Zero-valent iron shell reinforced microbial immobilized particles and preparation and application thereof

Abstract

This invention discloses a zero-valent iron (ZV) shell-reinforced microbial immobilized particle, its preparation, and its application, belonging to the field of wastewater treatment technology. The preparation method involves layering anaerobic digestive bacteria and ZV reinforcement materials within a porous organic gel formed by cross-linking polymerization of polyvinyl alcohol or sodium alginate. This reduces the stress on microorganisms from adverse external water quality and the ZV material itself. The ZV shell-reinforced microbial immobilized particle provides protection for microorganisms from adverse external environmental conditions, improving their environmental adaptability and enhancing the bioactivity of the microorganisms within the porous core. Furthermore, it reduces the biotoxicity of the ZV material to microorganisms and improves the broad applicability of ZV material.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a zero-valent iron shell reinforced microbial immobilized particle, its preparation and application. Background Technology

[0002] With the rapid development of industrialization and urbanization, the problem of organic wastewater treatment has become increasingly prominent, especially the remediation of low-biodegradability organic wastewater, which has become a key challenge. The organic matter in low-biodegradability organic wastewater has a complex structure and high molecular stability, making it difficult for microorganisms to effectively degrade it under conventional conditions. To promote the application of microbial degradation technology in low-biodegradability organic wastewater, researchers have developed a microbial-zero-valent iron coupled degradation technology. This technology comprehensively utilizes the biodegradation capacity of microorganisms and the reducing and biostimulating properties of zero-valent iron, thereby improving the conversion and removal rates of organic matter in the wastewater and ultimately converting organic matter into harmless substances.

[0003] However, low-biodegradability organic wastewater often contains toxic substances that inhibit microorganisms, and the environmental conditions in actual sites are complex and variable. Therefore, there is an urgent need to improve the environmental resistance of microorganisms. Currently, microbial immobilization technology is widely used in biological stabilization. This technology can enhance the adaptability and shock resistance of microorganisms to the external environment, while improving their degradation efficiency and facilitating their recovery. Therefore, combining microbial immobilization with zero-valent iron enhancement technology may be more effective in treating complex low-biodegradability organic wastewater.

[0004] Chinese patent CN110592066B discloses a method for preparing biochar-loaded nano-zero-valent iron coupled with phosphate-solubilizing bacteria immobilized spheres. By co-encapsulating the phosphate-solubilizing bacteria with biochar-fixed zero-valent iron, the resistance of the phosphate-solubilizing bacteria to external environmental stress is significantly improved. Furthermore, Chinese patent CN115872524A discloses a composite nano-zero-valent iron filler and its preparation method. This method involves embedding nano-zero-valent iron pretreated with a dispersant onto a porous sponge and co-encapsulating it with a microbial agent, effectively improving the reactivity between the nano-zero-valent iron and the microorganisms. However, existing technologies typically employ a mixed encapsulation and immobilization method with microorganisms and zero-valent iron, resulting in the microorganisms on the particle surface still being directly affected by external water quality conditions. Moreover, the relative distribution of zero-valent iron and microorganisms is difficult to control, which may lead to biological stress on the microorganisms caused by the zero-valent iron in the particles. Summary of the Invention

[0005] 1. The technical problem that the invention aims to solve

[0006] To address the shortcomings of existing technologies where the microorganisms on the surface of immobilized particles are directly affected by external water quality conditions, a microbial immobilized particle with a zero-valent iron shell is provided, along with its preparation and application.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0009] The present invention discloses a method for preparing microbial immobilized particles reinforced with a zero-valent iron shell, comprising the following steps:

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

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

[0012] S3. Add the porous core embedding liquid obtained in step S2 to the crosslinking agent for a first crosslinking treatment to obtain the porous core;

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

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

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

[0016] In step S2, the culture time of the porous core embedding solution is 12-24 hours, and the temperature is 30-35℃.

[0017] In step S3, the time for the first crosslinking 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 core formed by cross-linking has a large number of pores. Furthermore, the porous core embedding solution is cultured before the primary cross-linking treatment. The gas produced by microbial metabolism increases the gas content in the core embedding solution, further increasing the porosity of the porous core and promoting material exchange. Through the primary cross-linking treatment and the various types of pores generated by microbial culture, including macropores, mesopores, and micropores, organic matter can fully contact microorganisms, and materials can be fully exchanged. This allows the zero-valent iron shell reinforced microbial immobilized particles to fully function and improve the degradation efficiency.

[0019] Furthermore, in step S6, the secondary crosslinking treatment takes 20–24 hours and is carried out at a temperature of 20–25°C.

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

[0021] Further, in step S1, the weight ratio of the anaerobic digestive 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 helps reduce the need for anaerobic digestive bacteria.

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

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

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

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

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

[0028] Furthermore, 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 the following: 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 can be a sodium alginate aqueous solution with a mass fraction of 1.0 wt%, 2.0 wt%, or 3.0 wt%; or it can be a polyvinyl alcohol aqueous solution with a mass fraction of 1.0 wt%, 2.0 wt%, or 3.0 wt%.

[0031] Further, in steps S3 and S6, the crosslinking agent is one or both of the following: 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 nano-zero-valent iron and micron-zero-valent iron.

[0033] Furthermore, in step S1, the anaerobic digestive bacteria can be obtained in the following way:

[0034] The anaerobic digestive bacteria are centrifuged to obtain a solid precipitate.

[0035] The concentration of anaerobic digestive bacteria in the bacterial solution can be 10–20 g / L.

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

[0037] Further, step S1 can specifically be: adding anaerobic digestive bacteria to an aqueous solution of gelling agent and dispersing it evenly to obtain a porous core embedding solution.

[0038] Furthermore, in step S3, the porous core embedding liquid can be added to the crosslinking agent by dripping.

[0039] Specifically, it can be added drop by drop using a syringe.

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

[0041] This invention also provides a zero-valent iron shell reinforced microbial immobilized particle prepared by the above preparation method.

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

[0043] The porous core includes a porous organic gel and anaerobic digestive bacteria embedded in the porous organic gel;

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

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

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

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

[0048] For example, as the number of porous cores increases, the particle size of microbial immobilized particles reinforced with zero-valent iron shells also increases.

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

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

[0051] 3. Beneficial effects

[0052] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0053] (1) In the preparation method of the zero-valent iron shell reinforced microbial immobilized particles provided by the present invention, anaerobic digestive 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 in a two-step embedding process, forming a porous shell containing zero-valent iron and a porous core inside the porous shell, which reduces the stress of the external poor water quality environment and zero-valent iron materials on microorganisms; wherein, by controlling the reaction conditions of the first cross-linking treatment, the porous core formed by cross-linking has more pores, and the porous core embedding solution is cultured before the first cross-linking treatment, the gas produced by microbial metabolism increases the gas contained in the core embedding solution, increases the pores of the porous core, and promotes the exchange of substances such as pollutants. Through the multiple types of pores generated by the first cross-linking treatment and microbial culture, organic matter can fully contact microorganisms, and substances can be fully exchanged, so that the prepared zero-valent iron shell reinforced microbial immobilized particles can play a full role and improve the degradation efficiency.

[0054] (2) The zero-valent iron shell reinforced microbial immobilization particles provided by the present invention include a porous inner core and a porous outer shell covering the porous inner core. The porous inner core includes a porous organic gel and anaerobic digestive bacteria, which are embedded in the porous organic gel. The porous outer shell includes a porous organic gel and zero-valent iron, which are embedded in the porous organic gel. The immobilized particles have a core-shell structure. The porous outer shell containing zero-valent iron can protect microorganisms from disturbances by adverse external environmental conditions, improve the environmental adaptability of microorganisms, and at the same time enhance the biological activity of microorganisms in the porous inner core.

[0055] On the other hand, it reduces the biotoxicity of zero-valent iron materials to microorganisms and improves the broad applicability of zero-valent iron.

[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, the low biodegradability of organic matter in organic wastewater, such as p-nitrophenol, can be improved through the zero-valent iron shell, i.e., the porous shell, and then can penetrate into the microbial core, i.e. the porous core, for thorough degradation, so as to achieve thorough and efficient remediation of complex low biodegradability organic wastewater, and simultaneously improve the anaerobic methanogenic capacity;

[0057] Moreover, compared with traditional microbial immobilized particles, it can stably remove low biodegradable organic matter from industrial wastewater over a long period of time. Attached Figure Description

[0058] Figure 1 This is a flowchart illustrating the preparation method of the zero-valent iron shell reinforced microbial immobilized particles of the present invention.

[0059] Figure 2 This is a photograph of the microbial immobilized particles reinforced with a zero-valent iron shell, as shown in Embodiment 1 of the present invention.

[0060] Figure 3 The graph shows the degradation performance results of p-nitrophenol (PNP) in Example 1 and Comparative Example 1 of this invention.

[0061] Figure 4 The graph shows the degradation performance results of p-nitrophenol in Example 1 and Comparative Examples 2-4 of this invention. Detailed Implementation

[0062] This disclosure can be more readily understood by referring to the following description in conjunction with examples, all of which form part of this disclosure. It should be understood that this disclosure is not limited to the specific products, methods, conditions, or parameters described and / or shown herein. Furthermore, the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting, unless otherwise stated.

[0063] It should also be understood that, for clarity, certain features of this disclosure may be described herein in the context of individual embodiments, but may also be provided in combination with each other in individual embodiments. That is, unless obviously incompatible or specifically excluded, each individual embodiment is considered to be combinable with any other embodiment, and such combination is considered to represent another different embodiment. Conversely, for brevity, various features of this disclosure described in the context of individual embodiments may also be provided individually or in any sub-combination. Finally, while a particular embodiment may be described as part of a series of steps or part of a more general structure, each step or substructure may also be considered an independent embodiment in itself.

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

[0065] In this disclosure, the singular forms of the articles “a,” “one,” and “the” also include the corresponding plural references, and references to a particular value include at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “substance” is a reference to at least one of such substance and its equivalents.

[0066] When an item is described using the combined terms “...and / or ...", the description should be understood to include any one of the listed items and all combinations thereof.

[0067] Generally, the use of the term "about" indicates an approximation that can vary depending on the desired characteristics obtained from the disclosed subject matter and will be interpreted in a context-dependent manner based on function. Therefore, those skilled in the art will be able to interpret a 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 within a range of values ​​can be used to determine the range of differences allowed by the term "about." Furthermore, all ranges in this disclosure are inclusive and composable, and references to values ​​within a range include every 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 this invention pertains; the terms used herein and / or include any and all combinations of one or more of the associated listed items.

[0069] Unless otherwise specified in the following examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0070] Polyvinyl alcohol (PVA) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., model number P909857; sodium alginate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., model number S817374; calcium chloride was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., model number C915443.

[0071] In the embodiments and comparative examples of this invention, the bacterial solution containing anaerobic digesting bacteria was obtained by acclimatization culture of activated sludge in a glucose-based medium (COD = 2000 mg / L). The activated sludge originated from an anaerobic digester in Taixing Industrial Park, Jiangsu Province. The activated sludge was acclimatized and cultured in plastic buckets at room temperature for one month, with the medium being replaced every week. The composition of the medium (g / L) was: C6H 12 The bacterial solution was prepared with 0.188 g / L glucose (O6), 0.382 g / L NH4Cl, 0.148 g / L KH2PO4, 0.08 g / L CaCl2, 0.02 g / L MgSO4·7H2O, and 2 g / L NaHCO3, resulting in a concentration of 10 g / L and a pH of 7.5 ± 0.2. The anaerobic digestive bacteria in the acclimated activated sludge included species such as Bacteroides, Clostridium, and Methanosaeta.

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

[0073] The present invention will be further illustrated below with reference to specific embodiments, but these embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. The essential features and significant effects of the present invention can be seen from the following embodiments. The described embodiments are some, but not all, embodiments of the present invention, and therefore do not limit the present invention in any way. Any non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are within 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 was prepared. The specific steps are as follows:

[0076] (1) Centrifuge 10 mL of a bacterial solution containing anaerobic digestive bacteria at 5000 rpm and 4℃ for 5 min. After removing the supernatant, add the solid precipitate to 100 mL of 3.0 wt% sodium alginate aqueous solution and disperse evenly to obtain a porous core embedding solution.

[0077] (2) The porous core embedding solution was incubated in a constant temperature incubator at 35℃ for 12h;

[0078] (3) 100 mL of porous core embedding solution was added dropwise to 500 mL of 3.0 wt% calcium chloride solution, and crosslinking was performed at 35 °C for 1 h to obtain porous core;

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

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

[0081] (6) The mixed embedding solution containing one porous core was added to 500 mL of 3.0 wt% calcium chloride solution in turn, and crosslinked at 25 °C for 20 h to obtain microbial immobilized particles with zero-valent iron shell.

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

[0083] Performance testing: Prepare a 1L water sample with a p-nitrophenol concentration of 100mg / L, add 20mL of the prepared zero-valent iron shell reinforced microbial immobilized particles, shake at room temperature, and replace the water sample with the same volume and concentration every 5 days of each cycle. Take a sample every 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) Centrifuge 20 mL of anaerobic digestive bacteria solution with a concentration of 10 g / L at 5000 rpm and 4℃ for 5 min. After removing the supernatant, add the solid precipitate to 100 mL of 3.0 wt% sodium alginate aqueous solution and disperse evenly to obtain a porous core embedding solution.

[0086] (2) The porous core embedding solution was incubated in a constant temperature incubator at 30℃ for 24h;

[0087] (3) 100 mL of porous core embedding solution was added dropwise to 500 mL of 1.0 wt% calcium chloride solution, and crosslinking treatment was carried out at 30 °C for 4 h to obtain porous core;

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

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

[0090] (6) Add the mixed embedding solution containing one porous core to 500 mL of saturated boric acid solution containing 3.0 wt% calcium chloride, and crosslink at 20 °C for 24 h to obtain microbial immobilized particles with zero-valent iron shell.

[0091] Example 3

[0092] (1) Centrifuge 20 mL of bacterial solution containing anaerobic digestive bacteria at 5000 rpm and 4℃ for 5 min, remove the supernatant, add the solid precipitate to 100 mL of 3.0 wt% polyvinyl alcohol aqueous solution, and disperse evenly to obtain microbial embedding solution.

[0093] (2) The porous core embedding solution was incubated in a constant temperature incubator at 30℃ for 24h;

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

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

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

[0097] (6) Add the mixed embedding solution containing 3 porous cores to 500 mL of saturated boric acid solution containing 3.0 wt% calcium chloride, and crosslink at 20 °C for 24 h to obtain microbial immobilized particles with 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) Centrifuge 10 mL of anaerobic digestive bacteria solution with a concentration of 10 g / L at 5000 rpm and 4℃ for 5 min. After removing the supernatant, add the solid precipitate to 100 mL of 3.0 wt% sodium alginate aqueous solution and disperse evenly to obtain microbial embedding solution.

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

[0102] Combination Figure 3In the comparative example, the traditional microbial immobilized particles prepared in this study showed a p-nitrophenol concentration of 70.19–86.10 mg / L on day 1 of the four treatment cycles, gradually decreasing thereafter, and remaining at 3.99–5.33 mg / L after 5 days of treatment, indicating that p-nitrophenol was not completely degraded. In contrast, the zero-valent iron-shell-reinforced microbial immobilized particles prepared in Example 1 showed a nitrophenol concentration of approximately 64.16 mg / L after day 1 of treatment in the first treatment cycle. After 4 days of treatment, p-nitrophenol in the water sample was almost completely degraded. In the second, third, and fourth cycles, p-nitrophenol was completely degraded after 3 days of treatment, and the 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 microbial immobilization particles prepared in Example 1 protects the microorganisms from adverse external environmental conditions and enhances the bioactivity of the microorganisms within the porous core. Furthermore, the biochemical activity of p-nitrophenol is improved through the zero-valent iron shell, allowing it to penetrate deeply into the microbial core for complete degradation. Therefore, degradation can be initiated rapidly in multiple cycles, resulting in better p-nitrophenol degradation. In contrast, the traditional microbial immobilization particles in this comparative example, lacking the reinforcement of zero-valent iron, have lower degradation efficiency, and the anaerobic digestive bacteria are more susceptible to external water environmental influences.

[0103] Comparative Example 2

[0104] (1) Centrifuge 10 mL of a bacterial solution containing anaerobic digestive bacteria at 5000 rpm and 4℃ for 5 min. After removing the supernatant, add the solid precipitate to 100 mL of 3.0 wt% sodium alginate aqueous solution and disperse evenly to obtain a porous core embedding solution.

[0105] (2) 100 mL of porous core embedding solution was added dropwise to 500 mL of 3.0 wt% calcium chloride solution, and crosslinking treatment was carried out at 35 °C for 1 h to obtain porous core;

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

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

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

[0109] The process is basically the same as in Example 1, except that the porous core embedding solution obtained in step (1) was not subjected to constant temperature incubation.

[0110] The performance tests were basically the same as in Example 1, except that the microbial immobilized particles with a zero-valent iron shell prepared in this comparative example were used and tested for 5 days.

[0111] Combination Figure 4 In the comparative example, the lack of isothermal incubation during the preparation of the zero-valent iron shell-reinforced microbial immobilized particles resulted in fewer pores in the porous core of the particles, preventing sufficient contact between p-nitrophenol and the microorganisms and leading to lower degradation efficiency. Therefore, compared to Example 1, the zero-valent iron shell-reinforced microbial immobilized particles prepared in Example 1 can rapidly initiate the degradation of PNP.

[0112] Comparative Example 3

[0113] (1) Centrifuge 10 mL of a bacterial solution containing anaerobic digestive bacteria at 5000 rpm and 4℃ for 5 min. After removing the supernatant, add the solid precipitate to 100 mL of 3.0 wt% sodium alginate aqueous solution and disperse evenly to obtain a porous core embedding solution.

[0114] (2) The porous core embedding solution was incubated in a constant temperature incubator at 35℃ for 12h;

[0115] (3) 100 mL of porous core embedding solution was added dropwise to 500 mL of 3.0 wt% calcium chloride solution, and crosslinking treatment was carried out at 40 °C for 12 h to obtain porous core;

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

[0117] (5) Add 100ml of porous inner core to 50mL of porous outer shell embedding solution to obtain mixed embedding solution;

[0118] (6) The mixed embedding solution containing one porous core was added to 500 mL of 3.0 wt% calcium chloride solution in turn, and crosslinked at 25 °C for 20 h to obtain microbial immobilized particles with zero-valent iron shell.

[0119] The process is basically the same as in Example 1, except that in step (3), the crosslinking treatment is carried out at 40°C for 12 hours to obtain a porous inner core.

[0120] The performance tests were basically the same as those of Comparative Example 2, except that the microbial immobilized particles with a zero-valent iron shell were prepared using this comparative example.

[0121] Combination Figure 4 In the comparative example, the preparation of the zero-valent iron shell-reinforced microbial immobilized particles involved a longer first cross-linking time and a higher temperature. This resulted in fewer pores in the porous core of the obtained zero-valent iron shell-reinforced microbial immobilized particles, preventing sufficient contact between p-nitrophenol and the microorganisms, thus leading to a lower degradation rate. Therefore, compared to Example 1, the zero-valent iron shell-reinforced microbial immobilized particles prepared in Example 1 achieve a higher PNP degradation rate.

[0122] Comparative Example 4

[0123] (1) Centrifuge 10 mL of a bacterial solution containing anaerobic digestive bacteria at 5000 rpm and 4℃ for 5 min. After removing the supernatant, add the solid precipitate to 100 mL of 3.0 wt% sodium alginate aqueous solution and disperse evenly to obtain a porous core embedding solution.

[0124] (2) The porous core embedding solution was incubated in a constant temperature incubator at 35℃ for 12h;

[0125] (3) 100 mL of porous core embedding solution was added dropwise to 500 mL of 3.0 wt% calcium chloride solution, and crosslinking was performed at 35 °C for 1 h to obtain porous core;

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

[0127] (5) Add 100ml of porous inner core to 50mL of porous outer shell embedding solution to obtain mixed embedding solution;

[0128] (6) The mixed embedding solution containing one porous core was added to 500 mL of 3.0 wt% calcium chloride solution in turn, and crosslinked at 25 °C for 20 h to obtain microbial immobilized particles with zero-valent iron shell.

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

[0130] The performance tests were basically the same as those of Comparative Example 2, except that the microbial immobilized particles with a zero-valent iron shell were prepared using this comparative example.

[0131] Combination Figure 4In the preparation of the zero-valent iron shell-reinforced microbial immobilized particles in this comparative example, the amount of nano-zero-valent iron added was relatively small. Therefore, the microbial immobilized particles in this comparative example showed poor activation of microorganisms and limited improvement in the biochemical activity of p-nitrophenol, which was detrimental to rapid initiation and efficient degradation. Thus, compared to Example 1, the zero-valent iron shell-reinforced microbial immobilized particles prepared in Example 1 can achieve rapid initiation and efficient degradation of PNP.

Claims

1. A method for preparing zero-valent iron shell reinforced microbial immobilized particles, characterized in that, The method comprises the following steps: S1. preparing a porous inner core embedding solution containing anaerobic digestion bacteria and a gelling agent; S2. culturing the porous inner core embedding solution obtained in step S1 in a constant temperature incubator for a period of time; S3. adding the porous inner core embedding solution obtained in step S2 to a crosslinking agent for primary crosslinking treatment to obtain a porous inner core; S4. preparing a porous outer shell embedding solution containing zero-valent iron and a gelling agent; the weight ratio of the zero-valent iron to the gelling agent is 5-10:5-15; S5. mixing the porous inner core obtained in step S3 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 a zero-valent iron shell reinforced microbial immobilized particle; In step S2, the culture time of the porous inner core embedding solution is 12-24 h, and the temperature is 30-35℃; In step S3, the primary crosslinking treatment time is 1-4 h, and the temperature is 30-35℃; The zero-valent iron shell reinforced microbial immobilized particle comprises a porous inner core and a porous outer shell coated on the outer surface of 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 outer shell comprises a porous organic gel and zero-valent iron embedded in the porous organic gel.

2. The method according to claim 1, wherein in step S6, the secondary crosslinking treatment time is 20-24 h, and the temperature is 20-25℃.

3. The method according to claim 2, wherein in steps S1 and S4, the gelling agent is one or both of sodium alginate and polyvinyl alcohol.

4. The method according to claim 3, wherein in steps S3 and S6, the crosslinking agent is one or both of a calcium chloride solution with a mass fraction of 0.5-4.0 wt% and a saturated boric acid solution containing calcium chloride with a mass fraction of 0.5-4.0 wt% of calcium chloride.

5. The method according to any one of claims 1-4, wherein in step S1, the weight ratio of the anaerobic digestion bacteria to the gelling agent is 1-2:20-30; 6. The method according to claim 5, wherein the zero-valent iron is one or both of nano zero-valent iron and micro zero-valent iron.

7. The method according to claim 6, wherein the porous organic gel is obtained by crosslinking polymerization of at least one of sodium alginate and polyvinyl alcohol.

8. The method according to claim 7, wherein the particle size of the porous inner core is 3-5 mm. ​ ​ ​ ​ ​ ​ ​ ​ 9. Use of the zero-valent iron-coated microbial immobilized granules prepared according to the method of any one of claims 1 to 8 for the treatment of organic waste water.

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