Method for preparing iron phosphate from lithium extraction waste residues, iron phosphate and application of iron phosphate

Abstract

The invention provides a method for preparing iron phosphate from lithium extraction waste residues, iron phosphate and application of the iron phosphate, and the method comprises the following steps: (1) phosphorylating the lithium extraction waste residues, and then carrying out acid leaching to obtain an acid leaching solution; (2) adjusting the pH value of the obtained pickle liquor to 1-1.5, and then mixing the pickle liquor with resin to obtain first impurity-removed liquor; (3) mixing the obtained first impurity-removed liquid with iron powder to obtain a second impurity-removed liquid; (4) adjusting the iron-phosphorus ratio of the obtained second impurity removal liquid, oxidizing, and adjusting the pH value to 3-5 to obtain an iron phosphate crude product; and (5) washing the iron phosphate crude product with a pickling solution, and calcining to obtain iron phosphate powder. According to the method, impurities such as Al, Ti, Cu, Ca, Mg and Na in the iron phosphate are removed by adopting a multi-step impurity removal process, and the iron phosphate with relatively high purity is obtained; in addition, the method provided by the invention has low requirements on lithium extraction waste residue raw materials, has a wide application range, and is beneficial to large-scale popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries and relates to a method for preparing iron phosphate from lithium-extracted waste residue, and in particular to a method for preparing iron phosphate from lithium-extracted waste residue, iron phosphate and applications thereof. Background Art

[0002] Currently, widely used lithium-ion batteries can be divided into two main types: nickel-cobalt-manganese ternary lithium batteries and lithium iron phosphate batteries according to the different positive electrode materials used. The installed capacity of lithium iron phosphate batteries accounts for 61% of the total installed capacity of power batteries in the world. However, the design life of lithium-ion batteries is generally 6 to 7 years, and some can be up to 10 years. After a large number of lithium iron phosphate batteries reach the end of their life cycle, they need to be scrapped and recycled.

[0003] Currently, the recycling of lithium iron phosphate batteries is mainly done by acid leaching, which involves discharging, disassembling, crushing, and screening the batteries, and then using dilute hydrochloric acid to leach the lithium iron phosphate positive electrode material. The lithium extraction waste residue after acid leaching is mainly composed of iron phosphate, which contains harmful substances and is not suitable for direct treatment as solid waste. In addition, iron phosphate in lithium extraction waste residue is also an important resource, and its recycling has high economic value.

[0004] In the prior art, the main method for recycling lithium extraction waste slag is to prepare iron phosphate, and then use the prepared iron phosphate to prepare lithium iron phosphate black powder; however, since the iron phosphate prepared from lithium extraction waste slag 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 slag cannot meet the needs of practical applications.

[0005] The prior art discloses a method for recovering and preparing battery-grade iron phosphate from waste slag after lithium extraction from waste lithium iron phosphate. The method comprises the following steps: acid solution leaching, filtration, initial purification with salicylic acid, pH coarse precipitation and purification, so as to recover the iron phosphate in the slag after lithium extraction from waste lithium iron phosphate and purify it into battery-grade iron phosphate, so as to solve the problem of disposing of a large amount of phosphorus-containing iron slag generated after lithium recovery from waste lithium iron phosphate.

[0006] The prior art discloses a method for separating iron phosphate and graphite from lithium-extracting waste residue of retired lithium iron phosphate batteries. The separation method involves roasting the black powder of the waste lithium iron phosphate batteries, extracting lithium through acid leaching, then ball milling, and flotation. There is no need to separate the positive and negative electrode materials. Lithium and other metals are first recovered through acid leaching, and then flotation separation is performed to obtain graphite and iron phosphate.

[0007] The methods for preparing iron phosphate from lithium waste residue disclosed in the prior art have certain defects, such as low purity of the prepared iron phosphate and high content of impurities such as Al, Ti, Ca, Mg and Na. Therefore, it is very important to develop a new method for preparing iron phosphate from lithium waste residue, iron phosphate and its application. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing iron phosphate from lithium extraction waste slag, iron phosphate and its application. The method provided by the present invention adopts a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg and Na in iron phosphate, thereby obtaining iron phosphate with high purity (i.e., low impurity content). The Al content in the obtained iron phosphate is not higher than 47ppm, the Ti content is not higher than 45ppm, the Ca content is not higher than 25.2ppm, the Mg content is not higher than 5.5ppm, the Na content is not higher than 9.8ppm, and the Li content is not higher than 24ppm. In addition, the method provided by the present invention has low requirements for raw materials of lithium extraction waste slag, has a wide range of application, and is conducive to large-scale promotion and use.

[0009] To achieve this object, the present invention adopts the following technical solutions:

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

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

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

[0013] (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder to obtain a second impurity-removing liquid;

[0014] (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3), performing oxidation and adjusting the pH to 3 to 5, to obtain a crude iron phosphate;

[0015] (5) washing the crude iron phosphate obtained in step (4) with an acid wash solution and then calcining to obtain iron phosphate powder.

[0016] In step (2) of the method of the present invention, the pH of the acid extract 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, and other values ​​not listed within the numerical range are also applicable.

[0017] In step (4) of the method of the present invention, the pH is adjusted to 3-5, for example, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.8 or 5, but is not limited to the listed values, and other values ​​not listed within the numerical 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 the acid leaching solution for the purpose of removing impurities in the lithium extraction waste residue and achieving dissolution of 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 calcium and magnesium impurities in the acid leaching solution, and then mix it with the resin to remove the calcium and magnesium impurity precipitates through the adsorption effect of the resin.

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

[0021] The iron-to-phosphorus ratio 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-to-phosphorus ratio of the second impurity-removing liquid obtained in step (3) is to make the ratio of phosphorus to iron in the second impurity-removing liquid within a range that is conducive to the precipitation of ferric phosphate. The purpose of oxidation is to oxidize the divalent iron in the second impurity-removing liquid into trivalent iron. The purpose of adjusting the pH to 3-5 is to achieve the precipitation of ferric 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 wash solution, so as to remove impurities such as Al, Na, Ti adsorbed in the re-reaction process in the crude iron phosphate, and then the preparation of iron phosphate is achieved by calcination.

[0023] The method provided by the present invention adopts a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg and Na in ferric phosphate, thereby obtaining ferric phosphate with high purity, wherein the content of Al in the obtained ferric phosphate is not higher than 47ppm, the content of Ti is not higher than 45ppm, the content of Ca is not higher than 25.2ppm, the content of Mg is not higher than 5.5ppm, the content of Na is not higher than 9.8ppm, and the content of Li is not higher than 24ppm; in addition, the method provided by the present invention has low requirements on raw materials for lithium extraction waste slag, has a wide range of application, 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 ratio of the sum of the molar amounts of the Ti element and the Al element in the lithium extraction waste slag during the phosphorylation in step (1) to the molar amount of the P element in the phosphoric acid and / or phosphate is (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 is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] Preferably, the phosphate includes any one of ammonium phosphate, trisodium phosphate or potassium phosphate or a combination of at least two thereof, and 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 sintering time is 0.5-3 h.

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

[0029] The sintering time in the present invention is 0.5 to 3 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the acid leaching agent used in the acid leaching in step (1) includes any one of sulfuric acid solution, phosphoric acid solution, hydrochloric acid solution or nitric acid solution, or a combination of at least two of them. 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, during the acid leaching 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 sintered product 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 is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the acid leaching in step (1) is carried out at a temperature of 30 to 90° C. and for a time of 0.5 to 3 h.

[0033] The temperature of the acid leaching in step (1) of the present invention is 30-90°C, for example, 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 is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] The acid leaching time in step (1) of the present invention is 0.5 to 3 hours, for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

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

[0036] Preferably, the acid leaching in step (1) further comprises filtering to obtain an acid leaching solution.

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

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

[0039] Preferably, the mixing in step (2) further includes filtering to obtain a first impurity-free liquid.

[0040] The clean filtration mentioned in the present invention refers to the process of removing impurities, sediments, scale, etc. in the solution through filtration technology.

[0041] Preferably, during the mixing 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 is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, step (3) further comprises filtering after the mixing to obtain a second impurity-removing liquid.

[0043] Preferably, in step (4), the iron-phosphorus ratio of the second impurity removal liquid obtained in step (3) is adjusted to 0.95-0.98, 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, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, in step (4), the method of adjusting the iron-phosphorus ratio of the second impurity removal liquid obtained in step (3) comprises adding iron powder, iron 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, 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0047] Preferably, step (4) further comprises filtering after adjusting the pH.

[0048] Preferably, the pickling solution in step (5) comprises oxalic acid solution and / or phosphoric acid solution, and the acid concentration of the pickling solution is 0.1-1 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, and other values ​​not listed within the numerical range are also applicable.

[0049] Preferably, the mass ratio of the pickling solution to the crude iron phosphate in step (5) is 1:(0.1-0.3), 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0051] The washing temperature in step (5) of the present invention is 10-60°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] The washing time in step (5) of the present 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] Preferably, the washing and calcining in step (5) further include filter pressing, water washing and drying in sequence.

[0054] Preferably, the conductivity of the water in the washing process is less than 20 us / cm, for example, it can be 19 us / cm, 18 us / cm, 17 us / cm, 15 us / cm, 12 us / cm, 10 us / cm or 5 us / cm, but it is not limited to the listed values, and other unlisted values ​​within the numerical 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 in the present invention is 100-130°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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] The drying process described in the present invention is stopped when the free water content is less than 1.5%. The free water content may 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 values ​​not listed within the numerical range are also applicable.

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

[0059] The calcination temperature in step (5) of the present invention is 550-700°C, for example, 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 is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] The calcination time in step (5) of the present invention is 0.5 to 3 h, for example, 0.5 h, 0.7 h, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, 2.8 h or 3 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] As a preferred technical solution of the method of the present invention, the method comprises:

[0062] (1) mixing lithium extraction waste slag with phosphoric acid and / or phosphate, wherein the ratio of the sum of the molar amounts of Ti and Al in the lithium extraction waste slag to the molar amount of P in the phosphoric acid and / or phosphate is (1-3):1, and then sintering at 300-650° C. for 0.5-3 h to obtain phosphated lithium extraction waste slag; then acid leaching the obtained phosphated lithium extraction waste slag with an acid leaching agent at 30-90° C. for 0.5-3 h, while stirring the acid leaching, wherein the ratio of the molar amount of hydrogen ions in the acid leaching agent to the molar amount of Fe in the sintered product is (2-4):1, and then filtering to obtain an acid leaching solution;

[0063] (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1 to 1.5 with a pH adjusting agent, mixing the solution with a resin, and filtering the solution to obtain a first impurity-removed solution;

[0064] (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder, wherein the ratio of the molar amount of copper ions in the first impurity-removing liquid to the molar amount of iron element in the iron powder is 1:(2-5), and filtering to obtain a second impurity-removing liquid;

[0065] (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3) to 0.95-0.98 by adding iron powder, iron hydroxide or phosphoric acid, adding an oxidant for oxidation, and the oxidant reacts with Fe in the second impurity-removing liquid obtained in step (3) to form an oxidant. 2+ The molar ratio of is 1:(1-2), and the pH is adjusted to 3-5, and then filtered to obtain a crude iron phosphate;

[0066] (5) washing the crude iron phosphate obtained in step (4) with an acid washing solution having an acid concentration of 0.1 to 1 mol / L for 1 to 3 hours at 10 to 60° C., wherein the mass ratio of the acid washing solution to the crude iron phosphate is 1:(0.1 to 0.3), filtering the crude iron phosphate, washing the crude iron phosphate with water having an electrical conductivity of less than 20 us / cm, drying the crude iron phosphate at 100 to 130° C. until the free water content is less than 1.5%, and calcining the crude iron phosphate 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 iron phosphate, which is obtained by the method described in the first aspect.

[0068] In a third aspect, the present invention provides a lithium iron phosphate, which is prepared from the iron phosphate described in the second aspect.

[0069] In a fourth aspect, the present invention provides a lithium battery, wherein the lithium battery comprises the lithium iron phosphate described in the third aspect.

[0070] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists 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 the present invention adopts a multi-step impurity removal process to remove impurities such as Al, Ti, Cu, Ca, Mg and Na in ferric phosphate, thereby obtaining ferric phosphate with high purity, wherein the content of Al in the obtained ferric phosphate is not higher than 47ppm, the content of Ti is not higher than 45ppm, the content of Ca is not higher than 25.2ppm, the content of Mg is not higher than 5.5ppm, the content of Na is not higher than 9.8ppm, and the content of Li is not higher than 24ppm; in addition, the method provided by the present invention has low requirements on raw materials for lithium extraction waste slag, has a wide range of application, and is conducive to large-scale promotion and use. DETAILED DESCRIPTION

[0073] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0074] Example 1

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

[0076] (1) mixing lithium extraction waste slag with phosphoric acid, wherein the ratio of the sum of the molar amounts of Ti and Al in the lithium extraction waste slag to the molar amount of P in the phosphoric acid is 2:1, and then sintering at 500° C. for 1.5 hours to obtain phosphated lithium extraction waste slag; then acid leaching the obtained phosphated lithium extraction waste slag with sulfuric acid solution at 60° C. for 1.5 hours, accompanied by stirring during the acid leaching, wherein the ratio of the molar amount of hydrogen ions in the sulfuric acid solution to the molar amount of Fe in the sintered product is 3:1, and then filtering to obtain an acid leaching solution;

[0077] (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1.2 with aqueous ammonia, mixing the mixture with a chelating ion exchange resin, and filtering the mixture to obtain a first impurity-removed solution;

[0078] (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder, wherein the ratio of the molar amount of copper ions in the first impurity-removing liquid to the molar amount of iron in the iron powder is 1:3.5, and filtering to obtain a second impurity-removing liquid;

[0079] (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3) to 0.96, adding hydrogen peroxide for oxidation, and the hydrogen peroxide reacts with the Fe in the second impurity-removing liquid obtained in step (3) to form a phosphorus-iron-phosphorus mixture; 2+ The molar ratio is 1:1.5, and the pH is adjusted to 4, and then filtered to obtain a crude iron phosphate;

[0080] (5) The crude iron phosphate obtained in step (4) is washed with an oxalic acid solution having an acid concentration of 0.5 mol / L for 2 h at 35° C., wherein the mass ratio of the oxalic acid solution to the crude iron phosphate is 1:0.2, and then filtered and washed with water having a conductivity of 15 us / cm, and then dried at 115° C. to a free water content of 1.2%, and then calcined at 620° C. for 1.5 h to obtain iron phosphate powder.

[0081] Example 2

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

[0083] (1) mixing lithium extraction waste slag and ammonium phosphate, wherein the ratio of the sum of the molar amounts of Ti and Al in the lithium extraction waste slag to the molar amount of P in the ammonium phosphate is 1:1, and then sintering at 650° C. for 0.5 h to obtain phosphated lithium extraction waste slag; then acid leaching the obtained phosphated lithium extraction waste slag with hydrochloric acid solution at 30° C. for 3 h, accompanied by stirring during the acid leaching, wherein the ratio of the molar amount of hydrogen ions in the hydrochloric acid solution to the molar amount of Fe in the sintered product is 4:1, and then filtering to obtain an acid leaching solution;

[0084] (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1.5 with a sodium hydroxide solution, mixing the mixture with a chelating ion exchange resin, and filtering the mixture to obtain a first impurity-removed liquid;

[0085] (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder, wherein the ratio of the molar amount of copper ions in the first impurity-removing liquid to the molar amount of iron in the iron powder is 1:2, and filtering to obtain a second impurity-removing liquid;

[0086] (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3) to 0.98, adding hydrogen peroxide for oxidation, and the hydrogen peroxide reacts with the Fe in the second impurity-removing liquid obtained in step (3) to form a phosphorus-iron-phosphorus mixture; 2+ The molar ratio is 1:2, and the pH is adjusted to 5, and then filtered to obtain a crude iron phosphate;

[0087] (5) The crude iron phosphate obtained in step (4) is washed with a phosphoric acid solution having an acid concentration of 1 mol / L for 1 h at 10° C., wherein the mass ratio of the phosphoric acid solution to the crude iron phosphate is 1:0.3, and then filtered and washed with water having a conductivity of 18 us / cm, and then dried at 130° C. until the free water content is less than 0.8%, and then calcined at 700° C. for 0.5 h to obtain iron phosphate powder.

[0088] Example 3

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

[0090] (1) mixing lithium extraction waste slag with trisodium phosphate, wherein the ratio of the sum of the molar amounts of Ti and Al in the lithium extraction waste slag to the molar amount of P in the trisodium phosphate is 3:1, and then sintering at 300° C. for 3 h to obtain phosphated lithium extraction waste slag; then acid leaching the obtained phosphated lithium extraction waste slag with nitric acid solution at 90° C. for 0.5 h, accompanied by stirring during the acid leaching, wherein the ratio of the molar amount of hydrogen ions in the nitric acid solution to the molar amount of Fe in the sintered product is 2:1, and then filtering to obtain an acid leaching solution;

[0091] (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1 with aqueous ammonia, mixing the mixture with a chelating ion exchange resin, and filtering the mixture to obtain a first impurity-removed solution;

[0092] (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder, wherein the ratio of the molar amount of copper ions in the first impurity-removing liquid to the molar amount of iron in the iron powder is 1:5, and filtering to obtain a second impurity-removing liquid;

[0093] (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3) to 0.95, adding hydrogen peroxide for oxidation, and the hydrogen peroxide reacts with the Fe in the second impurity-removing liquid obtained in step (3) to form a phosphorus-iron-phosphorus mixture; 2+ The molar ratio is 1:1, and the pH is adjusted to 3, and then filtered to obtain a crude iron phosphate;

[0094] (5) The crude iron phosphate obtained in step (4) is washed with a phosphoric acid solution having an acid concentration of 0.1 mol / L at 60° C. for 3 h, wherein the mass ratio of the phosphoric acid solution to the crude iron phosphate is 1:0.1, and then filtered and washed with water having a conductivity of 10 us / cm, and then dried at 100° C. to a free water content of 1.4%, and then calcined at 550° C. for 3 h to obtain iron phosphate powder.

[0095] Example 4

[0096] The present embodiment provides a method for preparing iron phosphate from lithium extraction waste residue, which is the same as that of Example 1 except that the ratio of the sum of the molar amounts of Ti and Al in the lithium extraction waste residue during phosphorylation in step (1) to the molar amount of P in phosphoric acid is 4:1.

[0097] Example 5

[0098] This embodiment provides a method for preparing iron phosphate from lithium-extracted waste slag, which is the same as that of Embodiment 1 except that the sintering temperature in step (1) is 200°C.

[0099] Example 6

[0100] This embodiment provides a method for preparing iron phosphate from lithium-extracting waste slag, which is the same as that of Embodiment 1 except that the sintering temperature in step (1) is 800°C.

[0101] Example 7

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

[0103] Example 8

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

[0105] Comparative Example 1

[0106] This comparative example provides a method for preparing iron phosphate from lithium extraction waste slag, which is the same as Example 1 except that the mixing of lithium extraction waste slag and phosphoric acid in step (1) is omitted, the ratio of the sum of the molar amounts of Ti element and Al element in the lithium extraction waste slag to the molar amount of P element in phosphoric acid is 2:1, and then sintering is performed at 500° C. for 1.5 hours to obtain phosphated lithium extraction waste slag, that is, the lithium extraction waste slag is directly subjected to acid leaching.

[0107] Comparative Example 2

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

[0109] Comparative Example 3

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

[0111] Comparative Example 4

[0112] This comparative example provides a method for preparing iron phosphate from lithium-extracting waste residue, which is the same as Example 1 except that step (3) is omitted.

[0113] Comparative Example 5

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

[0115] The preparation method of the lithium extraction waste slag used in the present invention is: dismantling the waste lithium iron phosphate battery after discharge to obtain positive electrode powder, adding phosphoric acid solution and hydrogen peroxide, and after the iron phosphate is separated, performing solid-liquid separation by suction filtration, wherein the liquid is a lithium solution and the solid is lithium extraction waste slag. The main components of the lithium extraction waste slag used in the present invention are shown in Tables 1 and 2.

[0116] The method for preparing iron phosphate from lithium extraction waste slag provided in the above embodiments and comparative examples was used to prepare iron phosphate. The contents of Al, Ti, Cu, Ca, Mg and Na in the prepared iron phosphate were tested and 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 to 4, we can get:

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

[0128] (2) By comparing Example 1 with Example 4, it can be seen that the ratio of the sum of the molar amounts of Ti and Al in the lithium-extracting waste slag during the phosphorylation in step (1) of the present invention to the molar amount of P in phosphoric acid and / or phosphate will affect the content of impurities in the prepared iron phosphate and the purity of the iron phosphate; when the ratio of the sum of the molar amounts of Ti and Al to the molar amount of P is (1-3):1, the concentration of impurities such as Al, Ti, Cu, Ca, Mg and Na is low, and the purity of the iron phosphate is high. This is because when the ratio of the sum of the molar amounts of Ti and Al to the molar amount of P is (1-3):1, the phosphorylation of Ti and Al can be fully achieved 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 affects the content of impurities in the prepared ferric phosphate and the purity of the ferric phosphate; when the sintering temperature is 300-650°C, the concentration of impurities such as Al, Ti, Cu, Ca, Mg and Na is low, and the purity of the ferric phosphate is high. This is because when the sintering temperature is 300-650°C, it can ensure that the reaction in step (1) is more thorough and avoid the production of pyrophosphate;

[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 affects the content of impurities in the prepared iron phosphate and the purity of the iron 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 the iron phosphate is high. This is because when the acid concentration is 0.1 to 1 mol / L, it can not only achieve the removal of impurities such as Al, Na, Ti adsorbed in the re-reaction process in the crude iron phosphate, but also avoid the impurities dissolving into the iron phosphate due to excessive 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 adopts a multi-step impurity removal process to achieve the removal of impurities such as Al, Ti, Cu, Ca, Mg and Na in iron phosphate, and obtains iron phosphate with high purity; According to the data in Examples 1 to 3, it can be seen that the content of Al in the iron phosphate obtained by the method for preparing iron phosphate from lithium extraction waste slag provided in Examples 1 to 3 is not higher than 47ppm, the content of Ti is not higher than 45ppm, the content of Ca is not higher than 25.2ppm, the content of Mg is not higher than 5.5ppm, the content of Na is not higher than 9.8ppm, and the content of Li is not higher than 24ppm; In addition, the method provided by the present invention has low requirements for the raw materials of lithium extraction waste slag, has a wide range of application, and is conducive to large-scale promotion and use.

[0132] The above description is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing iron phosphate from lithium waste residue, characterized in that: The method comprises: (1) phosphorylating the lithium extraction waste residue and then acid leaching it to obtain an acid leaching solution; (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1 to 1.5 and then mixing it with a resin to obtain a first impurity-removing solution; (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder to obtain a second impurity-removing liquid; (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3), performing oxidation and adjusting the pH to 3 to 5, to obtain a crude iron phosphate; (5) washing the crude iron phosphate obtained in step (4) with an acid wash solution and then calcining to obtain iron phosphate powder.

2. The method according to claim 1, characterized in that: The phosphorylation method in step (1) includes: mixing the lithium extraction waste residue with phosphoric acid and / or phosphate and then sintering to obtain phosphorylated lithium extraction waste residue; Preferably, the ratio of the sum of the molar amounts of Ti and Al in the lithium-extracting waste slag during the phosphorylation in step (1) to the molar amount of P in phosphoric acid and / or phosphate is (1-3):1; Preferably, the sintering temperature is 300-650°C and the sintering time is 0.5-3h; Preferably, during the acid leaching 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 sintered product is (2-4):1; Preferably, the acid leaching in step (1) is carried out at a temperature of 30 to 90° C. and for a time of 0.5 to 3 h.

3. The method according to claim 1 or 2, characterized in that: The pH adjusting agent used in step (2) includes any one of ammonia water, liquid ammonia, sodium hydroxide solution or solid sodium hydroxide, or a combination of at least two thereof; Preferably, the resin in step (2) comprises a chelated ion exchange resin.

4. The method according to any one of claims 1 to 3, characterized in that: During the mixing in step (3), the ratio of the molar amount of copper ions in the first impurity removal liquid obtained in step (2) to the molar amount of iron elements in the iron powder is 1:(2-5).

5. The method according to any one of claims 1 to 4, characterized in that: In step (4), the iron-phosphorus ratio of the second impurity removal solution obtained in step (3) is adjusted to 0.95 to 0.98; 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).

6. The method according to any one of claims 1 to 5, characterized in that: The pickling solution in step (5) comprises oxalic acid solution and / or phosphoric acid solution, and the acid concentration of the pickling solution is 0.1 to 1 mol / L; Preferably, the mass ratio of the pickling solution to the crude iron phosphate in step (5) is 1:(0.1-0.3); Preferably, the washing temperature in step (5) is 10 to 60° C. and the washing time is 1 to 3 hours; Preferably, the calcination temperature in step (5) is 550-700° C. and the calcination time is 0.5-3 h.

7. The method according to any one of claims 1 to 6, characterized in that: The method comprises: (1) mixing lithium extraction waste slag with phosphoric acid and / or phosphate, wherein the ratio of the sum of the molar amounts of Ti and Al in the lithium extraction waste slag to the molar amount of P in the phosphoric acid and / or phosphate is (1-3):1, and then sintering at 300-650° C. for 0.5-3 h to obtain phosphated lithium extraction waste slag; then acid leaching the obtained phosphated lithium extraction waste slag with an acid leaching agent at 30-90° C. for 0.5-3 h, while stirring the acid leaching, wherein the ratio of the molar amount of hydrogen ions in the acid leaching agent to the molar amount of Fe in the sintered product is (2-4):1, and then filtering to obtain an acid leaching solution; (2) adjusting the pH of the acid leaching solution obtained in step (1) to 1 to 1.5 with a pH adjusting agent, mixing the solution with a resin, and filtering the solution to obtain a first impurity-removed solution; (3) mixing the first impurity-removing liquid obtained in step (2) with iron powder, wherein the ratio of the molar amount of copper ions in the first impurity-removing liquid to the molar amount of iron element in the iron powder is 1:(2-5), and filtering to obtain a second impurity-removing liquid; (4) adjusting the iron-phosphorus ratio of the second impurity-removing liquid obtained in step (3) to 0.95-0.98 by adding iron powder, iron hydroxide or phosphoric acid, adding an oxidant for oxidation, and the oxidant reacts with Fe in the second impurity-removing liquid obtained in step (3) to form an oxidant. 2+ The molar ratio of is 1:(1-2), and the pH is adjusted to 3-5, and then filtered to obtain a crude iron phosphate; (5) washing the crude iron phosphate obtained in step (4) with an acid washing solution having an acid concentration of 0.1 to 1 mol / L for 1 to 3 hours at 10 to 60° C., wherein the mass ratio of the acid washing solution to the crude iron phosphate is 1:(0.1 to 0.3), filtering the crude iron phosphate, washing the crude iron phosphate with water having an electrical conductivity of less than 20 us / cm, drying the crude iron phosphate at 100 to 130° C. until the free water content is less than 1.5%, and calcining the crude iron phosphate at 550 to 700° C. for 0.5 to 3 hours to obtain iron phosphate powder.

8. A kind of iron phosphate, characterized in that: The iron phosphate is obtained by the method according to any one of claims 1 to 7.

9. A lithium iron phosphate, characterized in that: The lithium iron phosphate is prepared from the iron phosphate described in claim 8.

10. A lithium battery, characterized in that: The lithium battery comprises the lithium iron phosphate as claimed in claim 9.

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