Nanometer gamma-Fe2O3 and preparation method thereof

Abstract

The application belongs to the technical field of magnetic nanoparticle preparation, and particularly relates to a kind of nano gamma-Fe2O3 and its preparation method. The application obtains the oxidation reaction liquid by mixing ferrous oxalate and hydrogen peroxide aqueous solution for oxidation reaction, and then the oxidation reaction liquid is mixed with alkaline solution to obtain the nano gamma-Fe2O3 after aging. The alkaline solution includes alkali metal hydroxide, organic dispersant and water. The preparation method provided by the application is based on the principle of solution potential-pH relationship diagram, and obtains gamma-Fe2O3 with stable Fe element under specific potential and pH aqueous solution system. The preparation method provided by the application does not need high-temperature calcination, and only needs to obtain nano gamma-Fe2O3 through simple liquid phase reaction under normal temperature and pressure. The yield of the target product nano gamma-Fe2O3 is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic nanoparticle preparation, and particularly relates to a kind of nano gamma-Fe2O3 and its preparation method. BACKGROUND

[0002] The gamma-Fe2O3 magnetic nanoparticle is brown or brown-black, has excellent magnetism, dispersibility and stability, is safe, environmentally friendly and non-polluting, has good magnetic resonance imaging contrast enhancement effect, can be widely applied to nano probe construction, magnetic resonance imaging and molecular imaging, magnetic heat therapy, drug carrier and target diagnosis and treatment integration research, etc.

[0003] At present, people have had certain research on the preparation of nano gamma-Fe2O3. For example, in the Chinese invention patent with publication number CN107572597A, Fe(NO3)3·9H2O and L-tartaric acid are used to obtain a reddish-brown viscous liquid through aqueous phase reaction, the reddish-brown viscous liquid is placed in a blast box for drying to obtain a gray-green solid powder, and the gray-green solid powder is placed in a muffle furnace for calcination to obtain gamma-Fe2O3 nanoparticles. However, this method needs high-temperature calcination in a muffle furnace, and the reaction condition is high temperature, which consumes a lot of energy. In the literature "Peculiar porous alpha-Fe2O3, gamma-Fe2O3 and Fe3O4 nanospheres: facile synthesis and electromagnetic properties", authors Wu H et al. dissolved D-glucose and metal source in distilled water, placed them in an autoclave, and then obtained alpha-Fe2O3 through hydrothermal treatment, and then heated and decomposed the synthesis product in different atmospheres. Studies have shown that the synthesis product is heated at 350℃ in Ar or H2 atmosphere at a rate of 2℃·min-1 to 800℃, and then cooled to room temperature at a rate of 2℃·min-1 to obtain gamma-Fe2O3. However, the above two methods need high-temperature calcination, which consumes a lot of energy. -1The porous α-Fe2O3, γ-Fe2O3 and Fe3O4 nanospheres are obtained by calcining the precursor at a heating rate from room temperature to 350℃ for 2.5h. However, the precursor needs to be prepared in an autoclave in the early stage, and then γ-Fe2O3 needs to be prepared by calcining at a high temperature in a specific atmosphere, and also needs to be prepared by reacting at a high temperature and high pressure. In the literature "Preparation and visible-light photocatalytic activity of α-Fe2O3 / γ-Fe2O3 magnetic heterophase photocatalyst", the authors Zhiwei Wei et al. use Fe2SO4·7H2O as the iron source, and react with (NH4)2C2O4·H2O to prepare a yellow ferrous oxalate precursor. The ferrous oxalate precursor is heated and decomposed in an air atmosphere at 550℃ for 2h to obtain α-Fe2O3. Then, the obtained α-Fe2O3 is mixed with PEG1000 in different mass ratios. The research shows that when the mass ratio of α-Fe2O3 to PEG1000 is 1:2 and the thermal decomposition treatment is carried out in an argon atmosphere at 400℃ for 30min, complete γ-Fe2O3 is obtained. When the mass ratio of α-Fe2O3 to PEG1000 is 1:1 and the thermal treatment is carried out by heating in an air atmosphere at 450℃ for 20min, a mixture of α-Fe2O3 and γ-Fe2O3 is obtained. However, the preparation process needs to prepare α-Fe2O3 as the precursor in the early stage, and then needs to mix with PEG in a specific mass ratio, and needs to be calcined at a high temperature in a specific atmosphere to obtain γ-Fe2O3. The preparation process is relatively complex, and the preparation period is long. The thermal decomposition reaction needs to be prepared at a high temperature, and the energy consumption is high.

[0004] In summary, in the existing technology, the target product needs to be calcined at a high temperature to obtain γ-Fe2O3, which has high energy consumption and is not conducive to the industrialization and expansion of production of γ-Fe2O3. SUMMARY

[0005] The purpose of the present application is to provide a kind of nano γ-Fe2O3 and preparation method thereof, the preparation method provided by the present application is mild, only needs to be at room temperature and normal pressure, without being calcined at a high temperature in high-pressure kettle or high-pressure kettle can obtain target product;And the yield of target product nano γ-Fe2O3 is high.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] The present application provides a kind of nano γ-Fe2O3 preparation method, comprising the following steps:

[0008] The ferrous oxalate and hydrogen peroxide aqueous solution are mixed to carry out oxidation reaction, and the oxidation reaction liquid is obtained;

[0009] The oxidation reaction solution and the alkaline solution are mixed and aged to obtain the nano γ-Fe2O3; the alkaline solution comprises an alkali metal hydroxide, an organic dispersant and water.

[0010] Preferably, the molar ratio of the hydrogen peroxide and the ferrous oxalate is 0.01-0.03:0.007.

[0011] Preferably, the alkali metal hydroxide comprises KOH and / or NaOH.

[0012] Preferably, the molar ratio of the alkali metal hydroxide and the ferrous oxalate is 0.014-0.07:0.007.

[0013] Preferably, the organic dispersant comprises one or more of ethanol, N,N-dimethylacetamide, N-methylpyrrolidone and N,N-diethylacetamide.

[0014] Preferably, the alkaline solution is obtained by mixing an aqueous alkali metal hydroxide solution and an organic dispersant; the aqueous alkali metal hydroxide solution has a molar concentration of 1-5 mol / L, and the volume ratio of the organic dispersant to the aqueous alkali metal hydroxide solution is (0-2):1, and is not 0.

[0015] Preferably, the aging is performed at a temperature of 20-80℃ for 1-2h.

[0016] Preferably, the alkaline reaction solution is obtained after the aging; the aging further comprises sequentially performing solid-liquid separation, water washing and drying on the alkaline reaction solution to obtain the nano γ-Fe2O3; the drying is performed at a temperature of 60-80℃ for 2-4h.

[0017] Preferably, the aqueous hydrogen peroxide solution has a molar concentration of 0.01-3 mol / L.

[0018] The application provides the nano γ-Fe2O3 described in the technical solution; the nano γ-Fe2O3 has a morphology of nanoparticles or nanorods; the particle size of the γ-Fe2O3 nanoparticles is 5-20nm; the length of the γ-Fe2O3 nanorods is 100-200nm, and the diameter is 10-20nm.

[0019] The application provides a preparation method of nano gamma-Fe2O3, comprising the following steps: mixing ferrous oxalate and hydrogen peroxide aqueous solution to perform an oxidation reaction, so as to obtain an oxidation reaction solution; mixing the oxidation reaction solution and an alkaline solution, and then aging, so as to obtain the nano gamma-Fe2O3; the alkaline solution comprises an alkali metal hydroxide, an organic dispersant and water. The preparation method provided by the application firstly mixes ferrous oxalate and hydrogen peroxide aqueous solution, so as to improve the potential of the solution, provide an oxidation environment for the ferrous oxalate, and oxidize the ferrous iron into ferric iron; then the obtained oxidation reaction solution is mixed with an alkaline solution containing an alkali metal hydroxide, so as to improve the pH of the solution system, and obtain gamma-Fe2O3 through the aging process. The preparation method provided by the application does not need high-temperature calcination, and can obtain nano gamma-Fe2O3 through a simple liquid-phase reaction at normal temperature and pressure, and the yield of the obtained target product nano gamma-Fe2O3 is high. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The preparation flow chart of the nano gamma-Fe2O3 in the application;

[0021] Figure 2 The XRD graph of the nano gamma-Fe2O3 prepared in the example 1 of the application;

[0022] Figure 3 The XRD graph of the nano gamma-Fe2O3 prepared in the example 2 of the application;

[0023] Figure 4 The XRD graph of the nano gamma-Fe2O3 prepared in the example 3 of the application;

[0024] Figure 5 The XRD graph of the nano gamma-Fe2O3 prepared in the example 4 of the application;

[0025] Figure 6 The XRD graph of the nano gamma-Fe2O3 prepared in the example 5 of the application;

[0026] Figure 7 The XRD graph of the nano gamma-Fe2O3 prepared in the example 6 of the application;

[0027] Figure 8 The XRD graph of the nano gamma-Fe2O3 prepared in the example 7 of the application;

[0028] Figure 9 The XRD graph of the nano gamma-Fe2O3 prepared in the example 8 of the application;

[0029] Figure 10 The SEM graph of the nano gamma-Fe2O3 prepared in the example 1 of the application;

[0030] Figure 11 SEM image of nano-sized γ-Fe2θ3 prepared in Example 2 of the present invention;

[0031] Figure 12 SEM image of nano-sized γ-Fe2θ3 prepared in Example 3 of the present invention;

[0032] Figure 13 SEM image of nano-sized γ-Fe2θ3 prepared in Example 4 of the present invention;

[0033] Figure 14 SEM image of nano-sized γ-Fe2θ3 prepared in Example 5 of the present invention;

[0034] Figure 15 SEM image of nano-sized γ-Fe2θ3 prepared in Example 6 of the present invention;

[0035] Figure 16 SEM image of nano-sized γ-Fe2θ3 prepared in Example 7 of the present invention;

[0036] Figure 17 SEM image of nano-sized γ-Fe2θ3 prepared in Example 8 of the present invention;

[0037] Figure 18 TEM image of nano-sized γ-Fe2θ3 prepared in Example 3 of the present invention;

[0038] Figure 19 TEM image of nano-sized γ-Fe2θ3 prepared in Example 6 of the present invention;

[0039] Figure 20 XRD pattern of the powdered product prepared in Comparative Example 1 of the present invention;

[0040] Figure 21 XRD pattern of the powdered product prepared in Comparative Example 2 of the present invention;

[0041] Figure 22 XRD pattern of the powdered product prepared in Comparative Example 3 of the present invention;

[0042] Figure 23 XRD pattern of the powdered product prepared in Comparative Example 4 of the present invention;

[0043] Figure 24 XRD pattern of the powdered product prepared in Comparative Example 5 of the present invention;

[0044] Figure 25 XRD pattern of the powdered product prepared in Comparative Example 6 of the present invention;

[0045] Figure 26XRD pattern of the powdered product prepared in Inventive Comparative Example 7;

[0046] Figure 27 XRD pattern of the powdered product prepared in Inventive Comparative Example 8;

[0047] Figure 28 XRD pattern of the powdered product prepared in Inventive Comparative Example 9;

[0048] Figure 29 XRD pattern of the powdered product prepared in Inventive Comparative Example 10;

[0049] Figure 30 SEM pattern of the powdered product prepared in Inventive Comparative Example 1;

[0050] Figure 31 SEM pattern of the powdered product prepared in Inventive Comparative Example 2;

[0051] Figure 32 SEM pattern of the powdered product prepared in Inventive Comparative Example 6;

[0052] Figure 33 Potential-PH data pattern measured in Inventive Example 1;

[0053] Figure 34 SEM comparison pattern of the products obtained in Inventive Example 1, Inventive Examples 6-8 using different types of dispersants. DETAILED DESCRIPTION

[0054] The present application provides a preparation method of nano γ-Fe2O3, comprising the following steps:

[0055] mixing ferrous oxalate and aqueous hydrogen peroxide solution to perform an oxidation reaction, to obtain an oxidation reaction liquor;

[0056] mixing the oxidation reaction liquor and an alkaline solution, and then aging, to obtain the nano γ-Fe2O3; the alkaline solution comprises an alkali metal hydroxide, an organic dispersant and water.

[0057] In the present application, all the preparation raw materials / components are commercially available products well known to those skilled in the art, unless otherwise specified.

[0058] The present application mixes ferrous oxalate and aqueous hydrogen peroxide solution (hereinafter referred to as first mixing) to perform an oxidation reaction, to obtain an oxidation reaction liquor.

[0059] In the specific embodiments of the present application, the ferrous oxalate is specifically FeC2O4·2H2O.

[0060] The present application does not have special requirements for the source of ferrous oxalate, and commercially available products or self-made according to the preparation method of the prior art can be used.

[0061] In the present application, the molar concentration of the aqueous hydrogen peroxide solution is preferably 0.01-3 mol / L, more preferably 0.1-2.8 mol / L.

[0062] In the present application, the molar ratio of hydrogen peroxide to ferrous oxalate is preferably 0.01-0.03:0.007, more preferably 0.015-0.03:0.007, and further preferably 0.03:0.007. In the present application, the molar ratio of hydrogen peroxide to ferrous oxalate cannot be too large or too small, and when the molar ratio of hydrogen peroxide to ferrous oxalate is too large or too small, nano γ-Fe2O3 cannot be prepared.

[0063] In the present application, the first mixing preferably comprises: wetting ferrous oxalate with water to obtain wet ferrous oxalate; preparing an aqueous hydrogen peroxide solution with deionized water; and adding the aqueous hydrogen peroxide solution dropwise to the wet ferrous oxalate. The dropwise addition speed of the aqueous hydrogen peroxide solution is preferably 1 mL / min. The dropwise addition is carried out under stirring, and the stirring is preferably magnetic stirring.

[0064] In the present application, the first mixing of ferrous oxalate and aqueous hydrogen peroxide solution is carried out simultaneously with the oxidation reaction, and after the first mixing is completed, no additional aging is required.

[0065] After obtaining the oxidation reaction solution, the present application mixes (hereinafter referred to as second mixing) the oxidation reaction solution and an alkaline solution to obtain the nano γ-Fe2O3; the alkaline solution comprises an alkali metal hydroxide, an organic dispersant and water.

[0066] In the present application, the alkali metal hydroxide preferably comprises KOH and / or NaOH, and more preferably KOH or NaOH.

[0067] In the present application, the molar ratio of the alkali metal hydroxide to ferrous oxalate is preferably 0.014-0.07:0.007, more preferably 0.014-0.06:0.007, and further more preferably 0.014:0.007. In the present application, the molar ratio of the alkali metal hydroxide to ferrous oxalate cannot be too large or too small, and when the molar ratio of the alkali metal hydroxide to ferrous oxalate is too large or too small, nano γ-Fe2O3 cannot be prepared.

[0068] In the present application, the organic dispersant preferably comprises one or more of ethanol, N,N-dimethylacetamide (DMA), N-methylpyrrolidone (NMP) and N,N-diethylacetamide (DEAC), more preferably DMA, NMP or DEAC, and further preferably DMA. In the present application, the ethanol is specifically anhydrous ethanol. The present application uses DMA, NMP or DEAC as the organic dispersant, and the obtained nano γ-Fe2O3 product is more uniformly distributed.

[0069] In the present application, the basic solution is preferably obtained by mixing an aqueous alkali metal hydroxide solution and an organic dispersant; the molar concentration of the aqueous alkali metal hydroxide solution is preferably 1-5 mol / L, and more preferably 1.5-4.55 mol / L; the volume ratio of the organic dispersant to the aqueous alkali metal hydroxide solution is preferably (0-2):1, and is not 0, and more preferably (0.5-2):1, and further preferably 2:1.

[0070] In the present application, the second mixing preferably comprises: adding the basic solution dropwise to the oxidation reaction solution; the speed of the dropwise addition is preferably 1.5-2 mL / min. In the present application, the second mixing is preferably carried out under stirring, and the stirring is preferably magnetic stirring; the temperature of the second mixing is preferably 20-80℃, and more preferably 20-45℃.

[0071] In the present application, the aging temperature is preferably 20-80℃, and more preferably 20-45℃; and the time is preferably 1-2 h. In the present application, the aging time is calculated from the end of the second mixing (i.e. the completion of the dropwise addition of the basic solution). The present application preferably obtains nano γ-Fe2O3 with higher crystallinity through aging.

[0072] In the present application, the basic reaction solution is obtained after the aging. The present application preferably further comprises, after the aging: sequentially carrying out solid-liquid separation, water washing and drying on the basic reaction solution to obtain the nano γ-Fe2O3; the temperature of the drying is preferably 60-80℃, and more preferably 65-75℃; and the time is preferably 2-4 h, and more preferably 2.5-3.5 h. In the present application, the solid-liquid separation is preferably centrifugation, and the rotation speed of the centrifugation is preferably 6000-7000 rpm, and more preferably 6500 rpm. The water washing is preferably deionized water washing, and the present application preferably washes the solid product obtained through solid-liquid separation to neutral. In the present application, the drying is preferably air drying.

[0073] The present application provides the nano γ-Fe2O3 prepared by the preparation method described in the above technical solution, and the morphology of the nano γ-Fe2O3 is nanoparticles or nanorods.

[0074] In the present application, when the morphology of the nano γ-Fe2O3 is nanoparticle, the particle size of the nano γ-Fe2O3 is preferably 5-20 nm, and more preferably 5-10 nm or 10-20 nm.

[0075] In the present application, when the morphology of the nano γ-Fe2O3 is nanorod, the length of the nano γ-Fe2O3 is 100 nm, and the diameter is 10-20 nm.

[0076] The preparation method of the nano γ-Fe2O3 provided by the present application has a simple flow, and the target product can be obtained through a simple liquid phase reaction. The reaction condition is mild, and the repeatability is good. The target product can be obtained at normal temperature and pressure without high-pressure kettle or high-temperature calcination. Finally, the yield of the target product obtained by the present application is 80-90%, which is high.

[0077] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application. The following examples are prepared according to the preparation flow chart of the nano γ-Fe2O3 shown in the present application. Figure 1

[0078] Example 1

[0079] (1) 0.007 mol of FeC2O4·2H2O was added with 5 mL of water to be wet at room temperature, and magnetic stirring (speed has no requirement) was carried out to make it uniformly dispersed;

[0080] (2) A H2O2 solution with a concentration of 1 mol / L was prepared with deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the manual drop was controlled for 10 min. The magnetic stirring was carried out during the drop.

[0081] (3) A certain amount of KOH solution (14 mL) was taken according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, and anhydrous ethanol (28 mL) was mixed to obtain a mixed solution according to the volume ratio of 1:2. The mixed solution was slowly added to the solution obtained in (2), and the manual drop was controlled for 25 min. The magnetic stirring was carried out during the drop, and the supernatant pH was 7 after the centrifugation (6500 rpm, the same below) of the reaction liquid obtained in (3) with deionized water. The precipitate was dried in a blast drying oven at 80℃ for 2-4 h to obtain γ-Fe2O3 nanoparticles with a particle size of 10-20 nm.

[0082] (4) The reaction liquid obtained in (3) was centrifuged (6500 rpm, the same below) with deionized water until the supernatant pH was 7. The precipitate was dried in a blast drying oven at 80℃ for 2-4 h to obtain γ-Fe2O3 nanoparticles with a particle size of 10-20 nm. Figure 2 ​The image shows the XRD pattern of the nano-γ-Fe2O3 prepared in Example 1. Figure 10 This is a SEM image of the nano-γ-Fe2O3 prepared in Example 1. Figure 10 It can be seen that the nano-γ-Fe2O3 prepared in this embodiment has a granular morphology.

[0083] During the reaction process in Example 1, the potential-pH data of the solution were measured every 5 minutes to obtain... Figure 33 ,Depend on Figure 33 It can be concluded that after the sequential addition of hydrogen peroxide and strong alkaline solution, the potential-pH state of the system is continuously and stably maintained within the potential-pH range that enables the formation of the target product.

[0084] Example 2

[0085] (1) At room temperature, add 5 mL of water to 0.007 mol FeC2O4·2H2O to moisten it, and stir magnetically (speed is not required) to disperse it evenly;

[0086] (2) Prepare a 1 mol / L H2O2 solution using deionized water. Take a certain amount of the prepared H2O2 solution (10 mL) according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution dropwise to the ferrous oxalate system manually over a period of 10 min, stirring magnetically during the addition. After the addition is complete, allow the mixture to age for 1 h.

[0087] (3) Take a certain amount of prepared KOH solution (14 mL) and anhydrous ethanol (28 mL) at a volume ratio of 1:2 according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol: 0.007 mol to obtain a mixed solution. Slowly add the mixed solution to the solution obtained in (2) by manual addition for 25 min. Stir magnetically during the addition process. After the addition is completed, let it age for 1 h.

[0088] (4) The reaction solution obtained in step (3) is centrifuged with deionized water (6500 rpm, the same below) and washed until the pH of the supernatant is 7. The precipitate is dried in a forced-air drying oven at 80°C for 2-4 hours to obtain γ-Fe2O3 nanoparticles with a particle size of 10-20 nm. Figure 3 The image shows the XRD pattern of the nano-γ-Fe2O3 prepared in Example 2. Figure 11 This is a SEM image of the nano-γ-Fe2O3 prepared in Example 2. Figure 11 As can be seen, the γ-Fe2O3 prepared in this embodiment has the morphology of nanoparticles. Furthermore, its particle size is essentially the same as that of the product prepared in Example 1.

[0089] Comparing Example 1 with Example 2, it can be seen that the γ-Fe2O3 nanoparticles with a particle size of 10-20 nm can be prepared without aging treatment after the oxidation reaction, the reaction steps and time are simplified, and the preparation method is simple and convenient.

[0090] Example 3

[0091] (1) 0.007 mol of FeC2O4·2H2O was wetted by adding 5 mL of water at room temperature, and was subjected to magnetic stirring (no speed requirement) to make it uniformly dispersed;

[0092] (2) A H2O2 solution with a concentration of 3 mol / L was prepared by using deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to a molar ratio of H2O2 to FeC2O4·2H2O of 0.03 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the manual dropwise addition was controlled for 10 min, and magnetic stirring was performed during the dropwise addition.

[0093] (3) A certain amount of KOH solution (14 mL) was taken according to a molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol, and was mixed with anhydrous ethanol (28 mL) according to a volume ratio of 1:2 to obtain a mixed solution, and the mixed solution was slowly added to the solution obtained in (2), and the manual dropwise addition was controlled for 25 min, and magnetic stirring was performed during the dropwise addition, and the reaction liquid was aged for 1 h after the dropwise addition was completed.

[0094] (4) The reaction liquid obtained in step (3) was washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain γ-Fe2O3 nanoparticles with a particle size of 5-10 nm. Figure 4 FIG. 1 is an XRD pattern of the nano γ-Fe2O3 prepared in Example 3, Figure 12 FIG. 2 is an SEM pattern of the nano γ-Fe2O3 prepared in Example 3, Figure 18 FIG. 3 is a TEM pattern of the nano γ-Fe2O3 prepared in Example 3. Comparing Example 1 with Example 3, it can be seen that increasing the molar ratio of hydrogen peroxide and ferrous oxalate can prepare γ-Fe2O3 nanoparticles with a smaller particle size.

[0095] Example 4

[0096] (1) 0.007 mol of FeC2O4·2H2O was wetted by adding 5 mL of water at room temperature, and was subjected to magnetic stirring (no speed requirement) to make it uniformly dispersed;

[0097] (2) Prepare H2O2 solution with concentration of 1 mol / L by using deionized water, and take a certain amount of prepared H2O2 solution (10 mL) according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution into the ferrous oxalate system, manually add, and control the time to be 10 min. Stir by magnetic force during the adding process.

[0098] (3) Mix a certain amount of prepared KOH solution (14 mL) with anhydrous ethanol (28 mL) according to the volume ratio of 1:2 to obtain a mixed solution, and slowly add the mixed solution into the solution obtained in (2), manually add, and control the time to be 25 min. Stir by magnetic force during the adding process, and age for 1 h after the adding is completed.

[0099] (4) Centrifuge the reaction solution obtained in step (3) by using deionized water (6500 rpm, the same below), wash until the pH of the supernatant is 7, dry the precipitate in a blast drying oven at 80℃ for 2-4 h, and obtain γ-Fe2O3 nanorods with length of 100-20 nm and diameter of 10-20 nm. Figure 5 The XRD pattern of the nanometer γ-Fe2O3 prepared in Example 4 is shown in Figure 1, Figure 13 The SEM pattern of the nanometer γ-Fe2O3 prepared in Example 4 is shown in Figure 2. It can be seen that, when the molar ratio of KOH to FeC2O4·2H2O is increased from 0.014 mol:0.007 mol to 0.07 mol:0.007 mol, the morphology of γ-Fe2O3 changes from nanoparticles to nanorods, and the length of the nanorods is increased from 20-100 nm to 100-200 nm. Figure 13 It can be seen that the product prepared in Example 4 is nanorods with diameter of about 10-20 nm and length of about 100-200 nm.

[0100] Example 5

[0101] (1) Add 5 mL water to 0.007 mol FeC2O4·2H2O at room temperature to wet it, and stir by magnetic force (no requirement for the rotating speed) to make it uniformly dispersed;

[0102] (2) Prepare H2O2 solution with concentration of 1 mol / L by using deionized water, and take a certain amount of prepared H2O2 solution (10 mL) according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. Slowly add the H2O2 solution into the ferrous oxalate system, manually add, and control the time to be 10 min. Stir by magnetic force during the adding process.

[0103] (3) According to the molar ratio of NaOH to FeC2O4*2H2O of 0.014 mol:0.007 mol, a certain amount of prepared NaOH solution (14 mL) and anhydrous ethanol (28 mL) were mixed in a volume ratio of 1:2 to obtain a mixed solution, and the mixed solution was slowly added to the solution obtained in (2). The manual dropwise addition was controlled for 25 min, and magnetic stirring was performed during the dropwise addition. After the dropwise addition was completed, the solution was aged for 1 h.

[0104] (4) The reaction solution obtained in the step (3) was washed by deionized water centrifugation (6500 rpm, the same below) until the pH of the supernatant was 7. The precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain γ-Fe2O3 nanoparticles with a particle size of 10-20 nm. Figure 6 FIG. 4 is an XRD pattern of the nano γ-Fe2O3 prepared in Example 5, Figure 14 FIG. 5 is an SEM pattern of the nano γ-Fe2O3 prepared in Example 5.

[0105] Example 6

[0106] (1) 0.007 mol of FeC2O4*2H2O was wetted by adding 5 mL of water at room temperature, and magnetic stirring (speed not required) was performed to make it uniformly dispersed;

[0107] (2) A 1 mol / L H2O2 solution was prepared using deionized water, and a certain amount of prepared H2O2 solution (10 mL) was taken according to the molar ratio of H2O2 to FeC2O4*2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the manual dropwise addition was controlled for 10 min. Magnetic stirring was performed during the dropwise addition.

[0108] (3) According to the molar ratio of KOH to FeC2O4*2H2O of 0.014 mol:0.007 mol, a certain amount of prepared KOH solution (14 mL) and DMA (28 mL) were mixed in a volume ratio of 1:2 to obtain a mixed solution, and the mixed solution was slowly added to the solution obtained in (2). The manual dropwise addition was controlled for 25 min, and magnetic stirring was performed during the dropwise addition. After the dropwise addition was completed, the solution was aged for 1 h.

[0109] (4) The reaction solution obtained in the step (3) was washed by deionized water centrifugation (6500 rpm, the same below) until the pH of the supernatant was 7. The precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain γ-Fe2O3 nanoparticles with a particle size of 5-20 nm. Figure 7 FIG. 9 is an XRD pattern of the nano γ-Fe2O3 prepared in Example 6, Figure 15 FIG. 10 is an SEM pattern of the nano γ-Fe2O3 prepared in Example 6, Figure 19TEM image of the nano γ-Fe2θ3 prepared in Example 6.

[0110] Example 7

[0111] (1) 0.007 mol of FeC2O4-2H2O was wetted with 5 mL of water at room temperature and magnetically stirred (no speed requirement) to disperse uniformly;

[0112] (2) A 1 mol / L H2O2 solution was prepared with deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to the molar ratio of H2O2 to FeC2O4-2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the manual addition was controlled for 10 min, and magnetic stirring was carried out during the addition.

[0113] (3) A certain amount of KOH solution (14 mL) was taken according to the molar ratio of KOH to FeC2O4-2H2O of 0.014 mol:0.007 mol, mixed with NMP (28 mL) according to the volume ratio of 1:2 to obtain a mixed solution, and the mixed solution was slowly added to the solution obtained in (2). The manual addition was controlled for 25 min, and magnetic stirring was carried out during the addition. After the addition was completed, the solution was aged for 1 h.

[0114] (4) The reaction solution obtained in step (3) was washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant was 7. The precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain γ-Fe2O3 nanoparticles with a particle size of 10-20 nm. Figure 8 XRD pattern of the nano γ-Fe2θ3 prepared in Example 7, Figure 16 SEM image of the nano γ-Fe2θ3 prepared in Example 7.

[0115] Example 8

[0116] (1) 0.007 mol of FeC2O4-2H2O was wetted with 5 mL of water at room temperature and magnetically stirred (no speed requirement) to disperse uniformly;

[0117] (2) A 1 mol / L H2O2 solution was prepared with deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to the molar ratio of H2O2 to FeC2O4-2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the manual addition was controlled for 10 min, and magnetic stirring was carried out during the addition.

[0118] (3) take a certain amount of KOH solution (14 mL) prepared according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol and DEAC (28 mL) according to the volume ratio of 1:2 to obtain a mixed solution, slowly drop the mixed solution into the solution obtained in (2), manually drop, the time control is 25 min, magnetic stirring is carried out during the dropping process, and the reaction liquid obtained in step (3) is aged for 1 h after the dropping is completed.

[0119] (4) the reaction liquid obtained in step (3) is washed by deionized water centrifugation (6500 rpm, the same below), the supernatant pH is 7, the precipitate is dried in a blast drying oven at 80℃ for 2-4 h, and γ-Fe2O3 nanoparticles with a particle size of 10-20 nm are obtained. Figure 9 The XRD pattern of the nano γ-Fe2O3 prepared in Example 8. Figure 17 The SEM pattern of the nano γ-Fe2O3 prepared in Example 8 of the application.

[0120] Figure 34 The SEM pattern comparison of the nano γ-Fe2O3 prepared by using different dispersants in Example 1, Example 6-8, wherein Figure 34 It can be seen that the particle size of the nano γ-Fe2O3 prepared by using anhydrous ethanol as a dispersant in Example 1 is 26 nm, the particle size of the nano γ-Fe2O3 prepared by using NMP as a dispersant in Example 7 is 20 nm, the particle size of the nano γ-Fe2O3 prepared by using DMA as a dispersant in Example 6 is 18 nm, and the particle size of the nano γ-Fe2O3 prepared by using DEAC as a dispersant in Example 8 is 22 nm.

[0121] Comparative Example 1

[0122] (1) 5 mL of water is added to 0.007 mol of FeC2O4·2H2O at room temperature to wet it, and magnetic stirring (speed has no requirement) is carried out to make it uniformly dispersed;

[0123] (2) take a certain amount of KOH solution (14 mL) prepared according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol and DEAC (28 mL) according to the volume ratio of 1:2 to obtain a mixed solution, slowly drop the mixed solution into the solution obtained in (2), manually drop, the time control is 25 min, magnetic stirring is carried out during the dropping process.

[0124] (3) Take a certain amount of H2O2 solution (10 mL) prepared in (2) and slowly drop it into the solution obtained in (2) at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. The dropping is manually controlled and the time is controlled to be 10 min. The magnetic stirring is carried out during the dropping. After the dropping is completed, the solution is aged for 1 h.

[0125] (4) The reaction solution obtained in (3) is washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant is 7. The precipitate is dried in a blast drying oven at 80℃ for 2-4 h to obtain a black powder product. Figure 20 The XRD pattern of the powder product prepared in Comparative Example 1 is shown in Figure 1. Figure 30 The SEM pattern of the powder product prepared in Comparative Example 1 is shown in Figure 2. It can be seen from Comparative Example 1 and Comparative Example 2 that when the order of the steps of alkaline solution precipitation and hydrogen peroxide aqueous solution oxidation is changed, the nano γ-Fe2O3 cannot be obtained.

[0126] Comparative Example 2

[0127] (1) 0.007 mol of FeC2O4·2H2O is wetted with 5 mL of water at room temperature and is magnetically stirred (the speed is not required) to make it uniformly dispersed;

[0128] (2) A certain amount of KOH solution (14 mL) prepared is mixed with anhydrous ethanol (28 mL) at a volume ratio of 1:2 to obtain a mixed solution. The mixed solution is slowly dropped into the ferrous oxalate system, and the dropping is manually controlled and the time is controlled to be 25 min. The magnetic stirring is carried out during the dropping. After the dropping is completed, the solution is aged for 1 h.

[0129] (3) Take a certain amount of H2O2 solution (10 mL) prepared in (2) and slowly drop it into the solution obtained in (2) at a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. The dropping is manually controlled and the time is controlled to be 10 min. The magnetic stirring is carried out during the dropping. After the dropping is completed, the solution is aged for 1 h.

[0130] (4) The reaction solution obtained in (3) is washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant is 7. The precipitate is dried in a blast drying oven at 80℃ for 2-4 h to obtain a black powder product. Figure 21 The XRD pattern of the powder product prepared in Comparative Example 2 is shown in Figure 3. Figure 31SEM image of the powder product prepared in Comparative Example 2 of the present application. From Comparative Example 2 and Comparative Example 3, it can be seen that, even if aging is performed after each step, the target product of nano γ-Fe2O3 cannot be obtained by adding KOH solution for precipitation reaction and then adding H2O2 solution for oxidation, which indicates that the effect of aging on the formation of the target product is not great, and the reaction sequence of adding base for precipitation after oxidation is a prerequisite for the formation of the target product of nano γ-Fe2O3.

[0131] Comparative Example 3

[0132] (1) 0.007 mol of FeC2O4·2H2O was wetted with 5 mL of water at room temperature, and magnetic stirring (speed not required) was performed to make it uniformly dispersed;

[0133] (2) A KOH solution with a concentration of 1 mol / L was prepared with deionized water, and a certain amount of the prepared KOH solution (14 mL) was mixed with anhydrous ethanol (28 mL) in a volume ratio of 1:2 to obtain a mixed solution, the mixed solution was slowly added to the ferrous oxalate system, and manual addition was performed, with a time control of 15 min, and magnetic stirring was performed during the addition process. After the addition was completed, aging was performed for 1 h.

[0134] (3) The reaction liquid obtained in step (2) was washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain a black powder product.

[0135] (4) A H2O2 solution with a concentration of 1 mol / L was prepared with deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to a molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the black powder obtained in (3), and manual addition was performed, with a time control of 10 min, and magnetic stirring was performed during the addition process. After the addition was completed, aging was performed for 1 h.

[0136] (5) The reaction liquid obtained in step (4) was washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain a black powder product. Figure 22 XRD image of the powder product prepared in Comparative Example 3 of the present application. From Comparative Example 2 and Comparative Example 3, it can be seen that, even if drying is performed after aging, the target product of nano γ-Fe2O3 cannot be obtained by adding KOH solution for precipitation reaction and then adding H2O2 solution for oxidation, which further indicates that the reaction sequence of adding base for precipitation after oxidation is a prerequisite and key factor for the formation of the target product of nano γ-Fe2O3.

[0137] Comparative Example 4

[0138] (1) 0.007 mol of FeC2O4.2H2O was wetted with 5 mL of water at room temperature, and was uniformly dispersed by magnetic stirring (no requirement for rotation speed) ;

[0139] (2) A H2O2 solution with a concentration of 1 mol / L was prepared using deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to a molar ratio of H2O2 to FeC2O4.2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and was manually added at a time control of 10 min, and magnetic stirring was performed during the adding process.

[0140] (3) A certain amount of a KOH solution (14 mL) was taken according to a molar ratio of KOH to FeC2O4.2H2O of 0.0014 mol:0.007 mol, and was mixed with anhydrous ethanol (28 mL) according to a volume ratio of 1:2 to obtain a mixed solution, and the mixed solution was slowly added to the solution obtained in (2), and was manually added at a time control of 25 min, and magnetic stirring was performed during the adding process, and the reaction liquid was aged for 1 h after the adding process was completed.

[0141] (4) The reaction liquid obtained in (3) was washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80°C for 2-4 h. A yellow powdery product was obtained. Figure 23 The XRD pattern of the powdery product prepared in Comparative Example 4 of the present application. As can be seen from Comparative Example 1 and Comparative Example 4, when the molar ratio of KOH to FeC2O4.2H2O is less than the protection scope of the present application, nano γ-Fe2O3 cannot be obtained.

[0142] Comparative Example 5

[0143] (1) 0.007 mol of FeC2O4.2H2O was wetted with 5 mL of water at room temperature, and was uniformly dispersed by magnetic stirring (no requirement for rotation speed) ;

[0144] (2) A H2O2 solution with a concentration of 1 mol / L was prepared using deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to a molar ratio of H2O2 to FeC2O4.2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and was manually added at a time control of 10 min, and magnetic stirring was performed during the adding process.

[0145] (3) according to the molar ratio of KOH to FeC2O4·2H2O of 0.007 mol:0.007 mol, a certain amount of prepared KOH solution (14 mL) and anhydrous ethanol (28 mL) were mixed in a volume ratio of 1:2 to obtain a mixed solution, the mixed solution was slowly added to the solution obtained in (2), manual addition, the time was controlled for 25 min, magnetic stirring was carried out during the addition process, and after the addition was completed, aging was carried out for 1 h.

[0146] (4) the reaction solution obtained in the step (3) was washed by deionized water centrifugation (6500 rpm, the same below) until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80℃ for 2-4 h. Yellow powder product was obtained. Figure 24 The XRD pattern of the powder product prepared in the present application Comparative Example 5. As can be seen from Comparative Example 1 and Comparative Example 5, when the molar ratio of KOH to FeC2O4·2H2O is less than the protection scope of the present application, γ-Fe2O3 cannot be obtained.

[0147] Comparative Example 6

[0148] (1) 0.007 mol of FeC2O4·2H2O was added with 5 mL of water at room temperature to wet it, and magnetic stirring (speed not required) was carried out to make it uniformly dispersed;

[0149] (2) a 1 mol / L H2O2 solution was prepared with deionized water, and a certain amount of prepared H2O2 solution (10 mL) was taken according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, manual addition, the time was controlled for 10 min, and magnetic stirring was carried out during the addition process.

[0150] (3) according to the molar ratio of KOH to FeC2O4·2H2O of 0.084 mol:0.007 mol, a certain amount of prepared KOH solution (14 mL) and anhydrous ethanol (28 mL) were mixed in a volume ratio of 1:2 to obtain a mixed solution, the mixed solution was slowly added to the solution obtained in (2), manual addition, the time was controlled for 25 min, magnetic stirring was carried out during the addition process, and after the addition was completed, aging was carried out for 1 h.

[0151] (4) the reaction solution obtained in the step (3) was washed by deionized water centrifugation (6500 rpm, the same below) until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80℃ for 2-4 h, and black powder product was obtained. Figure 25 The XRD pattern of the powder product prepared in the present application Comparative Example 8. Figure 32SEM image of the powdered product prepared in Inventive Example 6. As can be seen from Comparative Example 1 and Inventive Example 6, when the molar ratio of KOH to FeC2O4.2H2O is greater than the scope of the present application, it is not possible to obtain nano-sized γ-Fe2O3.

[0152] Comparative Example 7

[0153] (1) At room temperature, 0.007 mol of FeC2O4.2H2O was wetted with 5 mL of water and subjected to magnetic stirring (no requirement for the rotation speed) to disperse it uniformly;

[0154] (2) A 4 mol / L H2O2 solution was prepared using deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to a molar ratio of H2O2 to FeC2O4.2H2O of 0.04 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the addition was performed manually, with the time controlled to be 10 min, and magnetic stirring was performed during the addition.

[0155] (3) A certain amount of KOH solution (14 mL) was taken according to a molar ratio of KOH to FeC2O4.2H2O of 0.014 mol:0.007 mol, and mixed with anhydrous ethanol (28 mL) according to a volume ratio of 1:2 to obtain a mixed solution, which was slowly added to the solution obtained in (2), and the addition was performed manually, with the time controlled to be 25 min, and magnetic stirring was performed during the addition. After the addition was completed, the solution was aged for 1 h.

[0156] (4) The reaction solution obtained in (3) was washed by centrifugation (6500 rpm, the same below) using deionized water until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80°C for 2-4 h. A brown powdered product was obtained. Figure 26 XRD image of the powdered product prepared in Inventive Example 7. As can be seen from Comparative Example 1 and Inventive Example 7, when the molar ratio of H2O2 to FeC2O4.2H2O is greater than the scope of the present application, it is not possible to obtain nano-sized γ-Fe2O3.

[0157] Comparative Example 8

[0158] (1) At room temperature, 0.007 mol of FeC2O4.2H2O was wetted with 5 mL of water and subjected to magnetic stirring (no requirement for the rotation speed) to disperse it uniformly;

[0159] (2) A 0.01 mol / L H2O2 solution was prepared using deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to a molar ratio of H2O2 to FeC2O4.2H2O of 0.0001 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the addition was performed manually, with the time controlled to be 10 min, and magnetic stirring was performed during the addition.

[0160] (3) Take a certain amount of KOH solution (14 mL) prepared according to the molar ratio of KOH to FeC2O4·2H2O of 0.014 mol:0.007 mol and mix with anhydrous ethanol (28 mL) according to the volume ratio of 1:2 to obtain a mixed solution, slowly drop the mixed solution into the solution obtained in (2), manually drop, control the time for 25 min, and perform magnetic stirring during the dropping process. After the dropping process is completed, age for 1 h.

[0161] (4) Centrifuge (6500 rpm, the same below) the reaction solution obtained in the step (3) with deionized water until the pH of the supernatant is 7, dry the precipitate in a blast drying oven at 80°C for 2-4 h to obtain a black powder product. Figure 27 The XRD pattern of the powder product prepared in the present application Comparative Example 7 is shown in FIG. 6. As can be seen from Comparative Example 1 and Comparative Example 8, when the molar ratio of H2O2 to FeC2O4·2H2O is less than the protection scope of the present application, nano γ-Fe2O3 cannot be obtained.

[0162] Comparative Example 9

[0163] (1) Wet 0.0007 mol of FeC2O4·2H2O with 5 mL of water at room temperature, and perform magnetic stirring (no requirement for the rotation speed) to make it uniformly dispersed;

[0164] (2) Prepare a 0.1 mol / L H2O2 solution with deionized water, and take a certain amount of the prepared H2O2 solution (10 mL) according to the molar ratio of H2O2 to FeC2O4·2H2O of 0.001 mol:0.0007 mol. Slowly drop the H2O2 solution into the ferrous oxalate system, manually drop, control the time for 10 min, and perform magnetic stirring during the dropping process.

[0165] (3) Take a certain amount of Ca(OH)2 solution (70 mL) prepared according to the molar ratio of Ca(OH)2 to FeC2O4·2H2O of 0.0014 mol:0.0007 mol, and slowly drop the Ca(OH)2 solution into the solution obtained in (2), manually drop, control the time for 25 min, and perform magnetic stirring during the dropping process. After the dropping process is completed, age for 1 h.

[0166] (4) Centrifuge (6500 rpm, the same below) the reaction solution obtained in the step (3) with deionized water until the pH of the supernatant is 7, dry the precipitate in a blast drying oven at 80°C for 2-4 h to obtain a white powder product. Figure 28 The XRD pattern of the powder product prepared in the present application Comparative Example 9 is shown in FIG. 7. As can be seen from Comparative Example 1 and Comparative Example 9, when Ca(OH)2 is used as the alkali solution, nano γ-Fe2O3 cannot be prepared.

[0167] Comparative Example 10

[0168] (1) 0.007 mol of FeC2O4.2H2O was wetted with 5 mL of water and stirred magnetically (no speed requirement) to disperse uniformly;

[0169] (2) A H2O2 solution with a concentration of 1 mol / L was prepared using deionized water, and a certain amount of the prepared H2O2 solution (10 mL) was taken according to the molar ratio of H2O2 to FeC2O4.2H2O of 0.01 mol:0.007 mol. The H2O2 solution was slowly added to the ferrous oxalate system, and the dropping was manually controlled for 10 min, and magnetic stirring was performed during the dropping process.

[0170] (3) Ammonia water (14 mL) was mixed with anhydrous ethanol (28 mL) according to the volume ratio of 1:2 to obtain a mixed solution according to the molar ratio of NH4OH in ammonia water to FeC2O4.2H2O of 0.014 mol:0.007 mol, and the mixed solution was slowly added to the solution obtained in (2), and the dropping was manually controlled for 25 min, and magnetic stirring was performed during the dropping process. After the dropping was completed, the solution was aged for 1 h.

[0171] (4) The reaction solution obtained in step (3) was washed by centrifugation (6500 rpm, the same below) with deionized water until the pH of the supernatant was 7, and the precipitate was dried in a blast drying oven at 80°C for 2-4 h to obtain a yellow powder. Figure 29 The XRD pattern of the powder product prepared in Comparative Example 10 of the present application. As can be seen from Comparative Example 1 and Comparative Example 10, when ammonia water is used as the alkali solution, it is impossible to prepare nano γ-Fe2O3.

[0172] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for preparing nanosized γ-Fe2θ3, characterized in that, The method comprises the following steps: mixing ferrous oxalate and an aqueous hydrogen peroxide solution to perform an oxidation reaction, to obtain an oxidation reaction solution, wherein the molar ratio of the hydrogen peroxide to the ferrous oxalate is 0.01-0.03:0.007; mixing the oxidation reaction solution with an alkaline solution and aging, to obtain the nano γ-Fe2O3; the alkaline solution comprises an alkali metal hydroxide, an organic dispersant and water.

2. The method of claim 1, wherein the compound is prepared by the method of claim 1. The alkali metal hydroxide comprises KOH and / or NaOH.

3. The method according to claim 1 or 2, characterized in that The molar ratio of the alkali metal hydroxide to the ferrous oxalate is 0.014-0.07:0.

007.

4. The production method according to claim 1, characterized by, The organic dispersant comprises one or more of ethanol, N,N-dimethylacetamide, N-methylpyrrolidone and N,N-diethylacetamide.

5. The production method according to claim 1 or 4, characterized by, The alkaline solution is obtained by mixing an aqueous alkali metal hydroxide solution and an organic dispersant; the molar concentration of the aqueous alkali metal hydroxide solution is 1-5 mol / L, the volume ratio of the organic dispersant to the aqueous alkali metal hydroxide solution is (0-2):1, and the volume ratio is not 0.

6. The method of claim 1, wherein, The aging temperature is 20-80 ℃, and the aging time is 1-2 h.

7. The preparation method according to claim 1, characterized in that, After the aging, an alkaline reaction solution is obtained; after the aging, the alkaline reaction solution is sequentially subjected to solid-liquid separation, water washing and drying, to obtain the nano γ-Fe2O3; the drying temperature is 60-80 ℃, and the drying time is 2-4 h.

8. The method of claim 1, wherein, The molar concentration of the aqueous hydrogen peroxide solution is 0.01-3 mol / L.

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