Application of nano-silver catalyst in catalytic degradation of organic dyes

Abstract

The application belongs to the technical field of organic matter degradation, and discloses application of a nano silver catalyst in catalytic degradation of organic dyes. The application takes methylene blue, methyl orange, p-nitroaniline and p-nitrophenol as examples for experiments, and the four dyes are all degraded after a period of reaction. Among the four dyes, the catalytic effect of methylene blue is the worst, and the degradation degree within 20 minutes after the addition of the nano silver catalyst biotransformed and synthesized by endophytic fungus FL15 can reach the degradation degree of 6 hours of reaction without the addition of the catalyst; the degradation effect of the catalyst on methyl orange is the best, and the degradation rate can reach more than 95% within 10 minutes; the degradation rates of p-nitroaniline and p-nitrophenol can both reach more than 95% within 20 minutes. Therefore, the activity of the AgNPs mediated and synthesized by the endophytic fungus FL15 is relatively strong.

Description

Technical Field

[0001] This invention relates to the field of organic degradation technology, and in particular to the application of a nano-silver catalyst in the catalytic degradation of organic dyes. Background Technology

[0002] Silver nanoparticles (AgNPs) are a class of metallic elements with nanoscale particle sizes and stable physicochemical properties. Studies have shown that AgNPs not only have good antibacterial effects but also excellent electrical and thermal conductivity and ideal ductility. Therefore, AgNPs have been widely used in the pharmaceutical, electronics, and textile industries. As a nanomaterial, AgNPs has always been one of the research hotspots in the field of nanomaterials. From a crystallographic perspective, AgNPs with different crystal defects can form nanomaterials with different morphologies, and these materials have different properties. AgNPs synthesized by different methods also exhibit significant differences in properties. The synthesis methods of AgNPs are mainly divided into three categories: physical methods, chemical synthesis methods, and biosynthesis methods. Physical methods include mechanical grinding, laser ablation, and evaporation-condensation methods; chemical methods mainly include solution combustion, liquid-phase reduction, and electrochemical deposition methods; biosynthesis methods are divided into two main categories: one is synthesis through plant extracts, and the other is synthesis through microbial metabolites. Among these methods, biosynthesis has become a key focus of current research on AgNP synthesis due to its strong operational feasibility and environmental friendliness. This method mainly utilizes microorganisms or plant extracts to convert silver ions into AgNPs, and the synthesized AgNPs exhibit excellent performance, meeting the needs of most industries.

[0003] Methyl Orange (MO), chemically known as sodium p-dimethylaminoazobenzenesulfonate, is an azo-containing compound (-N=N-). It is widely used in analytical chemistry as an acid-base indicator and is also an important azo dye, primarily used in the textile industry. However, as an organic dye, MO produces various harmful substances during degradation, posing potential hazards to organisms. Methylene Blue (MB) belongs to the thiazide class of dyes and is used to treat cancer, bacterial and viral infections, and central nervous system diseases. It is also used as a disinfectant in aquaculture. Although MB has a wide range of applications, it also poses certain hazards; for example, excessive concentrations in water can cause varying degrees of toxicity to aquatic organisms. p-Nitroaniline (p-NA), also known as 4-nitroaniline, is an important dye, pesticide, and pharmaceutical intermediate with a wide range of applications. However, p-NA wastewater is highly toxic and difficult to degrade, and traditional biological treatment processes often fail to achieve ideal treatment results. p-Nitrophenol (p-NP), also known as 4-nitrophenol, has the molecular formula C6H5NO3. It is another important chemical raw material widely used in the petrochemical, plastics, dye, textile, pesticide, and pharmaceutical industries. p-NP is readily converted in living organisms and can cause serious harm to human health.

[0004] Therefore, how to environmentally and efficiently treat the aforementioned organic dyes in waste is an urgent problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide an application of nano-silver catalyst in the catalytic degradation of organic dyes, solving the problem that existing degradation methods cannot treat organic dyes in an environmentally friendly and efficient manner.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides an application of a nano-silver catalyst in the catalytic degradation of organic dyes, wherein the nano-silver catalyst is synthesized by biotransformation of cyanobacterium FL15.

[0008] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, the method for synthesizing the nano-silver catalyst includes the following steps:

[0009] (1) Activation of FL15 of Cyanobacterium: FL15 of Cyanobacterium was inoculated into potato liquid culture medium for the first culture; the bacterial cells obtained from the first culture were inoculated into potato solid culture medium for activation culture to obtain activated FL15.

[0010] (2) Preparation of secondary fermentation broth: The activated blue bacterium FL15 was inoculated into potato liquid culture medium for a second culture; the bacterial cells obtained from the second culture were mixed and dispersed with water for a third culture to obtain the secondary fermentation broth;

[0011] (3) Bioconversion synthesis of nano-silver catalyst: The secondary fermentation broth is mixed with silver nitrate solution and bioconversion synthesis is carried out to obtain nano-silver catalyst.

[0012] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, in the synthesis method of the nano-silver catalyst, in step (1), the conditions for the first culture include: a temperature of 25-32°C, a shaking speed of 120-220 rpm, and a time of 16-48 h; the conditions for the activation culture include: a temperature of 25-30°C and a time of 5-8 days.

[0013] In step (2), the conditions for the second culture include: a temperature of 25–32°C, a shaking speed of 150–220 rpm, and a time of 8–14 days; the ratio of the mass of the bacterial cells obtained in the second culture to the volume of the water is 10–30 g: 100 mL; the conditions for the third culture include: a temperature of 25–32°C, a shaking speed of 150–220 rpm, and a time of 20–48 h.

[0014] In step (3), the volume ratio of the secondary fermentation broth to the silver nitrate solution is 1-2:1-2; the concentration of the silver nitrate solution is 8-20 mmol / L; the conditions for the biotransformation synthesis include: a temperature of 25-35℃, a light intensity of 3500-4500 Lux, and a time of 20-40 min.

[0015] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, the method of application includes the following steps:

[0016] The catalyst solution, reducing agent solution, and organic dye solution are mixed to carry out a catalytic reaction, thereby achieving the catalytic degradation of organic dyes.

[0017] The catalyst in the catalyst solution is a nano-silver catalyst.

[0018] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, the concentration of the catalyst solution in the application method is 0.0375–0.5 mg / mL; and the particle size of the catalyst in the catalyst solution is 10–120 nm.

[0019] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, in the method of application, the concentration of the reducing agent solution is 0.01–0.10 mol / L; and the reducing agent in the reducing agent solution is NaBH4.

[0020] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, the concentration of the organic dye solution in the application method is 0.05 × 10⁻⁶. -3 ~0.2×10 -3 mol / L; the organic dyes in the organic dye solution include methylene blue, methyl orange, p-nitrophenol, or p-nitroaniline.

[0021] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, the volume ratio of the catalyst solution, the reducing agent solution, and the organic dye solution in the application method is 1-2:2-4:40.

[0022] Preferably, in the application of the nano-silver catalyst in the catalytic degradation of organic dyes, the catalytic reaction time in the application method is 10-20 min.

[0023] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention investigated the performance of AgNPs synthesized by biotransformation of cyanobacterium FL15 as a catalyst in the degradation of organic dyes. Methylene blue, methyl orange, p-nitroaniline, and p-nitrophenol were used as examples in the experiments. All four dyes began to degrade only after a certain reaction time. Among the four dyes, methylene blue showed the worst catalytic effect; the degradation rate within 20 minutes after adding the AgNPs catalyst was equivalent to the degradation rate after 6 hours without the catalyst. Methyl orange showed the best degradation effect, achieving a degradation rate of over 95% within 10 minutes. Both p-nitroaniline and p-nitrophenol achieved degradation rates of over 95% within 20 minutes. Therefore, AgNPs synthesized by the endophytic fungus FL15 exhibit strong activity. Attached Figure Description

[0025] 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.

[0026] Figure 1 The color change of the secondary fermentation broth and the silver nitrate mixed solution before and after the reaction;

[0027] Figure 2 The results of methyl orange degradation after reacting with different concentrations of AgNPs for 10 min;

[0028] Figure 3 The results are from the catalytic MB degradation reaction of Comparative Example 1, which took 0–6 h.

[0029] Figure 4 The results of the catalytic MB degradation reaction in Example 2 are shown from 0 to 20 minutes.

[0030] Figure 5 The color change before and after the catalytic MB degradation reaction in Example 2;

[0031] Figure 6 The results are from the catalytic degradation reaction of MO in Comparative Example 2, which took 0–6 h.

[0032] Figure 7 The results of the catalytic MO degradation reaction in Example 3 are shown in the figure from 0 to 10 min.

[0033] Figure 8 The color change before and after the catalytic degradation reaction of MO in Example 3;

[0034] Figure 9 The results are from the catalytic p-NA degradation reaction of Comparative Example 3, which took 0–6 h.

[0035] Figure 10 The results of the catalytic p-NA degradation reaction in Example 4 are shown from 0 to 20 minutes.

[0036] Figure 11 The color change before and after the catalytic p-NA degradation reaction in Example 4;

[0037] Figure 12 The results are for the catalytic p-NP degradation reaction of Comparative Example 4, which took 0–6 h.

[0038] Figure 13 The results of the catalytic p-NP degradation reaction in Example 5 are shown in the figure from 0 to 20 minutes.

[0039] Figure 14 The color change before and after the catalytic p-NP degradation reaction in Example 5 is shown. Detailed Implementation

[0040] This invention provides an application of a nano-silver catalyst in the catalytic degradation of organic dyes, wherein the nano-silver catalyst is synthesized by biotransformation of cyanobacterium FL15.

[0041] In this invention, the method for synthesizing the nano-silver catalyst includes the following steps:

[0042] (1) Activation of FL15 of Cyanobacterium: FL15 of Cyanobacterium was inoculated into potato liquid culture medium for the first culture; the bacterial cells obtained from the first culture were inoculated into potato solid culture medium for activation culture to obtain activated FL15.

[0043] (2) Preparation of secondary fermentation broth: The activated blue bacterium FL15 was inoculated into potato liquid culture medium for a second culture; the bacterial cells obtained from the second culture were mixed and dispersed with water for a third culture to obtain the secondary fermentation broth;

[0044] (3) Bioconversion synthesis of nano-silver catalyst: The secondary fermentation broth is mixed with silver nitrate solution and bioconversion synthesis is carried out to obtain nano-silver catalyst.

[0045] In this invention, in the synthesis method of the nano-silver catalyst, in step (1), the blue-green bacterium FL15 is preferably isolated from Huperzia spp. It is currently preserved at the Key Laboratory of Subtropical Plant Resources Conservation and Utilization, Jiangxi Province.

[0046] In the present invention, in the synthesis method of the nano-silver catalyst, in step (1), the conditions of the first culture include: the temperature is preferably 25-32℃, more preferably 26-30℃, more preferably 28℃; the shaking speed is preferably 120-220 rpm, more preferably 150-180 rpm, more preferably 160 rpm; and the time is preferably 16-48h, more preferably 18-32h, more preferably 24h.

[0047] In this invention, in the synthesis method of the nano-silver catalyst, in step (1), the preparation method of the potato solid culture medium (Potato Dextrose Agar, PDA) preferably includes the following steps: cooking 200g of potatoes, filtering and retaining the filtrate; dissolving 20g of glucose and 20g of agar in the filtrate, adding distilled water to 1000mL, autoclaving at 121℃ for 25min, pouring into plates, and cooling to solidify.

[0048] In the present invention, in the synthesis method of the nano-silver catalyst, the activation culture conditions in step (1) include: the temperature is preferably 25-30℃, more preferably 26-29℃, and even more preferably 28℃; the time is preferably 5-8 days, and even more preferably 7 days.

[0049] In this invention, in the synthesis method of the nano-silver catalyst, in steps (1) and (2), the method for preparing the potato liquid culture medium (Potato Dextrose Broth, PDB) preferably includes the following steps: cooking 200g of potatoes, filtering and retaining the filtrate; dissolving 20g of glucose in the filtrate, adding distilled water to 1000mL, autoclaving at 121°C for 25min, and cooling.

[0050] In the present invention, in the synthesis method of the nano-silver catalyst, in step (2), the conditions of the second culture include: the temperature is preferably 25-32℃, more preferably 26-30℃, and more preferably 28℃; the shaking speed is preferably 150-220 rpm, more preferably 160-200 rpm, and more preferably 180 rpm; the time is preferably 8-14 days, more preferably 9-12 days, and more preferably 10 days.

[0051] In this invention, in the method for synthesizing the nano-silver catalyst, in step (2), the water is preferably sterilized deionized water.

[0052] In the present invention, in the method for synthesizing the nano-silver catalyst, in step (2), the mass ratio of the second cultured bacterial cell to the volume of the water is preferably 10-30 g:100 mL, more preferably 15-25 g:100 mL, and more preferably 20 g:100 mL.

[0053] In the present invention, in the synthesis method of the nano-silver catalyst, the conditions of the third culture in step (2) include: the temperature is preferably 25-32℃, more preferably 26-30℃, and more preferably 28℃; the shaking speed is preferably 150-220 rpm, more preferably 160-200 rpm, and more preferably 180 rpm; the time is preferably 20-48h, more preferably 22-40h, and more preferably 24h.

[0054] In the present invention, in the method for synthesizing the nano-silver catalyst, in step (3), the concentration of the silver nitrate solution is preferably 8-20 mmol / L, more preferably 9-15 mmol / L, and even more preferably 10 mmol / L.

[0055] In the present invention, in the method for synthesizing the nano-silver catalyst, in step (3), the volume ratio of the secondary fermentation broth to the silver nitrate solution is preferably 1-2:1-2, more preferably 1:1-2, and even more preferably 1:1.

[0056] In this invention, in the synthesis method of the nano-silver catalyst, the conditions for the biotransformation synthesis in step (3) include: the temperature is preferably 25-35℃, more preferably 27-30℃, and even more preferably 28℃; the light intensity is preferably 3500-4500 Lux, more preferably 3700-4200 Lux, and even more preferably 4000 Lux; the time is preferably 20-40 min, more preferably 25-35 min, and even more preferably 30 min.

[0057] In this invention, the method of application preferably includes the following steps:

[0058] The catalyst solution, reducing agent solution, and organic dye solution are mixed to carry out a catalytic reaction, thereby achieving the catalytic degradation of organic dyes.

[0059] The catalyst in the catalyst solution is a nano-silver catalyst.

[0060] In this invention, in the method of application, the concentration of the catalyst solution is preferably 0.0375-0.5 mg / mL, more preferably 0.075-0.25 mg / mL, and even more preferably 0.25 mg / mL; the particle size of the catalyst in the catalyst solution is preferably 10-120 nm, more preferably 20-80 nm, and even more preferably 30-50 nm.

[0061] In this invention, in the method of application, the concentration of the reducing agent solution is preferably 0.01 to 0.10 mol / L, more preferably 0.04 to 0.07 mol / L, and even more preferably 0.06 mol / L; the reducing agent in the reducing agent solution is preferably NaBH4.

[0062] In this invention, in the method of application, the concentration of the organic dye solution is preferably 0.05 × 10⁻⁶. -3 ~0.2×10 -3 mol / L; the organic dye in the organic dye solution preferably includes methylene blue, methyl orange, p-nitrophenol or p-nitroaniline.

[0063] In this invention, in the method of application, the volume ratio of the catalyst solution, the reducing agent solution, and the organic dye solution is preferably 1-2:2-4:40, more preferably 1.2-1.8:2.5-3.5:40, and even more preferably 1.5:3:40.

[0064] In this invention, in the method of application, the time of the catalytic reaction is preferably 10 to 20 min, more preferably 12 to 18 min, and even more preferably 15 min.

[0065] 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.

[0066] In the preparation examples and embodiments of the present invention, the information on the reagents and instruments used is shown in Tables 1 and 2.

[0067] Table 1. Reagents

[0068]

[0069] Table 2. Instruments

[0070]

[0071] Preparation Example 1

[0072] This preparation example provides a method for synthesizing a nano-silver catalyst, comprising the following steps:

[0073] (1) PDA solid culture medium: Cook 200g of potatoes, filter and retain the filtrate; dissolve 20g of glucose and 20g of agar in the filtrate, add distilled water to 1000mL, autoclave at 121℃ for 25min, pour into plates, and cool to solidify; PDB liquid culture medium: Cook 200g of potatoes, filter and retain the filtrate; dissolve 20g of glucose in the filtrate, add distilled water to 1000mL, autoclave at 121℃ for 25min, and cool.

[0074] Activation of FL15 cyanobacteria: Endophytic fungi FL15 preserved in glycerol tubes were inoculated into PDB liquid medium and cultured at 28°C and 160 rpm for 24 h; the bacterial cells in PDB liquid medium were inoculated onto PDA solid medium plates in a clean bench for activation and cultured at 28°C for 7 days.

[0075] (2) Preparation of secondary fermentation broth: The activated endophytic fungus FL15 was inoculated into a 250mL Erlenmeyer flask containing 100mL of LPDB liquid medium in a clean bench and cultured in a shaker at 28℃ and 180rpm for 10 days. The bacterial cells were collected by aseptic filtration using a Buchner funnel. 20g of bacterial cells (wet weight) was weighed and added to 100mL of sterilized deionized water for dispersion and cultured in a shaker at 28℃ and 180rpm for 24h. The bacterial solution was collected by filtration using a Buchner funnel and then filtered again using a solution filter to obtain the secondary fermentation broth.

[0076] (3) Biotransformation synthesis of nano-silver catalyst: The secondary fermentation broth was mixed with silver nitrate solution (10 mmol / L) at a ratio of 1:1, shaken well and placed in a light incubator, and allowed to stand for 30 min at 3500 Lux and 28 °C; the obtained AgNPs solution was centrifuged (10000 rpm, 10 min), the supernatant was removed, and the remaining material was dried in a low-temperature vacuum dryer to obtain AgNPs powder (particle size 50-80 nm).

[0077] Due to the surface plasmon resonance (SPR) effect of AgNPs, once AgNPs are generated, the mixture of secondary fermentation broth and silver nitrate solution will turn into a colored transparent solution. Therefore, the presence or absence of AgNPs can be determined first by observing the color change of the solution, and then verified using a full-band ultraviolet scanner (AgNPs have a characteristic ultraviolet absorption peak at 400-460 nm). In step (3) of Preparation Example 1, after reacting the secondary fermentation broth and silver nitrate solution for 15 min, the solution color began to change. After reacting for 30 min, as shown... Figure 1 As shown, the fermentation broth changed from colorless (left) to light brown (right), which initially indicates the synthesis of AgNPs. Further full-band scanning revealed a maximum absorption peak at 400 nm, further confirming the synthesis of AgNPs.

[0078] AgNPs powder was dissolved in ultrapure water to prepare a 1 mg / mL AgNPs stock solution; the stock solution was then diluted to prepare AgNPs solutions of 0.5 mg / mL, 0.25 mg / mL, 0.125 mg / mL, 0.075 mg / mL, and 0.0375 mg / mL for later use.

[0079] Example 1

[0080] This embodiment provides a method for applying a nano-silver catalyst in the catalytic degradation of methyl orange (MO), including the following steps:

[0081] Add 2 mL of freshly prepared 0.06 mol / L NaBH4 solution to 20 mL of 0.10 × 10⁻⁶ mol / L NaBH₄ solution. -3 The solution was then mixed with 0.5 mL of AgNPs solutions of different concentrations (0.5 mg / mL, 0.25 mg / mL, 0.125 mg / mL, 0.075 mg / mL, 0.0375 mg / mL) in mol / L MO solution and reacted for 10 min.

[0082] Validation was performed using a full-band UV scanner, with no AgNPs added as a blank control. By comparing the degradation degree of MO within the same time period, the optimal concentration for observing AgNPs-catalyzed dye degradation was determined. The results are as follows: Figure 2 As shown. By Figure 2It can be seen that the degradation rate of MO varies under different concentrations of AgNPs catalysis, and the degradation rate of MO increases with increasing AgNPs concentration. When the AgNPs solution concentration is 0.5 mg / mL, the characteristic absorption peak at 463 nm disappears within 10 min, indicating that MO is basically completely degraded. When the AgNPs solution concentration is 0.0375 mg / mL, the decrease in the characteristic absorption peak at 463 nm within 10 min is very small, indicating that only a small portion of MO is degraded. To better observe the degradation process of each dye by AgNPs, a concentration of 0.25 mg / mL of AgNPs was chosen.

[0083] Example 2

[0084] This embodiment provides a method for applying a nano-silver catalyst in the catalytic degradation of methylene blue (MB), including the following steps:

[0085] Add 2 mL of freshly prepared 0.06 mol / L NaBH4 solution to 20 mL of 0.05 × 10⁻⁶ mol / L NaBH₄ solution. -3 After shaking and mixing, 0.5 mL of 0.25 mg / mL LAgNPs solution was added to the mol / L LMB solution. The dye concentration was observed over time (0–20 min) in the wavelength range of 200–800 nm using a UV full-band scanner.

[0086] Comparative Example 1

[0087] This comparative example provides a method for the catalytic degradation of MB, including the following steps:

[0088] Add 2 mL of freshly prepared 0.06 mol / L NaBH4 solution to 20 mL of 0.05 × 10⁻⁶ mol / L NaBH₄ solution. -3 The dye was mixed in a mol / L MMB solution by shaking, and the dye concentration was observed over time (0–6 h) in the wavelength range of 200–800 nm using a UV full-band scanner.

[0089] The observation results of Comparative Example 1 (MB degradation reaction without AgNPs catalysis) are as follows: Figure 3 As shown. By Figure 3 It can be seen that without the addition of AgNPs catalyst, the degradation rate of MB is relatively slow, and the decrease in the characteristic absorption peak is small, indicating that only a small portion is degraded within 6 hours. However, as... Figure 4 As shown, the method in Example 2, with the addition of AgNPs catalyst, achieved the degradation effect of 6 hours without AgNPs catalyst within 20 minutes, and the degradation rate was very uniform, with a consistent solution color. Figure 5 As shown, the color gradually changes from blue (left) to indigo (right). This indicates that AgNPs have the ability to catalyze the degradation of MB, but their catalytic effect is not ideal.

[0090] Example 3

[0091] This embodiment provides a method for applying a nano-silver catalyst in the catalytic degradation of MO, including the following steps:

[0092] Add 2 mL of freshly prepared 0.06 mol / L NaBH4 solution to 20 mL of 0.1 × 10⁻⁶ mol / L NaBH₄ solution. -3 After shaking and mixing, 0.5 mL of 0.25 mg / mL LAgNPs solution was added to the mol / L MO solution. The dye concentration was observed over time (0–10 min) in the wavelength range of 200–800 nm using a UV full-band scanner.

[0093] Comparative Example 2

[0094] This comparative example provides a method for the catalytic degradation of MO, including the following steps:

[0095] Add 2 mL of freshly prepared 0.06 mol / L NaBH4 solution to 20 mL of 0.1 × 10⁻⁶ mol / L NaBH₄ solution. -3 The dye was mixed in mol / L MO solution by shaking, and the dye concentration was observed over time (0-6 h) in the wavelength range of 200-800 nm using a UV full-band scanner.

[0096] The observation results of Comparative Example 2 (MO degradation reaction without AgNPs catalysis) are as follows: Figure 6 As shown. By Figure 6 It can be seen that without the addition of AgNPs as a catalyst, the intensity of the absorption peak of the MO solution at 463 nm hardly changed within 6 hours, indicating that the degradation rate of MO is extremely slow without the catalysis of AgNPs. And as... Figure 7 As shown, in Example 3, after the addition of AgNPs, MO was almost completely degraded within 10 minutes. For the first 6 minutes, MO showed almost no degradation, but the degradation rate suddenly accelerated after 6 minutes, and the solution color changed (…). Figure 8 As shown, the orange-yellow color (left) gradually disappears, turning into a pale yellow color (right). The absorption peak intensity of MO at 463 nm continuously decreases, while a new characteristic absorption peak appears at 250 nm. Research indicates that this is a characteristic absorption peak of hydrazine. Therefore, AgNPs can be concluded to be a highly efficient catalyst for the MO degradation reaction.

[0097] Example 4

[0098] This embodiment provides a method for applying a nano-silver catalyst in the p-NA catalytic degradation of p-nitroaniline, including the following steps:

[0099] Add 0.2×10 to 20mL of freshly prepared solution. -3Add 1 mL of freshly prepared 0.06 mol / L NaBH4 solution to the mol / L p-NA solution, shake to mix, and then add 0.5 mL of 0.25 mg / mL AgNPs solution. Use a UV full-band scanner to observe the change of dye concentration over time (0–20 min) in the wavelength range of 200–800 nm.

[0100] Comparative Example 3

[0101] This comparative example provides a method for p-NA catalytic degradation, including the following steps:

[0102] Add 0.2×10 to 20mL of freshly prepared solution. -3 Add 1 mL of freshly prepared 0.06 mol / L NaBH4 solution to the mol / L p-NA solution, shake to mix, and observe the change of dye concentration over time (0-6 h) using a UV full-band scanner in the wavelength range of 200-800 nm.

[0103] The observation results for Comparative Example 3 (p-NA degradation reaction without AgNPs catalysis) are as follows: Figure 9 As shown. By Figure 9 It can be seen that, without the addition of AgNPs as a catalyst, the characteristic absorption peak at 480 nm showed very little change within 6 hours when p-NA was reduced solely by NaBH4, indicating that only a small amount of p-NA reacted. However, as... Figure 10 As shown, in Example 4, after adding AgNPs as a catalyst, the characteristic absorption peak at 480 nm disappeared within 20 minutes, indicating complete degradation of p-NA. After the addition of the catalyst, as the reduction reaction proceeded, nitroaniline was converted to phenylenediamine, and the characteristic absorption peak at 480 nm gradually decreased until it disappeared. Simultaneously, a new characteristic absorption peak appeared at 350 nm, and the solution color ( Figure 11 As shown, the color changes from orange-yellow (left) to pale yellow (right). This demonstrates that AgNPs are a highly effective catalyst for the degradation of p-NA.

[0104] Example 5

[0105] This embodiment provides a method for applying a nano-silver catalyst in the p-NP catalytic degradation of p-nitrophenol, including the following steps:

[0106] Add 0.075×10 to 20mL of freshly prepared solution. -3 Add 1 mL of freshly prepared 0.06 mol / L NaBH4 solution to the mol / L p-NP solution, shake to mix, and then add 0.5 mL of 0.25 mg / mL AgNPs solution. Use a UV full-band scanner to observe the change of dye concentration over time (0–20 min) in the wavelength range of 200–800 nm.

[0107] Comparative Example 4

[0108] This comparative example provides a method for p-NP catalytic degradation, including the following steps:

[0109] Add 0.075×10 to 20mL of freshly prepared solution. -3 Add 1 mL of freshly prepared 0.06 mol / L NaBH4 solution to the mol / L p-NP solution, shake to mix, and observe the change of dye concentration over time (0-6 h) using a UV full-band scanner in the wavelength range of 200-800 nm.

[0110] The observation results of Comparative Example 4 (p-NP degradation reaction without AgNPs catalysis) are as follows: Figure 12 As shown. By Figure 12 It can be seen that, in the absence of a catalyst, the characteristic absorption peak at 400 nm remained almost unchanged over 6 hours when p-NP was reduced solely by NaBH4, indicating that only a very small amount of p-NP reacted. However, as... Figure 13 As shown, in Example 5, after the addition of AgNPs catalyst, the characteristic absorption peak at 400 nm gradually decreased until it disappeared within 20 minutes, and the solution color ( Figure 14 As shown, the color changes from yellow (left) to pale yellow, and then to almost colorless (right), indicating that p-NPs are almost completely degraded. This demonstrates that AgNPs are a highly efficient catalyst for p-NP degradation.

[0111] In summary, this invention uses AgNPs synthesized by *Cyanobacterium FL15* as the research object, sodium borohydride as the reducing agent, and AgNPs as the catalyst. By adding different concentrations of AgNPs, the degradation effect on organic dyes was detected, thereby evaluating the performance of biosynthesized AgNPs. Using 0.06 mol / L sodium borohydride as the reducing agent and AgNPs at a concentration of 0.25 mg / mL, methyl orange was completely degraded within 10 min, and p-nitroaniline and p-nitrophenol were completely degraded within 20 min. With the addition of AgNPs as the catalyst, the degradation degree of methylene blue within 20 min was comparable to that achieved after 6 hours of reaction without the catalyst. Based on the degradation of the four dyes, it can be preliminarily determined that the biosynthesized AgNPs possess good catalytic activity.

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a nano-silver catalyst in the catalytic degradation of organic dyes, characterized in that, The nano-silver catalyst was synthesized by biotransformation of Cyanobacterium FL15. The method of application includes the following steps: The catalyst solution, reducing agent solution, and organic dye solution are mixed to carry out a catalytic reaction, thereby achieving the catalytic degradation of organic dyes. The catalyst in the catalyst solution is a nano-silver catalyst; the particle size of the catalyst in the catalyst solution is 10~120nm; The volume ratio of the catalyst solution, the reducing agent solution, and the organic dye solution is 1~2:2~4:40; The organic dye in the organic dye solution is one of methylene blue, methyl orange, p-nitrophenol, or p-nitroaniline; The reducing agent in the reducing agent solution is NaBH4; The method for synthesizing the nano-silver catalyst includes the following steps: (1) Activation of FL15 of Cyanobacterium: FL15 of Cyanobacterium was inoculated into potato liquid medium and cultured for the first culture; the bacterial cells obtained from the first culture were inoculated into potato solid medium and cultured for activation to obtain activated FL15 of Cyanobacterium; (2) Preparation of secondary fermentation broth: The activated blue bacterium FL15 was inoculated into potato liquid culture medium for a second culture; the bacterial cells obtained from the second culture were mixed and dispersed with water for a third culture to obtain the secondary fermentation broth; (3) Bioconversion synthesis of nano-silver catalyst: The secondary fermentation broth is mixed with silver nitrate solution and bioconversion synthesis is carried out to obtain nano-silver catalyst; The conditions for the biotransformation synthesis include: a temperature of 25-35°C, a light intensity of 3500-4500 Lux, and a time of 20-40 min.

2. The application of the nano-silver catalyst according to claim 1 in the catalytic degradation of organic dyes, characterized in that, In the synthesis method of the nano-silver catalyst, in step (1), the conditions for the first culture include: a temperature of 25~32℃, a shaking speed of 120~220rpm, and a time of 16~48h; the conditions for the activation culture include: a temperature of 25~30℃ and a time of 5~8d. In step (2), the conditions for the second culture include: a temperature of 25-32℃, a shaking speed of 150-220 rpm, and a time of 8-14 days; the ratio of the mass of the bacterial cells obtained in the second culture to the volume of the water is 10-30 g: 100 mL; the conditions for the third culture include: a temperature of 25-32℃, a shaking speed of 150-220 rpm, and a time of 20-48 h. In step (3), the volume ratio of the secondary fermentation broth to the silver nitrate solution is 1~2:1~2; the concentration of the silver nitrate solution is 8~20 mmol / L.

3. The application of the nano-silver catalyst according to claim 1 in the catalytic degradation of organic dyes, characterized in that, In the method described, the concentration of the catalyst solution is 0.0375~0.5 mg / mL.

4. The application of the nano-silver catalyst according to claim 1 in the catalytic degradation of organic dyes, characterized in that, In the method described, the concentration of the reducing agent solution is 0.01~0.10 mol / L.

5. The application of the nano-silver catalyst according to claim 1 in the catalytic degradation of organic dyes, characterized in that, In the method described, the concentration of the organic dye solution is 0.05 × 10⁻⁶. -3 ~0.2×10 -3 mol / L.

6. The application of the nano-silver catalyst according to claim 1 in the catalytic degradation of organic dyes, characterized in that, In the method described, the catalytic reaction takes 10-20 minutes.

Images