Method for selectively recovering lithium through acid leaching of organic peroxy acid and application

Abstract

The invention provides a method for selectively recovering lithium by utilizing acid leaching of organic peroxy acid and application. The method comprises the following steps: step 1, carrying out heat treatment on lithium iron phosphate powder in an inert gas atmosphere to remove impurities; 2, uniformly mixing organic peroxy acid with water to obtain an organic peroxy acid solution, adding lithium iron phosphate powder into the organic peroxy acid solution, and reacting to obtain a lithium-rich solution and ferrophosphorus slag; 3, precipitating the lithium-rich liquid twice to obtain lithium carbonate precipitate and lithium phosphate precipitate respectively; and 4, cleaning, drying and crushing the lithium carbonate precipitate and the lithium phosphate precipitate obtained in the step 3 to obtain a finished lithium carbonate product and a finished lithium phosphate product. An oxidizing agent and inorganic acid commonly used in the acid leaching process are replaced with organic peroxy acid, the lithium element in the waste lithium iron phosphate material is selectively recycled, and consumption of excessive acid and alkali and a large amount of water in the leaching process is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery recovery, and specifically relates to a method and application of selectively recovering lithium by using organic peracid leaching. Background Art

[0002] With the rapid development of technology and the support of national policies, the electric vehicle market has expanded rapidly in recent years. The service life of lithium iron phosphate batteries is generally 5-8 years, so a large number of waste batteries will be retired and recycled. Due to the rapid growth of the lithium-ion battery market, lithium resources are very scarce. Since scrapped lithium iron phosphate batteries are rich in lithium resources, the effective recycling of waste lithium iron phosphate batteries can not only significantly alleviate the shortage of lithium resources, but also generate considerable economic benefits. The recycling of waste batteries also has significant environmental benefits.

[0003] At present, the methods for recycling lithium iron phosphate include pyrometallurgy, hydrometallurgy and direct recovery. The pyrometallurgical technology is simple, but the treatment route is long, it is easy to produce harmful gases, the overall recovery rate of valuable metals is low, and the energy consumption is very high. The direct recovery process is relatively green and environmentally friendly, but the recycled materials often have more impurities, poor electrochemical properties, and uneven quality. Traditional hydrometallurgy uses high-concentration inorganic acids, such as HCl, H2SO4, H3PO4, etc., to achieve lithium and iron leaching, but this leaching process consumes too much acid, produces a large amount of wastewater, and causes secondary pollution. There will be problems such as excessive acid consumption and difficulty in wastewater treatment. In order to achieve high-value utilization of iron, it is necessary to add oxidants such as oxygen (O2) and hydrogen peroxide (H2O2) to oxidize Fe2+ to Fe3+ and precipitate. In order to simplify the recovery process and reduce costs, the selective leaching of lithium has become a research hotspot in recent years. Summary of the invention

[0004] The present invention provides a method and application of selectively recovering lithium by acid leaching using organic peroxyacid, wherein an organic peroxyacid is used to replace the oxidant and inorganic acid commonly used in the acid leaching process to selectively recover lithium from waste lithium iron phosphate materials, thereby avoiding the consumption of excessive acid, alkali and a large amount of water in the leaching process. The specific scheme is as follows:

[0005] According to a first aspect of the present invention, one or more embodiments of the present application provide a method for selectively recovering lithium by acid leaching using an organic peroxy acid, comprising:

[0006] Step 1, heat treating lithium iron phosphate powder in an inert gas atmosphere to remove impurities;

[0007] Step 2, uniformly mixing an organic peracid with water to obtain an organic peracid solution, adding lithium iron phosphate powder to the organic peracid solution, and obtaining a lithium-rich solution and ferrophosphorus slag after reaction;

[0008] Step 3, subjecting the lithium-rich solution to two precipitations to obtain lithium carbonate precipitation and lithium phosphate precipitation respectively;

[0009] Step 4: Wash, dry and crush the lithium carbonate precipitate and lithium phosphate precipitate obtained in step 3 to obtain lithium carbonate finished products and lithium phosphate finished products.

[0010] According to the above technical solution of the present invention, the following improvements can also be made:

[0011] Wherein, the heat treatment in step 1 comprises the following steps:

[0012] The starting temperature is set at 20°C, the heating rate is 10°C / min, the heating time is set at 45-60min, after heating to 500-550°C, it is kept for 120-150min and then naturally cooled to room temperature, and the lithium iron phosphate powder after impurity removal is taken out.

[0013] The organic peroxy acid in step 2 includes an acid containing a peroxy group and having the properties of a peroxide and an acid, and an aromatic diperoxy acid having stability and oxidizability.

[0014] The water mixed with the organic peracid is deionized water. In the organic peracid solution, the volume ratio of the organic peracid to water is 1:5 to 1:10. The solid-liquid ratio of the lithium iron phosphate powder to the organic peracid solution is 1:1 to 1:10.

[0015] After lithium iron phosphate powder is added to the organic peracid and aqueous solution, the decomposition rate of the organic peracid is accelerated by catalysis; the catalysis method includes at least one of short-wave irradiation, heating, and increasing the concentration of metal ions.

[0016] Wherein, the reaction time of the lithium iron phosphate powder and the organic peracid solution is 2 to 8 hours.

[0017] Wherein, the reaction temperature of the lithium iron phosphate powder and the organic peracid solution is 80-180°C.

[0018] Wherein, in step 3, the two precipitations respectively include the following steps:

[0019] A primary precipitation is performed, wherein a precipitant 1 is added to the lithium-rich solution, wherein the precipitant 1 is a sodium carbonate solution mixed with sodium carbonate and deionized water, wherein the concentration of the sodium carbonate solution is 10-40%, and the amount of the precipitant 1 added is obtained based on the lithium ion concentration in the lithium-rich solution, the precipitation temperature is 60-100° C., and the precipitation time is 30-120 min. After the precipitation, a lithium carbonate precipitate and a residual solution are obtained;

[0020] Secondary precipitation, adding precipitant 2 to the remaining solution, precipitant 2 is sodium phosphate dodecahydrate, the theoretical addition amount of precipitant 2 is obtained based on the lithium ion concentration of the remaining solution, and the actual addition amount is 1 to 1.5 times of the theoretical addition amount, and lithium phosphate precipitate is obtained after standing.

[0021] The obtained lithium carbonate precipitate and lithium phosphate precipitate are respectively washed with 100° C. ionized water, vacuum dried at 80° C., and crushed to obtain lithium carbonate finished products and lithium phosphate finished products.

[0022] According to the second aspect of the present invention, one or more embodiments in the present application provide an application of a method for selectively recovering lithium by acid leaching using an organic peracid, wherein any of the above methods for selectively recovering lithium by acid leaching using an organic peracid is used to recover lithium elements in waste lithium iron phosphate positive electrode materials.

[0023] The beneficial effects of the present invention are:

[0024] Compared with the prior art, the present invention provides a method and application of selectively recovering lithium by acid leaching using organic peroxy acid, using peroxy organic acid instead of traditional high-concentration inorganic acid as a leaching agent to leach lithium iron phosphate materials. Organic acid has the advantages of being environmentally friendly, recyclable, and easy to degrade. In the acid leaching process, peroxy organic acid-peracetic acid (chemical formula: CH 3 COOOH decomposes upon heating to generate acetic acid (CH 3 COOH) and oxygen (O 2 ), and the metal ions in the solution will accelerate the decomposition. In addition, the decomposition of peracetic acid can be accelerated by short-wave radiation. The decomposition equation is 2CH 3 COOOH==2CH 3 COOH+O 2。 The oxygen produced by decomposition (O 2 ) as an oxidant, Fe 2+ Oxidized to Fe 3+ During the acid leaching process, peracetic acid plays both an acidic and oxidizing role, which simplifies the acid leaching process.

[0025] The first precipitation generates lithium carbonate precipitation, which recovers 80-87% of the lithium element in the lithium iron phosphate. The second precipitation generates lithium phosphate precipitation, which recovers 10-13% of the lithium element in the lithium iron phosphate, so that the recovery rate of the lithium element in the lithium iron phosphate reaches more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic flow chart of a method for selectively recovering lithium by acid leaching using organic peroxyacid provided by the present invention;

[0027] Figure 2This is the XRD diagram of lithium carbonate recovered from waste lithium iron phosphate in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0029] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present application should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in one or more embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Including" or "including" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] As attached Figure 1-Figure 2 As shown, this embodiment provides a method for selectively recovering lithium by acid leaching using organic peroxyacid, comprising the following steps:

[0031] (a1) waste lithium iron phosphate powder is placed in a quartz boat, subjected to high-temperature heat treatment in a tube furnace under an inert gas atmosphere, and the impurity-free lithium iron phosphate powder is taken out after natural cooling;

[0032] (a2) after uniformly mixing an organic peracid and deionized water in proportion, adding the impurity-removed lithium iron phosphate powder obtained in step (a1), stirring evenly, reacting for a certain period of time, and filtering to obtain a lithium-rich solution and ferrophosphorus slag;

[0033] (a3) precipitating the lithium-rich solution obtained in step (a2) with a sodium carbonate solution to obtain a lithium carbonate precipitate; and precipitating it with sodium phosphate dodecahydrate to obtain a lithium phosphate precipitate;

[0034] (a4) precipitating the lithium carbonate and lithium phosphate obtained in step (a3), and obtaining finished lithium carbonate and finished lithium phosphate products by washing, drying and crushing.

[0035] The method for selectively recovering lithium from waste lithium iron phosphate uses a peroxy organic acid having the properties of peroxide and acid to selectively leach lithium elements from the waste lithium iron phosphate, thereby simplifying the leaching process and reducing secondary pollution; and precipitating the lithium-rich liquid twice to increase the recovery rate of lithium ions.

[0036] Wherein, the temperature of the heat treatment in step (a1) is 400-600°C; preferably 500-550°C. The organic peroxy acid in step (a2) includes at least one of the acids containing a peroxy group (-OO-) and having the properties of a peroxide and an acid, such as peroxyformic acid, peroxyacetic acid, peroxypropionic acid, and peroxyisobutyric acid. The organic peroxy acid in step (a2) also includes aromatic diperoxy acids with higher stability and stronger oxidizing properties, such as 2,2'-peroxybiphenyl dicarboxylic acid, phthalic acid, and binaphthyl diperoxy acid. The ratio of the organic peroxy acid to deionized water in step (a2) is 1:1-1:10; preferably 1:5-1:10. After the organic peroxy acid in step (a2) is mixed with deionized water, the time for adding lithium iron phosphate powder is 1-10 minutes; preferably 1-5 minutes. The reaction time of the waste lithium iron phosphate powder and the organic peroxy acid solution in step (a2) is 2 to 8 hours, preferably 3 to 5 hours. The reaction temperature of the waste lithium iron phosphate powder and the organic peroxy acid solution in step (a2) is 80 to 180°C, preferably 120 to 150°C. The concentration of the solution of the precipitant sodium carbonate and deionized water in the first precipitation in step (a3) ​​is 10 to 40%, preferably 20 to 25%. The reaction temperature of the first precipitation in step (a3) ​​is 60 to 100°C, preferably 80 to 90°C. The reaction time of the first precipitation in step (a3) ​​is 30 to 120 minutes, preferably 60 to 80 minutes. The dosage of the precipitant sodium phosphate dodecahydrate in the second precipitation in step (a3) ​​is 1 to 1.5 times the theoretical amount, preferably 1.1 to 1.25 times the theoretical amount.

[0037] This embodiment uses peroxy organic acid instead of traditional high-concentration inorganic acid as a leaching agent to leach lithium iron phosphate materials. Organic acid has the advantages of being environmentally friendly, recyclable, and easy to degrade. During the acid leaching process, peroxy organic acid-peracetic acid (chemical formula: CH 3 COOOH decomposes upon heating to generate acetic acid (CH 3 COOH) and oxygen (O 2 ), and the metal ions in the solution will accelerate the decomposition. In addition, the decomposition of peracetic acid can be accelerated by short-wave radiation. The decomposition equation is 2CH 3 COOOH==2CH 3 COOH+O 2。 The oxygen produced by decomposition (O 2 ) as an oxidant, Fe2+ Oxidized to Fe 3+ And precipitate. Peracetic acid plays both acidic and oxidative roles during the acid leaching process, simplifying the acid leaching process. The first precipitation generates lithium carbonate precipitation, recovering 80-87% of the lithium element in lithium iron phosphate, and the second precipitation generates lithium phosphate precipitation, recovering 10-13% of the lithium element in lithium iron phosphate, making the recovery rate of lithium in lithium iron phosphate reach more than 90%.

[0038] In order to more intuitively describe the technical solutions and technical effects of the embodiments, the following two embodiments are used for further explanation:

[0039] Embodiment 1

[0040] like Figure 1 As shown, Figure 1 The present invention provides a method for selectively recovering lithium by acid leaching using organic peroxyacid; the specific steps are as follows:

[0041] (A1) 120 g of waste lithium iron phosphate positive electrode material powder was placed in a quartz boat, and subjected to high-temperature heat treatment in a tube furnace under a nitrogen atmosphere. The heat treatment temperature step was set to a starting temperature of 20° C., a heating rate of 10° C. / min, a heating time of 53 min, and the temperature was raised to 550° C., maintained for 120 min, and then naturally cooled to room temperature, and the lithium iron phosphate powder after impurity removal was taken out;

[0042] (A2) Use a measuring cylinder to measure 250 ml of peracetic acid, slowly pour it into a beaker containing 250 ml of deionized water, mix it evenly with a heated magnetic stirrer, add 100 g of lithium iron phosphate powder after impurities are removed, set the temperature to 150° C., stir evenly, and set the stirring time to 3 h;

[0043] (A3) After the reaction is completed, filtering is performed by a circulating water vacuum pump to separate the solid and liquid to obtain a lithium-rich solution and ferrophosphorus slag; the lithium ion concentration in the lithium-rich solution is tested by ICP-OES to calculate the required amount of precipitant sodium carbonate;

[0044] (A4) weighing sodium carbonate solid, preparing a 25% sodium carbonate solution with deionized water, slowly pouring the 25% sodium carbonate solution into the lithium-rich solution, aging to obtain lithium carbonate precipitate, filtering with a circulating water vacuum pump, and separating the solid from the liquid to obtain lithium carbonate solid and a filtrate;

[0045] (A5) testing the lithium ion concentration in the filtrate by ICP-OES and calculating the required amount of the precipitant sodium phosphate dodecahydrate; slowly pouring the sodium phosphate dodecahydrate into the filtrate and letting it stand for a period of time to obtain lithium phosphate precipitation;

[0046] (A6) The obtained lithium carbonate and lithium phosphate precipitates are washed with 100° C. ionized water, dried in a vacuum oven at 80° C., and crushed to obtain lithium carbonate products and lithium phosphate products.

[0047] Embodiment 2

[0048] like Figure 2 As shown, Figure 2 This is the XRD diagram of lithium carbonate recovered from waste lithium iron phosphate in Example 1 of the present invention. The specific steps are as follows:

[0049] (B1) 120 g of waste lithium iron phosphate positive electrode material powder was placed in a quartz boat and subjected to high-temperature heat treatment in a tube furnace under a nitrogen atmosphere. The heat treatment temperature program was set to a starting temperature of 20° C., a heating rate of 10° C. / min, a heating time of 48 min, and the temperature was raised to 500° C., maintained for 150 min, and then naturally cooled to room temperature, and the lithium iron phosphate powder after impurity removal was taken out;

[0050] (B2) Use a measuring cylinder to measure 250 ml of peracetic acid, slowly pour it into a beaker containing 500 ml of deionized water, mix it evenly with a heated magnetic stirrer, add 100 g of lithium iron phosphate powder after impurities are removed, set the temperature to 120° C., stir evenly, and set the stirring time to 4 h;

[0051] (B3) After the reaction is completed, filtering by a circulating water vacuum pump to separate the solid and liquid to obtain a lithium-rich solution and ferrophosphorus slag; testing the lithium ion concentration in the lithium-rich solution by ICP-OES to calculate the required amount of precipitant sodium carbonate;

[0052] (B4) weighing sodium carbonate solid, preparing a 30% sodium carbonate solution with deionized water, slowly pouring the 30% sodium carbonate solution into the lithium-rich solution, and obtaining lithium carbonate precipitate after aging, and filtering with a circulating water vacuum pump to obtain lithium carbonate solid and filtrate by solid-liquid separation;

[0053] (B5) testing the lithium ion concentration in the filtrate by ICP-OES and calculating the required amount of the precipitant sodium phosphate dodecahydrate; slowly pouring the sodium phosphate dodecahydrate into the filtrate and letting it stand for a period of time to obtain lithium phosphate precipitation;

[0054] (B6) The obtained lithium carbonate and lithium phosphate precipitates are washed with 100° C. ionized water, dried in a vacuum drying oven at 80° C., and crushed to obtain lithium carbonate products and lithium phosphate products.

[0055] In another embodiment, an application of a method for selectively recovering lithium by acid leaching using organic peracid is provided, wherein the above-mentioned method for selectively recovering lithium by acid leaching using organic peracid is used to recover lithium elements in waste lithium iron phosphate positive electrode materials.

[0056] In addition, in the above embodiment, the amount of precipitant is calculated according to the reaction equation:

[0057] Primary precipitation reaction: 2Li + +Na 2 CO 3 →Li 2 CO 3 ↓ +2Na +

[0058] Secondary precipitation reaction: 3Li + +Na 3 PO 4 →2Li 3 PO 4 ↓ +3Na +

[0059] The required amount of precipitant is calculated based on the chemical reaction equation and the tested lithium ion concentration. The reason why it is greater than the theoretical amount is that during the experiment or implementation process, changes in experimental or implementation conditions, such as temperature, pressure, etc., may affect the reaction efficiency of the reagent, thereby requiring an increase in the amount of the reagent.

[0060] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0061] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for selectively recovering lithium by acid leaching using organic peroxyacid, characterized in that: The following steps are involved: Step 1, heat treating lithium iron phosphate powder in an inert gas atmosphere to remove impurities; Step 2, uniformly mixing an organic peracid with water to obtain an organic peracid solution, adding lithium iron phosphate powder to the organic peracid solution, and obtaining a lithium-rich solution and ferrophosphorus slag after reaction; Step 3, subjecting the lithium-rich solution to two precipitations to obtain lithium carbonate precipitation and lithium phosphate precipitation respectively; Step 4: Wash, dry and crush the lithium carbonate precipitate and lithium phosphate precipitate obtained in step 3 to obtain lithium carbonate finished products and lithium phosphate finished products.

2. A method for selectively recovering lithium by acid leaching using organic peroxyacid as claimed in claim 1, characterized in that: The heat treatment in step 1 comprises the following steps: The starting temperature is set at 20°C, the heating rate is 10°C / min, the heating time is set at 45-60min, after heating to 500-550°C, it is kept for 120-150min and then naturally cooled to room temperature, and the lithium iron phosphate powder after impurity removal is taken out.

3. A method for selectively recovering lithium by acid leaching using organic peroxyacid as claimed in claim 1, characterized in that: The organic peroxy acid in step 2 includes an acid containing a peroxy group and having the properties of a peroxide and an acid, and an aromatic diperoxy acid having stability and oxidizing properties.

4. A method for selectively recovering lithium by acid leaching using organic peracid as claimed in claim 2, characterized in that: The water mixed with the organic peracid is deionized water. In the organic peracid solution, the volume ratio of the organic peracid to water is 1:5-1:10; the solid-liquid ratio of the lithium iron phosphate powder to the organic peracid solution is 1:1-1:

10.

5. A method for selectively recovering lithium by acid leaching using organic peracid as claimed in claim 4, characterized in that: After lithium iron phosphate powder is added to the organic peracid and aqueous solution, the decomposition rate of the organic peracid is accelerated by catalysis; the catalysis method includes at least one of short-wave irradiation, heating, and increasing the concentration of metal ions.

6. A method for selectively recovering lithium by acid leaching using organic peroxyacid as claimed in claim 5, characterized in that: The reaction time of the lithium iron phosphate powder and the organic peracid solution is 2 to 8 hours.

7. A method for selectively recovering lithium by acid leaching using organic peracid as claimed in claim 6, characterized in that: The reaction temperature of the lithium iron phosphate powder and the organic peroxyacid solution is 80-180°C.

8. A method for selectively recovering lithium by acid leaching using organic peroxyacid as claimed in claim 1, characterized in that: In step 3, the two precipitations respectively include the following steps: A primary precipitation is performed, wherein a precipitant 1 is added to the lithium-rich solution, wherein the precipitant 1 is a sodium carbonate solution mixed with sodium carbonate and deionized water, wherein the concentration of the sodium carbonate solution is 10-40%, and the amount of the precipitant 1 added is obtained based on the lithium ion concentration in the lithium-rich solution, the precipitation temperature is 60-100° C., and the precipitation time is 30-120 min. After the precipitation, a lithium carbonate precipitate and a residual solution are obtained; Secondary precipitation, adding precipitant 2 to the remaining solution, precipitant 2 is sodium phosphate dodecahydrate, the theoretical addition amount of precipitant 2 is obtained based on the lithium ion concentration of the remaining solution, and the actual addition amount is 1 to 1.5 times of the theoretical addition amount, and lithium phosphate precipitate is obtained after standing.

9. A method for selectively recovering lithium by acid leaching using organic peroxyacid as claimed in claim 1, characterized in that: The obtained lithium carbonate precipitate and lithium phosphate precipitate are respectively washed with 100° C. ionized water, vacuum dried at 80° C., and crushed to obtain lithium carbonate finished products and lithium phosphate finished products.

10. An application of a method for selectively recovering lithium by acid leaching using organic peroxyacid, characterized in that: The method for selectively recovering lithium by acid leaching using organic peracid as described in any one of claims 1 to 9 is used to recover lithium elements in waste lithium iron phosphate positive electrode materials.

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