Composite modified clay based on ferrate, preparation and application of composite modified clay and method for treating toxic algal blooms in seawater

Abstract

The invention belongs to the technical field of pollution prevention and control of harmful algal blooms and algal toxins, and particularly relates to composite modified clay based on ferrate, preparation and application of the composite modified clay and a method for treating toxic algal blooms in seawater. The composite modified clay is prepared from inorganic aluminum salt, ferrate and clay mineral according to the weight part ratio of (10-50): (1-20): (50-90). The method has the advantages of being wide in material source, easy and convenient to operate, rapid, efficient, capable of meeting the green sustainable development concept and capable of being widely applied to treatment of pollution of karenia brachystachya algal bloom and dunaliella brachystachya toxin.

Description

Technical Field

[0001] The invention belongs to the technical field of harmful algal blooms and algal toxin pollution prevention and control in seawater, and specifically relates to a composite modified clay based on ferrate and a method for preparing, applying and controlling toxic algal blooms in seawater. Background Art

[0002] Harmful Algal Blooms (HABs) are an abnormal proliferation phenomenon of microalgae that affects the growth of other organisms and the normal food chain structure, endangering the ecological environment and human health by producing algal toxins or increasing biomass. Studies have shown that harmful algal blooms can endanger the safety of marine ecosystems through multiple ways such as damaging the gill tissue of marine organisms, changing the physical and chemical environment of water bodies, and causing hypoxia. It is particularly noteworthy that some algae in the ocean can produce algal toxins, causing fish, shellfish and other farmed animals to be poisoned or die, and even endanger human health. Studies have shown that due to the combined effects of offshore eutrophication and global climate change, offshore harmful algal blooms are becoming more and more serious, the scope of impact and duration are constantly increasing, and the cause of algal blooms is gradually shifting to dinoflagellates and toxin-producing algae. Algal toxin pollution is becoming increasingly serious, and the harmful effects are intensifying, which seriously threatens the safety of marine ecosystems and the sustainable development of coastal economies.

[0003] Karenia brevis Karenia Brevis ) is a typical toxic dinoflagellate belonging to the phylum Dinophyta ( Dinoflagellate ), Gymnodinales ( Gymnodiniales ), Karenia ( Karenia ), which is distributed in the Gulf of Mexico, the Atlantic coast of the United States, Europe and my country's coastal waters, and can cause serious ecological disasters and economic losses. Karenia Brevis ) In addition to affecting the physical and chemical properties of water bodies and causing hypoxia, the most prominent hazard of algal blooms is that they can produce brevetoxins (BTXs), which seriously threaten biosafety and human health.

[0004] BTXs are a class of compounds with a polyether ring structure and belong to neurotoxic shellfish poisons. As a secondary metabolite produced by short Karen algae cells, BTXs have the characteristics of stable structure and difficulty in degradation. Its half-life is as long as dozens of days or even months, and it can exist for a long time in marine water, sediments and other environments. BTXs can be divided into type A and type B toxins according to their structure. Type A BTXs toxins mainly include BTX-1, and type B BTXs toxins mainly include BTX-2 and BTX-3. When the bloom of short Karen algae occurs, a large amount of short naked dinoflagellates toxins will be released into the water and accumulated in fish and shellfish, which will not only cause a large number of biological deaths and cause huge economic losses, but also cause human poisoning incidents through food chain transmission and biological enrichment, which seriously endangers human health. In addition, when short Karen algae cells are broken, aerosols contaminated with toxins will be formed, causing acute or subacute respiratory syndrome in humans, which is harmful to human health. In recent years, under the influence of global climate change and offshore eutrophication, the outbreak of Karenia brevis algae and the pollution of brevis dinoflagellates toxins have become increasingly prominent, posing a serious threat to offshore ecological security and human health.

[0005] Theoretically, there are many methods for the prevention and treatment of harmful algal blooms, which mainly include chemical methods, physical methods, biological methods and mineral flocculation methods. However, there are very few methods that can meet the requirements of rapidity, high efficiency, eco-friendliness, low cost and strong operability on site, so most methods remain at the laboratory research stage. The clay method / modified clay method is one of the few methods that can be applied to the prevention and treatment of harmful algal blooms and achieve ideal results, and it is low-cost, rapid and effective, and has no adverse ecological effects.

[0006] The modified clay method for treating harmful algal blooms is mainly based on: clay particles collide and combine with algal bloom organisms, flocculate, and cause algal bloom organisms to sink to the bottom and die; at the same time, this method can also damage the unflocculated algal bloom biological cells and reduce the eutrophication of the water body, thereby inhibiting the recurrence of algal blooms. While treating harmful algal blooms, modified clay can adsorb, oxidize and degrade some algal toxins such as domoic acid and paralytic shellfish poisoning (PSP) in the water body. However, due to the stability and difficulty of the BTXs structure produced by short naked dinoflagellates, the oxidation and degradation effect of BTXs is not obvious at present, and BTXs in the water body cannot be removed. In addition, when the traditional method is used to treat the short Karenia bloom, the algal cells rupture and cause a large amount of BTXs algal toxins to be released into the water body, and they continue to exist in the environment, bringing serious potential ecological risks. Therefore, on the basis of the traditional modified clay method for treating the short Karenia bloom, it is still a research problem to seek a method for efficiently degrading the algal toxins of short naked dinoflagellates. Summary of the invention

[0007] The purpose of the present invention is to provide a composite modified clay based on ferrate, a preparation method thereof, and an application of the composite modified clay in the efficient degradation of breve toxins and a method for controlling toxic algal blooms in seawater.

[0008] To achieve the above object, the present invention adopts the following technical solution: A composite modified clay based on ferrate, wherein the composite modified clay comprises inorganic aluminum salt, ferrate and clay mineral in a weight ratio of 10-50:1-20:50-90.

[0009] The inorganic aluminum salt is one or more of aluminum sulfate, aluminum chloride and their corresponding hydrates or polymers.

[0010] The ferrate is potassium ferrate and / or sodium ferrate.

[0011] The clay mineral is kaolin and / or montmorillonite.

[0012] A preparation method of the ferrate-based composite modified clay is as follows: clay minerals, inorganic aluminum salts and ferrate are mixed in proportion, a suspension having a mixture concentration of about 20-50 g / L is prepared after mixing, the suspension is heated and matured at 80°C for 2 hours, the suspension is allowed to stand and settle, the supernatant is removed and freeze-dried, and the suspension is then ground and sieved to obtain the composite modified clay.

[0013] An application of the ferrate-based composite modified clay, and the application of the composite modified clay in treating toxic algal blooms and degrading breve toxins.

[0014] The toxic algal bloom is caused by Karenia brevis, and the brevis toxins include BTX-1 and / or BTX-2 and their derivatives.

[0015] A method for treating toxic algal blooms, wherein the ferrate-based composite modified clay is added to an environment to be treated, thereby treating toxic Karenia brevis algal blooms and efficiently degrading brevis toxins.

[0016] Furthermore, the ferrate-based composite modified clay is prepared into a suspension with water, and then sprayed on the surface of the algal bloom water body so that the concentration of the ferrate-based composite modified clay in the system is 0.1-1.0 g / L, thereby achieving the control of toxic algal blooms and efficiently degrading the toxins released by them.

[0017] Beneficial effects of the present invention: The present invention uses inorganic aluminum salt (polyaluminum chloride or aluminum chloride or aluminum sulfate, etc.) and ferrate (potassium ferrate or sodium ferrate) to carry out composite modification on clay, and obtains a composite modified clay material that can quickly remove Karenia brevis and simultaneously and efficiently degrade the toxins of Gymnodinium brevis. The inorganic aluminum salt flocculant used in the present invention has the characteristics of high charge density, which can enhance the electrical neutralization effect, improve the flocculation ability of clay, and remove algae cells. The oxidation of ferrate can change the surface charge of algae cells, reduce the steric hindrance effect of algae cell structure, and make algae cells easy to form flocs. The nano iron oxide generated in situ after ferrate is reduced can be adsorbed on the surface of algae cells, increase the specific gravity of algae cells, and strengthen the flocculation effect; ferrate can also directly destroy the cell structure of algae bloom organisms, making them inactive, so as to achieve the effect of improving the removal rate of algae cells. Potassium ferrate can adsorb and oxidatively degrade algae toxins while strengthening flocculation and oxidation algae removal. The interaction between inorganic aluminum salt flocculants and ferrate can further improve the removal effect of Karenia brevis algal blooms and brevis dinoflagellates toxins.

[0018] Therefore, the present invention applies potassium ferrate and inorganic polymer flocculant to clay composite modification, and efficiently degrades and removes BTXs toxins while rapidly flocculating and removing algae. The method of the present invention is easy to implement, simple to operate, has a wide range of applications, and has high removal efficiency. The removal rate of Karenia brevis algae cells and brevis toxins can reach more than 80%, which can effectively reduce the ecological hazards and human health risks of toxic algal blooms. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram showing the algae removal effect of the ferrate-based composite modified clay provided in an embodiment of the present invention.

[0020] Figure 2 This is a diagram showing the removal effect of total algal toxins by the ferrate-based composite modified clay provided in an embodiment of the present invention.

[0021] Figure 3 This is a diagram showing the removal effect of intracellular algae toxins by the ferrate-based composite modified clay provided in an embodiment of the present invention.

[0022] Figure 4 This is a diagram showing the removal effect of extracellular algal toxins by the ferrate-based composite modified clay provided in an embodiment of the present invention.

[0023] Figure 5 This is a diagram showing the removal effect of BTX-2 toxin in water by a ferrate-based composite modified clay system (calculated as ferrate) with different concentrations provided in an embodiment of the present invention.

[0024] Figure 6 This is a comparison chart of the removal effects of different concentrations of ferrate-based composite modified clay and MCI on total BTX toxins in water provided in the embodiments of the present invention.

[0025] Figure 7 This is a comparison chart of the removal effects of different concentrations of ferrate-based composite modified clay and MCI+PMS on total BTX toxins in water provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0026] The present invention is explained below with reference to the accompanying drawings and embodiments.

[0027] The modified clay of the present invention is composed of clay, inorganic aluminum salt and potassium ferrate. In the preparation process, the clay is first surface-modified with inorganic aluminum salt and potassium ferrate, mixed evenly, and ground to a particle size of less than 200 meshes. The proportion of each component in the modified clay can be adjusted according to the abundance of algal bloom organisms to be removed, the environmental conditions of the water body, and the price of each component. When used, the modified clay is mixed with fresh water or seawater to form a suspension, which is sprayed on the algal bloom outbreak area according to a certain concentration.

[0028] The present invention uses short Karenia that can secrete neurotoxic shellfish poison (Karenia Brevis) The ferrate-modified clay was used as the research object to treat Karenia brevis. The algal cell removal rate was determined by microscopy, and the degradation effect of algal toxins was determined by high performance liquid chromatography-tandem mass spectrometry.

[0029] Example 1

[0030] The ferrate-based composite modified clay is a mixture obtained by mixing kaolin, polyaluminium chloride and potassium ferrate in a mass ratio (wherein the mass ratio of kaolin: polyaluminium chloride: potassium ferrate = 50:10:6). After mixing, ultrapure water is used to prepare a suspension with a concentration of about 20 g / L of the mixture, and the suspension is heated and matured at 80°C for 2 hours. After standing and settling, the supernatant is removed and freeze-dried, and then ground and sieved to prepare the suspension.

[0031] Then, the composite modified clay based on ferrate obtained above was sprayed on the surface of the algal bloom water body according to the biodensity of the algal bloom. The cell density of Karenia brevis in the water body treated in this embodiment was 12100 cells / mL.

[0032] The algae solution was mixed evenly, and 500 mL was measured into a measuring cup. In the experimental group, the ferrate-based composite modified clay obtained above was prepared into a solution with a concentration of 20 g / L by adding seawater, and then sprayed into the container, so that the concentration of the composite modified clay in the system was 0.1 g / L. At the same time, the algae solution without any treatment was used as the control group. At 3h and 24h, 2 mL of the mixed algae solution from the experimental group and the control group was taken into a centrifuge tube using a pipette, and the samples were fixed by Lugol's reagent and the algae cells were counted using an optical microscope. The algae cell removal rate was calculated accordingly (see Figure 1 ).

[0033] At the same time, the system was filtered through a GF / D membrane after 24 hours of treatment, and the filter membrane was collected for the determination of intracellular toxins. The toxins in the filtrate were enriched by solid phase extraction for the determination of extracellular toxins. The concentration of BTXs toxins was determined by high performance liquid chromatography tandem mass spectrometry (see Figure 2 ).

[0034] Depend on Figure 1 It can be seen that the algae cell density of the control group increased, while the algae cell density of the experimental group decreased significantly. The composite modified clay system can effectively remove toxic short Karenia algae cells at a concentration of 0.1 g / L, with a 24-hour removal rate of up to 92%. In this embodiment, the inorganic aluminum salt flocculant used has the characteristics of high charge density, which can enhance the electrical neutralization effect, improve the clay flocculation ability, and remove algae cells. The nano-iron oxides generated during the ferrate reaction have the effect of strengthening flocculation, and at the same time oxidize the algae cells, destroy the algae cell structure, make them inactive, and improve the algae removal effect.

[0035] Depend on Figure 2 It can be seen that the composite modified clay system can effectively remove BTXs toxins at a concentration of 0.1g / L, and the total removal rates of BTX-2 and BTX-3 are as high as 80% and 60%, respectively. The removal effect of ferrate composite modified clay on intracellular BTXs is more significant ( Figure 3 ). Specifically, 24 hours after adding ferrate-modified clay, compared with the control group, the intracellular BTX-1, BTX-2 and BTX-3 contents of the experimental group were significantly reduced, BTX-1 was below the detection limit, the BTX-2 concentration decreased from 18.27 μg / L in the control group to 0.4 μg / L, and the BTX-3 concentration decreased from 0.75μg / L in the control group to 0.14 μg / L. 24 hours after adding ferrate-modified clay, the extracellular BTX-1, BTX-2 and BTX-3 contents of the experimental group were also significantly reduced ( Figure 4 ). The extracellular BTX-1 concentration decreased from 0.06 μg / L in the control group to 0.01 μg / L, the extracellular BTX-2 concentration decreased from 20.51 μg / L in the control group to 5.27 μg / L, and the extracellular BTX-3 concentration decreased from 7.20 μg / L in the control group to 3.05 μg / L.

[0036] Mix the algae liquid evenly, measure 500 mL into a measuring cup, filter through a GF / D membrane, use a pipette to measure 200 mL of the filtrate and place it in a measuring cup; in the experimental group, the ferrate-based composite modified clay obtained above was prepared into a solution with a concentration of 20 g / L with seawater, and then sprayed in a measuring cup, so that the concentration of the composite modified clay in the system was 0.055 g / L, 0.11 g / L, 0.165 g / L and 0.22 g / L, and the algae liquid without any treatment was used as the control group. At 24 hours, the BTX toxins in the experimental group and the control group were collected and determined by high performance liquid chromatography tandem mass spectrometry. By Figure 5 It can be seen that with the increase of the concentration of ferrate composite modified clay, the removal rate of BTX gradually increased (taking BTX-2 as an example). When the ferrate concentration was 0.22 g / L, the removal rate of BTX-2 was as high as 91%.

[0037] Then, ferrate-based composite modified clays with different mass ratios were prepared according to the above preparation method, and the removal effects on algal cells and algal toxins were measured according to the above measurement method (see Table 1).

[0038] Table 1 Removal effect of composite modified clay based on ferrate at different mass ratios on algal cells and algal toxins (composite modified clay concentration is 0.1 g / L)

[0039] The ferrate-based composite modified clay is a mixture of kaolin, polyaluminium chloride and potassium ferrate in different mass ratios (wherein the mass ratios of potassium ferrate: polyaluminium chloride: kaolin are 0:10:50, 1:10:50, 2:10:50, 4:10:50, 6:10:50 and 10:10:50, respectively). After mixing, ultrapure water is used to prepare a suspension with a concentration of 20 g / L and then sprayed on the surface of the algal bloom water body, so that the concentrations of the potassium ferrate composite modified clay in different mass ratios in the system are all 0.1 g / L; the cell density of Karenia brevis in the water body treated in this embodiment is 12600 cells / mL.

[0040] It can be seen from the table that with the increase of the proportion of potassium ferrate, the removal rate of algae toxins is significantly improved.

[0041] Comparative Example 1 Modified clay (MCI) is a mixture of kaolin and polyaluminium chloride in a mass ratio (kaolin: polyaluminium chloride = 5:1). After mixing, ultrapure water is used to prepare a suspension with a concentration of about 20g / L, heated and aged at 80°C for 2h, and after standing and settling, the supernatant is removed and freeze-dried, and then ground and sieved to prepare the suspension. Among them, kaolin: polyaluminium chloride = 5:1.

[0042] The MCI and ferrate composite modified clay obtained above were respectively prepared into a suspension with a concentration of 20 g / L by seawater, and then sprayed on the surface of the algal bloom water body, so that the concentrations of MCI or ferrate composite modified clay in the system were 0.05 g / L and 0.1 g / L respectively; the cell density of Karenia brevis in the water body treated in this embodiment was 15600 cells / mL. At the same time, the algal liquid without any treatment was used as the control group.

[0043] At 24 h, use a pipette to measure 200 mL of the evenly mixed Karenia brevis algae solution, and measure the toxin content after enrichment.

[0044] Depend on Figure 6 It can be seen that MCI has no effect on removing BTX and stimulates the production of BTX toxins. However, the ferrate composite modified clay of this embodiment has a significant effect on removing BTX, and the removal effect of BTX is 72% at a concentration of 0.1 g / L.

[0045] Comparative Example 2 The modified clay (MCI+PMS) is prepared by mixing kaolin, polyaluminium chloride and potassium monopersulfate (PMS) in a mass ratio. After mixing, ultrapure water is used to prepare a suspension with a concentration of about 20 g / L, and the suspension is heated and matured at 80°C for 2 hours. After standing and settling, the supernatant is removed and freeze-dried, and then ground and sieved to prepare the suspension; wherein, kaolin: polyaluminium chloride: PMS = 5:1:0.6.

[0046] The MCI+PMS and ferrate composite modified clay obtained above were respectively prepared into a suspension with a concentration of 20 g / L by seawater, and then sprayed on the surface of the algal bloom water body, so that the concentration of MCI+PMS in the system was 0.05 g / L MCI+5ppm PMS and 0.1 g / LMCI+10ppm PMS, and the concentration of ferrate composite modified clay was 0.05 g / L and 0.1 g / L, respectively; the cell density of Karenia brevis in the water body treated in this embodiment was 15600 cells / mL. The algae solution without any treatment was used as the control group.

[0047] At 24 h, use a pipette to measure 200 mL of the evenly mixed Karenia brevis algae solution, and measure the toxin content after enrichment.

[0048] Depend on Figure 7 It can be seen that MCI+PMS has no effect on removing BTX and stimulates the production of BTX toxins. However, the ferrate composite modified clay of this embodiment has a significant effect on removing BTX, and the removal effect of BTX is 72% at a concentration of 0.1 g / L.

[0049] Compared with the existing method, the method of the invention is convenient to implement and simple to operate, and the removal rate of toxic algal bloom organisms can reach more than 95%, and the removal rate of BTX toxins can reach more than 80%.

Claims

1. A composite modified clay based on ferrate, characterized in that: The composite modified clay comprises inorganic aluminum salt, ferrate and clay mineral, in the proportions of 10-50:1-20:50-90 by weight.

2. The ferrate-based composite modified clay according to claim 1, characterized in that: The inorganic aluminum salt is one or more of aluminum sulfate, aluminum chloride and their corresponding hydrates or polymers.

3. The ferrate-based composite modified clay according to claim 1, characterized in that: The ferrate is potassium ferrate and / or sodium ferrate.

4. A method for preparing the ferrate-based composite modified clay according to claim 1, characterized in that: Clay minerals, inorganic aluminum salts and ferrate are mixed in proportion to prepare a suspension with a concentration of about 20-50 g / L. The suspension is heated and matured at 80°C for 2 hours. After standing and settling, the supernatant is removed and freeze-dried, and then ground and sieved to obtain the product.

5. The method for preparing the ferrate-based composite modified clay according to claim 4, characterized in that: The clay mineral is kaolin, the inorganic aluminum salt is polyaluminum chloride, and the ferrate is potassium ferrate.

6. An application of the ferrate-based composite modified clay according to claim 1, characterized in that: The composite modified clay is used in treating toxic algal blooms and degrading breve toxins.

7. The use of the ferrate-based composite modified clay according to claim 6, characterized in that: The toxic algal bloom is caused by Karenia brevis, and the brevis toxins include BTX-1 and / or BTX-2 and their derivatives.

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