A microalgae system for adsorbing co2 and a method of preparing the same

Abstract

The present application relates to a kind of microalgae system for adsorbing CO2 and its preparation method, including the preparation of metal organic framework, and the prepared metal organic framework is cultivated with microalgae and forms microalgae system, wherein the carboxyl, amino, phosphate group and other functional groups on the surface of microalgae cell interact with the active site-amino on the surface of metal organic framework, these interactions can stabilize the protein structure and function of microalgae, prevent microalgae inactivation or degradation during cultivation;Microalgae will also diffuse and propagate using the organic groups on metal organic framework, and the pore structure on the surface and inside of metal organic framework will guide the distribution and arrangement of microalgae diffusion and propagation, so that microalgae propagation and diffusion and gradually form a layer of thin film or film block, which not only enhances the stability and continuity of microalgae system, but also optimizes the growth and metabolism of microalgae in microalgae system, and then improve the efficiency of microalgae system adsorbing CO2.

Description

Technical Field

[0001] This invention relates to the field of novel materials for gas adsorption and separation, and in particular to a microalgae system for adsorbing CO2 and its preparation method. Background Technology

[0002] Climate change is a serious challenge facing humanity, and the increase in atmospheric CO2 concentration is one of the main problems related to climate change. Therefore, the development and large-scale application of microalgae technology to collect and store CO2 has received increasing attention in response to the problem of atmospheric CO2 pollution emissions. Although microalgae have high photosynthetic efficiency and good ecological characteristics, the low solubility of CO2 in water means that most of the CO2 is lost from the microalgae system in the form of bubbles. This results in a short residence time of CO2 in the solution, meaning that the CO2 gas introduced into the microalgae system cannot be utilized by the microalgae in a timely manner, thus affecting the CO2 adsorption efficiency.

[0003] Patent application number CN202010442920.4 discloses a biogas purification method using microalgae to solidify and adsorb CO2. This patent's method utilizes microalgae to adsorb CO2 from biogas. The culture medium used to cultivate the microalgae is a mixture of citric acid solution, sodium nitrate solution, and potassium phosphate solution. This culture medium is the sole nutrient source for the microalgae, and the microalgae consume the culture medium rapidly during CO2 adsorption. If the culture medium is not replenished in time, it will affect the microalgae's CO2 adsorption. Patent application number CN202310306342.5 discloses a method for preparing and applying a MOF-based composite material adsorbent for CO2 / N2 adsorption and separation. This method utilizes MOF to adsorb CO2. Since MOF fixes CO2 through its own porous structure and functional groups, it consumes a large amount of MOF during industrial-scale production, resulting in high costs and hindering industrial production.

[0004] Furthermore, when using microalgae systems to adsorb CO2, large-scale cultivation of microalgae is required. Since microalgae are independently suspended in the culture medium, they will spread outward irregularly during reproduction, resulting in an extremely unstable microalgae system. When the microenvironment in the microalgae system changes, it will lead to the inactivation or degradation of microalgae cells. In addition, the irregular growth of microalgae results in an irregular arrangement of microalgae in the system, which will not only affect the efficiency of photosynthesis between microalgae but also affect the lifespan of microalgae. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a microalgae system for CO2 adsorption and its preparation method. This invention not only enhances the stability and continuity of the microalgae system but also optimizes the growth and metabolic processes of microalgae within the system, thereby improving the efficiency of CO2 adsorption.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a metal-organic framework, wherein the structural formula of the metal-organic framework is shown below:

[0008]

[0009] The method for preparing the metal-organic framework includes the following steps:

[0010] S1: Dissolve zirconium tetrachloride and 2-aminoterephthalic acid in DMF solvent at a mass fraction of 1:1 to 2, then stir on a magnetic stirrer for 20 min to 40 min, preferably 30 min, and degas by ultrasonic vibration for 10 min to 20 min, preferably 15 min;

[0011] S2: Pour the mixed solution obtained in S1 into a container and place the container in a hydrothermal reactor at 120℃~200℃, preferably 120℃, for hydrothermal reaction for 12h~24h, preferably 18h;

[0012] S3: After the reaction is completed, the product is cooled and washed with deionized water, ethanol and acetone respectively. Then it is dried in a vacuum drying oven. Finally, the product is vacuum heated at 420℃~500℃, preferably 420℃ for 50min~80min, preferably 60min.

[0013] S4: Add the final product obtained in S3 to anhydrous hexane, then add an equivalent amount of alkylamine to the mixed solution, and stir in a magnetic stirrer for 18h to 24h, preferably 24h;

[0014] S5: After the reaction is complete, the mixed solution is filtered and the solid obtained from the reaction is washed with anhydrous hexane. Then the solid is dried at a temperature of 80℃~120℃, preferably 100℃, to remove residual solvent. The final grayish-white powder product is the metal-organic framework.

[0015] Furthermore, in step S2, the container is a polytetrafluoroethylene (PTFE) container.

[0016] Furthermore, the characteristic is that, in step S4, the mass ratio of the product to the anhydrous hexane is 1:8 to 10.

[0017] Furthermore, in step S4, the equivalent ratio of the product to the alkylamine is 1:1 to 1.5.

[0018] Furthermore, in step S4, the alkylamine is one of ethylenediamine, triethylenetetramine, and N,N'-dimethylethylenediamine.

[0019] Furthermore, the pore size of the metal-organic framework is 0.8–1.1 nm.

[0020] Furthermore, the BET specific surface area of ​​the metal-organic framework is 650-800 m². 2 / g.

[0021] A method for preparing a microalgae system for CO2 adsorption, the microalgae system comprising the aforementioned metal-organic framework; the steps of the method for preparing the microalgae system are as follows:

[0022] A1: Chlorella proteoglycans were inoculated into BG11 culture medium and cultured to obtain Chlorella proteoglycans culture medium;

[0023] A2: The prepared metal-organic framework is added to the algal solution containing Chlorella proteoglycans at a ratio of 0.1 to 0.5 g / L, preferably 0.1 g / L, and the metal-organic framework is uniformly dispersed in the algal solution to obtain a mixed solution;

[0024] A3: Place the mixed solution obtained in A2 in a light incubator and introduce CO2 for culture. Culture in the light incubator for 5 to 9 days with aeration to obtain a microalgae system for adsorbing CO2 according to the present invention.

[0025] Furthermore, in step A3, the conditions of the light incubator are: temperature 25℃~27℃, light intensity 3600lx~3800lx, preferably 3600lx, light cycle 8h~12h, preferably 12h, the volume fraction of CO2 introduced is 5%~8%, preferably 5%, and the flow rate is 0.1L / (L min). -1 0.26L / (L min) -1 ), preferably 0.1L / (L min) -1 ).

[0026] Furthermore, the microalgae used is Chlorella proteoglycans, preferably FACHB-9 (purchased from the Institute of Hydrobiology, Chinese Academy of Sciences).

[0027] The beneficial technical effects of this invention are as follows:

[0028] 1. The microalgal cell surface of the microalgal system for CO2 adsorption provided by this invention has functional groups such as carboxyl, amino, and phosphate groups that interact with the active sites - amino groups on the surface of the metal-organic framework. These interactions include electrostatic interactions, hydrogen bonds, and van der Waals forces. These interactions can stabilize the protein structure and function of microalgae and prevent microalgae from becoming inactive or degraded during cultivation.

[0029] 2. The microalgae in the CO2 adsorption microalgae system provided by this invention utilize the organic groups on the metal-organic framework for diffusion and reproduction. The surface and internal pore structure of the metal-organic framework guides the distribution and arrangement of the microalgae diffusion and reproduction, enabling the microalgae to reproduce and diffuse and gradually form a thin film or membrane block. This not only enhances the stability and continuity of the microalgae system and maintains the integrity of the cell structure in a high pH and dissolved oxygen environment, but also reduces the oscillation during the microalgae cultivation process, giving the microalgae better photosynthetic parameters. Furthermore, it optimizes the growth and metabolic processes of the microalgae in the microalgae system, thereby improving the efficiency of the microalgae system in adsorbing CO2.

[0030] 3. The metal-organic framework of the microalgae system for CO2 adsorption provided by this invention forms an unstable complexing bond when it comes into contact with carbon dioxide molecules. When the CO2 concentration in the solution of the microalgae system is high, the microalgae in the system cannot utilize and adsorb CO2 in time. Instead, CO2 is fixed in the microalgae system by forming a complexing bond with the amino group in the metal-organic framework. When the CO2 concentration in the solution is low, the CO2 in the complexing bond is released into the microalgae system and utilized by the microalgae, effectively improving the ability and efficiency of the microalgae system to adsorb CO2.

[0031] 4. The metal-organic framework (MOF) in the microalgae system for CO2 adsorption provided by this invention has a large pore size and high specific surface area, providing ample adsorption sites for CO2 adsorption and enabling efficient adsorption of CO2 molecules. The pore structure and functionalized surface of the MOF facilitate physical and chemical adsorption with CO2, improving CO2 adsorption capacity and selectivity.

[0032] 5. The pore size of the metal-organic framework provided by this invention can be adjusted by controlling the reaction conditions and ligand structure during the synthesis process, enabling the metal-organic framework to adapt to the loading and growth requirements of Chlorella proteoglycans of different sizes.

[0033] 6. The metal-organic framework provided by this invention is renewable and has good stability and durability. By optimizing the preparation method, it can be produced at low cost and on a large scale, making it a promising candidate for commercial application in CO2 capture and growth of Chlorella proteoglycans. The metal-organic framework can also reduce the loss of nutrients in Chlorella cells, increase the regeneration rate of Chlorella cells, extend the lifespan of microalgae, and improve the efficiency of microalgae systems, thereby enabling safe and controllable large-scale cultivation.

[0034] 7. The metal-organic framework provided by this invention has high thermal stability and the ability to resist temperature changes. It can also prevent the supported Chlorella from being disturbed by the external environment when it swims in water, so that Chlorella can grow in harsh environments. In addition, the metal-organic framework also has good mechanical properties and can support microalgae to be suspended in solution, providing a good growth environment for Chlorella. Attached Figure Description

[0035] Figure 1 These are infrared images of metal-organic framework-alkyl-attached UiO-66-NH2 at different hydrothermal reaction temperatures in Examples 1 and 2.

[0036] Figure 2 This is a diagram showing the specific surface area and pore size distribution of the metal-organic framework-alkylamine-added UiO-66-NH2 obtained in Example 2;

[0037] Figure 3 This is a graph showing the effect of the metal-organic framework obtained in Example 3 on the growth of Chlorella proteoglycans. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] Example 1:

[0040] S1: Dissolve 0.42 g of zirconium tetrachloride and 0.45 g of 2-aminoterephthalic acid in 50 mL of N,N-dimethylformamide solution, stir on a magnetic stirrer for 30 min to dissolve, and then degas by ultrasonic vibration for 15 min.

[0041] S2: Pour the mixed solution obtained in S1 into polytetrafluoroethylene and place the container in a hydrothermal reactor that has been heated to 120°C. The hydrothermal reaction is carried out for 18 hours.

[0042] S3: After the reaction is complete, the hydrothermal reactor is naturally cooled to room temperature. The product obtained from the reaction is washed with deionized water, ethanol, and acetone, and then placed in a vacuum drying oven to dry. Finally, the product is vacuum heated at 420°C for 60 minutes.

[0043] S4: Add the final product obtained in S3 to anhydrous hexane (the mass ratio of product to anhydrous hexane is 1:10), then add an equivalent amount of N,N'-dimethylethylenediamine (1 mL) to the mixed solution and stir in a magnetic stirrer for 24 h.

[0044] S5: After the reaction is complete, the mixed solution is filtered and the solid obtained from the reaction is washed with anhydrous hexane. Then the solid is dried at 100°C to remove residual solvent. The final grayish-white powder product is the metal-organic framework, which is alkylamine-added UiO-66-NH2.

[0045] Metal-organic frameworks prepared from S5 were used in the preparation of microalgal systems.

[0046] A1: The algal strain of Chlorella proteoglycans (FACHB-9, purchased from the Institute of Hydrobiology, Chinese Academy of Sciences) was inoculated into BG11 culture medium for culture to obtain microalgae solution;

[0047] A2: Add the prepared metal-organic framework to the microalgae solution at a ratio of 0.1 g / L, and disperse the metal-organic framework evenly in the microalgae solution to obtain a mixed solution;

[0048] A3: Place the mixed solution obtained in A2 in a light incubator (the conditions of the light incubator are: temperature 26℃, light intensity 3600lx, light cycle 12h) and introduce CO2 with a volume fraction of 5% for culture. Culture in the light incubator for 3 days with aeration to obtain a microalgae system for adsorbing CO2 as described in this embodiment.

[0049] Example 2:

[0050] S1: Dissolve 0.42 g of zirconium tetrachloride and 0.45 g of 2-aminoterephthalic acid in 50 mL of N,N-dimethylformamide solution, stir on a magnetic stirrer for 30 min to dissolve, and then degas by ultrasonic vibration for 15 min.

[0051] S2: Pour the mixed solution obtained in S1 into polytetrafluoroethylene and place the container in a hydrothermal reactor that has been heated to 200°C. The hydrothermal reaction is carried out for 24 hours.

[0052] S3: After the reaction is complete, the hydrothermal reactor is naturally cooled to room temperature. The product obtained from the reaction is washed with deionized water, ethanol, and acetone, and then placed in a vacuum drying oven to dry. Finally, the product is vacuum heated at 420°C for 60 minutes.

[0053] S4: Add the final product obtained in S3 to anhydrous hexane (the mass ratio of product to anhydrous hexane is 1:10), then add an equivalent amount of N,N'-dimethylethylenediamine (1 mL) to the mixed solution and stir in a magnetic stirrer for 24 h.

[0054] S5: After the reaction is complete, the mixed solution is filtered and the solid obtained from the reaction is washed with anhydrous hexane. Then the solid is dried at 100°C to remove residual solvent. The final grayish-white powder product is the metal-organic framework, which is alkylamine-added UiO-66-NH2.

[0055] Metal-organic frameworks prepared from S5 were used in the preparation of microalgal systems.

[0056] A1: The algal strain of Chlorella proteoglycans (FACHB-9, purchased from the Institute of Hydrobiology, Chinese Academy of Sciences) was inoculated into BG11 culture medium for culture to obtain microalgae solution;

[0057] A2: Add the prepared metal-organic framework to the microalgae solution at a ratio of 0.1 g / L, and disperse the metal-organic framework evenly in the microalgae solution to obtain a mixed solution;

[0058] A3: Place the mixed solution obtained in A2 in a light incubator (the conditions of the light incubator are: temperature 26℃, light intensity 3600lx, light cycle 12h) and introduce CO2 with a volume fraction of 5% for culture. Culture in the light incubator for 3 days with aeration to obtain a microalgae system for adsorbing CO2 as described in this embodiment.

[0059] Example 3:

[0060] S1: Dissolve 0.42 g of zirconium tetrachloride and 0.45 g of 2-aminoterephthalic acid in 50 mL of N,N-dimethylformamide solution, stir on a magnetic stirrer for 30 min to dissolve, and then degas by ultrasonic vibration for 15 min.

[0061] S2: Pour the mixed solution obtained in S1 into polytetrafluoroethylene and place the container in a hydrothermal reactor that has been heated to 200°C. The hydrothermal reaction is carried out for 24 hours.

[0062] S3: After the reaction is complete, the hydrothermal reactor is naturally cooled to room temperature. The product obtained from the reaction is washed with deionized water, ethanol, and acetone, and then dried in a vacuum drying oven. Finally, the product is vacuum heated at 500°C for 60 minutes.

[0063] S4: Add the final product obtained in S3 to anhydrous hexane (the mass ratio of product to anhydrous hexane is 1:10), then add an equivalent amount of N,N'-dimethylethylenediamine (1 mL) to the mixed solution and stir in a magnetic stirrer for 24 h.

[0064] S5: After the reaction is complete, the mixed solution is filtered and the solid obtained from the reaction is washed with anhydrous hexane. Then the solid is dried at 100°C to remove residual solvent. The final grayish-white powder product is the metal-organic framework, which is alkylamine-added UiO-66-NH2.

[0065] Metal-organic frameworks prepared from S5 were used in the preparation of microalgal systems.

[0066] A1: The algal strain of Chlorella proteoglycans (FACHB-9, purchased from the Institute of Hydrobiology, Chinese Academy of Sciences) was inoculated into BG11 culture medium for culture to obtain microalgae solution;

[0067] A2: Add the prepared metal-organic framework to the microalgae solution at a ratio of 0.1 g / L, and disperse the metal-organic framework evenly in the microalgae solution to obtain a mixed solution;

[0068] A3: Place the mixed solution obtained in A2 in a light incubator (the conditions of the light incubator are: temperature 26℃, light intensity 3600lx, light cycle 12h) and introduce CO2 with a volume fraction of 5% for culture. Culture in the light incubator for 3 days with aeration to obtain a microalgae system for adsorbing CO2 as described in this embodiment.

[0069] In Example 1, a metal-organic framework-alkylamine-attached UiO-66-NH2 was prepared using zirconium tetrachloride and 2-aminoterephthalic acid as raw materials. The synthesis involved a series of steps, including the reaction of activated UiO-66-NH2 with anhydrous hexane and N,N'-dimethylethylenediamine, to obtain the metal-organic framework-alkylamine-attached UiO-66-NH2. The preparation of the metal-organic framework in Example 2 was the same as in Example 1, except for an increase in the hydrothermal reaction temperature.

[0070] like Figure 1 As shown in the figure, the effect of different temperatures on the synthesis of the metal-organic framework -UiO-66-NH2 in Examples 1 and 2 is illustrated. It can be seen that at 120℃, the temperature ranges from 3000 to 2750 cm⁻¹. -1 The appearance of a broad peak indicates strong OH stretching absorption by the carboxylic acid dimer; this peak is observed at 3400-3500 cm⁻¹ after increasing the temperature. -1 1560-1640cm -1 The intensity of the primary amine peak increased to 3000 cm⁻¹. -1 The decrease in the secondary amine peak indicates the disappearance of the carboxylic acid dimer, representing the synthesis of UiO-66-NH2. Changing the reaction temperature and time during synthesis can significantly alter the properties of the metal-organic framework, indirectly affecting its specific surface area.

[0071] Figure 2 The figure shows the specific surface area and pore size distribution of the metal-organic framework-alkylamine-attached UiO-66-NH2 synthesized in Example 2. As can be seen from the figure, the metal-organic framework-alkylamine-attached UiO-66-NH2 obtained in Example 2 has a pore size of 37.46 cm⁻¹. 3 With a specific surface area of ​​ / g and a pore size distribution of 0.65-0.85nm, this high specific surface area and pore size are beneficial to improving the adsorption efficiency of CO2.

[0072] In Example 3, the same high-temperature conditions were used as in Example 2 to prepare metal-organic framework-alkylamine-added UiO-66-NH2. The prepared metal-organic framework-alkylamine-added UiO-66-NH2 was added to *Chlorella proteoglycans* and cultured for 9 days. Simultaneously, a control group was added, in which *Chlorella proteoglycans* was also cultured for 9 days without the addition of metal-organic framework-alkylamine-added UiO-66-NH2. The growth of *Chlorella proteoglycans* was as follows: Figure 3 As shown, in Figure 3 It can be seen that the metal-organic framework (MOF) has a significant growth-promoting effect on Chlorella proteoglycans starting from the fourth day. During the culture period, the UiO-66-NH2 added by the metal-organic framework-alkylamine can effectively promote the growth of Chlorella proteoglycans, showing good application prospects.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0074] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a microalgae system for adsorbing CO2, characterized in that, The microalgae system comprises a metal-organic framework; the preparation method of the microalgae system includes the following steps: A1: The Chlorella proteoglycans were inoculated into BG11 culture medium and cultured to obtain microalgae solution; A2: Add the prepared metal-organic framework to the microalgae solution at a ratio of 0.1~0.5 g / L, and disperse the metal-organic framework evenly in the microalgae solution to obtain a mixed solution; A3: Place the mixed solution obtained in A2 in a light incubator and introduce CO2 for culture. Culture in the light incubator for 5-9 days with aeration to obtain the microalgae system for adsorbing CO2. The metal-organic framework is an alkylamine-modified amino-functionalized zirconium-based metal-organic framework material. Using a UiO-66-NH2 type zirconium-based metal-organic framework as the parent structure, a three-dimensional porous framework is formed by zirconium-oxygen cluster nodes and 2-aminoterephthalic acid ligands connected via carboxylic acid coordination. This framework is further obtained through thermal activation and alkylamine modification. The metal-organic framework was prepared by the following method: S1: Dissolve zirconium tetrachloride and 2-aminoterephthalic acid in DMF solvent at a mass fraction of 1:1~2, then stir on a magnetic stirrer, followed by ultrasonic degassing for 10min~20min; S2: Pour the mixed solution obtained in S1 into a container and place the container in a hydrothermal reactor at 120℃~200℃ for 12h~24h. S3: After the reaction is completed, the product is cooled and washed with deionized water, ethanol and acetone respectively. Then it is dried in a vacuum drying oven. Finally, the product is heated in a vacuum oven at 420℃~500℃ for 50min~80min. S4: Add the final product obtained in S3 to anhydrous hexane, then add an equivalent amount of alkylamine to the mixed solution, and stir in a magnetic stirrer for 18h~24h; S5: After the reaction is complete, the mixed solution is filtered and the solid obtained from the reaction is washed with anhydrous hexane. Then the solid is dried at a temperature of 80℃~120℃ to remove residual solvent. The final grayish-white powder product is the metal-organic framework. In step S4, the alkylamine is N,N'-dimethylethylenediamine.

2. The method for preparing a microalgae system for CO2 adsorption according to claim 1, characterized in that, In step A3, the conditions of the light incubator are: temperature 25℃~27℃, light intensity 3600lx~3800lx, light cycle 8h~12h, the volume fraction of CO2 introduced is 5%~8%, and the flow rate is... .

3. The method for preparing a microalgae system for CO2 adsorption according to claim 1, characterized in that, The stirring time of the magnetic stirrer in step S1 is 20 min to 40 min.

4. The method for preparing a microalgae system for adsorbing CO2 according to claim 1, characterized in that, In step S2, the container is a polytetrafluoroethylene (PTFE) container.

5. The method for preparing a microalgae system for adsorbing CO2 according to claim 1, characterized in that, In step S4, the mass ratio of the product to the anhydrous hexane is 1:8~10.

6. The method for preparing a microalgae system for adsorbing CO2 according to claim 1, characterized in that, In step S4, the equivalent ratio of the product to the alkylamine is 1:1 to 1.

5.

7. The method for preparing a microalgae system for CO2 adsorption according to claim 1, characterized in that, The metal-organic framework has a pore size of 0.8~1.1 nm.

8. The method for preparing a microalgae system for adsorbing CO2 according to claim 1, characterized in that, The metal-organic framework has a BET specific surface area of ​​650-800 m². 2 / g.

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