ES2712483A1 - An ultrafiltration membrane and its preparation procedure (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

An ultrafiltration membrane and its preparation procedure. The present invention relates to a process for preparing an ultrafiltration membrane with a high mechanical property. In the present invention, since lignin, which has high mechanical properties, is added to the molding membrane solution, the retention rate of the ultrafiltration membrane of the present invention is improved. (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

An ultrafiltration membrane and its preparation procedure

Technical field

The present invention relates to a ultrafiltration membrane with high mechanical property and to its preparation process.

Background

At present, due to the fact that the ultrafiltration membrane is pressed for a long time but has poor mechanical properties, the life of the ultrafiltration membrane is shortened, and the ultrafiltration membrane in the membrane module needs to be replaced with frequency.

Therefore, it is necessary to develop an ultrafiltration membrane that can improve the mechanical property of the ultrafiltration membrane.

Summary of the invention

An object of the present invention is to provide a ultrafiltration membrane with high mechanical property and its preparation process.

The present invention relates to a process for preparing a ultrafiltration membrane with a high mechanical property. In the present invention, since lignin, which has a high mechanical property, is added to the molding membrane solution, the retention rate of the ultrafiltration membrane of the present invention is improved.

Detailed description of the realization modes

Example 1

Step 1: 16 g of polyethersulfone, 8 g of lignin and 0.8 g of polyvinyl pyrrolidone are added in a 3-neck flask;

Stage 2: 50 g of N, N-dimethylacetamide are then added to the 3-neck flask for obtain a mixture, stir the mixture at 65 ° C for 5 h;

step 3: it is allowed to stand to defoam in an environment with a temperature of 20 ° C and a humidity of 20% for 8 h to obtain a molding membrane solution without uniform foam;

step 4: the molding membrane solution is poured onto a glass substrate, and the molding membrane solution is applied to the glass substrate by a membrane applicator to obtain a membrane in the liquid state with a thickness of 200 μm;

step 5: the glass substrate is arranged with the membrane in the liquid state formed on it in an environment with a temperature of 20 ° C and a humidity of 20% for volatilization for 15 s;

step 6: the glass substrate is arranged with the membrane in the liquid state formed on it in deionized water, in order to solidify the membrane in the liquid state in a membrane in the solid state; Y

step 7: the solid state membrane is removed from the deionized water, dried in air and placed in a drying oven for 10 min to obtain the ultrafiltration membrane.

For the reference example, all the experimental conditions are the same as those in the realization mode 1, except that the lignin is not added.

Table 1

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

In Examples 1, 4 and 5, all experimental conditions are the same except that the mass ratios between lignin and polyethersulfone are 0.5: 1, 0.1: 1 and 1: 1, respectively.

In Examples 1, 6 and 7, all experimental conditions are the same except that the mass ratios between PVP and polyethersulfone are 0.05: 1, 0.01: 1 and 0.1: 1, respectively.

In the examples 1 and 8, all the experimental conditions are the same except that: in the example 1, the second and the third temperatures, the first and the second humidities are 20 ° C, 20 ° C, 20% and 20%, respectively; but in example 8, they are 15 ° C, 25 ° C, 10% and 30%, respectively. That is, the environments for defoaming and for forming the membrane in solid state are different.

In the examples 1, 9 and 10, all the experimental conditions are the same except that the first temperature, the first, second and third periods of them are different, that is, the temperature to prepare the molding membrane solution, the period to prepare the molding membrane solution, the period for volatilizing the applied liquid membrane and the period for drying the membrane sample are different.

Test example 1

The mechanical properties of the membranes prepared in Examples 1-10 and the comparative example are measured and compared, the measurement results are shown in Table 2.

Mechanical property test:

Test instrument: ZL-100A paper and cardboard traction testing machine

Test stages:

first, a membrane sample is cut to test in a form adapted to the testing machine and a scale distance is marked with two marking lines;

secondly, the cut membrane sample is arranged on the support of the testing machine, and carefully adjusted to a symmetrical position to allow the stretching force to be uniformly distributed across the cross section of the membrane sample;

finally, the testing machine is started and the maximum force (with the error of ± 1%) at which the membrane sample is broken and the distance (with the error of ± 1.25 mm) between the internal sides are recorded of the two dialing lines.

The mechanical property can be calculated as follows:

where P is the average tensile strength, F is the maximum breaking force, and A is the average initial cross-sectional area,

where a is the elongation at break, L is the breaking scale distance, and L0 is the initial scale distance.

Test example 2

Measurements of water flows and retention rates of methylene blue

Test pressure: 0.1 MPa.

Test stages:

First, the membrane sample is mounted on the membrane property testing machine;

secondly, the deionized water is filled into the membrane reservoir of the membrane property testing machine;

finally, the membrane reservoir is pressurized to allow the deionized water in the membrane reservoir to pass through the membrane and flow out of the outlet end, to calculate the water flow of the membrane sample.

The computational formula of the flow:

where B is the water flow of the membrane sample with the unit of

, V is the total volume of water flowing out of the exit end of the machine for membrane property tests, D is the area of the membrane sample and t is the total test time

Retention rate test:

Test instrument: ultrafiltration cylinder, ultraviolet-visible spectrophotometer Test pressure: 1 MPa.

Test stages:

first, the membrane sample is mounted in the ultrafiltration cylinder;

secondly, 1 g / l of aqueous solution of methylene blue is filled into the membrane deposit of the ultrafiltration cylinder;

third, the membrane reservoir is pressurized to allow the aqueous solution of methylene blue in the membrane reservoir to pass through the membrane, in which at least a part of the methylene blue is retained in the membrane and the membrane. rest of the aqueous solution of methylene blue flows out of the outlet end;

finally, the concentrations of methylene blue of the aqueous solution of methylene blue in the membrane deposit and of the aqueous solution of methylene blue flowing out of the exit end by the ultraviolet spectrophotometer are detected to calculate the retention rate of methylene blue of the membrane sample.

The computational formula of the withholding tax:

wherein R is the methylene blue retention rate of the membrane sample, c is the methylene blue concentration of the aqueous methylene blue solution flowing out of the outlet end, and - is the concentration of blue of methylene blue aqueous solution in the membrane deposit.

Table 2

It can be seen in table 2 that examples 1-10 have a greater tensile strength and elongation at break than those in the reference example, indicating that the addition of lignin can improve the mechanical property of the membrane.

In addition, the comparative results obtained by comparing the water fluxes and the methylene blue retention rates between examples 1-10 and the reference example indicate that: with the addition of an appropriate amount of lignin in the molding membrane solution of the present invention, the retention rate of the ultrafiltration membrane of the present invention is improved under the circumstance that the flow remains constant.

In combination with tables 1 and 2, the following conclusion is obtained:

in Examples 1-3, the bulk concentrations of the polyethersulfone are 32%, 20% and 50%, respectively, while the other experimental conditions are the same. It can be seen that Example 1 has the average tensile strength, elongation at break, water flow and methylene blue retention rate better than those in Examples 2 and 3, which indicates that the concentration in The preferred mass of polyethersulfone is 32%.

In Examples 1, 4 and 5, it can be seen that Example 1 has the best tensile strength, elongation at break, water flow and methylene blue retention rate better than those of Example 4 and Example 5, which indicates that the preferred mass average of lignin and polyethersulfone is 0.5: 1.

In Examples 1, 6 and 7, it can be seen that Example 1 has the best tensile strength, elongation at break, water flow and methylene blue retention rate better than those of Examples 6 and 7, which indicates that the preferential mass average of PVP and polyethersulfone is 0.05: 1.

Comparing Examples 1 and 8, it can be seen that Example 1 has the best tensile strength, elongation at break, water flow and methylene blue retention rate better than those of Example 8, which indicates that the second temperature, the third temperature, the first humidity and the second humidity are preferably 20 ° C, 20 ° C, 20% and 20%, respectively.

Comparing Examples 1, 9 and 10, it can be seen that Example 1 has the best tensile strength, elongation at break, water flow and methylene blue retention rate better than those of Examples 9- 10, which indicates that the first temperature, the first period, the second period and the third period are preferably 65 ° C, 8 h, 15 s and 10 min, respectively.

In conclusion, in comparison with the reference example, examples 1-10 are preferred; example 1, example 4, example 7 and example 8 are more preferred; and Example 1 is the most preferred.

Claims (5)

A method for preparing an ultrafiltration membrane, comprising the following steps: dissolving polyethersulfone, lignin and polyvinylpyrrolidone in N, N-dimethylacetamide at a first temperature to form an initial molding membrane solution, and allowing to stand to defoam at a second temperature and a first humidity for a first period to obtain a membrane solution of molding treated; pouring the treated molding membrane solution onto a glass substrate and obtaining a membrane in the liquid state with a thickness of 150-250 ^ m using a membrane applicator; to allow the membrane in the liquid state to volatilize at a third temperature and a second humidity during a second period and to arrange the glass substrate, together with the membrane in a liquid state formed on it, in a coagulation bath to allow the membrane in liquid state solidifies to obtain a membrane in solid state; and removing the solid state membrane from the coagulation bath, air drying and drying it in a drying oven for a third period to obtain the ultrafiltration membrane. 2. The method according to claim 1, wherein 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%; the second humidity is 10% -30%; the first period is 6-10 hours; the second period is 10-120 seconds; Y The third period is 60 minutes. 3. The process according to claim 1, wherein in the treated molding membrane solution the mass concentration of polyethersulfone is 20% -40%, the mass ratio between lignin and polyethersulfone is 0.1-1: 1, and the mass ratio between polyvinylpyrrolidone and polyethersulfone is 0.01-0.1: 1. 4. The process according to claim 1, wherein, in the third step, the coagulation bath is deionized water. 5. Ultrafiltration membrane prepared according to any one of claims 1-4.