Production and purification method of calcium and magnesium ions in ferrous sulfate solution

Abstract

The invention discloses a method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution. The method comprises the following steps: adding HF which is 1.2-2.5 times of the amount of substance of calcium and magnesium ions into a ferrous sulfate solution containing calcium and magnesium ions, then adding a neutralizer to adjust the pH value to 2.5-3.5, and reacting at 50-70 DEG C for 2-4 hours; adding calcium salt, keeping the temperature and reacting, and filtering; adjusting the pH value to 1.5-2.0, and freezing and crystallizing for 10-14 hours; and finally, carrying out centrifugal separation to obtain low-calcium and low-magnesium ferrous sulfate heptahydrate. The method is simple in process, easy and convenient to operate and low in raw material cost, the purification cost is reduced, the product quality is effectively improved, the market application space is widened, a new way is provided for removing calcium and magnesium ions through a fluorination method, and the method has extremely high practical value and application prospects.

Description

Technical Field

[0001] The invention belongs to the field of hydrometallurgy, and in particular relates to a method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution. Background Art

[0002] The purification of calcium and magnesium ions in ferrous sulfate solution has always been a major challenge faced by the industry, mainly because its price is relatively low, while the cost of removing Ca and Mg ions during the purification process is quite high. Specifically, the content of Mg ions in ferrous sulfate solution can reach the gram-liter level. If fluoride is used to remove calcium and magnesium ions, a large amount of F ions will remain in the treated solution, and the concentration is usually between 1500 and 2000 mg / L. If the solution is not further defluorinated, the F ion content in the ferrous sulfate heptahydrate product obtained after freeze crystallization will be as high as 400 to 1000 ppm. Such a high fluoride ion content greatly limits the application field of this product.

[0003] The production process of the low calcium, magnesium and extremely low F-containing ferrous sulfate heptahydrate products currently on the market often involves the conversion method to prepare other iron-based intermediates, which are then washed and then dissolved to remove calcium and magnesium elements, or the use of resin adsorption technology to separate calcium and magnesium ions, or directly using a high-purity iron source for dissolution preparation. However, these methods all face the problem of high costs, which limits their widespread promotion in industrial applications.

[0004] When trying to remove calcium and magnesium ions in ferrous sulfate solution by fluoridation, if the F ion content in the final ferrous sulfate heptahydrate product is to be reduced to less than 50ppm, the ferrous sulfate heptahydrate solution treated by fluoridation must be purified and defluorinated. At the same time, the selected fluoridation agent and defluoridation agent cannot introduce other new impurities. In the hydrometallurgical industry, the method of extractive defluoridation is usually adopted, but this process is long and cumbersome to operate. However, it is not suitable to adopt the method of extractive defluoridation in ferrous sulfate solution, because the Fe ions in the solution can cause the organic extractant to be "poisoned" and fail, and the cost of the extractant itself for extractive defluoridation is relatively high. Therefore, how to effectively use fluoridation to remove calcium and magnesium ions in ferrous sulfate solution has always been a major problem that the industry needs to solve. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of difficulty and high cost in separating calcium and magnesium and defluoridation by fluoridation in ferrous sulfate solution, and to provide a production and purification method for calcium and magnesium ions in ferrous sulfate solution to prepare a low-calcium and magnesium ferrous sulfate heptahydrate product.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution comprises the following steps:

[0008] S1: In a ferrous sulfate solution containing calcium and magnesium ions, HF (in terms of F ions) is added in an amount of 1.2 to 2.5 times the amount of calcium and magnesium ions, and then a neutralizer is added to adjust the pH of the solution to 2.5 to 3.5, and react at 50 to 70° C. for 2 to 4 hours; wherein the neutralizer is metallic iron powder or ferrous carbonate;

[0009] S2: adding calcium salt, keeping the temperature at 50-70° C. for 1-2 hours, and then filtering to obtain a solution saturated with calcium ions and free of magnesium ions; wherein the calcium salt is one or two of calcium carbonate, calcium sulfate, calcium hydroxide, and calcium oxide, and the amount of calcium salt added is 0.5-5.0 g / L (calculated as calcium ions);

[0010] S3: adding sulfuric acid solution to adjust the solution pH to 1.5-2.0;

[0011] S4: Freeze and crystallize the pH-adjusted solution at 1-3°C for 10-14h;

[0012] S5: The solution is centrifuged and the calcium ions are retained in the mother liquor. The crystals obtained by centrifugation are ferrous sulfate heptahydrate with low calcium and low magnesium.

[0013] Preferably, in the ferrous sulfate solution of step S1, Fe 2+ :100~160g / L,Ca 2+ :550~780mg / L,Mg 2 + : 1.0~2.0g / L; More preferably, in the ferrous sulfate solution of step S1, Fe 2+ :130~150g / L,Ca 2+ :550~780mg / L,Mg 2+ :1.0~2.0g / L.

[0014] Preferably, in step S1, HF is added according to twice the amount of calcium and magnesium ion substances in the ferrous sulfate solution, and after adding the neutralizer, the pH of the solution is adjusted to 4.5, and the reaction is carried out at 60° C. for 2 hours.

[0015] Preferably, the calcium salt described in step S2 is calcium sulfate, and the amount of calcium salt added is 4.0 g / L in terms of calcium ions, and the reaction is kept at 60° C. for 1 hour.

[0016] Preferably, the concentration of the sulfuric acid solution in step S3 is 20 g / L, and the pH of the solution is adjusted to 2.0.

[0017] Preferably, in step S4, the pH-adjusted solution is frozen and crystallized at 2°C for 12 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The invention provides a production and purification method for calcium and magnesium ions in a ferrous sulfate solution. The method effectively removes the magnesium element in the ferrous sulfate solution by adding hydrofluoric acid and a neutralizing agent; subsequently, the fluorine element in the solution is further removed by adding a calcium salt; thereafter, the solution is subjected to a freeze crystallization treatment, and centrifugal separation is performed to retain the calcium ions in the mother liquor so as to achieve the removal of the calcium ions, and finally a ferrous sulfate heptahydrate product with low calcium and magnesium content and extremely low fluorine content is obtained.

[0020] The production and purification method of the present invention has the remarkable advantages of simple process and simple operation, and the raw materials used are cheap and easy to obtain, which greatly reduces the purification cost. The method effectively improves the product quality and greatly broadens the market application space of ferrous sulfate heptahydrate products. In addition, the present invention also clears the obstacles for removing calcium and magnesium ions by fluoridation in ferrous sulfate solution, and has extremely high practical value and application prospects.

[0021] Instruction Manual

[0022] Figure 1 The present invention is a process flow chart of the production and purification method of calcium and magnesium ions in ferrous sulfate solution. DETAILED DESCRIPTION

[0023] The following is a detailed description in conjunction with specific embodiments, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. The raw materials used in the examples are all commercially available unless otherwise specified.

[0024] Example 1

[0025] See attached Figure 1 , a method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution, comprising the following steps:

[0026] (1) Take 1L of high calcium magnesium ferrous sulfate solution, Fe 2+ :140g / L, Ca 2+ :770mg / L,Mg 2+ :1.5g / L; add HF (in terms of F ions) according to 1.5 times the amount of calcium and magnesium ions, then add ferrous carbonate, adjust the solution pH to 3.5, and react at 60°C for 2h;

[0027] S2: adding calcium sulfate, continuing to react at 60°C for 1 hour, and then filtering to obtain a solution saturated with calcium ions and free of magnesium ions; wherein the amount of calcium sulfate added is 4.0 g / L (calculated as calcium ions);

[0028] S3: adding 20 g / L sulfuric acid solution to adjust the solution pH to 2.0;

[0029] S4: Freeze and crystallize the pH-adjusted solution at 2°C for 12 h;

[0030] S5: The solution is centrifuged and the calcium ions are retained in the mother liquor. The crystals are ferrous sulfate heptahydrate with low calcium and magnesium content.

[0031] The product index of ferrous sulfate heptahydrate of Example 1 was tested, and the results are shown in Table 1:

[0032] Table 1 Ferrous sulfate heptahydrate product index of Example 1

[0033]

[0034] Example 2

[0035] See attached Figure 1 , a method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution, comprising the following steps:

[0036] (1) Take 1L of high calcium magnesium ferrous sulfate solution, Fe 2+ :140g / L, Ca 2+ :770mg / L,Mg 2+ :1.5g / L; add HF (in terms of F ions) according to 2.0 times the amount of calcium and magnesium ions, then add ferrous carbonate, adjust the solution pH to 4.0, and react at 60°C for 2h;

[0037] S2: adding calcium sulfate, continuing to react at 60°C for 1 hour, and then filtering to obtain a solution saturated with calcium ions and free of magnesium ions; wherein the amount of calcium sulfate added is 4.0 g / L (calculated as calcium ions);

[0038] S3: adding 20 g / L sulfuric acid solution to adjust the solution pH to 2.0;

[0039] S4: Freeze and crystallize the pH-adjusted solution at 2°C for 12 h;

[0040] S5: The solution is centrifuged and the calcium ions are retained in the mother liquor. The crystals are ferrous sulfate heptahydrate with low calcium and magnesium content.

[0041] The product index of ferrous sulfate heptahydrate of Example 2 was tested, and the results are shown in Table 2:

[0042] Table 1 Ferrous sulfate heptahydrate product index of Example 2

[0043]

[0044] Example 3

[0045] See attached Figure 1 , a method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution, comprising the following steps:

[0046] (1) Take 1L of high calcium magnesium ferrous sulfate solution, Fe 2+ :150g / L, Ca 2+ :770mg / L,Mg 2+ :1.5g / L; add HF (in terms of F ions) according to 2.5 times the amount of calcium and magnesium ions, then add ferrous carbonate, adjust the solution pH to 4.5, and react at 60°C for 2h;

[0047] S2: adding calcium sulfate, continuing to react at 60°C for 1 hour, and then filtering to obtain a solution saturated with calcium ions and free of magnesium ions; wherein the amount of calcium sulfate added is 4.0 g / L (calculated as calcium ions);

[0048] S3: adding 20 g / L sulfuric acid solution to adjust the solution pH to 2.0;

[0049] S4: Freeze and crystallize the pH-adjusted solution at 2°C for 12 h;

[0050] S5: The solution is centrifuged and the calcium ions are retained in the mother liquor. The crystals are ferrous sulfate heptahydrate with low calcium and magnesium content.

[0051] The product index of ferrous sulfate heptahydrate of Example 3 was tested, and the results are shown in Table 3:

[0052] Table 1 Ferrous sulfate heptahydrate product index of Example 3

[0053]

[0054] As can be seen from Examples 1-3, the production and purification method of the present invention uses a fluorination method to remove the Mg element in ferrous sulfate, removes the F element in the solution by adding a calcium salt, and then separates the Ca element by centrifugation after freezing and crystallizing the solution, leaving it in the mother liquor. The Ca in the prepared ferrous sulfate heptahydrate is less than 50ppm, Mg is less than 30ppm, and F is less than 50ppm.

[0055] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for producing and purifying calcium and magnesium ions in a ferrous sulfate solution, characterized in that: The following steps are involved: S1: In a ferrous sulfate solution containing calcium and magnesium ions, HF is added according to 1.2 to 2.5 times the amount of calcium and magnesium ions, and then a neutralizer is added to adjust the pH of the solution to 2.5 to 3.5, and react at 50 to 70° C. for 2 to 4 hours; wherein the neutralizer is metallic iron powder or ferrous carbonate; S2: adding calcium salt, keeping the temperature at 50-70° C. for 1-2 hours, and then filtering to obtain a solution saturated with calcium ions and free of magnesium ions; wherein the calcium salt is one or two of calcium carbonate, calcium sulfate, calcium hydroxide, and calcium oxide, and the amount of calcium salt added is 0.5-5.0 g / L (calculated as calcium ions); S3: adding sulfuric acid solution to adjust the solution pH to 1.5-2.0; S4: Freeze and crystallize the pH-adjusted solution at 1-3°C for 10-14h; S5: The solution is centrifuged and the calcium ions are retained in the mother liquor. The crystals obtained by centrifugation are ferrous sulfate heptahydrate with low calcium and low magnesium.

2. The production purification method according to claim 1, characterized in that: In the ferrous sulfate solution of step S1, Fe 2 + :100~160g / L,Ca 2+ :550~780mg / L,Mg 2+ :1.0~2.0g / L.

3. The production purification method according to claim 1, characterized in that: In the ferrous sulfate solution of step S1, Fe 2 + :130~150g / L,Ca 2+ :550~780mg / L,Mg 2+ :1.0~2.0g / L.

4. The production purification method according to claim 1, characterized in that: In step S1, HF is added according to twice the amount of calcium and magnesium ions in the ferrous sulfate solution, and after adding a neutralizer, the pH of the solution is adjusted to 4.5, and the reaction is carried out at 60° C. for 2 hours.

5. The production purification method according to claim 1, characterized in that: The calcium salt described in step S2 is calcium sulfate. The amount of calcium salt added is 4.0 g / L in terms of calcium ions, and the reaction is kept at 60° C. for 1 hour.

6. The production purification method according to claim 1, characterized in that: The concentration of the sulfuric acid solution in step S3 is 20 g / L, and the pH of the solution is adjusted to 2.

0.

7. The production purification method according to claim 1, characterized in that: In step S4, the pH-adjusted solution is frozen and crystallized at 2°C for 12 hours.

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