MOFs / Polymer Floating Materials, Preparation Method and Application in Suppressing Harmful Algae

Abstract

The present invention provides MOFs / polymer floating materials, a preparation method thereof, and an application thereof in inhibiting harmful algae in water, relating to the technical field of water treatment, and aiming to solve the problem that metal-organic frameworks are not easily applied on a large scale to the treatment of harmful algae. The MOFs / polymer floating materials are composed of metal-organic frameworks and floating polymer resin particles. It can enable the metal-organic frameworks to be used for inhibiting and treating harmful algae in water.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular, to a MOFs / polymer floating material, a preparation method thereof, and an application thereof in inhibiting harmful algae in water. Background Art

[0002] Due to the increasing frequency of natural factors and human activities, a lot of nitrogen- and phosphorus-rich substances are released into natural water bodies through erosion, surface runoff, groundwater, and atmospheric deposition. Especially in relatively stagnant freshwater lakes, the rate of nutrient input exceeds the rate of consumption, resulting in a large accumulation of nutrients. Coupled with suitable light conditions and temperature, it induces large-scale regional outbreaks of many algal blooms. The main algae causing algal blooms is cyanobacteria. Among them, Microcystis aeruginosa is the most representative algal bloom species, with stronger stress resistance and adaptability than other algae, so it has become the dominant species in most freshwater lakes. In addition, the pseudo-vacuole structure in the cells of Microcystis aeruginosa is conducive to its growth floating on the water surface, thereby competitively absorbing more incident sunlight and inhibiting the growth of other aquatic organisms through the shading effect, destroying the ecological diversity in the water. In addition, Microcystis aeruginosa produces microcystin during its growth process. Its chemical stability is strong and it is difficult to degrade in nature. Ingestion of this toxin will greatly increase the risk of humans suffering from liver cancer. Therefore, it is urgent to solve the problem of algal blooms dominated by Microcystis aeruginosa.

[0003] At present, the traditional methods for removing harmful algae in natural water bodies are mainly physical methods, chemical methods, and biological methods. The relatively common methods currently in use are physical salvage and addition of chemical flocculants. The physical salvage method is currently the most widely used and relatively mature. Artificial mechanical equipment is used to remove the accumulated surface live algae and bottom algal dormant bodies. However, this method is difficult to completely remove the toxins produced by algae, and the labor cost consumed is very high; although the coagulation precipitation method can take effect quickly, it is easy to introduce secondary pollutants into the water body; the biological method has no additional risks, but the effective period is long, and the cost of pre-cultivating aquatic plants is also relatively high. Therefore, it is necessary to find a more efficient and thorough means to inhibit harmful algae to assist the above methods to more effectively control the algal blooms caused by harmful algae.

[0004] Metal-organic framework (MOFs) materials are currently hot materials. MOFs are periodic framework structures composed of metal ions and organic ligands. They have a generally large specific surface area and abundant active sites. They have been proven to effectively utilize various light sources and activate other oxides to generate photogenerated holes and a variety of reactive oxygen species for efficient oxidation and degradation of pollutants. The advantages of using MOFs-based materials to remove harmful algae are mainly: first, during the period when algal cells grow most vigorously using light, MOFs with photocatalytic properties can also use light to generate holes and other reactive oxygen species at the same time; second, at the appropriate temperature for algal cell growth, the catalytic / activation reaction activity of MOFs is also relatively strong; third, compared with physical methods, MOFs can also simultaneously degrade the released algal toxins. Therefore, MOFs are an ideal material for inhibiting harmful algae in water. However, most MOFs exist in the form of powders, which are easy to lose and agglomerate in water, which is not conducive to their placement and recycling in actual water bodies. Therefore, MOFs-based powder materials can be fixed on some larger substrates, which not only delays the rapid loss of MOFs powder in water, but also helps to improve the dispersibility of MOFs nanoparticles through the size confinement effect of the substrate. Summary of the invention

[0005] The first object of the present invention is to provide a MOFs / polymer floating material to solve the technical problem that the existing metal organic frameworks are not easily applied to the treatment of harmful algae in water.

[0006] The MOFs / polymer floating material provided by the invention consists of a metal organic framework and floating polymer resin particles.

[0007] The beneficial effects brought by the MOFs / polymer floating material of the present invention are:

[0008] The present invention combines the principles of interface engineering, and skillfully integrates the metal organic framework with solar photocatalytic performance and the high-density polymer resin particles with floating function, effectively reducing the preparation process and cost of floating materials. Among them, the various active oxygen species produced by the metal organic framework can produce oxidative stress on algal cells, and can further degrade the algal toxins released by the lysis of algal cells; the polymer resin particle substrate improves the operability, stability and recyclability of the metal organic framework material in water, while increasing the closeness of the metal organic framework to the floating algae, and improving the utilization efficiency of incident sunlight. The MOFs / polymer floating material has a rapid effect on the algal bloom problem represented by Microcystis aeruginosa, a short treatment cycle, and a thorough treatment effect, which greatly reduces the investment and cost of the actual water treatment process, has high economic benefits, and has guiding significance for the use of metal organic frameworks in the repair of actual small-scale water pollution problems.

[0009] In an alternative technical solution, the metal-organic framework is at least one of MIL-88A(Fe), MIL-88B(Fe), NH 2 -MIL-88B(Fe), MIL-101(Fe), NH 2 -MIL-101(Fe), MIL-100(Fe), and MIL-53(Fe); and / or, the floating polymer resin particles are granular polymer resin materials with a particle size of 1 mm to 5 mm, thermoplasticity, and a specific gravity lower than that of water.

[0010] In an alternative technical solution, the floating polymer resin particles have a particle size of 3 mm to 4 mm; and / or, the floating polymer resin particles are disc-shaped; and / or, the floating polymer resin particles are made of at least one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, and ethylene-vinyl alcohol copolymer.

[0011] The second object of the present invention is to provide a preparation method for preparing the above-mentioned MOFs / polymer floating material to solve the technical problem that metal-organic frameworks are not easily applied to the treatment of harmful algae in water.

[0012] The preparation method provided by the present invention for preparing the above-mentioned MOFs / polymer floating material includes: first, sowing an iron-based metal-organic framework precursor on the surface of floating polymer resin particles, and then growing the iron-based metal-organic framework on the floating polymer resin particles.

[0013] The invention evenly sows precursor particles of the metal-organic framework on the surface of the polymer resin as nucleation sites for the subsequent growth of the metal-organic framework. Subsequently, by introducing metal ions, the metal-organic framework is firmly attached to the polymer resin particles through the chemical coordination bonding between the metal ions and the precursor. It can ingeniously integrate the metal-organic framework with sunlight catalytic performance and the polymer resin particles with floating function closely.

[0014] The beneficial effects brought by the preparation method of the MOFs / polymer floating material of the present invention are:

[0015] In an alternative technical solution, the iron-based metal-organic framework precursor is an organic linker in the metal-organic framework molecule. The iron-based metal-organic framework precursor is at least one of terephthalic acid, 2-aminoterephthalic acid, trimesic acid, and fumaric acid. Further preferably, it is fumaric acid, and fumaric acid is preferably a solid powder.

[0016] In an alternative technical solution, the seeding of the iron-based metal-organic framework precursor on the surface of the floating polymer resin particles includes binding the metal-organic framework precursor to the surface of the floating polymer resin particles. In this surface binding, the metal-organic framework precursor powder is directly mixed with the floating polymer resin particles, preferably by the combined action of heating and magnetic stirring. Further preferably, the stirring speed is 20 rpm to 250 rpm, the heating temperature is 100 °C to 200 °C, and the stirring time is 5 min to 20 min. Even more preferably, the stirring rate is 150 rpm to 200 rpm, the heating temperature is 140 °C to 180 °C, and the stirring time is 7 min to 10 min. The mass ratio of the metal-organic framework precursor powder to the floating polymer resin particles is preferably 10:1 to 3:1, and further preferably 5:1 to 3:1.

[0017] During the seeding process of the precursor, the iron-based metal-organic framework precursor is blended with the polymer and stirred under high-temperature conditions. On the one hand, the high temperature causes the surface of the polymer resin particles to melt, forming a soft molten film structure at the interface, which can enrich the precursor particles on the surface of the polymer resin particles through van der Waals forces and hydrogen bonding. The physical isolation effect of the iron-based metal-organic framework precursor particles also prevents the polymer resin particles from sticking to each other. On the other hand, the high-temperature conditions prompt partial breakage and recombination of the molecular chains in the polymer resin, resulting in self-modification of the polymer. Some of the recombined molecular chains combine with oxygen in the air to form a large number of exposed oxygen-containing active functional groups. The unsaturated groups in the functional groups can undergo an esterification reaction with the iron-based metal-organic framework precursor and bond to each other, thereby anchoring the iron-based metal-organic framework precursor on the surface of the polymer resin particles. Combining the stirring process can ensure that the molecules in the iron-based metal-organic framework precursor particles come into full and uniform contact with the surface of the modified polymer resin particles.

[0018] In an alternative technical solution, the seeding of the iron-based metal-organic framework precursor on the surface of the floating polymer resin particles includes binding the metal-organic framework precursor to the surface of the floating polymer resin particles and cooling the surface-bound product. The metal-organic framework precursor is bound to the surface of the floating polymer resin particles to obtain the surface-bound product. During the cooling of the surface-bound product, the surface-bound product is placed at room temperature for natural cooling and re-hardens and forms. The cooling time is 10 min to 20 min.

[0019] In an alternative technical solution, the growth of the iron-based metal-organic framework on the floating polymer resin particles includes: immersing the surface-bound product in a metal salt solution, causing metal ions in the metal salt solution to undergo a coordination reaction with the precursor, and forming a metal-organic framework on the surface of the floating polymer particles; the temperature of the coordination reaction is room temperature, and the reaction time is 12 h to 48 h, more preferably 18 h to 24 h; it is further preferred to use magnetic stirring, and the stirring rate is further preferably 20 rpm to 250 rpm, and more preferably 150 rpm to 200 rpm.

[0020] Metal ions in the solution will coordinate with the oxygen-containing functional groups in the precursor on the surface of the polymer resin, thereby in-situ self-assembling to form a metal-organic framework on the surface of the polymer resin.

[0021] In an alternative technical solution, the metal salt in the metal salt solution is a solid compound composed of metal cations and inorganic anions; and / or, the solvent in the metal salt solution is at least one of deionized water, methanol, ethanol, acetone, and ether; and / or, the mass concentration of the solid compound is 1 g / L to 100 g / L; and / or, the mass ratio of the surface-bound product to the metal salt solution is 1:5 to 1:100, more preferably 1:20 to 1:30.

[0022] The third object of the present invention is to provide an application of MOFs / polymer floating materials in inhibiting harmful algae in water, so as to solve the technical problem that metal-organic frameworks are not easily applied to the treatment of harmful algae in water.

[0023] Since harmful algae represented by Microcystis aeruginosa generally grow floating on the water surface, and the light intensity of the incident sunlight will rapidly decay with the water depth, the present invention selects floating polymer resin particles with a density lower than that of water as the carrier of the iron-based metal-organic framework. On the one hand, as a sunlight catalyst, the iron-based metal-organic framework absorbs the most light energy at the water surface with the help of the floating carrier, so the photocatalytic activity is stronger, and more reactive oxygen species for inhibiting the growth and reproduction of algae are generated; on the other hand, the material floating on the water surface can be more fully and closely contacted with the algae floating on the water surface at the same time, which is conducive to improving the removal efficiency and selectivity of the material for algae. In addition, after water treatment, the floating material is easy to separate from the water, without additional operations such as air flotation or dredging of bottom mud, saving a large amount of labor costs and energy consumption generated by large equipment.

[0024] In an alternative technical solution, the algae are preferably at least one of Microcystis aeruginosa, Fragilaria, Pediastrum duplex, Merismopedia, Spirogyra, Anabaena, Scenedesmus dimorphus, Pediastrum astreoides, Chlorella vulgaris, and Cymbella cymbelliformis, more preferably Microcystis aeruginosa.

[0025] In an alternative technical solution, the algal strain is purchased from the Freshwater Algae Culture Collection of the Chinese Academy of Sciences, preferably with numbers ranging from FACHB-315 to FACHB-937, and more preferably FACHB-905.

[0026] In an alternative technical solution, the time of the MOFs / polymer floating material in the algal solution is preferably 30 min to 240 min, and more preferably 30 min to 90 min. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the background art, the following will briefly introduce the drawings required for the description of the embodiments or the background art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the preparation process of the MOFs / polymer floating material in Embodiment 1 of the present invention.

[0029] Figure 2 It is a photo of high-density polyethylene particles without loaded MIL-88A(Fe) in Embodiment 1 of the present invention.

[0030] Figure 3 It is a photo of high-density polyethylene particles loaded with MIL-88A(Fe) in Embodiment 1 of the present invention.

[0031] Figure 4 It is a scanning electron microscope image of the surface of high-density polyethylene particles without loaded MIL-88A(Fe) in Embodiment 1 of the present invention.

[0032] Figure 5 It is a scanning electron microscope image of the surface of high-density polyethylene particles loaded with MIL-88A(Fe) in Embodiment 1 of the present invention.

[0033] Figure 6 It is an X-ray diffraction pattern of the MIL-88A(Fe) powder scraped from the high-density polyethylene particles loaded with MIL-88A(Fe) in Embodiment 1 of the present invention.

[0034] Figure 7 It is an infrared spectrum of the surface of high-density polyethylene particles loaded with MIL-88A(Fe) in Embodiment 1 of the present invention.

[0035] Figure 8X-ray photoelectron spectroscopy of the surface of high-density polyethylene particles loaded with MIL-88A(Fe) in Embodiment 1 of the present invention. Among them, Figure (a) is the total elemental spectrum, and Figure (b) is the enlarged local spectrum of Fe 2p.

[0036] Fig. 9 Physical photo of the reactor in Embodiment 2 of the present invention.

[0037] Fig.10 Photo of the Microcystis aeruginosa suspension in Embodiment 2 of the present invention. Among them, the left side is the original algal solution of Microcystis aeruginosa, and the right side is the algal solution of Microcystis aeruginosa treated with the MOFs / polymer floating material of the present invention under sunlight.

[0038] Fig.11 Photos of algal cells in the Microcystis aeruginosa suspension taken by an optical microscope. Among them, Figure (a) is a photo of algal cells in the original algal solution of Microcystis aeruginosa, and Figure (b) is a photo of algal cells in the algal solution of Microcystis aeruginosa treated with the MOFs / polymer floating material of the present invention under sunlight for 90 min.

[0039] Fig.12 Optical density value (OD 680 ) curve of the Microcystis aeruginosa algal solution treated with the MOFs / polymer floating material of the present invention under sunlight over time.

[0040] Fig.13 Curve of the chlorophyll a content of Microcystis aeruginosa cells treated with the MOFs / polymer floating material of the present invention under sunlight over time.

[0041] Fig.14 Variation of intracellular organic matter of Microcystis aeruginosa cells treated with the MOFs / polymer floating material of the present invention under sunlight, characterized by three-dimensional fluorescence spectroscopy. Among them, Figures (a), (b), (c), and (d) are the three-dimensional fluorescence spectra of intracellular organic matter of Microcystis aeruginosa cells treated with the MOFs / polymer floating material of the present invention under sunlight for 0 min, 30 min, 60 min, and 90 min, respectively.

[0042] Fig.15 Signals of different reactive oxygen species generated by the MOFs / polymer floating material of the present invention under simulated sunlight, characterized by electron spin resonance spectroscopy. Among them, Figure (a) is the hydroxyl radical signal, and Figure (b) is the superoxide radical signal.

[0043] Fig.16 Degradation performance of the MOFs / polymer floating material of the present invention on microcystin released by the lysis of Microcystis aeruginosa cells under simulated sunlight. Detailed implementation mode

[0044] First, the preparation methods disclosed in the prior art documents of some iron-based metal-organic framework materials used in this application will be described. Specifically, the corresponding reference documents for these preparation methods are shown in Table 1

[0045] Table 1:

[0046] Preferred metal organic framework names Related references MIL-53(Fe) J. Alloys Compd., 2020, 844, 156147 MIL-100(Fe) Chin. J. Catal., 2019, 40(1), 70-79 MIL-101(Fe) J. Am. Chem. Soc., 2009, 131(25), 8775-8777 <![CDATA[NH 2 -MIL-101(Fe)]]> Polyhedron, 2017, 127, 464-470 MIL-88A(Fe) Mater. Res. Bull., 2020, 125, 110806 MIL-88B(Fe) Appl. Catal., B, 2023, 331, 122699 <![CDATA[NH 2 -MIL-88B(Fe)]]> Appl. Surf. Sci., 2020, 505, 144616

[0047] The suspension of Microcystis aeruginosa (FACHB-905) was purchased from the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences and stored sealed in a 10 mL centrifuge tube; the BG-11 medium was purchased from the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences, and the formula is shown in Tables 2 and 3

[0048] Table 2 Chemical components of BG-11 medium

[0049] Components Dosage Mother liquor concentration <![CDATA[NaNO 3 > 10mL / L <![CDATA[15 g / 100ml H 2 O]]> <![CDATA[K 2 HPO 4 > 10 mL / L <![CDATA[2g / 500 mL H 2 O]]> <![CDATA[MgSO 4 ·7H 2 O]]> 10 mL / L <![CDATA[3.75g / 500 mL H 2 O]]> <![CDATA[CaCl 2 ·2H 2 O]]> 10 mL / L <![CDATA[1.8g / 500 mL H 2 O]]> Citric Acid 10 mL / L <![CDATA[0.3g / 500 mL H 2 O]]> Ammonium Ferric Citrate 10 mL / L <![CDATA[0.3 g / 500 mL H 2 O]]> Disodium EDTA 10 ml / L <![CDATA[0.05 g / 500 mL H 2 O]]> <![CDATA[Na 2 CO 3 > 10 mL / L <![CDATA[1.0g / 500ml H 2 O]]> A5 solution 1 mL / L See Table 3 for details

[0050] Table 3 Chemical components in A5 solution

[0051] Components concentration <![CDATA[H 3 BO 3 > <![CDATA[2.86g / L H 2 O]]> <![CDATA[MnCl 2 ·4H 2 O]]> <![CDATA[1.86g / L H 2 O]]> <![CDATA[ZnSO 4 ·7H 2 O]]> <![CDATA[0.22g / L H 2 O]]> <![CDATA[Sodium 2 Molybdenum Oxide 4 ·2Hydrates 2 O]]> <![CDATA[0.39g / L H 2 O]]> <![CDATA[CuSO 4 ·5H 2 O]]> <![CDATA[0.08g / L H 2 O]]> <![CDATA[Co(NO 3 ) 2 ·6H 2 O]]> <![CDATA[0.05g / L H 2 O]]>

[0052] The floating polymer resin particles are preferably selected from those with a particle size of 3 mm to 4 mm, a disc-shaped particle shape, and the preferred materials are at least one of high-density polyethylene (HDPE, Shandong Yousuo Chemical Technology Co., Ltd.), low-density polyethylene (LDPE, Shandong Yousuo Chemical Technology Co., Ltd.), linear low-density polyethylene (LLDPE, Shandong Yousuo Chemical Technology Co., Ltd.), polypropylene (PP, Shandong Yousuo Chemical Technology Co., Ltd.), and ethylene-vinyl alcohol copolymer (EVOH, Kuraray Co., Ltd., Japan), and more preferably high-density polyethylene (HDPE, Shandong Yousuo Chemical Technology Co., Ltd.)

[0053] Preferably, in the typical embodiments of the present invention, HDPE particles are selected as the substrate for loading metal-organic frameworks, mainly for the following reasons: First, HDPE particles are the most common among the listed floating polymer resin particles; Second, HDPE particles will undergo more significant deformation under high-temperature conditions to form flat discs, expanding the sunlight absorption area of the floating materials, which is more conducive to using the incident sunlight for photocatalytic reactions

[0054] Preferably, the typical embodiment of the present invention selects MIL-88A (Fe) as a representative iron-based metal organic framework, mainly for the following reasons: First, compared with other iron-based metal organic frameworks, MIL-88A (Fe) can be directly generated under normal temperature and pressure conditions, without the need for high temperature and high pressure, thus saving energy; Second, compared with other iron-based metal organic frameworks, the precursor fumaric acid of MIL-88A (Fe) has the lowest biological toxicity under the same test conditions, so it is more environmentally friendly; Third, MIL-88A (Fe) can be used as a photocatalyst, directly using sunlight to produce a variety of reactive oxygen species to kill Microcystis aeruginosa and degrade the microcystin toxins released by it.

[0055] In addition, the sources of raw materials and equipment used in the examples of the present invention are shown in Table 4:

[0056] Table 4

[0057] Use of raw materials or equipment model Source or Manufacturer Ferric chloride Analytical grade Beijing Bailingwei Technology Co., Ltd. Fumaric Acid Analytical grade Beijing Bailingwei Technology Co., Ltd. Anhydrous ethanol Analytical grade Fuchen (Tianjin) Chemical Reagent Co., Ltd. acetone Spectral pure Fuchen (Tianjin) Chemical Reagent Co., Ltd. Magnesium carbonate Analytical grade Shanghai MacLean Biochemical Technology Co., Ltd. High density polyethylene (HDPE) granules DPE 5000S Shandong Yousuo Chemical Technology Co., Ltd. X-ray diffractometer (XRD) DX-2700B Dandong Haoyuan Co., Ltd. Fourier Transform Infrared Spectrometer (FTIR) Nicolet 6700 Nicole Corporation Scanning electron microscopy (SEM) SU8020 Hitachi Ltd. Pallet balance Scout SL Mettler-Toledo (Changzhou) Weighing Equipment Co., Ltd. sieve 10 mesh Zhenxing Screen Factory Electric constant temperature blast drying oven (referred to as "oven") 2000 W Shanghai Jingqi Instrument Co., Ltd. Microcystis aeruginosa FACHB-905 Freshwater Algae Seed Bank of Chinese Academy of Sciences Liquid culture medium BG-11 Freshwater Algae Seed Bank of Chinese Academy of Sciences 3D Fluorescence Spectrometer FL970 Plus Tianmei Group X-ray Photoelectron Spectrometer 250xi Thermo Fisher Scientific Inc. UV-Vis Spectrophotometer UV2600 Tianmei Group Electron Spin Resonance Spectrometer FA 200 JIOULU (BEIJING) TECHNOLOGY AND TRADE CO., LTD. Optical Microscope WZS-0870(0870T) Dongguan Weinius Optoelectronics Technology Co., Ltd. Ultrasonic cell disruptor JY92-II Ningbo Xinzhi Biotechnology Co., Ltd. High-speed refrigerated centrifuge Avanti JXN-30 Beckman Coulter International Trading (Shanghai) Co., Ltd. Low temperature refrigerator GY-A228N Wuxi Guanya Intelligent Equipment Co., Ltd. Thermostatic Magnetic Stirrer C-MAG HS 4 IKA GmbH High Performance Liquid Chromatography-Mass Spectrometry / Mass Spectrometry (HPLC-MS / MS) <![CDATA[TSQ Altis TM Plus]]> Thermo Fisher Scientific Inc.

[0058] Figure 1 Schematic diagram of the preparation process of the MOFs / polymer floating material of Example 1 of the present invention. Figure 1 As shown, the preparation and application of the MOFs / polymer floating material of the present application includes the following processes:

[0059] First, a metal organic framework precursor and floating polymer resin particles in a suitable proportion are mixed in a beaker and placed on a hot plate for continuous stirring. The sowing of the precursor on the surface of the floating polymer resin particles is promoted by adjusting the heating temperature, stirring rate and stirring time. The sown polymer resin particles are then cooled at room temperature to harden their surfaces again, and then immersed in a metal salt solution of a certain concentration and stirred continuously. By adjusting the stirring rate, the metal ions in the solution will coordinate with the precursor molecules loaded on the surface of the floating polymer resin particles, thereby realizing the in-situ self-assembly growth of the metal organic framework on the surface of the floating polymer resin particles, and finally forming a MOFs / polymer floating material. Furthermore, the prepared MOFs / polymer floating material is directly added to the algae solution of Microcystis aeruginosa in summer, so that it releases active substances under the action of sunlight to remove Microcystis aeruginosa and the microcystin toxins it produces.

[0060] The following implementation and application examples provide in detail the process of preparing MOFs / polymer floating materials and their application in inhibiting Microcystis aeruginosa in water.

[0061] Example 1: Preparation and characterization of HDPE floating material loaded with MIL-88A(Fe)

[0062] Weigh 10.0 g of HDPE particles and 30.0 g of fumaric acid powder into a 500 mL beaker, magnetically stir at 140 °C with a rotation speed of 200 rpm for 7 min. Subsequently, use a sieve to filter out the fumaric acid powder that has not been seeded on the surface of the HDPE particles. Cool the treated HDPE particles at room temperature for 10 min, then add them to an aqueous solution of ferric chloride at 30 g / L, continue to stir at room temperature with a rotation speed of 200 rpm for 24 h, then take them out and place them in an oven to dry, thus obtaining the HDPE floating material loaded with MIL-88A(Fe), denoted as MHDPE.

[0063] Figure 2 This is a photograph of the high-density polyethylene particles without loaded MIL-88A(Fe) in Example 1 of the present invention. Figure 3 This is a photograph of the high-density polyethylene particles loaded with MIL-88A(Fe) in Example 1 of the present invention. From Figure 2 and Figure 3 By comparison, it can be seen that the pure HDPE particles are milky white disc-shaped, while the color of the MHDPE floating material after loading MIL-88A(Fe) has changed to reddish-brown, and the shape has also changed to a flat disc.

[0064] Figure 4 This is a scanning electron micrograph of the surface of the high-density polyethylene particles without loaded MIL-88A(Fe) in Example 1 of the present invention. Figure 5 This is a scanning electron micrograph of the surface of the high-density polyethylene particles loaded with MIL-88A(Fe) in Example 1 of the present invention. From Figure 4 and Figure 5 By comparison, it can be seen that the surface of the pure HDPE particles is relatively smooth, while a large number of spindle-shaped MIL-88A(Fe) particles are attached to the surface of the MHDPE floating material after loading MIL-88A(Fe). The particle morphology is consistent with that of the MIL-88A(Fe) particles in the relevant reference (DOI: 10.1016 / j.materresbull.2020.110806).

[0065] After scraping off the MIL-88A(Fe) particles on the surface of MHDPE, use a powder X-ray diffractometer for characterization, and the results are as Figure 6 shown. The X-ray diffraction pattern of the loaded MIL-88A(Fe) particles corresponds one by one to the peaks in the X-ray diffraction pattern in the relevant reference (DOI: 10.1016 / j.materresbull.2020.110806), further confirming the successful synthesis of MIL-88A(Fe).

[0066] The surface infrared spectrum of MHDPE is as Figure 7As shown, compared with pure MIL-88A(Fe), MHDPE has a new stretching vibration peak of the C=O bond at a wavenumber of 1750 cm -1 ~1500 cm -1 , indicating the existence of a bonding interaction formed by the esterification reaction between the carboxyl group in fumaric acid and the oxygen-containing functional groups generated during the heating of HDPE in MHDPE. In the Fe 2p spectrum of MHDPE, an offset in the binding energy position compared to pure MIL-88A(Fe) can also be observed, as Figure 8 shown, further indicating a certain interaction between MIL-88A(Fe) and HDPE during the binding process.

[0067] Example 2: Activation and scale-up culture of Microcystis aeruginosa

[0068] Under sterile conditions, transfer all the Microcystis aeruginosa suspension to a 20 mL small Erlenmeyer flask using a pipette, seal the conical flask with a sterile sealing film, and then place the conical flask in an incubator to be activated for one week at room temperature and under weak light irradiation (set the light intensity to 1000 lux and the culture temperature to 25 °C). Subsequently, under sterile conditions, use a pipette to aspirate 10 mL of the algal solution from the Erlenmeyer flask and transfer it to a 250 mL ordinary Erlenmeyer flask, add 200 mL of BG-11 liquid medium, shake well and continue to culture in the incubator. Set the light intensity to 2000 - 3000 lux, the daily light cycle to 10 h, shake 2 - 3 times a day, and the culture temperature to 25 °C. When the algal solution in the Erlenmeyer flask shows dark green, under sterile conditions, aspirate 10 mL of the algal solution from the Erlenmeyer flask multiple times and transfer it to multiple 250 mL ordinary Erlenmeyer flasks respectively. Add 200 mL of BG-11 liquid medium to each Erlenmeyer flask, shake well and continue to culture in the incubator. The light intensity, daily light cycle and culture temperature remain unchanged, and so on. Subsequently, scale up the culture of the algal solution according to the same method.

[0069] Before carrying out the application example, under sterile conditions, use a pipette to aspirate 50 mL of the algal solution with a light green color and a strong pungent smell and place it in a centrifuge tube. Centrifuge at 8500 rpm for 5 min, discard the supernatant and re - volume to 50 mL with deionized water. Shake well and place the algal solution in the incubator for starvation culture for 24 h under the same light and temperature conditions as the target in the subsequent application example.

[0070] Application Example 1: Experiment on the removal performance of MOFs / polymer floating materials for Microcystis aeruginosa

[0071] First, to intuitively understand the changes in cell integrity and cell density of algal cells after the action of MHDPE, it is necessary to observe and count the morphology and number of cells. The observation of macroscopic morphology mainly uses an optical microscope. After dropping the algal solution on a hemocytometer, it can be directly observed under an optical microscope. The counting of algal cell numbers mainly uses the optical density method. The absorbance of the algal solution at 680 nm is directly measured using a UV-visible spectrophotometer and denoted as OD 680 . OD 680 The value is proportional to the cell density of Microcystis aeruginosa. Therefore, according to the changing trend of OD 680 over time before and after the action of MHDPE, the inhibitory effect of MHDPE on Microcystis aeruginosa can be reflected.

[0072] Specifically, 50 mL of the algal solution after starvation treatment in Example 2 was added to a culture dish with a volume of 50 mL, and 1.0 g of MOFs / polymer floating material MHDPE was added. It was placed under sunlight at 10 am in August. At 0 min, 30 min, 60 min, and 90 min, 2 mL of the sample was taken using a syringe. The sample was not processed and the absorbance of the sample at a wavelength of 680 nm was directly measured using a UV-visible spectrophotometer and denoted as OD 680t , where t is 0 min, 30 min, 60 min, and 90 min. A curve of OD 680t changing with time was plotted. At the same time, a part of the taken sample was dropped onto a hemocytometer and photographed using an optical microscope.

[0073] To exclude the influence of polymer resin particles on Microcystis aeruginosa, HDPE resin particles without loaded MIL-88A(Fe) with the same mass (1.0 g) were used as a control. Keeping other conditions the same, the measured absorbance values of the taken samples were respectively denoted as OD 680t, control , where t is 0 min, 30 min, 60 min, and 90 min. A curve of OD 680t, control changing with time was plotted.

[0074] Figure 10 shows the color change of the algal solution before and after the action of MHDPE. The original algal solution was light green, while the algal solution after MHDPE treatment was almost completely decolorized, and no precipitation was observed, indicating that the reactive oxygen species generated by MIL-88A(Fe) in MHDPE achieved almost complete degradation of algal cells.

[0075] Figure 11It is a photo of algal cells in a suspension of Microcystis aeruginosa taken by an optical microscope. Among them, Figure (a) is a photo of algal cells in the original algal solution of Microcystis aeruginosa, and Figure (b) is a photo of algal cells in the algal solution of Microcystis aeruginosa after being treated with the MOFs / polymer floating material of the present invention under sunlight for 90 min. From Figure 11 It can be seen that under the treatment of MHDPE, the number of cells of Microcystis aeruginosa decreased significantly.

[0076] Figure 12 It is a curve showing the change of the optical density value (OD 680 ) of the algal solution of Microcystis aeruginosa after being treated with the MOFs / polymer floating material of the present invention under sunlight over time. Figure 12 The significant decrease of the OD 680 value over time in 680 can further confirm that MHDPE can effectively reduce the cell density of Microcystis aeruginosa in water and achieve the control of Microcystis aeruginosa. The influence of pure HDPE on the OD 680 of algal cells is negligible, further confirming the leading role of MIL-88A(Fe) in the floating material in inhibiting Microcystis aeruginosa.

[0077] Application Example 2: Exploration of the change of chlorophyll a during the action of MOFs / polymer floating material on Microcystis aeruginosa

[0078] Chlorophyll a is the main photosynthetic pigment of the photosynthesis system of Microcystis aeruginosa, which can more accurately reflect the growth and proliferation of Microcystis aeruginosa, and is also an important characterization index for exploring whether the photosynthetic system of Microcystis aeruginosa works normally under the action of MHDPE. Generally, a suspension of magnesium carbonate is added before chlorophyll a extraction to prevent pigment decomposition. Then, it is selectively extracted with acetone under low-temperature conditions, and finally the absorbance of the extracted sample is measured at a specific wavelength using a UV-visible spectrophotometer, and the concentration of chlorophyll a is calculated using a formula.

[0079] Specifically, 50 mL of the algal solution after starvation treatment in Example 2 was added to a culture dish with a volume of 50 mL, 1.0 g of the MOFs / polymer floating material MHDPE was added, and it was placed under sunlight at 10 am in August. Samples of 8 mL were taken using a syringe at 0 min, 30 min, 60 min, and 90 min respectively. Referring to "Water Quality - Determination of Chlorophyll - Spectrophotometry" (SL 88-2012), magnesium carbonate and acetone were used to extract chlorophyll a, and then the concentration Chl-a t of the extracted chlorophyll a in different samples was measured and calculated respectively using a UV-visible spectrophotometer, where t is 0 min, 30 min, 60 min, and 90 min. A curve showing the change of Chl-a t over time was plotted.

[0080] To exclude the influence of polymer resin particles on Microcystis aeruginosa, HDPE resin particles without loaded MIL-88A(Fe) with the same mass (1.0 g) were used as a control, and other conditions were kept the same. The calculated values of chlorophyll a in the samples taken were denoted as Chl-a t, control , where t was 0 min, 30 min, 60 min, and 90 min. The curve of Chl-a t, control changing with time was plotted.

[0081] The results of the influence of MHDPE on the intracellular chlorophyll a of Microcystis aeruginosa are as Figure 13 shown. It can be seen that MHDPE particles can significantly reduce the level of intracellular chlorophyll a in Microcystis aeruginosa within 90 min, while pure HDPE has almost no effect on chlorophyll a, indicating that MIL-88A(Fe) in MHDPE plays a major role in damaging the photosynthetic system of Microcystis aeruginosa under sunlight.

[0082] Application Example 3: Exploration of the changes in the content and composition of intracellular organic matter during the interaction between MOFs / polymer floating materials and Microcystis aeruginosa

[0083] Three-dimensional fluorescence spectroscopy is an effective method for analyzing protein and humus components in liquids, and can evaluate the types and changes of intracellular organic matter in Microcystis aeruginosa under the action of MHDPE. Before the test, certain means need to be taken to lyse Microcystis aeruginosa cells to release the intracellular organic matter into the aqueous phase, and then enrich it and send it to a three-dimensional fluorescence spectrometer for measurement.

[0084] Specifically, 50 mL of the algal solution after starvation treatment in Example 2 was added to a culture dish with a volume of 50 mL, and 1.0 g of MOFs / polymer floating material MHDPE was added. It was placed under sunlight at 10 am in August, and 2 mL of samples were taken using a syringe at 0 min, 30 min, 60 min, and 90 min respectively. The taken samples were centrifuged at a speed of 5000 rpm for 10 min at 4 °C, and the respective precipitates were collected. 1 mL of deionized water was added to each precipitate, and after shaking, the precipitation was collected by centrifugation under the same conditions for 3 times. Subsequently, deionized water was added to the precipitate according to the mass ratio of water to precipitate of 300:1, and the samples were frozen at -80 °C for 20 min respectively, then taken out and ultrasonically treated with an ultrasonic cell disruptor until the samples just thawed. The above freezing-crushing steps were repeated 3 times. Subsequently, the samples were ultrasonically treated with an ultrasonic cell disruptor for 30 min respectively, and centrifuged at a speed of 5000 rpm for 20 min at 4 °C. The supernatant was collected and filtered through a 0.45 μm glass fiber filter membrane, and finally measured using a three-dimensional fluorescence spectrometer. During the measurement, the excitation wavelength range was set to 200 nm - 450 nm, and the emission wavelength range was set to 200 nm - 550 nm.

[0085] The three-dimensional fluorescence spectrogram of the intracellular organic matter of Microcystis aeruginosa changing with time during the treatment with MHDPE is as Figure 14 shown. It can be seen that the original Microcystis aeruginosa cells are rich in a large amount of fulvic acid-like organic matter, protein-like organic matter, tyrosine-like organic matter, and tryptophan-like organic matter. After adding MHDPE to the algal solution, the peak intensities of the above four types of organic matter gradually decreased with time and almost disappeared at 90 min, indicating that the reactive oxygen species in MHDPE can effectively rupture algal cells and degrade the internal organic matter.

[0086] Application Example 4: Identification of Reactive Oxygen Species Generated by MOFs / Polymer Floating Materials

[0087] To explore the types of reactive oxygen species generated by MOFs / polymer floating materials, MHDPE was irradiated under simulated sunlight using an electron spin resonance spectrometer, and the signals of reactive oxygen species generated in the reaction system were measured. The results are as Figure 15 shown. Under dark conditions, MHDPE did not generate any signals of reactive oxygen species, indicating that MHDPE cannot effectively inhibit Microcystis aeruginosa under dark conditions; while when simulated sunlight was present, MHDPE generated strong signals of hydroxyl radicals and superoxide radicals, indicating that during the process of MHDPE inhibiting Microcystis aeruginosa, the hydroxyl radicals and superoxide radicals generated through photocatalytic reactions played a dominant role in destroying Microcystis aeruginosa and degrading the organic matter released by it.

[0088] Application Example 5: Degradation Performance of MOFs / Polymer Floating Materials on Microcystin

[0089] After Microcystis aeruginosa is lysed by reactive oxygen species attack, microcystin will be released into the water body, posing a potential threat to aquatic organisms and human health. Monitoring microcystin in water can not only indirectly reflect the damage of MOFs to Microcystis aeruginosa cells, but also evaluate the control ability of MOFs / polymer floating materials for secondary pollution.

[0090] Specifically, 50 mL of the algal solution after starvation treatment in Example 2 was added to a 50 mL culture dish, and 1.0 g of MOFs / polymer floating material MHDPE was added. It was placed under sunlight at 10 am in August, and 1.5 mL of samples were taken using a syringe at 0 min, 30 min, 60 min, and 90 min respectively. The samples taken were centrifuged at 8000 rpm for 30 min using a centrifuge, and then filtered using a water-based filter membrane with a pore size of 0.22 μm. The content of microcystin remaining in the samples after different treatments was determined using a high performance liquid chromatography-mass spectrometry / mass spectrometry instrument. During the determination process, a 2.1×100 mm×1.8 μm chromatographic column was used, which was purchased from Waters Corporation, model HSS T3. The single injection volume of the instrument was 20 μL, mobile phase A was deionized water, mobile phase B was 0.1% formic acid solution, the solvent was methanol, the ratio of mobile phase A to mobile phase B was 4:1, and the flow rate was 0.2 mL / min. The microcystin concentrations of the samples taken at different times were recorded, denoted as MC-LR t , where t is 0 min, 30 min, 60 min, and 90 min. Plot the curve of MC-LR t changing with time.

[0091] It can be seen from Figure 16 that MHDPE can almost completely degrade the microcystin released by Microcystis aeruginosa within 90 min, indicating that MHDPE can not only effectively reduce the density of Microcystis aeruginosa during the photocatalytic process, but also simultaneously remove the secondary pollution caused by the lysis of Microcystis aeruginosa cells. The removal effect is very thorough, and it is an ideal environmental functional material for controlling water blooms.

[0092] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0093] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0094] Thus, the present invention will not be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a MOFs / polymer floating material, characterized in that: The MOFs / polymer floating material is composed of a metal organic framework and floating polymer resin particles, wherein the metal organic framework is at least one of MIL-88A (Fe), MIL-88B (Fe), NH2-MIL-88B (Fe), MIL-101 (Fe), NH2-MIL-101 (Fe), MIL-100 (Fe) and MIL-53 (Fe); the floating polymer resin particles are granular polymer resin materials with a particle size of 1 mm to 5 mm, thermoplasticity and a specific gravity lower than that of water; the material of the floating polymer resin particles is at least one of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene and ethylene-vinyl alcohol copolymer; The preparation method comprises: Firstly, an iron-based metal organic framework precursor is seeded on the surface of floating polymer resin particles, wherein the iron-based metal organic framework precursor is an organic linker in metal organic framework molecules; Combining the metal organic framework precursor with the surface of the floating polymer resin particles: in the surface combination, the metal organic framework precursor powder is directly mixed with the floating polymer resin particles, and heating and magnetic stirring are used together, and the heating temperature is 100° C. to 200° C.; Then the iron-based metal organic framework grows on the floating polymer resin particles: the surface-bound product is immersed in a metal salt solution, so that the metal ions in the metal salt solution react with the precursor to form a metal organic framework on the surface of the floating polymer particles.

2. The method for preparing the MOFs / polymer floating material according to claim 1, characterized in that: The particle size of the floating polymer resin particles is 3 mm to 4 mm; and / or the shape of the floating polymer resin particles is disc-shaped.

3. The method for preparing the MOFs / polymer floating material according to claim 1, characterized in that: In the surface bonding, the stirring speed is 20 rpm to 250 rpm, and the stirring time is 5 min to 20 min.

4. The method for preparing the MOFs / polymer floating material according to claim 1, characterized in that: The iron-based metal organic framework precursor is at least one of terephthalic acid, 2-aminoterephthalic acid, trimesic acid and fumaric acid.

5. The method for preparing the MOFs / polymer floating material according to claim 1, characterized in that: The mass ratio of the metal organic framework precursor powder to the floating polymer resin particles is 10:1 to 3:

1.

6. The method for preparing the MOFs / polymer floating material according to claim 1 or 4, characterized in that: The step of seeding the iron-based metal organic framework precursor on the surface of the floating polymer resin particles includes combining the metal organic framework precursor with the surface of the floating polymer resin particles, and cooling the surface combination; combining the metal organic framework precursor with the surface of the floating polymer resin particles to obtain the surface combination, and during the cooling of the surface combination, placing the surface combination at room temperature for natural cooling and re-hardening and molding, and the cooling time is 10 min to 20 min.

7. The method for preparing the MOFs / polymer floating material according to claim 1, characterized in that: The growth of the iron-based metal organic framework on the floating polymer resin particles includes: the coordination reaction temperature is room temperature, and the reaction time is 12 h to 48 h.

8. The method for preparing the MOFs / polymer floating material according to claim 6, characterized in that: The metal salt in the metal salt solution is a solid compound composed of metal cations and inorganic anions; and / or, the solvent in the metal salt solution is at least one of deionized water, methanol, ethanol, acetone and ether, and / or, the mass concentration of the solid compound is 1 g / L ~ 100 g / L; and / or, the mass ratio of the surface-bound product to the metal salt solution is 1:5 ~ 1:

100.

9. Use of the MOFs / polymer floating material prepared by the preparation method according to any one of claims 1 to 8 in inhibiting harmful algae in water.

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