CN114130198A - Method for controllably adjusting aperture of polyamide nanofiltration membrane - Google Patents
Method for controllably adjusting aperture of polyamide nanofiltration membrane Download PDFInfo
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- CN114130198A CN114130198A CN202111481616.1A CN202111481616A CN114130198A CN 114130198 A CN114130198 A CN 114130198A CN 202111481616 A CN202111481616 A CN 202111481616A CN 114130198 A CN114130198 A CN 114130198A
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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
- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
- B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
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- 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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Abstract
本发明提供了一种纳滤膜孔径可控调节的方法，利用表面活性剂溶液对纳滤膜进行处理，使表面活性剂与膜表面负电低聚物吸附、包裹、剥离，经过处理的纳滤膜孔径实现可控变大，通量显著提高，在保证硫酸钠截留99％前提下通量提升70％以上；通量达到处理前通量的200％后硫酸钠截留依然能保持在95％以上。本发明的后处理方法过程简单，可操作性强，成本低，工艺条件易于控制，具有广阔的规模化应用前景。
The invention provides a method for controllably adjusting the pore size of nanofiltration membrane. The nanofiltration membrane is treated with a surfactant solution, so that the surfactant and the negatively charged oligomers on the surface of the membrane are adsorbed, wrapped and peeled off. The pore size of the membrane can be controlled to become larger, and the flux is significantly improved. The flux is increased by more than 70% under the premise of ensuring that the sodium sulfate interception is 99%; the sodium sulfate interception can still remain above 95% after the flux reaches 200% of the flux before treatment. . The post-processing method of the invention has the advantages of simple process, strong operability, low cost, easy control of process conditions, and broad scale application prospect.
Description
Technical Field
The invention relates to the technical field of nanofiltration membranes and the field of water separation, in particular to a post-treatment method of a polyamide nanofiltration membrane, and particularly relates to a method for controllably adjusting the pore diameter of the polyamide nanofiltration membrane.
Background
Membrane separation is a separation technology which uses a membrane as a separation medium and realizes the purposes of purification, sieving, concentration and the like on a mixed system under the action of a driving force. Compared with the traditional separation technology, the method has the advantages of high selectivity, low energy consumption, simple operation, low maintenance and operation cost and the like. Since the industrial application in the 60 th of the 20 th century, the membrane separation technology has been widely applied to the fields of seawater desalination, wastewater treatment, gas separation, material purification and the like.
Nanofiltration is a microporous membrane between a porous ultrafiltration membrane and a dense reverse osmosis membrane. Compared with a reverse osmosis membrane, the nanofiltration membrane has relatively large flux under the condition of low operating pressure, so that the energy consumption and the treatment cost are greatly reduced. Because the pore diameter of the membrane is smaller than that of an ultrafiltration membrane and the surface of the membrane contains abundant functional groups, the small molecular organic matters or multivalent salts can be separated through pore diameter sieving and electrostatic effect. Therefore, the method is widely applied to the aspects of wastewater treatment, material concentration, separation and purification and the like.
The water flux of the nanofiltration membrane is an important index of the application performance of the nanofiltration membrane, the nanofiltration membrane is closely related to the separation cost and efficiency, and the high-flux nanofiltration membrane can obviously reduce the energy consumption and cost in the application. The method for preparing the polyamide nanofiltration membrane by the interfacial polymerization method has the advantages of low cost, simple operation, continuous production and the like, and is widely applied, but the interfacial polymerization occurs at the moment of contact of two monomers, so that more accurate regulation and control of reaction are difficult to realize, and the flux improvement is still the target pursued at present. The membrane aperture is regulated and controlled by post-processing the membrane, so that the flux is greatly improved, and the method has a great development prospect.
Disclosure of Invention
The invention aims to solve the technical problem of how to improve the water flux of a polyamide nanofiltration membrane, and provides a method for controllably adjusting the aperture of a polyamide nanofiltration membrane.
In order to solve the technical problems, the invention is realized by the following technical scheme:
the method for controllably adjusting the pore diameter of the polyamide nanofiltration membrane comprises the following steps:
1) building a cross flow testing device, forming a loop by the membrane component and the feed liquid tank, wherein the cross flow testing device is provided with a temperature control unit and a pressure control unit;
2) loading a polyamide nanofiltration membrane into a membrane component of a cross-flow testing device, and operating the cross-flow testing device by taking a surfactant solution as a feed liquid;
3) and (4) taking out the polyamide nanofiltration membrane after the operation is finished, and washing the polyamide nanofiltration membrane by using water to remove the surfactant to obtain a sample.
Preferably, the surfactant is one of cetyl trimethyl ammonium bromide and cetyl pyridinium bromide, and the mass concentration of the surfactant solution is 300-1000 ppm.
Preferably, the membrane module operating pressure is 0.2-0.7 Mpa.
Preferably, the membrane module run time is 0.5 to 3 hours.
Preferably, the membrane module operating temperature is 20-35 ℃.
Preferably, the rinsing time is 0.5 to 3 hours.
The invention has the beneficial effects that:
the invention provides a method for controllably adjusting the aperture of a nanofiltration membrane, which is characterized in that a surface active agent solution is used for processing the nanofiltration membrane, so that the surface active agent and negative electric oligomer on the surface of the membrane are adsorbed, wrapped and stripped, the aperture of the processed nanofiltration membrane is controllably enlarged, the flux is obviously improved, and the flux is improved by more than 70 percent on the premise of ensuring 99 percent interception of sodium sulfate; the sodium sulfate retention can still be kept above 95% after the flux reaches 200% of the flux before treatment.
The post-treatment method has the advantages of simple process, strong operability, low cost, easily controlled process conditions and wide scale application prospect.
Drawings
The following detailed description is made with reference to the accompanying drawings and embodiments of the present invention
FIG. 1 is a schematic view of a cross-flow apparatus;
FIG. 2 pore size variation for different pH treatments;
FIG. 3 pore size distribution for different pH treatments;
FIG. 4 flux variation and rejection for different pH treatments;
Detailed Description
The preparation environment of all the initial nanofiltration membranes in the invention is as follows: the temperature is 25 ℃, the humidity is 40%, and the pressure is normal.
The present invention will be illustrated and described in greater detail hereinafter with reference to a number of specific embodiments, which however are given purely by way of illustration and do not represent an exhaustive solution to the inventive concept, and therefore should not be taken as a limitation to the general solution of the present invention, but rather, it will be apparent to the skilled person that insubstantial modifications, for example simple changes or substitutions in technical features having the same or similar technical effect, are within the scope of protection of the present invention.
Example 1:
the embodiment provides a method for controllably adjusting the aperture of a nanofiltration membrane, which comprises the following steps:
(1) preparing a polyamide nanofiltration membrane: polysulfone (PSF) ultrafiltration membrane is used as a base membrane, 0.2% piperazine solution is used as a water phase, 0.25% TMC solution is used as an oil phase, 1% anhydrous sodium phosphate is used as a buffering agent, and the pH value is adjusted to 10 by concentrated hydrochloric acid; pouring the water phase onto the bottom film, standing for 5min, pouring off the oil phase for 1min, and oven drying at 60 deg.C for 10min to obtain polyamide film.
(2) Preparing a surfactant solution: cetyl trimethylammonium bromide was dissolved in deionized water at a mass concentration of 500 ppm.
(3) And (2) loading the nanofiltration membrane prepared in the step (1) into a membrane component, operating the prepared solution as a feed liquid at 25 ℃ and 0.5Mpa in a cross-flow device, and cleaning with deionized water after the flux is stable.
(4) And (3) testing the flux and desalination of the original membrane and the membrane obtained in the step (3) in a nanofiltration device, wherein the testing temperature is 25 ℃, the testing pressure is 5bar, and the water flux and desalination performance after treatment are measured.
Example 2:
the nanofiltration membrane was treated as in example 1, except that in step (2) cetyltrimethylammonium bromide was used instead of cetylpyridinium bromide.
Example 3:
the nanofiltration membrane was treated by the method of example 1, except that step (3) was not treated to stabilize the flux but was treated for 20min and then rinsed with deionized water.
Example 4:
the nanofiltration membrane was treated as in example 1, except that step (3) was not treated to stabilize flux but was rinsed with deionized water after 40min of treatment.
Example 5:
the nanofiltration membrane was treated by the method of example 1, except that step (3) was not treated to stabilize the flux but treated for 60min before the deionized water rinse.
Example 6:
the nanofiltration membrane was treated by the method of example 1, except that step (3) was not treated to stabilize the flux but was treated for 80min and then rinsed with deionized water.
Example 7:
the nanofiltration membrane was treated as in example 1, except that sodium phosphate was added at a concentration of 500ppm by mass in step (2) and the pH was adjusted to 4 with hydrochloric acid.
Example 8:
the nanofiltration membrane was treated in the same manner as in example 1, except that sodium phosphate was added in a concentration of 500ppm by mass in step (2) and the pH was adjusted to 5.5 with hydrochloric acid.
Example 9:
the nanofiltration membrane was treated as in example 1, except that sodium phosphate was added at a concentration of 500ppm by mass in step (2) and the pH was adjusted to 7 with hydrochloric acid.
Example 10:
the nanofiltration membrane was treated as in example 1, except that sodium phosphate was added at a concentration of 500ppm by mass in step (2) and the pH was adjusted to 8.5 with hydrochloric acid.
Example 11:
the nanofiltration membrane was treated as in example 1, except that sodium phosphate was added at a concentration of 500ppm by mass in step (2) and the pH was adjusted to 10 with hydrochloric acid.
Example 12:
the nanofiltration membrane was treated in the same manner as in example 1, except that sodium phosphate was added in an amount of 500ppm by mass in step (2).
Example 13:
the nanofiltration membrane was treated by the method of example 1, except that the TMC concentration in step (1) was 0.05%; (2) adding sodium phosphate with the mass concentration of 500 ppm.
Example 14:
the nanofiltration membrane was treated by the method of example 1, except that the TMC concentration in step (1) was 0.15%; (2) adding sodium phosphate with the mass concentration of 500 ppm.
Example 15:
building a cross flow testing device:
see figure 1. The cross flow testing device comprises a feed liquid tank 1, a constant temperature unit 2 is arranged on the feed liquid tank, a stirring paddle 3 and a thermometer 4 are arranged in the feed liquid tank, the feed liquid tank 1, a pump 6, a pressure gauge 7, a membrane module 8, a flowmeter 10 and a flow regulating valve 12 form a loop, wherein the membrane module 8 is provided with a clear liquid outlet 9, and a concentrated liquid outlet 11 of the membrane module returns to the feed liquid tank 1. The feed liquid tank is also provided with a water outlet 5.
The nanofiltration membrane sample obtained by the treatment in the above example and the nanofiltration membrane prepared in step (1) were tested for desalination rate and water flux, respectively, to examine the influence of different treatment conditions on the performance of the nanofiltration membrane. The average of three consecutive tests was taken as the final result in a cross-flow mode at a test temperature of 25 ℃ and a test pressure of 5 bar.
The water flux calculation formula is as follows:
wherein F represents water flux, V represents volume of collected produced water, A represents effective membrane area, and t represents produced water collection time.
The salt rejection calculation formula is as follows:
wherein R represents the salt rejection, C1 represents the conductivity of the test solution, and C2 represents the conductivity of the produced water
Wherein the test result of (1) preparing the nanofiltration membrane is as follows: water pipeAmount 9.0945. + -. 0.5 L.m-2·h-1·bar-1Sodium sulfate salt rejection of 99.16% + -1%
(I) Effect of different surfactants on salt rejection and Water flux
From the above table, it is seen that both surfactant solubilities have an enhancing effect on the flux of the membrane, with cetyltrimethylammonium bromide being preferred over cetylpyridinium bromide.
(II) influence of different surfactant treatment time on salt rejection rate and water flux
It is seen from the table above that flux increases with treatment time, but the magnitude of the flux increase slows down with time.
Examples 7-14 the flux and rejection were measured and the rejection was measured by PEG (200, 400, 600, 800, 1800) and the molecular weight at 90% rejection of the membrane. The Stokes diameter (ds, nm) of a PEG molecule can be calculated by the following formula:
(III) influence of surfactants with different pH on desalting rate, water flux and pore size
From the above table, it is seen that as the alkalinity of the surfactant solution increases, the pore size increases and the flux increases, but the rejection decreases under strong alkalinity, and the optimum pH should be between 5.5 and 8.5 in view of the combination of flux and rejection.
(IV) the influence of the treatment of nanofiltration membranes with different proportions by the surfactant on the desalination rate and water flux of the nanofiltration membranes
In conclusion, the piperazine polyamide nanofiltration membrane is treated by using a proper surfactant solution, so that the aperture can be increased, the water flux of the membrane material is obviously improved, and the original desalination rate can be kept at a higher level. In the treatment process, the types of the surfactants, the pH value and the treatment effect of the nanofiltration membrane during the soaking treatment have certain influences.
Although the preferred embodiments of the present invention have been described, the present invention is not limited to the above-mentioned embodiments, which are only illustrative and not restrictive, and those skilled in the art can make various modifications without departing from the spirit and scope of the present invention, which falls within the protection scope of the present invention.
Claims (6)
1. The method for controllably adjusting the pore diameter of the polyamide nanofiltration membrane comprises the following steps:
1) building a cross flow testing device, forming a loop by the membrane component and the feed liquid tank, wherein the cross flow testing device is provided with a temperature control unit and a pressure control unit;
2) loading a polyamide nanofiltration membrane into a membrane component of a cross-flow testing device, and operating the cross-flow testing device by taking a surfactant solution as a feed liquid;
3) and (4) taking out the polyamide nanofiltration membrane after the operation is finished, and washing the polyamide nanofiltration membrane by using water to remove the surfactant to obtain a sample.
2. The method of claim 1, wherein: the surfactant is one of cetyl trimethyl ammonium bromide and cetyl pyridinium bromide, and the mass concentration of the surfactant solution is 300-1000 ppm.
3. The method of claim 1, wherein: the operating pressure of the membrane component is 0.2-0.7 MPa.
4. The method of claim 1, wherein: the operation time of the membrane module is 0.5-3 h.
5. The method of claim 1, wherein: the operating temperature of the membrane module is 20-35 ℃.
6. The method of claim 1, wherein: the washing time is 0.5-3 h.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05131190A (en) * | 1991-11-11 | 1993-05-28 | Nitto Denko Corp | Treatment of spent liquid containing acrylate-based substance |
| JP2007253109A (en) * | 2006-03-24 | 2007-10-04 | Nitto Denko Corp | Method for manufacturing dry composite semipermeable membrane |
| JP2009112927A (en) * | 2007-11-05 | 2009-05-28 | Japan Organo Co Ltd | Method of modifying separation membrane, separation membrane modified thereby, modifier and apparatus for this modification |
| US20130324678A1 (en) * | 2011-03-09 | 2013-12-05 | Kurita Water Industries Ltd | Method for improving rejection of permeable membrane, treatment agent for improving rejection, and permeable membrane |
| CN104271220A (en) * | 2011-12-07 | 2015-01-07 | 杜邦营养生物科学有限公司 | Nanofiltration methods for enhanced solute flux through pretreatment |
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2021
- 2021-12-07 CN CN202111481616.1A patent/CN114130198A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05131190A (en) * | 1991-11-11 | 1993-05-28 | Nitto Denko Corp | Treatment of spent liquid containing acrylate-based substance |
| JP2007253109A (en) * | 2006-03-24 | 2007-10-04 | Nitto Denko Corp | Method for manufacturing dry composite semipermeable membrane |
| JP2009112927A (en) * | 2007-11-05 | 2009-05-28 | Japan Organo Co Ltd | Method of modifying separation membrane, separation membrane modified thereby, modifier and apparatus for this modification |
| US20130324678A1 (en) * | 2011-03-09 | 2013-12-05 | Kurita Water Industries Ltd | Method for improving rejection of permeable membrane, treatment agent for improving rejection, and permeable membrane |
| CN104271220A (en) * | 2011-12-07 | 2015-01-07 | 杜邦营养生物科学有限公司 | Nanofiltration methods for enhanced solute flux through pretreatment |
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Application publication date: 20220304 |