Recovery method of iron phosphate waste residue, iron phosphate, carbon powder and lithium iron phosphate

Abstract

The invention provides an iron phosphate waste residue recovery method, iron phosphate, carbon powder and lithium iron phosphate, and the recovery method comprises the following steps: carrying out acid leaching on the iron phosphate waste residue by using an acid solution to obtain a filter residue and an acid leaching solution, carrying out impurity removal on the obtained acid leaching solution, mixing the obtained acid leaching solution with a dispersant, carrying out evaporation crystallization, and sintering a solid obtained by evaporation crystallization to obtain the lithium iron phosphate waste residue. The recycled iron phosphate is obtained. According to the recovery method provided by the invention, the iron phosphate in the iron phosphate waste residues is recovered, the recovery rate of the iron phosphate is relatively high, and the recovered iron phosphate has relatively high purity. In addition, in the recovery method, the recovery of the carbon powder, the cyclic utilization of the acid liquor and the reutilization of water resources, heat and the dispersing agent can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of iron phosphate waste slag recovery, and relates to a method for recovering iron phosphate waste slag, and in particular to a method for recovering iron phosphate waste slag, iron phosphate, carbon powder and lithium iron phosphate. Background Art

[0002] Against the backdrop of global energy conservation, emission reduction and new energy development, there is a huge demand for lithium battery preparation and recycling; lithium iron phosphate has the advantages of high thermal stability, long cycle life and low cost, and is widely used in power batteries.

[0003] However, the service life of lithium iron phosphate is relatively short, so the recovery of lithium iron phosphate is crucial for the recycling of resources. In the prior art, the lithium iron phosphate black powder in the scrapped lithium iron phosphate battery is mainly used to recover lithium, and a large amount of iron phosphate waste residue is generated after lithium recovery. The iron phosphate waste residue is mainly treated as solid waste or phosphate rock, resulting in a waste of resources.

[0004] CN117963863A discloses a method for resource utilization of ferrophosphorus slag of lithium iron phosphate battery. The copper in the lithium extraction slag is first washed away by oxidation pickling by washing only, and only a small amount of copper is left in the lithium extraction slag leachate, which does not affect the product quality. The crude ferrophosphate obtained is then pickled, and the aluminum is washed and removed, and the washing liquid can be returned to the leaching section for reuse. The process is simple, the cost is low, and the recovery of battery-grade ferrophosphate is achieved. However, the method for resource utilization of ferrophosphorus slag of lithium iron phosphate battery has a low recovery rate of ferrophosphate, and the purity of the obtained ferrophosphate is low.

[0005] CN116692820A discloses a method for preparing graphite powder and ferrous manganese phosphate using ferrous phosphate waste residue, the method comprising the following steps: washing and separating the ferrous phosphate waste residue to obtain ferrous phosphate residue, reacting with dilute nitric acid to obtain a filter residue containing ferrous phosphate and carbon, mixing the filter residue with reduced manganese sand and inorganic acid, performing a preliminary reduction reaction, adding reduced iron powder for further reduction and adjusting the pH to obtain a carbon residue and a filtrate containing ferrous manganese and phosphorus by solid-liquid separation; washing and drying the carbon residue to obtain a crude graphite powder; reacting the filtrate containing ferrous manganese and phosphorus with a sodium sulfide solution to remove heavy metal residues, adding a divalent iron source or pure water to the filtrate, adding an antioxidant, adjusting the iron concentration in the mixed solution, adjusting the molar ratio of Fe to Mn and P and the pH of the solution, and using a coprecipitation method to react to obtain a ferrous manganese phosphate product. However, the recovery rate of the ferrous manganese phosphate product is low in this method.

[0006] The methods for recovering ferric phosphate waste residue disclosed in the prior art all have certain defects, such as low recovery rate of ferric phosphate and low purity of the obtained ferric phosphate. Therefore, it is very important to develop and design a new method for recovering ferric phosphate waste residue. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for recovering iron phosphate waste residue, iron phosphate, carbon powder and lithium iron phosphate. The recovery method provided by the present invention realizes the recovery of iron phosphate in iron phosphate waste residue, has a high recovery rate for iron phosphate, and the recovered iron phosphate has a high purity.

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

[0009] In a first aspect, the present invention provides a method for recovering ferric phosphate waste residue, the recovery method comprising:

[0010] Acid leaching is performed on the iron phosphate waste residue with acid solution to obtain filter residue and acid leaching solution. The obtained acid leaching solution is mixed with a dispersant after impurities are removed, and then evaporated and crystallized. The solid obtained by the evaporation and crystallization is sintered to obtain recovered iron phosphate.

[0011] The recovery method provided by the present invention realizes the recovery of iron phosphate in iron phosphate waste residue, has a high recovery rate for iron phosphate, and the recovered iron phosphate has a high purity.

[0012] Preferably, during the acid leaching process, the solid-liquid ratio of the ferric phosphate waste slag to the acid solution is 1:(1-6), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The unit of the solid-liquid ratio is g / mL.

[0013] Preferably, during the acid leaching process, the mass ratio of the iron phosphate waste slag to H3PO3 in the acid solution is 1:(1-5), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] Preferably, the acid leaching time is 2 to 6 hours, for example, it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The acid solution used in the acid leaching includes a phosphoric acid solution.

[0015] Preferably, the acid leaching process is accompanied by heating and stirring.

[0016] Preferably, the heating temperature is 40-95° C., and the stirring speed is 60-300 rpm.

[0017] The heating temperature in the present invention is 40-95°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or 95°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] The stirring speed in the present invention is 60 to 300 rpm, for example, it can be 60 rpm, 80 rpm, 100 rpm, 120 rpm, 150 rpm, 180 rpm, 200 rpm, 220 rpm, 250 rpm, 280 rpm or 300 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the recovery method further comprises: re-acid leaching the filter residue obtained after the acid leaching to obtain recovered carbon powder and recovered filtrate, and the recovered filtrate is reused in the acid leaching.

[0020] In the recovery method of the present invention, the filter residue obtained after acid leaching is subjected to re-acid leaching to achieve purification of carbon powder, thereby achieving recovery of carbon powder; in addition, the recovered filtrate obtained after re-acid leaching is reused in the acid leaching to achieve the recycling of acid solution in the recovery process.

[0021] Preferably, the acid solution for the re-pickling comprises phosphoric acid.

[0022] Preferably, after the re-acid leaching, the re-acid leaching residue is washed to obtain recovered carbon powder.

[0023] Preferably, the detergent used in the washing comprises water at a temperature of 40 to 65° C., and the washing is stopped when the pH of the generated washing water reaches 5 to 6.5.

[0024] The detergent used in the washing described in the present invention includes water with a temperature of 40 to 65°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C or 65°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] The washing process of the present invention is stopped when the pH of the washing water produced reaches 5 to 6.5, for example, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4 or 6.5, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0026] Preferably, the impurity removal comprises: adding an impurity remover to the obtained acid leaching solution, dissolving the impurities, and performing solid-liquid separation to obtain an impurity solid and an impurity-removed acid leaching solution.

[0027] Preferably, the impurity remover comprises iron powder and sodium fluoride, the molar ratio of the iron powder in the impurity remover to the copper ions in the acid leaching solution is (2-5):1, and the molar ratio of the sodium fluoride to the aluminum ions in the acid leaching solution is (6-8):1.

[0028] The molar ratio of the iron powder in the impurity remover of the present invention to the copper ions in the acid leaching solution is (2-5):1, for example, it can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] The molar ratio of sodium fluoride in the impurity remover of the present invention to aluminum ions in the acid leaching solution is (6-8):1, for example, it can be 6:1, 6.2:1, 6.4:1, 6.6:1, 6.8:1, 7:1, 7.2:1, 7.4:1, 7.6:1, 7.8:1 or 8:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the mass ratio of the acid extract after impurity removal to the dispersant in the mixing is 1000:(1-5), for example, it can be 1000:1, 1000:1.5, 1000:2, 1000:2.5, 1000:3, 1000:3.5, 1000:4, 1000:4.5 or 1000:5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the dispersant comprises any one of polyethylene glycol, triethylhexyl phosphoric acid or polyacrylic amine or a combination of at least two thereof, and typical but non-limiting combinations include a combination of polyethylene glycol and triethylhexyl phosphoric acid, a combination of triethylhexyl phosphoric acid and polyacrylic amine, or a combination of polyethylene glycol, triethylhexyl phosphoric acid and polyacrylic amine.

[0032] Preferably, the polyethylene glycol includes any one of PEG-200, PEG-400 or PEG-600 or a combination of at least two of them. Typical but non-limiting combinations include a combination of PEG-200 and PEG-400, a combination of PEG-400 and PEG-600, or a combination of PEG-200, PEG-400 and PEG-600.

[0033] Preferably, the evaporation and crystallization adopts mechanical compression steam recycling technology and / or triple-effect evaporation technology.

[0034] Preferably, the ratio of evaporated water to stock solution in the evaporation and crystallization is (65-85):100, and the temperature is 80-100°C.

[0035] The ratio of evaporated water to stock solution in the evaporation crystallization of the present invention is (65-85):100, for example, it can be 65:100, 68:100, 70:100, 72:100, 75:100, 78:100, 80:100, 82:100 or 85:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] The temperature in the evaporation crystallization of the present invention is 80-100°C, for example, it can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the evaporated water produced in the evaporation and crystallization is used to wash the obtained re-acid leaching residue.

[0038] Preferably, the residual liquid obtained after the evaporation and crystallization is reused in the re-acid leaching.

[0039] In the present invention, the evaporated water generated in the evaporation and crystallization process is used to wash the obtained re-acid leaching residue, and the residual liquid obtained after the evaporation and crystallization is reused in the re-acid leaching, thereby realizing the reuse of water resources, heat and dispersant in the process of iron phosphate recovery.

[0040] Preferably, the evaporation crystallization and sintering further include centrifugation, washing and drying in sequence.

[0041] Preferably, the pH of the solid obtained after washing until evaporation and crystallization is higher than 5, for example, it can be 5.1, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6 or 6.8, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the drying method includes disk drying and / or flash evaporation, and the moisture content measured at 120° C. is controlled to be within 1%, for example, it can be 0.99%, 0.95%, 0.9%, 0.85%, 0.8%, 0.75%, 0.7%, 0.65% or 0.6%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the sintering temperature is 450-650° C., the time is 1-3 hours, and the sintering is performed in a protective atmosphere.

[0044] The sintering temperature in the present invention is 450-650°C, for example, it can be 450°C, 480°C, 500°C, 520°C, 550°C, 580°C, 600°C, 620°C or 650°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

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

[0046] (1) using a phosphoric acid solution to acid-leach the iron phosphate waste residue for 2 to 6 hours to obtain a filter residue and an acid-leach solution;

[0047] The acid leaching process is accompanied by heating at a temperature of 40 to 95° C. and stirring at a speed of 60 to 300 rpm; the solid-liquid ratio of the iron phosphate waste residue to the acid solution during the acid leaching process is 1:(1 to 6), and the unit of the solid-liquid ratio is g / mL; the mass ratio of the iron phosphate waste residue to H3PO3 in the acid solution during the acid leaching process is 1:(1 to 5);

[0048] (2) re-acid leaching the filter residue obtained in step (1) with phosphoric acid, reusing the obtained recovered filtrate in the acid leaching of step (1), washing the obtained re-acid leaching filter residue with water at a temperature of 40 to 65° C. until the pH of the generated washing water reaches 5 to 6.5, thereby obtaining recovered carbon powder;

[0049] (3) adding iron powder and sodium fluoride to the acid leaching solution obtained in step (1), wherein the molar ratio of iron powder to copper ions in the acid leaching solution is (2-5):1, and the molar ratio of sodium fluoride to aluminum ions in the acid leaching solution is (6-8):1, dissolving and separating the solid and the liquid to obtain an impurity solid and an impurity-free acid leaching solution;

[0050] (4) mixing the acid leaching liquid after impurity removal in step (3) with a dispersant in a mass ratio of 1000:(1-5), and then evaporating and crystallizing by using mechanical compression steam recycling technology and / or triple-effect evaporation technology, wherein the ratio of evaporated water to original liquid in the evaporation and crystallization is (65-85):100, and the temperature is 80-100° C., and the evaporated water generated in the evaporation and crystallization is used to wash the re-acid leaching residue obtained in step (2), and centrifuging after evaporation and crystallization to obtain solid and residual liquid after evaporation and crystallization;

[0051] (6) washing the solid obtained after evaporation and crystallization in step (5) until the pH value is higher than 5, then drying by disk drying and / or flash evaporation, controlling the moisture content of the dried solid to be less than 1% at 120° C., and then sintering at 450 to 650° C. for 1 to 3 hours in a protective atmosphere to obtain recovered iron phosphate; and reusing the residual liquid obtained in step (5) in the re-acid leaching described in step (2).

[0052] In a second aspect, the present invention provides an iron phosphate, which is obtained by the recovery method described in the first aspect, and has a purity of not less than 99.5%.

[0053] The purity of the ferric phosphate described in the present invention is mass fraction.

[0054] In a third aspect, the present invention provides a carbon powder obtained by the recycling method described in the first aspect.

[0055] In a fourth aspect, the present invention provides a lithium iron phosphate, which is prepared from the iron phosphate described in the second aspect.

[0056] 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.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The recovery method provided by the present invention realizes the recovery of iron phosphate from iron phosphate waste residue, has a high recovery rate for iron phosphate, and the recovered iron phosphate has a high purity;

[0059] (2) In the recovery method provided by the present invention, the filter residue obtained after acid leaching is subjected to re-acid leaching to achieve purification of carbon powder, thereby achieving recovery of carbon powder; in addition, the recovered filtrate obtained after re-acid leaching is reused in the acid leaching, thereby achieving recycling of acid solution in the recovery process;

[0060] (3) In the present invention, the evaporated water generated in the evaporation and crystallization process is used to wash the obtained re-acid leaching residue, and the residual liquid obtained after the evaporation and crystallization is reused in the re-acid leaching, thereby achieving the reuse of water resources, heat and dispersant in the iron phosphate recovery process. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a flow chart of the method for recovering ferric phosphate waste provided in Examples 1 to 9. DETAILED DESCRIPTION

[0062] 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.

[0063] Example 1

[0064] This embodiment provides a method for recovering iron phosphate waste residue, such as Figure 1 As shown, the recycling method comprises:

[0065] (1) using a phosphoric acid solution to acid-leach the iron phosphate waste residue for 4 hours to obtain a filter residue and an acid leaching solution;

[0066] The acid leaching process is accompanied by heating at a temperature of 70° C. and stirring at a speed of 180 rpm; the solid-liquid ratio of the iron phosphate waste residue to the acid solution during the acid leaching process is 1:3, and the unit of the solid-liquid ratio is g / mL; the mass ratio of the iron phosphate waste residue to H3PO3 in the acid solution during the acid leaching process is 1:3;

[0067] (2) re-acid leaching the filter residue obtained in step (1) with phosphoric acid, reusing the obtained recovered filtrate in the acid leaching of step (1), washing the obtained re-acid leaching filter residue with water at a temperature of 50° C. until the pH of the generated washing water reaches 5.8, thereby obtaining recovered carbon powder;

[0068] (3) adding iron powder and sodium fluoride to the acid leaching solution obtained in step (1), wherein the molar ratio of iron powder to copper ions in the acid leaching solution is 3.5:1, and the molar ratio of sodium fluoride to aluminum ions in the acid leaching solution is 7:1, and dissolving and separating the solid and the liquid to obtain an impurity solid and an impurity-free acid leaching solution;

[0069] (4) mixing the impurity-removed acid leaching solution of step (3) with polyethylene glycol in a mass ratio of 1000:3 (since the residual liquid after evaporation and crystallization is reused in re-acid leaching, the loss of polyethylene glycol in the recovery process is small. After polyethylene glycol is added in the first recovery process, the acid leaching solution in the subsequent recovery process contains polyethylene glycol. Therefore, polyethylene glycol is supplemented in the subsequent recovery process according to the content of polyethylene glycol in the acid leaching solution, and the amount of each supplement is 1 / 10,000 to 5 / 10,000 of the mass of the acid leaching solution), and then evaporating and crystallizing by mechanical compression steam recycling technology. The ratio of evaporated water to stock solution in the evaporation and crystallization is 75:100, and the temperature is 90° C. The evaporated water generated in the evaporation and crystallization is used to wash the re-acid leaching residue obtained in step (2). After evaporation and crystallization, centrifugation is performed to obtain solid and residual liquid after evaporation and crystallization;

[0070] (6) washing the solid obtained after evaporation and crystallization in step (5) until the pH value is higher than 5, and then drying by flash evaporation, controlling the moisture content of the dried solid to be less than 1% at 120° C., and then sintering at 550° C. for 2 h in a protective atmosphere to obtain recovered iron phosphate; and reusing the residual liquid obtained in step (5) in the re-acid leaching described in step (2).

[0071] Example 2

[0072] This embodiment provides a method for recovering iron phosphate waste residue, the recovery method comprising:

[0073] (1) using a phosphoric acid solution to acid-leach the iron phosphate waste residue for 2 hours to obtain a filter residue and an acid leaching solution;

[0074] The acid leaching process is accompanied by heating at a temperature of 95° C. and stirring at a speed of 60 rpm; the solid-liquid ratio of the iron phosphate waste residue to the acid solution during the acid leaching process is 1:6, and the unit of the solid-liquid ratio is g / mL; the mass ratio of the iron phosphate waste residue to H3PO3 in the acid solution during the acid leaching process is 1:5;

[0075] (2) re-acid leaching the filter residue obtained in step (1) with phosphoric acid, reusing the obtained recovered filtrate in the acid leaching of step (1), washing the obtained re-acid leaching filter residue with water at a temperature of 65° C. until the pH of the generated washing water reaches 6.5, thereby obtaining recovered carbon powder;

[0076] (3) adding iron powder and sodium fluoride to the acid leaching solution obtained in step (1), wherein the molar ratio of iron powder to copper ions in the acid leaching solution is 5:1, and the molar ratio of sodium fluoride to aluminum ions in the acid leaching solution is 8:1, and dissolving and separating the solid and the liquid to obtain an impurity solid and an impurity-free acid leaching solution;

[0077] (4) mixing the impurity-removed acid leaching liquid of step (3) with triethylhexyl phosphoric acid in a mass ratio of 1000:5 (since the residual liquid after evaporation and crystallization is reused in re-acid leaching, the loss of triethylhexyl phosphoric acid in the recovery process is small. After adding triethylhexyl phosphoric acid in the first recovery process, the acid leaching liquid in the subsequent recovery process contains triethylhexyl phosphoric acid. Therefore, in the subsequent recovery process, triethylhexyl phosphoric acid is supplemented according to the content of triethylhexyl phosphoric acid in the acid leaching liquid, and the supplement amount each time is 1 / 10,000 to 5 / 10,000 of the mass of the acid leaching liquid), and then using triple-effect evaporation technology for evaporation and crystallization. The ratio of evaporated water to stock solution in the evaporation and crystallization is 65:100, and the temperature is 80° C. The evaporated water generated in the evaporation and crystallization is used to wash the re-acid leaching residue obtained in step (2). After evaporation and crystallization, centrifugation is performed to obtain solid and residual liquid after evaporation and crystallization;

[0078] (6) washing the solid obtained after evaporation and crystallization in step (5) until the pH value is higher than 5, drying it by disk drying, controlling the moisture content of the dried solid to be less than 1% at 120° C., and sintering it at 650° C. for 1 hour in a protective atmosphere to obtain recovered iron phosphate; and reusing the residual liquid obtained in step (5) in the re-acid leaching described in step (2).

[0079] Example 3

[0080] This embodiment provides a method for recovering iron phosphate waste residue, the recovery method comprising:

[0081] (1) using a phosphoric acid solution to acid-leach the iron phosphate waste residue for 6 hours to obtain a filter residue and an acid leaching solution;

[0082] The acid leaching process is accompanied by heating at a temperature of 45°C and stirring at a speed of 300 rpm; the solid-liquid ratio of the iron phosphate waste residue to the acid solution during the acid leaching process is 1:1, and the unit of the solid-liquid ratio is g / mL; the mass ratio of the iron phosphate waste residue to H3PO3 in the acid solution during the acid leaching process is 1:2;

[0083] (2) re-acid leaching the filter residue obtained in step (1) with phosphoric acid, reusing the obtained recovered filtrate in the acid leaching of step (1), washing the obtained re-acid leaching filter residue with water at a temperature of 40° C. until the pH of the generated washing water reaches 5, thereby obtaining recovered carbon powder;

[0084] (3) adding iron powder and sodium fluoride to the acid leaching solution obtained in step (1), wherein the molar ratio of iron powder to copper ions in the acid leaching solution is 2:1, and the molar ratio of sodium fluoride to aluminum ions in the acid leaching solution is 6:1, and dissolving and separating the solid and the liquid to obtain an impurity solid and an impurity-free acid leaching solution;

[0085] (4) mixing the impurity-removed acid leaching solution of step (3) with polyethylene glycol in a mass ratio of 1000:1 (since the residual liquid after evaporation and crystallization is reused in re-acid leaching, the loss of polyethylene glycol in the recovery process is small. After polyethylene glycol is added in the first recovery process, the acid leaching solution in the subsequent recovery process contains polyethylene glycol. Therefore, polyethylene glycol is supplemented in the subsequent recovery process according to the content of polyethylene glycol in the acid leaching solution, and the amount of each supplement is 1 / 10,000 to 5 / 10,000 of the mass of the acid leaching solution), and then evaporating and crystallizing by mechanical compression steam recycling technology. The ratio of evaporated water to stock solution in the evaporation and crystallization is 85:100, and the temperature is 100° C. The evaporated water generated in the evaporation and crystallization is used to wash the re-acid leaching residue obtained in step (2). After evaporation and crystallization, centrifugation is performed to obtain solid and residual liquid after evaporation and crystallization;

[0086] (6) The solid obtained after evaporation and crystallization in step (5) is washed until the pH value is higher than 5, and then dried by disk drying, the moisture content of the dried solid is controlled to be less than 1% at 120° C., and then sintered at 450° C. for 3 h in a protective atmosphere to obtain recovered iron phosphate; the residual liquid obtained in step (5) is reused in the re-acid leaching described in step (2).

[0087] Example 4

[0088] This embodiment provides a method for recovering ferric phosphate waste residue, which is the same as that of Embodiment 1 except that the mass ratio of ferric phosphate waste residue to H3PO3 in the acid solution during the acid leaching process in step (1) is 1:0.5.

[0089] Example 5

[0090] This embodiment provides a method for recovering iron phosphate waste residue, which is the same as that of Embodiment 1 except that the ratio of evaporated water to stock solution in the evaporation and crystallization in step (4) is 55:100.

[0091] Example 6

[0092] This embodiment provides a method for recovering iron phosphate waste residue, which is the same as that of Embodiment 1 except that the ratio of evaporated water to stock solution in the evaporation and crystallization in step (4) is 95:100.

[0093] Comparative Example 1

[0094] This comparative example provides a method for recovering iron phosphate waste residue, which is the same as Example 1 except that step (3) is omitted.

[0095] Comparative Example 2

[0096] This comparative example provides a method for recovering iron phosphate waste residue, which is the same as Example 1 except that the step (4) of mixing the impurity-removed acid leaching solution with polyethylene glycol is omitted.

[0097] The preparation method of the iron phosphate 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 the lithium solution and the solid is the iron phosphate waste slag.

[0098] The ferrous phosphate waste slag was subjected to ferrous phosphate recovery by the ferrous phosphate waste slag recovery method provided in the above embodiments and comparative examples. The main components of the ferrous phosphate waste slag used in the above embodiments and comparative examples are shown in Tables 1 and 2. The recovery rate of ferrous phosphate obtained by testing is shown in Table 3. The calculation method of the recovery rate is: 1-(n1+n2) / n, wherein n1 is the molar amount of undissolved ferrous phosphate in the recovered carbon powder obtained in step (2), n2 is the molar amount of ferrous phosphate adsorbed in the impurity solid obtained in step (3), and n is the total molar amount of ferrous phosphate in the added ferrous phosphate waste slag; the purity of the ferrous phosphate obtained by testing is shown in Table 3;

[0099] In addition, the contents of Fe, P, Ca, Mg, Al, Ti, Li, Na, Cu and C in the recovered ferric phosphate were tested, and the test results are shown in Tables 4 and 5.

[0100] In addition, the tap density, moisture content and D50 particle size of the recovered iron phosphate were tested. The test results are shown in Table 6.

[0101] Table 1

[0102]

[0103] Table 2

[0104]

[0105] Table 3

[0106]

[0107]

[0108] Table 4

[0109]

[0110] Table 5

[0111]

[0112]

[0113] Table 6

[0114]

[0115] From Tables 1 to 6, we can get:

[0116] (1) The recovery of iron phosphate by the method for recovering iron phosphate waste provided in Examples 1 to 3 can achieve a high recovery rate of iron phosphate, and the purity of the obtained iron phosphate is high; in addition, the content of impurity elements in the recovered iron phosphate is low, and the phosphorus-iron ratio, tap density, moisture content and D50 particle size meet the preparation requirements of lithium iron phosphate;

[0117] (2) By comparing Example 1 with Example 4, it can be seen that the mass ratio of the iron phosphate waste residue to the H3PO3 in the acid solution during the acid leaching process of the present invention will affect the recovery effect of iron phosphate; when the mass ratio of the iron phosphate waste residue to the H3PO3 in the acid solution is 1: (1-5), it is beneficial to the recovery of iron phosphate in the iron phosphate waste residue. This is because when the mass ratio of the iron phosphate waste residue to the H3PO3 in the acid solution is 1: (1-5), it can ensure that the iron phosphate waste residue has a higher solubility, thereby obtaining a higher recovery rate, and can avoid the excessive use of the acid solution, thereby increasing the production cost and causing pollution to the environment;

[0118] (3) By comparing Example 1 with Examples 5 and 6, it can be seen that the ratio of evaporated water to stock solution in the evaporation and crystallization of the present invention will affect the recovery effect of iron phosphate; when the ratio of evaporated water to stock solution in the evaporation and crystallization is (65-85):100, it is beneficial to the recovery of iron phosphate in iron phosphate waste residue. This is because when the ratio of evaporated water to stock solution is (65-85):100, it can ensure that the iron phosphate in the evaporation and crystallization can be fully precipitated, so that the recovery method has a higher iron phosphate recovery rate, and can avoid the increase of the precipitation amount of impurities in the evaporation and crystallization process, so that the iron phosphate recovered by the recovery method has a higher purity;

[0119] (4) By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the recovery method provided by the present invention realizes the recovery of iron phosphate in iron phosphate waste residue, has a high recovery rate for iron phosphate, and the recovered iron phosphate has a high purity; in the recovery method provided by the present invention, the filter residue obtained after acid leaching is subjected to re-acid leaching to achieve the purification of carbon powder, thereby achieving the recovery of carbon powder; in addition, the recovered filtrate obtained after re-acid leaching is reused in the acid leaching, thereby achieving the recycling of the acid solution in the recovery process; in the present invention, the evaporated water generated in the evaporation and crystallization process is used to wash the obtained re-acid leaching filter residue, and the residual liquid obtained after evaporation and crystallization is reused in the re-acid leaching, thereby achieving the reuse of water resources, heat and dispersant in the process of iron phosphate recovery.

[0120] 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 recovering ferric phosphate waste residue, characterized in that: The recovery method comprises: Acid leaching is performed on the iron phosphate waste residue with acid solution to obtain filter residue and acid leaching solution. The obtained acid leaching solution is mixed with a dispersant after impurities are removed, and then evaporated and crystallized. The solid obtained by the evaporation and crystallization is sintered to obtain recovered iron phosphate.

2. The recycling method according to claim 1, characterized in that: During the acid leaching process, the solid-liquid ratio of the iron phosphate waste residue to the acid solution is 1:(1-6), and the unit of the solid-liquid ratio is g / mL; Preferably, during the acid leaching process, the mass ratio of the iron phosphate waste residue to the H3PO3 in the acid solution is 1:(1-5); Preferably, the acid leaching time is 2 to 6 hours, and the acid solution used in the acid leaching includes a phosphoric acid solution.

3. The recycling method according to claim 1 or 2, characterized in that: The recovery method further comprises: re-acid leaching the filter residue obtained after the acid leaching to obtain recovered carbon powder and recovered filtrate, and the recovered filtrate is reused in the acid leaching; Preferably, the acid solution for the re-acid leaching comprises phosphoric acid; Preferably, after the re-acid leaching, the process further comprises washing the obtained re-acid leaching residue to obtain recovered carbon powder; Preferably, the detergent used in the washing comprises water at a temperature of 40 to 65° C., and the washing is stopped when the pH of the generated washing water reaches 5 to 6.

5.

4. The recycling method according to any one of claims 1 to 3, characterized in that: The impurity removal comprises: adding an impurity remover to the obtained acid leaching solution, dissolving the impurity remover, and separating the solid and the liquid to obtain an impurity solid and an impurity-removed acid leaching solution; Preferably, the impurity remover comprises iron powder and sodium fluoride, the molar ratio of the iron powder in the impurity remover to the copper ions in the acid leaching solution is (2-5):1, and the molar ratio of the sodium fluoride to the aluminum ions in the acid leaching solution is (6-8):1; Preferably, the mass ratio of the acid leaching liquid after impurities removal to the dispersant in the mixing is 1000:(1-5).

5. The recycling method according to claim 3, characterized in that: The evaporation and crystallization adopts mechanical compression steam recycling technology and / or triple-effect evaporation technology; Preferably, the ratio of evaporated water to stock solution in the evaporation crystallization is (65-85):100, and the temperature is 80-100°C; Preferably, the evaporated water produced in the evaporation and crystallization is used to wash the obtained re-acid leaching residue; Preferably, the residual liquid obtained after the evaporation and crystallization is reused in the re-acid leaching.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The sintering temperature is 450-650° C., the time is 1-3 hours, and the sintering is carried out in a protective atmosphere.

7. The recycling method according to any one of claims 1 to 6, characterized in that: The recovery method comprises: (1) using a phosphoric acid solution to acid-leach the iron phosphate waste residue for 2 to 6 hours to obtain a filter residue and an acid-leach solution; The acid leaching process is accompanied by heating at a temperature of 40 to 95° C. and stirring at a speed of 60 to 300 rpm; the solid-liquid ratio of the iron phosphate waste residue to the acid solution during the acid leaching process is 1:(1 to 6), and the unit of the solid-liquid ratio is g / mL; the mass ratio of the iron phosphate waste residue to H3PO3 in the acid solution during the acid leaching process is 1:(1 to 5); (2) re-acid leaching the filter residue obtained in step (1) with phosphoric acid, reusing the obtained recovered filtrate in the acid leaching of step (1), washing the obtained re-acid leaching filter residue with water at a temperature of 40 to 65° C. until the pH of the generated washing water reaches 5 to 6.5, thereby obtaining recovered carbon powder; (3) adding iron powder and sodium fluoride to the acid leaching solution obtained in step (1), wherein the molar ratio of iron powder to copper ions in the acid leaching solution is (2-5):1, and the molar ratio of sodium fluoride to aluminum ions in the acid leaching solution is (6-8):1, dissolving and separating the solid and the liquid to obtain an impurity solid and an impurity-free acid leaching solution; (4) mixing the acid leaching liquid after impurity removal in step (3) with a dispersant in a mass ratio of 1000:(1-5), and then evaporating and crystallizing by using mechanical compression steam recycling technology and / or triple-effect evaporation technology, wherein the ratio of evaporated water to original liquid in the evaporation and crystallization is (65-85):100, and the temperature is 80-100° C., and the evaporated water generated in the evaporation and crystallization is used to wash the re-acid leaching residue obtained in step (2), and centrifuging after evaporation and crystallization to obtain solid and residual liquid after evaporation and crystallization; (6) washing the solid obtained after evaporation and crystallization in step (5) until the pH value is higher than 5, then drying by disk drying and / or flash evaporation, controlling the moisture content of the dried solid to be less than 1% at 120° C., and then sintering at 450 to 650° C. for 1 to 3 hours in a protective atmosphere to obtain recovered iron phosphate; and reusing the residual liquid obtained in step (5) in the re-acid leaching described in step (2).

8. A kind of iron phosphate, characterized in that: The ferric phosphate is obtained by the recovery method according to any one of claims 1 to 7, and the purity of the ferric phosphate is not less than 99.5%.

9. A carbon powder, characterized in that: The carbon powder is obtained by the recycling method according to any one of claims 1 to 7.

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

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