A lanthanum-loaded carbon nanomaterial anti-pollution membrane suitable for sewage phosphorus recovery and a preparation method and application thereof

Abstract

This invention discloses an antifouling membrane made of lanthanum-loaded carbon nanomaterials suitable for phosphorus recovery in wastewater, its preparation method, and its applications. The invention involves loading lanthanum carbonate octahydrate onto the surface of multi-walled carbon nanotubes (MWCNTs) to form lanthanum-loaded carbon nanomaterials (La@MWCNTs), which are then deposited onto the surface of a polyethersulfone-based membrane using vacuum filtration to form a self-supporting membrane. The prepared lanthanum-loaded carbon nanomaterial antifouling membrane possesses both phosphorus removal and recovery capabilities, exhibiting high efficiency in phosphorus removal from water. This facilitates phosphorus elution and recovery, effectively solving the problems of lanthanum-loaded carbon nanomaterial aggregation and recovery, and effectively avoiding the risk of lanthanum-based adsorbent leakage during phosphorus removal. Furthermore, the lanthanum-loaded carbon nanomaterial antifouling membrane operates within a low-pressure range, exhibiting low energy consumption and effectively mitigating membrane fouling caused by humic acid. It shows promising application prospects in wastewater phosphorus recovery and eutrophication control.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of nanomaterial membrane surface modification and wastewater treatment technology, and relates to a lanthanum-loaded carbon nanomaterial antifouling membrane suitable for phosphorus recovery from wastewater, its preparation method and application. Background Technology

[0002] Eutrophication is a significant global water environment problem. Studies have shown that phosphorus is the limiting nutrient causing eutrophication; therefore, phosphorus removal is crucial for controlling eutrophication. Compared to common phosphorus removal methods such as biological and chemical precipitation, adsorption methods have gained considerable attention due to their high phosphorus removal efficiency and ease of operation.

[0003] Among numerous phosphorus adsorption materials, lanthanum-based adsorbents, due to their strong affinity for phosphates, have been extensively studied for their phosphorus adsorption properties. They can remove phosphates from water through electrostatic adsorption, ligand exchange, Lewis acid-base interactions, ion exchange, and surface precipitation. Furthermore, phosphorus adsorbed by lanthanum-based adsorbents can be eluted under strongly alkaline conditions, thus enabling phosphorus resource recovery. Although lanthanum-based adsorbents, represented by lanthanum-modified bentonite materials, have been practically applied to the remediation of eutrophic water bodies, the aggregation of lanthanum-based adsorbents reduces adsorption sites, resulting in a decrease in adsorption capacity. Moreover, micron- or nano-sized lanthanum-based adsorbents are difficult to recover and reuse after adsorption. Therefore, in application, the problems of adsorbent aggregation and recovery related to lanthanum-based adsorbents urgently need to be addressed.

[0004] Ultrafiltration is a commonly used technology in advanced wastewater treatment. However, compared with high-pressure membrane filtration, ultrafiltration is limited by pore size and cannot reduce phosphate in the effluent from advanced wastewater treatment, making it difficult to reduce the risk of eutrophication in receiving water bodies. In addition, ultrafiltration membranes suffer from more serious membrane fouling problems in advanced wastewater treatment.

[0005] Multi-walled carbon nanotubes (MWCNTs) are mesoporous materials with high specific surface area, making them ideal carriers for nanoscale lanthanum-based adsorbents. Studies have shown that MWCNTs exhibit extensive hydrogen bonding and strong van der Waals forces, enabling them to stably deposit on ultrafiltration membrane surfaces without any crosslinking agents, effectively preventing the shedding of lanthanum-based adsorbents during phosphorus removal. Furthermore, MWCNTs can be completely retained by nanoscale membranes without leakage into the filtrate. The self-supporting layer formed by the self-assembly of MWCNTs on the ultrafiltration membrane surface can remove pollutants from water through van der Waals forces, hydrogen bonding, and π-π interactions, reducing direct contact between the membrane and pollutants and effectively improving the membrane's antifouling ability. Patent application number 202310648532.5 discloses a lanthanum-loaded polyethersulfone membrane filtration phosphorus removal material. It utilizes a lanthanum chloride solution and sodium hydroxide solution to form lanthanum hydroxide on the polyethersulfone filter membrane via an impregnation co-precipitation method, achieving rapid and efficient treatment of low-concentration phosphorus-containing wastewater. However, actual wastewater also contains many natural organic compounds, and the lanthanum-loaded polyethersulfone membrane filtration phosphorus removal material prepared by this method still comes into direct contact with pollutants during actual filtration, leading to unavoidable contamination. By loading a lanthanum-based adsorbent onto the surface of carbon nanomaterials, and then pre-depositing the lanthanum-loaded carbon nanomaterials onto the membrane surface through vacuum filtration, a lanthanum-loaded carbon nanomaterial antifouling membrane can be prepared. This not only endows traditional low-pressure membranes with "phosphorus removal" and "phosphorus recovery" properties, but also solves the problem of lanthanum-based adsorbent recycling while potentially improving the membrane's antifouling ability. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a lanthanum-loaded carbon nanomaterial antifouling membrane suitable for phosphorus recovery in wastewater, its preparation method and application. The lanthanum-loaded carbon nanomaterial antifouling membrane provided by this invention has the ability to quickly remove phosphate from water while also having a good antifouling effect.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a lanthanum-loaded carbon nanomaterial antifouling membrane suitable for phosphorus recovery from wastewater includes the following steps:

[0009] (1) Weigh out lanthanum chloride heptahydrate (LaCl3·7H2O), dissolve it in ultrapure water to obtain a lanthanum chloride solution with a concentration of 0.05 mol / L;

[0010] (2) Weigh out multi-walled carbon nanotubes with an outer diameter of 8-15 nm or 10-20 nm, add them to the 0.05 mol / L lanthanum chloride solution obtained in step (1), and place them at 20±1℃ and stir magnetically for 4-8 h to obtain a carbon nanotube suspension. The mass ratio of lanthanum to multi-walled carbon nanotubes is 3:10, 4:10, 5:10, 6:10, 7:10, 8:10, or 9:10.

[0011] (3) Weigh anhydrous sodium carbonate (Na2CO3), dissolve it in ultrapure water to obtain a sodium carbonate solution;

[0012] (4) At 20±1℃, sodium carbonate solution was added dropwise to carbon nanotube suspension until the pH value of carbon nanotube suspension became 10. After stirring magnetically for 6 to 10 hours, the suspension was aged for 6 to 12 hours to obtain lanthanum-loaded carbon nanomaterial suspension.

[0013] (5) The obtained lanthanum-loaded carbon nanomaterial suspension was filtered and washed with ultrapure water 3 to 5 times until the pH value of the filtrate became 7. It was then placed in a vacuum drying oven and dried at 25 to 60°C. After grinding, the dried lanthanum-loaded carbon nanomaterial (La@MWCNTs) was obtained.

[0014] (6) Weigh out the lanthanum-loaded carbon nanomaterials and place them in 50 ml of anhydrous ethanol. Use an ultrasonic disruptor to sonicate in an ice bath at 300 W for 10-20 min to obtain a dispersion of lanthanum-loaded carbon nanomaterials.

[0015] (7) Place the polyethersulfone (PES) membrane with a molecular weight cutoff of 100 kDa into a vacuum filtration device, and use negative pressure filtration to filter the 50 ml lanthanum-loaded carbon nanomaterial dispersion obtained in step (6) to an effective filtration area of ​​13.4 cm². 2 A pressure of -0.075 MPa was applied to the surface of a PES-based membrane. After filtration and drying, the membrane was washed with ultrapure water to obtain an antifouling membrane loaded with lanthanum carbon nanomaterials. The ratio of the loading of lanthanum carbon nanomaterials to the effective filtration area of ​​the polyethersulfone-based membrane was 0.0005–0.002 g / cm³. 2 .

[0016] Preferably, the outer diameter of the multi-walled carbon nanotubes described in step (2) is 8 to 15 nm.

[0017] Preferably, the magnetic stirring time in step (2) is 4 hours.

[0018] Preferably, the mass ratio of lanthanum to multi-walled carbon nanotubes in step (2) is 6:10.

[0019] Preferably, the concentration of the sodium carbonate solution in step (3) is 1 mol / L.

[0020] Preferably, the magnetic stirring time in step (4) is 8 hours.

[0021] Preferably, the aging time in step (4) is 12 hours.

[0022] Preferably, the number of times the filter is cleaned in step (5) is 5.

[0023] Preferably, the vacuum drying temperature in step (5) is 35°C.

[0024] Preferably, the ultrasound time in step (6) is 10 min.

[0025] Preferably, the ratio of the loading amount of lanthanum-loaded carbon nanomaterials in step (7) to the effective filtration area of ​​the polyethersulfone-based membrane is 0.002 g / cm². 2 .

[0026] The advantages of this invention over the prior art are as follows:

[0027] (1) The antifouling membrane of lanthanum-loaded carbon nanomaterial prepared by this invention has a short preparation cycle and a simple preparation method, and does not require high temperature and high pressure.

[0028] (2) The antifouling membrane of lanthanum-loaded carbon nanomaterials prepared by the present invention achieves uniform loading of lanthanum-loaded carbon nanomaterials, improves the aggregation problem of lanthanum-based adsorbents, and can make full use of lanthanum active sites, thereby reducing the amount of lanthanum used and reducing the processing cost.

[0029] (3) The antifouling membrane of lanthanum-loaded carbon nanomaterials prepared by the present invention has the function of phosphorus removal and phosphorus recovery. The lanthanum carbonate octahydrate (La2(CO3)3·8H2O) forms an inner spherical complex through ligand exchange between lanthanum carbonate octahydrate (La2(CO3)3·8H2O) and phosphate, which realizes the efficient removal of phosphorus from water. The deposition of lanthanum-loaded carbon nanomaterials on the surface of polyethersulfone-based membrane facilitates the elution and recovery of phosphorus. In addition, the hydrogen bonding and van der Waals forces between multi-walled carbon nanotubes enable the lanthanum-loaded carbon nanomaterials to be stably deposited on the surface of polyethersulfone-based membrane, effectively reducing the loss of lanthanum-loaded carbon nanomaterials and facilitating the recovery and utilization of lanthanum-loaded carbon nanomaterials.

[0030] (4) The antifouling membrane with lanthanum-loaded carbon nanomaterials prepared by the present invention can quickly and efficiently remove phosphates in water within the operating pressure range of low-pressure membranes (below 1 to 2 bar), with low energy consumption during operation and good reusability.

[0031] (5) The antifouling membrane of lanthanum-loaded carbon nanomaterial prepared by the present invention has a good ability to remove humic acid, which can effectively alleviate the membrane fouling problem caused by natural organic matter represented by humic acid. It has good application prospects in wastewater phosphorus recovery and water eutrophication control. Attached Figure Description

[0032] Figure 1 The images shown are a photograph (a) and a scanning electron microscope (SEM) image (b) of the lanthanum-loaded carbon nanomaterials obtained in Example 1.

[0033] Figure 2 A photograph of the antifouling membrane made of lanthanum-loaded carbon nanomaterials obtained in Example 1;

[0034] Figure 3 The image shows the X-ray diffraction (XRD) pattern of the antifouling membrane of lanthanum-loaded carbon nanomaterials obtained in Example 1.

[0035] Figure 4 Scanning electron microscope (SEM) images of the polyethersulfone-based film (a) and the antifouling film of lanthanum-loaded carbon nanomaterials obtained in Example 1 (b);

[0036] Figure 5 The image shows the high-resolution X-ray photoelectron spectroscopy (XPS) spectrum of the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in Example 1 after adsorbing phosphate.

[0037] Figure 6 A comparison diagram of the contact angles of the polyethersulfone-based film and the lanthanum-loaded carbon nanomaterial antifouling film obtained in Example 1;

[0038] Figure 7 A comparison of the permeation flux of the polyethersulfone-based membrane and the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in Example 1;

[0039] Figure 8 This is a comparison of the phosphate removal rates of the polyethersulfone-based membrane and the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in Example 1 under different transmembrane pressures.

[0040] Figure 9 The graph shows the change in phosphate removal rate of the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in Example 1 after three adsorption-regeneration cycle experiments.

[0041] Figure 10 The image shows the X-ray diffraction (XRD) pattern of the antifouling membrane of lanthanum-loaded carbon nanomaterials after three adsorption-desorption regeneration processes.

[0042] Figure 11 This is a photograph of the antifouling membrane made of lanthanum-loaded carbon nanomaterials after three adsorption-desorption regeneration processes.

[0043] Figure 12 The removal rate of phosphate in actual water by the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in Example 1;

[0044] Figure 13The graph shows the changes in humic acid removal rate and specific flux of the polyethersulfone-based membrane (a) and the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in Example 1 (b). Detailed Implementation

[0045] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings, but it is not limited thereto.

[0046] Example 1

[0047] This embodiment prepares an antifouling membrane made of lanthanum-loaded carbon nanomaterials suitable for phosphorus recovery from wastewater according to the following steps:

[0048] (1) Weigh 18.57g of lanthanum chloride heptahydrate and dissolve it in 200ml of ultrapure water to obtain a lanthanum chloride solution with a concentration of 0.05mol / L;

[0049] (2) Weigh 2.32g of multi-walled carbon nanotubes with an outer diameter of 8-15nm and add them to the 0.05mol / L lanthanum chloride solution obtained in step (1). Stir the solution magnetically at 20±1℃ for 4h to obtain a carbon nanotube suspension. The mass ratio of lanthanum to multi-walled carbon nanotubes is 6:10.

[0050] (3) Weigh 10.60g of anhydrous sodium carbonate and dissolve it in 100ml of ultrapure water to obtain a sodium carbonate solution with a concentration of 1mol / L;

[0051] (4) At 20±1℃, sodium carbonate solution was added dropwise to carbon nanotube suspension until the pH value of carbon nanotube suspension became 10. After stirring magnetically for 8 hours, it was aged for 12 hours to obtain lanthanum-loaded carbon nanomaterial suspension.

[0052] (5) The obtained lanthanum-loaded carbon nanomaterial suspension was filtered and washed 5 times with ultrapure water until the pH of the filtrate became 7. It was then placed in a vacuum drying oven and dried at 35°C. After grinding, the dried lanthanum-loaded carbon nanomaterial was obtained.

[0053] (6) Weigh 0.0268g of lanthanum-loaded carbon nanomaterials and place them in 50ml of anhydrous ethanol. Use an ultrasonic disruptor to sonicate in an ice bath for 10min at a power of 300W to obtain a dispersion of lanthanum-loaded carbon nanomaterials.

[0054] (7) Place the polyethersulfone-based membrane with a molecular weight cutoff of 100 kDa into a vacuum filtration device, and use negative pressure filtration to filter the 50 ml lanthanum-loaded carbon nanomaterial dispersion obtained in step (6) to an effective filtration area of ​​13.4 cm². 2A pressure of -0.075 MPa was applied to the surface of a polyethersulfone-based membrane. After filtration and drying, the membrane was washed with ultrapure water to obtain an antifouling membrane loaded with lanthanum carbon nanomaterials. The ratio of the loading of lanthanum carbon nanomaterials to the effective filtration area of ​​the polyethersulfone-based membrane was 0.002 g / cm³. 2 .

[0055] Figure 1 The images (a) and (b) show the physical photograph of the lanthanum-loaded carbon nanomaterial obtained in this embodiment. It can be seen that it is a black powder solid, and a sheet-like structure appears on the surface of the multi-walled carbon nanotubes.

[0056] Figure 2 The image shown is a photograph of the antifouling membrane made of lanthanum-loaded carbon nanomaterials obtained in this embodiment. It can be seen that the lanthanum-loaded carbon nanomaterials form a black modified layer on the surface of the polyethersulfone-based membrane.

[0057] Figure 3 The X-ray diffraction pattern of the antifouling membrane of lanthanum-loaded carbon nanomaterials obtained in this embodiment shows that the main form of lanthanum on the membrane is lanthanum carbonate octahydrate (La2(CO3)3·8H2O).

[0058] Figure 4 The images are scanning electron microscope (SEM) images of the polyethersulfone-based membrane (a) and the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in this embodiment (b). It can be seen that the polyethersulfone-based membrane has a smooth surface and uniform pore distribution. The lanthanum-loaded carbon nanomaterials on the surface of the lanthanum-loaded carbon nanomaterial antifouling membrane are uniformly distributed and completely cover the surface of the polyethersulfone-based membrane.

[0059] Figure 5 The high-resolution X-ray photoelectron spectrum of the P 2p peak of the lanthanum-loaded carbon nanomaterial antifouling membrane obtained in this embodiment after adsorbing phosphate shows that the binding energy of the P 2p characteristic peak appears at 133.3 eV, which is higher than the binding energy of the standard P 2p characteristic peak of sodium dihydrogen phosphate dihydrate (NaH2PO4·2H2O) (132.9 eV) and the binding energy of the P 2p characteristic peak of phosphate removal by electrostatic adsorption (131.9 eV). This indicates that phosphate is mainly adsorbed by the lanthanum-loaded carbon nanomaterial antifouling membrane through ligand exchange and forms an inner spherical complex.

[0060] The advantages and beneficial results of this invention are verified through the following application examples:

[0061] Application Example 1

[0062] 1) The contact angles of the polyethersulfone-based film and the lanthanum-loaded carbon nanomaterial antifouling film prepared in Example 1 were tested, and the results are as follows: Figure 6 As shown.

[0063] from Figure 6It can be seen that the average contact angle of the polyethersulfone-based membrane is 69.1°, while the average contact angle of the antifouling membrane loaded with lanthanum carbon nanomaterials is 48.4°. The hydrophilicity of the antifouling membrane loaded with lanthanum carbon nanomaterials is improved after loading with lanthanum carbon nanomaterials.

[0064] 2) The polyethersulfone-based membrane and the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 were placed in a constant-pressure dead-end filtration experimental apparatus to determine the permeation flux. The membrane flux was stabilized by pre-pressurizing with ultrapure water at 0.04 MPa for 30 min. Then, the pressure in the nitrogen cylinder was adjusted to 0.1 MPa. The permeation flux was obtained by analyzing the mass and time intervals of ultrapure water recorded by the electronic balance-data acquisition system. The results are as follows: Figure 7 As shown.

[0065] from Figure 7 It can be seen that the permeation flux of the lanthanum-loaded carbon nanomaterial antifouling membrane is 282 L·m. -2 h -1 bar -1 The permeation flux of the polyethersulfone-based membrane is 160 L·m. -2 h -1 bar -1 The permeation flux of the antifouling membrane loaded with lanthanum carbon nanomaterials is significantly higher.

[0066] Application Example 2

[0067] Polyethersulfone-based membranes and the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 were placed in a constant-pressure dead-end filtration experimental apparatus to investigate phosphate removal performance under different pressures. The membrane flux was stabilized by pre-pressurizing with ultrapure water at 0.04 MPa for 30 min. Then, the ultrapure water in the apparatus was replaced with a 1 mg P / L phosphate solution, and the pressure of the nitrogen cylinder was adjusted to 0.02, 0.04, 0.08, and 0.16 MPa, respectively. Filtration was performed continuously for 10 min at each of the four pressures. The phosphate concentration in the filtrate was determined using the molybdate spectrophotometric method specified in the Chinese national standard "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method" (GB 11893-89). The phosphate removal rate was obtained by analyzing the phosphate concentration in the filtrate and the phosphate concentration in the influent. The corresponding membrane flux was obtained by analyzing the mass and time interval of ultrapure water recorded by the electronic balance-data acquisition system. The results are as follows: Figure 8 As shown.

[0068] from Figure 8 It can be seen that the lanthanum-loaded carbon nanomaterial antifouling membrane achieved a 100% phosphate removal rate under all four pressures, which is significantly higher than that of the polyethersulfone-based membrane (4.7–16.7%). Furthermore, the membrane flux of the lanthanum-loaded carbon nanomaterial antifouling membrane is greater than that of the polyethersulfone-based membrane; therefore, under the same filtration pressure and filtration time, the lanthanum-loaded carbon nanomaterial antifouling membrane can treat more phosphate-containing wastewater.

[0069] Application Example 3

[0070] 1) The lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 was placed in a constant-pressure dead-end filtration experimental apparatus. A solution with a sodium hydroxide to sodium bicarbonate molar ratio of 2:1 was used as the regeneration solution to investigate the reusability of the lanthanum-loaded carbon nanomaterial antifouling membrane. The membrane flux was stabilized by pre-pressurizing with ultrapure water at 0.04 MPa for 30 min. Then, the ultrapure water in the apparatus was replaced with a 10 mg P / L phosphate solution, and filtration was performed continuously for 30 min, collecting the filtrate every 5 min. The phosphate solution in the apparatus was replaced with the regeneration solution, the pressure of the nitrogen cylinder was adjusted to 0.1 MPa, and filtration was performed continuously for 30 min. The regeneration solution was then replaced with ultrapure water, and filtration was performed continuously for 30 min to wash away the residual regeneration solution, completing the regeneration of the lanthanum-loaded carbon nanomaterial antifouling membrane. Under the same experimental conditions, the regenerated lanthanum-loaded carbon nanomaterial antifouling membrane was used to filter the phosphate solution again, and a total of three adsorption-desorption regeneration experiments were conducted. The phosphate concentration in the filtrate was determined by molybdate spectrophotometry, and the phosphate removal rate was calculated. The results are as follows: Figure 9 As shown.

[0071] from Figure 9 As can be seen from the results, the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 can still remove more than 80% of the phosphate in a high-concentration phosphate solution (10 mg P / L) after three adsorption-desorption regeneration experiments, indicating that it can be repeatedly used for phosphate removal.

[0072] 2) Figure 10 The image shows the X-ray diffraction pattern of the lanthanum-loaded carbon nanomaterial antifouling membrane after three adsorption-desorption regeneration processes. As can be seen from the image, the main crystal structure of the regenerated lanthanum-loaded carbon nanomaterial antifouling membrane remains La2(CO3)3·8H2O, consistent with the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1, further demonstrating the membrane's good reusability.

[0073] 3) Figure 11 The image shows a photograph of the lanthanum-loaded carbon nanomaterial antifouling membrane after three adsorption-desorption regeneration cycles. As can be seen from the figure, compared to the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 (… Figure 2 The lanthanum-loaded carbon nanomaterials on the surface of the regenerated antifouling membrane did not show significant detachment, indicating that the membrane has good stability.

[0074] Application Example 4

[0075] The lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 was placed in a constant-pressure dead-end filtration experimental device. Secondary effluent and surface water were used as influent to investigate the phosphate removal performance of the lanthanum-loaded carbon nanomaterial antifouling membrane on actual water bodies. The membrane flux was stabilized by pre-pressurizing with ultrapure water at 0.04 MPa for 30 min. Then, the ultrapure water in the device was replaced with secondary effluent and surface water at 1 mg P / L, and filtration was performed continuously for 60 min, with filtrate collected every 10 min. The phosphate concentration in the filtrate was determined by molybdate spectrophotometry, and the phosphate removal rate was calculated. The results are as follows: Figure 12 As shown.

[0076] from Figure 12 As can be seen from the example, the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 can continuously remove phosphate from actual water bodies within 60 minutes, with a phosphate removal rate close to 100%, indicating that it can be used for the continuous removal of phosphate from actual water bodies.

[0077] Application Example 5

[0078] The polyethersulfone-based membrane and the lanthanum-loaded carbon nanomaterial antifouling membrane prepared in Example 1 were placed in a constant-pressure dead-end filtration experimental apparatus for membrane filtration fouling experiments. The membrane flux was stabilized by pre-pressurizing with ultrapure water at 0.04 MPa for 30 min. Then, the ultrapure water in the apparatus was replaced with a mixed solution of 1 mg P / L phosphate and 5 mg / L humic acid, and filtration was performed continuously for 90 min, with filtrate collected every 10 min. The phosphate concentration in the filtrate was determined using molybdate spectrophotometry, and UV concentration was measured using a spectrophotometer. 254 The absorbance of humic acid at the filtration point was used to calculate the removal rates of phosphate and humic acid. The membrane flux was obtained by analyzing the mass and time intervals of ultrapure water recorded by the electronic balance-data acquisition system, and the specific flux was further calculated. The results are as follows: Figure 13 As shown.

[0079] from Figure 13 The results show that the lanthanum-loaded carbon nanomaterial antifouling membrane achieved a 93.5% removal rate of humic acid and a 97.4% removal rate of phosphate after 90 minutes of filtration, both superior to the polyethersulfone-based membrane (47.4% and 6.9%, respectively). Furthermore, the specific flux of the lanthanum-loaded carbon nanomaterial antifouling membrane after 90 minutes of filtration was 0.78, higher than that of the polyethersulfone-based membrane (0.66), indicating that the antifouling effect of the lanthanum-loaded carbon nanomaterial antifouling membrane is superior to that of the polyethersulfone-based membrane.

[0080] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a lanthanum-loaded carbon nanomaterial antifouling membrane suitable for phosphorus recovery from wastewater, characterized in that, Includes the following steps: (1) Weigh out lanthanum chloride heptahydrate, dissolve it in ultrapure water to obtain a lanthanum chloride solution with a concentration of 0.05 mol / L; (2) Weigh out multi-walled carbon nanotubes (MWCNTs) with an outer diameter of 8–20 nm and add them to the 0.05 mol / L lanthanum chloride solution obtained in step (1). Stir the solution magnetically at 20±1℃ for 4–8 h to obtain a carbon nanotube suspension. The mass ratio of lanthanum to MWCNTs is 3:10–9:

10. (3) Weigh anhydrous sodium carbonate and dissolve it in ultrapure water to obtain a sodium carbonate solution with a concentration of 0.5 to 1 mol / L; (4) At 20±1℃, sodium carbonate solution was added dropwise to carbon nanotube suspension until the pH value of carbon nanotube suspension became 10. After stirring magnetically for 6 to 10 h, the suspension was aged for 6 to 12 h to obtain lanthanum-loaded carbon nanomaterial suspension. (5) The obtained lanthanum-loaded carbon nanomaterial suspension was filtered and washed with ultrapure water 3 to 5 times until the pH value of the filtrate became 7. It was then placed in a vacuum drying oven and dried at 25 to 60 °C. After grinding, the dried lanthanum-loaded carbon nanomaterial La@MWCNTs was obtained. (6) Weigh out lanthanum-loaded carbon nanomaterials La@MWCNTs and place them in anhydrous ethanol. Use an ultrasonic disruptor to sonicate in an ice bath at 300W for 10-20 min to obtain a dispersion of lanthanum-loaded carbon nanomaterials La@MWCNTs. (7) A polyethersulfone (PES) membrane with a molecular weight cutoff of 100 kDa is placed in a vacuum filtration device. The lanthanum-loaded carbon nanomaterial dispersion obtained in step (6) is filtered onto the surface of the PES membrane using negative pressure filtration. The pressure applied is -0.075 MPa. The ratio of the loading amount of lanthanum-loaded carbon nanomaterial to the effective filtration area of ​​the polyethersulfone membrane is 0.0005–0.002 g / cm³. 2 After filtration and washing with ultrapure water, an antifouling membrane loaded with lanthanum carbon nanomaterials was obtained.

2. The preparation method according to claim 1, characterized in that, The outer diameter of the multi-walled carbon nanotubes in step (2) is 8-15 nm, the magnetic stirring time is 4 h, and the mass ratio of lanthanum to multi-walled carbon nanotubes is 6:

10.

3. The preparation method according to claim 1, characterized in that, The concentration of the sodium carbonate solution in step (3) is 1 mol / L.

4. The preparation method according to claim 1, characterized in that, The magnetic stirring time in step (4) is 8 hours, and the aging time is 12 hours.

5. The preparation method according to claim 1, characterized in that, The number of times the filter is cleaned in step (5) is 5, and the vacuum drying temperature is 35℃.

6. The preparation method according to claim 1, characterized in that, The ultrasound time in step (6) is 10 min.

7. The antifouling membrane of lanthanum-loaded carbon nanomaterials prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the lanthanum-loaded carbon nanomaterial antifouling membrane according to claim 7 in wastewater phosphorus recovery or membrane fouling mitigation.

Images