CN111889064B

CN111889064B - Magnetic MgO nanoflower phosphate adsorbent and preparation method and application thereof

Info

Publication number: CN111889064B
Application number: CN202010908447.4A
Authority: CN
Inventors: 漆新华; 刘小宁
Original assignee: Nankai University
Current assignee: Nankai University
Priority date: 2020-09-02
Filing date: 2020-09-02
Publication date: 2021-10-08
Anticipated expiration: 2040-09-02
Also published as: CN111889064A

Abstract

The invention provides a magnetic MgO nanoflower phosphate adsorbent and a preparation method and application thereof, belonging to the technical field of adsorbents. The preparation method provided by the invention comprises the following steps: mixing polyvinylpyrrolidone, ethylene glycol, ammonia water, magnesium acetate and cobalt acetate, carrying out solvothermal reaction on the obtained mixed solution, and separating to obtain a solid product; calcining the solid product to obtain a magnetic MgO nanoflower phosphate adsorbent; the calcining temperature is 600-900 ℃. The adsorbent prepared by the method has a porous and lamellar flower-like structure, and the specific surface area is up to 209m²The effective adsorption sites are uniformly distributed in the flower-shaped lamellar layer, and the effective adsorption sites are more abundant due to the flower-shaped lamellar structure, so that the adsorption selectivity is higher under the interference of many anions, the pH adaptation range is wider, the phosphorus adsorption rate is higher, and the adsorption quantity of orthophosphate reaches 230.5 mg/g.

Description

Magnetic MgO nanoflower phosphate adsorbent and preparation method and application thereof

Technical Field

The invention relates to the technical field of adsorbents, and particularly relates to a magnetic MgO nanoflower phosphate adsorbent and a preparation method and application thereof.

Background

Excessive release of phosphorus (P) as one of the essential elements of biological growth and reproduction promotes explosive growth of harmful algal blooms to deteriorate water quality, leading to death of a large number of aquatic organisms and ultimately to disruption of ecosystem balance (i.e., eutrophication). Therefore, how to scientifically and efficiently remove and control the content of the phosphorus element in the water is an important means for treating the eutrophication pollution of the water body.

At present, in a plurality of water body phosphorus removal methods, an adsorption method is widely concerned due to low cost, easy operation, high selectivity and good cyclicity. However, the existing adsorbent still has the problems of small adsorption quantity, narrow pH adaptation range, poor selectivity, slow adsorption rate and the like.

Disclosure of Invention

The invention aims to provide a magnetic MgO nanoflower phosphate adsorbent, and a preparation method and application thereof.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a magnetic MgO nanoflower phosphate adsorbent, which comprises the following steps:

mixing polyvinylpyrrolidone, ethylene glycol, ammonia water, magnesium acetate and cobalt acetate, carrying out solvothermal reaction on the obtained mixed solution, and separating to obtain a solid product;

calcining the solid product to obtain a magnetic MgO nanoflower phosphate adsorbent;

the calcining temperature is 600-900 ℃.

Preferably, the temperature of the solvothermal reaction is 200 ℃ and the time is 12-36 h.

Preferably, the calcination is carried out under nitrogen protection.

Preferably, the calcination time is 2 h.

Preferably, the mixing of the polyvinylpyrrolidone, the ethylene glycol, the ammonia water, the magnesium acetate and the cobalt acetate comprises: dissolving polyvinylpyrrolidone in ethylene glycol, then dropwise adding ammonia water, then adding magnesium acetate and cobalt acetate for dissolving, and stirring after complete dissolution to obtain a mixed solution.

Preferably, the dosage ratio of the polyvinylpyrrolidone, the glycol, the ammonia water, the magnesium acetate and the cobalt acetate is 0.8 g: 80mL of: 400 μ L: (1.5-3) mmol: (1-2) mmol; the mass fraction of the ammonia water is 25%.

The invention provides the magnetic MgO nano flower phosphate adsorbent prepared by the preparation method in the scheme, which has a porous and lamellar flower-like structure and magnetism; the magnetic MgO nanoflower phosphate adsorbent comprises MgO and simple substance cobalt.

Preferably, the pore diameter of the magnetic MgO nanoflower phosphate adsorbent is 2-4 nm.

The invention provides an application of the magnetic MgO nanoflower phosphate adsorbent in the scheme in adsorbing phosphorus-containing substances in a water body.

Preferably, the pH value of the water body is 1-13.

The invention provides a preparation method of a magnetic MgO nanoflower phosphate adsorbent, which comprises the following steps: mixing polyvinylpyrrolidone, ethylene glycol, ammonia water, magnesium acetate and cobalt acetate, carrying out solvothermal reaction on the obtained mixed solution, and separating to obtain a solid product; calcining the solid product to obtain a magnetic MgO nanoflower phosphate adsorbent; the calcining temperature is 600-900 ℃.

The method comprises the steps of taking polyvinylpyrrolidone and ethylene glycol as solvents, ammonia water as a pH regulator, and magnesium acetate and cobalt acetate as a magnesium precursor and a cobalt precursor respectively, wherein in the process of solvothermal reaction, the ethylene glycol reacts with the magnesium acetate and the cobalt acetate to generate magnesium glycolate and cobalt glycolate, and meanwhile Ostwald ripening is carried out to enable the metal precursors to be spherical, then calcination is carried out to form a lamellar flower-shaped structure, and the magnesium glycolate and the cobalt glycolate are pyrolyzed in the calcination process to generate MgO and cobalt oxide; meanwhile, in the calcining process, the acetate is decomposed and carbonized to play a pore-forming role and generate a simple substance C, and the simple substance C reduces the cobalt oxide into simple substance cobalt to obtain the magnetic MgO nanoflower phosphate adsorbent.

The adsorbent prepared by the method has a porous and lamellar flower-like structure, and the specific surface area is up to 209m²And the effective adsorption sites (MgO) are uniformly distributed in the flower-shaped lamellar, and the effective adsorption sites are more abundant due to the flower-shaped structure of the lamellar. Therefore, the composite material has higher adsorption selectivity under the interference of many anions, wider pH adaptation range and faster phosphorus adsorption rate, and the adsorption amount of orthophosphate reaches 230.5 mg/g.

In addition, the adsorbent prepared by the invention contains simple substance cobalt, so that the adsorbent has magnetism and can be recycled.

Drawings

FIG. 1 is SEM and TEM images of an NFMgCo-600 sample;

FIG. 2 is a graph of N for the NFMgCo-400, NFMgCo-600, and NFMgCo-800 samples₂Adsorption-desorption isotherms and pore size distributions;

FIG. 3 is an XRD pattern of NFMgCo-400, NFMgCo-600, and NFMgCo-800 samples;

FIG. 4 is a photograph of the magnetic recovery performance of the NFMgCo-800 sample;

FIG. 5 is a graph of the adsorption performance of NFMgCo-400, NFMgCo-600, and NFMgCo-800 at different orthophosphate concentrations;

FIG. 6 is a graph of the adsorption performance of NFMgCo-400, NFMgCo-600, and NFMgCo-800 at different reaction times;

FIG. 7 is a graph showing the results of the adsorption amount of orthophosphate by NFMgCo-600 at various pH values;

FIG. 8 is a graph of the orthophosphate adsorption performance of NFMgCo-600 under different coexisting ions;

FIG. 9 is a graph showing the results of recycling of NFMgCo-600.

Detailed Description

the calcining temperature is 600-900 ℃.

In the present invention, the starting materials used are all commercially available products well known in the art, unless otherwise specified.

The invention mixes polyvinylpyrrolidone, glycol, ammonia water, magnesium acetate and cobalt acetate to obtain mixed solution.

In the present invention, the mixing process preferably includes: dissolving polyvinylpyrrolidone in ethylene glycol, then dropwise adding ammonia water, then adding magnesium acetate and cobalt acetate for dissolving, and stirring after complete dissolution to obtain a mixed solution. In the invention, the stirring time is preferably 30min, and the stirring speed is preferably 50-200 rpm, and more preferably 100-150 rpm.

In the present invention, the dosage ratio of the polyvinylpyrrolidone, the ethylene glycol, the ammonia water, the magnesium acetate and the cobalt acetate is preferably 0.8 g: 80mL of: 400 μ L: (1.5-3) mmol: (1-2) mmol, more preferably 0.8 g: 80mL of: 400 μ L: 2.68 mmol: 1.68 mmol; the mass fraction of the ammonia water is preferably 25%.

After the mixed solution is obtained, the mixed solution is subjected to solvothermal reaction, and a solid product is obtained after separation. In the invention, the temperature of the solvothermal reaction is preferably 200 ℃, and the time of the solvothermal reaction is preferably 12-36 h, and more preferably 24 h. In the process of the solvothermal reaction, glycol reacts with magnesium acetate and cobalt acetate respectively to generate magnesium glycolate and cobalt glycolate, and Ostwald ripening is carried out, so that the magnesium acetate and the cobalt acetate are combined into spheres in a direction with smaller combination energy. The invention is beneficial to improving the balling rate by controlling the conditions of the solvothermal reaction.

After the solvothermal reaction is completed, the product of the solvothermal reaction is separated to obtain a solid product. The present invention has no special requirement on the separation mode, and the solid-liquid separation mode can be realized by the methods well known in the art, such as centrifugation and filtration. After the separation is finished, the invention preferably also comprises the steps of washing the solid obtained by the separation for 3 times by adopting ethanol, and then putting the solid into a vacuum drying oven to dry for 12 hours.

After obtaining the solid product, the invention calcines the solid product to obtain the magnetic MgO nano flower phosphate adsorbent.

In the invention, the calcining temperature is 600-900 ℃, preferably 600-800 ℃, and more preferably 600 ℃. In the present invention, the time of the calcination is preferably 2 hours; the calcination is preferably carried out under nitrogen protection. In the calcining process, the magnesium glycolate and the cobalt glycolate are thermally decomposed into magnesium oxide and cobalt oxide; meanwhile, in the calcining process, acetate is decomposed into C at high temperature to play a pore-forming role, and the C reduces cobalt oxide into a cobalt simple substance, so that the magnetic material has stronger magnetism.

The invention can ensure that the synthesized precursor is completely decomposed to generate MgO by controlling the calcining temperature in the range, and the residual C in the decomposition process reduces the cobalt oxide into a Co simple substance.

The temperature is preferably increased from room temperature to the calcining temperature, the temperature increase rate is preferably 1 ℃/min, and the stable and slow temperature increase rate is adopted in the invention, so that the thermal decomposition degree and the reduction degree are favorably improved.

The magnetic MgO nanoflower phosphate adsorbent comprises, by atomic number percentage, 20-30% of Mg, 25-30% of Co, 15-25% of O, 1-10% of C and other elements. In the present invention, C is present in the form of simple substance C.

In the invention, the magnetic MgO nanoflower phosphate adsorbent has a porous structure, the aperture is preferably 2-4 nm, and the pore volume is preferably 0.2-0.6 cm³(ii) in terms of/g. In the invention, the specific surface area of the magnetic MgO nanoflower phosphate adsorbent is preferably 95-230 m²/g。

The adsorbent has a lamellar flower-shaped structure, and effective adsorption sites are richer. Therefore, the composite material has higher adsorption selectivity under the interference of many anions, wider pH adaptation range and faster phosphorus adsorption rate, and the adsorption amount of orthophosphate reaches 230.5 mg/g.

The invention provides an application of the magnetic MgO nanoflower phosphate adsorbent in the scheme in adsorbing phosphorus-containing substances in a water body. The invention has no special requirement on the source of the water body, and the water body with the source well known in the field can be used. In the present invention, the phosphorus-containing substance is preferably a phosphate. In an embodiment of the present invention, the phosphorus-containing substance is potassium dihydrogen phosphate. The invention has no special requirement on the concentration of the phosphorus-containing substance in the water body, and the concentration can be any. In the invention, the pH value of the water body is preferably 1-13, and more preferably 3-5. The dosage of the magnetic MgO nanoflower phosphate adsorbent has no special requirement, and can be adjusted according to the adsorption effect.

The following will explain the magnetic MgO nanoflower phosphate adsorbent and the preparation method and application thereof in detail with reference to the examples, but they should not be construed as limiting the scope of the present invention.

Example 1

Dissolving 0.8g PVP (polyvinylpyrrolidone) in 80mL EG (ethylene glycol), and dropping 400 μ L ammonia water; dissolving 2.68mmol of magnesium acetate and 1.68mmol of cobalt acetate in the mixed solution, after complete dissolution, stirring gently for 30min, after stirring, putting the mixed solution into a polytetrafluoroethylene lining, and heating in a reaction kettle at 200 ℃ for 24h to perform solvothermal reaction; after the solvothermal reaction is finished, centrifuging the solution, washing the obtained precipitate for 3 times by using ethanol, and then putting the precipitate into a vacuum drying oven to be dried for 12 hours; and (3) after drying, putting the sample into a muffle furnace, and calcining for 2h at 600 ℃ under the protection of nitrogen (the temperature raising program is 1 ℃/min) to obtain the magnetic MgO nanoflower phosphate adsorbent which is recorded as NFMgCo-600.

Example 2

The difference from example 1 is that the calcination temperature is 800 ℃ and is noted as NFMgCo-800.

Comparative example 1

The difference from example 1 is that the calcination temperature is 400 ℃ and is noted as NFMgCo-400.

Performance and structural characterization

Physical properties and chemical composition of the adsorbents prepared in examples 1-2 and comparative example 1 were characterized, and the results are shown in table 1.

TABLE 1 physical Properties and chemical compositions of NFMgCo samples

As is clear from Table 1, in the chemical composition, the ratio of Mg, Co and O elements increases with the increase of the calcination temperature, and the ratio of C element gradually decreases. The NFMgCo samples all have better specific surface area in terms of physical properties. Wherein when the calcining temperature is 600 ℃, the specific surface area of the material is the maximum and is 209m²/g。

SEM and TEM characterization of the NFMgCo-600 prepared in example 1 was performed, and the results are shown in fig. 1, in which a in fig. 1 is an SEM image of the NFMgCo sample, d in fig. 1 is a TEM image of the NFMgCo, b in fig. 1 is a distribution diagram of Co element, C in fig. 1 is a distribution diagram of Mg element, e in fig. 1 is a distribution diagram of C element, and f in fig. 1 is a distribution diagram of O element. FIG. 1 shows that the elements are uniformly distributed in the material and no agglomeration is observed.

The results of the isothermal curve tests of the NFMgCo adsorbents prepared in examples 1 to 2 and comparative example 1 are shown in fig. 2, and fig. 2 shows that the NFMgCo material shows a typical type IV isothermal line, and has a clear capillary condensation step and a clear H3 hysteresis loop, indicating that the material has a crack-like mesoporous structure. The pore size distribution is calculated through a BJH model, and the pore size of the material is mainly distributed in 2-4 nm.

XRD tests of the NFMgCo adsorbents prepared in examples 1-2 and comparative example 1 are shown in FIG. 3. As can be seen from fig. 3, the sample did not show a distinct characteristic peak at a calcination temperature of 400 c, indicating that the metal in the material was present in amorphous form at this calcination temperature. This is because the calcination temperature is low and the decomposition of the synthesized precursor is incomplete. As the calcining temperature is increased, the material has MgO and Co simple substance characteristic peaks at 600 ℃ and 800 ℃. The characteristic peak of MgO in NFMgCo-800 is sharper and shows obvious Co single peak, which shows that the synthesized precursor is completely decomposed at the calcining temperature, and the residual C in the process reduces the Co oxide into Co simple substance, thus showing stronger magnetism. As shown in FIG. 4, NFMgCo-800 exhibits better magnetic recovery.

Application example 1

20mg of adsorbent (NFMgCo-400, NFMgCo-600, NFMgCo-800) was placed in a series of polyethylene tubes containing 20mL (0, 5, 10, 25, 50, 100, 150, 200, 300, 400) mg/L of phosphorus solution (potassium dihydrogen phosphate) (pH 5). The tubes were then shaken in a constant temperature shaker at 25 ℃ for 24 hours (250 rpm). After the shaking time was over, the mixture in the polyethylene tube was filtered with a 0.45 μmPES filter and the filtrate was analyzed for phosphorus concentration. The phosphate concentration was determined colorimetrically and the experimental data were plotted using the Langmuir and Freundlich equations in a fit, all repeated 3 times. The results of the experiment are shown in FIG. 5.

As can be seen from FIG. 5, the adsorption capacity of the orthophosphate of NFMgCo-600 and NFMgCo-800 is higher than that of NFMgCo-400, and the maximum adsorption capacity of the orthophosphate of each material is respectively 148mg/g (NFMgCo-400), 242mg/g (NFMgCo-600) and 179mg/g (NFMgCo-800) through the Langmuir equation. This is higher than most Mg-based phosphate adsorbents.

Application example 2

20mg of adsorbent (NFMgCo-400, NFMgCo-600, NFMgCo-800) was poured into 20mL of orthophosphate (KH)₂PO₄) The initial concentration of the solution was 200 mg/L. And placing the polyethylene pipe into a constant temperature shaking table to vibrate, wherein the temperature is 25 ℃, and the rotating speed is 200 rpm. And the corresponding polyethylene tubes were removed at defined time points (5min, 15min, 30min, 1h, 2h, 4h, 6h, 8h, 12h, 18h, 24h, 36h, 48 h). Immediately after shaking, the liquid in the polyethylene tube was passed through a 0.45 μm aqueous filter membrane to determine the residual concentration of orthophosphate. The orthophosphate concentration was determined colorimetrically, the experimental data were plotted using Pseudo-first-order and Pseudo-second-order equations, and all experiments were repeated 3 times. The results of the experiment are shown in FIG. 6.

From FIG. 6, it can be seen that the absorption rate of orthophosphate is relatively fast in the reaction time of 0-48h for the NFMgCo-x material at each calcination temperature, wherein the absorption capacity of orthophosphate of NFMgCo-600 is the best. The NFMgCo-600 orthophosphate adsorption process is divided into three stages: 1. a rapid adsorption stage (0-2 h); 2. a slow adsorption stage (2-6 h); 3. the adsorption reached essentially equilibrium (after 6 h).

Application example 3

Putting 0.01g NFMgCo-600 into 50mL polyethylene tube, pouring 20mL 200mg/L orthophosphate (KH)₂PO₄) And (3) solution. The pH of the solution was adjusted with 0.01mol of HCl and NaOH, and the pH of the solution was controlled to 1, 3, 5, 7, 9 and 11, respectively. And placing the polyethylene pipe into a constant temperature shaking table to vibrate for 24h, wherein the temperature is 25 ℃, and the rotating speed is 200 rpm. Immediately after shaking, the liquid in the polyethylene tube was passed through a 0.45 μm aqueous filter and the remaining concentration of orthophosphate was measured. The orthophosphate concentration was determined colorimetrically and all experiments were repeated 3 times. The results of the experiment are shown in FIG. 7.

The pH in the environment is an important factor in the orthophosphate adsorption process, which affects not only the form of phosphorus in solution, but also the active components of the adsorbent surface. As shown in FIG. 7, the orthophosphate adsorption performance of the NFMgCo-600 under different initial pH values is shown, when the pH value ranges from 1 to 13, the orthophosphate adsorption amount of the NFMgCo-600 is more than 50mg/g, which shows that the NFMgCo-600 has high-efficiency orthophosphate adsorption performance in a wide pH range. Under the weak acid (pH is 3-5), the absorption effect of the orthophosphate of the NFMgCo-600 is better, and when the pH is 5, the absorption amount of the orthophosphate of the NFMgCo-600 is up to 225 mg/g.

Application example 4

Firstly, 0.01g of NFMgCo-600 is put into a 50mL polyethylene tube, and 40mL of KH with the initial concentration of 200mg/L is poured₂PO₄And (3) solution. And adding a certain amount of KNO into the tubes respectively₃、K₂SO₄、KHCO₃KCl reagent, to make NO in polyethylene tube₃ ^-、SO₄ ^2-、HCO₃ ^-、Cl^-The ion concentrations of (A) and (B) are respectively 0.01 and 0.1 mol/L. And placing the polyethylene pipe into a constant temperature shaking table to vibrate for 24h, wherein the temperature is 25 ℃, and the rotating speed is 200 rpm. Immediately after shaking, the liquid in the polyethylene tube was passed through a 0.45 μm aqueous filter and the residual concentration of phosphate was determined. The phosphate concentration was determined colorimetrically and all experiments were repeated 3 times. The results of the experiment are shown in FIG. 8.

NO₃ ^-、SO₄ ^2-、HCO₃ ^-、Cl^-The anion is common anion in water environment, and the existence of the anion and the anion can increase coulomb force or compete with orthophosphate for effective active sites on the surface of the adsorbent, thereby reducing the adsorption performance of the adsorbent to a certain extent. As shown in fig. 8: NO₃ ^-、SO₄ ^2-、HCO₃ ^-、Cl^-Can influence the phosphate adsorption capacity of NFMgCo-600. Wherein NO₃ ^-、SO₄ ^2-、Cl^-The influence is small, and the adsorption amount of the NFMgCo-600 to the orthophosphate is kept at a high level even under the condition of high ion concentration. HCO₃ ^-It can have an influence on the adsorption capacity of NFMgCo-600 because of HCO₃ ^-Produced by ionisation in aqueous solutionsCO₃ ^2-Can be combined with Mg ions to form insoluble or indissolvable substances, and reduce the active sites on the surface of the NFMgCo-600. But HCO₃ ^-When the ion concentration is up to 0.1mol/L, the adsorption quantity of the NFMgCo-600 to orthophosphate is still higher than 170mg/g, which proves that the surface of the NFMgCo-600 has enough effective adsorption sites, so that the NFMgCo-600 always keeps high-efficiency orthophosphate adsorption performance.

Application example 5

The reusability and stability of the NFMgCo-600 sample was investigated by performing successive adsorption-desorption tests. Wherein 0.2g of the adsorbent was added to 40mL of orthophosphate solution (potassium dihydrogen phosphate) (5mg/L) and shaken at 25 ℃ for 12 h. The NFMgCo-600 sample after phosphorus adsorption was separated from the mixture by filtration and put into 1mol/L NaOH aqueous solution for desorption at 25 ℃ for 8 hours. Then, the desorbed adsorbent is separated from the desorption liquid. And measuring the phosphorus concentration in the desorption solution to calculate the desorption efficiency of phosphorus. And drying the solid adsorbent separated by filtering at 80 ℃ for 8h, and using the dried solid adsorbent for the next adsorption-desorption cycle test.

In this study, the use of 1M NaOH solution to desorb orthophosphate from NFMgCo-600 after adsorption, the desorption and adsorbent cycling effects are shown in FIG. 9. The results show that the NFMgCo-600 still maintains the better adsorption performance after a plurality of regeneration cycles. After six regeneration cycles, the sorbent had nearly 100% phosphorus removal. In addition, the phosphorus desorption rate of the NFMgCo-600 adsorbent is higher than 90% in each desorption test, which shows that the NFMgCo sample has high recoverability and stability and has wide practical application prospect.

From the above embodiments, the magnetic MgO nanoflower phosphate adsorbent provided by the invention has the advantages of high adsorption capacity, adsorption rate, selectivity, recycling property, wide pH application range, and suitability for industrial application.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a magnetic MgO nanoflower phosphate adsorbent comprises the following steps:

the calcining temperature is 600-900 ℃; the dosage ratio of the polyvinylpyrrolidone, the glycol, the ammonia water, the magnesium acetate and the cobalt acetate is 0.8 g: 80mL of: 400 μ L: (1.5-3) mmol: (1-2) mmol; the mass fraction of the ammonia water is 25%;

the temperature of the solvothermal reaction is 200 ℃, and the time is 12-36 h.

2. The method according to claim 1, wherein the calcination is performed under nitrogen protection.

3. The method according to claim 1, wherein the calcination is carried out for a period of 2 hours.

4. The method of claim 1, wherein the mixing of polyvinylpyrrolidone, ethylene glycol, ammonia water, magnesium acetate, and cobalt acetate comprises: dissolving polyvinylpyrrolidone in ethylene glycol, then dropwise adding ammonia water, then adding magnesium acetate and cobalt acetate for dissolving, and stirring after complete dissolution to obtain a mixed solution.

5. The magnetic MgO nanoflower phosphate adsorbent prepared by the preparation method of any one of claims 1 to 4 has a porous and lamellar flower-like structure and is magnetic; the magnetic MgO nanoflower phosphate adsorbent comprises MgO and simple substance cobalt.

6. The magnetic MgO nanoflower phosphate adsorbent according to claim 5, wherein the pore size of the magnetic MgO nanoflower phosphate adsorbent is 2-4 nm.

7. Use of the magnetic MgO nanoflower phosphate adsorbent according to claim 5 or 6 for adsorbing phosphorus-containing substances in a water body.

8. The use according to claim 7, wherein the pH of the body of water is 1 to 13.