CN-121974315-A - Method for preparing battery-grade ferric phosphate by magnetite and reduction leaching

CN121974315ACN 121974315 ACN121974315 ACN 121974315ACN-121974315-A

Abstract

According to the method for preparing the battery-grade ferric phosphate by utilizing magnetite and reducing leaching, hydroquinone and ascorbic acid are added into a leaching agent phosphoric acid aqueous solution to serve as reducing agents together, on one hand, the hydroquinone and the ascorbic acid have strong reducibility, so that the moment that an iron source contacts with the leaching agent can be avoided, fe 2+ released by the magnetite is oxidized into Fe 3+ by liquid-phase residual oxygen, the reaction path of the Fe 2+ in a liquid phase oxidized into Fe 3+ is thoroughly blocked, the reaction of elemental iron and target Fe 3+ is promoted, and on the other hand, the hydroquinone and the ascorbic acid can respectively form a complex [ Fe (C 6 H 4 (OH) 2 )] 2+ 、[Fe(C 6 H 7 O 6 )] + ) with Fe 2+ in a leaching system under an acidic condition, the concentration of Fe 2+ in the liquid phase is reduced, the forward movement of the reaction balance of the magnetite releasing ferrous ions is promoted, and the leaching rate of iron element is greatly improved.

Inventors

LIU YUANWEI
LU MANMAN
ZHAN JISHAN
ZHANG HANQUAN
SUN KANG
MA WEI

Assignees

万华化学集团股份有限公司
武汉工程大学

Dates

Publication Date: 20260505
Application Date: 20260116

Claims (10)

1. A method for preparing battery grade ferric phosphate by magnetite and reducing leaching, which is characterized by comprising the following steps: S1, leaching an iron source in an atmosphere containing protective gas by taking a phosphoric acid aqueous solution containing hydroquinone and ascorbic acid as a leaching agent, and carrying out solid-liquid separation to obtain a ferrous dihydrogen phosphate solution and leaching residues, wherein the iron source comprises magnetite, elemental iron and an iron oxide source, and the molar ratio of ferric iron element in the iron oxide source to ferric iron element in the magnetite to elemental iron is 1:0.8-1.5:1.1-1.5; S2, adding an oxidant into the obtained ferrous dihydrogen phosphate solution, performing oxidation precipitation under an acidic condition, performing solid-liquid separation for the first time, dissolving the solid in a phosphoric acid solution, and performing crystal transformation treatment; And S3, carrying out solid-liquid separation on the product after crystal transformation for the second time to obtain ferric phosphate dihydrate, and removing crystal water to obtain the battery-grade ferric phosphate.
2. The method for producing battery grade iron phosphate using magnetite and reductive leaching according to claim 1, wherein the iron element content is 30-70wt% based on the mass of the iron oxide source, and/or wherein the iron oxide source comprises at least one of sulfuric acid residue, fly ash, metallurgical dust.
3. The method for preparing battery-grade ferric phosphate by magnetite and reductive leaching according to claim 1 or 2, wherein the mass content of phosphoric acid in the phosphoric acid aqueous solution is 16% -24%; and/or the mass ratio of the leaching agent to the iron source is 8-20:1; And/or leaching at 30-100 ℃ for 3-10 hours; and/or, based on the total mass of the leaching agent, the mass content of the hydroquinone is 0.2% -3%; and/or, based on the total mass of the leaching agent, the mass content of the ascorbic acid is 0.5% -5%; and/or the protective gas is at least one of N 2 , ar and He; and/or introducing the protective gas into the leaching agent at a flow rate of 40-150 mL/min in the leaching process.
4. A method for producing battery grade iron phosphate using magnetite and reductive leaching according to any of claims 1-3, wherein the method satisfies at least one of the following: A. the mol ratio of hydroquinone to ascorbic acid is 1:0.4-5, preferably 1:0.9-3.5; B. the sum of the molar amounts of hydroquinone and ascorbic acid provided in the leaching agent accounts for 50% -400% of the molar amount of ferrous element in the magnetite, and is preferably 80% -150%.
5. The method for preparing battery grade ferric phosphate by magnetite and reducing leaching according to any one of claims 1 to 4, wherein the oxidizing agent is at least one selected from the group consisting of oxygen, hydrogen peroxide, and air; Optionally, the molar ratio of ferrous ions to oxygen in the ferrous dihydrogen phosphate solution is 1:0.25-0.5; optionally, the molar ratio of ferrous ions in the ferrous dihydrogen phosphate solution to hydrogen peroxide in the hydrogen peroxide is 1:0.5-1.0; Optionally, the molar ratio of ferrous ions to air in the ferrous dihydrogen phosphate solution is 1:1.5-3.0.
6. The method for producing battery grade iron phosphate using magnetite and reductive leaching according to any one of claims 1 to 5, wherein in step S2, the oxidation precipitation process further comprises adding an alkaline solution to adjust the pH of the reaction system to 2.3 to 2.8, optionally, the alkaline solution is selected from one or more of ammonia water, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate.
7. The method for preparing battery grade ferric phosphate by magnetite and reductive leaching according to any one of claims 1-6, wherein the oxidative precipitation is a stirred reaction at a temperature of 60-80 ℃; and/or in the step S2, stirring and reacting at the temperature of 60-80 ℃ until the content of the iron element in the solution is not more than 0.4g/L, and completely oxidizing and precipitating.
8. The method for preparing battery-grade ferric phosphate by utilizing magnetite and reductive leaching according to any one of claims 1-7, wherein in step S2, the temperature of the crystal transformation treatment is 75-100 ℃ and the time is 15-180 min; and/or the pH value of the acid solution is 1.1-1.7; and/or the ratio of the volume of the acid solution to the mass of the solid is 10-20 mL/1 g.
9. The method for preparing battery grade ferric phosphate by utilizing magnetite and reducing leaching according to any one of claims 1-8, wherein the method is characterized in that the crystallization water is removed by roasting, and optionally, the roasting temperature is 500-700 ℃ and the time is 60-180 min.
10. A battery grade iron phosphate produced by the method of producing a battery grade iron phosphate using magnetite and reductive leaching of any one of claims 1-9.

Description

Method for preparing battery-grade ferric phosphate by magnetite and reduction leaching Technical Field The invention relates to the field of preparation of new energy battery materials, in particular to a method for preparing battery-grade ferric phosphate by utilizing magnetite and reduction leaching. Background With the rapid development of new energy industry, the lithium iron phosphate battery has increasingly high market demands by virtue of the advantages of high safety performance, long cycle life, relatively low cost and the like, and the demand of battery-grade ferric phosphate serving as a precursor of a positive electrode material of the lithium iron phosphate battery also increases greatly. At present, the production method of ferric phosphate mainly comprises a liquid phase precipitation method, a hydrothermal synthesis method, an electrolytic method, a sol-gel method, a microwave synthesis method and the like, wherein the liquid phase precipitation method has the advantages of uniform particle size distribution of the prepared product, small particles, easy realization of industrialization and the like, and is widely applied in industrial production, and the method needs to prepare ferrous dihydrogen phosphate solution by taking high-purity iron powder as an iron source, but the cost of the high-purity iron powder is higher, namely about 5000 yuan/t. In order to reduce the production cost, domestic enterprises often adopt sulfate slag, yellow phosphorus byproduct ferrophosphorus slag, waste residue after lithium extraction of waste batteries and ferrous sulfate which is an industrial byproduct of titanium dioxide as iron sources to prepare ferric phosphate, however, the sulfate slag, the waste residue after lithium extraction and the ferrophosphorus slag contain a large amount of Al, na, S, ca and other impurity elements, the acid leaching process is easy to enter a liquid phase, an impurity removal process is required to be additionally arranged, the ferrous sulfate is required to be purified through an extraction or ion exchange process, the process is complex, the cost is high, the battery-grade ferric phosphate cannot be directly obtained without additionally arranging the impurity removal process, in addition, the leaching rate of magnetite is lower, and a large amount of iron elements cannot be effectively utilized. Disclosure of Invention The invention provides a method for preparing battery-grade ferric phosphate by magnetite and reduction leaching, which aims to solve the problems that the content of impurities in the obtained ferric phosphate is high, the battery-grade ferric phosphate is difficult to directly obtain and the leaching rate is low in the prior art. To this end, the application provides a method for preparing battery grade ferric phosphate by magnetite and reducing leaching, comprising the following steps: S1, leaching an iron source in an atmosphere containing protective gas by taking a phosphoric acid aqueous solution containing hydroquinone and ascorbic acid as a leaching agent, and carrying out solid-liquid separation to obtain a ferrous dihydrogen phosphate solution and leaching residues, wherein the iron source comprises magnetite, elemental iron and an iron oxide source, and the molar ratio of ferric iron element in the iron oxide source to ferric iron element in the magnetite to elemental iron is 1:0.8-1.5:1.1-1.5; S2, adding an oxidant into the obtained ferrous dihydrogen phosphate solution, performing oxidation precipitation under an acidic condition, performing solid-liquid separation for the first time, dissolving the solid in a phosphoric acid solution, and performing crystal transformation treatment; And S3, carrying out solid-liquid separation on the product after crystal transformation for the second time to obtain ferric phosphate dihydrate, and removing crystal water to obtain the battery-grade ferric phosphate. In some embodiments, the iron element is present in an amount of 30 to 70wt% based on the mass of the iron oxide source, and/or the iron oxide source comprises at least one of sulfuric acid sludge, fly ash, metallurgical dust. In some embodiments, the mass content of phosphoric acid in the phosphoric acid aqueous solution is 16% -24%; and/or the mass ratio of the leaching agent to the iron source is 8-20:1; And/or leaching at 30-100 ℃ for 3-10 hours; and/or, based on the total mass of the leaching agent, the mass content of the hydroquinone is 0.2% -3%; and/or, based on the total mass of the leaching agent, the mass content of the ascorbic acid is 0.5% -5%; and/or the protective gas is at least one of N 2, ar and He; and/or introducing the protective gas into the leaching agent at a flow rate of 40-150 mL/min in the leaching process. In some embodiments, the method satisfies at least one of the following: A. the mol ratio of hydroquinone to ascorbic acid is 1:0.4-5, preferably 1:0.9-3.5; B. the sum of the molar amounts of hydroquinone and asco