Microalgae biofilm carrier with conductive coating as well as preparation method and application of microalgae biofilm carrier

Abstract

The invention discloses a microalgae biofilm carrier with a conductive coating as well as a preparation method and application of the microalgae biofilm carrier, and relates to the field of efficient culture of microalgae and resource treatment of wastewater. The microalgae biofilm carrier comprises a surface tension regulator modified substrate and a conductive active layer loaded on the surface of the substrate, and the conductive active layer comprises defect type UiO-66 (Zr)-NH2, a conductive agent and a surface tension regulator. The microalgae biofilm carrier has stronger surface tension, is more beneficial to attachment of microalgae organisms, can improve the extracellular electron transfer efficiency of the microalgae and the photosynthesis rate of the microalgae, and promotes rapid formation of the microalgae biofilm.

Description

Technical Field

[0001] This invention relates to the field of high-efficiency microalgae cultivation and wastewater resource utilization technology, specifically to a microalgae biofilm carrier with a conductive coating, its preparation method, and its application. Background Technology

[0002] High concentrations of ammonia nitrogen pollutants in wastewater from fertilizer production, livestock farming, and food processing can easily lead to eutrophication, posing risks to aquatic life and human drinking water safety, while also increasing wastewater treatment costs and complexity. Current treatment methods for high-ammonia nitrogen wastewater include physical stripping and activated sludge nitrification / denitrification. However, these methods cannot effectively utilize ammonia nitrogen pollutants for resource recovery. Microalgae, as photosynthetic autotrophic organisms, can convert ammonia nitrogen pollutants into high-value proteins, possessing significant economic value.

[0003] However, in actual wastewater treatment, suspended algal cells are easily discharged along with the wastewater, causing the loss of microalgae. Based on the biofilm method in biochemical wastewater treatment, previous researchers have further developed algal biofilm technology for immobilized microalgae cultivation, such as introducing cotton fibers, polyurethane foam, and mohair. However, the surfaces of these traditional carriers carry negative charges and have low conductivity, which is not conducive to the attachment and proliferation of microalgae. At the same time, when treating wastewater with high ammonia nitrogen and high color and turbidity, algae receive less incident light energy, resulting in low photosynthetic energy transfer efficiency. A common adjustment method is to add conductive nanomaterial powder, but this causes the powder to be suspended in the water, which is not conducive to contact with algae. In addition, suspended conductive nanomaterials are difficult to recycle. Summary of the Invention

[0004] To address the above technical problems, this invention provides a microalgal biofilm carrier with a conductive coating, its preparation method, and its applications. This invention aims to improve the surface electropositivity and conductivity of the microalgal biofilm carrier, and simultaneously combine these two properties through in-situ synthesis to enhance microalgal photosynthetic growth and improve the removal capacity of the microalgal biofilm for ammonia nitrogen wastewater. The microalgal biofilm carrier of this invention has stronger surface tension, which is more conducive to the attachment of microalgae, can improve the extracellular electron transfer efficiency and photosynthetic rate of microalgae, and promote the rapid formation of microalgal biofilms.

[0005] The first objective of this invention is to provide a microalgae biofilm carrier with a conductive coating, comprising a substrate modified with a surface tension modifier, and a conductive active layer loaded on the surface of the substrate, the conductive active layer comprising defective UiO-66(Zr)-NH2, a conductive agent, and a surface tension modifier.

[0006] In some embodiments of the present invention, the conductive agent includes one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), polypyrrole, and polyaniline.

[0007] In some embodiments of the present invention, the surface tension modifier includes one or more of polyethylene glycol, 1-ethyl-3-methylimidazolium tetrafluoroborate, dopamine, sodium dodecylbenzenesulfonate, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0008] In some embodiments of the present invention, the substrate is one or more of polyethylene terephthalate film, polyethylene, and polystyrene; In some embodiments of the present invention, the amount of UiO-66(Zr)-NH2 is 10~16wt% of the conductive agent; for example, it can be 10, 11, 12, 13, 14, 15 and 16wt%, or any range between two values. The amount of the surface tension modifier is 4-12 wt% of the conductive agent; for example, it can be 4, 5, 6, 7, 8, 9, 10, 11, 12 wt%, or any range between two values.

[0009] A second objective of this invention is to provide a method for preparing the aforementioned microalgal biofilm carrier with a conductive coating, comprising the following steps: Defective type UiO-66(Zr)-NH2 was added to the conductive agent solution, and a first surface tension modifier was added. The mixture was then stirred to obtain a suspension. The substrate was immersed in a second surface tension modifier solution and then dried to obtain the modified substrate; The suspension was spin-coated onto the surface of the modified substrate, washed, and freeze-dried to obtain the microalgae biofilm carrier.

[0010] In some embodiments of the present invention, the amount of the first surface tension modifier added is 1-3% of the mass of the conductive agent liquid; The solvent for the conductive agent solution is water. The concentration of the conductive agent solution is 1.5-3.5 wt%; The concentration of the second surface tension modifier solution is 4-6 wt%, and the solvent is water.

[0011] In some embodiments of the present invention, the first surface tension modifier and the second surface tension modifier are independently selected from one or more of polyethylene glycol, 1-ethyl-3-methylimidazolium tetrafluoroborate, dopamine, sodium dodecylbenzenesulfonate and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0012] In some embodiments of the present invention, the defective UiO-66(Zr)-NH2 is prepared by the following method: Zirconium source and 2-aminoterephthalic acid were dissolved in an organic solvent, and an organic acid was added as a modifier to prepare defects. The mixture was then subjected to a hydrothermal reaction to obtain the defect type UiO-66(Zr)-NH2.

[0013] In some embodiments of the present invention, the zirconium source is selected from one or more of zirconium tetrachloride, zirconium oxychloride, and zirconium nitrate; The organic acid is selected from one or more of formic acid, acetic acid, and propionic acid; The hydrothermal reaction is carried out at a temperature of 150-180℃ for 12-24 hours.

[0014] In some embodiments of the present invention, the mass-to-volume ratio of the zirconium source to 2-aminoterephthalic acid and the organic solvent is (0.2~0.4):(0.4~0.6). Further, the mass ratio of the zirconium source, 2-aminoterephthalic acid, and organic solvent is (0.2~0.4):(0.4~0.6):(40-60) g / g / ml; The volume ratio of the organic solvent to acetic acid is (20-30):(1-2); The organic solvents include DMF and / or DMA.

[0015] In some embodiments of the present invention, the soaking time is 2-4 hours.

[0016] A third objective of this invention is to provide the application of the aforementioned microalgal biofilm carrier in immobilized microalgal culture.

[0017] Surface tension modification of adhesive plastic sheets promotes the adhesion of a composite coating of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) and defective UiO-66(Zr)-NH2 to the carrier surface. Simultaneously, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) facilitates extracellular electron transport in microalgae, ultimately promoting microalgal growth. Compared to traditional microalgal biofilm carriers, the membrane carrier with higher surface tension is beneficial for microalgal attachment. Furthermore, the introduction of the composite coating of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) and defective UiO-66(Zr)-NH2 provides additional internalizable extracellular electrons, increasing the photosynthetic rate of microalgae and promoting rapid microalgal biofilm formation.

[0018] The beneficial effects of this invention are: 1. This invention introduces conductive substances into the membrane carrier, thereby enhancing the extracellular electron conduction capacity of the membrane carrier. Compared with traditional membrane carriers, this can further improve the electron utilization efficiency of microalgae and promote the biofilm growth of microalgae.

[0019] 2. After the surface of the membrane carrier is modified by a surface tension modifier, the surface tension of the carrier is reduced, the affinity of the membrane carrier for microalgae is enhanced, the rapid formation of microalgae into membranes is promoted, and the immobilization, cultivation and harvesting of microalgae are facilitated. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a comparison graph showing the change in algal biomass over time under the condition of adding microalgal biofilm carrier in Application Example 1.

[0021] Figure 2 Electron micrograph of algal deposition cross section under the condition of adding microalgal biofilm carrier. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” and “contain” used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0028] The polyethylene terephthalate sheet used in this embodiment of the invention has a thickness of 2 mm.

[0029] Example 1 This embodiment provides a method for preparing a microalgal biofilm carrier with a conductive coating, as detailed below: Step 1: Add the defective UiO-66(Zr)-NH2 to a 1.7% poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) solution, and add a surface tension modifier (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt). Stir for 1 hour in the dark to obtain a suspension. The amount of defective UiO-66(Zr)-NH2 added is 12 wt% of the mass of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid), and the amount of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt added is 10 wt% of the mass of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid).

[0030] Step 2: Immerse polyethylene terephthalate sheets in a surface tension regulating agent 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt solution for 12 hours at a concentration of 5 wt%, and then dry at 60°C for 12 hours to obtain modified polyethylene terephthalate sheets.

[0031] Step 3: Spin-coat the suspension obtained in Step 1 onto the surface of the modified polyethylene terephthalate sheet obtained in Step 2, with a spin coating thickness of 700 nm, and dry it in a dark vacuum environment at 60°C for 4 hours. After drying, wash the sample with ethanol and water, and dry it again in the dark at 40°C for 12 hours. Then wash it three times with distilled water and freeze-dry it to obtain the microalgae biofilm carrier.

[0032] The defective UiO-66(Zr)-NH2 was prepared by the following method: 0.466 g of zirconium tetrachloride and 0.726 g of 2-aminoterephthalic acid were simultaneously dissolved in 50 ml of N,N-dimethylformamide, and 2 ml of acetic acid was added. After thorough mixing, the mixture was transferred to a reaction vessel and hydrothermally reacted in an oven at 150 °C for 12 hours. The sample was then centrifuged, and the lower solid powder was collected and repeatedly washed with N,N-dimethylformamide and anhydrous ethanol. Finally, it was dried in a vacuum oven at 100 °C for 12 hours to obtain defective UiO-66(Zr)-NH2.

[0033] Example 2 The only difference from Example 1 is that in step 1, the surface tension modifier is replaced with dopamine; the rest of the steps and parameters are the same as in Example 1.

[0034] Example 3 The only difference from Example 1 is that in step 1, the surface tension modifier is replaced with sodium dodecylbenzenesulfonate; the remaining steps and parameters are the same as in Example 1.

[0035] Comparative Example 1 The only difference from Example 1 is that the addition of defect type UiO-66(Zr)-NH2 in step 1 is omitted; the remaining steps and parameters are the same as in Example 1.

[0036] Comparative Example 2 The only difference from Example 1 is that the addition of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) in step 1 is omitted; the remaining steps and parameters are the same as in Example 1.

[0037] Comparative Example 3: The difference from Example 1 is that the defect type UiO-66(Zr)-NH2 in step 1 is changed to ZIF-67; the remaining steps and parameters are the same as in Example 1.

[0038] Comparative Example 4: The difference from Example 1 is that the defect type UiO-66(Zr)-NH2 in step 1 is changed to BTC-Zn; the remaining steps and parameters are the same as in Example 1.

[0039] Application Example 1 Experiments were conducted on the microalgal biofilm carriers prepared in the above examples and comparative examples: The microalgal biofilm carriers prepared in Examples 1-3 and Comparative Examples 1-4 were processed to a size of 0.3*0.3 meters and fixed on a plastic support. The support was then placed in a 0.8*0.5*0.5 meter algal culture tank, with BG-11 medium added at a concentration of 1.7 g / L as the nutrient source. The initial biomass concentration of Chlorella was 0.5 g / L, the light intensity was 5000 Lux, and the light-dark time ratio was 14:10 h. The biofilm carriers were periodically removed, rinsed, and the algal biomass was collected, weighed, and the biomass of the algal biofilm was calculated.

[0040] from Figure 1 It can be seen that the microalgae biofilm carriers prepared in Examples 1-3 of the present invention can achieve surface growth rates of 4.32, 3.99, and 3.76 g / m³, respectively. 2·d, where Example 1 improved by 23% and 34% compared with Comparative Example 1 and Comparative Example 2, respectively. The results show that the conductive microalgal biofilm carrier prepared in Example 1 can significantly promote the immobilized growth of microalgae after rapid film formation, and has good application prospects in the field of microalgal resource cultivation.

[0041] Figure 2 Electron micrograph of cross-sectional algal deposition under conditions where microalgal biofilm carriers are added. Figure 2 It can be seen that the biofilm deposition thickness increased significantly, from 3.56 μm to 5.21 μm.

[0042] The embodiments described above are merely preferred embodiments for fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A microalgal biofilm carrier with a conductive coating, characterized in that, The invention includes a substrate modified with a surface tension modifier, and a conductive active layer loaded on the surface of the substrate, the conductive active layer comprising defect-type UiO-66(Zr)-NH2, a conductive agent, and a surface tension modifier.

2. The microalgal biofilm carrier with a conductive coating as described in claim 1, characterized in that, The conductive agent includes one or more of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), polyaniline, and polypyrrole.

3. The microalgal biofilm carrier with a conductive coating as described in claim 1, characterized in that, The surface tension modifier includes one or more of polyethylene glycol, 1-ethyl-3-methylimidazolium tetrafluoroborate, dopamine, and sodium dodecylbenzenesulfonate; the substrate is one or more of polyethylene terephthalate film, polyethylene, and polystyrene.

4. The microalgal biofilm carrier with a conductive coating as described in claim 1, characterized in that, The amount of UiO-66(Zr)-NH2 used is 10~16wt% of the conductive agent liquid.

5. The microalgal biofilm carrier with a conductive coating as described in claim 1, characterized in that, Place The amount of the surface tension modifier used is 4-12 wt% of the conductive agent liquid.

6. The method for preparing a microalgal biofilm carrier with a conductive coating as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Defective type UiO-66(Zr)-NH2 was added to the conductive agent solution, and a first surface tension modifier was added. The mixture was then stirred to obtain a suspension. The substrate was immersed in a second surface tension modifier solution and then dried to obtain the modified substrate; The suspension was spin-coated onto the surface of the modified substrate, washed, and freeze-dried to obtain the microalgae biofilm carrier.

7. The preparation method according to claim 6, characterized in that, The defective UiO-66(Zr)-NH2 was prepared by the following method: Zirconium source and 2-aminoterephthalic acid were dissolved in an organic solvent, and an organic acid was added as a modifier to prepare defects. The mixture was then subjected to a hydrothermal reaction to obtain the defect type UiO-66(Zr)-NH2.

8. The preparation method according to claim 7, characterized in that, The zirconium source is selected from one or more of zirconium tetrachloride, zirconium oxychloride, and zirconium nitrate. The hydrothermal reaction is carried out at a temperature of 150-180℃ for 12-24 hours.

9. The preparation method according to claim 7, characterized in that, The mass ratio of the zirconium source to 2-aminoterephthalic acid is (0.1~0.2):(0.2~0.3). The organic solvents include DMF and / or DMA.

10. The application of the microalgal biofilm carrier as described in any one of claims 1 to 5 in the immobilized microalgal culture.

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