A cocoon loaded nano-zinc oxide photocatalytic material, a preparation method and application thereof

Abstract

The present application relates to the field of photocatalytic material preparation. More particularly, it relates to a cocoon loaded nano-zinc oxide photocatalytic material and its preparation method and application. The preparation method comprises the following steps: S1, the natural cocoon is subjected to shallow activation treatment, so that the active functional groups are exposed while the silk fibroin integrity is maintained; S2, the activated cocoon is crushed into a flocculent state, then mixed with nano-zinc oxide nanoparticle suspension, ultrasonic immersion and drying; S3, low-temperature calcination in a muffle furnace, and grinding to obtain the product. Through the above preparation method, stable chemical bonding is formed between the active functional groups of the cocoon and the zinc oxide nanoparticles, effectively widening the light response range of the material, reducing the band gap width, significantly enhancing the photoelectric charge separation efficiency, improving the photocatalytic activity and the degradation ability of antibiotics in complex water bodies, and effectively alleviating the agglomeration problem of nano-zinc oxide nanoparticles.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic material preparation. More specifically, it relates to a photocatalytic material of silkworm cocoon-loaded nano-zinc oxide, its preparation method, and its application. Background Technology

[0002] Antibiotics are produced by bacteria, fungi, or other microorganisms through their own metabolism or synthesized artificially. Their application has greatly promoted the development of fields such as medicine and animal husbandry. However, their widespread overuse has led to serious environmental problems. Residual antibiotics damage aquatic ecosystems, induce the spread of drug-resistant bacteria and resistance genes, and threaten human health. Common methods for degrading antibiotics include physical methods, biodegradation methods, and chemical oxidation methods. Among these, photocatalysis technology in chemical oxidation methods has become a promising emerging approach in recent years. Its principle is that semiconductor photocatalysts are excited under light irradiation to generate electrons and holes, forming active free radicals on the catalyst surface, which then degrade organic pollutants through redox reactions.

[0003] Among numerous semiconductor photocatalysts, zinc oxide is considered one of the most promising photocatalytic materials for solving environmental pollution problems due to its stable chemical properties, high photocatalytic activity, low cost, and environmental friendliness. However, pure nano-zinc oxide faces three major bottlenecks in practical applications: First, as a wide-bandgap semiconductor (bandgap of approximately 3.37 eV), it mainly absorbs ultraviolet light and has low utilization of visible light, which accounts for a large proportion of sunlight; second, the rapid recombination rate of photogenerated electron-hole pairs leads to low quantum efficiency, limiting further improvement in its photocatalytic performance; third, nano-zinc oxide nanoparticles are prone to agglomeration in aqueous systems, reducing their effective specific surface area and active sites, and the catalyst is difficult to recover after use, easily causing secondary pollution.

[0004] To overcome the aforementioned shortcomings, loading nano-zinc oxide onto a support is a recognized effective strategy. While existing technologies disclose various loading methods, all have limitations. One type of loading method uses biological materials as sacrificial templates. For example, CN108855033A uses grapefruit peel as a template, retaining only its structural morphology after high-temperature calcination to obtain pure zinc oxide, sacrificing the synergistic effect between the support and the catalyst. Another type of loading method retains the support, but the binding mechanism is mainly physical adsorption. For example, in CN109420487A, the interaction between bamboo charcoal and zinc oxide is weak, resulting in limited synergistic effects; or the process is complex and time-consuming. For instance, CN105797703A involves microbial culture and long-term fermentation, while CN110433789A requires a 15-45 day bioaccumulation process using water hyacinth. It is evident that although existing technologies have explored various ZnO-supporting schemes, the following technical problems still exist: 1. Methods using biomaterials as sacrificial templates cannot achieve synergistic effects between the support and the catalyst; 2. Composite materials based on physical adsorption have weak bonding forces and the synergistic effect is not obvious; 3. Some preparation methods are complex, costly, or difficult to control.

[0005] Silkworm cocoons, as a natural protein biomaterial, are mainly composed of silk fibroin, which is rich in active functional groups such as amide and amino groups, and is characterized by its porous nature, light weight, and excellent mechanical properties. Currently, while the existing technology patent CN111420706A also uses silk, its process requires completely degumming and dissolving the silkworm cocoons into a silk fibroin solution before preparing a regenerated fiber membrane through electrospinning. This process is cumbersome and completely destroys the natural structure of the silkworm cocoon. Li et al. demonstrated the feasibility of using silkworm cocoons as a photocatalyst carrier by loading AgBr / BiOBr heterojunctions via ultrasonic-assisted impregnation for photocatalytic degradation and antibacterial purposes (Li R, Hu Z, Shen L, et al. Constructing AgBr / BiOBr@silkworm cocoons photocatalytic degradation and antibacterial material: Based on the excellent adsorption properties of silkworm cocoons. Inorganic Chemistry Communications, 2023, 153: 110815.). However, their focus was on the heterojunction system, without pretreatment of the silkworm cocoons or subsequent low-temperature calcination. Therefore, how to improve the photocatalytic ability of nano-zinc oxide remains a hot research topic. Summary of the Invention

[0006] Based on the above-mentioned shortcomings, the first objective of this invention is to provide a method for preparing a photocatalytic material of zinc oxide nanoparticles supported on silkworm cocoons. This preparation method, through a simple process, exposes more active sites in the silkworm cocoons and forms stable chemical bonds with the zinc oxide nanoparticles, thereby enabling the resulting photocatalytic material to exhibit excellent degradation capabilities in the application of antibiotics in degrading real water bodies.

[0007] The second objective of this invention is to provide a photocatalytic material of silkworm cocoon-loaded zinc oxide prepared by the preparation method described above.

[0008] The third objective of this invention is to provide an application of the photocatalytic material described above in the photocatalytic degradation of antibiotic wastewater.

[0009] To achieve the first objective mentioned above, the present invention adopts the following technical solution:

[0010] This invention discloses a method for preparing a photocatalytic material of nano-zinc oxide supported on silkworm cocoons, comprising the following steps:

[0011] S1. Natural silkworm cocoons are subjected to shallow activation treatment to expose abundant active functional groups while maintaining the integrity of sericin.

[0012] S2. The activated silkworm cocoons are crushed to make them flocculent, then mixed with a suspension of nano zinc oxide nanoparticles, ultrasonically impregnated and dried.

[0013] S3. Place it in a muffle furnace for low-temperature calcination, then grind it to obtain the final product;

[0014] The shallow activation treatment involves placing the cleaned natural silkworm cocoons into a prepared sodium bicarbonate solution and letting them stand at room temperature. During the standing process, the cocoons can be gently turned over several times to ensure that they are in full contact with the sodium bicarbonate solution.

[0015] The preparation method provided by this invention employs a shallow activation treatment using a weak alkaline solution, which differs from deep activation that removes sericin from the surface of the silkworm cocoon, exposes fibroin, and disrupts the main structure of the cocoon. This method, without damaging the integrity of the sericin and the main structure of the cocoon, moderately loosens the molecular structure, thereby maximizing the exposure of internal active functional groups (such as hydroxyl and amide groups), significantly improving its surface activity and creating conditions for a strong subsequent bond with zinc oxide. Furthermore, a calcination process is used as an auxiliary means. Its purpose is not to completely carbonize the cocoon, but to utilize the active sites exposed by the shallow activation treatment while preserving the core functional groups of the cocoon, promoting the formation of stable chemical bonds between the cocoon and zinc oxide nanoparticles. This shift from simple physical loading to chemical bonding effectively broadens the material's photoresponse range, reduces the band gap, and significantly enhances the photogenerated charge separation efficiency, thereby greatly improving photocatalytic activity and the ability to degrade antibiotics in complex water bodies, while effectively alleviating the aggregation problem of zinc oxide nanoparticles.

[0016] Furthermore, the mass concentration of the sodium bicarbonate solution should not be too high, generally 0.1-3%; for example, the mass concentration of the sodium bicarbonate solution can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0017] The crushing process in step S2 transforms the silkworm cocoon into a flocculent state, thereby increasing the specific surface area of ​​the cocoon and facilitating the loading of nano-zinc oxide for subsequent photocatalysis. In one specific embodiment, a high-speed blender is used for crushing, with a crushing time of 4-8 minutes.

[0018] Furthermore, the natural silkworm cocoons are left to stand in sodium bicarbonate solution for 6-24 hours.

[0019] Furthermore, the silkworm cocoons undergo a pretreatment process before shallow activation treatment. The pretreatment is mainly to remove impurities from the surface of the cocoons. In one specific embodiment, a pretreatment process is provided: select whole white natural silkworm cocoons, cut them into small pieces, rinse them repeatedly with deionized water to remove surface impurities, and dry them in a 60°C constant temperature oven to constant weight.

[0020] Furthermore, in step S2, the mass ratio of the activated silkworm cocoon to the zinc oxide nanoparticles is 2.4:0.1-3; for example, the mass ratio of the activated silkworm cocoon to the zinc oxide nanoparticles can be 2.4:0.1, 2.4:0.5, 2.4:1, 2.4:1.5, 2.4:2, 2.4:2.5, 2.4:3, etc.

[0021] Furthermore, the zinc oxide nanoparticle suspension is formed by dispersing zinc oxide nanoparticles in a solvent to form a stable zinc oxide-containing suspension. The selected solvent can be a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 1:1.

[0022] Furthermore, the low-temperature calcination described in step S3 is extremely crucial. It is essential to ensure that the calcination purpose is achieved without completely carbonizing the silkworm cocoons, thus allowing a stable chemical bond to form between the cocoons and zinc oxide nanoparticles. Through extensive experimental research, the low-temperature calcination conditions were ultimately controlled by heating to 300-400 °C at a rate of 4-6 °C / min and holding at that temperature for 100-150 min.

[0023] Furthermore, the ultrasonic impregnation time in step S2 is 30-60 minutes.

[0024] To achieve the second objective mentioned above, the present invention adopts the following technical solution:

[0025] This invention discloses a photocatalytic material of silkworm cocoon-loaded zinc oxide nanoparticles prepared by the preparation method described above. In the photocatalytic material, the zinc oxide nanoparticles form chemical bonds with the active functional groups on the silkworm cocoon carrier through chemical bonds, which is beneficial to promoting the separation of photogenerated electron-hole pairs, improving carrier utilization, broadening the photoresponse range and reducing the band gap width, thereby enhancing the photocatalytic activity of the photocatalytic material.

[0026] To achieve the third objective mentioned above, the present invention adopts the following technical solution:

[0027] This invention discloses an application of the photocatalytic material described above in the photocatalytic degradation of antibiotic wastewater.

[0028] Furthermore, the antibiotic contained in the antibiotic wastewater was ciprofloxacin.

[0029] Furthermore, the concentration of the antibiotic wastewater is 5-10 mg / L.

[0030] Furthermore, in the application, 0.0002-0.0005g of photocatalytic material is added per milliliter of antibiotic wastewater.

[0031] Furthermore, in the application, the photocatalytic degradation is irradiated with a light source with a wavelength λ < 1000 nm, and the photocatalytic degradation time is 60-180 min.

[0032] An example of a practical application process is provided:

[0033] The photocatalytic material described above was added to an antibiotic solution prepared in an actual water body, and then subjected to ultrasonic treatment and stirring to carry out the photodegradation process.

[0034] Furthermore, the actual water body is derived from one of the following: pure water, tap water, or artificial lake water.

[0035] Furthermore, the ultrasonic treatment time is 20-40 minutes.

[0036] Furthermore, the stirring time is 20-40 minutes.

[0037] Furthermore, in the application, the photocatalytic degradation is irradiated with a light source with a wavelength of 420nm≤λ<1000nm, and the photodegradation time is 60min.

[0038] The beneficial effects of this invention are as follows:

[0039] 1. The preparation method provided by this invention mainly utilizes silkworm cocoons, a natural material, to perform shallow activation, then uses them as a carrier to load nano-zinc oxide. Low-temperature calcination causes the silkworm cocoons and zinc oxide nanoparticles to form chemical bonds for immobilization. The zinc oxide nanoparticles, loaded onto the silkworm cocoon carrier, have limited agglomeration due to the carrier, resulting in relatively controllable size, uniform coverage on the carrier surface, and interfacial bonding, leading to a more compact structure. This alleviates the problem of zinc oxide nanoparticle agglomeration and is more conducive to photocatalysis. More importantly, the shallow activation treatment of the silkworm cocoons in this invention differs from deep activation. It allows the cocoons to absorb water and swell without damaging the sericin structure on the surface, making the molecular structure looser and exposing more active functional groups (such as hydroxyl and amide groups), thus improving the surface activity and wettability of the cocoons. Subsequent crushing treatment changes the cocoon morphology to a flocculent state, increasing the contact area with zinc oxide. All of these factors create conditions for better bonding between the silkworm cocoons and zinc oxide. Simultaneously, by using a low-temperature calcination process as a supplement, all the C=O and NH chemical bonds in the silkworm cocoon are preserved. These chemical bonds can form stable chemical coordination bonds with zinc oxide, which is different from traditional physical adsorption. Therefore, it promotes the separation of photogenerated electron-hole pairs, reduces recombination, improves carrier utilization, broadens the photoresponse range, and reduces the band gap width, thereby enhancing the photocatalytic activity of the photocatalytic material.

[0040] 2. The photocatalytic material provided by this invention has a stable structure. When used to adsorb methylene blue and photocatalytically degrade antibiotics, the adsorption capacity of methylene blue can reach 5.67 mg / g, which is not significantly lower than that of unactivated silkworm cocoon-supported zinc oxide photocatalytic material (SC-ZnO(calc.)) and uncalcined silkworm cocoon-supported zinc oxide photocatalytic material (SC-ZnO). The degradation rates of ciprofloxacin in pure water, tap water, and artificial lake water can reach 89%, 88%, and 81%, respectively. Compared with zinc oxide photocatalysts, uncalcined silkworm cocoon-supported zinc oxide photocatalytic material (SC-ZnO), and unactivated silkworm cocoon-supported zinc oxide photocatalytic material (SC-ZnO(calc.)), the degradation rate and degradation speed of ciprofloxacin are all improved.

[0041] 3. The preparation method provided by this invention is low in cost, simple in synthesis process, and easy to operate, making it suitable for large-scale production applications. Furthermore, the application of photocatalytic degradation technology to the degradation of antibiotics in different actual water bodies has high application prospects and practical value. Attached Figure Description

[0042] Figure 1 Scanning electron microscope (SEM) images of nano-zinc oxide as raw material and the photocatalytic material (SC-ZnO(Act.)) prepared in Example 1, wherein, Figure 1 In the image, (a) and (b) are photocatalytic materials (SC-ZnO(Act.)), and (c) and (d) are raw materials, such as nano-zinc oxide.

[0043] Figure 2 Transmission electron microscopy (TEM) images of nano-zinc oxide as raw material and the photocatalytic material (SC-ZnO(Act.)) prepared in Example 1, wherein... Figure 2 In the image, (a) is the photocatalytic material (SC-ZnO(Act.)) and (b) is the raw material nano zinc oxide.

[0044] Figure 3 The Fourier transform infrared spectra of the different photocatalytic materials prepared in Example 1 and Comparative Examples 1-3 are shown.

[0045] Figure 4 The ultraviolet light of different photocatalytic materials prepared in Example 1 and Comparative Examples 1-3 The diffuse reflectance spectrum and Tauc plot are visible, among which, Figure 4 (a) represents ultraviolet light. The diffuse reflectance spectrum is visible, and (b) is the Tauc plot.

[0046] Figure 5 Langmuir and Freundlich isotherm adsorption curves of methylene blue using nano zinc oxide, silkworm cocoons, and different photocatalytic materials prepared in Examples 1 and Comparative Examples 1-3 as raw materials.

[0047] Figure 6 The adsorption-desorption isotherm and pore size distribution of the photocatalytic material (SC-ZnO(Act.)) prepared in Example 1.

[0048] Figure 7 To test the photodegradation ability of various samples of ciprofloxacin in different water bodies, among which, Figure 7 (a) shows the degradation diagram of ciprofloxacin in pure water. Figure 7 (b) shows the degradation diagram of ciprofloxacin in tap water. Figure 7 (c) shows the degradation of ciprofloxacin in artificial lake water. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0051] Example 1

[0052] Step 1: Select intact white natural silkworm cocoons, cut them into small pieces, rinse them repeatedly with deionized water to remove surface impurities, and dry them in a 60℃ constant temperature oven until constant weight. Prepare a 1% sodium bicarbonate solution. Place the simply treated silkworm cocoons into the prepared sodium bicarbonate solution and let them stand at room temperature for 18 hours, gently turning them twice during this period to ensure full contact between the cocoons and the sodium bicarbonate solution. Immediately afterwards, quickly rinse the cocoons with room temperature deionized water to ensure the sodium bicarbonate solution is thoroughly rinsed off the surface. Dry them in a 60℃ constant temperature oven until constant weight to obtain silkworm cocoons with shallow activation treatment. Then, use a high-speed blender to break the cocoons into a flocculent form for later use.

[0053] Step 2: Weigh 2g of zinc oxide nanoparticles and add them to 40mL of a 1:1 mixture of anhydrous ethanol and deionized water. Disperse the mixture using ultrasound to form a uniform zinc oxide suspension. Weigh 2.4g of the silkworm cocoons treated in Step 1 and place them in the zinc oxide suspension. Sonicate the cocoons, then centrifuge at 3000rpm for 5min. Remove the top solution and dry the sample in a 60℃ oven until constant weight.

[0054] Step 3: Place the dried sample from Step 2 into a crucible and calcine it in a muffle furnace. Set the heating rate to 5℃ / min and heat it to 400℃. Hold this temperature for 120min. After cooling in the furnace, grind and mix evenly to obtain the photocatalytic material, denoted as SC-ZnO(Act.).

[0055] Depend on Figure 1 and Figure 2 It can be seen that unloaded nano-zinc oxide exhibits an approximately spherical aggregated state under SEM, with poor dispersibility and a loose structure; SC-ZnO(Act.) is blocky on the silkworm cocoon substrate, with zinc oxide nanoparticles loaded on the substrate, resulting in restricted aggregation, controllable size, and a more compact structure. Figure 2In the TEM, unsupported zinc oxide nanoparticles were spherical or ellipsoidal and agglomerated into large aggregates; the SC-ZnO(Act.) photocatalyst was an irregular polygonal shape with good dispersibility and less agglomeration. The silkworm cocoon substrate can inhibit agglomeration and improve the dispersibility of zinc oxide nanoparticles, which is beneficial to improving photocatalytic activity.

[0056] Comparative Example 1

[0057] Step 1: Select whole white natural silkworm cocoons, cut them into small pieces, rinse them several times with deionized water to remove surface impurities, dry them in a 60℃ constant temperature oven until constant weight, and then crush them with a high-speed blender to change the shape of the silkworm cocoons into flocculent form, and set them aside.

[0058] Weigh 2g of zinc oxide nanoparticles and add them to 40mL of a 1:1 mixture of anhydrous ethanol and deionized water. Disperse the mixture using ultrasonication to form a uniform zinc oxide suspension.

[0059] Step 2: Place the 2.4g silkworm cocoons processed in Step 1 into a zinc oxide suspension, sonicate, and then centrifuge at 3000 rpm for 5 minutes to remove the upper solution. Place the lower sample in a 60℃ constant temperature oven to dry to constant weight.

[0060] Step 3: Place the dried sample from Step 2 into a crucible and calcine it in a muffle furnace. Set the heating rate to 5℃ / min and heat it to 400℃. Hold this temperature for 120min. After cooling in the furnace, grind and mix evenly to obtain SC-ZnO(calc.) photocatalyst.

[0061] Comparative Example 2

[0062] Step 1: Select whole white natural silkworm cocoons, cut them into small pieces, rinse them several times with deionized water to remove surface impurities, dry them in a 60℃ constant temperature oven until constant weight, and then crush them with a high-speed blender to change the shape of the silkworm cocoons into flocculent form, and set them aside.

[0063] Weigh 2g of zinc oxide nanoparticles and add them to 40mL of a 1:1 mixture of anhydrous ethanol and deionized water. Disperse the mixture using ultrasonication to form a uniform zinc oxide suspension.

[0064] Step 2: Place the 2.4g silkworm cocoons processed in Step 1 into a zinc oxide suspension, sonicate, and then centrifuge at 3000 rpm for 5 minutes to remove the upper solution. Place the lower sample in a constant temperature oven to dry, and obtain the photocatalytic material SC-ZnO.

[0065] Depend on Figure 3It can be seen that the characteristic peaks of the amino and amide functional groups of the three loaded samples—SC-ZnO (Act.) of Example 1, SC-ZnO (calc.) of Comparative Example 1, and SC-ZnO of Comparative Example 2—showed shifts compared to the original silkworm cocoon (SC). This proves that the original active functional groups of the silkworm cocoon changed during the calcination process. Figure 4 It can be seen that the photocatalytic material (SC-ZnO(Act.)) of Example 1, compared with the photocatalytic material (SC-ZnO(calc.)) of Comparative Example 1, the photocatalytic material (SC-ZnO) of Comparative Example 2, and nano-zinc oxide, has a wider light absorption range, stronger light absorption intensity, and narrower band gap, which means enhanced visible light utilization. Pure ZnO exhibits a band gap of 3.20 eV due to its inherent electronic transition (2p of O to 4s of Zn), and the band gap of the uncalcined material SC-ZnO is also 3.20 eV. Therefore, it can be concluded that the loading mechanism of this material is that the nano-zinc oxide nanoparticles are mainly attached to the surface of silkworm cocoon fibers through physical adsorption and van der Waals forces. However, after co-calcination with silkworm cocoons, the band gap of SC-ZnO(calc.) significantly decreased to 2.96 eV, and that of SC-ZnO(Act) significantly decreased to 2.89 eV. The energy levels of the ZnO valence band top or conduction band bottom changed, the band gap narrowed, and the electron transition energy decreased. This band gap shift cannot be explained by physical adsorption, thus proving the existence of chemical bonding. Furthermore, after shallow surface activation, SC-ZnO(Act) exposed more active functional groups, better promoting the formation of chemical bonds between the functional groups and zinc oxide nanoparticles, resulting in a further reduction in band gap compared to SC-ZnO(calc.). The shallowly activated silkworm cocoons can better bind and load with zinc oxide, and the formed chemical bonding interface acts as a highly efficient charge transport channel, greatly promoting the separation of photogenerated electron-hole pairs and reducing recombination, thereby fundamentally improving quantum efficiency and photocatalytic activity. This also demonstrates the improved photocatalytic effect of the photocatalytic material (SC-ZnO(Act.)) in Example 1.

[0066] Comparative Example 3

[0067] Step 1: Select intact white natural silkworm cocoons, cut them into small pieces, rinse them repeatedly with deionized water to remove surface impurities, and dry them in a 60℃ constant temperature oven until constant weight. Prepare a 1% sodium bicarbonate solution. Place the simply treated silkworm cocoons into the prepared sodium bicarbonate solution, heat at 40℃ and let stand for 18 hours, gently turning them twice during this period to ensure full contact between the cocoons and the sodium bicarbonate solution. The sericin structure will be observed to be destroyed, indicating deep activation of the cocoons. Immediately afterward, quickly rinse the cocoons with room temperature deionized water to ensure the sodium bicarbonate solution is completely removed from the surface. Dry them in a 60℃ constant temperature oven until constant weight to obtain deeply activated silkworm cocoons. Then, use a high-speed blender to break the cocoons into a flocculent form for later use.

[0068] Step 2: Weigh 2g of zinc oxide nanoparticles and add them to 40mL of a 1:1 mixture of anhydrous ethanol and deionized water. Disperse the mixture using ultrasound to form a uniform zinc oxide suspension. Weigh 2.4g of the silkworm cocoons treated in Step 1 and place them in the zinc oxide suspension. Sonicate the cocoons, then centrifuge at 3000rpm for 5min. Remove the top solution and dry the sample in a 60℃ oven until constant weight.

[0069] Step 3: Place the dried sample from Step 2 into a crucible and calcine it in a muffle furnace. Set the heating rate to 5℃ / min and heat it to 400℃. Hold this temperature for 120min. After cooling in the furnace, grind and mix the samples evenly to obtain the photocatalytic material.

[0070] Comparative Example 4

[0071] Step 1: Select intact white natural silkworm cocoons, cut them into small pieces, rinse them repeatedly with deionized water to remove surface impurities, and dry them in a 60℃ constant temperature oven until constant weight. Prepare a 1% sodium bicarbonate solution. Place the simply treated silkworm cocoons into the prepared sodium bicarbonate solution and let them stand at room temperature for 18 hours, gently turning them twice during this period to ensure full contact between the cocoons and the sodium bicarbonate solution. Immediately afterwards, quickly rinse the cocoons with room temperature deionized water to ensure the sodium bicarbonate solution is thoroughly rinsed off the surface. Dry them in a 60℃ constant temperature oven until constant weight to obtain silkworm cocoons with shallow activation treatment. Then, use a high-speed blender to break the cocoons into a flocculent form for later use.

[0072] Step 2: Weigh 2g of zinc oxide nanoparticles and add them to 40mL of a 1:1 mixture of anhydrous ethanol and deionized water. Disperse the mixture using ultrasound to form a uniform zinc oxide suspension. Weigh 2.4g of the silkworm cocoons treated in Step 1 and place them in the zinc oxide suspension. Sonicate the cocoons, then centrifuge at 3000rpm for 5min. Remove the top solution and dry the sample in a 60℃ oven until constant weight.

[0073] Step 3: Place the dried sample from Step 2 into a crucible and calcine it in a muffle furnace. The calcine heating rate is set to 5℃ / min, and the sample is heated to 600℃ for high-temperature calcine. This temperature is maintained for 120 minutes. After cooling in the furnace, the sample is ground and mixed evenly to obtain the photocatalytic material. At this point, the silkworm cocoons have been completely carbonized, and some of the cocoons have been removed.

[0074] Performance testing

[0075] 1. Effect on methylene blue adsorption

[0076] Experimental group: 0.05 g of the photocatalytic material (SC-ZnO(Act.)) prepared in Example 1 was placed into a 50 mL quartz reaction flask, and then 40 mL of methylene blue solutions of 1 mg / L, 3 mg / L, 5 mg / L, 10 mg / L, 20 mg / L and 30 mg / L were added respectively. The mixture was stirred in the dark at room temperature, and samples were taken at 90 min. The absorbance was measured at a wavelength of 665 nm, the adsorption amount was calculated, and the isothermal adsorption curve was plotted.

[0077] Commonly used adsorption equilibrium isotherms include the Freundlich model and the Langmuir model. This experiment uses both models for simulation.

[0078] Control group 1: Except for replacing the photocatalytic material (SC-ZnO(Act.)) in the experimental group with nano zinc oxide nanoparticles, everything else was done in the same way as the experimental group.

[0079] Control group 2: Except for replacing the photocatalytic material (SC-ZnO(Act.)) in the experimental group with the natural material silkworm cocoon, everything else was done in the same way as the experimental group.

[0080] Control group 3: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the photocatalyst material SC-ZnO(calc.) in Comparative Example 1, all other procedures were carried out in the same manner as the experimental group.

[0081] Control group 4: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the photocatalyst material (SC-ZnO) in Comparative Example 2, all other procedures were carried out in the same manner as the experimental group.

[0082] Depend on Figure 5 As shown in the table below, the adsorption capacity of the photocatalytic material (SC-ZnO(Act.)) is 5.67 mg / g, and the adsorption process is more likely to be monolayer adsorption according to the Langmuir adsorption isotherm model. Figure 6 It can be seen that the sample isotherm curve belongs to the type IV H3 hysteresis loop adsorption isotherm curve, indicating that the pore structure is irregular. According to the pore size distribution diagram, the main pore type is mesoporous, which further illustrates that MB is mainly adsorbed on the surface of silkworm cocoons and samples by monolayer adsorption.

[0083] Table 1

[0084]

[0085] Depend on Figure 5It is known that by comparing the adsorption equilibrium isotherms of the three photocatalytic materials (SC-ZnO(calc.)), (SC-ZnO(calc.)), and (SC-ZnO), the shallow activation treatment and low-temperature calcination involved in the preparation process of Example 1 did not affect their adsorption capacity, and there was no significant difference between the two.

[0086] 2. Effects on photocatalytic degradation of ciprofloxacin

[0087] 2-1 Pure Water System

[0088] Experimental group: 1) Take pure water to prepare 40 mL of 5 mg / L ciprofloxacin aqueous solution, add 0.010 g of the photocatalytic material (SC-ZnO(Act.)) prepared in Example 1, first ultrasonically disperse for 30 min, set the temperature to 25℃, then stir in the dark for 30 min to make the solution a uniform mixture to reach adsorption equilibrium, and obtain the first mixture. Take 1.5 mL of the first sample, filter it through a 0.22 μm polytetrafluoroethylene (PTFE) filter membrane to obtain a clear solution, and put it into a brown liquid phase vial;

[0089] 2) Using the concentration of the first mixture as the initial concentration, irradiate it with visible light (λ≥420nm) for 1 hour to photodegrade the first mixture for 60 minutes. Take a sample of approximately 1.5 ml every 10 minutes, filter it through a 0.22μm polytetrafluoroethylene (PTFE) membrane to obtain a clear solution, and store it in a brown liquid chromatography vial for later use. Analyze the sample using high-performance liquid chromatography (HPLC). Mobile phase: methanol / 0.1% formic acid aqueous solution = 40 / 60 (V / V); flow rate: 1.0 mL / min; column temperature: 25℃; injection volume: 10 μL; UV detector: detection wavelength: 278 nm. Figure 7 As shown in (a), when the photodegradation time is 60 min, the degradation rate reaches 89%.

[0090] Control Group 1: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with nano-zinc oxide nanoparticles, everything else was done in the same manner as the experimental group. Figure 7 As shown in (a), when the photodegradation time is 60 min, the degradation rate reaches 68%.

[0091] Control Group 2: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the natural material silkworm cocoon, everything else was done in the same manner as the experimental group. Figure 7 As shown in (a), when the photodegradation time is 60 min, the degradation rate reaches 53%.

[0092] Control Group 3: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the photocatalyst material SC-ZnO(calc.) in Comparative Example 1, all other procedures were performed in the same manner as the experimental group. Figure 7 As shown in (a), when the photodegradation time is 60 min, the degradation rate reaches 80%.

[0093] Control Group 4: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the photocatalyst material (SC-ZnO) in Comparative Example 2, all other procedures were performed in the same manner as the experimental group. Figure 7 As shown in (a), when the photodegradation time is 60 min, the degradation rate reaches 58%.

[0094] Control group 5: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the photocatalyst material in Comparative Example 3, all other procedures were performed in the same manner as the experimental group. When the photodegradation time was 60 min, the degradation rate reached 70%.

[0095] Control group 6: Except for replacing the photocatalyst material (SC-ZnO(Act.)) in the experimental group with the photocatalyst material in Comparative Example 4, all other procedures were performed in the same manner as the experimental group. When the photodegradation time was 60 min, the degradation rate reached 60%.

[0096] 2-2 Tap water system

[0097] The photodegradation test was conducted using the same pure water system as in 2-1, except that tap water was used instead of pure water. The results are shown below. Figure 7 (b) From Figure 7 As shown in (b), when the photodegradation time is 60 min, the degradation rate of the experimental group reaches 88%, the degradation rate of control group 1 reaches 69%, the degradation rate of control group 2 reaches 57%, the degradation rate of control group 3 reaches 80%, the degradation rate of control group 4 reaches 63%, the degradation rate of control group 5 reaches 62%, and the degradation rate of control group 6 reaches 52%.

[0098] 2-3 Artificial Lake Water System

[0099] Photodegradation tests were conducted using the same pure water system as in 2-1, except that artificial lake water was used instead of pure water. The results are shown below. Figure 7 (c) Figure 7 As shown in (c), when the photodegradation time is 60 min, the degradation rate of the experimental group reaches 81%, the degradation rate of control group 1 reaches 60%, the degradation rate of control group 2 reaches 49%, the degradation rate of control group 3 reaches 75%, the degradation rate of control group 4 reaches 52%, the degradation rate of control group 5 reaches 52%, and the degradation rate of control group 6 reaches 41%.

[0100] The photocatalytic material in Comparative Example 3, employing a deep activation + low-temperature calcination technique, removed the sericin structure from the surface of the silkworm cocoon during deep activation, thus damaging the structure of the cocoon itself. In contrast, the photocatalytic material in Comparative Example 4, using a shallow activation + high-temperature calcination technique, completely carbonized the cocoon during high-temperature calcination, removing some of the cocoon material and causing significant damage. Compared to the other comparative examples, all of these deviated from the purpose of using the silkworm cocoon itself as a carrier, and the final degradation rate was also lower than that of the photocatalytic material (SC-ZnO(Act.)) in Experimental Example 1.

[0101] As shown in the table below, under the same conditions, the degradation rate constant of the photocatalytic material (SC-ZnO(Act.)) of Example 1 for degrading any antibiotic is greater than that of the photocatalytic material (SC-ZnO(calc.)) of Comparative Example 1, the photocatalytic material (SC-ZnO) of Comparative Example 2, nano zinc oxide and silkworm cocoon, regardless of the type of water body. This indicates that SC-ZnO(Act.) has a better degradation effect.

[0102] Table 2. Degradation rates of ciprofloxacin by different materials in actual water bodies.

[0103]

[0104] Example 2

[0105] A method for preparing photocatalytic materials using silkworm cocoons as a carrier to support zinc oxide is similar to that in Example 1, except that 0.2 g of nano-zinc oxide nanoparticles are weighed out. The degradation rates of ciprofloxacin in pure water, tap water, and artificial lake water reached 67%, 60%, and 59%, respectively.

[0106] Example 3

[0107] A method for preparing photocatalytic materials using silkworm cocoons as a carrier to support zinc oxide is similar to that in Example 1, except that 0.4 g of nano-zinc oxide nanoparticles are weighed out. The degradation rates of ciprofloxacin in pure water, tap water, and artificial lake water reached 72%, 66%, and 61%, respectively.

[0108] Example 4

[0109] A method for preparing photocatalytic materials using silkworm cocoons as a carrier to support zinc oxide is similar to that in Example 1, except that 1g of nano-zinc oxide nanoparticles are weighed out. The degradation rates of ciprofloxacin in pure water, tap water, and artificial lake water reached 78%, 72%, and 64%, respectively.

[0110] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a photocatalytic material of nano-zinc oxide supported on silkworm cocoons, characterized in that, Includes the following steps: S1. Natural silkworm cocoons are subjected to shallow activation treatment to expose active functional groups while maintaining the integrity of sericin. S2. The activated silkworm cocoons are crushed to make them flocculent, then mixed with a suspension of nano zinc oxide nanoparticles, ultrasonically impregnated and dried. S3. Place it in a muffle furnace for low-temperature calcination, then grind it to obtain the final product; The shallow activation treatment step involves placing the cleaned natural silkworm cocoons into a prepared sodium bicarbonate solution and letting it stand at room temperature to ensure that the silkworm cocoons are in full contact with the sodium bicarbonate solution. The sodium bicarbonate solution has a mass concentration of 0.1-3%; the natural silkworm cocoons are left to stand in the sodium bicarbonate solution for 6-24 hours. In step S2, the mass ratio of the activated silkworm cocoon to the zinc oxide nanoparticles is 2.4:0.1-3. The low-temperature calcination temperature in step S3 is 300-400 ℃.

2. The preparation method according to claim 1, characterized in that, The low-temperature calcination in step S3 involves heating to 300-400 °C at a rate of 4-6 °C / min and holding at that temperature for 100-150 min.

3. The preparation method according to claim 1, characterized in that, The ultrasonic impregnation time in step S2 is 30-60 minutes.

4. A photocatalytic material of silkworm cocoon-supported nano-zinc oxide, characterized in that, Prepared by the preparation method according to any one of claims 1-3; Among them, the zinc oxide nanoparticles form chemical bonds with the active functional groups on the silkworm cocoon carrier through chemical bonds.

5. The application of the photocatalytic material as described in claim 4 in the photocatalytic degradation of antibiotic wastewater.

6. The application according to claim 5, characterized in that, The antibiotic is ciprofloxacin.

7. The application according to claim 5, characterized in that, The concentration of the antibiotic wastewater is 5-10 mg / L.

8. The application according to claim 7, characterized in that, In this application, 0.0002-0.0005g of photocatalytic material is added per milliliter of antibiotic wastewater.

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