Self-cleaning photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a self-cleaning photocatalyst and a preparation method and application thereof.The tissue structure of the self-cleaning photocatalyst comprises a g-C3N4 two-dimensional nanosheet and AgI nanoparticles loaded on the surface of the g-C3N4 two-dimensional nanosheet, and the structural formula of the self-cleaning photocatalyst is shown as AgI / g-C3N4. According to the self-cleaning photocatalyst AgI / g-C3N4 provided by the invention, the capability of removing organic pollutants such as antibiotics in water is improved through the synergistic effect of adsorption and photocatalysis, the self-cleaning photocatalyst AgI / g-C3N4 has an excellent comprehensive removal effect, and the material has good stability and reusability.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a self-cleaning photocatalyst and a preparation method and application thereof. Background Art

[0002] At present, water treatment technologies for antibiotic organic pollutants mainly include adsorption and advanced oxidation. Among them, adsorption technology has the advantages of low cost, low energy consumption, simple operation, no damage to the original water quality, and no generation of high-risk by-products, and can be used to effectively remove antibiotics in water. However, in the actual application of adsorption technology, the adsorbent easily reaches adsorption saturation, and its regeneration process requires additional costs and excellent technology. At the same time, since antibiotics are not truly degraded, the dynamic balance of adsorption and desorption determines that it can pollute the water quality again through desorption, causing secondary pollution of the water body. Therefore, a single adsorption technology cannot completely remove antibiotic pollutants in water.

[0003] Advanced oxidation technology can promote the conversion of added oxidants, oxygen or water molecules into strong oxidizing free radicals such as OH through photocatalysis, high temperature and high pressure, electricity, etc., and then oxidize and degrade trace organic pollutants such as antibiotics. Among many advanced oxidation technologies, the reaction conditions of photocatalytic oxidation are relatively mild, but there is still the problem of incomplete degradation of trace organic pollutants. At the same time, the need to add oxidants and the response of catalysts in the non-visible light region increase the cost of photocatalytic technology. Therefore, cost and mineralization rate also limit the application of single photocatalytic technology in antibiotic water treatment.

[0004] To this end, the present invention is proposed. Summary of the invention

[0005] The main purpose of the present invention is to propose a self-cleaning photocatalyst and its preparation method and application. The self-cleaning photocatalyst AgI / g-C3N4 provided by the present invention improves its ability to remove organic pollutants such as antibiotics in water through the synergistic effect of adsorption and photocatalysis, has excellent comprehensive removal effect, and the material has good stability and reusability.

[0006] A first aspect of the present invention provides a self-cleaning photocatalyst, the organizational structure of which includes g-C3N4 two-dimensional nanosheets and AgI nanoparticles loaded on the surface of the g-C3N4 two-dimensional nanosheets, and the structural formula of the self-cleaning photocatalyst is expressed as AgI / g-C3N4.

[0007] In some embodiments of the present invention, based on the total mass of the self-cleaning photocatalyst, the mass ratio of the AgI nanoparticles to the g-C3N4 two-dimensional nanosheets is 1:5.

[0008] The second aspect of the present invention provides a method for preparing the self-cleaning photocatalyst described in the first aspect, the preparation method comprising: calcining urea as a raw material to prepare a precursor g-C3N4 powder; ultrasonically dispersing the precursor g-C3N4 powder and AgNO3 in deionized water under light-proof conditions, adding KI dropwise, and maintaining light-proof stirring; and obtaining the self-cleaning photocatalyst after centrifugation, filtration, washing, and drying.

[0009] In some embodiments of the present invention, the preparation of the precursor g-C3N4 powder includes: heating the urea to a calcination temperature and keeping the temperature for a period of time, then cooling it, and grinding it to obtain the precursor g-C3N4 powder.

[0010] In some embodiments of the present invention, the calcination temperature is 550° C. and the calcination time is 3 h.

[0011] In some embodiments of the present invention, the heating rate is 5°C / min.

[0012] In some embodiments of the present invention, the temperature is lowered and cooled at -121°C.

[0013] In some embodiments of the present invention, the molar ratio of the AgNO3 to the KI is 1:1.

[0014] In some embodiments of the present invention, the ultrasonic dispersion time is 0.5 h.

[0015] In some embodiments of the present invention, the light-shielded stirring time is maintained for 0.5 h.

[0016] The third aspect of the present invention provides a use of the self-cleaning photocatalyst described in the first aspect or the self-cleaning photocatalyst prepared by the preparation method described in the second aspect in removing antibiotic pollutants in water.

[0017] In some embodiments of the present invention, the self-cleaning photocatalyst removes antibiotic organic pollutants in water by adsorption and photo-induced generation of superoxide anion radicals under visible light irradiation.

[0018] In the self-cleaning photocatalyst AgI / g-C3N4 provided by the present invention, AgI nanoparticles are loaded on the surface of g-C3N4 two-dimensional nanosheets, and the advantages of synergistic adsorption and visible light catalysis can not only efficiently and thoroughly remove antibiotic pollutants, but also have self-cleaning properties to achieve recycling.

[0019] The self-cleaning photocatalyst AgI / g-C3N4 provided by the present invention has a wide range of raw materials for preparation, is low in price, has a pollution-free preparation method, is simple to operate, and is suitable for large-scale preparation; at the same time, the self-cleaning photocatalyst has a strong self-cleaning performance, does not require regeneration costs during use, does not require the addition of other oxidants, is easy to operate, and is suitable for water treatment applications.

[0020] The self-cleaning photocatalyst provided by the present invention can achieve an antibiotic removal rate of more than 90% within 2 hours of use, and after being recycled for 5 times, the pollutant removal rate is still more than 90%.

[0021] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only used for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. In the accompanying drawings:

[0023] Figure 1 This is a scanning electron microscope image of the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 of the present invention;

[0024] Figure 2 The UV-vis DRS graphs of the g-C3N4 powder and the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 of the present invention;

[0025] Figure 3 The self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 of the present invention has a removal effect on the antibiotic gatifloxacin under different conditions;

[0026] Figure 4 This is a diagram showing the cyclic removal effect of the antibiotic gatifloxacin by the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 of the present invention under light conditions;

[0027] Figure 5 This is a diagram showing the cyclic removal effect of the antibiotic gatifloxacin by the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 of the present invention under dark conditions. DETAILED DESCRIPTION

[0028] The exemplary embodiments of the present invention will be described in more detail below with reference to specific embodiments. It should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0030] In the description of the embodiments of the present invention, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0031] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this document generally indicates that the associated objects before and after are in an "or" relationship.

[0033] In the description of the embodiments of the present invention, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0034] In the description of the embodiments of the present invention, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention.

[0035] Comprehensive analysis of the advantages and limitations of adsorption and photocatalysis in the process of removing trace antibiotics from water, the development of adsorption-photocatalysis composite functional nanomaterials is expected to improve the comprehensive removal effect of antibiotics, reduce treatment costs and achieve self-cleaning of materials. Theoretically, in the adsorption-photocatalysis composite system, adsorption can increase the local concentration of antibiotics around the composite functional nanomaterials to improve the efficiency and mineralization rate of photocatalysis; while photocatalytic oxidation can rapidly degrade the adsorbed antibiotics, prompting the effective adsorption sites to be activated again, and the dynamic balance continues to move towards the adsorption direction. In this process, photocatalysis is also the regeneration process of the adsorbent, which can effectively reduce the secondary pollution and regeneration cost of the adsorbent. It can be seen that adsorption-photocatalysis composite functional nanomaterials can have the advantages of low cost, high removal rate, self-cleaning, etc., and have extremely high application prospects in removing trace antibiotic pollutants in water.

[0036] The present invention provides a self-cleaning photocatalyst, the organizational structure of which includes g-C3N4 two-dimensional nanosheets and AgI nanoparticles loaded on the surface of the g-C3N4 two-dimensional nanosheets, and the structural formula of the self-cleaning photocatalyst is expressed as AgI / g-C3N4.

[0037] In the embodiment of the present invention, the self-cleaning photocatalyst uses graphite carbon nitride (g-C3N4) as an adsorption unit and AgI as a photoactive unit, and has an adsorption-photocatalytic composite function. At the same time, AgI nanoparticles loaded on the surface of g-C3N4 two-dimensional nanosheets can effectively increase its absorption of visible light and enhance the photocatalytic activity of the material.

[0038] In an embodiment of the present invention, based on the total mass of the self-cleaning photocatalyst, the mass ratio of AgI nanoparticles to g-C3N4 two-dimensional nanosheets is 1:5.

[0039] In the embodiments of the present invention, the self-cleaning photocatalyst can be used for the efficient removal of antibiotic pollutants in water, has an excellent comprehensive removal effect on antibiotic pollutants in water, and has a good recycling effect of the material.

[0040] In an embodiment of the present invention, the self-cleaning photocatalyst removes antibiotic organic pollutants in water by adsorption and photo-induced generation of superoxide anion radicals under visible light irradiation.

[0041] The self-cleaning photocatalyst AgI / g-C3N4 in the present invention can improve the removal efficiency of organic pollutants such as antibiotics in water through the synergistic effect of adsorption and photo-induced generation of superoxide anion radicals under visible light irradiation, while increasing the service life of the catalyst.

[0042] The present invention also provides a method for preparing the above-mentioned self-cleaning photocatalyst. The key point is that the raw materials used in the preparation method are inexpensive and easily available, the preparation conditions are mild and easy to operate, and the preparation method as a whole is simple and easy to control.

[0043] In an embodiment of the present invention, the method for preparing the self-cleaning photocatalyst of the present invention is carried out according to the following steps.

[0044] 1) The precursor g-C3N4 powder was prepared by calcining urea as raw material.

[0045] In an embodiment of the present invention, the preparation of the precursor g-C3N4 powder includes heating urea to a calcination temperature and keeping the temperature for a period of time, then cooling it, and grinding it to obtain the precursor g-C3N4 powder.

[0046] In some embodiments of the present invention, the calcination temperature is 550° C. and the calcination time is 3 h.

[0047] In some embodiments of the present invention, the heating rate is 5° C. / min.

[0048] In some embodiments of the present invention, after the heat preservation is completed, the temperature is lowered and cooled at -121°C.

[0049] In some embodiments of the present invention, 10 g of urea is weighed and put into a crucible, which is then placed in a muffle furnace for calcination. During the calcination process, the temperature is continuously raised to 550°C at a rate of 5°C / min and maintained for 3 hours, and then cooled at -121°C. After cooling, a light yellow solid g-C3N4 is obtained, which is then ground evenly to obtain a precursor g-C3N4 powder for standby use.

[0050] 2) Under light-proof conditions, the precursor g-C3N4 powder and AgNO3 were ultrasonically dispersed in deionized water, KI was added dropwise, and stirring was maintained in the dark to obtain a turbid solution.

[0051] In an embodiment of the present invention, the molar ratio of AgNO3 to KI is 1:1.

[0052] In an embodiment of the present invention, the ultrasonic dispersion time is 0.5 h.

[0053] In an embodiment of the present invention, the light-shielded stirring time is maintained for 0.5 h.

[0054] In some embodiments of the present invention, 100 mg of g-C3N4 powder and 15 mg of AgNO3 are ultrasonically dispersed in 100 mL of deionized water and stirred for 0.5 h in the dark; then a saturated solution of KI is added dropwise to control the molar ratio of AgNO3 and KI to be 1:1, stirred for 0.5 h in the dark, and the mass ratio of AgI to g-C3N4 is controlled to be 1:5.

[0055] 3) Separation and drying.

[0056] In an embodiment of the present invention, the turbid liquid obtained in step 2) is centrifuged, filtered, washed and dried to obtain a self-cleaning photocatalyst.

[0057] In the embodiment of the present invention, ultrapure water is used for washing after filtration, and then low-temperature drying is performed to obtain light yellow solid AgI / g-C3N4, which is finally ground to make the particle size uniform.

[0058] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the amounts of the experimental reagents, unless otherwise specified, are the amounts of reagents used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0059] Example 1

[0060] A self-cleaning photocatalyst AgI / g-C3N4, the preparation steps of which are as follows:

[0061] 1) Weigh 10g of urea into a crucible and place it in a muffle furnace for calcination. During the calcination process, the temperature is continuously raised to 550°C at a rate of 5°C / min and maintained for 3h, then cooled at -121°C to obtain a light yellow solid g-C3N4. Finally, the obtained light yellow solid g-C3N4 is ground into g-C3N4 powder with uniform particle size.

[0062] 2) Ultrasonic disperse 100 mg of g-C3N4 powder and 15 mg of AgNO3 in 100 mL of deionized water, stir in dark for 0.5 h; then add KI saturated solution dropwise, control the molar ratio of AgNO3 and KI to 1:1, stir in dark for 0.5 h, and control the mass ratio of AgI and g-C3N4 to 1:5.

[0063] 3) The turbid liquid obtained in step 2) is centrifuged, filtered, washed with ultrapure water and then dried at low temperature to obtain light yellow solid AgI / g-C3N4, which is ground to a uniform particle size to obtain a self-cleaning photocatalyst AgI / g-C3N4.

[0064] Figure 1 This is a scanning electron microscope image of the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1. Figure 1 It can be seen that the self-cleaning photocatalyst AgI / g-C3N4 has a two-dimensional nanosheet structure, and AgI nanoparticles are loaded on the surface of the two-dimensional nanosheet structure, which is beneficial to provide a larger specific surface area and more reaction active sites.

[0065] Figure 2 The UV-vis DRS images of the g-C3N4 powder and the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 are shown in FIG. Figure 2 It can be seen that compared with the g-C3N4 material, the light absorption band of the catalyst AgI / g-C3N4 undergoes an obvious red shift and has a stronger visible light absorption ability, which will promote the generation of electron-hole pairs and accelerate the degradation of antibiotic pollutants.

[0066] In the detection test of the present invention, antibiotics, such as gatifloxacin, are added into the water to simulate pollutant wastewater.

[0067] Test 1

[0068] The removal effect of the self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 on the antibiotic gatifloxacin was detected.

[0069] Experimental group: The self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 was used and the experiment was carried out under light conditions.

[0070] The specific operation of the test is as follows:

[0071] (1) In a photolysis tube, add 50 mL of gatifloxacin (10 mg / L) and 30 mg of self-cleaning photocatalyst AgI / g-C3N4.

[0072] (2) Place in the dark and stir magnetically for 30 min to reach adsorption-desorption equilibrium.

[0073] (3) The suspension obtained in step (2) is placed in a photochemical reactor for photocatalytic experiment, the light source is a 350W xenon lamp, equipped with a 420nm filter. Under the action of visible light (wavelength λ>420nm), the degradation reaction is carried out. Samples are taken regularly and filtered through a 0.22μm filter membrane for sample analysis.

[0074] Control group 1: The rest of the operations were the same as those of the experimental group, except that in step (3) of the control group 1, the suspension obtained in step (2) was subjected to the experiment under dark conditions.

[0075] Control group 2: The rest of the operations were the same as those of the experimental group, except that the control group 2 used the g-C3N4 prepared in Example 1 instead of the self-cleaning photocatalyst AgI / g-C3N4 for the experiment.

[0076] Figure 3 The removal effects of g-C3N4 and AgI / g-C3N4 on the antibiotic gatifloxacin under light and dark conditions are shown.

[0077] from Figure 3 It can be seen that in the self-cleaning photocatalyst AgI / g-C3N4, although the loading of AgI nanoparticles slightly reduces the adsorption and removal capacity of g-C3N4, the comprehensive removal effect of gatifloxacin under light is significantly enhanced. The removal rate of gatifloxacin exceeds 97% within 3 hours, far exceeding that of g-C3N4. The active species that plays a major role in photocatalysis is ·O2 - .

[0078] Correspondingly, from Figure 3 It can also be seen that the self-cleaning photocatalyst AgI / g-C3N4 cannot achieve a better gatifloxacin removal effect under dark conditions. This also verifies that the self-cleaning photocatalyst AgI / g-C3N4 can improve the removal efficiency of organic pollutants such as antibiotics in water through the synergistic effect of adsorption and photo-induced generation of superoxide anion radicals under visible light irradiation.

[0079] Test 2

[0080] The self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 was tested for its cyclic removal effect on the antibiotic gatifloxacin under light conditions.

[0081] Experimental group: The self-cleaning photocatalyst AgI / g-C3N4 prepared in Example 1 was used and the experiment was carried out under light conditions.

[0082] The specific operation of the test is as follows:

[0083] (1) In a photolysis tube, add 50 mL of gatifloxacin (10 mg / L) and 30 mg of self-cleaning photocatalyst AgI / g-C3N4.

[0084] (2) Place in the dark and stir magnetically for 30 min to reach adsorption-desorption equilibrium.

[0085] (3) The suspension obtained in step (2) is placed in a photochemical reactor for photocatalytic experiment, the light source is a 350W xenon lamp, equipped with a 420nm filter. Under the action of visible light (wavelength λ>420nm), the degradation reaction is carried out. Samples are taken regularly and filtered through a 0.22μm filter membrane for sample analysis.

[0086] (4) After the photocatalytic experiment in step (3) is completed, the catalyst filtered through a 0.22 μm filter membrane is collected and dried in an oven, and a cycle experiment is performed to test the self-cleaning performance of the catalyst material.

[0087] Control group: The rest of the operations were the same as those of the experimental group, except that in step (3) of the control group, the suspension obtained in step (2) was subjected to the experiment under dark conditions.

[0088] Figure 4 The cyclic removal effect of the antibiotic gatifloxacin by the self-cleaning photocatalyst AgI / g-C3N4 under light conditions is shown.

[0089] Figure 5 The cyclic removal effect of the antibiotic gatifloxacin by the self-cleaning photocatalyst AgI / g-C3N4 under dark conditions is shown.

[0090] Combination Figure 4 and Figure 5 It can be seen that the self-cleaning photocatalyst AgI / g-C3N4 has excellent self-cleaning performance under light conditions. After 5 cycles, the material can still maintain a degradation efficiency of more than 90%.

[0091] The self-cleaning photocatalyst AgI / g-C3N4 in the present invention can improve the removal efficiency of organic pollutants such as antibiotics in water through the synergistic effect of adsorption and photo-induced generation of superoxide anion radicals under visible light irradiation, while increasing the service life of the catalyst.

[0092] The self-cleaning photocatalyst AgI / g-C3N4 provided in the present invention can solve the problems of single adsorption, difficulty in regenerating a single photocatalytic material, high operating cost, incomplete removal, etc.

[0093] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A self-cleaning photocatalyst, characterized in that: The organizational structure of the self-cleaning photocatalyst includes g-C3N4 two-dimensional nanosheets and AgI nanoparticles loaded on the surface of the g-C3N4 two-dimensional nanosheets. The structural formula of the self-cleaning photocatalyst is expressed as AgI / g-C3N4.

2. The self-cleaning photocatalyst according to claim 1, characterized in that Based on the total mass of the self-cleaning photocatalyst, the mass ratio of the AgI nanoparticles to the g-C3N4 two-dimensional nanosheets is 1:

5.

3. A method for preparing the self-cleaning photocatalyst according to claim 1 or 2, characterized in that: The preparation method comprises: The precursor g-C3N4 powder was prepared by calcining urea as raw material; Under light-proof conditions, the precursor g-C3N4 powder and AgNO3 are ultrasonically dispersed in deionized water, KI is added dropwise, and stirring is maintained under light-proof conditions; and The self-cleaning photocatalyst is obtained after centrifugation, suction filtration, washing and drying.

4. The preparation method according to claim 3, characterized in that: The preparation of the precursor g-C3N4 powder comprises: The urea is heated to a calcination temperature and kept at the temperature for a period of time, then cooled and ground to obtain the precursor g-C3N4 powder.

5. The preparation method according to claim 3 or 4, characterized in that: The calcination temperature is 550° C. and the calcination time is 3 hours.

6. The preparation method according to claim 4, characterized in that: The heating rate is 5°C / min; Preferably, the temperature is lowered and cooled at -121°C.

7. The preparation method according to claim 3, characterized in that: The molar ratio of the AgNO3 to the KI is 1:

1.

8. The preparation method according to claim 3, characterized in that: The ultrasonic dispersion time was 0.5 h; Preferably, the light-shielded stirring time is 0.5 h.

9. Use of the self-cleaning photocatalyst according to claim 1 or 2 or the self-cleaning photocatalyst prepared by the preparation method according to any one of claims 3 to 8 in removing antibiotic pollutants in water.

10. The use according to claim 9, characterized in that The self-cleaning photocatalyst removes antibiotic organic pollutants in water by adsorption and photo-induced generation of superoxide anion free radicals under visible light irradiation.

Images