Lithium extraction slag resourceful treatment method and device

Abstract

The invention provides a lithium extraction slag resourceful treatment method and device, and belongs to the field of waste lithium battery treatment. The lithium extraction slag resourceful treatment method provided by the invention comprises the following steps: a leaching procedure: contacting the lithium extraction slag with sulfur dioxide and acid liquor in an ultrasonic environment to carry out leaching reaction, and carrying out solid-liquid separation to obtain leachate and leaching slag; a first purification process: contacting the leachate with iron powder to carry out copper removal reaction, and carrying out solid-liquid separation to obtain copper-removed liquid and copper-removed slag; and a second purification process: contacting the copper-removed liquid with a neutralizer to carry out a first precipitation reaction, and carrying out solid-liquid separation to obtain a precipitated liquid and precipitation slag. By means of the lithium extraction slag resourceful treatment method, the consumption of auxiliary materials such as acid and alkali reagents in the waste lithium iron phosphate battery lithium extraction slag recycling process can be reduced, the production cost is promoted to be effectively reduced, the productivity is higher, the iron and phosphorus loss is reduced, and the iron and phosphorus utilization rate is effectively increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of waste lithium battery processing, and particularly relates to a lithium extraction residue resource processing method and device. BACKGROUND

[0002] The lithium extraction process using a sulfuric acid-hydrogen peroxide solution system to recover waste lithium iron phosphate positive electrode material has realized industrialized production. A large amount of lithium extraction residue is generated in the process, and the iron and phosphorus contents in part of the lithium extraction residue are 30-35 wt.% and 15-17 wt.% respectively, which have high recycling value.

[0003] At present, when the lithium extraction residue of waste lithium iron phosphate positive electrode material is recovered by using hydrometallurgical technology, the lithium extraction residue is mainly dissolved by high-concentration acid, then the leaching solution is impurity-removed, and dihydrate iron phosphate is obtained by chemical precipitation. In the process, the consumption of acid and alkali reagents, impurity-removing reagents and other auxiliary materials is high, the solution volume expands seriously, and the iron and phosphorus loss in the purification process is large, resulting in high production cost, low production capacity and low utilization rate of iron and phosphorus.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The present application provides a lithium extraction residue resource processing method and device, aiming to solve or alleviate at least one of the defects in the prior art.

[0006] In one aspect, the present application provides a lithium extraction residue resource processing method, comprising the following steps:

[0007] The leaching process is to contact the lithium extraction residue with sulfur dioxide and acid solution in an ultrasonic environment for leaching reaction, and to obtain leaching solution and leaching residue through solid-liquid separation;

[0008] The first purification process is to contact the leaching solution with iron powder for copper removal reaction, and to obtain copper-removed solution and copper-removed residue through solid-liquid separation;

[0009] The second purification process is to contact the copper-removed solution with a neutralizing agent for first precipitation reaction, and to obtain precipitated solution and precipitated residue through solid-liquid separation.

[0010] The lithium extraction residue resource processing method provided by the application can efficiently leach the target elements iron and phosphorus in the lithium extraction residue by performing leaching reaction on the lithium extraction residue, sulfur dioxide and acid liquor in an ultrasonic environment, and reduce the iron ions to ferrous ions to obtain a leaching liquor containing ferrous ions, phosphate or its acid form, aluminum and other metal ions, and a leaching residue containing graphite, so as to obtain a metal phosphate product. The leaching liquor is treated by the first purification process, can be contacted with iron powder to perform a copper removal reaction, so as to realize the displacement removal of copper ions and the deep reduction of residual iron ions in the leaching liquor, and obtain a copper-removed liquor and a copper-removed residue. The copper-removed liquor is subjected to a first precipitation reaction with a neutralizing agent in the second purification process, so as to realize the deep removal of most aluminum ions and other cation impurities such as titanium and chromium, and obtain a precipitated liquor with high iron and phosphorus content and a precipitated residue containing aluminum, chromium, titanium and other impurities.

[0011] In particular, since the properties of iron and aluminum are relatively close, it is difficult to separate them. In order to reduce the iron loss caused by the co-precipitation of iron and aluminum in the subsequent impurity removal process, most of the iron ions are reduced to ferrous ions by sulfur dioxide in the leaching process, and the residual iron ions are further reduced in the first purification process, so that the iron in the solution exists in the form of ferrous ion. In the second purification process, the pH of the reaction system is controlled by the neutralizing agent to precipitate most of the aluminum and remove other cation impurities, while inhibiting the precipitation of iron as much as possible, so as to reduce the loss rate of iron and phosphorus. In addition, sulfur dioxide as a reducing agent can efficiently dissolve the lithium extraction residue under relatively mild acidic conditions without introducing additional impurity elements. In addition, sulfur dioxide can generate sulfurous acid molecules and H+ after dissolving in aqueous solution, which can increase the acidity of the reaction system, thereby reducing the consumption of acid in the leaching process. Compared with pure acid leaching, the same or similar leaching effect can be achieved while reducing the consumption of neutralizing agent in the subsequent purification process, reducing the solution volume expansion, saving production cost, and processing more materials under the same equipment and production conditions to improve production capacity.

[0012] Further, the leaching reaction is performed in an ultrasonic environment, which can enhance the dispersion and emulsification of the gas reactant, produce micro-cracks on the surface of the solid phase, enhance the contact area between phases, and thus strengthen the mass transfer process between gas, solid and liquid phases, improve the leaching reaction effect, significantly improve the utilization rate of sulfur dioxide, and promote the deep reduction of iron ions to ferrous ions, thereby reducing the consumption of iron powder in the subsequent first purification process.

[0013] In summary, the lithium extraction residue resource processing method provided by the application can reduce the consumption of acid and alkali reagents, impurity removal reagents and other auxiliary materials in the recovery process of waste lithium iron phosphate battery lithium extraction residue, effectively reduce the production cost, improve the production capacity, and reduce the loss of iron and phosphorus, so as to effectively improve the utilization rate of iron and phosphorus.

[0014] In some embodiments, the leaching process comprises:

[0015] mixing the lithium extraction residue with water and / or acid liquor to obtain a slurry;

[0016] contacting the slurry with sulfur dioxide in an ultrasonic environment to perform leaching reaction, and obtaining leaching liquor and leaching residue through solid-liquid separation.

[0017] In some embodiments, during the contacting of the slurry with sulfur dioxide, the slurry is sprayed towards the sulfur dioxide in a direction opposite to the direction of the gas flow of the sulfur dioxide; and / or

[0018] contacting the slurry with sulfur dioxide in an ultrasonic environment to perform leaching reaction includes: contacting the slurry with sulfur dioxide in an ultrasonic environment to perform leaching, and repeatedly performing leaching on the slurry obtained by leaching until the slurry reaches the leaching end point pH value.

[0019] In some embodiments, the leaching process satisfies at least one of the following conditions:

[0020] A. the liquid-solid ratio during the mixing of the lithium extraction residue with water to obtain the slurry is 4-12 mL / g;

[0021] B. the acid liquor includes at least one of sulfuric acid solution, hydrochloric acid solution, and phosphoric acid solution;

[0022] C. the leaching reaction temperature is 25-95°C; optionally 40-80°C;

[0023] D. the leaching reaction time is 2-6h;

[0024] E. the leaching reaction end point pH value is 0.8-1.5;

[0025] F. the leaching reaction pressure is 0.2-0.3 MPa;

[0026] G. the flow rate of the sulfur dioxide is 0.5-2.5 m 3 / h;

[0027] H. the leaching residue is washed to obtain washing liquor and washing residue, and the washing liquor is recycled to mix with the lithium extraction residue to perform leaching reaction.

[0028] In some embodiments, the method further comprises:

[0029] a third purification process, adjusting the post-precipitation liquid to a target pH value, and using ion exchange resin to selectively adsorb aluminum from the post-precipitation liquid with adjusted pH value to obtain post-aluminum removal liquid;

[0030] a phosphorus iron preparation process, adding an oxidizing agent to the post-aluminum removal liquid to perform a second precipitation reaction, obtaining iron phosphate dihydrate precipitate, and obtaining iron phosphate through post-treatment.

[0031] In some embodiments, at least one of the following conditions is satisfied:

[0032] I. The amount of iron powder added in the first purification process is 1.0-2.0 times the total moles of copper ions and iron ions in the leaching solution;

[0033] J. The pH value of the copper removal reaction is 0.8-2.0;

[0034] K. The temperature of the copper removal reaction is 25-90℃;

[0035] L. The time of the copper removal reaction is 0.25-2h;

[0036] M. The neutralizing agent in the second purification process includes at least one of monobasic ammonium phosphate, dibasic ammonium phosphate, ammonium phosphate trihydrate, trisodium phosphate, ammonium carbonate, ammonium bicarbonate, and ammonia water; optionally, the neutralizing agent is ammonium carbonate or ammonium bicarbonate solid;

[0037] N. The pH value of the first precipitation reaction is 2.5-6.0, optionally 3.5-4.0;

[0038] O. The temperature of the first precipitation reaction is 25-80℃;

[0039] P. The first precipitation reaction of the copper-removed solution with the neutralizing agent is carried out in a non-oxidizing atmosphere, which includes at least one of nitrogen, argon, and helium;

[0040] Q. The target pH value of the third purification process is 1-2.5;

[0041] R. The ion exchange resin in the third purification process is a chelating resin;

[0042] S. In the preparation of ferric phosphate process, the molar ratio of phosphorus to iron in the aluminum-removed solution is adjusted to 1.02-1.2 before the addition of the oxidizing agent;

[0043] T. The oxidizing agent includes hydrogen peroxide solution; optionally, the amount of the oxidizing agent is 1.0-1.5 times the theoretical amount required to convert all ferrous ions in the ion-exchanged solution to ferric ions;

[0044] U. The pH value of the second precipitation reaction is 0.6-1.2;

[0045] V. The temperature of the second precipitation reaction is 80-120℃;

[0046] W. The time of the second precipitation reaction is 4-12h.

[0047] Another aspect of the present application provides a lithium-containing residue resource processing device for the leaching process in the resource processing method described above, comprising:

[0048] The ultrasonic reactor is capable of generating ultrasonic waves and is formed with a first reaction cavity, and a perforated plate is arranged in the first reaction cavity to divide the first reaction cavity into an upper chamber and a lower chamber which are communicated with each other in a height direction;

[0049] The lower chamber is provided with an ultrasonic discharge port;

[0050] The upper chamber is provided with a gas supply pipe and a feed injection pipe, and a gas outlet on the gas supply pipe is arranged opposite to a discharge port of the feed injection pipe, and the slurry containing lithium extraction residue and acid delivered by the feed injection pipe can be countercurrently contacted with sulfur dioxide delivered by the gas supply pipe.

[0051] In some embodiments, the lithium extraction residue resource treatment device further comprises a circulating pump, a discharge port of the circulating pump being communicated with a feed inlet of the feed injection pipe; and a leaching tank, the leaching tank being formed with a second reaction cavity, and a stirrer being arranged in the second reaction cavity, and the second reaction cavity being provided with a first feed inlet, a second feed inlet, a third feed inlet and a slurry outlet; the third feed inlet being communicated with the ultrasonic discharge port for receiving the material delivered by the ultrasonic discharge port; the slurry outlet being communicated with the feed inlet of the circulating pump; the first feed inlet being used for feeding the lithium extraction residue and / or acid, and the second feed inlet being used for feeding steam.

[0052] In some embodiments, the gas supply pipe and the perforated plate are arranged at intervals in the height direction, and the feed injection pipe is arranged at intervals between the gas supply pipe and the perforated plate in the height direction; and the gas outlet on the gas supply pipe is arranged opposite to the discharge port of the feed injection pipe in the height direction.

[0053] In some embodiments, the gas outlet of the gas supply pipe is provided with an ultrasonic generator for generating ultrasonic waves; and / or the gas supply pipe is provided with a gas flow meter for obtaining a sulfur dioxide flow parameter; and / or the first reaction cavity is provided with a pressure gauge for obtaining a pressure parameter in the first reaction cavity.

[0054] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the specific embodiments or prior art technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0056] Figure 1 A flowchart of a lithium extraction residue resource treatment method provided by an embodiment of the present application is shown;

[0057] Figure 2A structural schematic diagram of the lithium extraction residue resource treatment device provided by the embodiment of the application is shown.

[0058] Reference signs:

[0059] 1. A lithium extraction residue resource treatment device.

[0060] 10. An ultrasonic reactor; R1, a first reaction cavity; R11, an upper chamber; R12, a lower chamber; 20, a hole plate; 11, an ultrasonic discharge port; 30, a gas supply pipe; 40, a feed injection pipe;

[0061] 50. A circulating pump; 60, a leaching tank; R2, a second reaction cavity; 61, a first feed inlet; 62, a second feed inlet; 63, a third feed inlet; 64, a slurry outlet; 70, a stirrer; 80, an ultrasonic generator; 90, a gas flow meter; 100, a pressure gauge; 110, a valve. DETAILED DESCRIPTION

[0062] The ranges disclosed herein are defined by the lower and upper limits of the range, and the ranges are defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The ranges defined in this manner can include the end values or not, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand notation for any real combination of integers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when a parameter is stated to be ≥2 integers, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0063] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0064] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0065] If not specifically stated, all steps of the present application can be performed in sequence or randomly, optionally in sequence. For example, a method comprising steps (a) and (b) indicates that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, a method is mentioned to further comprise step (c) indicates that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0066] If not specifically stated, "comprise" and "include" mentioned in the present application are open-ended, and can also be closed. For example, "comprise" and "include" can also include or contain other components not listed, or can only include or contain the listed components.

[0067] If not specifically stated, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0068] As described above, when the wet metallurgical recovery method is used for the lithium extraction residue of the current waste lithium iron phosphate battery, the auxiliary material consumption is high, the solution volume expands seriously, the iron and phosphorus loss is large, and reference Figure 1 The embodiment of the present application provides a lithium extraction residue resource treatment method, comprising the following steps:

[0069] The leaching process is to contact the lithium extraction residue with sulfur dioxide and acid solution in an ultrasonic environment for leaching reaction, and to obtain leaching solution and leaching residue through solid-liquid separation;

[0070] The first purification process is to contact the leaching solution with iron powder for copper removal reaction, and to obtain copper-removed solution and copper-removed residue through solid-liquid separation;

[0071] The second purification process is to contact the copper-removed solution with a neutralizing agent for a first precipitation reaction, and to obtain precipitated solution and precipitated residue through solid-liquid separation.

[0072] It should be understood that, only using mechanical stirring method for leaching reaction, it is difficult to achieve the purpose of uniform dispersion, emulsification and fine bubble particle size of sulfur dioxide, resulting in low utilization rate of sulfur dioxide in the leaching process, greatly reducing the leaching rate of iron and phosphorus and the reduction rate of iron, and increasing the consumption of reducing agent sulfur dioxide.

[0073] In the embodiment of the present application, by designing the leaching process, the lithium extraction residue is contacted with sulfur dioxide and acid liquor in an ultrasonic environment to perform leaching reaction. Under the action of ultrasonic cavitation, sulfur dioxide can continuously collide with the slurry formed by the lithium extraction residue and acid liquor and generate a large number of micro-bubbles. These bubbles continuously move, grow and suddenly burst under the influence of the ultrasonic field. When the bubbles burst suddenly, high temperature and high pressure are generated locally, which intensifies the dispersion and emulsification of sulfur dioxide gas and generates micro-cracks on the surface of the solid phase, thereby enhancing the contact area between the phases and strengthening the mass transfer process among the gas-solid-liquid three phases, so as to significantly improve the utilization rate of sulfur dioxide and reduce the treatment amount of iron ions in the subsequent first purification process, thereby reducing the consumption of iron powder.

[0074] Further, since the properties of iron and aluminum are relatively close, it is difficult to separate them. In order to reduce the loss of iron caused by iron and aluminum co-precipitation in the subsequent impurity removal process, most of the iron ions are reduced to ferrous ions by sulfur dioxide in the leaching process, and the residual iron ions are further reduced in the first purification process, so that the iron in the solution exists in the form of ferrous ions. In the second purification process, the pH of the reaction system is controlled by a neutralizing agent to precipitate most of the aluminum and remove other impurity cations, while inhibiting the precipitation of iron as much as possible, thereby reducing the loss rate of iron and phosphorus. In the embodiment of the present application, sulfur dioxide is used as a reducing agent. Compared with sodium sulfite, sodium thiosulfate and sodium metabisulfite, sodium sulfite, sodium thiosulfate and sodium metabisulfite can introduce impurity metal sodium, which increases the cost of subsequent impurity removal or water treatment. Sulfur dioxide as a reducing agent can not introduce new impurities, and it can generate sulfurous acid by dissolving in water, which can reduce iron ions, and at the same time, it can ionize hydrogen ions to provide a certain acidity in the leaching process, thereby reducing the amount of acid liquor. In addition, compared with high-acid leaching, the leaching endpoint pH of high-acid leaching is lower, which needs to be below 0, resulting in a higher consumption of neutralizing agent in the subsequent first precipitation reaction. However, by using sulfur dioxide for reduction leaching, the leaching endpoint pH can be higher under the same or similar leaching effect, thereby reducing the consumption of neutralizing agent in the subsequent purification process, reducing the expansion of the solution volume, saving production cost, and processing more materials under the same equipment and production conditions to improve production capacity.

[0075] The leaching solution containing ferrous ions, phosphate or its acid form, and impurity ions obtained in the leaching process and the leaching residue containing graphite, and the leaching solution containing copper ions and residual iron ions, are contacted with iron powder in the first purification process to remove copper. Iron powder can react with copper ions and reduce residual ferric ions to ferrous ions, thereby removing copper ions and reducing iron ions. After solid-liquid separation, copper removal residue and copper removal solution are obtained. Moreover, since a large amount of iron ions have been reduced to ferrous ions in the leaching process, the consumption of iron powder in the first purification process can be reduced.

[0076] In the second purification process, the copper-removed solution is contacted with a neutralizing agent to perform a first precipitation reaction. The neutralizing agent can increase the pH of the copper-removed solution to generate aluminum phosphate precipitates by a chemical precipitation method, and achieve deep removal of titanium, chromium and other cation impurities, thereby obtaining a post-precipitation solution with high iron and phosphorus content and a precipitate slag containing aluminum, chromium, titanium and other impurities. The post-precipitation solution has high iron and phosphorus content, and can be used to prepare high-purity iron phosphate. In some embodiments, battery-grade iron phosphate can be obtained.

[0077] It should be noted that, in the first and second purification processes of the present application, copper and aluminum are removed in steps, which can make the copper-removed slag exist in the form of sponge copper, thereby having a high grade and being beneficial to recovery.

[0078] Therefore, the embodiments of the present application can reduce the consumption of iron powder, acid and alkali reagents and other auxiliary materials, effectively reduce the production cost, reduce the solution volume expansion, have higher production capacity, and reduce the loss of iron and phosphorus, thereby effectively improving the utilization rate of iron and phosphorus.

[0079] It should be noted that, in the embodiments of the present application, the lithium extraction residue includes iron phosphate and impurity elements; the impurity elements include copper and aluminum, and further include one or more of titanium, chromium, nickel, calcium, magnesium and lithium. In some embodiments, the lithium extraction residue is obtained from waste residue after lithium extraction of lithium iron phosphate battery recycling materials.

[0080] In some embodiments, the leaching process includes: mixing the lithium extraction residue with water and / or acid to form a slurry; and contacting the slurry with sulfur dioxide in an ultrasonic environment to perform a leaching reaction, thereby obtaining a leaching solution and a leaching residue.

[0081] In the embodiments of the present application, the lithium extraction residue is mixed with water and / or acid to form a slurry, for example, the lithium extraction residue is first mixed with water to form a uniform ore slurry, and then acid is added to obtain a slurry. This can ensure uniform contact between the acid and the solid particles, and provide a stable and controllable reaction starting point for the subsequent introduction of sulfur dioxide and ultrasonic waves for leaching reaction. By contacting the slurry with sulfur dioxide in an ultrasonic environment, the sulfur dioxide reacts with the slurry under the action of ultrasonic waves, and disperses and emulsifies and produces micro-cracks on the surface of the solid phase, thereby increasing the contact area between the phases and strengthening the mass transfer process between the gas, solid and liquid phases, and improving the leaching effect.

[0082] In some embodiments, during the process of contacting the slurry with sulfur dioxide, the slurry is sprayed towards the sulfur dioxide in a direction opposite to the direction of the sulfur dioxide gas flow. In this way, the slurry and sulfur dioxide form countercurrent contact to greatly increase the mass transfer area, shorten the reaction time, and significantly improve the utilization rate of sulfur dioxide gas and the efficiency of leaching reaction.

[0083] In some embodiments, the leaching reaction of the slurry with sulfur dioxide in the ultrasonic environment includes: leaching the slurry with sulfur dioxide in the ultrasonic environment, and repeatedly leaching the slurry obtained by leaching until the slurry reaches the leaching endpoint pH value.

[0084] In the embodiments of the present application, the slurry obtained by leaching is recycled for leaching until the slurry reaches the leaching endpoint pH value, so as to ensure that the slowly reacting particles are treated multiple times, improve the total recovery rate of the target components (iron and phosphorus), and ensure the thoroughness of the leaching.

[0085] In some embodiments, the liquid-solid ratio during the mixing and slurry of the lithium extraction residue with water is 4-12 mL / g. Within this range, the slurry has good fluidity, facilitating transportation and spraying towards sulfur dioxide, while maintaining a high reactant concentration, balancing reaction efficiency and energy consumption.

[0086] In some embodiments, the acid solution includes at least one of sulfuric acid solution, hydrochloric acid solution, and phosphoric acid solution, to provide an acidic environment and anions. In some embodiments, the acid solution is a sulfuric acid solution, which is low in cost and does not introduce new impurities.

[0087] For example, when the sulfuric acid solution is used as the acid solution, the mixing of the lithium extraction residue with water for slurry and the addition of the acid solution to obtain the slurry involves reactions that can include:

[0088] Al + H2SO4→ Al2(SO4)3+ H2;

[0089] CuO + H2SO4→ CuSO4+ H2O.

[0090] Further, the leaching reaction of the slurry with sulfur dioxide in the ultrasonic environment involves reactions that can include:

[0091] FePO4+ H2SO4+ SO2+ H2O→ FeSO4+ H3PO4;

[0092] Al + 3H2SO4→ Al2(SO4)3+ H2;

[0093] CuO + H2SO4→ CuSO4+ H2O.

[0094] AlPO4+ H2SO4→ Al2(SO4)3+ H3PO4.

[0095] In some embodiments, the leaching reaction temperature is 25-95°C, which is more conducive to accelerating the leaching reaction rate.

[0096] In some embodiments, the leaching reaction temperature is 40-80℃, within this range, it is more conducive to promote the leaching of valuable metals such as iron and aluminum, and it is also conducive to increasing the pressure in the ultrasonic leaching environment, promoting the dissolution of sulfur dioxide, and increasing the leaching reaction rate and sulfur dioxide utilization rate. At the same time, due to the high temperature, the trivalent iron and phosphate ions that are not reduced by SO2 will gradually combine to form hydrated ferric phosphate. In order to inhibit the generation of hydrated ferric phosphate phase, it is more appropriate to further control the upper limit of the leaching reaction temperature to be no more than 80℃.

[0097] In some embodiments, the leaching reaction time is 2-6h, within this range, it is more conducive to the completion of the leaching reaction.

[0098] In some embodiments, the leaching reaction end point pH value is 0.8-1.5, for example, the leaching reaction end point pH value can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or any value within the range of 0.8-1.5. Compared with high-acid leaching without the addition of sulfur dioxide, the leaching reaction end point pH value in the embodiments of the present application is higher, which is conducive to reducing the consumption of subsequent neutralizing agents, reducing the cost of auxiliary materials, and reducing the solution volume expansion.

[0099] In some embodiments, the leaching reaction pressure is 0.2-0.3Mpa, within this pressure range, it is conducive to the dispersion and emulsification of sulfur dioxide gas in the slurry, thereby increasing the reaction rate and gas utilization rate.

[0100] In some embodiments, the flow rate of sulfur dioxide is 0.5-2.5m 3 / h, controlling the flow rate of sulfur dioxide within this range is more conducive to achieving the best gas-liquid dispersion and reaction state, avoiding gas waste caused by too fast flow rate or insufficient reaction caused by too slow flow rate.

[0101] In some embodiments, the leaching residue is stirred and washed to obtain a stirred and washed liquid and a stirred and washed residue, and the stirred and washed liquid is reused for mixing with the lithium extraction residue for leaching reaction. Stirring and washing refers to stirring and washing the leaching residue. By stirring and washing the leaching residue to obtain a stirred and washed liquid and a stirred and washed residue, the valuable mother liquor attached to the leaching residue can be recovered, the total recovery rate of target elements (iron, phosphorus) can be improved, and the amount of wastewater and subsequent treatment load can be reduced. The graphite purity of the stirred and washed residue is high, which is more conducive to the recovery of graphite in the lithium extraction residue.

[0102] In order to realize the complete resource utilization path of the lithium extraction residue to ferric phosphate, in some embodiments, the resource utilization method further comprises:

[0103] In the third purification process, the post-precipitation liquid is adjusted to a target pH value, and ion exchange resin is used to selectively adsorb and remove aluminum from the post-precipitation liquid after adjusting the pH value, to obtain an aluminum-removed liquid;

[0104] The iron phosphate preparation process is to add an oxidizing agent to the solution after aluminum removal to perform a second precipitation reaction to obtain iron phosphate dihydrate precipitate, and to obtain iron phosphate through post-treatment.

[0105] It should be understood that, due to the close solubility product of iron and aluminum phosphate precipitates, the iron and aluminum co-precipitation is not used in the embodiments of the present application, but in the leaching process, the iron ions are first reduced to ferrous ions by sulfur dioxide, and then the aluminum is removed in steps through the first and second purification processes to reduce the iron precipitation, so as to reduce the loss of iron and phosphorus. In order to remove residual aluminum ions, in the embodiments of the present application, the post-precipitation solution is adjusted to a target pH value, and the difference in affinity of different valence cations in the solution system is used to selectively adsorb the residual aluminum ions in the post-precipitation solution adjusted to the target pH value, so as to achieve deep purification of aluminum ions, thereby avoiding the problems of incomplete removal of aluminum by chemical precipitation alone and large loss of valuable elements. In addition, selective adsorption of aluminum ions by ion exchange resin can also reduce the loss of phosphorus and improve the recovery rate of phosphorus. The solution after aluminum removal obtained in the third purification process is subjected to a second precipitation reaction by adding an oxidizing agent to the solution after aluminum removal in the iron phosphate preparation process, so as to obtain iron phosphate dihydrate precipitate, and after washing, drying, calcination and other post-treatment operations in sequence, anhydrous iron phosphate is obtained, so as to realize efficient transformation and comprehensive utilization of low-value lithium slag waste to iron phosphate. In some embodiments, the obtained iron phosphate is battery-grade iron phosphate.

[0106] In some embodiments, the amount of iron powder added in the first purification process is 1.0-2.0 times the total moles of copper ions and iron ions in the leaching solution, so as to facilitate complete displacement and removal of Cu 2+ , and at the same time, the residual Fe 3+ is deeply reduced to Fe 2+ , so as to prepare for subsequent iron and aluminum separation.

[0107] In some embodiments, the pH value of the copper removal reaction is 0.8-2.0, and by performing the displacement reaction under strong acidic conditions, the hydrolysis precipitation of Fe 2+ and the co-precipitation of impurity ions (such as Al3+) can be inhibited, the iron loss is reduced, and the purity of the copper removal residue is improved.

[0108] In some embodiments, the temperature of the copper removal reaction is 25-90°C, which is beneficial to accelerate the copper-iron displacement reaction rate and ensure that the iron ions are deeply reduced to ferrous ions.

[0109] In some embodiments, the time of the copper removal reaction is 0.25-2h, so as to ensure that the time required for sufficient copper removal and iron ion reduction is reached, and the reaction is sufficient.

[0110] In some embodiments, the neutralizing agent in the second purification process comprises at least one of monobasic ammonium phosphate, dibasic ammonium phosphate, ammonium phosphate trihydrate, trisodium phosphate, ammonium carbonate, ammonium bicarbonate, and aqueous ammonia. Using the above substances as the neutralizing agent to adjust the pH in the second purification process can help avoid local over-alkalization and excessive precipitation of iron in the second purification process, and increase the loss of iron and phosphorus.

[0111] In some embodiments, the neutralizing agent is ammonium carbonate or ammonium bicarbonate solid. In the embodiments of the present application, the neutralizing agent in the second purification process can be selected as ammonium carbonate or ammonium bicarbonate solid, which can synergize with sulfur dioxide to reduce acid consumption, jointly inhibit the expansion of the solution volume, significantly improve the production capacity (i.e., under the same equipment and production conditions, more materials can be processed), and reduce the pressure on ion exchange resin treatment and wastewater treatment. Moreover, the carbon dioxide generated during the action of the neutralizing agent is a common reagent for lithium precipitation in battery recycling, which is conducive to improving the industrial concentration and reducing the treatment cost of the three wastes.

[0112] In some embodiments, the pH value of the first precipitation reaction is 2.5-6.0. Within this range, Al3+ will form AlPO4 precipitate under non-oxidizing conditions, so that Fe 2+ It can be avoided as much as possible to be converted into iron ions and precipitated, thereby realizing selective precipitation and removing aluminum.

[0113] In some embodiments, the pH value of the first precipitation reaction is 3.5-4.0. A pH value of 3.5-4.0 is the most complete aluminum precipitation and the lowest risk of iron precipitation window, which is more conducive to the precipitation of metal cations such as aluminum, titanium, and chromium, and reduces the loss of iron.

[0114] In some embodiments, the temperature of the first precipitation reaction is 25-80°C, which is conducive to improving the first precipitation reaction rate.

[0115] In some embodiments, the time of the first precipitation reaction is 0.5-4h, so as to ensure complete reaction.

[0116] In some embodiments, the contact of the copper-removed liquid with the neutralizing agent for the first precipitation reaction is carried out in a non-oxidizing atmosphere, which comprises at least one of nitrogen, argon, and helium, so as to prevent Fe 2+ from being oxidized to Fe 3+ and then removed with aluminum ions.

[0117] In some embodiments, the target pH value of the third purification process is 1-2.5. Within this range, the post-precipitation liquid is adjusted to an acidic pH to meet the optimal adsorption conditions of the chelating resin for aluminum ions (Al3+), thereby realizing deep aluminum removal.

[0118] In some embodiments, the ion exchange resin in the third purification process is a chelating resin, which has high selectivity for Al3+.

[0119] In some embodiments, the ion exchange resin is activated and pretreated before selective adsorption to remove aluminum: the column is packed with a height-to-diameter ratio of about 3:1, and 1 BV of 3% dilute sulfuric acid is used for pretreatment and activation, with a column flow rate of 1-2 BV / h; the above activation and pretreatment can ensure the adsorption capacity of the resin.

[0120] In some embodiments, the column flow rate of the precipitated liquid is 1-5 BV / h. Controlling the column flow rate within this range helps to ensure sufficient contact time between aluminum ions and the functional groups of the resin. If the flow rate is too fast, the adsorption will be incomplete, and if it is too slow, the processing efficiency will be reduced.

[0121] In some embodiments, during the production of ferric phosphate, before adding the oxidant, the molar ratio of phosphorus to iron in the aluminum-removed liquid is adjusted to 1.02-1.2 to ensure that phosphorus is slightly in excess during the second precipitation reaction stage, generating pure ferric phosphate dihydrate (FePO4·2H2O) instead of other impurities, thus ensuring the stoichiometry and purity of the final product.

[0122] For example, by adding appropriate amounts of iron and phosphorus sources to the aluminum-removed liquid, the molar ratio of phosphorus to iron in the aluminum-removed liquid can be adjusted to 1.02-1.2.

[0123] In some embodiments, the oxidant includes a hydrogen peroxide solution; H2O2 is a clean oxidant that does not introduce impurities.

[0124] In some embodiments, the amount of oxidant added is 1.0-1.5 times the theoretical amount of oxidant required to completely convert ferrous ions in the ion-exchange solution into ferric ions. A slight excess of oxidant ensures that Fe... 2+ Completely oxidized to Fe 3+ For example, when the oxidant is hydrogen peroxide, the reaction between the oxidant and ferrous ions is: 2Fe 2+ +H₂O₂ + 2H₂ + →2Fe 3 + With the addition of 2H₂O, we know that each mole of hydrogen peroxide can oxidize two moles of ferrous ions. Therefore, the theoretical amount of oxidant required to completely convert ferrous ions into ferric ions is equal to the total molar amount of ferrous ions * 1 / 2.

[0125] In some embodiments, the pH value of the second precipitation reaction is 0.6-1.2; the temperature of the second precipitation reaction is 80-120°C.

[0126] In this embodiment, the second precipitation reaction in the ferric phosphate preparation process is carried out under a high-temperature, high-acid system. The one-step preparation of ferric phosphate dihydrate is mainly to suppress Al in the solution. 3+ Ni 2+ Co 2+ Mn2+ Ca 2+ Mg 2+ Impurity cations can co-precipitate during the synthesis of ferric phosphate dihydrate, thus affecting the purity of the ferric phosphate product. Simultaneously, by utilizing high-temperature and high-acid conditions, the dominant phosphorus form, H3PO4 / H2PO4, can be controlled. - The ionization of PO4 gradually and slowly releases PO4. 3- This regulates the nucleation rate of ferric phosphate dihydrate precipitate, which is beneficial for obtaining ferric phosphate precursors with good crystallinity and high tap density. In some embodiments, the obtained ferric phosphate precursor is a battery-grade ferric phosphate precursor.

[0127] In some embodiments, the second precipitation reaction takes 4-12 hours, which is beneficial for the slow growth and purification of iron phosphate dihydrate crystals, resulting in a more stable phase and better filtration and washing performance.

[0128] refer to Figure 2 As shown, another embodiment of this application provides a lithium extraction slag resource utilization treatment device 1, used in the leaching process of the resource utilization treatment method described above, including:

[0129] An ultrasonic reactor 10 is capable of generating ultrasonic waves and has a first reaction chamber R1. A perforated plate 20 is provided in the first reaction chamber R1 to divide the first reaction chamber R1 into an upper chamber R11 and a lower chamber R12 that are interconnected along the height direction.

[0130] The lower chamber R12 is equipped with an ultrasonic discharge port 11, which is used to output the slurry.

[0131] The upper chamber R11 is equipped with an air supply pipe 30 and a material supply nozzle 40. The air outlet on the air supply pipe 30 is opposite to the material outlet on the material supply nozzle 40. The slurry containing lithium extraction slag and acid transported by the material supply nozzle 40 can come into countercurrent contact with the sulfur dioxide transported by the air supply pipe 30.

[0132] In the embodiments of the present application, the ultrasonic reactor 10 is formed with a first reaction cavity R1. Since the ultrasonic reactor 10 can generate ultrasonic waves, the first reaction cavity R1 is covered by the ultrasonic waves. A circular hole plate 20 is designed at 1 / 3 of the height of the first reaction cavity R1. The hole plate 20 is provided with a plurality of through holes in the height direction, so as to divide the first reaction cavity R1 into an upper chamber R11 and a lower chamber R12 which are in communication with each other in the height direction. The upper chamber R11 provided with a gas supply pipe 30 and a feed injection pipe 40 is a main reaction zone. During the leaching process, the slurry enters the inside of the upper chamber R11 through the feed injection pipe 40 and is injected to the gas outlet on the gas supply pipe 30, and the sulfur dioxide molecules supplied to the gas outlet on the gas supply pipe 30 are fully mixed and reacted in the upper chamber R11 in a convection manner. At the same time, the mixed slurry is continuously collided under the ultrasonic cavitation effect, and tens of thousands of micro-bubbles are generated. These bubbles grow in the negative pressure area formed by the ultrasonic longitudinal propagation, and are quickly closed in the positive pressure area, so as to be compressed and stretched under the alternating positive and negative pressure, and suddenly and sharply burst. At the moment of the bubble burst, high temperature and high pressure are generated locally, and the sulfur dioxide is quickly dispersed and emulsified, so as to strengthen the mass transfer process among the gas, solid and liquid phases. In addition, the ultrasonic waves can continuously generate micro-cracks on the surface of the solid phase, and accelerate the peeling of the solid product film, so as to strengthen the leaching reaction process.

[0133] It should be understood that the upper chamber R11 is the main area of ultrasonic action and the main area of reaction. Part of the slurry in the upper chamber R11 is not fully reacted, and under the push of the high-speed airflow and the pressure difference in the kettle, the slurry enters the lower chamber R12 through the hole plate 20 in irregular motion and forms a strong shock wave, and in the process of contacting the lower chamber R12 or the residual slurry, the slurry rotates, splashes and backflows in multiple directions, so as to continue to strengthen the reaction process and promote the leaching reaction to be more sufficient.

[0134] In some embodiments, the lithium extraction residue resource treatment device 1 further comprises a circulating pump 50, the discharge port of the circulating pump 50 is in communication with the inlet of the feed injection pipe 40; and a leaching tank 60, the leaching tank 60 is formed with a second reaction cavity R2, and the second reaction cavity R2 is provided with a stirrer 70, and the second reaction cavity R2 is provided with a first inlet 61, a second inlet 62, a third inlet 63 and a slurry outlet 64. The third inlet 63 is in communication with the ultrasonic discharge port 11, and is used for receiving the material delivered by the ultrasonic discharge port 11. The slurry outlet 64 is in communication with the inlet of the circulating pump 50. The first inlet 61 is used for supplying lithium extraction residue and / or acid, and the second inlet 62 is used for supplying steam.

[0135] In the embodiment of the present application, the circulating pump 50 is used to provide power to transport the slurry from the leaching tank 60 to the ultrasonic reactor 10 through the feeding nozzle 40 for high-intensity reaction; the second reaction chamber R2 of the leaching tank 60 mainly undertakes the functions of slurry, preheating, storage and preliminary reaction, and the agitator 70 designed inside ensures uniform slurry of the material in the leaching tank 60. By connecting the ultrasonic discharge port 11 of the ultrasonic reactor 10 with the third feeding port 63 and connecting the slurry outlet 64 with the feeding port of the circulating pump 50, the slurry after leaching reaction in the lower chamber R12 can be transported into the leaching tank 60, and then injected into the upper chamber R11 by the circulating pump 50 for circulating leaching until the slurry reaches the leaching endpoint pH value, so as to ensure complete leaching of the lithium extraction residue. The first feeding port 61 of the leaching tank 60 is used to supply the lithium extraction residue and / or acid to supply the reaction raw materials to the second reaction chamber R2, and the second feeding port 62 is used to supply steam to promote the temperature in the second reaction chamber R2.

[0136] It should be understood that the leaching tank 60, the circulating pump 50 and the ultrasonic reactor 10 constitute an external circulation ultrasonic reaction system. In this external circulation ultrasonic intensification mode, slurry is mainly carried out in the second reaction chamber R2, so as to make the ultrasonic action point in the ultrasonic reactor 10 more concentrated, improve the utilization rate of sulfur dioxide gas and the leaching rate of phosphorus and iron, and further improve the utilization rate of phosphorus and iron.

[0137] In the embodiment of the present application, the leaching tank 60 is also provided with a steam coil (not shown), and the second feeding port 62 is connected with the steam coil to pass the steam into the steam coil, so that the heating mode in the leaching tank 60 is steam coil heating. In the leaching process, the lithium extraction residue, water and / or acid liquid are first put into the second reaction chamber R2 according to a certain liquid-solid ratio for slurry, and the slurry is heated to the required value by steam. During the heating process of the slurry, the steam enters the steam coil of the leaching tank 60 from the second feeding port 62, and the slurry is heated under the action of the steam, and then the steam coil leaves the leaching tank 60.

[0138] In some embodiments, the gas supply pipe 30 and the orifice plate 20 are arranged in the height direction, and the feeding nozzle 40 is arranged in the height direction between the gas supply pipe 30 and the orifice plate 20; the gas outlet of the gas supply pipe 30 and the discharge port of the feeding nozzle 40 are arranged in the height direction.

[0139] In the embodiments of the present application, the feeding nozzle 40 can be a straight pipe and is arranged between the hole plate 20 and the gas supply pipe 30. The feeding nozzle 40 is provided with a plurality of discharge ports at the top for slurry injection. Since the feeding nozzle 40 is located between the hole plate 20 and the gas supply pipe 30, the slurry is injected by the feeding nozzle 40 into the upper chamber R11 under the driving of the circulating pump 50 at a specific frequency, and is rapidly atomized under the action of ultrasonic waves. The sulfur dioxide introduced by the gas supply pipe 30 is fully refined, emulsified and rapidly dispersed under the action of ultrasonic waves, so as to promote the SO2 molecules to fully mix with the atomized slurry in the upper chamber R11 in a convection manner to perform a gas-liquid-solid three-phase contact reaction, thereby facilitating the improvement of the leaching rate of the slurry.

[0140] In addition, a negative pressure device can be designed at the bottom of the ultrasonic reactor 10. The negative pressure device can promote the formation of a pressure difference between the upper chamber R11 and the lower chamber R12, so that the partially reacted slurry is fully mixed with the remaining sulfur dioxide molecules under the action of ultrasonic waves in the upper chamber R11, and then enters the lower chamber R12 through the hole plate 20 under the combined action of the internal pressure of the upper chamber R11, the continuously supplied sulfur dioxide gas flow and the pressure difference between the upper chamber R11 and the lower chamber R12, to form a strong shock wave. In the process of contacting with the residual slurry in the lower chamber R12 or the chamber, the slurry rotates, splashes and flows backward in multiple directions, to continue to strengthen the reaction process and further improve the leaching rate of the slurry.

[0141] In some embodiments, the gas outlet of the gas supply pipe 30 is provided with an ultrasonic generator 80 for generating ultrasonic waves.

[0142] In the embodiments of the present application, the ultrasonic generator 80 can be designed in the upper chamber R11 and located at the bottom of the discharge port of the gas supply pipe 30 to generate ultrasonic waves. As an example, the ultrasonic generator 80 can be a vibration wave sheet to generate ultrasonic waves by vibration. Since the ultrasonic generator 80 is located at the bottom of the gas outlet of the gas supply pipe 30, the sulfur dioxide gas is introduced from the gas outlet of the gas supply pipe 30. The vibration frequency of the ultrasonic generator 80 is positively correlated with the gas flow rate. When the vibration frequency of the vibration wave sheet is greater than 20 KHz due to the gradual increase of the gas flow rate, ultrasonic waves of different intensities are generated and propagate longitudinally in different media.

[0143] In some embodiments, a gas flow meter 90 is arranged on the gas supply pipe 30 to obtain the sulfur dioxide flow parameter, so as to facilitate the real-time monitoring and control of the amount of SO2 added, thereby facilitating the control of the reaction process and the end point.

[0144] In some embodiments, a pressure gauge 100 is arranged on the first reaction chamber R1 to obtain the pressure parameter in the first reaction chamber R1, so as to facilitate the monitoring of the pressure in the first reaction chamber R1, and to make the pressure in the first reaction chamber R1 be within the optimal range.

[0145] In some embodiments, valves are respectively arranged on the gas supply pipe 30 and the pipes connected to the ultrasonic discharge port 11, the first feeding port 61, the second feeding port 62, the third feeding port 63 and the slurry outlet 64, so as to control the opening degree of the passages in the pipes, and then control the flow rate and injection timing of the materials such as sulfur dioxide, lithium extraction residue, acid liquid, steam and slurry supplied to the second reaction cavity R2.

[0146] The lithium extraction residue resource processing device 1 provided by the embodiments of the present application can adjust the pressure in the first reaction cavity R1 of the ultrasonic reactor by adjusting the temperature of the slurry, the frequency of the circulating pump 50, the opening degree of the valve 110 on the pipe of the ultrasonic discharge port 11 and the opening degree of the valve 110 on the gas supply pipe 30, so as to accelerate the chemical reaction process on the basis of improving the gas utilization rate through the pressurized leaching process and the simultaneous intensification of the ultrasonic waves.

[0147] It should be understood that the leaching tank in the embodiments of the present application is usually in an atmospheric environment, and the ultrasonic reactor 10 is sealed, and the internal pressure thereof can be adjusted by adjusting the temperature of the slurry, the frequency of the circulating pump 50, the opening degree of the valve 110 on the pipe of the ultrasonic discharge port 11 and the like, so as to facilitate maintaining the constant pressure.

[0148] In practical applications, increasing the temperature of the slurry can increase the saturated vapor pressure of the aqueous solution, thereby increasing the pressure inside the ultrasonic reactor 10; in the ultrasonic reactor 10, the input pressure of the slurry entering the feed nozzle 40 can be effectively increased by adjusting the frequency of the circulating pump 50; under the condition that the flow rate of the slurry at the inlet of the feed nozzle 40 remains unchanged, the flow rate of the slurry entering the second reaction chamber R2 in the ultrasonic reactor 10 can be controlled by adjusting the opening of the valve 110 on the ultrasonic discharge port 11, thereby further adjusting the internal pressure of the ultrasonic reactor 10; in addition, as a closed container, the ultrasonic reactor can regulate the flow rate of sulfur dioxide by adjusting the opening of the valve 110 on the gas supply pipe 30, and according to the Clapeyron equation PV = nRT (P represents pressure, V represents the volume of gas, n represents the amount of substance, T represents absolute temperature, and R represents the gas constant), the pressure will increase; the synergistic effect of the above-mentioned multiple adjustment methods enables the ultrasonic reactor 10 to maintain a constant pressure during the leaching reaction process, thereby improving the utilization rate of gas and accelerating the reaction process in cooperation with the cavitation effect of the ultrasonic reactor 10. In the embodiments of the present application, the higher the frequency of the circulating pump 50, the greater the flow rate of the slurry in the pipe of a specific diameter, and the greater the flow rate, so that the circulating pump 50 can reach its maximum set lift as much as possible. The relationship between lift and pressure is P = pgH (p is density, g is gravitational acceleration, and H is lift), so increasing the frequency of the circulating pump 50 naturally increases the pressure of the slurry. Since the ultrasonic reactor 10 is a closed container, a valve 110 is designed on the pipe of the ultrasonic discharge port 11, which can regulate the flow rate of the slurry delivered to the leaching tank 60. The flow rate of the slurry into the upper chamber R11 is large, but the flow rate of the ultrasonic discharge port 11 is smaller, so the pressure in the first reaction chamber R1 is naturally increased to improve the effective utilization rate of sulfur dioxide gas and accelerate the reaction process in cooperation with the cavitation effect of the ultrasonic reactor 10. The following examples more specifically describe the content disclosed in the present application, and these examples are only used for illustrative purposes, since various modifications and changes within the scope of the disclosure of the present application are obvious to those skilled in the art. Unless otherwise stated, all reagents and raw materials used in the examples are commercially available or synthesized according to conventional methods, and the instruments used in the examples are commercially available.

[0149] Example 1

[0150] 1) Leaching process: 50 kg of waste lithium iron phosphate black powder lithium extraction residue powder was weighed, deionized water was added according to a liquid-solid ratio of 6:1 L / kg for slurry in the leaching tank, concentrated sulfuric acid was added to the leaching tank, and the slurry was heated to 60°C by the heating steam coil. Next, the valve on the slurry outlet pipe at the bottom of the leaching tank was opened, the circulating pump was started, and the pump frequency was set to 40 Hz. The slurry flowed along the external pipe under the drive of the circulating pump, then entered the ultrasonic reactor upper chamber for reaction through the feed pipe. In addition, the flow rate of the slurry was 0.677 m3 The flow rate of the H2S gas is continuously supplied to the gas outlet of the gas supply pipe

[0151] SO2, and the internal pressure of the ultrasonic reactor is maintained at 0.25 MPa, and the external circulation of the lithium extraction residue resource treatment device is realized by the above operation. The slurry in the leaching tank is mechanically stirred for 6 h under constant temperature conditions, and the leaching end point pH is stabilized at about 1.1. After the reaction is completed, the leaching liquid and the leaching residue are obtained by solid-liquid separation, and the total iron concentration in the leaching liquid is 51501.45 mg / L, the ferrous iron concentration is 49214.78 mg / L, the aluminum concentration is 3356.98 mg / L, the copper concentration is 327.23 mg / L, the titanium concentration is 514.58 mg / L, the chromium concentration is 63.55 mg / L, the phosphorus concentration is 25674.71 mg / L, the iron and phosphorus leaching rates are 98.51% and 98.87% respectively, the iron reduction rate is 95.56%, and the effective utilization rate of SO2 in the leaching process is 75%.

[0152] 2) The first purification process: 476.31 g of reduced iron powder (the iron powder addition amount is 1.1 times the theoretical amount) is added to the leaching liquid, concentrated ammonia water is added to adjust the solution end point pH to 1.5, and then stirred at 60°C water bath for 1.0 h. The copper concentration in the copper-removed liquid is reduced to 0.3 mg / L, and the ferrous iron content in the solution is 99.5%.

[0153] 3) The second purification process: In a nitrogen protective atmosphere at 25°C, ammonium bicarbonate as a neutralizing agent is added to the copper-removed liquid to carry out the first precipitation reaction, and the pH value of the solution is adjusted to 3.75. After solid-liquid separation, 270 L of precipitated liquid is obtained. The detection shows that the concentrations of target elements iron and phosphorus in the precipitated liquid are 46213.83 mg / L and 21107.24 mg / L respectively, and the concentrations of impurity elements such as aluminum, titanium and chromium are reduced to 37.5 mg / L, 0.1 mg / L and 8.75 mg / L respectively. The iron and phosphorus loss rates in the second purification process are 8.52% and 9.15% respectively.

[0154] 4) The third purification process: The pH value of the precipitated liquid is adjusted to 2.5, and ion exchange resin is used for selective adsorption to remove aluminum. The detection shows that the aluminum concentration in the aluminum-removed liquid is reduced to 0.1 mg / L, and there is almost no loss of iron and phosphorus in this process.

[0155] 5) Ferric phosphate preparation process: Ferrous phosphate heptahydrate and ammonium dihydrogen phosphate are added to the aluminum-removed solution to adjust the molar ratio of phosphorus to iron to 1:1.05. Mechanical stirring is started to ensure thorough dissolution and mixing. Hydrogen peroxide (1.2 times the theoretical volume) is added dropwise to the mixed solution using a peristaltic pump. Concentrated sulfuric acid is added to control the pH of the reaction at 1.0. The solution is then heated to 95℃ for the second precipitation reaction. Timing is started after the temperature is reached, and the reaction is maintained at this temperature for 6 hours. After the reaction, solid-liquid separation is performed. The resulting ferric phosphate dihydrate precipitate is washed, dried, and then calcined at 550℃ for 4 hours to obtain battery-grade ferric phosphate.

[0156] Example 2

[0157] Unlike Example 1, the leaching temperature in Example 2 was 80°C.

[0158] 1) Leaching process: Weigh 50 kg of lithium extraction residue powder and add deionized water at a liquid-to-solid ratio of 5:1 L / kg in the leaching tank for slurry preparation. Add concentrated sulfuric acid to the leaching tank and heat the slurry to 80°C using a heating steam coil. Next, open the valve on the slurry outlet pipe at the bottom of the leaching tank, start the circulation pump, and set the pump frequency to 45 Hz. Driven by the circulation pump, the slurry flows along the external pipe and then enters the upper chamber of the ultrasonic reactor through the feed pipe to participate in the reaction. Additionally, at 0.952 m... 3 A flow rate of / h is continuously supplied to the outlet of the ultrasonic reactor's gas supply pipe.

[0159] SO2 was used to maintain the internal pressure of the ultrasonic reactor at 0.3 MPa, and the external circulation of the lithium residue resource utilization treatment device was achieved through the above operations. The slurry in the leaching tank was mechanically stirred for 4 hours under constant temperature conditions, and the pH at the leaching endpoint stabilized at around 1.0. After the reaction was completed, solid-liquid separation was performed to obtain the leachate and leaching residue. ICP and chemical titration tests showed that the leaching rates of iron and phosphorus were 99.68% and 99.02%, respectively, the iron reduction rate was 96.67%, and the effective utilization rate of SO2 in the leaching process was 80%.

[0160] 2) First purification process: 431.49g of reduced iron powder (the amount of iron powder added is 1.25 times the theoretical amount) was added to the leachate, concentrated ammonia was added to adjust the final pH of the solution to 1.35, and then the solution was stirred for 1.5h in a water bath at 25℃. After copper removal, the copper concentration in the solution was reduced to 0.48mg / L, and the ferrous iron content in the solution was 99.07%.

[0161] 3) Second purification process: under the protection of nitrogen atmosphere at 40°C, ammonium bicarbonate as neutralizing agent was added into the solution after copper removal to carry out the first precipitation reaction, and the pH value of the solution was adjusted to 3.6. After solid-liquid separation, 225 L of the solution after precipitation was obtained. The concentrations of target elements iron and phosphorus in the solution after precipitation were 56874.62 mg / L and 27184.64 mg / L respectively, and the concentrations of impurity elements such as aluminum, titanium and chromium were reduced to 62.2 mg / L, 0.1 mg / L and 11.75 mg / L respectively. The loss rates of iron and phosphorus in the second purification process were 7.32% and 8.25% respectively.

[0162] 4) Third purification process: the pH value of the solution after precipitation was adjusted to 2.0, and ion exchange resin was used for selective adsorption to remove aluminum. The concentration of aluminum in the solution after aluminum removal was reduced to 0.25 mg / L, and there was almost no loss of iron and phosphorus in this process.

[0163] 5) Preparation of iron phosphate process: ferrous phosphate heptahydrate and ammonium dihydrogen phosphate were added into the solution after aluminum removal to adjust the molar ratio of phosphorus to iron in the solution to 1:1.02, and mechanical stirring was started to make them fully dissolved and mixed. The theoretical amount of 1.2 times of hydrogen peroxide was added into the mixed solution by using a peristaltic pump, concentrated sulfuric acid was added to control the pH value of the reaction to 0.7, and then the solution was heated to 95°C to carry out the second precipitation reaction. After the temperature reached, the reaction was started to be timed and kept constant for 12 h. After the reaction was completed, solid-liquid separation was carried out, and the obtained iron phosphate dihydrate precipitate was washed, dried and calcined at 600°C for 3 h to obtain battery-grade iron phosphate.

[0164] Example 3

[0165] Different from example 1, in example 3, the pH value of the solution in the first precipitation reaction was adjusted to 4.35, and the remaining steps and operations were the same as those in example 1.

[0166] 1) Leaching process: 50 kg of lithium extraction residue powder of waste old lithium iron phosphate black powder was weighed, deionized water was added according to the liquid-solid ratio of 6:1 L / kg for slurry in the leaching tank, concentrated sulfuric acid was added into the leaching tank, and the slurry was heated to 60°C by heating steam coil. Secondly, the valve on the slurry outlet pipeline at the bottom of the leaching tank was opened, the circulating pump was started and the pump frequency was set to 40 Hz, and the slurry flowed along the external pipeline under the drive of the circulating pump, then entered the upper chamber of the ultrasonic reactor through the feeding pipeline to participate in the reaction. In addition, the gas outlet of the gas supply pipe was continuously supplied with 0.677 m 3 / h of air flow rate

[0167] SO2, the internal pressure of the ultrasonic reactor is maintained at 0.25 Mpa, and the external circulation of the lithium extraction residue resource treatment device is realized by the above operation. The slurry in the leaching tank is mechanically stirred for 6 h under constant temperature conditions, and the leaching end point pH is stabilized at about 1.1. After the reaction is completed, solid-liquid separation is performed to obtain a leaching solution and a leaching residue, and the leaching rates of iron and phosphorus are 97.65% and 98.32%, respectively, the iron reduction rate is 94.32%, and the effective utilization rate of SO2 is 75%, which are tested by ICP and chemical titration.

[0168] 2) The first purification process: 582.75 g of reduced iron powder (the amount of iron powder added is 1.1 times the theoretical amount) is added to the leaching solution, concentrated ammonia water is added to adjust the end point pH of the solution to 1.5, and then the solution is stirred in a 60°C water bath for 1.0 h. After detection, the copper concentration in the copper-removed solution is reduced to 0.25 mg / L, and the ferrous content in the solution is 99.5%.

[0169] 3) The second purification process: In a nitrogen atmosphere at 25°C, ammonium bicarbonate, a neutralizing agent, is added to the copper-removed solution to perform a first precipitation reaction, and the pH value of the solution is adjusted to 4.35. After solid-liquid separation, 255 L of precipitated solution is obtained. After detection, the concentrations of target elements iron and phosphorus in the precipitated solution are 27710.81 mg / L and 12714.37 mg / L, respectively, and the concentrations of impurity elements such as aluminum, titanium, and chromium are reduced to 10.46 mg / L, 0.1 mg / L, and 7.64 mg / L, respectively. The loss rates of iron and phosphorus in the second purification process are 45.35% and 55.23%, respectively.

[0170] 4) The third purification process: The precipitated solution is adjusted to a pH value of 2.5, and ion exchange resin is used for selective adsorption to remove aluminum. After detection, the aluminum concentration in the aluminum-removed solution is reduced to 0.36 mg / L, and there is almost no loss of iron and phosphorus in this process.

[0171] 5) The process of preparing iron phosphate: Seven water ferrous phosphate and ammonium dihydrogen phosphate are added to the aluminum-removed solution to adjust the molar ratio of phosphorus to iron in the solution to 1:1.05, and mechanical stirring is started to make them fully dissolved and mixed. The theoretical amount of 1.2 times of hydrogen peroxide is added to the mixed solution by using a peristaltic pump, concentrated sulfuric acid is added to control the reaction pH value to 1.0, and then the solution is heated to 95°C for a second precipitation reaction. After the temperature reaches, the timing starts and the temperature is kept constant for 6 h. After the reaction is completed, solid-liquid separation is performed, and the obtained iron phosphate dihydrate precipitate is washed, dried, and then calcined at 550°C for 4 h to obtain battery-grade iron phosphate.

[0172] Example 4

[0173] Different from example 1, the neutralizing agent for the first precipitation reaction in example 4 is ammonia water.

[0174] 1) Leaching process: 50 kg of waste lithium iron phosphate black powder lithium extraction residue powder was weighed, and deionized water was added in a liquid-solid ratio of 6: 1 L / kg for slurry in a leaching tank. Concentrated sulfuric acid was added to the leaching tank, and the slurry was heated to 60°C by heating the steam coil. Secondly, open the valve on the slurry outlet pipeline at the bottom of the leaching tank, start the circulating pump and set the pump frequency to 40 Hz. The slurry flows along the external pipeline under the drive of the circulating pump, and then enters the upper chamber of the ultrasonic reactor through the feed pipeline to participate in the reaction. In addition, SO2 is continuously introduced into the gas outlet of the gas supply pipe at a flow rate of 0.677 m3 / h, and the internal pressure of the ultrasonic reactor is maintained at 0.25 MPa. Through the above operation, the external circulation of the lithium extraction residue resource treatment device is realized. The slurry in the leaching tank is mechanically stirred for 6 h under constant temperature conditions, and the leaching endpoint pH is stabilized at about 1.1. After the reaction is completed, the leaching liquid and leaching residue are obtained by solid-liquid separation. The leaching rates of iron and phosphorus are 97.21% and 98.24%, respectively, the iron reduction rate is 95.28%, and the effective utilization rate of SO2 in the leaching process is 75%, as tested by ICP and chemical titration. 3 / h is continuously introduced into the gas outlet of the gas supply pipe

[0175] SO2, the internal pressure of the ultrasonic reactor is maintained at 0.25 MPa, and the external circulation of the lithium extraction residue resource treatment device is realized through the above operation. The slurry in the leaching tank is mechanically stirred for 6 h under constant temperature conditions, and the leaching endpoint pH is stabilized at about 1.1. After the reaction is completed, the leaching liquid and leaching residue are obtained by solid-liquid separation. The leaching rates of iron and phosphorus are 97.21% and 98.24%, respectively, the iron reduction rate is 95.28%, and the effective utilization rate of SO2 in the leaching process is 75%, as tested by ICP and chemical titration.

[0176] 2) First purification process: 500.35 g of reduced iron powder (iron powder addition amount is 1.1 times the theoretical amount) is added to the leaching liquid, concentrated ammonia water is added to adjust the solution endpoint pH to 1.5, and then stirred in a 60°C water bath for 1.0 h. After detection, the copper concentration in the copper-removed liquid is reduced to 0.3 mg / L, and the ferrous content in the solution is 99.25%.

[0177] 3) Second purification process: Under the protection of nitrogen atmosphere at 25°C, ammonia water is added to the copper-removed liquid for the first precipitation reaction, and the pH value of the solution is adjusted to 3.75. After solid-liquid separation, 295 L of precipitated liquid is obtained. The target elements iron and phosphorus in the precipitated liquid are 41137.55 mg / L and 17006.58 mg / L, respectively, and the concentrations of impurity elements such as aluminum, titanium and chromium are reduced to 39.74 mg / L, 0.1 mg / L and 14.37 mg / L, respectively. The loss rates of iron and phosphorus in the second purification process are 9.43% and 10.25%, respectively.

[0178] 4) Third purification process: The precipitated liquid is adjusted to a pH value of 2.5, and ion exchange resin is used for selective adsorption to remove aluminum. The aluminum concentration in the aluminum-removed liquid is reduced to 0.1 mg / L, and there is almost no loss of iron and phosphorus in this process.

[0179] 5) Iron phosphate preparation process: After aluminum removal, ferrous phosphate heptahydrate and ammonium dihydrogen phosphate were added to adjust the molar ratio of phosphorus to iron in the solution to 1:1.05, and mechanical stirring was started to fully dissolve and mix. The theoretical amount of 1.2 times of hydrogen peroxide was added to the mixed solution by using a peristaltic pump, concentrated sulfuric acid was added to control the pH value of the reaction to 1.0, and then the solution was heated to 95°C for the second precipitation reaction. After the temperature reached, the reaction was started and kept at 6h. After the reaction was completed, solid-liquid separation was carried out, and the obtained iron phosphate dihydrate precipitate was washed, dried, and calcined at 550°C for 4h to obtain battery-grade iron phosphate.

[0180] Example 5

[0181] 1) Leaching process: 50kg of lithium extraction residue powder was weighed, and slurry was prepared in a leaching tank according to a liquid-solid ratio of 5:1 L / kg of deionized water. Concentrated sulfuric acid was added to the leaching tank, and the slurry was heated to 40°C by heating the steam coil. Next, the valve on the slurry outlet pipe at the bottom of the leaching tank was opened, the circulation pump was started, and the pump frequency was set to 45Hz. The slurry flowed along the external pipeline under the drive of the circulation pump, then entered the upper chamber of the ultrasonic reactor through the feed pipe for reaction. In addition, SO2 was continuously supplied to the gas outlet of the ultrasonic reactor gas supply pipe at a flow rate of 1.02m 3 / h, and the internal pressure of the ultrasonic reactor was maintained at 0.2Mpa. The above operation realized the operation of the external circulation of the lithium extraction residue resource treatment device. The slurry in the leaching tank was mechanically stirred at a constant temperature for 4h, and the leaching endpoint pH was stabilized at about 1.0. After the reaction was completed, the leaching liquid and leaching residue were obtained by solid-liquid separation. The leaching rates of iron and phosphorus were 95.92% and 96.02%, respectively, the iron reduction rate was 89.67%, and the effective utilization rate of SO2 in the leaching process was 70%, as tested by ICP and chemical titration.

[0182] 2) First purification process: 1074.67g of reduced iron powder (the amount of iron powder added was 1.25 times the theoretical amount) was added to the leaching liquid, and concentrated ammonia water was added to adjust the final pH of the solution to 1.35. Then, it was stirred in a 45°C water bath for 1.0h. The copper concentration in the copper removal solution was reduced to 0.68mg / L, and the ferrous content in the solution was 98.97%, as detected.

[0183] 3) Second purification process: under the protection of nitrogen atmosphere at 40°C, ammonium bicarbonate as neutralizing agent was added into the solution after copper removal to carry out the first precipitation reaction, and the pH value of the solution was adjusted to 3.6. After solid-liquid separation, 223 L of the solution after precipitation was obtained. The concentrations of target elements iron and phosphorus in the solution after precipitation were 55743.23 mg / L and 25835.42 mg / L respectively, and the concentrations of impurity elements such as aluminum, titanium and chromium were reduced to 60.12 mg / L, 0.1 mg / L and 12.34 mg / L respectively. The loss rates of iron and phosphorus in the second purification process were 8.11% and 9.05% respectively.

[0184] 4) Third purification process: the pH value of the solution after precipitation was adjusted to 2.0, and ion exchange resin was used for selective adsorption to remove aluminum. The concentration of aluminum in the solution after aluminum removal was reduced to 0.95 mg / L, and there was almost no loss of iron and phosphorus in this process.

[0185] 5) Preparation of iron phosphate process: ammonium ferrous phosphate heptahydrate and ammonium dihydrogen phosphate were added into the solution after aluminum removal to adjust the molar ratio of phosphorus to iron in the solution to 1:1.02, and mechanical stirring was started to make them fully dissolved and mixed. The theoretical amount of 1.2 times of hydrogen peroxide was added into the mixed solution by using a peristaltic pump, concentrated sulfuric acid was added to control the pH value of the reaction to 0.7, and then the solution was heated to 95°C to carry out the second precipitation reaction. After the temperature reached, the reaction was started to be timed and kept constant for 12 h. After the reaction was completed, solid-liquid separation was carried out, and the obtained iron phosphate dihydrate precipitate was washed, dried and calcined at 600°C for 3 h to obtain battery-grade iron phosphate.

[0186] Example 6

[0187] Different from example 1, the pH value of the solution was adjusted to 2.75 in the first precipitation reaction of example 6.

[0188] 1) Leaching process: 50 kg of lithium extraction residue powder of waste lithium iron phosphate black powder was weighed, deionized water was added according to the liquid-solid ratio of 6:1 L / kg for slurry in the leaching tank, concentrated sulfuric acid was added into the leaching tank, and the slurry was heated to 60°C by heating steam coil. Secondly, the valve on the slurry outlet pipeline at the bottom of the leaching tank was opened, the circulating pump was started and the pump frequency was set to 40 Hz, and then the slurry flowed along the external pipeline under the drive of the circulating pump, and then entered the upper chamber of the ultrasonic reactor through the feeding pipeline to participate in the reaction. In addition, the gas outlet of the gas supply pipe was continuously supplied with 0.677 m 3 / h of air flow rate

[0189] SO2, the internal pressure of the ultrasonic reactor is maintained at 0.25 Mpa, and the external circulation of the lithium extraction residue resource treatment device is realized by the above operation. The slurry in the leaching tank is mechanically stirred for 6 h under constant temperature conditions, and the leaching end point pH is stabilized at about 1.1. After the reaction is completed, solid-liquid separation is performed to obtain a leaching solution and a leaching residue, and the leaching rates of iron and phosphorus are 98.15% and 98.46%, respectively, the iron reduction rate is 93.74%, and the effective utilization rate of SO2 in the leaching process is 75%, which are tested by ICP and chemical titration.

[0190] 2) The first purification process: 622.59 g of reduced iron powder (the amount of iron powder added is 1.1 times the theoretical amount) is added to the leaching solution, concentrated ammonia water is added to adjust the solution end point pH to 1.5, then stirred at 60°C water bath conditions for 1.0 h, and the copper concentration in the copper-removed solution is reduced to 0.3 mg / L, and the ferrous content in the solution is 99.5% after detection.

[0191] 3) The second purification process: under the protection of nitrogen atmosphere at 25°C, ammonium bicarbonate as a neutralizing agent is added to the copper-removed solution to carry out the first precipitation reaction, and the pH value of the solution is adjusted to 2.75, and 268 L of precipitated solution and are obtained after solid-liquid separation. The target elements iron and phosphorus in the precipitated solution are 52717.61 mg / L and 24959.09, respectively, and the concentrations of impurity elements such as aluminum, titanium and chromium are reduced to 1507.5 mg / L, 26.95 mg / L and 18.03 mg / L, respectively. The loss rates of iron and phosphorus in the second purification process are 2.399% and 4.15%, respectively.

[0192] 4) The third purification process: the precipitated solution is adjusted to a pH value of 2.5, and ion exchange resin is used for selective adsorption to remove aluminum. The aluminum concentration in the aluminum-removed solution is reduced to 542.5 mg / L after detection, and there is almost no loss of iron and phosphorus in this process.

[0193] 5) The process of preparing iron phosphate: supplement ferrous phosphate heptahydrate and ammonium dihydrogen phosphate to the aluminum-removed solution to adjust the molar ratio of phosphorus element to iron element in the solution to 1:1.05, and open the mechanical stirring to make it fully dissolved and mixed. The theoretical amount of 1.2 times of hydrogen peroxide is added to the mixed solution by using a peristaltic pump, concentrated sulfuric acid is added to control the reaction pH value to 1.0, and then the solution is heated to 95°C for the second precipitation reaction. Start timing after the temperature reaches and constant temperature reaction for 6 h. After the reaction is completed, solid-liquid separation is carried out, the obtained iron phosphate dihydrate precipitate is washed, dried and calcined at 550°C for 4 h to obtain iron phosphate.

[0194] Comparative Example 1

[0195] Different from Example 1, the external circulation ultrasonic reaction system is not used in the leaching process of Comparative Example 1.

[0196] 1) Leaching process: 50 kg of lithium extraction residue powder was weighed, and deionized water was added in a liquid-solid ratio of 6:1 L / kg in a leaching tank for slurry preparation. Concentrated sulfuric acid was then added, and the slurry was heated to 50°C by a heating steam coil. SO2 was continuously introduced into the leaching tank slurry at a flow rate of 1.692 m3 / h, and then mechanically stirred at a constant temperature for 6 h. The leaching endpoint pH stabilized at about 1.1. After the reaction was completed, the leaching liquid and leaching residue were separated by solid-liquid separation. The total iron concentration in the leaching liquid was 48354.86 mg / L, the ferrous iron concentration was 31628.91 mg / L, the aluminum concentration was 3125.54 mg / L, the copper concentration was 331.35 mg / L, the titanium concentration was 472.63 mg / L, the chromium concentration was 54.75 mg / L, the phosphorus concentration was 23599.46 mg / L, the iron and phosphorus leaching rates were 93.34% and 92.25%, respectively, the iron reduction rate was 65.41%, and the effective utilization rate of SO2 was 30%. 3 / h was continuously introduced into the leaching tank slurry, and then mechanically stirred at a constant temperature for 6 h, with the leaching endpoint pH stabilized at about 1.1. After the reaction was completed, the leaching liquid and leaching residue were separated by solid-liquid separation. The total iron concentration in the leaching liquid was 48354.86 mg / L, the ferrous iron concentration was 31628.91 mg / L, the aluminum concentration was 3125.54 mg / L, the copper concentration was 331.35 mg / L, the titanium concentration was 472.63 mg / L, the chromium concentration was 54.75 mg / L, the phosphorus concentration was 23599.46 mg / L, the iron and phosphorus leaching rates were 93.34% and 92.25%, respectively, the iron reduction rate was 65.41%, and the effective utilization rate of SO2 was 30%.

[0197] 2) First purification process: 2858.53 g of reduced iron powder (iron powder added amount was 1.1 times the theoretical amount) was added to the leaching liquid, and concentrated ammonia water was added to adjust the solution endpoint pH to 1.5. Then, it was stirred in a 60°C water bath for 1.0 h. After detection, the copper concentration in the copper-removed liquid was reduced to 0.16 mg / L, and the ferrous iron content in the solution was 99.28%.

[0198] 3) Second purification process: In a nitrogen atmosphere at 25°C, ammonium bicarbonate was added to the copper-removed liquid to perform the first precipitation reaction, and the solution pH was adjusted to 3.75. After solid-liquid separation, 272 L of precipitated liquid was obtained. After detection, the target element iron and phosphorus concentrations in the precipitated liquid were 52519.37 mg / L and 18719.51 mg / L, respectively, and the impurity element concentrations of aluminum, titanium, and chromium were reduced to 41.75 mg / L, 0.05 mg / L, and 12.23 mg / L, respectively. The iron and phosphorus loss rates in the second purification process were 9.32% and 10.85%, respectively.

[0199] 4) Third purification process: The precipitated liquid was adjusted to a pH of 2.5, and ion exchange resin was used for selective adsorption to remove aluminum. After detection, the aluminum concentration in the aluminum-removed liquid was reduced to 0.65 mg / L, and there was almost no loss of iron and phosphorus in this process.

[0200] 5) Iron phosphate preparation process: FeSO4.7H2O and NH4H2PO4 were added to the solution after aluminum removal to adjust the molar ratio of phosphorus to iron in the solution to 1:1.05, and mechanical stirring was started to fully dissolve and mix. The theoretical amount of 1.2 times of hydrogen peroxide was added to the mixed solution using a peristaltic pump, concentrated sulfuric acid was added to control the reaction pH to 1.0, and then the solution was heated to 95°C for the second precipitation reaction. After the temperature reached, the timer started and the temperature was kept constant for 6h. After the reaction was completed, solid-liquid separation was carried out, and the obtained FePO4.2H2O precipitate was washed, dried and calcined at 550°C for 4h to obtain battery-grade iron phosphate.

[0201] Comparative Example 2

[0202] Unlike Example 1, Comparative Example 2 did not add SO2 during the leaching process.

[0203] 1) Leaching process: 50kg of lithium extraction residue powder was weighed, deionized water was added according to the liquid-solid ratio of 6:1 L / kg for slurry in the leaching tank, then concentrated sulfuric acid was added, and the slurry was heated to 60°C by heating the steam coil. Secondly, open the valve on the slurry outlet pipe at the bottom of the leaching tank, start the circulating pump and set the pump frequency to 40Hz, the slurry flows along the external pipeline under the drive of the circulating pump, then enters the ultrasonic reactor upper chamber through the feed pipe to participate in the reaction. The slurry in the leaching tank was mechanically stirred for 6h under constant temperature conditions, and the leaching endpoint pH was stabilized at about 1.1. After the reaction was completed, solid-liquid separation was carried out to obtain leaching liquid and leaching residue, and ICP and chemical titration test showed that the iron concentration in the leaching liquid was 10121.43mg / L, the aluminum concentration was 2750.36mg / L, the copper concentration was 312.58mg / L, the titanium concentration was 474.24mg / L, the chromium concentration was 51.76mg / L, the phosphorus concentration was 6082.83mg / L, the iron and phosphorus leaching rates were 19.24% and 23.47% respectively, and the iron in the solution almost existed in the form of trivalent iron.

[0204] 2) First purification process: 1746.68g of reduced iron powder (iron powder added amount is 1.1 times of the theoretical amount) was added to the leaching liquid, concentrated ammonia was added to adjust the solution endpoint pH to 1.5, then stirred at 60°C water bath for 1.0h, and the copper concentration in the copper removal solution was reduced to 0.32mg / L, and the ferrous content in the solution was 99.35%.

[0205] 3) The second purification process: under the protection of nitrogen atmosphere at 25°C, ammonium bicarbonate as a neutralizing agent was added to the copper-removed solution to carry out the first precipitation reaction, and the pH value of the solution was adjusted to 3.75. After solid-liquid separation, 275 L of precipitated solution was obtained. The concentrations of target elements iron and phosphorus in the precipitated solution were 14138.54 mg / L and 5096.2 mg / L respectively, and the concentrations of impurity elements such as aluminum, titanium and chromium were reduced to 32.35 mg / L, 0.1 mg / L and 15.36 mg / L respectively. The loss rates of iron and phosphorus in the second purification process were 6.58% and 7.34% respectively.

[0206] 4) The third purification process: the pH value of the precipitated solution was adjusted to 2.5, and ion exchange resin was used for selective adsorption to remove aluminum. The concentration of aluminum in the aluminum-removed solution was reduced to 0.48 mg / L, and there was almost no loss of iron and phosphorus in this process.

[0207] 5) The process of preparing iron phosphate: ammonium ferrous phosphate heptahydrate and ammonium dihydrogen phosphate were added to the precipitated solution to adjust the molar ratio of phosphorus to iron in the solution to 1:1.05, and mechanical stirring was started to make them fully dissolved and mixed. The theoretical amount of 1.2 times of hydrogen peroxide was added to the mixed solution by using a peristaltic pump, concentrated sulfuric acid was added to control the pH value of the reaction to 1.0, and then the solution was heated to 95°C to carry out the second precipitation reaction. The temperature was recorded after reaching the temperature, and the constant temperature reaction was carried out for 6 hours. After the reaction was completed, solid-liquid separation was carried out, and the obtained iron phosphate dihydrate precipitate was washed, dried and calcined to obtain battery-grade iron phosphate.

[0208] It should be noted that the SO2 effective utilization rate in the present application = actual amount introduced / theoretical amount introduced. The loss of element M (%) = (C1*V1-C2 / V2) / (C1*V1)*100, wherein M = iron or phosphorus, C1 and C2 are the concentrations of iron before and after the second purification process, and V1 and V2 are the volumes of the material before and after the second purification process. The iron reduction rate in the leaching process = the amount of ferrous iron obtained / the total amount of iron.

[0209] It should be noted that the lithium extraction residue used in the above examples and comparative examples is the lithium extraction residue of waste lithium iron phosphate black powder, and the main chemical components are shown in Table 1:

[0210] Table 1, main chemical components of lithium extraction residue (wt.%)

[0211]

[0212] In order to verify the advantages of the embodiments of the present application, the chemical components of the battery-grade iron phosphate prepared in Examples 1 and 2 were tested and counted, and compared with the battery-grade iron phosphate standard HG / T4701-2021 as shown in Table 2:

[0213] Table 2, comparison table of chemical components of battery-grade iron phosphate

[0214]

[0215] In combination with Tables 1-2 above, the lithium extraction residue resource processing method of embodiments 1 and 2 can reduce the consumption of acid and alkali reagents and other auxiliary materials in the lithium extraction residue recovery process of waste lithium iron phosphate batteries, effectively reduce production costs, have higher production capacity, reduce iron and phosphorus loss, and the battery-grade iron phosphate prepared has high purity, which can meet the requirements of battery-grade iron phosphate standard HG / T 4701-2021.

[0216] Compared with Example 1 and Comparative Example 1, Comparative Example 1 does not introduce ultrasonic wave for leaching reaction, but only uses mechanical stirring for leaching, which is difficult to achieve uniform dispersion and emulsification of SO2, resulting in low utilization rate of SO2 in the reduction acid leaching process, which greatly reduces the iron and phosphorus leaching rate and the initial reduction rate of iron, and increases the consumption of reduced iron powder in the subsequent first purification process, and increases the auxiliary material cost of the whole process. Compared with Example 1 and Comparative Example 2, Comparative Example 2 does not add SO2 reducing agent in the leaching process, which sharply reduces the iron and phosphorus leaching rate in the leaching process and the iron in the solution exists in the form of Fe 3+ , which greatly increases the consumption of reduced iron powder and auxiliary materials.

[0217] Further verification is made that the lithium extraction residue is contacted with sulfur dioxide and acid solution for leaching reaction in the ultrasonic environment, and the ultrasonic wave can achieve uniform dispersion and emulsification of SO2. On the one hand, in the sulfuric acid system, SO2 is used as a reducing agent for acid leaching reaction, which can achieve efficient leaching and preliminary reduction of Fe 3+ without introducing other impurity elements, which is beneficial to the subsequent impurity removal process; on the other hand, the reaction of SO2 and H2O generates more H2SO3 molecules in the solution, and the ionization of H+ gradually increases the acidity of the solution, which reduces the consumption of concentrated sulfuric acid in the leaching process, ensures the leaching effect of the lithium extraction residue, reduces the consumption of reduced iron powder and neutralizing agent in the impurity removal process, and reduces the production cost of the whole process.

[0218] The technical features described above can be combined in any way. Although all possible combinations of the technical features are not described, any combination of the technical features should be considered to be covered by the present description, as long as such a combination does not contradict.

[0219] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for resourceful treatment of lithium extraction residue, characterized in that, The method comprises the following steps: An immersion process, in which the lithium extraction residue is contacted with sulfur dioxide and acid liquor in an ultrasonic environment to perform an immersion reaction, and an immersion liquor and an immersion residue are obtained through solid-liquid separation; A first purification process, in which the immersion liquor is contacted with iron powder to perform a copper removal reaction, and a copper-removed liquor and a copper removal residue are obtained through solid-liquid separation; A second purification process, in which the copper-removed liquor is contacted with a neutralizing agent to perform a first precipitation reaction, and a precipitation-removed liquor and a precipitation residue are obtained through solid-liquid separation.

2. The method of claim 1, wherein, The immersion process comprises: The lithium extraction residue is mixed with water and / or acid liquor to obtain a slurry; The slurry is contacted with sulfur dioxide in an ultrasonic environment to perform an immersion reaction, and an immersion liquor and an immersion residue are obtained through solid-liquid separation.

3. The method according to claim 2, wherein During the contacting of the slurry with sulfur dioxide, the slurry is sprayed towards the sulfur dioxide in a direction opposite to the airflow direction of the sulfur dioxide; and / or The contacting of the slurry with sulfur dioxide in an ultrasonic environment to perform an immersion reaction comprises: the slurry is contacted with sulfur dioxide in an ultrasonic environment to perform an immersion, and the slurry obtained by the immersion is repeatedly subjected to the immersion until the slurry reaches an immersion end point pH value.

4. The resourcing processing method according to claim 2 or 3, characterized in that, The immersion process satisfies at least one of the following conditions: A. The liquid-solid ratio during the mixing of the lithium extraction residue with water and / or acid liquor to obtain the slurry is 4-12 mL / g; B. The acid liquor comprises at least one of sulfuric acid solution, hydrochloric acid solution and phosphoric acid solution; C. The immersion reaction temperature is 25-95°C; optionally, 40-80°C; D. The immersion reaction time is 2-6 h; E. The immersion reaction end point pH value is 0.8-1.5; F. The immersion reaction pressure is 0.2-0.3 MPa; G. the flow rate of the sulfur dioxide is 0.5-2.5 m 3 / h; H. The immersion residue is subjected to stirring washing to obtain a stirring washing liquor and a stirring washing residue, and the stirring washing liquor is reused for the immersion reaction with the lithium extraction residue.

5. The method of claim 1, wherein, Further comprising: A third purification process, in which the precipitation-removed liquor is adjusted to a target pH value, and an ion exchange resin is used to selectively adsorb and remove aluminum from the precipitation-removed liquor after the adjustment of the pH value, to obtain an aluminum-removed liquor; A ferrophosphorus preparation process, in which an oxidizing agent is added to the aluminum-removed liquor to perform a second precipitation reaction, to obtain ferrophosphorus dihydrate precipitation, and ferrophosphorus is obtained through post-processing.

6. The method of claim 5, wherein, At least one of the following conditions is satisfied: I. The iron powder addition amount in the first purification process is 1.0-2.0 times the total molar amount of copper ions and iron ions in the immersion liquor; J. The pH value of the copper removal reaction is 0.8-2.0; K. The temperature of the copper removal reaction is 25-90°C; L. The time of the copper removal reaction is 0.25-2 h; M. The neutralizing agent in the second purification process comprises at least one of monobasic ammonium phosphate, dibasic ammonium phosphate, phosphoric acid ammonia trihydrate, trisodium phosphate, ammonium carbonate, ammonium bicarbonate and ammonia water; optionally, the neutralizing agent is ammonium carbonate or ammonium bicarbonate solid; N. The pH value of the first precipitation reaction is 2.5-6.0, optionally 3.5-4.0; O. The temperature of the first precipitation reaction is 25-80°C; P. The copper-removed liquid is contacted with a neutralizing agent to carry out a first precipitation reaction under a non-oxidizing atmosphere, which includes at least one of nitrogen, argon, and helium. Q. The target pH value of the third purification process is 1-2.5; R. The ion exchange resin in the third purification process is a chelating resin. S. In the process of producing ferric phosphate, before adding the oxidant, the molar ratio of phosphorus to iron in the dealuminated liquid is adjusted to 1.02-1.

2. T. The oxidant includes hydrogen peroxide solution; optionally, the amount of oxidant added is 1.0-1.5 times the theoretical amount of oxidant required to convert all ferrous ions in the ion-exchange solution into ferric ions. U, the pH value of the second precipitation reaction is 0.6-1.2; V. The temperature of the second precipitation reaction is 80-120℃; W. The second precipitation reaction takes 4-12 hours.

7. A device for resourceful treatment of lithium extraction residue, characterized in that, The leaching step in the resource recovery process according to any one of claims 1 to 6 includes: An ultrasonic reactor (10) is capable of generating ultrasonic waves and has a first reaction chamber (R1). A perforated plate (20) is provided in the first reaction chamber (R1) to divide the first reaction chamber (R1) into an upper chamber (R11) and a lower chamber (R12) that are interconnected along the height direction. The lower chamber (R12) is provided with an ultrasonic discharge port (11); The upper chamber (R11) is provided with an air supply pipe (30) and a material supply nozzle (40). The air outlet on the air supply pipe (30) is opposite to the material outlet of the material supply nozzle (40). The slurry containing lithium extraction residue and acid transported by the material supply nozzle (40) can come into countercurrent contact with the sulfur dioxide transported by the air supply pipe (30).

8. The lithium extraction residue resource processing device according to claim 7, characterized in that, Also includes: A circulating pump (50) is connected to the inlet of the feeding nozzle (40). The leaching tank (60) has a second reaction chamber (R2) and a stirrer (70) is provided in the second reaction chamber (R2). The second reaction chamber is provided with a first feed inlet (61), a second feed inlet (62), a third feed inlet (63) and a slurry outlet (64). The third feed port (63) is connected to the ultrasonic discharge port (11) and is used to receive the material conveyed by the ultrasonic discharge port (11); The slurry outlet (64) is connected to the feed inlet of the circulating pump (50); The first feed inlet (61) is used to feed lithium extraction slag and / or acid, and the second feed inlet (62) is used to feed steam.

9. The lithium extraction slag resource utilization device according to claim 7 or 8, characterized in that, The air supply pipe (30) and the orifice plate (20) are spaced apart along the height direction, and the material supply nozzle (40) is spaced apart between the air supply pipe (30) and the orifice plate (20) along the height direction; The air outlet on the air supply pipe (30) and the material outlet of the material supply nozzle (40) are arranged opposite each other in the height direction.

10. The lithium extraction residue resource treatment device according to claim 7 or 8, characterized in that, an ultrasonic generator (80) is arranged at the gas outlet of the gas supply pipe (30) for generating ultrasonic waves; and / or a gas flow meter (90) is arranged on the gas supply pipe (30) for obtaining a sulfur dioxide flow parameter; and / or a pressure gauge (100) is arranged on the first reaction cavity (R1) for obtaining a first reaction cavity internal pressure parameter.

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