Zero-discharge treatment method for wastewater resulting from production of sodium-ion battery positive electrode material

Abstract

Disclosed in the present invention is a zero-discharge treatment method for wastewater resulting from the production of a sodium-ion battery positive electrode material. The method comprises the following specific steps: mixing wastewater resulting from the production of a sodium-ion battery positive electrode material of Prussian blue and an analogue thereof with calcium chloride, carrying out solid-liquid separation after a reaction is completed, and enabling the resulting filtrate to undergo membrane filtration and to flow back; and preparing the resulting filter cake into a slurry and then heating the slurry, adding a sodium carbonate solution for a reaction for a certain period of time and then carrying out solid-liquid separation, and carrying out evaporative crystallization treatment on the resulting filtrate to obtain high-purity sodium citrate. In the present invention, citrate, ferrocyanide, and sulfate radicals in the wastewater resulting from the production of the sodium-ion battery positive electrode material can be recycled or removed by precipitation, avoiding the waste of resources and the risk of secondary pollution, and realizing low-cost green recycling of citrate and ferrocyanide radicals in the wastewater. The present invention has the advantages of low costs, a short process, energy conservation, a high utilization rate, no secondary pollution, etc., and exhibits excellent prospects for industrial application and promotion.

Description

A zero-discharge treatment method for sodium ion battery positive electrode material production wastewater Technical Field

[0001] The present invention relates to the technical field of sodium ion battery production wastewater treatment, and in particular to a zero-discharge treatment method for sodium ion battery Prussian blue and its analogues positive electrode material production wastewater based on a combination of membrane separation, physical methods and chemical methods. Background Art

[0002] The price of lithium carbonate has risen sharply in recent years, driven by the uneven global distribution of lithium reserves and the surge in electric vehicle production. Sodium-ion batteries (SIBs) have regained their research focus as new chemical power sources due to their abundant resources, low cost, and widespread distribution. As an economical alternative to lithium-ion batteries, SIBs hold great promise for applications in my country, including large-scale energy storage and low-speed electric bicycles.

[0003] Currently, mainstream sodium-ion battery cathode materials are primarily based on sodium transition metal oxides, phosphate-based polyanionic compounds, metal fluorides, Prussian blue analogs, and organic polymers. Prussian blue and its analogs demonstrate exceptional potential due to their rigid, open, three-dimensional framework, high theoretical specific capacity, structural tunability, and readily accessible synthesis methods. According to statistics, in the energy storage sector, installed capacity of sodium-ion batteries increased by 577% year-on-year in the first four months of 2023, with investment and financing expected to increase by over 200%.

[0004] As the industrialization of sodium-ion batteries accelerates, the amount of wastewater generated from production is increasing, posing increasingly serious risks to the ecological environment and human health. However, there is currently no comprehensive, low-cost, green treatment solution for sodium-ion battery production wastewater, both domestically and internationally. Failure to properly treat and dispose of this wastewater will lead to increased production costs, wasteful use of land, and environmental pollution for sodium-ion battery manufacturers. Therefore, the development of green, low-cost sodium-ion battery production wastewater treatment processes is urgently needed, with the industry's demand for zero-emission treatment technologies becoming particularly pressing.

[0005] Summary of the Invention

[0006] In response to the above problems, the main purpose of the present invention is to provide a zero-discharge treatment method for wastewater produced by the production of positive electrode materials for sodium ion batteries. The method of the present invention separates ferrocyanide, citrate, and sulfate in the wastewater, wherein the sulfate is removed in the form of calcium sulfate through solid-liquid separation, the citrate is recovered in the form of high-purity sodium citrate, and the ferrocyanide ion is refluxed as a raw material to the production process of positive electrode materials for sodium ion batteries. This solves the risk of secondary pollution of the wastewater to the ecological environment, avoids material waste, reduces production costs, and achieves efficient recovery of sodium citrate in the wastewater produced by the production of positive electrode materials for sodium ion batteries, Prussian blue and its analogs. The method has the advantages of low cost, short process, energy saving, high utilization rate, and no secondary pollution, showing excellent prospects for industrial application and promotion.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] A zero-discharge treatment method for sodium ion battery cathode material production wastewater comprises the following steps:

[0009] (1) After filtering and pre-treating the wastewater produced by the production of sodium ion battery Prussian blue and its analogs positive electrode materials (removing possible fine solid particulate residual products generated in the production wastewater), wastewater containing ferrocyanide, citrate and sulfate is obtained;

[0010] (2) adding an appropriate amount of calcium chloride to the wastewater obtained in step (1) and stirring and fully reacting the mixture; and after completion of the reaction, performing solid-liquid separation to obtain a filtrate containing chloride ions and ferrocyanide and a filter residue containing calcium sulfate and calcium citrate;

[0011] (3) The filtrate obtained in step (2) is subjected to membrane filtration twice in succession, so that ferrocyanide and chloride ions are retained by the membrane, wherein the ferrocyanide is refluxed as a raw material to the production process of the positive electrode material of the sodium ion battery;

[0012] (4) washing the filter residue obtained in step (2) multiple times and preparing a slurry with a certain mass fraction to obtain a mixture with calcium sulfate and calcium citrate as main components;

[0013] (5) The slurry obtained in step (4) is heated and stirred, and a sodium carbonate solution of a certain concentration is slowly added, while the pH value of the slurry is measured. When the pH value reaches a certain value, the addition of the sodium carbonate solution is stopped, and the reaction is maintained for a certain time.

[0014] (6) slowly adding citric acid to the slurry obtained in step (5) to adjust its pH value, and performing solid-liquid separation to obtain a filter residue with calcium sulfate and calcium carbonate as the main components and a filtrate with sodium citrate as the main component;

[0015] (7) Evaporating and crystallizing the filtrate obtained in step (6) to obtain a white powder with sodium citrate as the main component. In the present invention, the amount of calcium chloride added in step (2) needs to be appropriate, which means that the ratio of the molar amount of calcium chloride to the total molar amount of sodium citrate and sodium sulfate in the wastewater is 1.

[0016] In the present invention, the two membrane filtrations in step (3) are nanofiltration and reverse osmosis respectively.

[0017] In the present invention, the mass fraction of the slurry in step (4) is 8% to 20%. In the present invention, in step (5), the reaction temperature is 20°C to 90°C, the concentration of the sodium carbonate solution is 5% to 45%, the pH value is adjusted to 7 to 12 using the sodium carbonate solution, and the reaction time is 10 min to 70 min. Preferably, the reaction temperature is 50°C to 90°C, the concentration of the sodium carbonate solution is 15% to 45%, the pH value is adjusted to 9 to 12 using the sodium carbonate solution, and the reaction time is 30 min to 70 min.

[0018] In the present invention, in step (6), the concentration of citric acid used is 5% to 45%, and the pH value is adjusted to a range of 5 to 10 using citric acid.

[0019] The present invention enables citrate, ferrocyanide and sulfate in the wastewater produced by the production of positive electrode materials for sodium ion batteries to be recycled or removed by precipitation, thereby avoiding waste of resources and the risk of secondary pollution, and realizing low-cost green recycling of citrate and ferrocyanide in the wastewater. The invention has the advantages of low cost, short process, energy saving, high utilization rate and no secondary pollution, and shows excellent prospects for industrial application and promotion.

[0020] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following three aspects:

[0021] (1) The present invention provides a zero-discharge treatment method for wastewater produced by the production of positive electrode materials for sodium ion batteries, which solves the problem of the difficulty in separating sulfate, citrate and ferrocyanide in the wastewater produced by the production of positive electrode materials for sodium ion batteries such as Prussian blue and its analogs, and has the advantages of low reagent consumption, short process, low cost and high sodium citrate recovery rate.

[0022] (2) The present invention provides a zero-discharge treatment method for wastewater produced by the production of positive electrode materials for sodium ion batteries. The method adopts a method combining physical, chemical and membrane technologies to efficiently recover citrate and ferrocyanide, which are raw materials for the production of positive electrode materials for sodium ion batteries, such as Prussian blue and its analogues. This reduces the production cost of the products and has broad prospects for industrial application.

[0023] (3) The present invention provides a zero-discharge treatment method for wastewater produced by the production of positive electrode materials for sodium ion batteries. Starting from the physical and chemical properties of wastewater produced by the production of positive electrode materials for sodium ion batteries such as Prussian blue and its analogues, the entire treatment process is clean and free of secondary pollution, and can effectively improve the recovery rate of sodium citrate in the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a process flow chart of the zero-discharge treatment of wastewater produced by the production of Prussian blue and its analogues positive electrode materials for sodium ion batteries proposed by the present invention.

[0025] FIG2 is an XRD pattern of the powder obtained by evaporation and crystallization in Example 1. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0027] FIG1 is a flow chart of a zero-discharge treatment process for wastewater produced by the production of Prussian blue and its analogs as cathode materials for sodium ion batteries proposed by the present invention. The present invention provides a zero-discharge treatment method for wastewater produced by the production of cathode materials for sodium ion batteries, and the specific steps are as follows:

[0028] (1) After filtering and pre-treating the wastewater produced by the production of sodium ion battery Prussian blue and its analogs positive electrode materials, wastewater containing ferrocyanide and citrate is obtained;

[0029] (2) adding an appropriate amount of calcium chloride to the wastewater obtained in step (1) and stirring and fully reacting the mixture; after the reaction is completed, performing solid-liquid separation to obtain a filtrate containing chloride ions and ferrocyanide and a filter residue containing calcium sulfate and citrate;

[0030] (3) The filtrate obtained in step (2) is subjected to membrane filtration twice in succession, so that ferrocyanide and chloride ions are retained by the membrane, wherein the ferrocyanide is refluxed as a raw material to the production process of the positive electrode material of the sodium ion battery;

[0031] (4) washing the filter residue obtained in step (2) multiple times and preparing a slurry with a certain mass fraction to obtain a mixture with calcium sulfate and calcium citrate as main components;

[0032] (5) The slurry obtained in step (4) is heated and stirred, and a sodium carbonate solution of a certain concentration is slowly added, while the pH value of the slurry is measured. When the pH value reaches a certain value, the addition of the sodium carbonate solution is stopped, and the reaction is maintained for a certain time.

[0033] (6) slowly adding citric acid to the slurry obtained in step (5) to adjust its pH value, and performing solid-liquid separation to obtain a filter residue containing calcium sulfate and calcium carbonate as main components and a filtrate containing sodium citrate as main component;

[0034] (7) The filtrate obtained in step (6) is evaporated and crystallized to obtain a white powder with sodium citrate as the main component.

[0035] In the present invention, the calcium chloride added in step (2) needs to be in an appropriate amount, and the ratio of the molar amount of calcium chloride to the total molar amount of sodium citrate and sodium sulfate in the wastewater is 1.

[0036] In the present invention, the two membrane filtrations in step (3) are nanofiltration and reverse osmosis respectively.

[0037] In the present invention, the mass fraction of the slurry in step (4) is 8% to 20%.

[0038] In the present invention, in step (5), the reaction temperature is 20° C. to 90° C., the concentration of the sodium carbonate solution used is 5% to 45%, the pH value is adjusted to 7 to 12 using the sodium carbonate solution, and the reaction time is 10 min to 70 min.

[0039] In the present invention, in step (6), the concentration of citric acid used is 5% to 45%, and the pH value is adjusted to a range of 5 to 10 using citric acid.

[0040] Example 1

[0041] A zero-discharge treatment method for sodium ion battery cathode material production wastewater, comprising the following specific steps:

[0042] (1) Determination of sodium ion concentration in water samples

[0043] The sodium-ion battery cathode material production wastewater samples used in the present invention were provided by Jiangsu Energy Technology Co., Ltd. One mL of the water sample was diluted 2500-fold with 1% dilute nitric acid. The cation content was then quantitatively determined using an ICP-OES (ICAP700) from ThermoFisher Scientific. The results are shown in Table 1.

[0044] Table 1 Na in wastewater from the production of Prussian blue and its analogues as cathode materials for sodium ion batteries + Concentration

[0045] From the test results, we can see that Na + The concentration is 53150 mg / L, then n(Na + )=2.3mol / L

[0046] (2) Determination of sulfate concentration in water samples

[0047] The anion content was quantitatively determined using an ion chromatograph (CS1100) from ThermoFisher Scientific, USA. The results are shown in Table 2.

[0048] Table 2 SO4 in wastewater from the production of Prussian blue and its analogues as positive electrode materials for sodium ion batteries 2- Concentration

[0049] The results show that SO4 2- The concentration is 29546.86 mg / L. Due to SO4 2- In the form of Na2SO4, the original n(SO4 2- )=n(Na2SO4)=0.3mol / L.

[0050] (3) Determination of citrate concentration in water samples

[0051] The content of citrate was determined using a liquid chromatograph (LC1260-II) manufactured by Agilent Technologies, Inc., USA. The results are shown in Table 3.

[0052] Table 3 Citrate concentration in wastewater from the production of Prussian blue and its analogs cathode materials for sodium ion batteries

[0053] Therefore, in the original sample, n(Na3C6H5O7)=0.52mol / L, m(Na3C6H5O7)=134.2g / L.

[0054] (4) Removal of chloride ions

[0055] Measure 50mL of wastewater sample from the production of sodium ion battery Prussian blue and its analogs into a 100mL beaker, add an appropriate amount of CaCl2, stir and react for a certain period of time, and then filter to obtain a filtrate and a residue through solid-liquid separation. The filtrate is filtered through a nanofiltration membrane to separate Fe(CN)6 4- Retention, Cl - Interception, the removal rate of sodium ferrocyanide through nanofiltration membrane reaches more than 95%, and the removal rate of sodium chloride through reverse osmosis membrane reaches more than 97%.

[0056] (5) Recycling of citrate

[0057] The filter residue obtained in (4) was rinsed with deionized water several times to remove the residual CaCl2 on the surface. The filter cake was then prepared into a 15% slurry by mass and heated in an 80°C water bath. While stirring continuously, a 25% Na2CO3 solution was slowly added. During the addition process, the pH value of the reaction solution was continuously tested with a pH meter. When the pH value of the reaction solution rose to 11, the addition of the Na2CO3 solution was stopped. The reaction temperature was controlled at 80°C. After isothermal reaction for 60 minutes, the pH value was adjusted to 8.5 with citric acid (C6H8O7).

[0058] After the reaction is completed, the mixture is immediately filtered to obtain a filter cake and filtrate. The filter cake is rinsed multiple times with 80°C hot water. The filtrate is evaporated and crystallized using a rotary evaporator. After the solvent is evaporated to dryness, a white solid powder is obtained. The white solid powder is dried in a 60°C constant temperature drying oven for 1 day to obtain the final product, sodium citrate. 6.0686 g of sodium citrate is weighed, with a recovery rate of over 90%. Figure 2 shows the XRD pattern of the powder obtained by evaporation and crystallization in Example 1.

[0059] Example 2

[0060] This embodiment differs from Example 1 in that the mass fraction of the slurry in step (5) is 8%, the reaction temperature in step (5) is 20°C, the concentration of the sodium carbonate solution used is 5%, the pH value is adjusted to 9 using the sodium carbonate solution, and the reaction time is 10 minutes. All other aspects are the same as in Example 1. The measured sodium citrate recovery rate is 76.51%. This demonstrates efficient recovery of sodium citrate from wastewater produced from the production of Prussian blue and its analogues, a cathode material for sodium ion batteries.

[0061] Example 3

[0062] This embodiment differs from Example 1 in that the mass fraction of the slurry in step (5) is 20%, the reaction temperature in step (5) is 90°C, the concentration of the sodium carbonate solution used is 45%, the pH value is adjusted to 12 using the sodium carbonate solution, and the reaction time is 70 minutes. All other aspects are the same as in Example 1. The measured sodium citrate recovery rate is 84.18%. This effectively achieves the recovery of sodium citrate from wastewater produced from the production of Prussian blue and its analogues, a cathode material for sodium ion batteries.

[0063] Example 4

[0064] This embodiment differs from Example 1 in that the mass fraction of the slurry in step (5) is 15%, the reaction temperature in step (5) is 55°C, the concentration of the sodium carbonate solution used is 25%, the pH value is adjusted to 9.5 using the sodium carbonate solution, and the reaction time is 40 minutes. All other aspects are the same as in Example 1. The measured sodium citrate recovery rate is 81.49%. This effectively achieves the recovery of sodium citrate from wastewater produced from the production of Prussian blue and its analogues, a cathode material for sodium ion batteries.

[0065] Example 5

[0066] This embodiment differs from Example 1 in that the mass fraction of the slurry in step (5) is 17%, the reaction temperature in step (5) is 60°C, the concentration of the sodium carbonate solution used is 30%, the pH value is adjusted to 9 using the sodium carbonate solution, and the reaction time is 50 minutes. All other aspects are the same as in Example 1. The measured sodium citrate recovery rate is 88.25%. This effectively achieves the recovery of sodium citrate from wastewater produced from the production of Prussian blue and its analogues, a cathode material for sodium ion batteries.

[0067] Comparative Example 1

[0068] This comparative example differs from Example 1 in that calcium bicarbonate is used in place of calcium chloride in step (4), with all other processes being the same as in Example 1. The measured sodium citrate recovery rate was 64.56%. This method cannot efficiently recover sodium citrate from sodium ion battery cathode material production wastewater. Therefore, the amount of calcium chloride used in this wastewater treatment process is crucial to the present invention.

[0069] The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention, which is defined by the appended claims and their equivalents.

Claims

1. [Corrected according to Rule 26 on 04.09.2024] A method for zero-emission treatment of wastewater from the production of a sodium-ion battery cathode material, characterized in that, The method comprises the following steps: (1) After filtering and pre-treating the wastewater from the production of sodium-ion battery Prussian blue and its analogues cathode materials, wastewater containing ferrocyanide, citrate and sulfate is obtained; (2) An appropriate amount of calcium chloride is added to the wastewater obtained in step (1), followed by stirring and sufficient reaction. After the reaction ends, solid-liquid separation is carried out to obtain a filtrate containing chloride ions and ferrocyanide and a filter residue containing calcium sulfate and calcium citrate; (3) The filtrate obtained in step (2) is subjected to two membrane filtrations successively, so that ferrocyanide and chloride ions are retained by the membrane, and among them, ferrocyanide is refluxed as a raw material to the production process of sodium-ion battery cathode materials; (4) The filter residue obtained in step (2) is washed repeatedly and made into a slurry with a certain mass fraction by adding water; (5) The slurry obtained in step (4) is heated and stirred, and a sodium carbonate solution with a certain concentration is slowly added. At the same time, the pH value of the slurry is measured. When the pH value reaches a certain value, the addition of the sodium carbonate solution is stopped, and the reaction is maintained for a certain period of time; (6) Citric acid is slowly added to the slurry obtained in step (5) to adjust its pH value. After solid-liquid separation, a filter residue mainly composed of calcium sulfate and calcium carbonate and a filtrate mainly composed of sodium citrate are obtained; (7) The filtrate obtained in step (6) is subjected to evaporation crystallization to obtain a white powder mainly composed of sodium citrate.

2. [Corrected according to Rule 26 on 04.09.2024] The zero-discharge treatment method for the production wastewater of the positive electrode material of a sodium-ion battery according to claim 1, characterized in that: In step (2), adding an appropriate amount of calcium chloride means that the molar ratio of calcium chloride to the total molar amount of sodium citrate and sodium sulfate in the wastewater is 1.

3. [Corrected according to Rule 26 on 04.09.2024] The zero-emission treatment method for the production wastewater of the positive electrode material of a sodium-ion battery according to claim 1, characterized in that: In step (3), the two membrane filtrations successively are nanofiltration and reverse osmosis.

4. [Corrected according to Rule 26 on 04.09.2024] The zero-discharge treatment method for the production wastewater of the sodium-ion battery cathode material according to claim 1, wherein: In step (4), the mass fraction of the slurry is 8% - 20%.

5. [Corrected according to Rule 26 on 04.09.2024] The zero-discharge treatment method for the production wastewater of the positive electrode material of a sodium-ion battery according to claim 1, characterized in that: In step (5), the reaction temperature is 20°C - 90°C, the concentration of the sodium carbonate solution is 5% - 45%, the pH value range adjusted by the sodium carbonate solution is 7 - 12, and the reaction time is 10 min - 70 min.

6. [Corrected according to Rule 26 on 04.09.2024] The zero-emission treatment method for the production wastewater of the positive electrode material of a sodium-ion battery according to claim 1, characterized in that: In step (5), the reaction temperature is 50°C - 90°C, the concentration of the sodium carbonate solution is 15% - 45%, the pH value range adjusted by the sodium carbonate solution is 9 - 12, and the reaction time is 30 min - 70 min.

7. [Corrected according to Rule 26 on 04.09.2024] The zero-discharge treatment method for the production wastewater of the positive electrode material of a sodium-ion battery according to claim 1, characterized in that: In step (6), the concentration of citric acid is 5wt.% - 45wt.%, and the pH value range adjusted by citric acid is 5 - 10.

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