A process for preparing manganese tetraoxide precursor based on ammonium sulfate system

Abstract

The present invention relates to the field of metallurgical technology, and in particular to a process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system. The preparation process comprises the following steps: (1) crushing; (2) pretreatment; (3) roasting; (4) leaching; (5) impurity removal; (6) manganese precipitation; and (7) oxidation to obtain a manganese tetraoxide precursor. The process is used to treat high-iron rhodochrosite, thereby achieving efficient recovery of manganese and efficient removal of iron. The process has the characteristics of high efficiency and environmental protection. The total recovery rate of manganese reaches 92.82%, and the total removal rate of iron reaches 99.64%, which significantly improves the product purity and resource utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system. Background Art

[0002] Manganese tetraoxide (Mn3O4) is an important inorganic material whose unique physical and chemical properties make it a crucial component in the preparation of battery materials. During the preparation of battery materials, manganese tetraoxide serves as a precursor that, through further processing and treatment, can be converted into the final battery material. Specifically, manganese tetraoxide is a precursor to spinel lithium manganate, a structure that is crucial for improving battery performance and stability. Therefore, the quality and purity of the manganese tetraoxide precursor have a decisive impact on the performance of the final battery.

[0003] The precursor to manganese manganese tetroxide is typically obtained by processing manganese ore. Common manganese minerals found in nature include pyroxenite, hausmannite, ferroxenite, and rhodochrosite. Pyroxenite, the most economical manganese oxide ore, is becoming increasingly depleted in high-grade deposits due to large-scale mining. High-iron rhodochrosite, with high iron and sulfur contents but low manganese content, has not been fully utilized.

[0004] Currently, the most common manganese ore processing technologies are wet reduction leaching, roasting leaching, and microbial reduction leaching. The basic principle of wet reduction is to mix manganese ore with a reducing agent and carry out a leaching reaction in an acidic environment. Although wet reduction can achieve a higher extraction efficiency, the addition of the reducing agent will introduce impurity elements, increase the difficulty of manganese recovery, and produce a large amount of wastewater. The roasting leaching process is to roast under the conditions of adding a solid reducing agent or using a reducing gas to reduce the high-valent manganese oxide to manganese oxide, and then use an acid solution to leach and extract manganese. Compared with wet reduction, roasting leaching is more economical. Microbial reduction leaching is considered an environmentally friendly method, but its leaching rate is very slow, usually taking 6-8 days.

[0005] The ammonium sulfate roasting leaching process is a further improvement of the roasting leaching process. Its principle is to convert the metals in manganese ore into ammonium sulfate salts, which are then efficiently extracted through a water leaching process. The ammonium sulfate roasting leaching process is considered a promising method for simultaneously recovering valuable metals and being environmentally friendly. However, there are currently no reports on the extraction of manganese from high-iron rhodochrosite using this process. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to propose a process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system, which adopts an ammonium sulfate roasting and leaching method to effectively prepare a low-impurity manganese tetraoxide precursor from high-iron rhodochrosite.

[0007] Based on the above objectives, the present invention provides a process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system, comprising the following steps:

[0008] (1) Crushing: crushing the high iron rhodochrosite ore and grinding it through an 80-100 mesh sieve to obtain high iron rhodochrosite ore powder;

[0009] (2) Pretreatment: Add the high-iron rhodochrosite powder, urea and thiourea prepared in step (1) into deionized water, stir at 75-80°C until it becomes a sticky paste, and then dry and grind to obtain doped ore powder;

[0010] (3) Calcination: ammonium sulfate and the doped ore powder prepared in step (2) are mixed, spread on a crucible, placed in a tube furnace, and air is introduced. The temperature in the tube furnace is raised to 190-210°C at a rate of 8-12°C / min, kept at this temperature for 25-35 min, then raised to 390-410°C at a rate of 4-6°C / min, kept at this temperature for 100-140 min, and cooled to room temperature to obtain calcined ore powder;

[0011] (4) Leaching: Add the calcined powder prepared in step (3) to deionized water, heat to 65-75°C, stir for 40-80 minutes, filter at normal pressure to obtain a filtrate, which is the leachate;

[0012] (5) Impurity removal: add hydrogen peroxide to the leachate prepared in step (4), heat it to 55-65°C, stir it for 40-80 min, then adjust the pH to 4.9-5.1 with industrial ammonia water, let it stand for 4-8 h, filter it at normal pressure, take the filtrate, add sodium diethyldithiocarbamate trihydrate to the filtrate, heat it to 60-80°C, stir it for 20-40 min, let it stand for 10-14 h, filter it at normal pressure, then add ammonium fluoride, heat it to 80-95°C, stir it for 50-60 min, let it stand for 10-14 h, filter it at normal pressure to obtain a manganese-rich solution;

[0013] (6) Manganese precipitation: Use ammonia water to adjust the pH of the manganese-rich solution prepared in step (5) to 9.8-10.5, heat it to 55-65°C, stir it for 50-70 minutes, let it stand for 10-14 hours to precipitate manganese, filter it at normal pressure, and dry the filter cake to obtain the manganese precipitate;

[0014] (7) Oxidation: The manganese precipitate prepared in step (4) is added to deionized water and stirred for 20-40 min. Industrial ammonia water is then added to adjust the pH value to 9.5-10.5. Hydrazine hydrate is then added and the reaction is carried out for 7-9 h. After the reaction is completed, the mixture is filtered, washed, and dried at 70-80°C for 3-5 h to obtain a manganese tetraoxide precursor.

[0015] Furthermore, in step (2), the weight ratio of high iron rhodochrosite powder, urea and thiourea is 1:0.18-0.22:0.04-0.06.

[0016] Furthermore, the amount of ammonium sulfate added in step (3) is 1.7-1.9 times the weight of the high-iron rhodochrosite powder in the doped ore powder.

[0017] Preferably, the amount of ammonium sulfate added in step (3) is 1.8 times the weight of the high iron rhodochrosite powder in the doped ore powder.

[0018] Furthermore, in step (3), the end of the tube furnace is connected to a gas collecting bottle, and the liquid in the gas collecting bottle is a 1 mol / L sulfuric acid solution.

[0019] Furthermore, the air flow rate in step (3) is 0.8-1.2 L / min.

[0020] Furthermore, in step (5), the amount of hydrogen peroxide added to the leachate is 15-25 ml / L.

[0021] Preferably, the amount of hydrogen peroxide added to the leachate in step (5) is 20 ml / L.

[0022] Furthermore, in step (5), the amount of sodium diethyldithiocarbamate trihydrate added to the leachate is 0.13-0.16 g / L.

[0023] Preferably, the amount of sodium diethyldithiocarbamate trihydrate added to the leachate in step (5) is 0.15 g / L.

[0024] Furthermore, in step (5), the amount of ammonium fluoride added to the leachate is 4-4.5 g / L.

[0025] Preferably, the amount of ammonium fluoride added to the leachate in step (5) is 4.2 g / L.

[0026] Beneficial effects of the present invention:

[0027] The present invention proposes a process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system. By treating high-iron rhodochrosite ore through this process, efficient manganese recovery and iron removal are achieved. It has the characteristics of high efficiency and environmental protection. The total manganese recovery rate reaches 92.82%, and the total iron removal rate reaches 99.64%, significantly improving product purity and resource utilization. This method not only excels in economy and environmental protection, but also provides reliable technical support and improvement space for industrial production.

[0028] The invention uses urea and thiourea to treat high-iron rhodochrosite powder before ammonium sulfate roasting and leaching. The urea and thiourea are adsorbed in the pores of the high-iron rhodochrosite powder. During the ammonium sulfate roasting process, the high-iron rhodochrosite can be effectively refined and the roasting atmosphere can be optimized, thereby effectively improving the recovery rate of manganese. At the same time, the generated ferroalloy is insoluble in water and can be removed by water leaching, thereby improving the removal rate of iron impurities.

[0029] The invention adopts two-step iron removal, wherein the first step adopts ferroalloy water immersion removal, and the second step adopts oxidation precipitation removal. The two-step iron removal greatly improves the removal rate of iron impurities. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0031] The content of each element in the high-iron rhodochrosite in the examples of the present invention and the comparative examples is shown in Table 1:

[0032] Table 1 Element content of high iron rhodochrosite

[0033]

[0034] Example 1:

[0035] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0036] (2) Pretreatment: 1 kg of high-iron rhodochrosite powder prepared in step (1), 0.2 kg of urea and 0.05 kg of thiourea were added to 10 L of deionized water, stirred at 80 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0037] (3) Calcination: 1.8 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 1 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 200 °C at a rate of 10 °C / min, kept at that temperature for 30 min, then raised to 400 °C at a rate of 5 °C / min, kept at that temperature for 120 min, and cooled to room temperature to obtain calcined ore powder.

[0038] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 70°C, stir for 60 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0039] (5) Impurity removal: add 200 mL of 30% hydrogen peroxide to the leachate prepared in step (4), heat to 60°C, stir for 60 min, adjust the pH to 5.0 with industrial ammonia water, let it stand for 6 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.5 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 70°C, stir for 30 min, let it stand for 12 h to precipitate heavy metal impurities, filter at normal pressure, then add 42 g of ammonium fluoride, heat to 90°C, stir for 60 min, let it stand for 12 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0040] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 10 using ammonia water, the temperature was raised to 60°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0041] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 30 min. Then, industrial ammonia was added to adjust the pH value to 10. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 ° C for 4 h to obtain a manganese tetraoxide precursor.

[0042] Example 2:

[0043] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through an 80-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0044] (2) Pretreatment: 1 kg of the high-iron rhodochrosite powder prepared in step (1), 0.18 kg of urea, and 0.04 kg of thiourea were added to 10 L of deionized water, stirred at 75 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0045] (3) Calcination: 1.7 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 0.8 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 190°C at 8°C / min, kept at this temperature for 25 min, then raised to 390°C at 4°C / min, kept at this temperature for 100 min, and cooled to room temperature to obtain calcined ore powder.

[0046] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 65°C, stir for 40 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0047] (5) Impurity removal: add 150 mL of 30% hydrogen peroxide to the leachate prepared in step (4), heat to 55 ° C, stir for 40 min, adjust the pH to 4.9 with industrial ammonia water, let it stand for 4 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.3 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 60 ° C, stir for 20 min, let it stand for 10 h to precipitate heavy metal impurities, filter at normal pressure, add 40 g of ammonium fluoride, heat to 80 ° C, stir for 50 min, let it stand for 10 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0048] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 9.8 using aqueous ammonia, heated to 55°C, stirred for 50 minutes, and allowed to stand for 10 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0049] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 20 min. Industrial ammonia was then added to adjust the pH to 19.5. 15 mL of hydrazine hydrate was then added and the reaction was continued for 7 h. After the reaction was completed, the mixture was filtered, washed, and dried at 70 °C for 5 h to obtain a manganese tetraoxide precursor.

[0050] Example 3:

[0051] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0052] (2) Pretreatment: 1 kg of the high-iron rhodochrosite powder prepared in step (1), 0.22 kg of urea, and 0.06 kg of thiourea were added to 10 L of deionized water, stirred at 80 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0053] (3) Calcination: 1.9 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 1.2 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 210 ° C at a rate of 12 ° C / min, kept at this temperature for 40 min, then raised to 410 ° C at a rate of 6 ° C / min, kept at this temperature for 140 min, and cooled to room temperature to obtain a calcined ore powder.

[0054] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 75°C, stir for 80 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0055] (5) Impurity removal: add 250 mL of 30% hydrogen peroxide to the leachate prepared in step (4), heat to 65 ° C, stir for 80 min, adjust the pH to 5.1 with industrial ammonia water, let it stand for 8 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.6 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 80 ° C, stir for 40 min, let it stand for 14 h to precipitate heavy metal impurities, filter at normal pressure, add 45 g of ammonium fluoride, heat to 95 ° C, stir for 60 min, let it stand for 14 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0056] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 10.5 using aqueous ammonia, heated to 65°C, stirred for 70 minutes, and allowed to stand for 14 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0057] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 40 min. Then, industrial ammonia was added to adjust the pH value to 10.5. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 °C for 3 h to obtain a manganese tetraoxide precursor.

[0058] Comparative Example 1:

[0059] The difference between Comparative Example 1 and Example 1 is that no urea is added in step (2);

[0060] The specific steps are as follows:

[0061] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0062] (2) Pretreatment: 1 kg of the high-iron rhodochrosite powder prepared in step (1) and 0.05 kg of thiourea were added to 10 L of deionized water, stirred at 80 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0063] (3) Calcination: 1.8 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 1 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 200 °C at a rate of 10 °C / min, kept at that temperature for 30 min, then raised to 400 °C at a rate of 5 °C / min, kept at that temperature for 120 min, and cooled to room temperature to obtain calcined ore powder.

[0064] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 70°C, stir for 60 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0065] (5) Impurity removal: add 200 mL of 30% hydrogen peroxide to the leachate prepared in step (4), heat to 60°C, stir for 60 min, adjust the pH to 5.0 with industrial ammonia water, let it stand for 6 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.5 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 70°C, stir for 30 min, let it stand for 12 h to precipitate heavy metal impurities, filter at normal pressure, then add 42 g of ammonium fluoride, heat to 90°C, stir for 60 min, let it stand for 12 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0066] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 10 using ammonia water, the temperature was raised to 60°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0067] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 30 min. Then, industrial ammonia was added to adjust the pH value to 10. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 ° C for 4 h to obtain a manganese tetraoxide precursor.

[0068] Comparative Example 2:

[0069] The difference between Comparative Example 2 and Example 1 is that no thiourea is added in step (2);

[0070] The specific steps are as follows:

[0071] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0072] (2) Pretreatment: 1 kg of the high-iron rhodochrosite powder prepared in step (1) and 0.2 kg of urea were added to 10 L of deionized water, stirred at 80 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0073] (3) Calcination: 1.8 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 1 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 200 °C at a rate of 10 °C / min, kept at that temperature for 30 min, then raised to 400 °C at a rate of 5 °C / min, kept at that temperature for 120 min, and cooled to room temperature to obtain calcined ore powder.

[0074] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 70°C, stir for 60 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0075] (5) Impurity removal: add 200 mL of 30% hydrogen peroxide to the leachate prepared in step (4), heat to 60°C, stir for 60 min, adjust the pH to 5.0 with industrial ammonia water, let it stand for 6 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.5 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 70°C, stir for 30 min, let it stand for 12 h to precipitate heavy metal impurities, filter at normal pressure, then add 42 g of ammonium fluoride, heat to 90°C, stir for 60 min, let it stand for 12 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0076] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 10 using ammonia water, the temperature was raised to 60°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0077] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 30 min. Then, industrial ammonia was added to adjust the pH value to 10. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 ° C for 4 h to obtain a manganese tetraoxide precursor.

[0078] Comparative Example 3:

[0079] Comparative Example 3 differs from Example 1 in that: there is no pretreatment in step (2);

[0080] The specific steps are as follows:

[0081] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0082] (2) Calcination: 1.8 kg of ammonium sulfate and the high-iron rhodochrosite powder prepared in step (1) were mixed, spread on a crucible, and placed in a tubular furnace. Air was introduced at an air flow rate of 1 L / min. A gas collecting bottle was connected to the end of the tubular furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tubular furnace was raised to 200 °C at a rate of 10 °C / min, kept warm for 30 min, then raised to 400 °C at a rate of 5 °C / min, kept warm for 120 min, and cooled to room temperature to obtain a calcined ore powder.

[0083] (3) Leaching: Add the calcined powder prepared in step (2) to 10 L of deionized water, heat to 70°C, stir for 60 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0084] (4) Impurity removal: add 200 mL of 30% hydrogen peroxide to the leachate prepared in step (3), heat to 60°C, stir for 60 min, adjust the pH to 5.0 with industrial ammonia water, let it stand for 6 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.5 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 70°C, stir for 30 min, let it stand for 12 h to precipitate heavy metal impurities, filter at normal pressure, add 42 g of ammonium fluoride, heat to 90°C, stir for 60 min, let it stand for 12 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0085] (5) Manganese precipitation: The pH of the manganese-rich solution prepared in step (4) was adjusted to 10 using ammonia water, heated to 60°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0086] (6) Oxidation: The manganese precipitate prepared in step (5) was added to 3 L of deionized water and stirred for 30 min. Then, industrial ammonia was added to adjust the pH value to 10. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 ° C for 4 h to obtain a manganese tetraoxide precursor.

[0087] Comparative Example 4:

[0088] The difference between Comparative Example 4 and Example 1 is that: in step (3), the temperature in the tube furnace is directly raised to 400°C at a rate of 10°C / min and kept at this temperature for 150 min;

[0089] The specific steps are as follows:

[0090] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0091] (2) Pretreatment: 1 kg of high-iron rhodochrosite powder prepared in step (1), 0.2 kg of urea and 0.05 kg of thiourea were added to 10 L of deionized water, stirred at 80 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0092] (3) Calcination: 1.8 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 1 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 400 °C at a rate of 10 °C / min, kept warm for 150 min, and cooled to room temperature to obtain a calcined ore powder.

[0093] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 70°C, stir for 60 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0094] (5) Impurity removal: add 200 mL of 30% hydrogen peroxide to the leachate prepared in step (4), heat to 60°C, stir for 60 min, adjust the pH to 5.0 with industrial ammonia water, let it stand for 6 h to precipitate iron and aluminum impurities, filter at normal pressure, take the filtrate, add 1.5 g of sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 70°C, stir for 30 min, let it stand for 12 h to precipitate heavy metal impurities, filter at normal pressure, then add 42 g of ammonium fluoride, heat to 90°C, stir for 60 min, let it stand for 12 h to precipitate magnesium impurities, filter at normal pressure to obtain a manganese-rich solution;

[0095] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 10 using ammonia water, the temperature was raised to 60°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0096] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 30 min. Then, industrial ammonia was added to adjust the pH value to 10. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 ° C for 4 h to obtain a manganese tetraoxide precursor.

[0097] Comparative Example 5:

[0098] The difference between Comparative Example 5 and Example 1 is that: hydrogen peroxide is not added in step (5);

[0099] The specific steps are as follows:

[0100] (1) Crushing: crush the high-iron rhodochrosite ore and grind it through a 100-mesh sieve to obtain high-iron rhodochrosite ore powder;

[0101] (2) Pretreatment: 1 kg of high-iron rhodochrosite powder prepared in step (1), 0.2 kg of urea and 0.05 kg of thiourea were added to 10 L of deionized water, stirred at 80 ° C until it became a sticky paste, and then dried and ground to obtain doped ore powder;

[0102] (3) Calcination: 1.8 kg of ammonium sulfate and the doped ore powder prepared in step (2) were mixed, spread on a crucible, and placed in a tube furnace. Air was introduced at an air flow rate of 1 L / min. A gas collecting bottle was connected to the end of the tube furnace. The liquid in the gas collecting bottle was 1 mol / L sulfuric acid solution. The temperature in the tube furnace was raised to 200 °C at a rate of 10 °C / min, kept at that temperature for 30 min, then raised to 400 °C at a rate of 5 °C / min, kept at that temperature for 120 min, and cooled to room temperature to obtain calcined ore powder.

[0103] (4) Leaching: Add the calcined powder prepared in step (3) to 10 L of deionized water, heat to 70°C, stir for 60 min, and filter under normal pressure to obtain a filtrate, which is the leachate;

[0104] (5) Impurity removal: the pH of the leachate prepared in step (4) was adjusted to 5.0 with industrial ammonia water, and the solution was allowed to stand for 6 hours to precipitate iron and aluminum impurities, filtered at normal pressure, and the filtrate was taken. 1.5 g of sodium diethyldithiocarbamate trihydrate was added to the filtrate, the solution was heated to 70°C, stirred for 30 minutes, and allowed to stand for 12 hours to precipitate heavy metal impurities, filtered at normal pressure, and 42 g of ammonium fluoride was added. The solution was heated to 90°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate magnesium impurities, filtered at normal pressure, and a manganese-rich solution was obtained.

[0105] (6) Manganese precipitation: The pH of the manganese-rich solution prepared in step (5) was adjusted to 10 using ammonia water, the temperature was raised to 60°C, stirred for 60 minutes, and allowed to stand for 12 hours to precipitate manganese. The solution was filtered under normal pressure and the filter cake was dried to obtain the manganese precipitate.

[0106] (7) Oxidation: The manganese precipitate prepared in step (4) was added to 3 L of deionized water and stirred for 30 min. Then, industrial ammonia was added to adjust the pH value to 10. Then, 15 mL of hydrazine hydrate was added and the reaction was carried out for 8 h. After the reaction was completed, the mixture was filtered, washed, and dried at 80 ° C for 4 h to obtain a manganese tetraoxide precursor.

[0107] The contents of manganese and iron in the trimanganese tetraoxide precursors of the embodiment and the comparative example were tested, and the results are shown in Table 2.

[0108] Table 2 Manganese and iron content

[0109]

[0110] According to the mass conservation rule, the total recovery rate of manganese and the total removal rate of iron in the embodiment and the comparative example were calculated respectively. The results are shown in Table 3.

[0111] Table 3 Total recovery rate of manganese and total removal rate of iron

[0112]

[0113] Data Analysis:

[0114] From the data of Examples 1-3 in Table 2-3, it can be seen that the use of the ammonium sulfate system-based manganese tetraoxide precursor preparation process of the present invention to treat high-iron rhodochrosite can achieve a total manganese recovery rate of up to 92.82% and a total iron removal rate of up to 99.64%.

[0115] It can be seen from the data of Example 1 and Comparative Examples 1-3 in Table 2-3 that the addition of urea and thiourea during the pretreatment process can effectively improve the manganese recovery rate and the iron removal rate. This may be because the small molecules of urea and thiourea can be diffused and adsorbed in the pores of the high-iron rhodochrosite during the pretreatment process. In the later roasting process, they decompose to produce gas, and the pressure of the gas helps to further refine the high-iron rhodochrosite. At the same time, the reducing ammonia and hydrogen sulfide produced can effectively reduce the high-valent manganese to generate water-soluble ammonium manganese sulfate, while promoting the formation of poorly water-soluble ferrosite and inhibiting the formation of grass ferrosite with poor sedimentation performance and difficult to filter and wash, thereby achieving a high manganese recovery rate and iron removal rate.

[0116] From the data of Example 1 and Comparative Example 4 in Table 2-3, it can be seen that directly raising the temperature to 400°C during the roasting process will lead to a decrease in the total recovery rate of manganese. This is mainly because the gradient heating helps to refine the high-iron rhodochrosite and maintain a reducing atmosphere.

[0117] From the data of Example 1 and Comparative Example 5 in Table 2-3, it can be seen that the addition of hydrogen peroxide during the impurity removal process helps to remove iron impurities. This is mainly because hydrogen peroxide can oxidize the valence state of iron impurities from divalent to trivalent, which is easier to precipitate.

[0118] The impurity contents of the trimanganese tetraoxide precursors prepared in the examples were tested and compared with the national standard GB / T 21836-2008 for the content of impurities in trimanganese tetraoxide. The results are shown in Table 4.

[0119] Table 4 Impurity content in manganese tetraoxide products

[0120]

[0121] Note: The content below 0.001 is uniformly indicated by “ / ”.

[0122] Data analysis: From the data of Examples 1-3 in Table 4, it can be seen that the impurity content of the trimanganese tetraoxide precursor prepared by the present invention meets the standard of the national standard GB / T 21836-2008, and the impurity content is relatively low, providing favorable conditions for the preparation of high-performance and high-purity lithium manganate.

[0123] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system, characterized in that: The following steps are involved: (1) Crushing: crushing the high-iron rhodochrosite ore and grinding it through a 80-100 mesh sieve to obtain high-iron rhodochrosite ore powder; (2) Pretreatment: Add the high-iron rhodochrosite powder, urea and thiourea prepared in step (1) into deionized water, stir at 75-80° C. until it becomes a sticky paste, and then dry and grind to obtain doped ore powder; (3) Calcination: ammonium sulfate and the doped ore powder prepared in step (2) are mixed, spread on a crucible, placed in a tube furnace, and air is introduced. The temperature in the tube furnace is raised to 190-210° C. at a rate of 8-12° C. / min, kept at that temperature for 25-35 min, then raised to 390-410° C. at a rate of 4-6° C. / min, kept at that temperature for 100-140 min, and cooled to room temperature to obtain a calcined ore powder; (4) Leaching: adding the calcined powder prepared in step (3) into deionized water, heating to 65-75°C, stirring for 40-80 minutes, filtering at normal pressure to obtain a filtrate, which is the leachate; (5) impurity removal: add hydrogen peroxide to the leachate prepared in step (4), heat to 55-65°C, stir for 40-80 min, then adjust the pH to 4.9-5.1 with industrial ammonia water, let stand for 4-8 h, filter at normal pressure, take the filtrate, add sodium diethyldithiocarbamate trihydrate to the filtrate, heat to 60-80°C, stir for 20-40 min, let stand for 10-14 h, filter at normal pressure, then add ammonium fluoride, heat to 80-95°C, stir for 50-60 min, let stand for 10-14 h, filter at normal pressure to obtain a manganese-rich solution; (6) Manganese precipitation: adjust the pH of the manganese-rich solution prepared in step (5) to 9.8-10.5 using aqueous ammonia, raise the temperature to 55-65°C, stir for 50-70 minutes, let stand for 10-14 hours to precipitate manganese, filter under normal pressure, and dry the filter cake to obtain the manganese precipitate; (7) Oxidation: Add the manganese precipitate prepared in step (4) into deionized water, stir for 20-40 min, then add industrial ammonia water to adjust the pH value to 9.5-10.5, then add hydrazine hydrate, react for 7-9 h, filter, wash, and dry at 70-80 ° C for 3-5 h to obtain a trimanganese tetraoxide precursor; In the step (2), the weight ratio of high iron rhodochrosite powder, urea and thiourea is 1:0.18-0.22:0.04-0.

06.

2. The process for preparing a manganese tetraoxide precursor based on an ammonium sulfate system according to claim 1, characterized in that: The amount of ammonium sulfate added in step (3) is 1.7-1.9 times the weight of the high-iron rhodochrosite powder in the doped ore powder.

3. The process for preparing manganese tetraoxide precursor based on ammonium sulfate system according to claim 1, characterized in that: In step (3), the end of the tubular furnace is connected to a gas collecting bottle, and the liquid in the gas collecting bottle is a 1 mol / L sulfuric acid solution.

4. The process for preparing manganese tetraoxide precursor based on ammonium sulfate system according to claim 1, characterized in that: The air flow rate in step (3) is 0.8-1.2 L / min.

5. The process for preparing manganese tetraoxide precursor based on ammonium sulfate system according to claim 1, characterized in that: In step (5), the amount of hydrogen peroxide added to the leaching solution is 15-25 ml / L.

6. The process for preparing manganese tetraoxide precursor based on ammonium sulfate system according to claim 1, characterized in that: In the step (5), the amount of sodium diethyldithiocarbamate trihydrate added to the leaching solution is 0.13-0.16 g / L.

7. The process for preparing manganese tetraoxide precursor based on ammonium sulfate system according to claim 1, characterized in that: In the step (5), the amount of ammonium fluoride added to the leaching solution is 4-4.5 g / L.

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