Magnetic nano composite adsorbent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of wastewater treatment, and discloses a magnetic nano composite adsorbent as well as a preparation method and application thereof. The preparation method comprises the following steps: dissolving a divalent iron salt and a trivalent iron salt in water, adding ammonia water under a protective gas, and carrying out a stirring reaction at a rotating speed of 350-600 rpm to prepare Fe3O4 nanoparticles; the preparation method comprises the following steps: dispersing Fe3O4 nanoparticles in a mixed solution of acrylic acid and ethidene diamine, then adding an initiator, and carrying out a stirring reaction at a rotating speed of 150-300 rpm to prepare the magnetic nano composite adsorbent. The magnetic nano-composite adsorbent provided by the invention can efficiently remove lead ions in wastewater, is not influenced by mercury ions and copper ions, also has relatively good adsorption capacity on the mercury ions and the copper ions, and can treat various heavy metal ions in the wastewater at the same time. The magnetic nano composite adsorbent is easy to separate and good in reusability.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and specifically relates to a magnetic nano composite adsorbent and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern industry, mining, metallurgy, electroplating, chemical industry and other industries discharge a large amount of wastewater containing heavy metal ions during production. Heavy metal ions such as lead (Pb 2+ ), mercury (Hg 2+ ), copper (Cu 2+ ), etc., are highly toxic, non-biodegradable, and easily enriched in organisms. Once these heavy metal ions enter the water and soil environment, they will cause serious damage to the ecosystem. In water bodies, heavy metal ions will interfere with the physiological metabolism of aquatic organisms, affect their normal growth and reproduction, and lead to the death of aquatic organisms such as fish. In the soil, heavy metal ions will react chemically with minerals, organic matter, etc. in the soil, change the physical and chemical properties of the soil, affect the absorption of nutrients by plants, and inhibit plant growth. Moreover, through the transmission of the food chain, heavy metal ions will eventually enter the human body, endanger human health, and cause a variety of diseases. Lead poisoning can damage the human nervous system and hematopoietic system, leading to intellectual retardation in children and anemia in adults; mercury poisoning can cause irreversible damage to the kidneys and nervous system, such as causing serious diseases such as Minamata disease.

[0003] At present, there are many methods for treating heavy metal ion pollution. Adsorption has become one of the most widely used technologies due to its advantages such as simple operation, relatively low cost and high removal efficiency. However, traditional adsorbents have many defects. Although ordinary activated carbon on the market has a certain adsorption capacity, its adsorption selectivity is poor, and the difference in adsorption effect on different heavy metal ions is not obvious. When treating wastewater with multiple heavy metal ions, it is difficult to remove the target heavy metal ions in a targeted and efficient manner, and it is easily affected by other metal ions. Moreover, its adsorption capacity is limited. When treating high-concentration heavy metal wastewater, a large amount of addition is often required, which not only increases the treatment cost, but also brings about the problem of subsequent separation and disposal. In addition, the activated carbon particles are small and difficult to separate from the solution after adsorption. Usually, complex subsequent treatment methods such as filtration and centrifugation are required, which further increases the treatment cost and operation difficulty.

[0004] Although Fe3O4 nanoparticles without surface modification are magnetic and easy to separate using an external magnetic field, their adsorption capacity for heavy metal ions is extremely low due to the lack of functional groups on their surface that specifically bind to heavy metal ions. In practical applications, it is impossible to effectively remove heavy metal ions from wastewater, making it difficult to meet increasingly stringent environmental protection requirements. Although common ion exchange resins on the market have a certain exchange and adsorption capacity for certain heavy metal ions, they are difficult to regenerate. After repeated use, their exchange and adsorption performance will gradually decline, and the regeneration process requires the consumption of a large amount of chemical reagents, which is costly.

[0005] In summary, the development of a new heavy metal ion adsorbent with high adsorption capacity, fast adsorption speed, good adsorption selectivity, easy separation and good reusability is of great significance to solving the current heavy metal pollution problem. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a magnetic nanocomposite adsorbent and a preparation method and application thereof. The magnetic nanocomposite adsorbent provided by the present invention has high adsorption capacity, fast adsorption speed, good adsorption selectivity, and is easy to separate and has good reusability.

[0007] The invention provides a method for preparing a magnetic nano composite adsorbent.

[0008] Specifically, a method for preparing a magnetic nanocomposite adsorbent comprises the following steps: (1) Dissolving trivalent iron salt and divalent iron salt in water, adding ammonia water under protective gas, stirring and reacting at a speed of 350 rpm-600 rpm to obtain Fe3O4 nanoparticles; (2) The Fe3O4 nanoparticles prepared in step (1) are dispersed in a mixed solution of acrylic acid and ethylenediamine, and an initiator is added. The mixture is stirred at a speed of 150 rpm to 300 rpm to react, thereby obtaining a magnetic nanocomposite adsorbent.

[0009] Preferably, in step (1), the molar ratio of the ferric iron salt to the ferrous iron salt is (1.5-2.5):1; further preferably, the molar ratio of the ferric iron salt to the ferrous iron salt is (1.8-2.1):1.

[0010] Preferably, the divalent iron salt is FeCl2·4H2O, and the trivalent iron salt is FeCl3·6H2O.

[0011] Preferably, in step (1), the mass percentage of the aqueous ammonia is 20%-30%.

[0012] Preferably, in step (1), the stirring reaction temperature is 70° C.-90° C., and the stirring reaction time is 0.5-2 hours.

[0013] Preferably, in step (1), the stirring reaction is carried out at a rotation speed of 400 rpm-500 rpm.

[0014] Preferably, in step (2), the acrylic acid and ethylenediamine mixed solution comprises acrylic acid and ethylenediamine; the mass ratio of the acrylic acid to the ethylenediamine is (1-3):1; further preferably, the mass ratio of the acrylic acid to the ethylenediamine is (1.5-2.5):1.

[0015] Preferably, in step (2), the mass concentration of the acrylic acid and ethylenediamine mixed solution is 0.03 g / mL-0.15 g / mL; further preferably, in step (2), the mass concentration of the acrylic acid and ethylenediamine mixed solution is 0.05 g / mL-0.125 g / mL.

[0016] Preferably, in step (2), the ratio of the mass of the Fe3O4 nanoparticles to the total mass of the acrylic acid and the ethylenediamine is 1:(5-35); further preferably, the ratio of the mass of the Fe3O4 nanoparticles to the total mass of the acrylic acid and the ethylenediamine is 1:(10-25).

[0017] Preferably, in step (2), the initiator is a persulfate, such as potassium persulfate.

[0018] Preferably, in step (2), the rotation speed of the stirring reaction is 200 rpm-300 rpm, the temperature of the stirring reaction is 50° C.-70° C., and the time of the stirring reaction is 4-8 hours.

[0019] The invention also provides a magnetic nano composite adsorbent.

[0020] Specifically, a magnetic nanocomposite adsorbent is prepared by the above preparation method; the magnetic nanocomposite adsorbent comprises inner core Fe3O4 nanoparticles and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nanoparticles.

[0021] Preferably, the particle size of the Fe3O4 nanoparticles is in the range of 10 nm to 80 nm, and the average molecular weight of the polyacrylic acid-ethylenediamine graft copolymer is in the range of 3000 to 10000.

[0022] The invention also provides application of the magnetic nano composite adsorbent.

[0023] Specifically, the application of the above magnetic nanocomposite adsorbent in wastewater treatment.

[0024] Preferably, the wastewater contains one or more of lead ions, mercury ions and copper ions.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The magnetic nanocomposite adsorbent prepared by the present invention comprises a core Fe3O4 nanoparticle and a polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nanoparticle. A large number of carboxyl groups and amino groups on the polyacrylic acid-ethylenediamine graft copolymer react with lead ions to form a stable complex. The present invention achieves the purpose of controlling the core particle size and the coating layer structure by controlling the rotation speed in each step of the stirring reaction. The formed multi-level pore structure is conducive to the diffusion and adsorption of heavy metal ions inside the adsorbent, increasing the accessibility of the adsorption sites, thereby improving the adsorption capacity. In addition, the formed nanoscale size and porous structure enable the adsorbent to have a larger specific surface area, increase the adsorption sites, and shorten the diffusion path of heavy metal ions; the porous structure is conducive to the rapid transmission of heavy metal ions inside the adsorbent, so that the heavy metal ions can quickly react with the functional groups on the surface to achieve rapid adsorption. The magnetic nanocomposite adsorbent provided by the present invention has high adsorption capacity, fast adsorption speed, and good adsorption selectivity; (2) The magnetic nanocomposite adsorbent provided by the present invention can efficiently remove lead ions from wastewater. It is not affected by mercury ions and copper ions, and has good adsorption capacity for mercury ions and copper ions. It can simultaneously treat multiple heavy metal ions in wastewater. About half of the lead ions, mercury ions and copper ions can be removed in 10 minutes of adsorption; 85%-88% of the adsorption equilibrium can be reached within 25 minutes; after two hours of adsorption, the lead ion adsorption capacity is greater than or equal to 17.5 mg / g, up to 19.1 mg / g, the mercury ion adsorption capacity is greater than or equal to 8.1 mg / g, up to 9.4 mg / g, and the copper ion adsorption capacity is greater than or equal to 8.7 mg / g, up to 9.6 mg / g; (3) The magnetic nanocomposite adsorbent provided by the present invention is easy to separate, and the adsorbent and the solution can be efficiently separated within 5 minutes by using an external magnetic field; (4) The magnetic nanocomposite adsorbent provided by the embodiment of the present invention has good reusability. After 5 adsorption-desorption cycles, the adsorption capacity of the adsorbent can maintain more than 90% of the initial value. Specific implementation methods

[0026] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0027] Unless otherwise specified, the raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0028] Example 1 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0029] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 5mmol FeCl3·6H2O and 2.5mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 25% ammonia water was quickly added, and the mixture was stirred at 80℃ (speed was 450rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 30 nanometers. Subsequently, 0.5g Fe3O4 nanoparticles were dispersed in a reaction system containing 5g acrylic acid and 3g ethylenediamine, ultrasonically treated for 45 minutes, and 0.5g potassium persulfate was added. The mixture was stirred at 60℃ (speed was 250rpm) for 6 hours to obtain a magnetic nanocomposite adsorbent.

[0030] Example 2 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0031] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 6mmol FeCl3·6H2O and 3mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 28% ammonia water was quickly added and stirred at 75℃ (speed of 420rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 40 nanometers. Subsequently, 0.5g Fe3O4 nanoparticles were dispersed in a reaction system containing 5g acrylic acid and 3g ethylenediamine, ultrasonically treated for 40 minutes, and then 0.5g potassium persulfate was added. The reaction was stirred at 60℃ (speed of 220rpm) for 6 hours to obtain a magnetic nanocomposite adsorbent.

[0032] Example 3 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0033] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 5mmol FeCl3·6H2O and 2.5mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 25% ammonia water was quickly added, and the mixture was stirred at 80℃ (speed was 580rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 22nm. Subsequently, 0.5g Fe3O4 nanoparticles were dispersed in a reaction system containing 5g acrylic acid and 3g ethylenediamine, ultrasonically treated for 45 minutes, and 0.5g potassium persulfate was added. The mixture was stirred at 60℃ (speed was 150rpm) for 7 hours to obtain a magnetic nanocomposite adsorbent.

[0034] Example 4 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0035] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 5mmol FeCl3·6H2O and 2.5mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 25% ammonia water was quickly added, and the mixture was stirred at 80℃ (speed was 450rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 30 nanometers. Subsequently, 0.3g Fe3O4 nanoparticles were dispersed in a reaction system containing 6g acrylic acid and 3g ethylenediamine, ultrasonically treated for 45 minutes, 0.5g potassium persulfate was added, and the mixture was stirred at 60℃ (speed was 250rpm) for 6 hours to obtain a magnetic nanocomposite adsorbent.

[0036] Comparative Example 1 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0037] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 5mmol FeCl3·6H2O and 2.5mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 25% ammonia water was quickly added, and the mixture was stirred at 80℃ (speed was 150rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 180 nanometers. Subsequently, 0.5g Fe3O4 nanoparticles were dispersed in a reaction system containing 5g acrylic acid and 3g ethylenediamine, ultrasonically treated for 45 minutes, and 0.5g potassium persulfate was added. The mixture was stirred at 60℃ (speed was 150rpm) for 6 hours to obtain a magnetic nanocomposite adsorbent.

[0038] Comparative Example 2 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0039] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 5mmol FeCl3·6H2O and 2.5mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 25% ammonia water was quickly added, and the mixture was stirred at 80℃ (speed was 500rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 26 nanometers. Subsequently, 0.5g Fe3O4 nanoparticles were dispersed in a reaction system containing 5g acrylic acid and 3g ethylenediamine, ultrasonically treated for 45 minutes, and 0.5g potassium persulfate was added. The mixture was stirred at 60℃ (speed was 500rpm) for 6 hours to obtain a magnetic nanocomposite adsorbent.

[0040] Comparative Example 3 A magnetic nano composite adsorbent comprises Fe3O4 nano particles as inner core and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nano particles.

[0041] A method for preparing a magnetic nanocomposite adsorbent comprises the following steps: 5mmol FeCl3·6H2O and 2.5mmol FeCl2·4H2O were dissolved in 100mL deionized water. Under nitrogen protection, 25mL 25% ammonia water was quickly added, and the mixture was stirred at 80℃ (speed was 450rpm) for 1 hour to obtain Fe3O4 nanoparticles. Transmission electron microscopy (TEM) observation showed that the obtained Fe3O4 nanoparticles had a uniform particle size of about 30 nanometers. Subsequently, 0.5g Fe3O4 nanoparticles were dispersed in a reaction system containing 0.5g acrylic acid and 0.5g ethylenediamine, ultrasonically treated for 45 minutes, and 0.5g potassium persulfate was added. The mixture was stirred at 60℃ (speed was 250rpm) for 6 hours to obtain a magnetic nanocomposite adsorbent.

[0042] Product effect test: The magnetic nanocomposite adsorbents prepared in Examples 1-4 and Comparative Examples 1-3 were tested. 7 portions of 100 mL of simulated wastewater containing 100 mg / L lead ion concentration, 50 mg / L mercury ion concentration, and 50 mg / L copper ion concentration were prepared. 0.5 g of the magnetic nanocomposite adsorbents prepared in Examples 1-4 and Comparative Examples 1-3 were added respectively, and the concentrations of the remaining lead ions, mercury ions, and copper ions in the solution were measured (using an atomic absorption spectrometer) after 10 min and 2 hours of oscillation adsorption at 25°C and 150 rpm, and the adsorption capacity was calculated, where the adsorption capacity = (initial heavy metal ion concentration - remaining heavy metal ion concentration) × 0.1 / adsorbent addition amount.

[0043] The test results of the embodiments and comparative examples are shown in Table 1.

[0044] Table 1 Group time Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Lead ion adsorption capacity mg / g 10min 11.2 10.8 10 9.8 8.6 7.4 4.6 Lead ion adsorption capacity mg / g 2 hours 19.1 18.9 18.2 17.5 13.4 12.6 9.6 Mercury ion adsorption capacity mg / g 10min 4.8 4.7 4.2 4.5 3.7 3.6 3.2 Mercury ion adsorption capacity mg / g 2 hours 9.4 9.1 8.5 8.1 6.8 6.5 5.3 Copper ion adsorption capacity mg / g 10min 4.9 4.7 4.6 4.5 3.5 3.7 3.1 Copper ion adsorption capacity mg / g 2 hours 9.6 9.4 8.7 8.7 6.4 6.7 4.8 As can be seen from Table 1, in the simulated wastewater mainly composed of lead ions and also containing mercury ions and copper ions, the magnetic nanocomposite adsorbent provided by the embodiment of the present invention is not only not affected by mercury ions and copper ions, but also has good adsorption capacity for lead ions. At the same time, it also has good adsorption capacity for mercury ions and copper ions, and can simultaneously treat multiple heavy metal ions in wastewater. And about half of the lead ions, mercury ions and copper ions can be removed in 10 minutes of adsorption; the lead ion adsorption capacity is greater than or equal to 17.5 mg / g after two hours of adsorption, up to 19.1 mg / g; the mercury ion adsorption capacity is greater than or equal to 8.1 mg / g after two hours of adsorption, up to 9.4 mg / g; the copper ion adsorption capacity is greater than or equal to 8.7 mg / g after two hours of adsorption, up to 9.6 mg / g. The adsorption capacity of the magnetic nanocomposite adsorbent provided by the embodiment of the present invention is significantly better than that of the comparative example.

[0045] In addition, the study found that the magnetic nanocomposite adsorbent provided in the embodiment of the present invention can reach 85%-88% of the adsorption equilibrium within 25 minutes. Using an external magnetic field, the magnetic nanocomposite adsorbent provided in the embodiment of the present invention can be efficiently separated from the solution within 5 minutes. The magnetic nanocomposite adsorbent provided in Examples 1-3 of the present invention was subjected to an adsorption-desorption cycle experiment (each time the adsorbent was separated, recovered and analyzed, it was supplemented to 0.5g). After 5 adsorption-desorption cycles, the adsorption capacity of the adsorbent can maintain more than 90% of the initial value, among which Example 1 reached 92.8%.

[0046] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a magnetic nanocomposite adsorbent, characterized in that: The following steps are involved: (1) Dissolving a divalent iron salt and a trivalent iron salt in water, adding ammonia water under a protective gas, and stirring the mixture at a speed of 350 rpm to 600 rpm to obtain Fe3O4 nanoparticles; (2) The Fe3O4 nanoparticles prepared in step (1) are dispersed in a mixed solution of acrylic acid and ethylenediamine, and an initiator is added. The mixture is stirred at a speed of 150 rpm to 300 rpm to react, thereby obtaining a magnetic nanocomposite adsorbent.

2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the ferric iron salt to the ferrous iron salt is (1.5-2.5):

1.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the stirring reaction temperature is 70° C.-90° C., and the stirring reaction time is 0.5-2 hours.

4. The preparation method according to claim 1, characterized in that: In step (2), the acrylic acid and ethylenediamine mixed solution includes acrylic acid and ethylenediamine; the mass ratio of the acrylic acid to the ethylenediamine is (1-3):

1.

5. The preparation method according to claim 4, characterized in that: In step (2), the mass concentration of the acrylic acid and ethylenediamine mixed solution is 0.03 g / mL-0.15 g / mL.

6. The preparation method according to claim 4 or 5, characterized in that: In step (2), the ratio of the mass of the Fe3O4 nanoparticles to the total mass of the acrylic acid and the ethylenediamine is 1:(5-35).

7. The preparation method according to claim 6, characterized in that: In step (2), the rotation speed of the stirring reaction is 200 rpm-300 rpm, the temperature of the stirring reaction is 50° C.-70° C., and the time of the stirring reaction is 4-8 hours.

8. A magnetic nanocomposite adsorbent, characterized in that: The magnetic nanocomposite adsorbent is prepared by the preparation method described in any one of claims 1 to 7; the magnetic nanocomposite adsorbent comprises core Fe3O4 nanoparticles and polyacrylic acid-ethylenediamine graft copolymer coated on the surface of the Fe3O4 nanoparticles.

9. The magnetic nanocomposite adsorbent according to claim 8, characterized in that: The particle size of the Fe3O4 nanoparticles ranges from 10nm to 80nm, and the average molecular weight of the polyacrylic acid-ethylenediamine graft copolymer ranges from 3000 to 10000.

10. Use of the magnetic nanocomposite adsorbent according to claim 8 or 9 in wastewater treatment.