomposite ultrafiltration membrane loaded with zirconium oxide according to the present invention;

[0028] Figure 3 The figure shows the adsorption effect of phosphorus P(V) on ultrafiltration membrane loaded with hydrated zirconium oxide and quaternized ultrafiltration membrane loaded with hydrated zirconium oxide at different pH values;

[0029] Figure 4 This is a graph showing the stability of the phosphorus removal effect of a zirconia-loaded nanocomposite ultrafiltration membrane of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] like Figure 1 As shown, the preparation method of a nanocomposite ultrafiltration membrane loaded with zirconium oxide of the present invention comprises the following steps:

[0032] S10, placing a finished polyvinylidene fluoride (PVDF) ultrafiltration membrane (usually, with a molecular weight of 100K) in a mixed solution of 4% KMnO4 aqueous solution and 20% KOH aqueous solution, and heating at 60°C for 45 minutes while passing nitrogen; then washing with 2% H2SO4 solution and 2% NaHSO3 aqueous solution until the membrane turns white, thereby obtaining an activated membrane after activation treatment;

[0033] S20, adding the above-mentioned activated membrane to a mixture of chloromethylstyrene (VBC) and tetrahydrofuran (THF), wherein the volume ratio between the chloromethylstyrene and the tetrahydrofuran is 5:1, and adding benzoyl peroxide (BPO) as an initiator, and reacting at 65° C. for 4 hours under nitrogen protection; then washing with chloroform and placing in a 33% trimethylamine aqueous solution for quaternization reaction for 6 to 8 hours (preferably 7 hours), grafting positively charged quaternary ammonium groups on the ultrafiltration membrane skeleton to obtain a quaternized ammonium membrane (MQ), wherein the grafting rate of the quaternary ammonium groups is not less than 3%;

[0034] S30, placing the quaternized ammonium membrane MQ into an ultrafiltration device, preparing 50 mL of zirconium oxychloride octahydrate solution with a concentration greater than 30 mM, passing the membrane under a pressure of 0.05 to 0.20 mPa, repeating the cycle 2 to 20 times, and air-drying naturally;

[0035] S40. Add the naturally air-dried membrane to a 1-3 g / L dopamine Tris / HCl buffer solution, pH 8.5, and react at 25-45°C in an aerobic environment for more than 20 hours to form a dopamine coating on the membrane surface; after rinsing, place the membrane in a 50°C oven for 2 hours to obtain a zirconium oxide-loaded nanocomposite ultrafiltration membrane MQ-HZO, wherein the zirconium oxide loading is not less than 1.0 wt%.

[0036] Preferably, the ultrafiltration membrane can be a polyvinylidene fluoride ultrafiltration membrane, a polyethersulfone (PES) ultrafiltration membrane, or a polyamide (PA) ultrafiltration membrane. The specific preparation process of the ultrafiltration membrane is as follows: polyvinylidene fluoride, polyethersulfone, or polyamide monomer is dissolved in dimethylformamide (DMF) solvent, chloromethylstyrene and benzoyl peroxide are added, and the mixture is reacted under nitrogen protection; after vacuum degassing, the resulting casting solution is scraped onto a clean glass plate with a scraper to form a film, which is then immersed in a deionized water coagulation bath to fully solidify to obtain the ultrafiltration membrane.

[0037] More preferably, the specific preparation process of the PVDF ultrafiltration membrane is as follows: dissolving PVDF monomer (powder or granules) in DMF (mass concentration 10%), adding 2%wt VBC and 0.02%wt BPO, and reacting at 65°C for 4 hours under nitrogen protection; after vacuum degassing, the obtained casting solution is scraped onto a clean glass plate with a scraper to form a film, and then immersed in a deionized water coagulation bath to fully solidify it to obtain a finished PVDF ultrafiltration membrane.

[0038] It should be noted that the ultrafiltration membrane of the present invention retains the advantages of high flux and low energy consumption of the ultrafiltration membrane after the charged groups are grafted on the skeleton; at the same time, after the quaternary ammonium groups are grafted on the ultrafiltration membrane, the membrane surface has a positive charge, and the precursor of the hydrated zirconium oxide nanoparticles to be loaded is zirconium ion Zr 2+ , also carries a positive charge. In the case of the same charge, there is a charge repulsion between the load and the membrane. By using a precursor solution of nanomaterials to circulate through the membrane under a certain pressure, it is possible to well achieve that the precursor ions can be transferred to the charged groups on the membrane carrier through ion exchange. Compared with the traditional immersion method, this has a higher raw material utilization rate, a higher efficiency of the precursor entering the membrane pores, and a more uniform distribution. The membrane flux of the nanocomposite ultrafiltration membrane MQ-HZO loaded with zirconium oxide of the present invention is not less than 200L / (m 2 ·h).

[0039] The MQ-HZO nanocomposite ultrafiltration membrane loaded with zirconium oxide of the present invention is used in wastewater treatment, which can not only separate macromolecular components in water through the sieve separation effect of the membrane, but also enrich and separate ions in water through ion exchange, thereby enhancing the adsorption of target ions by the loaded nano-metal oxide. The adsorption capacity of the MQ-HZO membrane for phosphate in wastewater is not less than 1.0 mg / g, and can even reach 8.0 to 9.0 mg / g.

[0040] Example 1

[0041] The preparation method of a nanocomposite ultrafiltration membrane loaded with zirconium oxide in this embodiment specifically comprises the following steps:

[0042] S10, placing the finished polyvinylidene fluoride (PVDF) ultrafiltration membrane in a mixed solution of 4% KMnO4 aqueous solution and 20% KOH aqueous solution, and heating at 60° C. for 45 minutes while introducing nitrogen; then washing with 2% H2SO4 solution and 2% NaHSO3 aqueous solution until the membrane turns white, thereby obtaining an activated membrane after activation treatment;

[0043] S20, adding the activated membrane to a mixture of VBC and THF in a volume ratio of 5:1, and adding BPO as an initiator, and reacting at 65° C. under nitrogen protection for 4 hours; then washing with chloroform and placing in a 33% trimethylamine aqueous solution for quaternization reaction for 7 hours to obtain a quaternized membrane MQ;

[0044] S30, the quaternized ammonium membrane MQ is loaded into the ultrafiltration device, 50mL of 30mM zirconium oxychloride octahydrate solution is prepared, the membrane is passed under a pressure of 0.05mPa, the cycle is repeated 20 times, and the membrane is naturally air-dried;

[0045] S40, adding the naturally air-dried membrane to a 1 g / L dopamine Tris / HCl buffer solution, pH 8.5, and reacting at 25°C in an aerobic environment for 24 hours to form a dopamine coating on the membrane surface; after rinsing, placing the membrane in a 50°C oven for 2 hours to obtain a zirconium oxide-loaded nanocomposite ultrafiltration membrane MQ-HZO, wherein the zirconium oxide loading is about 2.03 wt%, the phosphorus adsorption capacity is about 2.54 mg / g, and the membrane flux is 203 L / (m 2 ·h).

[0046] The transmission electron microscope image of the zirconia-loaded nanocomposite ultrafiltration membrane MQ-HZO prepared in this example is as follows: Figure 2 shown.

[0047] Example 2

[0048] The basic content of this embodiment is the same as that of Example 1, except that: the preparation method of a nanocomposite ultrafiltration membrane loaded with zirconium oxide in this embodiment comprises the following specific steps:

[0049] S10, placing the finished polyvinylidene fluoride (PVDF) ultrafiltration membrane in a mixed solution of 4% KMnO4 aqueous solution and 20% KOH aqueous solution, and heating at 60° C. for 45 minutes while introducing nitrogen; then washing with 2% H2SO4 solution and 2% NaHSO3 aqueous solution until the membrane turns white, thereby obtaining an activated membrane after activation treatment;

[0050] S20, adding the activated membrane to a mixture of VBC and THF in a volume ratio of 5:1, and adding BPO as an initiator, and reacting at 65° C. under nitrogen protection for 4 hours; then washing with chloroform and placing in a 33% trimethylamine aqueous solution for quaternization reaction for 7 hours to obtain a quaternized membrane MQ;

[0051] S30, the quaternized ammonium membrane MQ is loaded into the ultrafiltration device, 50mL of 50mM zirconium oxychloride octahydrate solution is prepared, the membrane is passed under a pressure of 0.1mPa, the cycle is repeated 10 times, and the membrane is naturally air-dried;

[0052] S40, adding the naturally air-dried membrane to a 2 g / L dopamine Tris / HCl buffer solution, pH 8.5, and reacting at 35°C in an aerobic environment for 20 hours to form a dopamine coating on the membrane surface; after rinsing, placing the membrane in a 50°C oven for 2 hours to obtain a zirconium oxide-loaded nanocomposite ultrafiltration membrane MQ-HZO, wherein the zirconium oxide loading is about 5.65 wt%, the phosphorus adsorption capacity is about 8.82 mg / g, and the membrane flux is 312 L / (m 2 ·h).

[0053] Example 3

[0054] The basic content of this embodiment is the same as that of Example 1, except that: the preparation method of a nanocomposite ultrafiltration membrane loaded with zirconium oxide in this embodiment comprises the following specific steps:

[0055] S10, placing the finished polyvinylidene fluoride (PVDF) ultrafiltration membrane in a mixed solution of 4% KMnO4 aqueous solution and 20% KOH aqueous solution, and heating at 60° C. for 45 minutes while introducing nitrogen; then washing with 2% H2SO4 solution and 2% NaHSO3 aqueous solution until the membrane turns white, thereby obtaining an activated membrane after activation treatment;

[0056] S20, adding the activated membrane to a mixture of VBC and THF in a volume ratio of 5:1, and adding BPO as an initiator, and reacting at 65° C. under nitrogen protection for 4 hours; then washing with chloroform and placing in a 33% trimethylamine aqueous solution for quaternization reaction for 7 hours to obtain a quaternized membrane MQ;

[0057] S30, the quaternized ammonium membrane MQ is loaded into the ultrafiltration device, 50mL of 70mM zirconium oxychloride octahydrate solution is prepared, the membrane is passed under a pressure of 0.2mPa, the cycle is repeated 2 times, and the membrane is naturally air-dried;

[0058] S40, adding the naturally air-dried membrane to a 3 g / L dopamine Tris / HCl buffer solution, pH 8.5, and reacting at 45°C in an aerobic environment for 24 hours to form a dopamine coating on the membrane surface; after rinsing, placing the membrane in a 50°C oven for 2 hours to obtain a zirconium oxide-loaded nanocomposite ultrafiltration membrane MQ-HZO, wherein the zirconium oxide loading is about 1.89 wt%, the phosphorus adsorption capacity is about 2.08 mg / g, and the membrane flux is 231 L / (m 2 ·h).

[0059] Example 4

[0060] The basic content of this embodiment is the same as that of Example 1, except that: the preparation method of a nanocomposite ultrafiltration membrane loaded with zirconium oxide in this embodiment comprises the following specific steps:

[0061] S10, dissolving powdered or granular PVDF monomer in dimethylformamide (DMF) solvent (mass concentration 10%), adding 2wt% VBC and 0.02wt% BPO, reacting at 65°C under nitrogen protection for 4 hours, and vacuum degassing the obtained casting solution on a clean glass plate with a scraper to form a film, and then immersing it in a deionized water coagulation bath to fully solidify it to obtain a PVDF ultrafiltration membrane;

[0062] S20, placing the finished polyvinylidene fluoride (PVDF) ultrafiltration membrane in a mixed solution of 4% KMnO4 aqueous solution and 20% KOH aqueous solution, and heating at 60° C. for 45 minutes while introducing nitrogen; then washing with 2% H2SO4 solution and 2% NaHSO3 aqueous solution until the membrane turns white, thereby obtaining an activated membrane after activation treatment;

[0063] S30, placing the activated membrane in a 33% trimethylamine aqueous solution and performing a quaternization reaction for 7 hours to obtain a quaternized membrane MQ;

[0064] S40, the quaternized ammonium membrane MQ is loaded into the ultrafiltration device, 50 mL of 50 mM zirconium oxychloride octahydrate solution is prepared, the membrane is passed under a pressure of 0.1 mPa, the cycle is repeated 8 times, and the membrane is naturally air-dried;

[0065] S50, the air-dried membrane was added to a 2 g / L dopamine Tris / HCl buffer solution, pH 8.5, and reacted at 25°C in an aerobic environment for 26 hours to form a dopamine coating on the membrane surface; after rinsing, the membrane was placed in a 50°C oven for 2 hours to obtain a zirconia-loaded nanocomposite ultrafiltration membrane MQ-HZO, wherein the zirconia loading was about 5.16 wt%, the phosphorus adsorption capacity was about 8.53 mg / g, and the membrane flux was 355 L / (m 2 ·h).

[0066] Comparative Example 1

[0067] The basic content of this comparative example is the same as that of Example 1, except that: the preparation method of a nanocomposite ultrafiltration membrane loaded with zirconium oxide in this comparative example comprises the following specific steps:

[0068] S10, placing the finished polyvinylidene fluoride (PVDF) ultrafiltration membrane in a mixed solution of 4% KMnO4 aqueous solution and 20% KOH aqueous solution, and heating at 60° C. for 45 minutes while introducing nitrogen; then washing with 2% H2SO4 solution and 2% NaHSO3 aqueous solution until the membrane turns white, thereby obtaining an activated membrane after activation treatment;

[0069] S20. Immerse the activated membrane in a 50 mM zirconium oxychloride octahydrate solution, stir for 24 h, air-dry naturally, and then immerse in 5% NaOH at room temperature, stir for 24 h, rinse the residual alkali solution on the surface, and then place in a 50°C oven for 2 h to obtain a zirconium oxide-loaded nanocomposite ultrafiltration membrane MP-HZO, wherein the zirconium oxide loading is approximately 0.80 wt %, and the phosphorus adsorption capacity is approximately 0.88 mg / g.

[0070] Example 5

[0071] This example mainly examines the phosphorus removal performance of the MQ-HZO membrane of Example 1 and the MP-HZO membrane of Comparative Example 1 at different pH values.

[0072] 50 mL of 3 mg / L phosphorus solution was added to 9 100 mL conical flasks respectively, and the pH values of the solutions were adjusted to 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0 with NaOH and HNO3, respectively. Then, the MQ-HZO membrane of Example 1 and the MP-HZO membrane of Comparative Example 1 were placed in conical flasks, maintained at 298K and 110 rpm, and continuously oscillated in a constant temperature water bath oscillator for 24 hours. The phosphorus concentrations of the raw water and the post-reaction solution were measured respectively. The specific phosphorus removal adsorption effect is shown in FIG. Figure 3 shown.

[0073] Depend on Figure 3 It can be seen that the adsorption amount of MQ-HZO membrane and MP-HZO membrane gradually decreases with the increase of pH, but there is a sudden increase point of MQ-HZO membrane near pH = 6. Due to the ion exchange between chloride ions and target anions after the hydroxyl groups on the amino groups introduced during quaternization and dopamine coating are converted to chloride type, as the pH increases, H2PO4 - Converted into HPO4 2- Then converted into PO4 3- The increase in the negative charge of the target anion is beneficial to the ion exchange with the chloride ions on the surface of the membrane material. The combination of the two effects explains that the material has a bump in adsorption near pH = 6, which has good practical application value for wastewater treatment and phosphorus removal.

[0074] Example 6

[0075] This example mainly examines the stability of the phosphorus removal effect of the MQ-HZO membrane of Example 1.

[0076] The MQ-HZO membrane prepared in Example 1 was applied to the treatment of phosphorus-containing wastewater with a concentration of 0.5 mg / L. The membrane was run 1, 2, and 5 times, and the phosphorus concentrations in the influent and effluent wastewater were measured respectively. Figure 4 shown.

[0077] Depend on Figure 4 It can be seen that the nanocomposite ultrafiltration membrane loaded with zirconium oxide of the present invention still has a good phosphorus removal and adsorption effect after running for 5 times, and has good performance stability.

[0078] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The data used is only one embodiment of the present invention, and the actual data combination is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs similar embodiments and examples to the technical solution without creative design, they shall all fall within the scope of protection of the present invention.

Claims

1. A nanocomposite ultrafiltration membrane loaded with zirconium oxide, characterized in that: The ultrafiltration membrane modified with quaternary ammonium groups is used as the matrix, and a hydrated zirconium oxide precursor is loaded through the membrane in a pressure circulation manner. The loaded hydrated zirconium oxide precursor is converted into nano zirconium oxide in situ by soaking in a dopamine alkaline solution, and dopamine is coated on the membrane surface.

2. The nanocomposite ultrafiltration membrane loaded with zirconium oxide according to claim 1, characterized in that: The ultrafiltration membrane is a polyvinylidene fluoride ultrafiltration membrane, a polyethersulfone ultrafiltration membrane or a polyamide ultrafiltration membrane.

3. The zirconium oxide-loaded nanocomposite ultrafiltration membrane according to claim 1, characterized in that: The loading amount of the zirconium oxide is not less than 1.0 wt %.

4. A method for preparing a nanocomposite ultrafiltration membrane loaded with zirconium oxide, characterized in that: After grafting quaternary ammonium groups on the ultrafiltration membrane skeleton, a hydrated zirconium oxide precursor solution is circulated through the membrane at a pressure of 0.05~0.20 mPa, and the cycle is repeated 2~20 times. Then, the membrane is immersed in a dopamine alkaline solution to convert the precursor into nano-zirconium oxide in situ and load it onto the membrane. At the same time, a dopamine coating layer is formed on the membrane surface to obtain a nano-composite ultrafiltration membrane loaded with zirconium oxide, wherein the grafting rate of the quaternary ammonium group is not less than 3%.

5. The method for preparing a zirconium oxide-loaded nanocomposite ultrafiltration membrane according to claim 4, characterized in that: After the hydrated zirconium oxide precursor solution was circulated through the membrane under pressure, 1-3 g / L dopamine Tris / HCl buffer solution (pH 8.5) was added to the membrane and reacted at 25-35°C in an aerobic environment for more than 20 hours to form a dopamine coating on the membrane surface.

6. The method for preparing a zirconium oxide-loaded nanocomposite ultrafiltration membrane according to claim 4, wherein: The zirconium ion content in the hydrated zirconium oxide precursor solution is not less than 30 mM.

7. Use of a zirconia-loaded nanocomposite ultrafiltration membrane according to any one of claims 1 to 3 or a zirconia-loaded nanocomposite ultrafiltration membrane prepared by the preparation method according to any one of claims 4 to 6 in wastewater treatment, characterized in that: The adsorption capacity of the nanocomposite ultrafiltration membrane loaded with zirconium oxide for phosphate in water is greater than 1.0 mg / g; or the flux of the nanocomposite ultrafiltration membrane loaded with zirconium oxide is not less than 200 L / (m 2 ·h).

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