Method for promoting acidolysis of iron oxide red in phosphoric acid

Abstract

The invention discloses a method for promoting acidolysis of iron oxide red in phosphoric acid. The method comprises the following steps: 1) adding iron oxide red into a phosphoric acid solution at normal temperature; then adding reduced iron powder, and fully stirring; 2) carrying out continuous stirring reaction under a heating condition; and 3) filtering the reacted solution system to obtain the acidolysis solution of the iron oxide red. According to the method, iron oxide red and diluted industrial phosphoric acid are taken as main raw materials, a small amount of reduced iron powder is added under the conditions of normal temperature and relatively low H3PO4 concentration, and a heating and stirring reaction is performed, so that acidolysis of iron oxide red in phosphoric acid is effectively promoted, and the content of impurity metal ions in acidolysis liquid is reduced; the application of the obtained acidolysis solution in the fields of preparation of battery-grade iron phosphate products and the like is facilitated; and the related technological process is simple, the equipment requirement and energy consumption are low, the production cost can be effectively reduced, and the method is suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of phosphorus chemical industry and phosphorus-based new energy materials, and particularly relates to a method for promoting the acidolysis of iron oxide red in phosphoric acid. Background Art

[0002] In recent years, lithium iron phosphate batteries have been widely used in products such as new energy vehicles, mobile phones, and computers due to their excellent performance. When the lithium iron phosphate market has received unprecedented great attention, the main raw material of lithium iron phosphate, iron phosphate, has also seen a huge demand. As the precursor of lithium iron phosphate, iron phosphate has received extensive attention in the lithium battery field due to its low cost, stable structure, simple synthesis method, environmental friendliness, and easy industrialization.

[0003] At present, the development of industrial iron phosphate has been relatively mature, mainly including the sodium method, ammonium method, and iron method. Since a large amount of wastewater is generated during the production processes of the sodium method and ammonium method, and the raw material prices of the iron method (iron blocks, iron powders) are relatively high, the battery-grade iron phosphate produced by the current sodium method, ammonium method, and iron method does not have a cost advantage.

[0004] Using iron oxide red to prepare iron phosphate helps to reduce production costs, and the involved process flow is simple, without generating a large amount of harmful by-products, and the water used in the process can be recycled, with little environmental protection pressure. The literature "Research on the continuous preparation of battery-grade iron phosphate using iron oxide red as the iron source" (Chemical Industry Management, 2023, (25): 142-147) reported the optimization of the process conditions for the reaction of iron oxide red and phosphoric acid to prepare iron phosphate and the characterization of the obtained product; Patent CN112225190A discloses a method for preparing battery-grade anhydrous iron phosphate, in which iron oxide red from steel plant pickling is mixed with a phosphoric acid solution, and the filtrate and filter residue are obtained by filtration, and the filtrate is then used to prepare iron phosphate for batteries; although the above reports the methods for preparing battery-grade anhydrous iron phosphate from iron oxide red and phosphoric acid, neither of them involves the acidolysis rate of iron oxide red in phosphoric acid and the control of impurities.

[0005] Although appropriately increasing the acidolysis temperature (80-100 °C) and phosphoric acid concentration can both increase the acidolysis rate of iron red, when the phosphoric acid concentration is relatively high, polyphosphoric acid will be generated at a certain temperature, resulting in the inability of iron red to be acidolyzed. Currently, there will be filter residue remaining when using phosphoric acid to acidolyze iron oxide red, and the remaining filter residue contains more undissolved iron red. The loss of iron red in the filter residue will lead to an increase in the production raw material cost of battery-grade iron phosphate. Therefore, it is of great significance to reduce the content of impurity ions in the acidolysis solution while ensuring the acidolysis rate of iron red for the production of battery-grade iron phosphate from iron oxide red. Summary of the Invention

[0006] The object of the present invention is to provide a method for promoting the acidolysis of iron oxide red in phosphoric acid, aiming at the problems and deficiencies existing in the prior art, effectively improving the acidolysis rate of iron oxide and reducing the content of impurity metal ions in the acidolysis solution; the preparation process involved in this method is simple, the equipment requirements are low, the production cost can be effectively reduced, and it is suitable for industrial production.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for promoting the acidolysis of iron oxide red in phosphoric acid, comprising the following steps:

[0009] 1) Add iron oxide red to the phosphoric acid solution at room temperature; then add reduced iron powder and stir well.

[0010] 2) Carry out continuous stirring reaction under heating conditions.

[0011] 3) Filter the reaction solution system to obtain the acidolysis solution of iron oxide red.

[0012] In the above solution, the concentration of H3PO4 in the phosphoric acid solution is 45 - 59 wt%.

[0013] In the above solution, the dosage of iron oxide red depends on the total amount of phosphoric acid introduced, and the mass of iron oxide red is 0.18 - 0.25 times the mass of phosphoric acid (H3PO4) in the phosphoric acid solution.

[0014] In the above solution, in the iron oxide red, the content of Fe2O3 is 90.0 - 99.9 wt%; the contents of other main chemical components include: Ca 100 - 500 ppm, Mg 50 - 400 ppm, Mn 1000 - 3000 ppm, Cr 300 - 800 ppm, Al 100 - 500 ppm, Cu 50 - 300 ppm, Na 500 - 1000 ppm.

[0015] In the above solution, the phosphoric acid solution is obtained by diluting industrial phosphoric acid. In the industrial phosphoric acid, the contents of main chemical components include: Ca 0 - 10 ppm, Mg 2 - 10 ppm, Mn 0 - 5 ppm, Cr 10 - 20 ppm, Al 5 - 15 ppm, Cu 0 - 5 ppm, Na 1500 - 2000 ppm; P 25.60 - 27.10%.

[0016] In the above solution, the dosage of reduced iron powder is 0.01 - 0.05% of the total mass of the phosphoric acid solution and iron oxide red.

[0017] In the above solution, the temperature for the stirring reaction is 80 - 100 °C, and the time is 2 - 4 h.

[0018] The acidolysis solution of iron oxide red prepared according to the above scheme has the following impurity components and their contents: Al 10 - 30 ppm, Ca 20 - 50 ppm, Cr 20 - 70 ppm, Cu 5 - 10 ppm, Mg 5 - 20 ppm, Mn 100 - 300 ppm, Na 500 - 1500 ppm.

[0019] The acidolysis solution of iron oxide red obtained by the above scheme is applied to the preparation of battery - grade iron phosphate.

[0020] The principle of the present invention includes:

[0021] Under the normal temperature and acidic conditions described in the present invention, the introduced reduced iron powder reacts with the metal impurity ions in iron oxide red and industrial phosphoric acid to generate iron ions (Fe 3+ ).

[0022] xFe + 3M x+ = xFe 3+ + 3M

[0023] The generated iron ions (Fe 3+ ) further form complexes with phosphoric acid (H3PO4), and at the same time, more hydrogen ions (H + ) are generated, which further effectively promotes the acidolysis of iron oxide red in phosphoric acid and can effectively avoid the formation of substances such as polyphosphoric acid that are not conducive to the acidolysis of iron oxide red.

[0024]

[0025] Adding reduced iron powder can effectively increase the total iron content in the obtained acidolysis solution, and the increase of hydrogen ions (H + ) can also promote the reduction of the contents of impurities such as Al, Ca, Cr, Cu, Mg, and Mn in the acidolysis solution.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1) The present invention uses iron oxide red and diluted industrial phosphoric acid as the main raw materials. Under normal temperature and acidic conditions (lower H3PO4 conditions), adding a small amount of reduced iron powder and carrying out heating and stirring reactions can effectively promote the acidolysis of iron oxide red in phosphoric acid, and the residue amount after dissolution and filtration is reduced by more than 50%, improving the resource utilization value of iron oxide red;

[0028] 2) In the present invention, using iron oxide red and industrial phosphoric acid as the main raw materials and adding a small amount of reduced iron powder can effectively reduce the content of impurity metal ions in the acidolysis solution, which is beneficial to promoting the application of the obtained acidolysis solution in the fields such as the preparation of battery - grade iron phosphate products.

[0029] 3) First, the industrial phosphoric acid is diluted in the present invention to obtain a phosphoric acid solution with a certain concentration. Then, iron oxide red and reduced iron powder are added at room temperature. Finally, the temperature is raised for reaction. The involved technological process is simple, the equipment requirements and energy consumption are relatively low, the production cost can be effectively reduced, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic process flow diagram for promoting the acidolysis of iron oxide red in phosphoric acid according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] The method for promoting the acidolysis rate of iron oxide red in phosphoric acid according to the present invention includes the following steps:

[0033] 1) Weigh a certain mass of industrial-grade phosphoric acid, add pure water, and prepare a phosphoric acid solution A with a certain concentration;

[0034] 2) At room temperature, add a certain amount of iron oxide red to the phosphoric acid solution A;

[0035] 3) At room temperature, add a certain amount of reduced iron powder to the mixture obtained in step 2), stir well, and then stir and react at 80 - 100 °C for 2 - 4 h;

[0036] 4) Filter to obtain an acidolysis solution.

[0037] In the following embodiments, the main chemical components of the industrial phosphoric acid and iron oxide red used are shown in Table 1 below.

[0038] Table 1 Main components of industrial phosphoric acid and iron oxide red

[0039]

[0040] First, the present invention uses industrial phosphoric acid and pure water to prepare a phosphoric acid solution with a certain concentration. Then, a certain amount of iron oxide red is added to the phosphoric acid solution at room temperature. Finally, a certain amount of reduced iron powder is added at room temperature. With the above process design, the overall phosphorus loss rate is lower than 5%.

[0041] In a more preferred embodiment of the present invention, in step 1), the concentration of the prepared phosphoric acid solution is 45-59 wt%; in step 2), the amount of iron oxide red input depends on the total amount of phosphoric acid in the industrial phosphoric acid, and the mass of the introduced iron red is controlled to be 0.18-0.25 times the mass of phosphoric acid in the industrial phosphoric acid; in step 3), the amount of reduced iron powder introduced is 0.01-0.05% of the total mass of the phosphoric acid solution and iron oxide red.

[0042] Further, the mass of iron oxide red is more preferably 0.2 times the mass of phosphoric acid in the industrial phosphoric acid, the amount of reduced iron powder introduced is more preferably 0.05% of the total mass of the phosphoric acid solution and iron oxide red, the reaction temperature is 95 °C, and the reaction time is 3 h.

[0043] Adopting the above process, the operation is simple and can effectively improve the acidolysis rate of iron oxide red in phosphoric acid.

[0044] Example 1

[0045] A method for promoting the acidolysis degree of iron oxide red in phosphoric acid. The main components and their contents of the iron oxide red used specifically include: Ca 139.23 ppm, Mg 60.74 ppm, Mn 1667.28 ppm, Cr 326.94 ppm, Al 124.90 ppm, Cu 67.42 ppm, Na 720.82 ppm; the specific method for acidolysis of the iron oxide red includes the following steps:

[0046] 1) Weigh 300.00 g of industrial-grade phosphoric acid and add 149.49 g of pure water to prepare a phosphoric acid solution with a H3PO4 concentration of 56%;

[0047] 2) Add 50.40 g of iron oxide red (the mass of the iron red is 0.2 times the mass of phosphoric acid in the industrial phosphoric acid) to the phosphoric acid solution obtained in step 1) at room temperature;

[0048] 3) Add 0.23 g of reduced iron powder (the dosage is 0.05% of the total mass of the phosphoric acid solution and iron oxide red) to the mixture obtained in step 2) at room temperature, and continuously stir and react at 95 °C for 3 h;

[0049] 4) Filter to obtain a filter residue and an acidolysis solution of iron oxide red.

[0050] The obtained filter residue is dried and weighed, and the acidolysis rate of iron oxide red is calculated to be 99.78%; the specific component information of the obtained acidolysis solution is shown in Table 2 below.

[0051] Example 2

[0052] A method for promoting the acidolysis degree of iron oxide red in phosphoric acid. The main chemical components and their contents in the industrial phosphoric acid used include: Ca 4.77 ppm, Mg 3.91 ppm, Mn 0.48 ppm, Al 8.18 ppm, P 27.36 wt%, Cu 0.05 ppm; the main components and their contents of the iron oxide red used include: Ca 203.33 ppm, Mg 111.28 ppm, Mn 2310.79 ppm, Cr 530.89 ppm, Al 101.56 ppm, Cu 89.76 ppm, Na 876.33 ppm; the specific method for acidolysis of the iron oxide red includes the following steps:

[0053] 1) Weigh 300.00 g of industrial-grade phosphoric acid, add 149.49 g of pure water to prepare a phosphoric acid solution with a H3PO4 concentration of 56%;

[0054] 2) Add 50.40 g of iron oxide red (the mass of iron red is 0.2 times the mass of phosphoric acid in the industrial phosphoric acid) to the phosphoric acid solution obtained in step 1) at room temperature;

[0055] 3) Add 0.23 g of reduced iron powder (the dosage is 0.05% of the total mass of the phosphoric acid solution and iron oxide red) to the mixture obtained in step 2) at room temperature, and continuously stir and react at 92 °C for 4 h;

[0056] 4) Filter to obtain an acid dissolution solution. After drying and weighing the filter residue, the acidolysis rate is 99.01%. The specific data of the acidolysis solution is shown in Table 2 below.

[0057] Example 3

[0058] A method for promoting the acidolysis degree of iron oxide red in phosphoric acid. The specific main components and their contents of the iron oxide red used include: Ca 139.23 ppm, Mg 60.74 ppm, Mn 1667.28 ppm, Cr 326.94 ppm, Al 124.90 ppm, Cu 67.42 ppm, Na 720.82 ppm; the specific method for acidolysis of the iron oxide red includes the following steps:

[0059] 1) Weigh 300.00 g of industrial-grade phosphoric acid, add 149.49 g of pure water to prepare a phosphoric acid solution with a H3PO4 concentration of 56%;

[0060] 2) Add 50.40 g of iron oxide red (the mass of iron red is 0.2 times the mass of phosphoric acid in the industrial phosphoric acid) to the phosphoric acid solution in 1) at room temperature;

[0061] 3) Add 0.18 g of reduced iron powder (the dosage is 0.04% of the total mass of the phosphoric acid solution and iron oxide red) to 2) at room temperature, and continuously stir and react at 95 °C for 3 h;

[0062] 4) Filter to obtain the filter residue and the acidolysis solution of iron oxide red.

[0063] The obtained filter residue was dried and weighed, and the acidolysis rate of iron oxide red was calculated to be 99.40%; the specific composition information of the obtained acidolysis solution is shown in Table 2 below.

[0064] Comparative Example 1

[0065] A method for promoting the acidolysis degree of iron oxide red in phosphoric acid, using the same industrial phosphoric acid and iron oxide red as in Example 1. The specific method for dissolving the iron oxide red includes the following steps:

[0066] 1) Weigh 300.00 g of industrial-grade phosphoric acid and add 149.49 g of pure water to prepare a phosphoric acid solution with a H3PO4 concentration of 56%;

[0067] 2) Add 50.40 g of iron oxide red (the mass of iron red is 0.2 times the mass of phosphoric acid in the industrial phosphoric acid) to the phosphoric acid solution in step 1) at room temperature, and continuously stir and react at 95 °C for 3 h;

[0068] 3) Filter to obtain the filter residue and the acidolysis solution of iron oxide red.

[0069] The obtained filter residue was dried and weighed, and the acidolysis rate of iron oxide red was calculated to be 90.03%; the specific composition information of the obtained acidolysis solution is shown in Table 2 below.

[0070] Comparative Example 2

[0071] A method for promoting the acidolysis degree of iron oxide red in phosphoric acid, using the same industrial phosphoric acid and iron oxide red as in Example 2. The specific method for dissolving the iron oxide red includes the following steps:

[0072] 1) Weigh 300.00 g of industrial-grade phosphoric acid and add 149.49 g of pure water to prepare a phosphoric acid solution with a H3PO4 concentration of 56%;

[0073] 2) Add 50.40 g of iron oxide red (the mass of iron red is 0.2 times the mass of phosphoric acid in the industrial phosphoric acid) to the phosphoric acid solution obtained in step 1) at room temperature, and continuously stir and react at 92 °C for 4 h;

[0074] 3) Filter to obtain the filter residue and the acidolysis solution of iron oxide red.

[0075] The obtained filter residue was dried and weighed, and the acidolysis rate of iron oxide red was calculated to be 88.65%; the specific composition information of the obtained acidolysis solution is shown in Table 2 below.

[0076] Comparative Example 3

[0077] A method for promoting the acidolysis degree of iron oxide red in phosphoric acid. The industrial phosphoric acid and iron oxide red used are the same as those in Example 2. The specific method for dissolving the iron oxide red includes the following steps:

[0078] 1) Weigh 300.00 g of industrial-grade phosphoric acid, add 111.29 g of pure water, and prepare a phosphoric acid solution with a H3PO4 concentration of 62%;

[0079] 2) Add 50.40 g of iron oxide red (the mass of the iron red is 0.2 times the mass of phosphoric acid in the industrial phosphoric acid) to the phosphoric acid solution in step 1) at room temperature;

[0080] 3) Add 0.18 g of reduced iron powder (the dosage is 0.04% of the total mass of the phosphoric acid solution and iron oxide red) to step 2) at room temperature, and continuously stir and react at 95°C for 3 h;

[0081] The obtained filter residue is dried and weighed, and the acidolysis rate of the iron oxide red is calculated to be 87.53%. The specific component information of the obtained acidolysis solution is shown in Table 2 below.

[0082] Table 2 Detection data table of the acidolysis solutions prepared in the examples and comparative examples

[0083]

[0084] As can be seen from Table 2, the acidolysis rate of iron red in the comparative example is relatively low, the total iron content in the acidolysis solution is not high, and the contents of impurities such as Ca, Cr, Cu, and Mn in the acidolysis solution are relatively high. The process of the present invention can effectively improve the acidolysis rate of iron red in phosphoric acid, the total iron content in the obtained acidolysis solution is relatively high, and the contents of impurities such as Al, Ca, Cr, Cu, Mg, and Mn in the acidolysis solution are all reduced. Considering the process cost and process difficulty of the present invention, the overall cost is lower than the existing preparation process.

[0085] It is necessary to point out here that the above embodiments are only for further elaborating and explaining the technical solution of the present invention, and are not further limitations on the technical solution of the present invention. The method of the present invention is only a preferred implementation solution and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for promoting the acidolysis of iron oxide red in phosphoric acid, characterized in that, It includes the following steps: 1) Add iron oxide red to the phosphoric acid solution at room temperature; then add reduced iron powder and stir well; 2) Conduct continuous stirring reaction under heating conditions; 3) Filter the reaction solution system to obtain the acidolysis solution of iron oxide red.

2. The method according to claim 1, wherein The concentration of H3PO4 in the phosphoric acid solution is 45 - 59 wt%.

3. The method according to claim 1, wherein In the iron oxide red, the content of Fe2O3 is 90.0 - 99.9 wt%; the contents of other main chemical components include: Ca 100 - 500 ppm, Mg 50 - 400 ppm, Mn 1000 - 3000 ppm, Cr 300 - 800 ppm, Al 100 - 500 ppm, Cu 50 - 300 ppm, Na 500 - 1000 ppm.

4. The method according to claim 1, characterized in that The mass of iron oxide red is 0.18 - 0.25 times the mass of H3PO4 in the phosphoric acid solution.

5. The method according to claim 1, wherein The phosphoric acid solution is obtained by diluting industrial phosphoric acid.

6. The method according to claim 5, wherein In the industrial phosphoric acid, the contents of main chemical components include: Ca 0 - 10 ppm, Mg 2 - 10 ppm, Mn 0 - 5 ppm, Cr 10 - 20 ppm, Al 5 - 15 ppm, Cu 0 - 5 ppm, Na 1500 - 2000 ppm; P 25.60 - 27.10%.

7. The method according to claim 1, wherein The dosage of the reduced iron powder is 0.01 - 0.05% of the total mass of the phosphoric acid solution and iron oxide red.

8. The method according to claim 1, characterized in that The temperature for the stirring reaction is 80 - 100 °C, and the time is 2 - 4 h.

9. The method according to claim 1, characterized in that, For the prepared acidolysis solution of iron oxide red, the contents of its impurity components include: Al 10 - 30 ppm, Ca 20 - 50 ppm, Cr 20 - 70 ppm, Cu 5 - 10 ppm, Mg 5 - 20 ppm, Mn 100 - 300 ppm, Na 500 - 1500 ppm.

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