A method for utilizing ternary precursor wastewater

Abstract

A method for utilizing ternary precursor wastewater, comprising: adding a NaOH solution to the wastewater to adjust the pH to 12.50 - 13.50, evaporating ammonia in the wastewater, and absorbing it with an H2SO4 solution to obtain an ammonium sulfate solution; adding an H2SO4 solution to adjust the pH to 6.8 - 7.0, and sequentially adding FeSO4 and Na2SO3 to obtain a mixed solution A; introducing a protective gas, adding PVA or PVP and mixing evenly to obtain a mixed solution B; introducing nitrogen for evaporation to obtain a precursor of the positive electrode material for a sodium-ion battery; calcining the precursor; and pulverizing the sintered material to obtain a positive electrode material product for a sodium-ion battery with a honeycomb structure. The present invention solves the problems of low recovery rates of nickel, cobalt, and manganese, high production costs, and low economic benefits of the by-product sodium sulfate, and realizes the efficient utilization of ternary precursor wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly relates to a method for utilizing ternary precursor wastewater. Background Art

[0002] The rapid development of new energy vehicles has driven the rapid growth of the demand for ternary precursors. During the preparation of ternary precursors, a large amount of wastewater is generated, which mainly contains Na + , SO 4 2- , NH 4 + and a small amount of Ni 2+ , Co 2+ , Mn 2+ , and it needs to be treated before discharge.

[0003] Currently, the relatively mainstream treatment process for ternary precursor wastewater is as follows: First, the ternary precursor wastewater is subjected to stripping and ammonia removal treatment. Since ammonia has a strong complexing ability with Ni and Co ions, after stripping and ammonia removal, other ammonia removal processes need to be combined to reduce the ammonia nitrogen concentration in the mother liquor to the discharge standard; then, by adding sodium hydroxide to adjust the pH, the heavy metals Ni, Co, and Mn in the wastewater are precipitated, realizing the recovery of Ni, Co, and Mn; finally, through the method of evaporation and crystallization, Na 2 SO 4 crystals are precipitated from the waste liquid, and the distilled condensate is returned to the production system of ternary precursors. However, the contents of Ni, Co, and Mn in the wastewater are relatively low, and the precipitated particles formed by increasing the pH are relatively fine and difficult to settle, resulting in low recovery rates of nickel, cobalt, and manganese and high production costs. In addition, as a by-product, sodium sulfate increases the treatment cost of ternary precursor wastewater due to its low market price.

[0004] Therefore, how to achieve the efficient utilization of ternary precursor wastewater has become the subject to be studied and solved in the present invention. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for utilizing ternary precursor wastewater.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for utilizing ternary precursor wastewater, comprising:

[0008] Step 1: Add a NaOH solution with a concentration of 10 - 12 mol / L to the ternary precursor wastewater, adjust the pH to 12.50 - 13.50, and distill out the ammonia in the wastewater by steam heating. The distilled ammonia directly enters a H 2 SO4 Absorption is carried out in the solution to obtain an ammonium sulfate solution;

[0009] Step 2: Add an H 2 SO 4 solution with a concentration of 5 - 7 mol / L to the wastewater after ammonia evaporation in Step 1, adjust the pH to 6.8 - 7.0, then add FeSO 4 , and keep the molar ratio of Na + to Fe 2+ in the solution as 1:(0.94 - 0.98). Then add Na 2 SO 3 , and keep the molar ratio of SO 3 2- to Fe 2+ as (0.001 - 0.004):1 to obtain a mixed solution A;

[0010] Step 3: Continuously introduce a protective gas with a gas concentration ≥ 99.99% into the mixed solution A in Step 2, add polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP), and mix evenly to obtain a mixed solution B;

[0011] Step 4: Evaporate the mixed solution B in Step 3 (the evaporation method can be heating evaporation), and continuously introduce a protective gas with a gas concentration ≥ 99.99% during the evaporation process to obtain a precursor of the sodium-ion battery cathode material;

[0012] Step 5: Calcinate the precursor of the sodium-ion battery cathode material obtained in Step 4. Continuously introduce Ar during the calcination process, sinter at 170 - 190 °C for 3 - 5 h; then raise the temperature to 350 - 400 °C and sinter for 12 - 16 h; the heating rate is 2 - 4 °C / min;

[0013] Step 6: Crush the material after sintering in Step 5 to obtain a sodium-ion battery cathode material product with a honeycomb structure.

[0014] Further technical solution: In Step 1, the ammonium sulfate solution can be used as a complexing agent in the preparation process of the ternary precursor.

[0015] Further technical solution: In Step 3, the addition amount of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) accounts for 3 - 6% of the total mass of Na + , SO 4 2- and Fe 2+ in the mixed solution A.

[0016] Further technical solution: In Step 4, the condensed water evaporated can be used for the preparation of the ternary precursor.

[0017] In a further technical solution, in step six, the chemical formula of the sodium ion battery positive electrode material product having a honeycomb structure is Na 2 Fe a Ni b Co c Mn d (SO 4 ) 2 @C, where 0.997≤a<1, 0<b<0.003, 0<c<0.003, 0<d<0.003, and a+b+c+d=1;

[0018] The primary particle size of the positive electrode material is 250~400nm, and the honeycomb pore size is 50~200nm.

[0019] The working principle and advantages of the present invention are as follows:

[0020] In the present invention, before deamination, the pH of the ternary precursor wastewater is adjusted to 12.50-13.50 with NaOH, and then deamination is carried out by steam heating, and finally H 2 SO 4 The solution absorbs the evaporated ammonia. In a high pH environment, NH 4 + Easier to convert to NH 3 , Ni, Co, and Mn ions will be converted into hydroxide precipitates, further releasing ammonia complexed with Ni and Co ions, solving the problem of incomplete deammoniation by steam stripping.

[0021] The present invention adopts H with a concentration of 5-7 mol / L 2 SO 4 The solution absorbs the evaporated ammonia. When ammonia is introduced into H 2 SO 4 When in solution, it will quickly react with H 2 SO 4 The reaction generates stable ammonium sulfate to prevent further volatilization of ammonia. The ammonium sulfate solution can be used as a complexing agent for the subsequent synthesis of ternary precursors. 2 SO 4 H in solution 2 SO 4 The concentration needs to be controlled at 5~7mol / L. If it is too high, the concentration of ammonium sulfate in the final solution will be too high, resulting in crystal precipitation and pipe clogging; if it is too low, it will not be conducive to improving the absorption efficiency and increase the ammonia recovery cost.

[0022] 3. In step 2, add 5-8 mol / L H 2 SO 4The solution was adjusted to a pH of 6.8 - 7.0, and then FeSO 4 was added. Subsequently, Na 2 SO 3 was added while maintaining the molar ratio of SO 3 2- to Fe 2+ in the solution at (0.001 - 0.004):1. Adding H 2 SO 4 solution to adjust the pH to 6.8 - 7.0 was to redissolve a small amount of Ni, Co, and Mn hydroxide precipitates. Adding a certain amount of Na 2 SO 3 was to reduce all the high-valent metal ions in the solution to +2 valence. Adding too much Na 2 SO 3 would cause waste of raw materials, while adding too little would result in incomplete reduction.

[0023] 4. In both Step 3 and Step 4 of the present invention, a protective gas (such as nitrogen) was introduced into the mixed solution. This operation was mainly to prevent the oxidation of Fe 2+ , Co 2+ , and Mn 2+ in the solution.

[0024] 5. By utilizing Na + , SO 4 2- and a small amount of Ni 2+ , Co 2+ , and Mn 2+ in the ternary precursor wastewater as raw materials, the present invention prepared a sodium-ion battery cathode material with a honeycomb structure, solved the problems of low recovery rate of nickel, cobalt, and manganese, high production cost, and low economic benefit of by-product sodium sulfate, and realized the efficient utilization of ternary precursor wastewater.

[0025] 6. When preparing the sodium-ion battery cathode material, by adding an appropriate amount of PVA or PVP and calcining and carbonizing, a honeycomb-structured carbon skeleton was formed. This skeleton helped improve conductivity and electrochemical performance. In addition, the introduction of the carbon skeleton could effectively prevent the further growth of cathode material particles and shorten the sodium-ion transmission path. The addition amount of PVA or PVP needed to be controlled. Too low would cause the cathode material particles to grow too large and the electrical performance to deteriorate, while too high would reduce the content of the cathode material and lead to a decrease in capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attached Figure 1 is the process flow chart of the embodiment of the present invention;

[0027] Attached Figure 2Electron micrograph of the positive electrode material of the sodium-ion battery prepared in the embodiment of the present invention;

[0028] Appendix Figure 3 Electron micrograph of the positive electrode material of the sodium-ion battery prepared in Comparative Example 1 of the present invention;

[0029] Appendix Figure 4 Electron micrograph of the positive electrode material of the sodium-ion battery prepared in Comparative Example 2 of the present invention;

[0030] Appendix Figure 5 Powder diffraction pattern of Na 2 Fe 0.997 Ni 0.001 Co 0.001 Mn 0.001 (SO 4 ) 2 @C of the present invention;

[0031] Appendix Figure 6 First charge-discharge curve of Na 2 Fe 0.997 Ni 0.001 Co 0.001 Mn 0.001 (SO 4 ) 2 @C of the present invention. Detailed implementation manners

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0033] The following will clearly explain the present case with diagrams and detailed descriptions. After understanding the embodiments of the present case, any person skilled in the art can make changes and modifications to the technology taught by the present case without departing from the spirit and scope of the present case.

[0034] The terms used in this article are only for describing specific embodiments and are not intended to limit the present case. Singular forms such as "a", "this", "this", "the present", and "the" also include plural forms as used in this article.

[0035] Regarding the terms used in this article, unless otherwise specified, they generally have the ordinary meanings of each term used in this field, in the context of the present case, and in the context of special content. Some terms used to describe the present case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art regarding the description of the present case.

[0036] Embodiment: A method for utilizing ternary precursor wastewater successively includes the following steps:

[0037] Step 1. Add a NaOH solution with a concentration of 12 mol / L to the ternary precursor wastewater, adjust the pH to 13, and distill the ammonia in the wastewater by steam heating. The distilled ammonia directly enters a solution of H 2 SO 4 with a concentration of 6 mol / L for absorption to obtain an ammonium sulfate solution, which is used as a complexing agent in the preparation process of the ternary precursor;

[0038] Step 2. Add a solution of H 2 SO 4 with a concentration of 6 mol / L to the ternary precursor wastewater after ammonia distillation in Step 1, adjust the pH to 6.9, then add FeSO 4 , and maintain the molar ratio of Na + to Fe 2+ in the solution at 1:0.95. Then add Na 2 SO 3 , and maintain the molar ratio of SO 3 2- to Fe 2+ at 0.003:1 to obtain a mixed solution A;

[0039] Step 3. Continuously introduce nitrogen with a concentration ≥ 99.99% into the mixed solution A in Step 2, add polyvinyl alcohol (PVA) and mix evenly. The addition amount of PVA accounts for 4% of the total mass of Na + , SO 4 2- , and Fe 2+ in the mixed solution to obtain a mixed solution B;

[0040] Step 4. Evaporate the mixed solution B in Step 3. The evaporated condensed water is used for the preparation of the ternary precursor, and nitrogen with a concentration ≥ 99.99% is continuously introduced during the evaporation process to obtain a precursor of the sodium-ion battery cathode material;

[0041] Step 5. Calcinate the precursor of the sodium-ion battery cathode material obtained in Step 4. Continuously introduce Ar during the calcination process, sinter at 180 °C for 4 h; then raise the temperature to 380 °C and sinter for 12 h; the heating rate is 2 °C / min;

[0042] Step 6. Crush the material after sintering in Step 5 to obtain a sodium-ion battery cathode material product with a honeycomb structure. The chemical formula of this product is Na 2 Fe 0.997 Ni 0.001 Co 0.001 Mn 0.001 (SO 4 ) 2@C, the size of the primary particles of the positive electrode material is 250 - 400 nm, and the pore size of the honeycomb is 50 - 200 nm. The relevant electrical performance data are shown in Table 1.

[0043] Comparative Example 1:

[0044] The difference from the example is that PVA was not added in Step 3 of this Comparative Example 1, and the rest is exactly the same as the example. The relevant electrical performance data are shown in Table 1.

[0045] Comparative Example 2:

[0046] The difference from the example is that the addition amount of PVA in Step 3 of this Comparative Example 1 accounts for 10% of the total mass of Na + , SO 4 2- and Fe 2+ , and the rest is exactly the same as the example. The relevant electrical performance data are shown in Table 1.

[0047] Table 1 shows the relevant test data in the example and each comparative example.

[0048]

[0049] Comparing the data of each example and each comparative example in Table 1, it can be seen that:

[0050] Under the same other conditions, the discharge capacity of the positive electrode material prepared without adding PVA is relatively low. This is mainly because the absence of PVA will lead to a decrease in the conductivity of the prepared positive electrode material, thereby affecting the first charge-discharge efficiency; when the addition amount of PVA is too high, the content of the positive electrode material in the product decreases, and the capacity decreases.

[0051] Figure 1 is the process flow chart of the present invention, which clearly shows a method for the efficient utilization of ternary precursor waste liquid. This method is simple to implement and suitable for industrialization. Figure 2 , Figure 3 and Figure 4 are the morphologies of the positive electrode materials of sodium-ion batteries prepared in the example, Comparative Example 1, and Comparative Example 2 respectively. It can be seen from the electron microscope that the particles of the positive electrode material prepared without adding PVA are larger and denser, and adding excessive PVA will cause too high a carbon content in the positive electrode material. Figure 5 is the powder diffraction pattern (XRD) of the positive electrode material Na 2 Fe 0.997 Ni 0.001 Co 0.001 Mn 0.001 (SO 4 ) 2 @C prepared in the example, and this spectrum matches the standard PDF card.

[0052] Figure 6 is the cathode material of sodium-ion battery Na 2 Fe 0.997 Ni 0.001 Co 0.001 Mn 0.001 (SO 4 ) 2 @C first charge-discharge curve. At a current density of 1C, its first discharge specific capacity is 90.8 mAh / g and the efficiency is 96.7%, showing good electrochemical performance.

[0053] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for utilizing ternary precursor wastewater, characterized in that: comprising: Step 1. Add a NaOH solution with a concentration of 10 - 12 mol / L to the ternary precursor wastewater, adjust the pH to 12.50 - 13.50, and distill the ammonia in the wastewater by steam heating. The distilled ammonia directly enters a solution of H 2 SO 4 with a concentration of 5 - 7 mol / L for absorption to obtain an ammonium sulfate solution; Step 2: Add an H 2 SO 4 solution with a concentration of 5 - 7 mol / L to the wastewater after ammonia evaporation in Step 1, adjust the pH to 6.8 - 7.0, then add FeSO 4 , and maintain the molar ratio of Na + to Fe 2+ at 1:(0.94 - 0.98). Then add Na 2 SO 3 , and maintain the molar ratio of SO 3 2- to Fe 2+ at (0.001 - 0.004):1 to obtain a mixed solution A; Step 3: Continuously introduce a protective gas into the mixed solution A in Step 2, with the gas concentration ≥ 99.99%. Add polyvinyl alcohol or polyvinylpyrrolidone and mix evenly to obtain a mixed solution B; in Step 3, the addition amount of the polyvinyl alcohol or the polyvinylpyrrolidone accounts for 3-6% of the total mass of Na + , SO 4 2- and Fe 2+ in the mixed solution A; Step Four: Evaporate the mixed solution B in Step Three, and continuously introduce a protective gas during the evaporation process, with the gas concentration ≥ 99.99%, to obtain a precursor of the positive electrode material for a sodium-ion battery; Step Five: Calcinate the precursor of the positive electrode material for a sodium-ion battery obtained in Step Four, continuously introduce Ar during the calcination process, sinter at 170 - 190 °C for 3 - 5 h; then raise the temperature to 350 - 400 °C and sinter for 12 - 16 h; the heating rate is 2 - 4 °C / min; Step 6. Crush the material sintered in Step 5 to obtain a sodium-ion battery cathode material product with a honeycomb structure. The chemical formula of the product is Na 2 Fe a Ni b Co c Mn d (SO 4 ) 2 @C, where 0.997 ≤ a < 1, 0 < b < 0.003, 0 < c < 0.003, 0 < d < 0.003, and a + b + c + d = 1; the size of the primary particles of the cathode material is 250 - 400 nm, and the pore diameter of the honeycomb is 50 - 200 nm.

2. The method for utilizing ternary precursor wastewater according to claim 1, characterized in that: In Step One, the ammonium sulfate solution is used as a complexing agent in the preparation process of the ternary precursor.

3. The method for utilizing ternary precursor wastewater according to claim 1, characterized in that: In Step Four, the condensed water evaporated is used for the preparation of the ternary precursor.

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