An adsorbent for treating heavy metal wastewater and a preparation method thereof

Abstract

The present invention discloses an adsorbent for treating heavy metal wastewater and a preparation method thereof, relating to the technical field of wastewater treatment. In the present invention, polyacrylamide is mixed with the aqueous extract of myrtle and subjected to γ-ray irradiation to obtain irradiated modified polyacrylamide; Fe 3 O 4 nanoparticles and the ethanol extract of myrtle are subjected to modification treatment in ethylene glycol to obtain modified Fe 3 O 4 nanoparticles; then the irradiated modified polyacrylamide is used to load the modified Fe 3 O 4 nanoparticles in an organic solvent to obtain a heavy metal adsorbent. The adsorbent of the present invention exhibits excellent adsorption and removal effects on heavy metal ions, has good regeneration performance, and at the same time has the characteristics of simple preparation process and strong operability, and can effectively meet the actual needs of heavy metal wastewater treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly to an adsorbent for treating heavy metal wastewater and a preparation method thereof. Background Art

[0002] With the acceleration of the industrialization process, the discharge of heavy metal wastewater has become a serious environmental problem. Heavy metals such as lead, cadmium, mercury, and chromium are highly toxic, difficult to degrade, and bioaccumulative, posing a serious threat to the ecosystem and human health. Therefore, it is particularly urgent to develop efficient heavy metal wastewater treatment technologies. The adsorption method has become one of the main methods for treating heavy metal wastewater due to its simple operation, low cost, wide application range, etc. The adsorption method is a process of purifying wastewater by selectively adsorbing heavy metal ions in the wastewater on its surface through physical or chemical actions on the surface of the adsorbent. Its main advantages include: (1) High efficiency: It can effectively remove various heavy metal ions, especially suitable for low-concentration heavy metal wastewater. (2) Low cost: Compared with other treatment methods (such as chemical precipitation, ion exchange, etc.), the adsorption method has simple equipment and low operating costs. (3) Environmental friendliness: The adsorbent can be reused, reducing secondary pollution. (4) Strong adaptability: It is applicable to different types of heavy metal wastewater and is not sensitive to water quality changes.

[0003] Common types of adsorbents mainly include natural material adsorbents, modified material adsorbents, and new composite material adsorbents, etc. (1) Natural material adsorbents mainly include activated carbon, zeolite, bentonite, chitosan, etc. These materials have a rich pore structure and a high specific surface area, capable of providing a large number of adsorption sites. (2) Modified material adsorbents are obtained by chemically or physically modifying natural materials to improve their adsorption performance. Common modification methods include acid-base treatment, heat treatment, loading metal oxides, etc. For example, acid-base modified activated carbon can increase the surface functional groups of activated carbon and enhance the selective adsorption of heavy metal ions, mainly used to improve the adsorption efficiency for specific heavy metal ions (such as chromium, nickel); another example is that zeolite loaded with metal oxides can improve the adsorption performance by introducing metal oxides (such as Fe 2 O 3 、TiO 2)Enhance the adsorption activity, which can significantly improve the adsorption capacity for heavy metal ions (such as lead, cadmium, mercury); for another example, magnetic nanoparticle-modified bentonite can endow the adsorbent with magnetism, facilitating separation and recovery, mainly used for large-scale wastewater treatment, and is easy to operate and recycle. (3) The novel composite adsorbent combines the advantages of various materials, has a higher adsorption capacity and better mechanical strength. Common composite materials include carbon-based composite materials, polymer-based composite materials, metal-organic framework materials (MOFs), etc. Carbon-based composite materials have high conductivity, good stability and mechanical strength, can be widely used to remove various heavy metal ions, and have excellent regeneration performance; polymer-based composite materials have strong designability and can be adjusted according to needs, are suitable for complex wastewater systems, and can remove multiple pollutants simultaneously; metal-organic framework materials (MOFs) have a highly ordered pore structure and a high specific surface area, and have extremely high selective adsorption capacity for specific heavy metal ions (such as uranium, cobalt).

[0004] Although the adsorption method shows many advantages in the treatment of heavy metal wastewater, it still faces some challenges: 1. Limited adsorption capacity: For high-concentration heavy metal wastewater, the adsorption capacity of the adsorbent may be insufficient, and it needs to be replaced or regenerated frequently. 2. Difficult regeneration: Some adsorbents are prone to inactivation during the regeneration process, resulting in a shortened service life. Summary of the Invention

[0005] The purpose of the present invention is to provide an adsorbent for treating heavy metal wastewater and its preparation method to solve the problems existing in the above-mentioned prior art and ensure the adsorption treatment effect of heavy metal wastewater.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] The present invention provides a preparation method of a heavy metal adsorbent, which is characterized by comprising the following steps:

[0008] Mix polyacrylamide with the aqueous extract of myrtle and carry out γ-ray irradiation to obtain irradiated modified polyacrylamide;

[0009] Modify Fe 3 O 4 nanoparticles and the ethanol extract of myrtle in ethylene glycol to obtain modified Fe 3 O 4 nanoparticles;

[0010] Load the irradiated modified polyacrylamide on the modified Fe 3 O 4 nanoparticles in an organic solvent to obtain the heavy metal adsorbent.

[0011] As a further preference of the present invention, the irradiation energy of the γ-ray irradiation is 3-6 MeV, the irradiation dose is 25-60 kGy, and the irradiation time is 3-8 min.

[0012] As a further preference of the present invention, the mass ratio of the polyacrylamide to the aqueous extract of Myrtus communis is 10-12:1-3.

[0013] The aqueous extract of Myrtus communis is a substance obtained by water-extracting Myrtus communis at 45-60 °C; the ethanol extract of Myrtus communis is a substance obtained by heating and refluxing Myrtus communis with ethanol.

[0014] Furthermore, the more preferred preparation steps of the aqueous extract of Myrtus communis are as follows:

[0015] Crush Myrtus communis and add it to deionized water, perform water bath oscillation extraction at 45-60 °C for 1-2 h, let it stand, take the supernatant, cool it to room temperature and then filter it, let the filtrate stand, and then centrifuge and dry the upper clear liquid to obtain the aqueous extract of Myrtus communis.

[0016] Furthermore, the more preferred steps for modifying the Fe 3 O 4 nanoparticles are as follows:

[0017] a. Wash, dry, and crush Myrtus communis;

[0018] b. Add the Myrtus communis treated in step a to anhydrous ethanol and perform heating reflux extraction, with the reflux time being 2-4 h;

[0019] c. After the reflux extraction is completed, filter and separate the extraction solution to remove residues and insoluble substances;

[0020] d. Transfer the separated extraction solution to a rotary evaporator, perform vacuum concentration at 40-50 °C to remove most of the solvent, and finally dry the concentrate in a vacuum drying oven to obtain the ethanol extract of Myrtus communis;

[0021] e. Disperse the Fe 3 O 4 nanoparticles in ethylene glycol to form a suspension of 0.5 g / L, and perform ultrasonic treatment to make the Fe 3 O 4 nanoparticles disperse evenly. Then, according to the ratio of Fe 3 O 4 nanoparticles:ethanol extract of Myrtus communis = 1:1-3, add the ethanol extract of Myrtus communis to the system, and stir and react at 55-60 °C for 15-20 min to obtain the modified Fe 3 O 4 nanoparticles.

[0022] As a further preference of the present invention, the temperature of the modification treatment is 55 - 60 °C, and the time is 15 - 20 min.

[0023] As a further preference of the present invention, the 3 O 4 mass ratio of the nano-particles and the myrtle alcohol extract is 1:1 - 3.

[0024] As a further preference of the present invention, the mass ratio of the modified 3 O 4 nano-particles to the irradiated modified polyacrylamide is 5 - 6:1 - 2.

[0025] As a further preference of the present invention, the organic solvent is ethanol.

[0026] The present invention also provides a heavy metal adsorbent prepared by the above preparation method.

[0027] The present invention further provides the application of the above heavy metal adsorbent in adsorbing and removing heavy metals Cd 2+ , Pb 2+ and / or Hg 2 + in water.

[0028] Traditional adsorbents such as activated carbon and zeolite have problems such as high cost and difficult regeneration in practical applications. Although polyacrylamide is an efficient flocculant with good water solubility and film-forming property, its adsorption effect on heavy metal ions is limited. The present invention relates to a method of mixing and irradiating polyacrylamide (PAM) with natural substances and loading modified magnetite as the matrix to significantly improve its adsorption capacity for heavy metal ions. The material prepared by this method has excellent adsorption performance for heavy metals Cd 2+ , Pb 2+ and Hg 2+ and is suitable for the treatment of heavy metal wastewater.

[0029] The γ-ray irradiation method used in the present invention is applicable to large-scale sample treatment, facilitating industrial large-scale production. Irradiation can trigger the cross-linking reaction between polyacrylamide and the aqueous extract of myrtle, thus significantly improving its adsorption capacity for heavy metal ions.

[0030] Magnetite (Fe 3 O 4)() is a common magnetic nanomaterial widely used in the fields of biomedicine, catalysis, environmental remediation, etc. By performing alcohol modification on magnetite, not only can its physical and chemical properties be significantly improved, but also its application potential in multiple fields can be expanded. This modification method is simple, easy to implement, and has a low cost. Alcohol modification can improve its dispersibility, stability, and reactivity. Functional groups (such as hydroxyl groups, alkoxy groups, etc.) formed by alcohol molecules on the surface of nanoparticles can serve as active sites to promote chemical reactions with other substances. The modified nanoparticles of the present invention have a stronger adsorption capacity for heavy metals and better chemical stability at the same time. After being compounded with modified polyacrylamide, the adsorption performance of the composite material for heavy metals can be guaranteed.

[0031] The present invention discloses the following technical effects:

[0032] The present invention mixes polyacrylamide (PAM) with the water extract of Myrtus communis and performs mixed irradiation treatment, and uses it as a matrix to load and modify magnetite nanoparticles. The obtained adsorbent shows excellent adsorption and removal effects on heavy metal ions and has good regeneration performance.

[0033] The preparation process of the present invention is simple and easy to operate, and can effectively meet the actual needs of heavy metal wastewater treatment. Specific embodiments

[0034] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0035] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0037] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which will be obvious to those skilled in the art. Other embodiments obtained from the description of the present invention will be obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0038] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0039] The raw materials involved in the embodiments of the present invention are all commercially available products, and their sources do not affect the technical effects of the present invention.

[0040] The myrtle raw material described in the embodiments of the present invention is specifically dried myrtle fruits.

[0041] Example 1

[0042] The preparation process of the heavy metal adsorbent is as follows:

[0043] (1) Extraction of myrtle aqueous extract:

[0044] After crushing myrtle, add it to deionized water (material-liquid ratio 1 g: 10 mL), perform water bath oscillation extraction at 50 °C for 2 h, let it stand, take the supernatant, cool to room temperature and then filter, let the filtrate stand, and then centrifuge and dry the upper clear liquid to obtain the myrtle aqueous extract;

[0045] (2) Irradiation modification of polyacrylamide:

[0046] Mix polyacrylamide and myrtle aqueous extract evenly according to a mass ratio of 10:3, and then perform γ-ray irradiation to obtain irradiated modified polyacrylamide; the irradiation energy is 5 MeV, the irradiation dose is 45 kGy, and the irradiation time is 5 min.

[0047] (3) Fe 3 O 4 Nanoparticle modification:

[0048] a. Wash, dry and crush myrtle;

[0049] b. Add the myrtle processed in step a to absolute ethanol for heating and reflux extraction (material-liquid ratio 1 g: 10 mL), and the reflux time is 3 h;

[0050] c. After the reflux extraction is completed, filter and separate the extraction solution to remove residues and insoluble substances;

[0051] d. Transfer the separated extraction solution to a rotary evaporator, perform vacuum concentration at 45 °C to remove most of the solvent, and finally dry the concentrate in a vacuum drying oven to obtain the myrtle ethanol extract;

[0052] e. Disperse Fe 3 O 4 nanoparticles in ethylene glycol to form a suspension with a concentration of 0.5 g / L, and perform ultrasonic treatment to make the Fe 3 O 4 particles evenly dispersed. Then, according to the ratio of Fe 3 O 4 : myrtle ethanol extract = 1:2, add the myrtle ethanol extract to the system, and stir and react at 55 °C for 15 min to obtain modified Fe 3 O 4 nanoparticles.

[0053] (4) Preparation of heavy metal adsorbent:

[0054] Disperse the modified Fe 3 O 4 nanoparticles obtained in step (3) in ethanol, and then add irradiated modified polyacrylamide (the mass ratio of irradiated modified polyacrylamide to modified Fe 3 O 4 is 5:2), and perform stirring and loading to obtain a heavy metal adsorbent.

[0055] Example 2

[0056] The preparation process of the heavy metal adsorbent is as follows:

[0057] (1) Extraction of myrtle water extract:

[0058] Crush myrtle and add it to deionized water, perform water bath oscillation extraction at 45 °C for 1 h, let it stand, take the supernatant, cool it to room temperature and then filter it. Let the filtrate stand, and then centrifuge and dry the upper layer of the supernatant to obtain the myrtle water extract;

[0059] (2) Irradiation modification of polyacrylamide:

[0060] Mix polyacrylamide and myrtle water extract evenly according to the mass ratio of 12:1, and then perform γ-ray irradiation to obtain irradiated modified polyacrylamide; the irradiation energy is 6 MeV, the irradiation dose is 60 kGy, and the irradiation time is 3 min.

[0061] (3) Modification of Fe 3 O 4 nanoparticles:

[0062] a. Wash, dry and crush myrtle;

[0063] b. Add the myrtle treated in step a to absolute ethanol and perform heating and reflux extraction for 2 h;

[0064] c. After the reflux extraction is completed, filter and separate the extract to remove residues and insoluble substances;

[0065] d. Transfer the separated extract to a rotary evaporator, conduct vacuum concentration at 50 °C to remove most of the solvent, and finally dry the concentrate in a vacuum drying oven to obtain the ethanol extract of Myrtus communis;

[0066] e. Disperse Fe 3 O 4 nanoparticles in ethylene glycol to form a suspension of 0.5 g / L, and perform ultrasonic treatment to make the Fe 3 O 4 particles evenly dispersed. Then, according to the ratio of Fe 3 O 4 : ethanol extract of Myrtus communis = 1:1, add the ethanol extract of Myrtus communis to the system, and stir and react at 55 °C for 15 min to obtain modified Fe 3 O 4 nanoparticles.

[0067] (4)Preparation of heavy metal adsorbent:

[0068] Disperse the modified Fe 3 O 4 nanoparticles obtained in step (3) in ethanol, and then add irradiated polyacrylamide (the mass ratio of irradiated polyacrylamide to modified Fe 3 O 4 is 5:2), and perform stirring and loading to obtain the heavy metal adsorbent.

[0069] Example 3

[0070] The preparation process of the heavy metal adsorbent is as follows:

[0071] (1)Extraction of aqueous extract of Myrtus communis:

[0072] Crush Myrtus communis and add it to deionized water, perform water bath oscillation extraction at 55 °C for 1 h, let it stand, take the supernatant, filter it after cooling to room temperature, let the filtrate stand, and then centrifuge and dry the upper layer of the supernatant to obtain the aqueous extract of Myrtus communis;

[0073] (2)Irradiation modification of polyacrylamide:

[0074] Mix polyacrylamide and the aqueous extract of Myrtus communis evenly according to the mass ratio of 11:2, and then perform γ-ray irradiation to obtain irradiated polyacrylamide; the irradiation energy is 4 MeV, the irradiation dose is 45 kGy, and the irradiation time is 5 min.

[0075] (3)Modification of Fe 3 O 4 nanoparticles:

[0076] a. Wash, dry, and crush myrtle.

[0077] b. Add the myrtle processed in step a to absolute ethanol and perform heating reflux extraction for 3 h.

[0078] c. After the reflux extraction is completed, filter and separate the extract to remove residues and insoluble substances.

[0079] d. Transfer the separated extract to a rotary evaporator, perform vacuum concentration at 50 °C to remove most of the solvent, and finally dry the concentrate in a vacuum drying oven to obtain the ethanol extract of myrtle.

[0080] e. Disperse Fe 3 O 4 nanoparticles in ethylene glycol to form a suspension of 0.5 g / L, and perform ultrasonic treatment to make the Fe 3 O 4 particles evenly dispersed. Then, according to the ratio of Fe 3 O 4 : ethanol extract of myrtle = 1:2, add the ethanol extract of myrtle to the system, and stir and react at 55 °C for 18 min to obtain modified Fe 3 O 4 nanoparticles.

[0081] (4) Preparation of heavy metal adsorbent:

[0082] Disperse the modified Fe 3 O 4 nanoparticles obtained in step (3) in ethanol, and then add irradiated modified polyacrylamide (the mass ratio of irradiated modified polyacrylamide to modified Fe 3 O 4 is 6:1), and perform stirring and loading to obtain a heavy metal adsorbent.

[0083] Comparative Example 1

[0084] The difference from Example 1 is only that in step (2), myrtle water extract is not added during the irradiation process.

[0085] Comparative Example 2

[0086] The difference from Example 1 is only that in step (3), only the Fe 3 O 4 nanoparticles are modified with ethanol. The steps are as follows:

[0087] Steps (1)-(2) are the same as those in Example 1;

[0088] (3) Modification of Fe 3 O 4 nanoparticles:

[0089] Disperse Fe 3 O 4 nanoparticles in ethylene glycol to form a suspension with a concentration of 0.5 g / L, and perform ultrasonic treatment to make the Fe 3 O 4 particles evenly dispersed. Stir and react at 55 °C for 15 min to obtain modified Fe 3 O 4 nanoparticles.

[0090] (4)Prepare heavy metal adsorbent:

[0091] Disperse the modified Fe 3 O 4 nanoparticles obtained in step (3) in ethanol, and then add irradiated modified polyacrylamide (the mass ratio of irradiated modified polyacrylamide to modified Fe 3 O 4 nanoparticles is 5:2), and carry out stirring and loading to obtain a heavy metal adsorbent.

[0092] Comparative Example 3

[0093] The difference from Example 1 is only that in step (2), the irradiated modification of polyacrylamide uses an equal amount of myrtle ethanol extract. Among them, the preparation process of the myrtle ethanol extract is the same as steps a-d of Example 1.

[0094] Effect Verification Example 1

[0095] Perform heavy metal ion adsorption experiments on the heavy metal adsorbents prepared in Examples 1-3 and Comparative Examples 1-3.

[0096] Heavy metals in the polluted water body include Cd 2+ , Pb 2+ and Hg 2+ , and the specific contents are as follows: Cd 2+ 357.2 mg / L, Pb 2+ 258.6 mg / L, Hg 2+ 246.2 mg / L.

[0097] Respectively add the heavy metal adsorbents prepared in Examples 1-3 and Comparative Examples 1-3 to the above polluted water body, so that the concentration of the heavy metal adsorbent is 1 g / L, and adsorb until saturation at 30 °C, and calculate the adsorption removal rate of each heavy metal adsorbent for heavy metals. The results are shown in Table 1.

[0098] Among them, the adsorption removal rate (%) = (concentration of heavy metal ions before treatment - concentration of heavy metal ions after treatment) / concentration of heavy metal ions before treatment × 100%.

[0099] Table 1 Adsorption removal rate (%)

[0100]

[0101] Effect verification example 2

[0102] The heavy metal adsorbents saturated by adsorption in Examples 1 - 3 and Comparative Examples 1 - 3 were filtered, washed with ethanol, added to acetic acid with a concentration of 0.15 mol / L, stirred for 1.5 h and then filtered out, washed with deionized water until neutral, and adsorption removal experiments were carried out using the same adsorption removal method as in Effect Verification Example 1 to test the removal efficiency of the regenerated adsorbent for various heavy metal ions. The results showed that the adsorbent still had excellent heavy metal ion adsorption performance after being recycled 5 times, and still met the usage requirements after being recycled 6 times.

[0103] Table 2 Removal rate of Cd 2+ (%)

[0104]

[0105] Table 3 Removal rate of Pb 2+ (%)

[0106]

[0107] Table 4 Removal rate of Hg 2+ (%)

[0108]

[0109] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a heavy metal adsorbent, characterized in that: The following steps are involved: The polyacrylamide is mixed with the water extract of Myrtle, and subjected to gamma ray irradiation to obtain irradiation-modified polyacrylamide; Fe3O4 nanoparticles and myrtle alcohol extract were modified in ethylene glycol to obtain modified Fe3O4 nanoparticles; The irradiated modified polyacrylamide is loaded on the modified Fe3O4 nanoparticles in an organic solvent to obtain the heavy metal adsorbent; The myrtle water extract is a substance obtained by extracting myrtle with water at 45-60° C.; the myrtle alcohol extract is a substance obtained by heating myrtle with ethanol and refluxing.

2. The preparation method according to claim 1, characterized in that: The irradiation energy of the gamma ray irradiation is 3-6 MeV, the irradiation dose is 25-60 kGy, and the irradiation time is 3-8 min.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the polyacrylamide to the myrtle water extract is 10-12:1-3.

4. The preparation method according to claim 1, characterized in that: The temperature of the modification treatment is 55-60°C and the time is 15-20 minutes.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the Fe3O4 nanoparticles to the myrtle alcohol extract is 1:1-3.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the modified Fe3O4 nanoparticles to the irradiated modified polyacrylamide is 5-6:1-2.

7. The preparation method according to claim 1, characterized in that: The organic solvent is ethanol.

8. The heavy metal adsorbent prepared by the preparation method according to any one of claims 1 to 7.

9. The heavy metal adsorbent as claimed in claim 8 is used to adsorb and remove heavy metal Cd in water. 2+ , Pb 2+ and / or Hg 2+ Application in.

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