A method for preparing battery-grade ferric phosphate dihydrate using flotation copper tailings

Abstract

The present invention belongs to the technical field of new energy materials, and specifically discloses a method for preparing battery-grade iron phosphate dihydrate by using flotation copper tailings. The method comprises the following steps: (1) heating the flotation copper tailings; (2) mixing an acid with the flotation copper tailings, and stirring until the acid solution evaporates to dryness; (3) adding distilled water and stirring; (4) solid-liquid separation; (5) oxidizing the divalent iron in the iron-zinc solution obtained in step (4) into trivalent iron; (6) adding anhydrous disodium hydrogen phosphate solid or dodecahydrate disodium hydrogen phosphate solid to the solution obtained in step (5) until the molar ratio of iron to phosphorus in the solution is 1:1.0-1.3; (7) solid-liquid separation, drying the filter cake to obtain crude iron phosphate; (8) recrystallizing and removing impurities from the crude iron phosphate; (9) washing, filtering, and drying to obtain battery-grade iron phosphate dihydrate. The method realizes the effective separation of iron, silicon, and zinc in the flotation copper tailings, thereby realizing its high-value utilization, has a simple process flow, and has a good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy materials, and specifically discloses a method for preparing battery-grade ferric phosphate dihydrate by utilizing flotation copper tailings. Background Art

[0002] At present, most of the metal resources needed for human life and production come from mining and mineral resource development. Copper tailings are a large amount of industrial solid waste produced in the process of copper metallurgy (matte smelting). my country's copper tailings production is as high as 334 million tons, and a large amount of storage occupies land. Copper tailings can be further recovered by flotation, and the residue is flotation copper tailings. Although flotation recovers the copper in the copper tailings, the flotation copper tailings has not been reduced, and its large-scale storage occupies land. There are nearly 60wt% iron and 3wt% zinc in the flotation copper tailings. The existing resource recovery path mainly uses flotation copper tailings for steel smelting and cement preparation. The product value is low and zinc recovery cannot be achieved. Traditional acid leaching treatment will produce silica gel, which affects the recovery of metal elements.

[0003] As an important inorganic functional material, iron phosphate has broad application prospects in the preparation of ceramics, lithium-ion batteries, catalysis and coating materials. With the popularization of new energy electric vehicles, LiFePO 4 The demand for batteries has increased significantly, and their prices have also soared.

[0004] CN 101844756B discloses a method for preparing lithium iron phosphate from steel slag, which comprises selecting steel slag containing Fe and P, performing reduction treatment on the steel slag at 1200-1600° C. to obtain a Fe-P-based alloy containing doped elements; performing oxidation treatment on the Fe-P-based alloy containing doped elements in air at 500-1000° C. to obtain oxides of Fe, P and doped elements, that is, preparing LiFePO 4 However, the oxidation-reduction temperature of this technology is too high, and the energy consumption is huge, which is not conducive to the realization of the "dual carbon" goal.

[0005] CN 113184821A discloses a method for preparing ferric phosphate from iron-containing slag, which comprises pickling the iron-containing slag to obtain pickled iron slag, mixing the pickled iron slag with acid and phosphate to obtain mixed particles, and roasting to obtain a roasted product; heating the roasted product under acidic conditions to obtain iron phosphate slurry; and performing solid-liquid separation on the iron phosphate slurry to obtain a crude iron phosphate product and a valuable metal solution. However, the iron-containing slag in this technology does not contain silicon, which is different from the research object of this technology.

[0006] Therefore, based on the background of the development of the new energy industry, this technology proposes a resource utilization route of using flotation copper tailings to prepare battery-grade iron phosphate dihydrate and separate and recover zinc, thereby realizing the high-value utilization of flotation copper tailings, which has important application prospects and promotion value. Summary of the invention

[0007] In order to overcome the problems of high economic cost and great environmental impact of the above-mentioned prior art, the present invention provides a new method for preparing battery-grade ferric phosphate dihydrate using flotation copper tailings. The method is simple to operate, and the raw materials are cheap and easy to obtain compared with the traditional process. Moreover, the residue after iron and zinc are recovered still has utilization value, which provides a new way for the clean disposal and resource utilization of flotation copper tailings, and has broad application prospects.

[0008] The inventive concept of the present invention is: experiments show that acid leaching can achieve efficient leaching of iron and zinc in flotation copper tailings. However, when filtering and separating soluble components from residual solids, the production of silica gel will block filter paper / filter cloth, greatly affecting the filtering performance, making it difficult to separate and filter iron, zinc and residual solids in the leachate, and affecting the synthesis and preparation efficiency of subsequent precursors. It can be seen from the DLVO theory that increasing the ionic strength of the solution can reduce the activity coefficient of silicon, reduce the electrostatic repulsion between silica gel particles, and cause silica gel to aggregate and precipitate to form amorphous silicon dioxide. Based on this theory, the present invention first heats the flotation copper tailings, then adds an acid solution to the flotation copper tailings, and uses the heat energy after heating the flotation copper tailings to evaporate the acid solution, and through the reduction of the liquid phase volume, the ionic strength of the solution is increased, the activity coefficient of silicon is reduced, and the silica gel is aggregated and precipitated, which is easy to filter, so as to achieve efficient separation of metal ions and silicon in the flotation copper tailings.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for preparing battery-grade ferric phosphate dihydrate by using flotation copper tailings comprises the following steps:

[0011] (1) heating the flotation copper tailings;

[0012] (2) taking out the copper flotation tailings after the heat treatment in step (1), quickly mixing it with the acid solution, and stirring until the acid solution evaporates to dryness;

[0013] (3) adding distilled water to the solid obtained in step (2) and stirring;

[0014] (4) subjecting the solid-liquid mixture obtained in step (3) to solid-liquid separation to obtain an iron-zinc solution and a silicon-rich residue; the silicon-rich residue can be used as a cement admixture;

[0015] (5) oxidizing the divalent iron in the iron-zinc solution obtained in step (4) into trivalent iron;

[0016] (6) adding anhydrous disodium hydrogen phosphate solid or disodium hydrogen phosphate dodecahydrate solid to the solution obtained in step (5) until the molar ratio of iron to phosphorus in the solution is 1:1.0 to 1.3; at this time, the pH of the solution is 1.3 to 1.5;

[0017] (7) filtering the solid-liquid mixture obtained in step (6) to obtain a zinc-containing solution, and drying the filter cake to obtain crude iron phosphate; the zinc-containing solution can be used to prepare a zinc sulfate product;

[0018] (8) Recrystallizing and removing impurities from the crude ferric phosphate;

[0019] (9) Wash the product obtained in step (8) with distilled water, filter, and dry to obtain battery-grade iron phosphate dihydrate.

[0020] Furthermore, the heating treatment conditions in step (1) are: heating temperature is 120-200° C., and heating time is 30-90 min; preferably, heating temperature is 120-150° C., and heating time is 60-75 min.

[0021] Furthermore, in step (2), the acid solution is sulfuric acid or hydrochloric acid, the concentration of the acid solution is 2.0 to 6.0 mol / L, preferably, the concentration of the acid solution is 2.5 to 5 mol / L; the liquid-solid ratio of the acid solution to the flotation copper tailings is 1 to 10 mL: 1 g, preferably, the liquid-solid ratio is 2 to 4 mL: 1 g.

[0022] Furthermore, the liquid-to-solid ratio of the distilled water added in step (3) to the flotation copper tailings in step (1) is 5-20 mL:1 g, preferably, the liquid-to-solid ratio is 5-10 mL:1 g; the stirring time is 10-60 min, preferably, the stirring time is 25-35 min.

[0023] Furthermore, the step of oxidizing the divalent iron to the trivalent iron in step (5) is as follows: adding a hydrogen peroxide solution to the iron-zinc solution obtained in step (4), or aerating the iron-zinc solution obtained in step (4); preferably, the concentration of the hydrogen peroxide solution is 30wt%, and the liquid-to-solid ratio of the hydrogen peroxide solution added in step (5) to the flotation copper tailings in step (1) is 0.5-1mL:1g; or aerating for 60-120min.

[0024] Furthermore, in step (6), the molar ratio of iron to phosphorus is 1:1.1-1.3.

[0025] Furthermore, the recrystallization step in step (8) is as follows: crude ferric phosphate and a certain amount of hydrochloric acid are placed in a reaction kettle and heated at 150-210° C. for 2-5 hours, the concentration of the hydrochloric acid is 5-20wt%, and the liquid-to-solid ratio of hydrochloric acid to crude ferric phosphate is 0.5-3.0mL:1g.

[0026] The present invention proposes a technical route of evaporation and silicon inhibition - acid leaching of iron and zinc - impurity removal and synthesis - zinc solution recovery, which realizes the preparation of battery-grade ferric phosphate dihydrate and the recovery of zinc, and is a high-value flotation copper tailings resource utilization path.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The present invention heats the flotation copper tailings first, then mixes the acid solution with the flotation copper tailings, and uses the remaining heat to evaporate the acid solution, thereby increasing the solution ion strength and reducing the activity coefficient of silicon, reducing the electrostatic repulsion between silica gel particles, and causing silica gel to aggregate and precipitate to form amorphous silicon dioxide. This not only suppresses the influence of silica gel on subsequent steps in the conventional acid leaching process for recovering metals, but also the residue after recovering metal elements is rich in silicon, and is a high-quality raw material for cement admixture.

[0029] (2) The present invention not only adds a phosphorus source but also adjusts the pH value of the solution by adding anhydrous disodium hydrogen phosphate / disodium hydrogen phosphate dodecahydrate, thereby saving the cost of NaOH.

[0030] (3) The present invention realizes high-value utilization of flotation copper tailings, has a simple process flow and high resource utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a basic flow chart for preparing battery-grade iron phosphate dihydrate using flotation copper tailings;

[0032] Figure 2 This is the XRD spectrum of the battery-grade iron phosphate dihydrate prepared in Example 1, which is confirmed to be iron phosphate dihydrate after comparison with the standard spectrum;

[0033] Figure 3 This is the infrared spectrum of the battery-grade iron phosphate dihydrate prepared in Example 1. It can be seen from the figure that the wave number range of the vibration characteristic peak of crystal water is 3000-3600cm -1 and 1600-1670cm -1 , PO 4 3- The vibration characteristic peaks are 940-1120cm -1 , the symmetric and asymmetric vibrations of the Fe-OP ring are 700-800 cm -1 , the bending vibration of Fe-OP bond is 500-600cm -1 , FTIR proved that the sample was iron phosphate dihydrate. DETAILED DESCRIPTION

[0034] The applicant will further explain the present invention in detail below with reference to specific embodiments. The embodiments are only used to help understand the present invention, but the protection scope requested by the claims of the present invention is not limited thereto.

[0035] The flotation copper tailings used in the examples were all provided by a company in Hubei. The total iron content of the flotation copper tailings was 378.85 g / kg. The main chemical components and contents are shown in Table 1:

[0036] Table 1 Main components and contents of flotation copper tailings (wt%)

[0037]

[0038] *The iron-containing phases are mainly olivine and a small amount of iron oxide, and ferrous iron accounts for more than 90% of the total iron

[0039] Example 1 A method for preparing battery-grade iron phosphate dihydrate using flotation copper tailings, the specific steps are as follows:

[0040] (1) 20 g of flotation copper tailings were placed in a muffle furnace, heated from room temperature to 150 °C at a rate of 5 °C / min and kept at this temperature for 60 minutes;

[0041] (2) taking out the copper flotation tailings after the heat treatment in step (1), quickly pouring 60 mL of 3.5 mol / L sulfuric acid solution into the taken out copper flotation tailings, stirring, and using the residual heat of the copper flotation tailings to evaporate the acid solution to dryness;

[0042] (3) adding 100 mL of distilled water to the solid obtained in step (2) and stirring for 30 minutes;

[0043] (4) subjecting the solid-liquid mixture obtained in step (3) to solid-liquid separation to obtain an iron-zinc solution and a silicon-rich residue;

[0044] (5) adding 10 mL of 30 wt % hydrogen peroxide solution to the iron-zinc solution (pH=0.6) obtained in step (4) to oxidize the divalent iron in the solution into trivalent iron;

[0045] (6) adding 20.5 g of anhydrous disodium hydrogen phosphate solid to the solution obtained in step (5) so that the molar ratio of iron to phosphorus in the solution is 1:1.1, and the pH of the solution is 1.3;

[0046] (7) filtering the solid-liquid mixture obtained in step (6) to obtain a zinc-containing solution, and drying the filter cake to obtain crude iron phosphate (about 19.8 g);

[0047] (8) placing the crude iron phosphate obtained in step (7) and 10 mL of 8 wt % hydrochloric acid in a reaction kettle, and heating at 180° C. for 4 h to recrystallize and remove impurities;

[0048] (9) After the reaction kettle is cooled to room temperature, the product obtained in step (8) is washed with distilled water, filtered, and dried at 80° C. for 24 h to obtain battery-grade iron phosphate dihydrate. Its XRD and infrared spectra are shown in Figures 2-3 Its composition and content are shown in Table 2.

[0049] Example 2 A method for preparing battery-grade iron phosphate dihydrate using flotation copper tailings, the specific steps are as follows:

[0050] (1) 20 g of flotation copper tailings were placed in a muffle furnace, heated from room temperature to 120 °C at a rate of 5 °C / min and kept at this temperature for 75 minutes;

[0051] (2) taking out the copper flotation tailings after the heat treatment in step (1), quickly pouring 40 mL of 5.0 mol / L sulfuric acid solution into the taken out copper flotation tailings, stirring, and using the residual heat of the copper flotation tailings to evaporate the acid solution to dryness;

[0052] (3) adding 200 mL of distilled water to the solid obtained in step (2) and stirring for 30 minutes;

[0053] (4) subjecting the solid-liquid mixture obtained in step (3) to solid-liquid separation to obtain an iron-zinc solution and a silicon-rich residue;

[0054] (5) aerating the iron-zinc solution (pH=0.6) obtained in step (4) for 90 minutes to oxidize the divalent iron in the solution into trivalent iron;

[0055] (6) adding 56.7 g of solid disodium hydrogen phosphate dodecahydrate to the solution obtained in step (5) so that the molar ratio of iron to phosphorus in the solution is 1:1.2, and the pH of the solution is 1.4;

[0056] (7) filtering the solid-liquid mixture obtained in step (6) to obtain a zinc-containing solution, and drying the filter cake to obtain crude iron phosphate (about 20.2 g);

[0057] (8) placing the crude iron phosphate obtained in step (7) and 10 mL of 10 wt% hydrochloric acid in a reaction kettle, and heating at 200° C. for 3 h to perform recrystallization and impurity removal;

[0058] (9) After the reactor was cooled to room temperature, the product obtained in step (8) was washed with distilled water, filtered, and dried at 80° C. for 24 h to obtain battery-grade ferric phosphate dihydrate. The composition and content of the product are shown in Table 2.

[0059] Example 3 A method for preparing battery-grade iron phosphate dihydrate using flotation copper tailings, the specific steps are as follows:

[0060] (1) 20 g of flotation copper tailings were placed in a muffle furnace, heated from room temperature to 150 °C at a rate of 5 °C / min and kept at this temperature for 60 minutes;

[0061] (2) taking out the copper flotation tailings after the heat treatment in step (1), quickly pouring 80 mL of 2.5 mol / L sulfuric acid solution into the taken out copper flotation tailings, stirring, and using the residual heat of the copper flotation tailings to evaporate the acid solution to dryness;

[0062] (3) adding 160 mL of distilled water to the solid obtained in step (2) and stirring for 30 minutes;

[0063] (4) subjecting the solid-liquid mixture obtained in step (3) to solid-liquid separation to obtain an iron-zinc solution and a silicon-rich residue;

[0064] (5) adding 10 mL of a 30 wt % hydrogen peroxide solution to the iron-zinc solution (pH=0.8) obtained in step (4) to oxidize the divalent iron in the solution into trivalent iron;

[0065] (6) adding 24.4 g of anhydrous disodium hydrogen phosphate solid to the solution obtained in step (5) so that the molar ratio of iron to phosphorus in the solution is 1:1.3, and the pH of the solution is 1.5;

[0066] (7) filtering the solid-liquid mixture obtained in step (6) to obtain a zinc-containing solution, and drying the filter cake to obtain crude iron phosphate (about 20.5 g);

[0067] (8) placing the crude iron phosphate obtained in step (7) and 10 mL of 15 wt% hydrochloric acid in a reaction kettle, and heating at 150° C. for 5 h to recrystallize and remove impurities;

[0068] (9) After the reactor was cooled to room temperature, the product obtained in step (8) was washed with distilled water, filtered, and dried at 80° C. for 24 h to obtain battery-grade ferric phosphate dihydrate. The composition and content of the product are shown in Table 2.

[0069] Table 2 Main components and contents of samples in Examples 1 to 3 (wt%)

[0070] sample P Fe Ca Mg Na Cu Zn K Mn Ti Co Pb Cr Moisture Iron-phosphorus ratio Example 1 16.84 30.00 0.000 0.000 0.001 0.000 0.000 0.004 0.000 0.07 0.000 0.000 0.000 19.28 0.99 Example 2 16.76 29.30 0.003 0.000 0.000 0.000 0.000 0.005 0.000 0.09 0.000 0.000 0.000 20.60 0.97 Example 3 17.00 29.52 0.000 0.000 0.003 0.000 0.001 0.007 0.000 0.09 0.000 0.000 0.000 20.20 0.96 HG / T4701-2021 16.2～17.2 28.5～30.0 ≤0.005 ≤0.005 ≤0.01 ≤0.005 ≤0.005 ≤0.01 ≤0.02 ≤0.15 ≤0.005 ≤0.01 ≤0.005 19.0～21.0 0.96～1.02

Claims

1. A method for preparing battery-grade ferric phosphate dihydrate using flotation copper tailings, characterized in that: The steps include: (1) The flotation copper tailings are heated at a temperature of 120-200°C for a heating time of 30-90 minutes; (2) taking out the copper flotation tailings after the heat treatment in step (1), quickly mixing it with the acid solution, and stirring it until the acid solution evaporates to dryness; in step (2): the acid solution is sulfuric acid or hydrochloric acid, and the concentration of the acid solution is 2.0-6.0 mol / L; the liquid-to-solid ratio of the acid solution to the copper flotation tailings is 1-10 mL:1 g; (3) adding distilled water to the solid obtained in step (2) and stirring; (4) subjecting the solid-liquid mixture obtained in step (3) to solid-liquid separation to obtain an iron-zinc solution and a silicon-rich residue; (5) oxidizing the divalent iron in the iron-zinc solution obtained in step (4) into trivalent iron; (6) adding anhydrous disodium hydrogen phosphate solid or disodium hydrogen phosphate dodecahydrate solid to the solution obtained in step (5) until the molar ratio of iron to phosphorus in the solution is 1:1.1-1.3, and the pH of the solution is 1.3-1.5; (7) filtering the solid-liquid mixture obtained in step (6), and drying the filter cake to obtain crude ferric phosphate; (8) Recrystallizing the crude ferric phosphate to remove impurities; (9) Wash the product obtained in step (8) with distilled water, filter, and dry to obtain battery-grade iron phosphate dihydrate.

2. The method according to claim 1, characterized in that The heating temperature is 120~150℃ and the heating time is 60~75min.

3. The method according to claim 1, characterized in that: In step (2), the liquid-to-solid ratio of the acid solution to the flotation copper tailings is 2-4 mL: 1 g.

4. The method according to claim 1, characterized in that: In step (2): the concentration of the acid solution is 2.5~5 mol / L.

5. The method according to claim 1, characterized in that The liquid-to-solid ratio of the distilled water added in step (3) to the flotation copper tailings in step (1) is 5-20 mL: 1 g; and / or: the stirring time is 10-60 min.

6. The method according to claim 5, characterized in that The liquid-to-solid ratio is 5~10mL:1g; and / or: the stirring time is 25~35min.

7. The method according to claim 1, characterized in that The step of oxidizing the divalent iron into trivalent iron in step (5) is: adding a hydrogen peroxide solution to the iron-zinc solution, or aerating the iron-zinc solution.

8. The method according to claim 7, characterized in that The concentration of the hydrogen peroxide solution is 30 wt %, and the liquid-to-solid ratio of the hydrogen peroxide solution added in step (5) to the flotation copper tailings in step (1) is 0.5-1 mL:1 g; or aeration is performed for 60-120 min.

9. The method according to claim 1, characterized in that: The recrystallization step in step (8) is as follows: crude ferric phosphate and a certain amount of hydrochloric acid are placed in a reaction kettle and heated at 150-210° C. for 2-5 hours.

10. The method according to claim 9, characterized in that The concentration of the hydrochloric acid is 5-20wt%, and the liquid-solid ratio of the hydrochloric acid to the crude ferric phosphate is 0.5-3.0 mL: 1g.

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