Method for regenerating ferric phosphate from waste ferric phosphate battery

Abstract

According to the method for regenerating ferric phosphate from the waste ferric phosphate battery, after the waste ferric phosphate battery is subjected to acid leaching treatment in an inert atmosphere, impurities such as copper, titanium and aluminum are efficiently removed, and the method cannot cause loss of phosphorus and iron; the impurity removal process is short, less equipment is needed, the treatment cost is low, and iron phosphate can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of waste battery recycling, in particular to a method for regenerating iron phosphate from waste iron phosphate batteries. Background Art

[0002] Iron phosphate batteries, such as lithium iron phosphate (LiFePO4) and sodium iron phosphate, are the most widely used lithium-ion battery cathode materials in the market. Their large-scale use is inevitably accompanied by the retirement of a large number of waste batteries. In the recycling process of waste lithium iron phosphate batteries, the core goal is to regenerate high-purity iron phosphate and lithium resources from them for the preparation of battery-grade iron phosphate and lithium carbonate. The key to this process lies in the efficient separation of impurities such as aluminum, copper, and titanium to ensure that the purity of the recycled materials meets battery-grade standards, thereby achieving resource recycling and sustainable development. Due to the similar chemical properties of iron ions and aluminum ions, the separation process is extremely difficult, which usually results in the loss of iron and phosphorus, resulting in low yields and excessively long processes, resulting in increased processing costs.

[0003] CN113816353A discloses a method for removing aluminum from waste lithium iron phosphate acid leaching solution by iron-aluminum coprecipitation. 3+ Or by oxidizing a small amount of Fe in the acidic leaching solution 2+ Oxidized to Fe 3+ And coordinately control the pH and temperature of the reaction system to achieve the Fe 3+ With Al 3+ However, this process will Fe 3+ With Al 3+ Co-precipitation treatment was performed to make Al 3+ It is removed in the form of aluminum phosphate, which results in a very low yield of iron and phosphorus, and the precipitated iron phosphate and aluminum phosphate cannot be separated either.

[0004] CN112310500A discloses a method for separating aluminum from waste lithium iron phosphate materials. Utilizing the principle of complexation reaction, the addition of a complexing agent allows aluminum precipitation and separation under acidic conditions. The precipitation rate exceeds 99% by weight, and aluminum in the solution can be removed to below 10 ppm without causing loss of other elements. However, in this method, the precipitation pH of ferric fluoride is lower than that of aluminum fluoride. Sodium fluoride reacts more readily with trivalent iron to form ferric fluoride, which then precipitates during pH adjustment, affecting the iron yield.

[0005] CN112811404A discloses a method for recycling waste lithium iron phosphate positive electrode powder. In this method, trivalent iron is very easy to form after leaching with strong acid. Trivalent iron has a higher complexing strength than aluminum ions and is more likely to react with a complexing agent. At the same time, due to the low content of impurity aluminum ions, the higher the amount of complexing agent added, the greater the iron loss, and the aluminum ions are difficult to remove, resulting in low yields of iron and phosphorus, while copper and titanium impurities are not removed.

[0006] Due to the complex impurity composition of spent lithium iron phosphate batteries, the iron phosphate obtained by the above treatment process has a high impurity content, which does not meet battery-grade production requirements. Furthermore, the recycling process is too long, the additional equipment and site costs are too high, and the market competitiveness is low. Therefore, in order to reduce costs and survive in the fierce market competition, it is imperative to research and develop a process for efficiently removing impurities to obtain iron phosphate. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a method for regenerating iron phosphate from waste iron phosphate batteries. The waste iron phosphate batteries are fully leached with sulfuric acid in an inert atmosphere to keep the iron in the ferrous valence state, and copper and titanium are removed. Then, a chelating agent is added to cause a complex reaction between iron and aluminum, thereby efficiently removing aluminum impurities without affecting the phosphorus and iron yields, and recovering high-quality iron phosphate.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for regenerating iron phosphate from waste iron phosphate batteries, the method comprising the following steps:

[0010] (1) acid leaching, copper removal, and titanium removal are performed on waste iron phosphate batteries in sequence to obtain a titanium removal solution;

[0011] (2) mixing the titanium removal liquid and the complexing agent to carry out a complexing reaction to obtain a post-reaction solution;

[0012] (3) mixing the reaction solution and the first alkali solution to react to obtain crude ferrous phosphate;

[0013] Steps (1), (2) and (3) are all carried out in an inert atmosphere;

[0014] (4) The crude ferrous phosphate is subjected to oxidation reaction and recrystallization in sequence to obtain ferric phosphate.

[0015] The method for regenerating ferric phosphate from waste ferric phosphate batteries disclosed herein is rationally designed. First, the waste ferric phosphate batteries are fully leached with sulfuric acid in an inert atmosphere, leaving the iron in the form of ferrous iron. Impurities such as copper, titanium, and aluminum are then sequentially removed in the inert atmosphere, thereby reducing the impact of various impurities on the ferrophosphorus yield. This reduces the impact of these impurities on the yield of ferrophosphorus, resulting in high yields of phosphorus and iron, and high removal rates of the impurities copper, titanium, and aluminum. During the aluminum removal process, the added complexing agent complexes ferrous iron and aluminum ions to varying degrees, resulting in competitive complexation. The aluminum ions exhibit a higher complexing strength, making them easier to remove, and the aluminum removal process does not result in loss of phosphorus or iron.

[0016] The method for regenerating iron phosphate from waste iron phosphate batteries described in the present invention does not require, like the existing impurity removal technology for waste iron phosphate batteries, first separating phosphorus and iron and then removing impurities in the separated solution and solid with reagents, and finally synthesizing and preparing iron phosphate. The present application directly performs full leaching in an inert atmosphere without separating phosphorus and iron, and then sequentially removes impurities such as copper, titanium, and aluminum, making it easier to prepare iron phosphate, with a short preparation process, less equipment required, and low recycling cost.

[0017] Preferably, the complexing agent in step (2) comprises any one of ethylenediaminetetraacetic acid, citric acid, malic acid, gallic acid or acetylacetone, or a combination of at least two thereof, wherein typical but non-limiting combinations include a combination of ethylenediaminetetraacetic acid and citric acid, a combination of malic acid and gallic acid, a combination of acetylacetone and ethylenediaminetetraacetic acid, or a combination of citric acid and gallic acid.

[0018] Preferably, the amount of the complexing agent added in step (2) is 1-3 times the molar amount of aluminum in the waste iron phosphate battery, for example, it can be 1 times, 1.3 times, 1.5 times, 2 times, 2.5 times or 3 times, but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0019] Preferably, the temperature of the complexation reaction is 30-100° C., for example, 30° C., 35° C., 40° C., 50° C., 70° C., 90° C. or 100° C., etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0020] The reaction time is 0.5-5 h, for example, 0.5 h, 0.8 h, 1 h, 2 h, 3 h, 4 h or 5 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] Preferably, the inert atmosphere includes any one of a nitrogen atmosphere, a helium atmosphere or an argon atmosphere.

[0022] Preferably, the nitrogen flow rate in the nitrogen atmosphere is controlled to be 1.2-1.5 Nm 3 / h, for example, it can be 1.2Nm3 / h、1.25Nm 3 / h、1.28Nm 3 / h、1.3Nm 3 / h、1.35Nm 3 / h、1.4Nm 3 / h or 1.5Nm 3 / h, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the pH of the reaction in step (3) is 4.0-7.0, for example, 4.0, 4.5, 5, 6, 6.5 or 7.0, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] The pH of the reaction in step (3) of the present invention is 4.0-7.0, and further reaction forms a stable complex, and some free aluminum ions are also complexed. The chemical reaction formula is: Al(HY)+OH - →[Al(Y)] - +H2O;Al 3+ +Y 4- →[Al(Y)] - .

[0025] The reaction temperature is 30-100°C, for example, 30°C, 35°C, 40°C, 50°C, 70°C, 90°C or 100°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0026] The reaction time is 0.5-5 h, for example, 0.5 h, 0.8 h, 1 h, 2 h, 3 h, 4 h or 5 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, sulfuric acid is used for acid leaching in step (1).

[0028] Preferably, the amount of sulfuric acid used is 1-1.5 times the stoichiometric amount of the completely reacted leached ferric phosphate, for example, it can be 1 times, 1.2 times, 1.3 times, 1.4 times, 1.45 times or 1.5 times, etc., but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable, preferably 1-1.05 times.

[0029] The present invention preferably uses sulfuric acid in an amount of 1-1.05 times the stoichiometric amount of the ferric phosphate leached after complete reaction. This ensures that the amount of iron powder used for subsequent copper removal is low while completely leaching the ferric phosphate. In addition, the amount of alkali solution used for subsequent pH adjustment is low, thereby reducing treatment costs.

[0030] Preferably, the liquid-to-solid ratio of the sulfuric acid and the waste iron phosphate battery is 1:1-10:1, for example, it can be 1:1, 2:1, 3:1, 5:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within this numerical range are also applicable; preferably 1:1-5:1.

[0031] Preferably, the acid leaching temperature is 30-100°C, for example, 30°C, 35°C, 40°C, 50°C, 70°C, 90°C or 100°C, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;.

[0032] Preferably, the acid leaching time is 0.5-5h, for example, 0.5h, 0.8h, 1h, 2h, 3h, 4h or 5h, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the pH of the acid leaching solution is 0-1.0, for example, it can be 0, 0.1, 0.3, 0.5, 0.7, 0.9 or 1.0, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the copper removal in step (1) comprises performing a replacement reaction using iron powder.

[0035] Preferably, the amount of iron powder added is 1-2 times the molar amount of copper in the waste iron phosphate battery, for example, it can be 1 times, 1.2 times, 1.5 times, 1.7 times, 1.9 times or 2 times, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0036] Preferably, the temperature of the replacement reaction is 30-100° C., for example, 30° C., 35° C., 40° C., 50° C., 70° C., 90° C. or 100° C., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0037] The reaction time is 0.5-5 h, for example, 0.5 h, 0.8 h, 1 h, 2 h, 3 h, 4 h or 5 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the titanium removal in step (1) comprises carrying out a hydrolysis reaction using a second alkaline solution.

[0039] Preferably, the pH of the hydrolysis reaction is 2.0-3.0, for example, 2.0, 2.1, 2.3, 2.5, 2.7 or 3.0, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] The reaction temperature is 30-100°C, for example, 30°C, 35°C, 40°C, 50°C, 70°C, 90°C or 100°C, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0041] The reaction time is 0.5-5 h, for example, 0.5 h, 0.8 h, 1 h, 2 h, 3 h, 4 h or 5 h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the pH of the titanium removal solution is 2.0-3.0, for example, 2.0, 2.1, 2.3, 2.5, 2.7, 2.9 or 3.0, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, stirring is performed during the acid leaching, copper removal, titanium removal in step (1), the complex reaction in step (2), and the reaction in step (3), and the stirring speed is 200-800 r / min, for example, it can be 200 r / min, 230 r / min, 250 r / min, 300 r / min, 500 r / min, 700 r / min or 800 r / min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, the second alkali liquor used in the hydrolysis reaction and the first alkali liquor in step (2) both comprise any one or a combination of at least two of sodium hydroxide, ammonia water or ammonium bicarbonate, wherein typical but non-limiting combinations include a combination of sodium hydroxide and ammonia water, a combination of ammonium bicarbonate and sodium hydroxide, or a combination of ammonia water and ammonium bicarbonate.

[0045] As a preferred technical solution of the present invention, the method comprises the following steps:

[0046] (1) The waste iron phosphate battery is sequentially subjected to acid leaching at a temperature of 30-100°C for 0.5-5h, copper removal and titanium removal to obtain a titanium removal solution; the acid leaching uses sulfuric acid; the amount of sulfuric acid used is 1-1.5 times the stoichiometric amount of the iron phosphate leached after complete reaction; the liquid-to-solid ratio of the sulfuric acid to the waste iron phosphate battery is 1:1-10:1; the pH of the acid leaching solution is 0-1.0; the copper removal includes using iron powder for a replacement reaction; the amount of the iron powder added is 1-2 times the molar amount of copper in the waste iron phosphate battery; the temperature of the replacement reaction is 30-100°C, and the reaction time is 0.5-5h; the titanium removal includes using a second alkaline solution for a hydrolysis reaction; the pH of the hydrolysis reaction is 2.0-3.0, the reaction temperature is 30-100°C, and the reaction time is 0.5-5h; the pH of the titanium removal solution is 2.0-3.0;

[0047] (2) mixing the titanium removal liquid and a complexing agent, and performing a complexing reaction at a temperature of 30-100° C. for 0.5-5 hours to obtain a post-reaction solution; the complexing agent comprises any one of ethylenediaminetetraacetic acid, citric acid, malic acid, gallic acid, or acetylacetone, or a combination of at least two thereof; and the amount of the complexing agent added is 1-3 times the molar amount of aluminum in the waste iron phosphate battery;

[0048] (3) mixing the reaction solution and the first alkali solution and reacting at a pH of 4.0-7.0 and a temperature of 30-100° C. for 0.5-5 h to obtain crude ferrous phosphate;

[0049] Steps (1), (2) and (3) are all carried out in an inert atmosphere; the inert atmosphere includes any one of a nitrogen atmosphere, a helium atmosphere or an argon atmosphere; the flow rate of nitrogen in the nitrogen atmosphere is controlled to be 1.2-1.5 Nm 3 / h;

[0050] Stirring is performed during the acid leaching, copper removal, titanium removal in step (1), the complex reaction in step (2), and the reaction in step (3), and the stirring speed is 200-800 r / min; the second alkali solution used in the hydrolysis reaction and the first alkali solution in step (2) both include any one of sodium hydroxide, ammonia water, or ammonium bicarbonate, or a combination of at least two thereof;

[0051] (4) The crude ferrous phosphate is subjected to oxidation reaction and recrystallization in sequence to obtain ferric phosphate.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) The method for regenerating iron phosphate from waste iron phosphate batteries provided by the present invention removes impurities in an inert atmosphere, firstly uses sulfuric acid leaching, and iron exists in the form of divalent iron. Then, in the copper removal process, there is no need to add excessive iron powder to reduce trivalent iron, thereby reducing the amount of iron powder used. Then, the pH is adjusted and a chelating agent is added to remove titanium and aluminum. Since the chelating agent has different chelating degrees for divalent iron ions and aluminum ions, competitive chelation occurs, and the chelating strength of aluminum ions is higher, which is easy to be retained in the aqueous solution for removal without causing the loss of phosphorus and iron.

[0054] (2) The method for regenerating iron phosphate from waste iron phosphate batteries provided by the present invention does not require the prior art to leach and separate lithium, phosphorus, and iron and then use reagents to remove impurities in the filtrate or solid after separation before finally synthesizing and preparing iron phosphate. Instead, the method is to leach in an inert atmosphere without separating lithium, phosphorus, and iron. After removing impurities in sequence in one system, it is easier to prepare high-quality iron phosphate, with a short impurity removal process, less equipment required, and low recovery and preparation costs.

[0055] (3) The method for regenerating iron phosphate from waste iron phosphate batteries provided by the present invention can remove impurities from phosphorus, iron and lithium in one system, so the amount of reagents used is smaller and the loss of lithium, iron and phosphorus caused by liquid diversion is reduced, which is suitable for establishing a production line.

[0056] (4) The method for regenerating iron phosphate from waste iron phosphate batteries provided by the present invention has high yields of lithium, phosphorus and iron, and high removal rates of copper, titanium and aluminum. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic flow chart of the method for regenerating iron phosphate from waste iron phosphate batteries provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0058] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0059] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0060] Example 1

[0061] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries, and its flow diagram is as follows: Figure 1 The method comprises the following steps:

[0062] In the first step, the waste lithium iron phosphate electrode powder is mixed with 1 times the stoichiometric sulfuric acid with a liquid-to-solid ratio of 3:1. The leaching process is protected by nitrogen with a nitrogen flow rate of 1.2Nm 3 / h, leaching temperature is 80℃, leaching time is 2h, stirring speed is 400r / min; after leaching, filtration is performed to obtain acidic Fe with a pH of 0.3 2+ solutions and non-leachable waste residues;

[0063] The second step is to acidic Fe 2+ The solution was added with iron powder that was 1 times the molar amount of copper in the waste lithium iron phosphate electrode powder, and the replacement reaction was carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.2Nm 3 / h, reaction time 0.5h, reaction temperature controlled at 60°C, after completion of the reaction, filtration was performed to obtain a filtrate and copper slag after copper removal;

[0064] In the third step, 2M sodium hydroxide was added to the filtrate after copper removal in a nitrogen atmosphere to adjust the pH to 2.5 at a nitrogen flow rate of 1.2 Nm 3 / h, titanium hydrolysis reaction occurs, the reaction reaction is carried out for 1.5h, the reaction temperature is 60°C, titanium impurities are precipitated, and the filtrate after titanium removal with a pH of 3.0 and titanium slag are obtained by filtration;

[0065] The fourth step is to add ethylenediaminetetraacetic acid (EDTA) as a complexing agent to the filtrate after titanium removal. The added amount is 1.1 times the molar amount of aluminum in the waste lithium iron phosphate electrode powder. The complexation reaction is carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.2 Nm 3 / h, the reaction temperature was controlled at 70 °C, the reaction time was 1 h, and the stirring speed was 200 r / min;

[0066] Step 5: After the complexation reaction, add 2M sodium hydroxide to the solution and adjust the pH to 4.5 in a nitrogen atmosphere with a nitrogen flow rate of 1.2 Nm 3 / h, further complexation reaction occurs, the reaction is carried out for 0.5h, the reaction temperature is 60℃, and lithium-rich aluminum solution and crude ferrous phosphate are obtained by filtration;

[0067] In the sixth step, the obtained crude ferrous phosphate was mixed with deionized water at a solid-liquid ratio of 1:10, stirred for 0.5 h, and then hydrogen peroxide was added to oxidize the divalent iron. The amount of hydrogen peroxide added was 1.1 times the stoichiometric amount of completely oxidized divalent iron. The reaction was continued for 0.5 h at a reaction temperature of 50° C. After the reaction was completed, 2 M sodium hydroxide was added to adjust the pH to 5 to completely precipitate the ferric phosphate, which was then filtered to obtain the crude ferric phosphate.

[0068] In the seventh step, phosphoric acid was added to the crude ferric phosphate obtained to dissolve it, and the pH was adjusted to 2.0. The reaction time was 1 hour and the reaction temperature was 80°C. After the reaction, 5M sodium hydroxide was added and the pH was adjusted to 4.5 for recrystallization. The reaction time was 0.5 hour and the reaction temperature was 80°C. After the reaction was completed, the reaction was filtered and the obtained ferric phosphate solid was washed twice with deionized water at 80°C with a liquid-to-solid ratio of 2:1 and each washing time was 0.5 hour. The ferric phosphate was filtered and dried to obtain ferric phosphate.

[0069] Example 2

[0070] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries, the method comprising the following steps:

[0071] In the first step, the waste lithium iron phosphate electrode powder is mixed with 1.3 times the stoichiometric sulfuric acid, with a liquid-to-solid ratio of 1:1. The leaching process is protected by nitrogen with a nitrogen flow rate of 1.3Nm 3 / h, leaching temperature is 100℃, leaching time is 2h, stirring speed is 800r / min; after leaching is completed, filter and obtain acidic Fe 2+ solutions and non-leachable waste residues;

[0072] The second step is to acidic Fe 2+ The solution was added with iron powder 1.1 times the molar amount of copper in the waste lithium iron phosphate electrode powder, and the replacement reaction was carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.2Nm 3 / h, reaction time 0.5h, reaction temperature controlled at 60°C, after completion of the reaction, filtration was performed to obtain a filtrate and copper slag after copper removal;

[0073] In the third step, 2M sodium hydroxide was added to the filtrate after copper removal in a nitrogen atmosphere to adjust the pH to 3.0 with a nitrogen flow rate of 1.2 Nm 3 / h, titanium hydrolysis reaction occurs, the reaction reaction is carried out for 1.5h, the reaction temperature is 100°C, titanium impurities are precipitated, and the titanium-removed filtrate and titanium slag with a pH of 2.0 are obtained by filtration;

[0074] The fourth step is to add ethylenediaminetetraacetic acid (EDTA) as a complexing agent to the filtrate after titanium removal. The added amount is 1.2 times the molar amount of aluminum in the waste lithium iron phosphate electrode powder. The complexation reaction is carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.2 Nm 3 / h, the reaction temperature was controlled at 30 °C, the reaction time was 0.5h, and the stirring speed was 800r / min;

[0075] Step 5: After the complexation reaction, add 2M sodium hydroxide to adjust the pH to 5.0 in a nitrogen atmosphere with a nitrogen flow rate of 1.3 Nm 3 / h, further complexation reaction occurs, the reaction is carried out for 0.5h, the reaction temperature is 60℃, and lithium-rich aluminum solution and crude ferrous phosphate are obtained by filtration;

[0076] In the sixth step, the obtained crude ferrous phosphate was mixed with deionized water at a solid-liquid ratio of 1:10, stirred for 0.5 h, and then hydrogen peroxide was added to oxidize the divalent iron. The amount of hydrogen peroxide added was 1.1 times the stoichiometric amount of completely oxidized divalent iron. The reaction was continued for 0.5 h at a reaction temperature of 100° C. After the reaction was completed, 2 M sodium hydroxide was added to adjust the pH to 4 to completely precipitate the ferric phosphate, which was then filtered to obtain the crude ferric phosphate.

[0077] In the seventh step, phosphoric acid was added to the crude ferric phosphate obtained to redissolve it, and the pH was adjusted to 3.0. The reaction time was 1 hour and the reaction temperature was 80°C. After the reaction, 4M sodium hydroxide was added and the pH was adjusted to 4 for recrystallization. The reaction time was 0.5 hours and the reaction temperature was 80°C. After the reaction was completed, it was filtered and the obtained ferric phosphate solid was washed with 80°C deionized water 3 times with a liquid-to-solid ratio of 2:1 and each washing time was 0.5 hours. It was then filtered and dried to obtain ferric phosphate.

[0078] Example 3

[0079] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries, the method comprising the following steps:

[0080] In the first step, waste lithium iron phosphate black powder is mixed with 1.5 times the stoichiometric sulfuric acid, with a liquid-to-solid ratio of 5:1. The leaching process is protected by nitrogen with a nitrogen flow rate of 1.2Nm 3 / h, leaching temperature is 30℃, leaching time is 2h, stirring speed is 400r / min; after leaching is completed, filtration is performed to obtain acidic Fe with pH 0 2+ solutions and non-leachable waste residues;

[0081] The second step is to acidic Fe 2+ The solution was added with iron powder 1.5 times the molar amount of copper in the waste lithium iron phosphate black powder, and the displacement reaction was carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.27Nm 3 / h, the reaction time is 0.5h, the reaction temperature is controlled at 100°C, and after the reaction is completed, the filtrate and copper slag after copper removal are obtained;

[0082] In the third step, 2M sodium hydroxide was added to the filtrate after copper removal in a nitrogen atmosphere to adjust the pH to 2.5 at a nitrogen flow rate of 1.2 Nm 3 / h, titanium hydrolysis reaction occurs, the reaction reaction is carried out for 0.5h, the reaction temperature is 30°C, titanium impurities are precipitated, and the titanium-removed filtrate and titanium slag with a pH of 2.5 are obtained by filtration;

[0083] The fourth step is to add ethylenediaminetetraacetic acid (EDTA) as a complexing agent to the filtrate after titanium removal. The added amount is 1.1 times the molar amount of aluminum in the waste lithium iron phosphate electrode powder. The complexation reaction is carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.2 Nm 3 / h, the reaction temperature was controlled at 100 °C, the reaction time was 5 h, and the stirring speed was 200 r / min;

[0084] Step 5: After the complexation reaction, add 2M sodium hydroxide to adjust the pH to 5.5 in a nitrogen atmosphere with a nitrogen flow rate of 1.5 Nm 3 / h, further complexation reaction occurs, the reaction is carried out for 0.5h, the reaction temperature is 60℃, and lithium-rich aluminum solution and crude ferrous phosphate are obtained by filtration;

[0085] Step 6: The obtained crude ferrous phosphate was mixed with deionized water at a solid-liquid ratio of 1:10, stirred for 0.5 h, and then hydrogen peroxide was added to oxidize the divalent iron. The amount of hydrogen peroxide added was 1.1 times the stoichiometric amount of completely oxidized divalent iron. The reaction was continued for 5 h at a reaction temperature of 30°C. After the reaction was completed, 2M sodium hydroxide was added to adjust the pH to 7 to completely precipitate the ferric phosphate, which was then filtered to obtain the crude ferric phosphate.

[0086] In the seventh step, phosphoric acid was added to the crude ferric phosphate obtained to redissolve it, and the pH was adjusted to 2.5. The reaction time was 1 hour and the reaction temperature was 80°C. After the reaction, 4M sodium hydroxide was added and the pH was adjusted to 4.5 for recrystallization. The reaction time was 0.5 hours and the reaction temperature was 80°C. After the reaction was completed, the reaction was filtered and the obtained ferric phosphate solid was washed 4 times with 80°C deionized water at a liquid-solid ratio of 1:1 and a washing time of 0.5 hours. The solid was filtered and dried to obtain ferric phosphate.

[0087] Example 4

[0088] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries, the method comprising the following steps:

[0089] In the first step, waste lithium iron phosphate black powder is mixed with 1 times the stoichiometric sulfuric acid with a liquid-to-solid ratio of 5:1. The leaching process is protected by nitrogen with a nitrogen flow rate of 1.2Nm 3 / h, leaching temperature is 80℃, leaching time is 2h, stirring speed is 400r / min; after leaching, filtration is performed to obtain acidic Fe with a pH of 0.5 2+ solutions and non-leachable waste residues;

[0090] The second step is to acidic Fe 2+ Add 1.5 times the molar amount of iron powder in the waste lithium iron phosphate black powder to the solution, and carry out the replacement reaction in a nitrogen atmosphere with a nitrogen flow rate of 1.2Nm 3 / h, reaction time 0.5h, reaction temperature controlled at 50°C, after the reaction was completed, filtration was performed to obtain a filtrate and copper slag after copper removal;

[0091] In the third step, 2M sodium hydroxide was added to the filtrate after copper removal in a nitrogen atmosphere to adjust the pH to 3.0 with a nitrogen flow rate of 1.2 Nm 3 / h, titanium hydrolysis reaction occurs, the reaction reaction is carried out for 1h, the reaction temperature is 60°C, titanium impurities are precipitated, and the filtrate after titanium removal and titanium slag are obtained by filtration;

[0092] The fourth step is to add ethylenediaminetetraacetic acid (EDTA) as a complexing agent to the filtrate after titanium removal. The added amount is 1.1 times the molar amount of aluminum in the waste lithium iron phosphate electrode powder. The complexation reaction is carried out in a nitrogen atmosphere with a nitrogen flow rate of 1.2 Nm 3 / h, the reaction temperature was controlled at 70 °C, the reaction time was 1 h, and the stirring speed was 200 r / min;

[0093] Step 5: After the complexation reaction, add 2M sodium hydroxide to the solution and adjust the pH to 6.5 in a nitrogen atmosphere with a nitrogen flow rate of 1.2 Nm 3 / h, further complexation reaction occurs, the reaction is carried out for 0.5h, the reaction temperature is 60℃, and lithium-rich aluminum solution and crude ferrous phosphate are obtained by filtration;

[0094] The sixth step is to mix the obtained crude ferrous phosphate with deionized water at a solid-liquid ratio of 1:10, stir for 0.5 h, and then add hydrogen peroxide to oxidize the divalent iron. The amount of hydrogen peroxide added is 1.2 times the stoichiometric amount of completely oxidized divalent iron. The reaction is continued for 1 h at a reaction temperature of 50°C. After the reaction is completed, 2M sodium hydroxide is added to adjust the pH to 5 to completely precipitate the ferric phosphate, which is then filtered to obtain the crude ferric phosphate.

[0095] In the seventh step, phosphoric acid was added to the crude ferric phosphate obtained to dissolve it, and the pH was adjusted to 2.5. The reaction time was 1 hour and the reaction temperature was 80°C. After the reaction, 4M sodium hydroxide was added and the pH was adjusted to 4.5 for recrystallization. The reaction time was 0.5 hours and the reaction temperature was 80°C. After the reaction was completed, it was filtered and the obtained ferric phosphate solid was washed with 80°C deionized water 4 times with a liquid-to-solid ratio of 1:1 and each washing time was 0.5 hours. It was then filtered and dried to obtain ferric phosphate.

[0096] Example 5

[0097] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as that of Example 1, except that sodium hydroxide is added in the third step to adjust the pH to 1.0 for the hydrolysis reaction of titanium.

[0098] From the combination of Example 1 and Example 5, it can be seen that in Example 5, since the pH of the hydrolysis reaction of titanium is relatively low, the hydrolysis of titanium is inhibited, thereby reducing the removal efficiency of titanium.

[0099] Example 6

[0100] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as that of Example 1 except that the temperature of the complexation reaction in the fourth step is 20°C.

[0101] Example 7

[0102] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as that of Example 1 except that the temperature of the complexation reaction in the fourth step is 110°C.

[0103] From Example 1 and Examples 6 to 7, it can be seen that in Example 6, due to the low temperature of the complexation reaction, the complexation reaction rate is reduced, the selectivity is poor, and the aluminum removal rate is reduced; in Example 7, due to the high temperature of the complexation reaction, the complexing agent is degraded, the aluminum removal rate is also greatly reduced, and the purity of the iron phosphate finally prepared is reduced.

[0104] Example 8

[0105] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as that of Example 1, except that the amount of complexing agent added in the fourth step is 0.5 times the molar amount of aluminum in the waste iron phosphate battery.

[0106] Example 9

[0107] This embodiment provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as that of Example 1, except that the amount of complexing agent added in the fourth step is 4 times the molar amount of aluminum in the waste iron phosphate batteries.

[0108] From Example 1 and Examples 8 to 9, it can be seen that in Example 8, due to the small amount of complexing agent added, the complexing reaction rate is reduced, the selectivity is poor, the aluminum removal rate is reduced, and the purity of the iron phosphate finally prepared is reduced; in Example 9, due to the large amount of complexing agent added, part of the iron will react with the complexing agent, affecting the iron yield, and increasing the processing cost.

[0109] Comparative Example 1

[0110] This comparative example provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as Example 1 except that nitrogen is not introduced during the first step of leaching using sulfuric acid.

[0111] Comparative Example 2

[0112] This comparative example provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as Example 1 except that the order of the third step and the second step is swapped, that is, the acid leaching solution is first mixed with the first alkaline solution to perform a hydrolysis reaction to remove titanium, and then mixed with iron powder to perform a replacement reaction to remove copper.

[0113] Comparative Example 3

[0114] This comparative example provides a method for regenerating iron phosphate from waste iron phosphate batteries. The method is the same as Example 1 except that the fourth and fifth steps are reversed in order from the third step, that is, the copper removal solution is first subjected to a complexing reaction with a complexing agent and then a second liquid alkali is added for precipitation, and then the solution is mixed with the first alkali solution for a hydrolysis reaction except for titanium.

[0115] Comparative Example 4

[0116] This comparative example provides a method for recycling waste lithium iron phosphate positive electrode powder disclosed in Example 2 of CN112811404A, comprising the following steps:

[0117] (1) Weigh 100 g of waste lithium iron phosphate battery positive electrode powder into a reactor, add 200 mL of distilled water, then add 0.5 g (0.005 mol) of concentrated sulfuric acid and 15.7 g (0.053 mol) of EDTA. Stir at 20 r / min, heat to 80°C with continuous stirring, react for 3 h, and filter to obtain lithium iron phosphate with an aluminum content of less than 100 ppm. The amount of lithium iron phosphate in 100 g of waste lithium iron phosphate battery positive electrode powder and lithium iron phosphate with an aluminum content of less than 100 ppm is approximately 0.54 mol.

[0118] (2) Add 200 mL of distilled water and 27 g (0.27 mol) of concentrated sulfuric acid to a reactor, slurry the lithium iron phosphate, stir at 20 r / min, and dropwise add 47 g (0.38 mol) of hydrogen peroxide (content: 27.5%), controlling the reaction temperature to <70°C. Use o-phenanthroline to complete the color oxidation, react for 1 hour, filter the mother liquor, and the filter cake is the iron-phosphorus waste residue. The lithium sulfate solution can be further used to prepare lithium carbonate. The amount of phosphorus atoms in the iron-phosphorus waste residue is 0.54 mol.

[0119] (3) The above iron-phosphorus waste residue was placed in 200 mL of distilled water for slurrying, 81 g of concentrated sulfuric acid (content: 98%) was added, the stirring speed was 20 r / min, the reaction was carried out for 1 h, and 15 g of insoluble impurities (graphite and PVDF) were removed by filtration. The mother liquor was the iron-phosphorus filtrate.

[0120] (4) The above iron-phosphorus filtrate was again colored with o-phenanthroline to ensure complete oxidation. The stirring speed was 20 r / min, and ammonia water was added dropwise to a pH value of 2. The reaction was carried out for 2 h, and a large amount of yellow precipitate was precipitated. The yellow precipitate was filtered and washed. The yellow filter cake was hydrated iron phosphate (FePO4·nH2O). The filter cake was placed in an oven and dried at 105°C for 4 hours, and then transferred to a muffle furnace and calcined at 550°C for 3 hours. The filter cake was 80 g of industrial anhydrous iron phosphate.

[0121] Analysis of the impurity content of the prepared industrial anhydrous ferric phosphate shows that:

[0122] Al:37ppm / Ca:6ppm / Co:6ppm / Cr:5ppm / Cu:nd / K:3ppm / Mg:8ppm / Mn:5ppm / N a:10ppm / Ni:8ppm / Ti:20ppm / Zn:16 / Magnetic material: 0.2ppm.

[0123] The main chemical compositions of the waste lithium iron phosphate electrode powder and waste lithium iron phosphate black powder in the above embodiments and comparative examples were obtained by ICP test, as shown in Table 1, in wt%.

[0124] Table 1

[0125] Li Fe P Al Cu Ti Cr Ca Na Waste lithium iron phosphate electrode powder 3.935 33.57 19.3 0.61 0.049 0.197 0.039 0.031 0.031 Waste lithium iron phosphate black powder 3.68 31.9 17.9 1.21 0.49 0.997 0.059 0.035 0.061

[0126] The ICP test results of the solution composition after acid leaching of the waste lithium iron phosphate black powder in the first step of the above embodiments and comparative examples are shown in Table 2, in g / L.

[0127] Table 2

[0128] Li Fe P S Al Cu Ti Cr Ca Example 1 15.34 133.48 76.81 79.40 2.440 0.202 0.785 0.130 0.114 Example 2 39.04 335.26 192.45 237.90 6.075 0.487 1.920 0.370 0.304 Example 3 8.71 74.31 42.78 40.65 1.350 0.120 0.427 0.084 0.065 Example 4 8.13 70.62 39.65 37.99 3.350 1.220 0.430 0.084 0.065

[0129] The composition of the filtrate after copper removal obtained in the second step of the above embodiment and comparative example was obtained by ICP test and is shown in Table 3, in g / L.

[0130] Table 3

[0131] Li Fe P S Al Cu Ti Cr Ca Example 1 15.55 133.98 76.93 78.40 2.44 0.005 0.785 0.142 0.117 Example 2 39.04 335.26 192.45 237.90 6.075 0.487 1.920 0.370 0.304 Example 3 8.71 74.32 42.81 40.64 1.360 0.002 0.427 0.082 0.066 Example 4 8.15 70.64 39.68 38.02 3.360 0.003 0.440 0.082 0.066

[0132] The composition of the filtrate after titanium removal obtained in the third step of the above embodiment and comparative example was obtained by ICP test and is shown in Table 4, in g / L.

[0133] Table 4

[0134] Li Fe P S Al Cu Ti Cr Ca Na Example 1 11.55 95.82 55.49 56.23 2.33 0.004 0.07 0.03 0.08 13.52 Example 2 15.77 136.4 77.22 96.35 2.44 0.003 0.08 0.04 0.09 24.52 Example 3 7.829 66.85 38.51 36.55 1.22 0.002 0.05 0.03 0.06 12.85 Example 4 7.28 62.17 35.81 33.99 3.01 0.003 0.05 0.04 0.07 12.85 Example 5 11.55 95.82 55.49 56.23 2.33 0.004 0.77 0.03 0.08 4.52

[0135] The composition of the ferric phosphate obtained in the seventh step of the above embodiment and comparative example was obtained by ICP test and is shown in Table 5, in wt%.

[0136] The calculation formula for the yield of iron in Table 5 is W Fe收率 =W1 / W2×100%;

[0137] W1 is the mass of iron in the final ferric phosphate, and W2 is the mass of iron in the raw materials;

[0138] Table 5

[0139]

[0140]

[0141] As can be seen from Tables 2 to 5, in Examples 1 to 4, impurities are removed in an inert atmosphere, and sulfuric acid is first used for leaching. Iron exists in the form of divalent iron. Then, in the copper removal process, there is no need to add excessive iron powder to reduce trivalent iron, which reduces the amount of iron powder used. Titanium and aluminum are then removed by adjusting the pH and adding a complexing agent. Since the complexing agent has different complexing degrees for divalent iron ions and aluminum ions, competitive complexation occurs, and the complexing strength of aluminum ions is higher, which is easy to be retained in the aqueous solution for removal without causing loss of phosphorus and iron, and finally ferric phosphate is prepared;

[0142] The pH of the titanium hydrolysis reaction in Example 5 is low, resulting in a higher titanium content in the filtrate after titanium removal; the temperature of the complexation reaction in Example 6 is low, resulting in a higher aluminum content in the filtrate after aluminum removal; the temperature of the complexation reaction in Example 7 is high, resulting in a higher aluminum content in the filtrate after aluminum removal; the amount of complexing agent added in Example 8 is small, resulting in a higher aluminum content in the filtrate after aluminum removal; the amount of complexing agent added in Example 9 is large, resulting in part of the iron reacting with the complexing agent, affecting the iron yield and increasing the processing cost;

[0143] Comparative Example 1: In the first step of sulfuric acid leaching, nitrogen protection was not introduced, resulting in oxidation of iron to trivalent iron, which seriously affected the removal efficiency of impurities such as copper, titanium, and aluminum.

[0144] In Comparative Example 2, the acid leaching solution was first mixed with the first alkali solution to perform a hydrolysis reaction to remove titanium, and then mixed with iron powder to perform a replacement reaction to remove copper. This resulted in a higher amount of the first alkali solution added, which introduced more sodium ions and increased the treatment cost.

[0145] In comparative example 3, the copper removal solution first undergoes a complex reaction with a complexing agent and then adds a second liquid alkali for precipitation, and then is mixed with the first alkali solution for hydrolysis reaction to remove titanium, which will cause titanium and ferrophosphorus to precipitate simultaneously, thereby resulting in a lower purity of the finally prepared ferric phosphate.

[0146] The method in Comparative Example 4 is very easy to form trivalent iron after strong acid leaching, and trivalent iron has a higher complexing strength than aluminum ions and is more likely to react with complexing agents, resulting in a large loss of iron and difficulty in removing aluminum ions, resulting in a low yield of iron and phosphorus.

[0147] In summary, the method for regenerating iron phosphate from waste iron phosphate batteries provided by the present invention is rationally designed. Acid leaching, copper removal, titanium removal and aluminum removal are carried out in an inert atmosphere, thereby achieving efficient removal of various impurities without causing loss of phosphorus and iron. The impurity removal process is short, requires less equipment, and has low recovery and preparation costs.

[0148] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for regenerating iron phosphate from waste iron phosphate batteries, characterized in that: The method comprises the following steps: (1) acid leaching, copper removal, and titanium removal are performed on waste iron phosphate batteries in sequence to obtain a titanium removal solution; (2) mixing the titanium removal liquid and the complexing agent to carry out a complexing reaction to obtain a post-reaction solution; (3) mixing the reaction solution and the first alkali solution to react to obtain crude ferrous phosphate; Steps (1), (2) and (3) are all carried out in an inert atmosphere; (4) The crude ferrous phosphate is subjected to oxidation reaction and recrystallization in sequence to obtain ferric phosphate.

2. The method according to claim 1, characterized in that The complexing agent in step (2) includes any one of ethylenediaminetetraacetic acid, citric acid, malic acid, gallic acid or acetylacetone, or a combination of at least two thereof.

3. The method according to claim 1 or 2, characterized in that The amount of the complexing agent added in step (2) is 1-3 times the molar amount of aluminum in the waste iron phosphate battery; Preferably, the temperature of the complexation reaction is 30-100° C., and the reaction time is 0.5-5 h.

4. The method according to any one of claims 1 to 3, characterized in that The inert atmosphere includes any one of nitrogen atmosphere, helium atmosphere or argon atmosphere; Preferably, the nitrogen flow rate in the nitrogen atmosphere is controlled to be 1.2-1.5 Nm 3 / h.

5. The method according to any one of claims 1 to 4, characterized in that The pH of the reaction in step (3) is 4.0-7.0, the reaction temperature is 30-100° C., and the reaction time is 0.5-5 h.

6. The method according to any one of claims 1 to 5, characterized in that The acid leaching in step (1) adopts sulfuric acid; Preferably, the amount of sulfuric acid used is 1-1.5 times the stoichiometric amount of the ferric phosphate to be completely reacted and leached; Preferably, the liquid-to-solid ratio of the sulfuric acid and the waste iron phosphate battery is 1:1-10:1; Preferably, the acid leaching temperature is 30-100°C; Preferably, the acid leaching time is 0.5-5h; Preferably, the pH of the pickling solution is 0-1.

0.

7. The method according to any one of claims 1 to 6, characterized in that The copper removal in step (1) comprises performing a replacement reaction using iron powder; Preferably, the amount of iron powder added is 1-2 times the molar amount of copper in the waste iron phosphate battery; Preferably, the temperature of the replacement reaction is 30-100° C., and the reaction time is 0.5-5 h.

8. The method according to any one of claims 1 to 7, characterized in that The titanium removal in step (1) comprises performing a hydrolysis reaction using a second alkaline solution; Preferably, the pH of the hydrolysis reaction is 2.0-3.0, the reaction temperature is 30-100° C., and the reaction time is 0.5-5 h; Preferably, the pH of the titanium removal solution is 2.0-3.

0.

9. The method according to any one of claims 1 to 8, characterized in that Stirring is performed during the acid leaching, copper removal, titanium removal in step (1), the complexation reaction in step (2), and the reaction in step (3), and the stirring speed is 200-800 r / min.

10. The method according to claim 8, characterized in that The second alkali solution used in the hydrolysis reaction and the first alkali solution in step (2) both include any one of sodium hydroxide, ammonia water or ammonium bicarbonate or a combination of at least two of them.

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