Method for producing Prussian blue compound based on cyanide-containing mother liquor

Abstract

The invention relates to a method for producing a prussian blue compound based on a cyanide-containing mother solution, which comprises the following steps of: forming production wastewater from the cyanide-containing mother solution generated in the preparation of the prussian blue compound with a structural general formula of NaxMn [Mn (CN) 6] < 1-y >. Y.nH2O and washing water, and adjusting the CN <-> concentration to 0.05-0.10 mol / L, ferrous sulfate and organic acid sodium salt form a mixed solution, the mixed solution is dropwise added into production wastewater for precipitation reaction, and the iron-based prussian blue compound is obtained through aging treatment, washing and drying. The iron-based prussian blue compound is produced by using the CN-containing production waste liquid generated in the production of different types of prussian blue compounds, so that the resource comprehensive utilization of the production waste water is realized, and the quality of the prepared product is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive resource utilization of chemical production wastewater, and relates to comprehensive utilization of wastewater produced by Prussian blue compounds, and in particular to a method for utilizing Prussian blue compounds Na x Mn[Mn(CN)6] 1-y □ y · n A method for preparing other Prussian blue-like compounds from cyanide-containing mother liquor produced in H2O production. Background Art

[0002] Fossil energy is becoming increasingly depleted, and the pollution caused by fossil fuels is becoming increasingly serious, leading to a continuous increase in demand for renewable energy. The development of renewable energy is inseparable from the support of energy storage technology. Electrochemical energy storage has become an important force in new energy storage technology due to its advantages such as good safety performance, low cost, high energy conversion efficiency and energy density, and environmental friendliness.

[0003] Energy storage batteries are the core part of electrochemical energy storage systems. The mainstream batteries on the market can be roughly divided into lithium-ion batteries, sodium-ion batteries and flow batteries according to different technical routes. Lithium-ion batteries have the advantages of high energy density, high comprehensive efficiency, fast reaction speed, long service life and small impact on the ecological environment. They are undoubtedly one of the technologies with the fastest development momentum and the fastest commercialization process in electrochemical energy storage, and are also the most adaptable technical route in the development of energy storage products. However, the shortage of lithium resources and battery safety have undoubtedly limited its application in large-scale energy storage. Sodium-ion batteries have once again become a research hotspot in the field of energy storage due to their advantages such as abundant sodium resources, high energy conversion efficiency, long cycle life and good safety performance.

[0004] Sodium-ion batteries (SIBs) are rechargeable batteries that use sodium ions as charge carriers. Their working principle and structure are similar to those of lithium-ion batteries, except that sodium, which is in the same group in the periodic table and has similar chemical properties, replaces lithium. After decades of development, the current positive electrode materials for sodium-ion batteries mainly include transition metal oxides, polyanionic compounds, and Prussian blue compounds (PBAs).

[0005] The general chemical formula of PBAs is A x M1[M2(CN)6] 1-y □ y · n H2O(A:Na + , Li + , K + Equivalent mobile cations; M1: N-coordinated transition metal ion; M2: C-coordinated transition metal ion; □: represents [M2(CN)6] vacancy; 0≤x ≤2; 0≤ y ＜ 1). Compared with transition metal oxides and polyanionic compounds, PBAs have larger sodium storage sites and ion deintercalation channels due to their unique open framework and three-dimensional macroporous structure, which can realize Na + It can be quickly deintercalated without lattice distortion, and is very suitable for storing sodium ions with large ionic radius. At the same time, it has low cost and low toxicity, and can be synthesized at room temperature, so it has been widely studied in recent years.

[0006] At present, manganese hexacyanomanganate (MnHCMn, M1=Mn, M2=Mn) and hexacyanoferrate (HCFs, M1=Fe, Mn, Co, Ni, Cu and other transition metals, M2=Fe) are the most widely studied PBAs battery materials. II [Mn II The main raw materials for the synthesis of HCFs are Na4[Fe(CN)6] and soluble salts of transition metals such as Fe, Mn, Co, Ni, and Cu, such as sulfate, acetate, nitrate, and chloride. The main synthesis method of both is chemical precipitation, which involves dropping a solution containing transition metal ions into a solution containing CN. - or [Fe(CN)6] 4- of solution B and vice versa.

[0007] However, the rapid precipitation reaction leads to the presence of a large amount of [M2(CN)6] x- vacancies, introducing more crystal water, Na + The storage sites are reduced, which significantly reduces the electrochemical performance of PBAs.

[0008] Studies have shown that in the chemical precipitation process of PBAs, adding soluble sodium salts to the precursor solution can make more Na + Occupies the corresponding spatial sites, obtains a sodium-rich structure, and can slightly reduce the vacancy defects in the material. At the same time, it can also be combined with Mn by complexing agents such as trisodium citrate. 2+ or Fe 2+ The complexation of metal ions slows down the crystallization rate, reduces the vacancy amount, improves the integrity of the crystal structure, and makes Na + There is more access to lattice storage sites.

[0009] It can be seen that the precursor solution has a high concentration of Na +It is an important condition for the preparation of high-Na content PBAs. Adding excess sodium source can not only increase the sodium ion content of the product, but also help stabilize the crystal structure.

[0010] However, this also brings another problem, that is, this method will produce a large amount of sodium-containing wastewater that needs to be treated. Especially for hexacyanomanganate MnHCMn, due to the different raw materials used in production, it is different from the mother liquor wastewater produced by other Prussian blue compounds. Its sodium-containing wastewater also contains a large amount of CN - , which can be called cyanide-containing mother liquor.

[0011] Patent application 202411265817.1 involves a general structural formula of Na x Mn[Mn(CN)6] 1-y □ y · n H2O (where □ represents [Mn(CN)6] vacancy; 0< x ≤2; 0≤ y <1) The preparation method of Prussian blue compounds, the production process of which is to carry out chemical precipitation reaction with manganese sulfate and sodium cyanide, separate the reaction liquid into solid and liquid to obtain a precipitate, and then wash and vacuum dry the precipitate to obtain the product. Therefore, in the production process, two groups of waste liquids, cyanide-containing mother liquor and washing water, will be formed. If they are mixed, a large amount of production wastewater will be formed.

[0012] After testing, the main component of the above cyanide-containing mother liquor is SO4 2- , CN - and Na + , and contains a small amount of Mn 2+ , where CN - The concentration can reach 0.2mol / L, Na + The concentration reached 1.49 mol / L, SO4 2- The concentration reached 0.65 mol / L, Mn 2+ The concentration is generally around 15 mg / L. Even after diluting it with washing water, the CN in the production wastewater - The concentration is still 0.05-0.1 mol / L, and SO4 2- Concentration 0.17~0.35mol / L, Na + Concentration 0.37~0.75mol / L, Mn 2+ Concentration: 0.1~0.3mmol / L.

[0013] Therefore, it is necessary to develop comprehensive resource utilization technologies for its production wastewater to lay a solid foundation for its industrial-scale production. Summary of the invention

[0014] The purpose of the present invention is to provide a comprehensive resource utilization method for cyanide mother liquor of Prussian blue compounds, so as to fully utilize the cyanide mother liquor generated in the production process of Prussian blue compounds.

[0015] To achieve the above-mentioned purpose, the present invention provides a method for producing Prussian blue compounds based on cyanide mother liquor. The method provided by the present invention is suitable for having a general structural formula Na x Mn[Mn(CN)6] 1-y □ y · n The cyanide mother liquor produced in the preparation of Prussian blue compounds with H2O is specifically the filtrate produced in the process of collecting solid precipitates by suction filtration after precipitation reaction. The cyanide mother liquor contains not only a relatively high concentration of CN - , also contains a higher concentration of Na + and SO4 2- , and a smaller amount of Mn 2+ .

[0016] At the same time, in the above production process, a certain amount of washing water will be generated in the process of cleaning the solid precipitate. Therefore, the washing water can be mixed with the cyanide-containing mother liquor to form production wastewater, which can be comprehensively utilized as resources.

[0017] Therefore, the present invention specifically provides a method of using a general structural formula of Na x Mn[Mn(CN)6] 1-y □ y · n The method for preparing iron-based Prussian blue compounds by direct reaction of H2O-containing Prussian blue compound production wastewater with ferrous sulfate solution comprises the following steps: 1) CN in production wastewater - As a complex cyanide source, Na + As a partial supplementary sodium source, the concentration of the production wastewater is adjusted to meet the CN - The concentration is 0.05~0.10mol / L; 2) Using ferrous sulfate as the iron source, organic acid sodium salt as the complexing agent and partially supplementing the sodium source, the molar ratio of organic acid sodium salt to ferrous sulfate is (1-2):1 to prepare Fe 2+ A mixed solution with a concentration of 0.02 to 0.20 mol / L; 3) Under nitrogen protection, the mixed solution is added dropwise to the production wastewater after the concentration is adjusted at a dropping speed of 0.05-2 mL / min to perform a precipitation reaction, and a reaction slurry is obtained after aging treatment; 4) Centrifuging the reaction slurry, collecting the precipitate, washing and drying it, and preparing an iron-based Prussian blue compound.

[0018] For the sake of convenience, the iron-based Prussian blue compound prepared by the present invention is represented by the structural formula Na2Fe[Fe(CN)6].

[0019] Further, it is preferred that Fe 2+ Concentration and CN - The molar ratio of is 1:(1-3), and the mixed solution is added dropwise into the production wastewater to carry out precipitation reaction.

[0020] Specifically, in the above preparation method of the present invention, the organic acid sodium salt complexing agent may include but is not limited to at least one of sodium citrate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium lauryl sulfate, sodium tartrate, and sodium gluconate. Preferably, the organic acid sodium salt complexing agent is sodium citrate.

[0021] Furthermore, the precipitation reaction of the present invention is carried out under stirring conditions, and the preferred stirring speed is 100-1000 rpm.

[0022] More specifically, the precipitation reaction is preferably carried out at a temperature of 25 to 80°C.

[0023] Furthermore, after the precipitation reaction is completed, the reaction solution is preferably aged for 0.5 to 24 hours.

[0024] The precipitate collected by centrifugation in the present invention finally needs to be washed with water and ethanol respectively, and preferably vacuum dried at 60-120° C. for 10-24 hours.

[0025] The method for preparing the Prussian blue compounds of the present invention fully utilizes the production waste liquid generated in the production of different types of Prussian blue compounds, maximizes the use of valuable ions therein, and other ions contained therein have no effect on the compounds prepared by the present invention, especially the manganese ions contained in the production waste water will not appear in the iron-based Prussian blue compounds.

[0026] The invention controls the conditions of the precipitation reaction and selects a very low solution concentration and a very slow dropping speed, so that not only the designed product is prepared, but also the precipitation reaction rate is effectively reduced, the oxidation of iron hydroxide is inhibited, the crystallinity of the product is improved, and the quality of the final product is guaranteed. The final product is applied as a sodium ion battery electrode material and has good electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 1 is the X-ray diffraction diagram of the iron-based Prussian blue compounds prepared in Example 1 and Comparative Example 1.

[0028] Figure 2 is a scanning electron microscope image of the compound prepared in Example 1.

[0029] Figure 3 It is a scanning electron microscope image of the compound of Example 1 at a magnification.

[0030] Figure 4 This is a scanning electron microscope image of the compound prepared in Comparative Example 1.

[0031] Figure 5 The charge and discharge curves of the compound prepared in Example 1 as the positive electrode material of an organic sodium ion battery.

[0032] Figure 6 The charge and discharge curves of the compound prepared in Comparative Example 1 as the positive electrode material of an organic sodium ion battery.

[0033] Figure 7 It is a cycle performance diagram of the compounds prepared in Example 1 and Comparative Example 1 as positive electrode materials for organic sodium ion batteries.

[0034] Figure 8 It is a rate performance diagram of the compounds prepared in Example 1 and Comparative Example 1 as positive electrode materials for organic sodium ion batteries. Implementation

[0035] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of the present invention so that those skilled in the art can well understand and utilize the present invention, rather than limiting the scope of protection of the present invention.

[0036] The production processes, experimental methods or detection methods involved in the embodiments and comparative examples of the present invention are all conventional methods in the prior art unless otherwise specified, and their names and / or abbreviations are all conventional names in the field and are very clear and unambiguous in the relevant application fields. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment to implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0037] The various instruments, equipment, raw materials or reagents used in the embodiments of the present invention are not particularly limited in terms of their sources, and are all conventional products that can be purchased through regular commercial channels, or can be prepared according to conventional methods well known to those skilled in the art. Example

[0038] Example 1

[0039] The cyanide mother solution used in this embodiment is prepared in Example 1 of patent application 202411265817.1 and has a general structural formula of Na x Mn[Mn(CN)6]1-y □ y · n When the Prussian blue compound was added to H2O, the filtrate produced during the solid precipitation was collected by filtration. After testing, the cyanide-containing mother liquor contained 0.2 mol / L CN - , 1.49 mol / L Na + and 0.65 mol / L SO4 2- , and 15 mg / L Mn 2+ .

[0040] The washing water generated when the solid precipitate is subsequently washed with deionized water is collected and mixed with the cyanide-containing mother liquor to form production wastewater.

[0041] After testing, CN in the production wastewater obtained by diluting the cyanide-containing mother liquor was − The concentration is 0.06mol / L, Na + Concentration 0.45mol / L, SO4 2- Concentration 0.20mol / L, Mn 2+ Concentration: 0.2mmol / L.

[0042] Weigh 2 g of ferrous sulfate heptahydrate and 4.24 g of sodium citrate dihydrate and dissolve them in deionized water to obtain 300 mL of Fe 2+ A mixed solution with a concentration of 0.024mol / L.

[0043] Under nitrogen protection at 30°C and a stirring speed of 360 rpm, the mixed solution was slowly added dropwise to 300 mL of production wastewater at a dropping rate of 0.3 mL / min. After the addition was completed, the mixture was aged for 24 hours under stirring to obtain a reaction slurry.

[0044] The reaction slurry was centrifuged, and the solid precipitate was collected, washed with deionized water three times, washed with anhydrous ethanol once, and vacuum dried at 120° C. for 24 h to prepare an iron-based Prussian blue compound Na2Fe[Fe(CN)6].

[0045] ICP-OES (inductively coupled plasma emission spectroscopy) analysis of the iron-based Prussian blue compounds prepared above revealed that only sodium and iron elements were detected, but no manganese element was detected, which proves that the small amount of cyanide in the mother liquor has no effect on the preparation of iron-based Prussian blue compounds.

[0046] Then, the waste liquid generated by centrifugation of the reaction slurry was collected and the CN - The concentration dropped to below 0.5ppm.

[0047] Comparative Example 1

[0048] In this comparative example, the cyanide-containing mother solution in Example 1 which was not diluted with washing water was directly used for precipitation reaction.

[0049] Weigh 6.67 g of ferrous sulfate heptahydrate and 14.12 g of sodium citrate dihydrate and dissolve them in deionized water to obtain 300 mL of Fe 2+ A mixed solution with a concentration of 0.08 mol / L.

[0050] Under nitrogen protection at 30°C and a stirring speed of 360 rpm, the mixed solution was slowly added dropwise to 300 mL of cyanide-containing mother solution at a dropping rate of 0.3 mL / min. After the addition was completed, the mixture was aged for 24 hours under stirring to obtain a reaction slurry.

[0051] The reaction slurry was centrifuged, and the solid precipitate was collected, washed with deionized water three times, washed with anhydrous ethanol once, and vacuum dried at 120° C. for 24 h to prepare an iron-based Prussian blue compound Na2Fe[Fe(CN)6].

[0052] The iron-based Prussian blue compounds prepared in Example 1 and Comparative Example 1 were respectively taken for X-ray diffraction and scanning electron microscopy performance characterization.

[0053] Although from Figure 1 It can be seen from the XRD diffraction patterns that the iron-based Prussian blue compounds prepared in Example 1 and Comparative Example 1 both have a monoclinic phase structure, but the difference between the two can be further observed through a scanning electron microscope.

[0054] Figure 2 The scanning electron microscope image of the product prepared in Example 1 shows that the morphology is uniform cubic particles of about 1 to 2 μm. Figure 3 Observing the product structure at a higher magnification, it can be seen that it contains secondary particles of 2 to 3 μm formed by neatly stacked primary particles.

[0055] and Figure 4 In the scanning electron microscope image of the iron-based Prussian blue compound prepared in Comparative Example 1, its appearance is irregular secondary particles formed by the accumulation of primary particles of 2 to 3 μm.

[0056] Application Example 1

[0057] The products prepared in Example 1 and Comparative Example 1 were respectively mixed with conductive carbon black Super P and binder PVDF (polyvinylidene fluoride) in a mass ratio of 7:2:1 to assemble positive electrode sheets, metallic sodium was used as negative electrode sheets, glass fiber membrane was used as separator, and NaClO4 ethylene carbonate (EC) / propylene carbonate (PC) solution was used as electrolyte. CR2025 half-cells were assembled in a glove box filled with argon for electrochemical performance testing, with a test voltage range of 2 to 4 V, and 1C corresponding to 170 mA / g.

[0058] Depend on Figure 5 It shows that the first cycle discharge capacity of the iron-based Prussian blue compound prepared in Example 1 at 0.2C reaches 147.4 mAh / g, but Figure 6 It shows that the first cycle discharge specific capacity of the iron-based Prussian blue compound prepared in Comparative Example 1 at 0.2C is only 127.9 mAh / g.

[0059] and then, Figure 7 The specific capacities of the two products after multiple cycles at 1C were further investigated. The specific capacity of the product of Example 1 after 500 cycles at 1C was 115.2 mAh / g, and the capacity retention rate was 85.2%. However, the specific capacity of the product of Comparative Example 1 after 200 cycles at 1C was reduced to 75.2 mAh / g, and the capacity retention rate was only 62.3%.

[0060] from Figure 8 It can be further seen from the rate performance diagram that the discharge specific capacity of the product of Example 1 at 10C is 96.8 mAh / g, while the discharge specific capacity of the product of Comparative Example 1 at 10C is 75.8 mAh / g.

[0061] Example 2

[0062] The source of production wastewater is the same as that in Example 1, where CN - Concentration 0.1mol / L, Na + Concentration 0.75mol / L, SO4 2- Concentration 0.33 mol / L, Mn 2+ Concentration: 0.3mmol / L.

[0063] Weigh 3.34 g of ferrous sulfate heptahydrate and 7.06 g of sodium citrate dihydrate and dissolve them in deionized water to obtain 300 mL of Fe 2+ A mixed solution with a concentration of 0.04mol / L.

[0064] Under nitrogen protection at 30°C and a stirring speed of 360 rpm, the mixed solution was slowly added dropwise to 300 mL of production wastewater at a dropping rate of 0.3 mL / min. After the addition was completed, the mixture was aged for 24 hours under stirring to obtain a reaction slurry.

[0065] The reaction slurry was centrifuged, and the solid precipitate was collected, washed with deionized water for 3 times, washed with anhydrous ethanol once, and vacuum dried at 120° C. for 24 h to prepare an iron-based Prussian blue compound.

[0066] Example 3

[0067] The source of production wastewater is the same as that in Example 1, where CN −Concentration 0.08mol / L, Na + Concentration 0.60mol / L, SO4 2- Concentration 0.26mol / L, Mn 2+ Concentration: 0.2mmol / L.

[0068] Weigh 2.67 g of ferrous sulfate heptahydrate and 5.65 g of sodium citrate dihydrate and dissolve them in deionized water to obtain 300 mL of Fe 2+ A mixed solution with a concentration of 0.032 mol / L.

[0069] Under nitrogen protection at 30°C and a stirring speed of 360 rpm, the mixed solution was slowly added dropwise to 300 mL of production wastewater at a dropping rate of 0.3 mL / min. After the addition was completed, the mixture was aged for 24 hours under stirring to obtain a reaction slurry.

[0070] The reaction slurry was centrifuged, and the solid precipitate was collected, washed with deionized water for 3 times, washed with anhydrous ethanol once, and vacuum dried at 120° C. for 24 h to prepare an iron-based Prussian blue compound.

[0071] The above embodiments of the present invention do not describe all the details in detail, nor limit the present invention to the above embodiments. Various changes, modifications, substitutions and variations made by ordinary technicians in this field without departing from the principles and purpose of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for producing Prussian blue compounds based on cyanide mother liquor is to use a general structural formula of Na x Mn[Mn(CN)6] 1-y □ y · n The production wastewater of Prussian blue compounds containing H2O directly reacts with ferrous sulfate solution to prepare iron-based Prussian blue compounds, including: 1) CN in production wastewater - As a complex cyanide source, Na + As a partial supplementary sodium source, the concentration of the production wastewater is adjusted to meet the CN - The concentration is 0.05~0.10mol / L; 2) Using ferrous sulfate as the iron source, organic acid sodium salt as the complexing agent and partially supplementing the sodium source, the molar ratio of organic acid sodium salt to ferrous sulfate is (1-2):1 to prepare Fe 2+ A mixed solution with a concentration of 0.02 to 0.20 mol / L; 3) Under nitrogen protection, the mixed solution is added dropwise to the production wastewater after the concentration is adjusted at a dropping speed of 0.05-2 mL / min to perform a precipitation reaction, and a reaction slurry is obtained after aging treatment; 4) Centrifuging the reaction slurry, collecting the precipitate, washing and drying it, and preparing an iron-based Prussian blue compound; Wherein, the production wastewater has the structural formula Na x Mn[Mn(CN)6] 1-y □ y · n The cyanide mother liquor produced in the preparation of Prussian blue compounds with H2O is mixed with washing water, wherein the cyanide mother liquor is the filtrate produced in the process of collecting solid precipitates by suction filtration after the precipitation reaction, and the washing water is the water produced in the process of washing the solid precipitates.

2. The method for producing Prussian blue compounds according to claim 1, characterized in that According to Fe 2+ Concentration and CN - The molar ratio of is 1:(1-3), and the mixed solution is added dropwise into the production wastewater to carry out precipitation reaction.

3. The method for producing Prussian blue compounds according to claim 1, characterized in that The organic acid sodium salt complexing agent is at least one of sodium citrate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium lauryl sulfate, sodium tartrate, and sodium gluconate.

4. The method for producing Prussian blue compounds according to claim 3, characterized in that The organic acid sodium salt complexing agent is sodium citrate.

5. The method for producing Prussian blue compounds according to claim 1, characterized in that During the precipitation reaction, stirring is performed at a rotation speed of 100 to 1000 rpm.

6. The method for producing Prussian blue compounds according to claim 1, characterized in that The precipitation reaction temperature is 25-80°C.

7. The method for producing Prussian blue compounds according to claim 1, characterized in that The reaction solution of the precipitation reaction is aged for 0.5 to 24 hours.

8. The method for producing Prussian blue compounds according to claim 1, characterized in that The collected precipitate was vacuum dried at 60-120°C for 10-24h.

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