Composite nanofiltration membrane based on polyether amine / polyethyleneimine selection layer and preparation method thereof

Abstract

The invention relates to a composite nanofiltration membrane based on a polyether amine / polyethyleneimine selection layer and a preparation method thereof, the composite nanofiltration membrane is prepared by taking a chlorinated polyvinyl fluoride ultrafiltration membrane as a base membrane, taking polyether amine and polyethyleneimine as aqueous phase monomers, and carrying out interfacial polymerization with trimesoyl chloride. The flux range of the prepared composite nanofiltration membrane to simulated RB5 dye wastewater is 3.4-9.5 L / (m < 2 >. H. Bar), the retention rate of the composite nanofiltration membrane to RB5 is 93.1% or above, the retention rate of the composite nanofiltration membrane to inorganic salt is 9.2% or below, and dye and salt in the dye wastewater can be well separated.

Description

Technical Field

[0001] The invention belongs to the field of dye wastewater treatment and separation and recovery, and particularly relates to a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selection layer and a preparation method thereof. Background Art

[0002] Mixing two or even three amino monomers to replace a single amino monomer and preparing the selective layer of the composite nanofiltration membrane through interfacial polymerization can increase the free volume in the selective layer, make the microstructure of the selective layer loose, and achieve the separation of dyes and salts in the dye solution to a greater extent, promote the recycling of dyes and salts, and also significantly increase the flux of the dye solution. There are some literature and patents reporting on the preparation of the selective layer of the composite nanofiltration membrane by interfacial polymerization of PEI and other amino monomers. Ma Xiaohua et al. (Membrane Science and Technology, 2024, 44(04):8-16) blended sodium alginate (SA) and polyethyleneimine (PEI) as the aqueous phase solution for the interfacial polymerization reaction. The strong interaction between SA and PEI caused SA to be embedded in the polyamide layer, thereby improving the density of the membrane, and then Cu 2+ Combined with SA, the positive charge on the membrane surface is increased, and the retention performance of the membrane for multivalent cations is improved. Hamid et al. (Journal of Water Process Engineering, 2020, 33101032-101032) used different piperazine (PIP) and PEI mixing ratios to prepare thin film composite membranes (TFC membranes), and compared and discussed the effects of NF and FO systems on Cu 2+ The interception performance and membrane performance of the membrane have a good removal effect on heavy metal ions in wastewater, and Cu 2+ The retention rate is above 95%. Li et al. (Desalination, 2023, 556:116575) mixed cyclanine (Cyclen) with PEI as an amino monomer and prepared a composite nanofiltration membrane by interfacial polymerization with trimesoyl chloride (TMC). After introducing Cyclen into the aqueous phase, the PEI / Cyclen TMC selective layer had a higher degree of crosslinking than the PEI / TMC selective layer, and Li + The transport of Li provides a dedicated channel, which enhances the separation of magnesium and lithium, and is beneficial to the + / Mg 2+ Separation and recovery of Li +, which is suitable for extracting lithium from salt lake brine. Bera et al. (Journal of Membrane Science, 2016, 51964-76) mixed PEI-Dex conjugate (PEI-Dex) with PEI and prepared TFC membrane by interfacial polymerization with TMC, which is suitable for recovering sodium chloride in seawater. Tang Wenjing (CN115121119B) et al. mixed PEI with surfactant to prepare aqueous solution, added trimesoyl chloride to organic solvent to prepare organic solution, and obtained positively charged nanofiltration membrane by interfacial polymerization, which is suitable for the recovery of cationic Cs + and Sr 2+ The interception rate is high and it is suitable for treating nuclear radioactive wastewater. There is no patent report on the preparation of composite nanofiltration membranes by mixing PEI and PEA for the separation of dyes and salts in dye wastewater. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selective layer and a preparation method thereof, so as to promote the separation of dyes and salts in dye wastewater treatment, effectively recover dyes and salts, and reduce wastewater discharge.

[0004] The invention provides a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selection layer. The composite nanofiltration membrane is prepared by interfacial polymerization of a chlorinated polyvinyl fluoride (CPVC) ultrafiltration membrane as a base membrane, polyetheramine (PEA) and polyethyleneimine (PEI) as aqueous phase monomers and trimesoyl chloride (TMC).

[0005] The present invention also provides a method for preparing a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selective layer, comprising the following steps:

[0006] (1) Preparation of CPVC ultrafiltration membrane;

[0007] (2) mixing polyetheramine and polyethyleneimine as amine monomers and dissolving them together with a surfactant in deionized water to prepare an aqueous solution;

[0008] (3) After the aqueous phase solution of step (2) is deposited on the surface of the CPVC ultrafiltration membrane, interfacial polymerization is carried out with a n-hexane solution of TMC to obtain a composite nanofiltration membrane based on a PEA / PEI selective layer.

[0009] Preferably, in the step (1), the CPVC ultrafiltration membrane is prepared by a non-solvent induced phase separation (NIPS) method, comprising: uniformly mixing CPVC, poloxamer F127 and dimethylacetamide (DMAC), stirring in a constant temperature water bath at 80-90° C. for 4-6 hours to obtain a uniform and transparent CPVC casting solution, and standing until it is completely defoamed; finally, the CPVC casting solution is drooled into a film, and phase separation is performed in a gel water bath at 30-40° C. to obtain a CPVC ultrafiltration membrane.

[0010] More preferably, the mass fraction of CPVC is 18-20 wt %, the mass fraction of Poloxamer F127 is 5-10 wt %, and the mass fraction of DMAC is 70-78 wt %.

[0011] Preferably, in step (2), the total concentration of PEA and PEI is 1 to 1.5 g / L, and the value range of PEA / PEI is 1 / 9 to 5 / 5.

[0012] Preferably, the surfactant in step (2) is sodium dodecyl sulfate (SDS) with a concentration of 1 to 2 g / L.

[0013] Preferably, the deposition time in step (2) is 5 to 15 minutes.

[0014] Preferably, the concentration of the n-hexane solution of TMC in step (3) is 1-2 g / L.

[0015] Preferably, the time of interfacial polymerization in step (3) is 5 to 10 minutes.

[0016] The invention also provides an application of a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selection layer in dye wastewater treatment.

[0017] In the present invention, SDS is used as a surfactant to reduce surface tension and promote interfacial polymerization reaction; PEI has the characteristics of large molecular structure and easy to form a relatively loose network structure polyamide selection layer; PEA is a product in which the terminal hydroxyl group of polyether is replaced by an amine group, has a long chain structure, is composed of a polyether backbone and a terminal amine group, and is easy to polymerize with TMC. Due to the presence of polyether, PEA has strong hydrophilicity and presents electrical neutrality. Mixing PEA and PEI as amine monomers can obtain a composite nanofiltration membrane with excellent performance suitable for treating dye wastewater, which has a loose structure, strong hydrophilicity, large flux, high retention rate, and is suitable for treating dye wastewater.

[0018] Beneficial Effects

[0019] The composite nanofiltration membrane based on the polyetheramine / polyethyleneimine selective layer prepared by the present invention has a loose structure, strong hydrophilicity, and a flux range of 3.4 to 9.5 L / (m2 ·h·bar), the retention rate of RB5 is above 93.1%, and the retention rate of inorganic salts is below 9.2%. It can better separate the dye and salt in the dye wastewater, and the operation stability is good, and the anti-pollution performance of the membrane is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The membrane surface microstructure and membrane cross-section microstructure of the composite nanofiltration membrane in Example 2 of the present invention.

[0021] Figure 2 The membrane surface microstructure and membrane cross-section microstructure of the composite nanofiltration membrane in Example 4 of the present invention.

[0022] Figure 3 The membrane surface microstructure and membrane cross-section microstructure of the composite nanofiltration membrane in Example 5 of the present invention.

[0023] Figure 4 The membrane surface microstructure and membrane cross-section microstructure of the composite nanofiltration membrane in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0025] Example 1

[0026] This embodiment provides a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selective layer, and the preparation method thereof comprises the following steps:

[0027] (1) Preparation of CPVC ultrafiltration membrane by non-solvent induced phase separation method: a certain amount of CPVC (18-20wt%), poloxamer F127 (5-10wt%) and DMAC (70-78wt%) were mixed evenly in a conical flask, stirred in a constant temperature water bath at 85°C for 5 hours to obtain a uniform and transparent CPVC casting solution, and allowed to stand until it was completely defoamed. Finally, the CPVC casting solution was spilt into a film, and phase separation was performed in a gel water bath at 35°C to obtain a CPVC ultrafiltration membrane.

[0028] (2) Preparation of the surface selective layer of the CPVC ultrafiltration membrane: quantitative PEA, PEI and SDS were dissolved in deionized water to obtain an aqueous solution with an SDS concentration of 1.3 g / L, a total of PEA and PEI concentrations of 1 g / L, and a PEA / PEI ratio of 1 / 9; quantitative TMC was dissolved in n-hexane to obtain a 1.3 g / L n-hexane solution of TMC. Then, interfacial polymerization was performed, and the CPVC ultrafiltration membrane was immersed in 20 mL of the aqueous monomer solution, allowed to stand for 10 minutes, and the residual solution was removed with absorbent paper. Subsequently, the n-hexane solution of TMC was evenly poured on the membrane surface and reacted for 10 minutes. The excess reactants were washed with n-hexane solution, and the membrane was continued to react in a 50°C constant temperature box for 5 minutes, and then the membrane was stored in deionized water for use.

[0029] Example 2

[0030] The preparation of the composite nanofiltration membrane in this embodiment is the same as that in Example 1, except that the ratio of PEA / PEI in step (2) is 2 / 8. The microstructure of the composite nanofiltration membrane is as follows: Figure 1 shown.

[0031] Example 3

[0032] The preparation of the composite nanofiltration membrane in this example is the same as that in Example 1, except that in step (2), the ratio of PEA / PEI is 3 / 7.

[0033] Example 4

[0034] The preparation of the composite nanofiltration membrane in this embodiment is the same as that in embodiment 1, except that the ratio of PEA / PEI in step (2) is 4 / 6. The microstructure of the composite nanofiltration membrane is as follows: Figure 2 shown.

[0035] Example 5

[0036] The preparation of the composite nanofiltration membrane in this embodiment is the same as that in embodiment 1, except that the ratio of PEA / PEI in step (2) is 5 / 5. The microstructure of the composite nanofiltration membrane is as follows: Figure 3 shown.

[0037] Comparative Example 1

[0038] The preparation of the composite nanofiltration membrane in this comparative example is the same as in Example 1, except that the PEA content in step (2) is 0. The microstructure of the composite nanofiltration membrane obtained is as follows: Figure 4 shown.

[0039] Treatment of RB5 (Reactive Black 5) simulated dye wastewater by PEA / PEI / CPVC composite nanofiltration membrane: The concentrations of dye and salt in RB5 dye wastewater are 0.05-0.3 g / L and 0.025-0.1 g / L, respectively. The flux of RB5 simulated dye wastewater, RB5 retention rate, and MgSO4 and NaCl retention rates of the composite nanofiltration membranes prepared in Examples 1-5 and Comparative Example 1 were tested in a cup-type ultrafilter (MSC cup-type). The operating pressure is 0.1 MPa. The experimental results are shown in Table 1.

[0040] Table 1 Performance test of composite nanofiltration membrane prepared in Examples 1 to 5 and Comparative Example 1

[0041]

[0042] As shown in Table 1, the flux range of the composite nanofiltration membrane prepared in the present invention for the simulated RB5 dye wastewater is 3.4 to 9.5 L / (m 2 ·h·bar), the retention rate of RB5 is above 93.1%, and the retention rate of inorganic salts is below 9.2%. It can better separate the dye and salt in the dye wastewater, and the operation stability is good, and the anti-pollution performance of the membrane is improved.

Claims

1. A composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selective layer, characterized in that: The composite nanofiltration membrane is prepared by using a chlorinated polyvinyl fluoride ultrafiltration membrane as a base membrane, polyetheramine and polyethyleneimine as aqueous phase monomers, and performing interfacial polymerization with trimesoyl chloride.

2. A method for preparing a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selective layer, comprising the following steps: (1) preparing chlorinated polyvinyl fluoride ultrafiltration membrane; (2) mixing polyetheramine and polyethyleneimine as amine monomers and dissolving them together with a surfactant in deionized water to prepare an aqueous solution; (3) After the aqueous phase solution of step (2) is deposited on the surface of a chlorinated polyvinyl fluoride ultrafiltration membrane, interfacial polymerization is carried out with a n-hexane solution of trimesoyl chloride to obtain a composite nanofiltration membrane based on a polyetheramine / polyethyleneimine selective layer.

3. The preparation method according to claim 2, characterized in that: In the step (1), the chlorinated polyvinyl fluoride ultrafiltration membrane is prepared by a non-solvent induced phase separation method, comprising: uniformly mixing chlorinated polyvinyl fluoride, poloxamer F127 and dimethylacetamide, stirring in a constant temperature water bath at 80-90° C. for 4-6 hours to obtain a uniform and transparent chlorinated polyvinyl fluoride casting solution, and standing until it is completely defoamed; finally, the chlorinated polyvinyl fluoride casting solution is drooled into a film, and phase separation is performed in a gel water bath at 30-40° C. to obtain a chlorinated polyvinyl fluoride ultrafiltration membrane.

4. The preparation method according to claim 3, characterized in that: The mass fraction of the chlorinated polyvinyl fluoride is 18-20 wt %, the mass fraction of poloxamer F127 is 5-10 wt %, and the mass fraction of dimethylacetamide is 70-78 wt %.

5. The preparation method according to claim 2, characterized in that: In the step (2), the total concentration of the polyetheramine and the polyethyleneimine is 1 to 1.5 g / L, and the concentration ratio of the polyetheramine to the polyethyleneimine is in the range of 1 / 9 to 5 / 5.

6. The preparation method according to claim 2, characterized in that: In the step (2), the surfactant is sodium dodecyl sulfate with a concentration of 1 to 2 g / L.

7. The preparation method according to claim 2, characterized in that: The deposition time in step (2) is 5 to 15 minutes.

8. The preparation method according to claim 2, characterized in that: The concentration of the n-hexane solution of trimesoyl chloride in step (3) is 1-2 g / L.

9. The preparation method according to claim 2, characterized in that: The time of the interfacial polymerization in step (3) is 5 to 10 minutes.

10. Use of the composite nanofiltration membrane based on the polyetheramine / polyethyleneimine selective layer as claimed in claim 1 in the treatment of dye wastewater.

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