Method for the preparation and use of prussian blue and activated carbon-prussian blue materials

Abstract

The application provides a preparation method and application of Prussian blue and activated carbon-Prussian blue material. The preparation method of the Prussian blue comprises the following steps: adding a reducing agent to an aqueous solution containing ferricyanide complex for reduction treatment, so that the ferricyanide complex is reduced into ferrocyanide, and a ferrocyanide solution containing ferrocyanide and other reducing substances is obtained; adding a first iron salt solution to the ferrocyanide solution for de-reduction treatment, so that the other reducing substances contained in the ferrocyanide solution are removed, and a ferrocyanide ferrous carbonate precipitate and a post-precipitation liquid containing ferrocyanide are obtained through solid-liquid separation; and adding a second iron salt solution to the post-precipitation liquid for post-treatment, so that the ferrocyanide reacts with iron ions to obtain a Prussian blue slurry. The preparation method provided in the examples of the application can reduce the impurity content of the Prussian blue, improve the purity of the Prussian blue, and is beneficial to the preparation of activated carbon-Prussian blue material with better energy absorption performance.

Description

Technical Field

[0001] This application relates to the field of Prussian blue materials technology, and in particular to a method for preparing and applying Prussian blue and activated carbon-Prussian blue materials. Background Technology

[0002] Prussian blue is increasingly used in sodium-ion cathode materials, and its preparation and recycling processes have become a research hotspot.

[0003] Prussian blue is currently often prepared by chemical synthesis, which involves reacting specific chemical substances to produce Prussian blue. However, the performance of the prepared Prussian blue in applications, especially in the field of adsorption, needs to be improved. Summary of the Invention

[0004] This application provides a method for preparing Prussian blue and activated carbon-Prussian blue materials, as well as their applications. This application can prepare Prussian blue with good adsorption performance.

[0005] This application provides a method for preparing Prussian blue, comprising the following steps:

[0006] A reducing agent is added to an aqueous solution containing a ferricyanide complex to reduce the ferricyanide complex to ferrocyanide, resulting in a ferrocyanide solution containing ferrocyanide and other reducing substances.

[0007] The ferrocyanide solution is added to the first ferric salt solution for dereduction treatment to remove the other reducing substances contained in the ferrocyanide solution. After solid-liquid separation, ferrocyanide precipitate and precipitate containing ferrocyanide are obtained.

[0008] A second ferric salt solution is added to the precipitate for post-treatment, so that the ferrocyanide ion reacts with the ferric ion to obtain Prussian blue slurry.

[0009] The other reducing substances include substances that can reduce ferric ions to ferrous ions.

[0010] According to the preparation method provided in this application, a reducing agent is added to an aqueous solution, and the reducing agent reacts with the ferricyanide complex in the aqueous solution to reduce the ferricyanide complex to ferrocyanide, resulting in a ferrocyanide solution containing ferrocyanide and other reducing substances. Then, a first ferric salt solution is added to react with other reducing substances besides ferrocyanide in the ferrocyanide solution, thereby removing other reducing substances contained in the ferrocyanide solution. These other reducing substances include substances that can reduce ferric ions to ferrous ions, which may come from excess reducing agent or from other substances generated during the reduction process that can reduce ferric ions to ferrous ions. Next, a second ferric salt solution is added to combine ferric ions with ferrocyanide to form ferric ferrocyanide, thus preparing Prussian blue. Therefore, this application embodiment first performs a de-reduction treatment to remove other reducing substances contained in the ferrocyanide solution, which avoids the reduction of ferric ions in the second ferric salt solution to ferrous ions, leading to impurities. This is beneficial for improving the purity of Prussian blue and thus improving its adsorption performance.

[0011] When Prussian blue slurry is mixed with activated carbon to prepare activated carbon-Prussian blue materials, ferrous ferrocyanide and activated carbon can become anchored during the mixing process. Specifically, ferrous ferrocyanide can occupy adsorption sites on the activated carbon, leading to a decrease in the quality of the prepared activated carbon-Prussian blue material. Therefore, in this embodiment, by removing ferrous ferrocyanide from the Prussian blue slurry as much as possible, it is beneficial to avoid the negative impact of ferrous ferrocyanide on the quality of the prepared activated carbon-Prussian blue material, thereby facilitating the preparation of activated carbon-Prussian blue materials with better adsorption performance.

[0012] In some embodiments of this application, the reducing agent includes at least one of sulfite, thiosulfate, and metabisulfite.

[0013] In some embodiments of this application, the sulfite includes potassium sulfite, sodium sulfite, and ammonium sulfite.

[0014] In some embodiments of this application, the thiosulfate includes potassium thiosulfate, sodium thiosulfate, and ammonium thiosulfate.

[0015] In some embodiments of this application, the metabisulfite includes at least one of potassium metabisulfite, sodium metabisulfite, and ammonium metabisulfite.

[0016] In some embodiments of this application, the molar ratio of the ferricyanide complex to the reducing agent in the aqueous solution containing the ferricyanide complex is 2:(1.01-1.2);

[0017] In some embodiments of this application, the other reducing substances include at least one of sulfite, thiosulfate, and metabisulfite.

[0018] In some embodiments of this application, after adding the reducing agent, the reduction treatment further includes adding at least one of potassium salt, sodium salt, and ammonium salt to the ferrocyanide solution.

[0019] In some embodiments of this application, the potassium salt includes at least one of potassium sulfate and potassium chloride, the sodium salt includes at least one of sodium sulfate and sodium chloride, and the ammonium salt includes at least one of ammonium sulfate and ammonium chloride.

[0020] In some embodiments of this application, the potassium ion concentration of the ferrocyanide solution after adding the potassium salt is 10-35 g / L.

[0021] In some embodiments of this application, the sodium ion concentration of the ferrocyanide solution after adding the sodium salt is 6-21 g / L.

[0022] In some embodiments of this application, the ammonium ion concentration of the ferrocyanide solution after adding the ammonium salt is 5-16 g / L.

[0023] In some embodiments of this application, the first iron salt solution includes at least one of ferric sulfate solution and ferric chloride solution.

[0024] In some embodiments of this application, the concentration of the first iron salt solution is 8-12 g / L.

[0025] In some embodiments of this application, the second iron salt solution includes at least one of ferric sulfate solution and ferric chloride solution.

[0026] In some embodiments of this application, the concentration of the second iron salt solution is 8-12 g / L.

[0027] In some embodiments of this application, the reaction time for the post-processing is 3-7 hours.

[0028] In some embodiments of this application, the mass percentage of ferrous ferrocyanide in the Prussian blue paste is ≤0.1%;

[0029] In some embodiments of this application, the mass percentage of ferrous ferrocyanide in the Prussian blue paste is ≤0.01%.

[0030] In some embodiments of this application, the reduction process further includes adding a pH adjuster to the aqueous solution to adjust the pH value before adding the reducing agent.

[0031] In some embodiments of this application, the pH adjuster includes at least one of sulfuric acid and hydrochloric acid.

[0032] In some embodiments of this application, the pH value after adjustment by the pH adjuster is 8.0-10.0.

[0033] In some embodiments of this application, the preparation method further includes obtaining an aqueous solution containing a ferricyanide complex. Obtaining the aqueous solution containing the ferricyanide complex comprises: adding a first precipitant to a first wastewater for oxalic acid separation treatment, and obtaining an oxalic acid precipitate and a post-precipitation liquid after solid-liquid separation, wherein the post-precipitation liquid is used for the reduction treatment; or adding a second precipitant to the first wastewater for manganese separation treatment, and obtaining a manganese hydroxide precipitate and a post-precipitation liquid after solid-liquid separation, wherein the post-precipitation liquid is used for the reduction treatment; or adding a first precipitant to the first wastewater for oxalic acid separation treatment, and obtaining an oxalic acid precipitate and a post-precipitation liquid after solid-liquid separation; adding a second precipitant to the post-precipitation liquid for manganese separation treatment, and obtaining a manganese hydroxide precipitate and a post-precipitation liquid after solid-liquid separation, wherein the post-precipitation liquid is used for the reduction treatment.

[0034] In some embodiments of this application, the first wastewater includes a ferricyanide complex and at least one of oxalic acid and manganese;

[0035] In some embodiments of this application, the first precipitant includes at least one of ferrocyanide and metal oxide.

[0036] In some embodiments of this application, the ferrocyanide salt includes at least one of calcium ferrocyanide and manganese ferrocyanide, and the metal oxide includes calcium oxide.

[0037] In some embodiments of this application, the molar ratio of the first precipitant to the ferricyanide complex in the first wastewater is (1.01-1.15):1.

[0038] In some embodiments of this application, the second precipitant includes at least one of potassium hydroxide, sodium hydroxide, and ammonia water.

[0039] In some embodiments of this application, the reaction pH of the manganese separation treatment is 12-13.

[0040] In some embodiments of this application, a flocculant is added during the oxalic acid separation process and / or the manganese separation process.

[0041] In some embodiments of this application, the flocculant includes polyacrylamide.

[0042] Another embodiment of this application provides a method for preparing activated carbon-Prussian blue material, comprising mixing activated carbon with any of the above-mentioned Prussian blue slurry to prepare activated carbon-Prussian blue material.

[0043] According to the preparation method provided in the embodiments of this application, activated carbon and Prussian blue slurry are mixed, with activated carbon serving as the framework, so that Prussian blue in the Prussian blue slurry adheres to the activated carbon, thereby preparing an activated carbon-Prussian blue material. The resulting activated carbon-Prussian blue material can further enhance the adsorption performance of activated carbon and the advantages of Prussian blue, which is beneficial for effectively removing radioactive metal ions from the solution and has better application prospects.

[0044] Furthermore, the preparation method provided in this application embodiment, when using the first wastewater as raw material to prepare Prussian blue slurry and further prepare activated carbon-Prussian blue slurry, can be carried out in an alkaline environment throughout the entire process, reducing the number of pH adjustments, simplifying the production process, and benefiting industrial production.

[0045] In some embodiments of this application, the following steps are included: mixing the activated carbon with the Prussian blue slurry and washing it with an organic solvent to obtain a solid product, which is the activated carbon-Prussian blue material.

[0046] In some embodiments of this application, the ratio of activated carbon to Prussian blue slurry is 1g:(10-20)mL.

[0047] In some embodiments of this application, the activated carbon and the Prussian blue slurry are mixed and kept for 5-10 hours before being washed with an organic solvent to remove the Prussian blue that did not participate in the formation of the activated carbon-Prussian blue material.

[0048] In some embodiments of this application, the organic solvent includes at least one of ethanol and acetone.

[0049] In some embodiments of this application, the preparation method further includes drying the solid product to obtain the activated carbon-Prussian blue material.

[0050] In some embodiments of this application, the oxygen volume content of the dry atmosphere is ≤0.1%.

[0051] In some embodiments of this application, the drying temperature is 50-80°C.

[0052] In some embodiments of this application, the drying time is 6-12 hours.

[0053] In some embodiments of this application, the moisture content of the dried activated carbon-Prussian blue material is ≤2%.

[0054] In some embodiments of this application, before mixing the activated carbon with the Prussian blue slurry, the preparation method further includes reacting the activated carbon with an activator to form pores and then performing a high-temperature activation treatment.

[0055] In some embodiments of this application, the particle size of the activated carbon is 2-4 mm.

[0056] In some embodiments of this application, the activator comprises a potassium acetate solution with a concentration of 200-400 g / L.

[0057] In some embodiments of this application, the ratio of potassium acetate solution to activated carbon is (1-3) L: 1 g.

[0058] In some embodiments of this application, the reaction time between the potassium acetate solution and the activated carbon is 6-12 hours.

[0059] In some embodiments of this application, the high-temperature activation temperature is 750-800°C.

[0060] In some embodiments of this application, the high-temperature activation is performed under an inert atmosphere.

[0061] In some embodiments of this application, the high-temperature activation time is 2-4 hours.

[0062] Another embodiment of this application provides an activated carbon-Prussian blue material, prepared according to any of the preparation methods described above.

[0063] The activated carbon-Prussian blue material provided in the embodiments of this application can further enhance the adsorption performance of activated carbon and the advantages of Prussian blue, so as to effectively remove radioactive metal ions in the solution and has better application prospects.

[0064] Another embodiment of this application provides a method for treating a second wastewater using activated carbon-Prussian blue material, comprising mixing the activated carbon-Prussian blue material with the second wastewater to utilize the activated carbon-Prussian blue material to adsorb radioactive elements in the second wastewater.

[0065] According to the method provided in the embodiments of this application, activated carbon-Prussian blue material is used to treat the second wastewater. The activated carbon portion of the activated carbon-Prussian blue material can adsorb radioactive elements, making it easier for the radioactive elements to react with the Prussian blue portion of the activated carbon-Prussian blue material. That is, the radioactive elements can replace potassium ions, sodium ions, or ammonium ions in Prussian blue, thereby combining the radioactive elements in the second wastewater with the activated carbon-Prussian blue material to achieve the adsorption and separation of radioactive elements in the second wastewater.

[0066] In some embodiments of this application, the radioactive element includes at least one of thallium and cesium.

[0067] In some embodiments of this application, the method further includes filtering and / or adjusting the pH of the second wastewater before mixing the activated carbon-Prussian blue material with the second wastewater.

[0068] In some embodiments of this application, the total heavy metal concentration of the second wastewater after the filtration treatment is 0.1-1.5 mg / L.

[0069] In some embodiments of this application, the heavy metal includes at least one of Ni, Co, and Mn.

[0070] In some embodiments of this application, the pH value of the second wastewater after the pH adjustment treatment is 4.5-6.0.

[0071] In some embodiments of this application, the concentration of radioactive elements in the second wastewater after treatment by the method is 0.01-2.0 ug / L.

[0072] Additional technical solutions and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0073] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0074] Figure 1 The flowchart illustrates the preparation method of activated carbon-Prussian blue material and the method for treating wastewater provided in some embodiments of this application. Detailed Implementation

[0075] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0076] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0077] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0078] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0079] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0080] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0081] In this embodiment, Prussian blue is an iron cyanide complex whose unit cell is mainly composed of iron and cyano groups, and the intercellular voids can be filled with potassium, sodium, or other ions. Prussian blue exists in both soluble and insoluble forms depending on the different positions of the ferric and ferrous ions in its unit cell structure. It should be noted that "soluble" here refers to a tendency to form a gel-like substance and disperse in a solvent. Prussian blue can react with radioactive metal ions in solution, using these radioactive metal ions to displace excess potassium, sodium, or other ions from the Prussian blue, thereby removing some of the radioactive metal ions from the solution. This method has a wide range of applications.

[0082] In the embodiments of this application, the ferricyanide complex includes ferricyanide ions [Fe(CN)6]. 3- Salts and / or acids.

[0083] This application provides a method for preparing Prussian blue, comprising the following steps: adding a reducing agent to an aqueous solution containing a ferricyanide complex for reduction treatment to reduce the ferricyanide complex to ferrocyanide, obtaining a ferrocyanide solution containing ferrocyanide and other reducing substances; adding a first ferric salt solution to the ferrocyanide solution for dereduction treatment to remove other reducing substances contained in the ferrocyanide solution, and obtaining ferrocyanide precipitate and a precipitate solution containing ferrocyanide after solid-liquid separation; adding a second ferric salt solution to the precipitate solution for post-treatment to allow ferrocyanide to react with ferric ions to obtain Prussian blue slurry; other reducing substances include substances that can reduce ferric ions to ferrous ions.

[0084] According to the preparation method provided in the embodiments of this application, a reducing agent is added to an aqueous solution, and the reducing agent reacts with the ferricyanide complex in the aqueous solution to reduce the ferricyanide complex to ferrocyanide and obtain a ferrocyanide solution containing ferrocyanide and other reducing substances. A first iron salt solution is added to react with reducing impurities in the ferrocyanide solution to remove other reducing substances contained in the ferrocyanide solution. The reducing impurities may include an excess of reducing agent. A second iron salt solution is added to allow iron ions to combine with ferrocyanide to form ferric ferrocyanide.

[0085] It is understandable that ferrous ions can react with ferrocyanide ions to form ferrous ferrocyanide precipitate (white precipitate). Possible reactions include:

[0086] 2Fe 2+ +[Fe(CN)6] 4- →Fe2[Fe(CN)6]↓.

[0087] After converting ferrous ions into ferrous ferrocyanide precipitate, most of the ferrous ferrocyanide can be removed by solid-liquid separation. Therefore, in this embodiment, a dereduction treatment is first performed to remove other reducing substances contained in the ferrous cyanide solution. This can minimize the reduction of ferric ions in the second ferric salt solution to ferrous ions, which would lead to impurities and thus help improve the purity of Prussian blue slurry.

[0088] When Prussian blue slurry is mixed with activated carbon to prepare activated carbon-Prussian blue materials, ferrous ferrocyanide and activated carbon can become anchored during the mixing process. Specifically, ferrous ferrocyanide can compete for adsorption sites on the activated carbon, leading to a decrease in the quality of the prepared activated carbon-Prussian blue material. Therefore, in this embodiment, by removing ferrous ferrocyanide from the Prussian blue slurry as much as possible, it is beneficial to avoid the negative impact of ferrous ferrocyanide on the quality of the prepared activated carbon-Prussian blue material, thereby facilitating the preparation of activated carbon-Prussian blue materials with better adsorption performance.

[0089] In some embodiments of this application, the reducing agent includes at least one of sulfite, thiosulfate, and metabisulfite.

[0090] In some embodiments of this application, the sulfite includes potassium sulfite, sodium sulfite, and ammonium sulfite.

[0091] In some embodiments of this application, the thiosulfate includes potassium thiosulfate, sodium thiosulfate, and ammonium thiosulfate.

[0092] In some embodiments of this application, the metabisulfite includes at least one of potassium metabisulfite, sodium metabisulfite, and ammonium metabisulfite.

[0093] It is understandable that the above sulfites can effectively reduce the ferricyanide complex, and the potassium, sodium and ammonium ions introduced are also the ions needed to obtain Prussian blue. This can minimize the introduction of impurities and reduce the amount of potassium, sodium and ammonium ion solutions that need to be added to obtain Prussian blue in the subsequent process.

[0094] Since the adsorption capacity of activated carbon-Prussian blue materials for radioactive metal elements depends on the content of potassium, sodium, and ammonium ions in Prussian blue, more potassium, sodium, and ammonium ions can be introduced into the Prussian blue slurry when it is prepared.

[0095] It is understandable that the following reactions may occur when sulfites are added:

[0096] 2[Fe(CN)6] 3- +SO3 2- +2OH - →2[Fe(CN)6] 4- +H2O+SO4 2- ;

[0097] 2Fe 3+ +SO3 2- +H₂O→2Fe 2+ +SO4 2- +2H + .

[0098] The above reaction can reduce ferricyanide complexes and ferric ions to ferrous cyanide and ferrous ions, so as to recover and utilize the ferricyanide complexes contained in the aqueous solution and prepare Prussian blue slurry. Moreover, the sulfate ions produced by the sulfite reaction will not reduce the performance of the prepared Prussian blue slurry, nor will they affect the performance of the activated carbon-Prussian blue material that may be obtained later.

[0099] In some embodiments, the molar ratio of ferricyanide complex to reducing agent in the aqueous solution containing the ferricyanide complex is 2:(1.01-1.2). Exemplarily, the molar ratio of ferricyanide complex to reducing agent in the aqueous solution containing the ferricyanide complex can be 2:1.01, 2:1.04, 2:1.08, 2:1.12, 2:1.16, or 2:1.2. Within the above range of reducing agent dosage, the ferricyanide complex in the aqueous solution containing the ferricyanide complex can be reduced as much as possible without causing waste.

[0100] In some embodiments of this application, other reducing substances include at least one of sulfite, thiosulfate, and metabisulfite.

[0101] In some embodiments, the reduction treatment further includes adding at least one of a potassium salt, a sodium salt, and an ammonium salt to the ferrocyanide-containing solution. Adding potassium, sodium, or ammonium salts replenishes potassium, sodium, or ammonium ions, thereby further enhancing the adsorption capacity of Prussian blue and the adsorption capacity of any subsequently obtained activated carbon-Prussian blue material.

[0102] In some embodiments, the potassium salt includes at least one of potassium sulfate and potassium chloride, the sodium salt includes at least one of sodium sulfate and sodium chloride, and the ammonium salt includes at least one of ammonium sulfate and ammonium chloride. In some embodiments, selectively introducing sulfate ions can minimize the impact of introduced impurity ions on the performance of Prussian blue paste and result in better stability of the obtained Prussian blue paste under different temperature and pH conditions.

[0103] In some embodiments, the potassium ion concentration of the ferrocyanide solution after adding potassium salt is 10-35 g / L, for example, the potassium ion concentration can be any value between 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, or 10-35 g / L; in some embodiments, the sodium ion concentration of the ferrocyanide solution after adding sodium salt is 6-21 g / L, for example, the sodium ion concentration can be 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L. / L, 20g / L, 21g / L, or any value between 6-21g / L; in some embodiments, the ammonium ion concentration of the ferrocyanide solution after adding ammonium salt is 5-16g / L, for example, the ammonium ion concentration can be 5g / L, 6g / L, 7g / L, 8g / L, 9g / L, 10g / L, 11g / L, 12g / L, 13g / L, 14g / L, 15g / L, 16g / L, or any value between 5-16g / L; thus obtaining a potassium-rich, sodium-rich, or ammonium-rich solution. Subsequent reduction and post-treatment are then performed to prepare Prussian blue slurry, ensuring that the potassium, sodium, or ammonium ion content of Prussian blue in the slurry is maintained within a suitable range to promote the entry of potassium, sodium, or ammonium ions into the ferrocyanide unit cell, thereby maximizing the adsorption capacity of the prepared activated carbon-Prussian blue material.

[0104] In some embodiments, the first ferric salt solution includes at least one of ferric sulfate solution and ferric chloride solution. In some embodiments, the concentration of the first ferric salt solution is 8-12 g / L, for example, the concentration of the first ferric salt solution can be 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, or any value between 8-12 g / L. By selecting a suitable type and concentration of the first ferric salt solution, reducing impurities contained in the ferrocyanide solution can be effectively removed, and ferrous ferrocyanide can be separated, thereby improving the purity of Prussian blue in the Prussian blue slurry.

[0105] In some embodiments, the Prussian blue slurry contains 10-30% ferrous ferrocyanide (Prussian blue) by mass, and ≤0.1% ferrous ferrocyanide by mass. For example, the ferrous ferrocyanide (Prussian blue) content in the Prussian blue slurry can be any value between 10%, 15%, 20%, 25%, 30%, or 10-30%, and the ferrous ferrocyanide content can be 0.001%, 0.005%, 0.01%, 0.05%, or 0.1%. The resulting Prussian blue slurry can effectively adhere to activated carbon and reduce the preemption of adsorption sites on the activated carbon by ferrous ferrocyanide, thereby improving the adsorption effect of the prepared activated carbon-Prussian blue material on radioactive elements in solution.

[0106] In some embodiments, the mass percentage of ferrous ferrocyanide in Prussian blue paste is ≤0.01%.

[0107] In some embodiments, the second iron salt solution includes at least one of ferric sulfate solution and ferric chloride solution.

[0108] In some embodiments, the concentration of the second iron salt solution is 8-12 g / L. For example, the concentration of the second iron salt solution can be any value between 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, or 8-12 g / L.

[0109] In some embodiments, the post-processing reaction time is 3-7 hours, for example, the post-processing reaction time can be any value between 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 3-7 hours.

[0110] It is understandable that by selecting a suitable type and concentration of the second ferric salt solution and controlling the post-treatment within a suitable time range, ferric ions can fully combine with ferrous cyanide ions to form ferric ferrocyanide, thereby obtaining the desired Prussian blue paste. When the post-precipitate solution also contains sodium ions, potassium ions, or ammonium ions, within the aforementioned time range, sodium ions, potassium ions, and ammonium ions can be allowed to enter the ferrous cyanide unit cell as much as possible, improving the adsorption capacity of the obtained Prussian blue paste, especially its adsorption capacity for radioactive metal elements.

[0111] In some embodiments, the post-processing may also involve stirring to improve reaction efficiency.

[0112] In some embodiments of this application, the reduction process further includes adding a pH adjuster to the aqueous solution to adjust the pH value before adding the reducing agent.

[0113] In some embodiments of this application, the pH adjuster includes at least one of sulfuric acid and hydrochloric acid.

[0114] It should be noted that when sulfuric acid and hydrochloric acid are used to adjust the pH of the solution after manganese precipitation, sulfate ions or chloride ions are introduced. Sulfate ions and chloride ions have virtually no effect on the bonding between Prussian blue slurry and activated carbon. Therefore, the pH can be effectively adjusted without reducing the performance of the activated carbon-Prussian blue material.

[0115] In some embodiments, the pH value after adjustment by the pH adjuster is 8.0-10.0. For example, the pH value after adjustment by the pH adjuster can be 8.0, 8.2, 8.5, 8.8, 9.0, 9.2, 9.5, 9.8, 10.0 or any value between 8.0 and 10.0. This is beneficial to convert ferricyanide ions into ferrous cyanide ions as much as possible, thereby obtaining a ferrous cyanide solution mainly containing ferrous cyanide ions.

[0116] In some embodiments, the method for preparing Prussian blue further includes obtaining an aqueous solution containing a ferricyanide complex, wherein obtaining the aqueous solution containing the ferricyanide complex comprises:

[0117] A first precipitant is added to the first wastewater for oxalic acid separation treatment. After solid-liquid separation, oxalic acid precipitate and a post-precipitation liquid are obtained, wherein the post-precipitation liquid is used for the reduction treatment; or

[0118] A second precipitant is added to the first wastewater for manganese separation treatment. After solid-liquid separation, manganese hydroxide precipitate and a post-precipitation liquid are obtained. The post-precipitation liquid is used for the reduction treatment; or

[0119] A first precipitant is added to the first wastewater for oxalic acid separation treatment, and oxalic acid precipitate and oxalic acid precipitation liquid are obtained through solid-liquid separation; a second precipitant is added to the oxalic acid precipitation liquid for manganese separation treatment, and manganese hydroxide precipitate and manganese precipitation liquid are obtained through solid-liquid separation, wherein the manganese precipitation liquid is used for the reduction treatment.

[0120] In some embodiments, the first wastewater includes a ferricyanide complex, and also includes at least one of oxalic acid and manganese.

[0121] Specifically, in some embodiments, the first wastewater may be wastewater generated during the sodium-ion battery processing, which simultaneously contains ferricyanide complexes, oxalic acid, and manganese. Since the electrodes for sodium-ion batteries are often synthesized using one or more sodium hexacyanophosphates and one or more divalent manganese salts such as manganese chloride, manganese nitrate, manganese sulfate, manganese oxalate, and manganese acetate as raw materials, wastewater containing ferricyanide complexes, oxalates, and manganese salts may be generated during electrode preparation. Exemplarily, the components of the first wastewater may include CN... T (with [Fe(CN)6]) 4- Mainly (1000-7500 mg / L), Mn 250-350 mg / L, C2O42- The COD (Chemical Oxygen Demand) content is 2000-10000 mg / L. COD usually refers to the oxygen equivalent of substances (generally organic matter) in wastewater that can be oxidized by strong oxidants. In the embodiments of this application, it specifically refers to the oxygen equivalent of oxalate in wastewater.

[0122] In the separation process, the first wastewater is first treated to separate oxalic acid to remove oxalate ions; then, manganese is separated to remove manganese ions; next, a reduction treatment is performed to reduce the ferricyanide complex to ferrocyanide; finally, a post-treatment is carried out to combine ferric ions with ferrocyanide to form ferric ferrocyanide, thus obtaining Prussian blue paste. Therefore, Prussian blue paste can be prepared from the first wastewater, reducing its cost, and the oxalate and manganese resources in the first wastewater can be recovered, achieving resource utilization of the first wastewater.

[0123] In some embodiments, a first precipitant is added to the first wastewater for oxalic acid separation treatment, and oxalic acid precipitate and oxalic acid-prepared liquid are obtained through solid-liquid separation. During the oxalic acid separation process, the first precipitant converts oxalate ions into precipitate, and then oxalic acid in the first wastewater can be separated and recovered through solid-liquid separation.

[0124] In some embodiments, during oxalic acid separation, the first precipitant includes at least one of ferrocyanide and a metal oxide. The cations generated when the ferrocyanide and metal oxide dissolve in water can react with oxalate ions to form a precipitate. Furthermore, when ferrocyanide is used as the first precipitant, it not only reacts with oxalate ions to form a precipitate, effectively removing oxalic acid, but also replenishes ferrocyanide ions, thereby preventing the introduction of other impurities. Exemplarily, the ferrocyanide includes at least one of calcium ferrocyanide and manganese ferrocyanide, and the metal oxide includes calcium oxide.

[0125] In some embodiments, the ferrocyanide salt includes at least one of calcium ferrocyanide and manganese ferrocyanide, and the possible reactions that may occur when calcium ferrocyanide is added to the first wastewater include:

[0126] Ca2[Fe(CN)6]+2C2O4 2- →2CaC2O4↓+[Fe(CN)6] 4- .

[0127] Therefore, calcium ferrocyanide can convert oxalate ions in the first wastewater into calcium oxalate precipitate. Furthermore, when calcium ferrocyanide is used as a precipitant, it allows for the precipitation of as many oxalate ions as possible, thereby separating all oxalate ions and achieving resource recovery of oxalate ions.

[0128] In some embodiments, the molar ratio of the first precipitant to the ferricyanide complex in the first wastewater is (1.01-1.15):1. Exemplarily, the molar ratio of the first precipitant to the ferricyanide complex in the first wastewater can be 1.01:1, 1.03:1, 1.06:1, 1.09:1, 1.12:1, or 1.15:1. Controlling the amount of the first precipitant within the above range allows for the precipitation of oxalate as much as possible while maintaining a relatively low calcium content in the liquid after oxalate precipitation, for example, between 0.01-5 mg / L, to minimize the introduction of impurities.

[0129] Furthermore, to promote the formation and separation of oxalic acid precipitates, in some embodiments, a flocculant may be added during the oxalic acid separation process. Exemplarily, polyacrylamide (PAM) may be selected as the flocculant.

[0130] In some embodiments, a second precipitant is added to the oxalic acid precipitation solution for manganese separation treatment. Solid-liquid separation yields manganese hydroxide precipitate and a manganese precipitation solution, wherein the manganese precipitation solution is used for reduction treatment. During the manganese separation process, the pH value of the oxalic acid precipitation solution is adjusted by adding the second precipitant to precipitate manganese ions, and then solid-liquid separation removes manganese ions from the first wastewater.

[0131] In some embodiments, during the manganese separation process, the second precipitant comprises at least one of potassium hydroxide, sodium hydroxide, and ammonia water, and the possible reactions include:

[0132] Mn 2+ +2OH - →Mn(OH)2↓.

[0133] Therefore, manganese ions in the oxalic acid precipitate can combine with hydroxide ions to form manganese hydroxide precipitate. Furthermore, when potassium hydroxide is used as the second precipitant, manganese ions are effectively precipitated, and the introduced potassium ions subsequently participate in the formation of Prussian blue, thus avoiding the introduction of impurities.

[0134] In some embodiments, the reaction pH value for manganese separation treatment is 12-13. For example, the reaction pH value for manganese separation treatment can be any value between 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13, or 12-13. This is beneficial for converting manganese ions in the oxalic acid precipitate into manganese hydroxide precipitate as much as possible, so as to separate and recover manganese resources.

[0135] Furthermore, to promote the formation of manganese hydroxide precipitate, in some embodiments, a flocculant may be added during the manganese separation process. Exemplarily, polyacrylamide (PAM) may be selected as the flocculant.

[0136] It should be noted that in some embodiments, when the first wastewater contains only oxalic acid and not manganese, only the oxalic acid separation treatment in the above embodiments is required before the reduction treatment, and no manganese separation treatment is required; when the first wastewater contains only manganese and not oxalic acid, only the manganese separation treatment in the above embodiments is required before the reduction treatment, and no oxalic acid separation treatment is required. The specific treatment steps are the same as the corresponding steps in the above embodiments.

[0137] During the reduction process, a reducing agent is added to reduce the ferricyanide complex to ferrocyanide, thus obtaining a ferrocyanide solution. This simultaneously enables the resource recovery and utilization of the ferricyanide complex contained in the first wastewater. Furthermore, since ferrocyanide and ferricyanide ions can interconvert in solution, in some embodiments, a pH adjuster is added before adding the reducing agent to adjust the pH of the post-manganese precipitation solution to prevent the ferrocyanide formed by the reduction of the ferricyanide complex from converting back to ferricyanide ions.

[0138] This application also provides a method for preparing activated carbon-Prussian blue material, which includes mixing activated carbon with Prussian blue slurry to prepare activated carbon-Prussian blue material; wherein the raw material sources of activated carbon include fruit shells, coal, wood, etc.

[0139] According to the preparation method provided in the embodiments of this application, activated carbon and Prussian blue slurry are mixed, with activated carbon serving as the framework, so that Prussian blue in the Prussian blue slurry adheres to the activated carbon, thereby preparing an activated carbon-Prussian blue material. The resulting activated carbon-Prussian blue material can further enhance the adsorption performance of activated carbon and the advantages of Prussian blue, which is beneficial for effectively removing radioactive metal ions from the solution and has better application prospects.

[0140] Specifically, in some embodiments, activated carbon, as a porous material, has an extremely well-developed internal pore structure, possessing a large specific surface area and strong adsorption capacity. Prussian blue can react with radioactive metal ions in the solution to bind with them. Therefore, the activated carbon-Prussian blue material prepared in this application can adsorb radioactive metal ions in the solution using its own activated carbon component, and simultaneously bind with the radioactive metal ions using its own Prussian blue component. This allows for the synergistic effect of activated carbon and Prussian blue to effectively separate and remove radioactive metal ions from the solution.

[0141] In some embodiments, the mass percentage of ferrous ferrocyanide in the Prussian blue slurry is ≤0.1%, which can minimize the anchoring of activated carbon with ferrous ferrocyanide and facilitate the adhesion of Prussian blue to activated carbon to form a better activated carbon-Prussian blue material.

[0142] In some embodiments, the preparation method of activated carbon-Prussian blue material includes the following steps: mixing activated carbon and Prussian blue slurry, washing with an organic solvent, and then performing solid-liquid separation, such as filtration, to obtain a solid product, which is the activated carbon-Prussian blue material. Washing the mixture of activated carbon and Prussian blue slurry with an organic solvent can remove organic components from the mixture, including Prussian blue not adhering to the activated carbon. Furthermore, the organic components removed by washing can be recycled to reduce raw material waste.

[0143] In some embodiments, organic solvent washing is followed by solid-liquid separation. It is understood that the organic solvent washing process can be performed in equipment that includes solid-liquid separation or in equipment that does not include solid-liquid separation.

[0144] It should be noted that in some embodiments, the pH value is adjusted to 8.0-10.0 with a pH adjuster, and after reduction treatment, de-reduction treatment, and post-treatment to obtain Prussian blue slurry, it can be used together with activated carbon to prepare activated carbon-Prussian blue material without further pH adjustment, which simplifies the process, reduces acid consumption, and helps improve production economy.

[0145] In some embodiments, the organic solvent includes at least one of ethanol and acetone. Washing with ethanol or acetone can effectively remove organic components, and ethanol is widely available, inexpensive, and suitable for large-scale applications. Exemplarily, the organic solvent can be a 40-60% (w / w) aqueous solution of ethanol, i.e., alcohol, and the washing can be repeated multiple times, for example, 1-3 times, or the washing operation can be terminated after multiple washes until the ferric ferrocyanide content in the washed organic solvent is 0.01-0.05% (w / w).

[0146] To ensure that as much Prussian blue as possible adheres to the activated carbon, in some embodiments, the ratio of activated carbon to Prussian blue slurry is 1 g:(10-20) mL. For example, the ratio can be any value between 1 g:10 mL, 1 g:12 mL, 1 g:14 mL, 1 g:15 mL, 1 g:16 mL, 1 g:18 mL, 1 g:20 mL, or 1 g:(10-20) mL. By controlling the relative amounts of activated carbon and Prussian blue slurry within a suitable range, it is beneficial to combine all the Prussian blue contained in the Prussian blue slurry with the activated carbon to form an activated carbon-Prussian blue material.

[0147] In some embodiments, activated carbon and Prussian blue slurry are mixed and kept for 5-10 hours before being washed with an organic solvent. During this process, Prussian blue can fully combine with the activated carbon, facilitating the formation of an activated carbon-Prussian blue material.

[0148] To obtain dried activated carbon-Prussian blue material, in some embodiments, the preparation method further includes drying the solid product to obtain the activated carbon-Prussian blue material. Drying removes moisture from the solid product and prevents the Prussian blue component in the activated carbon-Prussian blue material from oxidizing and deteriorating.

[0149] In some embodiments, the oxygen volume content of the drying atmosphere is ≤0.1%, which is beneficial for creating a near-oxygen-free drying environment and can prevent the material from oxidizing and deteriorating. For example, the drying method can be vacuum drying.

[0150] In some embodiments, the drying temperature is 50-80°C, for example, the drying temperature can be any value between 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or 50-80°C. In some embodiments, the drying time is 6-12 hours, for example, the drying time can be any value between 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, or 6-12 hours. By controlling the drying within the above-mentioned suitable temperature and / or time range, it is beneficial to fully remove moisture from the activated carbon-Prussian blue material while avoiding oxidation and deterioration of the activated carbon-Prussian blue material.

[0151] In some embodiments, the moisture content of the dried activated carbon-Prussian blue material is ≤2%, for example, the moisture content of the activated carbon-Prussian blue material can be any value of 2%, 1.5%, 1%, 0.5%, 0.1%, 0.05%, 0.01%, or ≤2%. By controlling the moisture content range of the activated carbon-Prussian blue material, it is beneficial to obtain activated carbon-Prussian blue material with better adsorption performance.

[0152] Since activated carbon directly affects the performance of the prepared activated carbon-Prussian blue material, the activated carbon can be treated before mixing with the Prussian blue slurry to improve the performance of the activated carbon-Prussian blue material. For example, the treated activated carbon has an iodine adsorption value of 900-1000 mg / g, an ash content of 4.0-5.0%, and a specific surface area of ​​1000-1150 m². 2 / g, and increase the number of micropores, transforming macroporous activated carbon into microporous structure, which helps to prepare the target activated carbon-Prussian blue material by mixing activated carbon with Prussian blue.

[0153] In this embodiment, the adsorbed iodine value refers to the amount of iodine adsorbed per gram of activated carbon when the residual (equilibrium) concentration of iodine in the solution is 0.02 N / L (mcequivalent per liter), expressed in mg / g. The adsorbed iodine value is primarily used to characterize the development of the micropores in activated carbon, indicating its adsorption capacity for small molecules. For example, the method for detecting the adsorbed iodine value includes: taking a certain amount of activated carbon sample and thoroughly contacting and shaking it with an iodine standard solution of known concentration, then filtering (centrifuging), and then taking a certain amount of the clarified iodine solution, titrating it with sodium thiosulfate of known concentration, and determining the amount of iodine adsorbed per gram of activated carbon, which is the adsorbed iodine value.

[0154] In this embodiment, the ash content of activated carbon refers to the content of non-volatile substances in the activated carbon, also known as fixed carbon or ash content. During the production of activated carbon, the raw materials are generally organic matter with a high carbon content. Through processes such as carbonization and activation, the organic matter is converted into activated carbon. The ash content of activated carbon mainly consists of inorganic salts, minerals, and other impurities. Exemplarily, in some embodiments, the components contained in the ash include at least one of calcium and magnesium.

[0155] In some embodiments, before mixing activated carbon with Prussian blue slurry, the activated carbon is reacted with an activating agent to form pores and then subjected to high-temperature activation treatment. Activation treatment with an activating agent and high temperature allows for the formation of more fine pores on the activated carbon, thereby improving its adsorption capacity. This results in the prepared activated carbon-Prussian blue material having a more extensive microporous structure, which is beneficial for improving the adsorption performance of the activated carbon-Prussian blue material.

[0156] In some embodiments, the particle size of activated carbon is 2-4 mm. For example, the particle size of activated carbon can be any value between 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm or 2-4 mm. This is beneficial to further increase the filtration area of ​​the prepared activated carbon-Prussian blue material, increase the filtration rate, and have better mechanical strength and wear resistance, thereby improving the effect of industrial wastewater treatment.

[0157] It is understandable that the choice of activator directly affects the activation effect of activated carbon. In some embodiments, the activator includes a potassium acetate solution with a concentration of 200-400 g / L. For example, the concentration of the potassium acetate solution can be 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, or any value between 200-400 g / L. Appropriate activation capacity of potassium acetate is beneficial for the formation of more microporous structures on the original porous structure of activated carbon, which helps to improve the adsorption iodine value of activated carbon, thereby improving the adsorption performance of the prepared activated carbon-Prussian blue material.

[0158] When potassium acetate activates activated carbon, the following reactions may occur:

[0159] 2CH3COOK→K2CO3+CH3COCH3;

[0160] K2CO3→CO2+K2O;

[0161] CO2 + C → 2CO;

[0162] K2O + C → 2K + CO.

[0163] Through the above reaction, the CO2 and K2O generated by the decomposition of potassium acetate are used to consume the carbon material, while the generated K vapor promotes the expansion and destruction of the carbon material structure. This can fully activate the activated carbon, which is conducive to the formation of a large number of microporous structures on the activated carbon.

[0164] In some embodiments, the ratio of potassium acetate solution to activated carbon is (1-3) L:1 g, for example, the ratio can be any value between 1 L:1 g, 1.5 L:1 g, 2 L:1 g, 2.5 L:1 g, 3 L:1 g, or (1-3) L:1 g. In some embodiments, the reaction time between potassium acetate solution and activated carbon is 6-12 h, for example, the reaction time can be any value between 6 h, 8 h, 10 h, 12 h, or 6-12 h. By controlling the relative amounts of potassium acetate and activated carbon and the reaction time, it is beneficial to fully activate all the activated carbon, thereby improving the performance of the prepared activated carbon-Prussian blue material.

[0165] Furthermore, the conditions of high-temperature activation treatment also affect the performance of activated carbon. In some embodiments, the high-temperature activation temperature is 750-800°C, for example, the high-temperature activation temperature can be 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, or any value between 750-800°C. In some embodiments, high-temperature activation is carried out under an inert atmosphere, exemplaryly, a nitrogen atmosphere or an argon atmosphere, to reduce carbon loss during the high-temperature activation process. In some embodiments, the high-temperature activation time is 2-4 hours, for example, the high-temperature activation time can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or any value between 2 and 4 hours. By controlling the temperature and time of the high-temperature activation treatment within the above-mentioned suitable ranges, it is beneficial to further activate the activated carbon and obtain activated carbon with a larger specific surface area, thereby improving the adsorption performance of the prepared activated carbon-Prussian blue material.

[0166] In some embodiments, the process includes acid washing and water washing before and / or after high-temperature activation of activated carbon and activator to form pores. In some embodiments, the acid used for acid washing includes hydrochloric acid, the concentration of acid used for acid washing is 0.3-0.8 mol / L, the acid washing solution-to-solid ratio is (5-10) mL:1 g, and the number of acid washing cycles is 2-5. In some embodiments, the water washing solution-to-solid ratio is (5-10) mL:1 g, and the number of water washing cycles is 2-5. For example, the acid concentration used for pickling can be any value among 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, and 0.3-0.8 mol / L; the liquid-to-solid ratio for pickling or washing can be any value among 5 mL:1 g, 6 mL:1 g, 7 mL:1 g, 8 mL:1 g, 9 mL:1 g, 10 mL:1 g, and (5-10) mL:1 g; and the number of pickling or washing cycles can be 2, 3, 4, or 5.

[0167] It is understandable that acid washing before the activated carbon reacts with the activator to form pores can control the concentration of (Ca+Mg) in the acid washing solution to 0.01-5 mg / L, in order to reduce calcium and magnesium impurities in the activated carbon; acid washing after high-temperature activation can control the concentration of the activator in the acid washing solution to 0.01-5 mg / L. For example, when the activator is potassium acetate, acid washing after high-temperature activation can be performed until the concentration of potassium ions in the acid washing solution is 0.01-5 mg / L; water washing before the activated carbon reacts with the activator to form pores and / or after high-temperature activation can control the pH value of the washing water to 6.0-9.0, so as to obtain activated carbon that is more suitable for preparing activated carbon-Prussian blue materials.

[0168] In some embodiments, moisture on the activated carbon is removed after acid washing and / or water washing. Exemplarily, moisture on the activated carbon can be removed by draining or heat drying.

[0169] Another embodiment of this application provides an activated carbon-Prussian blue material, prepared according to the preparation method of any of the above embodiments.

[0170] The activated carbon-Prussian blue material provided in the embodiments of this application can further enhance the adsorption performance of activated carbon and the advantages of Prussian blue, thereby facilitating the effective removal of radioactive metal ions from solutions and showing better application prospects. For example, the activated carbon-Prussian blue material provided in the embodiments of this application can be used as an adsorption column packing material, which has a small footprint, saves space, and is beneficial for practical applications.

[0171] Another embodiment of this application provides a method for treating a second wastewater using activated carbon-Prussian blue material, comprising mixing the activated carbon-Prussian blue material with the second wastewater to utilize the activated carbon-Prussian blue material to adsorb radioactive elements in the second wastewater.

[0172] According to the method provided in the embodiments of this application, activated carbon-Prussian blue material is used to treat the second wastewater. The activated carbon portion of the activated carbon-Prussian blue material can adsorb radioactive elements, making it easier for the radioactive elements to react with the Prussian blue portion of the activated carbon-Prussian blue material. That is, the radioactive elements can replace potassium ions, sodium ions, or ammonium ions in Prussian blue, thereby combining the radioactive elements in the second wastewater with the activated carbon-Prussian blue material to achieve the adsorption and separation of radioactive elements in the second wastewater.

[0173] In some embodiments, the radioactive element includes at least one of thallium and cesium. The Prussian blue portion of the activated carbon-Prussian blue material provided in this application embodiment can effectively adsorb at least one of thallium and cesium ions in the second wastewater, thereby achieving the removal of thallium and cesium ions. In particular, the activated carbon-Prussian blue material provided in this application embodiment has a particularly significant adsorption effect on thallium ions, and is especially suitable for adsorbing and removing thallium from wastewater that does not meet thallium standards.

[0174] To avoid interference from other components in the second wastewater with the activated carbon-Prussian blue material, in some embodiments, the method of treating the second wastewater before mixing the activated carbon-Prussian blue material with the second wastewater further includes filtering and / or adjusting the pH of the second wastewater.

[0175] In some embodiments, the total heavy metal concentration of the second wastewater after filtration is 0.1-1.5 mg / L. For example, the total concentration of nickel, cobalt, and manganese can be 0.1 mg / L, 0.2 mg / L, 0.3 mg / L, 0.4 mg / L, 0.5 mg / L, 0.6 mg / L, 0.7 mg / L, 0.8 mg / L, 0.9 mg / L, 1.0 mg / L, 1.1 mg / L, 1.2 mg / L, 1.3 mg / L, 1.4 mg / L, 1.5 mg / L, or any value between 0.1 and 1.5 mg / L. In some embodiments, the heavy metals include at least one of Ni, Co, and Mn. Exemplarily, the filtration treatment can be to remove nickel, cobalt, and manganese heavy metals by filtering with an organic membrane filter. After separating the nickel, cobalt, and manganese components contained in the second wastewater by filtration treatment, the problem of nickel, cobalt, and manganese loss caused by the adsorption of nickel, cobalt, and manganese by activated carbon-Prussian blue materials can be avoided.

[0176] In some embodiments, the pH value of the second wastewater after pH adjustment treatment is 4.5-6.0, for example, the pH value can be any value between 4.5, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, or 4.5-6.0. For example, dilute sulfuric acid can be added to adjust the pH value of the second wastewater. By controlling the pH value of the second wastewater within the above-mentioned suitable range, it is beneficial to further improve the removal efficiency of the activated carbon-Prussian blue material for radioactive metal ions.

[0177] In some embodiments, the radioactive element concentration of the second wastewater treated with activated carbon-Prussian blue material is 0.01-2.0 ug / L, for example, the radioactive element concentration can be 0.01 ug / L, 0.1 ug / L, 0.2 ug / L, 0.4 ug / L, 0.5 ug / L, 0.8 ug / L, 1.0 ug / L, 1.2 ug / L, 1.4 ug / L, 1.6 ug / L, 1.8 ug / L, or 2.0 ug / L. It is evident that the treated wastewater contains only a very small amount of radioactive elements, which can solve the problem of non-compliance with radioactive element emission standards in wastewater.

[0178] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents and raw materials used in the embodiments are commercially available or synthesized by conventional methods, as are the instruments used in the embodiments.

[0179] Example 1

[0180] like Figure 1 As shown, this embodiment provides a method for preparing activated carbon-Prussian blue material and a method for treating wastewater, including the following steps:

[0181] (1) Activation treatment of activated carbon: Powdered activated carbon with a particle size of 3 mm was acid-washed with 0.5 mol / L hydrochloric acid at a liquid-to-solid ratio of 5 L: 1 g. After acid washing three times, the Ca+Mg concentration in the acid washing solution was measured to be 4.2 mg / L. After acid washing, the activated carbon was drained. The acid-washed activated carbon was then washed with water at a liquid-to-solid ratio of 5 L: 1 g, four times. The pH value of the washing water was 8.5. After rinsing with clean water, the activated carbon was drained. A 300 g / L potassium acetate solution was used. The previously washed activated carbon was soaked in a solution at a liquid-to-solid ratio of 2 L:1 g for 10 h, with the solution stirred during soaking. After soaking, the activated carbon was drained. The activated carbon soaked in potassium acetate was then activated at 800 °C in a nitrogen atmosphere at a rate of 5 °C / min, and held at that temperature for 3 h before natural cooling. The activated carbon was then acid-washed with 0.5 mol / L hydrochloric acid at a liquid-to-solid ratio of 5 L:1 g three times until the K+ in the wash water was reduced. + The concentration was 4.5 mg / L. After acid washing, the activated carbon was drained. The acid-washed activated carbon was then washed with water at a liquid-to-solid ratio of 5 L: 1 g, and washed 5 times until the pH of the wash water was 7.5. After washing, the activated carbon was drained. The activated carbon was then dried at 90°C for 10 hours to obtain the activated finished product.

[0182] (2) Preparation of Prussian blue slurry: Calcium ferrocyanide was added to the first wastewater containing ferricyanide complex. The molar ratio of ferricyanide complex in the first wastewater to the added calcium ferrocyanide was 1:1.05. The mixture was stirred for 1 hour, then 0.01% PAM was added, and the mixture was allowed to settle for 2 hours. Solid-liquid separation was performed to obtain calcium oxalate precipitate and filtrate 1 (the liquid after oxalic acid precipitation). Potassium hydroxide was added to filtrate 1 to adjust the pH to 12.51. Then, 0.01% PAM was added, and the mixture was allowed to settle for 1.5 hours. Solid-liquid separation was performed to obtain manganese hydroxide precipitate and filtrate 2 (the liquid after manganese precipitation). The pH of filtrate 2 was adjusted to 9.02 using dilute sulfuric acid. Potassium sulfite was added to filtrate 2. The added potassium sulfite complexed with the ferricyanide in the first wastewater. The molar ratio of the substances was 1.05:2, and the reaction was stirred for 1.5 h. Then, potassium sulfate was added to the solution to make the potassium ion concentration reach 30 g / L, resulting in a potassium-rich solution under reducing conditions. Under stirring, 10 g / L ferric sulfate solution was slowly added to the potassium-rich solution, producing a white precipitate. When the solution began to turn light blue, the addition of ferric sulfate was stopped, and the solution was allowed to settle. Solid-liquid separation was performed to obtain ferrous ferrocyanide precipitate and filtrate 3 (precipitate solution). Under stirring, 10 g / L ferric sulfate solution was slowly added to filtrate 3 until the slurry turned dark blue. The slurry was stirred for 6 h to allow for complete reaction, resulting in Prussian blue slurry with a ferrous ferrocyanide content of 0.003%.

[0183] (3) Preparation of activated carbon-Prussian blue material: Under stirring, the dried finished activated carbon and Prussian blue slurry were mixed at a ratio of 1g:20mL and reacted for 10h. The mixture was then drained and rinsed with 50% alcohol to remove organic matter (mainly unadsorbed Prussian blue). After washing three times, the mixture was vacuum dried at 60℃ for 10h to obtain activated carbon-Prussian blue material.

[0184] (4) Application of activated carbon-Prussian blue material: 10 kg of activated carbon-Prussian blue material (corresponding to 4.87 kg of finished activated carbon and 97.4 L of Prussian blue slurry) was placed in a fiberglass tank and used to adsorb and remove thallium from the second wastewater that failed the fine treatment. Before entering the thallium removal fiberglass tank, the second wastewater needs to pass through an organic membrane filter to remove heavy metals, and the concentration after filtration is Ni+Co+Mn=1.2 mg / L; the pH value is adjusted to 5.8 with dilute sulfuric acid. After passing through the thallium removal fiberglass tank, the thallium concentration in the second wastewater decreased from 5.7 ug / L to 0.3 ug / L.

[0185] Table 1. Changes in activated carbon in Example 1 of this application before and after activation treatment.

[0186]

[0187]

[0188] Example 2

[0189] This embodiment is the same as step (1) of embodiment 1, but some process parameters are different. The specific steps of this embodiment are as follows:

[0190] Powdered activated carbon with a particle size of 3 mm was acid-washed four times with 0.5 mol / L hydrochloric acid at a liquid-to-solid ratio of 7 L: 1 g. After acid washing, the Ca+Mg concentration in the acid washing solution was measured to be 3.8 mg / L. After acid washing, the activated carbon was drained. The acid-washed activated carbon was then rinsed with water at a liquid-to-solid ratio of 5 L: 1 g four times, with the pH of the rinse water being 7.8. After rinsing with clean water, the activated carbon was drained. The activated carbon was then soaked in a 300 g / L potassium acetate solution at a liquid-to-solid ratio of 3 L: 1 g for 12 h, with the soaking solution being stirred during soaking. After soaking, the activated carbon was drained. The activated carbon soaked in potassium acetate was then heated to 750 °C at a rate of 5 °C / min under a nitrogen atmosphere for high-temperature activation, and held at this temperature for 2.5 h before natural cooling. The high-temperature activated carbon was then acid-washed with 0.5 mol / L hydrochloric acid at a liquid-to-solid ratio of 7 L: 1 g four times until the K+ in the rinse water was reduced. +The concentration was 3.3 mg / L. After acid washing, the activated carbon was drained. The acid-washed activated carbon was then washed with water at a liquid-to-solid ratio of 7 L: 1 g, and washed 4 times until the pH of the wash water was 7.2. After washing, the activated carbon was drained. The activated carbon was then dried at 85°C for 10 hours to obtain the activated finished product.

[0191] Table 2. Changes in activated carbon in Example 2 of this application before and after activation treatment.

[0192] Adsorbed iodine value (mg / g) Ash content (%) aperture <![CDATA[Specific surface area (m 2 / g)]]> Before activation treatment 802 5.4 Exhibits a large number of macroporous structures 960 After activation treatment 943 4.61 Mainly microporous structure 1077

[0193] Example 3

[0194] This embodiment is the same as step (2) in embodiment 1, but some process parameters are different. Step (2) in this embodiment specifically includes the following steps:

[0195] (2) Preparation of Prussian blue slurry: Calcium ferrocyanide was added to the first wastewater containing ferricyanide complex. The molar ratio of ferricyanide complex in the first wastewater to the added calcium ferrocyanide was 1:1.10. The mixture was stirred for 1.5 h, then 0.01% PAM was added, and the mixture was allowed to settle for 1.5 h. Solid-liquid separation was performed to obtain calcium oxalate precipitate and filtrate 1 (the liquid after oxalate precipitation). Potassium hydroxide was added to filtrate 1 to adjust the pH to 12.81. Then, 0.01% PAM was added, and the mixture was allowed to settle for 1.5 h. Solid-liquid separation was performed to obtain manganese hydroxide precipitate and filtrate 2 (the liquid after manganese precipitation). The pH of filtrate 2 was adjusted to 8.77 using dilute sulfuric acid. Potassium sulfite was added to filtrate 2. The added potassium sulfite reacted with the ferricyanide complex in the first wastewater. The molar ratio of the complex was 1.1:1. The reaction was stirred for 1.5 h, and then potassium sulfate was added to the solution to make the potassium ion concentration reach 32 g / L, resulting in a potassium-rich solution under reducing conditions. Under stirring, 10 g / L ferric sulfate solution was slowly added to the potassium-rich solution, producing a white precipitate. When the solution began to turn light blue, the addition of ferric sulfate was stopped, and the solution was allowed to settle. Solid-liquid separation was performed to obtain ferrous ferrocyanide precipitate and filtrate 3 (precipitate solution). Under stirring, 10 g / L ferric sulfate solution was slowly added to filtrate 3 until the slurry turned dark blue. The slurry was stirred for 6 h to allow for complete reaction, resulting in Prussian blue slurry with a ferrous ferrocyanide content of 0.003%.

[0196] Example 4

[0197] The difference between this embodiment and Embodiment 1 is that the amount of finished activated carbon and Prussian blue slurry used in step (3) is different. Step (3) of this embodiment specifically includes the following steps:

[0198] (3) Preparation of activated carbon-Prussian blue material: Under stirring, the dried finished activated carbon and Prussian blue slurry were mixed at a ratio of 1g:10mL and reacted for 10h. The mixture was then drained and soaked in 50% alcohol to remove organic matter (mainly unadsorbed Prussian blue). After washing three times, the mixture was vacuum dried at 60℃ for 10h to obtain activated carbon-Prussian blue material.

[0199] Step (4) is the same as in Example 1, and the thallium concentration in the second wastewater after passing through the thallium removal fiberglass tank decreased from 5.7 ug / L to 1.49 ug / L.

[0200] Example 5

[0201] The difference between this embodiment and Embodiment 1 is that the amount of finished activated carbon and Prussian blue slurry used in step (3) is different. Step (3) of this embodiment specifically includes the following steps:

[0202] (3) Preparation of activated carbon-Prussian blue material: Under stirring, the dried finished activated carbon and Prussian blue slurry were mixed at a ratio of 1g:30mL and reacted for 10h. The mixture was then drained and soaked in 50% alcohol to remove organic matter (mainly unadsorbed Prussian blue). After washing three times, the mixture was vacuum dried at 60℃ for 10h to obtain activated carbon-Prussian blue material.

[0203] Step (4) is the same as in Example 1, and the thallium concentration in the second wastewater after passing through the thallium removal fiberglass tank decreased from 5.7 ug / L to 1.79 ug / L.

[0204] Example 6

[0205] The difference between this embodiment and Embodiment 1 lies in the amount of finished activated carbon and Prussian blue slurry used in step (3) and the reaction time. Step (3) of this embodiment specifically includes the following steps:

[0206] (3) Preparation of activated carbon-Prussian blue material: Under stirring, the dried finished activated carbon and Prussian blue slurry were mixed at a ratio of 1g:20mL and reacted for 5h. The mixture was then drained and soaked in 50% alcohol to remove organic matter (mainly unadsorbed Prussian blue). After washing three times, the mixture was vacuum dried at 60℃ for 10h to obtain activated carbon-Prussian blue material.

[0207] Step (4) is the same as in Example 1, and the thallium concentration in the second wastewater after passing through the thallium removal fiberglass tank decreased from 5.7 ug / L to 1.27 ug / L.

[0208] Example 7

[0209] The difference between this embodiment and Embodiment 1 lies in the amount of finished activated carbon and Prussian blue slurry used in step (3) and the reaction time. Step (3) of this embodiment specifically includes the following steps:

[0210] (3) Preparation of activated carbon-Prussian blue material: Under stirring, the dried finished activated carbon and Prussian blue slurry were mixed at a ratio of 1g:20mL and reacted for 15h. The mixture was then drained and soaked in 50% alcohol to remove organic matter (mainly unadsorbed Prussian blue). After washing three times, the mixture was vacuum dried at 60℃ for 10h to obtain activated carbon-Prussian blue material.

[0211] Step (4) is the same as in Example 1, and the thallium concentration in the second wastewater after passing through the thallium removal fiberglass tank decreased from 5.7 ug / L to 2.04 ug / L.

[0212] Comparative Example 1

[0213] The difference between this comparative example and Example 1 lies in step (4). Step (4) of this comparative example specifically includes the following steps:

[0214] (4) Application of activated carbon-Prussian blue material: 4.87 kg of the finished activated carbon obtained in step (1) was placed into a fiberglass tank and used to adsorb and remove thallium from the second wastewater that failed the fine treatment. Before entering the thallium removal fiberglass tank, the second wastewater needs to pass through an organic membrane filter to remove heavy metals, and the concentration after filtration is Ni+Co+Mn=1.2mg / L; the pH value is adjusted to 5.8 with dilute sulfuric acid. After passing through the thallium removal fiberglass tank, the thallium concentration in the second wastewater decreased from 5.7ug / L to 3.15ug / L.

[0215] Comparative Example 2

[0216] The difference between this comparative example and Example 1 lies in step (4). Step (4) of this comparative example specifically includes the following steps:

[0217] (4) Application of activated carbon-Prussian blue material: 97.4L of the Prussian slurry obtained in step (3) was loaded into a fiberglass tank and used to adsorb and remove thallium from the second wastewater that failed the fine treatment. Before entering the thallium removal fiberglass tank, the second wastewater needs to pass through an organic membrane filter to remove heavy metals, and the concentration after filtration is Ni+Co+Mn=1.2mg / L; the pH value is adjusted to 5.8 with dilute sulfuric acid. After passing through the thallium removal fiberglass tank, the thallium concentration in the second wastewater decreased from 5.7ug / L to 2.87ug / L.

[0218] Comparative Example 3

[0219] The difference between this comparative example and Example 1 lies in step (4). Step (4) of this comparative example specifically includes the following steps:

[0220] (4) Application of activated carbon-Prussian blue material: 4.87 kg of the finished activated carbon obtained in step (1) and 97.4 L of the Prussian blue slurry obtained in Example 1 were loaded into a fiberglass tank and used to adsorb and remove thallium from the second wastewater that failed the fine treatment. Before entering the thallium removal fiberglass tank, the second wastewater needs to pass through an organic membrane filter to remove heavy metals, and the concentration after filtration is Ni+Co+Mn=1.2mg / L; the pH value is adjusted to 5.8 with dilute sulfuric acid. After passing through the thallium removal fiberglass tank, the thallium concentration in the second wastewater decreased from 5.7 ug / L to 4.61 ug / L.

[0221] Table 3. Comparison of thallium removal effects between Example 1 and Comparative Examples 1-3

[0222]

[0223] Comparative Example 4

[0224] The difference between this comparative example and Example 1 is that the reduction process is omitted in step (2). Step (2) of this comparative example specifically includes the following steps:

[0225] (2) Preparation of Prussian blue slurry: Calcium ferrocyanide was added to the first wastewater containing ferricyanide complex. The molar ratio of ferricyanide complex to calcium ferrocyanide in the first wastewater was 1:1.05. The mixture was stirred for 1 hour, then 0.01% PAM was added, and the mixture was allowed to settle for 2 hours. Solid-liquid separation was performed to obtain calcium oxalate precipitate and filtrate 1 (after oxalic acid precipitation). Potassium hydroxide was added to filtrate 1 to adjust the pH to 12.51. Then, 0.01% PAM was added, and the mixture was allowed to settle for 1.5 hours. Solid-liquid separation was performed to obtain manganese hydroxide precipitate and filtrate 2 (after manganese precipitation). Diluted PAM was used to further prepare the filtrate. Sulfuric acid was used to adjust the pH of filtrate 2 to 9.02. Potassium sulfite was then added to filtrate 2, with a molar ratio of potassium sulfite to the ferricyanide complex in the first wastewater of 1.05:2. The mixture was stirred for 1.5 hours. Then, potassium sulfate was added to the solution to bring the potassium ion concentration to 30 g / L, resulting in a potassium-rich solution under a reducing environment. Under stirring, 10 g / L ferric sulfate solution was slowly added to the potassium-rich solution until the slurry turned deep blue. The slurry was stirred for 6 hours to allow for complete reaction, resulting in Prussian blue slurry with a ferrous ferrocyanide content of 0.24%.

[0226] Steps (3) and (4) are the same as in Example 1, and the thallium concentration in the second wastewater after passing through the thallium removal fiberglass tank decreased from 5.7 ug / L to 2.4 ug / L.

[0227] The content of ferrous ferrocyanide in the embodiments and comparative examples of this application can be detected by the following methods.

[0228] S1: Take mg of Prussian blue slurry as the sample to be tested, dissolve it in 2 mol / L sulfuric acid solution to obtain V1 L of test solution a; add sodium diphenylamine sulfonate as an indicator to test solution a, and titrate test solution b with 0.02 mol / L potassium dichromate standard solution until the solution turns purple-red and does not change color within 30 seconds. The amount of potassium dichromate standard solution consumed is V2 L.

[0229] S2: Take potassium ferrocyanide containing the same mass of ferrocyanide as S1, dissolve it in 2 mol / L sulfuric acid solution to obtain V1 L of test solution b. Add sodium diphenylamine sulfonate as an indicator to test solution b, and titrate test solution b with 0.02 mol / L potassium dichromate standard solution until the solution turns purple-red and does not change color within 30 seconds. The amount of potassium dichromate solution consumed is V3 L.

[0230] The amount of potassium dichromate consumed by the ferrous iron in S1 was calculated to be [0.02 mol / L × (V2 - V3) L]. Therefore, the content of ferrous iron cyanide in the sample is easily obtained. Where M is the molar mass of ferrous ferrocyanide.

[0231] Referring to the relevant data in Example 1, it can be seen that the ferrous ferrocyanide content of the prepared Prussian blue slurry is only 0.003%, indicating that the Prussian blue prepared in this application has low impurity content and high purity. The obtained Prussian blue can improve the performance of the subsequently prepared activated carbon-Prussian blue material. Specifically, referring to Tables 1 and 2, it can be seen from Examples 1 and 2 that after activation treatment, the activated carbon's adsorption iodine value increases, ash content decreases, and specific surface area increases, indicating that the activated carbon's microporous structure increases and its adsorption capacity becomes stronger, thereby improving the adsorption performance of the prepared activated carbon-Prussian blue material. From the adsorption effect of the activated carbon-Prussian blue material prepared in Examples 4-7 and Example 1 on thallium, it can be seen that when the relative dosage range of activated carbon and Prussian blue slurry is defined in the examples of this application, the obtained activated carbon-Prussian blue material can effectively adsorb most of the thallium in the wastewater, which is beneficial to ensuring that the thallium in the wastewater meets the discharge standards.

[0232] Referring to Table 3, a comparison between Comparative Example 1 and Example 1 shows that the adsorption effect of activated carbon alone on thallium is not as good as that of the activated carbon-Prussian blue material prepared in the embodiments of this application; a comparison between Comparative Example 2 and Example 1 shows that the adsorption effect of Prussian blue slurry alone on thallium is not as good as that of the activated carbon-Prussian blue material prepared in the embodiments of this application; a comparison between Comparative Example 3 and Example 1 shows that the adsorption effect of finished activated carbon + Prussian blue slurry on thallium is not as good as that of the activated carbon-Prussian blue material prepared in the embodiments of this application; it is evident that the activated carbon-Prussian blue material prepared in the embodiments of this application has excellent adsorption performance.

[0233] Therefore, according to the preparation method provided in the embodiments of this application, activated carbon-Prussian blue material can be prepared by using activated carbon as a framework and Prussian blue obtained from wastewater treatment and recovery as a modified raw material for activated carbon. This activated carbon-Prussian blue material can adsorb and treat thallium-contaminated wastewater, and has the advantages of resource recovery and waste treatment.

[0234] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0235] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing Prussian blue, characterized in that, Includes the following steps: A reducing agent is added to an aqueous solution containing a ferricyanide complex to reduce the ferricyanide complex to ferrocyanide, resulting in a ferrocyanide solution containing ferrocyanide and other reducing substances. The ferrocyanide solution is added to the first ferric salt solution for dereduction treatment to remove the other reducing substances contained in the ferrocyanide solution. After solid-liquid separation, ferrocyanide precipitate and precipitate containing ferrocyanide are obtained. A second ferric salt solution is added to the precipitate for post-treatment, so that the ferrocyanide ion reacts with the ferric ion to obtain Prussian blue slurry. The other reducing substances include substances that can reduce ferric ions to ferrous ions.

2. The method for preparing Prussian blue according to claim 1, characterized in that, The reducing agent includes at least one of sulfite, thiosulfate, and metabisulfite.

3. The method for preparing Prussian blue according to claim 2, characterized in that, The sulfites include potassium sulfite, sodium sulfite, and ammonium sulfite; The thiosulfate includes at least one of potassium thiosulfate, sodium thiosulfate, and ammonium thiosulfate; The metabisulfite includes at least one of potassium metabisulfite, sodium metabisulfite, and ammonium metabisulfite.

4. The method for preparing Prussian blue according to claim 1, characterized in that, The molar ratio of the ferricyanide complex to the reducing agent in the aqueous solution containing the ferricyanide complex is 2:(1.01-1.2).

5. The method for preparing Prussian blue according to claim 1, characterized in that, The other reducing substances include at least one of sulfite, thiosulfate, and metabisulfite.

6. The method for preparing Prussian blue according to claim 1, characterized in that, After adding the reducing agent, the reduction treatment further includes adding at least one of potassium salt, sodium salt and ammonium salt to the ferrocyanide solution.

7. The method for preparing Prussian blue according to claim 6, characterized in that, The potassium salt includes at least one of potassium sulfate and potassium chloride, the sodium salt includes at least one of sodium sulfate and sodium chloride, and the ammonium salt includes at least one of ammonium sulfate and ammonium chloride.

8. The method for preparing Prussian blue according to claim 6, characterized in that, The potassium ion concentration of the ferrocyanide solution after adding the potassium salt is 10-35 g / L; The sodium ion concentration of the ferrocyanide solution after adding the sodium salt is 6-21 g / L; The ammonium ion concentration of the ferrocyanide solution after adding the ammonium salt is 5-16 g / L.

9. The method for preparing Prussian blue according to claim 1, characterized in that, The first iron salt solution includes at least one of ferric sulfate solution and ferric chloride solution.

10. The method for preparing Prussian blue according to claim 9, characterized in that, The concentration of the first iron salt solution is 8-12 g / L.

11. The method for preparing Prussian blue according to claim 1, characterized in that, The second iron salt solution includes at least one of ferric sulfate solution and ferric chloride solution.

12. The method for preparing Prussian blue according to claim 11, characterized in that, The concentration of the second iron salt solution is 8-12 g / L.

13. The method for preparing Prussian blue according to claim 1, characterized in that, The reaction time for the post-treatment is 3-7 hours.

14. The method for preparing Prussian blue according to claim 1, characterized in that, The mass percentage of ferrous ferrocyanide in the Prussian blue paste is ≤0.1%.

15. The method for preparing Prussian blue according to claim 14, characterized in that, The mass percentage of ferrous ferrocyanide in the Prussian blue paste is ≤0.01%.

16. The method for preparing Prussian blue according to claim 1, characterized in that, Before adding the reducing agent, the reduction process also includes adding a pH adjuster to the aqueous solution to adjust the pH value.

17. The method for preparing Prussian blue according to claim 16, characterized in that, The pH adjuster includes at least one of sulfuric acid and hydrochloric acid; and / or, The pH value after adjustment with the pH adjuster is 8.0-10.

0.

18. The method for preparing Prussian blue according to claim 1, characterized in that, The preparation method further includes obtaining an aqueous solution containing a ferricyanide complex, wherein the aqueous solution containing the ferricyanide complex comprises: A first precipitant is added to the first wastewater to perform oxalic acid separation treatment. After solid-liquid separation, oxalic acid precipitate and oxalic acid-precipitated liquid are obtained, wherein the oxalic acid-precipitated liquid is used for the reduction treatment. or A second precipitant is added to the first wastewater to separate manganese. After solid-liquid separation, manganese hydroxide precipitate and manganese precipitation liquid are obtained. The manganese precipitation liquid is used for the reduction treatment. or A first precipitant is added to the first wastewater for oxalic acid separation treatment, and oxalic acid precipitate and oxalic acid precipitation liquid are obtained through solid-liquid separation; a second precipitant is added to the oxalic acid precipitation liquid for manganese separation treatment, and manganese hydroxide precipitate and manganese precipitation liquid are obtained through solid-liquid separation, wherein the manganese precipitation liquid is used for the reduction treatment.

19. The method for preparing Prussian blue according to claim 18, characterized in that, The first wastewater includes a ferricyanide complex, and further includes at least one of oxalic acid and manganese; and / or, The first precipitant includes at least one of ferrocyanide and metal oxide.

20. The method for preparing Prussian blue according to claim 19, characterized in that, The ferrocyanide salt includes at least one of calcium ferrocyanide and manganese ferrocyanide, and the metal oxide includes calcium oxide; and / or, The molar ratio of the first precipitant to the ferricyanide complex in the first wastewater is (1.01-1.15):

1.

21. The method for preparing Prussian blue according to claim 18, characterized in that, The second precipitant includes at least one of potassium hydroxide, sodium hydroxide, and ammonia water; and / or, The reaction pH value for the manganese separation treatment is 12-13.

22. The method for preparing Prussian blue according to claim 18, characterized in that, Flocculants are added during the oxalic acid separation process and / or the manganese separation process.

23. The method for preparing Prussian blue according to claim 22, characterized in that, The flocculant includes polyacrylamide.

24. A method for preparing an activated carbon-Prussian blue material, characterized in that, The activated carbon-Prussian blue material is prepared by mixing activated carbon with a slurry obtained by the preparation method of Prussian blue according to any one of claims 1-23.

25. The method for preparing activated carbon-Prussian blue material according to claim 24, characterized in that, Includes the following steps: The activated carbon and the Prussian blue slurry are mixed and washed with an organic solvent to obtain a solid product, which is the activated carbon-Prussian blue material.

26. The method for preparing activated carbon-Prussian blue material according to claim 25, characterized in that, The ratio of activated carbon to Prussian blue slurry is 1g:(10-20)mL; After the activated carbon and the Prussian blue slurry are mixed, they are kept for 5-10 hours and then washed with an organic solvent to remove the Prussian blue that did not participate in the formation of the activated carbon-Prussian blue material. The organic solvent includes at least one of ethanol and acetone.

27. The method for preparing activated carbon-Prussian blue material according to claim 25, characterized in that, The preparation method further includes drying the solid product to obtain the activated carbon-Prussian blue material.

28. The method for preparing activated carbon-Prussian blue material according to claim 27, characterized in that, The oxygen volume content of the dry atmosphere is ≤0.1%; The drying temperature is 50-80℃; The drying time is 6-12 hours; The moisture content of the dried activated carbon-Prussian blue material is ≤2%.

29. The method for preparing activated carbon-Prussian blue material according to claim 24 or 25, characterized in that, Before mixing the activated carbon with the Prussian blue slurry, the preparation method further includes reacting the activated carbon with an activator to form pores and then performing a high-temperature activation treatment.

30. The method for preparing activated carbon-Prussian blue material according to claim 29, characterized in that, The activated carbon has a particle size of 2-4 mm; and / or, The activator includes a potassium acetate solution with a concentration of 200-400 g / L.

31. The method for preparing activated carbon-Prussian blue material according to claim 30, characterized in that, The ratio of potassium acetate solution to activated carbon is (1-3) L: 1 g; and / or, The reaction time between the potassium acetate solution and the activated carbon is 6-12 hours.

32. The method for preparing activated carbon-Prussian blue material according to claim 29, characterized in that, The high-temperature activation temperature is 750-800℃; The high-temperature activation is carried out under an inert atmosphere; the high-temperature activation time is 2-4 hours.

33. An activated carbon-Prussian blue material, characterized in that, Prepared by the method according to any one of claims 24-32.

34. A method for treating secondary wastewater using activated carbon-Prussian blue materials, characterized in that, This includes mixing the activated carbon-Prussian blue material of claim 33 with the second wastewater to utilize the activated carbon-Prussian blue material to adsorb radioactive elements in the second wastewater.

35. The method according to claim 34, characterized in that, The radioactive element includes at least one of thallium and cesium.

36. The method according to claim 34, characterized in that, Before mixing the activated carbon-Prussian blue material with the second wastewater, the method further includes filtering and / or adjusting the pH of the second wastewater.

37. The method according to claim 36, characterized in that, The total heavy metal concentration of the second wastewater after the filtration treatment is 0.1-1.5 mg / L.

38. The method according to claim 37, characterized in that, The heavy metals include at least one of Ni, Co, and Mn.

39. The method according to claim 36, characterized in that, The pH value of the second wastewater after the pH adjustment treatment is 4.5-6.

0.

40. The method according to claim 34, characterized in that, The concentration of radioactive elements in the second wastewater after treatment by the method is 0.01-2.0 ug / L.

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