A method for recovering iron phosphate and lithium carbonate from waste material

Abstract

The present application relates to a kind of methods for recycling iron phosphate and lithium carbonate from waste, including iron phosphate, lithium carbonate and glucose in the waste, the method comprises the following steps: (1) waste is pickled to obtain iron phosphate crude material and lithium-containing solution;(2) lithium-containing solution obtained in step (1) is sequentially subjected to oxidative decomposition, neutralization precipitation, solid-liquid separation, enrichment concentration, impurity removal, lithium precipitation and post-treatment process, to obtain the lithium carbonate;(3) the iron phosphate crude material obtained in step (1) is washed with water to obtain the iron phosphate;Step (2) and step (3) are not in order of precedence.The method provided by the present application can effectively remove glucose and other impurities in the waste, achieve decolorization, and the obtained lithium carbonate can reach battery grade, realizing the recycling of iron phosphate and lithium carbonate in waste, improving the utilization value and economic benefits of waste in the production of lithium iron phosphate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery waste recycling, in particular to a method for recovering iron phosphate and lithium carbonate from waste. BACKGROUND

[0002] Lithium iron phosphate positive electrode material has the advantages of high specific capacity, long cycle life and good safety, and has become one of the most competitive lithium ion power battery positive electrode materials. With the rapid development of new energy vehicles, micro-electronic devices and energy storage, lithium iron phosphate electrode material has been widely used, and higher quality requirements have been put forward. However, due to quality control problems in the production process of lithium iron phosphate, mixed materials that do not meet the process requirements appear, and the main components of this part of the mixed materials are iron phosphate and lithium carbonate, and there is also a certain content of sugar. If the waste is not disposed reasonably, it will cause environmental pollution and resource waste problems. Therefore, it is necessary to realize the waste recycling, pollution-free treatment and resource recycling of lithium iron phosphate.

[0003] CN101383441A discloses a comprehensive recovery method of lithium iron phosphate battery positive electrode waste sheet. The positive electrode material waste sheet is mechanically broken into fragments, and after heat treatment at a temperature of 150-750℃, the aluminum foil matrix is separated from the fragments by mechanical separation or ultrasonic oscillation method, and a mixture of lithium iron phosphate positive electrode material, conductive agent and binder residue is obtained. After baking at a temperature of 80-150℃, the lithium iron phosphate positive electrode recovery material is obtained after grinding and grading. The method is simple and effective, but the lithium iron phosphate positive electrode recovery material obtained by the method has low purity, and the residual conductive agent or binder will affect the charge and discharge performance of the electrode material.

[0004] CN114538405A discloses a method for preparing lithium iron phosphate from lithium iron phosphate waste positive electrode material. In the method, the lithium iron phosphate waste positive electrode material is sequentially subjected to alkali leaching to separate the aluminum foil and ball milling treatment to obtain a granular material. The granular material is sequentially subjected to organic solvent soaking to separate the binder and calcination at a temperature of 200-400℃ to separate the carbon, and a mixture containing phosphorus, iron and lithium is obtained. The lithium carbonate obtained by the subsequent steps of acid leaching and lithium precipitation can be directly used to prepare lithium iron phosphate. The method uses calcination to remove the carbon source in the waste, and the reaction speed is fast and the efficiency is high under high temperature conditions, but the method has high requirements for equipment, and the decomposition of organic matter in the electrode material may produce harmful gases, which requires the addition of purification and recovery equipment to reduce environmental pollution. The processing cost and energy loss of the method are relatively high.

[0005] CN108394919A discloses the application of a metal ion complexing agent in the recycling process of waste lithium iron phosphate battery, wherein the metal ion complexing agent is an iron salt solution, which is used to remove PO4 3-interference. The waste battery is pretreated to obtain black powder, and then the black powder is dissolved in a compound solution of dilute acid and oxidant, and after heating and stirring, a filtrate containing iron and lithium is obtained; a metal ion complexing agent is added and the pH value is adjusted to obtain a lithium-containing enrichment liquid; the enrichment liquid is heated and concentrated, and then CO3 2- is introduced to obtain lithium carbonate precipitate. The method can improve the purity of lithium carbonate, and the process is simple, the recovery rate is high, and the method is easy to industrialize and popularize. However, the separation and decolorization of the lithium-containing solution and glucose in the lithium phosphate lithium waste recovery process have not been solved in the prior art. If the residual glucose is not effectively removed, it will affect the quality and purity of the lithium carbonate precursor, and then affect the performance of the lithium phosphate lithium positive material.

[0006] Therefore, the present application provides a method for recovering lithium phosphate and lithium carbonate from waste materials, which not only recovers lithium carbonate and lithium phosphate, but also separates and decolorizes the lithium-containing solution and glucose, removes other impurities, and improves the quality of lithium carbonate. SUMMARY

[0007] The present application provides a method for recovering lithium phosphate and lithium carbonate from waste materials, and in particular provides a method for recovering lithium phosphate and lithium carbonate from waste materials containing lithium phosphate, lithium carbonate and glucose. The lithium carbonate obtained by the method can reach battery grade, realizing the recycling of lithium phosphate and lithium carbonate in waste materials. The "battery grade" refers to the purity of the obtained lithium carbonate can reach more than 99.5%.

[0008] To achieve the purpose of the present application, the following technical solutions are adopted:

[0009] The present application provides a method for recovering lithium phosphate and lithium carbonate from waste materials, and in particular provides a method for recovering lithium phosphate and lithium carbonate from waste materials containing lithium phosphate, lithium carbonate and glucose. The lithium carbonate obtained by the method can reach battery grade, realizing the recycling of lithium phosphate and lithium carbonate in waste materials. The "battery grade" refers to the purity of the obtained lithium carbonate can reach more than 99.5%.

[0010] (1) The waste material is acid washed to obtain lithium-containing solution and lithium phosphate crude material;

[0011] (2) The lithium-containing solution obtained in step (1) is subjected to oxidation decomposition, neutralization precipitation, solid-liquid separation, enrichment concentration, impurity removal, lithium precipitation and post-treatment procedures in sequence to obtain the lithium carbonate;

[0012] (3) The lithium phosphate crude material obtained in step (1) is washed with water to obtain the lithium phosphate;

[0013] Step (2) and step (3) are not in a specific order.

[0014] The present application realizes the separation of lithium carbonate and glucose in the lithium-containing solution, completes decolorization, avoids the influence of glucose on the purity of lithium carbonate, and realizes the recycling of phosphorus iron and lithium carbonate, and the obtained lithium carbonate can reach the battery grade.

[0015] Preferably, the temperature of the acid washing in step (1) is 40-80℃, for example, it can be 40℃, 50℃, 60℃, 70℃ or 80℃, but is not limited to the values exemplified, and other values not exemplified in the value range are also applicable.

[0016] The acid washing in the present application is carried out at 40-80℃, which is beneficial to washing glucose and lithium carbonate into the lithium-containing solution, so as to obtain phosphorus iron with higher purity. When the temperature is less than 40℃, the glucose in the waste material cannot be fully washed into the lithium-containing solution, resulting in a slight decrease in the purity of the obtained phosphorus iron. When the temperature is higher than 80℃, part of the phosphorus iron will be dissolved in the lithium-containing solution, resulting in a decrease in the yield of phosphorus iron, and also affecting the purity of lithium carbonate.

[0017] Preferably, the acid used in the acid washing in step (1) includes any one or a combination of at least two of sulfuric acid, phosphoric acid or hydrochloric acid, and a typical but non-limiting combination includes a combination of sulfuric acid and phosphoric acid, a combination of sulfuric acid and hydrochloric acid, a combination of phosphoric acid and hydrochloric acid, or a combination of sulfuric acid, phosphoric acid and hydrochloric acid.

[0018] Preferably, the pH of the acid used in the acid washing in step (1) is 0.5-3, for example, it can be 0.5, 1, 1.5, 2, 2.5 or 3, but is not limited to the values exemplified, and other values not exemplified in the value range are also applicable.

[0019] Preferably, in the acid washing in step (1), the mass ratio of waste material to acid is 1:(3-5), for example, it can be 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, but is not limited to the values exemplified, and other values not exemplified in the value range are also applicable.

[0020] Preferably, the time of the acid washing in step (1) is 0.5-4h, for example, it can be 0.5h, 1h, 2h, 3h or 4h, but is not limited to the values exemplified, and other values not exemplified in the value range are also applicable.

[0021] Preferably, the oxidizing agent used in the oxidative decomposition of step (2) comprises any one or a combination of at least two of hydrogen peroxide, sodium chlorate, sodium hypochlorite or sodium persulfate, typically but not limitedly, the combination comprises hydrogen peroxide and sodium chlorate, hydrogen peroxide and sodium hypochlorite, hydrogen peroxide and sodium persulfate, hydrogen peroxide, sodium chlorate and sodium hypochlorite, or hydrogen peroxide, sodium chlorate, sodium hypochlorite and sodium persulfate, and further preferably, hydrogen peroxide.

[0022] Preferably, the concentration of the oxidizing agent is 5-30wt%, for example, it can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 28wt% or 30wt%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] Preferably, the reaction temperature of the oxidative decomposition of step (2) is 40-80℃, for example, it can be 40℃, 50℃, 60℃, 70℃ or 80℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0024] The temperature of the oxidative decomposition of the present application is 40-80℃, which is beneficial to the decomposition of glucose into carbon dioxide and water or the conversion into gluconic acid, and the improvement of the purity of lithium carbonate. When the temperature is less than 40℃, the glucose in the lithium-containing solution is not completely decomposed into carbon dioxide and water or converted into gluconic acid, resulting in incomplete removal of glucose and a decrease in the purity of lithium carbonate. When the temperature is higher than 80℃, the hydrogen peroxide is severely decomposed itself and cannot fully play a role, which also leads to incomplete removal of glucose and a decrease in the purity of lithium carbonate.

[0025] Preferably, the reaction endpoint of the oxidative decomposition of step (2) is the complete oxidation of ferrous iron in the lithium-containing solution.

[0026] Preferably, the neutralizing agent used in the neutralization and precipitation of step (2) comprises any one or a combination of at least two of calcium carbonate, calcium hydroxide or calcium oxide, typically but not limitedly, the combination comprises calcium carbonate and calcium hydroxide, calcium carbonate and calcium oxide, calcium hydroxide and calcium oxide, or calcium carbonate, calcium hydroxide and calcium oxide.

[0027] Preferably, the purity of the neutralizing agent is ≥98wt%, for example, it can be 98wt%, 98.5wt%, 99wt%, 99.5wt% or 100wt%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0028] Preferably, the average particle size of the neutralizing agent is ≤ 200 mesh, for example, it can be 200 mesh, 230 mesh, 250 mesh, 280 mesh, 300 mesh, 350 mesh or 400 mesh, but is not limited to the listed values, other values not listed within the value range are also applicable.

[0029] Preferably, the reaction temperature for the neutralization precipitation in step (2) is 40-80℃, for example, it can be 40℃, 50℃, 60℃, 70℃ or 80℃, but is not limited to the listed values, other values not listed within the value range are also applicable.

[0030] The reaction temperature for the neutralization precipitation in the present application is 40-80℃, which is beneficial to fully remove residual gluconic acid and other impurities. When the temperature is lower than 40℃, the gluconic acid and ferric ion produced after oxidative decomposition are not effectively removed, resulting in a decrease in the purity of lithium carbonate. When the temperature is higher than 80℃, the molecular thermal motion rate is accelerated, and the solution is not easy to form a precipitate, so that the impurities cannot be effectively removed, which also affects the purity of lithium carbonate.

[0031] Preferably, the reaction time for the neutralization precipitation in step (2) is 0.5-4h, for example, it can be 0.5h, 1h, 2h, 3h or 4h, but is not limited to the listed values, other values not listed within the value range are also applicable; the pH of the solution at the end of the reaction is 2.5-5.0, for example, it can be 2.5, 3.0, 3.5, 4.0, 4.5 or 5.0, but is not limited to the listed values, other values not listed within the value range are also applicable.

[0032] The present application does not excessively limit the amount of the neutralizing agent added, and it is only necessary to ensure that the pH at the end of the neutralization precipitation is within the range of 2.5-5.0.

[0033] Preferably, the method for the solid-liquid separation in step (2) comprises any one or a combination of at least two of pressure filtration, microfiltration or centrifugal filtration, and a typical but non-limiting combination includes a combination of pressure filtration and microfiltration, a combination of pressure filtration and centrifugal filtration, a combination of microfiltration and centrifugal filtration, or a combination of pressure filtration, microfiltration and centrifugal filtration.

[0034] Preferably, the method for the enrichment concentration in step (2) comprises MVR concentration.

[0035] Preferably, the end point of the enrichment concentration in step (2) is that the concentration of lithium is 23-28g / L, for example, it can be 23g / L, 24g / L, 25g / L, 26g / L, 27g / L or 28g / L, but is not limited to the listed values, other values not listed within the value range are also applicable.

[0036] Preferably, the method for the impurity removal in step (2) comprises ion exchange resin impurity removal.

[0037] Preferably, the impurity removal by ion exchange resin includes: adsorption by ion exchange resin, water washing and elution to complete the impurity removal and realize the regeneration of ion exchange resin.

[0038] Preferably, the ion exchange resin includes ion exchange resin with selective adsorption of calcium and magnesium.

[0039] Preferably, the precipitant for lithium precipitation in step (2) is a carbonate solution.

[0040] Preferably, the concentration of carbonate in the carbonate solution is 100-300 g / L, for example, it can be 100 g / L, 150 g / L, 200 g / L, 250 g / L or 300 g / L, but is not limited to the values exemplified, and other values not exemplified within the value range are also applicable.

[0041] Preferably, the carbonate includes sodium carbonate.

[0042] Preferably, the reaction temperature for lithium precipitation in step (2) is 90-100℃, for example, it can be 90℃, 93℃, 95℃, 98℃ or 100℃, but is not limited to the values exemplified, and other values not exemplified within the value range are also applicable.

[0043] Preferably, the reaction time for lithium precipitation in step (2) is 0.5-8h, for example, it can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h, but is not limited to the values exemplified, and other values not exemplified within the value range are also applicable.

[0044] Preferably, the post-treatment process in step (2) includes washing, filtering, drying, crushing and removing magnetic foreign matter.

[0045] Preferably, the temperature for washing is 90-100℃, for example, it can be 90℃, 93℃, 95℃, 98℃ or 100℃, but is not limited to the values exemplified, and other values not exemplified within the value range are also applicable.

[0046] Preferably, the temperature for drying is 95-105℃, for example, it can be 95℃, 98℃, 100℃, 103℃ or 105℃, but is not limited to the values exemplified, and other values not exemplified within the value range are also applicable.

[0047] Preferably, the mass ratio of iron phosphate crude material to water during water washing in step (3) is 1:(5-20), for example, it can be 1:5, 1:8, 1:10, 1:13, 1:15, 1:18 or 1:20, but is not limited to the values exemplified, and other values not exemplified within the value range are also applicable.

[0048] Preferably, the water washing in step (3) is performed 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times.

[0049] Preferably, the water washing in step (3) is performed 1-5 times, for example, 1 time, 2 times, 3 times, 4 times or 5 times.

[0050] Preferably, the water washing in step (3) is performed at a temperature of 90-98℃, for example, 90℃, 92℃, 94℃, 96℃ or 98℃, but is not limited to the exemplified values, and other values not exemplified in the value range are also applicable.

[0051] As a preferred technical solution of the method of the present application, the method comprises the following steps:

[0052] (1) adding the waste material to an acid solution with a pH of 0.5-3 at a mass ratio of 1:(3-5) at 40-80℃ for acid washing for 0.5-4h to obtain crude iron phosphate and a lithium-containing solution;

[0053] The acid used in the acid washing includes any one or a combination of at least two of sulfuric acid, phosphoric acid or hydrochloric acid;

[0054] (2) oxidizing and decomposing the lithium-containing solution obtained in step (1) with hydrogen peroxide at 40-80℃ until the divalent iron in the lithium-containing solution is completely oxidized; adding a neutralizing agent with a purity of ≥98wt% and an average particle size of ≤200 mesh at 40-80℃ for neutralization and precipitation, the reaction time being 0.5-4h, and the solution pH at the end of the reaction being 2.5-5.0; after solid-liquid separation, enrichment and concentration to a lithium content of 23-28g / L in the solution, removing impurities by ion exchange resin; then adding a carbonate solution with a concentration of 100-300g / L at 90-100℃ for lithium precipitation, and after reaction for 0.5-8h, washing, filtering and drying to obtain the lithium carbonate;

[0055] The neutralizing agent includes any one or a combination of at least two of calcium carbonate, calcium hydroxide or calcium oxide;

[0056] (3) water washing the crude iron phosphate in step (1) at 40-80℃ to obtain the iron phosphate;

[0057] Step (2) and step (3) are not in a specific order.

[0058] Compared with the prior art, the present application has the following beneficial effects:

[0059] The method provided by the present application can simultaneously realize comprehensive recovery of iron phosphate and lithium carbonate from waste material, remove glucose and other impurities in the waste material, realize decolorization, improve the purity and quality of lithium carbonate, and the obtained lithium carbonate can reach battery grade, thereby improving the utilization value and economic benefit of waste material in the production of lithium phosphate. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a process flow diagram of the method for recovering iron phosphate and lithium carbonate from waste provided in Example 1. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be further illustrated by specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0062] Example 1

[0063] The present embodiment provides a method for recovering iron phosphate and lithium carbonate from waste, as shown in Figure 1 The waste comprises iron phosphate, lithium carbonate and glucose, and the method comprises the following steps:

[0064] (1) The waste is added to a sulfuric acid solution with pH = 2 at a mass ratio of 1:4 at 60°C for acid pickling for 2h to obtain iron phosphate crude material and a lithium-containing solution;

[0065] (2) The lithium-containing solution obtained in step (1) is added to hydrogen peroxide for oxidative decomposition at 60°C until the divalent iron in the lithium-containing solution is completely oxidized; calcium hydroxide with a purity of 99wt% and an average particle size of 300 mesh is added at 60°C for neutralization and precipitation, and the reaction time is 2h, and the solution pH at the end of the reaction is 4; after pressure filtration, MVR concentration to a lithium content of 25g / L in the solution, and impurity removal using ion exchange resin, a sodium carbonate solution with a concentration of 200g / L is added at 95°C for lithium precipitation, and after reaction for 4h, washing, filtration, drying, crushing and removal of magnetic foreign matter, the lithium carbonate is obtained;

[0066] (3) The iron phosphate crude material in step (1) is washed with water at 60°C to obtain the iron phosphate;

[0067] Steps (2) and (3) are not in a specific order.

[0068] Example 2

[0069] The present embodiment provides a method for recovering iron phosphate and lithium carbonate from waste, the waste comprising iron phosphate, lithium carbonate and glucose, and the method comprising the following steps:

[0070] (1) The waste is added to a hydrochloric acid solution with pH = 0.5 at a mass ratio of 1:3 at 40°C for acid pickling for 4h to obtain iron phosphate crude material and a lithium-containing solution;

[0071] (2) the lithium-containing solution obtained in step (1) is added with sodium chlorate at 40℃ for oxidative decomposition until the divalent iron in the lithium-containing solution is completely oxidized; calcium carbonate with a purity of 98wt% and an average particle size of 200 mesh is added at 40℃ for neutralization and precipitation, the reaction time is 4h, and the solution pH at the end of the reaction is 3.6; after microfiltration and MVR concentration to a lithium content of 23g / L in the solution, ion exchange resin is used for impurity removal; then, a sodium carbonate solution with a concentration of 100g / L is added at 90℃ for lithium precipitation, after 8h of reaction, washing, filtration, drying, crushing and removal of magnetic foreign matters, the lithium carbonate is obtained;

[0072] (3) the crude iron phosphate in step (1) is washed with water at 40℃ to obtain the iron phosphate;

[0073] Steps (2) and (3) are not in a specific order.

[0074] Example 3

[0075] The present example provides a method for recovering iron phosphate and lithium carbonate from waste materials, the waste materials comprising iron phosphate, lithium carbonate and glucose, the method comprising the following steps:

[0076] (1) the waste materials are added into a phosphoric acid solution with a pH of 3 at a mass ratio of 1:5 at 80℃ for washing, the acid washing time is 0.5h, and the lithium carbonate and glucose enter the lithium-containing solution, and the crude iron phosphate is separated;

[0077] (2) the lithium-containing solution obtained in step (1) is added with sodium hypochlorite at 80℃ for oxidative decomposition until the divalent iron in the lithium-containing solution is completely oxidized; calcium oxide with a purity of 98wt% and an average particle size of 230 mesh is added at 80℃ for neutralization and precipitation, the reaction time is 4h, and the solution pH at the end of the reaction is 5; after centrifugal filtration and MVR concentration to a lithium content of 28g / L in the solution, ion exchange resin is used for impurity removal; then, a sodium carbonate solution with a concentration of 300g / L is added at 100℃ for lithium precipitation, after 0.5h of reaction, washing, filtration, drying, crushing and removal of magnetic foreign matters, the lithium carbonate is obtained;

[0078] (3) the crude iron phosphate in step (1) is washed with water at 80℃ to obtain the iron phosphate;

[0079] Steps (2) and (3) are not in a specific order.

[0080] Example 4

[0081] The present example provides a method for recovering iron phosphate and lithium carbonate from waste materials, except that the acid washing temperature in step (1) is 25℃, and the rest is the same as example 1.

[0082] Example 5

[0083] This example provides a method for recovering iron phosphate and lithium carbonate from waste materials, which is the same as example 1 except that the temperature of the acid washing in step (1) is 95°C.

[0084] Example 6

[0085] This example provides a method for recovering iron phosphate and lithium carbonate from waste materials, which is the same as example 1 except that the temperature of the oxidative decomposition in step (2) is 26°C.

[0086] Example 7

[0087] This example provides a method for recovering iron phosphate and lithium carbonate from waste materials, which is the same as example 1 except that the temperature of the oxidative decomposition in step (2) is 93°C.

[0088] Example 8

[0089] This example provides a method for recovering iron phosphate and lithium carbonate from waste materials, which is the same as example 1 except that the temperature of the neutralization and precipitation in step (2) is 25°C.

[0090] Example 9

[0091] This example provides a method for recovering iron phosphate and lithium carbonate from waste materials, which is the same as example 1 except that the temperature of the neutralization and precipitation in step (2) is 92°C.

[0092] Performance test

[0093] The methods provided in examples 1-9 were used to test the glucose content and purity of the obtained iron phosphate and lithium carbonate, and the obtained iron phosphate and lithium carbonate met the industry standards shown in Tables 1 and 2, respectively. The test results are shown in Table 3.

[0094] Table 1

[0095]

[0096]

[0097] Table 2

[0098]

[0099]

[0100] Table 3

[0101]

[0102]

[0103] As shown in Table 3, in the method provided by the present application, the glucose content in the obtained iron phosphate is only about 0.2wt%, and the purity of the iron phosphate can reach 36.6wt%; the glucose content in the obtained lithium carbonate is less than 0.1wt%, and the purity of the lithium carbonate is more than 99.5wt%, reaching the battery grade.

[0104] As shown by the comparison of Example 4, Example 5 and Example 1, in the method provided by the present application, the pickling temperature is controlled in the range of 40-80℃, which is beneficial to separate the iron phosphate from the waste material and also beneficial to wash the glucose and lithium carbonate in the waste material into the lithium-containing solution, thereby further improving the purity of the iron phosphate and the lithium carbonate; when the temperature is lower than 40℃, the glucose in the waste material cannot be sufficiently washed into the lithium-containing solution, and therefore the purity of the obtained iron phosphate is slightly reduced; when the temperature is higher than 80℃, part of the iron phosphate is dissolved in the lithium-containing solution, resulting in the reduction of the yield of the iron phosphate and also affecting the purity of the lithium carbonate.

[0105] As shown by the comparison of Example 6, Example 7 and Example 1, in the method provided by the present application, the temperature of the oxidative decomposition is controlled in the range of 40-80℃, which is beneficial to decompose the glucose into carbon dioxide and water or convert it into gluconic acid, thereby improving the purity of the lithium carbonate; when the temperature of the oxidative decomposition is lower than 40℃, the glucose in the lithium-containing solution is not completely decomposed into carbon dioxide and water or converted into gluconic acid, resulting in incomplete removal of the glucose and reduction of the purity of the lithium carbonate; when the temperature is higher than 80℃, the hydrogen peroxide is seriously decomposed by itself and cannot fully play a role, which also results in incomplete removal of the glucose and slight reduction of the purity of the lithium carbonate.

[0106] As shown by the comparison of Example 8, Example 9 and Example 1, in the method provided by the present application, the temperature of the neutralization and precipitation is controlled in the range of 40-80℃, which is beneficial to sufficiently remove the residual gluconic acid and other impurities, thereby further improving the purity of the lithium carbonate; when the temperature of the neutralization and precipitation is lower than 40℃, the gluconic acid and the trivalent iron ion generated after the oxidative decomposition are not effectively removed, resulting in reduction of the purity of the lithium carbonate; when the temperature is higher than 80℃, the molecular thermal motion rate is accelerated, and the solution is not easy to form a precipitate, so that the impurities cannot be effectively removed, which also affects the purity of the lithium carbonate.

[0107] In summary, the present application provides a method for recovering iron phosphate and lithium carbonate from waste material, in particular, a method for recovering iron phosphate and lithium carbonate from waste material containing iron phosphate, lithium carbonate and glucose. The method provided by the present application can effectively remove the glucose and other impurities in the waste material, realize decolorization, and the obtained lithium carbonate can reach the battery grade, thereby realizing the recycling of the iron phosphate and the lithium carbonate in the waste material and improving the utilization value and economic benefits of the waste material in the production of lithium phosphate.

[0108] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and all such changes and replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for recovering iron phosphate and lithium carbonate from waste, characterized in that, The waste material includes iron phosphate, lithium carbonate, and glucose, and the method includes the following steps: (1) The waste is acid-washed to obtain crude iron phosphate and lithium-containing solution; the pH of the acid used in the acid washing in step (1) is 2-3; the mass ratio of waste to acid is 1:(3-5); (2) The lithium-containing solution obtained in step (1) is subjected to oxidative decomposition, neutralization precipitation, solid-liquid separation, enrichment and concentration, impurity removal, lithium precipitation and post-treatment processes to obtain the lithium carbonate; the reaction temperature of the oxidative decomposition is 40-80℃; the reaction endpoint of the oxidative decomposition is the complete oxidation of divalent iron in the lithium-containing solution; The oxidizing agent used in the oxidative decomposition in step (2) is hydrogen peroxide, with a concentration of 5-30 wt%. The neutralizing agent used in the neutralization precipitation in step (2) includes any one or a combination of at least two of calcium carbonate, calcium hydroxide, or calcium oxide; the reaction temperature of the neutralization precipitation is 40-80℃; (3) The crude iron phosphate obtained in step (1) is washed with water to obtain the iron phosphate; Steps (2) and (3) are not in any particular order.

2. The method according to claim 1, characterized in that, The pickling temperature in step (1) is 40-80℃.

3. The method according to claim 1, characterized in that, The acid used in the pickling process in step (1) includes any one or a combination of at least two of sulfuric acid, phosphoric acid, or hydrochloric acid.

4. The method according to claim 1, characterized in that, The pickling time in step (1) is 0.5-4 hours.

5. The method according to claim 1, characterized in that, The purity of the neutralizing agent is ≥98wt%.

6. The method according to claim 1, characterized in that, The average particle size of the neutralizing agent is ≤200 mesh.

7. The method according to claim 1, characterized in that, The reaction time for neutralization precipitation in step (2) is 0.5-4h, and the pH of the solution at the end of the reaction is 2.5-5.

0.

8. The method according to claim 1, characterized in that, The solid-liquid separation method described in step (2) includes any one or a combination of at least two of the following: pressure filtration, microfiltration, or centrifugal filtration.

9. The method according to claim 1, characterized in that, The enrichment and concentration method described in step (2) includes MVR concentration.

10. The method according to claim 1, characterized in that, The endpoint of enrichment and concentration in step (2) is a lithium concentration of 23-28 g / L.

11. The method according to claim 1, characterized in that, The impurity removal method described in step (2) includes impurity removal using ion exchange resin.

12. The method according to claim 11, characterized in that, The ion exchange resin impurity removal process includes: adsorption using ion exchange resin, followed by water washing and desorption to complete impurity removal and regeneration of the ion exchange resin.

13. The method according to claim 12, characterized in that, The ion exchange resin includes an ion exchange resin that selectively adsorbs calcium and magnesium.

14. The method according to claim 1, characterized in that, The precipitant used in step (2) for lithium precipitation includes a carbonate solution.

15. The method according to claim 14, characterized in that, The concentration of carbonate in the carbonate solution is 100-300 g / L.

16. The method according to claim 15, characterized in that, The carbonates include sodium carbonate.

17. The method according to claim 1, characterized in that, The reaction temperature for lithium precipitation in step (2) is 90-100℃.

18. The method according to claim 1, characterized in that, The reaction time for lithium precipitation in step (2) is 0.5-8h.

19. The method according to claim 1, characterized in that, The post-processing steps in step (2) include washing, filtering, and drying.

20. The method according to claim 19, characterized in that, The washing temperature is 90-100℃.

21. The method according to claim 19, characterized in that, The drying temperature is 95-105℃.

22. The method according to claim 1, characterized in that, During the water washing process described in step (3), the mass ratio of crude iron phosphate to water is 1:(5-20).

23. The method according to claim 1, characterized in that, The number of times the water is washed in step (3) is 1-5 times.

24. The method according to claim 1, characterized in that, The water temperature for step (3) is 90-98℃.

25. The method according to claim 1, characterized in that, The method includes the following steps: (1) Under the condition of 40-80℃, the waste material is added to an acid solution with pH of 0.5-3 at a mass ratio of 1:(3-5) and acid washed for 0.5-4h to obtain crude iron phosphate and lithium-containing solution; The acid used in the pickling includes any one or a combination of at least two of sulfuric acid, phosphoric acid, or hydrochloric acid. (2) The lithium-containing solution obtained in step (1) is oxidized and decomposed by adding hydrogen peroxide at 40-80℃ until the divalent iron in the lithium-containing solution is completely oxidized; under the condition of 40-80℃, a neutralizing reagent with a purity ≥98wt% and an average particle size ≤200 mesh is added for neutralization and precipitation, the reaction time is 0.5-4h, and the pH of the solution at the reaction endpoint is >2.5; after solid-liquid separation and enrichment and concentration until the lithium content in the solution is 23-28g / L, impurities are removed by using ion exchange resin; then, under the condition of 90-100℃, a carbonate solution with a concentration of 100-300g / L is added for lithium precipitation, the reaction is carried out for 0.5-8h, and after washing, filtration and drying, the lithium carbonate is obtained; The neutralizing agent includes any one or a combination of at least two of calcium carbonate, calcium hydroxide, or calcium oxide. (3) The crude iron phosphate in step (1) is washed with water at 40-80℃ to obtain the iron phosphate; Steps (2) and (3) are not in any particular order.

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