Method for preparing manganese carbonate by roasting and reducing pyrolusite based on flotation copper tailings

Abstract

The invention belongs to the technical field of manganese extraction in the manganese smelting industry, and particularly discloses a method for preparing manganese carbonate by roasting and reducing pyrolusite on the basis of copper tailings after flotation. According to the method, the copper tailings obtained after flotation serve as the reducing agent and are roasted with pyrolusite at the high temperature to obtain MnO, stable alpha-Fe2O3 and SiO2, then dilute acid with the extremely low concentration is adopted for leaching to obtain a manganese sulfate solution, the manganese leaching efficiency reaches up to 94% or above, iron is selectively separated, and industrial grade manganese carbonate is further prepared from the recycled manganese solution through a CO2 method. According to the method, resource utilization of the copper tailings after flotation is achieved, waste is turned into wealth, the cost of manganese recovery in the manganese smelting industry is reduced, and meanwhile good economic and environmental benefits are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of manganese extraction in the manganese smelting industry, and particularly relates to a method for preparing manganese carbonate by roasting and reducing pyrolusite based on copper tailings slag after flotation. Background Art

[0002] Manganese, as an important strategic metal, is widely used in the fields of steel, metallurgy, battery materials, agricultural coatings, aluminum alloys, catalysts, and aerospace. With the development of the economy, the continuous increase in the demand for steel in the market has increased the global consumption and dependence on manganese. The manganese ore reserves in China mainly exist in the forms of rhodochrosite (MnCO3) and pyrolusite (MnO2). In the process of manganese extraction in the manganese smelting industry, the extraction of manganese from pyrolusite is more advantageous than that from rhodochrosite. Therefore, at present, manganese is mainly extracted by reducing pyrolusite, and metallic manganese or high-value products are prepared from the manganese solution. However, since pyrolusite is mainly composed of manganese dioxide (MnO2), manganese dioxide is difficult to be directly reduced by acid and requires a reducing agent to be mixed for reduction by wet or pyrometallurgical methods. Therefore, it is very important to select a reducing agent that is cheap, easily available, large in quantity, and high in reaction efficiency during the reduction process.

[0003] At present, the wet reduction of pyrolusite uses a reducing agent and acid to directly undergo an oxidation-reduction reaction with MnO2. At a given temperature, sufficient reaction time and high-concentration acid are required, so the acid concentration is high and the reaction time is long. The reducing agents mainly selected for wet reduction include ferrous sulfate (FeSO4), SO2, sawdust, molasses waste liquor, etc. Its advantages are that most operations are relatively simple and the leaching efficiency is relatively high. However, its disadvantages are long reaction time, high acid concentration, large acid consumption, a large amount of acid-leaching wastewater generated, and high treatment cost for up-to-standard discharge. At the same time, in the face of a large demand for manganese extraction, a large amount of reducing agent is also required in the corresponding process, and most of the reducing agents with high efficiency also have high costs, so the industrial application prospect is not high.

[0004] CN1940098A discloses a new method for leaching manganese dioxide in pyrolusite to prepare manganese sulfate solution, which belongs to the technical field of pyrolusite extraction and processing. The basic steps of the present invention are: crushing pyrolusite and preparing a pulp with 1-3 times the mass of water of pyrolusite; adding sulfuric acid with a concentration of 93-98% and 1.5-3.5 times the mass of pyrolusite of molasses alcohol waste liquor to the pulp, and stirring and reacting at a temperature of 50-98°C for 0.5-4 hours to obtain a reaction leaching solution. The pH of the reaction leaching solution is adjusted to 5.5-6.0, and then heavy metal ions, calcium, magnesium, silicon and other impurities are removed. The leaching rate of manganese is greater than 93%. Although the leaching process conditions are mild and the impurity removal process is simple, the sulfuric acid used has a high concentration and high cost, and a large amount of waste liquid is generated, so the industrial application value prospect is not high enough.

[0005] CN103757232A discloses a method for wet reduction leaching of manganese in pyrolusite. The characteristics are as follows: pyrolusite powder and forage powder are added into a reaction kettle resistant to pressure, sulfuric acid and nitric acid corrosion, a mixed solution of sulfuric acid and nitric acid is added, and stirring leaching is carried out under closed conditions. After leaching for a period of time, the reaction waste gas is discharged, and then industrial pure oxygen is introduced under closed conditions to oxidize the leaching solution. After the oxidation is completed, the slurry in the reaction kettle is discharged for solid-liquid separation to obtain the required leaching solution. The initial concentration of sulfuric acid in the mixed solution for leaching is 1 mol / L - 4 mol / L, the initial concentration of nitric acid is 2 g / L - 10 g / L, and the leaching rate of manganese is 98.3%. Although the leaching rate of this technology is high, the process is complex; the high acid concentration not only consumes a large amount of acid, but also generates waste gas, which has an adverse impact on the subsequent treatment of wastewater and waste gas.

[0006] Leaching after pyrometallurgical reduction is to reduce MnO2 to MnO during the roasting process, and MnO is easily washed out in dilute acid. Therefore, pyrometallurgical reduction will relatively reduce the acid consumption compared with hydrometallurgical reduction, and the reduction efficiency is relatively high. At present, the reducing agents used in pyrometallurgical reduction include pulverized coal, carbon powder, pyrite, etc. However, pulverized coal and carbon powder generally have a high temperature (≥1000°C) and a long time during the roasting reduction process, and are prone to generating waste gas, and the tail gas needs to be treated.

[0007] Generally speaking, pyrometallurgical reduction can not only reduce the acid consumption compared with hydrometallurgical reduction, but also has broad industrial applications. And most of the above methods only use reducing agents to reduce pyrolusite, and do not further prepare high-value products from the recovered manganese solution. At present, industrially produced manganese carbonate (MnCO3) prepared from the recovery of manganese solution has important value in many fields and is an important raw material for preparing lithium-ion batteries, soft magnetic materials, catalysts, etc., and is widely used in new energy, electronics, agriculture, medicine and other fields.

[0008] Copper tailings are a large amount of solid waste generated in the copper smelting process. The annual output of copper tailings in China is as high as 334 million tons. A large amount of stacking not only occupies land, but also the heavy metals in it will cause poisoning to the environment. Copper tailings contain 29-45% iron and 10-20% silicon, and are mainly composed of fayalite (Fe2SiO4) and magnetite (Fe3O4). The Fe(II) contained in it has good reducibility. When using wet reduction, there are the following deficiencies: silicon contained in copper tailings will produce silica sol in sulfuric acid solution with a concentration of 1 mol / L, causing serious difficulties in filtration; separating iron and manganese requires a large amount of alkali liquor, increasing the mud weight at the same time; it is difficult to achieve up-to-standard discharge treatment of high-concentration acid leaching wastewater during the reaction process (Co-recovery of Mn and Fe from pyrolusite and copper slag with hydrometallurgy process: Kinetics and leaching mechanisms. Lanbin Wang 1 , Yu Chen 1 etc, Environmental Science and Pollution Research, 30, 125877–125888, 2023). Summary of the Invention

[0009] Aiming at the problems of large acid consumption, high cost of reducing agent and low industrial application value in the existing wet reduction technology, and high reaction temperature, long time and complex tail gas treatment process in the pyrometallurgical reduction technology, the present invention proposes a method for preparing manganese carbonate by roasting and reducing pyrolusite with copper tailings after flotation. The present invention uses copper tailings after flotation as a reducing agent, which has good economy and high reduction efficiency. And by selectively recovering manganese and inhibiting the leaching of iron and silicon, the manganese carbonate prepared by the CO2 method from the leached manganese solution further meets the HG / T 4203-2011 industrial grade manganese carbonate standard. The present invention proposes a technical route for pyrometallurgical reduction of copper tailings, leaching manganese with dilute acid and preparing manganese carbonate by the CO2 method, which not only realizes the resource utilization of copper tailings, turning waste into treasure, but also reduces the cost of recovering manganese in the manganese smelting industry, and at the same time has good economic and environmental benefits.

[0010] The technical concept and principle of the present invention are as follows: (1) Pyrometallurgical reduction of pyrolusite with copper tailings slag. The main components of copper tailings slag are fayalite (Fe2SiO4) and magnetite (Fe3O4), containing a relatively high content of Fe(II). After thoroughly grinding and mixing the copper tailings slag with pyrolusite, by utilizing the reducibility of Fe(II) in the copper tailings slag and the oxidizability of Mn(IV) in the pyrolusite, they are combined under anaerobic conditions, and redox reactions occur during the roasting process, causing MnO2 to be gradually reduced to Mn2O3 → Mn3O4 → MnO, and Fe(II) in Fe2SiO4 and Fe3O4 is oxidized to Fe(III), generating a stable α-Fe2O3 structure and SiO2 crystals. (2) Leaching manganese with dilute acid. The α-Fe2O3 structure has good chemical and thermal stability and low solubility in an extremely dilute acid environment with a very low concentration; SiO2 is also not easily leached in a dilute acid environment due to its high chemical stability. Therefore, the roasted slag obtained by pyrometallurgical reduction is washed with an extremely dilute acid (0.3 mol / L - 0.4 mol / L) to obtain a manganese solution. Not only is the leaching rate of manganese high, but the leaching rate of iron is extremely low. During the recovery process of the manganese solution, compared with traditional leaching techniques, not only selective separation and recovery are achieved, but also the leaching of iron at a lower concentration reduces the amount of sodium hydroxide used for adjusting the pH of the manganese solution and the amount of precipitation sludge. (3) Preparation of manganese carbonate by the CO2 method. During the preparation of manganese carbonate, the present invention provides CO3 by introducing CO2 2- to prepare manganese carbonate to achieve the purpose of carbon reduction and emission reduction. Not only is the precipitation rate of the manganese solution over 99.9%, but the prepared manganese carbonate meets the HG / T 4203-2011 industrial-grade manganese carbonate standard, with high recovery efficiency.

[0011] To achieve the above object, the present invention provides the following technical solutions:

[0012] A method for preparing manganese carbonate by roasting and reducing pyrolusite with flotation copper tailings slag, comprising the following steps:

[0013] Using the flotation copper tailings slag as a reducing agent to roast with pyrolusite at high temperature to obtain roasted slag, the roasted slag includes MnO, α-Fe2O3, and SiO2, and may also include Mn2O3, excluding Mn2SiO4;

[0014] Leaching the manganese in the roasted slag with sulfuric acid at a concentration of 0.3 mol / L - 0.4 mol / L to obtain a manganese-containing solution;

[0015] Separating iron from the manganese-containing solution and recovering the manganese solution;

[0016] Preparing industrial-grade manganese carbonate from the recovered manganese solution by the CO2 method.

[0017] Furthermore, it includes the following steps:

[0018] (1) Mix pyrolusite with copper tailings after flotation evenly according to a certain mass ratio, and control the mass ratio of total manganese to total iron elements in the mixed powder to be 0.7 ± 0.01;

[0019] (2) Feed the solid obtained in step (1) into a tubular furnace for high-temperature anaerobic roasting. The roasting temperature is 800 ± 5 °C, and the roasting time is 60 ± 2 min;

[0020] (3) Add sulfuric acid with a concentration of 0.3 mol / L - 0.4 mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1 g:10 mL, and stir thoroughly at a certain temperature and for a certain time;

[0021] (4) Separate the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a residue rich in iron and silicon;

[0022] (5) Add sodium hydroxide solution to the manganese-iron-containing solution obtained in step (4) to adjust the pH value of the system to 3.5 - 4.0 for iron ion removal;

[0023] (6) Filter the solid-liquid mixture obtained in step (5) to obtain a manganese solution and an iron precipitate;

[0024] (7) Aerate the manganese solution obtained in step (6) by introducing CO2 gas at a certain flow rate, and add sodium hydroxide solution to adjust the pH value of the system to 6.6 - 7.0. Aerate for a certain time at a certain temperature to produce a precipitate;

[0025] (8) Filter the solid-liquid mixture obtained in step (7), wash the filter cake with ethanol and dry it to obtain industrial-grade manganese carbonate.

[0026] Further, in step (1), after mixing pyrolusite with copper tailings after flotation, grind evenly and pass through a 200-mesh sieve.

[0027] Further, the anaerobic roasting atmosphere in step (2) requires nitrogen as the protective gas.

[0028] Further, in step (3), the concentration of the added sulfuric acid is 0.3 mol / L.

[0029] Further, in step (3), the stirring temperature is 70 - 100 °C, and the stirring time is 60 - 120 min; preferably, the stirring temperature is 90 °C, and the stirring time is 90 min.

[0030] Further, in step (5), the pH value of the system is adjusted to 3.8.

[0031] Further, in step (7), the flow rate of the CO2 gas introduced is 0.3 - 0.6 L / min, and aeration is carried out at 40 - 60 °C for 60 - 120 min; preferably, the flow rate of the CO2 gas introduced is 0.3 L / min, and aeration is carried out at 40 °C for 120 min.

[0032] Further, in steps (5) and (7), the concentration of the sodium hydroxide solution added is 1 - 3 mol / L, preferably 2 mol / L.

[0033] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0034] (1) The process of the method of the present invention is simple, the requirements for equipment are low, and the reducing agent selected is the copper tailings after copper smelting flotation, which is a large amount of solid waste with a large annual output and low use cost, about 30 yuan / ton. The reducing agent has a high reduction efficiency, and the leaching rate of manganese can reach more than 94%. It not only realizes the resource utilization of copper tailings, turning waste into treasure, but also reduces the cost of recovering manganese in the manganese smelting industry, and at the same time has good economic and environmental benefits.

[0035] (2) The present invention uses pyrometallurgy to reduce pyrolusite, and uses very dilute acid (0.3 mol / L - 0.4 mol / L) to selectively leach manganese in the roasted slag and inhibit the leaching of iron and silicon. Iron and silicon exist in the forms of α-Fe2O3 and SiO2 respectively. This leaching process does not produce silica sol, and the leaching rate of manganese reaches more than 94%, and the leaching rate of iron is less than 1%. In the subsequent process of separating iron, the consumption of alkali liquor is small and the amount of precipitation sludge is also small.

[0036] (3) The present invention uses the CO2 method to prepare manganese carbonate from the recovered manganese solution. Not only is the precipitation rate of the manganese solution more than 99.9%, but the prepared manganese carbonate meets the HG / T 4203-2011 industrial grade manganese carbonate standard, and the recovery efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the basic flow chart of the present invention for preparing manganese carbonate by roasting and reducing pyrolusite based on copper tailings after flotation;

[0038] Figure 2 is the XRD pattern of the roasted slag after roasting the copper tailings roasted and reduced pyrolusite at roasting temperatures of 600 °C, 700 °C, 800 °C, and 900 °C for 60 min respectively;

[0039] Figure 3 is the XRD pattern of the roasted slag after roasting the copper tailings roasted and reduced pyrolusite at a roasting temperature of 800 °C for 60 min and the XRD pattern of the iron-rich and silicon-rich residue obtained after pickling the roasted slag;

[0040] Figure 4XRD pattern of the manganese carbonate prepared in Example 20 of the present invention. Detailed implementation manners

[0041] The applicant will further describe the present invention in detail with reference to specific embodiments below. The embodiments are only for helping to understand the present invention, but the scope of protection claimed in the claims of the present invention is not limited thereto.

[0042] The pyrolusite used in the examples was provided by a company in Guangxi, and the copper tailings after flotation were provided by a company in Hubei; the total manganese in the pyrolusite was 420.26 g / kg, and the total iron in the copper tailings was 387.01 g / kg. The main chemical components and contents are shown in Tables 1 and 2:

[0043] Table 1 Main components and contents of pyrolusite (wt%)

[0044]

[0045] Table 2 Main components and contents of copper tailings (wt%)

[0046]

[0047] * The iron-containing phases are mainly olivine and a small amount of iron oxide, and ferrous iron accounts for more than 90% of the total iron

[0048] Examples 1-5 A method for roasting and reducing pyrolusite based on copper tailings after flotation, comprising the following steps:

[0049] (1) Take pyrolusite and copper tailings after flotation and mix them in a certain mass ratio, grind them evenly, and pass through a 200-mesh sieve;

[0050] (2) Feed the solid obtained in step (1) into a tubular furnace and continuously pass nitrogen for high-temperature roasting. The roasting temperature is 800 °C and the roasting time is 60 min;

[0051] (3) Add sulfuric acid with a concentration of 0.3 mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1 g:10 mL, and stir well at 90 °C for 90 min;

[0052] (4) Perform solid-liquid separation on the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a ferrous-iron and silicon-rich residue. Measure the Mn and Fe contents in the solution by ICP-OES, and calculate the leaching rates of Mn and Fe through the following formula; the leaching rate results of Mn and Fe are shown in Table 3;

[0053] The leaching rate formulas for Fe and Mn are as follows:

[0054]

[0055] η(%) is the leaching rate of the metal (Fe or Mn); C0 (mg / L) is the metal content (Fe or Mn) in the copper tailings and pyrolusite; C1 (mg / L) is the metal (Fe or Mn) content in the leaching solution.

[0056] Table 3

[0057] Example Pyrolusite / g Copper tailings / g Mn / Fe mass ratio Leaching rate of Mn / % Leaching rate of Fe / % Example 1 1 1.98 0.5 64.04 3.6 Example 2 1 1.62 0.6 78.87 1.1 Example 3 1 1.37 0.7 94.89 0.8 Example 4 1 1.17 0.8 76.63 0.7 Example 5 1 0.90 0.9 60.73 0.2

[0058] Note: The "Mn / Fe mass ratio" refers to the mass ratio of the total manganese to the total iron elements in the mixture of pyrolusite and copper tailings.

[0059] It can be seen from Table 3 that before roasting the roasted slag, the mass ratio of the total manganese to the total iron elements in the mixture affects the leaching of Mn. As the Mn / Fe mass ratio increases, the leaching rate of Mn first increases and then decreases. When the Mn / Fe mass ratio is less than 0.7, there is too much copper tailings, and the decomposition rate of Fe(II) will decrease accordingly. At the same time, the copper tailings will decompose excessive SiO2, making the reduced MnO form stable Mn2SiO4, which will wrap the minerals and make them difficult to leach, resulting in a decrease in the leaching rate of manganese; when the Mn / Fe mass ratio is greater than 0.7, the amount of Fe(II) reducing agent in the copper tailings is insufficient, so the leaching rate of Mn is relatively low.

[0060] Examples 6 - 10 A method for roasting and reducing pyrolusite based on flotation copper tailings, comprising the following steps:

[0061] (1) Take 1.00 g of pyrolusite and mix it with 1.37 g of flotation copper tailings, grind evenly, and pass through a 200-mesh sieve;

[0062] (2) Feed the solid obtained in step (1) into a tubular furnace and continuously pass nitrogen for high-temperature roasting. The roasting temperature is 600°C - 900°C, and the roasting time is 60 min;

[0063] (3) Add sulfuric acid with a concentration of 0.3 mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1 g:10 mL, and stir well at 90°C for 90 min;

[0064] (4) Separate the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a rich-iron and rich-silicon residue. Measure the Mn and Fe contents in the solution by ICP-OES, and calculate the leaching rates of Mn and Fe through the following formula; the leaching rate results of Mn and Fe are shown in Table 4;

[0065] Among them, the leaching rate formulas for Fe and Mn are:

[0066]

[0067] η(%) is the leaching rate of metal (Fe or Mn); C0 (mg / L) is the metal content (Fe or Mn) in copper tailings and pyrolusite; C1 (mg / L) is the metal (Fe or Mn) content in the leaching solution.

[0068] Table 4

[0069] Example Roasting temperature / °C Leaching rate of Mn / % Leaching rate of Fe / % Example 6 700 61.83 0.2 Example 7 750 71.64 0.3 Example 8 800 94.89 0.8 Example 9 850 81.61 1.2 Example 10 900 77.01 8.1

[0070] As can be seen from Table 4: with the increase of roasting temperature, the leaching rate of Mn first increases and then decreases. The roasting temperature should not be less than 800 °C, otherwise the leaching of Mn is limited; the roasting temperature should not be greater than 800 °C, otherwise the leaching of Mn will be reduced. The possible reason is that Mn is transformed into other acid-insoluble states.

[0071] Figure 2 The XRD patterns of the roasted residues of copper tailings roasted and reduced pyrolusite at roasting temperatures of 600 °C, 700 °C, 800 °C, and 900 °C for 60 min in step (2) are shown. From Figure 2 It can be seen that: in the roasted residues roasted at 600 °C and 700 °C, Mn mainly exists in the form of Mn2O3, indicating that the reduction of Mn is incomplete; in the roasted residue with a roasting temperature of 800 °C, Mn is basically completely reduced to MnO and Mn3O4; in the roasted residue with a roasting temperature increased to 900 °C, the reduced MnO will form a manganese silicate (Mn2SiO4) structure with SiO2, and Mn2SiO4 is not easily leached under dilute acid (0.3 mol / L sulfuric acid) conditions, reducing the leaching rate of Mn.

[0072] Figure 3 The XRD pattern of the roasted residue of copper tailings roasted and reduced pyrolusite at a roasting temperature of 800 °C for 60 min in step (2) and the XRD pattern of the iron-rich and silicon-rich residue obtained after acid washing of the roasted residue are shown. From Figure 3 It can be seen that: the phases of α-Fe2O3 and SiO2 appear on the XRD pattern after roasting at 800 °C, indicating that Fe2SiO4 in the copper tailings has undergone an oxidation-reduction reaction with MnO2 in the pyrolusite, and Fe2SiO4 is oxidized to Fe(III) and SiO2; the existence of α-Fe2O3 and SiO2 still remains in the residue obtained after acid washing of the roasted residue, confirming the stability of α-Fe2O3 and SiO2, especially α-Fe2O3 is not easily dissolved under dilute acid (0.3 mol / L sulfuric acid) conditions.

[0073] Examples 11 - 15 A method for roasting and reducing pyrolusite based on flotation copper tailings, comprising the following steps:

[0074] (1) Take 1.00 g of pyrolusite and mix it with 1.37 g of flotation copper tailings, grind them evenly, and pass through a 200-mesh sieve;

[0075] (2) Feed the solid obtained in step (1) into a tubular furnace, continuously pass nitrogen, and carry out high-temperature roasting. The roasting temperature is 800 °C, and the roasting time is 30 min - 90 min;

[0076] (3) Add sulfuric acid with a concentration of 0.3 mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1 g:10 mL, and stir well at 90 °C for 90 min;

[0077] (4) Separate the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a residue rich in iron and silicon. Measure the contents of Mn and Fe in the solution by ICP-OES, and calculate the leaching rates of Mn and Fe through the following formula; the leaching rate results of Mn and Fe are shown in Table 5;

[0078] The leaching rate formulas for Fe and Mn are as follows:

[0079]

[0080] η(%) is the leaching rate of the metal (Fe or Mn); C0 (mg / L) is the metal content (Fe or Mn) in the copper tailings and pyrolusite; C1 (mg / L) is the metal (Fe or Mn) content in the leaching solution.

[0081] Table 5

[0082] Example Roasting time / min Leaching rate of Mn / % Leaching rate of Fe / % Example 11 30 53.45 0.1 Example 12 45 61.63 0.1 Example 13 60 94.89 0.8 Example 14 75 73.12 0.2 Example 15 90 63.75 9.8

[0083] It can be seen from Table 5 that: with the extension of the roasting time, the leaching rate of Mn first increases and then decreases. The roasting time should not be less than 60 min, otherwise the leaching of Mn is limited; the roasting time should not be longer than 60 min, otherwise it will reduce the leaching of Mn and increase the leaching of Fe. The possible reason is that Mn will transform into other acid-insoluble states when the roasting time is too long.

[0084] Examples 16 - 19 A method for roasting and reducing pyrolusite based on flotation copper tailings, comprising the following steps:

[0085] (1) Take 1.00 g of pyrolusite and mix it with 1.37 g of flotation copper tailings, grind them evenly, and pass through a 200-mesh sieve;

[0086] (2) Feed the solid obtained in step (1) into a tubular furnace, continuously pass nitrogen, and carry out high-temperature roasting. The roasting temperature is 800 °C, and the roasting time is 60 min;

[0087] (3) Add sulfuric acid with a concentration of 0.1 mol / L - 0.4 mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1 g:10 mL, and stir well at 90 °C for 90 min;

[0088] (4) Carry out solid-liquid separation on the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a residue rich in iron and silicon. Measure the contents of Mn and Fe in the solution by ICP-OES, and calculate the leaching rates of Mn and Fe through the following formula; the leaching rate results of Mn and Fe are shown in Table 6;

[0089] Among them, the leaching rate formulas for Fe and Mn are:

[0090]

[0091] η(%) is the leaching rate of the metal (Fe or Mn); C0 (mg / L) is the metal content (Fe or Mn) in the copper tailings and pyrolusite; C1 (mg / L) is the metal (Fe or Mn) content in the leaching solution.

[0092] Table 6

[0093] Example Concentration of sulfuric acid / mol / L Leaching rate of Mn / % Leaching rate of Fe / % Example 16 0.1 25.62 0.1 Example 17 0.2 70.29 0.1 Example 18 0.3 94.89 0.8 Example 19 0.4 98.92 21.8

[0094] It can be seen from Table 6 that as the sulfuric acid concentration used for acid leaching of the roasted slag increases, the leaching rate of Mn gradually increases. The sulfuric acid concentration used for acid leaching of the roasted slag should not be less than 0.3 mol / L, otherwise the leaching of Mn is limited; the sulfuric acid concentration used for acid leaching of the roasted slag should not be greater than 0.3 mol / L, otherwise it will greatly increase the leaching of Fe, and further increase the consumption of alkali for iron removal.

[0095] Example 20 A method for preparing manganese carbonate based on roasted and reduced pyrolusite from flotation copper tailings, comprising the following steps:

[0096] (1) Take 1.00 g of pyrolusite and mix it with 1.37 g of flotation copper tailings, grind evenly, and pass through a 200-mesh sieve;

[0097] (2) Feed the solid obtained in step (1) into a tubular furnace and continuously pass nitrogen for high-temperature roasting. The roasting temperature is 800 °C and the roasting time is 60 min;

[0098] (3) Add sulfuric acid with a concentration of 0.3 mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1 g: 10 mL, and stir well at 90 °C for 90 min;

[0099] (4) Carry out solid-liquid separation on the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a residue rich in iron and silicon;

[0100] (5) Add a 2 mol / L sodium hydroxide solution to the manganese-iron-containing solution obtained in step (4) to adjust the pH value of the system to 3.8 for iron ion removal;

[0101] (6) Filter the solid-liquid mixture obtained in step (5) to obtain a manganese solution and an iron precipitate;

[0102] (7) Introduce CO2 gas into the manganese solution obtained in step (6) at a flow rate of 0.3 L / min for aeration, and add 2 mol / L sodium hydroxide solution to adjust the pH value of the system to 6.8. Aerate for 120 min at 40 °C to produce a precipitate.

[0103] (8) Filter the solid-liquid mixture obtained in step (7), wash the filter cake with ethanol and dry it to obtain a manganese carbonate product. Measure the Mn content in the liquid by ICP-OES, and calculate the precipitation rate of Mn to be 99.94%.

[0104] Figure 4 It is the XRD pattern of the manganese carbonate product prepared in Example 20. After comparison with the standard pattern, it is confirmed to be manganese carbonate.

[0105] Table 7 shows the XRF analysis results of the manganese carbonate product prepared in Example 20. Compared with the standard HG / T 4203-2011 industrial grade manganese carbonate, it meets the requirements of industrial grade manganese carbonate.

[0106] Table 7

[0107]

Claims

1. A method for preparing manganese carbonate by roasting and reducing pyrolusite with copper tailings slag after flotation, which is characterized in that, It includes the following steps: using the copper tailings after flotation as a reducing agent to roast with pyrolusite at high temperature to obtain roasted slag, including MnO, α-Fe2O3 and SiO2; Leaching manganese in the roasted slag with sulfuric acid with a concentration of 0.3mol / L - 0.4mol / L to obtain a manganese-containing solution; Separating iron in the manganese-containing solution and recovering the manganese solution; Preparing industrial-grade manganese carbonate from the recovered manganese solution by the CO2 method.

2. The method according to claim 1, wherein It includes the following steps: (1) Mix pyrolusite and flotation copper tailings evenly according to a certain mass ratio, and control the mass ratio of total manganese to total iron elements in the mixed powder to be 0.7±0.01; (2) Feed the solid obtained in step (1) into a tubular furnace for high-temperature anaerobic roasting, with the roasting temperature being 800±5°C and the roasting time being 60±2min; (3) Add sulfuric acid with a concentration of 0.3mol / L - 0.4mol / L to the solid obtained in step (2) according to a solid-liquid ratio of 1g:10mL, and stir well at a certain temperature and for a certain time; (4) Perform solid-liquid separation on the solid-liquid mixture obtained in step (3) to obtain a manganese-iron-containing solution and a residue rich in iron and silicon; (5) Add sodium hydroxide solution to the manganese-iron-containing solution obtained in step (4) to adjust the pH value of the system to 3.5 - 4.0 for iron ion removal; (6) Filter the solid-liquid mixture obtained in step (5) to obtain a manganese solution and an iron precipitate; (7) Pass CO2 gas into the manganese solution obtained in step (6) at a certain flow rate for aeration, and add sodium hydroxide solution to adjust the pH value of the system to 6.6 - 7.0, and aerate for a certain time at a certain temperature to produce a precipitate; (8) Filter the solid-liquid mixture obtained in step (7), wash the filter cake with ethanol and dry it to obtain industrial-grade manganese carbonate.

3. The method according to claim 2, wherein In step (1), after mixing pyrolusite and flotation copper tailings, grind them evenly and pass through a 200-mesh sieve.

4. The method according to claim 2, wherein In step (3), the concentration of the added sulfuric acid is 0.3mol / L.

5. The method according to claim 2, characterized in that, In step (3), the stirring temperature is 70 - 100°C and the stirring time is 60 - 120min.

6. The method according to claim 5, wherein In step (3), the stirring temperature is 90°C and the stirring time is 90min.

7. The method according to claim 2, wherein In step (7), the flow rate of the CO2 gas passed in is 0.3 - 0.6L / min, and aerate for 60 - 120min at 40 - 60°C.

8. The method according to claim 7, wherein In step (7), the flow rate of the CO2 gas passed in is 0.3L / min, and aerate for 120min at 40°C.

9. The method according to claim 2, wherein In steps (5) and (7), the concentration of the added sodium hydroxide solution is 1 - 3mol / L.

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