阅读说明：本技术 一种光催化复合多孔膜的制备方法 (Preparation method of photocatalytic composite porous membrane ) 是由 赵健 田圣男 石海婷 朴洪伟 权全 肖长发 于 2020-06-03 设计创作，主要内容包括：本发明公开了一种光催化复合多孔膜的制备方法,包括：1)将聚醚砜和致孔剂加入有机溶剂中混合,加热至40～80℃并继续搅拌2-7h后得到铸膜液,经刮涂并在凝固浴水中固化成膜,室温干燥得到聚醚砜多孔膜；2)将所得聚醚砜多孔膜依次在镉离子溶液-去离子水-硫离子溶液-去离子水中浸渍,完成一个浸渍循环,称为循环A,重复循环A若干次,在聚醚砜多孔膜表面合成硫化镉,得到聚醚砜/硫化镉多孔膜；3)将所得聚醚砜/硫化镉多孔膜在铁离子溶液中浸渍,然后在吡咯中浸渍合成聚吡咯,得到光催化复合多孔膜。该光催化复合多孔膜可实现高水通量下水中污染物动态降解,同时克服了连续死端过滤时产生的膜污染问题,运行成本低,应用前景广阔。(The invention discloses a preparation method of a photocatalytic composite porous membrane, which comprises the following steps: 1) adding polyether sulfone and a pore-foaming agent into an organic solvent, mixing, heating to 40-80 ℃, continuously stirring for 2-7 hours to obtain a membrane casting solution, carrying out blade coating, curing in coagulating bath water to form a membrane, and drying at room temperature to obtain a polyether sulfone porous membrane; 2) sequentially dipping the obtained polyether sulfone porous membrane in a cadmium ion solution, deionized water, a sulfur ion solution and deionized water to finish a dipping cycle, namely cycle A, repeating cycle A for a plurality of times, and synthesizing cadmium sulfide on the surface of the polyether sulfone porous membrane to obtain the polyether sulfone/cadmium sulfide porous membrane; 3) and (3) dipping the obtained polyether sulfone/cadmium sulfide porous membrane in an iron ion solution, and then dipping in pyrrole to synthesize polypyrrole to obtain the photocatalytic composite porous membrane. The photocatalytic composite porous membrane can realize dynamic degradation of pollutants in water under high water flux, overcomes the problem of membrane pollution generated during continuous dead-end filtration, and has low operation cost and wide application prospect.)

1. A preparation method of a photocatalytic composite porous membrane is characterized by comprising the following steps: preparing a polyether sulfone porous base membrane, loading a photocatalyst on the surface of the polyether sulfone porous base membrane, and then depositing polypyrrole on the surface of the photocatalyst to form the photocatalyst composite porous membrane, wherein the preparation method comprises the following steps:

1) preparing a polyether sulfone porous base membrane: adding polyether sulfone and a pore-forming agent into an organic solvent for mixing, heating in a water bath to 40-80 ℃, continuously stirring for 2-7 hours to obtain a membrane casting solution, carrying out blade coating, curing in a deionized water coagulation bath to form a membrane, and drying at room temperature to obtain a porous membrane I;

2) dipping the porous membrane I obtained in the step 1) in a cadmium ion solution, deionized water, a sulfur ion solution and deionized water in sequence to finish a dipping cycle called cycle A, repeating the cycle A for a plurality of times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in an iron ion solution, and then dipping in an pyrrole solution to synthesize polypyrrole to obtain the photocatalytic composite porous membrane.

2. The method for preparing a photocatalytic composite porous membrane as set forth in claim 1, wherein the pore-forming agent in step 1) is selected from any one of polyvinylpyrrolidone and polyethylene glycol, and the organic solvent is selected from any one of dimethylformamide, dimethylacetamide and N-methylpyrrolidone.

3. The preparation method of the photocatalytic composite porous membrane according to claim 1, wherein the polyether sulfone content in the step 1) is 11-15 wt.%, and the pore-forming agent content is 5-13 wt.%.

4. The method for preparing a photocatalytic composite porous membrane according to claim 1, wherein the cadmium ion solution in step 2) is any one of a cadmium chloride solution and a cadmium nitrate solution, and the sulfur ion solution is any one of an ammonium sulfide solution and a sodium sulfide solution; the concentration of the cadmium ion solution in the step 2) is 0.1-2M, and the concentration of the sulfur ion solution is 0.1-2M; the concentration ratio of the cadmium ion solution to the sulfur ion solution in the step 2) is 1: 1.

5. The method for preparing a photocatalytic composite porous membrane as set forth in claim 1, wherein the cycle a in step 2) is repeated 5 to 25 times.

6. The method for preparing a photocatalytic composite porous membrane according to claim 1, wherein the ferric ion solution in step 3) is any one of ferric chloride solution and ferric nitrate solution, the concentration of the ferric ion solution is 0.1-2M, and the concentration of the pyrrole solution is 0.1-2M.

7. The preparation method of the photocatalytic composite porous membrane as claimed in claim 1, wherein the immersion time of the porous membrane II in the iron ion solution in the step 3) is 1-10 min, and the immersion time of the porous membrane II in the pyrrole solution is 1-10 min.

Technical Field

The invention belongs to the field of membrane materials, and particularly relates to preparation of a photocatalytic composite porous membrane with a separation function and photocatalytic degradation of organic matters.

Background

With the increasing discharge amount of waste water, the problem of organic waste water pollution becomes more and more serious, which brings great challenges to the living environment of human beings, and the waste water treatment is paid more and more attention. The organic waste water treatment method comprises a separation method and a conversion method, and a membrane separation technology for treating waste water by using a membrane material is one of the separation methods. The traditional membrane separation technology utilizes the selective permeability of a membrane to separate pollutants in water, and adjusts the pore diameter and the surface performance of the membrane material to improve the separation performance. The polyether sulfone membrane material has good chemical stability and temperature stability, simple preparation process and mature commercialization technology, and is widely applied to the field of wastewater treatment. In order to solve the problem, Celik and the like design a carbon nanotube blended polyether sulfone porous membrane for sewage treatment, the membrane pollution problem of the polyether sulfone porous membrane is effectively relieved by adding carbon nanotubes, but the cost of the carbon nanotubes is high, so that the cost is obviously increased, the technology is disclosed in Water research 2011 volume 45, No. 1, No. 274 and No. 282, article subjects: scale control in water treatment of Carbon nanotube polyethersulfone blended membranes, i.e. Carbon nanotube grafted polymeric sulfonic membranes for filtration control in water treatment, water Research, 2011, 45 (1): 274-282.. Generally, the smaller the pore size of the membrane material is, the smaller the particle size of the contaminant can be separated, the higher the rejection rate is, but at the same time, the larger the resistance of the water flow is, the lower the membrane flux is, and the more serious the membrane contamination problem is. Therefore, the polyethersulfone membrane material often needs to be modified or compounded with other materials to alleviate the membrane pollution problem. The congratulation and the like disclose a modified activated carbon fiber composite polyethersulfone ultrafiltration membrane, which is added with modified activated carbon fibers to improve the affinity of the modified activated carbon fibers with pollutant molecules and delay the pollution of the membrane, but the pollutants can not be effectively removed, and the patent number 201710842388.3 discloses a preparation method of the modified activated carbon fiber composite polyethersulfone ultrafiltration membrane and the obtained ultrafiltration membrane and application thereof.

The photocatalysis technology is a cleaning technology, can decompose organic pollutants into carbon dioxide, water and small molecular inorganic substances under sunlight, and shows good organic wastewater treatment capacity. Cadmium sulfide is a narrow-band-gap semiconductor material, has the forbidden band width of 2.4eV, has good visible light responsibility and high catalytic efficiency, is simple in preparation process, and can be used for degrading organic pollutants. The preparation method of the magnesium-doped cadmium sulfide polyvinyl alcohol composite nano film by Krishhnakumar and the like realizes the efficient degradation of methylene blue solution under visible light, and the technology is disclosed in the journal of Material science: electronic materials, volume 28, 18, th, 13990 and 13999 of 2017, title: the transparent magnesium-doped cadmium sulfide-polyvinyl alcohol nano composite membrane enhances the photocatalytic degradation of methylene blue under visible light, namely, Enhancement of photocatalytic degradation of methyl blue under visible light, namely, enhanced Mg-doped CdS-PVA nanocomposite films, journal of Materials Science: materials in Electronics, 2017, 28 (18): 13990-13999.. However, the single cadmium sulfide photocatalyst has poor stability, is easy to generate light corrosion in the photocatalysis process, and can obviously improve the stability of the cadmium sulfide by compounding with polypyrrole. Hiragond et al compared the effect of polythiophene, polypyrrole and polyaniline on the photocatalytic efficiency of cadmium sulfide quantum dots, found that the enhancement effect of polypyrrole on the photocatalytic efficiency of cadmium sulfide is most obvious, and disclosed in vacuum 2018, volume 155, 155: 159-168, article title: research on real-time photocatalytic activity of cadmium sulfide quantum dot sensitized conductive polymers, namely polythiophene, polypyrrole and polyaniline, namely combining the real-time photocatalytic activity of CdS QDs sensitive polymers: fed PTh, PPy and pani. vacuum, 2018, 155: 159-168.. At present, most of cadmium sulfide photocatalysis is in nanometer level, and the macroscopic form is powder. In the using process, the powdery cadmium sulfide is mixed with the organic wastewater to effectively degrade organic pollutants, but the recovery of the cadmium sulfide photocatalyst is very difficult. Zhang Kejie et al disclose a preparation method of cadmium sulfide-copper sulfide nano composite photocatalyst, which alleviates the photo-corrosion phenomenon of cadmium sulfide, but the recovery of the photocatalyst is still very difficult, see 'a preparation method of CdS-CuS nano composite photocatalyst', patent No. 201710406905.2. A large amount of manpower and material resources are consumed in the catalyst recovery process, and the secondary pollution of the water body can be caused due to incomplete recovery. Therefore, the photocatalysis technology is combined with the membrane material, so that the membrane separation and pollutant degradation process can be promoted, and the problem of difficult recovery of the photocatalyst can be solved.

The existing photocatalytic porous membrane generally has higher interception and filtration performance, and the cross-flow filtration method is usually adopted to realize the functions of degrading and intercepting organic pollutants simultaneously. Li et al prepared a Self-cleaning PDA/ZIF-67 modified polypropylene porous Membrane for wastewater treatment, which degrades pollutants under visible light to slow down Membrane fouling, but has very limited photocatalytic pollutant degradation effect due to rapid flow of water across the Membrane surface in cross-flow filtration, which is disclosed in "journal of Membrane Science" 2019, volume 591, page 117341, namely, the following methods: 117341.. The photocatalytic porous membrane with higher interception and filtration performance can work for a longer time in a cross-flow filtration mode, but the defect that cross-flow filtration is difficult to overcome is the low water flux, and after long-time operation, pollutants can be accumulated on the surface of the membrane to block membrane pores, so that membrane pollution is caused. The flux of the polluted photocatalytic porous membrane is sharply reduced, and the wastewater purification efficiency is greatly reduced. The preparation method of the photocatalytic composite porous membrane provided by the invention aims to be applied to a dead-end filtration process by regulating and controlling the raw material ratio and the membrane preparation process of the porous membrane, realizes photocatalytic degradation of pollutants in water under high water flux while keeping large water yield, and overcomes the problem of membrane pollution.

In conclusion, in the wastewater treatment process, the existing polyether sulfone membrane separation technology has the problems of serious membrane pollution and incapability of degrading pollutants, and the photocatalytic technology has the problem of difficult recovery of a powdery photocatalyst. The photocatalytic separation membrane combining the photocatalytic technology and the membrane separation technology is only suitable for the cross-flow filtration process, so that the effect of relieving membrane pollution by photocatalysis is very limited. Therefore, the preparation of the photocatalytic film material which is easy to recover, can efficiently degrade pollutants and is pollution-resistant is very important.

Disclosure of Invention

In order to solve the technical problems, the invention provides a preparation method of a photocatalytic composite porous membrane, which is characterized in that a polyether sulfone porous membrane is loaded with cadmium sulfide and polypyrrole to obtain the photocatalytic composite porous membrane which is easy to recover, resistant to pollution, long in service time and high in catalytic efficiency.

Therefore, the technical scheme of the invention is as follows:

a preparation method of a photocatalytic composite porous membrane comprises the following steps:

1) preparing a polyether sulfone porous base membrane: adding polyether sulfone and a pore-forming agent into an organic solvent for mixing, heating in a water bath to 40-80 ℃, continuously stirring for 2-7 hours to obtain a membrane casting solution, carrying out blade coating, curing in a deionized water coagulation bath to form a membrane, and drying at room temperature to obtain a porous membrane I;

2) dipping the porous membrane I obtained in the step 1) in a cadmium ion solution, deionized water, a sulfur ion solution and deionized water in sequence to finish a dipping cycle called cycle A, repeating the cycle A for a plurality of times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in an iron ion solution, and then dipping in an pyrrole solution to synthesize polypyrrole to obtain the photocatalytic composite porous membrane.

Further optimizing the technical scheme, in the step 1), the pore-forming agent is selected from any one of polyvinylpyrrolidone and polyethylene glycol, and the organic solvent is selected from any one of dimethylformamide, dimethylacetamide and N-methylpyrrolidone.

The technical scheme is further optimized, the polyether sulfone in the step 1) contains 11-15 wt.%, the pore-forming agent contains 5-13 wt.%, and the balance is organic solvent.

Further optimizing the technical scheme, the cadmium ion solution in the step 2) is any one of a cadmium chloride solution and a cadmium nitrate solution, and the sulfur ion solution is any one of an ammonium sulfide solution and a sodium sulfide solution. The concentration of the cadmium ion solution in the step 2) is 0.1-2M, and the concentration of the sulfur ion solution is 0.1-2M. The concentration ratio of the cadmium ion solution to the sulfur particle solution in the step 2) is 1: 1.

Further optimizing the technical scheme, the repetition frequency of the circulation A in the step 2) is 5-25 times.

Further optimizing the technical scheme, the iron ion solution in the step 3) is any one of a ferric chloride solution and a ferric nitrate solution, the concentration of the iron ion solution is 0.1-2M, and the concentration of the pyrrole solution is 0.1-2M.

Further optimizing the technical scheme, in the step 3), the dipping time of the porous membrane II in the ferric nitrate solution is 1-10 min, and the dipping time of the porous membrane II in the pyrrole solution is 1-10 min.

The method firstly prepares the polyether sulfone porous membrane, and sequentially deposits the cadmium sulfide and the polypyrrole on the surface of the polyether sulfone porous membrane. The polypyrrole can increase the binding force of the photocatalyst and the polyether sulfone porous membrane, and can be used as a conductive substance to separate photoproduction electrons from holes in time, so that the quantum efficiency is improved, and the photo-corrosion phenomenon of cadmium sulfide is inhibited. The device is shown in figure 1, methylene blue solution is used for simulating organic wastewater, a peristaltic pump is used as a negative pressure source of water flow, the diameter of a sample of the photocatalytic composite porous membrane is 4.5cm, the water flow is 30mL/h, a light source is provided by a 500W xenon lamp, and the visible light intensity of the surface of the sample is 100mW/cm²And running the sample for 24 hours, respectively testing the absorbance values of the methylene blue solution before and after each 1 hour of treatment, and calculating the dynamic degradation rate of the photocatalytic composite porous membrane. Under the test condition, the average dynamic degradation rate of the prepared photocatalytic composite porous membrane in 24h reaches 40-52%, the dynamic degradation rate in 24h reaches 40-50%, the dynamic degradation of methylene blue solution under high water flux is realized, the problem of membrane pollution is hardly caused by continuous operation, the preparation process is simple, the cost is low, the recovery is easy, and the method can be applied to the purification of organic wastewater such as dye wastewater.

Drawings

FIG. 1 is a schematic diagram of a photocatalytic reactor in test I.

Fig. 2 shows the dynamic degradation of the photocatalytic composite porous membrane prepared in example 1 to a methylene blue solution.

Detailed Description

The technical solution of the present invention is described in detail below with reference to examples.

Example 1

A preparation method of a photocatalytic composite porous membrane comprises the following steps:

1) preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in a 0.1M ferric nitrate solution for 2min, and then dipping in a 0.1M pyrrole solution for 2min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in this example was tested for catalytic efficiency, and the average dynamic degradation rate in 24h was as shown in fig. 2, the average dynamic degradation rate in 24h reached 52%, and the dynamic degradation rate in 24h reached 50%.

Example 2

1) Preparing a polyether sulfone porous base membrane: mixing 15 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 75 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in a 0.1M ferric nitrate solution for 2min, and then dipping in a 0.1M pyrrole solution for 2min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 52%, and the dynamic degradation rate in 24 hours reaches 50%.

Example 3

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium nitrate solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in a 0.1M ferric nitrate solution for 2min, and then dipping in a 0.1M pyrrole solution for 2min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 52%, and the dynamic degradation rate in 24 hours reaches 50%.

Example 4

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M sodium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in a 0.1M ferric nitrate solution for 2min, and then dipping in a 0.1M pyrrole solution for 2min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 52%, and the dynamic degradation rate in 24 hours reaches 50%.

Example 5

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in 0.1M ferric chloride solution for 2min, and then dipping in 0.1M pyrrole solution for 2min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 52%, and the dynamic degradation rate in 24 hours reaches 50%.

Example 6

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 6 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in a 0.1M ferric nitrate solution for 2min, and then dipping in a 0.1M pyrrole solution for 2min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 45%, and the dynamic degradation rate in 24 hours reaches 45%.

Example 7

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 14 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) soaking the porous membrane II obtained in the step 2) in 0.1M ferric nitrate solution for 2min, then soaking in 0.1M pyrrole solution for 2min, drying at room temperature, and depositing polypyrrole on the two surfaces of the porous membrane to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 47%, and the dynamic degradation rate in 24 hours reaches 47%.

Example 8

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in a 0.1M ferric nitrate solution for 2min, and then dipping in a 0.1M pyrrole solution for 1min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 50%, and the dynamic degradation rate in 24 hours reaches 45%.

Example 9

1) Preparing a polyether sulfone porous base membrane: mixing 13 wt.% of polyether sulfone, 10 wt.% of polyvinylpyrrolidone and 77 wt.% of dimethylacetamide, heating in a water bath to 75 ℃, continuously stirring for 6 hours, blade-coating, curing in a deionized water coagulation bath to form a film, and drying at room temperature to obtain a porous film I;

2) dipping the porous membrane I obtained in the step 1) in 0.1M cadmium chloride solution, deionized water, 0.1M ammonium sulfide solution and deionized water in sequence to finish a dipping cycle, namely cycle A, repeating the cycle A for 10 times, and synthesizing cadmium sulfide on the surface of the porous membrane I to obtain a porous membrane II;

3) dipping the porous membrane II obtained in the step 2) in 0.1M ferric nitrate solution for 2min, and then dipping in 0.1M pyrrole solution for 6min to synthesize polypyrrole, so as to obtain the photocatalytic composite porous membrane.

The final product prepared in the embodiment is subjected to a catalytic efficiency test, and the result shows that the average dynamic degradation rate in 24 hours reaches 50%, and the dynamic degradation rate in 24 hours reaches 48%.