Method for preparing iron phosphate by using laterite nickel ore tailings

Abstract

The application discloses a method for preparing iron phosphate by using laterite nickel ore tailings, wherein the laterite nickel ore tailings and polyethylene glycol are placed in a ball mill for 10-20 min for grinding to obtain ground laterite nickel ore tailings; the laterite nickel ore tailings are added into a mixed acid solution composed of phosphoric acid solution and primary phosphoric acid ester, and are leached at 50-100 DEG C under normal pressure for 4-12 h to obtain iron phosphate after solid-liquid separation and drying. The preparation method adopts weak acid phosphoric acid for acid leaching reaction, and then directly combines the leached iron ions with phosphate ions to generate iron phosphate, thereby omitting the step of using iron for reduction when strong acid sulfuric acid is used for leaching reaction, and simplifying the leaching reaction process flow; and meanwhile, the leaching reaction is carried out by using the mixed solution of phosphoric acid and primary phosphoric acid ester after grinding, so that effective leaching under normal pressure is realized, the application range of weak acid phosphoric acid is improved, and the feasibility of the one-step direct preparation process of iron phosphate is improved.

Description

Technical Field

[0001] This invention belongs to the field of iron phosphate preparation, and particularly relates to a method for preparing iron phosphate using laterite nickel ore tailings. Background Technology

[0002] In lateritic nickel ore leaching residue, the iron content can reach up to 60%. Efficient recovery and utilization of iron from lateritic nickel ore is crucial to significantly reduce iron resource waste and achieve high-value comprehensive utilization of lateritic nickel ore. Lithium iron phosphate (LiFePO4) is gradually becoming a new type of lithium-ion battery cathode material due to its high theoretical capacity, non-toxicity, and environmental friendliness. Iron phosphate is one of the main raw materials for preparing LiFePO4. Applying lateritic nickel ore tailings to the preparation of LiFePO4 could generate significant economic value. For example, patent CN110615420A discloses a method for preparing LiFePO4 from lateritic nickel ore leaching residue, utilizing phosphoric acid oxidative leaching and adjusting the pH value with hydrogen peroxide and ammonia to prepare LiFePO4.

[0003] However, in practical applications, it has been found that phosphoric acid, as a weak acid, cannot effectively leach iron ions to directly produce iron phosphate under normal pressure conditions. It can only be achieved under pressure conditions, but the reaction equipment and reaction conditions are quite demanding under pressure conditions.

[0004] Therefore, there is an urgent need to study a technology that can use weak acid phosphoric acid to achieve phosphorus leaching under normal pressure to directly prepare iron phosphate. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a novel method for preparing ferric phosphate from laterite nickel ore tailings. This method allows iron and phosphate ions in the laterite nickel ore tailings to fully react and generate ferric phosphate under normal pressure, thereby improving the leaching rate of phosphoric acid.

[0006] Technical solution: The present invention provides a method for preparing iron phosphate using laterite nickel ore tailings, comprising the following steps:

[0007] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 10-20 minutes to obtain the ground laterite nickel ore tailings.

[0008] (2) The tailings of laterite nickel ore obtained in step (1) are added to a mixed acid solution consisting of phosphoric acid solution and primary phosphate ester, and leached at 50-100℃ and normal pressure for 4-12 hours. After solid-liquid separation and drying, iron phosphate is obtained.

[0009] Before leaching, this invention first involves grinding lateritic nickel ore tailings with polyethylene glycol. The addition of polyethylene glycol improves the dispersibility of the lateritic nickel ore tailings during grinding, increases the specific surface area of ​​the ground tailings, and activates the activity of substances contained in the tailings. Furthermore, during leaching, a mixed solution composed of phosphoric acid and primary phosphate is used. The addition of the strongly acidic primary phosphate activates the leaching of Fe ions from the lateritic nickel ore tailings, thereby accelerating the leaching reaction rate using weak acid phosphoric acid, promoting the formation of the weak acid phosphoric acid leaching reaction, and increasing the binding of iron ions and phosphate ions. This enables the leaching of lateritic nickel ore tailings using weak acid phosphoric acid under normal pressure.

[0010] Furthermore, in step (1) of this method, the amount of polyethylene glycol added can account for 1-2% of the mass of laterite nickel ore tailings.

[0011] Furthermore, in step (2) of this method, the volume ratio of phosphoric acid solution to primary phosphate ester in the mixed acid solution composed of phosphoric acid solution and primary phosphate ester can be 10-20:1.

[0012] Furthermore, in step (2) of this method, the concentration of the phosphoric acid solution can be 1-3 mol / L.

[0013] Furthermore, in step (2) of this method, the mass ratio of phosphoric acid solution to the pulverized laterite nickel ore tailings can be 8-15:1.

[0014] Preferably, in step (2) of this method, leaching can be carried out at 70-90°C and normal pressure for 8-10 hours.

[0015] Furthermore, in step (2) of this method, drying can be carried out at a temperature of 50-70℃ for 3-5 hours.

[0016] Beneficial effects: Compared with the prior art, the significant advantages of this invention are: the preparation method uses weak acid phosphoric acid for acid leaching reaction, and then directly reacts the leached iron ions with phosphate ions to generate iron phosphate, eliminating the step of iron reduction required when using strong acid sulfuric acid for leaching reaction, thus simplifying the leaching reaction process; at the same time, by first grinding and then combining with a mixed solution of phosphoric acid and primary phosphate ester for leaching reaction, effective leaching under normal pressure is achieved, which improves the application scope of weak acid phosphoric acid and the feasibility of one-step direct preparation of iron phosphate. Attached Figure Description

[0017] Figure 1 This is a phase analysis diagram of the leaching residue prepared in Example 1 of the present invention;

[0018] Figure 2 This is an electron microscope image of the iron phosphate prepared in Example 1 of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the laterite nickel ore tailings used in this invention can be purchased from Huayou Cobalt Industry, and its composition content is shown in Table 1 below.

[0021] Table 1. Composition and content of raw material laterite nickel ore tailings

[0022]

[0023]

[0024] Example 1

[0025] The method for preparing iron phosphate using laterite nickel ore tailings in Example 1 includes the following steps:

[0026] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 15 minutes to obtain the ground laterite nickel ore tailings; wherein the amount of polyethylene glycol added accounts for 1.5% of the mass of the laterite nickel ore tailings.

[0027] (2) The tailings of laterite nickel ore obtained in step (1) are added to a mixed solution composed of phosphoric acid solution and primary phosphate ester, and leached at 90°C and normal pressure for 8 hours. Solid-liquid separation is performed and the residue is dried at 60°C for 4 hours to obtain iron phosphate. The concentration of phosphoric acid solution is 2 mol / L, the mass ratio of phosphoric acid solution to the ground laterite nickel ore tailings is 10:1, and the volume ratio of phosphoric acid solution to primary phosphate ester is 15:1.

[0028] The elemental content of the laterite nickel ore tailings after the leaching reaction in this embodiment was analyzed, and the results are shown in Table 2 below.

[0029] Table 2. Elemental content of lateritic nickel ore tailings after leaching in Example 1

[0030]

[0031] As shown in Table 2, the leaching rate of Fe in Example 1 of this invention can reach 18.66%, and this method can effectively leach Fe to generate iron phosphate.

[0032] Meanwhile, the leaching residue prepared in Example 1 was subjected to XRD phase analysis and structural characterization, and the results are as follows. Figure 1 and Figure 2 As shown. (Through) Figure 1 It can be seen that the XRD analysis of the leaching residue phase corresponds to the PDF#84-0876 card, indicating that this method can fully leach iron and react with phosphate ions to form ferric phosphate. Figure 2It can be seen that the iron phosphate prepared by this invention has a small particle size and uniform particle size.

[0033] Example 2

[0034] The method for preparing iron phosphate using laterite nickel ore tailings in Example 2 includes the following steps:

[0035] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 18 minutes to obtain the ground laterite nickel ore tailings; wherein the amount of polyethylene glycol added accounts for 1% of the mass of the laterite nickel ore tailings.

[0036] (2) The tailings of lateritic nickel ore obtained in step (1) are added to a mixed solution composed of phosphoric acid solution and primary phosphate ester, and leached at 70°C and normal pressure for 10 h. Solid-liquid separation is performed and the residue is dried at 65°C for 4 h to obtain iron phosphate. The concentration of phosphoric acid solution is 2 mol / L, the mass ratio of phosphoric acid solution to the ground lateritic nickel ore tailings is 12:1, and the volume ratio of phosphoric acid solution to primary phosphate ester is 18:1.

[0037] The elemental content of the laterite nickel ore tailings after the leaching reaction in this embodiment was analyzed, and the results are shown in Table 3 below.

[0038] Table 3. Elemental content of lateritic nickel ore tailings after leaching in Example 2

[0039]

[0040] As shown in Table 3, the leaching rate of Fe in Example 2 of this invention can reach 21.89%, and this method can effectively leach Fe to generate iron phosphate.

[0041] Example 3

[0042] This embodiment 3 describes a method for preparing iron phosphate using laterite nickel ore tailings, comprising the following steps:

[0043] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 20 minutes to obtain the ground laterite nickel ore tailings; wherein the amount of polyethylene glycol added accounts for 2% of the mass of the laterite nickel ore tailings.

[0044] (2) The tailings of laterite nickel ore obtained in step (1) are added to a mixed solution composed of phosphoric acid solution and primary phosphate ester, and leached at 100°C and normal pressure for 4 hours. The solid and liquid are separated and dried at 70°C for 3 hours to obtain iron phosphate. The concentration of phosphoric acid solution is 3 mol / L, the mass ratio of phosphoric acid solution to the ground laterite nickel ore tailings is 15:1, and the volume ratio of phosphoric acid solution to primary phosphate ester is 20:1.

[0045] The elemental content of the laterite nickel ore tailings after the leaching reaction in this embodiment was analyzed, and the results are shown in Table 4 below.

[0046] Table 4. Elemental content of lateritic nickel ore tailings after leaching in Example 3

[0047]

[0048] As shown in Table 4, the leaching rate of Fe in Example 3 of the present invention can reach 20.75%, and the method can effectively leach Fe to generate iron phosphate.

[0049] Example 4

[0050] This Example 4 describes a method for preparing iron phosphate using laterite nickel ore tailings, comprising the following steps:

[0051] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 10 minutes to obtain the ground laterite nickel ore tailings; wherein the amount of polyethylene glycol added accounts for 1.5% of the mass of the laterite nickel ore tailings.

[0052] (2) The tailings of laterite nickel ore obtained in step (1) are added to a mixed solution composed of phosphoric acid solution and primary phosphate ester, and leached at 50°C and normal pressure for 12 hours. The solid and liquid are separated and dried at 50°C for 5 hours to obtain iron phosphate. The concentration of phosphoric acid solution is 1 mol / L, the mass ratio of phosphoric acid solution to the ground laterite nickel ore tailings is 8:1, and the volume ratio of phosphoric acid solution to primary phosphate ester is 10:1.

[0053] The elemental content of the laterite nickel ore tailings after the leaching reaction in this embodiment was analyzed, and the results are shown in Table 5 below.

[0054] Table 5. Elemental content of lateritic nickel ore tailings after leaching in Example 4

[0055]

[0056] As shown in Table 5, the leaching rate of Fe in Example 4 of this invention can reach 25.34%, and this method can effectively leach Fe to generate iron phosphate.

[0057] Comparative Example 1

[0058] The basic steps are the same as in Example 1, except that only phosphoric acid is used for the leaching reaction, instead of a mixed acid solution composed of phosphoric acid and primary phosphate esters. It includes the following steps:

[0059] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 15 minutes to obtain the ground laterite nickel ore tailings; wherein the amount of polyethylene glycol added accounts for 1.5% of the mass of the laterite nickel ore tailings.

[0060] (2) The tailings of laterite nickel ore obtained in step (1) are added to a phosphoric acid solution and leached at 90°C and normal pressure for 8 hours. The solid and liquid are separated and dried at 60°C for 4 hours to obtain iron phosphate. The concentration of the phosphoric acid solution is 2 mol / L and the mass ratio of the phosphoric acid solution to the ground laterite nickel ore tailings is 10:1.

[0061] The elemental content of the tailings from the laterite nickel ore after the comparative leaching reaction was analyzed, and the results are shown in Table 6 below.

[0062] Table 6. Elemental content of lateritic nickel ore tailings after leaching in Comparative Example 1

[0063]

[0064] As shown in Table 6, without the addition of primary ferric phosphate, very few iron ions were leached, with a leaching rate of only 2.47%.

[0065] Comparative Example 2

[0066] The basic steps are the same as in Example 1, except that only phosphoric acid is used for the leaching reaction, instead of a mixed acid solution composed of phosphoric acid and primary phosphate esters, and the concentration of phosphoric acid is increased. It includes the following steps:

[0067] (1) Place the laterite nickel ore tailings and polyethylene glycol in a ball mill and grind for 15 minutes to obtain the ground laterite nickel ore tailings; wherein the amount of polyethylene glycol added accounts for 1.5% of the mass of the laterite nickel ore tailings.

[0068] (2) The tailings of laterite nickel ore obtained in step (1) are added to a phosphoric acid solution and leached at 90°C and normal pressure for 8 hours. The solid and liquid are separated and dried at 60°C for 4 hours to obtain iron phosphate. The concentration of the phosphoric acid solution is 5 mol / L and the mass ratio of the phosphoric acid solution to the ground laterite nickel ore tailings is 10:1.

[0069] The elemental content of the tailings from the laterite nickel ore after the comparative leaching reaction was analyzed, and the results are shown in Table 7 below.

[0070] Table 7. Elemental content of lateritic nickel ore tailings after leaching in Comparative Example 2

[0071]

[0072] As shown in Table 7, even with an increase in the concentration of phosphoric acid, the amount of iron ions leached out is still very small without the addition of primary ferric phosphate, with a leaching rate of only 1.71%.

[0073] Performance testing

[0074] The iron phosphates prepared in Examples 1-4 were subjected to performance tests, and the test results are shown in Table 8 below.

[0075] Table 8. Performance test results of the iron phosphate prepared in Examples 1-4

[0076]

[0077] As shown in Table 8, the iron phosphate prepared by the method provided in this invention has the same main parameters as lithium iron phosphate, such as iron-phosphorus ratio, particle size, tap density, and specific surface area.

[0078] The iron phosphates prepared in Examples 1-4 above were subjected to ICP impurity element testing and magnetic foreign matter testing. The test results are shown in Table 9 below.

[0079] Table 9 shows the ICP impurity element test and magnetic foreign matter properties of ferric phosphate in Examples 1-4.

[0080]

[0081] As can be seen from the data in Table 9, the iron phosphate prepared by this invention has significantly lower contents of impurity elements and magnetic foreign matter, meeting the requirements for finished products. Excessive magnetic material content can affect the safety performance of the material and increase the probability of cell accidents.

Claims

1. A method for preparing ferric phosphate using laterite nickel ore tailings, characterized in that... Includes the following steps: (1) Place lateritic nickel ore tailings and polyethylene glycol in a ball mill and grind for 10-20 minutes to obtain ground lateritic nickel ore tailings; the amount of polyethylene glycol added accounts for 1-2% of the mass of the lateritic nickel ore tailings; (2) The tailings of laterite nickel ore obtained in step (1) are added to a mixed acid solution consisting of phosphoric acid solution and primary phosphate ester, and leached at 50-100℃ and normal pressure for 4-12h. After solid-liquid separation and drying, iron phosphate is obtained; wherein the volume ratio of phosphoric acid solution to primary phosphate ester is 10-20:1, and the concentration of phosphoric acid solution is 1-3mol / L.

2. The method for preparing ferric phosphate using laterite nickel ore tailings according to claim 1, characterized in that: In step (2), the mass ratio of the phosphoric acid solution to the pulverized laterite nickel ore tailings is 8-15:

1.

3. The method for preparing ferric phosphate using laterite nickel ore tailings according to claim 1, characterized in that: In step (2), the leaching is carried out at 70-90℃ and normal pressure for 8-10 hours.

4. The method for preparing ferric phosphate using laterite nickel ore tailings according to claim 1, characterized in that: In step (2), the drying is carried out at a temperature of 50-70℃ for 3-5 hours.

Images