A method for preparing ferrate under acidic conditions
The acidic oxidation of trivalent iron salts with persulfate salts addresses the hazards and inefficiencies of chlorate-based ferrate production, achieving high yield and purity ferrate production through controlled crystallization and solvent purification.
Patent Information
- Application Number
- CN202311081410.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-25
- Publication Date
- 2025-07-15
- Estimated Expiration
- 2043-08-25
AI Technical Summary
The traditional ferrate preparation method has safety hazards and equipment corrosion problems, and the raw material utilization rate is low, so hypochlorite oxidation method is prone to precipitation during the production process.
The persulfate oxidation method is used under acidic conditions, and the reaction of trivalent iron salt with persulfate and silver nitrate under acidic conditions is carried out to prepare ferrate salt, avoid the use of chlorine, and remove impurities through n-hexane and methanol washing, improving the purity and raw material utilization rate.
The efficient and safe preparation of ferrate is achieved, which reduces the harm to the environment and equipment, improves the utilization rate of raw materials and product purity, with a yield of more than 83% and a purity of more than 92%.
Abstract
Description
Technical Field
[0001] The present invention relates to the field of preparation of ferrates, and particularly to a method for preparing ferrates under acidic conditions. Background Art
[0002] Ferrates are hexavalent iron salts, which have strong oxidizing properties across the entire pH range. Their oxidizing properties can be utilized to remove pollutants such as ammonia nitrogen, algae, heavy metals, antibiotic drugs, and endocrine disruptors in water. Through redox reactions, hexavalent iron is reduced to trivalent iron, forming iron hydroxide in water, which has good coagulation, flocculation, and adsorption effects on suspended solids, colloids, and organic matter in water. As a strong oxidizing agent, ferrates also have good bactericidal capabilities. Compared with chlorine disinfection, their greatest advantage is that they do not produce chlorinated disinfection by-products that are toxic to humans. Therefore, ferrates are known as green water treatment agents that combine oxidation, coagulation, flocculation, adsorption, and disinfection, and have broad application prospects.
[0003] The traditional method for preparing ferrates is the hypochlorite oxidation method. However, during the production process, to ensure the content of hypochlorite, chlorine gas needs to be continuously introduced into the sodium hydroxide solution. Due to the toxicity and corrosiveness of chlorine gas, high requirements are placed on the airtightness and corrosion resistance of the equipment, which easily causes safety accidents. Moreover, precipitation occurs during the production of ferrates, resulting in a relatively low utilization rate of raw materials. Summary of the Invention
[0004] Aiming at the problem of the easy generation of hazards during the preparation of ferrates by the hypochlorite oxidation method in the prior art, the present invention provides a method for preparing ferrates under acidic conditions. Ferrates are prepared by oxidizing persulfate under acidic conditions, which has less harm to the environment and equipment, a high utilization rate of raw materials, high productivity, and high purity.
[0005] To achieve the above object, the technical solution of the present invention is: A method for preparing ferrates under acidic conditions, comprising the following steps:
[0006] S1: Using a trivalent iron salt as a raw material, adding the trivalent iron salt, persulfate, and silver nitrate to deionized water and mixing evenly, then carrying out constant-temperature heating at 35°C until the mixed solution completely turns dark purple, and then placing it in an ice-water bath to obtain crystal precipitates;
[0007] S2: Dissolving the crystal precipitates prepared in step S1 with a 3 mol / L potassium sulfate solution and filtering to obtain a filter cake and a filtrate; the filtrate is placed in an ice-water bath for cooling and recrystallization, controlling the recrystallization temperature to be 0 - 5°C, and then filtering and washing to obtain ferrate K2FeO4. Finally, the obtained ferrate K2FeO4 is dried and reserved for use.
[0008] Further, the trivalent iron salt is ferric sulfate, ferric chloride, or ferric nitrate.
[0009] Further, the mass ratio of the persulfate to silver nitrate is 27:1.
[0010] Further, in step S1, the persulfate is sodium persulfate or potassium persulfate.
[0011] Further, the purity of the ferrate K2FeO4 is greater than 90%.
[0012] Further, in step S2, the washing operation is to wash the crude ferrate obtained by filtration with n-hexane and methanol in sequence.
[0013] Further, in step S2, the recrystallization time is not less than 1 hour.
[0014] Further, in step S2, the low-temperature drying treatment is: under the condition of 60°C, the drying treatment is not less than 1 hour.
[0015] In summary, the present invention has the following beneficial effects:
[0016] In this application, ferric salt is used as a raw material. At different reaction temperatures, potassium persulfate and silver nitrate are added to deionized water and mixed evenly to make the whole reaction system acidic. The mixed solution of potassium persulfate, silver nitrate and ferric salt is placed in a water bath and heated at a constant temperature to make the three react fully, oxidizing the ferric salt into ferrate. The obtained ferrate solution is placed in an ice bath at 0°C for crystallization and precipitation. The crude product is dissolved with 3 mol / L potassium sulfate, filtered, and the recrystallization temperature is controlled to obtain a ferrate solid. The ferrate crystals are obtained by repeatedly filtering and rinsing with n-hexane and methanol. Finally, the ferrate is dried at a low temperature to obtain a ferrate solid. Compared with the hypochlorite oxidation method, this method has less harm to the environment and equipment, and higher raw material utilization rate and product purity; the yield of K2FeO4 prepared by this method reaches more than 83%, and the purity reaches more than 92%.
[0017] In the present invention, n-hexane and methanol are used to wash the crude ferrate in sequence. Its function is to remove impurities. N-hexane can remove the organic matter in the ferrate, and methanol can remove the excess alkali in the ferrate. Specific Embodiments
[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0019] The reaction principle involved in this application is as follows:
[0020]
[0021] Na2FeO4 + K2SO4 = K2FeO4 + Na2SO4
[0022] Examples
[0023] Example 1
[0024] A method for preparing ferrate under acidic conditions, comprising the following steps:
[0025] S1: Add 2.7 g of Na2S2O8 and 0.1 g of AgNO3 to 200 mL of deionized water, and stir well. Then add 2 g of ferric sulfate to the solution, place it in a water bath, and heat it at a constant temperature of 35 °C for 1 h. Observe that the color of the solution turns dark purple, indicating a Na2FeO4 solution. Place the Na2FeO4 solution in ice water at 0 °C, and crystals will precipitate after 40 min.
[0026] S2: Dissolve the crystal precipitate obtained in step S1 with 3 mol / L potassium sulfate, filter, cool the filtrate with an ice water bath, and control the recrystallization temperature at 5 °C. Filter and rinse the crystals 4 times with 25 mL of n-hexane and 10 mL of methanol. Dry the obtained K2FeO4 crystals in a vacuum oven at 60 °C for 2 h. The yield of K2FeO4 reaches 83.6%, and the purity is above 90%.
[0027] Example 2
[0028] A method for preparing ferrate under acidic conditions, comprising the following steps:
[0029] S1: Add 4.05 g of Na2S2O8 and 0.1 g of AgNO3 to 200 mL of deionized water, and stir well. Then add 2 g of ferric sulfate to the solution, place it in a water bath, and heat it at a constant temperature of 35 °C for 1 h. Observe that the color of the solution turns dark purple, indicating a Na2FeO4 solution. Place the Na2FeO4 solution in ice water, and crystals will precipitate after 40 min.
[0030] S2: Dissolve the crystal precipitate obtained in step S1 with 3 mol / L potassium sulfate, filter, cool the filtrate with an ice water bath, and control the recrystallization temperature at 5 °C. Filter and rinse the crystals 4 times with 25 mL of n-hexane and 10 mL of methanol. Dry the obtained K2FeO4 crystals in a vacuum oven at 60 °C for 2 h. The yield of K2FeO4 reaches 83.1%, and the purity is above 92%.
[0031] Example 3
[0032] A preparation method of ferrate under acidic conditions, comprising the following steps:
[0033] S1: Add 4.05 g of Na2S2O8 and 0.4 g of AgNO3 to 200 mL of deionized water, and stir well. Then add 2 g of ferric sulfate to the solution, place it in a water bath, and heat it at a constant temperature of 35 °C for 1 h. Observe that the color of the solution turns dark purple, indicating a Na2FeO4 solution. Place the Na2FeO4 solution in ice water, and crystals will precipitate after 40 min.
[0034] S2: Dissolve the crystal precipitate obtained in step S1 with 3 mol / L potassium sulfate, filter, cool the filtrate with an ice water bath, and control the recrystallization temperature at 5 °C. Filter and rinse the crystals 4 times with 25 mL of n-hexane and 10 mL of methanol. Dry the obtained K2FeO4 crystals in a vacuum oven at 60 °C for 2 h. The yield of K2FeO4 reaches 84.1%, and the purity is above 92%.
[0035] Example 4
[0036] A preparation method of ferrate under acidic conditions, comprising the following steps:
[0037] S1: Add 4.05 g of Na2S2O8 and 0.1 g of AgNO3 to 200 mL of deionized water, and stir well. Then add 2 g of ferric sulfate to the solution, place it in a water bath, and heat it at a constant temperature of 50 °C for 1 h. Observe that the color of the solution turns dark purple, indicating a Na2FeO4 solution. Place the Na2FeO4 solution in ice water, and crystals will precipitate after 40 min.
[0038] S2: Dissolve the crystal precipitate obtained in step S1 with 3 mol / L potassium sulfate, filter, cool the filtrate with an ice water bath, and control the recrystallization temperature at 0 °C. Filter and rinse the crystals 4 times with 25 mL of n-hexane and 10 mL of methanol. Dry the obtained K2FeO4 crystals in a vacuum oven at 60 °C for 2 h. The yield of K2FeO4 reaches 83.2%, and the purity is above 93%.
[0039] Comparative example
[0040] Preparation principle of hypochlorite oxidation method:
[0041] 3NaClO + 2Fe(NO3)3 + 10NaOH = 2Na2FeO4 + 3NaCl + 6NaNO3 + 5H2O
[0042] Na2FeO4 + 2KOH = K2FeO4 + 2NaOH
[0043] Production process of potassium ferrate: Mix 200 g of NaOH and 280 g of NaClO solution in a 1 L reactor, dropwise add 320 g / L Fe(NO3)3 solution, stir, and react for 2 h. Place the Na2FeO4 solution in ice water, and crystals will precipitate after 40 min. Filter, cool the filtrate in an ice water bath, add 10 g of potassium sulfate, and control the recrystallization temperature at 0 °C. Filter and rinse the crystals 4 times with 25 mL of n-hexane and 10 mL of methanol. Dry the obtained K2FeO4 crystals in a vacuum oven at 60 °C for 2 hours. The yield of K2FeO4 reaches 80.7%, and the purity is above 91%.
[0044] Compared with the traditional method for preparing ferrate, which is the hypochlorite oxidation method, the method of this application does not require continuous introduction of chlorine gas. By using ferric salt as the raw material and adding potassium persulfate and silver nitrate to deionized water and mixing at different reaction temperatures, the entire reaction system becomes acidic, and it is not easy to generate iron hydroxide precipitation during the production of ferrate, comprehensively improving the utilization rate of raw materials.
[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing ferrate under acidic conditions, characterized in that, It includes the following steps: S1: Using ferric salts as raw materials, adding ferric salts, sodium persulfate and silver nitrate into deionized water and mixing evenly, then carrying out constant temperature heating at 35 °C until the mixed solution completely turns dark purple, and then placing it in an ice-water bath to obtain crystal precipitates. The mass ratio of sodium persulfate to silver nitrate is 27:1; S2: Dissolving the crystal precipitates prepared in step S1 with 3 mol / L potassium sulfate solution and filtering to obtain filter cakes and filtrates; the filtrates are cooled and recrystallized in an ice-water bath, controlling the recrystallization temperature at 0-5 °C, then filtering and washing to obtain potassium ferrate K2FeO4. Finally, the obtained potassium ferrate K2FeO4 is dried and reserved for use; In step S2, the washing operation is to wash the crude potassium ferrate obtained by filtration with n-hexane and methanol in sequence.
2. The preparation method of ferrate under acidic conditions according to claim 1, characterized in that, The ferric salt is ferric sulfate, ferric chloride or ferric nitrate.
3. The preparation method of ferrate under acidic conditions according to claim 1, characterized in that, The purity of the potassium ferrate K2FeO4 is greater than 90%.
4. A method for preparing ferrate under acidic conditions according to claim 1, characterized in that, In step S2, the recrystallization time is not less than 1 hour.
5. A preparation method of ferrate under acidic conditions according to claim 1, characterized in that, In step S2, the drying treatment is: under the condition of 60 °C, the drying treatment is not less than 1 hour.