Coffee residue coupled bismuth vanadate composite photocatalyst and preparation method and application thereof

Abstract

The application discloses a coffee residue coupled bismuth vanadate composite photocatalyst and a preparation method and application thereof. The photocatalyst is obtained by modifying bismuth vanadate by adding coffee residue and using a one-step calcination method. The coffee residue is used as a carbon skeleton to support bismuth vanadate after calcination. The photocatalyst prepared by the application can generate up to 130 muM of ·O2 ‑ under the irradiation of a single wavelength of 450 nm in 60 min, greatly improving the ability of the photocatalytic material to generate ·O2 ‑ , effectively reducing the recombination rate of photo-generated electron-hole pairs after compounding, and improving the photocatalytic performance. The prepared photocatalyst is also applied to the disinfection and killing of drug-resistant Shigella, and the nano structure of the photocatalyst provides more active sites for the disinfection and killing of Shigella flexneri.

Description

Technical Field

[0001] This application relates to the field of photocatalyst preparation technology, and in particular to a coffee grounds-coupled bismuth vanadate composite photocatalyst with high superoxide radical yield, its preparation method, and its application. Background Technology

[0002] With the increasing use of antibiotics in livestock and poultry farming, various antibiotic-resistant bacteria have been detected in livestock wastewater, including typical examples such as Shigella flexneri, Aeromonas hydrophila, and Klebsiella pneumoniae. These resistant bacteria are characterized by strong resistance, rapid reproduction, and high drug resistance, posing a serious threat to human and animal health in severe cases. Furthermore, urban wastewater treatment systems generally have limited effectiveness in removing drug-resistant bacteria; ordinary biological filters in urban wastewater treatment systems can only remove 80-90% of E. coli, and activated sludge processes can only remove 90-95%. Therefore, researching the efficient removal of drug-resistant bacteria in the aquatic environment is of great significance.

[0003] Photocatalysis technology can not only degrade organic matter, but it can also completely remove various pollutants, including antibiotics, bacteria, and related genes. The degradation mechanism of photocatalysts mainly utilizes light energy to excite and generate photogenerated electron-hole pairs and active species (·OH, ·OH, ·OH). 1 O2, O2 ·- These can be used to degrade trace organic pollutants.

[0004] Studies have found that photocatalysts such as g-C3N4, Fe2O3, TiO2, Ag2O, and Co3O4 can be used for the photocatalytic degradation of various organic compounds. Among different semiconductors, BiVO4 has gained great appeal due to its unique properties. However, its photocatalytic efficiency has remained unsatisfactory due to its low carrier lifetime, low quantum yield, and high electron-hole recombination rate. Therefore, researchers have explored methods such as morphology modulation, metal / non-metal doping, and heterojunction construction to overcome these shortcomings. Among these methods, the coupling of carbon and BiVO4 has been proven to significantly improve the photocatalytic performance of BiVO4, such as multi-walled carbon nanotube (MWCNT) coupled with BiVO4, rGO coupled with BiVO4, and glucose coupled with BiVO4.

[0005] However, the carbon materials currently used are complex to prepare or expensive, and have low yields of reactive oxygen species, which hinders their widespread use. Coffee grounds, as a common type of biocarbon waste in daily life, have advantages such as easy availability and low cost.

[0006] Therefore, it would be very meaningful to provide a photocatalyst with high superoxide radical yield by modifying BiVO4 with coffee grounds. Summary of the Invention

[0007] This invention provides a novel coffee grounds-coupled bismuth vanadate composite photocatalyst and its preparation method. The photocatalyst is obtained by modifying bismuth vanadate through a one-step calcination method after adding coffee grounds. The coffee grounds, after calcination, serve as a carbon framework to support the bismuth vanadate.

[0008] The present invention also provides a method for applying the above-mentioned coffee grounds coupled bismuth vanadate composite photocatalyst, which can use visible light to kill Shigella bacteria at a concentration of 10⁷.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a coffee grounds-coupled bismuth vanadate composite photocatalyst includes the following steps:

[0011] (1) Dissolve Bi(NO3)3·5H2O in a mixed solution of deionized water and HNO3, stir evenly at room temperature, and record it as solution A;

[0012] (2) Add coffee grounds and polyvinylpyrrolidone to solution A and stir until well mixed;

[0013] (3) Dissolve NH4VO3 in NaOH solution and stir until homogeneous at room temperature. This solution is denoted as solution B.

[0014] (4) Under stirring conditions, solution B is slowly added dropwise to solution A, and the mixture is stirred evenly. This mixture is denoted as solution C.

[0015] (5) Under stirring conditions, the pH value of solution C was adjusted to 1 using NaOH, and after stirring at room temperature, it was filtered and dried to obtain the photocatalyst precursor;

[0016] (6) The photocatalyst precursor was calcined, rinsed with deionized water, and dried to obtain a coffee grounds coupled bismuth vanadate composite photocatalyst.

[0017] Preferably, in step (1), the volume ratio of deionized water to HNO3 is 40:5, and the stirring time is 30 min.

[0018] Preferably, the coffee grounds in step (2) are pre-treated: the obtained coffee grounds are placed in an oven at 60°C for 24 hours and then passed through a 200-mesh sieve; the mass ratio of coffee grounds to polyvinylpyrrolidone is 3.75:1, and the stirring time is 5 minutes.

[0019] Preferably, in step (3), the concentration of NaOH solution is 2M and the stirring time is 30min.

[0020] Preferably, in step (4), the molar ratio of Bi(NO3)3·5H2O to NH4VO3 is 1:1, and the stirring time is 30 min.

[0021] Preferably, in step (5), a 0.22 μM organic filter membrane is used for filtration, the stirring time is 5 min, and the product is dried in an oven at 60 °C for 24 h.

[0022] Preferably, in step (6), the photocatalyst precursor is heated to 400°C at a rate of 2°C per minute and calcined at 400°C for 2 hours, and then naturally cooled to room temperature.

[0023] This invention also provides the application of the coffee grounds coupled with bismuth vanadate composite photocatalyst prepared by the above preparation method in the degradation of antibiotics in water.

[0024] This invention also provides the application of the coffee grounds coupled with bismuth vanadate composite photocatalyst prepared by the above preparation method in inhibiting or killing drug-resistant bacteria.

[0025] Preferably, the drug-resistant bacteria is Shigella flexneri.

[0026] Preferably, the photocatalyst is added to a 0.05M sodium sulfate solution, and Shigella flexneri is added to inactivate the drug-resistant Shigella under visible light irradiation.

[0027] The beneficial effects of this invention are:

[0028] This invention addresses the problems of complex preparation methods, low reactive oxygen species (ROS) yield, and lack of practical applications in existing photocatalyst technologies. This invention utilizes coffee grounds (a common household waste material) as the primary carbon source and employs a one-step calcination method to directly couple bismuth vanadate and biochar, constructing a bismuth vanadate / biochar photocatalyst. The prepared photocatalyst, under irradiation at a single wavelength of 450 nm, can generate up to 130 μM of O2 within 60 minutes. - This greatly improves the O2 production of photocatalytic materials. - The bismuth vanadate / biochar photocatalyst not only enhances the photocatalytic activity but also effectively reduces the recombination rate of photogenerated electron-hole pairs, thereby improving photocatalytic performance. This invention also applies the prepared bismuth vanadate / biochar photocatalyst to the eradication of drug-resistant Shigella, utilizing the nanostructure of bismuth vanadate / biochar to provide more active sites for the eradication of Shigella flexneri. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a scanning electron microscope image of the photocatalyst provided in Example 1 of the present invention;

[0031] Figure 2 The XRD spectra of the photocatalysts provided in Examples 1, 3, and 4 of this invention are shown.

[0032] Figure 3 The PL spectra of the photocatalysts provided in Example 1 and Comparative Example 3 of this invention are shown below.

[0033] Figure 4 The efficiency of photocatalytic elimination of Shigella provided in Example 1, Comparative Example 1, and Comparative Example 2 of this invention is shown in the graph.

[0034] Figure 5 The efficiency of photocatalysts and the photocatalysts without using the photocatalysts provided in Example 1 and Comparative Example 4 of this invention in disinfecting Shigella under different light conditions is shown in the graphs.

[0035] Figure 6 This is a standard curve of superoxide radical concentration-absorbance.

[0036] Figure 7 The amount of superoxide radicals generated by the photocatalysts provided in Example 1 and Comparative Example 4 of this invention under irradiation at a single wavelength of 450 nm. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the embodiments of this invention, the nitric acid (HNO3), sodium hydroxide (NaOH), polyvinylpyrrolidone (PVP), bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), and ammonium metavanadate (NH4VO3) used are all commercially available products, and the coffee grounds are freshly brewed coffee grounds from Starbucks.

[0039] Example 1:

[0040] Pre-processing of coffee grounds: The coffee grounds are obtained from freshly brewed coffee grounds from Starbucks and are dried in an oven at 60°C for 24 hours. The dried coffee grounds are then sieved through a 200-mesh sieve.

[0041] CB-BiVO4 photocatalyst was prepared by calcination. First, 4.85 g of Bi(NO3)3·5H2O was dissolved in a mixture of 40 mL of deionized water and 5 mL of HNO3, and stirred at room temperature for 30 min, denoted as solution A. Then, 0.375 g of coffee grounds and 0.1 g of polyvinylpyrrolidone were added to solution A, and stirred for 5 min. Next, 1.17 g of NH4VO3 was dissolved in 2M NaOH solution, and stirred at room temperature for 30 min, denoted as solution B. Then, under stirring, solution B was slowly added dropwise to solution A, and the mixture was stirred for 30 min, denoted as solution C. Finally, under stirring, the pH of solution C was adjusted to 1 using 6M NaOH, and then stirred at room temperature for 5 min.

[0042] After stirring at room temperature, the mixture was filtered through a 0.22 μM organic filter membrane (the filtrate was blue) to obtain the CB-BiVO4 photocatalyst precursor. The precursor was then placed in a 60 °C oven for 24 h. The precursor was transferred to a 100 mL alumina crucible and calcined at 400 °C for 2 h. The resulting material was collected, washed three times with deionized water, and finally placed in a 60 °C oven for 24 h. The prepared coffee grounds-coupled bismuth vanadate composite photocatalyst is designated CB-BiVO4.

[0043] Comparative Example 1

[0044] This comparative example provides a method for preparing a photocatalyst, comprising the following steps:

[0045] Pre-processing of coffee grounds: The coffee grounds are obtained from freshly brewed coffee grounds from Starbucks and are dried in an oven at 60°C for 24 hours. The dried coffee grounds are then sieved through a 200-mesh sieve.

[0046] CB-BiVO4-2 photocatalyst was prepared by calcination. First, 4.85 g of Bi(NO3)3·5H2O was dissolved in a mixed solution of 40 mL deionized water and 5 mL HNO3, and stirred at room temperature for 30 min, denoted as solution A. Then, 0.375 g of coffee grounds and 0.1 g of polyvinylpyrrolidone were added to solution A, and stirred for 5 min. Next, 1.17 g of NH4VO3 was dissolved in 2M NaOH solution, and stirred at room temperature for 30 min, denoted as solution B. Then, under stirring, solution B was slowly added dropwise to solution A, and the mixture was stirred for 30 min, denoted as solution C. Under stirring, the pH of solution C was adjusted to 2 using 6M NaOH, and then stirred at room temperature for 5 min. After stirring at room temperature, the mixture was filtered through a 0.22 μM organic filter membrane to obtain the CB-BiVO4-2 photocatalyst precursor, which was then placed in a 60℃ oven for 24 h. The photocatalyst precursor was transferred to a 100 mL alumina crucible and calcined at 400 °C for 2 h. The resulting material was collected, rinsed three times with deionized water, and finally transferred to a 60 °C oven for 24 h. The prepared photocatalyst is designated CB-BiVO4-2.

[0047] Comparative Example 2

[0048] This comparative example provides a method for preparing a photocatalyst, comprising the following steps:

[0049] Pre-processing of coffee grounds: The coffee grounds are obtained from freshly brewed coffee grounds from Starbucks and are dried in an oven at 60°C for 24 hours. The dried coffee grounds are then sieved through a 200-mesh sieve.

[0050] CB-BiVO4-3 photocatalyst was prepared by calcination. First, 4.85 g of Bi(NO3)3·5H2O was dissolved in a mixed solution of 40 mL deionized water and 5 mL HNO3, and stirred at room temperature for 30 min, denoted as solution A. Then, 0.375 g of coffee grounds and 0.1 g of polyvinylpyrrolidone were added to solution A, and stirred for 5 min. Next, 1.17 g of NH4VO3 was dissolved in 2M NaOH solution, and stirred at room temperature for 30 min, denoted as solution B. Then, under stirring, solution B was slowly added dropwise to solution A, and the mixture was stirred for 30 min, denoted as solution C. Under stirring, the pH of solution C was adjusted to 3 using 6M NaOH, and then stirred at room temperature for 5 min. After stirring at room temperature, the solution was filtered through a 0.22 μM organic filter membrane to obtain the CB-BiVO4-3 photocatalyst precursor, which was then placed in a 60 °C oven for 24 h. The photocatalyst precursor was transferred to a 100 mL alumina crucible and calcined at 400 °C for 2 h. The resulting material was collected, rinsed three times with deionized water, and finally transferred to a 60 °C oven for 24 h. The prepared photocatalyst is designated CB-BiVO4-3.

[0051] Comparative Example 3

[0052] This comparative example provides a method for preparing a photocatalyst, comprising the following steps:

[0053] BiVO4 photocatalyst was prepared by calcination. First, 4.85 g of Bi(NO3)3·5H2O was dissolved in a mixed solution of 40 mL deionized water and 5 mL HNO3, and stirred at room temperature for 30 min, denoted as solution A. Then, 0.1 g of polyvinylpyrrolidone was added to solution A, and the mixture was stirred for 5 min. Next, 1.17 g of NH4VO3 was dissolved in 2M NaOH solution, and stirred at room temperature for 30 min, denoted as solution B. Then, under stirring, solution B was slowly added dropwise to solution A, and the mixture was stirred for 30 min, denoted as solution C. Under stirring, the pH of solution C was adjusted to 1 using 6M NaOH, and then stirred at room temperature for 5 min. After stirring at room temperature, the mixture was filtered through a 0.22 μM organic filter membrane to obtain the BiVO4 photocatalyst precursor, which was then placed in a 60 °C oven for 24 h. The photocatalyst precursor was transferred to a 100 mL alumina crucible and calcined at 400 °C for 2 h. The resulting material was collected, rinsed three times with deionized water, and finally transferred to a 60 °C oven for 24 h. The prepared photocatalyst is denoted as BiVO4.

[0054] Comparative Example 4

[0055] This comparative example provides a method for preparing a photocatalytic powder material, including the following steps:

[0056] Pre-processing of coffee grounds: The coffee grounds are obtained from freshly brewed coffee grounds from Starbucks and are dried in an oven at 60°C for 24 hours. The dried coffee grounds are then sieved through a 200-mesh sieve.

[0057] C photocatalyst was prepared by calcination. First, 40 mL of a mixture of deionized water and 5 mL of HNO3 was added and stirred at room temperature for 30 min, denoted as solution A. 0.375 g of coffee grounds and 0.1 g of polyvinylpyrrolidone were added to solution A and stirred for 5 min. Next, 50 mL of 2M NaOH solution was added and stirred at room temperature for 30 min, denoted as solution B. Then, under stirring, solution B was slowly added dropwise to solution A, and the mixture was stirred for 30 min, denoted as solution C. Under stirring, the pH of solution C was adjusted to 1 using 6M NaOH, and then stirred at room temperature for 5 min. After stirring at room temperature, the mixture was filtered through a 0.22 μM organic filter membrane to obtain the C photocatalyst precursor, which was then placed in a 60 °C oven for 24 h. The photocatalyst precursor was transferred to a 100 mL alumina crucible and calcined at 400 °C for 2 h. The obtained material was collected, washed three times with deionized water, and finally transferred to a 60 °C oven for 24 h. The prepared photocatalyst is denoted as C.

[0058] Figure 1 The image shown is a scanning electron microscope image of the photocatalyst in Example 1. It can be observed that bismuth vanadate is attached to the surface of biochar as a framework, which shows the surface morphology of the photocatalyst.

[0059] Figure 2 The XRD patterns of CB-BiVO4, BiVO4, and C photocatalysts confirm the presence of BiVO4 crystals in CB-BiVO4, indicating the successful construction of CB-BiVO4.

[0060] Figure 3 Under excitation light of 320 nm, the materials prepared in Example 1 and Comparative Example 3 exhibit a distinct characteristic peak near 525 nm, representing their fluorescence spectra. Clearly, the photoluminescence (PL) intensity of BiVO4 is significantly higher than that of CB-BiVO4, indicating that CB-BiVO4 has a stronger photogenerated carrier transfer capability, demonstrating that the addition of biochar significantly improves its photocatalytic performance.

[0061] Figure 4 The sterilization efficiency of photocatalysts with different pH values ​​under a 15W LED lamp was measured, indicating that CB-BiVO4 with pH 1 had the best sterilization efficiency under illumination.

[0062] Figure 5 The red line represents the control experiment under pure light without a catalyst, the black line represents the control experiment of CB-BiVO4 without light, and the blue line represents the control experiment of BiVO4 under light. These three control experiments demonstrate that the active catalyst is CB-BiVO4 under light. Figure 5 Experimental light conditions with illumination and Figure 4 same.

[0063] Figure 7 To utilize three-dimensional fluorescence technology to study ·O2 - The fluorescence spectra of the materials prepared in Example 1 and Comparative Example 3 were measured. Figure 7 It is evident that after doping with biochar, the photocatalyst generates ·O2. - The ability to produce O2 is significantly improved; after 60 minutes of light exposure, the amount of O2 produced is significantly increased. - With a peak strength of up to 131 μM, CB-BiVO4 is a highly efficient photocatalyst for generating superoxide radicals compared to previous BiVO4-based photocatalysts.

[0064] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The application of a coffee grounds-coupled bismuth vanadate composite photocatalyst in inhibiting or killing drug-resistant Shigella flexneri, characterized in that, The preparation method of the coffee grounds coupled bismuth vanadate composite photocatalyst includes the following steps: (1) Dissolve Bi(NO3)3·5H2O in a mixed solution of deionized water and HNO3, stir evenly at room temperature, and record it as solution A; (2) Add coffee grounds and polyvinylpyrrolidone to solution A and stir until well mixed; (3) Dissolve NH4VO3 in NaOH solution and stir evenly at room temperature, and record it as solution B; (4) Under stirring conditions, solution B is slowly added dropwise to solution A, and the mixture is stirred evenly. This mixture is denoted as solution C. (5) Under stirring conditions, the pH value of solution C was adjusted to 1 using NaOH, and after stirring at room temperature, it was filtered and dried to obtain the photocatalyst precursor; (6) The photocatalyst precursor was calcined, rinsed with deionized water, and dried to obtain a coffee grounds coupled bismuth vanadate composite photocatalyst.

2. The application according to claim 1, characterized in that, In step (1), the volume ratio of deionized water to HNO3 is 40:5, and the stirring time is 30 min.

3. The application according to claim 2, characterized in that, The coffee grounds mentioned in step (2) are first pretreated: the obtained coffee grounds are placed in an oven at 60°C for 24 hours and then passed through a 200-mesh sieve; the mass ratio of coffee grounds to polyvinylpyrrolidone is 3.75:1, and the stirring time is 5 minutes.

4. The application according to claim 1, characterized in that, In step (3), the concentration of NaOH solution is 2 M and the stirring time is 30 min; in step (4), the molar ratio of Bi(NO3)3·5H2O to NH4VO3 is 1:1 and the stirring time is 30 min.

5. The application according to claim 1, characterized in that, In step (5), each step was filtered using a 0.22 μM organic filter membrane, stirred for 5 min, and dried in an oven at 60 °C for 24 h.

6. The application according to claim 1, characterized in that, In step (6), the photocatalyst precursor is heated to 400°C at a rate of 2°C per minute and calcined at 400°C for 2 hours, then naturally cooled to room temperature.

7. The application according to claim 1, characterized in that, Photocatalyst was added to a 0.05 M sodium sulfate solution, and Shigella flexneri was added. The drug-resistant Shigella was then inactivated under visible light irradiation.

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