A method for preparing battery-grade manganese sulfate based on activated carbon reduction method

Abstract

This invention discloses a method for preparing battery-grade manganese sulfate based on activated carbon reduction, comprising the following steps: preparing modified activated carbon loaded with Fe-Mn composite oxides; crushing and grinding a manganese source to obtain a manganese ore slurry; reacting the modified activated carbon with the manganese ore slurry under acidic conditions to reduce and leach manganese while adsorbing impurity ions; after solid-liquid separation, neutralizing, removing impurities, and deeply purifying the leaching solution through sulfidation; evaporating and crystallizing to obtain battery-grade manganese sulfate product; and regenerating the waste activated carbon through heat treatment, activation, and acid washing. The modified activated carbon of this invention possesses catalytic, reduction, and adsorption functions, achieving a manganese leaching rate of 99.2% and a manganese sulfate product purity of 99.35%. The content of impurities such as calcium, magnesium, and iron meets industry standards. The regenerated activated carbon has a specific capacitance greater than 200 F / g and can be used as an electrode material for supercapacitors. This invention achieves the coupling of efficient reduction leaching of manganese ore with in-situ removal of impurities, and utilizes waste activated carbon resources, making the process green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation technology, and in particular to a method for preparing battery-grade manganese sulfate based on activated carbon reduction. Background Technology

[0002] Battery-grade manganese sulfate is a key precursor for lithium-ion battery cathode materials, and its quality directly affects battery performance. Therefore, the requirements for the content of impurities such as calcium, magnesium, potassium, and sodium are extremely stringent, which poses a huge challenge to the efficient extraction and deep purification process of manganese ore resources.

[0003] Currently, the mainstream technologies for preparing battery-grade manganese sulfate from manganese ore revolve around two main stages: reduction leaching and deep purification. In the reduction leaching stage, the pyrometallurgical reduction roasting process reduces manganese dioxide to manganese monoxide at high temperatures followed by acid leaching. While technically mature, this method suffers from high energy consumption, large equipment investment, and the generation of sulfur-containing flue gas during roasting. Wet reduction leaching typically uses reducing agents such as pyrite, sulfur dioxide, or hydrogen peroxide. However, pyrite produces a large amount of leaching residue, sulfur dioxide poses a risk of gas escape, and hydrogen peroxide is expensive and has poor stability. Organic reducing agents such as biomass, explored in recent years, are prone to decomposition during leaching, generating organic byproducts that affect product purity.

[0004] In the deep purification stage of leachate, existing technologies have significant shortcomings for impurity ions with similar properties, such as calcium and magnesium. Recrystallization is a lengthy process with low manganese recovery rates; solvent extraction struggles to achieve efficient and selective separation of calcium and magnesium from manganese and is costly; fluoride precipitation is a commonly used industrial method, but the resulting fluorine-containing waste is hazardous, posing a significant environmental burden. Some processes introduce activated carbon in the purification stage to adsorb organic impurities, but activated carbon is consumed only as a single-use adsorbent, becoming solid waste after use. This not only fails to fully utilize its material value but also increases the disposal burden.

[0005] In summary, existing processes suffer from high energy consumption, high costs, and the introduction of new impurities in the reduction leaching stage, while facing challenges such as long process duration, low manganese recovery rate, and significant environmental pressure in the deep purification stage. Therefore, developing a new green process that can synergistically enhance the reduction process, achieve in-situ impurity control, and utilize process byproducts as resources is of great significance. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing battery-grade manganese sulfate based on activated carbon reduction.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing battery-grade manganese sulfate based on activated carbon reduction includes the following steps:

[0009] (1) Preparation of modified activated carbon: Fe-Mn composite oxide nanoparticles are loaded on the surface and in the pores of activated carbon through in-situ oxidation-reduction reaction, and then acid etching is performed to obtain modified activated carbon.

[0010] (2) Manganese source pretreatment: crush and grind the manganese source to obtain manganese ore slurry;

[0011] (3) Coupled reduction leaching and in-situ adsorption: The modified activated carbon is reacted with the manganese slurry under acidic conditions. While reducing and leaching manganese, the modified activated carbon adsorbs impurity ions in the leaching solution to obtain a leaching slurry containing manganese sulfate and waste activated carbon after the reaction.

[0012] Under acidic conditions, the modified activated carbon matrix acts as a reducing agent to remove Mn from manganese ore. 4+ Reduced to soluble Mn 2+ The reaction formula is C + 2MnO₂ + 4H₂O. + =2Mn 2+ +CO2 + 2H2O; Simultaneously, the supported Fe-Mn composite oxide acts as a catalytic center, accelerating the kinetics of the above reduction reaction. During the reductive leaching, the porous structure of the modified activated carbon, through a synergistic effect of physical adsorption (van der Waals forces, pore trapping) and chemical adsorption (complexation, ion exchange), effectively removes Ca from the leachate. 2+ Mg 2+ Pb 2 + Cd 2+ Impurity ions are adsorbed in situ, achieving "reduction leaching - impurity removal" in one step, avoiding manganese loss in subsequent purification processes.

[0013] (4) Solid-liquid separation and solution purification: The leaching slurry is subjected to solid-liquid separation to obtain crude manganese sulfate leaching solution; the crude manganese sulfate leaching solution is subjected to neutralization and impurity removal and sulfidation deep purification in sequence to obtain refined manganese sulfate solution;

[0014] (5) Evaporation and crystallization: The refined manganese sulfate solution is evaporated, concentrated and crystallized to obtain battery-grade manganese sulfate product;

[0015] (6) Resource recycling of waste activated carbon: The waste activated carbon after the reaction is subjected to heat treatment, activation and acid washing in sequence to recover manganese and obtain recycled activated carbon material.

[0016] Preferably, in step (1), the method for preparing the modified activated carbon includes the following steps:

[0017] A1: Carbon matrix pretreatment: Select commercial activated carbon with a specific surface area >1000m² / g and a mesoporous to macroporous volume ratio ≥50%, and wash it with water, alkali, and acid in sequence. Finally, wash it with water until it is neutral and dry it for later use.

[0018] A2: Anchoring and Loading: Adding pretreated activated carbon containing Fe 2+ Salt and Mn 2+ In a mixed solution, aminosulfonic acid was added and stirred to allow metal ions to be adsorbed and anchored; then potassium permanganate solution was added dropwise to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor.

[0019] A3: Acid etching dispersion: The supported precursor is acid etched with dilute hydrochloric acid, filtered, washed, and dried to obtain the modified activated carbon.

[0020] Preferably, in step A2, the total metal ion concentration of the mixed solution is 0.3-0.7 mol / L, and Fe... 2+ With Mn 2 + The molar ratio of the total metal ions to aminosulfonic acid in the mixed solution is 1:1.5-2.5; the molar ratio of the total metal ions to aminosulfonic acid in the mixed solution is 1:1.5-2.5; the concentration of the potassium permanganate solution is 0.05-0.15 mol / L, and the dropping rate is 0.5-2 mL / min.

[0021] Preferably, in step A3, the concentration of the dilute hydrochloric acid is 0.2-0.8 mol / L; the acid etching temperature is 25-30℃, and the time is 0.5-2h.

[0022] This invention uses high specific surface area activated carbon as a carrier, and loads Fe-Mn composite oxide nanoparticles on its surface and pores through in-situ redox reactions. The Fe-Mn composite oxides serve as catalytic active centers, which can reduce the activation energy of manganese ore reduction leaching and enhance the activation energy of activated carbon for Mn. 4+ The reducing power; acid etching can break the agglomeration structure of Fe-Mn composite oxides, increase the exposure of active sites, and form a rich microporous-mesoporous structure on the surface of activated carbon, enhancing the physical adsorption and chemical complexation ability for impurity ions. Aminosulfonic acid, as a complexing agent, can react with Fe... 2+ Mn 2+ This process forms stable complexes, preventing premature precipitation of metal ions and ensuring their uniform anchoring and loading on the activated carbon surface.

[0023] Preferably, in step (2), the manganese source is selected from one or more of pyrolusite, electrolytic manganese anode mud, manganese-containing dust or waste battery cathode material; and the proportion of particles with a particle size of 200 mesh in the manganese slurry exceeds 70%.

[0024] Preferably, in step (3), the contact reaction is carried out in a stirred reactor at a temperature of 80-95°C, the solid-liquid ratio of the reaction system is 1g:(2-6)mL, and the reaction time is 3-8h.

[0025] Preferably, in step (4), the neutralization and impurity removal involves adding manganese carbonate or manganese hydroxide to adjust the pH value to 3.5-5.0, so that Fe... 3+ Al 3+ Hydrolysis precipitation; the deep purification by sulfidation involves adding a sulfiding agent under pH conditions of 5.0-5.5 to remove heavy metal ions.

[0026] Preferably, in step (5), the evaporation concentration and crystallization process is repeated 2-3 times.

[0027] Preferably, step (6) includes:

[0028] Low-temperature heat treatment section: Under an inert atmosphere, heat treatment at 300-500℃ for 1-3 hours to remove organic matter;

[0029] High-temperature activation section: The temperature is raised to 700-900℃, and carbon dioxide or water vapor is introduced for physical activation, or it is mixed with potassium hydroxide for chemical activation;

[0030] Pickling: The activated carbon material is washed with dilute hydrochloric acid to recover manganese from the pickling solution and obtain regenerated activated carbon material.

[0031] Preferably, the specific capacitance of the regenerated activated carbon material is greater than 200 F / g, and it can be used as an electrode material for supercapacitors.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. Reduction-adsorption coupling improves process efficiency and product purity: Modified activated carbon has both reduction and adsorption functions. While achieving efficient reduction leaching of manganese ore, it adsorbs impurity ions in the leachate in situ, avoiding the loss of manganese in the traditional process where reduction and purification are carried out in separate steps. The manganese leaching rate can reach 99.2%, and the purity of manganese sulfate product reaches 99.35%. All impurity indicators are better than the HG / T4823-2023 qualified product standard.

[0034] 2. Enhanced catalytic reaction, reducing process energy consumption and cost: Fe-Mn composite oxide nanoparticles loaded on the surface of activated carbon serve as catalytic active centers, reducing the activation energy of manganese reduction leaching reaction, allowing the reaction to proceed under mild conditions of 80-95℃, significantly reducing energy consumption; moreover, the reduction efficiency of modified activated carbon is much higher than that of unmodified activated carbon, reducing the amount of reducing agent required, while avoiding the problem of introducing new impurities with traditional reducing agents.

[0035] 3. High-value regeneration of waste activated carbon to achieve resource recycling: Through the regeneration process of "low temperature impurity removal - high temperature activation - acid washing and recovery", not only is the structure and performance of waste activated carbon restored, but the specific capacitance of the regenerated activated carbon is also greater than 200F / g, which can be used as electrode material for supercapacitors to achieve high-value utilization. At the same time, the acid washing process recovers manganese ions, improves the total manganese recovery rate, avoids the generation of activated carbon solid waste, and reduces the environmental disposal burden.

[0036] 4. The process is green and efficient, and the manganese source and application scenarios are widely adaptable: The neutralization and impurity removal uses a manganese-based neutralizing agent, and no hazardous waste such as fluorine-containing waste residue is generated throughout the process, and no new impurities are introduced; the manganese source can be soft manganese ore, electrolytic manganese anode mud, manganese-containing dust or waste battery cathode material, etc., which not only utilizes conventional manganese ore resources, but also realizes the resource recovery of manganese resources in industrial solid waste. The process has both green environmental protection and comprehensive resource utilization value. Attached Figure Description

[0037] Figure 1 This is a flowchart of the experimental process proposed in this invention. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] Example 1: This example provides a method for preparing battery-grade manganese sulfate based on activated carbon reduction. The specific steps are as follows:

[0040] (1) Preparation of modified activated carbon

[0041] A1: Carbon matrix pretreatment: Select 100g of commercial activated carbon with a specific surface area of ​​1100m² / g and a mesoporous to macroporous volume ratio of 50%. Wash it with deionized water 3 times, alkali wash with 5% sodium hydroxide solution for 1h, acid wash with 5% hydrochloric acid solution for 1h, and finally wash it with deionized water until neutral. Dry it at 105℃ for 2h for later use.

[0042] A2: Anchoring and Loading: Add the pretreated activated carbon to 200 mL of a solution containing Fe. 2+ Salt and Mn 2+ In the mixed solution (total metal ion concentration 0.3 mol / L, Fe...) 2+ With Mn 2+The molar ratio of total metal ions to aminosulfonic acid in the mixed solution was 1:1.5. The mixture was stirred at 25°C for 30 min to allow the metal ions to be adsorbed and anchored. Then, a 0.05 mol / L potassium permanganate solution was added dropwise at a rate of 0.5 mL / min. After the addition was complete, the mixture was stirred for 1 h to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor.

[0043] A3: Acid etching dispersion: The supported precursor was acid etched with 0.2 mol / L dilute hydrochloric acid at 25℃ for 0.5 h, filtered, washed with deionized water until neutral, and dried at 105℃ for 2 h to obtain modified activated carbon, denoted as Fe-Mn / AC-H.

[0044] (2) Manganese source pretreatment: 500g of soft manganese ore was selected as the manganese source, crushed and ground in a grinder to obtain manganese ore slurry, of which 72% of the particles were 200 mesh.

[0045] (3) Coupled reduction leaching and in-situ adsorption: 80g of the modified activated carbon prepared above and manganese ore slurry were added to a stirred reactor. Dilute sulfuric acid was added to adjust the reaction system to acidity (pH=2.0). The reaction temperature was controlled at 80℃ and the solid-liquid ratio of the reaction system was 1g:2mL. The reaction was stirred for 3h. While reducing and leaching manganese, the modified activated carbon adsorbed impurity ions in the leaching solution to obtain leaching ore slurry containing manganese sulfate and waste activated carbon after the reaction.

[0046] (4) Solid-liquid separation and solution purification: The leaching slurry was subjected to solid-liquid separation by plate and frame filtration to obtain crude manganese sulfate leachate; manganese carbonate was added to the crude manganese sulfate leachate to adjust the pH value to 3.5, so that Fe 3+ Al 3+ Hydrolyze the precipitate, filter to remove the precipitate; then add sodium sulfide to the filtered solution, control the pH value to 5.0, stir the reaction for 30 min to remove heavy metal ions, and filter to obtain a refined manganese sulfate solution.

[0047] (5) Evaporation and crystallization: The refined manganese sulfate solution is placed in an evaporator crystallizer for evaporation, concentration and crystallization. This process is repeated twice. After centrifugation and drying at 105°C for 2 hours, battery-grade manganese sulfate product is obtained.

[0048] (6) Resource regeneration of waste activated carbon: The waste activated carbon after the reaction is placed in a tube furnace and heat-treated at 300°C for 1 hour under nitrogen to remove organic matter; then the temperature is raised to 700°C and carbon dioxide is introduced for physical activation for 2 hours; finally, the activated carbon material is washed with dilute hydrochloric acid, and the manganese in the acid washing solution is recovered by filtration to obtain the regenerated activated carbon material. Its specific capacitance is tested to be 205 F / g, which can be used as electrode material for supercapacitors.

[0049] Example 2: This example provides a method for preparing battery-grade manganese sulfate based on activated carbon reduction. The specific steps are as follows:

[0050] (1) Preparation of modified activated carbon

[0051] A1: Carbon matrix pretreatment: Select 100g of commercial activated carbon with a specific surface area of ​​1500m² / g and a volume ratio of mesopores to macropores of 60%. Wash it with deionized water 3 times, alkali wash with 5% sodium hydroxide solution for 1h, acid wash with 5% hydrochloric acid solution for 1h, and finally wash it with deionized water until neutral. Dry it at 105℃ for 2h for later use.

[0052] A2: Anchoring and Loading: Add the pretreated activated carbon to 200 mL of a solution containing Fe. 2+ Salt and Mn 2+ In the mixed solution (total metal ion concentration 0.4 mol / L, Fe...) 2+ With Mn 2+ The molar ratio of total metal ions to aminosulfonic acid in the mixed solution was 1:1.8. The mixture was stirred at 25°C for 30 min to allow the metal ions to be adsorbed and anchored. Then, a 0.08 mol / L potassium permanganate solution was added dropwise at a rate of 1.0 mL / min. After the addition was complete, the mixture was stirred for 1 h to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor.

[0053] A3: Acid etching dispersion: The supported precursor was acid etched with dilute hydrochloric acid at a concentration of 0.4 mol / L at 27℃ for 1.0 h, filtered, washed with deionized water until neutral, and dried at 105℃ for 2 h to obtain modified activated carbon, denoted as Fe-Mn / AC-H.

[0054] (2) Manganese source pretreatment: 500g of electrolytic manganese anode mud was selected as the manganese source, crushed and ground in a grinder to obtain manganese slurry, of which 78% of the particles were 200 mesh.

[0055] (3) Coupled reduction leaching and in-situ adsorption: 80g of the modified activated carbon prepared above and manganese ore slurry were added to a stirred reactor. Dilute sulfuric acid was added to adjust the reaction system to acidity (pH=2.0). The reaction temperature was controlled at 85℃ and the solid-liquid ratio of the reaction system was 1g:3mL. The reaction was stirred for 4h. While reducing and leaching manganese, the modified activated carbon adsorbed impurity ions in the leaching solution to obtain leaching ore slurry containing manganese sulfate and waste activated carbon after the reaction.

[0056] (4) Solid-liquid separation and solution purification: The leaching slurry was subjected to solid-liquid separation by plate and frame filtration to obtain crude manganese sulfate leachate; manganese hydroxide was added to the crude manganese sulfate leachate to adjust the pH value to 4.0, so that Fe 3+Al 3+ Hydrolyze the precipitate, filter to remove the precipitate; then add potassium sulfide to the filtered solution, control the pH value to 5.2, stir the reaction for 30 min to remove heavy metal ions, and filter to obtain a refined manganese sulfate solution.

[0057] (5) Evaporation and crystallization: The refined manganese sulfate solution is placed in an evaporator crystallizer for evaporation, concentration and crystallization. This process is repeated twice. After centrifugation and drying at 105°C for 2 hours, battery-grade manganese sulfate product is obtained.

[0058] (6) Resource regeneration of waste activated carbon: The waste activated carbon after the reaction is placed in a tube furnace and heat-treated at 380°C for 2 hours under nitrogen to remove organic matter; then the temperature is raised to 780°C and water vapor is introduced for physical activation for 2 hours; finally, the activated carbon material is washed with dilute hydrochloric acid, and the manganese in the acid washing solution is recovered by filtration to obtain the regenerated activated carbon material. Its specific capacitance is tested to be 220F / g, which can be used as electrode material for supercapacitors.

[0059] Example 3: This example provides a method for preparing battery-grade manganese sulfate based on activated carbon reduction. The specific steps are as follows:

[0060] (1) Preparation of modified activated carbon

[0061] A1: Carbon matrix pretreatment: Select 100g of commercial activated carbon with a specific surface area of ​​1800m² / g and a mesoporous to macroporous volume ratio of 65%. Wash it with deionized water 3 times, alkali wash with 5% sodium hydroxide solution for 1h, acid wash with 5% hydrochloric acid solution for 1h, and finally wash it with deionized water until neutral. Dry it at 105℃ for 2h for later use.

[0062] A2: Anchoring and Loading: Add the pretreated activated carbon to 200 mL of a solution containing Fe. 2+ In a mixed solution of salt and Mn²⁺ (total metal ion concentration 0.5 mol / L, Fe²⁺...) 2+ With Mn 2+ The molar ratio of total metal ions to aminosulfonic acid in the mixed solution was 1:2.0. The mixture was stirred at 25°C for 30 min to allow the metal ions to be adsorbed and anchored. Then, a 0.10 mol / L potassium permanganate solution was added dropwise at a rate of 1.2 mL / min. After the addition was complete, the mixture was stirred for 1 h to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor.

[0063] A3: Acid etching dispersion: The supported precursor was acid etched with 0.5 mol / L dilute hydrochloric acid at 28℃ for 1.2 h, filtered, washed with deionized water until neutral, and dried at 105℃ for 2 h to obtain modified activated carbon, denoted as Fe-Mn / AC-H;

[0064] (2) Manganese source pretreatment: 500g of manganese-containing dust was selected as the manganese source, crushed and ground in a grinder to obtain manganese slurry, of which 82% of the particles were 200 mesh.

[0065] (3) Coupled reduction leaching and in-situ adsorption: 80g of the modified activated carbon prepared above and manganese ore slurry were added to a stirred reactor. Dilute sulfuric acid was added to adjust the reaction system to acidity (pH=2.0). The reaction temperature was controlled at 88℃ and the solid-liquid ratio of the reaction system was 1g:4mL. The reaction was stirred for 5h. While reducing and leaching manganese, the modified activated carbon adsorbed impurity ions in the leaching solution to obtain leaching ore slurry containing manganese sulfate and waste activated carbon after the reaction.

[0066] (4) Solid-liquid separation and solution purification: The leaching slurry was subjected to solid-liquid separation by plate and frame filtration to obtain crude manganese sulfate leachate; manganese carbonate was added to the crude manganese sulfate leachate to adjust the pH value to 4.2, so that Fe 3+ Al 3+ Hydrolyze the precipitate, filter to remove the precipitate; then add ammonium sulfide to the filtered solution, control the pH value to 5.3, stir the reaction for 30 min to remove heavy metal ions, and filter to obtain a refined manganese sulfate solution.

[0067] (5) Evaporation and crystallization: The refined manganese sulfate solution is placed in an evaporator crystallizer for evaporation, concentration and crystallization. This process is repeated 3 times. After centrifugation and drying at 105°C for 2 hours, battery-grade manganese sulfate product is obtained.

[0068] (6) Resource regeneration of waste activated carbon: The waste activated carbon after the reaction is placed in a tube furnace and heat-treated at 420°C for 2 hours under argon to remove organic matter; then the temperature is raised to 820°C and chemically activated with potassium hydroxide (potassium hydroxide to waste activated carbon mass ratio 1:1) for 2 hours; finally, the activated carbon material is washed with dilute hydrochloric acid, and the manganese in the acid washing solution is recovered by filtration to obtain the regenerated activated carbon material. Its specific capacitance is tested to be 235 F / g, which can be used as electrode material for supercapacitors.

[0069] Example 4: This example provides a method for preparing battery-grade manganese sulfate based on activated carbon reduction. The specific steps are as follows:

[0070] (1) Preparation of modified activated carbon

[0071] A1: Carbon matrix pretreatment: Select 100g of commercial activated carbon with a specific surface area of ​​2000m² / g and a volume ratio of mesopores to macropores of 70%. Wash it with deionized water 3 times, alkali wash with 5% sodium hydroxide solution for 1h, acid wash with 5% hydrochloric acid solution for 1h, and finally wash it with deionized water until neutral. Dry it at 105℃ for 2h for later use.

[0072] A2: Anchoring and Loading: Add the pretreated activated carbon to 200 mL of a solution containing Fe. 2+ Salt and Mn 2+ In the mixed solution (total metal ion concentration 0.6 mol / L, Fe... 2+ With Mn 2+ The molar ratio of total metal ions to aminosulfonic acid in the mixed solution was 1:2.2. The mixture was stirred at 25°C for 30 min to allow the metal ions to be adsorbed and anchored. Then, a 0.12 mol / L potassium permanganate solution was added dropwise at a rate of 1.5 mL / min. After the addition was complete, the mixture was stirred for 1 h to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor.

[0073] A3: Acid etching dispersion: The supported precursor was acid etched with 0.6 mol / L dilute hydrochloric acid at 29℃ for 1.5 h, filtered, washed with deionized water until neutral, and dried at 105℃ for 2 h to obtain modified activated carbon, denoted as Fe-Mn / AC-H.

[0074] (2) Manganese source pretreatment: 500g of waste battery positive electrode material was selected as the manganese source, crushed and ground in a grinder to obtain manganese slurry, of which 85% of the particles were 200 mesh;

[0075] (3) Coupled reduction leaching and in-situ adsorption: 80g of the modified activated carbon prepared above and manganese ore slurry were added to a stirred reactor. Dilute sulfuric acid was added to adjust the reaction system to acidity (pH=2.0). The reaction temperature was controlled at 92℃ and the solid-liquid ratio of the reaction system was 1g:5mL. The reaction was stirred for 6h. While reducing and leaching manganese, the modified activated carbon adsorbed impurity ions in the leaching solution to obtain leaching ore slurry containing manganese sulfate and waste activated carbon after the reaction.

[0076] (4) Solid-liquid separation and solution purification: The leaching slurry was subjected to solid-liquid separation by plate and frame filtration to obtain crude manganese sulfate leachate; manganese hydroxide was added to the crude manganese sulfate leachate to adjust the pH value to 4.5, so that Fe 3+ Al 3+ Hydrolyze the precipitate, filter to remove the precipitate; then add sodium sulfide to the filtered solution, control the pH value to 5.4, stir the reaction for 30 min to remove heavy metal ions, and filter to obtain a refined manganese sulfate solution.

[0077] (5) Evaporation and crystallization: The refined manganese sulfate solution is placed in an evaporator crystallizer for evaporation, concentration and crystallization. This process is repeated 3 times. After centrifugation and drying at 105°C for 2 hours, battery-grade manganese sulfate product is obtained.

[0078] (6) Resource regeneration of waste activated carbon: The waste activated carbon after the reaction is placed in a tube furnace and heat-treated at 450°C for 2.5 h under argon to remove organic matter; then the temperature is raised to 850°C and carbon dioxide is introduced for physical activation for 2 h; finally, the activated carbon material is washed with dilute hydrochloric acid, and the manganese in the acid washing solution is recovered by filtration to obtain the regenerated activated carbon material. Its specific capacitance is tested to be 245 F / g, which can be used as electrode material for supercapacitors.

[0079] Example 5: This example provides a method for preparing battery-grade manganese sulfate based on activated carbon reduction. The specific steps are as follows:

[0080] (1) Preparation of modified activated carbon

[0081] A1: Carbon matrix pretreatment: Select 100g of commercial activated carbon with a specific surface area of ​​2200m² / g and a volume ratio of mesopores to macropores of 80%. Wash it with deionized water 3 times, alkali wash with 5% sodium hydroxide solution for 1h, acid wash with 5% hydrochloric acid solution for 1h, and finally wash it with deionized water until neutral. Dry it at 105℃ for 2h for later use.

[0082] A2: Anchoring and Loading: Add the pretreated activated carbon to 200 mL of a solution containing Fe. 2+ Salt and Mn 2+ In the mixed solution (total metal ion concentration 0.7 mol / L, Fe...) 2+ With Mn 2+ The molar ratio of total metal ions to aminosulfonic acid in the mixed solution was 1:2.5. The mixture was stirred at 25°C for 30 min to allow the metal ions to be adsorbed and anchored. Then, a 0.15 mol / L potassium permanganate solution was added dropwise at a rate of 2.0 mL / min. After the addition was complete, the mixture was stirred for 1 h to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor.

[0083] A3: Acid etching dispersion: The supported precursor was acid etched with dilute hydrochloric acid at a concentration of 0.8 mol / L at 30℃ for 2.0 h, filtered, washed with deionized water until neutral, and dried at 105℃ for 2 h to obtain modified activated carbon, denoted as Fe-Mn / AC-H.

[0084] (2) Manganese source pretreatment: 500g of pyrolusite and waste battery cathode material were mixed at a ratio of 1:1 as manganese source. After crushing, the mixture was ground in a grinder to obtain manganese slurry, in which 90% of the particles were 200 mesh.

[0085] (3) Coupled reduction leaching and in-situ adsorption: 80g of the modified activated carbon prepared above and manganese ore slurry were added to a stirred reactor. Dilute sulfuric acid was added to adjust the reaction system to acidity (pH=2.0). The reaction temperature was controlled at 95℃ and the solid-liquid ratio of the reaction system was 1g:6mL. The reaction was stirred for 8h. While reducing and leaching manganese, the modified activated carbon adsorbed impurity ions in the leaching solution to obtain leaching ore slurry containing manganese sulfate and waste activated carbon after the reaction.

[0086] (4) Solid-liquid separation and solution purification: The leaching slurry was subjected to solid-liquid separation by plate and frame filtration to obtain crude manganese sulfate leachate; manganese carbonate was added to the crude manganese sulfate leachate to adjust the pH value to 5.0, so that Fe 3+ Al 3+ Hydrolyze the precipitate, filter to remove the precipitate; then add potassium sulfide to the filtered solution, control the pH value to 5.5, stir the reaction for 30 min to remove heavy metal ions, and filter to obtain a refined manganese sulfate solution.

[0087] (5) Evaporation and crystallization: The refined manganese sulfate solution is placed in an evaporator crystallizer for evaporation, concentration and crystallization. This process is repeated 3 times. After centrifugation and drying at 105°C for 2 hours, battery-grade manganese sulfate product is obtained.

[0088] (6) Resource regeneration of waste activated carbon: The waste activated carbon after the reaction is placed in a tube furnace and heat-treated at 500℃ for 3 hours under nitrogen to remove organic matter; then the temperature is raised to 900℃ and chemically activated by mixing with potassium hydroxide (potassium hydroxide to waste activated carbon mass ratio 1:1) for 2 hours; finally, the activated carbon material is washed with dilute hydrochloric acid, and the manganese in the acid washing solution is recovered by filtration to obtain the regenerated activated carbon material. Its specific capacitance is tested to be 255F / g, which can be used as electrode material for supercapacitors.

[0089] Comparative Example 1: This comparative example provides a method for preparing manganese sulfate, using unmodified commercial activated carbon as a reducing agent. The specific steps are as follows:

[0090] (1) Activated carbon pretreatment: 100g of commercial activated carbon (specific surface area 1800m² / g, mesoporous and macroporous volume ratio 65%), the same as in Example 3, was selected and only water washing and acid washing were performed. Fe-Mn loading and acid etching modification were not performed.

[0091] (2) Reduction leaching: 80g of pretreated activated carbon was mixed with the same manganese ore slurry as in Example 3, and dilute sulfuric acid was added to adjust the pH to 2.0. The reaction temperature was controlled at 88℃, the solid-liquid ratio was 1g:4mL, and the reaction was stirred for 5h. After the reaction was completed, the mixture was filtered.

[0092] Steps (3) to (6) are the same as in Example 3.

[0093] Comparative Example 2: This comparative example provides a method for preparing manganese sulfate, which uses a conventional pyrite reduction process. The specific steps are as follows:

[0094] (1) Reduction leaching: Select 500g of manganese-containing dust, the same as in Example 3, add pyrite as a reducing agent (the amount used is 1.2 times the theoretical amount), add dilute sulfuric acid, and react at 95℃ for 5h.

[0095] (2) Solid-liquid separation and purification: After the reaction, the filter residue is large in quantity and complex in composition, making it difficult to utilize. The filtrate contains a large amount of introduced iron ions, requiring multiple pH adjustments for neutralization and precipitation to remove iron, resulting in significant manganese loss.

[0096] Steps (3) to (6) are the same as in Example 3.

[0097] Comparative Example 3: This comparative example provides a method for preparing manganese sulfate and investigates the effect of the acid etching step on the performance of modified activated carbon. The specific steps are as follows:

[0098] (1) Preparation of modified activated carbon: Fe-Mn oxide-loaded activated carbon precursor was prepared according to steps A1 and A2 of Example 3, but the acid etching and dispersion process of step A3 was omitted, and the modified activated carbon was directly dried and recorded as Fe-Mn / AC (unetched).

[0099] (2) Coupled reduction leaching and in-situ adsorption: The leaching and purification process is exactly the same as that in Example 3.

[0100] Steps (3) to (6) are the same as in Example 3.

[0101] Comparative Example 4: This comparative example provides a method for preparing manganese sulfate and investigates the effect of single Mn loading on catalytic performance. The specific steps are as follows:

[0102] (1) Preparation of modified activated carbon:

[0103] A1: Carbon matrix pretreatment: Same as in Example 3.

[0104] A2: Anchoring and Loading: Add the pretreated activated carbon to 200 mL of a solution containing only Mn. 2+ In salt solutions (Mn 2+ Concentration 0.5 mol / L, Fe-free 2+ Salt), and simultaneously add aminosulfonic acid (aminosulfonic acid and Mn). 2+ The mixture was stirred at 25°C for 30 min with a molar ratio of 1:2.0. Then, a 0.10 mol / L potassium permanganate solution was added dropwise at a rate of 1.2 mL / min. After the addition was complete, stirring was continued for 1 h to obtain the loaded precursor.

[0105] A3: Acid etching and dispersion: Modified activated carbon, denoted as Mn / AC-H, is obtained, as in Example 3.

[0106] Steps (2) to (6) are the same as in Example 3.

[0107] Comparative Examples 5-1 to 5-4: This comparative example provides a set of methods for preparing manganese sulfate, and investigates the effect of the Fe / Mn molar ratio on catalytic performance, respectively according to Fe 2+ :Mn 2+ Modified activated carbon was prepared in molar ratios of 1:0.5, 1:1, 1:3, and 1:4, while maintaining the same total metal ion concentration and other preparation conditions as in Example 3. Subsequent leaching and regeneration steps were the same as in Example 3.

[0108] The specific settings are as follows:

[0109] Comparative Example 5-1: Fe 2+ :Mn 2+ The molar ratio is 1:0.5, and the rest is the same as in Example 3;

[0110] Comparative Example 5-2: Fe 2+ :Mn 2+ The molar ratio is 1:1, and the rest is the same as in Example 3;

[0111] Comparative Example 5-3: Fe 2+ :Mn 2+ The molar ratio is 1:3, and the rest is the same as in Example 3;

[0112] Comparative Example 5-4: Fe 2+ :Mn 2+ The molar ratio is 1:4, and the rest is the same as in Example 3.

[0113] Comparative Example 6: This comparative example provides a method for preparing manganese sulfate and examines the economics of resource recycling of spent activated carbon. The specific steps are as follows:

[0114] Steps (1) to (5) are the same as in Example 3.

[0115] (6) Waste activated carbon treatment: The waste activated carbon after the reaction is directly disposed of as solid waste in landfill without heat treatment, activation, or acid washing recovery. Record the amount of waste activated carbon generated and detect the loss of manganese in the acid washing solution.

[0116] Comparative Example 7: This comparative example provides a method for regenerating waste activated carbon and investigates the effect of heat treatment process on the performance of regenerated carbon. The specific steps are as follows:

[0117] Steps (1) to (5) are the same as in Example 3.

[0118] (6) Regeneration of waste activated carbon: The waste activated carbon after the reaction is placed in a tube furnace and heated directly to 820℃ (without 300℃ low temperature pretreatment), and heat-treated under argon for 2 hours; then washed with dilute hydrochloric acid.

[0119] Test Example: The battery-grade manganese sulfate products prepared in Examples 1-5 and Comparative Examples 1-7 above were subjected to the following tests, and the test methods are as follows:

[0120] Test Example 1: Chemical Composition Analysis of Battery-Grade Manganese Sulfate Products

[0121] The chemical composition of the manganese sulfate monohydrate products prepared in Examples 1-5 and Comparative Examples 1-4 was tested according to the methods specified in the industry standard HG / T 4823-2023 Battery Grade Manganese Sulfate. The manganese content was determined by atomic absorption spectrometry (AAS), the calcium and magnesium contents by inductively coupled plasma optical emission spectrometry (ICP-OES), and the heavy metal content by inductively coupled plasma mass spectrometry (ICP-MS). The test results are shown in Table 1.

[0122] Test Example 2: Manganese Leaching Rate and Catalytic Synergistic Effect Test

[0123] The manganese leaching rates of Examples 1-5 and Comparative Examples 1-4 were statistically analyzed. The leaching rate was calculated based on the residual manganese content in the leaching residue. Manganese leaching rate (%) = (mass of manganese in the leachate / mass of manganese in the manganese source) × 100%; where, the mass of manganese in the leachate = volume of the leachate × manganese concentration of the leachate; and the total mass of manganese in the manganese source = mass of the manganese source × manganese grade of the manganese source. The results are shown in Table 2.

[0124] Test Example 3: Verification of the effect of Fe / Mn molar ratio on catalytic performance

[0125] Based on the experimental data from Example 3 and Comparative Examples 5-1 to 5-4, the effect of the Fe / Mn molar ratio on the manganese leaching rate and the specific capacitance of the regenerated carbon was investigated. The results are shown in Table 3.

[0126] Test Example 4: Evaluation of the Resource Regeneration Effect of Waste Activated Carbon

[0127] The specific surface area and electrochemical performance of the activated carbon materials obtained in Examples 1-5 and Comparative Examples 1, 6, and 7 were tested.

[0128] (1) Specific surface area test: determined by BET nitrogen adsorption method.

[0129] (2) Electrochemical performance test: The specific capacitance was tested in 6 mol / L KOH electrolyte at a current density of 0.5 A / g. The specific capacitance was calculated as follows: C = (I × Δt) / (m × ΔV), where I is the discharge current (A), Δt is the discharge time (s), m is the mass of the active material (g), and ΔV is the voltage window (V). The results are shown in Table 4.

[0130] Table 1. Results of chemical composition analysis of manganese sulfate products in the examples and comparative examples.

[0131]

[0132] Table 2 Comparison of manganese leaching rates under different modification strategies

[0133]

[0134] Table 3 Effect of Fe / Mn molar ratio on manganese leaching rate and specific capacitance of regenerated carbon

[0135]

[0136] Table 4 Comparison of Regeneration Effects of Waste Activated Carbon

[0137]

[0138] Data Analysis: In Table 1, the manganese sulfate content of Examples 1-5 all met the HG / T4823-2023 qualified product standard, and gradually increased with process optimization (such as increased specific surface area of ​​activated carbon and enhanced reaction conditions). The manganese sulfate mass fraction of Example 5 reached 99.35%. Comparative Example 1 was unqualified because the adsorption capacity of the unmodified activated carbon was weak, and the manganese sulfate content of 97.50% was lower than the standard requirement. Comparative Example 2 was also unqualified because the iron content of 0.0065% exceeded the limit (≤0.002%) due to the introduction of iron impurities in the pyrite reduction process. Although the products of Comparative Examples 3 and 4 met the standard, their purity was slightly lower than that of Example 3, which confirmed the auxiliary role of acid etching treatment and Fe-Mn synergistic loading in improving product quality.

[0139] In Table 2, the manganese leaching rate of Examples 1-5 gradually increased with increasing reaction temperature, reaction time, and specific surface area of ​​activated carbon, rising from 95.2% to 99.2%. Comparative Example 1 had a manganese leaching rate of only 82.5% due to the low reducing activity of the unmodified activated carbon, which was much lower than that of the examples. Although Comparative Example 2 achieved a manganese leaching rate of 96.0%, the product was unqualified due to the introduction of iron impurities. The modified activated carbon of the present invention can adsorb impurities in situ while reducing and leaching manganese, resulting in better overall process efficiency. Comparative Examples 3 and 4 had lower manganese leaching rates than Example 3 because the acid etching step was omitted or Fe element was not introduced, which proves the necessity of the key process steps of the present invention.

[0140] In Table 3, when Fe 2+ :Mn 2+ When the molar ratio is 1:2.0 (Example 3), the manganese leaching rate is 98.5% and the specific capacitance of the regenerated activated carbon is 235 F / g, both of which reach their peak values. When the ratio deviates from this ratio (1:0.5, 1:1, 1:3, 1:4), both performance indicators show a downward trend. For example, when the molar ratio is 1:0.5, the manganese leaching rate is 86.5% and the specific capacitance is 125 F / g, indicating that there is an optimal synergistic ratio between Fe and Mn, which verifies the rationality of limiting the range of this molar ratio in the claims of this invention.

[0141] In Table 4, the specific surface area and specific capacitance of the regenerated activated carbon in Examples 1-5 gradually increased with the optimization of the regeneration process (such as the use of chemical activation). Among them, the specific capacitance of the regenerated activated carbon in Example 5 reached 255 F / g, and the capacity retention rate was 99.0% after 1000 cycles, showing excellent electrochemical performance. In contrast, Comparative Example 7 did not use the stepwise heat treatment process of "low-temperature removal of organic matter + high-temperature activation", and the activated carbon pores were blocked due to the failure to remove organic matter, resulting in a specific capacitance of only 145 F / g, which was much lower than that of the other examples, proving the necessity of the stepwise regeneration strategy.

[0142] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing battery-grade manganese sulfate based on activated carbon reduction, characterized in that, Includes the following steps: (1) Preparation of modified activated carbon: Fe-Mn composite oxide nanoparticles are loaded on the surface and in the pores of activated carbon through in-situ oxidation-reduction reaction, and then acid etching is performed to obtain modified activated carbon. (2) Manganese source pretreatment: crush and grind the manganese source to obtain manganese ore slurry; (3) Coupled reduction leaching and in-situ adsorption: The modified activated carbon is reacted with the manganese slurry under acidic conditions. While reducing and leaching manganese, the modified activated carbon adsorbs impurity ions in the leaching solution to obtain a leaching slurry containing manganese sulfate and waste activated carbon after the reaction. (4) Solid-liquid separation and solution purification: The leaching slurry is subjected to solid-liquid separation to obtain crude manganese sulfate leaching solution; the crude manganese sulfate leaching solution is subjected to neutralization and impurity removal and sulfidation deep purification in sequence to obtain refined manganese sulfate solution; (5) Evaporation and crystallization: The refined manganese sulfate solution is evaporated, concentrated and crystallized to obtain battery-grade manganese sulfate product; (6) Resource recycling of waste activated carbon: The waste activated carbon after the reaction is subjected to heat treatment, activation and acid washing in sequence to recover manganese and obtain recycled activated carbon material.

2. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 1, characterized in that, In step (1), the method for preparing the modified activated carbon includes the following steps: A1: Carbon matrix pretreatment: Select commercial activated carbon with a specific surface area >1000m² / g and a mesoporous to macroporous volume ratio ≥50%, and wash it with water, alkali, and acid in sequence. Finally, wash it with water until it is neutral and dry it for later use. A2: Anchoring and Loading: Adding pretreated activated carbon containing Fe 2+ Salt and Mn 2+ In a mixed solution, aminosulfonic acid was added and stirred to allow metal ions to be adsorbed and anchored; then potassium permanganate solution was added dropwise to generate Fe-Mn composite oxide nanoparticles in situ on the surface of activated carbon, thus obtaining the supported precursor. A3: Acid etching dispersion: The supported precursor is acid etched with dilute hydrochloric acid, filtered, washed, and dried to obtain the modified activated carbon.

3. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 2, characterized in that, In step A2, the total metal ion concentration of the mixed solution is 0.3-0.7 mol / L, and Fe... 2+ With Mn 2+ The molar ratio of the total metal ions to aminosulfonic acid in the mixed solution is 1:1.5-2.5; the molar ratio of the total metal ions to aminosulfonic acid in the mixed solution is 1:1.5-2.5; the concentration of the potassium permanganate solution is 0.05-0.15 mol / L, and the dropping rate is 0.5-2 mL / min.

4. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 2, characterized in that, In step A3, the concentration of the dilute hydrochloric acid is 0.2-0.8 mol / L; the acid etching temperature is 25-30℃, and the time is 0.5-2h.

5. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 1, characterized in that, In step (2), the manganese source is selected from one or more of pyrolusite, electrolytic manganese anode mud, manganese-containing dust or waste battery cathode material; the proportion of particles with a particle size of 200 mesh in the manganese slurry exceeds 70%.

6. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 1, characterized in that, In step (3), the contact reaction is carried out in a stirred reactor at a temperature of 80-95°C, with a solid-liquid ratio of 1g:(2-6)mL and a reaction time of 3-8h.

7. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 1, characterized in that, In step (4), the neutralization and impurity removal involves adding manganese carbonate or manganese hydroxide to adjust the pH value to 3.5-5.0, so that Fe... 3+ Al 3+ Hydrolysis precipitation; the deep purification by sulfidation involves adding a sulfiding agent under pH conditions of 5.0-5.5 to remove heavy metal ions.

8. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 1, characterized in that, In step (5), the evaporation, concentration and crystallization process is repeated 2-3 times.

9. The method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 1, characterized in that, Step (6) includes: Low-temperature heat treatment section: Under an inert atmosphere, heat treatment at 300-500℃ for 1-3 hours to remove organic matter; High-temperature activation section: The temperature is raised to 700-900℃, and carbon dioxide or water vapor is introduced for physical activation, or it is mixed with potassium hydroxide for chemical activation; Pickling: The activated carbon material is washed with dilute hydrochloric acid to recover manganese from the pickling solution and obtain regenerated activated carbon material.

10. A method for preparing battery-grade manganese sulfate based on activated carbon reduction according to claim 9, characterized in that, The specific capacitance of the regenerated activated carbon material is greater than 200 F / g, and it can be used as an electrode material for supercapacitors.

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