CN115072686B - Method for preparing battery-grade ferric phosphate from pyrite cinder - Google Patents
Method for preparing battery-grade ferric phosphate from pyrite cinder Download PDFInfo
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- CN115072686B CN115072686B CN202210615482.6A CN202210615482A CN115072686B CN 115072686 B CN115072686 B CN 115072686B CN 202210615482 A CN202210615482 A CN 202210615482A CN 115072686 B CN115072686 B CN 115072686B
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- acid leaching
- ferrous sulfate
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- 238000000034 method Methods 0.000 title claims abstract description 132
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 title claims abstract description 53
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 229910052683 pyrite Inorganic materials 0.000 title claims abstract description 47
- 239000011028 pyrite Substances 0.000 title claims abstract description 47
- 239000003818 cinder Substances 0.000 title claims abstract description 46
- 239000005955 Ferric phosphate Substances 0.000 title claims abstract description 29
- 229940032958 ferric phosphate Drugs 0.000 title claims abstract description 29
- 229910000399 iron(III) phosphate Inorganic materials 0.000 title claims abstract description 29
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 121
- 238000002386 leaching Methods 0.000 claims abstract description 103
- 239000002253 acid Substances 0.000 claims abstract description 79
- 229910052742 iron Inorganic materials 0.000 claims abstract description 56
- 239000011790 ferrous sulphate Substances 0.000 claims abstract description 36
- 235000003891 ferrous sulphate Nutrition 0.000 claims abstract description 36
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims abstract description 36
- 229910000398 iron phosphate Inorganic materials 0.000 claims abstract description 24
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 20
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 20
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000012535 impurity Substances 0.000 claims abstract description 15
- 238000011946 reduction process Methods 0.000 claims abstract description 10
- 238000004537 pulping Methods 0.000 claims abstract description 8
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 7
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 5
- 239000010452 phosphate Substances 0.000 claims abstract description 5
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract 12
- 239000000243 solution Substances 0.000 claims description 108
- 238000006243 chemical reaction Methods 0.000 claims description 31
- 238000003756 stirring Methods 0.000 claims description 26
- 239000006184 cosolvent Substances 0.000 claims description 22
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 19
- 238000001914 filtration Methods 0.000 claims description 17
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 14
- 239000003638 chemical reducing agent Substances 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 9
- 230000035484 reaction time Effects 0.000 claims description 9
- 230000001105 regulatory effect Effects 0.000 claims description 8
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 8
- 239000003795 chemical substances by application Substances 0.000 claims description 7
- 150000003017 phosphorus Chemical class 0.000 claims description 7
- 239000012266 salt solution Substances 0.000 claims description 7
- 230000001276 controlling effect Effects 0.000 claims description 6
- 239000012065 filter cake Substances 0.000 claims description 6
- 239000011268 mixed slurry Substances 0.000 claims description 6
- FVAUCKIRQBBSSJ-UHFFFAOYSA-M sodium iodide Chemical compound [Na+].[I-] FVAUCKIRQBBSSJ-UHFFFAOYSA-M 0.000 claims description 6
- -1 aluminum ions Chemical class 0.000 claims description 5
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 4
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 4
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 4
- 235000010265 sodium sulphite Nutrition 0.000 claims description 4
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 3
- 238000010790 dilution Methods 0.000 claims description 3
- 239000012895 dilution Substances 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000004064 recycling Methods 0.000 claims description 3
- 239000002893 slag Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 2
- UYJXRRSPUVSSMN-UHFFFAOYSA-P ammonium sulfide Chemical compound [NH4+].[NH4+].[S-2] UYJXRRSPUVSSMN-UHFFFAOYSA-P 0.000 claims description 2
- DPLVEEXVKBWGHE-UHFFFAOYSA-N potassium sulfide Chemical compound [S-2].[K+].[K+] DPLVEEXVKBWGHE-UHFFFAOYSA-N 0.000 claims description 2
- 239000002516 radical scavenger Substances 0.000 claims description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 2
- 235000017550 sodium carbonate Nutrition 0.000 claims description 2
- 235000009518 sodium iodide Nutrition 0.000 claims description 2
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 claims description 2
- 235000019345 sodium thiosulphate Nutrition 0.000 claims description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims 2
- 230000003750 conditioning effect Effects 0.000 claims 1
- 235000017557 sodium bicarbonate Nutrition 0.000 claims 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 17
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 8
- 238000002425 crystallisation Methods 0.000 description 6
- 230000008025 crystallization Effects 0.000 description 6
- 239000012452 mother liquor Substances 0.000 description 5
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 5
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 4
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- RSIJVJUOQBWMIM-UHFFFAOYSA-L sodium sulfate decahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.[Na+].[Na+].[O-]S([O-])(=O)=O RSIJVJUOQBWMIM-UHFFFAOYSA-L 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 235000002639 sodium chloride Nutrition 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 229910018626 Al(OH) Inorganic materials 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 description 1
- 229940048086 sodium pyrophosphate Drugs 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 235000019818 tetrasodium diphosphate Nutrition 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Classifications
-
- 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
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention provides a method for preparing battery grade ferric phosphate by using pyrite cinder, which is characterized by comprising the following steps: (1) acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution; (2) removing impurities from the iron-containing leaching solution: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leaching solution to obtain a ferrous sulfate solution; (3) synthesizing iron phosphate: and (3) reacting the ferrous sulfate solution with a phosphate solution to obtain ferric phosphate. According to the method provided by the invention, the pyrite cinder is used as an iron source, and the iron source suitable for preparing the battery-grade ferric phosphate can be prepared through a simple acid leaching process and a impurity removing process, so that the cost can be obviously reduced, the process is simple, and the industrialization is easy.
Description
Technical Field
The invention relates to the field of batteries, in particular to a method for preparing battery-grade ferric phosphate by using pyrite cinder.
Background
The ferric phosphate is a salt produced by an iron source and a phosphorus source, and is a precursor of a new energy anode material lithium iron phosphate; currently, as the demand for lithium iron phosphate bursts, the demand for raw material iron phosphate is also continuously increasing. As one of the raw materials for preparing the ferric phosphate: the cost of the iron source is high, and therefore, it is necessary to develop a new process capable of producing battery grade iron phosphate using inexpensive raw materials.
Currently, a process for producing battery grade iron phosphate from pyrite cinder as an inexpensive raw material is known, in which the pyrite cinder is required to be acid-leached. The technology of the pyrite cinder acid leaching at the present stage mainly comprises the following steps: a direct acid leaching method and a reduction roasting acid leaching method, wherein the direct acid leaching method comprises the following steps: a mixed acid leaching method, a dissolution assisting leaching method and a curing leaching method. However, the existing direct acid leaching methods have low leaching rate of iron or severe conditions, and particularly, some processes for introducing chloride ions bring great difficulty to subsequent wastewater treatment and equipment maintenance, so that a process with high leaching rate of iron in pyrite cinder needs to be developed.
Disclosure of Invention
In view of the defects of the leaching process of iron in pyrite cinder in the prior art, the invention provides a novel method for preparing battery-grade ferric phosphate by adopting pyrite cinder, wherein the leaching process of iron in pyrite cinder in the method belongs to a dissolution-assisting acid leaching method in a direct acid leaching method, and the method can realize the leaching rate of more than 90% under mild conditions by only adopting single sulfuric acid for acid leaching and EDTA as a cosolvent; compared with a reduction roasting leaching method, the method has the advantages of simple process, energy conservation and convenient operation; compared with the mixed acid leaching method, the method is a single sulfuric acid system, and can not simultaneously use hydrochloric acid to introduce chloride ions like the common mixed acid leaching method, and the chloride ions have extremely strong corrosiveness to stainless steel, so that the equipment corrosion and the equipment requirement can be reduced due to the fact that the chloride ions are not introduced; compared with the general dissolution-assisting acid leaching method which adopts phosphoric acid, sodium chloride, sodium pyrophosphate, sodium hexametaphosphate and the like as the cosolvent, the method has the advantages of good dissolution-assisting effect and high iron recovery rate; compared with the curing acid leaching method, the process provided by the invention has the advantages of mild reaction conditions, easiness in realization, high leaching rate and high resource utilization rate.
The invention provides a method for preparing battery grade ferric phosphate by using pyrite cinder, which comprises the following steps:
(1) Acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution;
(2) Removing impurities from the iron-containing leaching solution: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leaching solution to obtain a ferrous sulfate solution;
(3) Synthesizing ferric phosphate: and (3) reacting the ferrous sulfate solution with a phosphate solution to obtain ferric phosphate.
As can be seen from the results of table 6 of the present invention, in example 1 using EDTA as a cosolvent, the leaching rate of iron was significantly improved and pyrite cinder was more effectively utilized, as compared with comparative example 1 (sodium hexametaphosphate as a cosolvent used in comparative example 1).
Moreover, as can be seen from the results of table 7 of the present invention, the method provided by the present invention adopts pyrite cinder as an iron source, and prepares the iron source suitable for preparing battery grade iron phosphate through a simple acid leaching process and a impurity removing process, the prepared battery grade anhydrous iron phosphate is equivalent to the anhydrous iron phosphate prepared by a conventional process in quality, the cost can be significantly reduced, and the process is simple and easy to industrialize.
Drawings
FIG. 1 is a preferred overall process flow diagram of the present invention.
Detailed Description
The invention provides a method for preparing battery grade ferric phosphate by using pyrite cinder, which comprises the following steps:
(1) Acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution;
(2) Removing impurities from the iron-containing leaching solution: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leaching solution to obtain a ferrous sulfate solution;
(3) Synthesizing ferric phosphate: and (3) reacting the ferrous sulfate solution with a phosphate solution to obtain ferric phosphate.
Specifically, the whole process flow is as follows:
the whole process flow is as follows:
and (3) acid leaching of pyrite cinder. Taking pyrite cinder which is a byproduct of pyrite acid production as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution.
First, elemental analysis of main impurities of pyrite cinder is shown in table 1 below:
TABLE 1
(1) And (3) pulping. Adding 90-99wt% concentrated sulfuric acid solution, preferably 98wt%, into the pyrite cinder, and mixing to obtain mixed slurry. Wherein, the weight ratio of the acid to the solid is controlled as follows: (1-5): 1, preferably (1-3): 1, the dropwise adding time of the concentrated sulfuric acid solution is controlled to be 10-120min, preferably 30-90min, and stirring can be continued for 20-60 min after the adding is finished.
(2) And (3) a primary acid leaching process. Adding pure water and cosolvent EDTA into the mixed slurry, and uniformly mixing to obtain a primary acid leaching solution.
Wherein the acid concentration in the primary acid leaching solution is controlled to be 20-85wt%, preferably 45-70wt%, the primary acid leaching solution is heated to 60-100 ℃, preferably 80-100 ℃, and the reaction is carried out under stirring, the stirring intensity is preferably 250-350rpm, more preferably 300rpm, and the reaction time is 1-7h, preferably 2-3h; wherein the addition amount of the cosolvent is 3-8% of the mass of the pyrite cinder.
In the present invention, all stirring intensities are not particularly limited as long as they can be uniformly stirred.
(3) And a secondary acid leaching process. The secondary acid leaching process comprises the following steps: pure water is added into the primary acid leaching solution, the acid concentration is controlled to be 30-45wt%, the reaction time is 0.5-2.5h, preferably 1-2h, the reaction temperature and the stirring strength are the same in the primary acid leaching process, and the iron-containing leaching solution is obtained through filtration.
The reason for controlling the acid concentration of the reaction system is that the concentration detection of iron ions is inconvenient to carry out, so that the concentration of iron ions in the solution is controlled by controlling the acid concentration, and meanwhile, the effect of reducing the viscosity of the solution is also achieved, thereby improving the movement speed of ions during the reaction and reducing the concentration of products to promote the forward reaction, and the specific operations are as follows: adding pure water or secondary acid leaching and filtering slag washing water into the reaction solution, controlling the concentration of acid in the added system to be 30-45wt%, reacting for 0.5-2.5h, preferably 1-2h, and filtering to obtain iron-containing leaching solution; sampling and measuring the content of ferric iron.
Preferably, the secondary acid leaching process may further include: washing the leached slag after filtration, and recycling washing water after washing to the secondary acid leaching process instead of pure water to adjust the acid concentration; the recycling purpose is to improve the recovery rate of pyrite cinder iron.
And (2) removing impurities from the iron-containing leaching solution. And sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leaching solution to obtain a ferrous sulfate solution.
(1) And (3) a reduction process. The reduction process includes: adding a reducing agent into the iron-containing leaching solution, reacting under stirring, and adding Fe into the solution 3+ Reduction to Fe 2+ Obtaining a crude ferrous sulfate solution;
wherein the reducing agent is one or more of sodium sulfite, sodium thiosulfate, sodium iodide and iron powder; the amount of reducing agent is 1.05-1.5 times, preferably 1.1-1.3 times the stoichiometric ratio; the reaction temperature is at normal temperature, the stirring strength is preferably 250-350rpm, more preferably 300rpm, and the reaction time is 10-30min.
Taking sodium sulfite as a reducing agent for example, the main reaction equation occurring in the reduction process is as follows:
2Fe 3+ +SO 3 2- +H 2 O＝2Fe 2+ +2H + +SO 4 2-
(2) aluminum removal procedure: adding a pH regulator into the crude ferrous sulfate solution under stirring, regulating the pH of the solution to 3.5-5.5, preferably 4.5-5.5, completely converting trivalent aluminum ions in the solution into aluminum hydroxide precipitate, continuously stirring for 20-60 min after regulating the pH, and filtering to obtain an aluminum-removed solution;
wherein the pH regulator is one or more of sodium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate, the reaction temperature is normal temperature, and the stirring strength is preferably 250-350rpm, more preferably 300rpm.
The main reaction equations that occur during the aluminum removal process are as follows:
Al 3+ +3OH - ＝Al(OH) 3 ↓
(3) and (3) heavy metal removal. Adding a heavy metal capturing agent into the solution after aluminum removal under stirring at 40-60 ℃ for reaction for 40-90min, and then filtering to obtain a pure ferrous sulfate solution;
wherein the heavy metal trapping agent comprises one or more of sodium sulfide, potassium sulfide and ammonium sulfide, and the stirring speed is controlled to be preferably 350-450rpm, more preferably 400rpm; the addition amount of the heavy metal scavenger is controlled to be 0.05-1g/L, preferably 0.1-0.7g/L.
(4) And (3) an iron concentration adjusting procedure. Preferably, in step (2), the method further comprises: an iron concentration adjusting process subsequent to the heavy metal removal process, the iron concentration adjusting process comprising: adding pure water into the ferrous sulfate solution for dilution, and controlling the ferrous sulfate concentration in the solution to be 180-230g/kg, preferably 200-220g/kg, so as to obtain a ferrous sulfate reaction solution for standby.
And (3) synthesizing ferric phosphate: and (3) reacting the ferrous sulfate solution with a phosphate solution to obtain ferric phosphate.
The method for synthesizing iron phosphate in the present invention is not particularly limited, and a conventional production method may be used.
In the invention, industrial phosphoric acid is taken as a phosphorus source for example to synthesize the ferric phosphate. Specifically, sodium hydroxide is added into phosphoric acid, the pH value of the solution is regulated to 7.0, wherein the oxidant is hydrogen peroxide with the weight percent of 20-30 percent, and the addition amount of the hydrogen peroxide is 1.13-1.2 times of the reaction metering; adding hydrogen peroxide into the phosphorus salt solution with the pH value of 7.0, and uniformly mixing to obtain a reaction phosphorus salt solution for later use.
During synthesis, n (P) of the reaction is controlled: and (2) n (Fe) = (1-1.05) 1, taking the ferrous sulfate reaction solution as a base solution, dropwise adding the prepared reaction phosphorus salt solution into the ferrous sulfate solution, heating to 88-96 ℃ after the dropwise adding is finished, reacting for 1-3h, filtering to obtain an iron phosphate filter cake, and washing, drying and calcining the iron phosphate filter cake to obtain the battery-grade anhydrous iron phosphate.
Finally, from the viewpoints of effective utilization of resources and energy conservation and environmental protection, the iron phosphate mother liquor (the main components are sodium sulfate and EDTA) obtained after filtration can be subjected to post-treatment, and the post-treatment comprises: evaporating, concentrating, cooling and crystallizing.
Introducing ferric phosphate mother liquor into mVR for concentration until the solution density is 1.17-1.2g/mL, then introducing the concentrated solution into a crystallization kettle for cooling crystallization, changing sodium sulfate in the solution into sodium sulfate decahydrate crystal to be separated out through cooling crystallization, and centrifuging by a centrifuge to obtain crystallization mother liquor and sodium sulfate decahydrate crystal, wherein the main component of the crystallization mother liquor is EDTA-containing solution, and the crystallization mother liquor can be used as a cosolvent for the primary acid leaching process; because EDTA is lost in the whole process, when EDTA is recycled and leached again, the leaching rate of more than 96% can be achieved by only adding 1-2% of EDTA. In addition, sodium sulfate decahydrate can be sold as a byproduct. Thus, the full effective utilization of the resources is completed.
The present invention will be described in more detail by way of examples with reference to fig. 1.
Example 1
This example is used to illustrate the method for preparing battery grade iron phosphate using pyrite cinder provided by the invention.
The pyrite cinder used in this example was derived from pyrite cinder of auspicious cloud group, and the iron content and impurity element analysis thereof were as shown in the following table 2:
TABLE 2
(1) Acid leaching of pyrite cinder:
(1) and (3) pulping. Adding 98wt% concentrated sulfuric acid solution into pyrite cinder, and mixing to obtain mixed slurry. Wherein, the weight ratio of acid to solid is controlled to be 1.7:1, the dripping time of the concentrated sulfuric acid solution is controlled to be 60min, and the stirring can be continued for 20min after the dripping is finished.
(2) And (3) a primary acid leaching process. Adding pure water and cosolvent EDTA into the mixed slurry, and uniformly mixing to obtain a primary acid leaching solution.
Wherein, the acid concentration in the primary acid leaching solution is controlled to be 50wt%, the primary acid leaching solution is heated to 98 ℃ and reacts under stirring, and the reaction time is 3 hours; wherein the addition amount of the cosolvent is 3 percent of the mass of the pyrite cinder.
(3) And a secondary acid leaching process. The secondary acid leaching process comprises the following steps: pure water is added into the primary acid leaching solution, so that the acid concentration is controlled to be 40wt%, the reaction time is 1h, and the iron-containing leaching solution is obtained through filtration.
(2) Removing impurities from the iron-containing leaching solution:
(1) and (3) a reduction process. The reduction process includes: adding sodium sulfite reducing agent into the iron-containing leaching solution, reacting under stirring, and adding Fe into the solution 3+ Reduction to Fe 2+ Obtaining a crude ferrous sulfate solution; wherein the dosage of the reducing agent is 1.1 times of the stoichiometric ratio; the reaction temperature was room temperature, the stirring strength was 300rpm, and the reaction time was 30min.
(2) Aluminum removal procedure: adding a sodium hydroxide pH regulator into the crude ferrous sulfate solution under stirring, regulating the pH value of the solution to 5.0, completely converting trivalent aluminum ions in the solution into aluminum hydroxide precipitate, continuously stirring for 20min after regulating the pH value, and filtering to obtain a solution after aluminum removal; wherein the reaction temperature was room temperature and the stirring strength was 300rpm. Impurity element analysis of the solution after aluminum removal is shown in table 3 below:
TABLE 3 Table 3
As can be seen from a comparison of Table 3 and Table 2, the aluminum content of the solution was greatly reduced through the aluminum removal process.
(3) And (3) heavy metal removal. Adding a sodium sulfide heavy metal capturing agent into the solution after aluminum removal under stirring at 40 ℃ for reaction for 40min, and then filtering to obtain a pure ferrous sulfate solution; wherein the stirring speed is controlled to be 400rpm, and the adding amount of the sodium sulfide heavy metal capturing agent is controlled to be 0.5g/L. Analysis of impurity elements in ferrous sulfate solution is shown in table 4 below:
TABLE 4 Table 4
As can be seen from a comparison of table 4 and table 3, the content of each impurity element was further reduced through the heavy metal removal process.
(4) And (3) an iron concentration adjusting procedure. Adding pure water into the ferrous sulfate solution for dilution, and controlling the ferrous sulfate concentration in the solution to be 200g/kg to obtain a ferrous sulfate reaction solution for later use.
(3) Synthesizing ferric phosphate:
adding sodium hydroxide into industrial phosphoric acid, and regulating the pH of the solution to 7.0, wherein the oxidant is hydrogen peroxide with the weight percent of 20%, and the adding amount of the hydrogen peroxide is 1.18 times of the reaction metering; adding hydrogen peroxide into the phosphorus salt solution with the pH value of 7.0, and uniformly mixing to obtain a reaction phosphorus salt solution for later use.
During synthesis, n (P) of the reaction is controlled: n (Fe) =1.02:1, taking the ferrous sulfate reaction solution as a base solution, dripping the prepared reaction phosphorus salt solution into the ferrous sulfate solution, heating to 94 ℃ after dripping, reacting for 2 hours, filtering to obtain an iron phosphate filter cake, and washing, drying and calcining the iron phosphate filter cake to obtain the battery-grade anhydrous iron phosphate.
Examples 2 to 3
These examples are presented to illustrate the method of the present invention for preparing battery grade iron phosphate using pyrite cinder.
The same procedure as in example 1 was used to prepare battery grade anhydrous ferric phosphate, except that the specific conditions of step (1) in example were as shown in table 5 below.
TABLE 5
Comparative example 1
Battery grade anhydrous ferric phosphate was prepared in the same manner as in example 1, except that the co-solvent EDTA was replaced with the existing co-solvent sodium hexametaphosphate.
Comparative example 2
Battery grade anhydrous iron phosphate was prepared in the same manner as in example 1, except that the addition amount of the cosolvent EDTA was changed from 3% to 1% of the pyrite cinder mass.
Comparative example 3
Battery grade anhydrous iron phosphate was prepared in the same manner as in example 1, except that the addition amount of the cosolvent EDTA was changed from 3% to 10% of the pyrite cinder mass.
The leaching rates of iron in examples 1 to 3 and comparative examples 1 to 3 were respectively tested, and the results are shown in table 6 below.
TABLE 6
| Numbering device | Leaching yield of iron (%) |
| Example 1 | 90.83 |
| Example 2 | 96.77 |
| Example 3 | 94.12 |
| Comparative example 1 | 78.81 |
| Comparative example 2 | 73.54 |
| Comparative example 3 | 92.34 |
As can be seen from the results in table 6, in example 1 using EDTA as a cosolvent, the leaching rate of iron was significantly improved and pyrite cinder was more effectively utilized, as compared with comparative example 1 (sodium hexametaphosphate as a conventional cosolvent was used in comparative example 1).
In addition, when the range of the cosolvent EDTA is not within the preferred "addition amount of the cosolvent is 3% -8% of the pyrite cinder mass" of the present invention in comparative examples 2-3, that is, the amount of the cosolvent EDTA is too small in comparative example 2, the leaching rate is low, as compared with example 1; in comparative example 3, the leaching rate is not obviously improved due to excessive cosolvent EDTA. Therefore, in the invention, the leaching rate and the EDTA consumption are comprehensively considered, and the addition amount of the cosolvent EDTA is preferably 3-8% of the pyrite cinder mass.
Comparative example
In this comparative example, battery grade anhydrous ferric phosphate was produced by the same method as in step (3) of example 1, except that ferrous sulfate heptahydrate was used instead of the ferrous sulfate reaction solutions produced in steps (1) to (2) of example 1.
The anhydrous iron phosphate prepared was tested as follows.
The anhydrous iron phosphate products prepared in example 1 and comparative example were each tested and the test results are shown in table 7.
TABLE 7
As can be seen from the results of Table 7, using the method provided by the present invention, i.e., the results of example 1, the content of each impurity was close to that of the anhydrous ferric phosphate prepared using ferrous sulfate heptahydrate as the iron source, and acceptable battery grade ferric phosphate products were obtained. By using pyrite cinder as an iron source and through a simple acid leaching process and a simple impurity removal process, the method provided by the invention can be used for preparing the qualified iron source suitable for preparing battery-grade ferric phosphate, can remarkably reduce the cost, has a simple process and is easy to industrialize.
Claims (17)
1. A method for preparing battery grade ferric phosphate by using pyrite cinder, which is characterized by comprising the following steps:
(1) Acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution;
(2) Removing impurities from the iron-containing leaching solution: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leaching solution to obtain a ferrous sulfate solution;
(3) Synthesizing ferric phosphate: reacting the ferrous sulfate solution with a phosphate solution to prepare ferric phosphate;
the primary acid leaching process comprises the following steps: adding water and cosolvent EDTA into the mixed slurry, and uniformly mixing to obtain a primary acid leaching solution;
wherein, the acid concentration in the primary acid leaching solution is controlled to be 20-85wt%; heating the primary acid leaching solution to 60-100 ℃, and reacting for 1-7h under stirring; the addition amount of the cosolvent is 3% -8% of the mass of the pyrite cinder; in step (1), the secondary acid leaching process includes: adding water into the primary acid leaching solution to control the acid concentration of the system to be 30-45wt%, reacting for 0.5-2.5h, and filtering to obtain the iron-containing leaching solution.
2. The method according to claim 1, characterized in that the acid concentration in the primary acid leaching solution is 45-70wt%.
3. The method of claim 1, wherein the primary acid leaching solution is heated to 80-100 ℃.
4. The method of claim 1, wherein the primary acid leaching process reaction time is 2-3 hours.
5. The method of claim 1, wherein the secondary acid leaching process reaction time is 1-2 hours.
6. The method of claim 1, wherein in step (1), the pulping process comprises: adding a sulfuric acid solution with the weight percent of 90-99% into the pyrite cinder, and uniformly mixing to obtain mixed slurry;
wherein, the weight ratio of acid to solid is controlled as (1-5): 1, preferably (1-3): 1, the dropping time of the sulfuric acid solution is 10-120min.
7. The method according to claim 6, wherein the sulfuric acid solution is added dropwise for 30 to 90 minutes.
8. The method of claim 1, wherein the secondary acid leaching process further comprises: washing the leached slag after filtration, and recycling washing water after washing to the secondary acid leaching process instead of water to adjust the acid concentration of the system.
9. The method of claim 1, wherein in step (2), the reducing step comprises: adding a reducing agent into the iron-containing leaching solution, reacting under stirring, and adding Fe into the solution 3+ Reduction to Fe 2+ Obtaining a crude ferrous sulfate solution;
wherein the reducing agent is one or more of sodium sulfite, sodium thiosulfate, sodium iodide and iron powder; the dosage of the reducing agent is 1.05-1.5 times of the stoichiometric ratio; the reaction time is 10-30min.
10. The method of claim 9, wherein the reducing agent is used in an amount of 1.1 to 1.3 times the stoichiometric ratio.
11. The method of claim 1, wherein in step (2), the aluminum removal process comprises: adding a pH regulator into the crude ferrous sulfate solution under stirring, regulating the pH of the solution to 3.5-5.5, completely converting trivalent aluminum ions in the solution into aluminum hydroxide precipitate, continuously stirring for 20-60 min after regulating the pH, and filtering to obtain a solution after aluminum removal;
wherein the pH regulator is one or more of sodium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate.
12. The method of claim 11, wherein the pH of the conditioning solution is 4.5-5.5.
13. The method according to claim 1, wherein in step (2), the heavy metal removal process comprises: adding a heavy metal capturing agent into the solution after aluminum removal under stirring at 40-60 ℃ for reaction for 40-90min, and then filtering to obtain ferrous sulfate solution;
wherein the heavy metal trapping agent is one or more of sodium sulfide, potassium sulfide and ammonium sulfide, and the adding amount of the heavy metal trapping agent is controlled to be 0.05-1 g/L.
14. The method of claim 13, wherein the heavy metal scavenger is added in an amount of 0.1-0.7g/L.
15. The method of claim 9, further comprising, in step (2): an iron concentration adjusting process subsequent to the heavy metal removal process, the iron concentration adjusting process comprising: adding water into the ferrous sulfate solution for dilution, and controlling the ferrous sulfate concentration in the solution to be 180-230g/kg to obtain ferrous sulfate reaction solution.
16. The method of claim 15, wherein the ferrous sulfate concentration in the control solution is 200-220g/kg.
17. The method according to claim 1, wherein in step (3), n (P): and (2) mixing the ferrous sulfate reaction solution and the phosphorus salt solution uniformly according to the ratio of n (Fe) = (1-1.05) to 1, reacting for 1-3h at 88-96 ℃, filtering to obtain an iron phosphate filter cake, and washing, drying and calcining the iron phosphate filter cake to obtain the battery-grade anhydrous iron phosphate.
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| CN102730659A (en) * | 2011-04-08 | 2012-10-17 | 江苏绿陵化工集团有限公司 | Method for preparing battery-level ferric phosphate using pyrite cinders |
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| CN114014294A (en) * | 2021-12-08 | 2022-02-08 | 高点(深圳)科技有限公司 | Method for preparing lithium iron phosphate by using pyrite and lithium iron phosphate material |
| CN114394581A (en) * | 2022-01-21 | 2022-04-26 | 雅安天蓝新材料科技有限公司 | Iron phosphate dihydrate, preparation method thereof, iron phosphate, lithium iron phosphate and lithium ion battery |
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| RU2172788C1 (en) * | 2000-07-17 | 2001-08-27 | Институт металлургии Уральского отделения РАН | Method of processing of pyrite cinders |
| CN102730659A (en) * | 2011-04-08 | 2012-10-17 | 江苏绿陵化工集团有限公司 | Method for preparing battery-level ferric phosphate using pyrite cinders |
| CN109368610A (en) * | 2018-10-09 | 2019-02-22 | 湖南雅城新材料有限公司 | A method of using pyrite cinder preparation high-speed rail phosphorus than ferric phosphate |
| CN114014294A (en) * | 2021-12-08 | 2022-02-08 | 高点(深圳)科技有限公司 | Method for preparing lithium iron phosphate by using pyrite and lithium iron phosphate material |
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