Preparation method of bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst

Abstract

The present invention discloses a method for preparing a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst. The photocatalytic material is prepared by an in-situ calcination method to form a composite photocatalyst of bismuth tungstate-bismuth silicate. The double Z-type heterojunction structure of bismuth tungstate-bismuth silicate-bismuth oxyhalide is obtained by controlling the addition of molten salt. This effectively solves the problem of unstable interface between bismuth tungstate and bismuth silicate, improves the separation and migration of photogenerated carriers, and simultaneously forms oxygen vacancies in the reaction system, thereby improving the light absorption capacity of the photocatalyst and greatly improving the utilization rate of light energy, alleviating current pollution problems. The photocatalytic material can be synthesized in a one-step process, which improves the synthesis efficiency and has a significant photocatalytic effect. It is expected to be put into industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and in particular relates to a method for preparing a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst. Background Art

[0002] Bismuth tungstate and bismuth silicate both have excellent visible light catalytic performance and stable physicochemical properties, and have been frequently used as photocatalytic materials in recent years. Single semiconductor photocatalysts have low stability, a limited light absorption range, and high electron-hole recombination efficiency, which cannot meet degradation requirements. Although there are attempts to improve photocatalytic performance by combining materials to form heterogeneous structures, the preparation process is cumbersome, the interface connection is unstable, and its performance cannot be regulated, which to some extent limits its photocatalytic performance. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst. The method has a simple process and simple equipment requirements, the prepared material has good dispersibility, the obtained composite photocatalyst has a uniform particle size distribution, has a smaller and thinner sheet structure, and has more active sites. This structure can effectively improve the utilization rate of light and enhance the photocatalytic activity.

[0004] In order to achieve the above object, the technical solution adopted in the present invention is:

[0005] A method for preparing a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst comprises the following steps:

[0006] Step 1: Place reactant 1 into a nylon jar and use zirconium oxide as a grinding ball to mix and ball-mill to obtain powder A, wherein reactant 1 is a mixture of Bi2O3 and SiO2;

[0007] Step 2: Put the second reactant into a nylon jar, use zirconium oxide as a grinding ball, and mix and mill to obtain B powder, wherein the second reactant is a mixture of Bi2O3 and WO3;

[0008] Step 3: Mix the A powder and the B powder with molten salt, grind and mix them, then calcine at 600° C. to 750° C. for 1 to 2 hours, air-cool to room temperature, and grind again to obtain C powder;

[0009] Step 4, halogen modification of the C powder; alternatively, water is added to the C powder and the pH is adjusted to , reacted in a water bath, and the obtained product is dried;

[0010] The bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst is obtained.

[0011] In one embodiment, in step 1, SiO2 and Bi2O3 are used in a Si:Bi molar ratio of 1:1 to 1:9.

[0012] In one embodiment, in step 2, Bi2O3 and WO3 are used in a molar ratio of 1:1 to 1:9.

[0013] In one embodiment, in step 2, Bi2O3 is first ground, and then Bi2O3 and WO3 are mixed and ground.

[0014] In one embodiment, the step 1 is ball milled for 3 hours to 5 hours, and the step 2 is ball milled for 3 hours to 5 hours.

[0015] In one embodiment, in step 3, the mass ratio of powder A to powder B is 1:1 to 1:3.

[0016] In one embodiment, the molten salt is a mixture of NaCl and KCl in a weight ratio of 1:1, and the amount of the molten salt is 20 wt% to 50 wt% of the total amount of the molten salt, the A powder, and the B powder.

[0017] In one embodiment, in step 3, after grinding and mixing, the temperature is increased at 5°C / min to 600°C to 750°C, and then kept at this temperature for calcination for 1 to 2 hours.

[0018] In one embodiment, the method of halogen modification in step 4 is as follows:

[0019] The C powder was washed alternately with water and alcohol for 3 to 5 times and dried to obtain the product. 0.2 g to 0.5 g of the powder was weighed, 30 mL of water was added and the mixture was stirred in a bath for 20 to 40 min. 1 g / L to 3 g / L of halogen salt was added to the obtained sample and the mixture was reacted for 30 min to 1 h, and then centrifuged three times to obtain the two-step modified product.

[0020] In one embodiment, in step 4, 0.1 g to 0.5 g of the powder material is weighed, 30 mL to 100 mL of water is added, and the mixture is stirred in a water bath for 20 min to 40 min. Nitric acid is added to adjust the pH, and the acid addition time is 5 min to 20 min. The mixture is washed alternately with water and alcohol to obtain a one-step modified product.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the present invention, by adding molten salt during the reaction process, a double Z-type heterostructure of bismuth tungstate-bismuth silicate-bismuth oxyhalide is directly obtained in the reaction. This structure can not only improve the separation and migration of photogenerated carriers at the composite interface, but also prevent the accumulation and recombination of photogenerated carriers. The introduced halogen ions enable better connection of the bismuth tungstate-bismuth silicate composite interface, making the heterogeneous interface more stable. In addition, the introduction of molten salt breaks up the large sheets of the prepared composite material, and the sheets are stacked to form a flower cluster structure, and the sheets become thinner. By effectively regulating the morphology and structure of the prepared material, it is beneficial to further catalytic reaction.

[0023] 2. The halogen ions introduced during the bismuth tungstate-bismuth silicate composite process of the present invention affect the absorption band edge of the reaction during the reaction, causing the valence band and conduction band positions of the photocatalyst to change, resulting in a significantly narrowed band gap of the prepared composite photocatalyst. After the introduction of halogen ion modification, oxygen vacancies are formed in the bismuth oxyhalide, resulting in adsorbed oxygen. At the same time, the fluorescence intensity of the prepared composite photocatalyst is significantly reduced by the addition of halogen, preventing the recombination between photogenerated electrons and holes, thereby improving the photocatalytic performance. At the same time, defects are formed on the catalyst surface, providing defect energy levels, which can not only improve its adsorption and activation capabilities, but also improve the light absorption characteristics of the photocatalyst.

[0024] 3. The method used in the present invention makes the independent structure of the sample more obvious, the layer becomes thinner, and the controllability is strong. The prepared powder has good dispersibility and has a good ability to degrade organic dyes and some antibiotics. At the same time, the mechanical properties and dielectric properties of the material are improved, and it can maintain good stability in a high temperature environment.

[0025] 4. The present invention has a short preparation cycle and a simple preparation process. The prepared powder has good dispersibility and a stable structure. Photocatalysts capable of degrading organic dyes and antibiotics such as norfloxacin can be prepared in one or two steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of the product after modification.

[0027] Figure 2 These are the degradation diagrams of Rhodamine B prepared by the one-step and two-step photocatalysts respectively. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings and examples. The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0029] A method for preparing a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst is disclosed, wherein the photocatalytic material is prepared by an in-situ calcination method to form a bismuth tungstate-bismuth silicate composite photocatalyst. The method specifically comprises the following steps:

[0030] Step 1:

[0031] Weigh Bi2O3 and SiO2 in a Si:Bi molar ratio of 1:1 to 1:9. Place the reactants in a nylon jar and mix and ball-mill for 3 to 5 hours using zirconium oxide as grinding balls to obtain powder A.

[0032] Step 2:

[0033] Weigh Bi2O3 and WO3 in a Bi:W molar ratio of 1:1 to 1:9. Grind the Bi2O3 first, then add the WO3 to the Bi2O3 in multiple batches and mix and grind until uniform. Place the reactants in a nylon jar and ball-mill using zirconium oxide balls for 3 to 5 hours to obtain powder B.

[0034] Step 3:

[0035] The two powders prepared in the above experiment were mixed with NaCl and KCl in a 1:1 weight ratio (Powder A:Powder B) at a mass ratio of 1:1 to 1:9, where the combined amount of NaCl and KCl accounted for 20% to 50% by weight of the total reactants. The ground and mixed powders were then calcined in a muffle furnace at 600°C to 750°C until they turned pale yellow. After the reaction, the sample was removed, cooled in air to room temperature, and ground to obtain Powder C.

[0036] Step 4:

[0037] The C powder was washed alternately with deionized water and anhydrous ethanol 3 to 5 times, centrifuged, and dried in a drying oven to obtain a product. The product was subjected to photocatalytic testing, and the best performance was selected according to the temperature and ratio. 0.2g to 0.5g of powder C and 30mL to 50mL of water were added. After stirring in a water bath for 20min to 40min, nitric acid was added to adjust the pH to approximately 1. Stirring in a water bath for 20min to 60min was continued. Halogen salts at concentrations of 1g / L to 3g / L were added to the sample obtained after stirring, and the reaction was carried out for 30min to 1h. After centrifugation 3 times, the sample after the two-step modification was obtained.

[0038] In this step, a two-step method is used to add a halogen salt to modify the photocatalyst. After the reaction, a bismuth halide oxycrystalline phase containing modified salt ions such as BiOCl and BiOBr appears, thereby improving the catalytic effect.

[0039] Step 5:

[0040] Based on step 3, weigh 0.1g to 0.5g of C powder, add 30mL to 100mL of water, stir in a water bath for 20min to 40min, add nitric acid to adjust the pH, and the acid addition time is 5min to 20min. Continue stirring in a water bath for 20min to 60min. The sample obtained after stirring is centrifuged once using water and alcohol alternately, and then dried to obtain the product after one-step modification.

[0041] This one-step method is a simplification of the two-step method in step 4. The reaction molten salt added during calcination is directly used as the halogen for modification, which reduces the step of washing the salt after calcination.

[0042] This method uses RhB organic contaminated solution as the target pollutant, tungsten oxide as the tungsten source, and bismuth oxide as the bismuth source to prepare Bi2WO6 powder. Based on the pure Bi2WO6 powder, a BWO-BSO composite photocatalyst is synthesized through solid-phase and molten salt methods, and modified by the introduction of a halide salt. Since BSO and BWO are mixed and calcined, the molten salt acts on both powders A and B during the calcination reaction, generating more B2 crystals to produce bismuth oxyhalide (BiOCl), resulting in a better photocatalytic effect. Furthermore, the addition of molten salts controlled the formation of a double Z-shaped heterostructure of bismuth tungstate-bismuth silicate-bismuth oxyhalide. This effectively addressed the unstable interface between the bismuth tungstate and bismuth silicate substrates, resulting in better connectivity at the bismuth tungstate-bismuth silicate composite interface and a more stable heterostructure. This enhanced the separation and migration of photogenerated carriers, while also creating oxygen vacancies within the reaction system, which increased the photocatalytic adsorption capacity and significantly improved light energy utilization, alleviating current pollution issues. Furthermore, the synthesis process can be performed in a single step, increasing synthesis efficiency. The photocatalytic performance of the BWO-BSO composite powder was investigated by varying factors such as calcination temperature, raw material silicon-bismuth ratio, acid addition time, and water content. This significantly increased the surface area and significantly improved the absorptivity of visible light radiation.

[0043] Example 1

[0044] (1) SiO2 and Bi2O3 were weighed in a Si:Bi molar ratio of 1:1, placed in a nylon jar, and mixed and ball-milled for 3 h using zirconium oxide as grinding balls to obtain powder material A;

[0045] (2) Next, Bi2O3 and WO3 were weighed separately at a Bi:W molar ratio of 1:1. The weighed Bi2O3 was first ground, and then the weighed WO3 was added to the Bi2O3 in four batches and mixed and ground evenly. The reactants were placed in a nylon jar and ball-milled for 3 hours using zirconium oxide as grinding balls to obtain powder material B.

[0046] (3) The two powders prepared in the above experiment were mixed at a ratio of 1:3 between BSO and BWO and a reaction molten salt (20 wt% in total) at a ratio of 1:1 between NaCl and KCl. The ground and mixed powders were then placed in a muffle furnace and calcined at 600°C until a light yellow powder was obtained. After the reaction, the sample was removed and cooled in air to obtain powder product C.

[0047] (4) The product C obtained in step 3 was washed three times with water and alcohol alternately, centrifuged and dried in a drying oven, and the obtained product was subjected to a photocatalytic test. According to the temperature ratio, a group of samples with the best performance was selected. 0.26 g of powder was weighed, 30 mL of water was added, and the mixture was stirred in a water bath for 20 min. Acid was added to adjust the pH to 1, and the mixture was stirred in a water bath for 30 min. The sample obtained after stirring was modified by adding a halogen salt with a concentration of 1.1 g / L for 30 min to obtain a sample after the two-step modification method;

[0048] (5) Weigh 0.1 g of powder material C, add 30 mL of water, stir in a water bath for 20 min, add nitric acid to adjust the pH, and add acid for 5 min. Continue stirring in a water bath for 20 min. The sample obtained after stirring is centrifuged once using water and alcohol alternately, and dried to obtain the final product after one-step modification.

[0049] Figure 1 The product of Example 2, prepared using a two-step process, exhibits a smooth, interlocking morphology of small flakes. The flakes vary in size, and the stacked flakes are spaced apart by small amounts of particles. The clustered structure of the stacked flakes is more pronounced. This structure is highly controllable and exhibits improved photocatalytic performance.

[0050] Figure 2 The following diagram shows the photocatalytic degradation of rhodamine B using a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst, prepared using both a one-step and two-step method. In the experiment, 0.03g of the catalyst was added to 30mL of 10mg / L rhodamine B. The photocatalytic reaction was then carried out for 90 minutes, with 60 minutes in the dark and 30 minutes in the light. The figure shows that after 30 minutes of illumination, the degradation rate for the two-step method is close to 100%, while the degradation rate for the one-step method is close to 90%.

[0051] Example 2

[0052] (1) SiO2 and Bi2O3 were weighed in a Si:Bi molar ratio of 1:6, placed in a nylon jar, and mixed and ball-milled for 4.5 h using zirconium oxide as grinding balls to obtain powder material A;

[0053] (2) Next, Bi2O3 and WO3 were weighed separately at a Bi:W molar ratio of 1:6. The weighed Bi2O3 was first ground, and then the weighed WO3 was added to the Bi2O3 in two batches and mixed and ground evenly. The reactants were placed in a nylon jar and ball-milled for 4 hours using zirconium oxide as grinding balls to obtain powder material B.

[0054] (3) The two powders prepared in the above experiment were mixed with a reaction molten salt (50 wt% in total) at a ratio of 1:4 of BSO and BWO and a ratio of 1:1 of NaCl and KCl. The ground and mixed powders were placed in a muffle furnace and calcined at 650°C until a light yellow powder was obtained. After the reaction, the sample was removed and cooled in air to obtain powder product C.

[0055] (4) The product C obtained in step 3 was washed alternately four times in the order of water-alcohol, centrifuged and dried in a drying oven, and the obtained product was subjected to a photocatalytic test. According to the temperature ratio, a group of samples with the best performance was selected. 0.3 g of powder was weighed, 35 mL of water was added, and the mixture was stirred in a water bath for 20 min. Acid was added for 8 min, and the pH was adjusted to 1. After the pH was adjusted, the mixture was stirred in a water bath for 40 min. The sample obtained after stirring was added with a halogen salt with a concentration of 1.6 g / L and reacted for 40 min to obtain a sample after the two-step modification;

[0056] (5) Weigh 0.3 g of powder material C, add 50 mL of water, stir in a water bath for 35 min, add nitric acid to adjust the pH, and continue stirring in a water bath for 40 min. The sample obtained after stirring is centrifuged once using water and alcohol alternating centrifugation, and dried to obtain the final product after one-step modification.

[0057] Example 3

[0058] (1) SiO2 and Bi2O3 were weighed in a Si:Bi molar ratio of 1:9, placed in a nylon jar, and mixed and ball-milled for 3 h using zirconium oxide as a grinding ball to obtain powder material A;

[0059] (2) Weigh Bi2O3 and WO3 separately at a Bi:W molar ratio of 1:3. Grind the weighed Bi2O3 first, then add the weighed WO3 to the Bi2O3 in two batches and mix and grind until uniform. Place the reactants in a nylon jar and use zirconium oxide as grinding balls. Mix and ball mill for 5 hours to obtain powder material B.

[0060] (3) The two powders prepared in the above experiment were mixed at a ratio of 1:9 of BSO and BWO with a reaction molten salt (total amount 40 wt%) at a ratio of 1:1 of NaCl and KCl. The ground and mixed powders were placed in a muffle furnace and calcined at 700°C until a light yellow powder was obtained. After the reaction was completed, the sample was removed and cooled in air to obtain powder product C.

[0061] (4) The product C obtained in step 3 was washed alternately 4 times in the order of water-alcohol, centrifuged and dried in a drying oven, and the obtained product was subjected to a photocatalytic test. According to the temperature ratio, a group of samples with the best performance was selected. 0.5 g of powder was weighed, 50 mL of water was added, and the mixture was stirred in a water bath for 40 min. Acid was added for 8 min, and the pH was adjusted to 1. After the pH was adjusted, stirring was continued in a water bath for 35 min. The sample obtained after stirring was added with a halogen salt with a concentration of 2.6 g / L and reacted for 1 h to obtain a sample modified by the two-step method;

[0062] (5) Weigh 0.5 g of powder material C, add 100 mL of water, stir in a water bath for 40 min, add nitric acid to adjust the pH, add acid for 20 min, continue stirring in a water bath for 60 min, and centrifuge the sample obtained after stirring once using water and alcohol alternating centrifugation. After drying, the final product after one-step modification is obtained.

[0063] The method of the present invention is simple to operate, and the prepared powder has uniform particle size distribution and good dispersibility. The obtained composite material not only has the effect of a new heterogeneous structure, but also has a smaller and thinner lamellar structure that provides more active sites, thereby exhibiting higher photocatalytic performance. In addition, the photocatalyst is generally applicable and recyclable to antibiotics, and has the ability to degrade tetracycline (TC), norfloxacin (NFX) and ciprofloxacin (CIP), greatly broadening its application scope and application prospects.

[0064] In more embodiments of the present invention, the aforementioned parameters are combined in different types. For example, in step 1), the mixing ratios of Bi2O3 and SiO2 are selected as 1:1, 1:3, 1:5, 1:6, and 1:9, respectively, and the ball milling times are selected as 3h, 3.3h, 4h, 4.3h, and 5h, respectively. The results show that powder A can be prepared in all of these cases.

[0065] Similarly, in step 2), Bi2O3 and WO3 were mixed in ratios of 1:1, 1:3, 1:6, and 1:8, respectively, and the ball milling time was 3h, 3.3h, 4h, 4.5h, and 5h, respectively. The results showed that powder B could be prepared.

[0066] Similarly, in step 3), the two powders prepared in the above experiment were used to conduct experiments with NaCl and KCl as experimental salts, and were mixed in proportions of 20wt%, 30wt%, 40wt%, and 50wt%, respectively. The ground and evenly mixed mixed powders were placed in a muffle furnace and calcined at temperatures of 600°C, 650°C, 690°C, and 720°C, respectively. After the reaction, the mixture was cooled to room temperature, centrifuged, and dried in a drying oven. The results showed that powder product C could be prepared.

[0067] Similarly, in step 4), the obtained product C was washed alternately with deionized water and anhydrous ethanol 3 times, 4 times, and 5 times, respectively, and then dried after centrifugation. The obtained product was subjected to photocatalytic test and tested according to temperature and ratio. The group with the best performance was selected for molten salt modification. 30 mL, 40 ml, and 50 ml of water were added and stirred for 20 min, 30 min, and 40 min, and then nitric acid was added to adjust the pH. The mixture was stirred in a water bath for 20 min, 40 min, and 60 min. Halogen salts with concentrations of 1.1 g / L, 1.6 g / L, 2.6 g / L, and 3 g / L were added to the stirred samples, stirred in a water bath for 1 h, 2 h, and 3 h, and then centrifuged 3 times to obtain the desired modified samples.

[0068] Similarly, in step 5), 0.1 g, 0.3 g, and 0.5 g of the powder material C were weighed, 30 mL, 50 mL, 70 mL, and 100 mL of water were added, and the mixture was stirred in a water bath for 20 min, 35 min, and 40 min. Then, nitric acid was added to adjust the pH, and the acid addition time was 5 min, 8 min, 10 min, and 20 min. The mixture was stirred in a water bath for 20 min, 40 min, and 60 min. The stirred samples were centrifuged alternately with water and alcohol once, dried, and photocatalytic tests were performed according to different factors. The group with the best performance was the final product.

[0069] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, substitutions, combinations, simplifications, etc. made based on the principles or spirit of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst, characterized in that: The steps include: Step 1: Place reactant 1 into a nylon jar and use zirconium oxide as a grinding ball to mix and ball-mill to obtain powder A, wherein reactant 1 is a mixture of Bi2O3 and SiO2; Step 2: Put the second reactant into a nylon jar, use zirconium oxide as a grinding ball, and mix and mill to obtain B powder, wherein the second reactant is a mixture of Bi2O3 and WO3; Step 3: Mix the A powder and the B powder with molten salt, grind and mix them, then calcine at 600° C. to 750° C. for 1 to 2 hours, air-cool to room temperature, and grind again to obtain C powder; The molten salt is a mixture of NaCl and KCl in a weight ratio of 1:1, and the amount of the molten salt is 20wt% to 50wt% of the total amount of the molten salt, the A powder, and the B powder; Step 4, halogen modification of the C powder is performed as follows: the C powder is washed alternately with water and alcohol 3 to 5 times, and dried to obtain a product, 0.2 g to 0.5 g of the powder is weighed, 30 mL of water is added, and the mixture is stirred in a bath for 20 min to 40 min, 1 g / L to 3 g / L of a halogen salt is added to the obtained sample, and the reaction is carried out for 30 min to 1 h, followed by centrifugation three times to obtain a bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst modified by the two-step method; or, Weigh 0.1 g to 0.5 g of C powder, add 30 mL to 100 mL of water, stir in a water bath for 20 min to 40 min, add nitric acid to adjust the pH, add acid for 5 min to 20 min, and wash alternately with water and alcohol to obtain a one-step modified bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst.

2. The method for preparing the bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst according to claim 1, characterized in that: In the step 1, SiO2 and Bi2O3 are taken according to a Si:Bi molar ratio of 1:1 to 1:

9.

3. The method for preparing the bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst according to claim 1, characterized in that: In the step 2, Bi2O3 and WO3 are taken in a molar ratio of 1:1 to 1:

9.

4. The method for preparing the bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst according to claim 1, characterized in that: In the step 2, Bi2O3 is first ground, and then Bi2O3 and WO3 are mixed and ground.

5. The method for preparing the bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst according to claim 1, characterized in that: In the step 1, the ball milling is performed for 3 hours to 5 hours, and in the step 2, the ball milling is performed for 3 hours to 5 hours.

6. The method for preparing the bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst according to claim 1, characterized in that: In the step 3, the mass ratio of powder A to powder B is 1:1 to 1:

3.

7. The method for preparing the bismuth tungstate-bismuth silicate-bismuth oxyhalide double Z-type heterojunction photocatalyst according to claim 1, characterized in that: In the step 3, after grinding and mixing, the temperature is increased at 5° C. / min to 600° C. to 750° C., and then kept at this temperature for 1 to 2 hours.

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