Manganese sulfate purification method based on membrane separation technology

Abstract

The invention provides a manganese sulfate purification method based on a membrane separation technology, and relates to the technical field of manganese sulfate purification, the manganese sulfate purification method comprises the following steps: S1, pretreatment and solution blending: starting a stirring tank for stirring at a stirring speed of 230-500 RPM; adding a raw material solution into the stirring tank; adding a mixed solvent into the raw material solution, wherein the total adding amount of the mixed solvent accounts for 1-2% of the mass of the raw material solution; according to the preparation method, a mixed solvent and a stability additive are introduced in the raw material solution preparation stage, and the stirring speed and the reaction temperature are regulated and controlled, so that the uniformity and the system stability of raw material components are enhanced, the solubility and the dispersity of impurity components are reduced, and subsequent impurities are promoted to be thoroughly and sufficiently settled; in the chemical precipitation stage, precipitation of the impurities is accelerated by controlling the proportion of a precipitator, the reaction temperature and the stirring speed, so that the precipitation rate and the particle size uniformity of precipitated particles are improved, and the impurities are fully separated from a main solution.

Description

Technical Field

[0001] The present invention relates to the technical field of manganese sulfate purification, and in particular to a method for purifying manganese sulfate based on membrane separation technology. Background Art

[0002] The field of manganese sulfate purification technology lies at the intersection of fine chemicals and inorganic material preparation. It mainly involves the process technology of accurately removing impurity elements (such as iron, calcium, magnesium, sodium, potassium, heavy metals, etc.) from industrial-grade or crude manganese sulfate raw materials through physical separation, chemical purification, crystallization and recrystallization, ion exchange, extraction, etc., in order to obtain high-purity manganese sulfate products with extremely low impurity content.

[0003] In existing technologies, the precipitation process uses crude control over stirring speed and reaction temperature, resulting in fine, highly dispersed impurity particles that are difficult to completely separate. Furthermore, the removal of trace organic impurities relies on a single method, lacking proper management of adsorbent dosage and adsorption conditions. Organic impurities, such as residual organic extractants, flocculants (such as polyacrylamide), solvents, equipment lubricants, or plastic additives, lead to significant fluctuations in product purity and unstable quality of high-purity manganese sulfate. Therefore, improvements are needed. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for purifying manganese sulfate based on membrane separation technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a method for purifying manganese sulfate based on membrane separation technology, comprising the following steps: S1, start the stirring tank for stirring at a stirring speed of 230-500 RPM; add the raw material solution into the stirring tank; add the mixed solvent to the raw material solution, the total amount of the mixed solvent added is 1-2% of the mass of the raw material solution; add the stability additive, the total amount of the stability additive added is 3-5% of the mass of the raw material solution; maintain the stirring time in the range of 30-50 minutes, and control the temperature at 35-45°C to obtain a preliminary prepared solution; S2, chemically precipitating the preliminary prepared solution; using a reaction tank equipped with a stirring blade, the speed of which is controlled in the range of 200-400 RPM; adding a precipitant, the total amount of which accounts for 5-7% of the volume of the preliminary prepared solution, and 5-7 grams of precipitant is required for every 100 ml of the preliminary prepared solution; controlling the reaction temperature at 50-60° C. and the reaction time at 40-60 minutes to obtain a chemically precipitated solution; S3, adding an adsorbent to the chemical precipitation solution, with the total mass accounting for 3-6% of the volume of the chemical precipitation solution; using a constant temperature water bath to maintain the solution temperature at 45-55° C., maintaining the stirring speed in the range of 250-450 RPM, and controlling the adsorption time at 40-60 min to obtain an adsorbed solution; A spiral nanofiltration membrane was used for membrane separation. At the end of the nanofiltration, the permeate was collected, the manganese sulfate content was determined and the purity was verified. The concentrated section was discarded to obtain a high-purity manganese sulfate solution.

[0006] Preferably, it also includes: S4, performing ion exchange on the adsorbed solution; using a fully stainless steel vertical ion exchange column filled with mixed ion exchange resin; controlling the solution flow rate in the range of 0.5-1.0 L / min to ensure sufficient contact of the liquid in the resin bed; and the ion exchange temperature at 25-35° C. to obtain an ion exchange solution.

[0007] Preferably, it also includes: S5, performing membrane separation on the ion-exchanged solution using a spiral nanofiltration membrane; the feed pressure is controlled in the range of 1.5-2.5 MPa, and the pore size of the nanofiltration membrane is in the range of approximately 1-2 nm; the solution is filtered through the membrane surface and separated into a permeate and a concentrate, and the temperature is maintained at 20-30° C. At the end of the nanofiltration, the permeate is collected, the manganese sulfate content is determined, and the purity is verified. The concentrate is discarded to obtain a high-purity manganese sulfate solution; In step S6, the high-purity manganese sulfate solution is introduced into a crystallization tank, the temperature in the crystallization tank is controlled in the range of 10-20° C., and a scraper-type agitator is used to prevent crystals from agglomerating. Seed crystals are added, wherein the seed crystals are prepared by mixing pure manganese sulfate powder and anhydrous sodium sulfate in a mass ratio of 3:1, and the total amount added accounts for 1-2% of the volume of the high-purity manganese sulfate solution. For every 100 ml of high-purity manganese sulfate solution, 1-2 grams of seed crystals are added. After the crystallization process is maintained for 40-60 minutes, the resulting crystals are separated from the mother liquor by a centrifuge. The solid is then dried in an oven at 90-110° C. for 30-50 minutes, and the mother liquor is refluxed to step S1 for recycling to obtain a high-purity manganese sulfate solid product.

[0008] Preferably, in step S1, the raw material solution is a manganese sulfate solution, the mixed solvent is composed of deionized water, anhydrous ethanol, and acetone in a mass ratio of 6-8:2-4:2-4, and the stability additive is composed of glycerol, sorbitol, and magnesium chloride in a mass ratio of 1-2:1-2:2-5.

[0009] Preferably, in step S2, the precipitant is prepared by mixing calcium hydroxide, sodium dihydrogen phosphate, sodium carbonate and barium chloride in a mass ratio of 1-2:2-4:3-5:4-6.

[0010] Preferably, in step S3, the adsorbent is formed by mixing coconut shell activated carbon, strong acid cation exchange resin, and silica adsorption material in a mass ratio of 2-4:1-2:1-2.

[0011] Preferably, in step S4, the mixed ion exchange resin is prepared by mixing a weak acid cation exchange resin and a strong base anion exchange resin in a mass ratio of 1-2:2-5.

[0012] Compared with the prior art, the present invention introduces a mixed solvent and a stability additive during the raw material solution preparation stage, and by regulating the stirring speed and reaction temperature, enhances the uniformity of the raw material components and the stability of the system, reduces the solubility and dispersibility of the impurity components, and promotes the thorough and sufficient precipitation of subsequent impurities. In the chemical precipitation stage, the precipitation of impurities is accelerated by controlling the precipitant ratio, reaction temperature, and stirring speed, thereby improving the precipitation rate and the uniformity of the precipitated particle size, and fully separating the impurities from the main solution. In the process of removing organic impurities, an adsorbent is used in combination with strict control of adsorption conditions to improve the removal efficiency of trace organic impurities in the solution, ensure that the cleanliness and quality stability of high-purity manganese sulfate are improved, achieve comprehensive removal of impurities as a whole, and promote the improvement of product purity and stability.

[0013] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 The present invention proposes a preparation step diagram of a method for purifying manganese sulfate based on membrane separation technology. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0017] Example 1, a method for purifying manganese sulfate based on membrane separation technology, comprising the following steps: S1, pretreatment and solution preparation, start the stirring tank for stirring at a speed of 500 RPM; add the raw material solution into the stirring tank; add the mixed solvent to the raw material solution, the total amount of the mixed solvent added is 1% of the mass of the raw material solution; add the stability additive, the total amount of the stability additive added is 3% of the mass of the raw material solution; maintain the stirring time at 30 minutes, and control the temperature at 45°C to obtain a preliminary prepared solution; S2, chemical precipitation to remove impurities, chemically precipitate the preliminary prepared solution; use a reaction tank equipped with a stirring blade, the speed of which is controlled at 200 RPM; add a precipitant, the total amount of which accounts for 5% of the volume of the preliminary prepared solution; control the reaction temperature at 60°C and the reaction time at 40 minutes to obtain a chemically precipitated solution; S3, adsorption to remove organic impurities, add an adsorbent to the solution after chemical precipitation, the total mass of which accounts for 6% of the volume of the solution after chemical precipitation; use a constant temperature water bath to maintain the solution temperature at 55°C, maintain the stirring speed at 450RPM, and control the adsorption time to 60min to obtain an adsorbed solution.

[0018] S4, ion exchange to remove heavy metals, ion exchange is carried out on the adsorbed solution; a fully stainless steel vertical ion exchange column is used, filled with mixed ion exchange resin; the solution flow rate is controlled at 0.5 L / min to ensure sufficient contact of the liquid in the resin bed, and the ion exchange temperature is maintained at 35°C to obtain the ion exchange solution; S5, membrane separation process, the ion exchange solution is subjected to membrane separation using a spiral nanofiltration membrane; the feed pressure is controlled in the range of 2.5 MPa, and the pore size of the nanofiltration membrane is about 1 nanometer; the solution is filtered on the membrane surface and separated into a permeate and a concentrate, and the temperature is maintained at 20°C. At the end of the nanofiltration, the permeate is collected, the manganese sulfate content is measured and the purity is verified, and the concentrate is discarded to obtain a high-purity manganese sulfate solution; S6, concentration and recovery, introduces the high-purity manganese sulfate solution into a crystallization tank, controls the temperature in the crystallization tank at 10°C, and uses a scraper-type agitator to prevent crystals from agglomerating; adds seed crystals, which are a mixture of pure manganese sulfate powder and anhydrous sodium sulfate in a mass ratio of 3:1, and the total amount added accounts for 1% of the volume of the high-purity manganese sulfate solution; the crystallization process is maintained for 60 minutes, and the resulting crystals and mother liquor are separated by a centrifuge; the solid is sent to an oven for drying at 90°C for 50 minutes, and the mother liquor is refluxed to step S1 for recycling to obtain a high-purity manganese sulfate solid product.

[0019] In this embodiment, in step S1, the raw material solution is a manganese sulfate solution, the mixed solvent is a mixture of deionized water, anhydrous ethanol, and acetone in a mass ratio of 8:4:2, and the stability additive is a mixture of glycerol, sorbitol, and magnesium chloride in a mass ratio of 2:1:5.

[0020] In this embodiment, in step S2, the precipitant is prepared by mixing calcium hydroxide, sodium dihydrogen phosphate, sodium carbonate and barium chloride in a mass ratio of 1:4:5:4.

[0021] In this embodiment, in step S3, the adsorbent is prepared by mixing coconut shell activated carbon, strong acid cation exchange resin, and silica adsorption material in a mass ratio of 4:2:1.

[0022] In this embodiment, in step S4, the mixed ion exchange resin is composed of a weak acid cation exchange resin and a strong base anion exchange resin in a mass ratio of 1:5.

[0023] Example 2 is otherwise the same as Example 1, except that a method for purifying manganese sulfate based on membrane separation technology comprises the following steps: S1, pretreatment and solution preparation, start the stirring tank for stirring at 350RPM; add the raw material solution into the stirring tank; add the mixed solvent to the raw material solution, the total amount of the mixed solvent added is 2% of the raw material solution mass; add the stability additive, the total amount of the stability additive added is 3% of the raw material solution mass; maintain the stirring time at 50min, and control the temperature at 38°C to obtain a preliminary prepared solution; S2, chemical precipitation to remove impurities, chemically precipitate the preliminary prepared solution; use a reaction tank equipped with a stirring blade, the speed of which is controlled at 400 RPM; add a precipitant, the total amount of which accounts for 7% of the volume of the preliminary prepared solution; control the reaction temperature at 60°C and the reaction time at 60 minutes to obtain a chemically precipitated solution; S3, adsorption to remove organic impurities, add an adsorbent to the solution after chemical precipitation, the total mass of which accounts for 5% of the volume of the solution after chemical precipitation; use a constant temperature water bath to maintain the solution temperature at 55°C, maintain the stirring speed at 450 RPM, and control the adsorption time to 60 minutes to obtain an adsorbed solution.

[0024] Experimental methods: Manganese sulfate (MnSO4) purity determination (EDTA titration method): Principle: Disodium ethylenediaminetetraacetic acid (EDTA) is used as a titrant to form a stable complex with manganese ions (Mn²⁺) under specific pH conditions. The endpoint of the titration is determined by the color change of the indicator, allowing the manganese content in the sample to be calculated and further converted into the purity of manganese sulfate. This method is a classic complexometric titration suitable for the determination of major metal ions.

[0025] Main reagents and instruments: Reagents: EDTA standard solution (about 0.05 mol / L, requires precise calibration), ammonia-ammonium chloride buffer solution (pH≈10), chrome black T indicator (ground and mixed with sodium chloride), hydroxylamine hydrochloride (solid, used as a reducing agent to prevent manganese oxidation), triethanolamine (1:2 aqueous solution, used as a masking agent to mask possible small amounts of interfering ions such as iron and aluminum), and high-purity water.

[0026] Instruments: analytical balance (precision 0.1 mg), conical flask (250 mL), volumetric flask (250 mL), acid burette (50 mL, precision 0.02 mL), pipette (25 mL), electromagnetic stirrer, pH meter.

[0027] Experimental Procedure: Sample Preparation: Accurately weigh approximately 0.5 g (accurate to 0.1 mg) of dried, high-purity manganese sulfate solid sample and record the mass m. Place the sample into a 250 mL Erlenmeyer flask and add approximately 50 mL of high-purity water to dissolve it. If the sample is a solution, accurately pipette a volume V. The density ρ must be known, or the manganese content can be directly determined.

[0028] Pretreatment: Add a small amount of solid hydroxylamine hydrochloride (about 0.1-0.2g) to the solution and shake it gently to dissolve it, ensuring that the manganese ion remains at +2. 3+ 、Al 3+ Interference can be masked by adding about 5 mL of triethanolamine solution.

[0029] pH adjustment and indicator addition: Add 10 mL of ammonia-ammonium chloride buffer solution to stabilize the solution pH at around 10 (check with a pH meter). Add approximately 0.1 g of Eriochrome Black T indicator mixture; the solution should appear wine red.

[0030] Titration: Place an Erlenmeyer flask on a magnetic stirrer and titrate with a precisely calibrated EDTA standard solution (concentration C). Maintain stirring during the titration. Slow the titration rate as the endpoint approaches, adding EDTA solution dropwise until the solution color changes from wine red to pure blue and does not fade within 30 seconds. This is the endpoint. Record the volume of EDTA standard solution consumed (V_EDTA).

[0031] Blank experiment: Perform a blank titration following the same steps except that no sample is added, and record the volume of EDTA standard solution consumed, V_blank (usually very small or zero).

[0032] Calculation: Mass fraction of Mn in the sample (%) = [(V_EDTA - V_blank) × C × M(Mn)] / (m × 1000) × 100% Purity of manganese sulfate (MnSO4) (%) = [Mass fraction of Mn in the sample / (M(Mn) / M(MnSO4))] × 100% Where, M(Mn) is the molar mass of manganese (approximately 54.938 g / mol), and M(MnSO4) is the molar mass of manganese sulfate (approximately 151.00 g / mol). Note that if the product is a hydrate (e.g., MnSO4·H2O), the molar mass of the corresponding hydrate should be used when calculating the purity.

[0033] Quality Control: Perform at least two replicate measurements, and the relative deviation of the results should meet the requirements. EDTA standard solution should be calibrated regularly. Ensure that the indicator color change is sharp and the endpoint is accurately determined.

[0034] Impurity content determination (Fe, Ca, Mg, total heavy metals) (ICP-OES method): Principle: Inductively coupled plasma atomic emission spectrometry (ICP-OES) is a spectral analysis technique that uses high-temperature plasma to excite atoms of the element being analyzed, causing them to emit characteristic spectral lines. By measuring the emission intensity of the spectral line at a specific wavelength and comparing it with a series of standard solutions of known concentrations, the content of multiple elements in the sample can be quantitatively determined. This method is particularly suitable for the analysis of trace and major elements. It offers high sensitivity, a wide linear range, and strong capability for simultaneous multi-element determination.

[0035] Main reagents and instruments: Reagents: high-purity nitric acid (used to acidify samples and standard solutions and stabilize element forms), multi-element mixed standard stock solution (containing target elements such as Fe, Ca, Mg, Pb, Cu, Zn, Cd, with known and traceable concentrations), single-element standard solution (for backup, for method development or interference checking), high-purity water (ASTM Type I or equivalent).

[0036] Instruments: ICP-OES spectrometer (including radio frequency generator, nebulizer, torch, optical system, detector), automatic sample injector (optional), analytical balance, volumetric flask (various specifications), pipette.

[0037] Experimental Procedure: Sample Preparation: Accurately weigh a certain amount (e.g., 1.0 g, adjusted depending on impurity content and instrument sensitivity) of high-purity manganese sulfate sample, recording the mass m_sample. Place the sample into a clean container (e.g., a polypropylene or PFA volumetric flask) and dissolve it in high-purity water. Acidify the solution by adding a small amount of high-purity nitric acid (e.g., a final concentration of 1-2% v / v) to stabilize the metal ions and provide compatibility with the standard solution matrix. Bring the volume to a final volume, V_final (e.g., 100 mL), with high-purity water, ensuring complete dissolution and mixing. Simultaneously, prepare a reagent blank solution (containing only water and nitric acid).

[0038] Preparation of a Standard Series: Prepare a set of calibration standard solutions containing at least 3-5 concentration points using a multi-element mixed standard stock solution by serial dilution. The concentration range of the standard solutions should cover the expected concentration range of the impurity elements in the samples. All standard solutions should be acidified with nitric acid at the same concentration as the sample solution and brought to volume with high-purity water.

[0039] Instrument parameter optimization: Based on the instrument manufacturer's recommendations and the characteristics of the elements to be analyzed, optimize the ICP-OES operating parameters, including plasma power, carrier gas flow rate, auxiliary gas flow rate, nebulizer gas flow rate, observation height, integration time, and analytical line selection (selecting lines with high sensitivity and minimal interference).

[0040] Measurement: The reagent blank, calibration standard solution series, and sample solution are sequentially introduced into the ICP-OES for measurement. Each solution is measured multiple times (e.g., three times) to improve precision. The instrument records the emission intensity of the characteristic spectral line for each element. For total heavy metals, typical heavy metal elements such as Pb, Cd, Cu, Zn, As, and Hg are typically measured separately. The results are then summed or reported based on the most stringent element (usually Pb) according to specific standards (e.g., pharmacopoeias) or customer requirements. Alternatively, if only a total heavy metal limit (expressed as Pb) is required, only Pb is measured.

[0041] Calculation: The instrument software automatically calculates the concentration of each impurity element, C_element, in the sample solution (typically in mg / L or μg / L) based on the calibration curve (emission intensity vs. concentration). The impurity element content in the sample (ppm, i.e., mg / kg) = (C_element × V_final) / (m_sample × dilution_factor), where dilution_factor is the dilution factor used during sample preparation (1 if undiluted after dissolution). Note that unit conversions are important (1 mg / L = 1 ppm in solution, 1 mg / kg = 1 ppm in solid). The total heavy metal content should be calculated based on specific requirements, such as simple addition or reported as Pb equivalents.

[0042] Quality Control: Run quality control standards (QCS) to verify the accuracy of the calibration curve. Regularly run blanks and drift correction standards to monitor baseline and instrument stability. For complex matrices, consider matrix matching or standard additions. Analytical line selection requires careful evaluation of potential spectral interferences.

[0043] Manganese (Mn) Recovery Determination: Principle: Recovery is the percentage of the target substance (manganese) in the final product relative to the target substance (manganese) in the starting materials during the entire purification process. It reflects the process's retention and loss of the target substance and is a key indicator for evaluating process economics and efficiency. Calculating recovery requires accurate measurement of the manganese content in the input and output materials, as well as the total amount of material.

[0044] Experimental steps and data collection: Determination of total manganese in the starting material (Mn_input): Accurately weigh the total mass (M_input_solution) or total volume (V_input_solution) of the raw material solution input into step S1.

[0045] Take a representative sample of the raw material solution and determine its mass concentration of manganese (C_input_Mn, in units such as g / L or g / kg) using the above-mentioned manganese sulfate (MnSO4) purity determination method (EDTA titration method or ICP-OES method).

[0046] Calculate the total manganese in the starting material: Mn_input = M_input_solution × C_input_Mn (if C is mass fraction) or Mn_input = V_input_solution × C_input_Mn (if C is mass / volume concentration). Make sure to use consistent units.

[0047] Determination of total manganese in the final product (Mn_output): Accurately weigh the total mass (M_output_product) of the high-purity manganese sulfate solid product obtained after drying in step S9.

[0048] Take a representative sample of the final product and use manganese sulfate (MnSO 4) Purity determination method: Determine the mass fraction of manganese element (Purity_Mn).

[0049] Calculate the total manganese mass in the final product: Mn_output = M_output_product × Purity_Mn.

[0050] Consider the circulating flow (mother liquor reflux): For steady-state processes that include a circulating flow, the recovery rate should be evaluated based on a complete cycle or after the system reaches a steady state. The recovery rate calculation of a single batch may require deducting or tracking the amount of manganese in the reflux mother liquor. However, a simple recovery rate calculation usually directly compares the raw manganese input and the product manganese output of a single batch. This method description is based on a single batch input-output calculation. It should be noted that the mother liquor in S9 is refluxed to S1. In theory, this part of manganese is not lost and will be used in subsequent batches. The steady-state recovery rate of long-term operation will be higher than the apparent recovery rate of a single batch.

[0051] Calculation: Manganese (Mn) recovery rate (%) = (Mn_output / Mn_input) × 100% Detailed considerations and explanations: Representative sampling: Whether it is the starting material solution or the final solid product, the sampling must be representative to ensure that the measurement results reflect the overall situation. For heterogeneous materials, they should be thoroughly mixed before sampling.

[0052] Measurement Accuracy: All mass, volume, and concentration measurements must be as precise as possible, using calibrated instruments. The accuracy and precision of the analytical method directly impact the reliability of recovery calculations.

[0053] Material Balance: A more comprehensive assessment involves performing a material balance. This involves measuring not only the input and output products but also the manganese content in various waste streams generated during the process (e.g., S2 precipitate, S3 spent adsorbent, S8 concentrate) to determine the pathways and total amount of manganese loss. In theory, input manganese = output manganese + manganese lost in various stages of loss + accumulated manganese within the system.

[0054] Benchmark definition: The benchmark for recovery calculation should be clearly defined: Is it based on the total amount of Mn element input or the theoretically obtainable amount of pure MnSO4? Usually, basing it on the element itself (Mn) is more direct and accurate.

[0055] Process stability: For continuous or semi-continuous processes, the recovery rate should be measured after the process operation stabilizes to reflect the true process efficiency. The results of a single experiment may be affected by the initial conditions.

[0056] Experiments were conducted on the finished materials prepared in Examples 1-2, where Comparative Example 1 was the finished material prepared according to Chinese Patent Publication No. CN111170367A. The experimental results are as follows: Table 1 Performance test data Performance indicators unit Comparative Example 1 Example 1 Example 2 <![CDATA[ Manganese sulfate (MnSO4) purity ]]> % 98.5 99.95 99.98 Iron (Fe) content ppm 50 5 2 Calcium (Ca) content ppm 100 10 8 Magnesium (Mg) content ppm 80 8 5 Total heavy metal impurity content (measured in Pb) ppm 20 ＜5 ＜3 Manganese (Mn) recovery rate % 90 95 96 As can be seen from Table 1, Examples 1-2 exhibit improved product purity (higher manganese sulfate content) and lower impurity content compared to Comparative Example 1. The results are particularly impressive in terms of the removal of iron, calcium, magnesium, and total heavy metals, resulting in a highly pure manganese sulfate product. Furthermore, the purification method of the present invention combines ion exchange, membrane separation, and innovative bubble introduction and electric field-assisted technologies, resulting in not only excellent purification results but also a higher manganese recovery rate, effectively reducing valuable metal losses and improving the economic benefits and resource utilization efficiency of the entire process.

[0057] The reason why Example 2 has better results than Example 1 is that it adopts stronger reaction conditions (higher stirring speed, more precipitant, longer reaction time) in the S2 chemical precipitation step, which improves the removal efficiency of metal impurities (Fe, Ca, Mg, heavy metals).

Claims

1. A method for purifying manganese sulfate based on membrane separation technology, characterized in that: The following steps are involved: S1, start the stirring tank for stirring at a speed of 230-500 RPM; add the raw material solution into the stirring tank; Add a mixed solvent to the raw material solution, with the total amount of the mixed solvent accounting for 1-2% of the mass of the raw material solution; add a stability additive, with the total amount of the stability additive accounting for 3-5% of the mass of the raw material solution; maintain the stirring time in the range of 30-50 minutes and control the temperature at 35-45°C to obtain a preliminary prepared solution; S2, performing chemical precipitation on the preliminary prepared solution; using a reaction tank equipped with a stirring blade, the rotation speed of which is controlled in the range of 200-400 RPM; Adding a precipitant, the total amount of which accounts for 5-7% of the volume of the preliminary prepared solution, that is, adding 5-7 grams of precipitant to every 100 milliliters of the preliminary prepared solution; controlling the reaction temperature at 50-60° C. and the reaction time at 40-60 minutes to obtain a chemically precipitated solution; S3, adding an adsorbent to the chemical precipitation solution, with the total mass accounting for 3-6% of the volume of the chemical precipitation solution; using a constant temperature water bath to maintain the solution temperature at 45-55° C., maintaining the stirring speed in the range of 250-450 RPM, and controlling the adsorption time at 40-60 min to obtain an adsorbed solution.

2. The method for purifying manganese sulfate based on membrane separation technology according to claim 1, characterized in that: Also includes: S4, performing ion exchange on the adsorbed solution; Use all-stainless steel vertical ion exchange columns filled with mixed ion exchange resins; The solution flow rate is controlled within the range of 0.5-1.0 L / min to ensure that the liquid is fully in contact with the resin bed. The ion exchange temperature is 25-35°C to obtain an ion-exchanged solution.

3. The method for purifying manganese sulfate based on membrane separation technology according to claim 2, characterized in that: Also includes: S5, performing membrane separation on the ion-exchanged solution using a spiral nanofiltration membrane; the feed pressure is controlled in the range of 1.5-2.5 MPa, and the pore size of the nanofiltration membrane is in the range of approximately 1-2 nm; the solution is filtered through the membrane surface and separated into a permeate and a concentrate, and the temperature is maintained at 20-30° C. At the end of the nanofiltration, the permeate is collected, the manganese sulfate content is determined, and the purity is verified. The concentrate is discarded to obtain a high-purity manganese sulfate solution; S6, introducing the high-purity manganese sulfate solution into a crystallization tank, controlling the temperature in the crystallization tank to be in the range of 10-20° C., and using a scraper-type agitator to prevent crystals from agglomerating; adding seed crystals, wherein the seed crystals are prepared by mixing pure manganese sulfate powder and anhydrous sodium sulfate in a mass ratio of 3:1, and the total amount added accounts for 1-2% of the volume of the high-purity manganese sulfate solution, that is, 1-2 grams of seed crystals are added for every 100 ml of the high-purity manganese sulfate solution; After the crystallization process is maintained within the range of 40-60 minutes, the obtained crystals and the mother liquor are separated by a centrifuge; the solid is sent to an oven and dried in the range of 90-110° C. for 30-50 minutes, and the mother liquor is refluxed to step S1 for recycling to obtain a high-purity manganese sulfate solid product.

4. The method for purifying manganese sulfate based on membrane separation technology according to claim 1, characterized in that: In step S1, the raw material solution is a manganese sulfate solution, the mixed solvent is prepared by mixing deionized water, anhydrous ethanol, and acetone in a mass ratio of 6-8:2-4:2-4, and the stability additive is prepared by mixing glycerol, sorbitol, and magnesium chloride in a mass ratio of 1-2:1-2:2-5.

5. The method for purifying manganese sulfate based on membrane separation technology according to claim 1, characterized in that: In step S2, the precipitant is prepared by mixing calcium hydroxide, sodium dihydrogen phosphate, sodium carbonate and barium chloride in a mass ratio of 1-2:2-4:3-5:4-6.

6. The method for purifying manganese sulfate based on membrane separation technology according to claim 1, characterized in that: In step S3, the adsorbent is prepared by mixing coconut shell activated carbon, strong acid cation exchange resin, and silica adsorption material in a mass ratio of 2-4:1-2:1-2.

7. The method for purifying manganese sulfate based on membrane separation technology according to claim 2, characterized in that: In step S4, the mixed ion exchange resin is prepared by mixing a weak acid cation exchange resin and a strong base anion exchange resin in a mass ratio of 1-2:2-5.

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