CN115155327A - Nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine and preparation method thereof - Google Patents
Nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine and preparation method thereof Download PDFInfo
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- 239000012528 membrane Substances 0.000 title claims abstract description 97
- 238000001728 nano-filtration Methods 0.000 title claims abstract description 46
- 239000012267 brine Substances 0.000 title claims abstract description 30
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 69
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims abstract description 30
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims abstract description 27
- GLUUGHFHXGJENI-UHFFFAOYSA-N Piperazine Chemical compound C1CNCCN1 GLUUGHFHXGJENI-UHFFFAOYSA-N 0.000 claims abstract description 26
- NSMWYRLQHIXVAP-UHFFFAOYSA-N 2,5-dimethylpiperazine Chemical compound CC1CNC(C)CN1 NSMWYRLQHIXVAP-UHFFFAOYSA-N 0.000 claims abstract description 16
- DXOHZOPKNFZZAD-UHFFFAOYSA-N 2-ethylpiperazine Chemical compound CCC1CNCCN1 DXOHZOPKNFZZAD-UHFFFAOYSA-N 0.000 claims abstract description 16
- MIOPJNTWMNEORI-GMSGAONNSA-N (S)-camphorsulfonic acid Chemical compound C1C[C@@]2(CS(O)(=O)=O)C(=O)C[C@@H]1C2(C)C MIOPJNTWMNEORI-GMSGAONNSA-N 0.000 claims abstract description 10
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims abstract description 10
- 235000019333 sodium laurylsulphate Nutrition 0.000 claims abstract description 10
- UWCPYKQBIPYOLX-UHFFFAOYSA-N benzene-1,3,5-tricarbonyl chloride Chemical compound ClC(=O)C1=CC(C(Cl)=O)=CC(C(Cl)=O)=C1 UWCPYKQBIPYOLX-UHFFFAOYSA-N 0.000 claims abstract description 9
- 239000000243 solution Substances 0.000 claims description 64
- 239000012071 phase Substances 0.000 claims description 32
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 24
- 238000005266 casting Methods 0.000 claims description 18
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 16
- 229920002492 poly(sulfone) Polymers 0.000 claims description 16
- 239000004745 nonwoven fabric Substances 0.000 claims description 12
- 239000004952 Polyamide Substances 0.000 claims description 10
- 229920002647 polyamide Polymers 0.000 claims description 10
- 238000012695 Interfacial polymerization Methods 0.000 claims description 8
- 239000008346 aqueous phase Substances 0.000 claims description 8
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- 238000007790 scraping Methods 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 229940083575 sodium dodecyl sulfate Drugs 0.000 claims description 2
- 239000007864 aqueous solution Substances 0.000 claims 1
- 230000004907 flux Effects 0.000 abstract description 20
- 238000000926 separation method Methods 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 6
- 238000007796 conventional method Methods 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 21
- 150000002500 ions Chemical class 0.000 description 11
- 239000000203 mixture Substances 0.000 description 9
- 150000003839 salts Chemical class 0.000 description 7
- IFNWESYYDINUHV-UHFFFAOYSA-N 2,6-dimethylpiperazine Chemical compound CC1CNCC(C)N1 IFNWESYYDINUHV-UHFFFAOYSA-N 0.000 description 4
- 238000002791 soaking Methods 0.000 description 4
- 238000004132 cross linking Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- JOMNTHCQHJPVAZ-UHFFFAOYSA-N 2-methylpiperazine Chemical compound CC1CNCCN1 JOMNTHCQHJPVAZ-UHFFFAOYSA-N 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 229910001424 calcium ion Inorganic materials 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910001425 magnesium ion Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000012466 permeate Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- -1 carbonate radical ion Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000001493 electron microscopy Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/027—Nanofiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0006—Organic membrane manufacture by chemical reactions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0081—After-treatment of organic or inorganic membranes
- B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/56—Polyamides, e.g. polyester-amides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
- B01D71/68—Polysulfones; Polyethersulfones
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/22—Thermal or heat-resistance properties
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- Life Sciences & Earth Sciences (AREA)
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Abstract
The invention belongs to the technical field of nanofiltration membranes, and particularly discloses a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine and a preparation method thereof, wherein the conventional method is adopted, only the components of a water phase and an oil phase are improved, and the mass percentage of the water phase is as follows: 0.8 to 1.2% of piperazine, 0.4 to 0.6% of 2, 5-dimethylpiperazine, 0.4 to 0.6% of 2-ethylpiperazine, 1.0 to 1.4% of camphorsulfonic acid, 0.5 to 0.7% of triethylamine, 0.08 to 0.12% of sodium lauryl sulfate, and the balance of water; the oil phase comprises the following components in percentage by mass: 0.18 to 0.22 percent of trimesoyl chloride, 3 to 7 percent of toluene and the balance of naphtha. The prepared nanofiltration membrane can be used for pretreatment of salt lake brine at low temperature, and can achieve a good separation effect and guarantee water flux.
Description
Technical Field
The invention relates to the technical field of nanofiltration membranes, in particular to a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine and a preparation method thereof.
Background
The salt lake is one of salt water lakes, and the lakes with high salinity in arid areas. The salt lake is a product developed to the old age in the lake, is rich in various salts and is an important mineral resource. China is one of the most salt lakes in the world, starts from Jilin province in northeast, continues to the west, and passes through inner Mongolia autonomous region, ningxia Hui autonomous region, gansu province, xinjiang Uygur autonomous region, qinghai province, and Tibet autonomous region, and thousands of salt lakes are distributed.
The content data of each ion in the brine of a salt lake in the autonomous region of Tibet: 480 to 660ppm of lithium ion Li + 1.19g/L of magnesium ion Mg 2+ 0.16-0.35 g/L of calcium ion Ca 2+ 6.65-11.22 g/L sulfate ion SO 4 2- 0.25-0.49 g/L of carbonate ion CO 3 2- . Salt lake brine is pretreated to separate monovalent and divalent ions. The influence factors of the water production performance of the nanofiltration membrane include the pH value of inlet water, the inlet water temperature, the inlet water pressure and the like, the influence factors are very sensitive to the change of the inlet water temperature, the water flux can linearly increase along with the increase of the water temperature, the water flux is mainly increased due to the fact that the viscosity of water molecules penetrating through the membrane is reduced, and the diffusion performance is enhanced, otherwise, the water flux of the nanofiltration membrane can be seriously influenced under the low-temperature condition, and the reduction degree is related to the uniformity of the membrane, the size of pores, the thickness of a separation layer and the like. The autonomous region of Tibet has a special climate of 'four seasons in one day and winter all the year round'. The nanofiltration membrane prepared by the conventional method or a commercially available product can treat the salt lake brine at a high temperature in the daytime, and the flux at a low temperature at night is sharply reduced, even water is not produced, so that the development of the nanofiltration membrane suitable for pretreating the salt lake brine at a low temperature is significant.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine and a preparation method thereof.
The invention firstly provides a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine.
In order to achieve the purpose, the invention provides a preparation method of a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine, which is realized by the following technical scheme:
a preparation method of a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine comprises the following steps:
s1, mixing polysulfone and N, N-dimethylformamide, stirring and dissolving to obtain a uniform membrane casting solution, standing and defoaming, directly scraping the membrane casting solution on non-woven fabric by using a scraper, immersing the non-woven fabric into water to precipitate a polysulfone layer, and washing off a solvent to obtain a supporting layer membrane;
s2, immersing the supporting layer membrane obtained in the step S1 into a water phase solution, taking out, draining, immersing into an oil phase solution, performing interfacial polymerization to form a polyamide layer, and draining residual solution on the surface;
s3, rinsing the membrane obtained in the step S2, and passing through NaHSO 3 Treating the solution, and then immersing the solution into a glycerol solution for protection;
wherein the water phase comprises the following components in percentage by mass: 0.8 to 1.2% of piperazine, 0.4 to 0.6% of 2, 5-dimethylpiperazine, 0.4 to 0.6% of 2-ethylpiperazine, 1.0 to 1.4% of camphorsulfonic acid, 0.5 to 0.7% of triethylamine, 0.08 to 0.12% of sodium lauryl sulfate, and the balance of water; the oil phase comprises the following components in percentage by mass: 0.18 to 0.22 percent of trimesoyl chloride, 3 to 7 percent of toluene and the balance of naphtha.
Because the cross-linking density of the nanofiltration membrane prepared by the conventional piperazine is higher, the piperazine, the 2, 5-dimethylpiperazine and the 2-ethylpiperazine are selected to be combined for use in the water phase, the piperazine with a group is selected to increase the steric hindrance, the cross-linking density is reduced, the flux is improved, and the combination can keep excellent performance under the low-temperature condition after being screened.
As a preferable technical scheme of the invention, in the step S1, the mass fraction of the polysulfone is 14-16.5%, the mass fraction of the N, N-dimethylformamide is 83.5-86%, the viscosity of the casting solution is 380-460 mPas, the casting solution is kept still and defoamed for 20-30 h, and the thickness of the polysulfone layer is 18-28 μm.
Preferably, the water phase composition in step S2 is 1.0% by mass of piperazine, 0.5% by mass of 2, 5-dimethylpiperazine, 0.5% by mass of 2-ethylpiperazine, 1.2% by mass of camphorsulfonic acid, 0.6% by mass of triethylamine, 0.1% by mass of sodium laurylsulfate, and the balance of water, and the oil phase composition is: 0.2 percent of trimesoyl chloride, 5 percent of toluene and the balance of naphtha.
Preferably, the supporting layer membrane is immersed in the water phase solution for 30 to 90 seconds in the step S2, the residual solution on the surface is taken out and drained, the whole membrane is immersed in the oil phase solution for 10 to 60 seconds to perform interfacial polymerization reaction to form a polyamide layer, and the polyamide layer is drained for subsequent treatment.
Preferably, deionized water is used for rinsing in step S3, and the rinsing time is 5-10 min.
Preferably, naHSO is described in step S3 3 The mass fraction of the solution is 5-7%, and the treatment time is 3-10 min.
Preferably, the mass fraction of the glycerol solution in the step S3 is 5-10%, and the protection time is 3-10 min.
The invention also provides the application of the nanofiltration membrane in pretreatment of salt lake brine at low temperature, and the nanofiltration membrane can be applied to a water treatment environment at the temperature of less than 10 ℃. Through the assembled membrane element, the water flux and the separation effect can be improved at a lower temperature (0 ℃) when the field test is carried out on the brine of a salt lake in the autonomous region of Tibet.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method is simple, the obtained nanofiltration membrane separation layer can be used for pretreating salt lake brine at a lower temperature, the monovalent and divalent ion separation effects are achieved, the water flux is increased, the defects of the prior art are overcome, the low-temperature resistance of the nanofiltration membrane is improved, and the use environment of the nanofiltration membrane is expanded.
Drawings
Fig. 1 is scanning electron micrographs of the surface (a) and cross section (b) of a nanofiltration membrane prepared in example 1 of the present invention.
FIG. 2 is a scanning electron microscope image of the surface (a) and cross section (b) of the nanofiltration membrane prepared in comparative example 7 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The test methods used in the examples of the present invention are all conventional methods unless otherwise specified; the materials, reagents and the like used are, unless otherwise specified, commercially available reagents and materials.
Example 1
A nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine is prepared by the following steps:
s1, mixing 15 percent of polysulfone with 85 percent of N and N-dimethylformamide, stirring and dissolving the mixture into a uniform membrane casting solution with the viscosity of 432mPa & S, standing and defoaming the uniform membrane casting solution for 24 hours, directly scraping the membrane casting solution on non-woven fabrics by using a scraper, immersing the non-woven fabrics into water to precipitate a polysulfone layer with the thickness of 20 mu m, and washing off a solvent to obtain a supporting layer membrane;
and S2, immersing the supporting layer membrane obtained in the step S1 into the water phase solution for 60S, taking out and draining the residual solution on the surface, immersing the whole membrane into the oil phase solution for 30S to perform interfacial polymerization reaction to form a polyamide layer, and draining for subsequent treatment.
S3, rinsing the membrane obtained in the step S2 by using deionized water for 10min, and processing the membrane by 6 percent 3 Treating the solution for 8min, and then soaking the solution in 8% glycerol solution for protection for 5min;
wherein the water phase comprises the following components in percentage by mass: 1.0% piperazine, 0.5%2, 5-dimethylpiperazine, 0.5% 2-ethylpiperazine, 1.2% camphorsulfonic acid, 0.6% triethylamine, 0.1% sodium lauryl sulfate, the balance water;
the oil phase comprises the following components in percentage by mass: 0.2 percent of trimesoyl chloride, 5 percent of toluene and the balance of naphtha.
Example 2
A nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine is prepared by the following method:
s1, mixing 14% of polysulfone with 86% of N and N-dimethylformamide, stirring and dissolving the mixture into a uniform membrane casting solution, keeping the viscosity of the uniform membrane casting solution at 380mPa & S, standing and defoaming the uniform membrane casting solution for 20 hours, directly scraping the membrane casting solution on non-woven fabrics by using a scraper, immersing the non-woven fabrics into water to precipitate a polysulfone layer with the thickness of 18 microns, and washing off a solvent to obtain a supporting layer membrane;
and S2, immersing the supporting layer membrane obtained in the step S1 into the water phase solution for 30S, taking out and draining the residual solution on the surface, immersing the whole membrane into the oil phase solution for 10S to perform interfacial polymerization reaction to form a polyamide layer, and draining for subsequent treatment.
S3, rinsing the membrane obtained in step S2 with deionized water for 5min, and% 3 Treating the solution for 10min, and then soaking in 5% glycerol solution for protection for 10min;
wherein the water phase comprises the following components in percentage by mass: 0.8% piperazine, 0.6%2, 5-dimethylpiperazine, 0.6% 2-ethylpiperazine, 1.0% camphorsulfonic acid, 0.5% triethylamine, 0.08% sodium lauryl sulfate, the balance water;
the oil phase comprises the following components in percentage by mass: 0.18 percent of trimesoyl chloride, 3 percent of toluene and the balance of naphtha.
Example 3
A nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine is prepared by the following method:
s1, mixing 16.5 percent of polysulfone with 83.5 percent of N and N-dimethylformamide, stirring and dissolving to obtain a uniform membrane casting solution, keeping the viscosity in a range of 460mPa & S, standing and defoaming for 30 hours, directly scraping the membrane casting solution on non-woven fabrics by using a scraper, immersing the non-woven fabrics into water to precipitate a 28 mu m polysulfone layer, and washing off a solvent to obtain a supporting layer membrane;
and S2, immersing the supporting layer membrane obtained in the step S1 into the water phase solution for 90S, taking out and draining the residual solution on the surface, immersing the whole membrane into the oil phase solution for 60S to perform interfacial polymerization reaction to form a polyamide layer, and draining for subsequent treatment.
S3, rinsing the membrane obtained in the step S2 by using deionized water for 8min, and processing the membrane to 7 percent 3 Treating the solution for 3min, and then soaking in 10% glycerol solution for protection for 3min;
wherein the water phase comprises the following components in percentage by mass: 1.2% piperazine, 0.4%2, 5-dimethylpiperazine, 0.4% 2-ethylpiperazine, 1.4% camphorsulfonic acid, 0.7% triethylamine, 0.12% sodium lauryl sulfate, the balance water;
the oil phase comprises the following components in percentage by mass: 0.22 percent of trimesoyl chloride, 7 percent of toluene and the balance of naphtha.
Example 4
A nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine is prepared by the following method:
s1, mixing 16.5% of polysulfone with 83.5% of N and N-dimethylformamide, stirring and dissolving to obtain a uniform membrane casting solution, wherein the viscosity range is 460mPa & S, standing and defoaming for 30h, directly scraping the membrane casting solution on non-woven fabrics by using a scraper, immersing the non-woven fabrics in water to precipitate a 28-micron polysulfone layer, and washing off a solvent to obtain a supporting layer membrane;
and S2, immersing the supporting layer membrane obtained in the step S1 into the water phase solution for 90S, taking out and draining the residual solution on the surface, immersing the whole membrane into the oil phase solution for 60S to perform interfacial polymerization reaction to form a polyamide layer, and draining for subsequent treatment.
S3, rinsing the membrane obtained in the step S2 by using deionized water for 8min, and processing the membrane to 7 percent 3 Treating the solution for 3min, and then soaking the solution in 10% glycerol solution for protection for 3min;
wherein the water phase comprises the following components in percentage by mass: 1.1% piperazine, 0.5%2, 5-dimethylpiperazine, 0.4% 2-ethylpiperazine, 1.4% camphorsulfonic acid, 0.7% triethylamine, 0.12% sodium lauryl sulfate, the balance water;
the oil phase comprises the following components in percentage by mass: 0.21 percent of trimesoyl chloride, 7 percent of toluene and the balance of naphtha.
Comparative example 1
Comparative example 1 differs from example 1 in that the aqueous phase composition in step S2 lacks 2, 5-dimethylpiperazine, and the other preparation steps and conditions are the same as in example 1 and will not be repeated here.
Comparative example 2
Comparative example 2 differs from example 1 in that the composition of the aqueous phase in step S2 lacks 2-ethylpiperazine, and the other preparation steps and conditions are the same as in example 1 and will not be repeated here.
Comparative example 3
Comparative example 3 differs from example 1 in that 2, 6-dimethylpiperazine and 2-methylpiperazine were used in the aqueous phase in step S2 instead of 2, 5-dimethylpiperazine and 2-ethylpiperazine, respectively, and the other preparation steps and conditions were the same as in example 1 and will not be described again here.
Comparative example 4
Comparative example 4 is different from example 1 in that 2, 6-dimethylpiperazine is used instead of 2, 5-dimethylpiperazine in the aqueous phase composition in step S2, and other preparation steps and conditions are the same as those in example 1 and will not be repeated here.
Comparative example 5
Comparative example 5 differs from example 1 in that the composition in the aqueous phase in step S2 is 2-methylpiperazine instead of 2-ethylpiperazine, and the other preparation steps and conditions are the same as in example 1 and will not be repeated here.
Comparative example 6
Comparative example 6 differs from example 1 in that the aqueous phase in step S2 consists of 1.5% piperazine, 0.25%2, 5-dimethylpiperazine, 0.25% 2-ethylpiperazine, 0.6% camphorsulfonic acid, 0.3% triethylamine, 0.04% sodium dodecylsulfate, and the balance water
Comparative example 7 differs from example 1 in that the aqueous phase composition in step S2 lacks 2, 5-dimethylpiperazine and 2-ethylpiperazine, and the other preparation steps and conditions are the same as in example 1 and will not be described again here.
The nanofiltration membranes prepared in the examples and the comparative examples are subjected to performance tests.
The nanofiltration membranes prepared in example 1 and comparative example 7 were subjected to surface topography electron microscopy characterization, as shown in fig. 1 and fig. 2, respectively. It can be seen that the nanofiltration membrane prepared in the comparative example 7 has high cross-linking density, compact appearance and low porosity, which results in low water flux, and the nanofiltration membrane prepared in the embodiment 1 of the invention has obviously improved porosity and greatly improved water flux.
The water flux and the desalination rate data of the membrane are measured according to a GB/T34242-2017 nanofiltration membrane test method:
measuring the water flux F and the salt rejection R of the nanofiltration membrane under the conditions that the pressure is 0.70MPa and the temperature is 25 ℃, and calculating the water flux F through the following formula:
f = V/(A.t), wherein F is water flux L/(m) 2 H), V is the volume L of the permeate collected in the time t, A is the effective membrane area (m) of the nanofiltration membrane 2 ) And t is the time (h) taken to collect a volume V of permeate.
The salt rejection R is calculated by the following formula:
r = (Cf-Cp)/Cf x 100%, wherein R is the salt rejection, the ion content in the Cp permeation solution is mg/L, and Cf is the ion content in the test solution is mg/L.
The results are shown in Table 1.
TABLE 1
As is clear from Table 1, the flux in examples 1 to 4 was 140.8 to 153.9L/(m) 2 H), the removal rate of the univalent ions is 22.44-23.81%, and the efficiency is better than that of a comparative example when the univalent ions are extracted from a salt lake. Comparative example water flux is much lower than that of example, and compared with comparative example 5, the 2-ethylpiperazine adopted in example 1 is superior because substituent chains are longer, the formed separation layer is smaller in compactness, the flux is correspondingly increased, and the influence of temperature reduction on the flux is reduced; comparative example 4 compared to example 1, 2, 6-dimethylpiperazine was inferior to 2, 5-dimethylpiperazine because 2, 6-dimethylpiperazine was highly sterically hindered and not easily crosslinked, and the uniformity of the film was poor. Therefore, the invention improves the water flux while ensuring the effect of separating monovalent and divalent ions by screening the water phase components during the preparation of the nanofiltration membrane.
Application example
The nanofiltration membrane, the water inlet grid and the water production grid prepared in the example 1 are rolled around a water production central pipe, and are packaged with an end cover and a shell to form a membrane element, the membrane element is tested on site in salt lake brine in a Tibetan autonomous region, and the ion content data of the salt lake brine in the Tibetan autonomous region are as follows: 480 to 660ppm of lithium ion Li + 1.19g/L of magnesium ion Mg 2+ 0.16-0.35 g/L of calcium ion Ca 2+ 6.65-11.22 g/L sulfate ion SO 4 2- 0.25-0.49 g/L carbonate radical ion CO 3 2- . The test conditions and the result data are shown in Table 2.
TABLE 2
As can be seen from Table 2, the nanofiltration membrane prepared by the invention can be used for low-temperature pretreatment of salt lake brine, has remarkable effect and is superior to the commercially available product, the water flux under the pressure of 15Bar can reach 160L/h, the rejection rate of monovalent ions is 6.03-8.24%, the rejection rate of divalent ions is 48.89-91.44%, and the good separation effect can be achieved when the temperature is as low as 0.8 ℃.
The above-mentioned embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, and are not intended to limit the specific embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention claims should be included in the protection scope of the present invention claims.
Claims (9)
1. A preparation method of a nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine is characterized by comprising the following steps:
s1, mixing, stirring and dissolving polysulfone and N, N-dimethylformamide to obtain a uniform membrane casting solution, standing and defoaming, directly scraping the membrane casting solution on non-woven fabric, then immersing the non-woven fabric into water to precipitate a polysulfone layer, and washing off a solvent to obtain a supporting layer membrane;
s2, immersing the supporting layer membrane obtained in the step S1 into a water phase solution, taking out, draining, immersing into an oil phase solution, performing interfacial polymerization to form a polyamide layer, and draining residual solution on the surface;
s3, rinsing the membrane obtained in the step S2, and passing through NaHSO 3 Treating the solution, and then immersing the solution into a glycerol solution for protection;
wherein the water phase comprises the following components in percentage by mass: 0.8 to 1.2% of piperazine, 0.4 to 0.6% of 2, 5-dimethylpiperazine, 0.4 to 0.6% of 2-ethylpiperazine, 1.0 to 1.4% of camphorsulfonic acid, 0.5 to 0.7% of triethylamine, 0.08 to 0.12% of sodium lauryl sulfate, and the balance of water; the oil phase comprises the following components in percentage by mass: 0.18 to 0.22 percent of trimesoyl chloride, 3 to 7 percent of toluene and the balance of naphtha.
2. The preparation method of the nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine according to claim 1, wherein in the step S1, the mass fraction of the polysulfone is 14-16.5%, the mass fraction of N, N-dimethylformamide is 83.5-86%, the viscosity of the casting solution is 380-460 mPa-S, standing and defoaming are performed for 20-30 h, and the thickness of the polysulfone layer is 18-28 μm.
3. The method of claim 1, wherein the aqueous phase in step S2 comprises 1.0% by weight of piperazine, 0.5% by weight of 2, 5-dimethylpiperazine, 0.5% by weight of 2-ethylpiperazine, 1.2% by weight of camphorsulfonic acid, 0.6% by weight of triethylamine, 0.1% by weight of sodium dodecylsulfate, and the balance of water, and the oil phase comprises: 0.2 percent of trimesoyl chloride, 5 percent of toluene and the balance of naphtha.
4. The preparation method of the nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine according to claim 1, wherein the supporting layer membrane is immersed in the aqueous solution for 30 to 90 seconds in step S2, the residual solution on the surface is removed, the whole membrane is immersed in the oil phase solution for 10 to 60 seconds to perform interfacial polymerization reaction, a polyamide layer is formed, and the polyamide layer is drained for subsequent treatment.
5. The preparation method of the nanofiltration membrane suitable for low-temperature pretreatment of salt lake brine according to claim 1, wherein the rinsing in step S3 is performed with deionized water for 5-10 min.
6. The method for preparing the nanofiltration membrane suitable for low-temperature pretreatment of the salt lake brine according to claim 1, wherein the NaHSO is obtained in step S3 3 The mass fraction of the solution is5 to 7 percent, and the treatment time is 3 to 10min.
7. The preparation method of the nanofiltration membrane suitable for low-temperature pretreatment of the salt lake brine according to claim 1, wherein the glycerol solution in the step S3 is 5-10% by mass, and the protection time is 3-10 min.
8. Nanofiltration membrane prepared by the process according to any one of claims 1 to 7.
9. The use of nanofiltration membranes according to claim 8 in salt lake brine pretreatment at low temperatures, wherein the nanofiltration membranes are suitable for use in water treatment environments at < 10 ℃.
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| CN117654272A (en) * | 2024-02-01 | 2024-03-08 | 蓝星（杭州）膜工业有限公司 | Positively charged nanofiltration membrane and preparation method and application thereof |
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