A bismuth oxybromide / carbon nitride-based photocatalytic paper, a preparation method thereof, and uses thereof

Abstract

The present invention discloses a bismuth oxybromide / carbon nitride-based photocatalytic paper in the field of photocatalytic materials, a preparation method thereof, and uses thereof. The bismuth oxybromide / carbon nitride-based photocatalytic paper is prepared by hydrothermal reaction and then hot-pressing and compounding on a constant-temperature heating table using bismuth nitrate pentahydrate, carbon nitride, plant fiber, and cationic starch as raw materials. The present invention selects bismuth oxybromide / carbon nitride with good visible-light photocatalytic performance as the catalyst and loads it on natural plant fibers, which can avoid the agglomeration of bismuth oxybromide / carbon nitride nanomaterials, thereby ensuring the physical adsorption and catalytic activity of the photocatalyst. The bismuth oxybromide / carbon nitride-based photocatalytic paper prepared by the method of the present invention has good visible-light photocatalytic and physical adsorption properties, and can effectively degrade organic pollutants and kill bacteria. It can be applied to the field of fruit and vegetable preservation, which can not only effectively inhibit the growth of microorganisms, but also the good air permeability can avoid the problem of rotting and deterioration caused by excessive humidity.

Description

Technical Field

[0001] The present invention relates to a photocatalytic material, and particularly to a preparation method and use of bismuth oxybromide / carbon nitride-based photocatalytic paper. Background Art

[0002] The growth of microorganisms is an important cause of the decay and deterioration of fruit and vegetable products. Fruit and vegetable products will come into contact with pathogenic bacteria during the processes of growth, transportation and storage. Inhibiting the growth of microorganisms is an important means to extend the fresh-keeping period of fruits and vegetables. Antibacterial fresh-keeping paper-based materials are used to inhibit the microorganisms generated during the growth, picking, storage and sales of fruits and vegetables. Mainly by means of impregnation, spraying and roll coating, etc., the bacteriostatic agent is added to the paper-based substrate and then the fruit is packaged, forming a microenvironment that inhibits the growth and reproduction of spoilage bacteria and is conducive to the preservation of fruits, so as to achieve the purpose of delaying the spoilage of fruits. Bismuth oxybromide has a suitable band gap (2.81 eV) and a wide visible light adsorption range (>410 nm). Its unique layered crystal structure can provide enough space for relevant atoms and orbitals to be polarized, and it is a highly active bismuth oxyhalide photocatalytic material. Combining bismuth oxybromide with carbon nitride to form an indirect Z-scheme heterojunction shows more excellent photocatalytic activity. This indirect Z-scheme composite high-efficiency photocatalyst shows significant potential for antibacterial and anti-fouling using light irradiation. The present invention finds that after the plant cellulose is combined with the photocatalyst bismuth oxybromide / carbon nitride, the prepared photocatalytic paper has antibacterial and anti-fouling effects.

[0003] However, in the prior art, most of bismuth oxybromide / carbon nitride is used in powder form. Some technologies use it to form a gel with sodium alginate or calcium alginate. Patent CN114602552A discloses a photocatalytic composite membrane and its preparation method and use. The photocatalytic composite membrane includes a base filter membrane and a photocatalytic functional layer. The photocatalytic functional layer includes a calcium alginate gel layer containing a photocatalyst. This membrane can be used for photocatalytic removal of organic pollutants and heavy metal ions in wastewater. In essence, the photocatalyst still exists in the form of a gel layer formed by calcium alginate, so it requires the upper and lower base filter membranes. Therefore, it is difficult to make the photocatalytic material into a paper with antibacterial effect, mainly because the dispersibility and adhesion of the photocatalytic material are poor, it is easy to separate from the carrier, and the forming effect is not good. In addition, when used as a fresh-keeping material, the existing photocatalytic composite membrane has poor air permeability, which limits its use in the fresh-keeping field. Summary of the Invention

[0004] To overcome the above defects, the present invention provides a bismuth oxybromide / carbon nitride-based photocatalytic paper, its preparation method and use, to solve the problems of poor dispersibility and adhesion of the bismuth oxybromide / carbon nitride photocatalyst as a powder-like nanomaterial, so that it can be made into a photocatalytic paper with photocatalytic effect with plant fibers.

[0005] To this end, the technical solution of the present invention is as follows: A preparation method of bismuth oxybromide / carbon nitride-based photocatalytic paper, comprising the following steps:

[0006] (1) The precursor of bismuth oxybromide, bismuth nitrate pentahydrate and potassium bromide are dissolved in the solvent ethylene glycol at a molar mass ratio of 1:1, stirred into a uniform solution, carbon nitride is added and stirring and ultrasonic treatment are continued to form a suspension, and then hydrothermal reaction is carried out; the mass ratio of bismuth nitrate pentahydrate to carbon nitride is 7.27:3-4; the temperature of the hydrothermal reaction is 150-170 °C, and the time of the hydrothermal reaction is 11-13 h;

[0007] (2) After the hydrothermal reaction is completed, the product is a bismuth oxybromide / carbon nitride solid precipitate. The upper layer of ethylene glycol solvent is filtered off, washed, dried and ground to obtain bismuth oxybromide / carbon nitride powder for standby;

[0008] (3) Solid plant fibers are added to an aqueous sodium hydroxide solution and subjected to alkali cooking in a heating jacket of a collecting type constant temperature magnetic stirrer; after the alkali cooking is completed, it is naturally cooled, placed in a nylon filter net, washed and filtered with distilled water to obtain plant fiber pulp;

[0009] (4) The above-mentioned pulp is placed in a blender, cationic starch is added, and stirred and mixed evenly to obtain a mixed pulp of plant fiber and cationic starch; the mass ratio of the plant fiber pulp to the cationic starch is 10:3.3-4;

[0010] (5) Weigh the mixed pulp obtained in step (4), add the bismuth oxybromide / carbon nitride powder obtained in step (2), and configure it into a uniformly dispersed bismuth oxybromide / carbon nitride photocatalytic pulp through ultrasonic treatment and stirring; the mass ratio of the mixed pulp to the bismuth oxybromide / carbon nitride is 40:3-4;

[0011] (6) The above-mentioned photocatalytic pulp is evenly coated on an iron filter net and hot-pressed on a constant temperature heating table to obtain the final product, bismuth oxybromide / carbon nitride-based photocatalytic paper.

[0012] Further, in step (6), the diameter of the iron filter net is 50-75 mm; the heating temperature of the constant temperature heating table is 105-120 °C, and the heating time is 10-20 min.

[0013] Further, in step (3), the molar concentration of the aqueous sodium hydroxide solution is 0.05-0.1 mol / L.

[0014] The above-mentioned bismuth oxybromide / carbon nitride-based photocatalytic paper is applied to photocatalytic oxidation degradation of organic pollutants and photocatalytic oxidation sterilization. The organic pollutant is taken as rhodamine B, and a rhodamine B solution with a concentration of 20-50 ppm is configured to simulate an aqueous solution polluted by organic pollutants; the target bacteria selected for sterilization is taken as Acinetobacter baumannii, and a concentration of 5-20*10 5An Acinetobacter baumannii bacterial solution of cfu / ml was used to simulate an aqueous solution contaminated with bacteria.

[0015] Further, in step (1), the carbon nitride is prepared by the following method: Urea powder is placed in a quartz tube furnace for thermal polycondensation reaction. After the reaction is completed, it is ground to obtain carbon nitride powder. Among them, the temperature of the thermal polycondensation reaction is 500 - 600 °C, the heating rate is 3 - 4 °C / min, and the thermal polycondensation reaction time is 6 - 8 h.

[0016] Furthermore, the use of the bismuth oxybromide / carbon nitride-based photocatalytic paper of the present invention is that it is used for fruit and vegetable preservation and used as a packaging material.

[0017] The performance of bismuth oxybromide / carbon nitride depends on the mass ratio of bismuth oxybromide and carbon nitride. When the amount of carbon nitride used is low, the excess bismuth oxybromide will exist in the formed bismuth oxybromide / carbon nitride in the form of impurities, resulting in crystal defects in the bismuth oxybromide / carbon nitride and affecting its photocatalytic performance; if the amount of carbon nitride used is high, the agglomeration phenomenon of carbon nitride is significantly enhanced, and the uniformity of bismuth oxybromide / carbon nitride is affected, thereby affecting its performance. When the ratio of carbon nitride is too high, the excessive aggregation of carbon nitride particles will even affect the adhesion of bismuth oxybromide / carbon nitride, resulting in the inability to form subsequent paper. In the hydrothermal reaction, bismuth oxybromide is produced by strictly controlling the addition amounts of bismuth nitrate pentahydrate and potassium bromide according to a molar mass ratio of 1:1. Therefore, the mass ratio of bismuth oxybromide and carbon nitride depends on the mass ratio of bismuth nitrate pentahydrate and carbon nitride.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0019] (1) The bismuth oxybromide / carbon nitride-based photocatalytic paper prepared by the present invention solves the problems of poor dispersibility and adhesion of the bismuth oxybromide / carbon nitride photocatalytic material, enabling it to be made into a paper with good structural strength. The raw materials selected are plant fibers, urea, starch, etc. The three major component materials of the raw materials are all low-cost, non-toxic, and easy to obtain. The operation process is simple, suitable for large-scale production, and reduces the production cost.

[0020] (2) The bismuth oxybromide / carbon nitride-based photocatalytic paper prepared by the present invention has good visible light photocatalytic activity and physical adsorption performance, can avoid the agglomeration of bismuth oxybromide / carbon nitride nanomaterials, can effectively degrade organic pollutants and kill bacteria, and provides a new idea for the popularization and application of photocatalytic materials.

[0021] (3) The bismuth oxybromide / carbon nitride-based photocatalytic paper prepared by the present invention has better air permeability than the photocatalytic composite gel film. It can avoid the problem of fruit and vegetable decay caused by the inability of the moisture generated by the respiration of fruits and vegetables to be discharged, resulting in an increase in the humidity of the preservation environment, and is more conducive to the long-term storage of fruits and vegetables. Description of the Drawings

[0022] Figure 1 SEM comparison diagrams of the base paper prepared based on Example 1 and the bismuth oxybromide / carbon nitride-based photocatalytic paper. No attached material was observed on the surface of the base paper, and the morphology of bismuth oxybromide / carbon nitride could be clearly observed on the surface of the bismuth oxybromide / carbon nitride-based photocatalytic paper, indicating the successful attachment of the photocatalyst bismuth oxybromide / carbon nitride powder;

[0023] Figure 2 The MAPPING diagram of the bismuth oxybromide / carbon nitride-based photocatalytic paper prepared based on Example 1 shows the presence of elements such as bromine, oxygen, carbon, bismuth, and nitrogen in the bismuth oxybromide / carbon nitride-based photocatalytic paper;

[0024] Figure 3 TEM comparison diagrams of the base paper prepared based on Example 1 and the bismuth oxybromide / carbon nitride-based photocatalytic paper. The base paper presents a porous structure of plant fibers, and the morphology of bismuth oxybromide / carbon nitride appears in the bismuth oxybromide / carbon nitride-based photocatalytic paper, indicating the successful attachment of the photocatalyst bismuth oxybromide / carbon nitride powder;

[0025] Figure 4 Confocal fluorescence comparison diagrams of the base paper prepared based on Example 1 and the bismuth oxybromide / carbon nitride-based photocatalytic paper. There is no change in fluorescence in the base paper, and another kind of dot-like fluorescence appears in the bismuth oxybromide / carbon nitride-based photocatalytic paper, indicating the attachment of a new substance compared with the base paper;

[0026] Figure 5 XRD comparison diagrams of the base paper prepared based on Example 1, carbon nitride-based paper, bismuth oxybromide / carbon nitride-based photocatalytic paper, and pure bismuth oxybromide / carbon nitride powder. The characteristic peaks in the bismuth oxybromide / carbon nitride-based photocatalytic paper basically correspond to the characteristic peaks of the base paper, carbon nitride-based paper, and pure bismuth oxybromide / carbon nitride powder, indicating the presence of plant fibers, carbon nitride, and bismuth oxybromide in the bismuth oxybromide / carbon nitride-based photocatalytic paper;

[0027] Figure 6 FT-IR comparison diagrams of the base paper prepared based on Example 1, carbon nitride-based paper, bismuth oxybromide / carbon nitride-based photocatalytic paper, and pure bismuth oxybromide / carbon nitride powder. The characteristic peaks in the bismuth oxybromide / carbon nitride-based photocatalytic paper basically correspond to the characteristic peaks of the base paper, carbon nitride-based paper, and pure bismuth oxybromide / carbon nitride powder, indicating the presence of plant fibers, carbon nitride, and bismuth oxybromide in the bismuth oxybromide / carbon nitride-based photocatalytic paper;

[0028] Figure 7 Efficiency comparison diagrams of the photocatalytic oxidation degradation of the organic pollutant Rhodamine B in Examples 1 - 5 of bismuth oxybromide / carbon nitride produced based on different ratios of bismuth oxybromide to carbon nitride (7.27:1 - 5);

[0029] Figure 8It is a graph comparing the efficiency of the photocatalytic oxidation degradation experiment of organic pollutant Rhodamine B using bismuth oxybromide / carbon nitride-based photocatalytic paper based on Example 2;

[0030] Figure 9 It is the effect diagram of the photocatalytic oxidation experiment for killing Acinetobacter baumannii using bismuth oxybromide / carbon nitride-based photocatalytic paper based on Example 3;

[0031] Figure 10 It is the effect diagram of the fruit preservation experiment using bismuth oxybromide / carbon nitride-based photocatalytic paper based on Example 4. Detailed implementation mode

[0032] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0033] Example 1

[0034] The preparation method of bismuth oxybromide / carbon nitride-based photocatalytic paper prepared by hot-pressing and compounding the photocatalyst bismuth oxybromide / carbon nitride with plant fiber and cationic starch as raw materials specifically includes the following steps:

[0035] 1. Obtaining of plant fiber

[0036] Purchase fresh sunflowers: Select sunflowers with healthy appearance, no rot or pests for peeling.

[0037] Prepare the working area: Prepare tools and materials in a dry and clean working area for the peeling process.

[0038] Remove the flowers and leaves: Remove all the flowers and leaves of the sunflower, leaving only the stem.

[0039] Cut the stem: Use a sharp tool such as a blade or a small knife to cut a small opening along the sunflower stem. Ensure that it is cut within the length range to be peeled.

[0040] Peel the stem pith: Insert the blade into the cut, cut along the stem, and then gently peel the pith core out of the stem using your fingers or other tools. If you encounter difficulties, you can insert the blade at the cut and gently push the blade along the stem to help separate.

[0041] Wash and dry: Put the peeled stem pith into clean water and wash it gently to remove the remaining dirt. Then place the stem pith in a dry and ventilated place to dry, obtaining solid plant fiber.

[0042] 2. Preparation of bismuth oxybromide / carbon nitride-based photocatalytic paper

[0043] (1) Accurately weigh 5.00 g of urea powder into a 30 mL covered alumina crucible, place it in a muffle furnace, and heat to 550°C at a rate of 3°C / min in an air atmosphere. Hold the temperature for 4 h and cool to room temperature to obtain a yellow solid. Rinse twice with deionized water, dry in a vacuum drying oven, and grind to obtain carbon nitride powder.

[0044] (2) Accurately weigh 0.727g of bismuth nitrate pentahydrate powder and 0.1785g of potassium bromide powder and dissolve them in 16.0ml of ethylene glycol solution. Place them on a magnetic stirrer and stir for 30min to obtain a mixed solution. Accurately weigh 0.3g of the above-mentioned carbon nitride powder and add it to the mixed solution. After ultrasonic vibration for 30min, place it on a magnetic stirrer and stir for 10min. The resulting milky yellow suspension is transferred to a 25ml polytetrafluoroethylene liner. The liner is placed in a stainless steel reactor for hydrothermal reaction at a reaction temperature of 160°C and a reaction time of 12h. After the hydrothermal reaction is completed, the liner is removed and the remaining gray crystals in the liner are washed twice with anhydrous ethanol and deionized water respectively, and placed in a 60°C forced air drying oven to dry. The reaction product is completely dried and ground to obtain bismuth oxybromide / carbon nitride powder.

[0045] (3) Accurately weigh 1.5 g of sodium hydroxide solid and dissolve it in 500 ml of water to obtain a 0.075 mol / L sodium hydroxide aqueous solution. Accurately weigh 10.0 g of the plant fiber obtained in step 1, add it to the sodium hydroxide aqueous solution, and place it in a heating mantle of a heat-collecting constant-temperature magnetic stirrer at 80°C and cook for 12 hours. After natural cooling, filter the filtrate using a nylon filter, and wash the remaining filter residue with distilled water several times until it becomes neutral, thereby obtaining a cellulose slurry;

[0046] (4) placing the neutral cellulose slurry and 5.0 g of cationic starch in a blender and stirring at a speed of 1800 to 2500 r / min for 120 s to prepare a mixed slurry;

[0047] (5) Accurately weigh 4.0 g of the mixed slurry and 0.3 g of the photocatalyst bismuth oxybromide / carbon nitride obtained in step (2), add 10.0 ml of water, and prepare a photocatalytic slurry by ultrasonication and stirring;

[0048] (6) The photocatalytic slurry was evenly coated on a circular iron filter with a diameter of 63 mm, placed on a constant temperature heating table at 110°C and hot pressed for 20 min, and peeled off after the hot pressing to obtain the final product, bismuth oxybromide / carbon nitride-based photocatalytic paper.

[0049] 3. Preparation of base paper

[0050] Repeat steps (3) and (4) in the above step 2. In step (5), do not add the photocatalyst bismuth oxybromide / carbon nitride, and make no other changes to obtain the base paper.

[0051] 4. Preparation of Carbon Nitride-based Photocatalytic Paper

[0052] Repeat the above three steps (1), (3), and (4) in Step 2. In Step (5), add 0.3 g of carbon nitride powder and make no other changes to prepare the carbon nitride-based photocatalytic paper.

[0053] Example 2

[0054] Use the bismuth oxybromide / carbon nitride-based photocatalytic paper prepared in Example 1 to conduct an experiment on photocatalytic oxidation degradation of organic pollutants. Measure the photocatalytic anti-pollution efficiency of the bismuth oxybromide / carbon nitride-based photocatalytic paper by degrading rhodamine B. Rhodamine B is a typical triphenylmethane dye, and experiments have proven its high toxicity and carcinogenicity. It is meaningful to select rhodamine B as the target degradation substance for the photocatalytic oxidation reaction.

[0055] Prepare a rhodamine B solution with a concentration of 20 ppm to simulate the organic pollutant solution. Each experimental group uses 50 ml of the rhodamine B solution and adds a circular sample with a diameter of 63 mm to conduct an experiment on photocatalytic oxidation degradation of organic pollutants. Place the experimental materials in a dark environment for 0.5 h to ensure that the sample and the rhodamine B solution reach adsorption-desorption equilibrium. Place the experimental materials after dark adsorption under a xenon lamp source for photocatalytic oxidation experiment. The power of the light source is 300 W, and the light intensity is 100 mW / cm -2 ². Take 4 mL of the reaction solution at 0, 30, 60, 90, and 120 min respectively. After filtration, use a UV-visible spectrophotometer to measure the absorbance value of the clarified reaction solution to obtain the absorbance value of the solution at 554 nm. Calculate the concentration of the reaction solution from the standard curve of the rhodamine B solution. The formula is as follows:

[0056]

[0057] In the formula, DR% is the degradation rate of the bismuth oxybromide / carbon nitride-based photocatalytic paper sample to the rhodamine B solution, C0 is the initial concentration of rhodamine B (mg / L), and C t is the concentration of rhodamine B at time t (mg / L).

[0058] Example 3

[0059] Use the bismuth oxybromide / carbon nitride-based photocatalytic paper prepared in Example 1 to conduct a photocatalytic oxidation sterilization experiment. Measure the photocatalytic sterilization performance of the bismuth oxybromide / carbon nitride-based photocatalytic paper by killing Acinetobacter baumannii. Acinetobacter baumannii is a multi-drug resistant opportunistic pathogen with serious harm in human society at present, and it has extremely strong vitality. It is one of the main pathogens in aquaculture and hospital infections. It is meaningful to select Acinetobacter baumannii as the target strain for photocatalytic oxidation sterilization.

[0060] (1) Bacterial strain resuscitation

[0061] 1. Take out the bacterial strain stored in a 1.5 ml ep tube from a refrigerator at -60°C.

[0062] 2. Pipette 100 μL of the bacterial strain into 5 mL of liquid medium and culture it in a shaker at 37°C for 16 h to obtain a bacterial liquid.

[0063] (2) Obtain a single colony

[0064] 1. Streak the bacterial liquid cultured in step (1) on a plate in three zones with an inoculation loop. Culture it in a plate incubator at 37°C for 16 h;

[0065] 2. Dip a single bacterium on the plate and then inoculate it into 5 mL of liquid medium. Culture it in a shaker at 37°C overnight for 16 h to obtain a single colony bacterial liquid of the target bacterial strain.

[0066] (3) Shake to measure OD

[0067] Pipette 200 μL of the single colony bacterial liquid in step (2) into 5 mL of liquid medium and culture it in a shaker at 37°C for 4.5 h until OD 600 = 0.5.

[0068] (4) Bactericidal experiment

[0069] 1. Take 20 mL of PBS, a bismuth oxybromide / carbon nitride-based photocatalytic paper with a diameter of 63 mm, and 400 μL of bacterial liquid. Mix them and start the experiment with a xenon lamp;

[0070] 2. Take samples at 0, 20, 40, 60, 80, 100, and 120 min and perform plate counting;

[0071] 3. Perform serial dilution by the method of 90 μL of PBS + 10 μL of bacterial liquid;

[0072] 4. After the experiment, soak all containers and waste materials that have come into contact with bacteria in 84 disinfectant and then clean or discard them.

[0073] 5. The sterilization rate formula is:

[0074]

[0075] In the formula, SR% is the killing rate of the bismuth oxybromide / carbon nitride-based photocatalytic paper sample against Acinetobacter baumannii, C0 is the initial concentration of Acinetobacter baumannii (mg / L), and C t is the concentration of Acinetobacter baumannii at time t (mg / L).

[0076] The effects obtained in Example 3 are as Figure 9As shown, there are a total of 7 petri dish samples. Among the 4 samples in the upper row, from left to right, they are the samples taken at 0 min, 20 min, 40 min, and 60 min respectively. Among the 3 samples in the lower row, from left to right, they are the samples taken at 80 min, 100 min, and 120 min respectively. There are 12 colonies in total, arranged in 4 rows and 3 columns, in each petri dish sample. From top to bottom, they represent the three colony samples taken without dilution, diluted 10 times, diluted 100 times, and diluted 1000 times respectively. It can be observed that as time goes by, the colonies gradually disappear from the 4th row upwards, indicating a gradual decrease in the bacterial concentration in the bacterial liquid. By comparing the petri dish samples at 0 min and 120 min and calculating the number of bacteria in their 4th row and 1st row respectively, it can be obtained that the killing rate of the bismuth oxybromide / carbon nitride-based photocatalytic paper prepared in Example 1 against Acinetobacter baumannii reaches 99.83% at 120 min. Killing Acinetobacter baumannii is a means to characterize the performance of the material in photocatalytic oxidation to kill bacteria. From Figure 9 it can be seen that the end product, bismuth oxybromide / carbon nitride-based photocatalytic paper, has excellent photocatalytic oxidation and sterilization performance.

[0077] Example 4

[0078] The bismuth oxybromide / carbon nitride-based photocatalytic paper prepared in Example 1 was used for a fruit preservation experiment, and the improvement degree of the preservation performance of the bismuth oxybromide / carbon nitride-based photocatalytic paper was determined by measuring the preservation effect of strawberries.

[0079] According to the packaging characteristics of strawberries during transportation, an experimental device with double-layer paper coating was designed. This experimental device requires two pieces of bismuth oxybromide / carbon nitride-based photocatalytic paper with a diameter of 63 mm. One piece is laid at the bottom of the strawberry, and the other is covered on top of the strawberry. The outer layer is coated with paperboard to imitate the actual situation during fruit transportation. Three strawberries with a diameter of 6.0 cm were selected and labeled as No. 1, No. 2, and No. 3. No. 1 was not coated and recorded as the blank group, No. 2 was coated with the original paper and recorded as the original paper group, and No. 3 was coated with bismuth oxybromide / carbon nitride-based photocatalytic paper and recorded as the catalytic group. Photos were taken and samples were taken every 24 hours.

[0080] The effects obtained in Example 4 are as Figure 10 shown. There are a total of 21 petri dishes arranged in 3 rows and 7 columns, which represent the morphological changes of strawberries in the blank group, the original paper group, and the catalytic group on the 1st to 7th days from left to right and from top to bottom respectively. It can be observed that the strawberries in the blank group began to rot after 1 day of preservation, the strawberries in the original paper group began to rot after 2 days of preservation, and the strawberries in the catalytic group began to rot after 4 days of preservation. By comparing the blank group and the catalytic group, it can be obtained that the preservation time of the strawberries with the bismuth oxybromide / carbon nitride-based photocatalytic paper prepared in Example 1 was extended from 1 day to 4 days. The strawberry preservation experiment is a means to characterize the performance of the material in fruit preservation. From Figure 10 it can be seen that in practical applications, the end product, bismuth oxybromide / carbon nitride-based photocatalytic paper, has improved the fruit preservation effect by 4 times.

[0081] To further illustrate the technical effects of the present invention, the present invention also provides more embodiments for effect comparison.

[0082] The following table lists the degradation rates of the product bismuth oxybromide / carbon nitride powder on a 20 ppm rhodamine B solution in Examples 1-5 where the amount of bismuth nitrate pentahydrate added in step (1) is 0.727 g and the amount of potassium bromide added is 0.1785 g (the molar mass ratio of bismuth nitrate pentahydrate to potassium bromide is constantly 1:1), while changing the amount of carbon nitride added.

[0083] Serial number Addition amount of bismuth nitrate pentahydrate (g) Addition amount of carbon nitride (g) Degradation rate at 25 min of the product (%) Example 1 7.27 0.1 70.04 Example 2 7.27 0.2 92.10 Example 3 7.27 0.3 98.52 Example 4 7.27 0.4 95.87 Example 5 7.27 0.5 91.49

[0084] Degrading rhodamine B dye is a means to characterize the photocatalytic oxidation performance of materials. As can be seen from the above table, when the mass ratio of bismuth nitrate pentahydrate to carbon nitride is 7.27:3-4, the photocatalytic oxidation performance of the final product bismuth oxybromide / carbon nitride-based photocatalytic paper is better.

[0085] Preferably, the temperature of the thermal polycondensation reaction is 550 °C, the heating rate is 3 °C / min, and the thermal polycondensation reaction time is 7 h; the mass ratio of bismuth nitrate pentahydrate to carbon nitride is 7.27:3; the temperature of the hydrothermal reaction is 160 °C, and the hydrothermal reaction time is 12 h. Of course, in other embodiments of the present invention, it can be selected according to needs, and the embodiments of the present invention are not limited.

[0086] Furthermore, in step (3), the molar concentration of the sodium hydroxide aqueous solution is 0.05-0.1 mol / L. Sodium hydroxide has strong alkalinity and can decompose long-chain cellulose in plant fibers into short-chain cellulose, which not only facilitates subsequent pulp preparation but also enables bismuth oxybromide / carbon nitride powder to contact more cellulose, improving the utilization rate of the photocatalyst; there are three reasons for choosing plant fibers as the cellulose source: firstly, as natural cellulose, plant fibers are a multi-layer structure formed by the irregular stacking of many lamellae, with rich pores, and the cross-section also shows an obvious honeycomb structure, which can avoid the agglomeration of bismuth oxybromide / carbon nitride powder, thus ensuring the physical adsorption and catalytic activity of the photocatalyst; secondly, plant fibers are natural, non-toxic and harmless, and the fruits and vegetables wrapped by the prepared bismuth oxybromide / carbon nitride-based photocatalytic paper will not cause harm to the human body after being eaten; secondly, plant fibers are inexpensive, easy to obtain, and the operation process is simple, suitable for large-scale production, reducing the production cost.

[0087] Preferably, the molar concentration of the sodium hydroxide aqueous solution is 0.075 mol / L. Of course, in other embodiments of the present invention, it can be selected according to needs, and the embodiments of the present invention are not limited.

[0088] Further, in step (4), the reason for adding the retention agent cationic starch is as follows: plant fibers are negatively charged, and bismuth oxybromide / carbon nitride powder is also negatively charged. According to the principle of charge repulsion, it is difficult to compound them. Therefore, it is necessary to add positively charged cationic starch to enhance the binding strength and improve the retention rate of bismuth oxybromide / carbon nitride powder in plant fibers. The mixing mass ratio of plant fibers to cationic starch is 10:3.3 - 4. When the addition amount of cationic starch is too low, the retention rate of bismuth oxybromide / carbon nitride powder will decrease significantly, and the photocatalytic oxidation performance of the formed paper will be reduced. When the addition amount of cationic starch is too high, since starch shows strong viscosity after contacting with water, the prepared mixed slurry will be too viscous to form paper.

[0089] The following table lists the retention rates of bismuth oxybromide / carbon nitride in the bismuth oxybromide / carbon nitride-based photocatalytic paper of Examples 6 - 11 in step (4) based on the above preferred steps, where the addition amount of plant fibers is controlled to be 10.0 g and the addition amount of cationic starch is changed.

[0090]

[0091] The higher the retention rate of bismuth oxybromide / carbon nitride, the better the photocatalytic oxidation performance of the formed paper. As can be seen from the above table, when the mixing mass ratio of plant fibers to cationic starch is 10:3.3 - 4, the photocatalytic oxidation performance of the final product bismuth oxybromide / carbon nitride-based photocatalytic paper is better.

[0092] Preferably, the mixing mass ratio of plant fibers to cationic starch is 10:4. Of course, in other embodiments of the present invention, it can be selected according to requirements, and the embodiments of the present invention are not limited.

[0093] In step (5), the mixing mass ratio of the mixed slurry to bismuth oxybromide / carbon nitride is 40:3 - 4. When the addition amount of bismuth oxybromide / carbon nitride powder is too low, the degradation rate of the final product bismuth oxybromide / carbon nitride-based photocatalytic paper for organic pollutants will decrease step by step. When the addition amount of bismuth oxybromide / carbon nitride powder is too high, the improvement of the degradation rate of the final product bismuth oxybromide / carbon nitride-based photocatalytic paper for organic pollutants is limited.

[0094] The following table lists the degradation rates of the final product bismuth oxybromide / carbon nitride-based photocatalytic paper for 20 ppm rhodamine B solution in Examples 12 - 16 in step (5) based on the above preferred steps, where the addition amount of the mixed slurry of plant fibers and cationic starch is controlled to be 4.0 g and the addition amount of bismuth oxybromide / carbon nitride powder is changed.

[0095]

[0096]

[0097] Degrading rhodamine B dye is a means to characterize the photocatalytic oxidation performance of materials. As can be seen from the above table, when the mass ratio of the mixed slurry of plant fiber and cationic starch to bismuth oxybromide / carbon nitride powder is 40:3 to 4, the photocatalytic oxidation performance of the final product, bismuth oxybromide / carbon nitride-based photocatalytic paper, is relatively good. Continue with the killing experiment on Acinetobacter baumannii at a concentration of 20*10 5 cfu / ml, as Figure 9 shown, when the mass ratio of the mixed slurry to bismuth oxybromide / carbon nitride is 40:3, the killing rate of Acinetobacter baumannii reaches 99.9%, meeting the requirements of the present invention.

[0098] In step (6), the hot pressing method refers to placing an iron filter screen on a constant temperature heating table and then pressing a heavy object. The heating temperature of the constant temperature heating table is 105-120°C, and the heating time is 10-20 minutes.

[0099] Preferably, the heating temperature of the constant temperature heating table is 110°C, and the heating time is 20 minutes. Of course, in other embodiments of the present invention, it can be selected according to requirements, and the embodiments of the present invention are not limited.

Claims

1. A preparation method of bismuth oxybromide / carbon nitride-based photocatalytic paper, characterized in that, It includes the following steps: (1) Bismuth nitrate pentahydrate, the precursor of bismuth oxybromide, and potassium bromide are dissolved in the solvent ethylene glycol at a molar mass ratio of 1:1, stirred into a uniform solution, carbon nitride is added, and stirring and ultrasonic treatment are continued. After forming a suspension, hydrothermal reaction is carried out; the mass ratio of bismuth nitrate pentahydrate to carbon nitride is 7.27:3 - 4; the temperature of the hydrothermal reaction is 150 - 170 °C, and the time of the hydrothermal reaction is 11 - 13 h; (2) After the hydrothermal reaction is completed, the product is a bismuth oxybromide / carbon nitride solid precipitate. The upper layer of ethylene glycol solvent is filtered off, washed, dried, and ground to obtain bismuth oxybromide / carbon nitride powder for standby; (3) Solid plant fibers are added to an aqueous sodium hydroxide solution and alkali-cooked in a heating jacket of a collecting type constant temperature magnetic stirrer; after alkali-cooking, it is naturally cooled, placed in a nylon filter net, washed and filtered with distilled water to obtain plant fiber pulp; (4) The above pulp is placed in a blender, cationic starch is added, and stirred and mixed evenly to prepare a mixed pulp of plant fibers and cationic starch; the mass ratio of the plant fiber pulp to the cationic starch is 10:3.3 - 4; (5) Weigh the mixed pulp obtained in step (4), add the bismuth oxybromide / carbon nitride powder obtained in step (2), and configure it into a photocatalytic pulp uniformly dispersed with bismuth oxybromide / carbon nitride through ultrasonic treatment and stirring; the mass ratio of the mixed pulp to the bismuth oxybromide / carbon nitride is 40:3 - 4; (6) The above photocatalytic pulp is uniformly coated on an iron filter net and hot-pressed on a constant temperature heating table to obtain the final product, bismuth oxybromide / carbon nitride-based photocatalytic paper.

2. The preparation method of the bismuth oxybromide / carbon nitride-based photocatalytic paper according to claim 1, wherein In step (6), the diameter of the iron filter net is 50 - 75 mm; the heating temperature of the constant temperature heating table is 105 - 120 °C, and the heating time is 10 - 20 min.

3. The preparation method of the bismuth oxybromide / carbon nitride-based photocatalytic paper according to claim 1, wherein In step (3), the molar concentration of the aqueous sodium hydroxide solution is 0.05 - 0.1 mol / L.

4. A bismuth oxybromide / carbon nitride-based photocatalytic paper, characterized in that: Prepared by the method according to any one of claims 1 - 3.

5. Use of the bismuth oxybromide / carbon nitride-based photocatalytic paper according to claim 4, characterized in that, For photocatalytic oxidation degradation of organic pollutants or photocatalytic oxidation sterilization.

6. Use of the bismuth oxybromide / carbon nitride-based photocatalytic paper according to claim 5, characterized in that, The organic pollutant is Rhodamine B.

7. Use of the bismuth oxybromide / carbon nitride-based photocatalytic paper according to claim 5, characterized in that, The target bacteria for photocatalytic oxidation sterilization are Acinetobacter baumannii.

8. Use of the bismuth oxybromide / carbon nitride-based photocatalytic paper according to claim 4, characterized in that For fresh-keeping of fruits and vegetables and used as a packaging material.

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