A zero-valent iron-microorganism nested coupling immobilization particle and its preparation and application

Abstract

The present invention discloses a zero-valent iron-microorganism nested coupling immobilized particle and its preparation and application, belonging to the technical field of wastewater treatment. The preparation method embeds zero-valent iron and anaerobic digestion bacteria in an organic porous gel in turn through two-step embedding and cross-linking, and improves the separation performance of the porous particle core and the porous shell, which is conducive to reducing the loss of zero-valent iron. The porous particle core and the porous shell are separated structures, which is conducive to the separation and recovery of the porous particle core, and then reused through embedding and cross-linking, effectively reducing the degradation cost of biodegradable organic matter, and improving the economy and environmental protection of the zero-valent iron-microorganism coupling system.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically to a zero-valent iron-microorganism nested coupling immobilized particle and its preparation and application. Background Art

[0002] Organic wastewater has a wide range of sources and complex components. Direct discharge will cause eutrophication of water bodies and reduce the self-purification capacity of water bodies. Among the many methods for treating organic wastewater, biological methods have long been favored due to their economy and thoroughness, and have become the preferred technology for treating organic wastewater. However, since there are fewer organic substances in low-biodegradable organic wastewater that can be degraded by microorganisms, a single biological method is prone to problems such as low treatment efficiency and large performance fluctuations, and it is difficult to adapt to complex and changeable practical application scenarios.

[0003] In order to overcome the shortcomings of conventional biological treatment methods, researchers have introduced chemical materials into biological systems to enhance biological processes, thereby constructing biochemical coupling systems to improve the performance of biological methods in the treatment of low-biodegradable organic wastewater. Among them, zero-valent iron has been shown to have a significant microbial synergistic enhancement effect in the treatment of low-biodegradable organic wastewater. Zero-valent iron not only improves the biodegradability of organic wastewater through physical and chemical processes, but also enhances biological processes by supplementing electron donors, improving biological activity and regulating community structure. However, adding powdered zero-valent iron directly to the bioreactor will also bring a series of problems. First, the biological toxicity of zero-valent iron may cause the start-up cycle of the biological process to be too long; second, the high loss of zero-valent iron makes it difficult to recover, which increases the cost of remediation of organic wastewater. Therefore, the development of a zero-valent iron-microorganism coupling process with low biological toxicity, recyclable and reusable zero-valent iron and stable performance is of great significance for the treatment of organic wastewater, especially low-biodegradable organic wastewater.

[0004] The Chinese patent with publication number CN116715373A discloses a physicochemical-biochemical treatment method for high-concentration organic wastewater. By attaching nano zero-valent iron and microorganisms to modified activated carbon fibers, the electron transfer in the coupling system is strengthened, but the loss of zero-valent iron and microorganisms has not been effectively solved. The Chinese patent with authorization announcement number CN110317801B discloses an immobilized quorum sensing quenching sterilization composite gel sphere and its preparation method and application. The preparation method is: polyvinyl alcohol, sodium alginate, powdered activated carbon and water are mixed, and then mixed with quorum sensing quenching sterilization bacterial suspension, the obtained mixture is first cross-linked with an aqueous solution of boric acid and calcium chloride to obtain gel spheres, and then the gel spheres are second cross-linked with a sodium sulfate solution to obtain composite gel spheres; however, the gel spheres in the composite gel spheres obtained by cross-linking this method cannot be separated and recycled repeatedly. Summary of the invention

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

[0006] In view of the deficiency that zero-valent iron in the zero-valent iron-microorganism coupling system in the prior art is difficult to recycle and reuse, a zero-valent iron-microorganism nested coupling immobilization particle and a preparation method thereof 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 zero-valent iron-microorganism nested coupling immobilized particles of the present invention comprises the following steps:

[0010] S1. preparing a zero-valent iron core embedding solution containing zero-valent iron and a gelling agent;

[0011] S2. adding the zero-valent iron core embedding solution obtained in step S1 to a cross-linking agent for a primary cross-linking treatment to obtain a porous particle core;

[0012] S3. Freezing the porous particle core obtained in step S2;

[0013] S4. preparing a microbial shell embedding solution containing anaerobic digestion bacteria and a gelling agent;

[0014] S5. mixing the frozen porous particle core obtained in step S3 with the microorganism shell embedding solution obtained in step S4 to obtain a mixed embedding solution having a porous particle core;

[0015] S6. adding the mixed embedding solution obtained in step S5 to a crosslinking agent for secondary crosslinking treatment to obtain zero-valent iron-microorganism nested coupling immobilized particles;

[0016] Wherein, in step S2, the time of the primary cross-linking treatment is 6 to 24 hours, and the temperature is 20 to 25° C.;

[0017] In step S6, the secondary cross-linking treatment is performed for 1 to 4 hours at a temperature of 30 to 35°C.

[0018] Specifically, the time of the primary cross-linking treatment can be 6 to 8 hours, 6 to 12 hours, 6 to 18 hours or 6 to 24 hours.

[0019] It should be noted that in step S3, the inner core of the porous particle is frozen to achieve increased mechanical strength and core-shell separation.

[0020] Furthermore, in step S3, the porous particle core is frozen for 12 to 24 hours at a temperature of -20 to -18°C.

[0021] It should be noted that controlling the freezing conditions within the above range is beneficial for the porous particle core to obtain better mechanical strength and core-shell separation performance.

[0022] Specifically, the freezing time of the porous particle core can be 12 to 24 hours, 12 to 16 hours, 12 to 20 hours or 12 to 24 hours.

[0023] Furthermore, in step S1, the mass ratio of the zero-valent iron to the gelling agent is 10-20:20-40.

[0024] It should be noted that controlling and increasing the zero-valent iron content in the porous particle core is beneficial to extending the service life of the porous particle core.

[0025] Specifically, the mass ratio of the zero-valent iron to the gelling agent may be 10-20:20-25, 10-20:20-30, 10-20:20-35 or 10-20:20-40.

[0026] Furthermore, in step S4, the mass ratio of the anaerobic digestion bacteria to the gelling agent is 1-2:5-15.

[0027] Furthermore, in step S5, the volume ratio of the porous particle core to the microorganism shell embedding solution is 100-150:50-75.

[0028] Furthermore, in step S1 and step S4, the gelling agent is one or both of sodium alginate and polyvinyl alcohol.

[0029] Furthermore, the gelling agent is added in the form of an aqueous solution of the gelling agent.

[0030] Furthermore, the concentration of sodium alginate in the sodium alginate aqueous solution is 1.0-3.0wt%;

[0031] The concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 1.0-3.0 wt %.

[0032] Furthermore, in step S2 and step S6, the cross-linking agent is one or both of a calcium chloride solution and a saturated boric acid solution containing calcium chloride.

[0033] Further, the concentration of the calcium chloride solution is 0.5-4.0wt%;

[0034] The concentration of calcium chloride in the saturated boric acid solution containing calcium chloride is 0.5-4.0wt%.

[0035] Furthermore, in step S1, the zero-valent iron is one or both of nano-zero-valent iron and micron-zero-valent iron.

[0036] Furthermore, step S1 may specifically include: adding zero-valent iron into the aqueous solution of the gelling agent and stirring evenly to obtain a zero-valent iron core embedding solution.

[0037] Furthermore, in step S2, the zero-valent iron core embedding solution is added to the cross-linking agent by dropwise addition.

[0038] Furthermore, the dripping method can be dropwise addition.

[0039] For example, dropwise addition can be performed using a syringe.

[0040] Furthermore, step S4 may specifically include: adding anaerobic digestion bacteria into the aqueous solution of the gelling agent and stirring evenly to obtain a microorganism shell embedding solution.

[0041] Furthermore, the anaerobic digestion bacteria can be obtained by the following method:

[0042] The anaerobic digestion bacteria are obtained by centrifuging the bacterial liquid containing the anaerobic digestion bacteria to obtain a solid precipitate.

[0043] Specifically, the bacterial solution containing anaerobic digestion bacteria is centrifuged at 5000 rpm and 4°C for 5 minutes, and after removing the supernatant, the solid precipitate, i.e., the anaerobic digestion bacteria, is collected;

[0044] The concentration of anaerobic digestion bacteria in the bacterial solution can be 10-20 g / L.

[0045] Furthermore, in step S5, the porous particle core and the microorganism shell embedding solution are mixed by dropping the microorganism shell embedding solution into the porous particle core or adding the porous particle core into the microorganism shell embedding solution.

[0046] The present invention also provides a zero-valent iron-microorganism nested coupling immobilization particle prepared by the above preparation method,

[0047] It comprises a porous particle inner core and a porous outer shell, wherein the porous particle inner core is nested in the porous outer shell;

[0048] The inner core of the porous particle comprises a porous organic gel and zero-valent iron, and the zero-valent iron is embedded in the porous organic gel;

[0049] The porous shell comprises a porous organic gel and anaerobic digestion bacteria, and the anaerobic digestion bacteria are embedded in the porous organic gel.

[0050] It should be noted that there are a number of holes in the inner core and the outer shell of the porous particle.

[0051] Furthermore, the porous organic gel is obtained by cross-linking polymerization of a gelling agent.

[0052] The gelling agent is one or both of sodium alginate and polyvinyl alcohol.

[0053] Furthermore, the particle size of the inner core of the porous particle is 3-5 mm.

[0054] Furthermore, the particle size of the zero-valent iron-microorganism nested coupling immobilization particles can be regulated according to the number of porous particle cores.

[0055] The present invention also provides a zero-valent iron-microorganism nested coupling immobilized particle prepared by the above preparation method or the use of the zero-valent iron-microorganism nested coupling immobilized particle in treating organic wastewater.

[0056] Furthermore, the organic wastewater contains at least one organic substance selected from the group consisting of p-nitrophenol, sulfamethoxazole, and 2,4-dichlorophenol.

[0057] 3. Beneficial effects

[0058] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0059] (1) The preparation method of zero-valent iron-microorganism nested coupling immobilized particles provided by the present invention is to embed zero-valent iron and anaerobic digestion bacteria in an organic porous gel in sequence through two-step embedding and cross-linking. The longer the cross-linking time, the greater the mechanical strength of the particles. The different cross-linking times of the porous particle core formed by the first cross-linking treatment and the porous shell formed by the second cross-linking treatment result in differences in the mechanical strength of the two. At the same time, the freezing of the porous particle core further enhances its mechanical strength, thereby improving the performance of core-shell separation.

[0060] Moreover, the cross-linking temperature of the inner core and the outer shell will also cause different gelation rates, which is conducive to the formation of a core-shell separation structure and a separation structure of a porous particle inner core and a porous outer shell.

[0061] (2) The zero-valent iron-microorganism nested coupling immobilized particles provided by the present invention include a porous particle core and a porous shell nested outside the porous particle core, wherein the porous particle core includes a porous organic gel and zero-valent iron, and the zero-valent iron is embedded in the porous organic gel, and the porous shell includes a porous organic gel and anaerobic digestion bacteria, and the anaerobic digestion bacteria are embedded in the porous organic gel. By embedding zero-valent iron in the porous particle core, the loss of zero-valent iron is reduced. The porous particle core and the porous shell are separated structures, and the porous particle core can be separated and recovered, and then reused through embedding and cross-linking, which effectively reduces the degradation cost of low-biodegradable organic matter, improves the economy and environmental protection of the zero-valent iron-microorganism coupling system, and can also obtain a longer-term and more stable organic matter removal effect than the immobilization of microorganisms or zero-valent iron alone.

[0062] (3) The zero-valent iron-microorganism nested coupling immobilized particles provided by the present invention have a core-shell structure, and the porous shell contains anaerobic digestion bacteria, so that the iron element and electrons of the zero-valent iron in the core of the porous particles need to pass through the porous shell containing the microorganisms for transfer and exchange, thereby enhancing the biological targeted regulation effect of zero-valent iron and avoiding direct contact between zero-valent iron and anaerobic digestion bacteria, reducing the biological toxicity of zero-valent iron, and effectively enhancing the positive regulation and positive stimulation of zero-valent iron on microorganisms.

[0063] (4) The particle size of the zero-valent iron-microorganism nested coupling immobilization particles provided by the present invention can be controlled by changing the number of porous particle cores containing zero-valent iron, which can meet the needs of application scenarios of different sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a schematic diagram of the preparation method of zero-valent iron-microorganism nested coupling immobilized particles in an embodiment of the present invention;

[0065] Figure 2 This is a graph showing the degradation performance results of p-nitrophenol (PNP) in the performance tests in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0066] 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.

[0067] 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.

[0068] 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".

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] The bacterial liquid containing anaerobic digestion bacteria used in the embodiments and comparative examples of the present invention is obtained by culturing activated sludge in a glucose-based medium (COD=2000 mg / L), 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): C6H 12 O6 (glucose) 0.188 g / L, NH4Cl 0.382 g / L, KH2PO4 0.148 g / L, CaCl2 0.08 g / L, MgSO4·7H2O 0.02 g / L, NaHCO3 2.0 g / L, pH 7.5±0.2, the concentration of the bacterial solution obtained by acclimation culture is 10 g / L. The anaerobic digestion bacteria in the bacterial solution include Bacteroides , Clostridium and Methanosaeta And other dominant functional bacterial genera.

[0076] 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.

[0077] The present invention is further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. The essential features and significant effects of the present invention can be reflected in the following examples, and the described examples are part of the embodiments of the present invention, rather than all of the embodiments, and therefore, they do not limit the present invention in any way. Those skilled in the art may 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.

[0078] Example 1

[0079] Combination Figure 1 In this embodiment, a zero-valent iron-microorganism nested coupling immobilization particle is prepared, and the specific steps are as follows:

[0080] (1) Add 1 g of nano-zero-valent iron into 100 mL of 2.0 wt% sodium alginate aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0081] (2) 100 mL of zero-valent iron core embedding solution was added dropwise into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 20 °C for 6 h to obtain a porous particle core;

[0082] (3) Freezing the obtained porous particle core at -20°C for 12 h;

[0083] (4) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 50 mL of a 2.0 wt% sodium alginate aqueous solution to obtain a microbial shell embedding solution;

[0084] (5) Add 100 mL of the frozen porous particle core into 50 mL of the microbial shell embedding solution to obtain a mixed embedding solution with a porous particle core;

[0085] (6) The mixed embedding solution containing one porous particle core was added gradually into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 30 °C for 1 h to obtain zero-valent iron-microorganism nested coupling immobilized particles.

[0086] The particle size of the zero-valent iron-microorganism nested coupling immobilized particles prepared in this embodiment is about 4 mm. Combined with Table 1, the zero-valent iron-microorganism nested coupling immobilized particles prepared in this embodiment have good particle core mechanical strength and core-shell separation performance.

[0087] Pollutant degradation performance test: Prepare 1L of water sample with a p-nitrophenol concentration of 100 mg / L, add the prepared zero-valent iron-microorganism nested coupling immobilization particles, and the dosage is 20mL. Oscillate at room temperature, replace the water sample with the same volume and concentration every 5 days for a total of four cycles, take samples every 1 day to measure the p-nitrophenol concentration in the water sample, and calculate the degradation rate.

[0088] Particle core integrity performance test: Place 50 porous particle cores obtained in step (2) in a 100 mL vial and run at 35°C and 100 rpm for 3 days. After the run, the particle core integrity of the particles is measured to determine the mechanical strength of the porous particle core, where particle core integrity = number of intact cores / 50.

[0089] Core-shell separation efficiency performance test: 50 zero-valent iron-microorganism nested coupled immobilized particles obtained in step (6) were placed in a 100 mL syringe bottle and operated at 35°C and 150 rpm for 3 days. After the operation, the core-shell separation performance of the nested coupled immobilized particles was characterized by the degree of shell peeling and the integrity of the inner core of the particles. Among them, the core-shell separation efficiency = the number of particles that achieved core-shell separation / 50. The evaluation criteria for achieving core-shell separation are: the outer shell is detached and the inner core is intact.

[0090] According to the test, the integrity of the inner core of the porous particle prepared in this embodiment is 92%, and the core-shell separation efficiency of the zero-valent iron-microorganism nested coupling immobilized particle is 94%.

[0091] Example 2

[0092] (1) Add 2 g of nano-zero-valent iron into 100 mL of 3.0 wt% polyvinyl alcohol aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0093] (2) 100 mL of zero-valent iron core embedding solution was added dropwise into 500 mL of saturated boric acid solution containing 4.0 wt% calcium chloride, and cross-linked at 25 °C for 24 h to obtain a porous particle core;

[0094] (3) Freezing the obtained porous particle core at -20°C for 24 h;

[0095] (4) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 50 mL of a 3.0 wt% polyvinyl alcohol aqueous solution to obtain a microbial shell embedding solution;

[0096] (5) Add 100 mL of the porous particle core into 50 mL of the microbial shell embedding solution to obtain a mixed embedding solution with the porous particle core;

[0097] (6) The mixed embedding solution containing two porous particle cores was added successively into 500 mL of a saturated boric acid solution containing 3.0 wt % calcium chloride, and cross-linked at 35 °C for 4 h to obtain zero-valent iron-microorganism nested coupling immobilized particles.

[0098] The zero-valent iron-microorganism nested coupling immobilization particles prepared in this example have a separation structure.

[0099] Example 3

[0100] (1) Add 1 g of micron zero-valent iron into 100 mL of 3.0 wt% polyvinyl alcohol aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0101] (2) 100 mL of the zero-valent iron core embedding solution was added dropwise into 500 mL of a 1.0 wt% saturated boric acid solution containing calcium chloride, and cross-linked at 25 °C for 12 h to obtain a porous particle core;

[0102] (3) freezing the obtained porous particle core at -18 °C for 18 h;

[0103] (4) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 75 mL of a 3.0 wt% polyvinyl alcohol aqueous solution to obtain a microbial shell embedding solution;

[0104] (5) Add 100 mL of the porous particle core into 75 mL of the microbial shell embedding solution to obtain a mixed embedding solution with the porous particle core;

[0105] (6) The mixed embedding solution containing one porous particle core was added to 500 mL of a 1.0 wt% saturated boric acid solution containing calcium chloride, and cross-linked at 35 °C for 4 h to obtain zero-valent iron-microorganism nested coupling immobilized particles.

[0106] Example 4

[0107] The porous particle core of the zero-valent iron-microorganism nested coupling immobilization particle after the pollutant degradation performance test in Example 1 is recovered to prepare the zero-valent iron-microorganism nested coupling immobilization particle

[0108] The method is basically the same as (3), (4), (5) and (6) in Example 1, except that the recycled porous particle core is used.

[0109] Finally, zero-valent iron-microorganism nested coupling immobilized particles-HS were obtained.

[0110] The core-shell separation efficiency performance test was basically the same as in Example 1, except that the zero-valent iron-microorganism nested coupling immobilization particles-HS prepared in this example were used; the particle core integrity performance test was not performed.

[0111] Combined with Table 1, the core-shell separation efficiency of the zero-valent iron-microorganism nested coupling immobilization particles prepared using the recycled porous particle core in this embodiment is 90%, which is basically the same as the core-shell separation of the zero-valent iron-microorganism nested coupling immobilization particles prepared in Example 1, and still has good core-shell separation.

[0112] Comparative Example 1

[0113] This comparative example prepared a microbial immobilized particle, and the specific steps are as follows:

[0114] (1) preparing 100 mL of 2.0 wt% sodium alginate aqueous solution to obtain an inner core embedding solution without any loading material;

[0115] (2) 100 mL of the core embedding solution was added dropwise into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 20 °C for 6 h to obtain a porous particle core;

[0116] (3) Freezing the obtained porous particle core at -20°C for 12 h;

[0117] (4) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 50 mL of a 2.0 wt% sodium alginate aqueous solution to obtain a microbial shell embedding solution;

[0118] (5) Add 100 mL of the frozen porous particle core into 50 mL of the microbial shell embedding solution to obtain a mixed embedding solution with a porous particle core;

[0119] (6) The mixed embedding solution containing one porous particle core was added gradually into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 30 °C for 1 h to obtain microbial immobilized particles.

[0120] The pollutant degradation performance test was the same as in Example 1, except that the microbial immobilized particles prepared in this example were used.

[0121] Combination Figure 2 In the first treatment cycle, the concentration of p-nitrophenol in the water sample of the microbial immobilized particles prepared in this comparative example dropped to 86.09 mg / L on the first day, and then gradually decreased. After 5 days of treatment, the concentration of p-nitrophenol dropped to 5.34 mg / L; and in the second, third and fourth treatment cycles, the concentration change trend of p-nitrophenol in the water sample was roughly the same. In the first treatment cycle, the concentration of p-nitrophenol in the water sample of the zero-valent iron-microorganism nested coupling immobilized particles prepared in Example 1 dropped to 46.47 mg / L on the first day, and dropped to 0 after 4 days of treatment. In the second, third and fourth treatment cycles, the concentration of p-nitrophenol in the water sample on the first day was basically stable and dropped to about 30 mg / L, and the concentration of p-nitrophenol in the water sample on the third day was dropped to 0. This is because the inner core of the microbial immobilized particles prepared in this comparative example does not contain zero-valent iron, and lacks the regulation and stimulation of zero-valent iron on microorganisms, resulting in low degradation efficiency; on the other hand, the porous shell of the zero-valent iron-microorganism nested coupling immobilized particles prepared in Example 1 contains anaerobic digestion bacteria, and the inner core of the porous particles contains zero-valent iron. The iron element and electrons of the zero-valent iron need to pass through the porous shell containing the microbial anaerobic digestion bacteria for transfer and exchange, which enhances the biological targeted regulation effect of zero-valent iron, and the zero-valent iron is not in direct contact with the anaerobic digestion bacteria, which reduces the biological toxicity of zero-valent iron and effectively enhances the positive regulation and positive stimulation of zero-valent iron on microorganisms, so it has more efficient and stable p-nitrophenol removal performance in multiple cycle operation cycles.

[0122] Comparative Example 2

[0123] In this comparative example, a zero-valent iron immobilized particle was prepared, and the specific steps were as follows:

[0124] (1) Add 1 g of nano-zero-valent iron into 100 mL of 2.0 wt% sodium alginate aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0125] (2) 100 mL of zero-valent iron core embedding solution was added dropwise into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 20 °C for 6 h to obtain a porous particle core;

[0126] (3) Freezing the obtained porous particle core at -20°C for 12 h;

[0127] (4) preparing 50 mL of 2.0 wt% sodium alginate aqueous solution to obtain a shell embedding solution without any loading material;

[0128] (5) Add 100 mL of the frozen porous particle core into 50 mL of the shell embedding solution to obtain a mixed embedding solution with a porous particle core;

[0129] (6) The mixed embedding solution containing one porous particle core was added successively into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 30 °C for 1 h to obtain zero-valent iron immobilized particles.

[0130] The pollutant degradation performance test was the same as in Example 1, except that the zero-valent iron immobilized particles prepared in this example were used.

[0131] Combination Figure 2 , in the first treatment cycle, the concentration of p-nitrophenol in the water sample of the zero-valent iron immobilized particles prepared in this comparative example dropped to 64.11 mg / L after 5 days of treatment; and, in the four treatment cycles, the concentration of p-nitrophenol in the final water sample gradually increased after 5 days of treatment. This is because the porous shell of the zero-valent iron immobilized particles prepared in this comparative example does not contain anaerobic digestion bacteria, so it can only be degraded by the zero-valent iron in the core of the porous particles, and the degradation effect is very poor. As the reaction proceeds, the surface of the zero-valent iron gradually passivates, and the degradation effect gradually deteriorates; the zero-valent iron-microorganism nested coupling immobilized particles prepared in Example 1 strengthen the biological targeted regulation effect of zero-valent iron and the positive regulation and positive stimulation of zero-valent iron on microorganisms. At the same time, anaerobic digestion bacteria can inhibit the gradual passivation of zero-valent iron, resulting in the zero-valent iron-microorganism nested coupling immobilized particles having more efficient and stable p-nitrophenol removal performance in multiple cycle operation cycles.

[0132] Comparative Example 3

[0133] This comparative example prepared a zero-valent iron-microorganism nested coupling immobilization particle, and the specific steps are as follows:

[0134] (1) Add 1 g of nano-zero-valent iron into 100 mL of 2.0 wt% sodium alginate aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0135] (2) 100 mL of zero-valent iron core embedding solution was added dropwise into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 35 °C for 0.5 h to obtain a porous particle core;

[0136] (3) Freezing the obtained porous particle core at -20°C for 12 h;

[0137] (4) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 50 mL of a 2.0 wt% sodium alginate aqueous solution to obtain a microbial shell embedding solution;

[0138] (5) Add 100 mL of the frozen porous particle core into 50 mL of the microbial shell embedding solution to obtain a mixed embedding solution with a porous particle core;

[0139] (6) The mixed embedding solution containing one porous particle core was added gradually into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 30 °C for 1 h to obtain zero-valent iron-microorganism nested coupling immobilized particles.

[0140] The method is basically the same as Example 1, except that in step (2), a cross-linking treatment is performed at 35° C. for 0.5 h to obtain a porous particle core.

[0141] The particle core integrity performance test and the core-shell separation efficiency performance test were basically the same as those in Example 1, except that the zero-valent iron-microorganism nested coupling immobilization particles prepared in this comparative example were used.

[0142] Combined with Table 1, the particle core integrity of the porous particle core prepared in this comparative example is 40%, and the core-shell separation efficiency of the zero-valent iron-microorganism nested coupling immobilization particles is 24%. The mechanical strength and core-shell separation of the porous particle core of the zero-valent iron-microorganism nested coupling immobilization particles prepared in this comparative example are lower than those of the zero-valent iron-microorganism nested coupling immobilization particles prepared in Example 1.

[0143] Comparative Example 4

[0144] This comparative example prepared a zero-valent iron-microorganism nested coupling immobilization particle, and the specific steps are as follows:

[0145] (1) Add 1 g of nano-zero-valent iron into 100 mL of 2.0 wt% sodium alginate aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0146] (2) 100 mL of zero-valent iron core embedding solution was added dropwise into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 20 °C for 6 h to obtain a porous particle core;

[0147] (3) Freezing the obtained porous particle core at -20°C for 12 h;

[0148] (4) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 50 mL of a 2.0 wt% sodium alginate aqueous solution to obtain a microbial shell embedding solution;

[0149] (5) Add 100 mL of the frozen porous particle core into 50 mL of the microbial shell embedding solution to obtain a mixed embedding solution with a porous particle core;

[0150] (6) The mixed embedding solution containing one porous particle core was added gradually into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 20 °C for 12 h to obtain zero-valent iron-microorganism nested coupling immobilized particles.

[0151] The method is basically the same as Example 1, except that in step (6), cross-linking is performed at 20° C. for 12 h to obtain a porous particle core.

[0152] The particle core integrity performance test and the core-shell separation efficiency performance test were basically the same as those in Example 1, except that the zero-valent iron-microorganism nested coupling immobilization particles prepared in this comparative example were used.

[0153] Combined with Table 1, the particle core integrity of the porous particle core prepared in this comparative example is 88%, and the core-shell separation efficiency of the zero-valent iron-microorganism nested coupling immobilized particles is 56%. The zero-valent iron-microorganism nested coupling immobilized particles prepared in this comparative example and Example 1 have little difference in the mechanical strength of the porous particle core, but the core-shell separation performance is lower than the zero-valent iron-microorganism nested coupling immobilized particles prepared in Example 1.

[0154] Comparative Example 5

[0155] This comparative example prepared a zero-valent iron-microorganism nested coupling immobilization particle, and the specific steps are as follows:

[0156] (1) Add 1 g of nano-zero-valent iron into 100 mL of 2.0 wt% sodium alginate aqueous solution and stir evenly to obtain a zero-valent iron core embedding solution;

[0157] (2) 100 mL of zero-valent iron core embedding solution was added dropwise into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 20 °C for 6 h to obtain a porous particle core;

[0158] (3) Centrifuge 10 mL of a 10 g / L bacterial solution containing anaerobic digestion bacteria at 5000 rpm and 4 °C for 5 min, collect the solid precipitate and add it to 50 mL of a 2.0 wt% sodium alginate aqueous solution to obtain a microbial shell embedding solution;

[0159] (4) Add 100 mL of the porous particle core into 50 mL of the microbial shell embedding solution to obtain a mixed embedding solution with the porous particle core;

[0160] (5) The mixed embedding solution containing one porous particle core was added gradually into 500 mL of 1.0 wt% calcium chloride solution and cross-linked at 30 °C for 1 h to obtain zero-valent iron-microorganism nested coupling immobilized particles.

[0161] The process is basically the same as Example 1, except that the porous particle core obtained in step (2) is not subjected to freezing treatment.

[0162] The particle core integrity performance test and the core-shell separation efficiency performance test were basically the same as those in Example 1, except that the zero-valent iron-microorganism nested coupling immobilization particles prepared in this comparative example were used.

[0163] Combined with Table 1, the particle core integrity of the porous particle core prepared in this comparative example is 32%, and the core-shell separation efficiency of the zero-valent iron-microorganism nested coupling immobilized particles is 28%. The mechanical strength and core-shell separation of the porous particle core of the zero-valent iron-microorganism nested coupling immobilized particles prepared in this comparative example are lower than those of the zero-valent iron-microorganism nested coupling immobilized particles prepared in Example 1.

[0164] Table 1 Performance test results of zero-valent iron-microorganism nested coupling immobilization particles prepared in different embodiments and comparative examples

[0165]

Claims

1. A method for preparing zero-valent iron-microorganism nested coupling immobilized particles, characterized in that: The following steps are involved: S1. preparing a zero-valent iron core embedding solution containing zero-valent iron and a gelling agent; S2. adding the zero-valent iron core embedding solution obtained in step S1 to a cross-linking agent for a primary cross-linking treatment to obtain a porous particle core; S3. Freezing the porous particle core obtained in step S2; S4. preparing a microbial shell embedding solution containing anaerobic digestion bacteria and a gelling agent; S5. mixing the frozen porous particle core obtained in step S3 with the microorganism shell embedding solution obtained in step S4 to obtain a mixed embedding solution having a porous particle core; S6. adding the mixed embedding solution obtained in step S5 to a crosslinking agent for secondary crosslinking treatment to obtain zero-valent iron-microorganism nested coupling immobilized particles; Wherein, in step S2, the time of the primary cross-linking treatment is 6 to 24 hours, and the temperature is 20 to 25° C.; In step S6, the secondary cross-linking treatment is performed for 1 to 4 hours at a temperature of 30 to 35° C. In step S1, the mass ratio of the zero-valent iron to the gelling agent is 10-20:20-40; In step S4, the mass ratio of the anaerobic digestion bacteria to the gelling agent is 1-2:5-15; In step S5, the volume ratio of the porous particle core to the microorganism shell embedding solution is 100-150:50-75.

2. The method for preparing zero-valent iron-microorganism nested coupling immobilized particles according to claim 1, characterized in that: In step S3, the porous particle core is frozen for 12 to 24 hours at a temperature of -20 to -18°C.

3. The method for preparing zero-valent iron-microorganism nested coupling immobilized particles according to claim 1, 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 zero-valent iron-microorganism nested coupling immobilized particles according to claim 3, characterized in that: In step S2 and step S6, the cross-linking agent is one or both of a calcium chloride solution and a saturated boric acid solution containing calcium chloride.

5. The method for preparing zero-valent iron-microorganism nested coupling immobilized particles according to claim 4, characterized in that: In step S1, the zero-valent iron is one or both of nano-zero-valent iron and micron-zero-valent iron.

6. A zero-valent iron-microorganism nested coupling immobilization particle prepared by the preparation method according to any one of claims 1 to 5, characterized in that: It comprises a porous particle inner core and a porous outer shell, wherein the porous particle inner core is nested in the porous outer shell; The inner core of the porous particle comprises a porous organic gel and zero-valent iron, and the zero-valent iron is embedded in the porous organic gel; The porous shell comprises a porous organic gel and anaerobic digestion bacteria, and the anaerobic digestion bacteria are embedded in the porous organic gel.

7. The zero-valent iron-microorganism nested coupling immobilization particle according to claim 6, characterized in that: The porous organic gel is obtained by cross-linking polymerization of a gelling agent. The gelling agent is one or both of sodium alginate and polyvinyl alcohol.

8. The zero-valent iron-microorganism nested coupling immobilization particle according to claim 7, characterized in that: The particle size of the porous particle core is 3~5 mm.

9. Use of the zero-valent iron-microorganism nested coupling immobilized particles as described in any one of claims 6 to 8 in treating organic wastewater.

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