Method for preparing ferromanganese phosphate from potassium permanganate

Abstract

The invention relates to a method for preparing ferromanganese phosphate from potassium permanganate, which comprises the following steps: adding an oxidizing agent into a solution containing iron ions, divalent manganese ions and phosphoric acid to form ferromanganese phosphate precipitate, and the oxidizing agent is selected from manganic acid, alkali metal salt of manganic acid, permanganate, alkali metal salt of permanganate or ferric permanganate, preferably potassium permanganate or ferric permanganate. According to the preparation method of the ferromanganese phosphate, the ferromanganese phosphate product can be stably obtained, and the proportion of Mn to Fe in the ferromanganese phosphate can be adjusted according to needs.

Description

[0001] This application claims the priority of a prior application with application number 202311659616.5, filed with the State Intellectual Property Office on December 6, 2023, and invention name “A method for preparing ferromanganese phosphate from potassium permanganate”, the full text of which is incorporated into this application. Technical Field

[0002] The invention belongs to the technical field of preparation of inorganic materials and lithium battery materials, and specifically relates to a lithium ion battery precursor material manganese (III) phosphate iron (III) and a preparation method thereof. Background Art

[0003] As positive electrode materials for lithium-ion batteries, phosphate materials represented by lithium iron phosphate have the advantages of long cycle life, high safety, abundant resources, environmental friendliness, and low cost, and they occupy an important position in the positive electrode material system of lithium-ion batteries. The synthesis process of phosphate series positive electrode materials can be divided into hydrothermal method, oxalate method, metal oxide method and phosphate method. Among them, the phosphate positive electrode material prepared by the phosphate method has the advantages of high compaction density, high electrochemical activity, simple preparation process, and good product batch stability.

[0004] Compared with lithium iron phosphate, lithium manganese iron phosphate has the advantages of stable voltage increase, long cycle life, and abundant resources, and has gradually emerged in recent years.

[0005] CN103762362B discloses a hydrothermal synthesis method of lithium manganese iron phosphate. In the method, a mixed solution containing Mn, Fe, Li and P is pumped into a mixed solution containing Li and P at a certain temperature for hydrothermal reaction, then cooled and washed to precipitate, mixed with an organic carbon source, spray dried to obtain powder, and then heat treated to obtain the product.

[0006] CN1632970A discloses a method for preparing spherical lithium iron phosphate and lithium manganese iron phosphate. Mn, Fe, P and ammonium ions are coprecipitated by coprecipitation to obtain a spherical ammonium manganese iron phosphate precursor, which is then mixed with lithium carbonate and heat treated to obtain a product.

[0007] CN107311853A discloses a method for synthesizing battery-grade ferromanganese oxalate. The method comprises the following steps: obtaining ferrous sulfate by reacting iron with dilute sulfuric acid, adding manganese sulfate to obtain a manganese-iron mixed solution, and then using a mixed solution of oxalic acid and ammonium oxalate as a precipitant to precipitate the manganese-iron to obtain manganese-iron oxalate as a precursor of lithium manganese iron phosphate.

[0008] CN105355885A discloses a method for preparing lithium manganese iron phosphate by high-energy ball milling. In this method, manganese, iron, phosphorus and an organic carbon source are uniformly mixed and then subjected to high-energy ball milling, and then heat-treated to obtain carbon-coated manganese iron pyrophosphate, which is then mixed with a lithium source and heat-treated to obtain the product. This process belongs to the high-energy ball milling process, and its elements are difficult to be evenly distributed, and the batch stability of the product is poor.

[0009] CN105185993A discloses a method for preparing lithium manganese iron phosphate. As described in Example 3, the preparation method uses ferrous oxalate as an iron source, phosphoric acid as a phosphorus source, and manganese dioxide as a manganese source. Manganese dioxide and ferrous oxalate are first mixed in a ball mill (speed 200 rpm, time 1 hour), and then phosphoric acid and polyvinyl pyrrolidone are mixed, and H 2 O 2 , stirring, aging, washing until pH = 7.0, filtering, and drying at 80°C to obtain yellow-white manganese-doped iron phosphate (Fe 0.97 Mn 0.03 PO 4 ·2H 2 O). With this iron phosphate as raw material, lithium carbonate as lithium source, sucrose was added, and LiFePO was synthesized at 750℃ for 8h in high-purity nitrogen. 4 / C material.

[0010] CN111908442A discloses a method for preparing ferromanganese phosphate, which uses manganese dioxide, ferrous oxalate, phosphoric acid and water, adds hydrogen peroxide under stirring, stirs evenly, heats up and maintains the temperature between 50-60°C, and reacts the system under ultrasonic action to obtain. The inventor repeated Examples 1-2 and did not obtain ferromanganese phosphate products, which is consistent with the common sense that manganese dioxide cannot be dissolved in phosphoric acid, especially in phosphoric acid at 50-60°C. Another possible reason for not being able to repeat the experiment is that manganese phosphate (III) is not easy to dissolve. Even if manganese phosphate is generated, it will cover the surface of manganese dioxide to form a manganese phosphate layer, preventing manganese dioxide from continuing to be reduced to form manganese phosphate. Therefore, it is understandable that the method disclosed in the patent application is difficult to repeat or has extremely high requirements for operation / raw materials, and is difficult to industrialize.

[0011] In conclusion, up to now, no effective method for preparing ferromanganese phosphate has been disclosed, and no ferromanganese phosphate product has been obtained. Summary of the invention

[0012] The invention discloses a method for preparing ferromanganese phosphate. An oxidant is added to a solution containing iron ions, divalent manganese ions and phosphoric acid to form ferromanganese phosphate precipitation, wherein the oxidant is selected from manganese acid, alkali metal salts of manganese acid, permanganic acid, alkali metal salts of permanganate or ferric permanganate, and is preferably potassium permanganate or ferric permanganate.

[0013] In the method of the present invention, in the solution containing iron ions, divalent manganese ions and phosphoric acid, the molar ratio of manganese to iron does not need to be too limited. The embodiments of the present invention prove that the relevant objectives can be achieved within the range of the molar ratio of Mn:Fe of 1:325-30:1. From the perspective of obtaining manganese iron phosphate with excellent properties, the molar ratio of Mn:Fe is preferably 1:30-30:1, more preferably 1:10-10:1, and more preferably 1:6-4:1.

[0014] In a solution containing iron ions, divalent manganese ions and phosphoric acid, the phosphoric acid content is not limited. Theoretically, it only needs to contain enough phosphate ions to form ferromanganese phosphate precipitation, that is, the ratio of the amount of phosphorus to the amount of manganese and iron (also written as phosphorus manganese iron ratio or P: (Fe + Mn)) is at least greater than 2: 1, but too much phosphoric acid is not economical and may cause ferromanganese phosphate to be difficult to precipitate, preferably 2.5≤P: (Fe + Mn) ≤ 20, more preferably 3≤P: (Fe + Mn) ≤ 10. The concentration of phosphoric acid is not limited. The embodiments of the present application have proved that the ferromanganese phosphate precipitation can be formed when the phosphoric acid concentration is between 5wt% and 80wt%, and the phosphoric acid content is preferably 10wt% to 70wt%.

[0015] The amount of oxidant added is calculated based on divalent manganese ions, and the equivalent molar amount (the molar amount required for complete reaction) is added as the best, that is, the amount of oxidant added according to the stoichiometric ratio is the best. The calculation of the equivalent molar amount needs to take into account the change of valence during the redox process. If potassium permanganate is used as an oxidant, the molar ratio of potassium permanganate to divalent manganese is 1:4, and the equivalent molar amount of potassium permanganate required to oxidize 1 mole of divalent manganese ions is 0.25 moles. Taking other factors into consideration, the ratio of the amount of oxidant of the present invention to the amount of divalent manganese ion substance is (0.1-10):1, preferably (0.9-1.1):1. In fact, the amount of oxidant added is small, such as 0.1, 0.2, and 0.3 times the molar number of divalent manganese (lower than the equivalent molar amount). Although high yield cannot be obtained, ferromanganese phosphate products will still be obtained. Similarly, the addition of too much oxidant, although uneconomical, will also obtain ferromanganese phosphate products.

[0016] The iron ion is a ferrous ion, a ferric ion, a ferrous complex ion or a ferric complex ion. When it is a ferrous ion or a ferrous complex ion, a supplementary oxidant should be added before or at the same time as the oxidant is added, preferably before the oxidant is added to reduce the consumption of the oxidant. The purpose of the supplementary oxidant of the present invention is to oxidize the ferrous ions into ferric ions to reduce the amount of oxidant used to oxidize Mn. Considering that the oxidizing property of trivalent manganese ions is stronger than that of trivalent iron ions, the oxidizing property of the supplementary oxidant can be lower than or equal to that of the oxidant. The supplementary oxidant is selected from any oxidant that can oxidize the ferrous ions into ferric ions in an acidic environment, such as an oxidant with a standard electrode potential exceeding +0.77, such as Ag ions (+0.80), Cl 2 (+1.36) etc. (see "General Chemistry Principles", Peking University Press, 4th edition, Table 10.1 on page 204), selected from hydrogen peroxide, ozone, manganic acid, manganate, permanganic acid or permanganate, preferably the supplementary oxidant is hydrogen peroxide. When the supplementary oxidant is the same as the oxidant, it indicates that more oxidants need to be added to oxidize the manganese ions while oxidizing the iron ions. Preferably, the iron ion is a ferric ion, or, as mentioned above, before adding the oxidant, the divalent iron ion or the divalent iron complex ion is oxidized to a ferric ion or a ferric complex ion by adding a supplementary oxidant.

[0017] Calculated with divalent iron ions, the amount of the supplementary oxidant added is the equivalent molar amount (according to the amount of the stoichiometric ratio) for the best. If hydrogen peroxide is the supplementary oxidant, the stoichiometric ratio of hydrogen peroxide to divalent iron ions is 1:2, then the equivalent molar amount of hydrogen peroxide corresponding to 1 mole of divalent iron ions is 0.5 moles, and the equivalent molar amounts of different oxidants are different. The amount of the supplementary oxidant is preferably greater than the equivalent molar amount. The supplementary oxidant is 80%-300% equivalent molar amount, preferably 100%-120% equivalent molar amount.

[0018] The divalent manganese ions are obtained by introducing manganous oxide or a divalent manganese salt soluble in phosphoric acid into a phosphoric acid solution or an iron-containing phosphoric acid solution. The divalent manganese salt soluble in phosphoric acid includes an inorganic acid salt of divalent manganese or an organic acid salt of divalent manganese, such as manganous sulfate, manganous chloride, manganous nitrate, manganous carbonate, manganous oxalate, manganous acetate, and manganous citrate. Preferably, the divalent manganese ions are derived from manganous oxide, manganous carbonate, and organic acid manganous salts without introducing new impurity anions.

[0019] The solution containing iron ions, divalent manganese ions and phosphoric acid is prepared from a solution, and the solution prepared from a solution refers to mixing a phosphoric acid solution, a iron ion solution and a divalent manganese ion solution in a desired proportion, or mixing a phosphoric acid solution with an iron salt and a divalent manganese salt in a desired proportion. Or the solution containing iron ions, divalent manganese ions and phosphoric acid is obtained by reacting phosphoric acid with an iron-containing substance and a divalent manganese-containing substance. The iron-containing substance is selected from one or more mixtures of ferrous oxide, ferrous oxide, ferric oxide, ferric hydroxide or ferric carbonate, and the divalent manganese-containing substance is selected from one or more mixtures of manganous oxide, manganous chloride, manganous sulfate, manganous nitrate, manganous carbonate, manganous acetate, manganous acetate or manganous citrate.

[0020] The divalent manganese-containing substance and divalent manganese salt are preferably compounds that do not introduce impurity anions, such as manganous oxide, manganous carbonate, and organic acid manganous salt. The organic acid salts remaining in the organic acid manganous salt will not introduce new impurity elements to the carbon-coated lithium manganese iron phosphate of the final product.

[0021] In the process of forming ferromanganese phosphate, water may be added or not added to the mixed solution containing iron ions, divalent manganese ions and phosphoric acid. The volume of water added is 0-10 times the volume of the aforementioned mixed solution. Adding water can promote the formation of ferromanganese phosphate from iron and manganese, and can be used to adjust the ratio of Mn and Fe in the final product ferromanganese phosphate.

[0022] The mother liquor after separation of manganese ferrophosphate is circulated back to the aforementioned step of preparing a solution containing iron ions, divalent manganese ions and phosphoric acid, which can effectively reduce the discharge of wastewater.

[0023] In one embodiment of the present invention, the present invention discloses a method for preparing ferromanganese phosphate, comprising:

[0024] S1, adding manganous oxide to a solution containing phosphoric acid and iron ions to form a solution containing iron ions, divalent manganese ions and phosphoric acid;

[0025] S2, adding an oxidant to the solution obtained in S1, heating, and performing solid-liquid separation to obtain a precipitate, which is manganese iron phosphate hydrate.

[0026] Wherein, the solution containing phosphoric acid and iron ion is prepared by solution preparation, or obtained by phosphoric acid and ferric oxide, ferrous oxide, ferric oxide, ferric hydroxide or ferric carbonate reaction, to form a phosphoric acid solution containing iron ion. The iron ion is ferrous ion, ferric ion, ferrous complex ion or ferric complex ion, preferably ferric ion or ferric complex ion. When the iron ion is partially or entirely ferrous ion or ferrous complex ion, more oxidant will be consumed, and the ferrous ion will be oxidized to ferric ion. Supplementary oxidant can also be added to oxidize the ferrous ion to become ferric ion. To ensure that the iron oxide and manganous oxide react completely, the ratio of the amount of phosphoric acid to the amount of manganese and iron [also written as P: (Fe+Mn)] is at least 2:1, preferably at least 2.5:1, but the ratio of the amount of phosphoric acid to the amount of manganese and iron should not be too high. Too high a ratio is not economical and may cause manganese iron phosphate to be difficult to precipitate. Preferably, the above ratio does not exceed 20:1, preferably 3≤P: (Fe+Mn)≤10, and more preferably 3≤P: (Fe+Mn)≤9.

[0027] The molar ratio of Mn:Fe (Mn:Fe) in the solution containing iron ions, divalent manganese ions and phosphoric acid is preferably 1:30-30:1, more preferably 1:10-10:1, and even more preferably 1:6-4:1.

[0028] The reaction in step S1 can be carried out at room temperature to 180°C, preferably at 40-120°C.

[0029] The heating temperature of step S2 is controlled between 50-140°C, preferably 60-120°C.

[0030] In one embodiment of the present invention, the present invention also discloses a method for preparing ferromanganese phosphate, comprising:

[0031] S1, adding an iron-containing oxide and manganese oxide simultaneously or in any order to a phosphoric acid solution to react and form a solution containing iron ions, divalent manganese ions and phosphoric acid;

[0032] S2, adding an oxidant to the solution obtained in S1, heating, and performing solid-liquid separation to obtain a precipitate, which is manganese iron phosphate hydrate.

[0033] The iron oxide and manganous oxide may be added to the phosphoric acid solution in any order as long as a solution containing iron ions, divalent manganese ions and phosphoric acid is ultimately formed.

[0034] Iron-containing oxide is selected from ferric oxide, ferrous oxide or ferric oxide, and iron-containing oxide can be replaced by ferric hydroxide or ferric carbonate. If iron-containing oxide contains ferrous element, ferrous ion or ferrous complex ion in solution can be oxidized to ferric ion or ferric complex ion by adding supplementary oxidant. If supplementary oxidant is not added, then in step S2, ferrous ion will first consume oxidant, increase the consumption of oxidant, from the economic point of view, preferably add supplementary oxidant in advance ferrous ion is first oxidized to ferric ion, to reduce the consumption of oxidant. Supplementary oxidant is shown in the aforementioned definition.

[0035] The molar ratio of phosphoric acid to manganese and iron [also written as P:(Fe+Mn)] is at least 2:1, preferably at least 2.5:1, but the molar ratio of phosphoric acid to manganese and iron should not be too high, as too high a ratio is uneconomical and may result in difficulty in precipitation of manganese iron phosphate. Preferably, the above ratio does not exceed 20:1, preferably 3≤P:(Fe+Mn)≤10, and more preferably 3≤P:(Fe+Mn)≤9.

[0036] The molar ratio of Mn:Fe (Mn:Fe) in the solution containing iron ions, divalent manganese ions and phosphoric acid is preferably 1:30-30:1, more preferably 1:10-10:1, and even more preferably 1:6-4:1.

[0037] The reaction in step S1 can be carried out at room temperature to 180°C, preferably at 40-120°C.

[0038] The heating temperature of step S2 is controlled between 50-140°C, preferably 60-120°C.

[0039] After the aforementioned iron oxide or / and manganous oxide reacts with phosphoric acid, the unreacted residual solid is separated and removed by solid-liquid separation, which is beneficial to reduce impurities. Solid-liquid separation is commonly used by filtering, centrifugation or static separation. Solid-liquid separation can be performed once or multiple times.

[0040] Similar to the above method, the mother liquor after separation of manganese iron phosphate is circulated back to the aforementioned step of preparing a solution containing iron ions, divalent manganese ions and phosphoric acid (step S1), which can effectively reduce the discharge of wastewater.

[0041] It should be noted that this application involves the reaction of iron oxide with phosphoric acid, and reference can be made to the method described in Chinese patent application 202210366746.9, which records various reaction conditions for the reaction of red iron oxide with phosphoric acid. For the reaction of divalent iron oxide with phosphoric acid, reference can be made to the record of Chinese patent application 202311181044.4. The corresponding contents of the two patents are introduced into this application.

[0042] The invention discloses a ferromanganese phosphate, wherein the ferromanganese phosphate has Mn x Fe 1-x PO 4 ·H 2 O, wherein 0.01≤x≤0.99, preferably 0.5≤x≤0.9, and the ferromanganese phosphate is prepared using the above method.

[0043] In fact, the inventors can formulate ferromanganese phosphate Mn x Fe 1-x PO 4 ·H 2 The ratio of Mn to Fe in O, x can be 0.1, 0.2, 0.3, 0.4, 0.6, 0.7, 0.8, 0.9, or any decimal greater than 0.01 and less than 1.

[0044] The present invention further discloses a method for preparing lithium ferromanganese phosphate, wherein ferromanganese phosphate, lithium hydroxide and a carbon source material are mixed and calcined at 500-1000°C to obtain carbon-coated lithium ferromanganese phosphate, wherein the ratio of the amount of lithium and ferromanganese substances [Li:(Mn+Fe)] is controlled to be (1.05-1.10):1, and the ratio of the amount of manganese and iron substances is (0.01-0.99):(0.99-0.01), and the ferromanganese phosphate is prepared by the aforementioned method.

[0045] Terminology explanation:

[0046] Ferric phosphate complex: Ferric phosphate-phosphate complex formed by iron phosphate and phosphoric acid, existing in the form of solution.

[0047] Iron phosphate dihydrate: also known as iron phosphate dihydrate or iron phosphate dihydrate, is iron phosphate containing two waters of crystallization. When iron phosphate precipitates from a solution, it often contains two waters of crystallization.

[0048] Phosphorus to iron ratio: In the present invention, the phosphorus to iron ratio (P:Fe) refers to the molar ratio (ratio of the amount of substance) of phosphorus element to iron element in the iron phosphate complex solution. Phosphorus refers to all phosphorus elements in the solution, and iron refers to all iron elements in the solution. For example, in the solution or product obtained by the reaction of 3 mol phosphoric acid with 1 mol ferric hydroxide, the phosphorus to iron ratio is 3:1, while the phosphorus to iron ratio of 6 mol phosphoric acid to 1 mol ferrosoferric oxide is 2:1. In the present invention, the phosphorus to iron ratio is described as 3:1 or 3, which have the same meaning, both indicating phosphorus: iron = 3:1.

[0049] Phosphorus-manganese ratio: In the present invention, it refers to the ratio of the amount of phosphorus to the amount of manganese, and is sometimes written as P:Mn.

[0050] Phosphorus-manganese-iron ratio: written as P:(Mn+Fe) or P:(Fe+Mn), it refers to the ratio of the amount of phosphorus to the amount of manganese + iron.

[0051] Ferromanganese phosphate: The ferromanganese phosphate described in the present invention is a ferromanganese phosphate having Mn x Fe 1-x PO 4 A compound composed of wherein X is a positive number less than 1.

[0052] Manganous: Manganous in the present invention refers to divalent manganese (ion or element), such as manganous oxide, manganous carbonate, and manganous organic acid. Sometimes it is also represented by "manganese (II)", such as manganese (II) oxalate.

[0053] Manganese phosphate: The manganese phosphate described in the present invention is MnPO 4 , Mn is a trivalent ion. In the present invention, monohydrated manganese phosphate MnPO 4 ·H 2 The method for preparing manganese phosphate in the present invention often refers to the method for preparing manganese phosphate monohydrate or monohydrated manganese phosphate.

[0054] Iron ions: The iron ions described in the present invention include free iron ions or iron ions in the form of complex ions. The free iron ions include divalent iron ions (Fe 2+ ), ferric ions (Fe 3+ ), complex ions include ferric complex ions and ferrous complex ions. Ferric ions tend to form ferric phosphate complex ions (belonging to ferric complex ions) in phosphoric acid solution, and ferrous ions tend to form ferrous phosphate complex ions (belonging to ferrous complex ions) in phosphoric acid solution. Since iron in ferrous complex ions and ferric complex ions still exists in the form of ferrous ions or ferric ions, thus, in the present invention, ferrous ions include ferric complex ions, and ferric ions also include ferric complex ions. In addition, in the present invention, complex also refers to complex ions, especially in solution state.

[0055] The equivalent molar amount, the equivalent molar number described in the present invention, refers to the theoretically calculated amount (amount of substance) of the oxidant or supplementary oxidant required to completely oxidize the reducing agent. The calculation of the equivalent molar amount needs to be calculated based on the change in valence during the redox reaction. To oxidize 1 mole of divalent manganese ions, the equivalent mole of ozone is 0.5 mole, and the equivalent amount of potassium permanganate is 0.25 mole.

[0056] Supplementary oxidant: any oxidant that can oxidize divalent iron ions into trivalent iron ions in an acidic environment. Generally, oxidants with a standard electrode potential exceeding +0.77 can be used as the supplementary oxidant of the present invention, such as Ag ions (+0.80), Cl 2(+1.36) etc. (See Principles of General Chemistry, Peking University Press, 4th edition, Table 10.1 on page 204). In actual processes, the supplementary oxidant and the oxidant may be the same compound or substance. It is also possible to define the oxidant as the first oxidant and the supplementary oxidant as the second oxidant.

[0057] Room temperature: refers to the indoor temperature. In the present invention, the room temperature is between 15-25°C, a temperature that does not require heating.

[0058] Gauge pressure: refers to the amount by which the total absolute pressure exceeds the surrounding atmospheric pressure or the pressure at a certain point in the liquid that is higher than the atmospheric pressure. In the present invention, gauge pressure refers to the pressure value higher than the atmospheric pressure. When converted to absolute pressure, the atmospheric pressure value should be added. In the present invention, if not specifically indicated, the pressure is absolute pressure.

[0059] min: indicates minutes.

[0060] H: indicates hours

[0061] Beneficial Effects

[0062] 1. The present invention provides a new method for preparing ferromanganese phosphate, which can stably obtain ferromanganese phosphate products and can adjust the ratio of Mn to Fe in ferromanganese phosphate as needed.

[0063] 2. The method of the present invention effectively reduces the discharge of three wastes and is a green and environmentally friendly method. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is the XRD pattern of the precipitate obtained in Example 2-3.

[0065] Figure 2 The XRD patterns of the products obtained in Examples 14-16 are shown in FIG.

[0066] Figure 3 The following are SEM images of the products obtained in Examples 14-16. DETAILED DESCRIPTION

[0067] The present invention is further described below in conjunction with the examples. It should be noted that the examples cannot be used as a limitation on the protection scope of the present invention, and those skilled in the art understand that any improvements and changes made on the basis of the present invention are within the protection scope of the present invention.

[0068] The conventional reagents used in the following examples are all commercially available.

[0069] The ozone generator used in the embodiment of the present invention is purchased from Beijing Tonglin Technology Co., Ltd., model 3S-T10, gas production, air source ≤4.5g / h, oxygen source ≤10g / h. The air source is used in the present invention.

[0070] The present application involves reacting iron oxide with phosphoric acid. Reference may be made to the method described in Chinese patent application 202210366746.9, which describes various reaction conditions for the reaction of iron red oxide with phosphoric acid. The present application example hopes to introduce the contents described in the patent application to avoid unnecessary duplication of content. The reaction temperature of iron red and phosphoric acid in the present application example is 110 ° C. In fact, as described and demonstrated in Chinese patent application 202210366746.9, other reaction temperatures are also available. In addition, the inventors also used iron black instead of iron red to react with phosphoric acid, and then added hydrogen peroxide to oxidize to obtain a phosphoric acid solution containing iron ions. These methods have been described in the prior art (such as Chinese patent ZL202311181044.4, etc.) and do not need to be repeated.

[0071] Example 1

[0072] Accurately weigh 20.9 ml of 85% wt industrial grade phosphoric acid and 29.1 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 3 3.1938g of powder was added to the phosphoric acid aqueous solution, and the mixture was heated to 110℃, kept warm for 2h, and filtered to obtain the filtrate. 3.4050g of MnO powder was added to the filtrate, and kept warm at 90℃ for 1h, and the filtrate was collected. Weigh KMnO 4 Solid 1.8965g, dissolved in 20ml H 2 O. Fe 2 O 3 The mixed solution formed by KMnO and phosphoric acid aqueous solution was heated to 90℃, and then 4 After the solution was pumped dropwise into the mixed solution, the mixture was incubated for 4 hours to obtain a turquoise precipitate. The precipitate was subjected to XRD test and the result was MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test. The ICP test results confirmed that its chemical composition was Mn 0.650 Fe 0.350 PO 4 ·H 2 O.

[0073] Example 2

[0074] Accurately weigh 31.4 ml of 85% wt industrial grade phosphoric acid and 18.6 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 33.1938g of powder was added to phosphoric acid aqueous solution, the mixture was heated to 110℃, kept warm for 2h, and filtered to obtain the filtrate. The weight of the filtrate residue was 0.0247g. 3.4050g of MnO powder was added to the filtrate, kept warm at 90℃ for 1h, and then filtered. The weight of the filtrate residue was 0.1412g. The filtrate was collected. Weigh KMnO 4 Solid 1.8965g (0.012mol), dissolved in 50ml H 2 O. Fe 2 O 3 The mixed solution formed by KMnO and phosphoric acid aqueous solution was heated to 90℃, and then 4 The solution was pumped dropwise into the mixed solution and kept warm for 4 h to obtain a cyan precipitate.

[0075] The precipitate mass was 15.0719 g, and the yield was 89.81%. The precipitate was subjected to XRD test, and the test results are shown in Figure 1 , the result is MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test. The ICP test results confirmed that its chemical composition was Mn 0.70 Fe 0.30 PO 4 ·H 2 O.

[0076] Example 3

[0077] Accurately weigh 41.9 ml of 85% wt industrial grade phosphoric acid and 8.1 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 3 3.1938g of powder was added to phosphoric acid aqueous solution, the mixture was heated to 110℃, kept warm for 2h and filtered to obtain filtrate. 3.4050g of MnO powder was added to the filtrate and kept warm at 90℃ for 1h, then filtered with suction, the residue was 0.012g, and the filtrate was collected. Weigh KMnO 4 Solid 1.8965g (0.012mol), dissolved in 50ml H 2 O. Fe 2 O 3 The mixed solution formed by KMnO and phosphoric acid aqueous solution was heated to 90℃, and then 4 The solution was pumped dropwise into the mixed solution and kept warm for 4 h to obtain a cyan precipitate.

[0078] The precipitate mass was 13.7325 g, and the yield was 81.83%. The precipitate was subjected to XRD test, and the test results are shown in Figure 1 , the result is MnPO 4 ·H 2O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test. The ICP test results confirmed that its chemical composition was Mn 0.77 Fe 0.23 PO 4 ·H 2 O.

[0079] Example 4

[0080] Accurately weigh 20.9 ml of 85% wt industrial grade phosphoric acid and 29.1 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 3 6.3876 g of powder was added to phosphoric acid aqueous solution, and the mixture was heated to 110°C and kept warm for 2 h. A large amount of turbid solid appeared in the reaction system, which was filtered. 6.81 g of MnO powder was added to the filtrate obtained after filtration. When about 2 / 3 of the powder was added, sticky solid appeared in the system and the reaction was terminated.

[0081] It is speculated that this is related to the low P:(Fe+Mn) ratio during the reaction process. In this experiment, the P:(Fe+Mn) ratio was 3:2.

[0082] Example 5

[0083] Accurately weigh 31.4 ml of 85% wt industrial grade phosphoric acid and 18.6 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 3 12.7752g of powder was added to phosphoric acid aqueous solution, the mixture was heated to 110℃, kept warm for 2h and filtered to obtain filtrate. 6.81g of MnO powder was added to the filtrate and kept warm at 90℃ for 1h, then filtered with suction, the residue was 0.012g, and the filtrate was collected. Weigh KMnO 4 Solid 3.792g (0.024mol), dissolved in 50ml H 2 O. Fe 2 O 3 The mixed solution formed by KMnO and phosphoric acid aqueous solution was heated to 90℃, and then 4 The solution was pumped dropwise into the mixed solution and kept warm for 4 h to obtain a cyan precipitate.

[0084] The mass of the precipitate was 16.4166 g, and the yield was 48.91%. The precipitate was subjected to XRD test, and the result was MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test. The ICP test results confirmed that its chemical composition was Mn 0.62 Fe 0.38 PO 4 ·H 2 O.

[0085] Example 6

[0086] Accurately weigh 20.9 ml of 85% wt industrial grade phosphoric acid and 29.1 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 3 1.5969g of powder was added to phosphoric acid aqueous solution, the mixture was heated to 110℃, kept warm for 2h, and filtered to obtain filtrate with a residue mass of 0.5781g. 4.54g of MnO powder was added to the filtrate and kept warm at 90℃ for 1h, then filtered with suction to obtain a residue mass of 0.3276g. The filtrate was collected. Weigh KMnO 4 Solid 2.5288g (0.016mol), dissolved in 50ml H 2 O. Fe 2 O 3 The mixed solution formed by KMnO and phosphoric acid aqueous solution was heated to 90℃, and then 4 The solution was pumped dropwise into the mixed solution and kept warm for 4 h to obtain a cyan precipitate.

[0087] The mass of the precipitate was 15.0922 g, and the yield was 89.93%. The precipitate was subjected to XRD test, and the result was MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test. The ICP test results confirmed that its chemical composition was Mn 0.82 Fe 0.18 PO 4 ·H 2 O.

[0088] Example 7

[0089] Accurately weigh 41.9 ml of 85% wt industrial grade phosphoric acid and 8.1 ml of pure water to prepare a phosphoric acid aqueous solution. 2 O 3 1.5969g of powder was added to phosphoric acid aqueous solution, the mixture was heated to 110℃, kept warm for 2h, and filtered to obtain filtrate with a residue mass of 0.5781g. 4.54g of MnO powder was added to the filtrate and kept warm at 90℃ for 1h, then filtered with suction to obtain a residue mass of 0.3276g. The filtrate was collected. Weigh KMnO 4 Solid 2.5288g (0.016mol), dissolved in 50ml H 2 O. Fe 2 O 3 The mixed solution formed by KMnO and phosphoric acid aqueous solution was heated to 90℃, and then 4 The solution was pumped dropwise into the mixed solution and kept warm for 4 h to obtain a cyan precipitate.

[0090] The mass of the precipitate was 14.9201 g, and the yield was 88.91%. The precipitate was subjected to XRD test, and the result was MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test. The ICP test results confirmed that its chemical composition was Mn 0.84 Fe 0.16 PO 4 ·H 2 O.

[0091] Embodiment 8-11

[0092] The same experimental operation as in Example 7 was performed using different phosphoric acid, water, Fe 2 O 3 , MnO and KMnO 4 The specific values ​​of the added amount are shown in Table 1, and the product composition results are also shown in Table 1.

[0093] Table 1 Experimental conditions and results of Examples 8-11

[0094]

[0095] Example 12

[0096] The recovered phosphoric acid obtained by the iron phosphate preparation process adopted in the present application has a density of 1.395 g / ml and a phosphoric acid concentration of 57%, wherein the iron content is 19585 mg / L and the manganese impurity content is 4237 mg / L.

[0097] Experimental process:

[0098] (1) Weigh 0.6094 g KMnO 4 Dissolve in 60 ml of water and connect to a peristaltic pump, setting the flow rate to 0.25 ml / min;

[0099] (2) Take 200 ml of recovered phosphoric acid, add 40 ml of water and place in a three-necked flask and heat in a water bath. Set the temperature of the water bath to 90°C. At this time, the solution is light pink;

[0100] (3) Raise the temperature to 90°C and pump KMnO into the solution. 4(addition rate is 15ml / h), the color of the system gradually changes to purple-red; after the system is kept warm for 20 minutes, the color of the system deepens, sampling, centrifugation, observation shows that no precipitation is produced; after 40 minutes, the color of the system deepens and becomes turbid; after 1h, the system is still turbid, sampling, centrifugation, and observation of the upper layer is purple-red transparent liquid, and the lower layer is dark green precipitation; after 2h, the system is still turbid, the color changes to dark red, sampling, centrifugation, and observation of the upper layer is purple-red transparent liquid, and the lower layer is dark green precipitation; after 3h, the system is still turbid, the color changes to brown-green, sampling, centrifugation, and observation of the upper layer is purple-red transparent liquid, and the lower layer is dark green precipitation; after 4h, the system is still turbid, sampling, centrifugation, and observation of the upper layer is purple-red transparent liquid, and the lower layer is dark green precipitation. The precipitation is washed and dried, and XRD and ICP are measured to prove that the precipitation is manganese iron phosphate monohydrate.

[0101] Example 13 Experiment of Mn:Fe=10:1

[0102] Configuration 50ml 6M H 3 PO 4 Solution (20.7 ml H 3 PO 4 +29.3ml H 2 O), take 6.4494g (0.091mol) of MnO and add it to the flask, start heating, keep it at 90℃ for 1h. Filter, keep the filtrate and transfer it to the flask. 2 O 3 0.7261 g (0.009 mol of iron) was added to the flask, and the temperature was raised and kept at 90°C for 2 h. Filtered and the filtrate was retained.

[0103] Add 50 ml H 2 O, transfer to a flask, start heating, heat to 90°C, introduce ozone (0.4L / min), and keep warm for 3h. Stop the reaction, centrifuge the reaction solution, collect the filter cake, wash, dry, and weigh.

[0104] The mass of the product is 14.1439 g. The product is subjected to ICP test to measure the content of Mn and Fe in the product. 0.946 Fe 0.054 PO 4 ·H 2 O.

[0105] Although ozone is used as the oxidant in Example 13, it is also shown that when the molar ratio of Mn:Fe is as high as 10:1, potassium permanganate having an oxidizing power equivalent to that of ozone can still be used to obtain ferromanganese phosphate product.

[0106] Embodiment 14

[0107] Weigh 3.1938g Fe 2 O 3 Powder, add 29.397g of 85%wt industrial grade phosphoric acid and 29.3g of pure water, heat to 90℃ and keep warm under stirring at 400rpm, reaction time is about 2h. Filter to obtain filtrate. Add 11.8746gMnCl 2 ·4H 2 O, heated to 90 °C with stirring at 400 rpm and kept warm until MnCl 2 ·4H 2 O is completely dissolved. MnCl 2 ·4H 2 After O is dissolved, 50 g of pure water is added and mixed, and the temperature is raised to 90°C with stirring at 500 rpm. Ozone is introduced at a rate of 0.4 L / min, and the reaction time is 3 h.

[0108] The reaction mixture was cooled, filtered, and the filtrate and filter cake were collected. The filter cake was recorded as MnCl 2 -MFP. The filter cake was weighed after drying, and the mass of the filter cake was 14.55 g, with a yield of 86.6. The dried filter cake was subjected to XRD, ICP, and SEM tests, and the XRD results were as follows: Figure 2 As shown, it is MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test, and its chemical composition was determined to be Mn 0.640 Fe 0.360 PO 4 ·H 2 O. Its SEM image is shown in Figure 3 .

[0109] Embodiment 15

[0110] Weigh 3.1938g Fe 2 O 3 Powder, add 29.397g of 85%wt industrial grade phosphoric acid and 29.3g of pure water, heat to 90℃ and keep warm under stirring at 400rpm, and react for about 2h. Filter to obtain filtrate. Add 10.1412gMnSO 4 ·H 2 O, heated to 90 °C with stirring at 400 rpm and kept warm until MnSO 4 ·H 2 O is completely dissolved. MnSO 4 ·H 2 After O is dissolved, 50 g of pure water is added and mixed, and the temperature is raised to 90°C with stirring at 500 rpm. Ozone is introduced at a rate of 0.4 L / min, and the reaction time is 3 h.

[0111] The reaction mixture was cooled, filtered, and the filtrate and filter cake were collected. The filter cake was recorded as MnSO 4 -MFP. The filter cake was weighed after drying, and the mass of the filter cake was 16.68 g, with a yield of 99.3%. The dried filter cake was subjected to XRD, ICP, and SEM tests, and the XRD results were as follows: Figure 2 As shown, it is MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test, and its chemical composition was determined to be Mn 0.664 Fe 0.336 PO 4 ·H 2 O. Its SEM image is shown in Figure 3 .

[0112] Example 16

[0113] Weigh 3.1938g Fe 2 O 3 Powder, add 29.397g of 85%wt industrial grade phosphoric acid and 29.3g of pure water, heat to 90℃ and keep warm under stirring at 400rpm, and react for about 2h. Filter to obtain filtrate. Add 6.897g MnCO 3 , heated to 90°C under stirring at 400 rpm and kept warm, filtered after 1 hour to obtain filtrate. 50 g of pure water was added to the filtrate, mixed, heated to 90°C under stirring at 500 rpm, ozone was introduced at a rate of 0.4 L / min, and the reaction time was 3 hours.

[0114] The reaction mixture was cooled, filtered, and the filtrate and filter cake were collected. The filter cake was recorded as MnCO 3 -MFP. The filter cake was weighed after drying, and the mass of the filter cake was 14.53 g, with a yield of 86.5%. The dried filter cake was subjected to XRD, ICP, and SEM tests, and the XRD results were as follows: Figure 2 As shown, it is MnPO 4 ·H 2 O structure, and the contents of Mn and Fe in the filter cake were obtained by ICP test, and its chemical composition was determined to be Mn 0.569 Fe 0.431 PO 4 ·H 2 O. Its SEM image is shown in Figure 3 .

[0115] Examples 13-16 are 4 examples in another patent application filed by the applicant on the same day, and all of them are introduced in this application. Example 13 shows that when the raw material ratio of Mn:Fe is as high as 10:1, potassium permanganate with an oxidizing power equivalent to that of ozone can still obtain ferromanganese phosphate products. Examples 14-16 also show that divalent manganese ions are not only derived from manganous oxide, but other salts containing divalent manganese can also achieve the purpose of the invention.

[0116] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing ferromanganese phosphate, characterized in that: An oxidant is added to a solution containing iron ions, divalent manganese ions and phosphoric acid to form a ferromanganese phosphate precipitate. The oxidant is selected from manganese acid, an alkali metal salt of manganese acid, permanganic acid, an alkali metal salt of permanganate or ferric permanganate, preferably potassium permanganate or ferric permanganate.

2. The method according to claim 1, characterized in that The iron ion is a divalent iron ion, a ferric iron ion, a divalent iron complex ion or a ferric iron complex ion; when it is a divalent iron ion or a divalent iron complex ion, a supplementary oxidant is added, and the supplementary oxidant is added before or at the same time as the oxidant; the supplementary oxidant is selected from an oxidant having a standard electrode potential exceeding +0.77 and capable of oxidizing the divalent iron ion into a ferric iron ion in an acidic environment, preferably hydrogen peroxide, ozone, manganic acid, manganate, permanganic acid or permanganate, and preferably the supplementary oxidant is hydrogen peroxide; the divalent manganese ion is obtained by introducing manganous oxide or a divalent manganese salt soluble in phosphoric acid into a phosphoric acid solution or an iron-containing phosphoric acid solution, and the divalent manganese salt soluble in phosphoric acid includes an inorganic acid salt of divalent manganese or an organic acid salt of divalent manganese, preferably manganous sulfate, manganous chloride, manganous nitrate, manganous carbonate, manganous oxalate, manganous acetate or manganous citrate.

3. The method according to claim 1, characterized in that The solution containing iron ions, divalent manganese ions and phosphoric acid is prepared from a solution. The solution prepared from a solution means that a phosphoric acid solution, an iron ion solution and a divalent manganese ion solution are mixed in a required proportion, or a phosphoric acid solution is mixed with an iron salt and a divalent manganese salt in a required proportion; or the solution containing iron ions, divalent manganese ions and phosphoric acid is obtained by reacting phosphoric acid with an iron-containing substance and a divalent manganese-containing substance, wherein the iron-containing substance is selected from one or more mixtures of ferrous oxide, ferrous oxide, ferric oxide, ferric hydroxide or ferric carbonate, and the divalent manganese-containing substance is selected from one or more mixtures of manganous oxide, manganous chloride, manganous sulfate, manganous nitrate, manganous carbonate, manganous acetate, manganous acetate or manganous citrate.

4. The method according to claim 1, characterized in that The steps include: S1, adding manganous oxide to a solution containing phosphoric acid and iron ions to form a solution containing iron ions, divalent manganese ions and phosphoric acid; S2, adding an oxidant to the solution of step S1, heating, and performing solid-liquid separation to obtain a precipitate, which is manganese iron phosphate hydrate; The solution containing phosphoric acid and iron ions is prepared by solution preparation, or is obtained by reacting phosphoric acid with ferric oxide, ferrous oxide, ferroferric oxide, ferric hydroxide or ferric carbonate.

5. The method according to claim 1, characterized in that The steps include: S1, adding an iron-containing oxide and manganese oxide simultaneously or in any order to a phosphoric acid solution to react and form a solution containing iron ions, divalent manganese ions and phosphoric acid; S2, adding an oxidant to the solution obtained in S1, heating, and solid-liquid separation to obtain a precipitate, which is manganese iron phosphate hydrate. Wherein, the iron-containing oxide is selected from ferric oxide, ferrous oxide or ferric oxide, or the iron-containing oxide is replaced by ferric hydroxide or ferric carbonate; when the iron-containing oxide contains divalent iron element, a supplementary oxidant is added.

6. The method according to any one of claims 1 to 5, characterized in that: In a solution containing iron ions, divalent manganese ions and phosphoric acid, the molar ratio of phosphoric acid to manganese element and iron element is controlled to be 2.5:1-20:1, preferably (3-10):1, and more preferably (3-9):1; the molar ratio of manganese element: iron element is controlled to be 1:30-30:1, preferably 1:10-10:

1.

7. The method according to any one of claims 1 to 5, characterized in that: The amount of the oxidant added is calculated based on the divalent manganese ion, and the molar ratio of the oxidant: the divalent manganese ion is (0.1-10):

1.

8. The method according to any one of claims 1 to 5, characterized in that: Before adding the oxidant, water is added to the solution containing iron ions, divalent manganese ions and phosphoric acid, and the volume of the added water is 0-10 times the volume of the solution containing iron ions, divalent manganese ions and phosphoric acid.

9. The method according to claim 4 or 5, characterized in that The reaction in step S1 is carried out at room temperature-180°C, preferably at 40-120°C.

10. The method according to claim 4 or 5, characterized in that The heating temperature in step S2 is controlled between 50-140°C, preferably 60-120°C.

11. The method according to claim 4 or 5, characterized in that After the iron oxide and / or manganous oxide reacts with phosphoric acid, unreacted residual solid is separated and removed by solid-liquid separation.

12. The method according to claim 2 or 5, characterized in that The amount of the supplementary oxidant is calculated based on the molar amount of the divalent iron ion and is 80%-300% of the equivalent molar amount, preferably 100%-120% of the equivalent molar amount.

13. The method according to any one of claims 1 to 12, characterized in that: The mother liquor after separation of ferromanganese phosphate is circulated back to the step of preparing a solution containing iron ions, divalent manganese ions and phosphoric acid.

14. A ferromanganese phosphate having Mn x Fe 1-x PO4·H2O, wherein 0.01≤x≤0.99, and the ferromanganese phosphate is prepared by the method described in any one of claims 1-13.

15. A method for preparing lithium iron manganese phosphate, comprising: mixing iron manganese phosphate, lithium hydroxide and a carbon source material, and calcining at 500-1000° C. to obtain carbon-coated lithium iron manganese phosphate, wherein: The amount ratio of lithium and ferromanganese substances [Li:(Mn+Fe)] is controlled to be (1.05-1.10):1, the amount ratio of manganese and iron substances is (0.01-0.99):(0.99-0.01), and the ferromanganese phosphate is prepared by the method described in any one of claims 1-13.

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