Method for recovering manganese from pyrolusite waste residues

Abstract

The invention discloses a method for recovering manganese from pyrolusite waste residues. The method is characterized by comprising the following steps: crushing the pyrolusite waste residues, uniformly mixing and grinding, and drying; the method comprises the following steps: uniformly mixing dried pyrolusite waste residues with the ternary flux according to the claim 1, heating to 110 DEG C in a tubular furnace, roasting for 55-65 minutes at a constant temperature, continuously heating to 280 DEG C, continuously roasting for 25-35 minutes, then heating to 500 DEG C, continuously roasting for 55-65 minutes, cooling to room temperature after the reaction is completed, taking out a roasted residue sample, adding deionized water, leaching manganese sulfate at room temperature, filtering and separating, and drying to obtain the pyrolusite waste residues. Manganese sulfate crude liquid and leaching residues are obtained; metal oxides in the pyrolusite waste residues are reduced by the flux and then sulfated, so that the process of extracting manganese from the pyrolusite waste residues to produce high-purity manganous-manganic oxide is accelerated, and meanwhile, the problems of resource waste and environmental pollution caused by the pyrolusite waste residues are solved.

Description

Technical Field

[0001] This invention relates to the field of industrial waste resource utilization, specifically a method for recovering manganese from pyrolusite ore residue. Background Technology

[0002] The main component of waste from pyrolusite is MnO2, a core raw material for the manganese industry. During open-pit or underground mining of pyrolusite, a large amount of waste rock and low-grade tailings (mainly MnO2, also containing aluminum oxide and silicon dioxide) are generated along with the main ore mining. This type of waste accounts for more than 60% of the total mining volume. Although the manganese content in this type of waste is not high, the total amount is enormous. Various wastes are generated during the processing and utilization of pyrolusite. For example, leaching pyrolusite produces leaching residue (mainly containing iron, silicon dioxide, and a small amount of residual manganese (5-10%)); electrolytic manganese production is produced during the pressure filtration stage, resulting in electrolytic manganese slag (mainly containing MnSO4, MnO2, PbSO4, CaSO4, and small amounts of SiO2 and Fe2(SO4)3). The large amount of pyrolusite waste required for disposal occupies significant land resources, leading to waste. Furthermore, pyrolusite waste typically contains heavy metals; if improperly disposed of or discharged without treatment, these heavy metals may enter the soil and water bodies through rainwater leaching and infiltration. Heavy metals and other harmful substances in manganese ore pollute the environment, posing potential threats to soil and aquatic ecosystems and human health. Current treatment methods include recovering metal elements, producing building materials, preparing fertilizers, or stabilizing / solidifying the ore to immobilize heavy metals and other harmful substances in a solidified form, reducing their migration and bioavailability in the environment and minimizing environmental damage. Traditional chemical acid leaching, extraction, and precipitation methods are costly and place a heavy environmental burden on the acid leaching waste. While pyrometallurgical roasting combined with water leaching under neutral conditions reduces material costs and alleviates environmental pressure, further development of low-temperature pyrometallurgical methods is needed to reduce energy consumption and improve the selective separation efficiency of manganese from pyrometallurgical waste. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a method for recovering manganese from pyrolusite waste residue. This method utilizes a ternary mixed flux to reduce and sulfate the metal oxides in the pyrolusite waste residue, thereby accelerating the process of extracting manganese from pyrolusite waste residue to produce high-purity manganese tetroxide. Simultaneously, it solves the problems of resource waste and environmental pollution caused by pyrolusite waste residue.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution: a ternary flux, characterized in that it is composed of 70% ammonium sulfite, 20% thiourea and 10% urea by mass.

[0005] A method for recovering manganese from pyrolusite ore residue, characterized by: crushing and grinding the pyrolusite ore residue evenly, and drying it; mixing the dried pyrolusite ore residue evenly with a ternary flux, heating it to 110°C in a tube furnace, roasting it at a constant temperature for 55-65 minutes, then continuing to heat it to 280°C and roasting it for another 25-35 minutes, then heating it to 500°C and roasting it for another 55-65 minutes; after the reaction is complete, waiting for the temperature to drop to room temperature, taking out the roasted residue sample, adding deionized water to leach manganese sulfate at room temperature, filtering and separating to obtain crude manganese sulfate solution and leaching residue;

[0006] Manganese powder was added to the crude manganese sulfate solution, and after reacting at room temperature, the solution was separated and filtered to remove heavy metal ions, yielding a primary purified manganese sulfate solution. Ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, and the solution was filtered to obtain a secondary purified manganese sulfate solution. A flocculant was added to remove a small amount of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution was filtered to obtain a tertiary purified manganese sulfate solution. The pH of the tertiary purified manganese sulfate solution was adjusted to 6-7 with ammonia water, and citric acid was added to complex with magnesium ions in the solution. After filtration and separation, the solution was obtained as a quaternary purified manganese sulfate solution.

[0007] In the above scheme: ammonium bicarbonate is added to the fourth purification solution of manganese sulfate, and the reaction yields manganese carbonate precipitate. The precipitate is filtered to obtain manganese carbonate precipitate and ammonium sulfate solution. The manganese carbonate precipitate is washed with water and then calcined to obtain manganese tetroxide. This method can convert manganese sulfate into battery-grade manganese tetroxide.

[0008] In the above scheme: after crushing the soft manganese ore waste residue, it is passed through a 200-300 mesh sieve and dried at 100-110℃.

[0009] In the above scheme, the mass ratio of pyrolusite waste residue to ternary flux is 1:2-2.2.

[0010] In the above scheme: during leaching, the amount of deionized water added is 8-12 times the mass of the pyrolusite waste residue, and the leaching time is 50-70 minutes.

[0011] In the above scheme: the amount of metallic manganese powder added is 2-3‰ of the mass of pyrolusite waste residue; the amount of ammonium sulfide added is 1-2‰ of the mass of pyrolusite waste residue.

[0012] In the above scheme: the flocculant is polyacrylamide, and the amount added is 1-2‰ of the mass of pyrolusite waste residue.

[0013] In the above scheme: the temperature is raised to 110℃ at a heating rate of 5-10℃ / min in a tube furnace, raised to 280℃ at a heating rate of 5-10℃ / min, and raised to 500℃ at a heating rate of 8-12℃ / min.

[0014] The valence state distribution of manganese in pyrolusite ore residue is quite complex, with manganese dioxide being the main component. To achieve efficient recovery of manganese from pyrolusite ore residue, it is necessary to ensure efficient reduction of manganese dioxide and efficient sulfation of manganese monoxide, while also preliminarily separating a large number of impurity elements through the sulfation process.

[0015] The mixed flux used in this invention has a decomposition temperature of 70°C for ammonium sulfite, a melting point of 180°C for thiourea, and 133°C for urea. The eutectic point formed by the mixture of these three is approximately 100°C, meaning that the pyrolusite waste residue and the ternary mixed flux begin to flow at a low temperature of 100°C, thus improving the mass and heat transfer efficiency of the ternary mixed flux in the reaction process of the pyrolusite waste residue. Simultaneously, the lower decomposition temperature of thiourea and urea at 100°C generates a large amount of ammonia, sulfur dioxide, isothiocyanate, cyanic acid, and a small amount of biuret. Under these reducing atmospheres, manganese dioxide in the pyrolusite waste residue is reduced to manganese dioxide. When the temperature is raised to 280℃, with the generation of sulfur trioxide, the sulfuric acid vapor formed reacts with the reduced metal oxides in the pyrolusite ore residue to undergo a sulfation reaction. To prevent the sulfuric acid from gradually decomposing to form sulfur trioxide and reduce the sulfation reaction process, this invention controls the secondary roasting temperature to 280℃ (sulfuric acid decomposition temperature 300℃). Under these low-temperature reaction conditions, the main products of thiourea are sulfur dioxide, ammonia, and nitrogen, while the main products of urea are ammonia, carbon dioxide, and water. Sulfur dioxide, in conjunction with hydrogen sulfide, further reacts manganese dioxide to low-valence manganese, accelerating the sulfation process of manganese oxide through the generation of sulfur dioxide. The formation of nitrogen and carbon dioxide helps to alleviate the rapid decomposition of ammonium sulfate to form sulfur trioxide, thus strengthening the sulfation reaction process and playing a protective role. This invention controls the calcination temperature to 500℃ for three stages. At this temperature, the sulfation products of some metallic impurities begin to decompose and form metal oxides, especially iron impurities. At this temperature, ferric sulfate can almost completely decompose to form iron oxide, while manganese sulfate does not decompose, facilitating subsequent iron removal through water leaching. Simultaneously, the reducing atmosphere created under this high-temperature ammonia atmosphere keeps manganese in a low valence state, preventing secondary oxidation reactions between manganese and oxygen in the air, thereby improving manganese recovery efficiency. The resulting calcined residue is leached with deionized water at room temperature to remove manganese sulfate. Then, impurities are further removed by adding metallic manganese powder, ammonium sulfide, flocculants, citric acid, etc., to obtain a high-purity manganese sulfate purified solution. This achieves the goal of manganese recovery. The obtained manganese sulfate purified solution can be further reacted to form manganese carbonate, which is then calcined to produce high-purity manganese tetroxide (MNT). The obtained MNT is battery-grade MNT.

[0016] Beneficial effects:

[0017] (1) The present invention utilizes the low eutectic point to reduce the initial roasting temperature of soft manganese ore slag to 100°C and the maximum roasting temperature to 500°C, which greatly reduces energy consumption and extends the service life of the equipment.

[0018] (2) The present invention utilizes molten salt + water leaching to remove impurities, and the recovery rate of manganese extracted from soft manganese ore waste can reach more than 99%.

[0019] (3) The present invention utilizes a mixed flux to reduce metal oxides and then sulfatate them, which has a better reduction effect and higher sulfatation efficiency than the existing technology. This accelerates the process of extracting manganese from pyrolusite waste slag to produce high-purity manganese tetroxide, while solving the problems of resource waste and environmental pollution caused by pyrolusite waste slag. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments.

[0021] Example 1

[0022] The main chemical composition of soft manganese ore waste (which is a mixture of low-grade tailings, leaching residue and electrolytic manganese slag) is: manganese 11.3%, iron 26.5%, aluminum 8.7%, calcium 3.8%, silicon 35.6%, magnesium 1.3%, and heavy metal elements such as lead, cadmium, copper, nickel and chromium are in trace amounts.

[0023] After crushing the pyrolusite ore residue, it was passed through a 200-mesh sieve and dried to constant weight at 100-110℃. 100g of the crushed pyrolusite ore residue was accurately weighed and mixed with 200g of a mixed flux (composed of 70% ammonium sulfate, 20% thiourea, and 10% urea by mass). The mixture was then subjected to gradient roasting in a tube furnace. First, the temperature was increased to 100℃ at a rate of 5℃ / min and roasted at this temperature for 60min. Then, the temperature was increased to 280℃ at a rate of 5℃ / min and roasted for another 30min. Finally, the temperature was increased to 500℃ at a rate of 10℃ / min and roasted for another 60min. After the reaction was complete and the temperature was lowered to room temperature, the roasted residue sample was removed. 1L of deionized water was added and the manganese sulfate was leached at constant room temperature. After leaching for 60min, the mixture was filtered to obtain crude manganese sulfate solution. At room temperature, 2‰ of the mass of manganese powder (based on the weight of pyrolusite waste) was added to the crude manganese sulfate solution. After reacting at room temperature for 30 minutes, the solution was separated and filtered to remove heavy metals, yielding a primary purified manganese sulfate solution. 2‰ of ammonium sulfide was added to the primary purified manganese sulfate solution for further reaction to remove heavy metals. After filtration, a secondary purified manganese sulfate solution was obtained. 1‰ of polyacrylamide was added to the secondary purified manganese sulfate solution to remove residual aluminum and silicon. After filtration, a tertiary purified manganese sulfate solution was obtained. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6, and 7g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. An excess of ammonium bicarbonate (5% excess based on the molar excess of manganese in the pyrolusite waste) was added to the quaternary purified manganese sulfate solution to obtain manganese carbonate precipitate. Manganese carbonate precipitate was washed five times with deionized water and then calcined at 890℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide. The manganese recovery rate reached 99.3%.

[0024] Example 2

[0025] The main chemical composition of soft manganese ore waste (which is a mixture of low-grade tailings, leaching residue and electrolytic manganese slag) is: manganese 11.3%, iron 26.5%, aluminum 8.7%, calcium 3.8%, silicon 35.6%, magnesium 1.3%, and heavy metal elements such as lead, cadmium, copper, nickel and chromium are in trace amounts.

[0026] After crushing the pyrolusite ore residue and passing it through a 200-mesh sieve, it was dried to constant weight at 100-110℃. 100g of the crushed pyrolusite ore residue was accurately weighed and mixed with 220g of a mixed flux (composed of 70% ammonium sulfate, 20% thiourea, and 10% urea by mass). The mixture was then subjected to gradient roasting in a tube furnace. First, the temperature was increased to 100℃ at a rate of 10℃ / min and roasted at this temperature for 65min. Then, the temperature was increased to 280℃ at a rate of 10℃ / min and roasted for another 35min. Finally, the temperature was increased to 500℃ at a rate of 12℃ / min and roasted for another 65min. After the reaction was complete and the temperature was lowered to room temperature, the roasted residue sample was removed. 1.2L of deionized water was added and the manganese sulfate was leached at a constant room temperature. After leaching for 50min, the mixture was filtered to obtain crude manganese sulfate solution. At room temperature, 3‰ metallic manganese powder was added to crude manganese sulfate solution. After reacting at room temperature for 30 minutes, the solution was separated and filtered to remove heavy metals, yielding a primary purified manganese sulfate solution. 1‰ ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, followed by filtration to obtain a secondary purified manganese sulfate solution. 2‰ polyacrylamide was added to the secondary purified manganese sulfate solution to remove residual aluminum and silicon, followed by filtration to obtain a tertiary purified manganese sulfate solution. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 6.6, and 7g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. An excess of ammonium bicarbonate (5% excess based on the molar excess of manganese in the pyrolusite ore residue) was added to the quaternary purified manganese sulfate solution to obtain manganese carbonate precipitate. Manganese carbonate precipitate was washed five times with deionized water and then calcined at 890℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide. The manganese recovery rate reached 99.2%.

[0027] Example 3

[0028] The main chemical composition of soft manganese ore waste (which is a mixture of low-grade tailings, leaching residue and electrolytic manganese slag) is: manganese 11.3%, iron 26.5%, aluminum 8.7%, calcium 3.8%, silicon 35.6%, magnesium 1.3%, and heavy metal elements such as lead, cadmium, copper, nickel and chromium are in trace amounts.

[0029] After crushing the pyrolusite ore residue and passing it through a 200-mesh sieve, it was dried to constant weight at 100-110℃. 100g of the crushed pyrolusite ore residue was accurately weighed and mixed with 200g of a mixed flux (composed of 70% ammonium sulfate, 20% thiourea, and 10% urea by mass). The mixture was then subjected to gradient roasting in a tube furnace. First, the temperature was increased to 100℃ at a rate of 6℃ / min and roasted at this temperature for 55min. Then, the temperature was increased to 280℃ at a rate of 8℃ / min and roasted for another 25min. Finally, the temperature was increased to 500℃ at a rate of 8℃ / min and roasted for another 55min. After the reaction was complete and the temperature was lowered to room temperature, the roasted residue sample was removed. 0.8L of deionized water was added and the manganese sulfate was leached at a constant room temperature. After leaching for 70min, the mixture was filtered to obtain crude manganese sulfate solution. At room temperature, 2‰ metallic manganese powder was added to crude manganese sulfate solution. After reacting at room temperature for 30 minutes, the solution was separated and filtered to remove heavy metals, yielding a primary purified manganese sulfate solution. 2‰ ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, followed by filtration to obtain a secondary purified manganese sulfate solution. 1‰ polyacrylamide was added to the secondary purified manganese sulfate solution to remove residual aluminum and silicon, followed by filtration to obtain a tertiary purified manganese sulfate solution. Ammonia was added to the tertiary purified manganese sulfate solution to adjust the pH to 7, and 7g of citric acid was added to complex with magnesium ions in the solution. After filtration and separation, a quaternary purified manganese sulfate solution was obtained. An excess of ammonium bicarbonate (5% excess based on the molar excess of manganese in the pyrolusite ore residue) was added to the quaternary purified manganese sulfate solution to obtain manganese carbonate precipitate. Manganese carbonate precipitate was washed five times with deionized water and then calcined at 890℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then pulverized or sand-milled, washed with deionized water, and dried to obtain high-purity manganese tetroxide. The manganese recovery rate reached 99.1%.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A ternary flux, characterized in that: According to the weight, it consists of 70% ammonium sulfite, 20% thiourea and 10% urea.

2. A method for recovering manganese from pyrolusite ore waste, characterized in that: After crushing and grinding the pyrolusite waste residue evenly, dry it; mix the dried pyrolusite waste residue evenly with the ternary flux described in claim 1, heat it to 110°C in a tube furnace, roast it at a constant temperature for 55-65 min, then continue to heat it to 280°C and roast it for 25-35 min, then heat it to 500°C and roast it for 55-65 min. After the reaction is completed, wait for the temperature to drop to room temperature, take out the roasted residue sample, add deionized water to leach manganese sulfate at room temperature, filter and separate to obtain crude manganese sulfate solution and leaching residue; Manganese powder was added to the crude manganese sulfate solution, and after reacting at room temperature, the solution was separated and filtered to remove heavy metal ions, yielding a primary purified manganese sulfate solution. Ammonium sulfide was added to the primary purified manganese sulfate solution to further remove heavy metals, and the solution was filtered to obtain a secondary purified manganese sulfate solution. A flocculant was added to remove a small amount of residual aluminum and silicon from the secondary purified manganese sulfate solution, and the solution was filtered to obtain a tertiary purified manganese sulfate solution. The pH of the tertiary purified manganese sulfate solution was adjusted to 6-7 with ammonia water, and citric acid was added to complex with magnesium ions in the solution. After filtration and separation, the solution was obtained as a quaternary purified manganese sulfate solution.

3. The method for recovering manganese from pyrolusite ore waste according to claim 2, characterized in that: Ammonium bicarbonate was added to the manganese sulfate solution after four purification processes, and the reaction yielded manganese carbonate precipitate. The precipitate was filtered to obtain manganese carbonate precipitate and ammonium sulfate solution. The manganese carbonate precipitate was washed with water and then calcined to obtain manganese tetroxide.

4. The method for recovering manganese from pyrolusite ore residue according to claim 3, characterized in that: After crushing, the pyrolusite ore residue is passed through a 200-300 mesh sieve and dried at 100-110℃.

5. The method for recovering manganese from pyrolusite ore residue according to claim 4, characterized in that: The mass ratio of pyrolusite waste residue to ternary flux is 1:2-2.

2.

6. The method for recovering manganese from pyrolusite ore residue according to claim 5, characterized in that: During leaching, the amount of deionized water added is 8-12 times the mass of the pyrolusite waste residue, and the leaching time is 50-70 minutes.

7. The method for recovering manganese from pyrolusite ore waste according to claim 6, characterized in that: The amount of metallic manganese powder added is 2-3‰ of the mass of pyrolusite waste residue; the amount of ammonium sulfide added is 1-2‰ of the mass of pyrolusite waste residue.

8. The method for recovering manganese from pyrolusite ore residue according to claim 7, characterized in that: The flocculant is polyacrylamide, and the amount added is 1-2‰ of the mass of pyrolusite waste residue.

9. The method for recovering manganese from pyrolusite ore residue according to claim 2, characterized in that: In a tube furnace, the temperature is increased to 110℃ at a heating rate of 5-10℃ / min, to 280℃ at a heating rate of 5-10℃ / min, and to 500℃ at a heating rate of 8-12℃ / min.