Preparation method and application of S-type photocatalytic material Bi2MoO6 / CdS

Abstract

The invention discloses a preparation method and application of an S-type photocatalytic material Bi2MoO6 / CdS. According to the preparation method, an S-type Bi2MoO6 / CdS heterojunction is synthesized by adopting a simple hydrothermal method. When the mass ratio of Bi2MoO6 to CdS is 1: 4, the degradation efficiency of Cr (VI) (20 mg / L, pH = 3) is 100% after 16 min of visible light irradiation, and the reaction kinetic constants (0.2339 min 1) are respectively 334.1 and 3.5 times that of single Bi2MoO6 and CdS. After five times of circulation, the photocatalytic activity is basically kept unchanged (llt; 4%). Therefore, the photocatalyst has great application potential in the aspect of removing Cr (VI) through photocatalysis.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic materials, and specifically relates to an S-type photocatalytic material Bi 2 MoO 6 / CdS preparation method and application. Background Art

[0002] With the development of industry, the treatment of heavy metal industrial wastewater, especially chromium-containing wastewater, has gradually become an issue that cannot be ignored. Traditional hexavalent chromium wastewater treatment methods are often accompanied by high costs, complex operations, and insufficient treatment effects. There is still room for improvement in practical applications.

[0003] As an environmentally friendly, economically efficient, safe and green treatment technology, semiconductor photocatalysis technology has a very broad application prospect in the field of water pollution control. Bismuth molybdate, as a material with simple preparation and excellent performance in the bismuth-based semiconductor family, has attracted widespread attention in recent years; bismuth-containing semiconductors have attracted widespread attention in the field of semiconductor photocatalysis due to their unique layered structure and excellent performance in promoting photocatalytic reactions.

[0004] Bismuth molybdate (Bi 2 MoO 6 ) has a suitable band gap (2.5~2.8 eV) and has [MoO 4 ] 2− and [Bi 2 O 2 ] 2+ The unit alternately stacked layer structure, mild synthesis conditions, adjustable morphology and properties, has attracted extensive attention from researchers due to its excellent performance. However, the large-scale application in wastewater purification is hampered by the serious recombination of photogenerated carriers, narrow visible light response, and low quantum yield.

[0005] The application of metal sulfides in the field of photocatalysis is becoming more and more prominent, among which cadmium sulfide (CdS) is highly favored due to its small band gap and good band structure.

[0006] Currently, there is no 2 MoO 6 The band structure of CdS is combined with the band structure of CdS to enhance the photocatalytic reduction ability of Cr(VI). Summary of the invention

[0007] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0008] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0009] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide an S-type photocatalytic material Bi 2 MoO 6 / CdS preparation method.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions: an S-type photocatalytic material Bi 2 MoO 6 / CdS preparation method, comprising, Thioacetamide and Cd(CH 3 COO 2 ∙2H 2 O is dissolved in ethylene glycol and stirred evenly, and ethanol is added to prepare a mixture; Add Bi to the mixture 2 MoO 6 , ultrasonic mixing, solvent thermal reaction, natural cooling, collection of precipitation, washing, drying, and preparation of Bi 2 MoO 6 / CdS; Among them, Bi 2 MoO 6 The theoretical mass ratio of ethylene glycol to ethanol is 3:4.

[0011] As a preferred embodiment of the preparation method of the present invention, wherein: the Bi 2 MoO 6 The preparation method comprises: Bi(NO) 3 .5H 2 O is dissolved in ethylene glycol to obtain Bi(NO) 3 .5H 2 O Ethylene glycol solution; Will Na 2 MoO 6 ⋅2H 2 O is dissolved in ethylene glycol to produce Na 2 MoO 6 ⋅2H 2 O Ethylene glycol solution; Bi(NO) 3 ⋅5H 2 O ethylene glycol solution was added dropwise to Na 2 MoO 6 ⋅2H 2 O ethylene glycol solution to obtain a mixed solution; Ethanol was added to the mixture, heated at 160 °C for 12 h, and the product was dried to obtain Bi 2 MoO 6 .

[0012] As a preferred embodiment of the preparation method of the present invention, wherein: the Bi(NO) 3 .5H 2 Bi(NO) in ethylene glycol solution 3 ⋅5H 2 The ratio of O to ethylene glycol is 0.9702 g:15 mL.

[0013] As a preferred embodiment of the preparation method of the present invention, wherein: the Na 2 MoO 6 ⋅2H 2 The ratio of ethylene glycol solution is 0.2425 g:15 mL.

[0014] As a preferred embodiment of the preparation method of the present invention, wherein: Bi(NO) in the mixed solution 3 ⋅5H 2 O and Na 2 MoO 6 ⋅2H 2 The ratio of O is 0.9702 g:0.2425 g.

[0015] As a preferred embodiment of the preparation method of the present invention, wherein: ethanol is added to the mixed solution, wherein the volume ratio of ethylene glycol to ethanol is 3:4, and Bi(NO) 3 ⋅5H 2 The dropping speed of ethylene glycol solution was 1 mL / min.

[0016] As a preferred embodiment of the preparation method of the present invention, the mixture, wherein thioacetamide, Cd(CH 3 COO 2 ∙2H 2 The ratio of O, ethylene glycol, and ethanol is 0.5638 g: 1 g: 30 mL: 40 mL.

[0017] As a preferred embodiment of the preparation method of the present invention, the solvent thermal reaction has a reaction temperature of 180° C. and a reaction time of 12 h.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide an S-type photocatalytic material Bi 2 MoO 6 S-type photocatalytic material Bi / CdS prepared by the preparation method 2 MoO 6 / CdS.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide an S-type photocatalytic material Bi 2 MoO 6 / Application of CdS in photocatalytic degradation of Cr(VI) in wastewater, including: 10 mg of photocatalytic material Bi 2 MoO 6 / CdS was suspended in 50 mL of 20 mg / L Cr(VI), and the suspension was stirred in the dark for 1 h before illumination to reach adsorption-desorption equilibrium; After reaching adsorption-desorption equilibrium, turn on the light and let the reaction proceed for 16 min; The reaction conditions are as follows: irradiation with a 300 W xenon lamp and visible light radiation at room temperature.

[0020] Beneficial effects of the present invention: (1) The present invention provides an S-type photocatalytic material Bi 2 MoO 6 / CdS preparation method, Bi(NO) 3 ⋅5H 2 O ethylene glycol solution was added dropwise to Na 2 MoO 6 ⋅2H 2 Then the mixture was transferred into a 100 ml Teflon autoclave and 40 ml ethanol was added, i.e. the volume ratio of ethylene glycol to ethanol was 3:4, which formed a special micro-reaction condition and was conducive to the nanosheet Bi 2 MoO 6 The formation of Cr(VI) has an excellent degradation effect.

[0021] (2) The present invention is 2 MoO 6 When the input amount of / CdS is small, when it is 0.2 g / L, after 16 min of visible light irradiation, the degradation efficiency of Cr(VI) 20 mg / L pH = 3 is 100%, and the reaction kinetic constants are single Bi 2 MoO 6 and 334.1 and 3.5 times that of CdS.

[0022] (3) Bi of the present invention 2 MoO 6 Bi is preferred in the preparation of CdS 2 MoO 6 : The theoretical mass ratio of CdS is 1:4, which has the best catalytic effect and shows excellent stability. After 5 cycles, the reduction efficiency remains at 96.2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them: Figure 1 The S-type Bi prepared in the embodiment of the present invention 2 MoO 6 / CdS heterojunction XRD pattern.

[0024] Figure 2 The S-type Bi prepared in the embodiment of the present invention 2 MoO 6 SEM image of / CdS heterojunction.

[0025] Figure 3 The S-type Bi prepared in the embodiment of the present invention 2 MoO 6 EDS image of / CdS heterojunction.

[0026] Figure 4 The S-type Bi prepared in the embodiment of the present invention 2 MoO 6 TEM image of / CdS heterojunction.

[0027] Figure 5 The S-type Bi prepared in the embodiment of the present invention 2 MoO 6 , CdS and Bi 2 MoO 6 / CdS heterojunction Cr(VI) reduction diagram.

[0028] Figure 6 The S-type Bi prepared in the embodiment of the present invention 2 MoO 6 / CdS heterojunction five-cycle stability diagram.

[0029] Figure 7 Bi in the embodiment of the present invention 2 MoO 6 Effect of the mass ratio of / CdS on the removal performance of Cr(VI).

[0030] Figure 8 Bi in Example 5 of the present invention 2 MoO 6 / CdS performance test results; a is Bi 2 MoO6 The bandgap width diagram obtained by converting the solid diffuse reflection test data through the Kubelka-Munk function, b is the bandgap width diagram obtained by converting the CdS solid diffuse reflection test data through the Kubelka-Munk function, and c is the Bi obtained by VB-XPS test 2 MoO 6 and CdS valence band diagram, d is the Bi obtained by theoretical simulation 2 MoO 6 The work function is used to obtain the Femi energy level position diagram. e is the work function of CdS obtained by theoretical simulation and the Femi energy level position diagram is obtained. f is the Bi 2 MoO 6 Schematic diagram of the energy band structure of / CdS photocatalytic material and the interface electron transfer pathway.

[0031] Fig. 9 This is an electron paramagnetic resonance test diagram of hydroxyl radicals and superoxide radicals in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments. The raw materials in the present invention are all common commercially available products.

[0035] Example 1 This embodiment provides a Bi 2 MoO 6 The main steps of preparation are: (1) Change Bi(NO) 3 ⋅5H 2 O 0.9702 g dissolved in 15 mL ethylene glycol for 30 min; Put 0.2425 g Na 2 MoO 6 ⋅2H 2 O was dissolved in 15 mL of ethylene glycol for 30 min; Then Bi(NO) 3 ⋅5H 2 O ethylene glycol solution was added dropwise to Na 2 MoO 6 ⋅2H 2 O ethylene glycol solution, with a dropwise addition rate of 1 ml / min, to obtain a mixture; (2) The mixture was transferred into a 100 ml Teflon autoclave, and 40 ml of ethanol was added, i.e., the volume ratio of ethylene glycol to ethanol was 3:4. After stirring for 30 min, it was heated at 160 °C for 12 h. After the solvent thermal reaction, it was naturally cooled and the precipitate was collected and washed alternately with distilled water and ethanol. (3) Finally, the product was dried at 80 °C for 6 h to obtain Bi 2 MoO 6 .

[0036] Example 2 (1) Mix 0.5638 g of thioacetamide and 1 g of Cd(CH 3 COO 2 ∙2H 2 O was dissolved in 30 mL of ethylene glycol and stirred for 30 min, then 40 mL of ethanol was added; (2) The mixture was poured into a 100 mL Teflon-lined autoclave and 0.1355 g of Bi prepared in Example 1 was added. 2 MoO 6 ,Bi 2 MoO 6 :CdS theoretical mass ratio is 1:4, ultrasonic treatment is performed for 0.5 h, heating is performed at 180℃ for 12 h, and the precipitate is collected after natural cooling; (3) Finally, rinse with deionized water and ethanol and dry at 80 °C for 6 h. The catalyst Bi was obtained by solvothermal method. 2 MoO 6 / CdS spare.

[0037] The S-type Bi prepared in this embodiment 2 MoO 6 / CdS heterojunction, see Figure 1 ;from Figure 1 It can be seen that the prepared Bi 2 MoO 6 / CdS heterojunction materials and Bi 2 MoO 6 One-to-one correspondence with the standard card number of CdS proves that Bi 2 MoO 6 / CdS heterojunction material was successfully prepared.

[0038] The S-type Bi prepared in this embodiment 2 MoO 6 SEM image of / CdS heterojunction, see Figure 2 , through the scanning electron microscope test, it can be seen from the figure that Bi 2 MoO 6 and CdS are evenly mixed together.

[0039] The S-type Bi prepared in this embodiment 2 MoO 6 EDS image of / CdS heterojunction, see Figure 3 Through the EDS analysis of the scanning electron microscope, it can be seen from the figure that the prepared Bi 2 MoO 6 The element mass ratio of Cd / CdS 1:4 is basically consistent with the theoretical value.

[0040] The S-type Bi prepared in this embodiment 2 MoO 6 TEM image of / CdS heterojunction, see Figure 4 ; Transmission electron microscopy test From the figure, we can see that Bi 2 MoO 6 and CdS in nanosheet form and evenly compounded to form Bi 2 MoO 6 and CdS interface, providing an effective basic guarantee for the S-type electron transfer pathway.

[0041] Example 3 0.5638 g of thioacetamide and 1 g of Cd(CH 3 COO 2 ∙2H 2 O was dissolved in 30 mL of ethylene glycol for 30 min, then 40 mL of ethanol was added, and the mixture was poured into a 100 mL Teflon autoclave and treated at 180 °C for 12 h; The obtained yellow CdS was washed alternately with deionized water and ethanol four times; The product was dried in an oven at 80°C overnight to obtain CdS.

[0042] Photocatalytic reaction conditions in the embodiments of the present invention: All batches of photoreduction experiments were carried out at room temperature, using a 300 W xenon lamp system equipped with a 420 nm cut-off filter as a visible light source, and under the irradiation of a visible light source; The specific steps are as follows: 10 mg of sample was suspended in 50 mL of 20 mg / L Cr(VI), and the suspension was stirred in the dark for 1 h before irradiation to reach adsorption-desorption equilibrium; After reaching adsorption-desorption equilibrium, the light was turned on and 5 ml of solution was taken out every 4 minutes; the concentration of Cr(VI) was detected at 542 nm using the diphenylurea (DPC) colorimetric method.

[0043] from Figure 5 It can be seen that when Bi 2 MoO 6 When the input amount of / CdS was 0.2 g / L, after 16 min of visible light irradiation, the degradation efficiency of Cr(VI) 20 mg / L pH = 3 was 100%, and the reaction kinetic constant was 0.2339 min −1 Single Bi 2 MoO 6 and 334.1 and 3.5 times that of CdS.

[0044] from Figure 6 It can be seen that Bi 2 MoO 6 / CdS showed excellent stability, and the reduction efficiency remained at 96.2% after 5 cycles.

[0045] Example 4 0.5638 g of thioacetamide and 1 g of Cd(CH 3 COO 2 ∙2H 2 O was dissolved in 30 mL of ethylene glycol and stirred for 30 min, then 40 mL of ethanol was added and the mixture was poured into a 100 mL Teflon-lined autoclave; Add different qualities of Bi 2 MoO 6 (Bi 2 MoO 6 / CdS mass ratio was 1:1, 1:2, 1:3, 1:4, 1:5), ultrasonic treatment was performed for 0.5 h, heating was performed at 180 °C for 12 h, the precipitate was collected by natural cooling, and finally rinsed with deionized water and ethanol, and dried at 80 °C for 6 h; The above catalyst Bi with different mass ratios was obtained by solvothermal method. 2 MoO 6 / CdS is used as a backup and the performance of removing Cr(VI) is tested.

[0046] Results Figure 7 , it can be seen that Bi 2 MoO 6 / CdS As the mass of CdS increases, Bi 2 MoO 6The photocatalytic activity of CdS / CdS was enhanced, and the catalytic effect of the mass ratio of 1:4 was the best. After 16 min of visible light irradiation, the degradation efficiency of Cr(VI) 20 mg / L pH = 3 was 100%, and the degradation efficiency of Bi 2 MoO 6 / CdS 1:4 reaction kinetic constants are 0.2339 min−1 for single Bi 2 MoO 6 and 334.1 and 3.5 times that of CdS, and the reduction efficiency remained at 96.2% after 5 cycles; the catalytic activity decreased when the mass ratio was 1:5, which may be due to the excessive CdS covering the active sites.

[0047] Example 5 Determination of Bi prepared in Example 2 2 MoO 6 / CdS heterojunction performance, see Figure 8 , Fig. 9 ,from Figure 8 As can be seen from a and b, the solid diffuse reflection test data is converted into Bi by Kubelka-Munk function. 2 MoO 6 The band gaps of CdS and CdS are 2.64 and 2.3 eV respectively. Figure 8 c is Bi obtained by VB-XPS test 2 MoO 6 and CdS valence bands, 2.43 and 1.44 eV, respectively. Figure 8 Theoretical simulations of d and e in Bi 2 MoO 6 The Femi energy level positions of CdS and Bi are 1.797 and 1.146 eV respectively. The Femi energy level position of CdS is higher than that of Bi 2 MoO 6 ,from Figure 8 e,Bi 2 MoO 6 After uniform contact with CdS, the interface electrons flow from CdS to Bi 2 MoO 6 , and then form a built-in electric field at the interface. Under visible light irradiation, Bi 2 MoO 6 Under the action of the built-in electric field, the electrons in the conduction band transfer to the valence band of CdS to form an S-type electron transfer mode, which helps to improve the separation efficiency of photogenerated carriers and maintain the original high oxidizability and reducibility; Figure 8 It can be seen in figure f that under the action of the built-in electric field, the photogenerated carriers form an S-type electron transfer mode, maintaining the original high oxidizability and reducibility, thereby effectively improving the photocatalytic activity.

[0048] from Fig. 9 The electron paramagnetic resonance test of hydroxyl radical and superoxide radical can prove that there are hydroxyl radical and superoxide radical signals under the action of light and the signals increase with the increase of light exposure time. The carriers are transferred according to the S-type electron transfer mode. Otherwise, there will be no hydroxyl radical and superoxide radical signals under the action of light according to the traditional II-type electron transfer mode.

[0049] In summary, the present invention provides an S-type photocatalytic material Bi 2 MoO 6 / CdS preparation method, Bi(NO) 3 ⋅5H 2 O ethylene glycol solution was added dropwise to Na 2 MoO 6 ⋅2H 2 Then the mixture was transferred into a 100 ml Teflon autoclave and 40 ml ethanol was added, i.e. the volume ratio of ethylene glycol to ethanol was 3:4, which formed a special micro-reaction condition and was conducive to the nanosheet Bi 2 MoO 6 The formation of Cr(VI) has an excellent degradation effect; when the volume ratio of ethylene glycol: ethanol is not 3:4, the effect is not good.

[0050] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A method for preparing an S-type photocatalytic material Bi2MoO6 / CdS, characterized in that: include, Thioacetamide and Cd(CH3COO)2∙2H2O are dissolved in ethylene glycol and stirred evenly, and ethanol is added to prepare a mixture; Bi2MoO6 is added to the mixture, mixed evenly by ultrasonication, reacted by solvent heat, cooled naturally, precipitated, washed and dried to obtain Bi2MoO6 / CdS; Among them, the theoretical mass ratio of Bi2MoO6:CdS is 1:4, and the volume ratio of ethylene glycol:ethanol in the solvothermal reaction is 3:

4.

2. The preparation method according to claim 1, characterized in that: The preparation method of Bi2MoO6 comprises: Dissolving Bi(NO)3.5H2O in ethylene glycol to prepare a Bi(NO)3.5H2O ethylene glycol solution; Dissolve Na2MoO6⋅2H2O in ethylene glycol to prepare Na2MoO6⋅2H2O ethylene glycol solution; The Bi(NO)3⋅5H2O ethylene glycol solution was added dropwise to the Na2MoO6⋅2H2O ethylene glycol solution to prepare a mixed solution; Ethanol was added to the mixed solution, heated at 160°C for 12 h, and the product was dried to obtain Bi2MoO6.

3. The preparation method according to claim 2, characterized in that: The ratio of Bi(NO)3⋅5H2O to ethylene glycol in the Bi(NO)3.5H2O ethylene glycol solution is 0.9702 g:15 mL.

4. The preparation method according to claim 2 or 3, characterized in that: The ratio of the Na2MoO6⋅2H2O ethylene glycol solution is 0.2425 g:15 mL.

5. The preparation method according to claim 4, characterized in that: The ratio of Bi(NO)3⋅5H2O to Na2MoO6⋅2H2O in the mixed solution is 0.9702 g:0.2425 g.

6. The preparation method according to claim 5, characterized in that: The step of adding ethanol to the mixed solution has a volume ratio of ethylene glycol to ethanol of 3:4, and a dropping speed of the Bi(NO)3⋅5H2O ethylene glycol solution of 1 mL / min.

7. The preparation method according to claim 1, characterized in that: The mixture includes thioacetamide, Cd(CH3COO)2∙2H2O, ethylene glycol and ethanol in a ratio of 0.5638 g: 1 g: 30 mL: 40 mL.

8. The preparation method according to claim 1 or 7, characterized in that: The solvent thermal reaction has a reaction temperature of 180° C. and a reaction time of 12 h.

9. The S-type photocatalytic material Bi2MoO6 / CdS prepared by the preparation method described in any one of claims 1 to 8.

10. The use of the S-type photocatalytic material Bi2MoO6 / CdS according to claim 9 in photocatalytic degradation of Cr(VI) in wastewater, characterized in that: include, 10 mg of photocatalytic material Bi2MoO6 / CdS was suspended in 50 mL of 20 mg / L Cr(VI). Before irradiation, the suspension was stirred in the dark for 1 h to reach adsorption-desorption equilibrium. After reaching adsorption-desorption equilibrium, turn on the light and let the reaction proceed for 16 min; The reaction conditions are as follows: irradiation with a 300 W xenon lamp and visible light radiation at room temperature.

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