Modified-zeolite-immobilized algae ball, preparation method therefor, and use thereof

Abstract

Provided are a modified-zeolite-immobilized algae ball, a preparation method therefor, and a use thereof. The modified-zeolite-immobilized algae ball uses sodium bicarbonate and chitosan to modify zeolite, and subsequently immobilizes the modified zeolite and chlorella in an embedding gel ball so as to achieve immobilization of the algae ball.

Description

Modified zeolite immobilized algae balls and their preparation method and application

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202311653214.4, filed on December 4, 2023, entitled “Modified zeolite immobilized algae balls, preparation methods and applications thereof,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of wastewater treatment, and in particular to a modified zeolite-immobilized algae ball and a preparation method and application thereof. Background Art

[0004] With the rapid development of social economy and the continuous improvement of people's living standards, people's demand for the quality of livestock and poultry products has continued to increase, which has further promoted the high-quality development of related aquaculture industries. The tail water of the breeding base after high-density breeding contains a large amount of NH4 + -N, organic matter, NO3 - -N and other pollutants. Therefore, if the tail water is not treated and discharged directly, the water quality in the local area will deteriorate and the dissolved oxygen concentration in the water body will decrease.

[0005] Research has shown that Chlorella has a high removal efficiency for pollutants such as nitrogen and phosphorus in water. Chlorella can photosynthesize nutrients in wastewater, synthesizing cellular substances while releasing oxygen. However, due to its tiny size, direct wastewater treatment suffers from poor impact resistance, high risk of loss, and difficulty in harvesting, making it unsuitable for water quality treatment. Encapsulation and immobilization technology can encapsulate Chlorella in spheres, but limited mass transfer results in a low degradation efficiency for nitrogen and phosphorus pollutants in water. Furthermore, long-term use can lead to leakage of some algal cells, resulting in high toxicity to microorganisms.

[0006] Zeolite has a large specific surface area, strong electrostatic force and dispersion force, and strong adsorption performance. In addition, the lattice of zeolite contains K + 、Na + , Ca 2+ Ions can exchange with other cations in the solution without affecting the stability of the zeolite structure. The adsorption and cation exchange properties of zeolite make it + -N has excellent absorption effect. In practical applications, zeolite is often crushed to micron level to give full play to the adsorption effect of zeolite, but too small particle size makes it difficult to settle quickly and difficult to separate from wastewater, resulting in an increase in corresponding treatment time and cost. In addition, zeolite has a strong effect on NO3 --N has a poor adsorption capacity, and its removal potential for total phosphorus (TP), chemical oxygen demand (COD) and total nitrogen (TN) needs to be further developed.

[0007] Summary of the Invention

[0008] According to various embodiments of the present application, a modified zeolite-immobilized algae ball and a preparation method and application thereof are provided.

[0009] In a first aspect of the present application, a method for preparing modified zeolite-immobilized algae pellets is provided, comprising the following steps:

[0010] obtaining a porous zeolite;

[0011] Mixing the porous zeolite with a mixed solution of chitosan, glacial acetic acid and water to prepare a chitosan-modified porous zeolite; and

[0012] The chitosan-modified porous zeolite is mixed with an embedding agent, chlorella, and a cross-linking agent to prepare the modified zeolite-immobilized algae ball.

[0013] In one embodiment, the chitosan comprises at least one of the following characteristics:

[0014] (1) Deacetylation degree ≥95%;

[0015] (2) Viscosity is 100mpas-200mpas.

[0016] In one embodiment, the preparation of the chitosan-modified porous zeolite satisfies at least one of the following conditions:

[0017] (1) The mass fraction of the chitosan in the mixed solution is 0.4%-1.5%;

[0018] (2) the mass fraction of the glacial acetic acid in the mixed solution is 2%-6%;

[0019] (3) The mass volume ratio of the porous zeolite to the mixed solution is (2-6) g:100 mL.

[0020] In one embodiment, the embedding agent includes polyvinyl alcohol and sodium alginate.

[0021] In one embodiment, the cross-linking agent includes saturated boric acid solution and calcium chloride.

[0022] In one embodiment, the mass ratio of the polyvinyl alcohol to the sodium alginate is (4-8): (2-4); the mass ratio of the polyvinyl alcohol to the chitosan-modified porous zeolite is (4-8): (2-6).

[0023] In one embodiment, the mass volume ratio of the calcium chloride to the saturated boric acid solution is (10-20) g:500 mL.

[0024] In one embodiment, the porous zeolite includes Na-type porous zeolite.

[0025] In one embodiment, the preparation method of the Na-type porous zeolite comprises the following steps:

[0026] The zeolite is added into a sodium bicarbonate solution and heated at a temperature of 300-450° C. to prepare a Na-type porous activated zeolite.

[0027] In one embodiment, the preparation of the Na-type porous zeolite satisfies at least one of the following conditions:

[0028] (1) The zeolite includes one or more of clinoptilolite, mordenite, heulandite and chabazite;

[0029] (2) the concentration of the sodium bicarbonate solution is 0.7 mol / L-1.0 mol / L;

[0030] (3) The mass volume ratio of the zeolite to the sodium bicarbonate solution is (10-30) g:1 L;

[0031] (4) The high temperature heating time is 120 min-240 min.

[0032] In one embodiment, the particle size of the modified zeolite immobilized algae balls is 4.2 mm-5.4 mm.

[0033] In one embodiment, the density of the modified zeolite immobilized algae ball is 1.09 g / cm 3 -1.21g / cm 3 .

[0034] The second aspect of the present application provides a modified zeolite-immobilized algae ball, which is prepared using the preparation method described in the first aspect.

[0035] The third aspect of the present application provides an application of the modified zeolite-immobilized algae balls described in the second aspect in wastewater treatment.

[0036] In one embodiment, the application includes adding the modified zeolite-immobilized algae balls to wastewater at a ratio of 10 g / L-20 g / L for treatment; the C / N ratio of the wastewater is 1-3.

[0037] The details of one or more embodiments of the present application are set forth in the description below. Other features, objects, and advantages of the present application will become apparent from the description and claims. DETAILED DESCRIPTION

[0038] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0040] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0041] As used herein, "one or more" refers to any one, any two, or any two or more of the listed items.

[0042] Herein, the optional scope of "and / or", "or / and", and "and / or" includes any one of two or more relevant listed items, and also includes any and all combinations of the relevant listed items, and the said any and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items.

[0043] Herein, “further”, “further”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0044] In this document, “first aspect”, “second aspect”, “third aspect”, “fourth aspect”, etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. In addition, “first”, “second”, “third”, “fourth”, etc. only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on quantity. Therefore, the features defined as “first” and “second” may explicitly or implicitly include at least one of such features. In the description of this application, “multiple” means at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of this application, “several” means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0045] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0046] Unless otherwise specified, the percentage contents mentioned in this application refer to mass percentage for solid-liquid mixture and solid-solid mixture, and refer to volume percentage for liquid-liquid mixture.

[0047] The percentage concentrations mentioned in this application, unless otherwise specified, refer to the final concentration, which refers to the percentage of the added component in the system after the addition of the component.

[0048] The temperature parameters in this application, unless otherwise specified, allow both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the ranges of ±5°C, ±2°C, ±1°C, ±0.5°C, ±0.4°C, ±0.3°C, ±0.2°C, and ±0.1°C are allowed. The room temperature in this application refers to no temperature control operation, generally 4°C to 35°C, preferably 20±5°C.

[0049] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0050] Natural zeolite is a widely distributed type of silicate mineral, composed of a three-dimensional lattice of silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra linked by shared oxygen. As a non-metallic mineral material, natural zeolite has the advantages of abundant reserves and low cost. It has adsorption, ion exchange, and shape-selective catalysis properties. In particular, due to its highly selective adsorption of pollutants such as ammonia nitrogen, it is often used as an ammonia nitrogen adsorbent. In practical applications, natural zeolite is often crushed to the micron level to increase the specific surface area of ​​the zeolite, fully utilizing the adsorption effect of the zeolite and further improving its ammonia nitrogen removal rate. However, due to the small particle size of the crushed zeolite, when added to wastewater to exert its adsorption effect, it often has difficulty settling to the bottom quickly and being difficult to effectively separate from the wastewater.

[0051] In addition, although zeolite has good adsorption performance, especially for NH4 in wastewater + -N has excellent absorption effect, but it has a strong - -N has poor adsorption capacity. Chitosan can adsorb NO3- -N, and at the same time promotes algal cell flocculation and enrichment through adsorption and netting effects, reducing algal cell loss. However, chitosan has problems such as poor stability and easy agglomeration when used alone, which affects the wastewater treatment effect.

[0052] Immobilized microbial technology involves fixing specially selected microorganisms on a selected carrier, achieving a high density while maintaining biological activity and enabling rapid, large-scale proliferation under suitable conditions. Applied to wastewater treatment, this technology helps increase the concentration of microorganisms (especially those with specialized functions) within the bioreactor, helps them resist adverse environmental influences, facilitates solid-liquid separation after the reaction, and shortens treatment time. Among microbial immobilization methods, encapsulation is the most commonly used. Its principle is to trap biological cells in a porous network of a water-insoluble gel polymer. This is achieved through polymerization, ion network formation, precipitation, or by varying the solvent, temperature, or pH. The gel polymer network prevents cell leakage while allowing matrix infiltration and product diffusion.

[0053] During the experiment, the technicians of the present application unexpectedly discovered that by adding porous activated zeolite to chitosan and glacial acetic acid solution and stirring the mixture, chitosan-modified zeolite can be obtained; by uniformly mixing the chitosan-modified zeolite with a cross-linking agent, adding cultured Chlorella algae liquid, and adding the cross-linking agent to the algae mixture, modified zeolite-immobilized algae balls can be prepared; by fixing the modified zeolite and Chlorella in an embedding rubber ball to achieve the immobilization of the algae ball, the removal effect of pollutants in water can be improved, while having low toxicity to microorganisms and making it easier to separate Chlorella and zeolite from wastewater.

[0054] In a first aspect of the present application, a method for preparing modified zeolite-immobilized algae pellets is provided, comprising the following steps:

[0055] obtaining a porous zeolite;

[0056] Mixing the porous zeolite with a mixed solution of chitosan, glacial acetic acid and water to prepare a chitosan-modified porous zeolite; and

[0057] The chitosan-modified porous zeolite is mixed with an embedding agent, chlorella, and a cross-linking agent to prepare the modified zeolite-immobilized algae ball.

[0058] This application uses chitosan to modify zeolite to make it resistant to NH4 + -N adsorption capacity is further enhanced while also being able to adsorb NO3 - -N performance; then the chitosan modified zeolite and Chlorella are fixed in the embedded rubber balls to realize the immobilization of algae balls, which can not only improve the removal effect of pollutants in water, but also reduce the leakage and loss of algae cells in the rubber ball particles and have low toxicity to microorganisms.

[0059] Furthermore, the prepared modified zeolite immobilized algae balls have good stability, moderate particle size and density, and are effective in treating NH4 + -N, NO3 - The removal effects of -N, TP, COD and TN are significantly improved, which can improve the mechanical strength, embedding performance and service life of the immobilized algae balls. At the same time, it can reduce the operational difficulty and cost of separating Chlorella and zeolite from wastewater, and has good application prospects.

[0060] Specifically, the amino and hydroxyl groups in chitosan are protonated and electrostatically adsorb to NO3 in water. - -N combines to form ion pairs. Since zeolite has a high surface area and strong mechanical stability, zeolite is added to chitosan to enhance the mechanical properties of chitosan. Zeolite attached to chitosan can effectively adsorb NO3 in water. - -N; At the same time, chitosan can promote the flocculation and enrichment of algae cells through adsorption, electrical neutralization and polymer netting effect, and reduce the loss and exudation of algae cells.

[0061] In some embodiments, the deacetylation degree of the chitosan is ≥95%. It is understood that the deacetylation degree of the chitosan includes but is not limited to 95%, 96%, 97%, 98% and 99%.

[0062] In some embodiments, the viscosity of the chitosan is 100-200 mpas. It is understood that the viscosity of the chitosan includes but is not limited to 100 mpas, 110 mpas, 120 mpas, 130 mpas, 140 mpas, 150 mpas, 160 mpas, 170 mpas, 180 mpas, 190 mpas and 200 mpas.

[0063] In some embodiments, in the preparation of the chitosan-modified porous zeolite, the mass fraction of the chitosan in the mixed solution is 0.4%-1.5%. It is understood that the mass fraction of the chitosan in the mixed solution includes but is not limited to 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% and 1.5%.

[0064] Furthermore, the chitosan-attached zeolite can effectively adsorb NO3 in water. - -N, while chitosan promotes algae cell flocculation and enrichment through adsorption, electrical neutralization and polymer capture effect, reducing the loss and exudation of algae cells. However, too high a concentration of chitosan solution will reduce the absorption of zeolite to NH4 + -N adsorption performance.

[0065] In some embodiments, in the preparation of the chitosan-modified porous zeolite, the mass fraction of the glacial acetic acid in the mixed solution is 2%-6%. It is understood that the mass fraction of the glacial acetic acid in the mixed solution includes but is not limited to 2%, 3%, 4%, 5% and 6%.

[0066] In some embodiments, in the preparation of the chitosan-modified porous zeolite, the mass-to-volume ratio of the porous zeolite to the mixed solution is (2-6) g:100 mL. It is understood that the mass-to-volume ratio of the porous zeolite to the mixed solution includes, but is not limited to, 2 g:100 mL, 3 g:100 mL, 4 g:100 mL, 5 g:100 mL, and 6 g:100 mL.

[0067] In some embodiments, the embedding agent includes polyvinyl alcohol and sodium alginate. The addition of polyvinyl alcohol helps to enhance the strength of the gel spheres. Using sodium alginate and polyvinyl alcohol as embedding agents, the resulting gel has a porous network structure. Adding zeolite to the embedding agent enhances the mechanical strength of the sodium alginate / polyvinyl alcohol gel spheres and their ability to adsorb TN in water. This promotes the formation of a Chlorella biofilm that is less susceptible to loss and facilitates the bioregeneration of the zeolite by the Chlorella.

[0068] In some embodiments, the mass ratio of the polyvinyl alcohol to the sodium alginate is (4-8): (2-4). It can be understood that the mass ratio of the polyvinyl alcohol to the sodium alginate includes but is not limited to 4:2, 4:3, 4:4, 5:2, 5:3, 5:4, 6:2, 6:4, 7:2, 7:3, 7:4, 8:2 and 8:3.

[0069] In some embodiments, the mass ratio of the polyvinyl alcohol to the chitosan-modified porous zeolite is (4-8): (2-6). It can be understood that the mass ratio of the polyvinyl alcohol to the chitosan-modified porous zeolite includes but is not limited to 4:2, 4:3, 4:4, 4:5, 4:6, 5:2, 5:3, 5:4, 5:6, 6:2, 6:4, 6:5, 7:2, 7:3, 7:4, 7:5, 7:6, 8:2, 8:3, 8:5 and 8:7.

[0070] Furthermore, the addition of polyvinyl alcohol is beneficial to enhancing the strength of the rubber balls, but too high a concentration of polyvinyl alcohol will reduce the mass transfer performance of the rubber balls.

[0071] In one specific example, the polyvinyl alcohol includes one or more of polyvinyl alcohol 124, polyvinyl alcohol 1788, polyvinyl alcohol 1799 and polyvinyl alcohol 2488.

[0072] In one specific example, the alcoholysis degree of the polyvinyl alcohol is 98%-99%. It is understood that the alcoholysis degree of the polyvinyl alcohol includes but is not limited to 98%, 98.2%, 98.4%, 98.6%, 98.8% and 99%.

[0073] In one specific example, the average degree of polymerization of the polyvinyl alcohol is 2400-2500. It can be understood that the average degree of polymerization of the polyvinyl alcohol includes but is not limited to 2400, 2410, 2420, 2430, 2440, 2450, 2460, 2470, 2480, 2490 and 2500.

[0074] In one specific example, the viscosity of the polyvinyl alcohol is 54-66 mpas. It is understood that the viscosity of the polyvinyl alcohol includes but is not limited to 54 mpas, 55 mpas, 56 mpas, 57 mpas, 58 mpas, 59 mpas, 60 mpas, 61 mpas, 62 mpas, 63 mpas, 64 mpas, 65 mpas and 66 mpas.

[0075] In some embodiments, the cross-linking agent includes saturated boric acid solution and calcium chloride.

[0076] Furthermore, the cross-linking agent contains both boric acid and calcium chloride. Calcium chloride reacts with sodium alginate to form stable gel balls. Boric acid cross-links with polyvinyl alcohol to form stable aldehyde condensates, which is beneficial to the ion exchange between calcium chloride and sodium alginate, further enhancing the mechanical properties of the immobilized algae balls.

[0077] In some embodiments, in the preparation reaction of the cross-linking agent, the mass volume ratio of the calcium chloride to the saturated boric acid solution is (10-20) g:500 mL. It is understood that the mass volume ratio of the calcium chloride to the saturated boric acid solution includes but is not limited to 10 g:500 mL, 12:500 mL, 14 g:500 mL, 16 g:500 mL, 18 g:500 mL, and 20 g:500 mL.

[0078] In some embodiments, the porous zeolite comprises a Na-type porous zeolite.

[0079] In some embodiments, the preparation method of the Na-type porous zeolite comprises the following steps:

[0080] The zeolite is added into a sodium bicarbonate solution and heated at a temperature of 300-450° C. to prepare a Na-type porous activated zeolite.

[0081] Furthermore, during the calcination of zeolite, the sodium bicarbonate impregnated into its structure decomposes into CO2 and H2O at high temperature to generate more pores, which increases the average pore size of zeolite and has a higher surface area. + The addition of zeolite and NH4 in water + -N ion exchange capacity is enhanced to adsorb NH4 + -N provides more active sites.

[0082] In some embodiments, in the preparation reaction of the Na-type porous zeolite, the zeolite includes one or more of clinoptilolite, mordenite, heulandite, and chabazite.

[0083] In some embodiments, the particle size of the zeolite is 0.3 mm to 0.5 mm. It is understood that the particle size of the zeolite raw material includes but is not limited to 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm and 0.5 mm.

[0084] In some embodiments, in the preparation reaction of the Na-type porous zeolite, the concentration of the sodium bicarbonate solution is 0.7 mol / L-1.0 mol / L. It is understood that the concentration of the sodium bicarbonate solution includes but is not limited to 0.7 mol / L, 0.8 mol / L, 0.9 mol / L and 1.0 mol / L.

[0085] In some embodiments, in the preparation reaction of the Na-type porous zeolite, the mass volume ratio of the zeolite to the sodium bicarbonate solution is (10-30) g:1 L. It is understood that the mass volume ratio of the zeolite to the sodium bicarbonate solution includes but is not limited to 10 g:1 L, 15 g:1 L, 20 g:1 L, 25 g:1 L and 30 g:1 L.

[0086] In some embodiments, in the preparation reaction of the Na-type porous zeolite, the high-temperature heating time is 120 min-240 min. It is understood that the high-temperature heating time includes but is not limited to 120 min, 140 min, 160 min, 180 min, 200 min, 220 min and 240 min.

[0087] In some embodiments, during the preparation reaction of the Na-type porous zeolite, the high-temperature heating apparatus comprises a muffle furnace; the muffle furnace heating rate is 4°C / min-6°C / min. It is understood that the muffle furnace heating rate includes, but is not limited to, 4°C / min, 5°C / min, and 6°C / min.

[0088] In some embodiments, the particle size of the modified zeolite immobilized algae ball is 4.2 mm to 5.4 mm. It is understood that the particle size of the modified zeolite immobilized algae ball includes but is not limited to 4.2 mm, 4.4 mm, 4.6 mm, 4.8 mm, 5.0 mm, 5.2 mm and 5.4 mm.

[0089] In some embodiments, the density of the modified zeolite immobilized algae ball is 1.09 g / cm 3 -1.21g / cm 3 It is understood that the density of the modified zeolite immobilized algae ball includes but is not limited to 1.09 g / cm 3 , 1.11g / cm 3 , 1.13g / cm 3 , 1.15g / cm 3 , 1.17g / cm 3 , 1.19g / cm 3 and 1.21 g / cm 3 .

[0090] In some embodiments, the method for preparing the modified zeolite-immobilized algae pellet comprises the following steps:

[0091] (1) adding zeolite to a sodium bicarbonate solution, stirring, filtering, drying, and heating at a temperature of 300° C. to 450° C. to prepare a Na-type porous activated zeolite;

[0092] (2) mixing water, chitosan, and glacial acetic acid to prepare a first mixed solution; adding the Na-type porous activated zeolite to the first mixed solution, stirring, filtering, drying, and grinding to prepare Na-CS porous activated zeolite;

[0093] (3) mixing polyvinyl alcohol, sodium alginate, the Na-CS porous activated zeolite and water, and stirring to prepare a second mixed solution;

[0094] (4) sterilizing the second mixed solution with high-temperature steam, cooling it to room temperature, mixing it with Chlorella vulgaris, and stirring it to prepare a third mixed solution;

[0095] (5) adding calcium chloride to the saturated boric acid solution, adjusting the pH of the resulting solution to 6.4-6.6 using sodium bicarbonate, and sterilizing with high-temperature steam to prepare a cross-linking agent; dripping the third mixed solution into the cross-linking agent, fixing the cross-linking at low temperature, and preparing a modified zeolite-immobilized algae ball.

[0096] In some embodiments, in step (3), the mass volume ratio of the Na-CS porous activated zeolite to water is (2-6) g:100 mL. It is understood that the mass volume ratio of the Na-CS porous activated zeolite to water includes but is not limited to 2 g:100 mL, 3 g:100 mL, 4 g:100 mL, 5 g:100 mL, and 6 g:100 mL.

[0097] In some embodiments, in step (3), the mass volume ratio of the polyvinyl alcohol to water is (4-8) g:100 mL. It is understood that the mass volume ratio of the polyvinyl alcohol to water includes but is not limited to 4 g:100 mL, 5 g:100 mL, 6 g:100 mL, 7 g:100 mL and 8 g:100 mL.

[0098] In some embodiments, in step (3), the mass volume ratio of sodium alginate to water is (2-4) g:100 mL. It is understood that the mass volume ratio of sodium alginate to water includes but is not limited to 2 g:100 mL, 3 g:100 mL and 4 g:100 mL.

[0099] In some embodiments, the preparation step of step (5) includes: using a 5 ml syringe to dropwise add the third mixed solution into the prepared crosslinker to obtain an immobilized algae ball, transferring it to a refrigerator for refrigeration, and fixing and crosslinking it at a low temperature of 4°C for 24 hours.

[0100] In some embodiments, the needle of the syringe drips 1 drop per second at a distance of 10 cm to 15 cm from the cross-linking agent, and the operation process is completed at 25° C. to 30° C.

[0101] The second aspect of the present application provides a modified zeolite-immobilized algae ball, which is prepared using the preparation method described in the first aspect.

[0102] This application uses chitosan to modify zeolite to make it resistant to NH4 + -N adsorption capacity is further enhanced while also being able to adsorb NO3 - -N performance; then the modified zeolite and Chlorella are fixed in the embedded rubber balls to realize the immobilization of algae balls, which can not only improve the removal effect of pollutants in water, but also reduce the leakage and loss of algae cells in the rubber ball particles, and make it easier to separate Chlorella and zeolite from wastewater.

[0103] The third aspect of the present application provides an application of the modified zeolite-immobilized algae balls described in the second aspect in wastewater treatment.

[0104] In some embodiments, the C / N ratio of the wastewater is 1-3.

[0105] In some embodiments, the application includes adding the modified zeolite-immobilized algae pellets into wastewater at a ratio of 10 g / L-20 g / L for treatment.

[0106] In some embodiments, the application includes adding the modified zeolite-immobilized algae balls at a ratio of 10 g / L-20 g / L to wastewater with a C / N ratio of 1-3 for treatment.

[0107] In some embodiments, after the wastewater treatment steps described above are performed, the NH4 + -N removal rate is more than 75%; NO3 - The removal rate of -N is over 55%; the removal rate of TP is over 61%; the removal rate of TN is over 58%; and the removal rate of COD is over 60%.

[0108] The following is further described with reference to specific examples. Unless otherwise specified, the raw materials involved in the following specific examples can all be commercially available; the instruments used can all be commercially available, unless otherwise specified; the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art, who may first refer to the guidance provided in this application document, and may also refer to experimental manuals in the field or other experimental methods known in the field, or refer to the experimental conditions recommended by the manufacturer.

[0109] The parameters and preparation methods of some raw materials used in the examples and comparative examples of this application are as follows:

[0110] The zeolite raw material is natural clinoptilolite, which can be purchased from Henan Guanghui Water Treatment Materials Co., Ltd.

[0111] Chitosan has a deacetylation degree of 95.0% and a viscosity of 105 mPas; it can be purchased from Shanghai MacLean Biochemical Technology Co., Ltd., model number C804726-100g;

[0112] The concentration of glacial acetic acid is 99.5 wt %, which can be purchased from Shanghai MacLean Biochemical Technology Co., Ltd., model number A801295-500 ml;

[0113] The polyvinyl alcohol is polyvinyl alcohol 124, with a degree of alcoholysis of 99.0%, an average degree of polymerization of 2500, and a viscosity of 56 mpas, which can be purchased from Shanghai MacLean Biochemical Technology Co., Ltd. under the model number P909857-100g;

[0114] Sodium alginate can be purchased from Shanghai MacLean Biochemical Technology Co., Ltd., model number S817374-100g;

[0115] Boric acid can be purchased from Shanghai MacLean Biochemical Technology Co., Ltd., model number B802844-500g;

[0116] BG-11 culture medium can be purchased from Qingdao High-Tech Industrial Park Haibo Biotechnology Co., Ltd., model HB8793.

[0117] Preparation method of Chlorella liquid: Chlorella is inoculated into BG-11 culture medium. The culture conditions of Chlorella are temperature 25℃-30℃, light conditions 5000±1000Lux, and pH is adjusted to 6-7 with sodium bicarbonate. The Chlorella liquid is prepared by culturing for 7 days.

[0118] Preparation method of saturated boric acid solution: Mix boric acid and water in a mass volume ratio of 7g:100ml at room temperature, then heat to 80℃-100℃, stir thoroughly until the boric acid powder is completely dissolved, and after natural cooling, take the upper clear solution, which is the saturated boric acid solution.

[0119] Method for detecting the particle size of immobilized algae balls: Take 10 immobilized algae balls with uniform morphology and size, use a vernier caliper to measure the diameters of the immobilized algae balls respectively and take the average value.

[0120] Density detection method for immobilized algae balls: After weighing and recording the mass of 10 immobilized algae balls, place them in a measuring cylinder filled with a certain volume of water. Record the volume difference of water in the measuring cylinder before and after placing the immobilized algae balls. The density of the immobilized algae balls can be calculated using the density formula.

[0121] Example 1

[0122] (1) The zeolite raw material was rinsed 3 times with deionized water and dried in an oven at 60°C for 240 min. The natural zeolite was added to a 0.7 mol / L sodium bicarbonate solution at a mass volume ratio (g / L) of zeolite to sodium bicarbonate solution of 10:1. The mixture was stirred at 200 r / min for 12 h, filtered, and dried. The dried zeolite was placed in a muffle furnace and heated at a high temperature. The muffle furnace heating rate was 4°C / min, the high temperature heating temperature was 300°C, and the heating time was 120 min to obtain Na-type porous activated zeolite.

[0123] (2) dissolving chitosan in water, stirring at 30° C. for 5 min, adding glacial acetic acid and mixing uniformly to prepare a mixed solution with a chitosan mass fraction of 0.4% and a glacial acetic acid mass fraction of 4%; adding 2 g of the Na-type porous activated zeolite prepared in step (1) to 100 mL of the mixed solution, shaking and stirring at 140 r / min for 24 h, washing with deionized water until the filtrate is neutral, and drying at a drying temperature of 60° C. for 120 min to obtain Na-CS porous activated zeolite; grinding the obtained Na-CS porous activated zeolite, and sieving it with a 300-mesh filter screen to obtain Na-CS porous activated zeolite with uniform particle size;

[0124] (3) Add 4 g of polyvinyl alcohol 124 to 100 ml of water and heat to 195° C. using an electric heating plate. After all the water is dissolved, add 3 g of sodium alginate (slowly added in 5 times) and 2 g of the Na-CS porous activated zeolite obtained in step (2) in sequence. Stir with a glass rod for 20 min to obtain a Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture.

[0125] (4) The Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture prepared in step (3) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and then cooled to room temperature. 50 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0126] (5) Add 15g of calcium chloride to 500ml of saturated boric acid solution, stir until completely dissolved, and then use sodium bicarbonate to adjust the pH of the resulting solution to 6.6 to obtain a cross-linking agent; use a 5ml syringe to drip the algae mixture obtained in step (4) into the prepared cross-linking agent drop by drop to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain a modified zeolite immobilized algae ball. The particle size of the obtained immobilized algae ball is 4.7mm, and the density is 1.09g / cm 3 .

[0127] Example 2

[0128] (1) The zeolite raw material was rinsed 3 times with deionized water and dried in a drying oven at 60°C for 240 min. The natural zeolite was added to a 0.8 mol / L sodium bicarbonate solution at a mass volume ratio (g / L) of zeolite to sodium bicarbonate solution of 15:1. The mixture was stirred at 200 r / min for 12 h, filtered, and dried. The dried zeolite was placed in a muffle furnace and heated at a high temperature. The muffle furnace heating rate was 6°C / min, the high temperature heating temperature was 350°C, and the heating time was 180 min to obtain Na-type porous activated zeolite.

[0129] (2) dissolving chitosan in water, stirring at 30° C. for 5 min, adding glacial acetic acid and mixing evenly to prepare a mixed solution with a chitosan mass fraction of 0.5% and a glacial acetic acid mass fraction of 2%; adding 4 g of the Na-type porous activated zeolite prepared in step (1) to 100 ml of the mixed solution, shaking and stirring at 140 r / min for 24 h, washing with deionized water until the filtrate is neutral, and drying at a drying temperature of 60° C. for 120 min to obtain Na-CS porous activated zeolite; grinding the obtained Na-CS porous activated zeolite, and sieving it with a 300-mesh filter screen to obtain Na-CS porous activated zeolite with uniform particle size;

[0130] (3) Add 6 g of polyvinyl alcohol 124 to 100 ml of water and heat to 195° C. using an electric heating plate. After all the water is dissolved, add 2 g of sodium alginate (slowly added in 5 times) and 4 g of the Na-CS porous activated zeolite obtained in step (2) in sequence. Stir with a glass rod for 20 min to obtain a Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture.

[0131] (4) The Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture prepared in step (3) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and then cooled to room temperature. 80 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0132] (5) Add 20g of calcium chloride to 500ml of saturated boric acid solution and stir until completely dissolved. Use sodium bicarbonate to adjust the pH of the solution to 6.6 to obtain a cross-linking agent. Use a 5ml syringe to add the algae mixture obtained in step (4) dropwise into the prepared cross-linking agent to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain a modified zeolite immobilized algae ball. The particle size of the obtained immobilized algae ball is 5.1mm and the density is 1.14g / cm 3 .

[0133] Example 3

[0134] (1) The zeolite raw material was rinsed 3 times with deionized water and dried in a drying oven at 60°C for 240 min. The natural zeolite was added to a 1.0 mol / L sodium bicarbonate solution at a mass volume ratio (g / L) of zeolite to sodium bicarbonate solution of 20:1. The mixture was stirred at 200 r / min for 12 h, filtered, and dried. The dried zeolite was placed in a muffle furnace and heated at a high temperature. The muffle furnace heating rate was 6°C / min, the high temperature heating temperature was 400°C, and the heating time was 240 min to obtain Na-type porous activated zeolite.

[0135] (2) dissolving chitosan in water, stirring at 30° C. for 5 min, adding glacial acetic acid and mixing uniformly to prepare a mixed solution with a chitosan mass fraction of 1.0% and a glacial acetic acid mass fraction of 4%; adding 5 g of the Na-type porous activated zeolite prepared in step (1) to 100 ml of the mixed solution, shaking and stirring at 140 r / min for 24 h, washing with deionized water until the filtrate is neutral, and drying at a drying temperature of 60° C. for 120 min to obtain Na-CS porous activated zeolite; grinding the obtained Na-CS porous activated zeolite, and sieving it with a 300-mesh filter screen to obtain Na-CS porous activated zeolite with uniform particle size;

[0136] (3) Add 8 g of polyvinyl alcohol 124 to 100 ml of water and heat to 195° C. using an electric heating plate. After all the water is dissolved, add 2 g of sodium alginate (slowly added in 5 times) and 5 g of the Na-CS porous activated zeolite obtained in step (2) in sequence. Stir with a glass rod for 20 min to obtain a Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture.

[0137] (4) The Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture prepared in step (3) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and cooled to room temperature. 100 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0138] (5) Add 10g of calcium chloride to 500ml of saturated boric acid solution, stir until completely dissolved, and then use sodium bicarbonate to adjust the pH of the solution to 6.6 to obtain a cross-linking agent; use a 5ml syringe to drip the algae mixture obtained in step (4) into the prepared cross-linking agent drop by drop to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain a modified zeolite immobilized algae ball. The particle size of the obtained modified zeolite immobilized algae ball is 5.4mm, and the density is 1.21g / cm 3 .

[0139] Example 4

[0140] (1) The zeolite raw material was rinsed 3 times with deionized water and dried in a drying oven at 60°C for 240 min. The natural zeolite was added to a 0.8 mol / L sodium bicarbonate solution at a mass volume ratio (g / L) of zeolite to sodium bicarbonate solution of 25:1. The mixture was stirred at 200 r / min for 12 h, filtered, and dried. The dried zeolite was placed in a muffle furnace and heated at a high temperature. The muffle furnace heating rate was 6°C / min, the high temperature heating temperature was 400°C, and the heating time was 240 min to obtain Na-type porous activated zeolite.

[0141] (2) dissolving chitosan in water, stirring at 30° C. for 5 min, adding glacial acetic acid and mixing uniformly to prepare a mixed solution with a chitosan mass fraction of 0.7% and a glacial acetic acid mass fraction of 6%, adding 6 g of the Na-type porous activated zeolite prepared in step (1) to 100 ml of the mixed solution, shaking and stirring at 140 r / min for 24 h, washing with deionized water until the filtrate is neutral, and drying at a drying temperature of 60° C. for 120 min to obtain Na-CS porous activated zeolite; grinding the obtained Na-CS porous activated zeolite, and sieving it with a 300-mesh filter screen to obtain Na-CS porous activated zeolite with uniform particle size;

[0142] (3) Add 4 g of polyvinyl alcohol 124 to 100 ml of water and heat to 195° C. using an electric heating plate. After all the water is dissolved, add 4 g of sodium alginate (slowly added in 5 times) and 6 g of the Na-CS porous activated zeolite obtained in step (2) in sequence. Stir with a glass rod for 20 minutes to obtain a Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture.

[0143] (4) The Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture prepared in step (3) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and then cooled to room temperature. 110 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0144] (5) Add 10g of calcium chloride to 500ml of saturated boric acid solution, stir until completely dissolved, and then use sodium bicarbonate to adjust the pH of the solution to 6.6 to obtain a cross-linking agent; use a 5ml syringe to drip the algae mixture obtained in step (4) into the prepared cross-linking agent drop by drop to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain a modified zeolite immobilized algae ball. The particle size of the obtained modified zeolite immobilized algae ball is 4.5mm, and the density is 1.17g / cm 3 .

[0145] Example 5

[0146] (1) The zeolite raw material was rinsed 3 times with deionized water and dried in a drying oven at 60°C for 240 min. The natural zeolite was added to a 0.9 mol / L sodium bicarbonate solution at a mass volume ratio (g / L) of zeolite to sodium bicarbonate solution of 30:1. The mixture was stirred at 200 r / min for 12 h, filtered, and dried. The dried zeolite was placed in a muffle furnace and heated at a high temperature. The muffle furnace heating rate was 5°C / min, the high temperature heating temperature was 450°C, and the heating time was 120 min to obtain Na-type porous activated zeolite.

[0147] (2) dissolving chitosan in water, stirring at 30° C. for 5 min, adding glacial acetic acid and mixing uniformly to prepare a mixed solution with a chitosan mass fraction of 1.5% and a glacial acetic acid mass fraction of 4%, adding 4 g of the Na-type porous activated zeolite prepared in step (1) to 100 ml of the mixed solution, shaking and stirring at 140 r / min for 24 h, washing with deionized water until the filtrate is neutral, and drying at a drying temperature of 60° C. for 120 min to obtain Na-CS porous activated zeolite; grinding the obtained Na-CS porous activated zeolite, and sieving it with a 300-mesh filter screen to obtain Na-CS porous activated zeolite with uniform particle size;

[0148] (3) Add 4 g of polyvinyl alcohol 124 to 100 ml of water and heat to 195° C. using an electric heating plate. After all the water is dissolved, add 2 g of sodium alginate (slowly added in 5 times) and 4 g of the Na-CS porous activated zeolite obtained in step (2) in sequence. Stir with a glass rod for 20 min to obtain a Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture.

[0149] (4) The Na-CS zeolite-sodium alginate / polyvinyl alcohol mixture prepared in step (3) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and then cooled to room temperature. 120 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0150] (5) Add 20g of calcium chloride to 500ml of saturated boric acid solution, stir until completely dissolved, and then use sodium bicarbonate to adjust the pH of the solution to 6.6 to obtain a cross-linking agent; use a 5ml syringe to drip the algae mixture obtained in step (4) into the prepared cross-linking agent drop by drop to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain a modified zeolite immobilized algae ball. The particle size of the obtained modified zeolite immobilized algae ball is 4.2mm, and the density is 1.12g / cm 3 .

[0151] Comparative Example 1

[0152] (1) Rinse the zeolite raw material three times with deionized water and dry it in a drying oven at 60° C. for 240 min; grind the dried zeolite and sieve it with a 300-mesh filter screen to obtain natural zeolite with uniform particle size;

[0153] (2) 2 g of sodium alginate (slowly added in 5 portions) and 5 g of the zeolite obtained in step (1) were added to 100 ml of water and stirred continuously with a glass rod for 20 min to obtain a zeolite-sodium alginate mixture;

[0154] (3) The zeolite-sodium alginate mixture prepared in step (2) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and cooled to room temperature. 100 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0155] (4) Add 10g of calcium chloride to 500ml of water, stir until completely dissolved, and then use sodium bicarbonate to adjust the pH of the solution to 6.6 to obtain a cross-linking agent; use a 5ml syringe to drip the algae mixture obtained in step (3) into the prepared cross-linking agent drop by drop to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain an immobilized algae ball. The particle size of the obtained immobilized algae ball is 3.9mm and the density is 1.06g / cm 3 .

[0156] Comparative Example 2

[0157] (1) The zeolite raw material was rinsed 3 times with deionized water and dried in an oven at 60°C for 240 min. The natural zeolite was added to a 0.7 mol / L sodium bicarbonate solution at a mass volume ratio (g / L) of zeolite to sodium bicarbonate solution of 10:1. The mixture was stirred at 200 r / min for 12 h, filtered, and dried. The dried zeolite was placed in a muffle furnace and heated at a high temperature. The muffle furnace heating rate was 4°C / min, the high temperature heating temperature was 300°C, and the heating time was 120 min to obtain Na-type porous activated zeolite.

[0158] (2) grinding the obtained Na-type porous activated zeolite and sieving it through a 300-mesh filter screen to obtain a Na-type porous activated zeolite with uniform particle size;

[0159] (3) 4 g of polyvinyl alcohol 124 (with a degree of alcoholysis of 99%, an average degree of polymerization of 2500, and a viscosity of 56 mPas) was added to 100 ml of water and heated to 195° C. using an electric heating plate. After the mixture was completely dissolved, 3 g of sodium alginate (slowly added in 5 portions) and 2 g of the Na-type porous activated zeolite obtained in step (2) were added in sequence. The mixture was stirred with a glass rod for 20 min to obtain a Na-type zeolite-sodium alginate / polyvinyl alcohol mixture.

[0160] (4) The Na-type zeolite-sodium alginate / polyvinyl alcohol mixture prepared in step (3) was placed in an autoclave, steam sterilized at 121°C for 20 minutes, and then cooled to room temperature. 50 ml of the Chlorella algae solution was centrifuged at 8000 rpm for 10 minutes, and the resulting Chlorella precipitate was added to the mixture, and stirred at 300 rpm for 30 minutes to obtain a uniformly dispersed algae mixture.

[0161] (5) Add 15g of calcium chloride to 500ml of saturated boric acid solution, stir until completely dissolved, and then use sodium bicarbonate to adjust the pH of the resulting solution to 6.6 to obtain a cross-linking agent; use a 5ml syringe to drip the algae mixture obtained in step (4) into the prepared cross-linking agent drop by drop to obtain an immobilized algae ball, transfer it to a refrigerator for refrigeration, and fix and cross-link it at a low temperature of 4°C for 24h. Pour out the cross-linking agent, wash the immobilized algae ball 3 times with deionized water, and obtain a modified zeolite immobilized algae ball. The particle size of the obtained immobilized algae ball is 4.5mm, and the density is 1.08g / cm 3 .

[0162] The immobilized algae balls prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were poured into raw water samples with the same water quality at a ratio of 15 g / L to test the adsorption performance. After running for 2 days, the NH4 + -、NO3 - -N, TP, TN and COD concentrations and algal cell exudation, NH4 + -N, NO3 - The test methods for -N, TP, TN and COD concentrations are shown in Table 1, and the test results are shown in Table 2.

[0163] Among them, the raw water indicators used in the adsorption performance test are: NH4 + -N is 15.77 mg / L, NO3 - -N is 35.13 mg / L, TP is 2.41 mg / L, TN is 50.9 mg / L, and COD is 64 mg / L.

[0164] Table 1

[0165] The test method for algal cell exudation is as follows: the biomass of Chlorella is determined by measuring the dry weight of the algal solution. Since direct measurement of the dry weight of the algal solution is not convenient for dynamic monitoring of the algal cell biomass, the absorbance of the algal solution at a wavelength of 680nm is converted into the dry weight of the algal solution to reflect the biomass. The absorbance of Chlorella solutions of different concentrations at a wavelength of 680nm is measured using an ultraviolet-visible spectrophotometer. At the same time, Chlorella solutions of different concentrations are filtered through a 0.45μm fiber filter membrane that has been dried to a constant weight, dried to a constant weight at 105°C, and after cooling to room temperature, the 0.45μm fiber filter membrane is weighed to determine the dry weight of the algal cells in the algal solution. A standard curve between the absorbance of Chlorella solution and the biomass is established: Y=0.4361·x-0.00642(R 2 =0.998)

[0166] Where x is the OD680 of Chlorella liquid; Y is the biomass of Chlorella (g / L).

[0167] Table 2

[0168] As can be seen from the table above, compared with the traditional sodium alginate algae balls in comparative example 1 and the immobilized algae balls prepared using chitosan-modified zeolite as raw materials in comparative example 2, the modified zeolite immobilized algae balls prepared in Examples 1 to 5 of the present application have a higher NH4 + -N, NO3 - -N, TP and COD removal rates were significantly increased, and algae cell exudation was significantly reduced; especially the modified zeolite immobilized algae balls prepared in Example 3 were effective in removing NH4 + -N, NO3 - The removal rates of -N, TP, TN and COD were increased by 42.68%, 34.78%, 42.74%, 39.16% and 35.94% respectively compared with the control example 1, and the algae cell exudation was reduced by 20.5 mg / L compared with the traditional sodium alginate algae balls, which further proved that the modified zeolite immobilized algae balls provided in this application have excellent adsorption properties, can improve the mechanical strength, embedding performance and service life of the immobilized algae balls, and at the same time reduce the operational difficulty and cost of separating Chlorella and zeolite from wastewater, and have good application prospects.

[0169] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A preparation method of modified zeolite immobilized algal balls, characterized in that, it comprises the following steps: Obtain porous zeolite; Mix the porous zeolite with a mixed solution of chitosan, glacial acetic acid and water to prepare chitosan-modified porous zeolite; and Mix the chitosan-modified porous zeolite with an embedding agent, Chlorella vulgaris and a crosslinking agent to prepare the modified zeolite immobilized algal balls.

2. The preparation method of modified zeolite immobilized algal balls according to claim 1, characterized in that, the chitosan includes at least one of the following characteristics: (1) The degree of deacetylation ≥ 95%; (2) The viscosity is 100mpas - 200mpas.

3. The preparation method according to claim 1 or 2, characterized in that, the preparation of the chitosan-modified porous zeolite satisfies at least one of the following conditions: (1) The mass fraction of the chitosan in the mixed solution is 0.4% - 1.5%; (2) The mass fraction of the glacial acetic acid in the mixed solution is 2% - 6%; (3) The mass-volume ratio of the porous zeolite to the mixed solution is (2 - 6) g: 100 mL.

4. The preparation method according to any one of claims 1 - 3, characterized in that, the embedding agent includes polyvinyl alcohol and sodium alginate.

5. The preparation method according to any one of claims 1 - 4, characterized in that, the crosslinking agent includes saturated boric acid solution and calcium chloride.

6. The preparation method according to claim 4, characterized in that, the mass ratio of the polyvinyl alcohol to the sodium alginate is (4 - 8): (2 - 4); the mass ratio of the polyvinyl alcohol to the chitosan-modified porous zeolite is (4 - 8): (2 - 6).

7. The preparation method according to claim 5, characterized in that, the mass-volume ratio of the calcium chloride to the saturated boric acid solution is (10 - 20) g: 500 mL.

8. The preparation method according to any one of claims 1 - 7, characterized in that, the porous zeolite includes Na-type porous zeolite.

9. The preparation method according to claim 8, characterized in that, the preparation method of the Na-type porous zeolite includes the following steps: Add zeolite to a sodium bicarbonate solution and carry out high-temperature heating at a temperature of 300°C - 450°C to prepare Na-type porous activated zeolite.

10. The preparation method according to claim 9, characterized in that, the preparation of the Na-type porous zeolite satisfies at least one of the following conditions: (1) The zeolite includes one or more of clinoptilolite, mordenite, heulandite and chabazite; (2) The concentration of the sodium bicarbonate solution is 0.7mol / L - 1.0mol / L; (3) The mass-volume ratio of the zeolite to the sodium bicarbonate solution is (10 - 30) g: 1 L; (4) The time of the high-temperature heating is 120min - 240min.

11. The preparation method according to any one of claims 1 - 10, characterized in that, the particle size of the modified zeolite immobilized algal balls is 4.2mm - 5.4mm.

12. The preparation method according to any one of claims 1 - 11, characterized in that, The density of the modified zeolite immobilized algal balls is 1.09 g / cm 3 -1.21 g / cm 3 .

13. A modified zeolite-immobilized algal ball, Characterized in that, It is prepared by the preparation method described in any one of claims 1-12.

14. Application of a modified zeolite-immobilized algal ball as described in claim 13 in wastewater treatment.

15. According to the application described in claim 14, Characterized in that, It includes adding the modified zeolite-immobilized algal ball to the wastewater for treatment at a ratio of 10 g / L - 20 g / L; the C / N of the wastewater is 1 - 3.

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