Method for preparing battery-grade manganese sulfate through purification and impurity removal of electrolytic manganese anode slime leachate

Abstract

The invention discloses a method for preparing battery-grade manganese sulfate through purification and impurity removal of electrolytic manganese anode slime lixivium, which comprises the following steps: S1, adding a precipitator MnF2, and filtering out insoluble fluoride; step S2; adding an extracting agent P204; s3, an extracting agent P507 is added for Mn < 2 + > back extraction; s4, MnO2 is added, and filtering is performed after uniform stirring; s5, sodium dimethyl dithiocarbamate with the molar weight 1.2-1.8 times that of the heavy metal in the leachate is added and then fully stirred, and precipitates are filtered out; and S6, concentrating the leachate at 70-90 DEG C to a saturated concentration, and slowly cooling to separate out crystals. According to the design, a precipitant, an extraction agent and an oxidizing agent are added, a step-by-step deepening purification mode is adopted according to different impurity characteristics of the electrolytic manganese anode slime leaching solution, Ca, Mg and Pb ion impurities are efficiently removed through fluorination precipitation, residual heavy metal impurities are deeply removed through solvent extraction, and Fe, Na and K ion impurities are controlled through combination of oxidation precipitation and ion exchange; and finally, the purity of the battery-grade manganese sulfate is ensured through multi-stage crystallization.

Description

Technical Field

[0001] This invention relates to the field of electrolytic manganese anode mud technology, and in particular to a method for purifying and removing impurities from the leachate of electrolytic manganese anode mud to prepare battery-grade manganese sulfate. Background Technology

[0002] Electrolytic manganese anode mud is generated during the electrolysis process, formed by the shedding of the oxide film on the anode plate surface. Approximately 100 kg of anode mud is produced for every ton of electrolytic manganese produced. The leachate from this electrolytic manganese anode mud is a key intermediate product in the electrolytic production of metallic manganese. Acid leaching is a highly efficient method for extracting manganese, with the manganese ion concentration in the leachate typically around 40-55 g / L. Therefore, the extraction and recovery of manganese ions from the electrolytic manganese anode mud leachate has high economic value. The leachate can be purified and treated to produce battery-grade manganese sulfate, meeting the stringent high-purity requirements of high-end applications such as lithium-ion battery cathode materials, thereby enhancing the product's market competitiveness.

[0003] Based on the impurity control standards for battery-grade manganese sulfate and the actual composition analysis of the leachate from electrolytic manganese anode mud, the composition of the leachate is complex. Current technologies often only remove magnesium and sodium ions through relatively simple evaporation and crystallization, assuming that other ions meet the requirements for battery-grade manganese sulfate. If this leachate is used hastily as battery-grade manganese sulfate, impurities in the leachate will not be completely removed, severely affecting battery performance. Therefore, a multi-stage purification process for electrolytic manganese anode mud leachate is needed to meet the requirements for battery-grade manganese sulfate. This improves the utilization rate of manganese resources and reduces waste. Summary of the Invention

[0004] This invention addresses the technical problem that incomplete purification and impurity removal of electrolytic manganese anode mud leachate leads to severe internal impurities that significantly affect battery performance when used as manganese sulfate in batteries. The invention provides a method for preparing battery-grade manganese sulfate from electrolytic manganese anode mud leachate through a multi-stage purification and impurity removal process.

[0005] To solve the above technical problems, the present invention provides a method for purifying and removing impurities from the leachate of electrolytic manganese anode mud to prepare battery-grade manganese sulfate, comprising the following steps: Step S1: Add an acid regulator to the leachate after acid leaching of electrolytic manganese anode mud in the reaction vessel until the pH of the leachate is 2, then add a precipitant MnF2, stir evenly and let stand for 12-15 minutes, and filter out insoluble fluorides.

[0006] Step S2: Add an alkaline regulator to the treated leachate until the pH of the leachate is 4-4.2. Add the extractant P204 to the leachate, stir until the reaction is complete, and let it stand for 10 minutes.

[0007] Step S3: Add extractant P507 to Mn2+ Back-extraction, stir well and let stand;

[0008] Step S4: Adjust the pH of the extract in the reaction vessel to 1.2-2.5, add MnO2, stir for 30-40 minutes until homogeneous, and then filter.

[0009] Step S5: Add an alkaline regulator to adjust the pH of the leachate to 4.0-6.0, add sodium thiram at 1.2-1.8 times the molar amount of heavy metals in the leachate, stir thoroughly, and filter out the precipitate;

[0010] Step S6: Pump the purified leachate into the evaporator and concentrate it to saturation at 70-90℃. Then transfer the concentrate to the crystallization vessel and slowly cool it to precipitate crystals.

[0011] Preferably, in the above technical solution, the amount of MnF2 added in step 1 is 4.5 times the total molar amount of impurity ions.

[0012] Preferably, in the above technical solution, in step 2, the volume fraction of the extractant P204 added is 30–40% based on the total volume of the leachate.

[0013] Preferably, in the above technical solution, in step 3, the volume fraction of extractant P507 added is 20% based on the total volume of the leachate.

[0014] Preferably, in the above technical solution, the stirring time in step 3 is 8–10 min, and the settling time is 15–30 min.

[0015] Preferably, in the above technical solution, the amount of MnO2 added in step 4 is equal to the amount of Fe in the leachate. 2+ 0.5-0.75 times the molar concentration.

[0016] Preferably, in the above technical solution, the reactor in step 4 is a titanium alloy acid-resistant reactor.

[0017] Preferably, in the above technical solution, a small amount of activated carbon is added in step 5, and after standing for 10 minutes, it is filtered out along with the precipitate.

[0018] Preferably, in the above technical solution, the acidity regulator is H2SO4 and the alkalinity regulator is ammonia.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention employs a step-by-step purification method targeting the different impurity characteristics of electrolytic manganese anode mud leachate by adding precipitants, extractants, and oxidants. Fluorination precipitation efficiently removes Ca, Mg, and Pb ion impurities; solvent extraction deeply removes residual heavy metal impurities; and oxidation precipitation combined with ion exchange controls Fe, Na, and K ion impurities. Finally, multi-stage crystallization ensures the purity of battery-grade manganese sulfate. Electrolytic manganese anode mud is typically a waste product from the electrolytic manganese production process. Purifying and removing impurities to prepare battery-grade manganese sulfate not only turns waste into treasure, reducing raw material procurement costs, but also lowers waste disposal expenses for enterprises, achieving effective cost control. Effectively recovering manganese from electrolytic manganese anode mud and converting it into battery-grade manganese sulfate improves the utilization rate of manganese resources, reduces waste, and achieves resource recycling, playing a positive role in ensuring the security of manganese resource supply. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1:

[0023] This invention discloses a method for purifying and removing impurities from the leachate of electrolytic manganese anode mud to prepare battery-grade manganese sulfate, comprising the following steps:

[0024] Step S1: Add acidic regulator H2SO4 to the leachate after acid leaching of electrolytic manganese anode mud in the reactor until the pH of the leachate is 2. Then add precipitant MnF2, stir evenly, and let stand for 12-15 minutes to filter out sparingly soluble fluorides. The amount of MnF2 added is 4.5 times the total molar amount of impurity ions. In actual operation, it is necessary to first determine the concentrations of Ca, Mg, and Pb in the leachate and calculate the total molar amount. To achieve efficient reaction, excess MnF2 can ensure complete impurity removal. The reaction involves MnF2 reacting with the Ca in the leachate after acid leaching of electrolytic manganese anode mud. 2+ Mg 2+ Pb 2+ The reaction produces sparingly soluble CaF2, MgF2, and PbF2 precipitates. When the pH of the leachate is 2, the acidic conditions inhibit the dissolution of MnF2, preventing Mn loss, while simultaneously promoting the precipitation of CaF2, MgF2, and PbF2.

[0025] Step S2: Add ammonia to the treated leachate until the pH of the leachate is 4-4.2. Add the extractant P204 to the leachate, stir until the reaction is complete, and let it stand for 10 minutes. Based on the total volume of the leachate, the volume fraction of extractant P204 added is 30-40%. Excessive concentration will lead to increased viscosity, slower phase separation, increased risk of emulsification, and loss of the organic phase. P204 (di(2-ethylhexyl)phosphoric acid) is an acidic extractant. Under weakly acidic conditions of pH 4.0, its molecular structure preferentially binds to heavy metal ions (such as Pb). 2+ Zn 2+ Cu 2+ A complex is formed. At this point, manganese, due to its relatively low affinity for the extractant P204, mainly remains in the aqueous phase, thus achieving preliminary separation of heavy metal impurities. During operation, to prevent H2O from forming during extraction... + The release causes a drop in pH, so a saponification pretreatment is required to react P2O4 with NaOH to produce sodium soap. The saponification rate is usually controlled at 30% to 50% to balance extraction efficiency and reagent cost.

[0026] Step S3: Add extractant P507 to Mn 2+ Back-extraction was performed, followed by uniform stirring for 8–10 min and then standing for 15–30 min. The volume fraction of extractant P507 added was 20% based on the total volume of the leachate. P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) is a highly efficient acidic phosphorus-based extractant. Using the more selective extractant P507 (compared to extractant P204), manganese was extracted from the mixed back-extraction solution. P507 is effective for extracting Mn. 2+ Its affinity is higher than that of Mg 2+ It can achieve Mn / Mg separation at pH 3.5~4.5.

[0027] Step S4: Adjust the pH of the leachate extracted in the titanium alloy acid-resistant reactor to 1.2-2.5, add MnO2, stir for 30-40 minutes until homogeneous, and then filter. The amount of MnO2 added is equal to the Fe content in the leachate. 2+ The molar concentration is 0.5-0.75 times that of Fe. MnO2 acts as a strong oxidant in a strongly acidic environment (pH 1.2-2.5), capable of oxidizing Fe in the leachate. 2+ Oxidized to Fe 3+ Then Fe 3+ Subsequently, hydrolysis forms a colloidal Fe(OH)3 precipitate, which can be removed by filtration. 2 The removal of the acidic environment (pH=1.2-2.5) requires an acid-resistant and corrosion-resistant reactor to ensure the smooth progress of the reaction. In this embodiment, an acid-resistant titanium alloy reactor is used.

[0028] Step S5: Adjust the pH of the leachate to 4.0-6.0 by adding ammonia water. Add sodium thiram (SDD) at 1.2-1.8 times the molar amount of heavy metals in the leachate, stir thoroughly, add a small amount of activated carbon, let stand for 10 minutes, and then filter out the insoluble precipitate. Sodium thiram (SDD) is a multifunctional organic sulfur compound that can precipitate Co in the leachate. 2+ Ni 2+ Cd 2+ The core principle of this method is to utilize the dithiocarboxyl groups in sodium formoxamate to create stable chelate precipitates with heavy metal ions. These chelate precipitates can be removed by filtration or centrifugation. Furthermore, the Co and Ni chelate residues can be roasted to recover the metal elements.

[0029] Step S6: Pump the purified leachate into an evaporator and concentrate it to a saturated concentration at 70-90℃. Then transfer the concentrate to a crystallization vessel and slowly cool it to precipitate crystals. The solubility of manganese sulfate decreases significantly with decreasing temperature, while sodium and potassium salts (such as Na2SO4 and K2SO4) maintain relatively high solubility at low temperatures. Pump the purified leachate into an MVR (mechanical vapor recompression) evaporator and concentrate it to a saturated concentration at 70-90℃. To prevent corrosion of the evaporator, a titanium evaporator is used. The concentrate is then transferred to a crystallization vessel and slowly cooled to 20-30℃ at a rate of 5℃ / h. MnSO4·H2O seed crystals can also be added to inhibit fine crystal formation. Finally, wet crystals are obtained by centrifugation.

[0030] This invention employs a step-by-step purification method targeting the different impurity characteristics of electrolytic manganese anode mud leachate by adding precipitants, extractants, and oxidants. It uses fluorination precipitation to efficiently remove Ca, Mg, and Pb ion impurities, solvent extraction to deeply remove residual heavy metal impurities, and oxidation precipitation combined with ion exchange to control Fe, Na, and K ion impurities. Finally, multi-stage crystallization ensures the purity of battery-grade manganese sulfate.

[0031] Electrolytic manganese anode sludge is typically a waste product from the electrolytic manganese production process. Purifying and removing impurities from it to produce battery-grade manganese sulfate not only turns waste into treasure and reduces raw material procurement costs, but also lowers waste disposal expenses for enterprises, achieving effective cost control. Effectively recovering manganese from electrolytic manganese anode sludge and converting it into battery-grade manganese sulfate improves the utilization rate of manganese resources, reduces waste, and achieves resource recycling, playing a positive role in ensuring the security of manganese resource supply.

[0032] Example 2:

[0033] In this embodiment, the limit ranges of various impurities in the leachate of electrolytic manganese anode mud without in-depth impurity removal treatment and battery-grade manganese sulfate will be measured and compared through Experiment 1.

[0034] Table 1 Comparison of elemental impurities in electrolytic manganese anode mud leachate and battery-grade manganese sulfate.

[0035] element Leachate concentration (mg / L) Battery-grade manganese sulfate limit (mg / kg) Exceeding the standard <![CDATA[Mg 2+ ]]> 1256.3 ≤50 2512% <![CDATA[Ca 2+ ]]> 391.8 ≤30 1306% <![CDATA[Pb 2+ ]]> 1092.5 ≤20 5462.5% <![CDATA[Fe 2+ ]]> 866.7 ≤10 8667% <![CDATA[Cu 2+ ]]> 63.1 ≤10 631% <![CDATA[Zn 2+ ]]> 57.3 ≤10 573% <![CDATA[Na + ]]> 6206 ＜100 6206%

[0036] As can be seen from the data in the table above, the content of various ionic impurities in the leachate of electrolytic manganese anode mud is much higher than the limit in battery-grade manganese sulfate.

[0037] If no impurity removal treatment is performed on the leaching solution of electrolytic manganese anode mud, the residual Ca will remain. 2+ Fe 3+ Ions with equal charge density will react with SO4 2 - Forming strong electrostatic pairs hinders ion migration, reducing effective ion concentration and conductivity. Residual Ca in some purified solutions... 2+ The reaction with HF, a product of electrolyte decomposition, forms CaF2 precipitate, which blocks electrode pores and simultaneously consumes the active Li in the battery. + .

[0038] Example 3:

[0039] This embodiment will compare the partial purification treatment of the electrolytic manganese anode mud leachate with the full purification treatment of the electrolytic manganese anode mud leachate. The differences in the concentration of each ion, conductivity under normal room temperature conditions, interfacial impedance, and other data will be compared, and the underlying reasons for the differences in conductivity will be analyzed.

[0040] Table 2 Comparison of Partial and Full-Process Purification Treatment of Leachate from Electrolytic Manganese Anode Sludge

[0041] parameter Partial purification solution except for Mg / Na Full-process deep purification solution Influence of electrical conductivity <![CDATA[Ca 2+ Concentration 165.3ppm 46.9 ppm <![CDATA[Ca 2+ For every 50 ppm increase, conductivity decreases by 8%-10%. <![CDATA[Fe 3+ Concentration 16.5ppm 0.9 ppm <![CDATA[Fe 3+ This leads to electron tunneling, increasing leakage current. <![CDATA[Na + Concentration 159.2ppm 8.3 ppm <![CDATA[Na + Competition migration path, Li + The number of migrations decreased by 0.15-0.20. electrical conductivity 66mS / cm 95mS / cm The conductivity of the entire purification process is increased by 15%-30%. Interface impedance (EIS) 298Ω·cm² 105Ω·cm² Deposits cause a 40% increase in charge transfer resistance.

[0042] Based on the data in the table above, it can be seen that multivalent ions (Ca) 2+ Fe 3+ All of these factors affected conductivity to varying degrees, resulting in a high charge number but low mobility. Experimental measurements showed that Ca... 2+ The mobility is only Li + 60%, significantly reducing the overall conductivity.

[0043] The conductivity of the purified solution increases more significantly (approximately 30%–50%) at high temperatures (>50℃) due to Mn. 2+ The liquid is predominantly conductive and free from impurities interfering with the thermal motion of ions; however, some of the purified liquid contains Ca... 2+ Fe 3+Intensified ion association actually leads to a decrease in conductivity at high temperatures. When a portion of the purified solution is used as a battery solution, its battery retention rate differs by approximately 30% compared to the purified solution used throughout the entire process. This difference is due to increased interfacial impedance and loss of active lithium.

[0044] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying and removing impurities from the leachate of electrolytic manganese anode mud to prepare battery-grade manganese sulfate, characterized in that, Includes the following steps: Step S1: Add an acid regulator to the leachate after acid leaching of electrolytic manganese anode mud in the reactor until the pH of the leachate is 2. Then add precipitant MnF2, stir evenly, let stand for 12-15 minutes, and filter out the sparingly soluble fluorides. Step S2: Add an alkaline regulator to the treated leachate until the pH of the leachate is 4-4.

2. Add the extractant P204 to the leachate, stir until the reaction is complete, and let it stand for 10 minutes. Step S3: Add extractant P507 to Mn 2+ Back-extraction, stir well and let stand; Step S4: Adjust the pH of the extract in the reaction vessel to 1.2-2.5, add MnO2, stir for 30-40 minutes until homogeneous, and then filter. Step S5: Add an alkaline regulator to adjust the pH of the leachate to 4.0-6.0, add sodium thiram at 1.2-1.8 times the molar amount of heavy metals in the leachate, stir thoroughly, and filter out the precipitate; Step S6: Pump the purified leachate into the evaporator and concentrate it to saturation at 70-90℃. Then transfer the concentrate to the crystallization vessel and slowly cool it to precipitate crystals.

2. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: In step 1, the amount of MnF2 added is 4.5 times the total molar amount of impurity ions.

3. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: In step 2, the volume fraction of extractant P204 added is 30–40% based on the total volume of the leachate.

4. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: In step 3, the volume fraction of extractant P507 added is 20%, based on the total volume of the leachate.

5. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: The stirring time in step 3 is 8–10 min, and the settling time is 15–30 min.

6. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: In step 4, the amount of MnO2 added is equal to the amount of Fe in the leachate. 2+ 0.5-0.75 times the molar concentration.

7. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leachate of electrolytic manganese anode mud according to claim 1, characterized in that: The reactor used in step 4 is an acid-resistant titanium alloy reactor.

8. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: Add a small amount of activated carbon in step 5, let it stand for 10 minutes, and then filter it out along with the precipitate.

9. The method for preparing battery-grade manganese sulfate by purifying and removing impurities from the leaching solution of electrolytic manganese anode mud according to claim 1, characterized in that: The acidity regulator is H2SO4, and the alkalinity regulator is ammonia.