Manganese-cadmium-sulfur and manganese sulfide heterojunction composite photocatalytic material and preparation method thereof

Abstract

The invention relates to a manganese cadmium sulfur and manganese sulfide heterojunction composite photocatalytic material, which is composed of Mn < 0.7 > Cd < 0.3 > S and MnS. The invention also discloses a preparation method of the manganese-cadmium-sulfur-coated manganese sulfide heterojunction composite photocatalytic material. The preparation method specifically comprises the following steps: preparing the manganese-cadmium-sulfur-coated manganese sulfide heterojunction photocatalytic material through a one-step hydrothermal method; (CH3COO) 2Mn. 4H2O and (CH3COO) 2Cd. 2H2O are added, and the mixture is stirred and dissolved in water; adding the mixture into TAA and stirring for 30 minutes to obtain a fully mixed solution; and carrying out a hydrothermal reaction to obtain the final manganese-cadmium-sulfur-coated manganese sulfide heterojunction photocatalytic material. According to the invention, the photoresponse range is widened through the construction of the heterojunction, the transfer and separation efficiency of photo-induced electron holes is obviously improved, the compounding of photo-induced electron hole pairs is inhibited, and the efficiency of photocatalytic uranium reduction is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of photocatalytic materials, and particularly relates to a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, and also relates to a preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material. Background Art

[0002] Manganese cadmium sulfide (Mn x Cd 1-x S), as a solid solution photocatalyst with an adjustable energy band structure, can simultaneously meet the potential requirements of the oxidation half-reduction and reduction half-reactions, and has a high overpotential, which helps to improve the selectivity for the uranium reduction reaction. However, the Mn x Cd 1-x S catalyst faces challenges such as easy recombination of photo-generated carriers, narrow photo-response range, and insufficient active sites. Although strategies such as element doping, defect engineering, and noble metal deposition can improve these problems to a certain extent, the effects are limited and cannot be comprehensively solved.

[0003] Among all heterojunction schemes, the S-type heterojunction combines an oxidative semiconductor (OP) and a reductive semiconductor (RP), and uses the band bending caused by the Fermi level difference between the two to form a built-in electric field (IEF). This built-in electric field helps the effective separation of photo-generated carriers, concentrates electrons (e - ) on the valence band (VB) of the RP, and holes (h + ) on the conduction band (CB) of the OP, thereby effectively suppressing the recombination of electron-hole pairs and enhancing the photocatalytic activity of the catalyst.

[0004] Manganese sulfide (MnS) is a typical semiconductor metal sulfide photocatalyst. Due to the cluster characteristics during its synthesis process, MnS has extremely easy recombination of photo-generated electron-hole pairs and is prone to photocorrosion problems, seriously affecting the photocatalytic activity of MnS.

[0005] Aiming at the problems existing in Mn x Cd 1-x S and MnS, the two materials are compounded to form a heterojunction composite photocatalytic material, which not only expands the photo-response range of Mn x Cd 1-x S, but also improves the separation efficiency of photo-generated carriers of Mn x Cd 1-x S and MnS, and then develops a new type of highly efficient visible light photocatalytic material with broad-spectrum response, which is of great significance for the practical application of Mn x Cd 1-x S and MnS in the field of photocatalysis. Summary of the Invention

[0006] The first object of the present invention is to provide a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, which solves the problem of low photocatalytic activity of existing single metal sulfide semiconductor photocatalytic materials.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, which is composed of Mn 0.7 Cd 0.3 S and MnS. Among them, the mass ratio of Mn 0.7 Cd 0.3 S and MnS synthesized is 5-9:2-5.

[0008] The second object of the present invention is to provide a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, which solves the problem of low photocatalytic activity of existing single metal sulfide semiconductor photocatalytic materials.

[0009] To achieve the above object, the technical solution adopted by the present invention is: a preparation method of a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, which is specifically implemented according to the following steps:

[0010] Step 1: First, weigh (CH3COO)2Mn·4H2O and (CH3COO)2Cd·2H2O and add them to ultrapure water, and then continuously stir until all solid substances are completely dissolved in water; the molar ratio of (CH3COO)2Mn·4H2O to (CH3COO)2Cd·2H2O is: 5-10:1-4;

[0011] Step 2: Add thioacetamide (TAA) to the solution obtained in Step 1 and continue to stir; the molar ratio of (CH3COO)2Mn·4H2O to thioacetamide (TAA) is 5-10:7-13

[0012] Step 3: Transfer the mixed solution obtained in Step 2 to a reaction kettle and continuously heat it;

[0013] Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0014] Step 5: After the precipitate is washed three times with deionized water and ethanol, it is placed in a vacuum drying oven for drying;

[0015] Step 6: Grind the orange powder obtained after drying in Step 5 to obtain a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material.

[0016] The technical solution of the present invention also has the following characteristics:

[0017] As a further improvement of the technical solution of the present invention, in the step 1, the continuous stirring time is 8 min - 12 min.

[0018] As a further improvement of the technical solution of the present invention, in the step 2, the continuous stirring time is 20 min - 40 min.

[0019] As a further improvement of the technical solution of the present invention, in the step 3, the temperature of continuous heating is 150 °C - 170 °C.

[0020] As a further improvement of the technical solution of the present invention, in the step 3, the continuous heating time is 20 h - 28 h.

[0021] As a further improvement of the technical solution of the present invention, in the step 3, the reaction kettle is a stainless - steel autoclave with a Teflon lining.

[0022] As a further improvement of the technical solution of the present invention, in the step 5, the drying temperature in the vacuum drying oven is 50 °C - 70 °C.

[0023] As a further improvement of the technical solution of the present invention, in the step 5, the drying time in the vacuum drying oven is 6 h - 10 h.

[0024] The beneficial effect of the present invention is as follows: The preparation method of the manganese cadmium sulfide @ manganese sulfide heterojunction composite photocatalytic material of the present invention uses a one - step hydrothermal method to prepare a manganese cadmium sulfide @ manganese sulfide heterojunction composite photocatalytic material with enhanced IEF. The preparation process is simple, and the photocatalytic reduction uranium activity of the prepared composite photocatalytic material is significantly higher than that of MnS and Mn 0.7 Cd 0.3 S photocatalysts. The MCS@M photocatalyst prepared by the one - step hydrothermal method of the present invention has super strong IEF, can generate more photo - generated carriers, and the uranium extraction rate can reach 86.81% within one hour, which is suitable for industrial production. Description of the Drawings

[0025] Figure 1 It is the XRD pattern of CdS, MnS, MCS, MCS - n (n = 1 - 6), M / MCS of Comparative Examples 1 - 5 and the MCS@M heterojunction composite photocatalytic material of Example 2;

[0026] Figure 2 It is the XPS pattern of CdS, MnS, MCS, MCS - n (n = 1 - 6), M / MCS of Comparative Examples 1 - 5 and the MCS@M heterojunction composite photocatalytic material of Example 2;

[0027] Figure 3SEM images of CdS, MnS, MCS, MCS-n (n = 1 - 6), M / MCS of Comparative Examples 1 - 5 and the MCS@M heterojunction composite photocatalytic material of Example 2;

[0028] Figure 4 Solid UV-Vis absorption spectra and VB-XPS spectra of CdS, MnS, MCS, MCS-n (n = 1 - 6), MS / MCS of Comparative Examples 1 - 5 and the MCS@MS heterojunction composite photocatalytic material of Example 2.

[0029] Figure 5 Performance graphs of uranium extraction by CdS, MnS, MCS, MCS-n (n = 1 - 6), M / MCS of Comparative Examples 1 - 5 and the MCS@M heterojunction composite photocatalytic material of Example 2. Detailed implementation manners

[0030] The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings and specific examples.

[0031] Example 1

[0032] A preparation method of a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material of the present invention is specifically implemented according to the following steps:

[0033] Step 1: First, weigh 10 mmol of (CH3COO)2Mn·4H2O and 1 mmol of (CH3COO)2Cd·2H2O and add them to 40 ml of ultrapure water, and then continuously stir for 12 min until all solid substances are completely dissolved in water;

[0034] Step 2: Add 7 mmol of thioacetamide (TAA) to the solution obtained in Step 1 and continue stirring for 40 min;

[0035] Step 3: Transfer the mixed solution obtained in Step 2 to a stainless-steel autoclave with a Teflon liner (hereinafter referred to as the reaction kettle), and continuously heat it at 170 °C for 20 h;

[0036] Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0037] Step 5: After the precipitate is washed three times with deionized water and ethanol, put it into a vacuum drying oven, set the temperature to 70 °C and keep it for 6 h to achieve complete drying;

[0038] Step 6: Grind the orange powder obtained after drying in Step 5 to obtain a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material.

[0039] The present invention synthesizes a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material by a one-step hydrothermal method. This method has simple, efficient and low-cost preparation process. The introduction of MnS broadens the light response range, significantly improves the transfer and separation efficiency of photo-generated electrons and holes, inhibits the recombination of photo-generated electron-hole pairs, and improves the extraction rate of uranium.

[0040] Example 2

[0041] A preparation method of a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material of the present invention is specifically implemented according to the following steps:

[0042] Step 1: First, weigh 8 mmol of (CH3COO)2Mn·4H2O and 2 mmol

[0043] (CH3COO)2Cd·2H2O and add them to 40 ml of ultrapure water, and then continuously stir for 10 min until all solid substances are completely dissolved in water;

[0044] Step 2: Add 10 mmol of thioacetamide (TAA) to the solution obtained in Step 1, and continue to stir for 30 min;

[0045] Step 3: Transfer the mixed solution obtained in Step 2 to a stainless-steel autoclave with a Teflon liner (hereinafter referred to as the reaction kettle), and continuously heat it at 160 °C for 24 h;

[0046] Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0047] Step 5: After the precipitate is washed three times with deionized water and ethanol, put it into a vacuum drying oven, set the temperature to 60 °C and keep it for 80 h to achieve complete drying;

[0048] Step 6: Grind the orange powder obtained after drying in Step 5 to obtain a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material.

[0049] The present invention synthesizes a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material by a one-step hydrothermal method. This method has simple, efficient and low-cost preparation process. The introduction of MnS broadens the light response range, significantly improves the transfer and separation efficiency of photo-generated electrons and holes, inhibits the recombination of photo-generated electron-hole pairs, and improves the extraction rate of uranium.

[0050] Example 3

[0051] A preparation method of a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material of the present invention is specifically implemented according to the following steps:

[0052] Step 1: Weigh 5 mmol of (CH3COO)2Mn·4H2O and 4 mmol of (CH3COO)2Cd·2H2O and add them to 40 ml of ultrapure water. Then stir continuously for 8 min until all solid substances are completely dissolved in the water;

[0053] Step 2: Add 13 mmol of thioacetamide (TAA) to the solution obtained in Step 1 and continue stirring for 20 min;

[0054] Step 3: Transfer the mixed solution obtained in Step 2 to a stainless-steel autoclave with a Teflon liner (hereinafter referred to as the reaction kettle), and continuously heat it at 150 °C for 28 h;

[0055] Step 4: After the reaction is completed, wait for the reaction kettle to cool down to room temperature naturally, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0056] Step 5: After the precipitate is washed three times with deionized water and ethanol, put it into a vacuum drying oven, set the temperature to 50 °C and keep it for 10 h to achieve complete drying;

[0057] Step 6: Grind the orange powder obtained after drying in Step 5 to obtain a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material.

[0058] The present invention synthesizes a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material by a one-step hydrothermal method. This method has a simple, efficient and low-cost preparation process. The introduction of MnS broadens the light response range, significantly improves the transfer and separation efficiency of photo-generated electron-hole pairs, inhibits the recombination of photo-generated electron-hole pairs, and improves the extraction rate of uranium.

[0059] Comparative Example 1

[0060] Step 1: Weigh 10 mmol of (CH3COO)2Cd·2H2O and add it to 40 mL of deionized water, and stir for 10 min to ensure that all solid substances are completely dissolved in the water;

[0061] Step 2: Add 10 mmol of thioacetamide (TAA) to the solution and continue stirring for 30 min;

[0062] Step 3: Transfer the obtained mixed solution to a 100 ml stainless-steel autoclave with a Teflon liner (hereinafter referred to as the reaction kettle), and continuously heat it at 160 °C for 24 h;

[0063] Step 4: After the reaction is completed, wait for the reaction kettle to cool down to room temperature naturally, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0064] Step 5: After washing the precipitate three times with deionized water and ethanol, place it in a vacuum drying oven, set the temperature to 60 °C and hold for 8 h to achieve complete drying;

[0065] Step 6: Grind the dried orange powder, and the obtained material is CdS.

[0066] Comparative Example 2

[0067] Step 1: Weigh 10 mmol of (CH3COO)2Mn·4H2O and add it to 40 mL of deionized water, stir for 10 min to ensure that all solid substances are completely dissolved in water;

[0068] Step 2: Add 10 mmol of thioacetamide (TAA) to the solution and continue stirring for 30 min;

[0069] Step 3: Transfer the obtained mixed solution to a 100 ml stainless steel autoclave with a Teflon lining (hereinafter referred to as the reaction kettle), and continuously heat it at 160 °C for 24 h;

[0070] Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0071] Step 5: After washing the precipitate three times with deionized water and ethanol, place it in a vacuum drying oven, set the temperature to 60 °C and hold for 8 h to achieve complete drying;

[0072] Step 6: Grind the dried dark brown powder, and the obtained material is MnS.

[0073] Comparative Example 3

[0074] Step 1: Weigh 10x mmol of (CH3COO)2Mn·4H2O (x = 0.1 - 0.6) and 10(1 - x) mmol of (CH3COO)2Cd·2H2O (x = 0.1 - 0.6) and add them to 40 ml of ultrapure water, continuously stir for 10 min to ensure that all solid substances are completely dissolved in water;

[0075] Step 2: Add 10 mmol of thioacetamide (TAA) to the solution and continue stirring for 30 min;

[0076] Step 3: Transfer the obtained mixed solution to a 100 ml stainless steel autoclave with a Teflon lining (hereinafter referred to as the reaction kettle), and continuously heat it at 160 °C for 24 h;

[0077] Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0078] Step 5: After washing the precipitate three times with deionized water and ethanol, place it in a vacuum drying oven, set the temperature to 60 °C and keep it for 8 h to achieve complete drying;

[0079] Step 6: Grind the dried orange powder, and the obtained product is the MCS-n (n = 1 - 6) material.

[0080] Comparative Example 4

[0081] Step 1: Weigh 7 mmol of (CH3COO)2Mn·4H2O and 3 mmol of (CH3COO)2Cd·2H2O and add them to 40 ml of ultrapure water, stir continuously for 10 min to ensure that all solid substances are completely dissolved in water;

[0082] Step 2: Add 10 mmol of thioacetamide (TAA) to the solution and continue stirring for 30 min;

[0083] Step 3: Transfer the obtained mixed solution to a 100 ml stainless steel autoclave with a Teflon lining (hereinafter referred to as the reaction kettle), and continuously heat it at 160 °C for 24 h;

[0084] Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0085] Step 5: After washing the precipitate three times with deionized water and ethanol, place it in a vacuum drying oven, set the temperature to 60 °C and keep it for 8 h to achieve complete drying;

[0086] Step 6: Grind the dried orange powder, and the obtained product is the MCS material.

[0087] Comparative Example 5

[0088] Step 1: Weigh 7 mmol of (CH3COO)2Mn·4H2O and 3 mmol of (CH3COO)2Cd·2H2O and add them to 40 ml of ultrapure water, stir continuously for 10 min to ensure that all solid substances are completely dissolved in water;

[0089] Step 2: Add 3 mmol of MnS synthesized in Comparative Example 2 and 10 mmol of thioacetamide (TAA), and continue stirring for 30 min;

[0090] Step 3: Transfer the obtained mixed solution to a 100 ml stainless steel autoclave with a Teflon lining (hereinafter referred to as the reaction kettle), and continuously heat it at 160 °C for 24 h;

[0091] Step 4: After the reaction is completed, wait for the autoclave to cool down to room temperature naturally, and then use a high-speed centrifuge to separate the precipitate in the solution;

[0092] Step 5: After washing the precipitate three times with deionized water and ethanol, place it in a vacuum drying oven, set the temperature to 60 °C and maintain it for 8 h to achieve a completely dry effect;

[0093] Step 6: Grind the dried orange powder, and the obtained product is the M / MCS composite photocatalytic material.

[0094] Figure 1 XRD patterns of CdS, MnS, MCS, MCS-n (n = 1 - 6), M / MCS of Comparative Examples 1 - 5, and the MCS@M heterojunction composite photocatalytic material of Example 2. According to the XRD patterns ( Figure 1 a - b), it can be observed that the solid solution photocatalyst MCS-n (n = 1 - 6) exhibits a typical cubic crystal structure of CdS, and its characteristic diffraction peaks are located at 2θ = 26.55°, 44.04°, and 54.67°, corresponding to the (111), (220), and (222) crystal planes of the CdS (PDF#No.80 - 0019) structure. In addition, in the MCS@M and M / MCS samples, we also detected additional characteristic peaks at 2θ = 34.33°, 49.34°, and 61.48°, which are attributed to the (200), (220), and (222) crystal planes of MnS (PDF#No.88 - 2223). It is worth noting that, as Figure 1 c - d, with the gradual increase of the Mn content, the XRD diffraction peaks of MCS show a larger angular shift compared to CdS. This phenomenon indicates that Mn atoms are replacing Cd atoms, thereby causing lattice distortion and resulting in the shift of the diffraction peaks. At the same time, after the synthesis of the MCS@M composite photocatalyst, the diffraction peaks also shift towards higher angles. The above results clearly demonstrate the successful preparation of the samples.

[0095] Figure 2 XPS spectra of CdS, MnS, MCS, MCS-n (n = 1 - 6), M / MCS of Comparative Examples 1 - 5, and the MCS@M heterojunction composite photocatalytic material of Example 2. XPS spectroscopy was used to analyze the valence states and chemical compositions of the prepared photocatalysts. The results of the XPS full-spectrum analysis of the MCS@M and MCS samples show that Mn, Cd, and S elements coexist in the samples; for the XPS full-spectrum of MnS, it can be seen that it contains Mn and S elements ( Figure 2 a). According to the XPS fine spectrum of S ( Figure 2 b), it can be known that MCS@M has two obvious peaks, which are 162.07 eV (S2p 3 / 2 ) and 160.87 eV (S2p1 / 2 ), which is due to the presence of S 2+ . In addition, there is also a small peak, indicating the presence of oxidized forms of sulfur in the sample. In the analysis of the Cd 3d orbitals, the MCS photocatalyst has characteristic peaks at 404.53 eV (Cd 3d 5 / 2 ) and 411.27 eV (Cd 3d 3 / 2 ), and these peaks are attributed to Cd 2+ ions ( Figure 2 c). The two characteristic peaks of MCS@M shift towards a larger binding energy compared to the characteristic peaks of MCS. At the same time, in the Figure 2 XPS spectrum of d Mn 2p, two characteristic peaks of MCS@M are observed at 652.06 eV and 640.53 eV, which correspond to Mn 2p 3 / 2 and Mn 2p 1 / 2 orbitals. Compared with MnS, the peaks in MCS@M shift towards a lower binding energy, where Mn 2p 3 / 2 and Mn 2p 1 / 2 shift by 0.74 eV and 0.23 eV respectively. This result indicates that there is a strong interfacial interaction between MCS and MnS in the MCS@M composite material, proving the successful formation of the heterojunction. At the same time, the change in the binding energy in XPS also preliminarily indicates that e - migrates from the CB of MCS to the CB of MnS.

[0096] Figure 3 SEM images of CdS, MnS, MCS of Comparative Examples 1-3 and the MCS@M heterojunction composite photocatalytic material of Example 2. MnS mainly appears in the form of nanometer particles piled up into clusters. CdS is mainly composed of nanosheets and a few nanoparticles. When the Mn source is introduced to form the solid solution MCS, MCS exhibits nanosheet and more nanoparticle morphologies ( Figure 3 a-c). Figure 3 In d, it can be clearly observed that the nanoparticle clusters wrap the nanoplates in MCS@M.

[0097] Figure 4 are the solid UV-Vis absorption spectra and VB-XPS diagrams of CdS, MnS, MCS, MCS-n (n = 1-6), MS / MCS of Comparative Examples 1-5 and the MCS@MS heterojunction composite photocatalytic material of Example 2. Figure 4 a-b show the UV-Vis absorption spectra. It can be found that during the synthesis process, as the Mn content increases, the MCS and MCS@M photocatalysts exhibit a red shift towards the visible light region. This indicates that the addition of Mn significantly improves the visible light absorption ability of MCS@M. MCS@M can utilize more visible light and enhance the photocatalytic activity. By calculation, the band gap values of the photocatalysts are obtained (Figure 4 c-d). The VB position of the photocatalyst can be further studied using VB-XPS ( Figure 4 e-i). The energy band structure of the final solid solution catalyst is obtained through the band gap and VB-XPS.

[0098] The manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material prepared by the preparation method of the present invention is used for uranium extraction to illustrate its photocatalytic performance.

[0099] The specific photocatalytic performance test process is as follows: 10 mg of catalyst powder is dispersed in 100 mL of uranyl acetate solution with a concentration of 100 mg·L -1 . After 30 min of dark reaction to reach the adsorption-desorption equilibrium, it is irradiated with a 300 W xenon lamp (30.72 mW·cm -2 ) as a simulated light source for 1 h. To eliminate the influence of temperature on the photocatalytic process, circulating water is continuously introduced into the reactor to ensure constant temperature.

[0100] The specific sampling method is as follows: Take 1 mL of the reaction solution sample and clarify it with a filter head. At a wavelength of 651 nm, the absorbance is measured using the same test method as described above. The actual concentration of the uranyl acetate solution after the reaction is calculated using the standard curve.

[0101] The specific test method for the concentration of uranyl acetate is as follows:

[0102] (1) Add 0.5 μL (0.1 M) of HCl to a 10 mL centrifuge tube. (2) Add 0.5 μL of uranyl acetate solution with a specific concentration (25 mg L -1 , 50 mg L -1 , 100 mg L -1 , 150 mg L -1 , 200 mg L -1 , 300 mg L -1 , 400 mg L -1 ). (3) Add 3 mL of deionized water to the centrifuge tube to dilute the mixture. (4) Add 1 mL of ArsenazoIII (500 mg L -1 ). (5) Let it stand at room temperature for 10 min. (6) Measure the absorbance of each concentration of uranium solution at a wavelength of 651 nm using a UV-visible spectrophotometer, and construct a standard curve with this data.

[0103] Figure 5It is a performance graph of extracting uranium by CdS, MnS, MCS, MCS-n (n = 1-6), M / MCS of Comparative Examples 1-5, and the MCS@M heterojunction composite photocatalytic material of Example 1. Considering that the photocatalytic process may be affected by various conditions, for comparison, control experiments were carried out under dark conditions without adding a photocatalyst and with a catalyst. Under these conditions, the reduction amount of uranium can be ignored ( Figure 5 a-5b). As shown in Figure 5 c, under light illumination conditions, the extraction rates of uranium by MCS, MCS@M, M / MCS, and CdS reached 74.83%, 86.81%, 58.86%, and 2.95% within 60 min, respectively. According to the photocatalytic data, the curve of -ln(C t / C0) versus the extraction time t can be fitted into a linear curve, as shown in Figure 5 d, which conforms to the pseudo-first-order reaction kinetics, -ln(C t / C0) = kt, where C0 represents the initial concentration (mg L -1 ), C t represents the current concentration of uranium in the solution, and k is the rate constant. It should be noted that the k value of MCS@M in Example 2 is 0.03436 min -1 , which is about 1.5 times the efficiency of MCS and 101.1 times the efficiency of pure CdS. In particular, the value of MCS@M is 2.4 times that of M / MCS, indicating that the metal compatibility and interfacial electric field of MCS@M are significantly enhanced. Under the action of the heterojunction, the construction of IEF-induced photocarrier separation greatly promotes the photocatalytic extraction of uranium. Among all the photocatalysts, MCS@M exhibits the most excellent photocatalytic activity ( Figure 4 e). This achievement is attributed to the MCS@M catalyst synthesized by the one-step hydrothermal method, which has more active sites due to its better metal matching and stronger built-in electric field, thus improving the photocatalytic performance.

[0104] The above description shows and describes several preferred embodiments of the invention. However, as mentioned above, it should be understood that the invention is not limited to the forms disclosed herein, should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications, and environments, and can be changed within the scope of the inventive concept described herein through the above teachings or the technology or knowledge in the relevant field. And any changes and variations made by those skilled in the art without departing from the spirit and scope of the invention shall fall within the protection scope of the appended claims of the invention.

Claims

1. A manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, characterized in that, Consisting of Mn 0.7 Cd 0.3 S and MnS, wherein, Mn 0.7 Cd 0.3 The mass ratio of the synthesis of S and MnS is 5-9:2-5.

2. A preparation method of a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material, characterized in that, The implementation is carried out according to the following steps: Step 1: Weigh (CH3COO)2Mn·4H2O and (CH3COO)2Cd·2H2O first and add them to ultrapure water, then continuously stir until all solid substances are completely dissolved in water; the molar ratio of (CH3COO)2Mn·4H2O to (CH3COO)2Cd·2H2O is 5 - 10:1 - 4; Step 2: Add thioacetamide (TAA) to the solution obtained in Step 1 and continue to stir; the molar ratio of (CH3COO)2Mn·4H2O to thioacetamide (TAA) is 5 - 10:7 - 13 Step 3: Transfer the mixed solution obtained in Step 2 to a reaction kettle and carry out continuous heating; Step 4: After the reaction is completed, wait for the reaction kettle to cool naturally to room temperature, and then use a high-speed centrifuge to separate the precipitate in the solution; Step 5: After the precipitate is washed three times with deionized water and ethanol, put it into a vacuum drying oven for drying; Step 6: Grind the orange powder obtained after drying in Step 5 to obtain a manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material.

3. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 2, characterized in that, In Step 1, the continuous stirring time is 8 min - 12 min.

4. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 3, characterized in that, In Step 2, the continuous stirring time is 20 min - 40 min.

5. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 4, characterized in that, In Step 3, the temperature of continuous heating is 150 °C - 170 °C.

6. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 5, characterized in that, In Step 3, the continuous heating time is 20 h - 28 h.

7. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 6, characterized in that, In Step 3, the reaction kettle is a stainless steel autoclave with a Teflon lining.

8. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 7, characterized in that, In Step 5, the drying temperature in the vacuum drying oven is 50 °C - 70 °C.

9. The preparation method of the manganese cadmium sulfide@manganese sulfide heterojunction composite photocatalytic material according to claim 8, characterized in that, In Step 5, the drying time in the vacuum drying oven is 6 h - 10 h.

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