A K4FeO4 solid and its preparation method and application at room temperature

Abstract

The invention discloses a K4FeO4 solid and a preparation method and application thereof at room temperature. A method for preparing a K4FeO4 solid at room temperature comprises the following steps: S1: adding potassium hydroxide solid to a potassium ferrate K2FeO4 aqueous solution, so that the free alkali content in the solution is greater than 120mmol / L, and obtaining an alkaline potassium ferrate solution; S2: adding a trivalent iron salt solid to the alkaline potassium ferrate solution obtained in step S1, controlling the temperature at 15°C-25°C, reacting for 150min-240min and filtering, and the filtrate is a K4FeO4 solution; S3: vacuum concentrating the K4FeO4 solution obtained in step S2, cooling the concentrated solution to room temperature, and precipitating crystals; washing the obtained crystals with an organic solvent, and recrystallizing with water to obtain pure K4FeO4 crystals. The method for preparing a K4FeO4 solid at room temperature disclosed by the invention has the advantages of high yield, green environmental protection and low cost.

Description

Technical Field

[0001] The invention relates to the technical field of potassium ferrate production, and in particular to a K4FeO4 solid and a preparation method and application thereof at room temperature. Background Art

[0002] Potassium ferrate, an iron salt containing hexavalent iron ions, has many functions such as strong oxidation, sterilization, adsorption, flocculation, coagulant, decolorization, deodorization, etc. It is mainly used in water treatment and aquaculture. Since high-valent metal ion active substances have stronger resistance in complex water environment systems. At present, the main way to produce high-valent iron is from low-valent iron ions (such as Fe 2 + / Fe 3+ ) is oxidized to high-valent iron (Fe(VI)), and then reduced to high-valent iron (such as Fe(IV) / Fe(V)); or directly reduced to high-valent ferrate. However, the cost of these methods is relatively high, and the high-valent active substances produced are random, which leads to significant restrictions on the use of these methods.

[0003] Quadrivalent iron ions have a higher oxidizing power and can oxidize pollutants more strongly. At the same time, quadrivalent iron ions are more likely to form floccules in water environments and can more effectively precipitate pollutants. These characteristics make quadrivalent iron salts more advantageous in treating certain pollutants and have a wider range of application potential.

[0004] Currently, the preparation of tetravalent iron salt FeO4 4- The solid method is limited to the melting method, which requires high temperature and high pressure reaction, harsh reaction conditions, high production cost, and the product is a mixture of ferrites with various valence states, which is easy to absorb moisture and unstable. Therefore, the green, environmentally friendly and low-cost preparation method of tetravalent iron salts still attracts the attention of researchers from all walks of life. Summary of the invention

[0005] Preparation of tetravalent iron salt FeO4 in the prior art 4- The solid method has the problems of high cost and low yield. The purpose of the present invention is to provide a K4FeO4 solid and its preparation method and application at room temperature, which has the advantages of high yield, green environmental protection and low cost.

[0006] In order to achieve the above object, the technical solution of the present invention is: a method for preparing K4FeO4 solid at room temperature, comprising the following steps:

[0007] S1: adding potassium hydroxide solid to the potassium ferrate K2FeO4 aqueous solution to make the free alkali content in the solution greater than 120 mmol / L, thereby obtaining an alkaline potassium ferrate solution;

[0008] S2: adding solid trivalent iron salt to the alkaline potassium ferrate solution obtained in step S1, controlling the temperature at 15°C-25°C, reacting for 150min-240min, and then filtering, the filtrate is a K4FeO4 solution;

[0009] S3: vacuum concentrating the K4FeO4 solution obtained in step S2, cooling the concentrated solution to room temperature, and precipitating crystals; washing the obtained crystals with an organic solvent, and recrystallizing with water to obtain pure K4FeO4 crystals.

[0010] Further, in step S1, the concentration of the potassium ferrate K2FeO4 aqueous solution is 0.05-0.5 mol / L, and the concentration of the potassium hydroxide solution is 0.25 mol / L-1 mol / L.

[0011] Further, in step S2, the concentration of trivalent iron ions in the trivalent iron salt aqueous solution is 0.25 mmol / L to 50 mmol / L.

[0012] Furthermore, the trivalent iron salt is selected from any one of ferric nitrate, ferric sulfate or ferric chloride.

[0013] Furthermore, in step S3, the organic solvent is selected from at least one of benzene, methanol or diethyl ether.

[0014] Furthermore, in step S3, the purity of the pure K4FeO4 crystals is above 92%.

[0015] A K4FeO4 solid is prepared by adopting the method.

[0016] An application of K4FeO4 solid, wherein the K4FeO4 solid is used for removing pollutants in water.

[0017] Furthermore, the K4FeO4 solid is used to remove the harmful substance quinoline yellow in water.

[0018] Furthermore, the K4FeO4 solid is used to remove TOC from water.

[0019] Furthermore, the TOC removal rate of K4FeO4 solid is above 53.63%.

[0020] In summary, the present invention has the following beneficial effects:

[0021] This application adopts the method of strictly controlling potassium ferrate (K2FeO4), OH -, Fe(Ⅲ), and a K4FeO4 solution is obtained by the neutralization reaction between potassium ferrate (K2FeO4) and Fe(Ⅲ), and then a relatively pure K4FeO4 solid is obtained by vacuum concentration, washing and recrystallization. This method has the advantages of relatively mild reaction conditions and low production cost.

[0022] The preparation method of K4FeO4 solid in the present application not only greatly reduces the production cost in the production process, but also makes the entire production process more stable and efficient. The purity of the product obtained by the preparation method of the present invention can reach more than 92%, and the yield can reach more than 85%, which can be used for the treatment of quinoline yellow and TOC pollutants in water.

[0023] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0024] 1. Low cost and simple operation: Compared with the traditional method of preparing tetravalent iron salt by melting, the method proposed in this application is carried out at room temperature and pressure, avoiding the requirement of high temperature and high pressure conditions, thereby reducing the preparation cost. In addition, the operation process is relatively simple and does not require complicated equipment and conditions.

[0025] 2. The K4FeO4 solid prepared by the present invention has high purity. During the preparation process, through the steps of vacuum distillation and organic solvent washing, impurities and impure substances can be effectively removed to obtain pure K4FeO4 crystals. This is conducive to ensuring product quality and improving application performance.

[0026] 3. The experimental reactor is small, simple, easy to carry, and can be prepared on site. When used for industrial scale-up production, the equipment can be simply improved according to the existing equipment, which can reduce the cost of production to a certain extent. The improved equipment is easy to operate and has good operability and controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 This is a SEM image of the K2FeO4 crystal disclosed in Example 4 of the present invention;

[0029] Figure 2 It is the chromaticity removal rate of quinoline yellow by the K4FeO4 solid prepared in the present invention. DETAILED DESCRIPTION

[0030] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1-2 , the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The reaction principle involved in the technical solution of the present invention is:

[0032] FeO4 2- +16OH - +2Fe 3+ →3FeO4 4- +8H2O

[0033] Example

[0034] Example 1

[0035] Add 3g of potassium hydroxide solid to 200mL of 0.1mol / L potassium ferrate (K2FeO4) solution (so that the free alkali content in the solution is greater than 120mmol / L), and add 1g of ferric sulfate solid while stirring, control the temperature to 20±0.5℃, react for 150min, and obtain K4FeO4 solution after suction filtration;

[0036] The obtained K4FeO4 solution was concentrated in vacuo, and the concentrated solution was cooled to room temperature to precipitate crystals; the obtained crystals were washed with benzene and recrystallized with water to obtain pure K4FeO4 crystals with a purity of 98% and a yield of 85%.

[0037] Example 2

[0038] Add 4 g of potassium hydroxide solid to 200 mL of 0.1 mol / L potassium ferrate (K2FeO4) solution (so that the free alkali content in the solution is greater than 120 mmol / L), add 1 g of ferric sulfate solid while stirring, control the temperature to 20±0.5°C, react for 180 min, and obtain a K4FeO4 solution after suction filtration;

[0039] The obtained K4FeO4 solution was concentrated in vacuo, the obtained crystals were washed with methanol, and recrystallized with water to obtain pure K4FeO4 solid with a purity of 93.7% and a yield of 90%.

[0040] Example 3

[0041] Add 3g of potassium hydroxide solid to 200mL of 0.1mol / L potassium ferrate (K2FeO4) solution (so that the free alkali content in the solution is greater than 120mmol / L), add 0.2g of ferric nitrate solid while stirring, control the temperature to 20±0.5℃, react for 200min, and obtain K4FeO4 solution after suction filtration;

[0042] The obtained K4FeO4 solution was concentrated in vacuo, the obtained crystals were washed with ether, and recrystallized with water to obtain pure K4FeO4 solid with a purity of 95% and a yield of 88%.

[0043] Example 4

[0044] Add 3g of potassium hydroxide solid to 200mL of 0.2mol / L potassium ferrate (K2FeO4) solution (so that the free alkali content in the solution is greater than 120mmol / L), add 1g of ferric sulfate solid while stirring, control the temperature to 20±0.5℃, react for 150min, and obtain K4FeO4 solution after suction filtration;

[0045] The obtained K4FeO4 solution was concentrated in vacuo, the obtained crystals were washed with benzene and methanol, and recrystallized with water to obtain pure K4FeO4 solid with a purity of 98.5% and a yield of 86%.

[0046] Figure 1 This is the SEM image of K2FeO4 crystal. Figure 1 It can be seen that the surface of the K2FeO4 material is flat and smooth, and the prepared K2FeO4 crystals have a regular structure.

[0047] Comparative Example

[0048] Comparative Example 1

[0049] Mix 10g of ferric sulfate and 10g of potassium persulfate evenly, and add the mixture to a preheated reactor. Control the temperature of the reactor to be stable at 500°C, keep the mixture in the reactor in a molten state, and continue the reaction for 360 minutes. After the reaction is completed, remove the reactor from the heat source and slowly cool it to room temperature. Wash the cooled reaction product with benzene and methanol. Dry the separated and washed product to remove residual solvent and dry it completely. The yield of the obtained K4FeO4 product is 38% and the purity is 47.5%.

[0050] Comparative Example 2

[0051] To 200 mL of 0.1 mol / L potassium ferrate (K2FeO4) solution, add 1 g of solid ferric sulfate while stirring, and control the temperature to 20±0.5°C. No matter how long the reaction is, only a turbid purple solution will be obtained.

[0052] Application Examples

[0053] Application Example 1

[0054] The K4FeO4 crystals prepared in Examples 1-4 and Comparative Examples 1-3 of the present application are used to remove the harmful substance quinoline yellow in water.

[0055] Application method: Quinoline yellow is a dye commonly used in food coloring, with a chemical formula of C 18 H 11 NO2. Studies have shown that quinoline yellow is genotoxic and its genotoxicity has acted on cell model systems.

[0056] Take a quinoline yellow sample solution with a concentration of 50 mg / L (200 mL) and add K4FeO4 crystals (0.03 mol / L) to it. After stirring, adjust the pH to 4.0. The chromaticity removal rate of quinoline yellow is as follows Figure 2 shown.

[0057] from Figure 2 It can be seen that the K4FeO4 solid prepared by the present invention achieves complete decolorization of the quinoline yellow sample within 15 minutes, indicating that the K4FeO4 solid can quickly remove the harmful substance quinoline yellow in water.

[0058] Application Example 2

[0059] The K4FeO4 crystals prepared in Examples 1-4 and Comparative Examples 1-3 of the present application were used to remove TOC from water.

[0060] The application method is: take a quinoline yellow sample solution with a concentration of 50 mg / L (200 mL, TOC = 38.6 mg / L), add K4FeO4 crystals (0.03 mol / L) to it. After stirring, adjust the pH to 4.0. Measure the TOC of the solution after one hour. The TOC removal rate is shown in Table 1 below.

[0061] Table 1 TOC removal rate

[0062]

[0063] As shown in Table 1, the removal rate of TOC by K4FeO4 solid reached 53.6% within one hour, indicating that K4FeO4 solid has a certain effect on the removal of TOC in water.

[0064] Below is an in-depth analysis of the impact trends of key influencing factors on performance, reaction principles, and synergies between related factors:

[0065] K4FeO4 can release active oxygen species (such as peroxyl radicals) in water, which react with organic matter to oxidize. The carbon in the organic matter is oxidized into carbon dioxide (CO2) and water (H2O), thereby reducing the concentration of TOC. K4FeO4 solid has better reaction performance under alkaline conditions. The alkaline environment can provide more suitable reaction conditions and promote the degradation and removal of organic matter. In addition, alkaline conditions also help to improve the stability of K4FeO4 and the generation of active oxygen species. The crystal structure and surface properties of K4FeO4 solid have an impact on the reaction performance. A larger specific surface area and a more regular crystal structure help provide more reactive sites, enhancing the reaction rate and efficiency.

[0066] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 K4FeO4 solid at room temperature, characterized in that: The steps include: S1: adding potassium hydroxide solid to the potassium ferrate K2FeO4 aqueous solution to make the free alkali content in the solution greater than 120 mmol / L, thereby obtaining an alkaline potassium ferrate solution; S2: Add solid trivalent iron salt to the alkaline potassium ferrate solution obtained in step S1, control the temperature at 15°C-25°C, react for 150min-240min, and then filter, the filtrate is a K4FeO4 solution; S3: vacuum concentrate the K4FeO4 solution obtained in step S2, cool the concentrate to room temperature, and precipitate crystals; wash the obtained crystals with an organic solvent, and recrystallize with water to obtain pure K4FeO4 crystals.

2. The method for preparing K4FeO4 solid at room temperature according to claim 1, characterized in that: In step S1, the concentration of the potassium ferrate K2FeO4 aqueous solution is 0.05-0.5 mol / L, and the concentration of the potassium hydroxide solution is 0.25 mol / L-1 mol / L.

3. The method for preparing K4FeO4 solid at room temperature according to claim 1, characterized in that: In step S2, the concentration of trivalent iron ions in the trivalent iron salt aqueous solution is 0.25 mmol / L to 50 mmol / L.

4. The method for preparing K4FeO4 solid at room temperature according to claim 1 or 3, characterized in that: The ferric iron salt is selected from any one of ferric nitrate, ferric sulfate or ferric chloride.

5. The method for preparing K4FeO4 solid at room temperature according to claim 1, characterized in that: In step S3, the organic solvent is selected from at least one of benzene, methanol or diethyl ether.

6. The method for preparing K4FeO4 solid at room temperature according to claim 1, characterized in that: In step S3, the purity of the pure K4FeO4 crystals is above 92%.

7. Use of K4FeO4 solid prepared by the method for preparing K4FeO4 solid at room temperature according to any one of claims 1 to 6, characterized in that: The K4FeO4 solid is used to remove the harmful substance quinoline yellow in water.

8. Use of K4FeO4 solid prepared by the method for preparing K4FeO4 solid at room temperature according to any one of claims 1 to 6, characterized in that: The K4FeO4 solid is used to remove TOC from water.

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