BiO2-x / CdS photocatalyst as well as preparation method and application thereof

Abstract

The invention provides a BiO2-x / CdS photocatalyst as well as a preparation method and application thereof, and belongs to the technical field of photocatalytic materials. The BiO < 2-x > / CdS photocatalyst provided by the invention comprises BiO < 2-x > / CdS and CaCO3 doped in the BiO < 2-x > / CdS, wherein the CaCO3 is doped in the BiO < 2-x > / CdS; the mass ratio of BiO2-x to CdS in the BiO2-x / CdS is 1: (1-4); the doping amount of the CaCO3 is 7.69 wt% to 25.00 wt%. According to the preparation method, CaCO3 is doped in BiO2-x / CdS, so that the stability of the prepared BiO2-x / CdS photocatalytic material in a three-time cycle Cr (VI) photocatalytic reduction experiment is improved to 68.91% from 8.51% of BiO2-x / CdS which is not doped with CaCO3, and the BiO2-x / CdS photocatalytic material has excellent cycle stability; and the photocatalytic performance of the BiO2-x / CdS photocatalyst disclosed by the invention is also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic materials, and in particular to a BiO 2-x / CdS photocatalyst and its preparation method and application. Background Art

[0002] Nowadays, stainless steel is widely used, and more Cr(VI) is introduced into the environment, causing more environmental pollution problems. Therefore, it is necessary to find effective methods to solve this problem. In recent years, photocatalytic technology is considered to be an efficient and clean environmental pollution treatment technology. A series of modification studies have been conducted to improve the photocatalytic activity of materials. 2-x As a kind of photocatalytic material, it has been widely studied due to its unique electronic and layered structure, but its narrow band gap and poor stability limit its use. CdS, as an excellent photocatalytic material, has been used in photocatalytic hydrogen production, degradation and heavy metal reduction, but the material has poor stability and severe photocorrosion. 2-x After being compounded with CdS, its cyclic stability of photocatalytic reduction of Cr(VI) is also poor, with only low photocatalytic performance after one cycle, and a defect of poor stability. Summary of the invention

[0003] The present invention aims to provide a BiO 2-x / CdS photocatalyst and its preparation method and application, BiO prepared by the present invention 2-x / CdS photocatalyst has excellent stability and still has high photocatalytic performance after multiple cycles.

[0004] In order to achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0005] A BiO 2-x / CdS photocatalysts, including BiO 2-x / CdS and doped in the BiO 2-x / CaCO3 in CdS;

[0006] The BiO 2-x BiO in CdS 2-x The mass ratio of CaCO3 to CdS is 1:1-4; the doping amount of CaCO3 is 7.69-25.00wt%.

[0007] The present invention also provides the BiO 2-x The preparation method of the CdS photocatalyst comprises the following steps:

[0008] The water-soluble sulfur source, water-soluble cadmium source, BiO 2-x, CaCO3 and water are mixed to precipitate to obtain the BiO 2-x / CdS photocatalyst.

[0009] Preferably, the water-soluble sulfur source is Na2S; the water-soluble cadmium source is Cd(NO3)2.

[0010] Preferably, the BiO 2-x The preparation method comprises the following steps:

[0011] The bismuth source, the alkaline reagent and water are mixed and subjected to hydrothermal treatment to obtain the BiO 2-x Powder.

[0012] Preferably, the bismuth source is bismuthate; and the alkaline agent is a strong base.

[0013] Preferably, the temperature of the hydrothermal treatment is 160-180° C., and the time is 6-10 hours.

[0014] Preferably, the precipitation temperature is room temperature and the time is 60 to 120 minutes.

[0015] The present invention also provides the BiO 2-x / CdS photocatalyst or BiO prepared by the preparation method described in the above technical scheme 2-x Application of / CdS photocatalyst in reduction of Cr(VI).

[0016] The present invention provides a BiO 2-x / CdS photocatalysts, including BiO 2-x / CdS and doped in the BiO 2-x / CaCO3 in CdS; the BiO 2-x BiO in CdS 2-x The mass ratio of BiO to CdS is 1:1-4; the doping amount of CaCO3 is 7.69-25.00wt%. 2-x When CaCO3 is doped in CdS, the prepared BiO 2-x The stability of the / CdS photocatalytic material in three-cycle photocatalytic reduction of Cr(VI) compared with BiO without CaCO3 doping 2-x / CdS increased from 8.51% to 68.91%, with excellent cycle stability; and the BiO prepared by the present invention 2-x The photocatalytic performance of the BiO / CdS photocatalyst is better than that of the undoped CaCO3 2-x / CdS also slightly improved. In addition, the incorporation of CaCO3 can reduce the cost of photocatalytic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 paying creative labor.

[0018] Figure 1 BiO prepared in Comparative Examples 1 to 4 2-x / XRD spectrum of CdS photocatalytic material;

[0019] Figure 2 BiO prepared in Examples 1 to 4 2-x XRD spectrum of / CdS / CaCO3 photocatalytic material;

[0020] Figure 3 The BiO prepared in Example 2 2-x SEM image of / CdS / CaCO3 photocatalytic material;

[0021] Figure 4 BiO prepared in Comparative Example 1 2-x / CdS photocatalytic materials, CdS, BiO 2-x , CaCO3 and BiO prepared in Examples 1 to 4 2-x / CdS / CaCO3 photocatalytic material Cr(VI) reduction concentration C / C O Plotted against time;

[0022] Figure 5 BiO prepared in Comparative Example 1 2-x / The result of three cycles of photocatalytic reduction of Cr(VI) by CdS photocatalytic material;

[0023] Figure 6 The BiO prepared in Example 2 2-x The results of three cycles of photocatalytic reduction of Cr(VI) by / CdS / CaCO3 photocatalytic material. DETAILED DESCRIPTION

[0024] The present invention provides a BiO 2-x / CdS photocatalysts, including BiO 2-x / CdS and doped in the BiO 2-x / CaCO3 in CdS; the BiO 2-x BiO in CdS 2-x The mass ratio of CdS is 1:1~4.

[0025] In the present invention, the doping amount of CaCO3 can be 7.69-25.00wt%. In a specific embodiment, it can be 7.69wt%, 14.28wt%, 20.00wt% or 25.00wt%.

[0026] In the present invention, the BiO 2-x BiO in CdS 2-x The mass ratio of Ag and CdS is 1:1-4, and in a specific embodiment, can be 1:1, 1:2, 1:3 or 1:4.

[0027] The present invention also provides the BiO 2-x The preparation method of the CdS photocatalyst comprises the following steps:

[0028] The water-soluble sulfur source, water-soluble cadmium source, BiO 2-x , CaCO3 and water are mixed to precipitate to obtain the BiO 2-x / CdS photocatalyst.

[0029] In the present invention, unless otherwise specified, all preparation raw materials are preferably commercially available products well known to those skilled in the art.

[0030] In the present invention, the water-soluble sulfur source can be Na2S, specifically Na2S·9H2O; the water-soluble cadmium source can be Cd(NO3)2, specifically Cd(NO3)2·4H2O; the molar ratio of the sulfur source to the cadmium source is 1:1.

[0031] In the present invention, the BiO 2-x The preparation method comprises the following steps:

[0032] The bismuth source, the alkaline reagent and water are mixed and subjected to hydrothermal treatment to obtain the BiO 2-x Powder.

[0033] In the present invention, the bismuth source may be bismuthate; the bismuthate may be NaBiO3·2H2O; the alkaline reagent is a strong base, and the strong base may be a sodium hydroxide solution; the concentration of the alkaline reagent may be 1.00 to 1.60 mol / L.

[0034] In the present invention, the solid-liquid ratio of the bismuth source and the alkaline reagent can be 1.68 g:20 mL, and in a specific embodiment, can be 1.68 g:20 mL, 0.84 g:10 mL or 3.36 g:40 mL. The present invention has no special limitation on the amount of water.

[0035] In the present invention, the bismuth source, alkaline reagent and water can be mixed for 1 to 2 hours, and in a specific embodiment can be 1 hour, 1.5 hours or 2 hours; the mixing can be stirring mixing, and the present invention has no special limitation on the stirring mixing rate.

[0036] In the present invention, the temperature of the hydrothermal treatment may be 160-180° C., and in a specific embodiment, may be 170° C.; the time may be 6-10 hours, and in a specific embodiment, may be 8 hours.

[0037] In the present invention, after the hydrothermal treatment, the obtained hydrothermal product is subjected to solid-liquid separation, washing and drying in sequence; the solid-liquid separation can be suction filtration; the washing reagent can be alcohol and deionized water for alternating washing.

[0038] In the present invention, a water-soluble sulfur source, a water-soluble cadmium source and water are first mixed to obtain a sulfur source aqueous solution and a cadmium source aqueous solution, respectively; the concentrations of the sulfur source aqueous solution and the cadmium source aqueous solution are independently 0.1 to 0.3 mol / L, and in a specific embodiment can be 0.1 mol / L or 0.2 mol / L.

[0039] In the present invention, the precipitation temperature can be room temperature, and the time can be 60 to 120 minutes; the precipitation is carried out under stirring conditions; and the stirring rate can be 150 to 300 rpm.

[0040] In the present invention, after the precipitation, the obtained precipitation product is further subjected to solid-liquid separation and washing in sequence; the solid-liquid separation and washing are consistent with the above-mentioned solid-liquid separation and washing, and will not be repeated here.

[0041] The present invention also provides the BiO 2-x / CdS photocatalyst or BiO prepared by the preparation method described in the above technical scheme 2-x Application of / CdS photocatalyst in reduction of Cr(VI).

[0042] In order to further illustrate the present invention, the following is a BiO 2-x / CdS photocatalyst and its preparation method and application are described in detail, but they should not be understood as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] 20 mL of deionized water and 1.68 g of NaBiO3·2H2O were mixed, and 20 mL of 1.6 mol / L NaOH solution was added dropwise. The mixture was stirred at room temperature for 1 h, and then hydrothermally treated at 180 °C for 6 h. The obtained product was filtered and washed successively, and then dried at 60 °C for 10 h to obtain dark brown BiO 2-xPowder;

[0045] Weigh 2.5mmol Cd(NO3)2·4H2O and 2.5mmol Na2S·9H2O and dissolve them in 25mL deionized water to obtain Cd(NO3)2 solution and Na2S solution respectively. 2-x The powder was mixed with 25 mL Cd(NO3)2 solution and stirred to obtain a mixed solution; 0.18 g CaCO3 was added, and after 10 min, 25 mL Na2S solution was slowly added dropwise to the mixed solution, and stirring was continued. The precipitation was carried out at room temperature for 1 to 2 h. The obtained product was filtered and washed in turn, and dried at 60 ° C for 10 h to obtain BiO 2-x / CdS / CaCO3(1:2:1wt) powder.

[0046] Example 2

[0047] Prepare BiO according to the preparation method described in Example 1 2-x / CdS / CaCO3 (1:2:0.75wt) powder, the only difference is that the amount of CaCO3 used is 0.13g.

[0048] Example 3

[0049] Prepare BiO according to the preparation method described in Example 1 2-x / CdS / CaCO3 (1:2:0.50wt) powder, the only difference is that the amount of CaCO3 used is 0.18g.

[0050] Example 4

[0051] Prepare BiO according to the preparation method described in Example 1 2-x / CdS / CaCO3 (1:2:0.25wt) powder, the only difference is that the amount of CaCO3 used is 0.05g.

[0052] Comparative Example 1

[0053] 20 mL of deionized water and 1.68 g of NaBiO3·2H2O were mixed, and 20 mL of 1.6 mol / L NaOH solution was added dropwise. The mixture was stirred at room temperature for 1 h, and then hydrothermally treated at 180 °C for 6 h. The obtained product was filtered and washed successively, and then dried at 60 °C for 10 h to obtain dark brown BiO 2-x Powder;

[0054] Weigh 2.5mmol Cd(NO3)2·4H2O and Na2S·9H2O and dissolve them in 25mL deionized water to obtain Cd(NO3)2 solution and Na2S solution respectively.2-x The powder was mixed with 25 mL of Cd(NO3)2 solution and stirred to obtain a mixed solution; 25 mL of Na2S solution was slowly added dropwise to the mixed solution to precipitate at room temperature; the obtained product was filtered and washed in turn, and dried at 60°C for 10 h to obtain BiO 2-x / CdS (1:2wt) powder.

[0055] Comparative Example 2

[0056] According to the preparation method described in Comparative Example 1, BiO 2-x / CdS (1:1wt) powder, the only difference is that BiO 2-x The dosage is 0.36g.

[0057] Comparative Example 3

[0058] According to the preparation method described in Comparative Example 1, BiO 2-x / CdS (1:3wt) powder, the only difference is that BiO 2-x The dosage is 0.12g.

[0059] Comparative Example 4

[0060] According to the preparation method described in Comparative Example 1, BiO 2-x / CdS (1:4wt) powder, the only difference is that BiO 2-x The dosage is 0.09g.

[0061] Test Example 1

[0062] The BiO prepared in Examples 1 to 4 2-x / CdS / CaCO3 photocatalytic material and BiO prepared in Comparative Examples 1 to 4 2-x / CdS photocatalytic materials were characterized. Figures 1 to 3 shown.

[0063] Figure 1 BiO prepared in Comparative Examples 1 to 4 2-x / XRD spectrum of CdS photocatalytic material; Figure 2 BiO prepared in Examples 1 to 4 2-x / CdS / CaCO3 photocatalytic material XRD spectrum; As can be seen from the figure, in the samples with different composite ratios, except for the absence of other impurity peaks, no obvious position shift was found in the diffraction peaks of each single phase in the composite, indicating that BiO 2-x / CdS and BiO 2-x / CdS / CaCO3 photocatalytic material was successfully prepared.

[0064] Figure 3 The BiO prepared in Example 22-x / CdS / CaCO3 (1:2:0.75wt) photocatalytic material SEM image; it can be seen from the image that small particles of CdS, layered BiO 2-x Combined with bulk CaCO3, BiO 2-x / CdS / CaCO3 photocatalytic material, and each single phase has good morphology and structure, which further confirms that the photocatalytic material has been successfully synthesized.

[0065] Test Example 2

[0066] Weigh 0.50 g of BiO prepared in Examples 1 to 4 2-x / CdS / CaCO3 photocatalytic material and BiO prepared in Comparative Examples 1 to 4 2-x / CdS photocatalytic material was added to the prepared K2Cr2O7 solution (concentration 2.5mg / L), and the mixed solution was placed in a dark reaction box for 30min to achieve adsorption equilibrium. The resulting solution was then irradiated under a 300W xenon lamp (λ>420nm), and the UV-visible diffuse reflectometer was baseline calibrated with deionized water. Then different illumination times (0, 5, 10, 15, 20, 25 and 30min) were tested and recorded. In addition, the reaction samples were recovered under the same conditions to conduct a cyclic stability test of the photocatalyst, and the test results are shown below.

[0067] Figure 4 BiO prepared in Comparative Example 1 2-x / CdS photocatalytic materials, CdS, BiO 2-x , CaCO3 and BiO prepared in Examples 1 to 4 2-x The relationship between the Cr(VI) reduction concentration C / CO and time of the / CdS / CaCO3 photocatalytic material. It can be seen from the figure that the photocatalytic reduction performance of Cr(VI) in both the binary composite phase and the ternary composite phase is significantly improved compared with the three single phases. It is worth noting that the addition of CaCO3 does not inhibit the reduction of BiO 2-x / CdS (1:2wt) photocatalytic material itself, and to a certain extent the composite ratio has the effect of promoting the photocatalytic reduction activity of Cr(VI) in the sample.

[0068] Figure 5 BiO prepared in Comparative Example 1 2-x The result of three cycles of photocatalytic reduction of Cr(VI) by CdS photocatalytic material. Figure 6 The BiO prepared in Example 2 2-x The result of three cycles of photocatalytic reduction of Cr(VI) by / CdS / CaCO3 photocatalytic material. It can be seen from the figure that BiO 2-xThe cyclic stability of the / CdS binary composite phase is poor, and its Cr(VI) reduction rate is only 8.51% after three cycles; when CaCO3 is added, the cyclic stability of the photocatalytic material is significantly improved, and its stability is increased from 8.51% to 68.91%, and it can still maintain a good stability after three cycles. And when exposed to visible light for 30 minutes, the BiO prepared in Example 2 2-x The reduction rate of Cr(VI) solution by the photocatalytic sample of / CdS / CaCO3 is about 86.87%, which is higher than that of BiO 2-x / CdS is slightly higher at 82.68%.

[0069] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A BiO 2-x / CdS photocatalyst, characterized in that Including BiO 2-x / CdS and doped in the BiO 2-x / CaCO3 in CdS; The BiO 2-x BiO in CdS 2-x The mass ratio of CaCO3 to CdS is 1:1-4; the doping amount of CaCO3 is 7.69-25.00wt%.

2. BiO according to claim 1 2-x A method for preparing a CdS photocatalyst, characterized in that: The following steps are involved: The water-soluble sulfur source, water-soluble cadmium source, BiO 2-x , CaCO3 and water are mixed to precipitate to obtain the BiO 2-x / CdS photocatalyst.

3. The preparation method according to claim 2, characterized in that: The water-soluble sulfur source is Na2S; the water-soluble cadmium source is Cd(NO3)2.

4. The preparation method according to claim 2, characterized in that: The BiO 2-x The preparation method comprises the following steps: The bismuth source, the alkaline reagent and water are mixed and subjected to hydrothermal treatment to obtain the BiO 2-x Powder.

5. The preparation method according to claim 4, characterized in that: The bismuth source is bismuth salt; and the alkaline agent is a strong base.

6. The preparation method according to claim 4, characterized in that: The temperature of the hydrothermal treatment is 160-180° C., and the time is 6-10 hours.

7. The preparation method according to claim 2, characterized in that: The temperature of the precipitation is room temperature, and the time is 60 to 120 minutes.

8. BiO according to claim 1 2-x / CdS photocatalyst or BiO prepared by the preparation method according to any one of claims 2 to 7 2-x Application of / CdS photocatalyst in reduction of Cr(VI).

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