A method for recovering phosphorus from a nickel-containing iron phosphate mother liquor

Abstract

The present disclosure provides a method for recovering phosphorus from a nickel-containing iron phosphate mother liquor, comprising the following steps: S1: mixing the nickel-containing iron phosphate mother liquor with an iron source solution and adding iron phosphate seeds to obtain a first slurry; S2: mixing the first slurry with an oxidizing agent and heating to obtain a second slurry; S3: performing solid-liquid separation on the second slurry to obtain a post-phosphorus recovery liquid and iron phosphate dihydrate, and mixing the iron phosphate dihydrate with concentrated sulfuric acid and a reducing agent to obtain an acid leaching liquid containing phosphate after solid-liquid separation.

Description

Technical Field

[0001] This disclosure pertains to the field of new energy material resource recycling, specifically involving a method for recovering phosphorus from nickel-containing iron phosphate mother liquor. Background Technology

[0002] Lithium-ion batteries, with their advantages of high voltage, high energy density, and long cycle life, have become a major player in the new energy industry, sparking a surge in research and development of battery materials. Currently, lithium iron phosphate (LFP) and ternary cathode materials (NCM / NCA) are the mainstream materials in the market. Demand for iron phosphate and nickel sulfate continues to increase.

[0003] The nickel-iron alloy obtained by pyrometallurgical smelting of laterite nickel ore has a nickel content of over 15% and an iron content of over 60%. Currently, many companies in the market have begun to use nickel-iron alloy as raw material to prepare ferric phosphate dihydrate and nickel sulfate solution, thereby fully improving the utilization rate of nickel-iron alloy.

[0004] Currently, in one of the production methods of battery-grade iron phosphate, the main process involves removing impurities from the nickel-iron alloy leaching solution, adding phosphoric acid as a phosphorus source, adding an oxidant, and then controlling parameters such as pH to produce battery-grade iron phosphate products. The synthesis mother liquor of this method has a high residual phosphorus content (3-5 g / L). If it is not recycled and treated, it will result in the loss of phosphorus resources and increase the cost of solid waste treatment.

[0005] The following problems still exist in some existing technologies: First, in most current iron phosphate synthesis technologies, the cost of auxiliary materials such as alkalis and flocculants used for phosphorus removal is high; second, phosphorus resources are not fully utilized, and existing technologies basically only consider phosphorus removal without considering phosphorus recovery; third, the auxiliary materials used can introduce impurities, affecting the crystal structure and morphology of the downstream battery-grade iron phosphate products. Therefore, there is an urgent need to propose a synthesis method with high resource utilization. Summary of the Invention

[0006] This disclosure aims to address at least one of the technical problems existing in the prior art. To this end, this disclosure proposes a method for recovering phosphorus from nickel-containing iron phosphate mother liquor, achieving a phosphorus recovery rate of over 90%. This method offers advantages such as low raw material cost, simple process flow, high resource utilization, low impurity removal cost, and good economic benefits.

[0007] According to a first aspect of this disclosure, a method for recovering phosphorus from nickel-containing mother liquor of ferric phosphate is proposed, comprising the following steps:

[0008] S1: Mix the nickel-containing iron phosphate mother liquor with the iron source solution, add iron phosphate seed crystals, and obtain the first slurry;

[0009] S2: Mix the first slurry with the oxidant and heat it to obtain the second slurry;

[0010] S3: The second slurry is subjected to solid-liquid separation to obtain a phosphorus-recovered liquid and ferric phosphate dihydrate. The ferric phosphate dihydrate is mixed with concentrated sulfuric acid and a reducing agent, and after solid-liquid separation, an acid leaching solution containing phosphate is obtained.

[0011] The aforementioned nickel-containing mother liquor of ferric phosphate refers to the nickel-containing mother liquor produced by removing impurities from the sulfuric acid leaching solution of nickel-iron alloy, adding phosphoric acid as a phosphorus source, adding an oxidant, and then controlling parameters such as pH to produce battery-grade ferric phosphate. Therefore, it contains a certain concentration of sulfuric acid and phosphate ions.

[0012] This disclosure involves adding an iron source to nickel-containing iron phosphate mother liquor to form crude iron phosphate dihydrate precipitate. Since the crude iron phosphate dihydrate precipitate contains some impurities such as nickel and sulfur, and its morphology is amorphous, it needs to be redissolved and sent to the downstream phosphorus preparation process. After being prepared with phosphorus according to a certain iron-phosphorus ratio, it enters the synthesis process. The synthesis process will synthesize battery-grade iron phosphate products with certain morphological characteristics and meeting the requirements for impurity element content under specific process conditions.

[0013] The method disclosed herein is used to process nickel-containing mother liquor of ferric phosphate, and the resulting acid leaching solution containing phosphate is used in the phosphorus preparation process of the upstream nickel-iron leaching solution, thereby improving the utilization rate of phosphorus resources.

[0014] In some embodiments, in step S3, after the second slurry is subjected to solid-liquid separation to obtain ferric phosphate dihydrate, the ferric phosphate dihydrate is further subjected to pulping and washing, and the filtrate obtained after solid-liquid separation is used for nickel recovery in the MHP pulping process.

[0015] In some implementations, the following steps are also included:

[0016] S4: The recovered phosphorus solution is used for nickel-cobalt hydroxide leaching to remove impurities.

[0017] The nickel-containing mother liquor of ferric phosphate contains a certain concentration of sulfuric acid and phosphate ions. Therefore, the residual acid and phosphate ions in the liquor after phosphorus recovery can be used in the leaching and impurity removal process of nickel-cobalt hydroxide (MHP). The main reaction equations that occur in this process are as follows:

[0018] H₂SO₄ + Ni(OH)₂ = NiSO₄ + 2H₂O

[0019] H₂SO₄ + Co(OH)₂ = CoSO₄ + 2H₂O

[0020] Al 3+ +PO4 3- =AlPO4↓

[0021] 3Zn2+ +2PO4 3- =Zn3(PO4)2↓

[0022] In some preferred embodiments, in step S4, the recovered phosphorus solution is mixed with nickel-cobalt hydroxide, and after adding an oxidant and an alkaline solution, solid-liquid separation is performed to obtain purified nickel sulfate and cobalt sulfate.

[0023] In some embodiments, the concentration of phosphorus in the nickel-containing iron phosphate mother liquor is 3 to 5.5 g / L.

[0024] In some embodiments, the concentration of hydrogen ions in the nickel-containing iron phosphate mother liquor is approximately 2 mol / L. The nickel-containing iron phosphate mother liquor contains a certain concentration of residual acid; the recovered phosphorus solution obtained after phosphorus removal is used to react with MHP, which can reduce the amount of acid required for MHP leaching.

[0025] In some implementations, step S1 satisfies one or more of the following conditions:

[0026] a. Fe in the iron source solution 2+ The concentration is 40–50 g / L;

[0027] b. The iron source solution is the chromium-removed solution after leaching nickel-iron alloy;

[0028] c. After the nickel-containing iron phosphate mother liquor is mixed with the iron source solution, the molar ratio of iron to phosphorus is 1 to 3:1;

[0029] d. The particle size D50 of the iron phosphate seed crystals is 5–12 μm;

[0030] e. The mass of the iron phosphate seed crystals is 0.5% to 10% of the total mass of the nickel-containing iron phosphate mother liquor and the iron source solution.

[0031] By introducing the purified solution after leaching nickel-iron alloy with high iron concentration as the iron source, firstly, it can effectively reduce the high cost brought about by introducing new raw and auxiliary materials from the outside, and secondly, it can avoid introducing more other impurity elements, ensure the stability of the reaction process, facilitate the subsequent preparation of nickel sulfate solution, and effectively improve the resource recycling rate.

[0032] Excess iron in the solution promotes the chemical reaction to the right, making the phosphorus removal process more thorough. If the iron-to-phosphorus ratio is too high, the residual iron will form a large amount of iron slag in the subsequent MHP leaching and impurity removal process, increasing the cost of iron removal; if the iron-to-phosphorus ratio is too low, it will affect the recovery rate of phosphorus.

[0033] By adding ferric phosphate seed crystals to form a precipitate, the efficiency of phosphorus removal can be greatly improved.

[0034] In some embodiments, in step S2, the oxidant is at least one of oxygen, hydrogen peroxide, chlorate, or perchlorate; and / or, the oxidant reacts with Fe in the first slurry. 2+ The molar ratio is 1 to 1.5:1. Taking hydrogen peroxide as an example, the reaction equation is as follows:

[0035] 2Fe 2+ +H₂O₂ + 2H₂ + =2Fe 3+ +2H2O

[0036] In some embodiments, in step S2, the mixing temperature is room temperature, and the mixing time is 30–90 min; and / or, the heating temperature is 60–90 °C, and the heating time is 2–10 h. When hydrogen peroxide is used as an oxidant, excessively high temperatures will cause hydrogen peroxide to decompose, reducing oxidation efficiency; low-temperature oxidation can improve the utilization rate of hydrogen peroxide.

[0037] The precipitation reaction of ferric phosphate is an endothermic process. Increasing the temperature is beneficial for accelerating molecular thermal motion and mass transfer efficiency, thereby improving the precipitation efficiency of phosphorus. The reaction equation is as follows:

[0038] Fe 3+ +H3PO4+2H2O=FePO4·2H2O↓+3H +

[0039] In some embodiments, in step S3, the concentrated sulfuric acid has a mass concentration of approximately 98%; and / or, the amount of concentrated sulfuric acid used is 100–150 g / L; and / or, the reducing agent is nickel-iron powder; and / or, the molar ratio of the reducing agent to the ferric phosphate dihydrate is 1.2–2:1. Using nickel-iron powder, a raw material for ferric phosphate synthesis, as a reducing agent can reduce the cost of purchasing iron powder.

[0040] In some embodiments, in step S3, the mixing temperature is 60–90°C and the mixing time is 2–4 hours.

[0041] Ferric phosphate dihydrate is dissolved using concentrated sulfuric acid, and then nickel-iron powder is introduced as a reducing agent to dissolve the Fe. 3+ Reduced to Fe 2+ After solid-liquid separation, the solution is transported to the phosphorus preparation process, and finally enters the iron phosphate synthesis process, realizing the recycling of valuable elements such as phosphorus and iron. The utilization rate of phosphorus can reach over 90%, avoiding resource waste. The relevant reaction equations are as follows:

[0042] 2FePO4·2H2O+3H2SO4=Fe2(SO4)3+2H3PO4+4H2O

[0043] Fe + 2Fe3+ =3Fe 2+

[0044] Ni+2Fe 3+ =2Fe 2+ +Ni 2+

[0045] In some embodiments, in step S3, the phosphorus content in the phosphorus recovery solution is 0.1–0.5 g / L. Retaining a certain phosphorus content in the phosphorus recovery solution allows it to enter the MHP leaching and impurity removal process. The residual phosphorus reacts with impurity ions in the MHP leaching solution to form a precipitate, thus reducing the impurity removal cost of MHP.

[0046] In some embodiments, in step S4, after the phosphorus recovery solution is mixed with nickel-cobalt hydroxide, the pH is 1.5–2.0. The phosphorus reacts with high-content impurity ions such as zinc and aluminum in the MHP leaching solution to form precipitates such as zinc phosphate and aluminum phosphate. This method is more effective at removing impurities than the conventional method of adjusting the pH with alkali after acid leaching, and it is also less costly.

[0047] The residual phosphorus content in the leaching solution after phosphorus recovery should not be too high or too low. Too high a phosphorus content will affect the phosphorus recovery rate, while too low a phosphorus content means that the iron-phosphorus ratio needs to be increased significantly, which will greatly increase the residual iron concentration. This will also greatly increase the amount of solid waste generated after entering the MHP leaching and impurity removal process, creating a risk of secondary pollution.

[0048] According to a second aspect of this disclosure, a method for preparing ferric phosphate is provided, comprising the steps of the method described in the first aspect of this disclosure.

[0049] According to one embodiment of this disclosure, at least the following beneficial effects are achieved:

[0050] (1) The nickel-containing mother liquor of ferric phosphate contains a certain concentration of phosphate ions. By adding iron source solution and ferric phosphate seed crystals, ferric phosphate dihydrate precipitate can be generated, which improves the utilization rate of phosphorus resources.

[0051] (2) The pH of the nickel-containing mother liquor after preparing ferric phosphate using nickel-iron alloy is low. During the process of phosphorus element recovery and utilization, there will be almost no nickel precipitation in the solution. Therefore, the loss rate of nickel is very small, not exceeding 1%, which avoids the increase in cost and effectively achieves the purpose of saving costs.

[0052] (3) In a low-phosphorus system (phosphorus concentration below 5.5 g / L), the addition of ferric phosphate seed crystals can promote the precipitation process of amorphous ferric phosphate without introducing impurities into the solution.

[0053] (4) The recovered iron phosphate precipitate can be used to synthesize iron phosphate materials or as seed crystals in the above process, which improves the utilization rate of valuable elements such as phosphorus and iron.

[0054] (5) This disclosure does not use other additives containing impurity ions, does not require acid-base neutralization to remove phosphorus, has low cost, and avoids the impact of impurity ions on the downstream process of synthesizing iron phosphate products. Attached Figure Description

[0055] The present disclosure will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0056] Figure 1 This is a schematic diagram of the process flow of Embodiment 1 of this disclosure. Detailed Implementation

[0057] The following will describe the concept and technical effects of this disclosure clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of this disclosure.

[0058] Example 1

[0059] A method for recovering phosphorus from nickel-containing mother liquor of ferric phosphate, such as Figure 1 As shown, it includes the following steps:

[0060] Step (1): Take 300 mL of nickel-containing mother liquor after iron phosphate synthesis, introduce it into the chromium-removed nickel-iron alloy liquid and mix it evenly so that the iron-phosphorus concentration ratio in the mixed liquid is 1:1;

[0061] Step (2): Add iron phosphate dihydrate seed crystals to the mixture in step (1). The seed crystal particle size D50 is 5μm, and the amount added is 0.5% of the total mass of the mixture.

[0062] Step (3): Add hydrogen peroxide to the mixed slurry obtained in step (2), based on the total Fe in the solution. 2+ For content calculation, the amount of hydrogen peroxide added is 1.0 times the molar content of ferrous ions, the oxidation temperature is room temperature, the oxidation time is 30 min, and the stirring speed is 300 r / min; after complete oxidation, steam is used to start the reaction, the reaction temperature is 60℃, the reaction time is 2 h, and the stirring speed is 300 r / min.

[0063] Step (4): After the reaction in step (3) is completed, the slurry is subjected to solid-liquid separation to obtain the phosphorus recovery liquid and ferric phosphate dihydrate precipitate. The phosphorus recovery liquid is then introduced into the MHP leaching and impurity removal process.

[0064] Step (5): The ferric phosphate dihydrate precipitate generated in step (4) is pulped, washed, and filtered. The filtrate is returned to the MHP pulping process to recover nickel. The filter residue is then pulped in a pulping tank, and concentrated sulfuric acid (98% mass concentration) is added to dissolve and stir, controlling the acidity at 100 g / L. At the same time, nickel-iron powder is added as a reducing agent to remove Fe. 3+ Reduced to Fe 2+The amount of nickel-iron powder added is 1.2 times the theoretical amount in the chemical reaction equation. The reaction temperature is 60℃, the stirring reaction time is 2h, the stirring speed is 300r / min, and after solid-liquid separation, a primary acid solution is obtained and returned to the front-end phosphorus preparation process.

[0065] Example 2

[0066] A method for recovering phosphorus from nickel-containing mother liquor of ferric phosphate includes the following steps:

[0067] Step (1): Take 300 mL of nickel-containing mother liquor after iron phosphate synthesis, introduce it into the chromium-removed nickel-iron alloy liquid and mix it evenly so that the iron-phosphorus concentration ratio in the mixed liquid is 1.5:1;

[0068] Step (2): Add iron phosphate dihydrate seed crystals to the mixture in step (1). The seed crystal size D50 is 8μm, and the amount added is 1% of the total mass of the mixture.

[0069] Step (3): Add hydrogen peroxide to the mixed slurry obtained in step (2), based on the total Fe in the solution. 2+ For content calculation, the amount of hydrogen peroxide added was 1.2 times the molar content of ferrous ions, the oxidation temperature was room temperature, the oxidation time was 50 min, and the stirring speed was 330 r / min; after complete oxidation, the temperature was raised to 70℃, the reaction time was 3 h, and the stirring speed was 330 r / min.

[0070] Step (4): After the reaction in step (3) is completed, the slurry is subjected to solid-liquid separation to obtain the phosphorus recovery liquid and ferric phosphate dihydrate precipitate. The phosphorus recovery liquid is then introduced into the MHP leaching and impurity removal process.

[0071] Step (5): The ferric phosphate dihydrate precipitate generated in step (4) is pulped, washed, and filtered. The filtrate is returned to the MHP pulping process to recover nickel. The filter residue is then pulped in a pulping tank. Concentrated sulfuric acid (98% mass concentration) is added to dissolve and stir, controlling the acidity at 120 g / L. At the same time, nickel-iron powder is added as a reducing agent to remove Fe. 3+ Reduced to Fe 2+ The amount of nickel-iron powder added is 1.5 times the theoretical amount in the chemical reaction equation. The reaction temperature is 70℃, the stirring reaction time is 3h, the stirring speed is 330r / min, and after solid-liquid separation, a primary acid solution is obtained and returned to the front-end phosphorus preparation process.

[0072] Example 3

[0073] A method for recovering phosphorus from nickel-containing mother liquor of ferric phosphate includes the following steps:

[0074] Step (1): Take 300 mL of nickel-containing mother liquor after iron phosphate synthesis, introduce it into the chromium-removed nickel-iron alloy liquid and mix it evenly so that the iron-phosphorus concentration ratio in the mixed liquid is 2:1;

[0075] Step (2): Add iron phosphate dihydrate seed crystals to the mixture in step (1). The seed crystal size D50 is 10 μm, and the amount added is 5% of the total mass of the mixture.

[0076] Step (3): Add hydrogen peroxide to the mixed slurry obtained in step (2), based on the total Fe in the solution. 2+ For content calculation, the amount of hydrogen peroxide added was 1.3 times the molar content of ferrous ions, the oxidation temperature was room temperature, the oxidation time was 70 min, and the stirring speed was 360 r / min; after complete oxidation, the temperature was raised to 85℃, the reaction time was 7 h, and the stirring speed was 360 r / min.

[0077] Step (4): After the reaction in step (3) is completed, the slurry is subjected to solid-liquid separation to obtain the phosphorus recovery liquid and ferric phosphate dihydrate precipitate. The phosphorus recovery liquid is then introduced into the MHP leaching and impurity removal process.

[0078] Step (5): The ferric phosphate dihydrate precipitate generated in step (4) is pulped, washed, and filtered. The filtrate is returned to the MHP pulping process to recover nickel. The filter residue is then pulped in a pulping tank. Concentrated sulfuric acid (98% mass concentration) is added to dissolve and stir, controlling the acidity at 130 g / L. At the same time, nickel-iron powder is added as a reducing agent to remove Fe. 3+ Reduced to Fe 2+ The amount of nickel-iron powder added is 1.7 times the theoretical amount in the chemical reaction equation, the reaction temperature is 80℃, the stirring reaction time is 3.5h, the stirring speed is 360r / min, and after solid-liquid separation, a primary acid solution is obtained and returned to the front-end phosphorus preparation process.

[0079] Example 4

[0080] A method for recovering phosphorus from nickel-containing mother liquor of ferric phosphate includes the following steps:

[0081] Step (1): Take 300 mL of nickel-containing mother liquor after iron phosphate synthesis, introduce it into the chromium-removed nickel-iron alloy liquid and mix it evenly so that the iron-phosphorus concentration ratio in the mixed liquid is 3:1;

[0082] Step (2): Add iron phosphate dihydrate seed crystals to the mixture in step (1). The seed crystal size D50 is 12μm, and the amount added is 10% of the total mass of the mixture.

[0083] Step (3): Add hydrogen peroxide to the mixed slurry obtained in step (2), based on the total Fe in the solution. 2+For content calculation, the amount of hydrogen peroxide added is 1.5 times the molar content of ferrous ions, the oxidation temperature is room temperature, the oxidation time is 90 min, and the stirring speed is 400 r / min; after complete oxidation, the temperature is increased to 90℃, the reaction time is 10 h, and the stirring speed is 400 r / min.

[0084] Step (4): After the reaction in step (3) is completed, the slurry is subjected to solid-liquid separation to obtain the phosphorus recovery liquid and ferric phosphate dihydrate precipitate. The phosphorus recovery liquid is then introduced into the MHP leaching and impurity removal process.

[0085] Step (5): The ferric phosphate dihydrate precipitate generated in step (4) is pulped, washed, and filtered. The filtrate is returned to the MHP pulping process to recover nickel. The filter residue is then pulped in a pulping tank. Concentrated sulfuric acid (98% mass concentration) is added to dissolve and stir, controlling the acidity at 150 g / L. At the same time, nickel-iron powder is added as a reducing agent to remove Fe. 3+ Reduced to Fe 2+ The amount of nickel-iron powder added is twice the theoretical amount in the chemical reaction equation. The reaction temperature is 90℃, the stirring reaction time is 4h, and the stirring speed is 400r / min. After solid-liquid separation, a primary acid solution is obtained and returned to the front-end phosphorus preparation process.

[0086] Test case

[0087] The raw materials, phosphorus recovery solution, and primary acid solution in the above embodiments were tested. The contents of P, Fe, and Ni in the nickel-containing mother liquor and the chromium removal solution of the nickel-iron alloy are shown in Table 1. The experimental data of phosphorus recovery in steps (1) to (4), the experimental data of MHP leaching for impurity removal in step (4), and the experimental data of ferric phosphate acid dissolution in step (5) are shown in Table 2, Table 3, and Table 4, respectively.

[0088] Table 1 Raw Material Composition Table

[0089] raw material P / (g / L) <![CDATA[Fe 2+ / (g / L)]]> <![CDATA[Ni 2+ / (g / L)]]> <![CDATA[H + / (mol / L)]]> Nickel-containing mother liquor of ferric phosphate (g / L) 5.2 1.5 34 2 Nickel-iron alloy after impurity removal solution (g / L) 0.4 42 53 —

[0090] Table 2. Results of Phosphorus Recovery Experiment

[0091]

[0092] The phosphorus recovery rate is calculated as follows: (Phosphorus content in the nickel-containing mother liquor of ferric phosphate - Phosphorus content in the liquor after phosphorus recovery) / Phosphorus content in the nickel-containing mother liquor of ferric phosphate. Therefore, the phosphorus recovery rate can reach over 90% after the treatment described in this disclosure.

[0093] Using the recovered phosphorus solution for MHP leaching and impurity removal utilizes both the residual small amount of phosphorus and the high concentration of sulfuric acid in the solution, thus reducing the cost of MHP leaching and impurity removal. The experiment used both the recovered phosphorus solution and sulfuric acid for MHP leaching as an example, while sulfuric acid alone served as a control. Hydrogen peroxide was added to the MHP leachate to oxidize ferrous iron to ferric iron, and liquid alkali was added to adjust the pH to 5.0–5.5. The experimental results are shown in Table 3.

[0094] Table 3. Data of MHP leaching and impurity removal experiments.

[0095]

[0096]

[0097] It is evident that by employing the technical solution disclosed herein, using the recovered phosphorus solution for MHP leaching and impurity removal can achieve acid recovery and utilization. Furthermore, the residual phosphorus in the recovered phosphorus solution has a significant beneficial effect on the removal of impurities from the MHP leaching solution. In conventional acid leaching + alkali conditioning schemes, the zinc and aluminum contents of the leaching solution after impurity removal are both above 50 mg / L. However, by using the recovered phosphorus solution for leaching, the introduction of phosphorus allows it to react with impurity ions such as zinc and aluminum in the MHP leaching solution to form precipitates such as zinc phosphate and aluminum phosphate. Under the synergistic effect, the impurity removal effect is better and more thorough.

[0098] After washing the precipitate of ferric phosphate dihydrate obtained from phosphorus recovery, concentrated sulfuric acid and reduced nickel-iron powder were added to conduct experiments, resulting in a primary acid solution and filter residue. The filter residue was dried, weighed, and the dry residue rate was calculated. The experimental results are shown in Table 4.

[0099] Table 4. Results of the acid solubility experiment of ferric phosphate dihydrate

[0100] experiment P / (g / L) Fe / (g / L) Dry residue rate / % Experiment 7 44.25 82.15 5.6 Experiment 8 41.2 85.32 6.8 Experiment 9 40.3 77.89 7.4

[0101] It is evident that ferric phosphate dihydrate can be dissolved under reducing conditions, and the resulting primary leaching solution contains phosphate and reduced ferrous iron. Therefore, the primary leaching solution can be returned to the phosphorus preparation process after the nickel-iron leaching and impurity removal system. After being mixed with phosphorus in the large system according to a certain iron-phosphorus ratio, it enters the synthesis workshop to synthesize ferric phosphate products, thus truly realizing the recycling of phosphorus.

[0102] The following is a rough cost calculation:

[0103] (1) Nickel-containing iron phosphate mother liquor (3000m) 3 The hydrogen ion concentration in / d) is 2mol / L, the sulfuric acid concentration is about 100g / L, and the price of concentrated sulfuric acid is calculated at 400 yuan / ton. The value of the recovered acid is: 3000×100÷1000×300 days×400÷10000=36 million yuan / year.

[0104] (2) Value of recovered iron phosphate: The phosphorus content of the nickel-containing mother liquor of iron phosphate is calculated as 5g / L, and the phosphorus content of the liquid after phosphorus recovery is calculated as 0.5g / L. The price of recovered iron phosphate is calculated at 50% of 10,000 yuan / ton; then 3000×4.5÷1000×300 days×5000÷10000=20.25 million yuan / year;

[0105] The above two items combined will increase revenue by 56.25 million yuan per year.

[0106] It is evident that the technical solution disclosed herein not only improves resource utilization but also offers significant economic benefits.

Claims

1. A method for recovering phosphorus from nickel-containing mother liquor of ferric phosphate, characterized in that, Includes the following steps: S1: Mix the nickel-containing iron phosphate mother liquor with the iron source solution, add iron phosphate seed crystals, and obtain the first slurry; S2: Mix the first slurry with the oxidant and heat it to obtain the second slurry; S3: The second slurry is subjected to solid-liquid separation to obtain phosphorus recovery liquid and ferric phosphate dihydrate. The ferric phosphate dihydrate is mixed with concentrated sulfuric acid and reducing agent, and after solid-liquid separation, an acid leaching solution containing phosphate is obtained. The acid leaching solution is used in the phosphorus preparation process of nickel-iron leaching solution. The nickel-containing mother liquor of ferric phosphate refers to the nickel-containing mother liquor produced by removing impurities from the sulfuric acid leaching solution of nickel-iron alloy, adding phosphoric acid as a phosphorus source, adding an oxidant, and then controlling the pH to produce battery-grade ferric phosphate. It contains sulfuric acid and phosphate ions. The reducing agent is nickel-iron powder.

2. The method according to claim 1, characterized in that, It also includes the following steps: S4: The recovered phosphorus solution is used for nickel-cobalt hydroxide leaching to remove impurities.

3. The method according to claim 1, characterized in that, The concentration of phosphorus in the nickel-containing iron phosphate mother liquor is 3~5.5 g / L.

4. The method according to claim 1, characterized in that, Step S1 satisfies one or more of the following conditions: a. Fe in the iron source solution 2+ The concentration is 40~50g / L; b. The iron source solution is the chromium-removed solution after leaching nickel-iron alloy; c. After the nickel-containing iron phosphate mother liquor is mixed with the iron source solution, the molar ratio of iron to phosphorus is 1~3:1; d. The particle size D50 of the iron phosphate seed crystals is 5~12μm; e. The mass of the iron phosphate seed crystals is 0.5% to 10% of the total mass of the nickel-containing iron phosphate mother liquor and the iron source solution.

5. The method according to claim 1, characterized in that, In step S2, the oxidant is at least one of oxygen, hydrogen peroxide, chlorate, or perchlorate; and / or, the oxidant reacts with Fe in the first slurry. 2+ The molar ratio is 1~1.5:

1.

6. The method according to claim 1, characterized in that, In step S2, the mixing temperature is room temperature, and the mixing time is 30~90 min; and / or, the heating temperature is 60~90℃, and the heating time is 2~10 h.

7. The method according to claim 1, characterized in that, In step S3, the mass concentration of the concentrated sulfuric acid is 98%; and / or, the amount of the concentrated sulfuric acid used is 100~150g / L; and / or, the molar ratio of the reducing agent to the ferric phosphate dihydrate is 1.2~2:

1.

8. The method according to claim 1, characterized in that, In step S3, the mixing temperature is 60~90℃ and the mixing time is 2~4h.

9. The method according to claim 1, characterized in that, In step S3, the phosphorus content in the recovered phosphorus solution is 0.1~0.5 g / L.

Images