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CN-122010067-A - Lithium dihydrogen phosphate iron removing agent, preparation process thereof and lithium dihydrogen phosphate electrolytic iron removing process

CN122010067ACN 122010067 ACN122010067 ACN 122010067ACN-122010067-A

Abstract

The invention relates to the technical field of lithium dihydrogen phosphate purification, and particularly discloses a lithium dihydrogen phosphate deironing agent and a preparation process thereof, and a lithium dihydrogen phosphate electrolytic deironing process, aiming at the problems of insufficient chelation stability and easy decomposition and failure in a high-temperature electrolysis process in the existing process for deironing a lithium dihydrogen phosphate battery material through a chelating agent, wherein the lithium dihydrogen phosphate deironing agent comprises 50-60wt% of a main chelating agent, 15-20wt% of an auxiliary reducing agent, 5-10wt% of a dispersing aid agent and the balance of a pH regulator and a solvent, the main chelating agent is one or more selected from aminotrimethylene phosphonic acid, hydroxyethylidene diphosphonic acid and ethylenediamine tetramethylene phosphonic acid, the auxiliary reducing agent is one or more selected from L-ascorbic acid, isoascorbic acid, sodium gluconate and thiolactic acid, and the dispersing aid agent is one or more selected from polyaspartic acid, polymaleic anhydride or polyacrylic acid. The lithium dihydrogen phosphate iron remover is suitable for a lithium dihydrogen phosphate electrolysis process, can realize high-efficiency adsorption iron removal, and has low consumption of the iron remover and low lithium loss rate.

Inventors

  • HUANG FUSHEN
  • YUAN GANG
  • WANG QIANG

Assignees

  • 四川省绵竹市汉旺无机盐化工有限公司

Dates

Publication Date
20260512
Application Date
20260203

Claims (10)

  1. 1. The lithium dihydrogen phosphate iron removing agent is characterized by comprising 50-60wt% of main chelating agent, 15-20wt% of auxiliary reducing agent, 5-10% of auxiliary dispersing agent and the balance of pH regulator and solvent according to mass fraction; The main chelating agent is one or more selected from amino trimethylene phosphonic acid, hydroxy ethylidene diphosphonic acid and ethylenediamine tetramethylene phosphonic acid, the auxiliary reducing agent is one or more selected from L-ascorbic acid, isoascorbic acid, sodium gluconate and thiolactic acid, and the auxiliary dispersing agent is one or more selected from polyaspartic acid, polymaleic anhydride or polyacrylic acid.
  2. 2. The lithium dihydrogen phosphate iron removing agent as defined in claim 1, comprising 55wt% of aminotrimethylene phosphonic acid, 18wt% of L-ascorbic acid, 8wt% of polyaspartic acid, 2wt% of lithium hydroxide, and 17wt% of deionized water, in terms of mass fraction.
  3. 3. A process for preparing the lithium dihydrogen phosphate iron removing agent as defined in claim 1 or 2, comprising the steps of: a1, respectively placing a main chelating agent, an auxiliary reducing agent and an auxiliary dispersing agent in a vacuum drying oven, and drying for later use; A2, firstly taking a solvent, heating and stirring, then adding a main chelating agent and an auxiliary dispersing agent once, and continuously stirring until the main chelating agent and the auxiliary dispersing agent are dissolved to obtain a primary mixed solution; a3, maintaining a heating and stirring state, adding an auxiliary reducing agent into the primary mixed solution under the protection of nitrogen, and continuing stirring to obtain a premix; And A4, dropwise adding a pH regulator into the premix, regulating the pH value of the premix to be acidic, heating and stirring, curing, and filtering to remove insoluble impurities to obtain the liquid lithium dihydrogen phosphate iron remover.
  4. 4. The process for preparing a lithium dihydrogen phosphate iron removing agent as defined in claim 3, wherein in step A2, heating is performed to 40-50 ℃, stirring speed is 200-300r/min, stirring is continued for 1-2h after charging, and in step A3, stirring is continued for 20-40min after adding the auxiliary reducing agent.
  5. 5. The process for preparing a lithium dihydrogen phosphate iron remover according to claim 3, wherein in step A4, the pH value of the premix is adjusted to 2.5-3.5, and the premix is heated to 50-60 ℃ and stirred for 0.5-2h.
  6. 6. A process for electrolytic iron removal of lithium dihydrogen phosphate, characterized in that the lithium dihydrogen phosphate iron removing agent according to claim 1 or 2 or the lithium dihydrogen phosphate iron removing agent prepared by the preparation process according to any one of claims 3 to 5 is adopted.
  7. 7. The lithium dihydrogen phosphate electrolytic iron removal process as defined in claim 6, comprising the steps of: b1 pretreatment before electrolysis: Dissolving a lithium dihydrogen phosphate crude product in deionized water to prepare electrolyte, heating and stirring the electrolyte, adding the lithium dihydrogen phosphate iron removing agent for pretreatment, and filtering to obtain pretreated electrolyte; b2 electrolysis and synergic iron removal: injecting the pretreated electrolyte into an electrolytic tank for electrolysis, and adding the lithium dihydrogen phosphate iron removing agent at regular time to obtain lithium dihydrogen phosphate crystal liquid after electrolysis; b3 separation after electrolysis: and (3) exporting the lithium dihydrogen phosphate crystal liquid, carrying out suction filtration, separating to obtain lithium dihydrogen phosphate crystals and mother liquor, washing and drying the lithium dihydrogen phosphate crystals to obtain a lithium dihydrogen phosphate product, and returning the mother liquor obtained by separation to the step (B1) for recycling.
  8. 8. The process for electrolytic iron removal from lithium dihydrogen phosphate according to claim 6, wherein in step B1, the concentration of the electrolyte is controlled to be 0.8-1.2mol/L, and the addition amount of the lithium dihydrogen phosphate iron remover is 0.3-0.5wt% of the mass of the electrolyte.
  9. 9. The process for electrolytic iron removal from lithium dihydrogen phosphate according to claim 6, wherein in step B2, the addition amount of the lithium dihydrogen phosphate iron removing agent is 0.03 to 0.08% of the circulating amount of the electrolyte per hour in terms of volume fraction.
  10. 10. The process according to claim 6, wherein in step B3, the mother liquor is recycled 2 to 3 times, a new lithium dihydrogen phosphate iron removing agent is added, and the adding amount is 20 to 50% of the initial adding amount by volume fraction.

Description

Lithium dihydrogen phosphate iron removing agent, preparation process thereof and lithium dihydrogen phosphate electrolytic iron removing process Technical Field The invention relates to the technical field of lithium dihydrogen phosphate purification, in particular to a lithium dihydrogen phosphate iron removing agent, a preparation process thereof and a lithium dihydrogen phosphate electrolytic iron removing process. Background The lithium dihydrogen phosphate is used as a core raw material of a lithium ion battery anode material and an electrolyte additive, has extremely high purity requirements, and particularly iron impurities (Fe 2+/Fe3+) can seriously influence the cycle stability and the rate capability of the battery, and the content of the lithium dihydrogen phosphate needs to be controlled below 5 ppm. In the lithium dihydrogen phosphate electrolysis preparation process, iron impurities are easy to be introduced in the processes of raw slag, electrolysis equipment corrosion and electrolyte circulation. The existing iron removal technology has obvious defects that the traditional neutralization precipitation method is adopted to generate Fe (OH) 3 precipitate by adjusting the pH value, but Fe (OH) 3 exists in a colloid form, the filtering performance is extremely poor, lithium ions are easy to adsorb to cause the lithium loss rate to exceed 5%, the single chelating agent is adopted to complex the iron ions, but the chelating stability is insufficient under the acidic electrolysis environment, the chelating agent is easy to decompose and lose efficacy during high-temperature electrolysis, and part of the chelating agent has poor biodegradability and higher cost, and the reduction precipitation method is adopted, needs to strictly control the pH range, has great operation difficulty and is easy to cause the reduction of the crystal purity of lithium dihydrogen phosphate. Aiming at the iron removal by adopting a chelating way in the prior art, a carboxylic acid chelating agent or an amino acid chelating agent and the like are mostly adopted at present. As disclosed in the patent publication No. CN106414805A, a chemical cleaning method and a chemical cleaning apparatus are proposed, wherein the cleaning liquid includes a chelating agent, a reducing agent or a mixture of the chelating agent and the reducing agent, and the chelating agent is any one of an amino acid chelating agent, a hydroxy acid chelating agent and an organic phosphorus chelating agent, and the reducing agent is any one of metal ions, sulfite, oxalic acid, formic acid, ascorbic acid, pyrogallol, hydrazine and hydrogen. However, the chelation stability is insufficient in the way of removing iron through the chelation agent, and the chelation agent is easy to decompose and lose efficacy in the high-temperature electrolysis process. In the existing lithium dihydrogen phosphate electrolysis process, in the process of removing iron by adding iron removing auxiliary agents such as chelating agents, the iron content of the treated lithium dihydrogen phosphate product is usually 10-20ppm. Based on the above, there is a need to develop an iron remover and an iron removal process which are suitable for the acidic and high-temperature environment characteristics of the lithium dihydrogen phosphate electrolysis process, and have the advantages of high iron removal efficiency, low lithium loss, environmental friendliness and simple process. Disclosure of Invention The invention aims to solve the problems of insufficient chelation stability and easy decomposition and failure in the high-temperature electrolysis process existing in the existing process for removing iron from a lithium dihydrogen phosphate battery material by using a chelating agent. The invention is realized by the following technical scheme: the invention provides a lithium dihydrogen phosphate iron remover adopting a chelate-reduction-dispersion ternary composite system, which comprises the following components in percentage by mass: (1) 50-60 wt% main chelating agent, phosphonic acid chelating agent. The phosphonic acid chelating agent molecule contains stable C-P bond and a plurality of phosphonic acid groups (-PO 3H2), has high charge density and strong C-P bond stability, is not easy to hydrolyze in an acidic environment with pH of about 2-6 and an electrolysis temperature of 60-80 ℃, can form stable five-membered or six-membered chelate with Fe 3+/Fe2+ by synergistic coordination of a central nitrogen atom and three phosphonic acid groups, has higher chelation priority than lithium ions, and does not influence crystallization of lithium dihydrogen phosphate. Specifically, the phosphonic acid chelating agent may be selected from one or more of aminotrimethylene phosphonic Acid (ATMP), hydroxyethylidene diphosphonic acid (HEDP), ethylenediamine tetramethylene phosphonic acid (EDTMP), and the like. More preferably, the chelate stability constant of the amino trimethylene phospho