CN114950352B - Lanthanum carbonate modified Fe 3 O 4 Dephosphorization adsorbent at@C and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the field of environmental wastewater treatment and discloses a lanthanum carbonate-modified Fe ₃ O ₄ @C composite adsorption material and its preparation method and application. The preparation method of the adsorbent includes the following steps: using a solvothermal method to prepare Fe ₃ O ₄ nanoparticles; then coating Fe ₃ O ₄ with a carbon layer using a hydrothermal method; and finally using a precipitation deposition method to coat Fe ₃ O ₄ @C Lanthanum carbonate is loaded on the carrier to obtain a composite phosphorus removal adsorbent. The invention has strong magnetism, and the adsorbent can perform solid-liquid separation and recovery by applying an external magnetic field after the adsorption is completed. Carbon coating makes Fe ₃ O ₄ less susceptible to oxidation and improves the dispersion of the material's active substances; lanthanum carbonate has a strong affinity for phosphate and can achieve efficient adsorption of acidic or neutral phosphorus-containing wastewater.

Description

A kind of lanthanum carbonate modified Fe3O4@C phosphorus removal adsorbent and its preparation method and application

Technical field

The invention belongs to the field of environmental adsorption, and particularly relates to a lanthanum carbonate-modified Fe ₃ O ₄ @C phosphorus removal adsorbent and its preparation method and application.

Background technique

Phosphorus is an important element for the life activities of humans, various animals, plants, and bacteria, but the discharge of large amounts of phosphorus-containing wastewater may lead to eutrophication of water bodies. The natural cycle of phosphorus is very slow. Eutrophic water bodies can cause a series of environmental problems such as algae reproduction, deterioration of water quality, and death of aquatic organisms. Therefore, it is very necessary to treat phosphorus-containing wastewater.

Many methods for phosphorus removal from water have been developed, including chemical precipitation, membrane separation, biological and adsorption methods. Among many methods, the adsorption method has attracted widespread attention due to its advantages such as simple operation, low cost, wide application range, and no secondary pollution.

Lanthanum is one of the relatively abundant and environmentally friendly rare earth elements on Earth. Lanthanum and its compounds have specific adsorption properties for phosphorus and have a strong affinity even in trace amounts. Currently, the most commonly used active lanthanum compounds in environmental phosphorus removal agents are lanthanum hydroxide or lanthanum oxide. For example, Chinese patent publication CN104722271A discloses an expanded graphite-loaded lanthanum hydroxide phosphorus removal adsorbent; Chinese patent publication CN105214629A discloses a biomass-based nano-lanthanum oxide phosphorus removal composite adsorbent. However, when these two lanthanum compounds are combined with phosphate, the pH of the solution will rapidly increase due to coordination exchange, resulting in a significant reduction in their adsorption efficiency. Therefore, changing the anions in lanthanum compounds and reducing the impact of pH changes on the system during the adsorption process is one of the methods to improve the phosphorus removal efficiency of adsorbents.

Lanthanum carbonate is another compound form of lanthanum. It is highly insoluble and has little effect on the pH of the solution when exchanged with phosphate. Lanthanum carbonate has been approved by the U.S. Food and Drug Administration (FDA) as an adhesive agent for the treatment of hyperphosphatemia because of its relatively low toxicity to humans and organisms. Although lanthanum carbonate has been well studied in the medical field, there are relatively few reports on its application in the treatment of environmental phosphorus-containing wastewater.

Traditional adsorbents have the problem of being difficult to separate and regenerate during use. The development of a magnetic composite material is a good solution. Fe ₃ O ₄ is widely used due to its strong magnetism and simple preparation process. Unfortunately, Fe ₃ O ₄ is easily oxidized in the air, leading to particle agglomeration and weakened magnetism. In order to overcome this, many researchers have tried to cover the surface of Fe ₃ O ₄ particles with an inert shell. This method not only prevents the oxidation of Fe ₃ O ₄ , but also causes the material to generate steric repulsion and improves the composite adsorbent. dispersion and specific surface area. For example, Chinese patent publication CN103964538A discloses a CeO ₂ modified SiO ₂ coated Fe ₃ O ₄ magnetic phosphorus adsorbent. However, the phosphate adsorption effect of this publication is significantly weaker than that of the lanthanum compound-modified adsorbent in other patents.

Contents of the invention

In order to overcome the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a method for preparing a lanthanum carbonate-modified Fe ₃ O ₄ @C phosphorus removal adsorbent.

Another object of the present invention is to provide a lanthanum carbonate-modified Fe ₃ O ₄ @C phosphorus removal adsorbent prepared by the above method. The adsorbent not only has strong adsorption performance, but also has strong magnetism and is convenient for separation and recovery.

Another object of the present invention is to provide the application of the above-mentioned lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent in phosphate adsorption.

The object of the present invention is achieved through the following solutions:

A preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent, including the following steps:

(1) Preparation of Fe ₃ O ₄ nanoparticles by solvothermal method: Add the iron salt to the ethylene glycol solvent and dissolve it with ultrasound, then add anhydrous sodium acetate and polyethylene glycol, stir and dissolve, then transfer to the reaction kettle for reaction. The obtained product is purified to obtain Fe ₃ O ₄ nanoparticles;

(2) Preparation of Fe ₃ O ₄ @C material by hydrothermal method: Evenly disperse the Fe ₃ O ₄ nanoparticles prepared in step (1) in water, add glucose or sucrose, stir evenly and transfer to a reactor for hydrothermal reaction. , the obtained product is purified to obtain Fe ₃ O ₄ @C;

(3) Preparation of lanthanum carbonate modified Fe ₃ O ₄ @C material by precipitation deposition method: Dissolve the lanthanum salt in water ultrasonically, then add the Fe ₃ O ₄ @C prepared in step (2), oscillate and stir to mix evenly, and add carbonic acid dropwise Hydrogen aqueous salt solution until the pH is neutral, and the resulting suspension is allowed to stand overnight, then washed and dried to obtain the lanthanum carbonate-modified Fe ₃ O ₄ @C material.

The iron salt described in step (1) is at least one of FeCl ₃ ·6H ₂ O, Fe(NO ₃ ) ₃ ·9H ₂ O, and Fe ₂ (SO ₄ ) ₃ ·9H ₂ O.

The amount of iron salt and ethylene glycol described in step (1) is such that every 1 to 4 mmol of iron salt is added to 30-50 ml of ethylene glycol; preferably, every 2 mmol of iron salt is added to 40 ml of ethylene glycol. Alcoholic.

The amount of iron salt, anhydrous sodium acetate, and polyethylene glycol described in step (1) satisfies: for every 1 to 4 mmol of iron salt, add 0.5 to 1 g of polyethylene glycol and 2.4 to 7.2 g of anhydrous sodium acetate. ; The degree of polymerization of polyethylene glycol in step (1) is 500 to 10,000.

The stirring and dissolving time described in step (1) is preferably 30 to 120 minutes.

The reaction described in step (1) refers to placing the reaction kettle in an oven at 150-220°C for reaction, preferably in an oven at 200°C; the reaction time described in step (1) is 8-16h , preferably 12h.

The purification described in step (1) means that after the reaction is completed, the obtained product is naturally cooled and then magnetically separated to collect the solid product. After washing three times with deionized water and absolute ethanol and drying, the purified Fe ₃ O is obtained. ₄ nanoparticles, the drying is preferably vacuum drying, the drying temperature is 60-100°C, and the drying time is 8-12 hours.

Before being dispersed in water, the Fe ₃ O ₄ nanoparticles described in step (2) are preferably first dispersed in an HNO ₃ solution, and then magnetically separated and washed with water before being dispersed in the water, wherein the concentration of the HNO ₃ solution is preferably is 1mol/L. Fe ₃ O ₄ is hydrophobic, and treatment with HNO ₃ is to introduce hydrophilic functional groups into Fe ₃ O ₄ , making it easy for Fe ₃ O ₄ to be coated with glucose or sucrose.

The amount of glucose or sucrose described in step (2) is such that for every 1 g of Fe ₃ O ₄ nanoparticles, 2 to 4 g of glucose or sucrose are added.

The hydrothermal reaction described in step (2) refers to the reaction in an oven at 150-220°C, preferably 200°C; the hydrothermal time described in step (2) is 8-16h, preferably 12h .

The purification described in step (2) refers to cooling the reaction product naturally, magnetically separating the solid product, washing it three times with deionized water and drying to obtain purified Fe ₃ O ₄ @C, where the drying is preferably Air blast drying, drying temperature is 60~100℃, drying time is 8~12h.

The lanthanum salt described in step (3) is at least one of LaCl ₃ ·7H ₂ O, La(NO ₃ ) ₃ ·6H ₂ O, and La ₂ (SO ₄ ) ₃ ·9H ₂ O.

The dosage of the lanthanum salt and Fe ₃ O ₄ @C described in step (3) satisfies: the mass ratio of the mass of La ³⁺ in the lanthanum salt to Fe ₃ O ₄ @C is 0.5 to 2:1.

The bicarbonate salt described in step (3) is preferably at least one of NaHCO ₃ , KHCO ₃ , and NH ₄ HCO ₃ ; the concentration of the bicarbonate aqueous solution described in step (3) is preferably 1 mol/L; the dripping speed It is 0.2~1ml/min, preferably 0.4ml/min.

The drying described in step (3) is blast drying, the drying temperature is 60 to 100°C, and the drying time is 8 to 12 hours.

A lanthanum carbonate-modified Fe ₃ O ₄ @C phosphorus removal adsorbent prepared by the above method.

Application of the above lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent in adsorbing phosphate under acidic or neutral conditions.

Compared with the existing technology, the present invention has the following advantages and beneficial effects:

(1) The prepared adsorbent has a high adsorption capacity for phosphates in water. As shown in Figure 2, the adsorption of phosphate by the adsorbent of the present invention is more consistent with the Langmuir model. The model calculates the adsorption conditions when the adsorbent dosage is 0.4g/L, the solution pH=7±0.1, and the adsorption temperature is 298K. The maximum theoretical adsorption capacity can reach 74.63mg-P/g.

(2) It has good adsorption performance under acidic or neutral conditions, see Figure 3.

(3) The adsorbent has strong magnetism and can easily perform solid-liquid separation operations, see Figure 4.

(4) Compared with common lanthanum hydroxide or lanthanum oxide, the present invention uses lanthanum carbonate with better adsorption performance for phosphates for modification.

(5) The carbon coating layer effectively protects Fe ₃ O ₄ nanoparticles and prevents Fe ₃ O ₄ from being oxidized in air or water. The Fe ₃ O ₄ @C substrate has a certain dispersion effect and avoids the agglomeration of the active material lanthanum carbonate.

Description of the drawings

Figure 1 is a comparison chart of the adsorption performance of the adsorbents on phosphate in Examples 1-4 and Comparative Examples 1-3.

Figure 2 is the isothermal adsorption line diagram of the corresponding material in Example 2 (adsorbent dosage is 0.4g/L, initial pH of the solution=7±0.1, adsorption temperature is 298K)

Figure 3 is a diagram of the adsorption capacity of the corresponding materials in Example 2 under different initial pH (adsorbent dosage is 0.4g/L, initial solution concentration is 50mg-P/L, adsorption temperature is 298K)

Figure 4 is a magnetic separation diagram of the corresponding material in Example 2.

Detailed ways

The present invention will be described in further detail below with reference to the examples and drawings, but the implementation of the present invention is not limited thereto. All similar structures or similar changes of the present invention should be included in the protection scope of the present invention.

Example 1

A method for preparing a lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a La ³⁺ : Fe ₃ O ₄ @C mass ratio of 0.5:1, including the following steps:

(1) 2 mmol FeCl ₃ ·6H ₂ O was added to 40 ml of ethylene glycol solvent and dissolved by ultrasound. Add 1 g of polyethylene glycol 4000 and 3.6 g of anhydrous sodium acetate. Stir magnetically for 30 min and then transfer to a reaction kettle at 200°C for 12 h. , natural cooling, magnetic separation, the solid product was washed three times each with deionized water and absolute ethanol, and vacuum dried at 60°C for 12 hours to obtain Fe ₃ O ₄ nanoparticles.

(2) Disperse 1 g of Fe ₃ O ₄ prepared in step (1) ultrasonically in a 0.1 mol/LHNO ₃ solution for 10 minutes, magnetically separate, wash three times with deionized water, and disperse the particles in 30 ml of deionized water with mechanical stirring. Add 2g glucose to the above suspension, stir mechanically for 10 minutes, transfer the solution to the reactor, react at 200°C for 12 hours, cool naturally, and magnetically separate. The solid product is washed three times with deionized water and dried at 60°C for 12 hours. Obtain Fe ₃ O ₄ @C for later use.

(3) Dissolve 0.743g LaCl ₃ ·7H ₂ O in 50 ml deionized water by ultrasonic, add 0.556g Fe ₃ O ₄ @C prepared in step (2), and oscillate and stir in a constant temperature oscillator for 4 hours. While rapidly mechanically stirring, add 1 mol/L NaHCO ₃ solution dropwise to the above suspension at a speed of 0.4 ml/min until the pH is neutral, and let it stand overnight. After magnetic separation, the solid was washed three times with deionized water and dried at 60°C for 12 h.

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=7.0±0.1. The lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a mass ratio of 0.02gLa ³⁺ :Fe ₃ O ₄ @C is 0.5:1 was used for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used for analysis. The results showed that the adsorption capacity of phosphate was 50.90mg-P/g.

Example 2

A method for preparing a lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a La ³⁺ : Fe ₃ O ₄ @C mass ratio of 1:1, including the following steps:

(1) 2 mmol FeCl ₃ ·6H ₂ O was added to 40 ml of ethylene glycol solvent and dissolved by ultrasound. Add 1 g of polyethylene glycol 4000 and 3.6 g of anhydrous sodium acetate. Stir magnetically for 30 min and then transfer to a reaction kettle to react at 200°C for 12 h. After natural cooling, magnetic separation, the solid product was washed three times each with deionized water and absolute ethanol, and vacuum dried at 60°C for 12 hours to obtain Fe ₃ O ₄ nanoparticles.

(2) Disperse 1 g of Fe ₃ O ₄ prepared in step (1) ultrasonically in a 0.1 mol/LHNO ₃ solution for 10 minutes, magnetically separate, wash three times with deionized water, and disperse the particles in 30 ml of deionized water with mechanical stirring. Add 2g glucose to the above suspension, stir mechanically for 10 minutes, transfer the solution to the reactor, react at 200°C for 12 hours, cool naturally, and magnetically separate. The solid product is washed three times with deionized water and dried at 60°C for 12 hours. Obtain Fe ₃ O ₄ @C for later use.

(3) Dissolve 1.486g LaCl ₃ ·7H ₂ O in 50 ml deionized water under ultrasonic, add 0.556g Fe ₃ O ₄ @C prepared in step (2), and oscillate and stir in a constant temperature oscillator for 4 hours. While rapidly mechanically stirring, add 1 mol/L NaHCO ₃ solution dropwise to the above suspension at a speed of 0.4 ml/min until the pH is neutral, and let it stand overnight. After magnetic separation, the solid was washed three times with deionized water and dried at 60°C for 12 h.

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=7.0±0.1. The lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a mass ratio of 0.02gLa ³⁺ :Fe ₃ O ₄ @C is 1:1 was used for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used for analysis. The results showed that the adsorption capacity of phosphate was 63.64mg-P/g.

Example 3

A method for preparing a lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a La ³⁺ : Fe ₃ O ₄ @C mass ratio of 2:1, including the following steps:

(1) 2 mmol FeCl ₃ ·6H ₂ O was added to 40 ml of ethylene glycol solvent and dissolved by ultrasound. Add 1 g of polyethylene glycol 4000 and 3.6 g of anhydrous sodium acetate. Stir magnetically for 30 min and then transfer to a reaction kettle at 200°C for 12 h. , natural cooling, magnetic separation, the solid product was washed three times each with deionized water and absolute ethanol, and vacuum dried at 60°C for 12 hours to obtain Fe ₃ O ₄ nanoparticles.

(2) Disperse 1 g of Fe ₃ O ₄ prepared in step (1) ultrasonically in a 0.1 mol/L HNO ₃ solution for 10 minutes, then magnetically separate. After washing with deionized water three times, the particles are mechanically stirred and dispersed in 30 ml of deionized water. Add 2g glucose to the above suspension, stir mechanically for 10 minutes, transfer the solution to the reactor, react at 200°C for 12 hours, cool naturally, and magnetically separate. The solid product is washed three times with deionized water and dried at 60°C for 12 hours. Obtain Fe ₃ O ₄ @C for later use.

(3) Dissolve 2.972g LaCl ₃ ·7H ₂ O in 50 ml deionized water under ultrasonic, add 0.556g Fe ₃ O ₄ @C prepared in step (2), and oscillate and stir in a constant temperature oscillator for 4 hours. While rapidly mechanically stirring, add 1 mol/L NaHCO ₃ solution dropwise to the above suspension at a speed of 0.4 ml/min until the pH is neutral, and let it stand overnight. After magnetic separation, the solid was washed three times with deionized water and dried at 60°C for 12 h.

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=7.0±0.1. The lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a mass ratio of 0.02gLa ³⁺ :Fe ₃ O ₄ @C is 2:1 is used for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used for analysis. The results showed that the adsorption capacity of phosphate was 69.30mg-P/g.

Example 4

The preparation method of the lanthanum carbonate modified Fe ₃ O ₄ @C composite material in this example is the same as that in Example 2

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=4.0±0.1. The lanthanum carbonate-modified Fe ₃ O ₄ @C composite material with a mass ratio of 0.02gLa ³⁺ :Fe ₃ O ₄ @C is 1:1 was used for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used for analysis. The results showed that the adsorption capacity of phosphate was 74.25mg-P/g.

Comparative example 1

Fe ₃ O ₄ @C composite material, the difference between the material preparation method of this comparative example and the corresponding material of Example 2 above is that there is no lanthanum carbonate modification in step (3).

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=7.0±0.1. 0.02gFe ₃ O ₄ @C composite material was used for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used for analysis. The results showed that the adsorption capacity of phosphate was 9.125mg-P/g.

Comparative example 2

The preparation method of pure lanthanum carbonate includes the following steps:

After ultrasonically dissolving 1.486g LaCl ₃ ·7H ₂ O in 50ml deionized water, add 1mol/L NaHCO ₃ solution dropwise at a speed of 0.4ml/min with rapid mechanical stirring until the pH is neutral, and let it stand overnight. After magnetic separation, the solid was washed three times with deionized water and dried at 60°C for 12 h.

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=7.0±0.1. Use 0.02g of pure lanthanum carbonate for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used to analyze the material. The results showed that the phosphate adsorption capacity of the material was 47.13mg-P/g.

Comparative example 3

A method for preparing a lanthanum hydroxide-modified Fe ₃ O ₄ @C composite material with a La ³⁺ : Fe ₃ O ₄ @C mass ratio of 1:1, including the following steps:

Steps (1) and (2) are the same as in Example 2.

Step (3) Ultrasonically dissolve 1.486g LaCl ₃ ·7H ₂ O in 50 ml deionized water, add 0.556g Fe ₃ O ₄ @C prepared in step (2), and oscillate and stir in a constant temperature oscillator for 4 hours. While rapidly mechanically stirring, add 1 mol/L NaOH solution dropwise to the above suspension at a speed of 0.4 ml/min until the pH is 11±0.1, and let it stand overnight. After magnetic separation, the solid was washed three times with deionized water and dried at 60°C for 12 h.

Adsorbent activity test:

To a 100 ml Erlenmeyer flask, add 50 ml of KH ₂ PO ₄ solution with a concentration of 50 mg-P/L and pH=7.0±0.1. The lanthanum hydroxide-modified Fe ₃ O ₄ @C composite material with a mass ratio of 0.02gLa ³⁺ :Fe ₃ O ₄ @C is 1:1 was used for adsorption. The adsorption conditions were a temperature of 298K and a rotation speed of 200rpm with constant temperature shaking for 24h.

After the reaction, the ammonium molybdate spectrophotometric method was used for analysis. The results showed that the adsorption capacity of phosphate was 36.98mg-P/g.

The comparison chart of the adsorption performance of the adsorbents for phosphate in Examples 1-4 and Comparative Examples 1-3 is shown in Figure 1. Examples 1-3 are lanthanum carbonate-modified Fe ₃ O ₄ @C prepared at different mass ratios. Examples of adsorption of composite materials under simulated neutral conditions; Example 4 is an example of adsorption under simulated acidic conditions. It can be seen that the adsorbent of the present invention has good adsorption capacity regardless of whether the phosphorus-containing simulated wastewater is in acidic or neutral conditions.

Comparative Examples 1 to 3 are compared with Example 2. Comparative Example 1 shows that the Fe ₃ O ₄ @C substrate has extremely small self-adsorption capacity; Comparative Example 2 has less adsorption capacity than Example 2, indicating that the Fe ₃ O ₄ @C substrate contributes to the dispersion of the active material lanthanum carbonate; Comparative Example 3 is more The amount of adsorption in Example 2 is small, indicating that modification with lanthanum carbonate is more superior than modification with lanthanum hydroxide.

The isothermal adsorption diagram of the corresponding material in Example 2 (adsorbent dosage is 0.4g/L, initial solution pH=7±0.1, adsorption temperature is 298K) is shown in Figure 2. From Figure 2, it can be prepared by the present invention The lanthanum carbonate-modified Fe ₃ O ₄ @C composite material has a high adsorption capacity. The adsorption of phosphate by the adsorbent of the present invention is more consistent with the Langmuir model. The model calculates that the adsorbent dosage is 0.4g/L. , solution pH=7±0.1, and the maximum theoretical adsorption capacity can reach 74.63mg-P/g under the adsorption conditions of adsorption temperature of 298K.

The adsorption capacity diagram of the corresponding material in Example 2 at different initial pH (adsorbent dosage is 0.4g/L, initial solution concentration is 50mg-P/L, adsorption temperature is 298K) is shown in Figure 3. From Figure It can be seen from 3 that the lanthanum carbonate modified Fe ₃ O ₄ @C composite material prepared by the present invention has good adsorption performance under acidic or neutral conditions.

The magnetic separation diagram of the corresponding material in Example 2 is shown in Figure 4. It can be seen from Figure 4 that the lanthanum carbonate-modified Fe3O4@C composite material prepared by the present invention has strong magnetism and can easily perform solid-liquid separation operations.

Comparing Example 2 with Comparative Examples 1 and 2, it can be seen that when the same amount of adsorbent is used, the lanthanum carbonate-modified Fe ₃ O ₄ @C composite material is better than the lanthanum carbonate alone and the Fe ₃ O ₄ @C alone. The adsorption effects are all good, indicating that lanthanum carbonate and Fe ₃ O ₄ @C have a synergistic effect.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, etc. may be made without departing from the spirit and principles of the present invention. All simplifications should be equivalent substitutions, and are all included in the protection scope of the present invention.

Claims (10)

1. A preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent, which is characterized by comprising the following steps: (1) Preparation of Fe ₃ O ₄ nanoparticles by solvothermal method: Add the iron salt to the ethylene glycol solvent and dissolve it with ultrasound, then add anhydrous sodium acetate and polyethylene glycol, stir and dissolve, then transfer to the reaction kettle for reaction. The obtained product is purified to obtain Fe ₃ O ₄ nanoparticles; (2) Preparation of Fe ₃ O ₄ @C material by hydrothermal method: Evenly disperse the Fe ₃ O ₄ nanoparticles prepared in step (1) in water, add glucose or sucrose, stir evenly and transfer to a reactor for hydrothermal reaction. , the obtained product is purified to obtain Fe ₃ O ₄ @C; (3) Preparation of lanthanum carbonate modified Fe ₃ O ₄ @C material by precipitation deposition method: Dissolve the lanthanum salt in water ultrasonically, then add the Fe ₃ O ₄ @C prepared in step (2), oscillate and stir to mix evenly, and add carbonic acid dropwise Hydrogen aqueous salt solution until the pH is neutral, and the resulting suspension is allowed to stand overnight, then washed and dried to obtain the lanthanum carbonate-modified Fe ₃ O ₄ @C material. 2. The preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 1, characterized in that: The iron salt described in step (1) is at least one of FeCl ₃ ·6H ₂ O, Fe(NO ₃ ) ₃ ·9H ₂ O, and Fe ₂ (SO ₄ ) ₃ ·9H ₂ O; The amount of iron salt and ethylene glycol described in step (1) is such that every 1 to 4 mmol of iron salt is added to 30-50 ml of ethylene glycol; the iron salt and anhydrous acetic acid described in step (1) The dosage of sodium and polyethylene glycol is as follows: for every 1 to 4 mmol of iron salt, add 0.5 to 1g of polyethylene glycol and 2.4 to 7.2g of anhydrous sodium acetate; The reaction described in step (1) refers to placing the reaction kettle in an oven at 150-220°C for reaction, and the reaction time is 8-16 hours. 3. The preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 1, characterized in that: The amount of glucose or sucrose described in step (2) is such that for every 1 g of Fe ₃ O ₄ nanoparticles, 2 to 4 g of glucose or sucrose are added. 4. The preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 1, characterized in that: The hydrothermal reaction described in step (2) refers to the reaction in an oven at 150 to 220°C, and the hydrothermal time described in step (2) is 8 to 16 hours. 5. The preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 1, characterized in that: The Fe ₃ O ₄ nanoparticles described in step (2) are first dispersed in the HNO ₃ solution before being dispersed in the water, and then are magnetically separated and washed with water before being dispersed in the water. 6. The preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 1, characterized in that: The lanthanum salt described in step (3) is at least one of LaCl ₃ ·7H ₂ O, La(NO ₃ ) ₃ ·6H ₂ O, and La ₂ (SO ₄ ) ₃ ·9H ₂ O; The dosage of the lanthanum salt and Fe ₃ O ₄ @C described in step (3) satisfies: the mass ratio of the mass of La ³⁺ in the lanthanum salt to Fe ₃ O ₄ @C is 0.5 to 2:1. 7. The preparation method of lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 1, characterized in that: The bicarbonate aqueous solution described in step (3) refers to at least one of NaHCO ₃ , KHCO ₃ , and NH ₄ HCO ₃ ; The concentration of the bicarbonate aqueous solution described in step (3) is 1mol/L; the dropping speed is 0.2~1ml/min; The drying described in step (3) is blast drying, the drying temperature is 60 to 100°C, and the drying time is 8 to 12 hours. 8. A lanthanum carbonate-modified Fe ₃ O ₄ @C phosphorus removal adsorbent prepared by the method of any one of claims 1 to 7. 9. Application of the lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 8 in adsorbing phosphate. 10. Application of the lanthanum carbonate modified Fe ₃ O ₄ @C phosphorus removal adsorbent according to claim 8 in adsorbing phosphate under acidic or neutral conditions.