Modified seaweed residue-based filter membrane, preparation thereof and application thereof in removing pollutants

Abstract

The present application relates to modified seaweed residue-based filter membrane and its preparation and application for removing pollutants, wherein industrial waste seaweed residue is used as raw material, and graphene oxide is used as modifier, after mixing seaweed residue and graphene oxide and fully stirring, ZrO2 nanoparticles are biomimetic mineralized on the graphene oxide loaded seaweed residue hybrid, and the functional GO / seaweed residue-ZrO2 hybrid membrane is prepared by vacuum filtration method, the composite membrane has good adsorption and removal performance on fluoride, heavy metal ions and radioactive elements in water body, and the composite membrane also has excellent antibacterial effect.

Description

Modified seaweed residue-based filter membrane, its preparation and application in removing pollutants Technical Field

[0001] This invention relates to a modified seaweed residue-based filter membrane, its preparation and application, and belongs to the field of marine environmental technology. Background Technology

[0002] With the rapid development of society, economy, and industrial production, environmental pollution has become increasingly severe. Water pollution is one of the most serious environmental problems. Various pollutants in the aquatic environment not only adversely affect human health and natural resources but also lead to a continuous reduction in freshwater supply. Therefore, removing pollutants from water bodies and subsequent wastewater purification has become a research hotspot. Currently, conventional water purification technologies such as sedimentation, coagulation, membrane separation, and electrochemical methods suffer from drawbacks such as low treatment efficiency, high cost, complex operation processes, and adverse toxic effects on the environment and ecosystems, hindering their practical application in water treatment. Adsorption, as a commonly used water treatment method, has advantages such as simple operation, low cost, good adsorption effect, and reusable adsorbents, and is widely recognized as a practical method for removing pollutants from water. The key technology lies in the development and research of adsorption materials. However, current conventional water purification technologies for removing pollutants from water bodies suffer from drawbacks such as low treatment efficiency, high cost, complex operation processes, and adverse toxic effects on the environment and ecosystems.

[0003] Seaweed residue is a residue generated during the production of alginic acid, mannitol, iodine, and other products from seaweed. Systematic analysis of the composition of seaweed residue revealed that it contains abundant crude protein, cellulose, trace elements, and small amounts of polysaccharides and crude fats. These important components are not only unutilized but are also discharged as waste, becoming a source of pollution. These components are rich in amino, carboxyl, and hydroxyl groups, which can be easily modified to increase their active sites. Graphene oxide is composed of carbon atoms arranged in sp... 2 Hexagonal honeycomb lattice planar thin films composed of hybrid orbitals are two-dimensional carbon atom materials with a single atom thickness. They possess high specific surface area and abundant oxygen-containing functional groups (such as hydroxyl, carboxyl, and epoxy groups), and are considered one of the most promising adsorbent materials. However, graphene oxide exhibits easy aggregation in aqueous solutions, has a small usable specific surface area, and is difficult to separate, which limits its direct use.

[0004] Furthermore, Chinese patent document CN110655138 A discloses a method for preparing MOF composite materials, which uses seaweed residue as raw material to prepare MOF composite materials containing abundant functional groups. After carbonization, a large number of porous structures are formed on the surface, which can be used to adsorb a large number of heavy metal ions in wastewater. However, the preparation process of this composite material requires calcination, resulting in high energy consumption. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a modified seaweed residue-based filter membrane and its preparation and application in pollutant removal. A modified seaweed residue-based filter membrane (abbreviated as aGO / SW-ZrO2 composite filter membrane) is prepared by biomimetic mineralization of ZrO2 nanoparticles on seaweed residue supported by graphene oxide, followed by vacuum filtration. Results show that the aGO / SW-ZrO2 composite filter membrane not only exhibits excellent performance in removing fluoride from water, demonstrating high fluoride adsorption capacity and excellent selectivity, but also effectively removes radioactive elements uranium and strontium from water. Furthermore, the significantly enhanced antibacterial properties after biomimetic mineralization demonstrate the great application potential of this biomass polymer filter membrane in wastewater treatment. The entire process of this invention requires no heating and produces no harmful substances, enabling the high-value utilization of waste biomass seaweed residue resources.

[0006] Terminology Explanation:

[0007] EDC: 1-Ethyl-(3-dimethylaminopropyl)carbodiimide.

[0008] NHS: N-hydroxysuccinimide.

[0009] GO: Graphene oxide.

[0010] aGO: Activated graphene oxide.

[0011] MES: 2-(N-morpholine)ethanesulfonic acid monohydrate is a commonly used biochemical experimental buffer, mainly used to maintain the stability of biological systems within a specific pH range.

[0012] The technical solution of the present invention is as follows:

[0013] A modified seaweed residue-based filter membrane, the material structure of which includes biomimetic mineralized ZrO2 nanoparticles on seaweed residue supported by graphene oxide.

[0014] According to the present invention, preferably, the mass ratio of seaweed residue to graphene oxide is (3-6):1, and more preferably (4-5):1.

[0015] According to the present invention, preferably, the mass ratio of seaweed residue to zirconium oxide is 1:(1-5), more preferably 1:(1.5-4.5).

[0016] According to the present invention, preferably, the particle size of the seaweed residue is less than 200 mesh.

[0017] According to the present invention, preferably, the thickness of the modified seaweed residue-based filter membrane is 0.01 mm to 10 mm.

[0018] According to the present invention, the preparation method of the above-mentioned modified seaweed residue-based filter membrane includes the following steps:

[0019] After drying, crushing and sieving the seaweed residue, it is added to the activated graphene oxide aqueous solution and stirred evenly. Then, ZrOCl·8H2O is added and stirring is continued. The pH is then adjusted to 3-5 and filtered to obtain the modified seaweed residue-based filter membrane.

[0020] According to the present invention, preferably, the concentration of the graphene oxide aqueous solution is 1-10 mg / mL, more preferably 3-6 mg / mL.

[0021] According to the present invention, the preferred activation process of graphene oxide is as follows:

[0022] EDC (50 mg / mL) and NHS (25 mg / mL) were dissolved in MES buffer solution at pH 5.4. 5 mL of EDC and 5 mL of NHS were added to 10 mL of GO aqueous solution (4 mg / mL) with stirring. After 24 hours, the mixed GO solution was centrifuged and washed three times to obtain a black aGO precipitate, which was then dissolved in 10 mL of ultrapure water.

[0023] According to the present invention, preferably, seaweed residue is added to the activated graphene oxide aqueous solution and stirred for 10-30 hours, more preferably 15-25 hours.

[0024] According to the present invention, preferably, ZrOCl·8H2O is added and stirring is continued for 3-8 hours, more preferably 5-6 hours.

[0025] According to the present invention, sodium hydroxide is preferably used to adjust the pH.

[0026] According to the present invention, the above-mentioned modified seaweed residue-based filter membrane is used to remove pollutants from water bodies.

[0027] According to the application of the present invention, preferably, the contaminants are fluorides, radioactive elements, and bacteria;

[0028] Preferably, the radioactive element includes strontium or uranium;

[0029] Preferably, the bacteria include Escherichia coli or Staphylococcus aureus.

[0030] The principles and beneficial effects of this invention are as follows:

[0031] 1. This invention synthesizes a graphene oxide / algae residue hybrid through graft copolymerization, and then biomimetic mineralizes ZrO2NPs in the binary structure to prepare a functional aGO / SW-ZrO2 composite filter membrane.

[0032] The results showed that the aGO / SW-ZrO2 composite filter membrane exhibited excellent adsorption and removal performance for pollutants in water. For F concentrations in water ranging from 100-400 mg / L... - The removal rate can reach over 99%. Furthermore, even with a high concentration of interfering ions, F... - The removal rate can still reach 99.19%. The charged surface of ZrO2NPs interacts with F... - electrostatic interactions and F - The adsorption mechanism is the substitution of -OH groups on the ZrO2NPs surface.

[0033] For the radioactive elements uranium and strontium, the uranium removal efficiency was 99.15% when the initial concentration of the uranium ion solution was 200 mg / L; 98.33% when the initial concentration was 100 mg / L; and 90.85% when the initial concentration was 20 mg / L. For strontium, the removal efficiency was 86.46% when the initial concentration of the strontium ion solution was 100 mg / L; and 73.79% when the initial concentration was 300 mg / L. The main adsorption mechanisms were the coordination interactions between NH₂, -OH, and -COOH groups and metal ions, and the electrostatic attraction between oxygen-containing functional groups and metal ions.

[0034] In addition, due to the synergistic antibacterial effect of seaweed residue, graphene oxide and ZrO2NPs, the aGO / SW-ZrO2 composite filter membrane showed significant inhibitory ability against Escherichia coli and Staphylococcus aureus.

[0035] 2. The entire process of this invention is simple to operate, requires no heating and does not produce harmful substances, and can realize the high-value utilization of waste biomass seaweed residue resources. Attached Figure Description

[0036] Figure 1 shows AFM photographs of different substances in Experimental Example 1 of this invention.

[0037] Figure 2 is a TEM image of the aGO / SW-ZrO2 hybrid after biomineralization in Experimental Example 2 of the present invention.

[0038] Figure 3 shows the FT-IR images of different substances in Experimental Example 3 of this invention.

[0039] Figure 4 shows the performance of the aGO / SW-ZrO2 composite filter membrane in removing fluoride ions in Experiment Example 4 of this invention.

[0040] Figure 5 shows the performance of the aGO / SW-ZrO2 composite filter membrane in removing uranium ions in Experimental Example 5 of this invention.

[0041] Figure 6 is a process flow diagram of the preparation of the modified seaweed residue-based filter membrane of the present invention. Detailed Implementation

[0042] The present invention will be further described below through specific embodiments, but is not limited thereto.

[0043] All raw materials in the embodiments are commercially available, wherein:

[0044] The seaweed residue used was obtained from South American brown algae through processes such as rinsing, crushing, alkali dissolution and grinding, and foaming and filtration. After drying the seaweed residue in an oven at 110℃, it was crushed and ground by a crusher and passed through a 500-mesh sieve to obtain seaweed residue powder samples with a particle size of less than 25.8μm.

[0045] The activation process of graphene oxide is as follows:

[0046] EDC (50 mg / mL) and NHS (25 mg / mL) were dissolved in MES buffer solution at pH 5.4. 5 mL of EDC and 5 mL of NHS were added to 10 mL of GO aqueous solution (4 mg / mL) with stirring. After 24 hours, the mixed GO solution was centrifuged and washed three times to obtain a black aGO precipitate, which was then dissolved in 10 mL of ultrapure water.

[0047] Example 1

[0048] Weigh 0.2g of 200-mesh seaweed residue and add it to 10ml of activated graphene oxide aqueous solution (4mg / ml). Mix well and stir for 24 hours to form a GO / seaweed residue mixture.

[0049] 0.3 g of ZrOCl·8H2O was added to the GO / seaweed residue mixture solution. After stirring for 6 hours, the pH of the mixture solution was adjusted to 3.5-4 with a 0.2 M NaOH solution to form a hybrid. After biomineralization, the formed hybrid was filtered into a hybrid membrane using vacuum filtration technology to obtain the aGO / SW-ZrO2 composite filter membrane.

[0050] Example 2

[0051] Weigh 0.2g of 200-mesh seaweed residue and add it to 10ml of activated graphene oxide aqueous solution (4mg / ml). Mix well and stir for 24 hours to form a GO / seaweed residue mixture.

[0052] 0.6 g of ZrOCl·8H2O was added to the GO / seaweed residue mixture solution. After stirring for 6 hours, the pH of the mixture solution was adjusted to 3.5-4 with a 0.2 M NaOH solution to form a hybrid. After biomineralization, the formed hybrid was filtered into a hybrid membrane using vacuum filtration technology to obtain the aGO / SW-ZrO2 composite filter membrane.

[0053] Example 3

[0054] Weigh 0.2g of 200-mesh seaweed residue and add it to 10ml of activated graphene oxide aqueous solution (4mg / ml). Mix well and stir for 24 hours to form a GO / seaweed residue mixture.

[0055] 0.9 g of ZrOCl·8H2O was added to the GO / seaweed residue mixture solution. After stirring for 6 hours, the pH of the mixture solution was adjusted to 3.5-4 with a 0.2 M NaOH solution to form a hybrid. After biomineralization, the formed hybrid was filtered into a hybrid membrane using vacuum filtration technology to obtain the aGO / SW-ZrO2 composite filter membrane.

[0056] Experimental Example 1

[0057] According to the present invention, seaweed residue is first directly mixed with activated aGO to obtain a grafted GO / SW hybrid. EDC / NHS is used to activate the carboxyl groups in the GO aqueous solution. The activated carboxyl groups have a lower chemical potential energy and can react with the amino groups on the seaweed residue at room temperature to form amide bonds, thereby grafting seaweed residue onto the GO surface. MES acts as a buffer in the reaction, adjusting the pH value of the reaction environment.

[0058] AFM images of seaweed residue and GO / SW hybrid before and after GO activation in Test Example 1 are shown in Figure 1, where (a,b) seaweed residue, (c) GO, (d) aGO, and (e,f) GO / SW hybrid.

[0059] Figures 1a and 1b show two morphologies of seaweed residue in aqueous solution: one is sheet-like structures with an average height of 1-2 nm and an average length of 100-200 nm; the other is sheet-like aggregates with an average height of 10-20 nm and an average length of 100-400 nm. This may be due to the weak repulsive forces between seaweed residue particles, making them prone to aggregation. Figure 1c shows that the average height of a single layer of graphene oxide nanosheets is approximately 1 nm, and the average length is approximately 2-5 μm. After activation, the graphene oxide sheets exhibit aggregation and folding phenomena. Even smaller graphene oxide nanosheets can be obtained through ultrasonic treatment (Figure 1d). Figures 1e and 1f show AFM images of the GO / SW hybrid. In Figure 1e, it is clearly visible that a large number of seaweed residue particles with a length of 150-300 nm aggregate on the same aGO nanosheet; in Figure 1f, seaweed residue particles with an average length of 200-400 nm aggregate individually on aGO nanofragments. This is consistent with the seaweed residue sizes measured in Figures 1a and 1b.

[0060] Experimental Example 2

[0061] According to the present invention, the prepared aGO / SW hybrid contains abundant negatively charged active groups: -OH, -COOH, and -NH2. Simultaneously, the seaweed residue nanoparticles and aGO nanosheets exhibit electrostatic interactions and chemical linkages, which support the formation of ZrO2NPs on the aGO / SW hybrid through a heat-free biomineralization process. During the biomimetic synthesis process, the negatively charged groups on aGO and seaweed residue, through electrostatic interactions and synergistic effects, facilitate the binding of positively charged Zr. 4+ It provides adsorption sites, and adjusting the solution pH between 3.5 and 4 can promote the in-situ formation of very fine ZrO2NPs.

[0062] The aGO / SW-ZrO2 hybrids after biomineralization in Example 1 were characterized by TEM, as shown in Figure 2. It can be seen that the particles with a diameter of 5-20 nm are consistent with the size of ZrO2 NPs.

[0063] Experimental Example 3

[0064] The GO, aGO, SW, GO / SW, and GO / SW-ZrO2 in Example 1 were characterized using FT-IR spectroscopy, as shown in Figure 3. Figure 3 shows that the FT-IR spectrum of GO exhibits the following characteristics at 3330, 1720, 1630, 1350, and 1050 cm⁻¹. -1 There are clear absorption peaks at 1720, 1630, 1350, and 1050 cm⁻¹, corresponding to the stretching vibration of -OH, the stretching vibration of C=O on the carboxyl group of graphene oxide, the stretching vibration of C=C in the benzene ring structure, the deformation vibration of -OH on the carboxyl group of graphene oxide, and the stretching vibration of COC, respectively. After activation, the FT-IR spectrum of aGO is at 1720, 1630, 1350, and 1050 cm⁻¹. -1 An absorption peak appears at 1720 cm⁻¹. -1 The absorption peak at 1350 cm⁻¹ weakens because a conjugated system is formed during activation, lowering the C=O vibrational frequency on GO. The N atom, which supplies electrons in the conjugated system, participates in bond vibrations through resonance, reducing the polarizability of the C=O bond, thus lowering the energy and frequency. -1 The weakening of the absorption peak is attributed to the reduction of -OH groups in GO during activation. A comparison of the two spectra leads to the conclusion that GO was successfully activated into aGO. After reacting with seaweed residue, the absorption peak of aGO at 1350 cm⁻¹... -1 The characteristic peak at 1410 cm⁻¹ disappears. -1 The appearance of a new characteristic peak suggests that this may be due to the stretching vibration of -OH groups in seaweed residue, and the condensation reaction between amino groups in seaweed residue and carboxyl groups in graphene oxide, which replaces the -OH groups in the carboxyl groups to generate CN stretching vibration peaks, proving that aGO has undergone a grafting reaction with seaweed residue. (1410 cm⁻¹) -1The weakening of the absorption peak at this point may be due to the combination of -OH atoms in GO / SW with zirconium atoms, leaving only a portion of the -OH atoms, indicating that the biomineralization of GO / SW-ZrO2 was successful.

[0065] Test Example 4

[0066] The performance of the aGO / SW-ZrO2 composite filter membrane obtained in Example 1 in removing fluoride ions is shown in Figure 4. Figure 4 shows the fluoride ion removal performance of different concentrations (100, 200, 300 and 400 mg / L) of fluoride. - The adsorption efficiency of the aGO / SW-ZrO2 composite filter membrane after rapid filtration is shown in Figure 4. As can be seen from Figure 4, when the F- concentration is 100, 200, 300, and 400 mg / L, the F- adsorption efficiency is... - The removal rate can reach over 99%. In this case, approximately 0.50 mg / L of F... - The residue is below the minimum concentration (1.5 mg / L) set by the World Health Organization (WHO) that could pose a health risk.

[0067] Experimental Example 5

[0068] The adsorption performance of the aGO / SW-ZrO2 composite filter membrane prepared in Example 1 on uranium in aqueous solution was tested. The removal rates at different U(VI) concentrations were measured, as shown in Figure 5. The results showed that the uranium removal efficiency was 99.15% when the initial uranium ion concentration was 200 mg / L, and 98.33% when the initial concentration was 100 mg / L. Similarly, the uranium removal efficiency was 90.85% at a lower concentration of 20 mg / L. The aGO / SW-ZrO2 composite filter membrane effectively removed uranium at both low and high uranium concentrations.

[0069] Experimental Example 6

[0070] The adsorption performance of the aGO / SW-ZrO2 composite filter membrane prepared in Example 1 on strontium in aqueous solution was tested, and the removal rate for different Sr(II) concentrations was examined. When the initial concentration of strontium ions in the solution was 100 mg / L, the strontium removal efficiency was 86.46%; when the initial concentration was 300 mg / L, the strontium removal rate was 73.79%. The results indicate that the aGO / SW-ZrO2 composite filter membrane also has a good removal effect on the radioactive element strontium.

[0071] Experimental Example 7

[0072] The modified seaweed residue-based filter membranes prepared in Examples 1-3 were used as filters to filter bacteria containing different concentrations of common Escherichia coli (1.5 × 10⁻⁶). 5 -1.5×10 8Water samples (CFU / mL) were subjected to rapid vacuum filtration. The removal rate of E. coli in the purified water after filtration reached over 99%.

[0073] Experimental Example 8

[0074] The modified seaweed residue-based filter membranes prepared in Examples 1-3 were used as filters to filter materials containing different concentrations of Staphylococcus aureus (1.5 × 10⁻⁶). 5 -1.5×10 8 Water samples (CFU / mL) were subjected to rapid vacuum filtration. The removal rate of Staphylococcus aureus in the purified water after filtration reached over 99%.

[0075] The aGO / SW-ZrO2 composite filter membrane of this invention exhibits a synergistic antibacterial effect of seaweed residue, graphene oxide, and ZrO2 NPs. Brown algae contain compounds with antibacterial activity, such as carbonyl groups, polysaccharides, fatty acids, brown algal polyphenols, terpenes, and halogenated compounds. Graphene oxide, as a substrate for seaweed residue, can effectively prevent its aggregation. The antibacterial mechanism of graphene oxide may be attributed to membrane stress and oxidative stress. Through direct contact with bacteria, the sharp edges of graphene oxide nanosheets cause irreversible physical damage to the bacterial cell membrane, leading to bacterial death. The ROS generated by graphene oxide induces oxidative stress in bacteria, damaging their internal structure and causing rapid bacterial demise. Biomineralized ZrO2 NPs, due to their large surface area, spherical structure, and microcrystalline size, may further enhance the antibacterial activity of the aGO / SW-ZrO2 composite filter membrane. Furthermore, since ZrO2 NPs have a positive charge on their surface, while Escherichia coli and Staphylococcus aureus carry a negative charge, the electromagnetic attraction between the metal oxide NPs and the bacteria also leads to oxidation, thereby killing the bacteria. Therefore, based on the synergistic effect of seaweed residue, graphene oxide, and ZrO2 NPs on antibacterial properties, the aGO / SW-ZrO2 composite filter membrane of this invention exhibits excellent antibacterial properties against Escherichia coli and Staphylococcus aureus.

Claims

1. A modified seaweed residue-based filter membrane, characterized in that, The material structure of this filter membrane comprises biomimetic mineralized ZrO2 nanoparticles on seaweed residue supported by graphene oxide. The graphene oxide is activated graphene oxide, and the activation process of graphene oxide is as follows: 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are dissolved in 2-(N-morpholine)ethanesulfonic acid monohydrate buffer solution at pH=5.4, respectively. Under stirring, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are added to the graphene oxide aqueous solution. After 24 hours, the mixed graphene oxide solution is centrifuged and washed three times to obtain the activated graphene oxide precipitate, which is then dissolved in water.

2. The modified seaweed residue-based filter membrane according to claim 1, characterized in that, The mass ratio of seaweed residue to graphene oxide is (3-6):

1.

3. The modified seaweed residue-based filter membrane according to claim 1, characterized in that, The mass ratio of seaweed residue to zirconium oxide is 1:(1-5).

4. A method for preparing the modified seaweed residue-based filter membrane according to any one of claims 1-3, comprising the following steps: drying, pulverizing and sieving seaweed residue, adding it to an activated graphene oxide aqueous solution, stirring evenly, adding ZrOCl·8H2O and continuing stirring, then adjusting the pH to 3-5, filtering to obtain the modified seaweed residue-based filter membrane; the activation process of graphene oxide is as follows: dissolving 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide in a 2-(N-morpholine)ethanesulfonic acid monohydrate buffer solution at pH=5.4, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide to the graphene oxide aqueous solution under stirring; after 24 hours, centrifuging and washing the mixed graphene oxide solution three times to obtain the activated graphene oxide precipitate, which is then dissolved in water.

5. The method for preparing the modified seaweed residue-based filter membrane according to claim 4, characterized in that, The concentration of the aqueous solution of graphene oxide is 1-10 mg / mL.

6. The method for preparing the modified seaweed residue-based filter membrane according to claim 4, characterized in that, Add seaweed residue to the activated graphene oxide aqueous solution and stir for 10-30 hours.

7. The method for preparing the modified seaweed residue-based filter membrane according to claim 4, characterized in that, Add ZrOCl·8H2O and continue stirring for 3-8 hours.

8. The method for preparing the modified seaweed residue-based filter membrane according to claim 4, characterized in that, Sodium hydroxide was used to adjust the pH.

9. The application of the modified seaweed residue-based filter membrane according to any one of claims 1-3, characterized in that, Used to remove pollutants from water bodies.

10. The application according to claim 9, characterized in that, The pollutants mentioned are fluorides, radioactive elements, and bacteria.

11. The application according to claim 10, characterized in that, The radioactive element is strontium or uranium, and the bacteria is Escherichia coli or Staphylococcus aureus.

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