CN116040689A - Method for preparing alpha-Fe 2O3 powder with assistance of microwaves, alpha-Fe 2O3 powder and application thereof - Google Patents

Abstract

The invention discloses a microwave-assisted preparation method of alpha-Fe ₂ O ₃ Method for preparing powder, alpha-Fe ₂ O ₃ The method comprises mixing ferric salt solution with precipitant to obtain mixed solutionA body; reacting the mixed liquid under microwaves; collecting insoluble substances after the microwave reaction is finished to obtain alpha-Fe ₂ O ₃ And (3) powder. The invention expands the microwave-assisted preparation of alpha-Fe ₂ O ₃ The preparation process does not need to heat any structure guiding or adjusting reagent, and a series of alpha-Fe with spherical morphology and average granularity less than 100nm is successfully prepared by controlling proper microwave heating temperature and reaction time by using different iron precursors and precipitants ₂ O ₃ And (3) powder. At the same time, the influence of temperature gradient and concentration segregation is eliminated based on microwave reaction, the alpha-Fe of the invention ₂ O ₃ The powder also has the characteristic of uniform particle size. alpha-Fe prepared by the invention ₂ O ₃ The powder can be applied to cosmetic-grade iron pigments or iron sources of biomedical iron nano materials.

Description

A microwave-assisted method for preparing α-Fe2O3 powder, α-Fe2O3 powder and its application

technical field

The invention relates to the technical field of inorganic chemistry and functional material preparation, in particular to a method for preparing α-Fe ₂ O ₃ powder assisted by microwaves, α-Fe ₂ O ₃ powder and application thereof.

Background technique

α-Fe ₂ O ₃ is a deep red powder, commonly known as iron red, with a hexagonal corundum structure, O ² - arranged in a hexagonal close-packed arrangement, Fe ³⁺ is between the oxygen ion layers, but only fills two-thirds of the eight Surface voids. α-Fe ₂ O ₃ belongs to the rhombohedral crystal system, the space group is R-3c structure, and the lattice constants are: a=0.50349nm, c=1.3752nm. α-Fe ₂ O ₃ is the most stable iron oxide phase at room temperature. It has the characteristics of non-toxic, environmentally friendly, low price, and high thermal stability. It is mainly used in lithium-ion battery anode materials, radar absorbing materials, photocatalysis, Biomedical engineering, gas-sensitive materials, adsorbents and other fields. As a functional material, α-Fe ₂ O ₃ has high potential application value and broad application prospect, and is of great research and development value.

The traditional preparation methods of α-Fe ₂ O ₃ include solid method, hydro(solvo) thermal method, chemical precipitation method, sol-gel method, thermal decomposition method and so on. Although the solid method has the advantages of large amount of one-time treatment and simple operation, the obtained nano-powder has uneven particle size, low purity, unstable performance, and is difficult to prepare nano-scale iron oxide powder; water (solvent) thermal method The crystal structure and morphology of nanoparticles can be adjusted by changing the experimental conditions, and it is easy to obtain products with high purity, good dispersion and uniform particle size. It is also one of the most widely used methods for synthesizing nano-iron oxide; chemical precipitation method It belongs to the liquid phase method, and the operation is relatively simple. The surface of the powder can be modified by adding a surfactant to improve the dispersibility of the powder and effectively control the particle size of the powder. The sol-gel method is based on the hydrolysis and polycondensation of metal alkoxides. The resulting products have high purity and good quality, and are easy to coat on various carriers, but the output is small and the operation is complicated. The thermal decomposition method can prepare ultra-fine particle size powder, but there are few types of decomposition precursors and high temperature is required.

There are also some methods that use microwaves to quickly prepare α-Fe ₂ O ₃ powders. For example, CN106587165A discloses a shuttle-shaped α-Fe ₂ O ₃ powder and its preparation method. Fe ₂ (SO ₄ ) ₃ and Na ₂ SO ₄ was used as the raw material to prepare iron solution, and then the pH value was adjusted with NaOH solution to obtain the precursor solution, and the α-Fe ₂ O ₃ powder with nano-spindle structure was synthesized in one step by microwave hydrothermal method. This method can be quickly prepared Shuttle-shaped α-Fe ₂ O ₃ with a length of 50-400nm and an end face size of 20-50nm; CN103073065A discloses a method for preparing α-Fe ₂ O ₃ nanospheres, using ferric chloride hexahydrate as an iron source, Urea is a hydroxide ion initiator dissolved in a mixed solvent of glycerin and water, and microwave hydrothermally prepares α-Fe ₂ O ₃ nanospheres. This method has the advantages of fast reaction time and environmental protection, and can prepare average diameters of 300-500nm, The overall structure consists of α-Fe ₂ O ₃ nanospheres of rod-like nano-subunits with a size of about 20-50 nm.

It can be seen that microwave-assisted α-Fe ₂ O ₃ powder can be rapidly prepared and the morphology of α-Fe ₂ O ₃ can be effectively adjusted by adding the corresponding structure directing agent. However, the current microwave-assisted α-Fe ₂ O ₃ powder method uses a single type of iron precursor, and it is difficult to prepare spherical α-Fe ₂ O ₃ powder without using a structure-directing agent and α-Fe ₂ O ₃ is larger in size. According to market feedback, the iron red currently sold in China mainly has the problems of coarse powder particle size, uneven distribution and high impurity content. High-end iron red still needs to rely on imports to prepare α-Fe with small particle size and high purity. ₂ O ₃ powder is still a huge problem. Therefore, it is urgent to provide a method for effectively preparing α-Fe ₂ O ₃ powder with small particle size by using microwave assistance.

Contents of the invention

In order to solve the problems existing in the prior art, the present invention designs a variety of iron precursors and suitable precipitants, and assists the microwave precipitation method to rapidly prepare ultrafine nano-α-Fe ₂ O ₃ . It is cheap, the reaction temperature is low, and the reaction time is short. The prepared α-Fe ₂ O ₃ powder has a uniform particle size and can be adjusted. It can be used as an iron source for cosmetic grade iron pigments or the most high-end iron nanomaterials.

In order to achieve the above object, the present invention provides a microwave-assisted method for preparing α-Fe ₂ O ₃ powder, comprising:

Mixing the iron salt solution with the precipitant to obtain a mixed liquid;

Reacting the mixed liquid under microwave;

After the microwave reaction, the insoluble matter was collected to obtain α-Fe ₂ O ₃ powder.

Further, said mixing the iron salt solution with the precipitating agent to obtain the mixed liquid includes,

According to the fact that the molar amount of the precipitating agent is 1-30 times of the molar amount of the iron salt in the iron salt solution, the precipitating agent is added to the 0.1-0.5 mol/L iron salt solution and mixed uniformly to obtain a mixed liquid.

Further, the iron salt solution is prepared by dissolving iron salt in water;

The iron salt includes at least one of ferric chloride hexahydrate, ferric sulfate, ferric nitrate nonahydrate, ferrous chloride tetrahydrate and ferrous sulfate heptahydrate.

Further, the precipitant includes at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium carbonate, ammonium bicarbonate, and ammonia water.

Further, the reaction under microwave comprises,

React at 100-250°C for 1-5h under microwave treatment.

Further, after the microwave reaction is completed, the insoluble matter is collected to obtain α-Fe ₂ O ₃ powder including,

After the microwave reaction, the insoluble matter was collected, washed with alcohol and water, and then dried to obtain the precursor powder;

The precursor powder is heat-treated under a protective gas to obtain α-Fe ₂ O ₃ powder.

Further, the heat treatment includes keeping the temperature at 600-900° C. for 10-90 minutes.

The present invention also provides an α-Fe ₂ O ₃ powder prepared according to the method.

Further, the shape of the α-Fe ₂ O ₃ powder is spherical, and the average particle size is less than 100 nm.

The present invention also provides the application of the α-Fe ₂ O ₃ powder, which is applied to the iron source of cosmetic-grade iron-based pigments or biomedical iron nanomaterials.

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

The present invention expands the selection of iron precursors and precipitants for microwave-assisted preparation of α-Fe ₂ O ₃ powders. The preparation process does not need to heat any structure-guiding or adjusting reagents, and uses different iron precursors and precipitants to control appropriate microwave heating. A series of α-Fe ₂ O ₃ powders with spherical shape and average particle size less than 100nm were successfully prepared by temperature and reaction time. At the same time, the influence of temperature gradient and concentration segregation is also eliminated based on the microwave reaction, and the α-Fe ₂ O ₃ powder of the present invention also has the characteristics of uniform particle size. The α-Fe ₂ O ₃ powder prepared by the invention can be applied to the iron source of cosmetic-grade iron-based pigments or biomedical iron nanomaterials.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and attained by the steps or procedures pointed out in the description and accompanying drawings.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 shows a kind of microwave-assisted preparation of the present invention α-Fe ₂ O ₃ The flow diagram of the method for powder;

Fig. 2 shows a scanning electron micrograph of the α-Fe ₂ O ₃ powder prepared in Example 1 of the present invention.

Detailed ways

Neither the endpoints of the ranges nor any values disclosed herein are limited to such precise ranges or values, and these ranges or values are understood to include values approaching these ranges or values. For numerical ranges, between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, these values Ranges should be considered as specifically disclosed in the present invention.

The design idea of the present invention is that, based on microwave reaction, the influence of temperature gradient and concentration segregation is eliminated and the reaction time is fast, a variety of suitable iron precursors and suitable precipitants are selected, and the conditions of microwave reaction are controlled. In the absence of any structure modifier or structure directing agent, an ultrafine structured α-Fe ₂ O ₃ powder is prepared. Therefore, the applicability and application scenarios of microwave-assisted preparation of α-Fe ₂ O ₃ powder are improved.

For this reason, as shown in Figure 1, the present invention provides a kind of microwave-assisted method for preparing α-Fe ₂ O ₃ powders, comprising the following steps,

S101. Mix the iron salt solution and the precipitating agent to obtain a mixed liquid.

In step S101, the precipitant is added to the 0.1-0.5 mol/L iron salt solution and mixed evenly to obtain a mixed liquid, assuming that the molar amount of the precipitant is 1-30 times that of the iron salt in the iron salt solution.

Preferably, the molar amount of the precipitation agent is 5-15 times that of the iron salt in the iron salt solution.

The iron salt solution is prepared by dissolving iron salts in water; the iron salts are inorganic iron salts, including ferric chloride hexahydrate, ferric sulfate, ferric nitrate nonahydrate, ferrous chloride tetrahydrate and sulfurous acid heptahydrate at least one of iron.

Preferably, the iron salt includes one of ferric chloride hexahydrate, ferric sulfate, ferric nitrate nonahydrate, ferrous chloride tetrahydrate and ferrous sulfate heptahydrate.

More preferably, the iron salt is one of ferric chloride hexahydrate, ferric sulfate and ferric nitrate nonahydrate.

The precipitant includes at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium carbonate, ammonium bicarbonate and ammonia water.

Preferably, the precipitant includes one of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium carbonate, ammonium bicarbonate and ammonia water.

More preferably, the precipitation agent is one of sodium bicarbonate, ammonium carbonate and sodium carbonate.

S102, reacting the mixed liquid under microwave.

In step S102, the reacting under microwave includes reacting under microwave treatment at 100-250° C. for 1-5 h.

Preferably, the microwave temperatures are 100°C, 150°C and 200°C.

More preferably, the microwave temperature is 150°C.

Preferably, the microwave time is 1h, 1.5h and 2h.

More preferably, the microwave time is 1.5h.

The reaction under the microwave is carried out in a microwave digestion tank.

S103. After the microwave reaction is completed, the insoluble matter is collected to obtain α-Fe ₂ O ₃ powder.

In step S103, after the microwave reaction is completed, the insoluble matter is collected, washed with alcohol and water, and then dried to obtain a precursor powder; the precursor powder is heat-treated under a protective gas to obtain α-Fe ₂ O ₃ powder.

The alcohol is selected as ethanol according to economy, environmental protection and safety.

The drying includes vacuum drying and conventional constant temperature drying.

The protective gas includes inert gas and nitrogen.

Preferably, the protective gas is argon or nitrogen.

The heat treatment includes keeping the temperature at 600-900° C. for 10-90 minutes.

Preferably, the heat treatment is carried out at a temperature of 700-800° C. for 20-60 minutes.

More preferably, the heat treatment temperature is 700°C, 750°C and 800°C, and the heat treatment time is 20min, 30min and 60min.

The following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the specific embodiments of the present invention and the accompanying drawings. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

A method for microwave-assisted preparation of α-Fe ₂ O ₃ powder, comprising the following steps,

Step 1, take ferric chloride hexahydrate and sodium bicarbonate, wherein, the molar weight of sodium bicarbonate is 5 times of the molar weight of ferric chloride hexahydrate; Ferric chloride hexahydrate is dissolved in water and is prepared as 1mol/L hexahydrate Ferric chloride hydrate solution; sodium bicarbonate is added to 1mol/L ferric chloride hexahydrate solution and mixed evenly under stirring to obtain a mixed solution.

Step 2. Transfer the mixed solution obtained in step 1 to a microwave digestion tank. The volume of the mixed solution does not exceed 2/3 of the volume of the microwave digestion tank; then transfer the microwave digestion tank to a microwave reactor and react with microwaves at a heating temperature of 100°C 1.5h; after the microwave reaction, cool the microwave digestion tank to room temperature naturally, filter to obtain a black precipitate, alternately wash with ethanol and deionized water for 3 times, and put it in a vacuum drying oven at 60°C for 3h to obtain the precursor powder;

Step 3. Put the precursor powder obtained in step 2 in a nitrogen atmosphere muffle furnace for heat treatment at 750° C. for 20 minutes, and take it out after natural cooling to room temperature to obtain a brick-red α-Fe ₂ O ₃ powder.

Figure 2 shows the scanning electron microscope image of the α-Fe ₂ O ₃ powder prepared in this example. It can be seen that the prepared α-Fe ₂ O ₃ powder has no agglomeration and has a relatively uniform spherical structure. According to the scanning electron microscope Results The average particle size of the α-Fe ₂ O ₃ powder in this example was less than 60 nm.

Example 2

A method for microwave-assisted preparation of α-Fe ₂ O ₃ powder, comprising the following steps,

Step 1, weigh ferric sulfate and ammonium carbonate, wherein, the molar weight of ammonium carbonate is 10 times of the molar weight of ferric sulfate; Ferric sulfate is dissolved in water and is prepared as 0.5mol/L ferric sulfate solution; Ammonium carbonate is added to 0.5mol /L ferric sulfate solution and mix evenly under stirring to obtain a mixed solution.

Step 2. Transfer the mixed solution obtained in step 1 to a microwave digestion tank. The volume of the mixed solution does not exceed 2/3 of the volume of the microwave digestion tank; then transfer the microwave digestion tank to a microwave reactor and react with microwaves at a heating temperature of 150°C 1.5h; after the microwave reaction, cool the microwave digestion tank to room temperature naturally, filter to obtain a black precipitate, alternately wash with ethanol and deionized water for 3 times, and put it in a vacuum drying oven at 60°C for 3h to obtain the precursor powder;

Step 3. Put the precursor powder obtained in step 2 in a nitrogen atmosphere muffle furnace for heat treatment at 700° C. for 60 minutes, and take it out after natural cooling to room temperature to obtain a brick-red α-Fe ₂ O ₃ powder.

According to the results of the scanning electron microscope, the α-Fe ₂ O ₃ powder of this embodiment does not agglomerate, has a relatively uniform spherical structure and an average particle size of less than 80 nm.

Example 3

A method for microwave-assisted preparation of α-Fe ₂ O ₃ powder, comprising the following steps,

Step 1, take ferric nitrate nonahydrate solution and sodium carbonate, wherein, the molar weight of sodium bicarbonate is 15 times of the molar weight of ferric nitrate nonahydrate; Ferric chloride hexahydrate is dissolved in water and prepared as 1.5mol/L hexahydrate Ferric chloride solution: Add sodium carbonate to 1.5mol/L ferric chloride hexahydrate solution and mix evenly under stirring to obtain a mixed solution.

Step 2. Transfer the mixed solution obtained in step 1 to a microwave digestion tank. The volume of the mixed solution does not exceed 2/3 of the volume of the microwave digestion tank; then transfer the microwave digestion tank to a microwave reactor and react with microwaves at a heating temperature of 200°C 1.5h; After the microwave reaction, cool the microwave digestion tank to room temperature naturally, filter to obtain an orange-red precipitate, wash with ethanol and deionized water alternately for 3 times, and put it in a vacuum drying oven at 60°C for 3 hours to obtain the precursor powder;

Step 3. Put the precursor powder obtained in step 2 in a nitrogen atmosphere muffle furnace for heat treatment at 800° C. for 30 minutes, and take it out after natural cooling to room temperature to obtain a brick-red α-Fe ₂ O ₃ powder.

According to the results of the scanning electron microscope, the α-Fe ₂ O ₃ powder of this embodiment does not have agglomeration, has a relatively uniform spherical structure and an average particle size of less than 100 nm.

Table 1 summarizes the iron precursors, precipitation agents, microwave reaction conditions and product characteristics of Examples 1-3.

Table 1 embodiment 1-3 comparative result

As can be seen from Table 1, in the embodiment of the present invention, a series of ultrafine (less than 100nm) particles with different particle sizes were successfully prepared by selecting suitable precipitants with different iron precursors and adjusting the appropriate microwave reaction temperature and time. α-Fe ₂ O ₃ powder.

In summary, the present invention eliminates the influence of temperature gradient and concentration segregation based on the microwave reaction and has the advantages of fast reaction time, selects a variety of suitable iron precursors and suitable precipitants, and controls the conditions of the microwave reaction. In the case of any structure regulator or structure directing agent, a series of α-Fe ₂ O ₃ powders with spherical morphology and an average particle size of less than 100 nm were prepared. Such fine-grained α-Fe ₂ O ₃ powder can be applied to cosmetic-grade iron-based pigments or iron sources of biomedical iron nanomaterials. The whole process of the invention is simple, the source of raw materials is wide and does not contain any toxic and harmful reagents, and the invention has strong applicability and good application prospect.

Finally, it should be noted that: the above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still It is possible to modify the technical solutions recorded in the foregoing embodiments, or to perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. within the spirit and principles of the present invention shall be included in the within the protection scope of the present invention.

Claims (10)

1. A microwave-assisted method for preparing α-Fe ₂ O ₃ powders, characterized in that, comprising, Mixing the iron salt solution with the precipitant to obtain a mixed liquid; Reacting the mixed liquid under microwave; After the microwave reaction, the insoluble matter was collected to obtain α-Fe ₂ O ₃ powder. 2. The microwave-assisted preparation of α-Fe according to claim ₁ The method for O ₃ powders is characterized in that the mixing of the iron salt solution and the precipitating agent to obtain the mixed liquid comprises, According to the fact that the molar amount of the precipitating agent is 1-30 times of the molar amount of the iron salt in the iron salt solution, the precipitating agent is added to the 0.1-0.5 mol/L iron salt solution and mixed uniformly to obtain a mixed liquid. 3. The method for microwave-assisted preparation of α-Fe ₂ O ₃ powder according to claim 1, wherein the iron salt solution is prepared by dissolving iron salt in water; The iron salt includes at least one of ferric chloride hexahydrate, ferric sulfate, ferric nitrate nonahydrate, ferrous chloride tetrahydrate and ferrous sulfate heptahydrate. 4. microwave according to claim 1 is assisted to prepare α-Fe ₂ O ₃ methods of powder, it is characterized in that, described precipitation agent comprises sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium carbonate, ammonium bicarbonate, At least one of ammonia water. 5. microwave-assisted preparation of α-Fe according to claim ₁ The method of O ₃ powders, characterized in that the reaction under microwaves comprises, React at 100-250°C for 1-5h under microwave treatment. 6. The method for microwave-assisted preparation of α-Fe ₂ O ₃ powder according to any one of claims 1-5, characterized in that, after the microwave reaction ends, the insoluble matter is collected to obtain α-Fe ₂ O ₃ powder include, After the microwave reaction, the insoluble matter was collected, washed with alcohol and water, and then dried to obtain the precursor powder; The precursor powder is heat-treated under a protective gas to obtain α-Fe ₂ O ₃ powder. 7 . The method for preparing α-Fe ₂ O ₃ powder assisted by microwaves according to claim 6 , wherein the heat treatment includes keeping the temperature at 600-900° C. for 10-90 minutes. 8. An α-Fe ₂ O ₃ powder, characterized in that it is prepared according to any one of claims 1-5 or the method of claim 7. 9. The α-Fe ₂ O ₃ powder according to claim 8, characterized in that the shape is spherical and the average particle size is less than 100 nm. 10. An application of the α-Fe ₂ O ₃ powder according to claim 8, characterized in that it is used as an iron source for cosmetic-grade iron-based pigments or biomedical iron nanomaterials.

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