CN113373321A - Method for wet recovery of lithium element from scrapped lithium iron phosphate battery - Google Patents

Method for wet recovery of lithium element from scrapped lithium iron phosphate battery Download PDF

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CN113373321A
CN113373321A CN202110708812.1A CN202110708812A CN113373321A CN 113373321 A CN113373321 A CN 113373321A CN 202110708812 A CN202110708812 A CN 202110708812A CN 113373321 A CN113373321 A CN 113373321A
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lithium
filtrate
filtering
auxiliary agent
iron phosphate
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CN113373321B (en
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董振伟
熊海岩
易贺迪
张翼东
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Xuchang University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/10—Obtaining alkali metals
    • C22B26/12—Obtaining lithium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/37—Phosphates of heavy metals
    • C01B25/375—Phosphates of heavy metals of iron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • C22B7/007—Wet processes by acid leaching
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
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    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

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Abstract

The invention discloses a method for recovering lithium element from a scrapped lithium iron phosphate battery by a wet method, which comprises the steps of adding an auxiliary agent A and an auxiliary agent B one by one after precipitating iron phosphate, wherein the auxiliary agent A can react with phosphate radical and hydrogen phosphate radical to generate precipitate by utilizing calcium ions in one step before the phosphate radical and the hydrogen phosphate radical react with lithium ions, the auxiliary agent B can remove residual ferric iron ions in a solution, and simultaneously removes a byproduct calcium sulfate generated when the auxiliary agent A is added, so that the loss of the lithium element is greatly reduced, the first recovery rate of the lithium element can reach 86.14 percent, the purity can reach 99.89 percent, the recycling rate can reach 95.2 percent, the method can omit the steps of washing and impurity removal of lithium salt, simplify the process, save water resources and reduce the production cost.

Description

Method for wet recovery of lithium element from scrapped lithium iron phosphate battery
Technical Field
The invention belongs to the field of lithium battery recovery, and particularly relates to a method for recovering lithium elements from scrapped lithium iron phosphate batteries by a wet method.
Background
In recent years, lithium iron phosphate (LiFePO)4) The battery is electrically safe due to its excellent thermal safety, relatively low non-toxicity, high reversibility and low costThe renewable energy storage fields such as automobiles, hybrid automobiles and smart grids are developed very rapidly, and the consumption of lithium iron phosphate batteries for automobiles in the whole world is expected to exceed 2200 billion dollars from 2015 to 2024 according to prediction; after the lithium iron phosphate battery is retired, a large amount of waste LiFePO can be generated4The battery needs to be treated.
At present, the method applicable to lithium iron phosphate battery recovery comprises a pyrometallurgical recovery method, a physical disassembly-cooperative wet recovery method and a physical disassembly-cooperative direct regeneration method, wherein the most common and mature method is wet recovery, the wet recovery mainly comprises performing acid leaching on a lithium iron phosphate positive active material, adjusting the pH of an acid leaching solution by using a sodium hydroxide solution, thereby precipitating iron phosphate, then continuously adjusting the pH of the remaining solution by using a sodium hydroxide solution, and adding sodium carbonate to generate lithium carbonate to achieve the purpose of recovering lithium elements, but the method has obvious defects, for example, after the iron phosphate is precipitated by using sodium hydroxide, partial phosphate radical, monohydrogen phosphate and ferric iron ions exist in a residual solution, after sodium hydroxide is continuously added, the pH rises to convert monohydrogen phosphate into phosphate radical, and the content of the phosphate radical is increased, phosphate radicals and lithium ions generate lithium phosphate precipitates, part of lithium ions are consumed, ferric ions and hydroxide radicals generate ferric hydroxide, the ferric hydroxide has a flocculation effect, the lithium phosphate and a small amount of lithium ions can be agglomerated together, the content of the lithium ions in the solution is further reduced, and therefore the first recovery rate of lithium elements is only about 75%, and the recovery rate of the lithium in the circulating solution is not high and is basically about 86%; and because the impurities in the solution are more, the purity of the lithium salt prepared for the first time is lower, and the impurities are required to be removed by repeated washing, so that the recovery cost is increased, and a small amount of lithium salt is dissolved to cause lithium loss, so that the recovery rate of the refined lithium salt is lower and is only about 80.7%.
Therefore, the existing wet recovery method of lithium iron phosphate has the technical defects of low lithium element recovery rate, complex process and high recovery cost.
Disclosure of Invention
The invention aims to provide a method for recovering lithium element from a scrapped lithium iron phosphate battery by a wet method, and aims to overcome the technical defects of low lithium element recovery rate, complex process and high recovery cost in the existing process of recovering lithium iron phosphate materials by the wet method.
In order to achieve the purpose, the invention adopts the technical scheme that the method for recovering lithium element from the scrapped lithium iron phosphate battery by a wet method comprises the following steps:
1) preparing an auxiliary agent A: according to the mass percentage, 10% -15% of ethylene Carbonate (CE), 1% -5% of bentonite and 74.5% -87.7% of calcium hydroxide (Ca (OH)2) Uniformly mixing 1-2.5% of ethylenediamine tetraacetic acid (EDTA), 0.1-1.5% of dispersant CNF (benzyl naphthalene sulfonic acid formaldehyde condensate), 0.1-1% of AGITAN P803 (a mixture of liquid hydrocarbon, polyethylene glycol and amorphous silicon dioxide) and 0.1-0.5% of fatty acid polyoxyethylene ester, and performing ball milling to obtain an auxiliary agent A;
2) preparing an auxiliary agent B: according to the mass percentage, 0.1% -5% of ethylene Carbonate (CE), 1% -2.5% of Ethylene Diamine Tetraacetic Acid (EDTA), 85% -97.6% of sodium hydroxide (NaOH) and 1% -5.5% of ammonium bicarbonate (NH)4HCO3) 0.1% -1% of polyacrylamide ((C)3H5NO) n), 0.1-0.5% of sodium dodecyl benzene sulfonate and 0.1-0.5% of organopolysiloxane, and performing ball milling to obtain an auxiliary agent B;
3) acid leaching is carried out on the lithium iron phosphate positive electrode active material, sodium hydroxide solution is used for adjusting the pH value of the acid leaching solution so as to precipitate iron phosphate, and filtering and collecting filtrate are carried out;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5-6.5, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9-10, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), when the lithium content in the filtrate reaches more than wt2% (sampling every 1-3 h, and detecting the lithium ion content in the solution by using an inductively coupled plasma spectrometer), keeping the temperature of the solution between 50 and 100 ℃, preparing lithium salt and collecting the filtrate;
7) adding the filtrate obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Preferably, the rotating speed in ball milling in the step 1) and the step 2) is 250-350 r/min, and the time is 0.5-2 h;
preferably, the detailed steps of step 3) are: acid leaching a lithium iron phosphate positive electrode active material by using sulfuric acid with the mass concentration of 1-20%, wherein the molar mass ratio of lithium iron phosphate to sulfuric acid is 1: 2-1: 2.2, the soaking time is 0.5-2 h, the reaction temperature is 10-75 ℃, filtering is performed after the reaction is finished, the pH value of the acid leaching solution is adjusted to 1.8-2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, filtering is performed, and filtrate is collected;
preferably, the reaction temperature in the step 4) is 15-50 ℃;
preferably, the reaction temperature in the step 5) is 15-50 ℃;
preferably, the preparing of the lithium salt in the step 6) includes adding sodium carbonate to prepare lithium carbonate, adding trisodium phosphate to prepare lithium phosphate, and adding sodium carbonate and calcium hydroxide to prepare lithium hydroxide.
The invention has the following beneficial effects:
before the reaction of phosphate radical and hydrogen phosphate radical with lithium ion, the assistant A can react with phosphate radical and hydrogen phosphate radical in one step to produce precipitate, and the assistant B can eliminate residual ferric ion from solution and calcium sulfate as side product of the assistant A to eliminate waste LixFePO4Recovery of FePO from C4And then, the loss of the lithium element recovered from the residual liquid is greatly reduced, so that the recovery benefit is improved, the first recovery rate of the lithium element can reach 86.14 percent, the purity can reach 99.89 percent, the recycling recovery rate can reach 95.2 percent, the steps of washing and impurity removal of lithium salt can be omitted, the process is simplified, water resources are saved, and the production cost is reduced.
Detailed Description
In order to make the objects and advantages of the present invention more apparent, the present invention is further described below with reference to the following examples; furthermore, various changes and modifications may be made by those skilled in the art after reading the teachings herein, and such equivalents are intended to fall within the scope of the appended claims.
Example 1
1) Taking 10% of ethylene Carbonate (CE), 1% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 87.7 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 1 percent of dispersant CNF (purchased from Guangzhou Li Hongyun chemical Co., Ltd.), AGITAN P8030.1 percent (purchased from Nanjing Yuelai New Material science and technology Co., Ltd.), and 0.1 percent of polyoxyethylene fatty acid ester, uniformly mixing the obtained raw materials, and performing ball milling at 250r/min for 1h to obtain an assistant A20 g;
2) taking 0.1% of ethylene Carbonate (CE), 1% of Ethylene Diamine Tetraacetic Acid (EDTA), 97.6% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 1% polyacrylamide ((C)3H5NO) n) 0.1 percent, sodium dodecyl benzene sulfonate 0.1 percent and organopolysiloxane 0.1 percent, the raw materials are uniformly mixed and ball milled for 1 hour at the speed of 250r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 2
1) Taking 10% of ethylene Carbonate (CE), 1% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 87.7 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 1 percent of dispersant CNF, 0.1 percent of AGITAN P8030.1 percent and 0.1 percent of fatty acid polyoxyethylene ester, uniformly mixing the obtained raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 0.1% of ethylene Carbonate (CE), 1% of Ethylene Diamine Tetraacetic Acid (EDTA), 97.6% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 1% polyacrylamide ((C)3H5NO) n) 0.1 percent, sodium dodecyl benzene sulfonate 0.1 percent and organopolysiloxane 0.1 percent, the raw materials are evenly mixed and ball milled for 1 hour at 300r/min to obtain the auxiliary agent B20g
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 3
1) Taking 10% of ethylene Carbonate (CE), 1% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 87.7 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 1 percent of dispersant CNF, 0.1 percent of AGITAN P8030.1 percent and 0.1 percent of fatty acid polyoxyethylene ester, uniformly mixing the obtained raw materials, and carrying out ball milling at 350r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 0.1 percent of ethylene Carbonate (CE) and ethylene glycol according to the mass ratio1% of EDTA, 97.6% of sodium hydroxide (NaOH), and ammonium bicarbonate (NH)4HCO3) 1% polyacrylamide ((C)3H5NO) n) 0.1 percent, sodium dodecyl benzene sulfonate 0.1 percent and organopolysiloxane 0.1 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 350r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 4
1) Taking 11% of ethylene Carbonate (CE), 2.5% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 84.25%, 1.3% of Ethylene Diamine Tetraacetic Acid (EDTA), 0.4% of dispersant CNF, 0.2% of AGITAN P8030.35% and 0.2% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary A20 g;
2) taking 1.5 percent of ethylene Carbonate (CE), 1.3 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 93.95 percent of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 2.5% polyacrylamide ((C)3H5NO) n) 0.35 percent, sodium dodecyl benzene sulfonate 0.2 percent and organopolysiloxane 0.2 percent, and the raw materials are evenly mixed at 300r/mPerforming in-ball milling for 1h to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 15 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 15 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 5
1) Taking 11% of ethylene Carbonate (CE), 2.5% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 84.25%, 1.3% of Ethylene Diamine Tetraacetic Acid (EDTA), 0.4% of dispersant CNF, 0.2% of AGITAN P8030.35% and 0.2% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary A20 g;
2) taking 1.5 percent of ethylene Carbonate (CE), 1.3 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 93.95 percent of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 2.5% polyacrylamide ((C)3H5NO) n) 0.35 percent, sodium dodecyl benzene sulfonate 0.2 percent and organopolysiloxane 0.2 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 6
1) Taking 11% of ethylene Carbonate (CE), 2.5% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 84.25%, 1.3% of Ethylene Diamine Tetraacetic Acid (EDTA), 0.4% of dispersant CNF, 0.2% of AGITAN P8030.35% and 0.2% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary A20 g;
2) taking 1.5 percent of ethylene Carbonate (CE), 1.3 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 93.95 percent of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 2.5% polyacrylamide ((C)3H5NO) n) 0.35 percent, sodium dodecyl benzene sulfonate 0.2 percent and organopolysiloxane 0.2 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 35 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 35 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 7
1) Taking 11% of ethylene Carbonate (CE), 2.5% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 84.25%, 1.3% of Ethylene Diamine Tetraacetic Acid (EDTA), 0.4% of dispersant CNF, 0.2% of AGITAN P8030.35% and 0.2% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary A20 g;
2) taking 1.5 percent of ethylene Carbonate (CE), 1.3 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 93.95 percent of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 2.5% polyacrylamide ((C)3H5NO) n) 0.35 percent, sodium dodecyl benzene sulfonate 0.2 percent and organopolysiloxane 0.2 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 50 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 50 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 8
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the auxiliary agent A into the filtrate obtained in the step 3) until the pH value reaches 6 when the reaction temperature is 25 ℃, filtering, separating and precipitating, and collecting the filtrate;
5) adding the auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 9
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the auxiliary agent A into the filtrate obtained in the step 3) until the pH value reaches 6 when the reaction temperature is 25 ℃, filtering, separating and precipitating, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 10
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65 percent of Ethylene Diamine Tetraacetic Acid (EDTA) 1.7 percent of dispersant CNF0.8 percent of dispersant AUniformly mixing the obtained raw materials by using GITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the auxiliary agent A into the filtrate obtained in the step 3) until the pH value reaches 6 when the reaction temperature is 25 ℃, filtering, separating and precipitating, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 10 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 11
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3 percent of ethylene Carbonate (CE), 1.7 percent of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65 percent of sodium hydroxide (NaOH) and carbonic acid according to the mass ratioAmmonium hydrogen (NH)4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 12
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding the auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 13
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 10 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 14
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 6.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 15
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 6.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding the auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Example 16
1) Taking 12% of ethylene Carbonate (CE), 4% of bentonite and calcium hydroxide (Ca (OH) according to the mass ratio2) 80.65% of Ethylene Diamine Tetraacetic Acid (EDTA), 1.7% of EDTA, 0.8% of dispersant CNF, AGITAN P8030.55% and 0.3% of fatty acid polyoxyethylene ester, uniformly mixing the raw materials, and performing ball milling at 300r/min for 1h to obtain an auxiliary agent A20 g;
2) taking 3% of ethylene Carbonate (CE), 1.7% of Ethylene Diamine Tetraacetic Acid (EDTA), 90.65% of sodium hydroxide (NaOH) and ammonium bicarbonate (NH) according to the mass ratio4HCO3) 3.5% polyacrylamide ((C)3H5NO) n) 0.55 percent, sodium dodecyl benzene sulfonate 0.3 percent and organopolysiloxane 0.3 percent, the raw materials are uniformly mixed and ball milled for 1 hour at 300r/min to obtain an auxiliary agent B20 g;
3) 15.7760g of lithium iron phosphate positive electrode active material is taken, sulfuric acid with the mass concentration of 2% is used for acid leaching, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1:2, the reaction time is 1h, the reaction temperature is 45 ℃, filtering is carried out after the reaction is finished, the pH of an acid leaching solution is adjusted to 2 by using a sodium hydroxide solution, so that iron phosphate is precipitated, and filtering and collecting filtrate;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 6.5 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 10 when the reaction temperature is 25 ℃, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), keeping the temperature of the solution at 80 ℃ when the lithium content in the filtrate reaches more than wt2%, adding sodium carbonate and stirring until the sodium carbonate is completely dissolved, filtering after 0.5h, and respectively collecting lithium carbonate and the filtrate;
7) adding the lithium carbonate residual liquid obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
Comparative example 1
On the basis of example 8, steps 5), 6), 7) were omitted and step 4) was replaced by "adding sodium hydroxide to the filtrate obtained in step 3) at a reaction temperature of 25 ℃ until the pH reached 6, filtering, separating the precipitate, collecting the filtrate", and the other steps were not changed;
the content of lithium element in the residual liquid in the step 3) is about 0.08 wt%, after sodium hydroxide is used for impurity removal, the pH value of the solution is 6, the content of iron and phosphorus elements in the solution after filtration is relatively high, but the content of lithium element is reduced to 0.0534 wt%, only 66.75% of the initial content (0.08 wt%), a lot of lithium element cannot be recovered, waste is caused, and economic benefit is reduced.
Comparative example 2
On the basis of example 8, steps 5), 6), 7) are omitted, and the other steps are unchanged;
after the additive A is used for removing impurities from the residual liquid, the pH value of the solution is 6, the content of iron and phosphorus elements in the filtered solution is obviously reduced compared with that in a comparative example 1, the content of the lithium element is reduced to 0.0751 percent by weight and accounts for 93.875 percent of the initial content, and the loss of the lithium element is 27.125 percent less than that of the residual liquid obtained by directly adding sodium hydroxide for removing impurities.
Comparative example 3
On the basis of the embodiment 8, the auxiliary agents A and B are respectively replaced by sodium hydroxide, and other steps are not changed;
this comparative example was made using sodium hydroxide to remove impurities until the solution was able to produce a lithium salt, after which the lithium content was reduced to 0.0406% by weight, 50.75% of the initial content, and only nearly half of the lithium could be recovered.
Comparative example 4
On the basis of the example 8, the auxiliary agent B is replaced by sodium hydroxide, and other steps are not changed;
in the comparative example, the additive A is used firstly, then sodium hydroxide is used for removing impurities, the content of the lithium element is reduced to wt0.0586 percent, which accounts for 73.25 percent of the initial content, compared with the comparative example 3 in which sodium hydroxide is directly used, the lithium recovery efficiency of the comparative example 4 is greatly improved, and the use of the additive A is necessary.
Comparative example 5
On the basis of the embodiment 8, the auxiliary agent A is replaced by sodium hydroxide, and other steps are not changed;
in the comparative example, sodium hydroxide is used firstly, then the auxiliary agent B is used for removing impurities, the content of the lithium element is reduced to 0.0394 wt%, which accounts for 49.25% of the initial content, compared with the comparative example 3 in which the sodium hydroxide is directly used, the lithium recovery efficiency of the comparative example 5 is not improved, but the content of the iron-phosphorus element is obviously reduced, the auxiliary agent B mainly has the function of removing redundant calcium ions generated by adding the auxiliary agent A, and the content of the calcium ions in the final filtrate can be reduced to 0.001% and is almost not contained by combining with the examples 1-16, which indicates that the use of the auxiliary agent B is necessary.
The results of the examples and the comparative examples show that when the lithium salt is produced by using the method, the lithium content in the solution is high, the iron and phosphorus content is very low, the method is beneficial to producing high-purity lithium salt, and the method can also omit the step of washing and impurity removal of the lithium salt, simplify the process, save water resources, reduce the production cost and increase the production benefit.
TABLE 1 table of the contents of the components of the remaining liquid after addition of the auxiliaries
Figure DEST_PATH_IMAGE002A
TABLE 2 ingredient content table of raffinate after addition of auxiliary agent in comparative example
Figure DEST_PATH_IMAGE004A
TABLE 3 comparison of impurity content, recovery and purity in lithium salt preparation for the first time
Figure DEST_PATH_IMAGE006A
TABLE 4 example and comparative example lithium cycle (10 cycles) recovery
Figure DEST_PATH_IMAGE008

Claims (6)

1. A method for recovering lithium element from a scrapped lithium iron phosphate battery by a wet method is characterized by comprising the following steps:
1) preparing an auxiliary agent A: uniformly mixing 10-15% of ethylene carbonate, 1-5% of bentonite, 74.5-87.7% of calcium hydroxide, 1-2.5% of ethylenediamine tetraacetic acid, 0.1-1.5% of dispersant CNF, 0.1-1% of AGITAN P803 and 0.1-0.5% of polyoxyethylene fatty acid ester according to mass percent, and performing ball milling to obtain an auxiliary agent A;
2) preparing an auxiliary agent B: uniformly mixing 0.1-5% of ethylene carbonate, 1-2.5% of ethylene diamine tetraacetic acid, 85-97.6% of sodium hydroxide, 1-5.5% of ammonium bicarbonate, 0.1-1% of polyacrylamide, 0.1-0.5% of sodium dodecyl benzene sulfonate and 0.1-0.5% of organopolysiloxane according to mass percent, and performing ball milling to obtain an auxiliary B;
3) acid leaching is carried out on the lithium iron phosphate positive electrode active material, sodium hydroxide solution is used for adjusting the pH value of the acid leaching solution so as to precipitate iron phosphate, and filtering and collecting filtrate are carried out;
4) adding the aid A into the filtrate obtained in the step 3) until the pH value reaches 5.5-6.5, filtering, separating precipitates, and collecting the filtrate;
5) adding an auxiliary agent B into the filtrate obtained in the step 4) until the pH value reaches 9-10, filtering, separating precipitates, and collecting the filtrate;
6) heating and concentrating the filtrate obtained in the step 5), and when the lithium content in the filtrate reaches more than wt2%, keeping the temperature of the solution between 50 and 100 ℃, preparing lithium salt and collecting the filtrate;
7) adding the filtrate obtained in the step 6) into the filtrate obtained in the step 4) for circulation.
2. The method of claim 1, wherein: the rotating speed in the ball milling process in the steps 1) and 2) is 250-350 r/min, and the time is 0.5-2 h.
3. The method of claim 1, wherein: the detailed steps of the step 3) are as follows: acid leaching is carried out on the lithium iron phosphate positive electrode active material by using sulfuric acid with the mass concentration of 1% -20%, the molar mass ratio of the lithium iron phosphate to the sulfuric acid is 1: 2-1: 2.2, the soaking time is 0.5-2 h, the reaction temperature is 10-75 ℃, filtering is carried out after the reaction is finished, the pH value of the acid leaching solution is adjusted to 1.8-2 by using a sodium hydroxide solution, so that the iron phosphate is precipitated, filtering is carried out, and filtrate is collected.
4. The method of claim 1, wherein: the reaction temperature in the step 4) is 15-50 ℃.
5. The method of claim 1, wherein: the reaction temperature in the step 5) is 15-50 ℃.
6. The method of claim 1, wherein: the preparation of the lithium salt in the step 6) comprises the steps of adding sodium carbonate to prepare lithium carbonate, adding trisodium phosphate to prepare lithium phosphate, and adding sodium carbonate and calcium hydroxide to prepare lithium hydroxide.
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CN106684485A (en) * 2016-12-19 2017-05-17 天齐锂业股份有限公司 Method for recovering waste/used lithium iron phosphate positive-pole material by acid leaching method
CN106848472A (en) * 2017-04-18 2017-06-13 中科过程（北京）科技有限公司 A kind of method that lithium is reclaimed in waste lithium iron phosphate battery
CN107381604A (en) * 2017-07-12 2017-11-24 深圳佳彬科技有限公司 A kind of method that lithium carbonate is reclaimed from ferric phosphate lithium cell
WO2018036568A1 (en) * 2016-08-26 2018-03-01 湖南金源新材料股份有限公司 Method for extracting lithium carbonate from lithium iron phosphate battery waste material, and lithium carbonate obtained thereby
CN109650415A (en) * 2018-12-04 2019-04-19 谭春波 A method of extracting lithium carbonate from the lithium iron phosphate battery anode powder scrapped

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WO2018036568A1 (en) * 2016-08-26 2018-03-01 湖南金源新材料股份有限公司 Method for extracting lithium carbonate from lithium iron phosphate battery waste material, and lithium carbonate obtained thereby
CN106684485A (en) * 2016-12-19 2017-05-17 天齐锂业股份有限公司 Method for recovering waste/used lithium iron phosphate positive-pole material by acid leaching method
CN106848472A (en) * 2017-04-18 2017-06-13 中科过程（北京）科技有限公司 A kind of method that lithium is reclaimed in waste lithium iron phosphate battery
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