A flocculation composition prepared by compounding a microbial flocculant with nano-Fe3O4, and a preparation method and application thereof

Abstract

The present invention belongs to the technical field of microbial fermentation and flocculation, and particularly relates to a flocculation composition obtained by compounding a microbial flocculant with nano-Fe3O4, and a preparation method and application thereof. The flocculation composition obtained by compounding the microbial flocculant with nano-Fe3O4 includes a microbial flocculant, nano-Fe3O4 particles and a coagulant aid, wherein the microbial flocculant is prepared from the Pseudoxanthomonas sp. NRG9 strain with the preservation number of CGMCC No. 29401. The flocculation composition provided by the present invention can produce excellent flocculation effects at a relatively low dosage through the synergistic effect of the microbial flocculant, nano-Fe3O4 particles and the coagulant aid, overcomes the disadvantages of microbial flocculants and chemical flocculants, and can achieve the purpose of purifying sewage.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial fermentation and flocculation, and particularly relates to a flocculation composition prepared by compounding a microbial flocculant with nano-Fe3O4, and a preparation method and application thereof. Background Art

[0002] Adding a flocculant is an essential unit in the sewage treatment process. The flocculant can aggregate and enlarge suspended particles in water or liquid or form flocs, thereby accelerating the sedimentation of particles to achieve the purpose of solid-liquid separation. Traditional flocculants mainly include chemical flocculants such as iron salts and aluminum salts. They generally contain certain chemical substances, which may be released into the water during the treatment process, resulting in a decline in water quality. In addition, if the dosage of the flocculant is inappropriate, it may disrupt the chemical balance in the water, damage the aquatic ecosystem, and may also pose a certain risk to human health. Some chemical flocculants may contain carcinogenic substances or other toxic substances. If people come into long-term contact with or ingest these substances, it may have an adverse impact on health. In addition, other components in the flocculant may also damage the internal organs of the human body, such as the liver and kidneys. Microbial flocculants are non-toxic, harmless, and have no secondary pollution, but have high production costs and poor stability. Summary of the Invention

[0003] Aiming at the above technical problems, the present invention provides a flocculation composition prepared by compounding a microbial flocculant with nano-Fe3O4, and a preparation method and application thereof. The flocculation composition provided by the present invention has good stability, and has the advantages of small dosage, remarkable flocculation effect, non-toxicity, no secondary pollution, low production cost, and good treatment effect when used for purifying sewage.

[0004] To achieve the above invention purpose, the present invention adopts the following technical scheme:

[0005] The first aspect of the present invention provides a flocculation composition prepared by compounding a microbial flocculant with nano-Fe3O4, which includes a microbial flocculant, nano-Fe3O4 particles, and a coagulant aid. The microbial flocculant is prepared from the Pseudoxanthomonas sp. NRG9 strain. The Pseudoxanthomonas NRG9 strain was deposited at the China General Microbiological Culture Collection Center on December 25, 2023, and its deposit number is CGMCC No. 29401; the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0006] The above-mentioned Pseudoxanthomonas sp. NRG9 strain for preparing microbial flocculant can secrete an extracellular polysaccharide, which has high flocculation activity and can be used for the flocculation treatment of sewage. Through research, the present invention finds that this microbial flocculant has a synergistic effect with nano-Fe3O4 particles and a coagulant aid. Under the same dosage, the flocculation effect produced is significantly better than that of only using the microbial flocculant or only using nano-Fe3O4 particles and the coagulant aid. Therefore, its production and use costs are lower than those of the microbial flocculant, its safety is better than that of the chemical flocculant, and it has a better flocculation effect.

[0007] Preferably, the mass ratio of the microbial flocculant, nano-Fe3O4 particles and the coagulant aid is (1-6):(2-8):50.

[0008] Preferably, the coagulant aid is calcium chloride (CaCl2).

[0009] Preferably, the preparation method of the microbial flocculant specifically includes the following operations:

[0010] Inoculate the Pseudoxanthomonas sp. NRG9 strain on a solid medium for cultivation, and then inoculate the obtained single colony into a liquid medium for fermentation cultivation to obtain a fermentation broth; the C / P mass ratio of the liquid medium is 1-10, the C / N mass ratio is 5-40, the concentration of KH2PO4 is 2-3 g / L, the concentration of K2HPO4 is 4-6 g / L, and the pH is 5-11;

[0011] Centrifuge the fermentation broth, subject the precipitate to ultrasonic treatment and then take the supernatant, and perform alcohol precipitation together with the centrifuged supernatant: add it to anhydrous ethanol at 0-5°C with a volume 2-4 times that of the fermentation broth, place it at 0-5°C for at least 6 h, and perform solid-liquid separation; dissolve the obtained solid phase in distilled water, repeat the alcohol precipitation at least once, then perform solid-liquid separation, and dry the obtained solid phase to obtain the flocculant.

[0012] This preparation method first performs two-step fermentation on the Pseudoxanthomonas sp. NRG9 strain, and then makes the extracellular polysaccharide settle by adding ethanol. After repeating the operation, the purity of the extracellular polysaccharide can be improved, so that the obtained microbial flocculant has stronger flocculation ability and more stable performance when used in combination with nano-Fe3O4 particles and the coagulant aid.

[0013] Optionally, the solid medium is a beef extract peptone medium.

[0014] Preferably, the composition of the beef extract peptone medium is: 3 g of beef extract, 10 g of peptone, 5 g of NaCl, 15-20 g of agar, 1000 mL of water, and the pH is 7.0-7.2. The beef extract peptone medium is sterilized before use, and specifically, it can be sterilized at 121°C for 20 min.

[0015] Preferably, the composition of the liquid medium is: glucose 18 - 22 g / L, K2HPO4 4.5 - 5.5 g / L, KH2PO4 2 - 2.5 g / L, NaCl 0.09 - 0.11 g / L, (NH4)2SO4 0.18 - 0.22 g / L, urea 0.45 - 0.55 g / L, yeast extract 0.45 - 0.55 g / L, MgSO4 0.18 - 0.22 g / L, and the solvent is water. This liquid medium also needs to be sterilized before use, specifically, it can be sterilized at 112°C for 30 min.

[0016] More preferably, the composition of the liquid medium is: glucose 20 g / L, K2HPO4 5 g / L, KH2PO4 2 g / L, NaCl 0.1 g / L, (NH4)2SO4 0.2 g / L, urea 0.5 g / L, yeast extract 0.5 g / L, MgSO4 0.2 g / L, and the solvent is water.

[0017] More preferably, the temperature for culturing on the beef extract peptone medium is 25 - 30°C.

[0018] More preferably, the temperature for fermentation culture in the liquid medium is 25 - 30°C.

[0019] Preferably, the Pseudoxanthomonas sp. NRG9 strain is cultured on the solid medium until the bacterial concentration reaches 10 5 ~10 7 CFU / mL.

[0020] More preferably, the single colony is fermented and cultured in the liquid medium until the bacterial concentration in the fermentation broth reaches 10 5 ~10 7 CFU / mL.

[0021] Preferably, the solid-liquid separation is centrifugation, the rotation speed is 8000 - 10000 r / min, and the centrifugation time is 10 - 15 min.

[0022] Preferably, the drying temperature is room temperature and the drying time is 1 - 2 h.

[0023] Preferably, the preparation method of the nano-Fe3O4 particles specifically includes the following operations: Dissolve soluble ferrous salts and soluble iron salts in water. The mass ratio of ferrous ions in the soluble ferrous salts to iron ions in the soluble iron salts is (0.5-1):1. Add dilute HCl to make the HCl concentration in the solution 0.015-0.025 mol / L. Then, adjust its pH to pH≥10 with 0.3-0.5 mol / L NH3·H2O solution at 29-31 °C under stirring. Then react at 60-80 °C for 1-2 h. After the reaction, obtain a Fe3O4 suspension. Place it in ultrasonic oscillation for 20-30 min, filter at room temperature, wash with absolute ethanol and then wash with distilled water until the pH of the washing liquid is 6.9-7.1, and dry to obtain the nano-Fe3O4 particles.

[0024] In the above operations, adding dilute hydrochloric acid to the solution containing soluble ferrous salts and soluble iron salts can prevent Fe 2+ and Fe 3+ from undergoing hydrolysis; after adding ammonia water to pH≥10, Fe 2+ and Fe 3+ begin to react to form Fe3O4, and the reaction is accelerated after heating to obtain a Fe3O4 suspension; subject the Fe3O4 suspension to ultrasonic oscillation. The pulse action generated during ultrasonic cavitation will increase the vibration of the particles, weaken the interaction energy between the particles at a very high intensity, thereby reducing the tendency of particle aggregation and dispersing them, thus obtaining nano-scale Fe3O4 particles.

[0025] Optionally, the soluble ferrous salts can be selected from ferrous sulfate, ferrous chloride, etc., and the soluble iron salts can be selected from ferric sulfate, ferric chloride, ferric perchlorate, etc. The soluble ferrous salts and soluble iron salts in this method can be selected as their anhydrous or hydrated forms according to the experimental conditions, and the input amount can be calculated according to the molecular weight.

[0026] Preferably, the stirring speed is 100-120 r / min.

[0027] The second aspect of the present invention provides the application of the above-mentioned flocculation composition obtained by compounding the microbial flocculant and nano-Fe3O4 in treating sewage.

[0028] Preferably, the sewage is the water in the pretreatment process section of an urban sewage treatment plant.

[0029] The third aspect of the present invention provides a sewage treatment method: Add the above-mentioned flocculation composition obtained by compounding the microbial flocculant and nano-Fe3O4 to the sewage to be treated and mix at room temperature. After mixing, the flocculation precipitate can be removed by natural sedimentation, filtration, etc., so as to achieve the purpose of purifying the water quality.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention uses the strain Pseudoxanthomonas sp. NRG9 to prepare a microbial flocculant, and then combines it with nano-Fe3O4 particles and a coagulant aid to form a flocculation composition. Since the extracellular polysaccharide produced by the strain Pseudoxanthomonas sp. NRG9 has high flocculation activity and has a synergistic effect with nano-Fe3O4 particles and the coagulant aid, this flocculation composition can produce a significant flocculation effect with a small dosage. Its flocculation effect is significantly better than that of only using a microbial flocculant and a coagulant aid or only using nano-Fe3O4 particles and a coagulant aid at the same dosage. Moreover, it has a lower production cost compared to microbial flocculants and is safer for the environment compared to chemical flocculants. Detailed implementation manners

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the present invention in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0033] Flocculants are essential in the process of sewage treatment. Traditional flocculants are mainly chemical flocculants. Although they have good flocculation effects, they may damage water quality and the ecosystem and may also bring harmful substances that affect human health. Microbial flocculants are non-toxic and harmless, but they have high production costs and poor stability.

[0034] The embodiment of the present invention provides a flocculation composition obtained by compounding a microbial flocculant and nano-Fe3O4. This composition includes a microbial flocculant prepared using the new strain Pseudoxanthomonas sp. NRG9, as well as nano-Fe3O4 particles and a coagulant aid. Through experimental verification, there is a synergistic effect among the microbial flocculant, nano-Fe3O4 particles and the coagulant aid in this flocculation composition, making its flocculation effect significantly better than that of using only the microbial flocculant or only using nano-Fe3O4 particles and the coagulant aid at the same dosage. The flocculation effect is remarkable, with the advantage of a small dosage, and it is non-toxic and has no secondary pollution, overcoming the defects of microbial flocculants and chemical flocculants.

[0035] The embodiment of the present invention also provides a method for sewage treatment using the flocculation composition obtained by compounding a microbial flocculant and nano-Fe3O4: adding the above-mentioned flocculation composition to the sewage to be treated and mixing at room temperature.

[0036] The following illustrates the solution of the present invention through specific embodiments.

[0037] The composition of the beef extract peptone medium used in the following examples is as follows: 3 g of beef extract, 10 g of peptone, 5 g of NaCl, 15 g of agar, 1000 mL of water, pH 7.1. Sterilize at 121 °C for 20 min.

[0038] The Pseudomonas pseudoalcaligenes NRG9 strain used in the following examples was provided by the Water Pollution Control Laboratory of the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. The strain was deposited at the China General Microbiological Culture Collection Center on December 25, 2023, with the deposit number CGMCC No. 29401.

[0039] The sewage involved in the following examples was from the influent of the pretreatment process section of a certain urban sewage treatment plant, with a COD of 85 mg / L, a turbidity of 15.42 NTU, and a pH of 7.

[0040] Unless otherwise specified, the technical means used in the following examples are conventional means well-known to those skilled in the art; the materials, reagents, culture media, etc. used in the following examples are all commercially available.

[0041] Example 1

[0042] This example provides a flocculation composition obtained by compounding a microbial flocculant and nano-Fe3O4. The flocculation composition is composed of a microbial flocculant, nano-Fe3O4 particles, and a coagulant aid CaCl2 in a mass ratio of 1:2:50.

[0043] The preparation method of the microbial flocculant is as follows:

[0044] S1. Inoculate the Pseudomonas pseudoalcaligenes NRG9 strain onto the beef extract peptone medium and culture at 30 °C until the bacterial concentration reaches 10 6 CFU / mL, and then inoculate the obtained single colony into a liquid medium at 30 °C and ferment and culture until the bacterial concentration reaches 10 6 CFU / mL to obtain a fermentation broth; the composition of the liquid medium is: 20 g of glucose, 5 g of K2HPO4, 2 g of KH2PO4, 0.1 g of NaCl, 0.2 g of (NH4)2SO4, 0.5 g of urea, 0.5 g of yeast extract, 0.2 g of MgSO4, 1000 mL of water, pH 8.0, sterilize at 112 °C for 30 min.

[0045] S2. Centrifuge the fermentation broth at 8000 r / min for 10 min. After ultrasonic treatment of the precipitate, take the supernatant, add it to 2 volumes of anhydrous ethanol at 4°C, let it stand at 4°C for 24 h, centrifuge at 8000 r / min for 10 min. Dissolve the obtained precipitate in distilled water, add 2 volumes of anhydrous ethanol at 4°C, let it stand at 4°C for 24 h, centrifuge at 8000 r / min for 10 min. Dry the obtained precipitate in a vacuum drying oven at room temperature for 2 h to obtain the microbial flocculant.

[0046] The preparation method of nano-Fe3O4 particles is as follows:

[0047] Weigh 2.7801 g of FeSO4·7H2O and 2.7030 g of FeCl3·6H2O, put them into a 500 mL beaker, add 200 mL of water to dissolve, then add dilute HCl to make the HCl concentration in the solution 0.02 mol / L to prevent Fe 2+ and Fe 3+ from hydrolysis. Place the beaker in an electric stirrer and stir, control the stirring speed at 120 r / min, control the temperature at (30±1)°C. While stirring strongly, slowly dropwise add 0.4 mol / L NH3·H2O solution until pH≥10, then transfer the solution into a 500 mL Erlenmeyer flask, keep it in a constant temperature water bath (60°C) for 1 h. After the reaction, it can be observed that bright black Fe3O4 particles are formed. Place the prepared Fe3O4 suspension in an ultrasonic oscillator and oscillate for 30 min, filter at room temperature, wash with anhydrous ethanol and then wash with distilled water until the pH of the washing liquid is 7, dry in an electrothermal constant temperature forced air drying oven to obtain nano-Fe3O4 particles.

[0048] The above-mentioned microbial flocculant, nano-Fe3O4 particles and coagulant aid CaCl2 can be packaged separately and mixed before use, or can be packaged after mixing.

[0049] Example 2

[0050] This example provides a flocculation composition obtained by compounding a microbial flocculant and nano-Fe3O4. The flocculation composition is composed of a microbial flocculant, nano-Fe3O4 particles and coagulant aid CaCl2 combined in a mass ratio of 2:3:50.

[0051] The preparation methods of the microbial flocculant and nano-Fe3O4 particles are the same as those in Example 1.

[0052] Example 3

[0053] This example provides a flocculation composition obtained by compounding a microbial flocculant and nano-Fe3O4. The flocculation composition is composed of a microbial flocculant, nano-Fe3O4 particles and coagulant aid CaCl2 combined in a mass ratio of 3:8:50.

[0054] The preparation method of the microbial flocculant is as follows:

[0055] S1. Inoculate the Pseudoxanthomonas sp. NRG9 strain onto a nutrient agar medium and culture it at 25 °C until the bacterial concentration reaches 10 5 CFU / mL. Then inoculate the obtained single colony into a liquid medium at 25 °C and ferment and culture it until the bacterial concentration reaches 10 5 CFU / mL to obtain a fermentation broth. The composition of the liquid medium is: 22 g of glucose, 5.5 g of K2HPO4, 2 g of KH2PO4, 0.11 g of NaCl, 0.22 g of (NH4)2SO4, 0.45 g of urea, 0.55 g of yeast extract, 0.18 g of MgSO4, 1000 mL of water, sterilized at 112 °C for 30 min.

[0056] S2. Centrifuge the fermentation broth at 8000 r / min for 15 min. After ultrasonic treatment of the precipitate, take the supernatant, and add it together with the centrifuged supernatant to 3 times the volume of absolute ethanol at 5 °C. Let it stand at 5 °C for 24 h, then centrifuge at 8000 r / min for 15 min. Dissolve the obtained precipitate in distilled water, add 3 times the volume of absolute ethanol at 5 °C, let it stand at 5 °C for 24 h, centrifuge at 8000 r / min for 15 min, and dry the obtained precipitate in a vacuum drying oven at room temperature for 1.5 h to obtain the microbial flocculant.

[0057] The preparation method of the nano-Fe3O4 particles is the same as that in Example 1.

[0058] Example 4

[0059] This example provides a flocculation composition prepared by compounding a microbial flocculant and nano-Fe3O4. The flocculation composition is composed of a microbial flocculant, nano-Fe3O4 particles, and a coagulant aid CaCl2 combined in a mass ratio of 6:7:50.

[0060] The preparation method of the microbial flocculant is as follows:

[0061] S1. Inoculate the Pseudoxanthomonas sp. NRG9 strain onto a nutrient agar medium and culture it at 30 °C until the bacterial concentration reaches 10 7 CFU / mL. Then inoculate the obtained single colony into a liquid medium at 30 °C and ferment and culture it until the bacterial concentration reaches 10 7 CFU / mL to obtain a fermentation broth. The composition of the liquid medium is: 18 g of glucose, 4.5 g of K2HPO4, 2.5 g of KH2PO4, 0.09 g of NaCl, 0.18 g of (NH4)2SO4, 0.55 g of urea, 0.45 g of yeast extract, 0.22 g of MgSO4, 1000 mL of water, sterilized at 112 °C for 30 min.

[0062] S2. Centrifuge the fermentation broth at 10,000 r / min for 10 min. After ultrasonic treatment of the precipitate, take the supernatant and add it to 4 volumes of absolute ethanol at 1°C. Let it stand at 1°C for 24 h, then centrifuge at 10,000 r / min for 10 min. Dissolve the obtained precipitate in distilled water, add 4 volumes of absolute ethanol at 1°C, let it stand at 1°C for 24 h, and centrifuge at 10,000 r / min for 10 min. Dry the obtained precipitate in a vacuum drying oven at room temperature for 1 h to obtain the microbial flocculant.

[0063] The preparation method of nano-Fe3O4 particles is the same as that in Example 1.

[0064] Example 5

[0065] This example provides a flocculation composition prepared by compounding a microbial flocculant and nano-Fe3O4. The flocculation composition is composed of a microbial flocculant, nano-Fe3O4 particles, and a coagulant aid CaCl2 combined in a mass ratio of 1:2:50.

[0066] The preparation method of the microbial flocculant is the same as that in Example 1.

[0067] The preparation method of nano-Fe3O4 particles is as follows:

[0068] Weigh 1.5191 g of FeSO4 and 3.9988 g of Fe2(SO4)3, put them into a 500 mL beaker, add 200 mL of water to dissolve, and then add dilute HCl to make the HCl concentration in the solution 0.015 mol / L. Place the beaker on an electric stirrer and stir at a speed of 100 r / min, with the temperature controlled at (30 ± 1)°C. While stirring strongly, slowly add a 0.3 mol / L NH3·H2O solution until pH ≥ 10. Then transfer the solution to a 500 mL Erlenmeyer flask and keep it in a constant temperature water bath (80°C) for 1 h. After the reaction, it can be observed that bright black Fe3O4 particles are formed. Place the prepared Fe3O4 suspension in an ultrasonic oscillator and oscillate for 20 min, filter at room temperature, wash with absolute ethanol and then with distilled water until the pH of the washing solution is 7.1, and dry in an electrothermal constant temperature forced air drying oven to obtain nano-Fe3O4 particles.

[0069] Example 6

[0070] This example provides a flocculation composition prepared by compounding a microbial flocculant and nano-Fe3O4. The flocculation composition is composed of a microbial flocculant, nano-Fe3O4 particles, and a coagulant aid CaCl2 combined in a mass ratio of 1:2:50.

[0071] The preparation method of the microbial flocculant is the same as that in Example 1.

[0072] The preparation method of nano-Fe3O4 particles is as follows:

[0073] Weigh 1.2675 g of FeCl2 and 3.5419 g of Fe(ClO4)3, put them into a 500 mL beaker, add 200 mL of water to dissolve, and then add dilute HCl to make the HCl concentration in the solution 0.025 mol / L. Place the beaker on an electric stirrer and stir at a speed of 100 r / min, and control the temperature at (30 ± 1) °C. While stirring strongly, slowly add 0.5 mol / L NH3·H2O solution until pH ≥ 10, and then transfer the solution into a 500 mL Erlenmeyer flask, and keep it in a constant temperature water bath (60 °C) for 2 h. After the reaction is completed, it can be observed that bright black Fe3O4 particles are formed. Place the prepared Fe3O4 suspension in an ultrasonic oscillator and oscillate for 25 min, filter at room temperature, wash with absolute ethanol and then wash with distilled water until the pH of the washing solution is 6.9, and dry it in an electrothermal constant temperature forced air drying oven to obtain nano-Fe3O4 particles.

[0074] Example 7

[0075] This example provides an application of a flocculation composition prepared by compounding the microbial flocculant obtained in Example 1 with nano-Fe3O4 in treating sewage.

[0076] Take sewage (COD = 85 mg / L, turbidity = 15.42 NTU, pH = 7), add the flocculation composition prepared by compounding the microbial flocculant obtained in Example 1 with nano-Fe3O4, so that the dosage of the microbial flocculant is 10 mg / L, the dosage of nano-Fe3O4 particles is 20 mg / L, and the dosage of the coagulant aid CaCl2 is 0.5 g / L. Mix at room temperature for 20 min, take the supernatant for detection after natural precipitation for 1 h, and its turbidity removal rate is 68.5%, and the COD removal rate is 43.6%.

[0077] Example 8

[0078] This example provides an application of a flocculation composition prepared by compounding the microbial flocculant obtained in Example 2 with nano-Fe3O4 in treating sewage.

[0079] Take sewage (COD = 85 mg / L, turbidity = 15.42 NTU, pH = 7), add the flocculation composition prepared by compounding the microbial flocculant obtained in Example 2 with nano-Fe3O4, so that the dosage of the microbial flocculant is 20 mg / L, the dosage of nano-Fe3O4 particles is 30 mg / L, and the dosage of the coagulant aid CaCl2 is 0.5 g / L. Mix at room temperature for 20 min, take the supernatant for detection after natural precipitation for 1 h, and its turbidity removal rate is 66.5%, and the COD removal rate is 88.5%.

[0080] Comparative Example 1

[0081] This comparative example investigated the treatment effects of microbial flocculant and coagulant aid CaCl2 on sewage (the same as in Example 7).

[0082] The microbial flocculant prepared in Example 1 and coagulant aid CaCl2 were added to the sewage in different amounts, stirred at a speed of 200 r / min for 20 min at room temperature, and after natural sedimentation for 1 h, the supernatant was taken to measure its turbidity and COD. The results are shown in Table 1.

[0083] Table 1 Treatment effects of microbial flocculant on sewage at different dosages

[0084]

[0085] As can be seen from Table 1, when only the microbial flocculant prepared in Example 1 and coagulant aid CaCl2 were used, the turbidity removal rate and COD removal rate were significantly lower than those of the flocculation composition prepared by compounding the microbial flocculant and nano-Fe3O4 obtained in Example 1 and Example 2.

[0086] Comparative Example 2

[0087] This comparative example investigated the treatment effects of nano-Fe3O4 particles and coagulant aid CaCl2 on sewage (the same as in Example 7).

[0088] The nano-Fe3O4 particles prepared in Example 1 and coagulant aid CaCl2 were added to the sewage in different amounts, stirred at a speed of 200 r / min for 20 min at room temperature, and after natural sedimentation for 1 h, the supernatant was taken to measure its turbidity and COD. The results are shown in Table 2.

[0089] Table 2 Treatment effects of nano-Fe3O4 particles and coagulant aid CaCl2 on sewage at different dosages

[0090]

[0091] As can be seen from Table 2, when only the nano-Fe3O4 particles prepared in Example 1 and coagulant aid CaCl2 were used, the turbidity removal rate and COD removal rate were significantly lower than those of the flocculation composition prepared by compounding the microbial flocculant and nano-Fe3O4 obtained in Example 1 and Example 2.

[0092] From the test conditions and results of Comparative Example 1 and Comparative Example 2, it can be seen that under the same test conditions, when only microbial flocculant and coagulant aid CaCl2 or only nano-Fe3O4 particles and coagulant aid CaCl2 were added to the sewage to be treated, the sum of the turbidity removal rates and the sum of the COD removal rates were significantly lower than those of the flocculation composition prepared by compounding the microbial flocculant and nano-Fe3O4, indicating that there is a synergistic effect between the microbial flocculant, nano-Fe3O4 particles and coagulant aid CaCl2.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flocculation composition of a microbial flocculant and nano-Fe3O4, characterized in that: The invention comprises a microbial flocculant, nano Fe3O4 particles and a coagulant, wherein the mass ratio of the microbial flocculant, nano Fe3O4 particles and the coagulant is (1-6): (2-8): 50, the coagulant is calcium chloride, and the microbial flocculant is prepared from Pseudomonas aeruginosa ( Pseudoxanthomonas sp. ) NRG9 strain, the Pseudoxanthomonas NRG9 strain was deposited in the China General Microbiological Culture Collection Center on December 25, 2023, and its deposit number is CGMCC No.29401; the deposit address is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing; the preparation method of the microbial flocculant specifically includes the following operations: The pseudoxanthomonas NRG9 strain is inoculated on a solid culture medium for culture, and then the obtained single colony is inoculated into a liquid culture medium for fermentation culture to obtain a fermentation broth; the liquid culture medium has a C / P mass ratio of 1 to 10, a C / N mass ratio of 5 to 40, a KH2PO4 concentration of 2 to 3 g / L, a K2HPO4 concentration of 4 to 6 g / L, and a pH of 5 to 11; The fermentation broth is centrifuged, the precipitate is ultrasonically treated, and the supernatant is taken out, and alcohol precipitation is performed together with the centrifuged supernatant: 2-4 times the volume of 0-5°C anhydrous ethanol is added, and the mixture is placed at 0-5°C for at least 6 hours to separate the solid and the liquid; the obtained solid phase is dissolved in distilled water, and the alcohol precipitation is repeated at least once, followed by solid-liquid separation, and the obtained solid phase is dried to obtain the microbial flocculant.

2. The flocculation composition of the microbial flocculant and nano-Fe3O4 according to claim 1, characterized in that: The solid culture medium is beef extract peptone culture medium; and / or The liquid culture medium is composed of: 18-22 g / L glucose, 4.5-5.5 g / L K2HPO4, 2-2.5 g / L KH2PO4, 0.09-0.11 g / L NaCl, 0.18-0.22 g / L (NH4)2SO4, 0.45-0.55 g / L urea, 0.45-0.55 g / L yeast extract, 0.18-0.22 g / L MgSO4, and the solvent is water.

3. The flocculation composition of the microbial flocculant and nano-Fe3O4 according to claim 2, characterized in that: The culture temperature on the beef extract peptone medium is 25-30° C.; and / or The temperature of the fermentation culture in the liquid culture medium is 25-30°C.

4. The flocculation composition of the microbial flocculant and nano-Fe3O4 according to claim 1, characterized in that: The Pseudomonas NRG9 strain was cultured on the solid medium until the bacterial concentration was 10 5 ~10 7 / mL; and / or The single colony is fermented on the liquid culture medium until the bacterial concentration in the fermentation liquid is 10 5 ~10 7 / mL; and / or The solid-liquid separation is centrifugal, with a rotation speed of 8000-10000 r / min and a centrifugal time of 10-15 min; and / or The drying temperature is room temperature, and the drying time is 1 to 2 hours.

5. The flocculation composition of microbial flocculant and nano-Fe3O4 according to claim 1, characterized in that: The preparation method of the nano Fe3O4 particles specifically includes the following operations: dissolving a soluble ferrous salt and a soluble ferric salt in water, wherein the mass ratio of the ferrous ions in the soluble ferrous salt to the ferric ions in the soluble ferric salt is (0.5-1):1, adding dilute HCl to make the HCl concentration in the solution 0.015-0.025 mol / L, then adjusting the pH to pH≥10 with 0.3-0.5 mol / L NH3·H2O solution at 29-31°C and under stirring, and then reacting at 60-80°C for 1-2 h. After the reaction is completed, a Fe3O4 suspension is obtained, which is placed under ultrasonic oscillation for 20-30 min, filtered at room temperature, washed with anhydrous ethanol and then with distilled water until the pH of the eluate is 6.9-7.1, and dried to obtain the nano Fe3O4 particles.

6. Use of a flocculation composition comprising a microbial flocculant and nano-Fe3O4 as claimed in any one of claims 1 to 5 in treating sewage.

7. A sewage treatment method, characterized in that: Add the flocculation composition of the microbial flocculant and nano-Fe3O4 described in any one of claims 1 to 5 to the sewage to be treated and mix them at room temperature.

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