CN108927015A - A kind of preparation method of big flux ultrafiltration membrane - Google Patents

Abstract

The invention provides a method for preparing a large-flux ultrafiltration membrane, comprising the following steps: kaolin and saturated urea solution are evenly stirred, dried to obtain an intercalation compound, and the intercalation compound is added to HCl solution for ultrasonication to obtain Kaolin nano-sheet solution; the kaolin nano-sheet solution is adjusted to PH>9 with a pH regulator to obtain a kaolin nano-sheet dispersion; the obtained kaolin nano-sheet dispersion and cationic polyacrylamide are stacked to form a kaolin nano-sheet loaded onto the surface of a cellulose acetate microfiltration membrane. The initial flux of the kaolin ultrafiltration membrane prepared by the present invention is ten times that of the polyvinylidene fluoride ultrafiltration membrane, which greatly reduces the attenuation of the membrane flux, reduces membrane pollution, improves the service life, and improves the water treatment efficiency. The stability of the kaolin ultrafiltration membrane in water is improved, the method is simple, easy to operate and easy to use on a large scale, and is beneficial to popularization.

Description

A kind of preparation method of large flux ultrafiltration membrane

technical field

The invention belongs to the technical field of ultrafiltration membranes, and in particular relates to a preparation method of a large flux ultrafiltration membrane.

Background technique

Membrane technology is a simple and efficient water treatment technology. It is widely used in the field of environmental protection water treatment and has gradually become one of the foundations of the world's sustainable development strategy. Membrane technology is widely used in water treatment in various fields due to its wide applicability. However, the complexity and high cost of the membrane preparation process is an important obstacle to the promotion and application of membrane technology. There are many materials that can be used to prepare thin films, among which inorganic and ceramic materials and organic and polymer materials are the most important. Due to the high cost, high brittleness and low mechanical strength of inorganic and ceramic materials used to prepare thin films, organic and polymer materials have been widely used to prepare thin films and treat natural organic matter in surface water in recent years. For example, in recent years, graphene oxide and polyvinylidene fluoride have been widely used to prepare stable microfiltration membranes, ultrafiltration membranes, and nanofiltration membranes to treat natural organic matter in water. However, the preparation process is complex, costly and not environmentally friendly. Therefore, it is imperative to find new materials or new preparation methods to reduce costs and simplify the preparation process.

Contents of the invention

In view of this, the present invention aims to propose a method for preparing a large-flux ultrafiltration membrane, which is simple, low in cost, has good filtering effect and long service life.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

A method for preparing a large flux ultrafiltration membrane, comprising the steps of:

Step 1: Stir kaolin and saturated urea solution at 55-70°C with a disperser at a speed of 200r for 80 hours, dry to obtain an intercalation compound, add the intercalation compound to HCl solution for ultrasonication, and obtain kaolin nanosheets solution;

Step 2: The kaolin nanosheet solution is adjusted to PH>9 with a pH regulator, so that the kaolin nanosheet is negatively charged to increase the repulsion between the nanosheets to prevent the re-aggregation of the stripped nanosheets, and then stir with a high-speed mixer Five minutes, due to the adsorption of kaolin nanosheets, the pH of the solution will decrease after a period of time, so it is necessary to readjust the pH>9 afterwards, and then stir for five minutes with a high-speed mixer to obtain a dispersion of kaolin nanosheets;

Step 3: The kaolin nanosheet dispersion obtained in step 2 and cationic polyacrylamide are used to load the kaolin nanosheets on the surface of the cellulose acetate microfiltration membrane by layer-by-layer stacking.

Further, 40-50 g of kaolin is mixed with 50-100 ml of saturated urea solution.

Further, the molecular weight of the cationic polyacrylamide is >7 million, and the solubility of the cationic polyacrylamide is 0.1-10 mg/L.

Further, the pH regulator is one or both of NaOH or KOH.

Further, the number of loaded layers of kaolin nanosheets in step 3 is 1-300 layers.

Further, the kaolin nanosheets in step 1 are single-layer kaolin nanosheets or multilayer kaolin nanosheets.

Further, in the first step, the concentration of HCl is 1M, and the ultrasound is 8-15min.

Further, the pore size of the cellulose acetate microfiltration membrane in step three is 0.45um.

Cationic polyacrylamide was purchased from: Tianjin Guangfu Fine Chemical Research Institute.

Compared with the prior art, the preparation method of the large flux ultrafiltration membrane of the present invention has the following advantages:

According to the preparation method of the large-flux ultrafiltration membrane of the present invention, the initial flux of the prepared kaolin ultrafiltration membrane is ten times that of the polyvinylidene fluoride ultrafiltration membrane, and can also greatly reduce the membrane flux. attenuation, reduce membrane fouling, increase the service life of the membrane, and improve water treatment efficiency; the cationic polyacrylamide crosslinking agent enhances the binding force between kaolin nanosheets through electrostatic interaction, and improves the stability of kaolin ultrafiltration membrane in water. The present invention The method is simple, easy to operate, and easy to use on a large scale, which is conducive to popularization.

Description of drawings

Figure 1: Scanning electron microscope image of 50 layers of kaolin nanosheets loaded on the surface of 0.45um cellulose acetate microfiltration membrane with cationic polyacrylamide as crosslinking agent by layer stacking method;

Figure 2: BET diagram of the kaolin ultrafiltration membrane loaded with 10 layers of kaolin nanosheets.

Figure 3: BET plot of commercial polyvinylidene fluoride ultrafiltration membranes.

Figure 4: Using a kaolin ultrafiltration membrane loaded with 10 layers of kaolin nanosheets and a commercial polyvinylidene fluoride ultrafiltration membrane to filter 300mL BIT lake, 300mL ZGC river, 300mL 10mg/L BSA (bovine serum albumin), 300mL 10mg /LHA (humic acid), 300mL 10mg/L SA (sodium alginate) solution to obtain the initial flux figure of the membrane when filtering the organic solution;

Figure 5: Zeta potential map of kaolin nanosheets after adding CPAM and Al ³⁺ ;

Figure 6: Photometric dispersion analysis (PDA) diagram of kaolin nanosheets after adding CPAM and Al ³⁺ ;

Figure 7: 300mL BIT lake, 300mL ZGC river, 300mL 10mg/L BSA (bovine serum albumin), 300mL 10mg/L HA (humic acid), 300mL 10mg/L were filtered with a kaolin ultrafiltration membrane loaded with 10 layers of kaolin nanosheets. LSA (sodium alginate) solution to obtain the relative flux diagram of the membrane when filtering the organic solution;

Figure 8: Commercial polyvinylidene fluoride ultrafiltration membrane filtration 300mL BIT lake, 300mL ZGC river, 300mL 10mg/L BSA (bovine serum albumin), 300mL 10mg/L HA (humic acid), 300mL 10mg/L SA (alginic acid Sodium) solution to obtain the relative flux diagram of the membrane when filtering the organic solution.

Detailed ways

Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods, unless otherwise specified, are conventional methods.

The present invention will be described in detail below in conjunction with the embodiments and accompanying drawings.

Stir 50g of kaolin in 80ml of saturated urea solution at 65°C with a disperser at a speed of 200r for 80h, then add the dried intercalation complex into 1M HCl and ultrasonicate at 60°C for ten minutes , to obtain a kaolin nanosheet solution, then adjust the kaolin nanosheet solution to pH>9 with NaOH, then stir for five minutes with a high-speed mixer, then readjust the pH>9 and then stir for five minutes with a high-speed mixer to obtain kaolin nanosheets Dispersions.

Afterwards, the kaolin solution was taken out and diluted to a concentration of 50 mg/L as a stock solution. Two parts of 50ml stock solution were taken out, one was added to CPAM, the other was added to Al ³⁺ and tested with a photometric disperser and recorded the flocculation index value (FI value).

Then take out two 50ml stock solutions, add one to CPAM, and one to add Al ³⁺ to test with zeta potential and particle size analyzer and record the zeta potential value.

As shown in Figure 5 and Figure 6, Figure 5 shows that when the zeta potential is equal to zero, the amount of Al ³⁺ required is nearly 100 times that of CPAM; Figure 6 shows that when the same amount of CPAM and Al ³⁺ is added, the The FI value is larger. It can be seen from Figure 5 and Figure 6 that CPAM has better adhesion to kaolin nanosheets and is more suitable for adhesives.

Drop 1mL of 100ppm cationic polyacrylamide (CPAM) with a molecular weight of 8 million to 15 million onto a cellulose acetate microfiltration membrane, shake for 60s, pour it out and wash it twice with 5mL of ultrapure water, then add 2mL of 0.3g/L The kaolin was filtered under the condition of 0.1MPa, and then washed three times with 5mL of ultrapure water. At this time, a layer of kaolin was loaded on the cellulose acetate microfiltration membrane, and then loaded for 10 layers, and finally washed with 200mL of ultrapure water. membrane.

Filter 300mL BIT lake, 300mL ZGC river, 300mL 10mg/L BSA (bovine serum albumin), 300mL 10mg/L HA with kaolin ultrafiltration membrane loaded with 10 layers of kaolin nanosheets and commercial polyvinylidene fluoride ultrafiltration membrane (humic acid), 300mL 10mg/L SA (sodium alginate) solution, and at the same time, use an electronic balance to connect to the data display to collect data, so as to obtain the initial flux diagram of the membrane when filtering the organic solution.

As shown in Figure 4, the initial flux of the prepared kaolin ultrafiltration membrane is about ten times that of the polyvinylidene fluoride ultrafiltration membrane.

Filter 300mL BIT lake, 300mL ZGC river, 300mL 10mg/L BSA (bovine serum albumin), 300mL 10mg/L HA with kaolin ultrafiltration membrane loaded with 10 layers of kaolin nanosheets and commercial polyvinylidene fluoride ultrafiltration membrane (humic acid), 300mL 10mg/L SA (sodium alginate) solution, and at the same time, use an electronic balance to connect to the data display to collect data, so as to obtain the relative flux diagram of the membrane when filtering the organic solution.

As shown in Figures 7 and 8, the relative flux of the prepared kaolin ultrafiltration membrane was lower than that of the commercial polyvinylidene fluoride ultrafiltration membrane after filtering 300 mL of solution.

The initial flux is a characterization: the treatment efficiency of the membrane is the amount of wastewater that the membrane can treat in unit time.

The relative flux is a characterization: the anti-fouling ability of the membrane. This is because the pores of the membrane will be blocked by pollutants in the wastewater in wastewater treatment, causing membrane fouling and resulting in a decrease in the relative flux.

The faster the relative flux decreases (ie, the steeper the curve), the worse the anti-fouling ability of the membrane.

At the same time, the electronic balance is connected to the data display to collect data, so as to obtain the relative flux diagram of the membrane when filtering the organic solution. As shown in Figure 7 and Figure 8: the relative flux of the prepared kaolin ultrafiltration membrane after filtering 300mL solution is less than that of the commercial polyvinylidene fluoride ultrafiltration membrane.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (9)

1. a preparation method of large flux ultrafiltration membrane, is characterized in that: comprise the steps: Step 1: kaolin and saturated urea solution are fully stirred, dried to obtain an intercalation compound, and the intercalation compound is added to HCl solution for ultrasonication to obtain a kaolin nanosheet solution; Step 2: the kaolin nanosheet solution is adjusted to pH>9 with a pH regulator to obtain a kaolin nanosheet dispersion; Step 3: The kaolin nanosheet dispersion obtained in step 2 and cationic polyacrylamide are used to load the kaolin nanosheets on the surface of the cellulose acetate microfiltration membrane by layer-by-layer stacking. 2. The preparation method of the large flux ultrafiltration membrane according to claim 1, characterized in that: 40-50 g of kaolin is mixed with the saturated urea solution of 50-100 ml. 3. The preparation method of the large flux ultrafiltration membrane according to claim 1, characterized in that: the molecular weight of the cationic polyacrylamide is >7 million, and the solubility of the cationic polyacrylamide is 0.1-10 mg/L. 4. The preparation method of large flux ultrafiltration membrane according to claim 1, characterized in that: the pH regulator is one or both of NaOH or KOH. 5. The preparation method of the large-flux ultrafiltration membrane according to claim 1, characterized in that: the number of loaded layers of kaolin nanosheets in step 3 is 1-300 layers. 6 . The method for preparing a large flux ultrafiltration membrane according to claim 1 , wherein the kaolin nanosheets in step 1 are single-layer kaolin nanosheets or multilayer kaolin nanosheets. 7. The preparation method of the large-flux ultrafiltration membrane according to claim 1, characterized in that: kaolin and saturated urea solution are stirred at 55-70°C for 70-80h with a disperser at a rotating speed of 200r in step 1 . 8. The preparation method of the large-flux ultrafiltration membrane according to claim 1, characterized in that: in step 1, the concentration of HCl is 1M, and the ultrasound is 8-15min. 9. The preparation method of the large flux ultrafiltration membrane according to claim 1, characterized in that: the pore size of the cellulose acetate microfiltration membrane in step 3 is 0.45um.