Microbial immobilized particle reinforced by zero-valent iron shell as well as preparation and application of microbial immobilized particle

Abstract

The invention discloses zero-valent iron shell reinforced microbial immobilized particles as well as preparation and application thereof, and belongs to the technical field of wastewater treatment. According to the preparation method, anaerobic digestion bacteria and a zero-valent iron reinforced material are embedded in porous organic gel formed by cross-linking polymerization of polyvinyl alcohol or sodium alginate in a layered manner, so that stress of an external poor water quality environment and the zero-valent iron material on microorganisms is reduced; in the prepared zero-valent iron shell reinforced microbial immobilized particle, the shell containing the zero-valent iron can protect microorganisms from being disturbed by external adverse environmental conditions, the environmental adaptability of the microorganisms is improved, and meanwhile the biological activity of the microorganisms in the porous inner core is reinforced; on the other hand, the biological toxicity of the zero-valent iron material to microorganisms is reduced, and the broad-spectrum applicability of the zero-valent iron is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically to a microorganism immobilization particle reinforced with a zero-valent iron shell, and the preparation and application thereof. Background Art

[0002] With the rapid development of industrialization and urbanization, the problem of organic wastewater treatment has become increasingly prominent, especially the remediation of low-biodegradable organic wastewater has become a key difficulty. The organic matter in low-biodegradable organic wastewater has a complex structure and high molecular stability, making it difficult for microorganisms to effectively degrade it under normal conditions. In order to promote the application of microbial degradation technology in low-biodegradable organic wastewater, researchers have developed a microbial-zero-valent iron coupled degradation technology, which comprehensively utilizes the biodegradability of microorganisms and the reducibility and biostimulation of zero-valent iron, thereby improving the conversion rate and removal rate of organic matter in wastewater, and ultimately converting organic matter into harmless substances.

[0003] However, low-biodegradable organic wastewater often contains toxic substances, which have a certain inhibitory effect on microorganisms. The environmental conditions in the actual site are also complex and changeable, so there is an urgent need to improve the environmental resistance of microorganisms. At present, microbial embedding and immobilization technology is widely used in biological stabilization. This technology can enhance the adaptability and impact resistance of microorganisms to the external environment, while improving the degradation efficiency of microorganisms and facilitating the recovery of microorganisms. Therefore, combining microbial immobilization with zero-valent iron enhancement technology may be more effective in treating complex low-biodegradable organic wastewater.

[0004] A Chinese patent with the authorization announcement number CN110592066B discloses a method for preparing a biochar-loaded nano-zero-valent iron coupled phosphate-solubilizing bacteria immobilized pellet. By co-encapsulating the phosphate-solubilizing bacteria with the zero-valent iron fixed by biochar, the resistance of the phosphate-solubilizing bacteria to external environmental pressure is significantly improved. In addition, a Chinese patent with the publication number CN115872524A discloses a composite nano-zero-valent iron filler and a preparation method thereof. This method embeds the nano-zero-valent iron pretreated with a dispersant on a porous sponge and co-embeds it with a microbial agent, thereby effectively improving the reaction activity of the nano-zero-valent iron and the microorganism. However, the prior art generally adopts a method of mixed embedding and immobilization of microorganisms and zero-valent iron, resulting in that the microorganisms on the surface of the particles are still directly affected by the external water quality conditions, and the relative distribution of zero-valent iron and microorganisms is difficult to regulate, which may cause the zero-valent iron in the particles to produce biological stress on the microorganisms. Summary of the invention

[0005] 1. Technical problem to be solved by the invention

[0006] In view of the deficiency in the prior art that the microorganisms on the surface of the immobilized particles are directly affected by the external water quality conditions, a zero-valent iron shell-reinforced microorganism immobilized particle and its preparation and application are provided.

[0007] 2. Technical solution

[0008] In order to achieve the above object, the technical solution provided by the present invention is:

[0009] The method for preparing a zero-valent iron shell-reinforced microorganism immobilized particle of the present invention comprises the following steps:

[0010] S1. Prepare a porous core embedding solution containing anaerobic digestion bacteria and a gelling agent;

[0011] S2. The porous core embedding solution obtained in step S1 is cultured in a constant temperature incubator for a period of time;

[0012] S3. The porous core embedding solution obtained in step S2 is added to a cross-linking agent for a cross-linking treatment to obtain a porous core;

[0013] S4. preparing a porous shell embedding solution containing zero-valent iron and a gelling agent;

[0014] S5. The porous inner core obtained in step S3 is mixed with the porous outer shell embedding solution obtained in step S4 to obtain a mixed embedding solution;

[0015] S6. adding the mixed embedding solution obtained in step S5 to a crosslinking agent for secondary crosslinking treatment to obtain microbial immobilization particles reinforced with a zero-valent iron shell;

[0016] Wherein, in step S2, the incubation time of the porous core embedding solution is 12 to 24 hours, and the temperature is 30 to 35°C;

[0017] In step S3, the time of the primary cross-linking treatment is 1 to 4 hours, and the temperature is 30 to 35°C.

[0018] It should be noted that by controlling the reaction conditions of the primary cross-linking treatment, the porous inner core formed by cross-linking has more pores, and the porous inner core embedding liquid is cultured before the primary cross-linking treatment. The gas produced by microbial metabolism increases the gas contained in the inner core embedding liquid, increases the pores of the porous inner core, and promotes material exchange. The various types of pores produced by the primary cross-linking treatment and microbial culture, including macropores, mesopores and micropores, allow organic matter to fully contact with microorganisms and substances to be fully exchanged, so that the prepared zero-valent iron shell-reinforced microbial immobilization particles can fully play their role and improve the degradation efficiency.

[0019] Furthermore, in step S6, the secondary cross-linking treatment is performed for 20 to 24 hours at a temperature of 20 to 25°C.

[0020] It should also be noted that controlling the reaction conditions of the secondary cross-linking treatment, increasing the degree of cross-linking of the porous shell formed by cross-linking, and reducing the macroscopic pores on the zero-valent iron shell can effectively protect the microorganisms in the porous core from being directly disturbed by adverse external environmental conditions, and the organic matter in the wastewater can penetrate into the porous core through the pores of the porous shell and be effectively removed.

[0021] Furthermore, in step S1, the weight ratio of the anaerobic digestion bacteria to the gelling agent is 1-2:20-30.

[0022] It should be noted that the zero-valent iron shell promotes the proliferation of microorganisms, which is beneficial to reduce the addition of anaerobic digestion bacteria.

[0023] Specifically, the weight ratio of the anaerobic digestion bacteria to the gelling agent may be 1-2:20-25, 1-2:20-30 or 2:20-30.

[0024] Furthermore, in step S4, the weight ratio of the zero-valent iron to the gelling agent is 5-10:5-15.

[0025] Specifically, the weight ratio of the zero-valent iron to the gelling agent may be 5-10:5-10, 5-10:10-15 or 5-10:5-15.

[0026] Furthermore, in step S5, the volume ratio of the embedding solution of the porous inner core to that of the porous outer shell is 100-150:50-75.

[0027] Furthermore, in step S1 and step S4, the gelling agent is one or both of sodium alginate and polyvinyl alcohol.

[0028] Further, the gelling agent is added in the form of an aqueous solution;

[0029] The aqueous solution of the gelling agent is one or both of a sodium alginate aqueous solution with a mass fraction of 1.0 to 3.0 wt % and a polyvinyl alcohol aqueous solution with a mass fraction of 1.0 to 3.0 wt %.

[0030] Specifically, the aqueous solution of the gelling agent may be a sodium alginate aqueous solution with a mass fraction of 1.0 wt%, 2.0 wt% or 3.0 wt%; or may be a polyvinyl alcohol aqueous solution with a mass fraction of 1.0 wt%, 2.0 wt% or 3.0 wt%.

[0031] Furthermore, in step S3 and step S6, the cross-linking agent is one or both of a calcium chloride solution with a mass fraction of 0.5 to 4.0 wt% and a saturated boric acid solution containing calcium chloride with a mass fraction of 0.5 to 4.0 wt%.

[0032] Furthermore, the zero-valent iron includes one or both of nanometer zero-valent iron and micrometer zero-valent iron.

[0033] Furthermore, in step S1, the anaerobic digestion bacteria can be obtained by the following method:

[0034] The anaerobic digestion bacteria are centrifuged through a bacterial liquid containing the anaerobic digestion bacteria to obtain a solid precipitate;

[0035] The concentration of anaerobic digestion bacteria in the bacterial solution may be 10-20 g / L.

[0036] Specifically, the bacterial solution containing anaerobic digestion bacteria is centrifuged at 5000 rpm and 4° C. for 5 min, and after removing the supernatant, the solid precipitate, namely the anaerobic digestion bacteria, is collected.

[0037] Furthermore, step S1 may specifically include: adding anaerobic digestion bacteria into the aqueous solution of the gelling agent, and dispersing the mixture evenly to obtain the porous inner core embedding solution.

[0038] Furthermore, in step S3, the porous core embedding solution may be added to the cross-linking agent in a dropwise manner.

[0039] Specifically, a syringe may be used for dropwise addition.

[0040] Furthermore, step S4 may specifically be: adding zero-valent iron into the aqueous solution of the gelling agent and dispersing it evenly to obtain a porous shell embedding solution.

[0041] The present invention also provides a microorganism immobilization particle with a zero-valent iron shell reinforced prepared by the above preparation method,

[0042] It comprises a porous inner core and a porous outer shell covering the porous inner core.

[0043] The porous inner core comprises a porous organic gel and anaerobic digestion bacteria embedded in the porous organic gel;

[0044] The porous shell includes a porous organic gel and zero-valent iron embedded in the porous organic gel.

[0045] Furthermore, the porous organic gel is obtained by cross-linking polymerization of at least one of sodium alginate and polyvinyl alcohol.

[0046] Furthermore, the particle size of the porous inner core is 3 to 5 mm.

[0047] It should be noted that the particle size of the zero-valent iron shell-reinforced microorganism immobilization particles can be controlled by adjusting the number of porous inner cores.

[0048] For example, when the number of porous inner cores increases, the particle size of the microbial immobilization particles reinforced with the zero-valent iron shell also increases.

[0049] The present invention also provides an application of the zero-valent iron shell-reinforced microbial immobilization particles in treating organic wastewater.

[0050] Furthermore, the organic wastewater contains at least one organic substance selected from the group consisting of p-nitrophenol, sulfamethoxazole, and 2,4-dichlorophenol.

[0051] 3. Beneficial effects

[0052] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0053] (1) In the preparation method of the zero-valent iron shell-reinforced microorganism immobilized particles provided by the present invention, anaerobic digestion bacteria and zero-valent iron-reinforced materials are layered and embedded in a porous organic gel formed by cross-linking polymerization of polyvinyl alcohol or sodium alginate through a two-step embedding method, forming a porous shell containing zero-valent iron and a porous core inside the porous shell, thereby reducing the stress of the external poor water quality environment and the zero-valent iron material on the microorganisms; wherein, the reaction conditions of the primary cross-linking treatment are controlled, the porous core formed by cross-linking has a large number of pores, and the porous core embedding liquid is cultured before the primary cross-linking treatment, the gas generated by microbial metabolism increases the gas contained in the core embedding liquid, increases the pores of the porous core, and promotes the exchange of substances such as pollutants. Through the various types of pores generated by the primary cross-linking treatment and microbial culture, organic matter can fully contact with the microorganisms, and substances can be fully exchanged, so that the prepared zero-valent iron shell-reinforced microorganism immobilized particles can fully play their role and improve the degradation efficiency.

[0054] (2) The microbial immobilized particles reinforced with a zero-valent iron shell provided by the present invention include a porous inner core and a porous outer shell coated outside the porous inner core, wherein the porous inner core includes a porous organic gel and anaerobic digestion bacteria, wherein the anaerobic digestion bacteria are embedded in the porous organic gel, and the porous outer shell includes a porous organic gel and zero-valent iron, wherein the zero-valent iron is embedded in the porous organic gel; the immobilized particles have a core-shell structure, and the porous outer shell containing zero-valent iron can protect the microorganisms from being disturbed by external adverse environmental conditions, thereby improving the environmental adaptability of the microorganisms and enhancing the biological activity of the microorganisms in the porous inner core;

[0055] On the other hand, the biotoxicity of zero-valent iron materials to microorganisms is reduced, and the broad-spectrum applicability of zero-valent iron is improved.

[0056] (3) In the application of the zero-valent iron shell-reinforced microbial immobilized particles provided by the present invention in the degradation of p-nitrophenol, low-biodegradable organic matter in organic wastewater, such as p-nitrophenol, can be biodegradable by the zero-valent iron shell, i.e., the porous shell, and then penetrate into the microbial core, i.e., the porous core, for thorough degradation, thereby achieving thorough and efficient remediation of complex low-biodegradable organic wastewater and simultaneously achieving the improvement of anaerobic methane production capacity;

[0057] Moreover, compared with traditional microbial immobilized particles, it can remove low-biodegradable organic matter in industrial wastewater in a long-term and stable manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The flowchart of the preparation method of the zero-valent iron shell-reinforced microorganism immobilized particles of the present invention;

[0059] Figure 2 This is a photo of the microorganism immobilization particles reinforced with zero-valent iron shell in Example 1 of the present invention;

[0060] Figure 3 The degradation performance results of p-nitrophenol (PNP) in Example 1 and Comparative Example 1 of the present invention are shown in FIG.

[0061] Figure 4 It is a graph showing the degradation performance results of p-nitrophenol in Example 1 and Comparative Examples 2-4 of the present invention. DETAILED DESCRIPTION

[0062] The present disclosure may be more easily understood by reference to the following description in conjunction with examples, all of which constitute a part of the present disclosure. It should be understood that the present disclosure is not limited to the specific products, methods, conditions or parameters described and / or illustrated herein. Further, the terms used herein are only used for the purpose of describing specific embodiments by way of example and are not intended to be limiting unless otherwise indicated.

[0063] It should also be understood that, for the sake of clarity, certain features of the present disclosure may be described herein in the context of separate embodiments, but may also be provided in combination with each other in a single embodiment. That is, unless clearly incompatible or specifically not included, each separate embodiment is considered to be combinable with any other embodiment, and the combination is considered to represent another different embodiment. Conversely, for the sake of simplicity, the various features of the present disclosure described in the context of a single embodiment may also be provided individually or in any sub-combination. Finally, although a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure itself may also be considered to be an independent embodiment.

[0064] Unless otherwise indicated, it should be understood that each individual element in a list and each combination of individual elements in the list will be interpreted as a different embodiment. For example, a list of embodiments represented as "A, B, or C" should be interpreted to include embodiments "A", "B", "C", "A or B", "A or C", "B or C", or "A, B, or C".

[0065] In the present disclosure, the singular forms of the articles "a," "an," and "the" also include the corresponding plural references, and a reference to a specific value includes at least that specific value unless the context clearly indicates otherwise. Thus, for example, a reference to "a substance" is a reference to at least one of that substance and equivalents thereof.

[0066] When items are described by using the conjunction terms "... and / or...," etc., the description should be understood to include any one of the associated listed items and all combinations of one or more thereof.

[0067] In general, the use of the term "about" indicates an approximate value that can vary depending on the desired properties obtained by the disclosed subject matter, and will be interpreted in a context-dependent manner based on function. Therefore, one of ordinary skill in the art will be able to interpret a certain degree of difference on a case-by-case basis. In some cases, the number of significant figures used when expressing a particular value can be a representative technique for determining the difference allowed by the term "about". In other cases, a gradient in a range of values ​​can be used to determine the range of differences allowed by the term "about". Further, all ranges in this disclosure are inclusive and combinable, and reference to a value in a range includes each value within that range.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0069] In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be purchased commercially.

[0070] Polyvinyl alcohol is polyvinyl alcohol 124, purchased from Shanghai McLean Biochemical Technology Co., Ltd., model P909857; sodium alginate was purchased from Shanghai McLean Biochemical Technology Co., Ltd., model S817374; calcium chloride was purchased from Shanghai McLean Biochemical Technology Co., Ltd., model C915443.

[0071] The bacterial liquid containing anaerobic digestion bacteria used in the examples and comparative examples of the present invention is obtained by acclimating activated sludge in a culture medium (COD = 2000 mg / L) with glucose as a substrate, wherein the activated sludge comes from the anaerobic digestion tank of Taixing Industrial Park, Jiangsu Province. The activated sludge is acclimated and cultured in a plastic barrel at room temperature for 1 month, and the culture medium is renewed every 1 week. The composition of the culture medium is (g / L): C 6 H 12 O 6 (Glucose) 0.188 g / L, NH 4 Cl 0.382g / L, KH 2 PO 4 0.148g / L, CaCl 2 0.08,MgSO 4 7H 2 O 0.02 g / L, NaHCO 3 2g / L, the concentration of the obtained bacterial solution is 10g / L, and the pH is 7.5±0.2; in the activated sludge after acclimation, the anaerobic digestion functional bacteria include Bacteroides, Clostridium, Methanosaeta and other genera.

[0072] It should be noted that the activated sludge acclimation scheme is also applicable to the acclimation process of activated sludge from other sources in anaerobic digesters.

[0073] The present invention is further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The essential characteristics and remarkable effects of the present invention can be reflected from the following examples, and the described embodiments are part of the embodiments of the present invention, rather than all the embodiments, and therefore, they do not limit the present invention in any way, and those skilled in the art make some non-essential improvements and adjustments based on the content of the present invention, which all belong to the protection scope of the present invention.

[0074] Example 1

[0075] Combination Figure 1 In this embodiment, a microbial immobilization particle reinforced with a zero-valent iron shell is prepared, and the specific steps are as follows:

[0076] (1) 10 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % sodium alginate aqueous solution and dispersed evenly to obtain a porous core embedding solution;

[0077] (2) incubating the porous core embedding solution in a constant temperature incubator at 35°C for 12 h;

[0078] (3) 100 mL of the porous core embedding solution was added dropwise into 500 mL of a 3.0 wt% calcium chloride solution, and cross-linked at 35° C. for 1 h to obtain a porous core;

[0079] (4) adding 0.5 g of nano-zero-valent iron into 50 mL of 2.0 wt % sodium alginate aqueous solution and dispersing the mixture evenly to obtain a porous shell embedding solution;

[0080] (5) adding 100 mL of the porous inner core into 50 mL of the porous outer shell embedding solution to obtain a mixed embedding solution;

[0081] (6) The mixed embedding solution containing one porous inner core was added successively into 500 mL of 3.0 wt % calcium chloride solution and cross-linked at 25° C. for 20 h to obtain microbial immobilization particles reinforced with a zero-valent iron shell.

[0082] Combination Figure 2 The particle size of the zero-valent iron shell-reinforced microbial immobilization particles prepared in this embodiment is about 5 mm.

[0083] Performance test: Prepare 1L of water sample with a p-nitrophenol concentration of 100mg / L, add 20mL of the prepared zero-valent iron shell-reinforced microbial immobilized particles, oscillate at room temperature, replace the water sample of the same volume and concentration every 5d, take samples every other day to measure the p-nitrophenol concentration in the water sample, for a total of four cycles, lasting 20 days, and calculate the degradation rate.

[0084] Example 2

[0085] (1) 20 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % sodium alginate aqueous solution and dispersed evenly to obtain a porous core embedding solution;

[0086] (2) incubating the porous core embedding solution in a constant temperature incubator at 30°C for 24 hours;

[0087] (3) 100 mL of the porous core embedding solution was added dropwise into 500 mL of a 1.0 wt% calcium chloride solution, and cross-linked at 30° C. for 4 h to obtain a porous core;

[0088] (4) adding 1.0 g of nano-zero-valent iron into 50 mL of a 3.0 wt % polyvinyl alcohol aqueous solution and dispersing the mixture evenly to obtain a porous shell embedding solution;

[0089] (5) adding 100 mL of the porous inner core into 50 mL of the porous outer shell embedding solution to obtain a mixed embedding solution;

[0090] (6) The mixed embedding solution containing one porous inner core was added to 500 mL of a saturated boric acid solution containing 3.0 wt % calcium chloride, and cross-linked at 20° C. for 24 h to obtain microbial immobilization particles reinforced with a zero-valent iron shell.

[0091] Example 3

[0092] (1) 20 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % polyvinyl alcohol aqueous solution and dispersed evenly to obtain a microorganism embedding solution;

[0093] (2) incubating the porous core embedding solution in a constant temperature incubator at 30°C for 24 hours;

[0094] (3) 100 mL of the porous core embedding solution was added dropwise into 500 mL of a saturated boric acid solution containing 3.0 wt % calcium chloride, and cross-linked at 30° C. for 4 h to obtain a porous core;

[0095] (4) adding 1.0 g of nano-zero-valent iron into 50 mL of a 3.0 wt % polyvinyl alcohol aqueous solution and dispersing the mixture evenly to obtain a porous shell embedding solution;

[0096] (5) adding 100 mL of the porous inner core into 50 mL of the porous outer shell embedding solution to obtain a mixed embedding solution;

[0097] (6) The mixed embedding solution containing three porous cores was added to 500 mL of a saturated boric acid solution containing 3.0 wt % calcium chloride, and cross-linked at 20° C. for 24 h to obtain microbial immobilization particles reinforced with a zero-valent iron shell.

[0098] Comparative Example 1

[0099] This comparative example prepared a traditional microbial immobilization particle, and the specific steps are as follows:

[0100] (1) 10 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % sodium alginate aqueous solution and dispersed evenly to obtain a microorganism embedding solution;

[0101] (2) 100 mL of microorganism embedding solution was added dropwise into 500 mL of 3.0 wt% calcium chloride solution, and cross-linked at 35° C. for 1 h to obtain traditional microorganism immobilized particles;

[0102] Combination Figure 3In the four treatment cycles of the conventional microbial immobilized particles prepared in this comparative example, the p-nitrophenol concentration was 70.19-86.10 mg / L on the first day, and then gradually decreased, and was still 3.99-5.33 mg / L after 5 days of treatment, and p-nitrophenol could not be completely degraded. In the first treatment cycle of the zero-valent iron shell-reinforced microbial immobilized particles prepared in Example 1, the nitrophenol concentration was about 64.16 mg / L after 1 day of treatment, and the p-nitrophenol in the water sample was almost completely degraded after 4 days of treatment. In the second, third, and fourth cycles, p-nitrophenol could be completely degraded after 3 days of treatment, and the nitrophenol concentration was 16.72-26.23 mg / L after 1 day of treatment. This is because the porous shell containing zero-valent iron in the zero-valent iron shell-reinforced microbial immobilized particles prepared in Example 1 can protect the microorganisms from the disturbance of external adverse environmental conditions, and also strengthen the biological activity of the microorganisms in the porous inner core, and p-nitrophenol can be biochemically improved through the zero-valent iron shell, i.e., the porous shell, and then can penetrate into the microbial inner core, i.e., the porous inner core, for thorough degradation, so the degradation can be quickly started in multiple cycle experiments and has a better p-nitrophenol degradation effect. However, the conventional microbial immobilized particles in this comparative example only contain microorganisms and lack the reinforcement of zero-valent iron, so the degradation efficiency is low, and the microbial anaerobic digestion bacteria are also easily affected by the external water sample environment.

[0103] Comparative Example 2

[0104] (1) 10 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % sodium alginate aqueous solution and dispersed evenly to obtain a porous core embedding solution;

[0105] (2) 100 mL of the porous core embedding solution was added dropwise into 500 mL of a 3.0 wt% calcium chloride solution, and cross-linked at 35° C. for 1 h to obtain a porous core;

[0106] (3) adding 0.5 g of nano-zero-valent iron into 50 mL of 2.0 wt % sodium alginate aqueous solution and dispersing the mixture evenly to obtain a porous shell embedding solution;

[0107] (4) adding 100 mL of the porous inner core into 50 mL of the porous outer shell embedding solution to obtain a mixed embedding solution;

[0108] (5) The mixed embedding solution containing one porous core was added gradually into 500 mL of 3.0 wt % calcium chloride solution, and cross-linked at 25° C. for 20 h to obtain microbial immobilization particles reinforced with a zero-valent iron shell.

[0109] The method is basically the same as Example 1, except that the porous core embedding solution obtained in step (1) is not cultured at a constant temperature.

[0110] The performance test was basically the same as Example 1, except that the zero-valent iron shell-reinforced microbial immobilization particles prepared in this comparative example were used and the test was conducted for 5 days.

[0111] Combination Figure 4 In the process of preparing the zero-valent iron shell-reinforced microorganism immobilized particles obtained in this comparative example, there is a lack of constant temperature culture, resulting in fewer voids in the porous inner core of the obtained zero-valent iron shell-reinforced microorganism immobilized particles, and p-nitrophenol cannot fully contact with the microorganisms, resulting in a low degradation efficiency. Therefore, compared with Example 1, the zero-valent iron shell-reinforced microorganism immobilized particles prepared in Example 1 can quickly start the degradation of PNP.

[0112] Comparative Example 3

[0113] (1) 10 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % sodium alginate aqueous solution and dispersed evenly to obtain a porous core embedding solution;

[0114] (2) incubating the porous core embedding solution in a constant temperature incubator at 35°C for 12 h;

[0115] (3) 100 mL of the porous core embedding solution was added dropwise into 500 mL of a 3.0 wt% calcium chloride solution, and cross-linked at 40° C. for 12 h to obtain a porous core;

[0116] (4) adding 0.5 g of nano-zero-valent iron into 50 mL of 2.0 wt % sodium alginate aqueous solution and dispersing the mixture evenly to obtain a porous shell embedding solution;

[0117] (5) adding 100 ml of the porous inner core into 50 ml of the porous outer shell embedding solution to obtain a mixed embedding solution;

[0118] (6) The mixed embedding solution containing one porous inner core was added successively into 500 mL of 3.0 wt % calcium chloride solution and cross-linked at 25° C. for 20 h to obtain microbial immobilization particles reinforced with a zero-valent iron shell.

[0119] The method is basically the same as Example 1, except that in step (3), a cross-linking treatment is performed at 40° C. for 12 hours to obtain a porous inner core.

[0120] The performance test is basically the same as that of Comparative Example 2, except that the microbial immobilization particles reinforced with a zero-valent iron shell prepared in this comparative example are used.

[0121] Combination Figure 4 In the process of preparing the zero-valent iron shell-reinforced microorganism immobilized particles in this comparative example, the first cross-linking time is long and the temperature is high, resulting in fewer voids in the porous core of the obtained zero-valent iron shell-reinforced microorganism immobilized particles, and p-nitrophenol cannot fully contact with the microorganisms, so the degradation rate is low. Therefore, compared with Example 1, the zero-valent iron shell-reinforced microorganism immobilized particles prepared in Example 1 can obtain a higher PNP degradation rate.

[0122] Comparative Example 4

[0123] (1) 10 mL of a bacterial solution containing anaerobic digestion bacteria at a concentration of 10 g / L was centrifuged at 5000 rpm and 4° C. for 5 min. After removing the supernatant, the solid precipitate was added to 100 mL of a 3.0 wt % sodium alginate aqueous solution and dispersed evenly to obtain a porous core embedding solution;

[0124] (2) incubating the porous core embedding solution in a constant temperature incubator at 35°C for 12 h;

[0125] (3) 100 mL of the porous core embedding solution was added dropwise into 500 mL of a 3.0 wt% calcium chloride solution, and cross-linked at 35° C. for 1 h to obtain a porous core;

[0126] (4) adding 0.1 g of nano-zero-valent iron into 50 mL of 2.0 wt % sodium alginate aqueous solution and dispersing the mixture evenly to obtain a porous shell embedding solution;

[0127] (5) adding 100 ml of the porous inner core into 50 ml of the porous outer shell embedding solution to obtain a mixed embedding solution;

[0128] (6) The mixed embedding solution containing one porous inner core was added successively into 500 mL of 3.0 wt % calcium chloride solution and cross-linked at 25° C. for 20 h to obtain microbial immobilization particles reinforced with a zero-valent iron shell.

[0129] The method is basically the same as Example 1, except that in step (4), the mass ratio of nano zero-valent iron to the gelling agent sodium alginate is 1:10.

[0130] The performance test is basically the same as that of Comparative Example 2, except that the microbial immobilization particles reinforced with a zero-valent iron shell prepared in this comparative example are used.

[0131] Combination Figure 4In the process of preparing the zero-valent iron shell-reinforced microbial immobilized particles in this comparative example, the amount of nano zero-valent iron added is small, and the microbial immobilized particles in this comparative example have poor activation of microorganisms and improvement of the biochemical properties of p-nitrophenol, which is not conducive to the rapid start-up and efficient degradation of degradation. Therefore, compared with Example 1, the zero-valent iron shell-reinforced microbial immobilized particles prepared in Example 1 can achieve rapid start-up and efficient degradation of PNP degradation.

Claims

1. A method for preparing microbial immobilized particles reinforced with zero-valent iron shell, characterized in that: The following steps are involved: S1. Prepare a porous core embedding solution containing anaerobic digestion bacteria and a gelling agent; S2. The porous core embedding solution obtained in step S1 is cultured in a constant temperature incubator for a period of time; S3. The porous core embedding solution obtained in step S2 is added to a cross-linking agent for a cross-linking treatment to obtain a porous core; S4. preparing a porous shell embedding solution containing zero-valent iron and a gelling agent; S5. The porous inner core obtained in step S3 is mixed with the porous outer shell embedding solution obtained in step S4 to obtain a mixed embedding solution; S6. adding the mixed embedding solution obtained in step S5 to a crosslinking agent for secondary crosslinking treatment to obtain microbial immobilization particles reinforced with a zero-valent iron shell; Wherein, in step S2, the incubation time of the porous core embedding solution is 12 to 24 hours, and the temperature is 30 to 35°C; In step S3, the time of the primary cross-linking treatment is 1 to 4 hours, and the temperature is 30 to 35°C.

2. The method for preparing the zero-valent iron shell-reinforced microorganism immobilized particles according to claim 1, characterized in that: In step S6, the secondary cross-linking treatment is performed for 20 to 24 hours at a temperature of 20 to 25°C.

3. The method for preparing the zero-valent iron shell-reinforced microorganism immobilized particles according to claim 2, characterized in that: In step S1 and step S4, the gelling agent is one or both of sodium alginate and polyvinyl alcohol.

4. The method for preparing the zero-valent iron shell-reinforced microorganism immobilized particles according to claim 3, characterized in that: In step S3 and step S6, the cross-linking agent is one or both of a calcium chloride solution with a mass fraction of 0.5 to 4.0 wt% and a saturated boric acid solution containing calcium chloride with a mass fraction of 0.5 to 4.0 wt%.

5. The method for preparing the zero-valent iron shell-reinforced microorganism immobilized particles according to any one of claims 1 to 4, characterized in that: In step S1, the weight ratio of the anaerobic digestion bacteria to the gelling agent is 1-2:20-30; In step S4, the weight ratio of the zero-valent iron to the gelling agent is 5-10:5-15; In step S5, the volume ratio of the embedding solution of the porous inner core to that of the porous outer shell is 100-150:50-75.

6. The method for preparing the zero-valent iron shell-reinforced microorganism immobilized particles according to claim 5, characterized in that: The zero-valent iron is one or both of nano zero-valent iron and micron zero-valent iron.

7. A microorganism immobilized particle with a zero-valent iron shell reinforced by the preparation method according to any one of claims 1 to 6, characterized in that: It comprises a porous inner core and a porous outer shell covering the porous inner core. The porous inner core comprises a porous organic gel and anaerobic digestion bacteria embedded in the porous organic gel; The porous shell includes a porous organic gel and zero-valent iron embedded in the porous organic gel.

8. The zero-valent iron shell-reinforced microorganism immobilized particle according to claim 7, characterized in that: The porous organic gel is obtained by cross-linking polymerization of at least one of sodium alginate and polyvinyl alcohol.

9. The zero-valent iron shell-reinforced microorganism immobilized particle according to any one of claims 7 to 8, characterized in that: The particle size of the porous inner core is 3 to 5 mm.

10. Use of the zero-valent iron shell-reinforced microorganism immobilization particles according to any one of claims 7 to 9 in treating organic wastewater.

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