Method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residues

Abstract

The invention provides a method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residues. The preparation method comprises the following steps: drying the electrolytic manganese residues and preparing the electrolytic manganese residues into electrolytic manganese residue powder; mixing the electrolytic manganese residue powder with an ammonium chloride solution, and reacting to obtain a mixed solution; carrying out solid-liquid separation on the mixed solution to obtain a first filtrate; adding sulfuric acid into the first filtrate to adjust the pH value to 2-4, aging to obtain a solid-liquid mixture, and performing solid-liquid separation to obtain a filter cake and filtrate; washing and drying the filter cake to obtain high-purity anhydrous calcium sulfate powder; wherein the phase of the high-purity anhydrous calcium sulfate powder is an anhydrite phase, the purity of the anhydrous calcium sulfate powder is greater than 99%, the whiteness of the anhydrous calcium sulfate powder is greater than 90, and the microscopic morphology of the powder comprises a particle shape and / or a plate shape. According to the method, the high-purity and high-whiteness anhydrous calcium sulfate powder can be prepared by taking the electrolytic manganese residues as the raw material without adding a crystal form control agent.

Description

Technical Field

[0001] The present invention relates to the field of resource utilization of electrolytic manganese slag. Specifically, it relates to a method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag. Background Art

[0002] Anhydrite powder is obtained by crushing and grinding anhydrite ore, or by calcining natural gypsum at high temperature. Compared with gypsum, anhydrite has better high-temperature resistance, acid and alkali resistance. At present, anhydrite powder is widely used in plastics, papermaking, chemical industry, agriculture, building materials and other fields as fillers, desiccants, soil conditioners, etc.

[0003] The main components of electrolytic manganese slag are calcium sulfate dihydrate, silicon dioxide, pyrite, etc. The presence of these components makes electrolytic manganese slag have high comprehensive utilization value. However, electrolytic manganese slag also contains a certain amount of harmful substances, such as soluble salts magnesium ammonium sulfate, manganese ammonium sulfate and heavy metal ions, etc. If not properly treated, it will cause serious environmental pollution. Producing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag can not only realize the resource utilization of electrolytic manganese slag, but also save natural anhydrite / gypsum resources.

[0004] So far, no research on preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag has been found, and no relevant reports on recycling salt solution and preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag under low-temperature and normal-pressure conditions as proposed in the present invention have been found. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies existing in the prior art. For example, the purpose of the present invention is to provide a method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag.

[0006] To achieve the above purpose, the present invention provides a method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag, which is characterized in that the preparation method includes: (1) drying electrolytic manganese slag and making it into electrolytic manganese slag powder; (2) mixing electrolytic manganese slag powder and ammonium chloride solution, and obtaining a mixed solution after reaction; (3) performing solid-liquid separation on the mixed solution to obtain a first filtrate; (4) adding sulfuric acid to the first filtrate to adjust the pH value to 2-4, aging to obtain a solid-liquid mixture, and performing solid-liquid separation to obtain a filter cake and a second filtrate; (5) washing and drying the filter cake to obtain high-purity anhydrous calcium sulfate powder; wherein the phase of the high-purity anhydrous calcium sulfate powder is anhydrite phase, the purity of the anhydrous calcium sulfate powder is greater than 99%, the whiteness is greater than 90, and the microscopic morphology of the powder is plate-shaped.

[0007] Optionally, the concentration of the ammonium chloride solution is 1-5 mol / L; the ratio of the ammonium chloride solution to the electrolytic manganese slag powder is 3-10 mL / g.

[0008] Optionally, the reaction described in step (2) includes reacting in a constant temperature water bath shaker, and the rotation speed of the shaker is 150 - 240 r / min; the temperature of the reaction is from room temperature to 100 °C, and the reaction time is 2 - 60 min.

[0009] Optionally, the aging temperature is 1 - 10 °C, and the aging time is 10 - 30 h.

[0010] Optionally, the electrolytic manganese slag powder described in step (1) can pass through an 80 - mesh sieve, and the drying includes drying by baking, and the baking temperature does not exceed 40 °C.

[0011] Optionally, the drying temperature in step (5) is from room temperature to 100 °C to remove the adsorbed water on the surface of the anhydrous calcium sulfate powder.

[0012] Optionally, the preparation method further includes adjusting the pH value of the second filtrate to neutral by adding ammonia water and then repeating steps (1) - (5) instead of the ammonium chloride solution to continue preparing the high - purity anhydrous calcium sulfate powder.

[0013] Further optionally, when repeating steps (1) - (5) until the soluble salts in the filtrate are supersaturated, the ammonium chloride and ammonium sulfate in the filtrate are recovered; then the pH value is adjusted by adding ammonia water so that the enriched manganese ions in the filtrate precipitate in the form of manganese hydroxide and are separated and recovered to obtain a third filtrate, and the third filtrate is used to prepare the ammonium chloride solution described in step (2).

[0014] Optionally, the microscopic morphology of the high - purity anhydrous calcium sulfate powder includes granular and / or plate - like.

[0015] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0016] (1) The present invention innovatively uses ammonium chloride as an auxiliary agent to first separate and dissolve the calcium sulfate dihydrate in the electrolytic manganese slag, so as to separate it from pyrite, mica, etc. that affect whiteness. And this method directly and completely utilizes the calcium sulfate dihydrate in the electrolytic manganese slag, which is essentially different from the existing partial research that only uses the calcium component to prepare calcium carbonate.

[0017] (2) The present invention adjusts the pH value of the system by adding sulfuric acid, and then realizes the preparation of anhydrous calcium sulfate powder. Compared with the chemical components of the system, no new impurity ions are introduced, and the entire preparation process does not involve wastewater treatment.

[0018] (3) In the present invention, calcium sulfate dihydrate in electrolytic manganese residue is extracted using ammonium chloride as an auxiliary agent. The original calcium sulfate dihydrate, ammonium magnesium sulfate, and manganese ions in the raw materials are transferred into the solution, and the remaining pyrite, mica, quartz, etc., which are insoluble in ammonium chloride solution, are enriched. The direct reason restricting the application of electrolytic manganese residue in building materials is the large amount of soluble salts and heavy metal ions it contains. Through the dissolution of ammonium chloride, these soluble components have been separated from components such as quartz, so that the ammonium chloride leaching residue of electrolytic manganese residue can be directly used in the building materials field, thereby realizing the comprehensive utilization of all components of electrolytic manganese residue.

[0019] (4) The present invention comprehensively utilizes the calcium sulfate dihydrate in the dissolved electrolytic manganese residue. The added ammonium chloride auxiliary agent always exists in the solution in the form of ions and can be recycled for the dissolution of calcium sulfate dihydrate in the raw materials until the amount of ammonium magnesium sulfate dissolved in the filtrate continuously increases and the ammonium sulfate contained in the solution reaches supersaturation and precipitates. Therefore, the entire preparation process is carried out at low temperature and normal pressure, and the auxiliary agent can be recycled multiple times. The entire process has no wastewater discharge and is green and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Through the following description in conjunction with the drawings, the above and other objects and / or features of the present invention will become clearer, wherein:

[0021] Figure 1 Shows the XRD pattern of the high-purity anhydrous calcium sulfate powder prepared in Example 1 of the present invention.

[0022] Figure 2 Shows the SEM image of the high-purity anhydrous calcium sulfate powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In the following, a method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residue of the present invention will be described in detail in conjunction with exemplary embodiments.

[0024] It should be noted that "first", "second", "third", etc. are only for convenience of description and easy distinction, and cannot be understood as indicating or implying relative importance.

[0025] Exemplary Embodiment 1

[0026] This exemplary embodiment provides a method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residue, characterized in that the preparation method may include:

[0027] S1. Dry the electrolytic manganese residue and make it into electrolytic manganese residue powder.

[0028] In this embodiment, the electrolytic manganese residue powder can pass through an 80-mesh sieve, and the drying may include drying by baking, and the baking temperature does not exceed 40°C, such as 15°C, 25°C, 36°C, and 40°C, etc.

[0029] Among them, the electrolytic manganese residue powder can pass through an 80-mesh sieve to improve the dissolution rate of calcium sulfate dihydrate in the electrolytic manganese residue, and the purpose of drying is to remove the adsorbed water of the electrolytic manganese residue.

[0030] S2. Mix the electrolytic manganese residue powder and ammonium chloride solution, and obtain a mixed solution after the reaction.

[0031] In this embodiment, the concentration of the ammonium chloride solution is 1-5 mol / L, such as 1.2 mol / L, 1.7 mol / L, 3.1 mol / L, 3.8 mol / L, and 4.9 mol / L, etc.; the ratio of the ammonium chloride solution to the electrolytic manganese residue powder is 3-10 mL / g, such as 3.5 mL / g, 5.2 mL / g, 6.8 mL / g, 8.1 mL / g, and 9.8 mL / g, etc.

[0032] Among them, too low a concentration of ammonium chloride is not conducive to the dissolution of calcium sulfate dihydrate in the electrolytic manganese residue, and too high a concentration of ammonium chloride is close to the supersaturation of ammonium chloride, which is not conducive to the preparation of the solution; the electrolytic manganese residue contains a large amount of soluble salts, and the addition of the ammonium chloride solution makes the total concentration of soluble ions in the solution relatively high. Therefore, too low a liquid-solid ratio makes the concentration of soluble ions in the system relatively high, which is not conducive to the dissolution of calcium sulfate dihydrate in the electrolytic manganese residue; while too high a liquid-solid ratio will reduce the concentration of calcium ions in the system, making it difficult to precipitate anhydrous calcium sulfate subsequently.

[0033] In this embodiment, the reaction includes reacting in a constant-temperature water bath shaking table, the rotation speed of the shaking table is 150-240 r / min, such as 150 r / min, 160 r / min, 210 r / min, and 230 r / min, etc.; the reaction temperature is from room temperature to 100°C, such as 30°C, 45°C, 60°C, 84°C, and 99°C, etc.; the reaction time is 2-60 min, such as 2 min, 15 min, 34 min, 45 min, and 58 min, etc.

[0034] Among them, too low a reaction temperature and too short a reaction time are not conducive to the dissolution of calcium sulfate dihydrate, while too high a reaction temperature and too long a reaction time will increase the reaction cost. Therefore, the above reaction time and reaction temperature are selected.

[0035] S3. Perform solid-liquid separation on the mixed solution to obtain a first filtrate.

[0036] The solid-liquid separation in step S3 also obtains a filter cake, which is washed and dried and used for subsequent resource utilization research, such as being used as a raw material in the building materials field through chemical composition analysis.

[0037] S4. Add sulfuric acid to the first filtrate to adjust the pH value to 2-4. After aging, a solid-liquid mixture is obtained. After solid-liquid separation, a filter cake and a second filtrate are obtained.

[0038] In this embodiment, the purpose of adding sulfuric acid to adjust the pH value to 2-4 is to facilitate the precipitation of anhydrous calcium sulfate. Too low a pH value increases the consumption of sulfuric acid, while too high a pH value cannot precipitate pure anhydrous calcium sulfate.

[0039] S5. Wash and dry the filter cake to obtain high-purity anhydrous calcium sulfate powder; wherein the phase of the high-purity anhydrous calcium sulfate powder is anhydrite phase, the purity of the anhydrous calcium sulfate powder is greater than 99%, the whiteness is greater than 90, and the microscopic morphology of the powder is plate-shaped.

[0040] In this embodiment, the temperature of the aging is 1-10°C, such as 2°C, 4°C, 6°C, and 9°C, etc.; the time of the aging is 10-30 h, such as 10.5 h, 15 h, 19 h, 21 h, and 29 h, etc.

[0041] Among them, too low an aging temperature results in a low combination rate of calcium ions and sulfate ions in the system, which is not conducive to the recrystallization of anhydrous calcium sulfate; too high an aging temperature increases the solubility of calcium sulfate, causing part of the anhydrous calcium sulfate to be converted into calcium sulfate dihydrate, thereby reducing the purity of the anhydrous calcium sulfate. Too short an aging time is not conducive to the precipitation of anhydrous calcium sulfate powder, and too long an aging time leads to an increase in cost. Therefore, the above aging time and aging temperature are selected.

[0042] In this embodiment, the temperature of the drying is from room temperature to 100°C, such as 25°C, 50°C, 65°C, 84°C, and 99°C, etc., in order to remove the adsorbed water on the surface of the anhydrous calcium sulfate.

[0043] In this embodiment, the preparation method further includes adjusting the pH value of the second filtrate to neutral by adding ammonia water, and then repeating steps S1-S5 to continue preparing high-purity anhydrous calcium sulfate powder instead of the ammonium chloride solution.

[0044] In this embodiment, when repeating steps S1-S5 until the soluble salts in the filtrate are supersaturated, ammonium chloride and ammonium sulfate in the filtrate are recovered; then, the pH value is adjusted by adding ammonia water to precipitate and separate and recover the enriched manganese ions in the filtrate in the form of manganese hydroxide, obtaining a third filtrate, and the third filtrate is used to prepare the ammonium chloride solution described in step S2, such as replacing water to prepare the ammonium chloride solution.

[0045] In this embodiment, the microscopic morphology of the high-purity anhydrous calcium sulfate powder includes granular and / or plate-shaped.

[0046] To better understand the above exemplary embodiments of the present invention, the following further describes them with specific examples.

[0047] Example 1

[0048] Take a certain amount of electrolytic manganese slag sample, dry it at 40 °C, grind it into powder, and sieve it through an 80-mesh sieve to obtain electrolytic manganese slag powder; take 50 g of the electrolytic manganese slag sample and place it in a 1000 mL conical flask. Add 500 mL of 4 mol / L ammonium chloride solution to the conical flask, place the conical flask in a shaker, with the shaker speed at 200 r / min, react at 450 °C for 40 min, and then filter to obtain the first filtrate.

[0049] Take 40 mL of the above-mentioned Ca 2+ leaching solution, i.e., the first filtrate, pour it into a 500 mL beaker, control the pH value of the solution to 2 by adding sulfuric acid, place the beaker in a reactor, control the temperature of the reactor through a high and low temperature integrated machine, age at 9 °C for 25 hours, and then filter to obtain a filter cake. Wash the filter cake and dry it at 80 °C to obtain anhydrous calcium sulfate powder. The phase of the obtained powder is anhydrite ( Figure 1 ), the microscopic morphology is plate-like ( Figure 2 ), the whiteness of the powder is 96.1, and the purity of the powder is 99.32%.

[0050] Perform XRD testing on the obtained high-purity anhydrous calcium sulfate powder. The results are as Figure 1 shown. It can be seen from Figure 1 that the phase of the prepared anhydrous calcium sulfate powder is the anhydrite phase, and the diffraction peaks of anhydrite are relatively sharp, indicating that the crystallization degree of anhydrite crystals in the sample is good; no diffraction peaks of other crystals are found except for anhydrite, indicating that the purity of the product is high and its phase is the only anhydrite phase.

[0051] Perform scanning electron microscopy testing on the obtained high-purity anhydrous calcium sulfate powder to obtain the SEM image as Figure 2 shown. It can be seen from Figure 2 that the microscopic morphology of the prepared anhydrous calcium sulfate powder is plate-like and granular.

[0052] Example 2

[0053] Take a certain amount of electrolytic manganese slag sample, dry it at 40 °C, grind it into powder, and sieve it through an 80-mesh sieve to obtain electrolytic manganese slag powder; take 100 g of the electrolytic manganese slag powder and place it in a 1000 mL conical flask. Add 800 mL of 4.5 mol / L ammonium chloride solution to the conical flask, place the conical flask in a shaker, with the shaker speed at 200 r / min, react at 75 °C for 45 min, and then filter to obtain the first filtrate.

[0054] Take 600 mL of the above-mentioned Ca 2+The leaching solution, i.e., the first filtrate, is poured into a 1000 mL beaker. The pH value of the solution is controlled to be 3.5 by adding sulfuric acid. The beaker is placed in a reactor, and the temperature of the reactor is controlled by a high and low temperature integrated machine. After aging at 10 °C for 18 hours, filtration is carried out to obtain a filter cake. The filter cake is washed and then dried at 80 °C to obtain anhydrous calcium sulfate powder. The phase of the obtained powder is gypsum, the microscopic morphology is plate-like, the whiteness of the powder is 97.7, and the purity of the powder is 99.63%.

[0055] Although the present invention has been described above in conjunction with exemplary embodiments and the accompanying drawings, those of ordinary skill in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag, characterized in that, The preparation method includes: (1) drying electrolytic manganese residue and making it into electrolytic manganese residue powder; (2) mixing the electrolytic manganese residue powder with ammonium chloride solution, and obtaining a mixed solution after reaction; (3) performing solid-liquid separation on the mixed solution to obtain a first filtrate; (4) adding sulfuric acid to the first filtrate to adjust the pH value to 2-4, aging to obtain a solid-liquid mixture, and obtaining a filter cake and a second filtrate after solid-liquid separation; (5) washing and drying the filter cake to obtain high-purity anhydrous calcium sulfate powder; wherein the phase of the high-purity anhydrous calcium sulfate powder is anhydrite phase, the purity of the anhydrous calcium sulfate powder is greater than 99%, and the whiteness is greater than 90.

2. The method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residue according to claim 1, characterized in that, The concentration of the ammonium chloride solution is 1-5 mol / L; the ratio of the ammonium chloride solution to the electrolytic manganese residue powder is 3-10 mL / g.

3. The method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residue according to claim 1, characterized in that, In step (2), the reaction includes reacting in a constant temperature water bath shaking table, the rotation speed of the shaking table is 150-240 r / min; the reaction temperature is from room temperature to 100 °C, and the reaction time is 2-60 min.

4. The method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese residue according to claim 1, wherein, The aging temperature is 1-10 °C, and the aging time is 10-30 h.

5. The method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag according to claim 1, characterized in that, In step (1), the electrolytic manganese residue powder can pass through an 80-mesh sieve, and the drying includes drying, and the drying temperature does not exceed 40 °C.

6. The method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag according to claim 1, wherein In step (5), the drying temperature is from room temperature to 100 °C to remove the adsorbed water on the surface of the anhydrous calcium sulfate powder.

7. A method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag according to claim 1, characterized in that, The preparation method further includes adjusting the pH value of the second filtrate to neutral by adding ammonia water, and then repeating steps (1)-(5) to continue preparing high-purity anhydrous calcium sulfate powder instead of the ammonium chloride solution.

8. A method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag according to claim 1, characterized in that, When repeating steps (1)-(5) until the soluble salts in the filtrate are supersaturated, ammonium chloride and ammonium sulfate in the filtrate are recovered; then the pH value is adjusted by adding ammonia water so that the enriched manganese ions in the filtrate precipitate in the form of manganese hydroxide and are separated and recovered to obtain a third filtrate, and the third filtrate is used to prepare the ammonium chloride solution described in step (2).

9. The method for preparing high-purity anhydrous calcium sulfate powder from electrolytic manganese slag according to claim 1, characterized in that, The microscopic morphology of the high-purity anhydrous calcium sulfate powder includes granular and / or plate-like.

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