CN106955718A - A kind of ZnS/Bi2O3Hetero-junctions molecular engram photocatalysis membrana and preparation method and purposes - Google Patents

Abstract

The invention provides a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalyst film and its preparation method and application. The preparation method is as follows: Step 1, prepare Bi ₂ O ₃ photocatalyst; Step 2, prepare ZnS/Bi ₂ O ₃ Heterojunction photocatalyst; step 3, preparing a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film. The photocatalytic degradation process of the molecularly imprinted catalytic membrane for selective degradation of rhodamine B prepared by the present invention can effectively realize the purpose of selective identification, adsorption and catalytic degradation of target pollutants, and the post-treatment is simple and convenient, which improves the effective efficiency of target substances. The degradation efficiency has the advantages of strong selective treatment of dye wastewater.

Description

A ZnS/Bi2O3 heterojunction molecularly imprinted photocatalytic membrane, its preparation method and application

technical field

The invention relates to a method for preparing a molecularly imprinted catalytic film with a heterojunction structure semiconductor and photocatalysis by using phase inversion technology, in particular to a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalyst for efficiently degrading rhodamine B. The preparation method and application of the catalytic membrane belong to the technical field of material preparation and environmental pollution control.

Background technique

Rhodamine B is a synthetic basic fluorescent dye, and it is also a common analytical reagent, widely used in environmental protection, mining, steel, medicine and other fields, and can also be used as a fluorescent stain for cells in laboratories. It was once used as a food additive, but experiments have proved that rhodamine B can cause cancer, and it is now not allowed to be used as a food additive and food dye. Since these compounds are excreted into the water environment, they become a potential risk to the environment and human health, which has aroused widespread concern in environmental ecology. Therefore, it is necessary to establish and develop effective and economical treatment methods to selectively remove Rhodamine B residues are extremely urgent.

Photocatalytic technology is a method that uses semiconductors or compound semiconductors to be excited under light conditions to generate electron-hole pairs with redox functions, thereby degrading pollutants. Now it has been widely used to study the residue of dyes in the water environment. People have improved the photocatalytic performance by modifying the photocatalyst, but it is still not selective, and it is difficult to remove the target substance in the complex water body where multiple pollutants coexist. Therefore, we propose to use molecular imprinting technology combined with photoelectrocatalytic technology to make it have specific recognition function and preferentially select and remove target pollutants.

Molecularly imprinted membrane technology is a new type of selective separation membrane that has the ability to specifically recognize target molecules. The synthesis method of molecularly imprinted polymers can be used in the preparation of separation membrane materials, or it can be introduced in the production process of separation membranes. imprinted molecules. Molecularly imprinted membrane technology combines the advantages of molecular imprinting and membrane technology, and can effectively separate specific target molecules from mixtures and their structural analogs.

Combining molecularly imprinted membrane technology with photocatalytic technology, a molecularly imprinted catalytic membrane with selective degradation of target substances is prepared. The catalytic membrane can firstly adsorb target molecules and degrade them preferentially. After degradation, the cycle system of adsorption and degradation can be realized again, and then To achieve the purpose of synergizing and promoting selective photocatalytic degradation of target pollutants. Therefore, it has broad application prospects in the selective removal of rhodamine B dye residues in the environment.

Contents of the invention

The invention uses the phase inversion technology as a preparation means to prepare a molecularly imprinted catalytic membrane composite photocatalyst with specific selectivity to target pollutant rhodamine B. Its advantage lies in the construction of a cyclic process in the system, which realizes the cyclic process of adsorbing the target substance first, then catalytically degrading it, and then adsorbing and degrading it, and then effectively using the light source to effectively degrade the rhodamine B dye wastewater in the environment.

Technical scheme of the present invention is:

A ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film, the molecularly imprinted photocatalytic film is composed of zinc sulfide spheres and raised Bi ₂ O ₃ crystals, the Bi ₂ O ₃ Crystals are supported on the surface of the zinc sulfide spheres.

A method for preparing a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film, the steps are as follows:

Step _1. Prepare _Bi2O3 photocatalyst: Dissolve bismuth nitrate pentahydrate in deionized water to obtain bismuth nitrate solution; add sodium hydroxide solution to bismuth nitrate solution, adjust pH, stir, and react at room temperature, after the reaction is complete Centrifuge the mixed solution, wash with deionized water and absolute ethanol several times, and dry to obtain a light yellow powder A; place the light yellow powder A in a muffle furnace and calcinate at a certain temperature for a certain period of time to obtain Bi ₂ O photocatalyst, stand _- by;

Step 2. Preparation of ZnS/Bi ₂ O ₃ heterojunction photocatalyst: take zinc acetate dihydrate and thiourea, dissolve them in deionized water under stirring, and add Bi ₂ O ₃ photocatalyst to obtain mixed solution B; mix mixed solution B Move it into a stainless steel high-pressure hydrothermal kettle, perform solvothermal reaction, and obtain a mixed solution C after cooling; filter the mixed solution C, wash the solid product, dry and grind to obtain a ZnS/Bi ₂ O ₃ heterojunction photocatalyst, which is stored in In the sampling tube, spare;

Step 3. Preparation of ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic membrane: take ZnS/Bi ₂ O ₃ heterojunction photocatalyst and add it to dimethyl sulfoxide, and ultrasonically disperse it to obtain ZnS/Bi ₂ O ₃ heterostructure Junction photocatalyst dispersion; add cellulose acetate, chitosan and rhodamine B to the ZnS/Bi ₂ O ₃ heterojunction photocatalyst dispersion, stir and mix at 40±5°C, and mechanically stir evenly to obtain a cast film liquid; keep the casting solution at 40±5°C and keep it warm, remove the bubbles generated by stirring, then take a clean glass plate, spread the casting solution on the glass plate, scrape out a certain thickness with a glass rod, After standing for a period of time, slowly immerse it in deionized water for a period of time and then take it out to obtain a blended film; peel off the blended film from the glass plate, place it in a methanol/acetic acid mixed extraction solution, and soak for a period of time to remove the template molecules, and then store the membrane in deionized water at room temperature until use.

In step 1, in the bismuth nitrate solution, the mass ratio of the bismuth nitrate pentahydrate powder used to deionized water is 9.7:100; the concentration of the sodium hydroxide solution used is 0.5mol/L, and the pH is 8; The calcination temperature is 300°C-500°C; the calcination time is 2h-6h.

In step 2, when making mixed solution B, used zinc acetate dihydrate, thiourea, Bi ₂ O _The photocatalyst and deionized water mass ratio are 1.1:1.9:0.1:35; The temperature of described solvothermal reaction is 170°C-210°C, the time is 5h-24h; the drying temperature is 60°C-80°C, and the drying time is 12h-24h.

In step 3, when preparing the ZnS/Bi ₂ O ₃ heterojunction photocatalyst dispersion, the mass ratio of the ZnS/Bi ₂ O ₃ heterojunction catalyst to dimethyl sulfoxide used is 0.1-0.4:16.74-17.04; The time for the ultrasonic dispersion is 1 to 2 hours; in the casting solution, the mass fraction of cellulose acetate is 13% of the casting solution, the mass fraction of chitosan is 1.0% of the casting solution, rhodamine The mass fraction of B is 0.3% of the casting liquid, the time of the mechanical stirring is 4h; the time of the heat preservation and standing is 12～24h, and the thickness of the blend film is 1.0mm; the time of the standing is at least 30s, soaking time in deionized water is at least 10min; in the methanol/acetic acid mixed extract, the volume ratio of methanol to acetic acid is 9:1.

The prepared ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film was used as a photocatalyst to degrade rhodamine B.

The dimethyl sulfoxide described in the above technical scheme acts as a solvent to dissolve cellulose acetate and rhodamine B to prepare a casting solution.

The cellulose acetate described in the above-mentioned technical scheme acts as a matrix.

The chitosan described in the above-mentioned technical scheme acts as a functional polymer.

The deionized water described in the above-mentioned technical scheme acts as a non-solvent.

The methanol/acetic acid mixed extract solution described in the above technical solution functions to block the hydrogen bond between the template molecule and the functional polymer, thereby eluting the template molecule.

The molecularly imprinted catalytic membrane with selectivity to rhodamine B prepared by using the molecularly imprinted membrane technology of the present invention has a relatively high selective degradation effect on the template molecule rhodamine B.

The preparation method of the corresponding non-imprinted blend membrane (NIM) was the same as above, but no template molecule rhodamine B was added.

Evaluation of photocatalytic activity: carried out in DW-01 photochemical reaction apparatus, irradiated by visible light lamps, adding 100mL of rhodamine B simulated wastewater with a certain concentration into the reactor and measuring its initial value, and then adding a certain amount of imprinted membrane and non-imprinted membrane Membrane photocatalyst, open the aeration device and let in the air, which can provide oxygen in the photocatalytic process. During the photocatalytic process, samples are taken and analyzed at intervals of 30 minutes. After centrifugation, the supernatant is taken and measured at the UV-visible spectrophotometer at λ _max = 554nm Absorbance, and calculate the degradation rate by the formula: DC=[(A ₀ -A _i )/A ₀ ]×100%, where A ₀ is the absorbance of rhodamine B solution when adsorption equilibrium is reached, and A _i is the rhodamine measured by regular sampling The absorbance of the bright B solution.

Technical advantage of the present invention:

First of all, both ZnS and Bi ₂ O ₃ belong to photocatalysts, but ZnS has a wide band gap and can only catalyze under ultraviolet light conditions, while Bi ₂ O ₃ has a narrow band gap and can be excited by visible light. Two kinds of semiconductors are combined to form a heterojunction structure, which can make the photogenerated electrons injected from one semiconductor into another semiconductor, thereby effectively preventing the recombination of electrons and holes, so as to improve the photocatalytic efficiency and the degradation rate of target substances . Secondly, the technology adopts the hydrothermal synthesis method, and the steps are relatively simple. Finally, the photocatalytic degradation process of the molecularly imprinted catalytic membrane that selectively degrades rhodamine B can effectively achieve the purpose of selective recognition, adsorption and catalytic degradation of target pollutants, and the post-treatment is simple and convenient, which improves the effective degradation of target substances The efficiency has the advantages of strong selective treatment of dye wastewater.

Description of drawings

Figure 1 is the scanning electron micrograph of ZnS, Bi ₂ O ₃ , ZnS/Bi ₂ O ₃ , wherein, picture a is the scanning electron micrograph of ZnS, picture b is the scanning electron micrograph of Bi ₂ O ₃ , and picture c is the scanning electron micrograph of ZnS/Bi SEM image of ₂ O ₃ ;

Fig. 2 is the XRD spectrum of ZnS, Bi ₂ O ₃ , ZnS/Bi ₂ O ₃ .

detailed description

The present invention will be further described below in conjunction with specific implementation examples.

In the present invention, the total mass of the casting solution is 20g as an example.

Example 1:

(1) Preparation of ZnS/Bi ₂ O ₃ heterojunction catalyst

First, dissolve 9.7 g of bismuth nitrate pentahydrate in 100 mL of deionized water to obtain a bismuth nitrate solution, then take 500 mL of 0.5 mol L ^-1 sodium hydroxide solution and add it dropwise to the bismuth nitrate solution, stir, and react at room temperature to obtain a white Or pale yellow precipitate. Centrifuged, then washed three times with deionized water and absolute ethanol, dried at 60°C for 12 hours after centrifugal separation, put the above powder into a muffle furnace and calcined at 400°C for ₂ hours to obtain a _Bi2O3 catalyst, stand-by. Dissolve 2.2g of zinc acetate dihydrate and 3.8g of thiourea in 70mL of deionized water, then take 0.2g _{of Bi2O3} photocatalyst and disperse in the above solution, after standing for 0.5h, transfer the above solution to a stainless steel autoclave , heated at 170°C for 5h, cooled to room temperature, then vacuum-filtered with a Buchner funnel and washed three times with deionized water and absolute ethanol respectively, and vacuum-dried at 60°C-80°C for 12h-24h, and finally obtained ZnS/Bi ₂ O ₃ heterojunction catalyst.

(2) Preparation of molecularly imprinted catalytic membrane

First, take 0.1g of ZnS/Bi ₂ O ₃ heterojunction catalyst and add it into 17.04g of dimethyl sulfoxide (DMSO), ultrasonically disperse for 1~2h to obtain ZnS/Bi ₂ O ₃ heterojunction catalyst dispersion, then add 0.06g of template Molecule (rhodamine B), 2.6g membrane matrix (cellulose acetate) and 0.2g functional polymer (chitosan), mechanically stirred at 40±5°C for 4h until dissolved to obtain a casting solution, at 40±5°C Keep it warm at ℃ for 12-24 hours, remove the bubbles generated by stirring, then take a clean glass plate, spread the casting solution on the glass plate, scrape out a film with a thickness of 1.0mm with a glass rod, and slowly remove it after 30s Immerse it in deionized water, take it out after soaking for 30 minutes, and store the molecularly imprinted catalytic membrane in deionized water. The non-imprinted membrane was prepared in the same way as above, but without adding the template molecule rhodamine B. Finally, the mixed solution of methanol/acetic acid with a volume ratio of 9:1 was used as the extraction solution to remove the template molecule rhodamine B, and then washed with water several times to neutrality, and the prepared molecularly imprinted catalytic membrane was stored in deionized water. As a comparison, a blank non-imprinted catalytic membrane was synthesized by the same method and steps, except that no template molecule rhodamine B was added during the polymerization process.

(3) Photocatalytic activity experiment of molecularly imprinted catalytic membrane

Take 10 g of the sample prepared in step (2) and carry out the photocatalytic degradation test in a photochemical reaction apparatus, add 100 mL, 20 mg L ^-1 rhodamine B solution, magnetically stir for 1 h, turn on the circulating water source, light source, and carry out photocatalytic degradation test. For the catalytic degradation experiment, absorb the photocatalytic degradation solution in 4-6ml reactor every 30min, measure its absorbance at 554nm with a UV-visible spectrophotometer, and use the formula: DC%=[(A ₀ -A _i )/ A ₀ ] × 100% to calculate the degradation rate, wherein A ₀ is the absorbance of the rhodamine B solution when the adsorption equilibrium is reached, and A _i is the absorbance of the rhodamine B solution measured by regular sampling. The degradation rate indicates the photocatalytic activity of the catalyst prepared in (2).

Fig. 1 is a scanning electron microscope image of ZnS, Bi ₂ O ₃ , ZnS/Bi ₂ O ₃ . It can be seen from Figure a that ZnS is spherical, Figure b is the crystallization state of Bi ₂ O ₃ , and it can be seen from Figure c that there are convex Bi ₂ O ₃ crystals around the ZnS sphere.

Figure 2 is the XRD spectra of ZnS, Bi ₂ O ₃ and ZnS/Bi ₂ O ₃ composite materials. Bismuth oxide has sharp characteristic peaks at 27° and 34°, and zinc sulfide has obvious diffraction peaks at 28.9°, 48.8° and 57.2°, corresponding to (111), (220), (311) crystal planes of zinc sulfide , At the same time, it can be seen from the composite XRD figure that the diffraction peaks of (220) and (311) crystal planes of zinc sulfide obviously exist, and the diffraction peaks of (111) crystal plane coincide with the diffraction peaks of bismuth oxide.

Example 2:

Under the condition that other conditions remain unchanged, the comparative experiment is established as follows: (1) When preparing Bi ₂ O ₃ photocatalyst, the calcination temperature is 300°C, the calcination time is 4h, and the ZnS/Bi ₂ O ₃ heterojunction photocatalyst is synthesized by hydrothermal method. For the catalyst, the reaction temperature of the reactor is 210°C, and the reaction time is 5 hours. After the reaction, wash and dry in the same way, and grind to obtain a powder catalyst for use. (2) When preparing Bi ₂ O ₃ photocatalyst, the calcination temperature is 500°C, and the calcination time is 6h; when the ZnS/Bi ₂ O ₃ heterojunction photocatalyst is synthesized by hydrothermal method, the reaction temperature of the reactor is 170°C, and the reaction time is 24h , after the reaction is over, wash and dry in the same way, and grind to obtain a powder catalyst, which is ready for use. The obtained catalysts prepared under different conditions were used to degrade rhodamine B, and the degradation efficiency was observed and calculated.

Example 3:

(1) By changing the amount of ZnS/Bi ₂ O ₃ heterojunction photocatalyst (0.2g, 0.3g, 0.4g) to examine the effect of catalyst dosage on photocatalytic degradation, when changing ZnS/Bi ₂ O ₃ While changing the amount of photocatalyst, change the amount of dimethyl sulfoxide (16.94g, 16.84g, 16.74g) to ensure that the total mass fraction of ZnS/Bi ₂ O ₃ heterojunction photocatalyst and dimethyl sulfoxide is 85.7 %, the results show that when the catalyst dosage is 0.4g, its degradation efficiency to Rhodamine B is the highest, which can reach more than 90%. Therefore, the amount of catalyst selected in the experiment was 0.4 g.

(2) Molecularly imprinted catalytic membrane prepared with 0.4g photocatalyst degrades rhodamine B solutions with different concentrations (10, 20, 30, 40, 50 mg·L ^-1 ) under visible light, and examines the molecular imprinted membrane at different concentrations The degradation kinetics of rhodamine B by the photocatalytic film is calculated and fitted to the kinetic equation. It can be known that the process of molecularly imprinted photocatalyst degradation of rhodamine B conforms to the pseudo-first-order kinetic model. When the initial concentration of rhodamine B is 20mg· At L ^-1 , the average degradation rate of rhodamine B by the molecularly imprinted photocatalytic membrane was 0.048min ^-1 .

Example 4:

The photocatalytic film prepared in (2) in Example 1 was used to degrade the mixed solution of rhodamine B and interfering substance (methylene blue) at the same concentration, and the selectivity coefficient for different substances was calculated by calculating the degradation efficiency of different substances.

Among them, C ₀ , C _e are the initial and degraded concentrations of rhodamine B (mg·L ^-1 ); D is the partition coefficient, D _CIP , and D _M are the partition coefficients of rhodamine B and interfering substances; α is The selectivity coefficients, α _i , α _n are the selectivity coefficients of imprinted and blank polymer photocatalysts, respectively, and α _r is the relative selectivity coefficient.

The experimental results show that the degradation efficiency of the molecularly imprinted photocatalytic membrane on rhodamine B is significantly higher than that of other contrasting substances, and the selectivity coefficients are also greater than other interfering substances. The relative selectivity coefficient of the molecularly imprinted photocatalytic membrane on rhodamine B and methylene blue 3.28 and 1.57, respectively. It shows that the molecularly imprinted catalytic membrane synthesized by this method has good selectivity to rhodamine B, thus realizing the purpose of selective catalytic degradation of target substance rhodamine B.

Example 5:

(1) First use the photocatalyst prepared in (2) in Example 1 to separately adsorb different concentrations of rhodamine B, methylene blue, and methyl orange solutions. The adsorption capacity of the imprinted catalytic membrane for different species was calculated according to the formula. Q=(C ₀ -C _e )*V/m, where Q is the adsorption capacity of the adsorbent (mg·g ^-1 ), C ₀ , and C _e are the concentration of rhodamine B before adsorption and after adsorption equilibrium (mg ·L ⁻¹ ), V is the volume (L) of the rhodamine B solution, and m is the mass (g) of the adsorbent. The experimental results show that the adsorption capacity of the molecularly imprinted photocatalytic membrane for the template molecule rhodamine B is generally greater than that of other substances, while the adsorption capacity of the non-imprinted catalytic membrane for these substances is not much different.

(2) The photocatalytic membrane prepared in (2) in Example 1 is used to adsorb the mixed solution of rhodamine B, methylene blue and methyl orange of the same concentration respectively, and through the same adsorption time, the suspended solution is centrifuged to measure the concentration of the supernatant. Concentration, according to the formula to calculate the adsorption capacity of the catalyst for different species, and then calculate its adsorption selectivity for different substances. The results showed that the adsorption capacity of molecularly imprinted photocatalytic membranes for rhodamine B was significantly higher than that of methylene blue and methyl orange, while the adsorption capacities of non-imprinted catalytic membranes were not much different, which indicated that the adsorption capacity of rhodamine B was increased during the imprinting process. Adsorption capacity of imprinted membranes for Rhodamine B.

Claims (6)

1. _A ZnS/ _Bi2O3 heterojunction molecularly imprinted photocatalyst film, characterized in that the molecularly imprinted photocatalyst film is composed _of zinc sulfide spheres and raised _Bi2O3 crystals, The Bi ₂ O ₃ crystals are supported on the surface of the zinc sulfide spheres. 2. A method for preparing a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film, characterized in that the steps are as follows: Step _1. Prepare _Bi2O3 photocatalyst: Dissolve bismuth nitrate pentahydrate in deionized water to obtain bismuth nitrate solution; add sodium hydroxide solution to bismuth nitrate solution, adjust pH, stir, and react at room temperature, after the reaction is complete Centrifuge the mixed solution, wash with deionized water and absolute ethanol several times, and dry to obtain a light yellow powder A; place the light yellow powder A in a muffle furnace and calcinate at a certain temperature for a certain period of time to obtain Bi ₂ O photocatalyst, stand _- by; Step 2. Preparation of ZnS/Bi ₂ O ₃ heterojunction photocatalyst: take zinc acetate dihydrate and thiourea, dissolve them in deionized water under stirring, and add Bi ₂ O ₃ photocatalyst to obtain mixed solution B; mix mixed solution B Move it into a stainless steel high-pressure hydrothermal kettle, perform solvothermal reaction, and obtain a mixed solution C after cooling; filter the mixed solution C, wash the solid product, dry and grind to obtain a ZnS/Bi ₂ O ₃ heterojunction photocatalyst, which is stored in In the sampling tube, spare; Step 3. Preparation of ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic membrane: take ZnS/Bi ₂ O ₃ heterojunction photocatalyst and add it to dimethyl sulfoxide, and ultrasonically disperse it to obtain ZnS/Bi ₂ O ₃ heterostructure Junction photocatalyst dispersion; add cellulose acetate, chitosan and rhodamine B to the ZnS/Bi ₂ O ₃ heterojunction photocatalyst dispersion, stir and mix at 40±5°C, and mechanically stir evenly to obtain a cast film solution; keep the casting solution at 40±5°C and keep it still, then take a clean glass plate, spread the casting solution on the glass plate, scrape out a certain thickness with a glass rod, and after standing for a period of time, slowly It is immersed in deionized water for a period of time and then taken out to obtain a blended film; the blended film is peeled off from the glass plate, placed in a methanol/acetic acid mixed extract, soaked for a period of time, and then the film is stored in deionized water at room temperature ,spare. 3. A method for preparing a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film according to claim 2, characterized in that the steps are as follows: in step 1, in the bismuth nitrate solution, the pentahydrate used The mass ratio of bismuth nitrate powder to deionized water is 9.7:100; the concentration of the sodium hydroxide solution used is 0.5mol/L, and the pH is 8; the calcination temperature is 300°C to 500°C; the calcination The time is 2h ~ 6h. 4. The preparation method of a ZnS/ _Bi2O3 heterojunction molecularly imprinted photocatalytic film according to claim ₂ , characterized in that, in step 2, when preparing the mixed solution B, the used zinc acetate dihydrate , thiourea, Bi ₂ O ₃ photocatalyst and deionized water mass ratio is 1.1:1.9:0.1:35; the temperature of the solvothermal reaction is 170 ℃ ~ 210 ℃, the time is 5h ~ 24h; the drying temperature The temperature is 60℃～80℃, and the drying time is 12h～24h. 5. The preparation method of a ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film according to claim 2, characterized in that, in step 3, the ZnS/Bi ₂ O ₃ heterojunction photocatalyst dispersed liquid, the mass ratio of ZnS/Bi ₂ O ₃ heterojunction catalyst to dimethyl sulfoxide is 0.1-0.4:16.74-17.04; the ultrasonic dispersion time is 1-2h; , the massfraction of the cellulose acetate is 13% of the casting solution, the massfraction of chitosan is 1.0% of the casting solution, the massfraction of Rhodamine B is 0.3% of the casting solution, and the mechanical stirring The time is 4h; the heat preservation time is 12-24h, and the thickness of the blend film is 1.0mm; the time for placing is at least 30s, and the time for soaking in deionized water is at least 10min; the methanol/ In the acetic acid mixed extract, the volume ratio of methanol to acetic acid is 9:1. 6. The use of the ZnS/Bi ₂ O ₃ heterojunction molecularly imprinted photocatalytic film prepared by the method according to any one of claims 1 to 5, characterized in that the prepared ZnS/Bi ₂ O ₃ heterojunction molecules Imprinted photocatalytic film was used as photocatalyst to degrade rhodamine B.