Fe2+ / Fe3 + composite iron-based deep eutectic solvent, preparation thereof and application of Fe2+ / Fe3 + composite iron-based deep eutectic solvent in magnetite preparation

Abstract

The invention belongs to the field of nano material preparation, and particularly relates to a preparation method of a Fe < 2 + > / Fe < 3 + > composite iron-based deep eutectic solvent, which comprises the following steps: mixing a hydrogen bond donor, a hydrogen bond acceptor and a reducing agent for reaction to obtain the Fe < 2 + > / Fe < 3 + > composite iron- The hydrogen bond acceptor comprises FeX2 and FeX3; wherein X is Cl <-> and / or Br <->; the hydrogen bond donor comprises at least one of urea and polyol. The invention also comprises a scheme for preparing the superfine magnetite by using the eutectic solvent precipitation. The invention provides a brand new eutectic solvent, and the eutectic solvent has unexpected advantages in preparation of magnetite.

Description

Technical Field

[0001] The present invention relates to the field of material preparation, in particular to the field of magnetite synthesis. Background Art

[0002] The resource utilization of iron is a breakthrough in achieving green and circular development in the zinc smelting industry. Using the magnetite method to convert elemental iron into nanomagnetite particles is a key approach to high-value utilization of iron resources. Magnetite, with a theoretical iron content of 72.4%, exhibits strong magnetic properties, with a theoretical magnetic saturation strength of 94 emu / g, facilitating subsequent solid-liquid separation and possessing significant potential for recycling. Furthermore, beyond metal smelting, magnetite with specific morphologies can be used in heavy metal adsorption, catalysis, and pollutant degradation. Therefore, the targeted synthesis of nanomagnetite is key to achieving resource utilization.

[0003] At present, there are many preparation methods involved in synthesizing nanomagnetites with various microscopic morphologies, including three major categories: solid-phase method, gas-phase method and liquid-phase method. Solid-phase methods such as high-energy ball milling and amorphous crystallization have simple processes and low costs, but the product morphology is difficult to control, impurities are easily mixed in, and the efficiency is low. Gas-phase methods such as gas-phase gel and chemical vapor precipitation can effectively control the morphology and crystal structure of the synthesized materials, but their equipment is complex, energy consumption is high, and the cost is high, making them difficult to apply to industrial production. The liquid-phase method is more widely used, and commonly used liquid-phase methods include hydrothermal method and co-precipitation method. They are simple to operate, simple in instrumentation, and low in cost, but the control of the morphology of magnetite synthesis is more difficult, and it is easier to synthesize large-scale magnetite particles. Therefore, it is urgent to explore an economical, fast, efficient and stable synthesis route.

[0004] In recent years, deep eutectic solvents (DESs) have entered people's field of vision as emerging green solvents. They have been widely studied in the cross-disciplinary fields of chemistry, materials, environment, biology, catalysis and energy, and have great application potential. DESs are formed by hydrogen bond donors (urea, polysaccharides, ethylene glycol, etc.) and hydrogen bond acceptors (choline chloride, etc.) through hydrogen bond interactions to form binary and ternary systems, and their melting points are significantly lower than those of single components. DESs have many advantages, such as simple synthesis, low cost, and environmental friendliness, but the types of deep eutectic solvents reported in the prior art are still relatively single, and there is no Fe 2+ / Fe 3+ There are no reports on composite iron-based deep eutectic solvents or the controllable synthesis of magnetite based on iron-based deep eutectic solvents. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the first object of the present invention is to provide a Fe 2+ / Fe 3+ Preparation method of composite iron-based deep eutectic solvent, aiming to prepare a new Fe 2+ / Fe 3+Complex iron-based deep eutectic solvent.

[0006] The second object of the present invention is to provide Fe 2+ / Fe 3+ Complex iron-based deep eutectic solvent.

[0007] The third object of the present invention is to utilize the Fe 2+ / Fe 3+ The invention discloses a method for preparing nano-magnetite using a composite iron-based deep eutectic solvent, which aims to prepare magnetite with controllable morphology, ultrafine fineness and uniform particle size.

[0008] A Fe 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent comprises the following steps: mixing a hydrogen bond donor, a hydrogen bond acceptor and a reducing agent to react;

[0009] The hydrogen bond acceptor comprises FeX2 and FeX3; wherein X is Cl - and / or Br - ;

[0010] The hydrogen bond donor includes at least one of urea and polyol.

[0011] The present invention innovatively uses FeX2 and FeX3 as hydrogen bond acceptors, cooperates with the above hydrogen bond donor type, and reacts the donor and acceptor in a reducing agent-assisted manner to unexpectedly obtain Fe 2+ / Fe 3+ Composite iron-based deep eutectic solvent, not only that, the present invention also unexpectedly found that the Fe 2+ / Fe 3+ The composite iron-based deep eutectic solvent can controllably produce ultrafine nano-scale magnetite with good particle size uniformity and controllable morphology.

[0012] In the present invention, the combination of the required hydrogen bond donor and the composite acceptor can unexpectedly achieve synergy, which is beneficial to obtaining the deep eutectic solvent, and can also unexpectedly facilitate the subsequent preparation of magnetite and help improve the particle size, morphology and phase purity of the prepared magnetite.

[0013] Preferably, the polyol includes at least one of ethylene glycol and glycerol.

[0014] In the present invention, the molar ratio of FeX2 to FeX3 in the hydrogen bond acceptor is 1-5:1-5; preferably 1-2:1-2.

[0015] In the present invention, the type of reducing agent is not particularly limited, and may include, for example, at least one of citrate and isoascorbate. Research in the present invention has shown that the addition of such a reducing agent facilitates the successful preparation of the composite iron-based deep eutectic solvent and facilitates the subsequent combined control of magnetite, its phase, and particle size.

[0016] In the present invention, the molar ratio of total iron in the hydrogen bond acceptor, hydrogen bond donor, and reducing agent is 1:1-5:0.1-2.5, and more preferably 1:3-5:0.2-0.5. Research in the present invention has shown that this ratio not only successfully prepares the composite iron-based deep eutectic solvent, but also facilitates the subsequent combined control of magnetite particle size, morphology, and phase purity.

[0017] In the present invention, the reaction temperature is 30 to 90°C, and can further be 50 to 80°C;

[0018] Preferably, the reaction time is 0.5 to 2.0 hours.

[0019] Preferably, the reaction is carried out in a protective atmosphere, such as nitrogen or argon.

[0020] The present invention also provides a Fe prepared by the preparation method. 2+ / Fe 3+ Complex iron-based deep eutectic solvent.

[0021] The preparation method of the present invention can produce a new composite iron-based deep eutectic solvent, and the composite iron-based deep eutectic solvent can unexpectedly facilitate the preparation of ultrafine magnetite with controllable morphology and uniform particle size.

[0022] The present invention also provides a method for utilizing the Fe 2+ / Fe 3+ Preparation method of nano magnetite prepared by composite iron-based deep eutectic solvent, Fe 2+ / Fe 3+ A composite iron-based deep eutectic solvent and an alkali metal hydroxide are mixed and reacted, followed by solid-liquid separation to obtain nano-magnetite.

[0023] Magnetite is difficult to synthesize ultrafine nano-scale materials due to its intrinsic energy barrier and magnetic problems. 2+ / Fe 3+ The preparation of magnetite using a composite iron-based deep eutectic solvent can solve the problems faced in magnetite synthesis and facilitate the production of ultrafine magnetite with controllable morphology and uniform particle size.

[0024] In the present invention, the alkali metal hydroxide includes at least one of sodium hydroxide and potassium hydroxide;

[0025] Preferably, the Fe 2+ / Fe 3+ The molar ratio of the iron element to the alkali metal hydroxide in the composite iron-based deep eutectic solvent is 1:0.5-4, and can be further increased to 1:0.9-1.2 in consideration of material utilization.

[0026] The present invention also provides nano magnetite prepared by the preparation method.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The present invention provides a new Fe 2+ / Fe 3+ Complex iron-based deep eutectic solvent.

[0029] The present invention innovatively uses FeX2 and FeX3 as hydrogen bond acceptors, and cooperates with the use of the reducing agent and hydrogen bond donor, so that Fe 2+ / Fe 3+ Complex iron-based deep eutectic solvent.

[0030] The present invention innovatively converts Fe 2+ / Fe 3+ Magnetite was prepared by using a composite iron-based deep eutectic solvent. 2 + / Fe 3+ The preparation conditions of the composite iron-based deep eutectic solvent, such as the combined control of hydrogen bond donors and the ratio of components, are helpful to further control the morphology and particle size of magnetite, and help to obtain high-quality magnetite. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a process flow chart of the method of the present invention;

[0032] Figure 2 Characterization of the nanomagnetite synthesized in Example 1; wherein, (a) XRD pattern of magnetite; (b) infrared spectrum of nanomagnetite, 521cm -1 Characteristic peak; (c) Raman spectrum of nanomagnetite, 557cm -1 (d) SEM image of uniform nanomagnetite with a particle size of ~13 nm (the sizes of three randomly selected points in d are 13.02 nm, 13.61 nm, and 10.29 nm, respectively).

[0033] Figure 3 This is the SEM image of the nanomagnetite synthesized in Example 2; wherein A represents ethylene glycol, X, Y, and Z represent Fe 3+ :Fe 2 +=1:1, 2:1, 1:2; 1, 2, 3 represent the acceptor-to-donor ratio = 1:3 / 4 / 5. (The size of the random three dots of A1X is 10.67-12.4 nm, the size of the random three dots of A1Z is 10.29-14.51 nm, the size of the random three dots of A2X is 12.48-15.55 nm, the size of the random three dots of A2Y is 10.29-12.73 nm, the size of the random three dots of A3X is 15.02-15.63 nm, and the size of the random three dots of A3Z is 13.02-15.51 nm)

[0034] Figure 4 This is the SEM image of the nanomagnetite synthesized in Example 3; where B represents urea, X, Y, and Z represent Fe 3+ :Fe 2+ =1:1, 2:1, 1:2; 1, 2, 3 represent the acceptor-to-donor ratio = 1:3 / 4 / 5. Among them, the size of the random three dots of B1Y is 13.07-16.10 nm, the size of the random three dots of B1Z is 10.53-13.81 nm, the size of the random three dots of B2Y is 11.50-12.48 nm, the size of the random three dots of B2Z is ​​10.29-13.81 nm, the size of the random three dots of B3X is 13.81-15.790 nm, and the size of the random three dots of B3Z is 11.22-13.58 nm;

[0035] Figure 5 This is the SEM image of the nanomagnetite synthesized in Example 4; C represents glycerol, X, Y, and Z represent Fe 3+ :Fe 2+ =1:1, 2:1, 1:2; 1, 2, 3 represent the acceptor to donor ratio = 1:3 / 4 / 5. Among them, the size of the random three dots of C1X is 12.48-15.19 nm; the size of the random three dots of C1Y is 14.98-17.65 nm; the size of the random three dots of C2X is 14.56-16.75 nm; the size of the random three dots of C2Z is ​​11.50-11.66 nm;

[0036] Figure 6 This is an SEM image of the magnetite prepared in Comparative Example 1. The size of the three random dots ranges from 310.4 nm to 1265 nm. Specific implementation plan

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] A typical Fe 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent, for example, comprises mixing a hydrogen bond donor (such as urea, ethylene glycol, glycerol) with a hydrogen bond acceptor (such as FeCl3·6H2O and FeCl2·4H2O complex monomers) and a reducing agent (such as sodium citrate dihydrate), stirring under a N2 atmosphere, and synthesizing a DESs solvent containing the valuable metal Fe at a temperature of 60°C.

[0039] Preferably, the DESs composition raw material Fe 3+ :Fe 2+ The molar ratios are 1-2:1-2 (for example, 1:1, 1:2, 2:1), the molar ratios of total iron to hydrogen bond donors are 1:1-5; the ratio of total iron to reducing agent is 0.1-2.5, and can further be 1:0.2-0.5. Considering the cost, it can further be 1:0.2-0.4.

[0040] The present invention also provides a Fe 2+ / Fe 3+ A method for preparing magnetite using a composite iron-based deep eutectic solvent, for example, involves adding NaOH particles to the DESs solvent obtained after treatment in step 1, continuing to stir under a nitrogen atmosphere, and allowing the reaction to proceed until a uniformly mixed black solution is obtained. The resulting solution is then filtered, rinsed multiple times with distilled water, and the filtered product is dried and ground to obtain the final product, magnetite.

[0041] The molar ratio of total iron to NaOH in DESs is 1:0.5-4 (can further be 1:0.9-1.2), and the stirring speed is 500-800 r / min.

[0042] The obtained solution was filtered and washed with distilled water during the filtration process. The solution was filtered 2-4 times and dried at 60-80°C.

[0043] Example 1

[0044] Step (1): Preparation of DESs:

[0045] Weigh 2.70 g of FeCl₃·6H₂O, FeCl₂·4H₂O, and urea (hydrogen bond donor) into a sealable vial and stir to mix at 50°C. Add sodium citrate dihydrate (reducing agent) to the vial and heat with stirring under a nitrogen atmosphere until a transparent, uniform deep eutectic liquid is formed (the molar ratio of urea:Fe₃+:Fe₂+:sodium citrate is 0.09:0.01:0.02:0.009).

[0046] Step (2): Sodium hydroxide (with a molar ratio of 1:1 to the total iron in step 1) was added to the eutectic liquid of step 1, and the mixture was heated and stirred for 1 h. The product was then washed repeatedly with water and separated by suction filtration, and then dried at 70 ° C to obtain ultrafine nano magnetite (XRD, SEM, FTIR and Raman were respectively shown as Figure 2 ).

[0047] The product was identified by XRD, SEM, FTIR and Raman, indicating that the product synthesized by the method of the present invention is nanomagnetite, which shows that it has excellent phase purity, ultrafine nanometer size and particle uniformity.

[0048] Example 2 - Conditions such as hydrogen bond donor, Fe ratio, and donor / acceptor molar ratio

[0049] Compared with Example 1, the only difference is that in step 1, the hydrogen bond donor is changed to ethylene glycol, Fe 3+ :Fe 2+ The molar ratios of hydrogen bond acceptors and donors are 1:1, 2:1, and 1:2, respectively; the molar ratios of hydrogen bond acceptors and donors are 1:3, 1:4, or 1:5, respectively.

[0050] Other operations and parameters are the same as in Example 1.

[0051] Finally, pure phase ultrafine nano magnetite was obtained. The SEM images of magnetite in each experimental group are shown in Figure 2. Figure 3 .

[0052] As can be seen from the SEM image, the synthesized nano-magnetite has uniform particle size and can be controlled within the range of 10 nm to 15 nm.

[0053] Example 3 - Conditions such as hydrogen bond donor, Fe ratio, and donor / acceptor molar ratio

[0054] Compared with Example 1, the only difference is that in step 1, the hydrogen bond donor is changed to urea, Fe 3+ :Fe 2+ The molar ratios of hydrogen bond acceptors and donors are 1:1, 2:1, and 1:2, respectively; the molar ratios of hydrogen bond acceptors and donors are 1:3, 1:4, or 1:5, respectively.

[0055] Other operations and parameters are the same as in Example 1.

[0056] Finally, pure phase ultrafine nano magnetite was obtained. The SEM images of magnetite in each experimental group are shown in Figure 2. Figure 4 .

[0057] As can be seen from the SEM image, the synthesized nano-magnetite has uniform particle size and can be controlled within the range of 10 nm to 15 nm.

[0058] Example 4 - Conditions such as hydrogen bond donor, Fe ratio, and donor / acceptor molar ratio

[0059] Compared with Example 1, the only difference is that in step 1, the hydrogen bond donor is changed to glycerol, Fe 3+ :Fe 2+ The molar ratios of hydrogen bond acceptors and donors are 1:1, 2:1, and 1:2, respectively; the molar ratios of hydrogen bond acceptors and donors are 1:3, 1:4, or 1:5, respectively.

[0060] Other operations and parameters are the same as in Example 1.

[0061] Finally, pure phase ultrafine nano magnetite was obtained. The SEM images of magnetite in each experimental group are shown in Figure 2. Figure 4 .

[0062] As can be seen from the SEM image, the synthesized nano-magnetite has uniform particle size and can be controlled within the range of 10 nm to 15 nm.

[0063] Comparative Example 1:

[0064] Compared with Example 1, the only difference is that in step 1, instead of using composite iron, a single divalent iron source (FeCl2·4H2O) or a trivalent iron source (FeCl3·6H2O) is used; the amount of iron used is the same as the total iron in Example 1, and the other operations and parameters are the same as Example 1. The synthesized product is hematite, and no magnetite mineral phase is formed.

[0065] Comparative Example 2:

[0066] The only difference compared to Example 1 is that in step 1, no reducing agent is added; other operations and parameters are the same as in Example 1. The synthesized product is impure and a uniform pure magnetite mineral phase cannot be formed.

[0067] Comparative Example 3:

[0068] Compared with Example 1, the only difference is that the hydrogen bond donor is replaced by ascorbic acid; the other operations and parameters are the same as Example 1. A uniform deep eutectic solvent cannot be formed, and the product is hematite.

[0069] Comparative Example 4:

[0070] Compared with Example 1, the only difference is that magnetite is not prepared based on eutectic, that is, in step 1, deionized water is used instead of hydrogen bond donor to form magnetite. The physical purity of its magnetite is not as good as that of Example 1, and the SEM image (see Figure 5 ) It can be observed that the synthesized magnetite is conventional large particles ~5 μm and has poor particle size uniformity.

[0071] Table 1. Summary of synthetic magnetite in Comparative Examples 1 to 4:

[0072] in conclusion Comparative Example 1 The synthetic product is hematite, which cannot form a magnetite mineral phase Comparative Example 2 The synthetic product is impure and cannot form a uniform magnetite mineral phase. Comparative Example 3 A uniform deep eutectic solvent cannot be formed and the product is hematite. Comparative Example 4 Synthetic magnetite particles are uneven and have large particle size.

[0073] It can be seen from Table 1 that the process of the present invention can form a new composite eutectic solvent, and through the combined control of the eutectic solvent and conditions, it can unexpectedly facilitate the subsequent control of the physical phase, particle size, and particle size uniformity of the magnetite, thereby facilitating the acquisition of high-quality magnetite.

Claims

1. A kind of Fe 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent is characterized in that: The hydrogen bond donor, hydrogen bond acceptor and reducing agent are mixed and reacted to obtain; The hydrogen bond acceptor comprises FeX2 and FeX3; wherein X is Cl - and / or Br - ; The hydrogen bond donor includes at least one of urea and polyol.

2. Fe as claimed in claim 1 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent is characterized in that: The polyol includes at least one of ethylene glycol and glycerol.

3. Fe as claimed in claim 1 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent is characterized in that: In the hydrogen bond acceptor, the molar ratio of FeX2 to FeX3 is 1-5:1-5; preferably 1-2:1-2.

4. Fe as claimed in claim 1 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent is characterized in that: The reducing agent includes at least one of citrate and erythorbic acid salt.

5. Fe according to any one of claims 1 to 4 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent is characterized in that: The molar ratio of total iron in the hydrogen bond acceptor, hydrogen bond donor, and reducing agent is 1:1-5:0.1-2.

5.

6. Fe as claimed in claim 1 2+ / Fe 3+ The preparation method of the composite iron-based deep eutectic solvent is characterized in that: The reaction temperature is 30-90°C, and can further be 50-80°C; Preferably, the reaction time is 0.5 to 2.0 hours; Preferably, the reaction process is carried out in a protective atmosphere.

7. Fe prepared by the preparation method according to any one of claims 1 to 6 2+ / Fe 3+ Complex iron-based deep eutectic solvent.

8. A method of utilizing the Fe according to claim 7 2+ / Fe 3+ The method for preparing nano-magnetite using a composite iron-based deep eutectic solvent is characterized in that: Fe 2+ / Fe 3+ A composite iron-based deep eutectic solvent and an alkali metal hydroxide are mixed and reacted, followed by solid-liquid separation to obtain nano-magnetite.

9. The preparation method according to claim 8, wherein The alkali metal hydroxide includes at least one of sodium hydroxide and potassium hydroxide; Preferably, the Fe 2+ / Fe 3+ The molar ratio of iron element to alkali metal hydroxide in the composite iron-based deep eutectic solvent is 1:0.5-4.

10. Nano-magnetite obtained by the preparation method according to claim 8 or 9.

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