Modified graphite phase carbon nitride photocatalyst and its preparation method and application

Abstract

The preparation method of the modified graphite phase carbon nitride photocatalyst comprises the following steps: (1) mixing melamine and cyanuric acid powders respectively in deionized water, stirring, and drying to obtain a white mixed solid; (2) calcining the white mixed solid in a muffle furnace, cooling to room temperature after the reaction is completed to obtain a light yellow product and grinding it into powder; (3) adding the light yellow product powder and cobalt salt and gadolinium salt to deionized water for oscillation, and drying to obtain a mixed solid; (4) grinding the mixed solid, placing it in a tube furnace for high-temperature polymerization, and cooling to room temperature after the reaction is completed to obtain a powder; (5) washing the powder with anhydrous ethanol and deionized water alternately to remove impurities, and finally drying to obtain the modified graphite phase carbon nitride photocatalyst. The modified graphite phase carbon nitride photocatalyst can efficiently degrade antibiotics, has a good photocatalytic effect on antibiotics, can achieve a high-efficiency removal effect under a low-power light source, and has a simple preparation process, low cost, and can be produced on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysis, and in particular relates to a modified graphite phase carbon nitride photocatalyst and a preparation method and application thereof. Background Art

[0002] Graphitic carbon nitride (g-C3N4) is a metal-free semiconductor photocatalyst with a band gap of 2.7 eV. It has excellent chemical and thermal stability, is harmless to the human body, and is easy to modify. It is considered an ideal candidate material in the field of photocatalysis. However, it also has some disadvantages, such as low preparation yield, small surface area, few active sites, a narrow visible light response range (l < 450nm), and limited light absorption that easily leads to rapid recombination of photogenerated electron-hole pairs. However, research on modified graphite-phase carbon nitride photocatalyst materials has not been reported. Therefore, how to provide a modified graphite-phase carbon nitride photocatalyst material that is simple to prepare, has a large surface area, is stable, and is highly efficient is a technical problem that needs to be solved by those skilled in the art.

[0003] Antibiotics have been widely used as clinical therapeutic agents to treat infections in humans and animals. The overuse of antimicrobials has led to an increase in antibiotic residues in wastewater and natural water environments, posing serious health risks and environmental concerns. Untreated wastewater from hospitals, the pharmaceutical industry, aquaculture, and animal husbandry often contains large amounts of antibiotic residues. The migration and transformation of these antibiotics and their metabolites inevitably lead to serious ecosystem risks. Ecosystem risks posed by antibiotic contamination can be categorized as direct risks of toxic effects on organisms or potential risks of inducing antibiotic resistance genes (ARGs) and altering microbial community structure. The toxic effects of antibiotics can disrupt microbial communities and disrupt ecological balance. Even at low concentrations, antibiotics and their metabolites exhibit biotoxicity and may produce synergistic toxic effects with other coexisting pollutants, such as microplastics and heavy metals. Antibiotic residues in soil and aquatic environments, in particular, reach animals and humans through food (e.g., vegetables and fish) and drinking water. Therefore, research on antibiotic removal in aquatic environments is urgent and necessary.

[0004] Currently, researchers use different physical and chemical methods to purify wastewater containing antibiotics. Membrane filtration, adsorption, chemical oxidation, electrocatalytic oxidation, coagulation and flocculation, microwave-assisted catalysis, photocatalysis, etc. are all used as the main means of treating antibiotics. Compared with other traditional water treatment technologies, photocatalytic technology, driven by light (such as sunlight, artificial light), has the advantages of high efficiency, no subsequent processes, and environmental protection. However, high-power light sources of 300w, 500w or even 1000w are often used as light sources for photocatalysis. The temperature generated under high-power light sources can reach 100-200℃, which places high requirements on photocatalytic equipment and consumes a lot of energy, hindering the application of photocatalytic technology. Therefore, it is necessary to explore a photocatalytic effect under low-power light sources to provide new ideas for the application of photocatalysis and energy conservation and environmental protection. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a modified graphite phase carbon nitride photocatalyst and its preparation method and application, the purpose of which is to use rare earth modified graphite phase carbon nitride to obtain a modified graphite phase carbon nitride photocatalyst with simple preparation, rich pore structure and high photocatalytic efficiency.

[0006] To achieve the above object, the specific solutions of the present invention are as follows:

[0007] The preparation method of modified graphite phase carbon nitride photocatalyst comprises the following steps:

[0008] (1) Melamine and cyanuric acid powders were placed in deionized water, mixed, stirred, and then dried to obtain a white mixed solid;

[0009] (2) calcining the white mixed solid in a muffle furnace, cooling to room temperature after the reaction to obtain a light yellow product, and grinding the light yellow product into powder to obtain a light yellow product powder;

[0010] (3) adding the light yellow product powder obtained in step (2) and the cobalt salt and gadolinium salt to deionized water for dissolution, shaking, and drying to obtain a mixed solid;

[0011] (4) grinding the mixed solid material described in step (3) and placing it in a tube furnace for high-temperature pyrolysis reaction. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0012] (5) The powder of step (4) is washed alternately with anhydrous ethanol and deionized water to remove impurities, and finally dried to obtain a modified graphite phase carbon nitride photocatalyst.

[0013] Furthermore, in step (1), the mass ratio of melamine, cyanuric acid powder and deionized water is 1:1:5, the stirring is magnetic stirring, and the stirring time is 8 to 12 hours; the drying temperature is 70 to 100° C., and the drying time is 10 to 12 hours.

[0014] Furthermore, the calcination temperature of the muffle furnace in step (2) is 350-550° C., and the calcination time is 2-4 hours.

[0015] Furthermore, the cobalt salt in step (3) is cobalt nitrate hexahydrate, the gadolinium salt is gadolinium nitrate hexahydrate, the oscillation time is 30-60 minutes, the drying temperature is 70-100° C., and the drying time is 10-12 hours.

[0016] Furthermore, the mass ratio of the light yellow product powder described in step (4) to the cobalt salt and the gadolinium salt is 1:0.01~0.09:0.04~0.20, the heating rate of the tubular furnace is 10±1°C / min, the high-temperature pyrolysis temperature in the tubular furnace is 300~500°C, and the high-temperature pyrolysis time in the tubular furnace is 1~4h.

[0017] Furthermore, the content of anhydrous ethanol in step (5) is ≥99.7%, the number of alternating washings is 3 to 7 times, the drying temperature is 70 to 100° C., and the drying time is 10 to 12 hours.

[0018] A modified graphite phase carbon nitride photocatalyst obtained by the preparation method of the modified graphite phase carbon nitride photocatalyst.

[0019] Furthermore, the modified graphite-phase carbon nitride photocatalyst is used in the catalytic degradation of antibiotics.

[0020] Furthermore, the antibiotic is any one or a combination of two or more of ciprofloxacin hydrochloride, enrofloxacin, levofloxacin, norfloxacin, tetracycline, and chlortetracycline.

[0021] Furthermore, the method includes the following steps: adding modified graphite phase carbon nitride to antibiotic wastewater with a concentration of 10 to 200 mg / L at a mass ratio of 10 to 80:1, stirring for 30 to 60 minutes, catalytically degrading under the irradiation of an LED lamp with a power of 30 W and a wavelength range of 450 to 470 nm, and filtering the liquid obtained after the reaction for 20 to 200 minutes using a filter membrane with a pore size of 0.22 to 0.45 μm to obtain a water sample after photocatalysis.

[0022] Advantages of the present invention

[0023] 1. The present invention utilizes metallic cobalt and rare earth metal gadolinium for modification to obtain a modified graphite-phase carbon nitride photocatalyst with a large specific surface area, multiple active sites, and good photocatalytic performance. The specific surface area is further expanded or the chemical composition of the surface is changed, thereby enhancing its photocatalytic ability and achieving a higher removal effect under a low-power light source. This broadens the application scope of rare earth elements in the field of photocatalytic materials, helps reduce the use of electrical energy, and provides a more energy-saving and environmentally friendly method for treating antibiotic wastewater. In addition, the preparation process of the modified graphite-phase carbon nitride photocatalyst is simple, the preparation cost is low, and it has the characteristics of large-scale production.

[0024] 2. The modified graphite phase carbon nitride photocatalyst prepared by the present invention has an increased specific surface area and more active sites, which accelerates the separation of electron and hole pairs, has high photocatalytic activity and good recycling performance, and the photocatalytic efficiency of the modified graphite phase carbon nitride photocatalyst is about 4 times that of the original graphite phase carbon nitride.

[0025] 3. The modified graphite-phase carbon nitride prepared by the present invention is applied to the catalytic degradation of antibiotics in water. Under a 30W LED light with a wavelength range of 450-470nm, the antibiotics can be efficiently degraded, with a good photocatalytic effect on the antibiotics. Compared to the currently commonly used 500W high-power light source, the use of a 30W low-power light source is a more environmentally friendly approach. On the one hand, the use of a low-power light source can reduce the impact of temperature on the photocatalytic process; on the other hand, the use of a low-power light source for photocatalysis can reduce the use of electrical energy, providing a more energy-efficient approach for the photocatalytic degradation of antibiotic wastewater. Furthermore, the modified graphite-phase carbon nitride can also photocatalytically degrade various types of compounds in water, broadening the avenues for controlling antibiotic pollution in water bodies, providing a new method for treating antibiotic wastewater, and expanding the treatment of anti-hydrochloric acid wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 These are SEM images of the original graphite phase carbon nitride powder and the modified graphite phase carbon nitride prepared in Example 1.

[0027] Figure 2 This is the XRD pattern of the modified graphite phase carbon nitride prepared in Example 1.

[0028] Figure 3 This is the UV-Vis image of the modified graphite phase carbon nitride prepared in Example 1.

[0029] Figure 4 The degradation efficiency of the modified graphite phase carbon nitride prepared in Example 1 on ciprofloxacin hydrochloride under LED light.

[0030] Figure 5This is the recycling effect of the modified graphite phase carbon nitride prepared in Example 2 in photocatalytic degradation of ciprofloxacin hydrochloride under LED light.

[0031] Figure 6 In Example 6, the degradation efficiency of the modified graphite phase carbon nitride prepared in Example 1, Example 4 and Example 5 on ciprofloxacin hydrochloride was tested under LED light.

[0032] Figure 7 Example 9 is a test of the degradation efficiency of ciprofloxacin hydrochloride of the modified graphite phase carbon nitride prepared in Example 1, Example 7 and Example 8 under LED light.

[0033] Figure 8 The effect of different preparation temperatures on the photocatalytic performance of the modified graphite phase carbon nitride catalyst of Example 1.

[0034] Figure 9 The effect of different calcination times on the photocatalytic performance of the modified graphite phase carbon nitride catalyst of Example 1.

[0035] Figure 10 This is the effect of initial concentration on the photocatalytic performance of the modified graphite phase carbon nitride catalyst in Example 1.

[0036] Figure 11 The effect of the pH value of the initial solution on the photocatalytic performance of the modified graphite phase carbon nitride catalyst of Example 1.

[0037] Figure 12 This is the effect of the photocatalytic light source power on the photocatalytic performance of the modified graphite phase carbon nitride catalyst in Example 1.

[0038] Figure 13 It is the main free radical group generated in the low-power photocatalytic reaction of the modified graphite phase carbon nitride catalyst of Example 1. DETAILED DESCRIPTION

[0039] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be noted that this specific embodiment is not intended to limit the scope of rights of the present invention.

[0040] Example 1

[0041] The preparation method of the modified graphite-phase carbon nitride photocatalyst provided in this embodiment 1 comprises the following steps:

[0042] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0043] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0044] (3) adding 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.12 g of gadolinium nitrate hexahydrate, and 0.05 g of cobalt nitrate hexahydrate to 50 ml of deionized water for dissolution, shaking for 30 minutes, and drying at 80° C. for 12 hours to obtain a mixed solid;

[0045] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 450°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 2 hours. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0046] (5) Washing the powder in step (4) alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally drying at a temperature of 70 to 100° C. for 10 to 12 hours to obtain a modified graphite phase carbon nitride photocatalyst.

[0047] A modified graphite-phase carbon nitride photocatalyst obtained by the above-mentioned preparation method, and use of the above-mentioned modified graphite-phase carbon nitride photocatalyst in catalytic degradation of antibiotics, wherein the antibiotic is any one or a combination of two or more of ciprofloxacin hydrochloride, enrofloxacin, levofloxacin, norfloxacin, tetracycline, and chlortetracycline. The use of the modified graphite-phase carbon nitride photocatalyst in catalytic degradation of antibiotics specifically comprises the following steps: adding the modified graphite-phase carbon nitride to antibiotic wastewater with a concentration of 10-200 mg / L at a mass ratio of 10-80:1, stirring for 30-60 minutes, catalytically degrading under irradiation of an LED lamp with a power of 30W and a wavelength range of 450-470nm, and filtering the liquid obtained after the reaction for 20-200 minutes using a filter membrane with a pore size of 0.22-0.45μm to obtain a water sample after photocatalysis.

[0048] The SEM characterization of the original graphite phase carbon nitride powder obtained in step (2) and the modified graphite phase carbon nitride photocatalyst obtained in step (5) is as follows: Figure 1 As shown, (a) and (b) are scanning electron microscope images of original graphite phase carbon nitride powder; (c) and (d) are scanning electron microscope images of modified graphite phase carbon nitride photocatalyst.

[0049] from Figure 1 From the parts (a) and (b), we can see that the original graphite phase carbon nitride powder presents a rod-like morphology and has a large specific surface area and a loosely cross-linked three-dimensional structure. Figure 2As can be seen from parts (c) and (d) in the figure, the morphology of the modified graphite-phase carbon nitride photocatalyst prepared in step (5) does not change significantly compared to the original graphite-phase carbon nitride powder prepared in step (1), but it exhibits more pores and a larger specific surface area, and the surface is smoother without obvious grooves. The porous three-dimensional structure and large specific surface area can produce more active sites, which is conducive to the photocatalytic degradation of pollutants in the porous three-dimensional structure of the modified graphite-phase carbon nitride, thereby improving its photocatalytic degradation ability for pollutants.

[0050] The original graphite phase carbon nitride powder obtained in step (2) and the modified graphite phase carbon nitride photocatalyst obtained in step (5) were characterized by XRD. The test results are as follows: Figure 2 As shown:

[0051] It can be seen that the (002) crystal plane characteristic peak of the original graphite phase carbon nitride material is obvious, and there is no obvious characteristic peak of cobalt and gadolinium in the modified graphite phase carbon nitride photocatalyst. This is due to its low content, amorphous shape, small particle size (≤10nm) and high dispersibility.

[0052] 3. UV-Vis characterization was performed on the original graphite phase carbon nitride material obtained in step (2) and the modified graphite phase carbon nitride photocatalyst obtained in step (5). The test results are as follows: Figure 3 As shown:

[0053] It can be seen that the absorption wavelength region of the modified graphite phase carbon nitride photocatalyst obtained in step (5) and the original graphite phase carbon nitride material obtained in step (2) shows an obvious red shift. The reason is that the photocatalytic performance of the original graphite phase carbon nitride material after loading cobalt and gadolinium is significantly improved.

[0054] Example 2

[0055] The photocatalytic performance of the original graphite-phase carbon nitride material obtained in step (2) of Example 1 and the modified graphite-phase carbon nitride photocatalyst obtained in step (5) was studied, specifically comprising the following steps:

[0056] 80 mg of original graphite-phase carbon nitride material and 80 mg of modified graphite-phase carbon nitride photocatalyst were added to two bottles of the same 100 mL concentration of 20 mg·L -1 The solution was stirred in the dark for 30 minutes in a 50% ciprofloxacin hydrochloride aqueous solution to achieve adsorption-desorption equilibrium. A 30W LED light was then used to simulate light exposure, irradiating the target solution. Samples were collected every 30 minutes, filtered through a 0.45μm microporous membrane, and the ciprofloxacin hydrochloride concentration in the solution was measured using a UV-visible spectrophotometer at a wavelength of 271nm.

[0057] The test results are as follows Figure 4As shown, it can be seen that the photocatalytic degradation efficiency of ciprofloxacin hydrochloride by the modified graphite phase carbon nitride photocatalyst under 30W LED light for 150 minutes reaches about 85%. Compared with the original graphite phase carbon nitride material prepared in step (2) of Example 1, the photocatalytic efficiency of the modified graphite phase carbon nitride photocatalyst prepared in step (5) is significantly improved.

[0058] Example 3

[0059] The modified graphite phase carbon nitride photocatalyst prepared in step (5) of Example 1 was subjected to a study on its cycling performance, comprising the following steps:

[0060] The modified graphite phase carbon nitride photocatalyst after the reaction in Example 2 was recovered, rinsed with deionized water and ethanol alternately for 3 to 7 times, and dried at 80°C for 12 hours for later use. The recovered modified graphite phase carbon nitride photocatalyst was subjected to the above process again, and the recycling effect was as follows: Figure 5 After five cycles, the photocatalytic degradation efficiency of the modified graphite-phase carbon nitride photocatalyst for ciprofloxacin hydrochloride still reached more than 80%, indicating that the prepared modified graphite-phase carbon nitride photocatalyst has excellent stability.

[0061] Example 4

[0062] A method for preparing a modified graphite-phase carbon nitride photocatalyst comprises the following steps:

[0063] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0064] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0065] (3) adding 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.04 g of gadolinium nitrate hexahydrate, and 0.05 g of cobalt nitrate hexahydrate to 50 ml of deionized water for dissolution, shaking for 30 minutes, and drying at 80° C. for 12 hours to obtain a mixed solid;

[0066] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 450°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 2 hours. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0067] (5) Washing the powder in step (4) alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally drying at a temperature of 70 to 100° C. for 10 to 12 hours to obtain a modified graphite phase carbon nitride photocatalyst.

[0068] Example 5

[0069] A method for preparing a modified graphite-phase carbon nitride photocatalyst comprises the following steps:

[0070] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0071] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0072] (3) 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.20 g of gadolinium nitrate hexahydrate, and 0.05 g of cobalt nitrate hexahydrate were added to 50 ml of deionized water and dissolved, shaken for 30 minutes, and then dried at 80° C. for 12 hours to obtain a mixed solid;

[0073] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 450°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 2 hours. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0074] (5) Washing the powder in step (4) alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally drying at a temperature of 70 to 100° C. for 10 to 12 hours to obtain a modified graphite phase carbon nitride photocatalyst.

[0075] Example 6

[0076] The modified graphite-phase carbon nitride photocatalyst prepared in step (5) of Example 1 is recorded as 0.12Gd-0.05Co-CN; the modified graphite-phase carbon nitride photocatalyst prepared in step (5) of Example 4 is recorded as 0.04Gd-0.05Co-CN; and the modified graphite-phase carbon nitride photocatalyst prepared in step (5) of Example 5 is recorded as 0.20Gd-0.05Co-CN. The photocatalytic performance of the catalyst is studied, which specifically includes the following steps:

[0077] 80 mg 0.04 Gd-0.05 Co-CN, 80 mg 0.12 Gd-0.05 Co-CN, and 80 mg 0.20 Gd-0.05 Co-CN were added to three bottles of the same 100 mL concentration of 20 mg·L -1 The solution was stirred in the dark for 30 minutes in a 50% ciprofloxacin hydrochloride aqueous solution to achieve adsorption-desorption equilibrium. A 30W LED light was then used to simulate light exposure, irradiating the target solution. Samples were collected every 30 minutes, filtered through a 0.45μm microporous membrane, and the ciprofloxacin hydrochloride concentration in the solution was measured using a UV-visible spectrophotometer at a wavelength of 271nm.

[0078] The test results are as follows Figure 6 As shown in the figure, after 150 minutes of irradiation with a 30W LED light, the photocatalytic degradation efficiencies of 0.04Gd-0.05Co-CN, 0.12Gd-0.05Co-CN, and 0.20Gd-0.05Co-CN for ciprofloxacin hydrochloride were 80.62%, 84.98%, and 72.36%, respectively, demonstrating that 0.12Gd-0.05Co-CN possesses excellent photocatalytic degradation performance. This is because 0.04Gd-0.05Co-CN contains only a small amount of gadolinium. This low gadolinium loading on the graphitic carbon nitride surface results in fewer active sites, reducing the photocatalytic efficiency. Excessive gadolinium loading accumulates on the graphitic carbon nitride, inhibiting light absorption and photocatalytic activity, and even blocking the active sites of the graphitic carbon nitride.

[0079] Example 7

[0080] A method for preparing a modified graphite-phase carbon nitride photocatalyst comprises the following steps:

[0081] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0082] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0083] (3) adding 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.12 g of gadolinium nitrate hexahydrate, and 0.01 g of cobalt nitrate hexahydrate to 50 ml of deionized water for dissolution, shaking for 30 minutes, and drying at 80° C. for 12 hours to obtain a mixed solid;

[0084] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 450°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 2 hours. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0085] (5) Washing the powder in step (4) alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally drying at a temperature of 70 to 100° C. for 10 to 12 hours to obtain a modified graphite phase carbon nitride photocatalyst.

[0086] Example 8

[0087] A method for preparing a modified graphite-phase carbon nitride photocatalyst comprises the following steps:

[0088] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0089] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0090] (3) adding 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.12 g of gadolinium nitrate hexahydrate, and 0.09 g of cobalt nitrate hexahydrate to 50 ml of deionized water for dissolution, shaking for 30 minutes, and drying at 80° C. for 12 hours to obtain a mixed solid;

[0091] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 450°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 2 hours. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0092] (5) Washing the powder in step (4) alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally drying at a temperature of 70 to 100° C. for 10 to 12 hours to obtain a modified graphite phase carbon nitride photocatalyst.

[0093] Example 9

[0094] The modified graphite-phase carbon nitride photocatalyst prepared in step (5) of Example 1 is recorded as 0.12Gd-0.05Co-CN; the modified graphite-phase carbon nitride photocatalyst prepared in step (5) of Example 7 is recorded as 0.12Gd-0.01Co-CN; and the modified graphite-phase carbon nitride photocatalyst prepared in step (5) of Example 8 is recorded as 0.12Gd-0.09Co-CN. The photocatalytic performance of the catalyst is studied, which specifically includes the following steps:

[0095] 80 mg 0.12Gd-0.01Co-CN, 80 mg 0.12Gd-0.05Co-CN, and 80 mg 0.12Gd-0.09Co-CN were added to three bottles of the same 100 mL solution to a concentration of 20 mg·L -1 The solution was stirred in the dark for 30 minutes in a 50% ciprofloxacin hydrochloride aqueous solution to achieve adsorption-desorption equilibrium. A 30W LED light was then used to simulate light exposure, irradiating the target solution. Samples were collected every 30 minutes, filtered through a 0.45μm microporous membrane, and the ciprofloxacin hydrochloride concentration in the solution was measured using a UV-visible spectrophotometer at a wavelength of 271nm.

[0096] The test results are as follows Figure 7 As shown in the figure, after irradiation with a 30W LED light for 150 minutes, the photocatalytic degradation efficiencies of 0.12Gd-0.01Co-CN, 0.12Gd-0.05Co-CN, and 0.12Gd-0.09Co-CN for ciprofloxacin hydrochloride were 73.43%, 84.98%, and 84.94%, respectively, indicating that 0.12Gd-0.05Co-CN has good photocatalytic degradation performance. The reason is that less cobalt loaded on the surface of graphitic carbon nitride leads to fewer active sites, resulting in reduced photocatalytic efficiency. Excessive cobalt loading and accumulation on graphitic carbon nitride inhibits light absorption and photocatalytic activity, and even blocks the active sites of graphitic carbon nitride.

[0097] Example 10

[0098] A method for preparing a modified graphite-phase carbon nitride photocatalyst comprises the following steps:

[0099] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0100] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0101] (3) adding 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.12 g of gadolinium nitrate hexahydrate, and 0.05 g of cobalt nitrate hexahydrate to 50 ml of deionized water for dissolution, shaking for 30 minutes, and drying at 80° C. for 12 hours to obtain a mixed solid;

[0102] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 300°C, 350°C, 400°C, 450°C, and 500°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 2 hours. After the reaction is completed, cooling it to room temperature to obtain a powder;

[0103] (5) The powder of step (4) is washed alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally dried at a temperature of 70 to 100° C. for 10 to 12 hours to obtain modified graphite phase carbon nitride photocatalysts under different preparation temperature conditions.

[0104] The modified graphite carbon nitride photocatalyst prepared at different temperatures was added to five bottles of the same 100 mL solution with a concentration of 20 mg·L -1 The solution was stirred in the dark for 30 minutes in a 50% ciprofloxacin hydrochloride aqueous solution to achieve adsorption-desorption equilibrium. A 30W LED light was then used to simulate light exposure, irradiating the target solution. Samples were collected every 30 minutes, filtered through a 0.45μm microporous membrane, and the ciprofloxacin hydrochloride concentration in the solution was measured using a UV-visible spectrophotometer at a wavelength of 271nm.

[0105] The test results are as follows Figure 8 As shown in the figure, it can be seen that as the preparation temperature increases from 300°C to 500°C, the photocatalytic degradation efficiency of the modified graphite-phase carbon nitride photocatalyst for ciprofloxacin hydrochloride also increases from 76.45% to 87.73%. This is because temperature is another determining factor in the elemental composition of the prepared Gd-Co-CN. The higher the temperature, the more stable the prepared Gd-Co-CN. However, as the preparation temperature further increases, the yield of the Gd-Co-CN product decreases and the structure collapses.

[0106] Example 11

[0107] A method for preparing a modified graphite-phase carbon nitride photocatalyst comprises the following steps:

[0108] (1) 2 g of melamine and 2 g of cyanuric acid powder were added to 100 ml of deionized water, mixed, and magnetically stirred for 12 h. After mixing evenly, the mixture was dried at 80° C. for 12 h to obtain a white mixed solid.

[0109] (2) The white mixed solid was placed in a muffle furnace at a calcination temperature of 550° C. and calcined for 4 h. After the reaction was completed, the mixture was cooled to room temperature to obtain a light yellow product. The light yellow product was ground into powder to obtain a light yellow product powder, which was the original graphite phase carbon nitride powder.

[0110] (3) adding 1 g of the original graphite phase carbon nitride powder obtained in step (2), 0.12 g of gadolinium nitrate hexahydrate, and 0.05 g of cobalt nitrate hexahydrate to 50 ml of deionized water for dissolution, shaking for 30 minutes, and drying at 80° C. for 12 hours to obtain a mixed solid;

[0111] (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace, heating it to 450°C at a heating rate of 10±1°C / min, and maintaining the high temperature for pyrolysis reaction for 1h, 2h, 3h, and 4h respectively. After the reaction is completed, cooling it to room temperature to obtain powder;

[0112] (5) The powder of step (4) is washed alternately with anhydrous ethanol and deionized water for 3 to 7 times to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally dried at a temperature of 70 to 100° C. for 10 to 12 hours to obtain modified graphite phase carbon nitride photocatalysts with different calcination times.

[0113] The modified graphite carbon nitride photocatalysts with different calcination times were added to four bottles of the same 100 mL concentration of 20 mg·L -1 The solution was stirred in the dark for 30 minutes in a 50% ciprofloxacin hydrochloride aqueous solution to achieve adsorption-desorption equilibrium. A 30W LED light was then used to simulate light exposure, irradiating the target solution. Samples were collected every 30 minutes, filtered through a 0.45μm microporous membrane, and the ciprofloxacin hydrochloride concentration in the solution was measured using a UV-visible spectrophotometer at a wavelength of 271nm.

[0114] The test results are as follows Figure 9 As shown, it can be seen that with the increase of calcination time, the photocatalytic degradation efficiency of the modified graphite phase carbon nitride photocatalyst for ciprofloxacin hydrochloride gradually increases, but too long calcination time will cause the collapse of the Gd-Co-CN structure, thereby reducing the photocatalytic degradation efficiency.

[0115] Example 12

[0116] The modified graphite-phase carbon nitride catalyst prepared in Example 1 was used to degrade ciprofloxacin hydrochloride solutions with different initial concentrations under a 30W LED lamp, comprising the following steps:

[0117] Three 250 mL Erlenmeyer flasks were charged with 100 mL of ciprofloxacin hydrochloride wastewater containing initial concentrations of 10 mg / L, 20 mg / L, and 30 mg / L, respectively. 80 mg of the modified graphite-phase carbon nitride catalyst from Example 1 was then added to each of the three 250 mL Erlenmeyer flasks. The mixture was stirred in the dark for 30 minutes to achieve adsorption-desorption equilibrium. A 30 W LED lamp was used to simulate light exposure, and samples were collected every 30 minutes. The samples were filtered through a 0.45 μm microporous membrane and the ciprofloxacin hydrochloride concentration in the solutions was measured using a UV-visible spectrophotometer at a wavelength of 271 nm.

[0118] The above test results are as follows Figure 9 As shown, the photocatalytic degradation efficiency of the modified graphite phase carbon nitride catalyst prepared in Example 1 for ciprofloxacin hydrochloride decreases with the increase of ciprofloxacin hydrochloride concentration, but still has good degradation efficiency in a 30 mg / L ciprofloxacin hydrochloride solution.

[0119] Example 13

[0120] The modified graphite phase carbon nitride catalyst prepared in Example 1 was used to degrade ciprofloxacin hydrochloride solutions with different initial pH values ​​under a 30W LED lamp, comprising the following steps:

[0121] Three 250 mL Erlenmeyer flasks were charged with 100 mL of ciprofloxacin hydrochloride wastewater (at an initial pH of 3, 7, and 11, respectively) at a mass concentration of 20 mg / L. 80 mg of the modified graphite-phase carbon nitride catalyst from Example 1 was then added to each of the three Erlenmeyer flasks. The mixture was stirred in the dark for 30 minutes to achieve adsorption-desorption equilibrium. A 30 W LED lamp was used to simulate light exposure, and samples were collected every 30 minutes. The samples were filtered through a 0.45 μm microporous membrane, and the ciprofloxacin hydrochloride concentration in the solutions was measured using a UV-visible spectrophotometer at a wavelength of 271 nm.

[0122] The above test results are as follows Figure 10 As shown in the figure, when the pH is neutral 7, the modified graphite phase carbon nitride catalyst has the best degradation effect on ciprofloxacin hydrochloride. Excessive acidity or alkalinity will reduce the adsorption effect of the dark reaction on ciprofloxacin hydrochloride, thereby affecting the photocatalytic efficiency of the modified graphite phase carbon nitride on ciprofloxacin hydrochloride.

[0123] Example 14

[0124] The modified graphite-phase carbon nitride catalyst prepared in Example 1 was used to degrade ciprofloxacin hydrochloride under light sources of different powers, comprising the following steps:

[0125] Three 250 mL Erlenmeyer flasks were charged with 100 mL of ciprofloxacin hydrochloride wastewater at a mass concentration of 20 mg / L. 80 mg of the modified graphite-phase carbon nitride catalyst from Example 1 was then added to each flask and stirred in the dark for 30 minutes to achieve adsorption-desorption equilibrium. The target solutions were illuminated using simulated light from 30 W, 150 W, and 300 W LED lamps, respectively. Samples were collected every 30 minutes, filtered through a 0.45 μm microporous membrane, and then the ciprofloxacin hydrochloride concentration in the solutions was measured using a UV-visible spectrophotometer at a wavelength of 271 nm.

[0126] The above test results are as follows Figure 11 As shown in the figure, the photocatalytic effect of the modified graphite phase carbon nitride catalyst on ciprofloxacin hydrochloride increases with the increase of the light source power, which shows that high-power light sources can improve the photocatalytic effect to a certain extent, but good photocatalytic effects can still be achieved under low-power light sources, and the requirements for photocatalytic equipment are reduced.

[0127] Example 15

[0128] The modified graphite phase carbon nitride catalyst prepared in Example 1 is used for free radical detection, comprising the steps of:

[0129] 100 mL of ciprofloxacin hydrochloride wastewater was added to three 250 mL conical flasks with a mass concentration of 20 mg / L. Then, 80 mg of the modified graphite phase carbon nitride catalyst of Example 1 was added to each of the three conical flasks and stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Methanol, disodium salt of ethylenediaminetetraacetic acid (EDTA-2Na) and p-benzoquinone (p-BQ) were then added to the three conical flasks as hydroxyl radicals (·OH), hole pairs (h + ) and superoxide radicals (·O 2- ) quencher. A 30W LED lamp was used to simulate light exposure to illuminate the target solution. Samples were collected every 30 minutes, filtered through a 0.45μm microporous membrane, and then the ciprofloxacin hydrochloride concentration in the solution was measured using a UV-visible spectrophotometer at a wavelength of 271nm.

[0130] The above test results are as follows Figure 12 As shown in the figure, the addition of methanol had little effect on the degradation of ciprofloxacin hydrochloride over the modified graphite carbon nitride catalyst, with a removal efficiency of 81.89%. The addition of EDTA-2Na and p-BQ significantly inhibited the degradation of ciprofloxacin hydrochloride, reducing their removal rates to 36.82% and 25.08%, respectively. This indicates that active groups can be generated during the low-power photocatalytic reaction, and the main active groups generated, ·O 2- and h + It can achieve efficient degradation of ciprofloxacin hydrochloride.

Claims

1. A method for preparing a modified graphite-phase carbon nitride photocatalyst, characterized in that: The steps include: (1) Melamine and cyanuric acid powders are placed in deionized water, mixed, stirred, and then dried to obtain a white mixed solid; (2) calcining the white mixed solid in a muffle furnace, cooling to room temperature after the reaction is completed to obtain a light yellow product, and grinding the light yellow product into powder to obtain a light yellow product powder; (3) adding the light yellow product powder obtained in step (2) and the cobalt salt and gadolinium salt to deionized water for dissolution, wherein the cobalt salt is cobalt nitrate hexahydrate and the gadolinium salt is gadolinium nitrate hexahydrate, shaking and drying to obtain a mixed solid; (4) Grinding the mixed solid material of step (3) and placing it in a tube furnace for high-temperature pyrolysis reaction. The high-temperature pyrolysis temperature in the tube furnace is 300-500°C, and the high-temperature pyrolysis time in the tube furnace is 1-4 hours. After the reaction is completed, cooling to room temperature to obtain powder; (5) The powder of step (4) is washed alternately with anhydrous ethanol and deionized water to remove impurities, wherein the content of anhydrous ethanol is ≥99.7%, and finally dried to obtain a modified graphite phase carbon nitride photocatalyst.

2. The method for preparing the modified graphite-phase carbon nitride photocatalyst according to claim 1, characterized in that: In step (1), the mass ratio of the melamine powder, cyanuric acid powder and deionized water is 1:1:50, the stirring is magnetic stirring, and the stirring time is 8 to 12 hours; the drying temperature is 70 to 100° C., and the drying time is 10 to 12 hours.

3. The method for preparing the modified graphite-phase carbon nitride photocatalyst according to claim 1, characterized in that: The calcination temperature of the muffle furnace in step (2) is 350-550° C., and the calcination time is 2-4 hours.

4. The method for preparing the modified graphite-phase carbon nitride photocatalyst according to claim 1, wherein: The oscillation time in step (3) is 30-60 min, the drying temperature is 70-100° C., and the drying time is 10-12 h.

5. The method for preparing the modified graphite-phase carbon nitride photocatalyst according to claim 1, wherein: The mass ratio of the light yellow product powder to the cobalt salt and gadolinium salt in step (3) is 1:0.01~0.09:0.04~0.20, and the heating rate of the tube furnace is 10±1°C / min.

6. The method for preparing the modified graphite-phase carbon nitride photocatalyst according to claim 1, characterized in that: The number of alternating washings in step (5) is 3 to 7 times, the drying temperature is 70 to 100° C., and the drying time is 10 to 12 hours.

7. A modified graphite-phase carbon nitride photocatalyst obtained by the preparation method of the modified graphite-phase carbon nitride photocatalyst according to any one of claims 1 to 6.

8. Use of the modified graphite phase carbon nitride photocatalyst according to claim 7 in catalytic degradation of antibiotics.

9. Use of the modified graphite phase carbon nitride photocatalyst according to claim 8 in catalytic degradation of antibiotics, characterized in that: The antibiotic is any one of ciprofloxacin hydrochloride, enrofloxacin, levofloxacin, norfloxacin, tetracycline, and chlortetracycline, or a combination of two or more thereof.

10. Use of the modified graphite phase carbon nitride photocatalyst according to claim 8 in catalytic degradation of antibiotics, characterized in that: The method comprises the following steps: adding modified graphite phase carbon nitride into antibiotic wastewater with a concentration of 10 to 200 mg / L at a mass ratio of 10 to 80:1, stirring for 30 to 60 minutes, catalytically degrading the product under the irradiation of an LED light with a power of 30 W and a wavelength range of 450 to 470 nm, and filtering the liquid obtained after the reaction for 20 to 200 minutes using a filter membrane with a pore size of 0.22 to 0.45 μm to obtain a water sample after photocatalysis.

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