Preparation method and application of magnetic mesoporous iron-manganese bimetal

Abstract

The invention discloses a preparation method and application of magnetic mesoporous ferro-manganese bimetal, and belongs to the technical field of environmental functional materials. The method comprises the following steps: firstly, preparing iron-manganese bimetallic gel, and then calcining to prepare the magnetic mesoporous iron-manganese bimetallic material. According to the method, firstly, iron-manganese bimetallic gel is prepared, and then the iron-manganese bimetallic gel is converted into the magnetic mesoporous iron-manganese bimetallic material through calcination. The preparation method is simple in process and short in time. The prepared ferro-manganese bimetal has the mesoporous channel characteristic, and mass transfer and adsorption removal of pollutants are facilitated. The manganese element in the prepared ferro-manganese bimetal has the capability of oxidizing As (III) and Sb (III). In addition, the prepared ferro-manganese bimetal has magnetism and is convenient to recycle, and the adsorption effect of the material on arsenic and antimony is stable.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials, and specifically relates to a preparation method and application of a magnetic mesoporous iron-manganese bimetal. Background Art

[0003] At present, the treatment methods for arsenic and antimony polluted wastewater include coagulation, membrane separation, electrochemical method, adsorption method, etc. Compared with other methods, adsorption method is widely used in the treatment of arsenic and antimony wastewater because of its easy operation, high treatment efficiency, low treatment cost and less secondary pollution. Therefore, the development of adsorbents with high adsorption performance for arsenic and antimony has become a research hotspot.

[0004] The hydroxyl groups on the surface of iron oxide can react with arsenic and antimony to form inner layer complexes, so it has a strong adsorption force on arsenic and antimony. Iron oxide-based adsorption materials have been widely used in the adsorption of arsenic and antimony. However, iron oxide cannot oxidize highly toxic and difficult to remove As(III) and Sb(III) into low-toxic and easy-to-remove As(V) and Sb(V). High-valent manganese oxides (Mn(III) and Mn(IV)) can achieve the oxidation conversion of As(III) and Sb(III) to As(V) and Sb(V). Therefore, iron-manganese bimetallic oxide materials with adsorption-oxidation dual functions are used to remove As(III) and Sb(III) from water. The adsorption capacities of iron-manganese bimetallic oxides for As(V), Sb(III) and Sb(V) reported in existing literature are 53.7 mg / g (Zhang, G, Liu F, Liu H, et al. Respective role of Fe and Mn oxide contents for arsenic sorption in iron and manganese binary oxide: an x-ray absorption spectroscopy investigation[J]. Environmental Science & Technology, 2014, 48(17), 10316-10322.), 124.2 mg / g (Liu R, Liu F, Hu C, et al. Simultaneous removal of Cd(II)and Sb(V)by Fe-Mn binary oxide: Positive effects of Cd(II)onSb(V)adsorption[J]. Journal of Hazardous Materials, 2015, 300: 847-854.), 169.2 mg / g (Xu W, Wang H, Liu R, Zhao X, et al. The mechanism of antimony(III)removal and its reactions on the surfaces of Fe-Mn binary oxide[J]. Journal of Colloid&Interface Science, 2011, 363(1), 320-326.).Although iron-manganese bimetallic oxide materials have good removal effects on As(V), Sb(III) and Sb(V) in water, there are still two defects in the removal of the above heavy metal ions by iron-manganese bimetallic: ① The traditional iron-manganese bimetallic is prepared by the redox co-precipitation method between FeSO4 and KMnO4, which leads to the problems of easy agglomeration, low specific surface area and few active sites in the synthesized iron-manganese bimetallic, thereby limiting its removal effect on the above metals; ② The synthesized iron-manganese bimetallic material does not have magnetic separation characteristics, which is not conducive to the separation and recovery of the adsorbent in the actual wastewater treatment process.

[0005] For example, the Chinese patent application document with application number 202011369902.4 discloses a modified iron-manganese bimetallic material and its preparation method and application. The modified iron-manganese bimetallic material contains sulfur and has magnetism. It is used in the adsorption treatment of pollutants in water to facilitate magnetic separation and recovery. The magnetic iron-manganese bimetallic material prepared by this method is based on the cross-linking effect between high-concentration iron salts and organic matter to form an iron-manganese-organic gel, and then calcined to form a magnetic iron-manganese bimetallic material. However, this method has the problem that the iron-manganese ratio is difficult to control, and a high concentration of iron-manganese salt solution remains after the reaction, resulting in a large amount of waste of chemical reagents.

[0006] Therefore, the development of iron-manganese bimetallic materials with magnetic separation ability, high specific surface area and fully exposed active sites is particularly important for the efficient treatment of arsenic and antimony wastewater by iron-manganese bimetallic materials. Summary of the invention

[0007] 1. Problem to be solved

[0008] The present invention aims at the problem that the traditional iron-manganese bimetal has limited effect on the removal of arsenic and antimony, and provides a method for preparing a magnetic mesoporous iron-manganese bimetal. The iron-manganese bimetal has a mesoporous channel structure, a high specific surface area, and fully exposed active sites on the surface of the material, which is conducive to accelerating the mass transfer process of heavy metal ions from the solution body to the surface of the iron-manganese bimetal, and then quickly captured by the adsorption sites on the surface of the iron-manganese bimetal. In addition, the iron-manganese bimetal prepared by the method has superparamagnetic properties, which is convenient for rapid separation and recovery of adsorbents through an external magnetic field in actual engineering applications.

[0009] 2. Technical solution

[0010] The present invention provides a method for preparing a magnetic mesoporous iron-manganese bimetal, the method comprising:

[0011] S1: dissolve organic matter in water;

[0012] S2: Add iron salt and manganese salt to the solution in S1 while stirring until they are completely dissolved;

[0013] S3: The obtained S2 solution is placed in a water bath and reacted at 100°C for 5-10 hours to concentrate the reaction solution into a paste. After the reaction, the obtained paste liquid is dried in an oven to obtain a red iron-manganese bimetallic gel.

[0014] S4: The iron-manganese bimetallic gel obtained in S3 is calcined in a muffle furnace to obtain a black solid, which is a magnetic mesoporous iron-manganese bimetallic.

[0015] Furthermore, in the method for preparing a magnetic mesoporous iron-manganese bimetallic material, the organic matter includes at least one compound selected from polyvinyl pyrrolidone, P123 polyether, dopamine and citric acid.

[0016] Furthermore, in the method for preparing a magnetic mesoporous iron-manganese bimetallic material, the concentration of organic matter in the solution after dissolution in S1 is 20-50 g / L.

[0017] Furthermore, in the method for preparing a magnetic mesoporous iron-manganese bimetallic material, the molar ratio of iron salt to manganese salt in S2 is (1-6):1, and the mass ratio of the total mass of iron salt and manganese salt to organic matter is (0.5-2):1.

[0018] Furthermore, in the method for preparing a magnetic mesoporous iron-manganese bimetal, the iron salt includes at least one compound selected from ferric nitrate, ferric acetylacetonate and ferric chloride.

[0019] Furthermore, in the method for preparing a magnetic mesoporous iron-manganese bimetal, the manganese salt includes at least one compound selected from manganese nitrate, manganese acetate and manganese chloride.

[0020] Furthermore, in the method for preparing the magnetic mesoporous iron-manganese bimetal, the calcination temperature is 300-500° C. and the calcination time is 2-4 hours.

[0021] The present invention also provides a magnetic mesoporous iron-manganese bimetal prepared by the above preparation method.

[0022] Furthermore, the magnetic mesoporous iron-manganese bimetal contains iron, manganese and oxygen elements, and the magnetic mesoporous iron-manganese bimetal has a mesoporous channel structure with an average pore size of The magnetic mesoporous iron-manganese bimetal has magnetism, and the saturation magnetization intensity is 5.25-22.76emu / g.

[0023] The present invention also provides a method for preparing the magnetic mesoporous iron-manganese bimetal or the application of the magnetic mesoporous iron-manganese bimetal in the treatment of arsenic and / or antimony wastewater.

[0024] 3. Beneficial effects

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention provides a method for preparing a magnetic mesoporous iron-manganese bimetallic material. The method firstly dissolves an organic substance in water, then adds an iron salt and a manganese salt, and forms an iron-manganese bimetallic gel by heating and evaporating the organic substance in a water bath, and finally obtains a magnetic mesoporous iron-manganese bimetallic material by calcining the iron-manganese bimetallic gel. The manganese element in the iron-manganese bimetallic material prepared by the method mainly exists in the form of high-valent Mn(IV) and Mn(III) oxides, which can oxidize highly toxic As(III) and Sb(III) into low-toxic As(V) and Sb(V), respectively, thereby achieving oxidation and detoxification of highly toxic As(III) and Sb(III). At the same time, due to the synergistic effect between iron and manganese, the generated As(V) and Sb(V) are efficiently removed.

[0027] (2) The magnetic mesoporous iron-manganese bimetallic prepared in the present invention has superparamagnetic properties, which facilitates the rapid separation and recovery of the adsorbent after the adsorption reaction.

[0028] (3) The present invention provides a method for preparing a magnetic mesoporous iron-manganese bimetal, which is compared with the prior art (application number 202011369902.4) in which an iron-manganese-organic gel is formed by cross-linking between high-concentration iron salts and organic matter, and then calcined to form a magnetic iron-manganese bimetallic material. The present invention uses iron salts, manganese salts and organic matter to evaporate and concentrate to form an iron-manganese bimetallic gel, and then calcined to form a magnetic mesoporous iron-manganese bimetallic. In the preparation method of the present invention, all the reaction raw materials are converted into iron-manganese bimetallic gel, and then further calcined to form a magnetic mesoporous iron-manganese bimetallic, and there is no discharge of waste liquid during the entire preparation process. In addition, the ratio of the iron-manganese bimetal can be precisely controlled simply by the ratio of the reaction raw materials. The prepared iron-manganese bimetal has superparamagnetic properties, a mesoporous channel structure, and a high specific surface area. It has a high adsorption capacity and adsorption rate for As(V), Sb(V) and Sb(III). It can basically reach a balanced state of adsorption for As(V), Sb(V) and Sb(III) in about 240 minutes, with high treatment efficiency. Its maximum adsorption capacity for As(V), Sb(V) and Sb(III) is 145mg / g, 203mg / g and 336mg / g respectively, which is higher than the adsorption effect of traditional iron-manganese bimetallic. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 hysteresis curve and magnetic separation effect diagram of the magnetic mesoporous iron-manganese bimetal in Example 1 of the present invention;

[0030] Figure 2 is the X-ray diffraction pattern of the magnetic mesoporous iron-manganese bimetal in Example 1 of the present invention;

[0031] Figure 3This is a scanning electron microscope image of the magnetic mesoporous iron-manganese bimetal in Example 1 of the present invention;

[0032] Figure 4 This is a scanning electron microscope image of the magnetic mesoporous iron-manganese bimetal in Example 2 of the present invention;

[0033] Figure 5 This is the XPS spectrum of the manganese element in the magnetic mesoporous iron-manganese bimetal in Example 2 of the present invention;

[0034] Figure 6 The N2 adsorption-desorption isotherm diagram (a) and pore size distribution diagram (b) of the magnetic mesoporous iron-manganese bimetallic in Example 2 of the present invention;

[0035] Figure 7 The adsorption kinetics of As(V), Sb(V) and Sb(III) by the magnetic mesoporous iron-manganese bimetallic in Example 3 of the present invention;

[0036] Figure 8 This is the adsorption isotherm diagram of the magnetic mesoporous iron-manganese bimetallic material for As(V), Sb(V) and Sb(III) in Example 4 of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with specific embodiments.

[0038] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0039] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement or value. The degree of flexibility for a particular variable can be easily determined by one skilled in the art.

[0041] Example 1

[0042] This embodiment provides a method for preparing a magnetic mesoporous iron-manganese bimetal, comprising:

[0043] 10g of polyvinyl pyrrolidone was slowly dissolved in 200mL of deionized water, and then 14.54g of ferric nitrate nine hydrate and 2.94g of manganese acetate tetrahydrate were added; the resulting mixture was placed in a water bath and stirred at 100°C for 6h. After the reaction was completed, the resulting paste was dried in an oven to obtain a red iron-manganese bimetallic gel. The obtained iron-manganese bimetallic gel was placed in a muffle furnace and calcined at 450°C for 3h to obtain a black solid, which was a magnetic mesoporous iron-manganese bimetallic.

[0044] Result analysis:

[0045] Figure 1 The hysteresis curve and magnetic separation effect diagram of the magnetic mesoporous iron-manganese bimetal prepared in this embodiment. It can be seen from the figure that the iron-manganese bimetal in this embodiment has superparamagnetic properties and a saturation magnetization intensity of 19.68emu / g. Under the action of an external magnetic field, the magnetic mesoporous iron-manganese bimetal can be quickly and efficiently separated from the solution.

[0046] Figure 2 This is the X-ray diffraction spectrum of the magnetic mesoporous iron-manganese bimetal prepared in this example. It can be seen from the figure that the obtained magnetic mesoporous iron-manganese bimetal has good crystallinity. By comparison, it can be seen that magnetic γ-Fe2O3 (JCPDS 39-1346) exists in the iron-manganese bimetallic crystal phase.

[0047] Figure 3 (a) and (b) are microscopic morphology images of the magnetic mesoporous iron-manganese bimetal prepared in this embodiment. It can be seen from the figure that the prepared iron-manganese bimetal has a honeycomb-like loose and porous structure. Its rich pore structure is conducive to the mass transfer of metal ions and exposes more active sites on the surface of the iron-manganese bimetal, which is beneficial to the removal of arsenic and antimony.

[0048] Example 2

[0049] This embodiment provides a method for preparing a magnetic mesoporous iron-manganese bimetal, comprising:

[0050] 7g of P123 polyether was slowly dissolved in 100mL of deionized water, and then 7.06g of ferric acetylacetonate and 5.02g of manganese nitrate tetrahydrate were added; the resulting mixture was placed in a water bath and stirred at 100°C for 5h. After the reaction was completed, the resulting paste was dried in an oven to obtain a red iron-manganese bimetallic gel. The obtained iron-manganese bimetallic gel was placed in a muffle furnace and calcined at 500°C for 2h to obtain a black solid, which was a magnetic mesoporous iron-manganese bimetallic.

[0051] Figure 4(a) and (b) are microscopic morphology images of the magnetic mesoporous iron-manganese bimetal prepared in this embodiment. It can be seen from the figure that the prepared iron-manganese bimetal has a rich pore structure, and the pore structure is interconnected, which is conducive to the diffusion process of arsenic and antimony to the surface of the iron-manganese bimetal, and accelerates the removal of arsenic and antimony.

[0052] Figure 5 This is the XPS spectrum of manganese in the magnetic mesoporous iron-manganese bimetallic prepared in this embodiment. It can be seen from the figure that the manganese on the surface of the material mainly exists in the form of high-valent Mn(IV) and Mn(III). Due to its high oxidation potential, it can effectively oxidize highly toxic As(III) and Sb(III) to low-toxic As(V) and Sb(V). At the same time, due to the redox reaction on the surface, more active sites are exposed, which enhances the removal effect of the iron-manganese bimetallic on the generated As(V) and Sb(V).

[0053] Figure 6 (a) and (b) N2 adsorption-desorption isotherms and pore size distribution of the magnetic mesoporous iron-manganese bimetallic prepared in this example. The specific surface area of ​​the material is 124 m 2 / g, it has a mesoporous channel structure, and its average pore size is The specific surface area of ​​the iron-manganese bimetallic prepared by the traditional coprecipitation method is 93.1 m 2 / g(Wen Z, Zhang Y, Dai C, et al. Synthesis of ordered mesoporous iron manganese bimetal oxides for arsenic removal from aqueous solutions[J]. Microporous and mesoporous materials, 2014, 200: 235-244.), the magnetic mesoporous iron manganese bimetal prepared by the present invention has a larger specific surface area, which is more conducive to the removal of arsenic and antimony.

[0054] Example 3

[0055] This embodiment provides a preparation method and application of a magnetic mesoporous iron-manganese bimetal, including:

[0056] 9g dopamine was slowly dissolved in 100mL deionized water, and then 13.51g ferric chloride hexahydrate and 1.97g manganese chloride tetrahydrate were added; the resulting mixture was placed in a water bath and stirred at 100°C for 6h. After the reaction, the resulting paste was dried in an oven to obtain a red iron-manganese bimetallic gel. The obtained iron-manganese bimetallic gel was placed in a muffle furnace and calcined at 450°C for 3h to obtain a black solid, which is a magnetic mesoporous iron-manganese bimetallic.

[0057] The magnetic mesoporous iron-manganese bimetallic prepared in Example 3 is used as an adsorbent to treat wastewater containing arsenic and antimony, comprising the following steps:

[0058] 0.025g of magnetic mesoporous iron-manganese bimetallic was added to 50mL of 100mg / L As(V), Sb(V) and Sb(III) solutions, respectively, and adsorption reaction was carried out at 25°C in a constant temperature oscillating box at a speed of 200r / min, and samples were taken at different time points. Then, the concentration of metal ions in the samples was analyzed by inductively coupled plasma emission spectrometry.

[0059] Figure 7 The adsorption effect of the magnetic mesoporous iron-manganese bimetallic prepared in this embodiment on As(V), Sb(V) and Sb(III) changes over time. It can be seen from the figure that within 200 minutes, the adsorption effect of the magnetic mesoporous iron-manganese bimetallic on As(V), Sb(V) and Sb(III) increases rapidly with the increase of time. After more than 200 minutes, as the adsorption sites on the surface of the magnetic mesoporous iron-manganese bimetallic are gradually occupied and the concentration of metal ions in the bulk of the solution gradually decreases, the adsorption rate gradually slows down and eventually tends to equilibrium. The magnetic mesoporous iron-manganese bimetallic prepared in this embodiment can quickly reach adsorption reaction equilibrium within 240 minutes, thereby greatly improving its treatment efficiency for arsenic-antimony wastewater, and has good practical application potential.

[0060] Example 4

[0061] This embodiment provides a preparation method and application of a magnetic mesoporous iron-manganese bimetal, including:

[0062] Dissolve 5g of polyvinyl pyrrolidone and 5g of citric acid in 100mL of deionized water, then add 10.59g of ferric acetylacetonate and 2.45g of tetrahydrated manganese acetate; place the resulting mixture in a water bath and stir at 100°C for 6h. After the reaction is completed, the resulting paste is dried in an oven to obtain a red iron-manganese bimetallic gel. The obtained iron-manganese bimetallic gel is placed in a muffle furnace and calcined at 400°C for 4h to obtain a black solid, which is a magnetic mesoporous iron-manganese bimetallic.

[0063] The magnetic mesoporous iron-manganese bimetallic prepared in Example 4 is used as an adsorbent to treat wastewater containing arsenic and antimony, comprising the following steps:

[0064] 0.025g of magnetic mesoporous iron-manganese bimetallic was added to 50mL of As(V), Sb(V) and Sb(III) solutions with concentrations of 25-350mg / L, respectively, and adsorption reaction was carried out in a constant temperature oscillating box at 25°C and 200r / min. Samples were taken after 24h. The concentration of metal ions in the samples was then analyzed using an inductively coupled plasma emission spectrometer.

[0065] Figure 8 The adsorption effect of the magnetic mesoporous iron-manganese bimetallic prepared in this embodiment on As(V), Sb(V) and Sb(III) varies with the equilibrium concentration. As can be seen from the figure, the magnetic mesoporous iron-manganese bimetallic has a good adsorption effect on As(V), Sb(V) and Sb(III). According to the calculation results of the Langmuir isotherm model, its maximum adsorption capacity for As(V), Sb(V) and Sb(III) is 145mg / g, 203mg / g and 336mg / g, respectively, which is higher than the adsorption effect of traditional iron-manganese bimetallic and has good practical application potential.

Claims

1. A magnetic mesoporous iron-manganese bimetallic material, characterized in that: The material contains iron, manganese and oxygen elements, and the molar ratio of iron to manganese in the raw material is (1-6):

1. The material has a mesoporous channel structure with an average pore size of The material has magnetism, and the saturation magnetization intensity is 5.25-22.76emu / g.

2. A method for preparing a magnetic mesoporous iron-manganese bimetal, characterized in that: The steps include: S1: dissolve organic matter in water; S2: Add iron salt and manganese salt to the solution in S1 while stirring until they are completely dissolved; S3: The obtained S2 solution is placed in a water bath and reacted at 100°C for 5-10 hours to concentrate the reaction solution into a paste. After the reaction, the obtained paste liquid is dried in an oven to obtain a red iron-manganese bimetallic gel. S4: The iron-manganese bimetallic gel obtained in S3 is calcined in a muffle furnace to obtain a black solid, which is a magnetic mesoporous iron-manganese bimetallic.

3. The method for preparing a magnetic mesoporous iron-manganese bimetal according to claim 2, characterized in that: The organic matter comprises at least one compound selected from polyvinyl pyrrolidone, P123 polyether, dopamine and citric acid.

4. The method for preparing a magnetic mesoporous iron-manganese bimetal according to claim 2, characterized in that: The concentration of organic matter in the solution after dissolution in S1 is 20-50 g / L.

5. The method for preparing a magnetic mesoporous iron-manganese bimetal according to claim 2, characterized in that: The molar ratio of iron salt to manganese salt in S2 is (1-6):1, and the mass ratio of the total mass of iron salt and manganese salt to organic matter is (0.5-2):

1.

6. The method for preparing a magnetic mesoporous iron-manganese bimetal according to claim 2, characterized in that: The iron salt comprises at least one compound selected from ferric nitrate, ferric acetylacetonate and ferric chloride.

7. The method for preparing a magnetic mesoporous iron-manganese bimetal according to claim 2, characterized in that: The manganese salt comprises at least one compound selected from manganese nitrate, manganese acetate and manganese chloride.

8. The method for preparing a magnetic mesoporous iron-manganese bimetal according to claim 2, characterized in that: The calcination temperature is 300-500°C and the calcination time is 2-4h.

9. A magnetic mesoporous iron-manganese bimetal, characterized in that: Prepared by the preparation method described in any one of claims 2 to 8.

10. The method for preparing the magnetic mesoporous iron-manganese bimetal according to any one of claims 2 to 8 or the magnetic mesoporous iron-manganese bimetal according to claim 1 or 9 is used for treating arsenic and / or antimony wastewater.

Images