A method for preparing NaFeO2 under alkaline conditions

Abstract

The invention discloses a method for preparing NaFeO2 under alkaline conditions, comprising S1: adding a certain amount of sodium hydroxide to a persulfate solution, mixing uniformly, and filtering after standing under an alkaline environment. The filtered solution is transferred to a three-necked flask, a trivalent iron salt is added to the three-necked flask, and then constant-temperature heating is performed at 100°C for 180 minutes. Fe(OH)3 precipitates are removed by centrifugation to obtain a green filtrate of Fe; S2: under normal pressure and a temperature of 15-20°C, the green filtrate of Fe obtained in S1 is recrystallized. When green crystals are precipitated and the volume of the filtrate is reduced by half, concentration is stopped, and then filtering and washing are performed to obtain triferrate NaFeO2. Finally, the triferrate NaFeO2 is dried at low temperature for standby use. The method for preparing NaFeO2 under alkaline conditions disclosed in the present invention uses trivalent iron salt as a raw material, can prepare NaFeO2 only under normal pressure and 100°C, does not require continuous introduction of argon, has relatively low cost, simple steps, and is suitable for large-scale production and promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of NaFeO2 preparation, and in particular to a method for preparing NaFeO2 under alkaline conditions. Background Art

[0002] Ferrite is a commonly used water treatment agent, used to remove pollutants such as heavy metal ions, ammonia nitrogen, and organic matter from water. It can remove pollutants through adsorption, precipitation, and ion exchange, achieving water purification. Furthermore, ferrite plays an important role in catalysis. For example, it can be used as a catalyst to promote oxidation and cyclization reactions. In summary, ferrite has broad application prospects in water treatment, sewage treatment, industrial wastewater treatment, and other fields.

[0003] The current method for preparing the triferrite NaFeO2 requires high-temperature grinding of a mixture of Fe2O3 and Na2O2 powders in an agate mortar to uniformly mix the two. The mixture is then heated at 650°C for 12 hours under an argon flow to finally prepare NaFeO2. The existing method requires continuous flow of argon, and the preparation requires high temperatures, high energy consumption, and complex steps. As a result, the cost of preparing NaFeO2 is high, making it unsuitable for large-scale production. Summary of the Invention

[0004] The present invention provides a method for preparing NaFeO2 under alkaline conditions to solve the above problems.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] A method for preparing NaFeO2 under alkaline conditions comprises the following steps:

[0007] S1: Add a certain amount of sodium hydroxide to the persulfate solution, mix well, let it stand in an alkaline environment, and then filter it. The filtered solution is transferred to a three-necked flask, and trivalent iron salt is added to the three-necked flask. Then, the solution is heated at 100°C for 180 minutes. The Fe (OH) 3 precipitate is removed by centrifugation to obtain a green filtrate containing Fe;

[0008] S2: Under normal pressure and temperature of 15-20°C, the green filtrate of Fe obtained in S1 is recrystallized. When green crystals are precipitated and the volume of the filtrate is reduced by half, the concentration is stopped, and then the filtrate is filtered and washed to obtain triferrite NaFeO2. Finally, the triferrite NaFeO2 is dried at low temperature for use.

[0009] Furthermore, in step S1, the trivalent iron salt is ferric sulfate.

[0010] Furthermore, the molar ratio of the persulfate to the ferric salt is 4:3.

[0011] Furthermore, the persulfate is sodium peroxodisulfate.

[0012] Furthermore, in step S1, the alkaline environment is a strong alkaline environment.

[0013] Furthermore, in step S2, the washing operation is to sequentially wash the crude triferrite obtained by filtration using n-hexane and methanol.

[0014] Furthermore, in step S2, the recrystallization time is not less than 1 hour.

[0015] Furthermore, in step S2, the low-temperature drying treatment is: drying treatment at 70°C for no less than 1 hour.

[0016] Furthermore, in step S1, the standing time is 10-15 minutes.

[0017] The present invention sequentially uses n-hexane and methanol to wash the crude NaFeO2 to remove impurities. The n-hexane can remove organic matter in the NaFeO2, and the methanol can remove excess alkali in the NaFeO2.

[0018] The beneficial effects of the present invention are:

[0019] The present invention discloses a method for preparing NaFeO2 under alkaline conditions. The method uses a trivalent iron salt as a raw material, adds sodium persulfate and sodium hydroxide to mix, and makes the entire reaction system strongly alkaline. The method can prepare NaFeO2 only at a relatively low temperature and normal pressure, has low energy consumption, and does not require continuous introduction of argon gas, so the cost is relatively low. The method has simple steps and is suitable for large-scale production and promotion. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] The preparation principle of this method is:

[0022] In an alkaline environment, the mixture is heated at a constant temperature of 100°C for 180 minutes. Under the action of peroxydisulfate, trivalent ferric sulfate is converted into NaFeO2.

[0023] S2O82- + 2Fe 3+ + 12OH - = 2FeO3 2- + 2SO4 2- + 6 H2O

[0024] FeO3 2- + H2O = FeO2 - + 2OH -

[0025] Example 1

[0026] A method for preparing ferrate under alkaline conditions comprises the following steps:

[0027] S1: Add 3.57g Na2S2O8 and 25g NaOH to 100mL deionized water, stir thoroughly, let stand for 10 minutes, and then filter. Transfer the filtered solution to a three-necked flask, then add 8g ferric sulfate to the three-necked flask, place the three-necked flask in a water bath, and heat at a constant temperature of 100℃ for 180min. Then, remove the Fe(OH)3 precipitate by centrifugation to obtain a green solution of Fe, expressed as NaFeO2.

[0028] S2: The green solution of Fe was recrystallized and concentrated at atmospheric pressure and 15°C. The concentration process was stopped when the volume of the filtrate was reduced by half. After filtration, the filtered green crystals were thoroughly washed with deionized water, methanol, and n-hexane. The treated crystals were placed in a vacuum drying oven and dried at low temperature to obtain NaFeO2. The NaFeO2 yield reached 55.32%.

[0029] Example 2

[0030] A method for preparing ferrate under alkaline conditions comprises the following steps:

[0031] S1: Add 7.14g Na2S2O8 and 15g NaOH to 100mL deionized water, stir thoroughly, let stand for 10 minutes, and then filter. Transfer the filtered solution to a three-necked flask, then add 8g ferric sulfate to the three-necked flask, place the three-necked flask in a water bath, and heat at a constant temperature of 100℃ for 180min. Then, remove the Fe(OH)3 precipitate by centrifugation to obtain a green Fe solution, expressed as NaFeO2.

[0032] S2: The green solution of Fe was recrystallized and concentrated at atmospheric pressure and 15°C. The concentration process was stopped when the volume of the filtrate was reduced by half. After filtration, the filtered green crystals were thoroughly washed with deionized water, methanol, and n-hexane. The treated crystals were placed in a vacuum drying oven and dried at low temperature to obtain NaFeO2. The NaFeO2 yield reached 54.71%.

[0033] Example 3

[0034] A method for preparing ferrate under alkaline conditions comprises the following steps:

[0035] S1: Add 3.57g Na2S2O8 and 15g NaOH to 100mL deionized water, stir thoroughly, let stand for 10 minutes, and then filter. Transfer the filtered solution to a three-necked flask, then add 8g ferric sulfate to the three-necked flask, place the three-necked flask in a water bath, and heat at a constant temperature of 100℃ for 180min. Then, remove the Fe(OH)3 precipitate by centrifugation to obtain a green solution of Fe, expressed as NaFeO2.

[0036] S2: The green solution of Fe was recrystallized and concentrated at atmospheric pressure and 15°C. The concentration process was stopped when the volume of the filtrate was reduced by half. After filtration, the filtered green crystals were thoroughly washed with deionized water, methanol, and n-hexane. The treated crystals were placed in a vacuum drying oven and dried at low temperature to obtain NaFeO2. The NaFeO2 yield reached 53.3%.

[0037] Compared with the ferrite preparation method in the prior art, the method of the present application does not require the continuous introduction of argon. By using ferric sulfate as the raw material and adding sodium persulfate and sodium hydroxide, the entire reaction system becomes strongly alkaline. NaFeO2 can be generated only under normal pressure and 100°C. In addition, ferric hydroxide precipitation is not easily generated during the NaFeO2 generation process. The method has low energy consumption, low cost and simple steps, and is suitable for large-scale industrial production.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing NaFeO2 under alkaline conditions, characterized in that: The following steps are involved: S1: Add a certain amount of sodium hydroxide to the persulfate solution, mix well, let it stand in a strong alkaline environment, and then filter it. The filtered solution is transferred to a three-necked flask, and ferric sulfate is added to the three-necked flask. Then, the mixture is heated at 100°C for 180 minutes. The Fe (OH) 3 precipitate is removed by centrifugation to obtain a green filtrate containing Fe; S2: Recrystallize the green filtrate of Fe obtained in S1 under normal pressure and temperature of 15-20°C. When green crystals precipitate and the volume of the filtrate is reduced by half, stop concentrating, then filter and wash to obtain triferrite NaFeO2, and finally dry the triferrite NaFeO2 at low temperature for later use; The molar ratio of the persulfate to the ferric sulfate is 4:3; The persulfate is sodium peroxydisulfate; In step S2, the washing operation is to wash the crude triferrite obtained by filtration with n-hexane and methanol in sequence; the low-temperature drying treatment is: drying at 70°C for no less than 1 hour.

2. The method for preparing NaFeO2 under alkaline conditions according to claim 1, wherein: In step S2, the recrystallization time is not less than 1 hour.

3. The method for preparing NaFeO2 under alkaline conditions according to claim 1, wherein: In step S1, the standing time is 10-15 minutes.