High-purity electronic-grade ferrous chloride, preparation method thereof and application of high-purity electronic-grade ferrous chloride in preparation of iron phosphate

Abstract

The invention discloses high-purity electronic-grade ferrous chloride, a preparation method thereof and application of the high-purity electronic-grade ferrous chloride in preparation of iron phosphate. According to the method disclosed by the invention, industrial-grade ferrous chloride tetrahydrate with low cost is taken as a raw material, and high-purity ferrous chloride solid can be obtained by washing without evaporative crystallization in the whole process, so that the production energy consumption is greatly reduced, the production efficiency is improved, and the production cost is reduced; and the obtained high-purity ferrous chloride solid meets the requirements of producing high-quality ferric trichloride and further producing battery-grade iron phosphate.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to high-purity electronic-grade ferrous chloride, a preparation method thereof, and application of the same in the preparation of ferric phosphate. Background Art

[0002] Ferrous chloride is an inorganic substance with the chemical formula FeCl2, which is green to yellow. It has a tetrahydrate FeCl2·4H2O, which is a transparent blue-green monoclinic crystal. Its density is 1.93g / cm 3 It is easily deliquescent and soluble in water, ethanol, and acetic acid, slightly soluble in acetone, and insoluble in ether. Anhydrous ferrous chloride is a yellow-green hygroscopic crystal that forms a light green solution when dissolved in water. The tetrahydrate salt converts to the dihydrate salt when heated to 36.5°C.

[0003] Ferrous chloride can be used directly in sewage and wastewater treatment, as a reducing agent and mordant, and is widely used in textile printing and dyeing, pigment dyeing, and manufacturing. It is also used as a component of ultra-high-pressure lubricants and is also used in medicine, metallurgy, and photography. Ferrous chloride is also used in the production of products such as ferric chloride and polyferric chloride.

[0004] Ferric chloride, produced by oxidation of ferrous chloride, can be used to produce battery-grade ferric phosphate. However, this process requires high purity of the ferrous chloride, specifically heavy metal content, to be controlled below 10 ppm. Traditionally, ferrous chloride is produced by reacting a pure iron source with hydrochloric acid, but this process has high raw material costs and is difficult to scale up. Domestic companies have used evaporation, concentration, cooling, and crystallization to purify ferrous chloride. While this method is effective, it consumes extremely high energy, hindering cost control and meeting low-carbon requirements.

[0005] Publication number CN110980833A Chinese patent discloses a method for preparing electronic-grade ferrous chloride, which uses iron-containing waste hydrochloric acid as raw material. Heavy metals such as Mn and Zn in the iron-containing waste hydrochloric acid can be effectively removed by multiple recrystallization and centrifugal filtration until electronic-grade ferrous chloride that meets control standards is obtained. Although this method realizes the industrial production of electronic-grade ferrous chloride with low-cost raw materials, its multiple recrystallization energy consumption is extremely high, and the production cost is too high. Summary of the Invention

[0006] The present invention aims to provide high-purity electronic-grade ferrous chloride, a preparation method thereof and application thereof in the preparation of ferric phosphate, thereby reducing the production energy consumption of the high-purity electronic-grade ferrous chloride, improving production efficiency and reducing production costs.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing high-purity electronic-grade ferrous chloride, comprising the following steps:

[0009] (1) placing ferrous chloride solid in a reaction kettle and adding a washing liquid equivalent to 10% to 50% of the mass of ferrous chloride;

[0010] (2) fully stirring the mixture obtained in step (1) to ensure that the solid and liquid are fully contacted and mixed;

[0011] (3) transferring the mixture obtained in step (2) to a centrifuge, separating the solid and the liquid by centrifugation to obtain washed ferrous chloride solid;

[0012] (4) Repeating steps (1) to (3) 1 to 3 times with the washed ferrous chloride solid obtained in step (3) to obtain high-purity electronic grade ferrous chloride.

[0013] As a preferred technical solution, in step (1), the ferrous chloride solid before the first washing is industrial grade ferrous chloride tetrahydrate.

[0014] As a preferred technical solution, the washing liquid is hydrochloric acid, water or ethanol with a concentration of 1% to 10%.

[0015] As a preferred technical solution, in step (2), the stirring temperature is 5°C to 50°C, and the stirring time is 10 to 60 minutes.

[0016] As a preferred technical solution, in step (3), the centrifuge speed is 800 to 2000 r / min.

[0017] As a preferred technical solution, the preferred control indicators of the high-purity electronic-grade ferrous chloride are: Zn≤1ppm, Pb≤8ppm, Co≤10ppm, Cr≤1ppm, Mg≤3ppm, Ca≤3ppm, Cu≤1ppm, Ti≤1ppm, Al≤5ppm, Na≤20ppm, and K≤10ppm.

[0018] As a preferred technical solution, in step (3), the mother liquor separated by centrifugation is used as a sewage treatment agent.

[0019] The present invention also provides high-purity electronic-grade ferrous chloride, which is prepared by the preparation method of high-purity electronic-grade ferrous chloride.

[0020] The present invention also provides an application of high-purity electronic-grade ferrous chloride in the preparation of ferric phosphate, wherein the high-purity electronic-grade ferrous chloride is oxidized into ferric oxide, which is then used to prepare ferric phosphate.

[0021] Beneficial effects of the present invention:

[0022] Traditional recrystallization purification method, first ferrous chloride is completely dissolved, now ferrous chloride and impurity therein are all dissolved in solution, then ferrous concentration is raised to reach supersaturation by evaporation concentration, then cooling is carried out, supersaturated ferrous chloride is separated from solution, and impurity elements are far from reaching saturation concentration and therefore stay in crystallization mother liquor, finally the ferrous chloride solid crystallized out is separated with the saturated ferrous chloride mother liquor with impurity, thus reach the effect of removal of impurities. The inventor of the present invention has found that the soluble metal impurities in industrial ferrous chloride overwhelming majority are attached to ferrous chloride particle surface, adopt the mode of washing, add a small amount of water or dilute hydrochloric acid, the soluble impurities and part ferrous chloride of particle surface can be dissolved, form the mixture of ferrous chloride solid and saturated mother liquor, separate ferrous chloride and mother liquor, the ferrous chloride crystal purity obtained is substantially identical with the crystal obtained by crystallization method. The technique of crystallization method purification of ferrous chloride, not only efficiency is low, its evaporation process also consumes a large amount of energy, adopts washing method to streamline technological process, improves the efficiency of purification work, especially significantly reduces production energy consumption, reduces production cost.

[0023] The invention uses low-cost industrial-grade ferrous chloride tetrahydrate as a raw material, and the obtained high-purity ferrous chloride solid meets the requirements of producing high-quality ferric chloride and further producing battery-grade ferric phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of the ferrous chloride washing and purification device used in the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described below with reference to the accompanying drawings.

[0026] Figure 1 The present invention is a schematic diagram of the structure of the ferrous chloride washing and purification device used in the present invention. The device has a simple structure. The main equipment includes a reactor 1 with stirring, a pump 2, and a centrifuge 3. There is no need to use equipment such as an evaporation concentration system and a crystallization kettle, which greatly simplifies the process and reduces production costs.

[0027] Example 1

[0028] (1) placing industrial ferrous chloride tetrahydrate solid in a reactor and adding hydrochloric acid (concentration 5%) equivalent to 15% of the mass of ferrous chloride;

[0029] (2) stirring the mixture obtained in step (1) at room temperature for 30 min to ensure sufficient contact and mixing of the solid and liquid;

[0030] (3) transferring the mixture obtained in step (2) to a centrifuge and centrifuging at a speed of 2000 r / min until no mother liquor remains, to obtain a ferrous chloride solid after washing once;

[0031] (4) Repeating steps (1) to (3) once with the ferrous chloride solid obtained in step (3) after washing once, to obtain a ferrous chloride solid after washing twice.

[0032] The heavy metal detection data of the ferrous chloride solid before and after washing in Example 1 are shown in Table 1:

[0033] Table 1

[0034]

[0035] Example 2

[0036] (1) placing industrial ferrous chloride tetrahydrate solid in a reactor and adding hydrochloric acid (concentration 5%) equivalent to 15% of the mass of ferrous chloride;

[0037] (2) stirring the mixture obtained in step (1) at room temperature for 30 min to ensure sufficient contact and mixing of the solid and liquid;

[0038] (3) transferring the mixture obtained in step (2) to a centrifuge and centrifuging at a speed of 2000 r / min until no mother liquor remains, to obtain a ferrous chloride solid after washing once;

[0039] (4) Repeat steps (1) to (3) twice with the ferrous chloride solid obtained in step (3) after washing once, to obtain the ferrous chloride solid after washing three times.

[0040] Example 2 The heavy metal detection data of the ferrous chloride solid before and after washing are shown in Table 2:

[0041] Table 2

[0042]

[0043] Example 3

[0044] (1) placing industrial ferrous chloride tetrahydrate solid in a reactor and adding ethanol equivalent to 20% of the mass of ferrous chloride;

[0045] (2) stirring the mixture obtained in step (1) at room temperature for 30 min to ensure sufficient contact and mixing of the solid and liquid;

[0046] (3) transferring the mixture obtained in step (2) to a centrifuge and centrifuging at a speed of 2000 r / min until no mother liquor remains, to obtain a ferrous chloride solid after washing once;

[0047] (4) Repeat steps (1) to (3) twice with the ferrous chloride solid obtained in step (3) after washing once, to obtain the ferrous chloride solid after washing three times.

[0048] Example 3 Heavy metal detection data of ferrous chloride solid before and after washing are shown in Table 3:

[0049] Table 3

[0050]

[0051] Example 4

[0052] (1) placing industrial ferrous chloride tetrahydrate solid in a reactor and adding water equivalent to 15% of the mass of ferrous chloride;

[0053] (2) stirring the mixture obtained in step (1) at room temperature for 30 min to ensure sufficient contact and mixing of the solid and liquid;

[0054] (3) transferring the mixture obtained in step (2) to a centrifuge and centrifuging at a speed of 2000 r / min until no mother liquor remains, to obtain a ferrous chloride solid after washing once;

[0055] (4) Repeat steps (1) to (3) twice with the ferrous chloride solid obtained in step (3) after washing once, to obtain the ferrous chloride solid after washing three times.

[0056] Example 4 Heavy metal detection data of ferrous chloride solid before and after washing are shown in Table 4:

[0057] Table 4

[0058]

[0059] It can be seen from the above examples that the present invention uses low-cost industrial-grade ferrous chloride tetrahydrate as raw material, and can obtain high-purity electronic-grade ferrous chloride only by washing without using evaporation or crystallization in the whole process.

[0060] The experimental results show that the impurity content of ferrous chloride solid obtained by washing with dilute acid is lower overall. During the experiment, we found that when washing with water and ethanol, there are certain insoluble substances in the mixture, which is caused by the hydrolysis of metal ions, including ferric ions, ferrous ions and other metal ions. These hydrolysis products still remain in the solid after centrifugation. When washing with dilute acid, the lower pH inhibits the hydrolysis of metal ions, and the impurity metal ions are dissolved in the dilute acid and separated during the centrifugation process, so the impurity removal effect is better.

[0061] In the experiment, it was found that when the same mass of dilute acid and water were used for washing, since the dilute acid contained less water and a certain amount of chloride ions, the dilute acid dissolved less ferrous chloride, so more ferrous chloride could be recovered after centrifugation.

[0062] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-purity electronic-grade ferrous chloride, characterized in that: The following steps are involved: (1) placing ferrous chloride solid in a reaction kettle and adding a washing liquid equivalent to 10% to 50% of the mass of ferrous chloride; (2) fully stirring the mixture obtained in step (1) to ensure that the solid and liquid are fully contacted and mixed; (3) transferring the mixture obtained in step (2) to a centrifuge, separating the solid and the liquid by centrifugation to obtain washed ferrous chloride solid; (4) Repeating steps (1) to (3) 1 to 3 times with the washed ferrous chloride solid obtained in step (3) to obtain high-purity electronic grade ferrous chloride.

2. The preparation method of high-purity electronic-grade ferrous chloride according to claim 1, wherein: In the step (1), the ferrous chloride solid before the first washing is industrial grade ferrous chloride tetrahydrate.

3. The preparation method of high-purity electronic grade ferrous chloride according to claim 1, wherein: The washing liquid is hydrochloric acid, water or ethanol with a concentration of 1% to 10%.

4. The preparation method of high-purity electronic grade ferrous chloride according to claim 1, wherein: In the step (2), the temperature during stirring is 5° C. to 50° C., and the stirring time is 10 to 60 minutes.

5. The preparation method of high-purity electronic grade ferrous chloride according to claim 1, wherein: In the step (3), the centrifuge speed is 800-2000 r / min.

6. The preparation method of high-purity electronic grade ferrous chloride according to claim 1, wherein: The control indicators of the high-purity electronic grade ferrous chloride are: Zn≤1ppm, Pb≤8ppm, Co≤10ppm, Cr≤1ppm, Mg≤3ppm, Ca≤3ppm, Cu≤1ppm, Ti≤1ppm, Al≤5ppm, Na≤20ppm, and K≤10ppm.

7. The method for preparing high-purity electronic-grade ferrous chloride according to claim 1, wherein: In the step (3), the mother liquor separated by centrifugation is used as a sewage treatment agent.

8. A high-purity electronic grade ferrous chloride, characterized in that: The high-purity electronic-grade ferrous chloride is prepared by the preparation method of any one of claims 1 to 7.

9. Use of the high-purity electronic grade ferrous chloride according to claim 8 in the preparation of ferric phosphate, characterized in that: High-purity electronic grade ferrous chloride is oxidized to ferric oxide, which is then used to prepare ferric phosphate.

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