Er / Cd doped nano Bi4O5Br2 photocatalyst and preparation method thereof

Abstract

The invention relates to the technical field of photocatalysts, and particularly discloses an Er / Cd doped nanometer Bi4O5Br2 photocatalyst and a preparation method thereof.The preparation method of the Er / Cd doped nanometer Bi4O5Br2 photocatalyst comprises the following steps that firstly, a bismuth salt solution is prepared, and the molar concentration of Bi < 3 + > in the bismuth salt solution is 4-6 mmol / L; 2, adding a cetyl trimethyl ammonium bromide solution into the bismuth salt solution, carrying out ultrasonic stirring, and adjusting the pH value to obtain a first solution; and step 3, adding erbium salt and cadmium salt into the first solution, stirring and dissolving, reacting under a microwave condition, washing, drying, grinding and sieving to prepare the Er / Cd doped nano Bi4O5Br2 photocatalyst. The preparation method is simple, low in cost, easily available in raw materials and easy to produce. The invention provides the Er / Cd doped nanometer Bi4O5Br2 photocatalyst. The band gap of the catalyst is narrow, and various and more types of free radicals are generated. Through co-doping of Er and Cd ions, the charge separation efficiency can be improved, and electron-hole recombination is inhibited, so that excellent photocatalytic performance is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysts, and in particular to an Er / Cd-doped nano Bi4O5Br2 photocatalyst and a preparation method thereof. Background Art

[0002] SMX, as a broad-spectrum antibiotic with typical difficult-to-degrade properties, will produce residues in wastewater. These residual substances are difficult to degrade during normal water treatment and will cause harm to species in nature.

[0003] Single catalysts often face some problems in practical applications, such as inappropriate band gap width, low solar energy absorption and conversion efficiency, easy breakage, easy aggregation, and rapid recombination of photogenerated charge carriers. Most single catalysts are limited by low solar energy utilization or high recombination rate of photogenerated electron-hole pairs, and may not provide enough active sites or catalytic activity, resulting in low SMX degradation efficiency. A single catalyst may mainly degrade through one mechanism or reaction pathway, which may not fully activate all reaction steps in the degradation process, limiting the thoroughness of the degradation.

[0004] Due to these limitations, a single catalyst may not provide enough active sites or catalytic activity, resulting in low SMX degradation efficiency. A single catalyst may mainly degrade through one mechanism or reaction pathway, which may not fully activate all reaction steps in the degradation process, limiting the thoroughness of the degradation. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a method for preparing Er / Cd doped nano Bi4O5Br2 photocatalyst. The preparation method is simple, low in cost, and the raw materials are readily available and easy to produce.

[0006] The second object of the present invention is to provide an Er / Cd doped nano Bi4O5Br2 photocatalyst. The band gap of the catalyst is narrow and it produces a variety of more types of free radicals. The co-doping of Er and Cd ions can improve the charge separation efficiency and inhibit electron-hole recombination, thereby obtaining excellent photocatalytic performance.

[0007] The first technical solution adopted by the present invention is: a method for preparing Er / Cd-doped nano Bi4O5Br2 photocatalyst, comprising the following steps:

[0008] Step 1: Prepare a bismuth salt solution, wherein Bi 3+ The molar concentration is 4-6 mmol / L;

[0009] Step 2: adding hexadecyltrimethylammonium bromide solution to the bismuth salt solution, stirring with ultrasound, and adjusting the pH value to obtain a first solution;

[0010] Step 3: Add erbium salt and cadmium salt to the first solution, stir to dissolve, react under microwave conditions, wash, dry, grind and sieve to prepare Er / Cd doped nano Bi4O5Br2 photocatalyst.

[0011] Preferably, the bismuth salt in the bismuth salt solution is bismuth nitrate, and the solvent of the bismuth salt solution is a polyol.

[0012] Preferably, the ultrasonic stirring conditions are: ultrasonication for 15 minutes and stirring for 30 minutes under an ultrasonic stirrer.

[0013] Preferably, hexadecyltrimethylammonium bromide and bismuth salt solution Bi 3+ The molar ratio is 1:1.6.

[0014] Preferably, the method for adjusting the pH value is: using sodium hydroxide solution to adjust the pH to 8.5.

[0015] Preferably, the microwave conditions are: microwave reactor power is 350-750W, 180°C, and heating is 25min.

[0016] Preferably, the erbium salt is erbium nitrate, and the cadmium salt is cadmium nitrate.

[0017] Preferably, the molar ratio of erbium nitrate to bismuth nitrate is 1:200 to 1:33.

[0018] Preferably, the molar ratio of cadmium nitrate to bismuth nitrate is 1:200 to 1:33.

[0019] The second technical solution adopted by the present invention is: an Er / Cd doped nano Bi4O5Br2 photocatalyst.

[0020] Beneficial effects of the above technical solution:

[0021] (1) The co-doping of Er and Cd ions in the Er / Cd-doped Bi4O5Br2 nanoparticles prepared by the present invention can improve the charge separation efficiency and inhibit electron-hole recombination, thereby obtaining excellent photocatalytic performance. The degradation rate of SMX is 8 times that of pure Bi4O5Br2, exceeding that of Bi4O5Br2 doped with Er or Cd, because Er / Cd-Bi4O5Br2 can generate more types of free radicals.

[0022] (2) The preparation method of the present invention is simple, low-cost, and the raw materials are readily available and easy to produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A SEM image of ErCd-Bi4O5Br2 nanoparticles provided as an embodiment of the present invention;

[0024] Figure 2 An EDS element mapping diagram of ErCd-Bi4O5Br2 provided in one embodiment of the present invention;

[0025] Figure 3 An X-ray powder diffraction analysis (XRD) spectrum of ErCd-Bi4O5Br2 provided in one embodiment of the present invention;

[0026] Figure 4 X-ray photoelectron spectroscopy (XPS) diagram of Bi4O5Br2 and ErCd-Bi4O5Br2 provided for one embodiment of the present invention;

[0027] Figure 5 A graph showing the relationship between SMX concentration and ErCd-Bi4O5Br2 degradation time provided in one embodiment of the present invention;

[0028] Figure 6 A performance diagram of the cyclic use of SMX degradation by ErCd-Bi4O5Br2 provided in one embodiment of the present invention;

[0029] Figure 7 The XRD diagram of degraded SMX of ErCd-Bi4O5Br2 provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the implementation methods of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0031] The terms "first", "second", etc. (if any) in the specification and claims are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0032] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0033] The Er / Cd doped nano Bi4O5Br2 photocatalyst provided by the present invention is a Bi4O5Br2 photocatalyst prepared by a microwave hydrothermal method and co-doped with Er and Cd ions. The energy band structure of Bi4O5Br2 can be adjusted by bimetallic doping, and the light response range can be broadened, so that it absorbs light energy in a wider spectrum range. Bimetallic doping can further promote the effective separation of electron-hole pairs, improve the photocatalytic efficiency, and also generate a large number of oxygen vacancies (OVs), forming more active sites on the surface of Bi4O5Br2, and directly generating oxidized h + , OH - , O2 - The overall photocatalytic degradation performance was synergistically improved.

[0034] The specific preparation method comprises the following steps:

[0035] 1) Dissolve bismuth salt in polyol to obtain solution A, wherein Bi 3+ The molar concentration is 4-6 mmol / L;

[0036] 2) adding hexadecyltrimethylammonium bromide solution dropwise to solution A, ultrasonicating for 15 min under ultrasonic agitator, stirring for 30 min, to obtain solution B;

[0037] 3) adding the obtained sodium hydroxide solution dropwise to solution B to adjust the pH to 8.5 to obtain solution C;

[0038] 4) Add different amounts of erbium nitrate and cadmium nitrate to solution C, stir thoroughly to dissolve, and obtain solution D;

[0039] 5) placing solution D into a microwave reactor and heating at 180° C. for 25 min to obtain sample A;

[0040] 6) washing sample A with deionized water and anhydrous ethanol to obtain sample B;

[0041] 7) Drying sample B in a vacuum oven at 80° C. to obtain sample C;

[0042] 8) Grinding sample C;

[0043] 9) After grinding, the product is passed through a vibrating screen to obtain the final sample of Er / Cd-doped nano-Bi4O5Br2.

[0044] The bismuth salt is bismuth nitrate, the polyol is ethylene glycol, the erbium salt is erbium nitrate, and the cadmium salt is cadmium nitrate. The polyol is an organic solvent, and its function is to dissolve the bismuth salt in the organic solvent.

[0045] The power of the microwave reactor is 350-750W.

[0046] The product after the reaction is washed with ethanol and water and then dried at a drying temperature of 50°C to 100°C.

[0047] Example 1

[0048] The preparation method of Er / Cd doped nano Bi4O5Br2 photocatalyst comprises the following steps:

[0049] In this embodiment, preferably, the bismuth salt solution Bi 3+ The molar concentration is 4mmol / L;

[0050] Step 1, dissolving 4 mmol of bismuth nitrate in 40 mL of ethylene glycol, adding 2.5 mmol of hexadecyltrimethylammonium bromide, then ultrasonicating for 15 min, and stirring for 30 min to obtain a mixed solution;

[0051] Step 2, adjusting the pH of the mixed solution to 8.5 with a sodium hydroxide solution, and then stirring for 30 minutes to obtain a precursor solution;

[0052] Step 3, add 0.36mmol / L erbium nitrate and 0.36mmol / L cadmium nitrate to the precursor solution, stir thoroughly to dissolve, put into a microwave reactor, heat at 180°C for 25min, collect samples in turn, wash, dry and grind with deionized water and anhydrous ethanol respectively, to obtain 8% Er / Cd doped nano-Bi4O5Br2.

[0053] Example 2

[0054] The preparation method of Er / Cd doped nano Bi4O5Br2 photocatalyst comprises the following steps:

[0055] In this embodiment, preferably, the bismuth salt solution Bi 3+ The molar concentration is 5mmol / L;

[0056] Step 1, dissolving 5 mmol of bismuth nitrate in 40 mL of ethylene glycol, adding 3.125 mmol of hexadecyltrimethylammonium bromide, and then ultrasonicating for 15 min and stirring for 30 min to obtain a mixed solution;

[0057] Step 2, adjusting the pH of the mixed solution to 8.5 with a sodium hydroxide solution, and then stirring for 30 minutes to obtain a precursor solution;

[0058] Step 3, add 0.5mmol / L erbium nitrate and 0.5mmol / L cadmium nitrate to the precursor solution, stir thoroughly to dissolve, put into a microwave reactor, heat at 180°C for 25min, collect samples in turn, wash, dry and grind with deionized water and anhydrous ethanol respectively, to obtain 10% Er / Cd doped nano-Bi4O5Br2.

[0059] Example 3

[0060] The preparation method of Er / Cd doped nano Bi4O5Br2 photocatalyst comprises the following steps:

[0061] In this embodiment, preferably, the bismuth salt solution Bi 3+ The molar concentration is 6mmol / L;

[0062] Step 1, dissolving 6 mmol of bismuth nitrate in 40 mL of ethylene glycol, adding 3.75 mmol of hexadecyltrimethylammonium bromide, and then ultrasonicating for 15 min and stirring for 30 min to obtain a mixed solution;

[0063] Step 2, adjusting the pH of the mixed solution to 8.5 with a sodium hydroxide solution, and then stirring for 30 minutes to obtain a precursor solution;

[0064] Step 3, add 0.72mmol / L erbium nitrate and 0.72mmol / L cadmium nitrate to the precursor solution, stir thoroughly to dissolve, put into a microwave reactor, heat at 180°C for 25min, collect samples in turn, wash, dry and grind with deionized water and anhydrous ethanol respectively, to obtain 12% Er / Cd doped nano-Bi4O5Br2.

[0065] Performance Testing of Er / Cd Doped Nano-Bi4O5Br2 Photocatalyst

[0066] The Er / Cd doped nano Bi4O5Br2 photocatalyst prepared in Example 3 was characterized by SEM-EDS, XRD and XPS. Figures 1 to 4 shown. Figure 1 The scanning electron microscope photo of Er / Cd doped nano Bi4O5Br2 photocatalyst particles shows the morphological characteristics of the photocatalyst. Figure 2 From the SEM-EDS image, we can see that the five elements Er, Cd, Bi, O, and Br are evenly distributed on the surface of the photocatalyst material. Figure 3 The XRD spectrum of the catalyst clearly shows that the catalyst is a pure phase catalyst with good crystallization and no other impurities. Figure 4 The XPS graph shows the types and chemical states of elements on the catalyst surface, proving that the ErCd-Bi4O5Br2 catalyst was successfully synthesized.

[0067] Er / Cd doped nano Bi4O5Br2 photocatalyst for SMX degradation

[0068] The Er / Cd doped nano Bi4O5Br2 photocatalyst prepared in Example 3 was subjected to photocatalytic degradation of SMX under simulated visible light irradiation to determine PCA. A 50ml solution containing 5mg / L SMX and 50mg catalyst was mixed into a quartz catalyst tube. Next, the photocatalyst and SMX solution were stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. A 500W long arc xenon lamp and a 420nm filter were used to irradiate the photocatalytic reaction mixture to simulate the irradiation of light. At intervals, 5mL samples were extracted from the absorbance measurement of the irradiated suspension. The supernatant was extracted with a centrifuge, and the absorbance of SMX in the sample was measured near 262nm using a UV-visible spectrophotometer (UV1901PC).

[0069] The Er / Cd-doped nano-Bi4O5Br2 photocatalyst prepared in Example 3 was used to perform a degradation experiment on SMX under simulated visible light irradiation. The results are as follows: Figure 5 As shown, it can be seen that the Er / Cd doped nano Bi4O5Br2 photocatalyst of the present invention has better photodegradation activity than the Er-Bi4O5Br2, Cd-Bi4O5Br2 and pure Bi4O5Br2 photocatalysts in the prior art. Under simulated visible light irradiation, the photodegradation rate of SMX solution by 12% Er / Cd doped nano Bi4O5Br2 photocatalyst reaches 100% within 70 minutes. After 5 cycles, the Er / Cd doped nano Bi4O5Br2 photocatalyst still maintains a high photocatalytic activity for the degradation of SMX, as shown in FIG. Figure 6 The XRD images of Er / Cd doped nano Bi4O5Br2 photocatalyst before and after the photocatalytic reaction between the photocatalyst and SMX antibiotics are shown in Figure 2. Figure 7 As shown, it can be seen that the structure and phase of the Er / Cd doped nano Bi4O5Br2 photocatalyst of the present invention have no obvious changes. The simulated visible light is irradiated with a 500W long arc xenon lamp and a 420nm filter to irradiate the photocatalytic reaction mixture.

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing Er / Cd-doped nano Bi4O5Br2 photocatalyst, characterized in that: The steps include: Step 1: Prepare a bismuth salt solution, wherein Bi 3+ The molar concentration is 4-6 mmol / L; Step 2: adding hexadecyltrimethylammonium bromide solution to the bismuth salt solution, stirring with ultrasound, and adjusting the pH value to obtain a first solution; Step 3: Add erbium salt and cadmium salt to the first solution, stir to dissolve, react under microwave conditions, wash, dry, grind and sieve to prepare Er / Cd doped nano Bi4O5Br2 photocatalyst.

2. The method for preparing the Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 1, characterized in that: The bismuth salt in the bismuth salt solution is bismuth nitrate, and the solvent of the bismuth salt solution is polyol.

3. The method for preparing Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 1, characterized in that: The conditions of ultrasonic stirring were as follows: ultrasonic stirring for 15 min and stirring for 30 min.

4. The method for preparing the Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 1, characterized in that: Bi in hexadecyltrimethylammonium bromide and bismuth salt solution 3+ The molar ratio is 1:1.

6.

5. The method for preparing Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 1, characterized in that: The method for adjusting the pH value is: using sodium hydroxide solution to adjust the pH to 8.

5.

6. The method for preparing Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 1, characterized in that: The microwave conditions are as follows: microwave reactor power is 350-750W, 180°C, and heating is performed for 25 minutes.

7. The method for preparing Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 1, characterized in that: The erbium salt is erbium nitrate, and the cadmium salt is cadmium nitrate.

8. The method for preparing the Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 7, characterized in that: The molar ratio of the erbium nitrate to the bismuth nitrate is 1:200 to 1:

33.

9. The method for preparing Er / Cd doped nano Bi4O5Br2 photocatalyst according to claim 7, characterized in that: The molar ratio of the cadmium nitrate to the bismuth nitrate is 1:200 to 1:

33.

10. An Er / Cd-doped nano-Bi4O5Br2 photocatalyst prepared by the preparation method according to any one of claims 1 to 9.

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