CN110902799A

CN110902799A - Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions and preparation method and application thereof

Info

Publication number: CN110902799A
Application number: CN201911028540.XA
Authority: CN
Inventors: 孙东; 曹楠; 莫裕科; 赵松江; 张志鹏; 龚正君; 熊亭亭; 沈莉萍
Original assignee: Sichuan Huadi New Energy Environmental Protection Science And Technology LLC; Southwest Jiaotong University
Current assignee: Sichuan Huadi New Energy Environmental Protection Science And Technology LLC; Southwest Jiaotong University
Priority date: 2019-10-28
Filing date: 2019-10-28
Publication date: 2020-03-24

Abstract

The invention discloses a Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions, and a preparation method and application thereof. The Fe/Cu/Ag trimetal degrading agent for degrading hexavalent chromium ions comprises a powdery Fe matrix and Cu and Ag attached to the particle surface of the Fe matrix. The preparation method comprises the following steps: (1) in the presence of Cu²⁺Adding a Fe matrix into the copper salt solution, and reacting for a period of time to deposit Cu on the surface of the Fe matrix to obtain a precursor; (2) in the presence of Ag⁺The precursor is added into the silver salt solution, and the reaction is carried out for a period of time, so that Ag is deposited on the surface of the precursor, and the Fe/Cu/Ag trimetal degradation agent is obtained. The invention obtains Cr by loading two metal particles on the particle surface of the Fe matrix⁶⁺The degradation efficiency is obviously higher than that of the trimetal degradation agent of Fe-based bimetal or modified Fe-based bimetal. The two loaded metal particles are easy to obtain, and the degradation of Cr can be remarkably reduced⁶⁺The cost of (a).

Description

Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions and preparation method and application thereof

Technical Field

The invention relates to the technical field of chromium-containing wastewater treatment, in particular to a Fe/Cu/Ag trimetal degrading agent for degrading hexavalent chromium ions, and a preparation method and application thereof.

Background

Chromium is a common heavy metal in nature, mainly hexavalent chromium ion (Cr)⁶⁺) And trivalent chromium ion (Cr)³⁺) Two forms exist. Cr (chromium) component⁶⁺Has a toxicity of about Cr ³⁺500 times of that of Cr³⁺Are generally considered to be non-toxic at low concentrations. Cr (chromium) component⁶⁺Is highly toxic, highly soluble, flowable, non-biodegradable, and even induces cancer, mutagenicity and teratogenicity, whereas Cr⁶⁺Due to their special properties, they are usually produced in industrial processes such as leather tanning, electroplating, pigment synthesis and chromium salt production. Therefore, an effective method for removing Cr in wastewater is sought⁶⁺Is of critical importance.

At present, iron-based bimetallic particles have extensive research in the field of environmental remediation. For example, Fe/Cu bimetallic has been found to decompose p-nitrophenol at higher concentrations; the iron-nickel bimetal can degrade tetrabromobisphenol A; and so on. However, the research on the iron-based bimetallic particles mainly focuses on degrading organic pollutants, and few inorganic substances, particularly Cr⁶⁺Removal study of (2). And the traditional iron-based bimetallic particles are harsh in preparation conditions, which greatly limits the application in the aspect of practical engineering. For example, Chinese invention patent CN107200392A discloses a sulfuration modified Fe-Cu bimetallic materialAlthough the material can be directly used for treating chromium-containing wastewater, the preparation process of the material is complicated, and for example, the pH needs to be accurately controlled by using a buffer solution, and sulfide salt is used for modification. Therefore, it would be desirable to find a method for removing Cr with simple preparation conditions and low cost⁶⁺The preparation method of the iron-based metal and the iron-based metal with good effects can effectively promote the practical application in the field of environmental remediation.

Disclosure of Invention

The first purpose of the invention is to provide a Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions so as to solve the problem of Cr in the prior art⁶⁺The degradation efficiency of the degradation agent is poor.

The second purpose of the invention is to provide a preparation method of Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions, so as to solve the problem of Cr in the prior art⁶⁺The preparation process of the degradation agent is complex.

The second purpose of the invention is to provide a method for degrading hexavalent chromium ions in wastewater, so as to solve the technical problem of poor treatment effect of chromium-containing wastewater in the prior art.

In order to achieve the first object, the present invention provides a Fe/Cu/Ag trimetallic degradant for degrading hexavalent chromium ions. The Fe/Cu/Ag trimetal degrading agent for degrading hexavalent chromium ions comprises a powdery Fe matrix and Cu and Ag attached to the particle surface of the Fe matrix.

The invention obtains Cr by loading two metal particles on the particle surface of the Fe matrix⁶⁺The degradation efficiency is obviously higher than that of the trimetal degradation agent of Fe-based bimetal or modified Fe-based bimetal. The two loaded metal particles are easy to obtain, and the degradation of Cr can be remarkably reduced⁶⁺The cost of (a).

Further, the particle size of the Fe matrix is micron-sized; the particle appearance of the Fe matrix is ellipsoidal. The Fe matrix is not easy to agglomerate and has proper specific surface area, so that Cu and Ag can be distributed more uniformly.

Further, the Fe matrix also contains a trace amount of Mn, Ca and Cr. Such Fe matrix is more readily available, and for example, industrial-grade iron powder can be used as it is.

Further, the preparation method of the Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions comprises the following steps:

(1) in the presence of Cu²⁺Adding a Fe matrix into the copper salt solution, and reacting for a period of time to deposit Cu on the surface of the Fe matrix to obtain a precursor;

(2) in the presence of Ag⁺The precursor is added into the silver salt solution, and the reaction is carried out for a period of time, so that Ag is deposited on the surface of the precursor, and the Fe/Cu/Ag trimetal degradation agent is obtained.

In order to achieve the second object, the invention provides a preparation method of the Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions. The preparation method of the Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions comprises the following steps:

(1) in the presence of Cu²⁺Adding a Fe matrix into the copper salt solution, and reacting for a period of time to deposit Cu on the particle surface of the Fe matrix to obtain a precursor;

(2) in the presence of Ag⁺The precursor is added into the silver salt solution, and the reaction is carried out for a period of time, namely Ag is deposited on the particle surface of the precursor, namely Cu and Ag are deposited on the particle surface of the Fe matrix, so as to obtain the Fe/Cu/Ag trimetal degradation agent.

The preparation method has the advantages of simple process, no need of high temperature and high pressure or special atmosphere, easily obtained raw materials, easy control of reaction conditions and popularization significance, and the replacement reaction is carried out under normal temperature and neutral reaction conditions.

Further, the products of the step (1) and the step (2) are adsorbed and collected by a magnet. This allows for rapid and thorough collection of the reactants. The magnet is preferably an electromagnet, namely the electromagnet is magnetic when being electrified and disappears after being powered off, so that the collected reactants are convenient to transfer, and the loss of materials in the transfer process can be reduced.

Further, the copper salt is CuSO₄·5H₂O; the silver salt is Ag₂SO₄。

Further, the weight ratio of the Fe matrix, Cu in the copper salt solution, and Ag in the silver salt solution is 10: (0.25-2): (0.0125-0.2). Preferably, the weight ratio of the Fe matrix, Cu in the copper salt solution and Ag in the silver salt solution is 10: (0.5-1): (0.025 to 0.1).

In order to achieve the third object, the present invention provides a method for degrading hexavalent chromium ions in wastewater, comprising: the Fe/Cu/Ag trimetal degrading agent for degrading hexavalent chromium ions or the Fe/Cu/Ag trimetal degrading agent for degrading hexavalent chromium ions prepared by the method is put into wastewater.

Furthermore, the degradation temperature is 15-45 ℃, the pH value is 3-8, and the stirring speed is 100-600 r/min. Therefore, the condition for treating the chromium-containing wastewater is mild and easy to control, and the method can be popularized in a large scale.

The invention is further described with reference to the following figures and detailed description. Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to assist in understanding the invention, and are included to explain the invention and their equivalents and not limit it unduly. In the drawings:

FIG. 1 is a spectrum of Fe matrix.

Fig. 2 is a lower magnification non-oriented SEM photograph of the Fe matrix.

FIG. 3 is a higher magnification non-oriented SEM photograph of a Fe matrix.

FIG. 4 is a lower magnification non-oriented SEM of a Fe/Cu/Ag trimetal degrader.

FIG. 5 is a higher magnification non-oriented SEM photograph of a Fe/Cu/Ag trimetal degrader.

FIG. 6 is the spectrum of the Fe/Cu/Ag trimetal degradant.

FIG. 7 is the spectrum of the Fe/Cu/Ag trimetal degrader after use.

FIG. 8 shows the three metal degradants, Fe/Cu/Ag, versus Cr of examples 1-6⁶⁺Comparative figure (c).

FIG. 9 shows the three metal degradants of Fe/Cu/Ag for examples 1, 7-11 versus Cr⁶⁺Comparative figure (c).

FIG. 10 shows the three metal degradants of Fe/Cu/Ag and Fe matrix versus Cr of examples 7, 9 and 12⁶⁺Comparative figure (c).

FIG. 11 shows the three metal degradants of Fe/Cu/Ag for examples 9 and 13-16 versus Cr⁶⁺Comparative figure (c).

FIG. 12 shows the three metal degradants of Fe/Cu/Ag for examples 9 and 17-19 versus Cr⁶⁺Comparative figure (c).

FIG. 13 shows the three metal degradants of Fe/Cu/Ag for examples 9, 20-14 versus Cr⁶⁺Comparative figure (c).

Detailed Description

The invention will be described more fully hereinafter with reference to the accompanying drawings. Those skilled in the art will be able to implement the invention based on these teachings. Before the present invention is described in detail with reference to the accompanying drawings, it is to be noted that:

the technical solutions and features provided in the present invention in the respective sections including the following description may be combined with each other without conflict.

Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

With respect to terms and units in the present invention. The terms "comprising," "having," and any variations thereof in the description and claims of this invention and the related sections are intended to cover non-exclusive inclusions.

In the following examples, SEM photographs were taken using a scanning electron microscope (brand: FEI, model: aspect-F, origin: USA) and energy spectrum using an energy dispersive X-ray fluorescence spectrometer (brand: Shimadzu, model: EDX-7000, origin: Japan).

Example 1

The preparation method of the Fe/Cu/Ag trimetal degradation agent comprises the following steps:

(1) mixing a certain mass of CuSO₄·5H₂Dissolving O in 200ml of ultrapure water, adding an Fe matrix, and stirring for 5min by using a mechanical stirrer, namely depositing Cu on the particle surface of the Fe matrix; collecting and transferring the solid product by adopting an electromagnet, and repeatedly washing the solid product for three times by using pure water to obtain a precursor (Fe/Cu);

(2) mixing a certain mass of Ag₂SO₄Dissolving the precursor in 200ml of ultrapure water, adding the precursor, and stirring for 2min by using a mechanical stirrer, so that Ag is deposited on the particle surface of the precursor; and collecting and transferring the solid product by adopting an electromagnet, repeatedly washing the solid product for three times by using pure water and washing the solid product for one time by using ethanol, and drying to obtain the Fe/Cu/Ag trimetal degradation agent.

Wherein, CuSO₄·5H₂O and Ag₂SO₄All used analytically pure raw materials. The weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:1: 0.1. FIG. 1 is a spectrum of Fe matrix. As can be seen from the analysis of FIG. 1, the Fe matrix also contains trace amounts of Mn, Ca and Cr, and the specific contents are shown in Table 1.

TABLE 1

Composition (I)	Fe	Mn	Ca	Cr
					Mass fraction (%)	99.038	0.450	0.413	0.099

Fig. 2 is a lower magnification non-oriented SEM photograph of the Fe matrix. As can be seen from FIG. 1, the Fe matrix has a particle shape of an ellipsoid and a particle size of a micrometer, and the major axis of the particle is about 320 μm and the minor axis is about 240 μm.

FIG. 3 is a higher magnification non-oriented SEM photograph of a Fe matrix. As can be seen from fig. 2, the particle surface of the Fe matrix is relatively smooth.

FIG. 4 is a lower magnification non-oriented SEM of a Fe/Cu/Ag trimetal degrader. FIG. 5 is a higher magnification non-oriented SEM photograph of a Fe/Cu/Ag trimetal degrader. Comparing fig. 2 and 4 or fig. 3 and 5, it can be seen that the particle surface roughness of the Fe/Cu/Ag trimetallic degradant is significantly higher than that of the Fe matrix, indicating that a chemical reaction occurs on the particle surface of the Fe matrix.

FIG. 6 is a spectrum of the ternary Fe/Cu/Ag metal degradant, with the component contents shown in Table 2. As can be seen from the analysis of FIG. 6, characteristic peaks of Ag and Cu appear in the spectrum of the Fe/Cu/Ag trimetal degradant, which indicates that Ag and Cu are successfully deposited on the particle surface of the Fe matrix.

TABLE 2

Composition (I)	Fe	Cu	Ag	Mn	Cr
						Mass fraction (%)	69.363	27.933	2.271	0.359	0.073

The method for degrading hexavalent chromium ions in the wastewater comprises the following steps: the pH was controlled to 7 and 5g of a trimetallic Fe/Cu/Ag degradant was added to 100mL of 50mg/L Cr at 25 ℃ with a stirring speed of 600rpm⁶⁺In aqueous solution.

Cr pair with Fe/Cu/Ag trimetal degradation agent⁶⁺The degradation effect of (A) is characterized by the following method: taking 1ml of Fe/Cu/Ag trimetal degradation agent and Cr every 2min⁶⁺The reaction solution was further centrifuged (7000rpm, 5min), and the residual Cr in the supernatant was finally separated⁶⁺And (6) detecting.

Fe/Cu/Ag trimetal degradation agent and Cr⁶⁺After the reaction solution of the aqueous solution reacts for 20min, the Fe/Cu/Ag trimetal degradation agent is taken out by an electromagnet and is washed and dried by pure water. FIG. 7 is the spectrum of the used Fe/Cu/Ag trimetal degradant, and the contents of the components are shown in Table 3. As can be seen from a comparison of fig. 6 and 7 and tables 2 and 3, the content of Cr is significantly increased, which indicates that Cr is deposited on the surface of the particles of the trimetallic Fe/Cu/Ag degradant in the form of precipitates on the one hand.

TABLE 3

Composition (I)	Fe	Cu	Ag	Mn	Cr
						Mass fraction (%)	77.401	21.398	0.529	0.410	0.262

Example 2

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:1:0, i.e., only step (1) of example 1 was performed.

Example 3

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:1: 0.0125.

example 4

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:1: 0.025.

example 5

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:1: 0.05.

example 6

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:1: 0.2.

Fe/Cu/Ag trimetallic degradants of examples 1-6 for Cr⁶⁺The degradation effect of (2) is shown in fig. 8. From FIG. 8, it can be seen that the ternary Fe/Cu/Ag degrader pairs Cr when Fe: Cu is 10:1⁶⁺The removal effect of (2) is accelerated as the addition amount of Ag increases, and particularly when Fe: Cu: Ag is 10:1:0.1 (example 1), the amount of Cr is increased at 20min⁶⁺The removal of (a) was 90.9%. However, when the addition ratio of Ag exceeds 0.1, the removal effect is greatly reduced.

Example 7

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10: 0:0.1, i.e. adding Fe matrix directly to Ag₂SO₄The reaction is carried out in solution.

Example 8

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10: 0.25: 0.1.

example 9

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:0.5: 0.1.

example 10

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10: 1.5: 0.1.

example 11

Compared with the example 1, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10: 2: 0.1.

Fe/Cu/Ag trimetallic degradants for Cr of examples 1, 7-11⁶⁺The degradation effect of (2) is shown in fig. 9. As can be seen from FIG. 9, the ternary Fe/Cu/Ag degradant for Cr is shown to be present when Fe: Ag is 10:0.1⁶⁺The removal effect of (3) is accelerated as the amount of Cu added is increased, and particularly, when Fe: Cu: Ag is 10:0.5:0.1 (example 9), the amount of Cr is increased by 20min⁶⁺The removal of (a) was 91.8%. However, when the addition ratio of Ag exceeds 1, the removal effect is greatly reduced.

Example 12

Compared with example 9, the preparation method of the Fe/Cu/Ag trimetal degradation agent of the embodiment has the following differences: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10:0.5:0.

Fe/Cu/Ag trimetallic degradants and Fe matrix of examples 7, 9, 12 vs Cr⁶⁺The degradation effect of (2) is shown in fig. 10. As can be seen from FIG. 10, the addition of Cu and Ag removes Cr from Fe-based material⁶⁺The effect of (A) is promoted and the order of reactivity is Fe/Cu/Ag>Fe/Ag>Fe/Cu>Fe。

Example 13

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the amount of the Fe/Cu/Ag trimetal degradation agent used was 2 g.

Example 14

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the usage amount of the Fe/Cu/Ag trimetal degradation agent is 3 g.

Example 15

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the usage amount of the Fe/Cu/Ag trimetal degradation agent is 4 g.

Example 16

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the amount of the Fe/Cu/Ag trimetal degradation agent used was 6 g.

Fe/Cu/Ag Trigold of examples 9, 13-16Belongs to a degradation agent to Cr⁶⁺The degradation effect of (2) is shown in fig. 11. As can be seen from FIG. 11, the three metal degradants Fe/Cu/Ag are applied to Cr in water⁶⁺The removal effect of (a) increases with increasing dosage; when the dosage of the Fe/Cu/Ag trimetal degradation agent is more than or equal to 5g, the Cr can be added within 20min⁶⁺The solution was almost completely removed.

Example 17

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the reaction temperature was 15 ℃.

Example 18

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the reaction temperature was 35 ℃.

Example 19

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the reaction temperature was 45 ℃.

Fe/Cu/Ag trimetallic degradants for Cr of examples 9, 17-19⁶⁺The degradation effect of (2) is shown in fig. 12. As can be seen from FIG. 12, the Fe/Cu/Ag trimetal degradation agent is used for 20min in the temperature range of 15-45 ℃ and then applied to Cr⁶⁺The removal rate of the Fe/Cu/Ag trimetal degradation agent is over 90 percent, which shows that the Fe/Cu/Ag trimetal degradation agent has good tolerance to the temperature of the wastewater and can play an excellent degradation effect in a larger temperature range.

Example 20

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the pH of the reaction was 3.

Example 21

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the pH of the reaction was 4.

Example 22

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the pH of the reaction was 5.

Example 23

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the pH of the reaction was 6.

Example 24

Compared with example 9, the method for degrading hexavalent chromium ions in wastewater of the present example has the following differences: the pH of the reaction was 8.

Fe/Cu/Ag trimetallic degradants for Cr of examples 9, 20-14⁶⁺The degradation effect of (2) is shown in fig. 13. As can be seen from FIG. 13, the Fe/Cu/Ag trimetal degradant was used for 20min in the pH range of 3-8 for Cr⁶⁺The removal rate of the Fe/Cu/Ag trimetal degradation agent is over 90 percent, which shows that the Fe/Cu/Ag trimetal degradation agent has good tolerance to the pH value of the wastewater and can play an excellent degradation effect in a larger pH range.

Example 25

Compared with the example 1, the deposition steps of Ag and Cu in the preparation method of the Fe/Cu/Ag trimetal degradation agent are opposite, and are specifically as follows:

(1) mixing a certain mass of Ag₂SO₄Dissolving in 200ml of ultrapure water, adding the Fe matrix, and stirring for 2min by using a mechanical stirrer to deposit Ag on the surface of the Fe matrix; collecting and transferring the solid product by an electromagnet, and repeatedly washing the solid product for three times by pure water to obtain a precursor (Fe/Ag);

(1) mixing a certain mass of CuSO₄·5H₂Dissolving O in 200ml of ultrapure water, adding the precursor, and stirring for 5min by using a mechanical stirrer to deposit Cu on the surface of the precursor; and collecting and transferring the solid product by adopting an electromagnet, repeatedly washing the solid product for three times by using pure water and washing the solid product for one time by using ethanol, and drying to obtain the Fe/Cu/Ag trimetal degradation agent.

It is verified that the Fe/Cu/Ag trimetal degradation agent prepared in example 1 has significantly higher degradation efficiency under the same usage amount, temperature, pH and stirring speed, and therefore, Cu is preferably deposited first and Ag is preferably deposited later.

The contents of the present invention have been explained above. Those skilled in the art will be able to implement the invention based on these teachings. All other embodiments, which can be derived by a person skilled in the art from the above description without inventive step, shall fall within the scope of protection of the present invention.

Claims

1. The Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions is characterized in that: comprising a powdered Fe matrix and Cu and Ag attached to the particle surfaces of the Fe matrix.

2. The Fe/Cu/Ag trimetallic degrader for degrading hexavalent chromium ions of claim 1, wherein: the granularity of the Fe matrix is micron-sized; the particle appearance of the Fe matrix is ellipsoidal.

3. The Fe/Cu/Ag trimetallic degrader for degrading hexavalent chromium ions of claim 2, wherein: the Fe matrix also contains a trace amount of Mn, Ca and Cr.

4. The preparation method of the Fe/Cu/Ag trimetal degradation agent for degrading hexavalent chromium ions comprises the following steps:

5. The method of preparing a Fe/Cu/Ag trimetallic degradant for degrading hexavalent chromium ions of claim 4, wherein: and (3) adsorbing and collecting the products in the step (1) and the step (2) by using a magnet.

6. The method of preparing a Fe/Cu/Ag trimetallic degradant for degrading hexavalent chromium ions of claim 4, wherein: the copper salt is CuSO₄·5H₂O; the silver salt is Ag₂SO₄。

7. The method of preparing a Fe/Cu/Ag trimetallic degradant for degrading hexavalent chromium ions of claim 4, wherein: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10: (0.25-2): (0.0125-0.2).

8. The method of preparing a Fe/Cu/Ag trimetallic degradant for degrading hexavalent chromium ions of claim 7, wherein: the weight ratio of Cu in the Fe matrix and the copper salt solution to Ag in the silver salt solution is 10: (0.5-1): (0.025 to 0.1).

9. A method for degrading hexavalent chromium ions in wastewater, comprising: placing the Fe/Cu/Ag trimetal degradant for degrading hexavalent chromium ions according to any one of claims 1 to 3 or the Fe/Cu/Ag trimetal degradant for degrading hexavalent chromium ions prepared by the method according to any one of claims 4 to 8 into wastewater.

10. The method of degrading hexavalent chromium ions in wastewater according to claim 9, wherein: the degradation temperature is 15-45 ℃, the pH value is 3-8, and the stirring speed is 100-600 r/min.