Method for producing manganese sesquioxide from soft-manganese ore waste residue

Abstract

The application discloses a method for producing trimanganese tetraoxide from pyrolusite waste residue, and the method comprises the following steps: (1) crushing and screening the pyrolusite waste residue, and drying the pyrolusite waste residue; (2) mixing the dried pyrolusite waste residue with a flux of claim 1, gradient roasting the mixture in a tube furnace, naturally cooling the roasted residue to room temperature, taking out the roasted residue, adding deionized water, water immersion at room temperature, filtering and separating, and obtaining a crude manganese sulfate leaching solution; (3) adding various impurity removal reagents to the crude manganese sulfate leaching solution for purification; (4) adding ammonium bicarbonate to the four-time purified manganese sulfate solution, obtaining manganese carbonate precipitate, washing with deionized water, calcining to obtain trimanganese tetraoxide, crushing, sand grinding, washing and drying to obtain high-purity trimanganese tetraoxide. The recovery rate of manganese reaches more than 99.4%, the method can be used for preparing high-purity trimanganese tetraoxide, the energy consumption and reagent cost are lower, and the problems of resource waste and environmental pollution caused by the pyrolusite waste are solved.

Description

Technical Field

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

[0002] The main component of pyrolusite waste is MnO2, a core raw material in 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 alongside the main ore mining. This type of waste accounts for more than 60% of the total mined amount. Although the manganese content in this waste is not high, the total amount is enormous. Various wastes are also generated during the processing and utilization of pyrolusite. For example, during the leaching process of pyrolusite, leaching residue (mainly containing iron, silicon dioxide, and a small amount of residual manganese (5-10%)) is produced; during the electrolytic manganese production process, the pressure filtration stage produces electrolytic manganese slag (mainly containing MnSO4, MnO2, PbSO4, CaSO4, and small amounts of SiO2 and Fe2(SO4)3). Large quantities of pyrolusite waste require land dumping, consuming significant land resources and leading to waste. Furthermore, pyrolusite waste typically contains heavy metals; if left untreated and improperly dumped or discharged, these heavy metals can leach into soil, water bodies, and the atmosphere through rainwater, causing environmental pollution and posing potential threats to soil and aquatic ecosystems and human health. Currently, the main treatment methods include recovering metal elements, producing building materials, preparing fertilizers, or stabilizing / solidifying the waste to immobilize heavy metals and other harmful substances in a solidified form, reducing their migration and bioavailability in the environment and minimizing environmental harm. 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 in pyrolusite waste. Summary of the Invention

[0003] To solve the above-mentioned technical problems, the first objective of this invention is to provide a flux, and the second objective is to provide a method for producing manganese tetroxide from pyrolusite waste, wherein the recovery rate of manganese extracted from pyrolusite waste reaches more than 99.4%, and high-purity manganese tetroxide is obtained.

[0004] To achieve the first objective mentioned above, the present invention is implemented through the following technical solution: a flux, characterized in that it is composed of 60% ammonium sulfite and 40% thiourea.

[0005] The second objective of this invention is achieved as follows: a method for producing manganese tetroxide from pyrolusite waste residue, characterized by the following steps: (1) crushing, sieving, and drying the pyrolusite waste residue;

[0006] (2) The dried soft manganese ore slag is mixed with the flux of claim 1 and subjected to gradient roasting in a tube furnace. The roasted slag is then cooled to room temperature by natural cooling. The roasted slag is removed, deionized water is added, and the slag is leached at room temperature. The slag is then filtered and separated to obtain crude manganese sulfate leachate. The main components of the leachate slag are calcium sulfate, barium sulfate and metal oxides.

[0007] (3) Add flocculant to crude manganese sulfate leachate to remove residual aluminum and silicon, filter to obtain manganese sulfate primary purification solution; add metallic manganese powder to manganese sulfate primary purification solution to remove residual heavy metal impurities, filter to obtain manganese sulfate secondary purification solution; add ammonium sulfide to manganese sulfate secondary purification solution to further remove residual heavy metals, filter to obtain manganese sulfate tertiary purification solution; add ammonia water to manganese sulfate tertiary purification solution to adjust pH to 6-7, add citric acid to complex with magnesium ions in the solution, filter to obtain manganese sulfate quaternary purification solution.

[0008] (4) Add ammonium bicarbonate to the manganese sulfate four-stage purification solution to obtain manganese carbonate precipitate, wash with deionized water, calcine to obtain manganese tetroxide, crush, grind, wash and dry to obtain high-purity manganese tetroxide.

[0009] In the above scheme: in step (1), the soft manganese ore waste is crushed and passed through a 200-300 mesh sieve.

[0010] In the above scheme: in step (2), the mass ratio of soft manganese ore slag to flux is 1:1.5-2.

[0011] In the above scheme, the gradient calcination conditions are as follows: First stage, the temperature is increased to 220℃ at a rate of 5-10℃ / min, and calcined at a constant temperature for 50-65 min; second stage, the temperature is increased to 520℃ at a rate of 5-10℃ / min, and calcined at a constant temperature for 25-35 min; third stage, the temperature is increased to 620℃ at a rate of 5-10℃ / min, and calcined at a constant temperature for 80-90 min. The calcination temperature is low.

[0012] In the above scheme: in step (2), the amount of deionized water added is 8-12 times the mass of the roasted residue, and the water soaking time is 50-70 min.

[0013] In the above scheme: in step (3), the flocculant is polyacrylamide, and the addition amount is 1‰-2‰ of the mass of the pyrolusite waste residue; the addition amount of metallic manganese powder is 2‰-3‰ of the mass of the pyrolusite waste residue; the addition amount of ammonium sulfide is 1‰-2‰ of the mass of the pyrolusite waste residue; and the addition amount of ammonium bicarbonate is 0.5%-5% excess of the amount of manganese in the pyrolusite waste residue. In the above scheme: in step (4), the calcination temperature is 800-900℃. The suspension low-temperature instantaneous calcination system disclosed in ZL 201110100752.1 is used for calcination.

[0014] Ammonium sulfite in the mixed flux begins to decompose at a low temperature of 60℃, first forming ammonium bisulfite and releasing ammonia ((NH4)2SO3→NH4HSO3+NH3). Ammonium bisulfite further decomposes into sulfur dioxide and ammonia at a temperature of 100℃ (NH4HSO3→SO2+NH3+H2O). Metal oxides, including manganese dioxide, in the pyrolusite waste are converted into sulfates under this atmosphere, with manganese dioxide mainly reacting to form manganese sulfate ((NH4)2SO3+MnO2→MnSO4+NH3+H2O).

[0015] Thiourea in the mixed flux begins to decompose at a low temperature of 176℃, initially producing cyanamide and hydrogen sulfide (SC(NH4)2→NH2CN+H2S). When the temperature exceeds 200℃, cyanamide further decomposes to produce ammonia, dicyandiamide, melamine, etc. When the temperature exceeds 500℃, the main products of thiourea are sulfur dioxide, ammonia, and nitrogen. The main reaction between hydrogen sulfide and sulfur dioxide and manganese dioxide is the reduction of high-valence manganese to low-valence manganese, ultimately producing manganese sulfate (H2S+MnO2→MnO+SO2+H2O, 2MnO+2SO2+O2→2MnSO4). However, due to the vigorous decomposition reaction of ammonium sulfite, it readily undergoes a peroxidation side reaction with manganese dioxide in pyrolusite waste to produce manganese oxide ((NH4)2SO3+MnO2→MnO+(NH4)2SO4). To suppress side reactions, this invention incorporates a mixed flux of thiourea and ammonium sulfite. The addition of thiourea generates hydrogen sulfide, which partially reduces manganese dioxide; the generation of sulfur dioxide accelerates the sulfation of manganese oxide; the release of ammonia inhibits the rapid decomposition of ammonium sulfite; and the nitrogen generated by thermal decomposition provides protection, mitigating the rapid decomposition of ammonium sulfite and thus reducing the formation of side products. When the temperature rises to 620℃, all manganese in the pyrolusite waste is completely converted to manganese sulfate, while some other metal sulfates (ferric sulfate, nickel sulfate, etc.) decompose to form corresponding oxides. Ferric sulfate, in particular, completely decomposes to form water-insoluble iron oxide. Leaching the insoluble matter with deionized water removes some of the metallic impurities from the manganese sulfate. The crude manganese sulfate leachate undergoes further impurity removal steps to obtain a high-purity manganese sulfate solution, which is then converted to manganese carbonate and calcined to finally obtain high-purity manganese tetroxide.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) Using the above technical solution, the recovery rate of manganese extracted from soft manganese ore waste by using molten salt + water leaching to remove impurities reaches more than 99.4%.

[0018] (2) The addition of thiourea inhibited the violent reaction of ammonium sulfite, thus improving the stability and reliability of the operation process.

[0019] (3) The impurity removal is more thorough. The iron content of this invention is much less than 10 ppm, which can be used to prepare high-purity manganese tetroxide.

[0020] (4) Lower energy consumption and reagent costs, while solving the problems of resource waste and environmental pollution caused by soft manganese ore waste. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments.

[0022] Example 1

[0023] The main chemical composition of the pyrolusite waste residue (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 trace amounts of heavy metals such as lead, cadmium, copper, nickel, and chromium. The pyrolusite waste is crushed, passed through a 200-mesh sieve, and dried. 100g of pyrolusite waste and 150g of mixed flux (60% ammonium sulfite and 40% thiourea) are accurately weighed and mixed evenly in a tube furnace for gradient roasting. In the first stage, the temperature is increased to 220℃ at a rate of 10℃ / min and roasted at a constant temperature for 60min; in the second stage, the temperature is increased to 520℃ at a rate of 10℃ / min and roasted at a constant temperature for 30min; in the third stage, the temperature is increased to 620℃ at a rate of 10℃ / min and roasted at a constant temperature for 90min. The roasted residue sample was naturally cooled to room temperature, then removed and 1 L of deionized water was added. After soaking in water at room temperature for 60 min, the sample was filtered to obtain a crude manganese sulfate leachate. The main components of the leachate residue were calcium sulfate, barium sulfate, silicon dioxide, and metal oxides. The crude manganese sulfate leachate was then subjected to fractional purification at room temperature. The content of impurity elements in the crude manganese sulfate leaching solution was determined by ICP-OES. The residual concentrations of aluminum and silicon were 23 ppm and 38 ppm, respectively. Polyacrylamide flocculant (1‰ of the mass of pyrolusite waste residue) was added to the crude manganese sulfate leaching solution, and after flocculation for 30 min, it was filtered to obtain a primary purified manganese sulfate solution. Metallic manganese powder (2‰ of the mass of pyrolusite waste residue) was added to the primary purified solution, and after stirring for 30 min, it was separated and filtered to obtain a secondary purified manganese sulfate solution. Ammonium sulfide (2‰ of the mass of pyrolusite waste residue) was added to the secondary purified manganese sulfate solution, and after stirring for 30 min, it was filtered to further remove heavy metals, resulting in a tertiary purified manganese sulfate solution. Ammonia water was added to the tertiary purified manganese sulfate solution to adjust the pH to 6.6, and 7 g of citric acid was added to complex with magnesium ions in the solution. After filtration, a quaternary purified manganese sulfate solution was obtained. Ammonium bicarbonate (5% excess of manganese molar amount in the pyrolusite waste) was added to the manganese sulfate four-stage purification solution to completely convert the manganese sulfate into manganese carbonate. The solution was filtered, and the manganese carbonate precipitate was washed three times with deionized water. The precipitate was then calcined for 3 seconds at 800-900℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose the manganese carbonate into solid manganese tetroxide. The solid manganese tetroxide was then crushed or sand-milled, washed with deionized water, and dried to obtain high-purity battery-grade manganese tetroxide with a manganese recovery rate of 99.5%.

[0024] Example 2

[0025] The main chemical composition of the pyrolusite waste residue (a mixture of low-grade tailings, leaching residue, and electrolytic manganese slag) is: manganese 12.1%, iron 24.3%, aluminum 7.2%, calcium 3.48%, silicon 32.5%, magnesium 1.4%, with trace amounts of heavy metals such as lead, cadmium, copper, nickel, and chromium. The pyrolusite waste is crushed, passed through a 300-mesh sieve, and dried. 100g of pyrolusite waste and 200g of mixed flux (60% ammonium sulfite and 40% thiourea) are accurately weighed and mixed evenly in a tube furnace for gradient roasting. In the first stage, the temperature is increased to 220℃ at a rate of 5℃ / min and roasted at a constant temperature for 50min; in the second stage, the temperature is increased to 520℃ at a rate of 5℃ / min and roasted at a constant temperature for 25min; in the third stage, the temperature is increased to 620℃ at a rate of 5℃ / min and roasted at a constant temperature for 80min. The roasted residue sample was naturally cooled to room temperature, then removed and 1.2 L of deionized water was added. After soaking in water at room temperature for 70 min, the sample was filtered to obtain crude manganese sulfate leachate. The main components of the leachate residue were calcium sulfate, barium sulfate, silicon dioxide, and metal oxides. The crude manganese sulfate leachate was then subjected to fractional purification at room temperature. The content of impurity elements in the crude manganese sulfate leaching solution was determined by ICP-OES. The residual concentrations of aluminum and silicon were 25 ppm and 36 ppm, respectively. Polyacrylamide flocculant (2‰ of the weight of pyrolusite waste residue) was added to the crude manganese sulfate leaching solution, and after flocculation for 30 min, it was filtered to obtain a primary purified manganese sulfate solution. Metallic manganese powder (3‰ of the weight of pyrolusite waste residue) was added to the primary purified solution, and after stirring for 30 min, it was separated and filtered to obtain a secondary purified manganese sulfate solution. Ammonium sulfide (1‰ of the weight of pyrolusite waste residue) was added to the secondary purified manganese sulfate solution, and after stirring for 30 min, it was filtered to further remove heavy metals, resulting in a tertiary purified manganese sulfate solution. Ammonia water was added to the tertiary purified manganese sulfate solution to adjust the pH to 7, and 8 g of citric acid was added to complex with magnesium ions in the solution. After filtration, a quaternary purified manganese sulfate solution was obtained. Ammonium bicarbonate (0.5% excess of manganese molar amount in the pyrolusite waste) was added to the manganese sulfate four-stage purification solution to completely convert the manganese sulfate into manganese carbonate. The solution was filtered, and the manganese carbonate precipitate was washed three times with deionized water. The precipitate was then calcined for 3 seconds at 800-900℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose the manganese carbonate into solid manganese tetroxide. The solid manganese tetroxide was then crushed or sand-milled, washed with deionized water, and dried to obtain high-purity battery-grade manganese tetroxide with a manganese recovery rate of 99.4%.

[0026] Example 3

[0027] The main chemical composition of the pyrolusite waste residue (a mixture of low-grade tailings, leaching residue, and electrolytic manganese slag) is: manganese 10.8%, iron 27.2%, aluminum 8.9%, calcium 3.28%, silicon 37.5%, magnesium 2.2%, with trace amounts of heavy metals such as lead, cadmium, copper, nickel, and chromium. The pyrolusite waste is crushed, passed through a 200-mesh sieve, and dried. 100g of pyrolusite waste and 160g of mixed flux (60% ammonium sulfite and 40% thiourea) are accurately weighed and mixed evenly in a tube furnace for gradient roasting. In the first stage, the temperature is increased to 220℃ at a rate of 8℃ / min and roasted at a constant temperature for 65min; in the second stage, the temperature is increased to 520℃ at a rate of 8℃ / min and roasted at a constant temperature for 35min; in the third stage, the temperature is increased to 620℃ at a rate of 8℃ / min and roasted at a constant temperature for 90min. The roasted residue sample was naturally cooled to room temperature, then removed and 0.8 L of deionized water was added. After soaking in water at room temperature for 70 min, the sample was filtered to obtain crude manganese sulfate leachate. The main components of the leachate residue were calcium sulfate, barium sulfate, silicon dioxide, and metal oxides. The crude manganese sulfate leachate was then subjected to fractional purification at room temperature. The content of impurity elements in the crude manganese sulfate leaching solution was determined by ICP-OES. The residual concentrations of aluminum and silicon were 32 ppm and 29 ppm, respectively. Polyacrylamide flocculant (1.5‰ of the weight of pyrolusite waste residue) was added to the crude manganese sulfate leaching solution, and after flocculation for 30 min, it was filtered to obtain a primary purified manganese sulfate solution. Metallic manganese powder (2‰ of the weight of pyrolusite waste residue) was added to the primary purified solution, and after stirring for 30 min, it was separated and filtered to obtain a secondary purified manganese sulfate solution. Ammonium sulfide (2‰ of the weight of pyrolusite waste residue) was added to the secondary purified manganese sulfate solution, and after stirring for 30 min, it was filtered to further remove heavy metals, resulting in a tertiary purified manganese sulfate solution. Ammonia water was added to the tertiary purified manganese sulfate solution to adjust the pH to 6, and 12 g of citric acid was added to complex with magnesium ions in the solution. After filtration, a quaternary purified manganese sulfate solution was obtained. Ammonium bicarbonate (2% excess of manganese molar amount in pyrolusite waste) was added to the manganese sulfate four-stage purification solution to completely convert the manganese sulfate into manganese carbonate. The solution was filtered, and the manganese carbonate precipitate was washed three times with deionized water. The precipitate was then calcined for 3 seconds at 800-900℃ using a suspension low-temperature instantaneous calcination system (ZL 201110100752.1) to decompose and obtain solid manganese tetroxide. The solid manganese tetroxide was then crushed or sand-milled, washed with deionized water, and dried to obtain high-purity battery-grade manganese tetroxide with a manganese recovery rate of 99.48%.

[0028] 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 method for producing manganese tetroxide from pyrolusite waste, characterized in that, Production is carried out according to the following steps: (1) Crushing, sieving, and drying the soft manganese ore waste; (2) The dried pyrolusite slag is mixed with flux, wherein flux 1 is composed of 60% ammonium sulfite and 40% thiourea; the mass ratio of pyrolusite slag to flux is 1:1.5-2, and gradient roasting is carried out in a tube furnace. Then the roasted slag is naturally cooled to room temperature, the roasted slag is taken out, deionized water is added, water is soaked at room temperature, filtered and separated to obtain crude manganese sulfate leachate; the gradient roasting conditions are: first stage, heating to 220℃ at a heating rate of 5-10℃ / min, and constant temperature roasting for 50-65 min; second stage, heating to 520℃ at a heating rate of 5-10℃ / min, and constant temperature roasting for 25-35 min; third stage, heating to 620℃ at a heating rate of 5-10℃ / min, and constant temperature roasting for 80-90 min; (3) Add flocculant to crude manganese sulfate leaching solution to remove residual aluminum and silicon, filter to obtain manganese sulfate primary purification solution; add metallic manganese powder to manganese sulfate primary purification solution to remove residual heavy metal impurities, filter to obtain manganese sulfate secondary purification solution; add ammonium sulfide to manganese sulfate secondary purification solution to further remove residual heavy metals, filter to obtain manganese sulfate tertiary purification solution; add ammonia water to manganese sulfate tertiary purification solution to adjust pH to 6-7, add citric acid to complex with magnesium ions in solution, filter to obtain manganese sulfate quaternary purification solution. (4) Add ammonium bicarbonate to the manganese sulfate four-stage purification solution to obtain manganese carbonate precipitate, wash with deionized water, calcine to obtain manganese tetroxide, crush, grind, wash and dry to obtain high-purity manganese tetroxide.

2. The method for producing manganese tetroxide from pyrolusite waste slag according to claim 1, characterized in that: In step (1), the soft manganese ore waste is crushed and passed through a 200-300 mesh sieve.

3. The method for producing manganese tetroxide from pyrolusite waste slag according to claim 2, characterized in that: In step (2), the amount of deionized water added is 8-12 times the mass of the roasted residue, and the water soaking time is 50-70 min.

4. The method for producing manganese tetroxide from pyrolusite waste slag according to claim 3, characterized in that: In step (3), the flocculant is polyacrylamide, and the amount added is 1‰-2‰ of the mass of the pyrolusite waste residue. The amount of metallic manganese powder added is 2‰-3‰ of the mass of the pyrolusite waste residue. The amount of ammonium sulfide added is 1‰-2‰ of the mass of the pyrolusite waste residue. The amount of ammonium bicarbonate added is 0.5%-5% more than the amount of manganese in the pyrolusite waste residue.

5. The method for producing manganese tetroxide from pyrolusite waste slag according to claim 4, characterized in that: In step (4), the calcination temperature is 800-900℃.