A method for preparing ferric phosphate from lithium extraction waste, ferric phosphate and its applications

Abstract

This invention provides a method for preparing iron phosphate from lithium extraction waste residue, iron phosphate, and its application. The method includes: (1) phosphorylating the lithium extraction waste residue and then acid leaching it to obtain an acid leaching solution; (2) adjusting the pH of the obtained acid leaching solution to 1-1.5 and mixing it with resin to obtain a first impurity removal solution; (3) mixing the obtained first impurity removal solution with iron powder to obtain a second impurity removal solution; (4) adjusting the iron-to-phosphorus ratio of the obtained second impurity removal solution, oxidizing it, and adjusting the pH to 3-5 to obtain crude iron phosphate; (5) washing the crude iron phosphate with an acid leaching solution and then calcining it to obtain iron phosphate powder. The method uses a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg, and Na from iron phosphate, resulting in iron phosphate with high purity. In addition, the method provided by this invention has low requirements for the raw materials of lithium extraction waste residue, has a wide range of applications, and is conducive to large-scale promotion and use.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a method for preparing iron phosphate from lithium extraction waste residue, and more particularly to a method for preparing iron phosphate from lithium extraction waste residue, iron phosphate and its applications. Background Technology

[0002] Currently, widely used lithium-ion batteries can be divided into two main types based on the cathode material used: nickel-cobalt-manganese ternary lithium batteries and lithium iron phosphate batteries. Among them, lithium iron phosphate batteries account for 61% of the total installed capacity of power batteries worldwide. However, the design life of lithium-ion batteries is generally 6 to 7 years, and some can last up to 10 years. After a large number of lithium iron phosphate batteries reach the end of their life cycle, it is necessary to scrap and recycle these batteries.

[0003] Currently, the main method for recycling lithium iron phosphate batteries is acid leaching. This involves discharging, disassembling, crushing, and screening the batteries, then leaching the lithium iron phosphate cathode material with dilute hydrochloric acid. The lithium extraction waste residue after acid leaching mainly consists of iron phosphate, which contains harmful substances and is not suitable for direct solid waste treatment. In addition, iron phosphate in the lithium extraction waste residue is also an important resource, and its recycling has high economic value.

[0004] The main method for recycling lithium extraction waste in the existing technology is to prepare iron phosphate, and then use the prepared iron phosphate to prepare lithium iron phosphate black powder. However, because the iron phosphate prepared from lithium extraction waste has a high content of impurities such as Al, Ti, Cu, Ca, Mg and Na, the performance of the iron phosphate recovered from lithium extraction waste cannot meet the needs of practical applications.

[0005] The prior art discloses a method for recovering and preparing battery-grade iron phosphate from waste lithium iron phosphate extraction residue. The method involves acid leaching, filtration, salicylic acid initial purification, pH coarse precipitation and purification, etc., to recover and purify the iron phosphate in the waste residue after lithium extraction from waste lithium iron phosphate into battery-grade iron phosphate, so as to solve the problem of disposal of a large amount of phosphorus-containing iron waste residue generated after lithium recovery from waste lithium iron phosphate.

[0006] A method for separating iron phosphate and graphite from lithium extraction waste from retired lithium iron phosphate batteries is disclosed in the prior art. This separation method involves roasting the waste lithium iron phosphate battery black powder, extracting lithium through acid leaching, followed by ball milling and flotation. It eliminates the need to separate the positive and negative electrode materials, preferentially recovering lithium and other metals through acid leaching, and then separating graphite and iron phosphate through flotation.

[0007] Existing methods for preparing iron phosphate from lithium extraction waste all have certain drawbacks, including low purity and high levels of impurities such as Al, Ti, Ca, Mg, and Na. Therefore, developing a novel method for preparing iron phosphate from lithium extraction waste, as well as iron phosphate and its applications, is crucial. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing iron phosphate from lithium extraction waste, iron phosphate, and its applications. The method provided by the present invention employs a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg, and Na from iron phosphate, resulting in iron phosphate with high purity (i.e., low impurity content). The obtained iron phosphate contains no more than 47 ppm Al, no more than 45 ppm Ti, no more than 25.2 ppm Ca, no more than 5.5 ppm Mg, no more than 9.8 ppm Na, and no more than 24 ppm Li. Furthermore, the method provided by the present invention has low requirements for lithium extraction waste raw materials, a wide range of applicability, and is conducive to large-scale promotion and use.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing iron phosphate from lithium extraction waste residue, the method comprising:

[0011] (1) Phosphorylate the lithium extraction waste residue and then leach it with acid to obtain an acid leaching solution;

[0012] (2) Adjust the pH of the acid leaching solution obtained in step (1) to 1-1.5 and then mix it with the resin to obtain the first impurity removal solution;

[0013] (3) Mix the first impurity removal solution obtained in step (2) with iron powder to obtain the second impurity removal solution;

[0014] (4) Adjust the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3), oxidize it and adjust the pH to 3-5 to obtain crude iron phosphate;

[0015] (5) The crude iron phosphate obtained in step (4) is washed with pickling solution and then calcined to obtain iron phosphate powder.

[0016] In step (2) of the method of the present invention, the pH of the acid leaching solution obtained in step (1) is adjusted to 1 to 1.5. For example, it can be 1, 1.1, 1.2, 1.3, 1.4 or 1.5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] In step (4) of the method described in this invention, the pH is adjusted to 3 to 5, for example, it can be 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8 or 5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] In step (1) of the method provided by the present invention, the lithium extraction waste residue is phosphorylated and then acid-leached to obtain an acid leaching solution. The purpose of this acid leaching solution is to remove impurities from the lithium extraction waste residue and to dissolve the lithium extraction waste residue.

[0019] The purpose of adjusting the pH of the acid leaching solution obtained in step (1) to 1-1.5 in step (2) of the method provided by the present invention is to precipitate the calcium and magnesium impurities in the acid leaching solution, and then mix it with the resin to remove the calcium and magnesium impurity precipitate through the adsorption of the resin.

[0020] In step (3) of the method provided by the present invention, the first impurity removal solution obtained in step (2) is mixed with iron powder, and the copper ions in the first impurity removal solution are removed by the displacement reaction between the iron powder and copper ions.

[0021] The iron-phosphorus ratio mentioned in step (4) of the method provided by the present invention is the molar ratio of iron to phosphorus. The purpose of adjusting the iron-phosphorus ratio of the second impurity removal solution obtained in step (3) is to make the ratio of phosphorus to iron in the second impurity removal solution within a range that is conducive to the precipitation of iron phosphate. The purpose of oxidation is to oxidize the ferrous iron in the second impurity removal solution to ferric iron. The purpose of adjusting the pH to 3-5 is to achieve the precipitation of iron phosphate.

[0022] In step (5) of the method provided by the present invention, the crude iron phosphate obtained in step (5) is washed with an acid washing solution, which can remove impurities such as Al, Na, and Ti adsorbed in the re-reaction process of the crude iron phosphate, and then iron phosphate is prepared by calcination.

[0023] The method provided by this invention employs a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg, and Na from ferric phosphate, resulting in high-purity ferric phosphate. The obtained ferric phosphate contains no more than 47 ppm Al, no more than 45 ppm Ti, no more than 25.2 ppm Ca, no more than 5.5 ppm Mg, no more than 9.8 ppm Na, and no more than 24 ppm Li. Furthermore, the method provided by this invention has low requirements for lithium extraction waste residue raw materials, a wide range of applicability, and is conducive to large-scale promotion and use.

[0024] Preferably, the phosphorylation method in step (1) includes: mixing lithium extraction waste residue with phosphoric acid and / or phosphate and then sintering to obtain phosphorylated lithium extraction waste residue.

[0025] Preferably, the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue during phosphoric acid treatment in step (1) is in the ratio of the molar amounts of P elements in phosphoric acid and / or phosphate to (1-3):1. For example, it can be 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1 or 3:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the phosphate includes any one or a combination of at least two of ammonium phosphate, trisodium phosphate, or potassium phosphate. Typical but non-limiting combinations include a combination of ammonium phosphate and trisodium phosphate, a combination of trisodium phosphate and potassium phosphate, or a combination of ammonium phosphate, trisodium phosphate, and potassium phosphate.

[0027] Preferably, the sintering temperature is 300–650°C and the time is 0.5–3 hours.

[0028] The sintering temperature described in this invention is 300 to 650°C, for example, it can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or 650°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] The sintering time described in this invention is 0.5 to 3 hours, for example, it can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the acid leaching agent used in step (1) includes any one or a combination of at least two of sulfuric acid solution, phosphoric acid solution, hydrochloric acid solution or nitric acid solution. Typical but non-limiting combinations include a combination of sulfuric acid solution and phosphoric acid solution, a combination of phosphoric acid solution and hydrochloric acid solution, a combination of hydrochloric acid solution and nitric acid solution, or a combination of sulfuric acid solution, phosphoric acid solution and hydrochloric acid solution.

[0031] Preferably, the ratio of the molar amount of hydrogen ions in the leaching agent to the molar amount of Fe element in the sintered product during acid leaching in step (1) is (2-4):1, for example, it can be 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1 or 4:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the acid leaching temperature in step (1) is 30-90°C and the time is 0.5-3h.

[0033] In this invention, the acid leaching temperature in step (1) is 30 to 90°C, for example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C or 90°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] In this invention, the acid leaching time in step (1) is 0.5 to 3 hours, for example, it can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the acid leaching in step (1) is accompanied by stirring.

[0036] Preferably, step (1) further includes filtration after acid leaching to obtain an acid leaching solution.

[0037] Preferably, the pH adjuster used in step (2) includes any one or a combination of at least two of ammonia, liquid ammonia, sodium hydroxide solution or solid sodium hydroxide. Typical but non-limiting combinations include a combination of ammonia and liquid ammonia, a combination of liquid ammonia and sodium hydroxide solution, and a combination of ammonia, liquid ammonia and sodium hydroxide solution.

[0038] Preferably, the resin in step (2) comprises a chelating ion exchange resin.

[0039] Preferably, step (2) further includes filtration after mixing to obtain a first impurity-removed solution.

[0040] The filtration process described in this invention refers to the process of removing impurities, precipitates, and scale from a solution using filtration technology.

[0041] Preferably, during the mixing process in step (3), the ratio of the molar amount of copper ions in the first impurity removal solution obtained in step (2) to the molar amount of iron in the iron powder is 1:(2-5), for example, it can be 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8, 1:4, 1:4.2, 1:4.5, 1:4.8 or 1:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, step (3) further includes filtration after mixing to obtain a second impurity-removing solution.

[0043] Preferably, in step (4), the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3) is adjusted to 0.95 to 0.98, for example, it can be 0.95, 0.955, 0.96, 0.965, 0.97, 0.975 or 0.98, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the method of adjusting the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3) in step (4) includes adding iron powder, ferric hydroxide, or phosphoric acid.

[0045] Preferably, the oxidation method in step (4) includes adding an oxidant, wherein the oxidant reacts with Fe in the second impurity removal solution obtained in step (3). 2+ The molar ratio is 1:(1~2), for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the oxidant includes any one or a combination of at least two of hydrogen peroxide, ozone, or air atomization.

[0047] Preferably, step (4) further includes filtration after pH adjustment.

[0048] Preferably, the pickling solution in step (5) includes oxalic acid solution and / or phosphoric acid solution, and the acid concentration of the pickling solution is 0.1 to 1 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L or 1 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] Preferably, the mass ratio of the pickling solution to the crude ferric phosphate in step (5) is 1:(0.1 to 0.3), for example, 1:0.1, 1:0.12, 1:0.15, 1:0.17, 1:0.2, 1:0.22, 1:0.25, 1:0.27 or 1:0.3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the washing temperature in step (5) is 10-60°C and the washing time is 1-3 hours.

[0051] The washing temperature described in step (5) of this invention is 10 to 60°C, for example, it can be 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] The washing time in step (5) of this invention is 1 to 3 hours, for example, it can be 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, 2.2 hours, 2.5 hours, 2.7 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, step (5) includes sequential pressure filtration, water washing and drying between washing and calcination.

[0054] Preferably, the conductivity of the water used in the washing process is less than 20 μS / cm, for example, it can be 19 μS / cm, 18 μS / cm, 17 μS / cm, 15 μS / cm, 12 μS / cm, 10 μS / cm or 5 μS / cm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the drying temperature is 100-130°C, and the drying is stopped when the free water content is less than 1.5%.

[0056] The drying temperature described in this invention is 100 to 130°C, for example, it can be 100°C, 102°C, 105°C, 108°C, 110°C, 115°C, 120°C, 125°C or 130°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] The drying process described in this invention is stopped when the free water content is below 1.5%. The free water content can be, for example, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.8%, 0.5%, or 0.1%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Preferably, the calcination temperature in step (5) is 550–700°C and the time is 0.5–3 h.

[0059] The calcination temperature in step (5) of this invention is 550 to 700°C, for example, it can be 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 650°C, 680°C or 700°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] The calcination time in step (5) of this invention is 0.5 to 3 hours, for example, it can be 0.5 hours, 0.7 hours, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] As a preferred embodiment of the method described in this invention, the method includes:

[0062] (1) Mix lithium extraction waste residue with phosphoric acid and / or phosphate, wherein the molar ratio of the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue to the molar amount of P elements in the phosphoric acid and / or phosphate is (1-3):1, and then sinter at 300-650℃ for 0.5-3h to obtain phosphorylated lithium extraction waste residue; then acid leaching the obtained phosphorylated lithium extraction waste residue at 30-90℃ with an acid leaching agent for 0.5-3h, with stirring during acid leaching, wherein the molar ratio of the hydrogen ions in the acid leaching agent to the molar amount of Fe elements in the sintered product is (2-4):1, and then filter to obtain acid leaching solution;

[0063] (2) The pH of the acid leaching solution obtained in step (1) is adjusted to 1 to 1.5 by using a pH adjuster and then mixed with resin. After further filtration, the first impurity-removed solution is obtained.

[0064] (3) Mix the first impurity removal solution obtained in step (2) with iron powder. The ratio of the molar amount of copper ions in the first impurity removal solution to the molar amount of iron in the iron powder is 1:(2~5). After filtration, the second impurity removal solution is obtained.

[0065] (4) Adjust the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3) to 0.95–0.98 by adding iron powder, ferric hydroxide, or phosphoric acid. Add an oxidant for oxidation. The oxidant reacts with the Fe in the second impurity removal solution obtained in step (3). 2+ The molar ratio was 1:(1~2), and the pH was adjusted to 3~5. After filtration, crude iron phosphate was obtained.

[0066] (5) The crude iron phosphate obtained in step (4) is washed for 1 to 3 hours at 10 to 60 °C with an acid washing solution of 0.1 to 1 mol / L. The mass ratio of the acid washing solution to the crude iron phosphate is 1:(0.1 to 0.3). After pressure filtration, it is washed with water with a conductivity of less than 20 μS / cm. Then it is dried at 100 to 130 °C until the free water content is less than 1.5%. Finally, it is calcined at 550 to 700 °C for 0.5 to 3 hours to obtain iron phosphate powder.

[0067] In a second aspect, the present invention provides an iron phosphate, which is obtained by the method described in the first aspect.

[0068] Thirdly, the present invention provides a lithium iron phosphate, which is obtained by preparing iron phosphate as described in the second aspect.

[0069] Fourthly, the present invention provides a lithium battery comprising the lithium iron phosphate described in the third aspect.

[0070] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] The method provided by this invention employs a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg, and Na from ferric phosphate, resulting in high-purity ferric phosphate. The obtained ferric phosphate contains no more than 47 ppm Al, no more than 45 ppm Ti, no more than 25.2 ppm Ca, no more than 5.5 ppm Mg, no more than 9.8 ppm Na, and no more than 24 ppm Li. Furthermore, the method provided by this invention has low requirements for lithium extraction waste residue raw materials, a wide range of applicability, and is conducive to large-scale promotion and use. Detailed Implementation

[0073] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0074] Example 1

[0075] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue, the method comprising:

[0076] (1) Mix lithium extraction waste residue with phosphoric acid, wherein the molar ratio of the sum of the Ti and Al elements in the lithium extraction waste residue to the molar ratio of the P element in the phosphoric acid is 2:1, and then sinter at 500℃ for 1.5h to obtain phosphorylated lithium extraction waste residue; then acid leaching the obtained phosphorylated lithium extraction waste residue with sulfuric acid solution at 60℃ for 1.5h, with stirring during acid leaching, wherein the molar ratio of the hydrogen ions in the sulfuric acid solution to the molar ratio of the Fe element in the sintered product is 3:1, and then filter to obtain acid leaching solution;

[0077] (2) After adjusting the pH of the acid leaching solution obtained in step (1) to 1.2 with ammonia water, it is mixed with chelating ion exchange resin and then filtered to obtain the first impurity-removed solution.

[0078] (3) Mix the first impurity removal solution obtained in step (2) with iron powder. The ratio of the molar amount of copper ions in the first impurity removal solution to the molar amount of iron in the iron powder is 1:3.5. After filtration, the second impurity removal solution is obtained.

[0079] (4) Adjust the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3) to 0.96, add hydrogen peroxide for oxidation, and the hydrogen peroxide reacts with the Fe in the second impurity removal solution obtained in step (3). 2+ The molar ratio was 1:1.5, and the pH was adjusted to 4. After filtration, crude iron phosphate was obtained.

[0080] (5) The crude iron phosphate obtained in step (4) was washed for 2 hours at 35°C with an oxalic acid solution with an acid concentration of 0.5 mol / L. The mass ratio of the oxalic acid solution to the crude iron phosphate was 1:0.2. After pressure filtration, it was washed with water with a conductivity of 15 μS / cm. After drying at 115°C until the free water content was 1.2%, it was calcined at 620°C for 1.5 hours to obtain iron phosphate powder.

[0081] Example 2

[0082] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue, the method comprising:

[0083] (1) Mix lithium extraction waste residue with ammonium phosphate, wherein the molar ratio of the sum of the Ti and Al elements in the lithium extraction waste residue to the molar ratio of the P element in the ammonium phosphate is 1:1, and then sinter at 650℃ for 0.5h to obtain phosphorylated lithium extraction waste residue; then acid leaching the obtained phosphorylated lithium extraction waste residue with hydrochloric acid solution at 30℃ for 3h, with stirring during acid leaching, wherein the molar ratio of the hydrogen ions in the hydrochloric acid solution to the molar ratio of the Fe element in the sintered product is 4:1, and then filter to obtain acid leaching solution;

[0084] (2) After adjusting the pH of the acid leaching solution obtained in step (1) to 1.5 with sodium hydroxide solution, it is mixed with chelating ion exchange resin and then filtered to obtain the first impurity-removed solution.

[0085] (3) Mix the first impurity removal solution obtained in step (2) with iron powder. The ratio of the molar amount of copper ions in the first impurity removal solution to the molar amount of iron in the iron powder is 1:2. After filtration, the second impurity removal solution is obtained.

[0086] (4) Adjust the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3) to 0.98, add hydrogen peroxide for oxidation, and the hydrogen peroxide reacts with the Fe in the second impurity removal solution obtained in step (3). 2+ The molar ratio was 1:2, and the pH was adjusted to 5. After filtration, crude ferric phosphate was obtained.

[0087] (5) The crude iron phosphate obtained in step (4) was washed for 1 hour at 10°C with a phosphoric acid solution with an acid concentration of 1 mol / L. The mass ratio of the phosphoric acid solution to the crude iron phosphate was 1:0.3. After pressure filtration, it was washed with water with a conductivity of 18 μS / cm. Then it was dried at 130°C until the free water content was less than 0.8%. Finally, it was calcined at 700°C for 0.5 hours to obtain iron phosphate powder.

[0088] Example 3

[0089] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue, the method comprising:

[0090] (1) Mix lithium extraction waste residue with trisodium phosphate, wherein the molar ratio of the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue to the molar amount of P element in trisodium phosphate is 3:1, and then sinter at 300℃ for 3 hours to obtain phosphorylated lithium extraction waste residue; then acid leaching the obtained phosphorylated lithium extraction waste residue with nitric acid solution at 90℃ for 0.5 hours, with stirring during acid leaching, wherein the molar ratio of the hydrogen ions in the nitric acid solution to the molar amount of Fe element in the sintered product is 2:1, and then filter to obtain acid leaching solution;

[0091] (2) After adjusting the pH of the acid leaching solution obtained in step (1) to 1 with ammonia water, it is mixed with chelating ion exchange resin and then filtered to obtain the first impurity removal solution.

[0092] (3) Mix the first impurity removal solution obtained in step (2) with iron powder. The ratio of the molar amount of copper ions in the first impurity removal solution to the molar amount of iron in the iron powder is 1:5. After filtration, the second impurity removal solution is obtained.

[0093] (4) Adjust the iron-to-phosphorus ratio of the second impurity removal solution obtained in step (3) to 0.95, add hydrogen peroxide for oxidation, and the hydrogen peroxide reacts with the Fe in the second impurity removal solution obtained in step (3). 2+ The molar ratio was 1:1, and the pH was adjusted to 3. After filtration, crude iron phosphate was obtained.

[0094] (5) The crude iron phosphate obtained in step (4) was washed for 3 hours at 60°C with a phosphoric acid solution with an acid concentration of 0.1 mol / L. The mass ratio of the phosphoric acid solution to the crude iron phosphate was 1:0.1. After pressure filtration, it was washed with water with a conductivity of 10 μS / cm. After drying at 100°C until the free water content was 1.4%, it was calcined at 550°C for 3 hours to obtain iron phosphate powder.

[0095] Example 4

[0096] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue. Except for step (1), in which the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue during phosphoric acid is 4:1, all other steps are the same as in Example 1.

[0097] Example 5

[0098] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue. Except for the sintering temperature of 200°C in step (1), the rest is the same as in embodiment 1.

[0099] Example 6

[0100] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue. Except for the sintering temperature of 800°C in step (1), the rest is the same as in embodiment 1.

[0101] Example 7

[0102] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue. Except for the oxalic acid solution in step (5) having an acid concentration of 0.02 mol / L, the rest is the same as in Example 1.

[0103] Example 8

[0104] This embodiment provides a method for preparing iron phosphate from lithium extraction waste residue. Except for the oxalic acid solution concentration of 2 mol / L in step (5), the rest is the same as in Example 1.

[0105] Comparative Example 1

[0106] This comparative example provides a method for preparing iron phosphate from lithium extraction waste residue. Except for omitting step (1) of mixing lithium extraction waste residue and phosphoric acid, the ratio of the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue to the molar amount of P element in the phosphoric acid is 2:1, and then sintering at 500°C for 1.5 hours to obtain phosphorylated lithium extraction waste residue, i.e., directly acid leaching the lithium extraction waste residue, the rest is the same as in Example 1.

[0107] Comparative Example 2

[0108] This comparative example provides a method for preparing iron phosphate from lithium extraction waste residue. Except for adjusting the pH of the acid leaching solution obtained in step (1) to 0.5, the rest is the same as in Example 1.

[0109] Comparative Example 3

[0110] This comparative example provides a method for preparing iron phosphate from lithium extraction waste residue. Except for adjusting the pH of the acid leaching solution obtained in step (1) to 2.5, the rest is the same as in Example 1.

[0111] Comparative Example 4

[0112] This comparative example provides a method for preparing iron phosphate from lithium extraction waste residue. Except for omitting step (3), the rest is the same as in Example 1.

[0113] Comparative Example 5

[0114] This comparative example provides a method for preparing ferric phosphate from lithium extraction waste residue. Except for omitting step (5), in which the crude ferric phosphate obtained in step (4) is washed at 35°C with an oxalic acid solution of 0.5 mol / L for 2 hours, the rest is the same as in Example 1.

[0115] The preparation method of lithium extraction waste residue used in this invention is as follows: waste lithium iron phosphate batteries are disassembled after discharge to obtain positive electrode powder, phosphoric acid solution and hydrogen peroxide are added, and after the iron phosphate is separated, solid-liquid separation is carried out by vacuum filtration, wherein the liquid is lithium solution and the solid is lithium extraction waste residue. The main components of the lithium extraction waste residue used in this invention are shown in Table 1 and Table 2.

[0116] Iron phosphate was prepared using the method for preparing iron phosphate from lithium extraction waste provided in the above embodiments and comparative examples. The contents of Al, Ti, Cu, Ca, Mg and Na in the prepared iron phosphate were tested and are shown in Tables 3 and 4.

[0117] Table 1

[0118]

[0119] Table 2

[0120]

[0121] Table 3

[0122]

[0123] Table 4

[0124]

[0125]

[0126] From Tables 1-4, we can obtain:

[0127] (1) The method for preparing iron phosphate from lithium extraction waste provided in Examples 1 to 3 was used to prepare iron phosphate. The iron phosphate prepared had low concentrations of impurities such as Al, Ti, Cu, Ca, Mg and Na, and high purity, which met the requirements of practical applications.

[0128] (2) By comparing Example 1 and Example 4, it can be seen that the ratio of the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue during phosphoric acid treatment in step (1) of this invention to the molar amounts of P elements in phosphoric acid and / or phosphate will affect the content of impurities and the purity of iron phosphate in the prepared iron phosphate. When the ratio of the sum of the molar amounts of Ti and Al elements to the molar amounts of P elements is (1~3):1, the concentrations of impurities such as Al, Ti, Cu, Ca, Mg and Na are lower, and the purity of iron phosphate is higher. This is because when the ratio of the sum of the molar amounts of Ti and Al elements to the molar amounts of P elements is (1~3):1, the phosphorylation of Ti and Al elements can be fully realized without forming insoluble substances such as aluminum phosphate, titanium phosphate, calcium phosphate, and magnesium phosphate.

[0129] (3) By comparing Example 1 with Examples 5 and 6, it can be seen that the sintering temperature in step (1) of the present invention will affect the content of impurities and the purity of iron phosphate in the prepared iron phosphate. When the sintering temperature is 300-650℃, the concentration of impurities such as Al, Ti, Cu, Ca, Mg and Na is lower and the purity of iron phosphate is higher. This is because when the sintering temperature is 300-650℃, the reaction in step (1) can be more complete and the formation of pyrophosphate can be avoided.

[0130] (4) By comparing Example 1 with Examples 7 and 8, it can be seen that the acid concentration of the pickling solution in step (5) of the present invention will affect the content of impurities and the purity of the prepared ferric phosphate. When the acid concentration is 0.1 to 1 mol / L, the concentration of impurities such as Al, Ti, Cu, Ca, Mg and Na is low and the purity of ferric phosphate is high. This is because when the acid concentration is 0.1 to 1 mol / L, it can remove impurities such as Al, Na and Ti adsorbed in the re-reaction process in the crude ferric phosphate, and avoid the impurities from dissolving into the ferric phosphate due to excessively high acid concentration.

[0131] (6) By comparing Example 1 with Comparative Examples 1 to 5, it can be seen that the method provided by the present invention uses a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg and Na from iron phosphate, and obtains iron phosphate with high purity. According to the data in Examples 1 to 3, the iron phosphate obtained by the method of preparing iron phosphate from lithium extraction waste provided in Examples 1 to 3 has an Al content of no more than 47 ppm, a Ti content of no more than 45 ppm, a Ca content of no more than 25.2 ppm, a Mg content of no more than 5.5 ppm, a Na content of no more than 9.8 ppm, and a Li content of no more than 24 ppm. In addition, the method provided by the present invention has low requirements for lithium extraction waste raw materials, a wide range of applications, and is conducive to large-scale promotion and use.

[0132] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing iron phosphate from lithium extraction waste residue, characterized in that, The method comprises: (1) performing phosphating on the lithium extraction waste residue and then performing acid leaching to obtain an acid leaching solution; The phosphating manner comprises: mixing the lithium extraction waste residue with phosphoric acid and / or a phosphate and then sintering to obtain phosphated lithium extraction waste residue; The ratio of the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue to the molar amount of P element in the phosphoric acid and / or the phosphate is (1-3):1; The sintering temperature is 300-650 DEG C, and the sintering time is 0.5-3 h; (2) mixing the acid leaching solution obtained in step (1) with resin after adjusting the pH of the acid leaching solution to 1-1.5 to obtain a first impurity removal solution; (3) mixing the first impurity removal solution obtained in step (2) with iron powder to obtain a second impurity removal solution; (4) adjusting the iron-phosphorus ratio of the second impurity removal solution obtained in step (3), performing oxidation and adjusting the pH to 3-5 to obtain a crude iron phosphate product; (5) washing the crude iron phosphate product obtained in step (4) with an acid washing solution and then calcining to obtain an iron phosphate powder.

2. The method of claim 1, wherein, In step (1), the ratio of the molar amount of hydrogen ions in the acid leaching agent to the molar amount of Fe element in the sintering product is (2-4):

1.

3. The method of claim 1, wherein, In step (1), the acid leaching temperature is 30-90 DEG C, and the acid leaching time is 0.5-3 h.

4. The method of claim 1, wherein, In step (2), the pH adjusting agent used for adjusting the pH of the acid leaching solution comprises any one or a combination of at least two of ammonia water, liquid ammonia, sodium hydroxide solution or solid sodium hydroxide.

5. The method of claim 1, wherein, In step (2), the resin comprises a chelating ion exchange resin.

6. The method of claim 1, wherein, In step (3), the ratio of the molar amount of copper ions in the first impurity removal solution obtained in step (2) to the molar amount of iron element in the iron powder is 1:(2-5) during the mixing.

7. The method of claim 1, wherein, In step (4), the molar ratio of iron to phosphorus of the second impurity removal solution obtained in step (3) is adjusted to 0.95-0.

98.

8. The method of claim 1, wherein, The oxidation in step (4) is carried out by adding an oxidizing agent in a molar ratio of 1:(1~2) with respect to Fe in the second impurity-removing solution obtained in step (3). 2+ The oxidation in step (4) is carried out by adding an oxidizing agent in a molar ratio of 1:(1~2) with respect to Fe in the second impurity-removing solution obtained in step (3).

9. The method of claim 1, wherein, In step (5), the acid washing solution comprises an oxalic acid solution and / or a phosphoric acid solution, and the acid concentration of the acid washing solution is 0.1-1 mol / L.

10. The method of claim 1, wherein, In step (5), the mass ratio of the acid washing solution to the crude iron phosphate product is 1:(0.1-0.3).

11. The method of claim 1, wherein, In step (5), the washing temperature is 10-60 DEG C, and the washing time is 1-3 h.

12. The method of claim 1, wherein, In step (5), the calcination temperature is 550-700 DEG C, and the calcination time is 0.5-3 h.

13. The method of claim 1, wherein, The method comprises: (1) mixing lithium extraction waste residue with phosphoric acid and / or a phosphate, the ratio of the sum of the molar amounts of Ti and Al elements in the lithium extraction waste residue to the molar amount of P element in the phosphoric acid and / or the phosphate is (1-3):1, then sintering at 300-650 DEG C for 0.5-3 h to obtain phosphated lithium extraction waste residue, then performing acid leaching on the obtained phosphated lithium extraction waste residue at 30-90 DEG C for 0.5-3 h using an acid leaching agent, the acid leaching is accompanied by stirring, the ratio of the molar amount of hydrogen ions in the acid leaching agent to the molar amount of Fe element in the sintering product is (2-4):1, then filtering to obtain an acid leaching solution; (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1-1.5 using a pH adjusting agent, then mixing with resin, then filtering to obtain a first impurity removal solution; (3) mixing the first impurity removal solution obtained in step (2) with iron powder, the ratio of the molar amount of copper ions in the first impurity removal solution to the molar amount of iron in the iron powder being 1:(2-5), and then filtering to obtain a second impurity removal solution; (4) Adjusting the molar ratio of iron to phosphorus of the second impurity removal liquid obtained in step (3) to 0.95-0.98 by adding iron powder, iron hydroxide or phosphoric acid, adding an oxidizing agent to perform oxidation, the molar ratio of the oxidizing agent to Fe in the second impurity removal liquid obtained in step (3) being 1:(1-2), and adjusting the pH to 3-5, and then performing filtration to obtain a crude iron phosphate product; 2+ (4) Adjusting the molar ratio of iron to phosphorus of the second impurity removal liquid obtained in step (3) to 0.95-0.98 by adding iron powder, iron hydroxide or phosphoric acid, adding an oxidizing agent to perform oxidation, the molar ratio of the oxidizing agent to Fe in the second impurity removal liquid obtained in step (3) being 1:(1-2), and adjusting the pH to 3-5, and then performing filtration to obtain a crude iron phosphate product; (5) washing the crude iron phosphate obtained in step (4) with an acid solution having an acid concentration of 0.1-1 mol / L at 10-60 ℃ for 1-3 h, the mass ratio of the acid solution to the crude iron phosphate being 1:(0.1-0.3), then performing pressure filtration, washing with water having a conductivity of less than 20 us / cm, and then drying at 100-130 ℃ until the free water content is less than 1.5%, and then calcining at 550-700 ℃ for 0.5-3 h to obtain iron phosphate powder.

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