KR102464154B1 - An ultrafiltration membrane and its preparation method - Google Patents

Abstract

The present invention relates to an ultrafiltration membrane having high mechanical properties and a method for manufacturing the same. In the present invention, since ammonium lignosulfonate having high mechanical properties is added to the cast membrane solution, the retention rate of the ultrafiltration membrane of the present invention is improved.

Description

Ultrafiltration membrane and its manufacturing method

The present invention relates to an ultrafiltration membrane, and more particularly, to an ultrafiltration membrane having high mechanical properties and a method for manufacturing the same.

At present, the ultrafiltration membrane is pressurized for a long time and its mechanical properties are not good, so that the product life of the ultrafiltration membrane is shortened, so that the ultrafiltration membrane in the membrane module needs to be replaced frequently.

Therefore, it is necessary to develop an ultrafiltration membrane with improved mechanical properties. It is an object of the present invention to provide an ultrafiltration membrane having excellent mechanical properties and a method for manufacturing the same.

According to one aspect of the present invention, ammonium lignosulfonate is added to the cast membrane solution.

According to one aspect of the present invention there is provided a method for manufacturing an ultrafiltration membrane, the method comprising:

Sulfonated polysulfone, ammonium lignosulfonate and aluminum oxide are dissolved in N,N-dimethylacetamide at a first temperature to form an initial cast film solution, and at a second temperature and second temperature to obtain a treated cast film solution. 1 left for defoaming for a first period of time at 1 humidity;

pouring the treated cast film solution onto a glass substrate using a film applicator to obtain a liquid state film with a thickness of 150-250 μm;

allowing the liquid state film to volatilize at a third temperature and a second humidity for a second period and leaving the glass substrate on which the liquid state film is formed in a coagulation bath to solidify the liquid state film to obtain a solid state film;

removing the solid state membrane from the coagulation bath, air drying and drying in an oven for a third period to form an ultrafiltration membrane.

In an embodiment, the first temperature is 50-90°C, the second temperature is 15-25°C, the third temperature is 15-25°C, the first humidity is 10-30%, and the second temperature is 15-25°C. 2 Humidity is 10-30%, the first period is 6-10 hours, the second period is 10-120 seconds, and the third period is 60 minutes.

In one embodiment, in the treated cast membrane solution, the mass concentration of the sulfonated polysulfone is 20-40%, and the mass ratio between the ammonium lignosulfonate and the sulfonated polysulfone is 0.1-1:1 and the mass ratio between the aluminum oxide and the sulfonated polysulfone is 0.01-0.1:1.

In one embodiment, the coagulation bath uses deionized water.

According to one aspect of the present invention, an ultrafiltration membrane according to the above method is provided.

According to the present invention, ammonium lignosulfonate is added to the cast membrane solution to improve the reaction rate of the ultrafiltration membrane.

Example 1

Step 1: 32 g of sulfonated polysulfone, 16 g of ammonium lignosulfonate and 1.6 g of aluminum oxide were added to a three-necked flask;

Step 2: 50 g of N,N-dimethylacetamide was added to a three-necked flask to obtain a mixture, as a result of which the mixture was stirred at 65° C. for 5 hours;

Step 3: To remove foam, it was left in an atmosphere of 20° C. and 20% humidity for 8 hours to remove foam and obtain a uniform casting membrane solution without foam;

Step 4: The cast film solution was poured onto the glass substrate by a film applicator to obtain a 200 μm thick liquid state film;

Step 5: The glass substrate with the liquid state film was left for 15 seconds in an atmosphere of 20° C. and 20% relative humidity for volatilization;

Step 6: The glass substrate with the liquid state film was placed in deionized water to solidify the liquid state film into a solid state film;

Step 7: The solid state membrane was taken out of deionized water, air dried and left in a drying oven for 10 minutes to obtain an ultrafiltration membrane.

For the control experiment, a control membrane was obtained under the same conditions as in Example 1 except that ammonium lignosulfonate was not added.

Item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 contrast example Mass concentration of sulfonated polysulfone (%) 32 20 50 32 32 32 32 32 32 32 Mass ratio of ammonium lignosulfonate to sulfonated polysulfone 0.5:1 0.5:1 0.5:1 0.1:1 1:1 0.5:1 0.5:1 0.5:1 0.5:1 0.5:1 - Mass ratio of aluminum oxide and sulfonated polysulfone 0.05:1 0.05:1 0.05:1 0.05:1 0.05:1 0.01:1 0.1:1 0.05:1 0.05:1 0.05:1 0.05:1 first temperature (°C) 65 65 65 65 65 65 65 65 50 90 65 Second temperature (°C) 20 20 20 20 20 20 20 15 20 20 20 Third temperature (°C) 20 20 20 20 20 20 20 25 20 20 20 First Humidity (%) 20 20 20 20 20 20 20 10 20 20 20 Second Humidity (%) 20 20 20 20 20 20 20 30 20 20 20 1st period (hours) 8 8 8 8 8 8 8 8 10 6 8 2nd period (seconds) 15 15 15 15 15 15 15 15 10 120 13 3rd period (minutes) 10 10 10 10 10 10 10 10 5 60 10

In Examples 1-3, all experimental conditions were the same except that the mass concentrations of the sulfonated polysulfone were 32%, 20%, and 50%, respectively.

All other experimental conditions were the same except that in Examples 1, 4, and 5, the mass ratios between ammonium lignosulfonate and sulfonated polysulfone were 0.5:1, 0.1:1, and 1:1, respectively.

In Examples 1, 6 and 7, all other experimental conditions were the same except that the mass ratios between aluminum oxide and sulfonated polysulfone were 0.05:1, 0.01:1 and 0.1:1, respectively.

In Examples 1 and 8, all other experimental conditions were the same except for the following: In Example 1, the second temperature and the third temperature, the first humidity and the second humidity were 20°C and 20°C, 20% and 20, respectively. %, but in Example 8 at 15°C and 25°C, 10% and 30%. That is, the atmosphere and defoaming conditions for the solid state film were different.

In Examples 1, 9 and 10, all other conditions were the same except that the first temperature, the first period, the second period, and the third period were different. That is, the temperature for preparing the cast film solution, the period for preparing the cast film solution, the period for volatilization of the applied liquid powder, and the period for drying the film sample were different.

test example 1

The mechanical properties of the membranes prepared in Examples 1-10 of Table 1 and the mechanical properties of the control example were measured and compared, and the results are summarized in Table 2 below.

Mechanical property test:

Test equipment: paper and paper board tensile tester ZL-100A

Test steps:

First, a membrane sample to be tested was cut into a shape suitable for the tester and the scale distance was marked with two mark lines;

Then, the cut membrane sample was placed in the holder of the tester and carefully adjusted to a symmetrical position so that the stretching force was uniformly distributed over the cross-section of the membrane sample;

Finally, the tester was operated and the maximum force at which the membrane sample ruptured (±1% error) and the distance between the inside of the two mark lines (±1.25 mm error) were recorded.

The mechanical properties can be calculated as follows:

P(MPa) = F/A (Equation 1), where P is the average tensile force, F is the maximum force at break, A is the average initial cross-sectional area,

α(%) = {(LL ₀ )/L _0} } x 100 (Equation 2), where α is the elongation at rupture, L is the scale distance at the rupture, and L ₀ is the initial scale distance.

test example 2

Measurement of water flux and methylene blue retention

Test pressure: 0.1Mpa

Test steps:

First the membrane sample is loaded into the membrane property tester;

Next, deionized water is filled into the membrane pool of the membrane property tester;

Finally, to calculate the flow rate of the membrane sample, the membrane was pressurized so that the deionized water in the membrane pool passed through the membrane and exited the outlet.

Calculation formula for flow rate:

B(L·m ^-2 ·h ^-1 ) = V/(D·t) (Equation 3), where B is the flow rate of the membrane sample and the unit is L·m ^{-2 ·} h ^-1 , and V is the membrane is the total volume of water flow exiting the outlet stage of the property tester, D is the area of the membrane sample, and t is the barrel test time.

Retention rate test:

Test apparatus: ultrafiltration cup, UV spectrometer

Test pressure: 1Mpa

Test steps:

First the membrane sample was mounted in an ultrafiltration cup;

Then, 1 g/L aqueous methylene blue solution was charged into the membrane pool of the ultrafiltration cup;

Then, the membrane pool was pressed so that the aqueous methylene blue aqueous solution in the membrane pool passed through the membrane, wherein at least a portion of the methylene blue was retained on the membrane and the remainder of the methylene blue aqueous solution came out of the outlet end;

Finally, in order to calculate the methylene blue retention rate of the membrane sample, the concentration of methylene blue in the aqueous methylene blue solution in the membrane pool and the concentration of the methylene blue aqueous solution exiting the outlet were detected using UV spectroscopy.

Calculation formula for retention rate:

R (%) = (c/c ₀ ) x 100 (Equation 4), where R is the methylene blue retention of the membrane sample, c is the concentration of methylene blue in the methylene blue aqueous solution exiting the outlet terminal, c ₀ is the concentration of methylene blue in the aqueous methylene blue solution in the membrane pool.

Yes Average Tensile Force (Mpa) (23°C) Elongation at rupture (%) Flow rate (L m ^-2 MPa ^-1 h ^-1 ) Methylene blue retention (%) Example 1 150.9 100 139.2 56 Example 2 101.1 60 144.5 19 Example 3 129.3 76 100.7 47 Example 4 104.1 58 135.5 39 Example 5 136.9 90 99.7 49 Example 6 149.5 93 94.8 41 Example 7 143.2 80 112.4 38 Example 8 141.1 93 130.2 52 Example 9 132.1 86 128.9 36 Example 10 134.5 87 105.9 62 contrast example 89.7 55 103.6 34

In Table 2, it can be seen that Examples 1-10 exhibited higher elongation at break and average tensile force than the control example, which means that the addition of ammonium lignosulfonate improves the mechanical properties of the membrane.

In addition, the results obtained by comparing the flow rate and methylene blue retention rate between Examples 1-10 and the control example were: The addition of an appropriate amount of ammonium lignosulfonate to the cast membrane solution was a condition in which the retention rate of the ultrafiltration membrane was maintained at a constant flow rate. indicates an improvement in

Combining Tables 1 and 2, the following conclusions can be drawn:

In Examples 1-3, the mass concentrations of the sulfonated polysulfone were 32%, 20%, and 50%, respectively, and the remaining experimental conditions were the same. Example 1 had better elongation at rupture, average tensile force, flow rate and methylene blue retention than Examples 2 and 3, indicating that the mass concentration of the sulfonated polysulfone is preferably 32%.

In Examples 1, 4, and 5, Example 1 had better elongation at rupture, average tensile force, flow rate and methylene blue retention than Examples 4 and 5, indicating that the mass ratio of ammonium lignosulfonate to sulfonated polysulfone was 0.5: 1 indicates that it is preferable.

In Examples 1, 6 and 7, Example 1 had better elongation at rupture, average tensile force, flow rate and methylene blue retention than Examples 6 and 7, which is preferably 0.05:1 in mass ratio of aluminum oxide to sulfonated polysulfone. indicates that

Comparing Example 1 and Example 8, Example 1 had better elongation at rupture, average tensile force, flow rate and methylene blue retention than Example 8, indicating that the second temperature, the third temperature, the first humidity, and the second humidity were 20 ° C. , 20°C, 20% and 20% are preferred.

Comparing Examples 1, 9, and 10, Example 1 had better elongation at rupture, average tensile force, flow rate and methylene blue retention than Examples 9 and 10, which was found in the first temperature, the first period, the second period and the third period. This indicates that 65° C., 8 hours, 15 seconds and 10 minutes are preferred, respectively.

Consequently, compared with the control example, Examples 1-10 are preferable, Examples 1, 4, 7 and 8 are more preferable, and Example 1 is the most preferable.

Claims (5)

A method for manufacturing an ultrafiltration membrane, the method comprising:
Sulfonated polysulfone, ammonium lignosulfonate and aluminum oxide are dissolved in N,N-dimethylacetamide at a first temperature to form an initial cast film solution, and at a second temperature and second temperature to obtain a treated cast film solution. 1 left for defoaming for a first period of time at 1 humidity;
pouring the treated cast film solution onto a glass substrate using a film applicator to obtain a liquid state film with a thickness of 150-250 μm;
allowing the liquid state film to volatilize at a third temperature and a second humidity for a second period and leaving the glass substrate on which the liquid state film is formed in a coagulation bath to solidify the liquid state film to obtain a solid state film;
removing the solid state membrane from the coagulation bath, air drying and drying in an oven for a third period to form an ultrafiltration membrane;
In the treated cast membrane solution, the mass concentration of the sulfonated polysulfone is 20-40%,
The mass ratio between the ammonium lignosulfonate and the sulfonated polysulfone is 0.1-1:1;
The mass ratio between the aluminum oxide and the sulfonated polysulfone is 0.01-0.1:1. The method according to claim 1,
The first temperature is 50-90 ℃,
The second temperature is 15-25 ℃,
The third temperature is 15-25 ℃,
The first humidity is 10-30%,
The second humidity is 10-30%,
wherein the first period is 6-10 hours;
the second period is 10-120 seconds;
wherein said third period is 60 minutes. delete The method according to claim 1,
The coagulation bath is a method of using deionized water. An ultrafiltration membrane prepared by the method of any one of claims 1 or 2 or 4.