Process for removing iron from electrolytic manganese leach liquor

Abstract

The application relates to the technical field of hydrometallurgy, and particularly discloses a process for removing iron from electrolytic manganese leaching solution, wherein the pumping speed of hydrogen peroxide is controlled at 1.8-2.7 mL / (L.h), so that Fe 2+ The gradual oxidation is carried out, the system is maintained at a moderate supersaturation, iron precipitates are orderly converted along a thermodynamic stable path of ferrihydrite-goethite-hematite, and finally, a precipitated product with good crystallinity and large particle size is formed, and the filtration speed is greatly improved; the application only needs to adjust the process operation parameters (pH, temperature and hydrogen peroxide adding mode) of the existing production line, does not need to add or transform main equipment, and is easy to popularize and apply in existing electrolytic manganese enterprises. Meanwhile, the 60-75 DEG C low-temperature process can greatly reduce the steam consumption, and provides a low-cost alternative scheme for enterprises with limited steam supply.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to an iron removal process for electrolytic manganese leaching solution. Background Technology

[0002] Metallic manganese is a crucial raw material for industries such as steel, non-ferrous alloys, and batteries. my country ranks among the world's leading producers and consumers of manganese. Currently, the main industrial process for producing metallic manganese is sulfuric acid leaching followed by electrolysis. Iron compounds are often present in manganese ore; during sulfuric acid leaching, the iron is converted into Fe. 2+ and Fe 3+ The iron content in the leachate is reduced to below 0.5 mg / L before entering the electrolysis process. Excessive iron impurities will reduce the current efficiency of the electrolysis process, causing electrolysis to fail. Therefore, the iron content in the leachate must be reduced to below 0.5 mg / L before entering the electrolysis process.

[0003] The domestic electrolytic manganese industry commonly uses hydrolysis precipitation to remove iron. The basic process of this method is: adding an oxidant (usually hydrogen peroxide or air) to the leachate to remove Fe. 2+ Oxidized to Fe 3+ At the same time, alkaline neutralizing agents such as ammonia are added to neutralize Fe. 3+ Hydrolysis produces Fe(OH)3 precipitate, which is then separated into solid and liquid by pressure filtration. The hydrolysis precipitation method is simple to operate and requires simple equipment, but it has revealed several technical drawbacks in actual production.

[0004] Firstly, the filtration performance is poor. The Fe(OH)3 generated by hydrolysis and precipitation is mainly an amorphous colloid with fine particles (nanometer to submicron level). This dense packing results in a filter cake with high specific resistance and poor permeability. Under industrial conditions, the filtration rate is only about 0.003 mL / (s·cm²), leading to long solid-liquid separation times, slow equipment turnaround, and the filtration process becoming a bottleneck in production, increasing electricity consumption and labor costs.

[0005] Secondly, manganese resources are severely depleted. Fe(OH)3 colloids have a large specific surface area, which affects the concentration of Mn in solution. 2+ It exhibits strong physical adsorption and entrainment effects, causing a significant amount of manganese to be lost with the iron slag. On the other hand, under medium-high pH conditions (pH 6-7), hydrogen peroxide has a strong effect on the removal of manganese. 2+ Enhanced oxidation activity, some Mn 2+ It is oxidized to MnO2 and enters the slag phase. With these two factors combined, the manganese loss rate in traditional processes is usually above 6%, and even exceeds 15% when the manganese ore grade is low. Based on an annual production of 10,000 tons of electrolytic manganese, the manganese lost annually due to the iron removal process can reach hundreds of tons, resulting in considerable raw material cost losses.

[0006] Third, the iron removal process generates a large amount of slag with a high moisture content. Traditional iron removal processes produce slag with a moisture content close to 60%, and the amount of slag produced per unit volume of leachate is approximately 17.75 g / L. The high moisture content increases the cost of slag transportation and storage, and a large amount of manganese-containing wastewater enters the slag yard along with the slag, causing secondary resource loss and increasing environmental risks.

[0007] To improve the filtration performance of iron slag removal and reduce manganese loss, researchers have attempted to introduce seed crystals into the system. The role of seed crystals is to provide heterogeneous nucleation sites, allowing iron hydrolysis products to crystallize directionally on the seed crystal surface rather than forming amorphous colloids. This increases the crystallinity and size of the precipitate particles, thus improving filtration performance. However, current seed crystal technologies rely on purchasing commercial seed crystals (such as α-FeOOH, iron oxide powder, etc.), resulting in high procurement and transportation costs.

[0008] To address the urgent need for iron removal technology in the electrolytic manganese industry, we will develop a low-cost iron removal method that does not rely on purchased auxiliary materials, requires minimal process modifications, and can reduce manganese loss and solid waste production at the source. This method has significant engineering application value and practical significance. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide an iron removal process for electrolytic manganese leaching solutions, solving the problems of difficult filtration, high manganese loss rate, large solid waste production, and increased costs due to reliance on purchased seed crystals in existing electrolytic manganese leaching solutions for iron removal.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Preparation of slurry Fe 2+ The electrolytic manganese leaching solution is heated to 60-75℃, and the pH is adjusted to 3.5-4.5 using dilute ammonia as a neutralizing agent to obtain a slurry.

[0011] In this step, the mass fraction of the dilute ammonia solution is 5-10%, more preferably 10%.

[0012] In this step, dilute ammonia is used instead of sodium hydroxide or sodium carbonate as a neutralizing agent. This can form an NH3·H2O-(NH4)2SO4 buffer pair in the system, effectively buffering local pH fluctuations and preventing the formation of a local strong alkaline zone near the neutralizing agent addition point, which could lead to Mn(OH)2 precipitation.

[0013] S2, slow oxidation and crystallization reaction Seed crystals were added to the slurry obtained in step S1, followed by hydrogen peroxide, and the pH of the system was maintained at 3.5-4.5 with dilute ammonia. The reaction was then heated.

[0014] In this step, the seed crystal is prepared as follows: take dried and pulverized iron-rich manganese slag and magnesium-rich steel slag, ball mill and mix them evenly to obtain a mixture; then place the mixture in a muffle furnace for calcination, cool it to room temperature after calcination, grind and sieve it to obtain the seed crystal.

[0015] Specifically, the selected iron-rich manganese slag is iron-rich electrolytic manganese slag, in which the mass fraction of Fe2O3 is not less than 40% and the mass fraction of MnO is 8%-11%.

[0016] Specifically, the selected magnesium-rich steel slag contains 40-52% CaO, 12-16% MgO, 10-15% Fe2O3, and 10-19% SiO2.

[0017] Specifically, the iron-rich manganese slag and the magnesium-rich steel slag are first dried, crushed, and sieved through a 100-mesh sieve.

[0018] The mass ratio of iron-rich manganese slag to magnesium-rich steel slag is 3-5:1. For example, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1 can be selected, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Specifically, the calcination temperature is 750-850℃, and the calcination time is 2-3 hours.

[0020] During calcination, MgO in magnesium-rich steel slag reacts chemically with Fe2O3 in iron-rich manganese slag, forming an in-situ magnesium-iron spinel (MgFe2O4) structure. This newly formed spinel structure is sensitive to iron ions (Fe... 3+ With a high degree of lattice matching, it can serve as a highly active heterogeneous nucleation catalytic center, significantly reducing the interfacial activation energy for the directional crystallization of iron into goethite (FeOOH), thereby promoting the crystallization growth of iron precipitates at lower temperatures.

[0021] In this step, the amount of seed crystal added is 0.5-2 g / L. For example, you can choose 0.5 g / L, 0.6 g / L, 0.8 g / L, 1 g / L, 1.2 g / L, 1.5 g / L, 1.8 g / L, or 2 g / L, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In this step, the hydrogen peroxide addition rate is 1.8-2.7 mL / (L·h) based on the volume of the slurry.

[0023] In this step, the heating reaction temperature is 60-75℃, and the heating reaction time is 0.5-1.5h.

[0024] Under traditional iron removal conditions at pH 6-7, hydrogen peroxide can effectively remove Mn. 2+ Mn has strong oxidizing ability.2+ Oxidation to form MnO2, which enters the slag phase, is one of the main sources of manganese loss. This invention strictly controls the system pH between 3.5 and 4.5, and Mn... 2+ The oxidation potential is significantly increased, and oxidation side reactions are greatly suppressed, thereby reducing the chemical loss of manganese from the source.

[0025] This invention controls the hydrogen peroxide pumping rate at 1.8-2.7 mL / (L·h) to achieve Fe 2+ Through gradual oxidation, the system is maintained at a moderate degree of supersaturation. The iron precipitate undergoes an orderly transformation along the thermodynamically stable path of ferrohydrate → goethite → hematite, ultimately forming a precipitate product with good crystallinity and large particle size, which greatly improves the filtration speed.

[0026] S3, Aging and Solid-Liquid Separation After the oxidation reaction is complete, maintain the reaction temperature and age for 0.5-1.5 hours to promote further growth and aggregation of iron crystals. After aging, perform solid-liquid separation to obtain a manganese-containing purified solution and an iron-containing filter residue. The manganese-containing purified solution, after subsequent conventional impurity removal processes, can be used as a qualified electrolytic solution; the iron-containing filter residue can be used as a raw material for preparing iron oxide red pigment.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) Under conventional iron removal conditions with a pH of 6-7, hydrogen peroxide has a significant effect on Mn. 2+ Mn has strong oxidizing ability. 2+ Oxidation to form MnO2, which enters the slag phase, is one of the main sources of manganese loss. This invention strictly controls the system pH between 3.5 and 4.5, and Mn... 2+ The oxidation potential is significantly increased, and oxidation side reactions are greatly suppressed, thereby reducing the chemical loss of manganese from the source.

[0028] (2) In this invention, the hydrogen peroxide pumping rate is controlled at 1.8-2.7 mL / (L·h), so that Fe 2+ Through gradual oxidation, the system is maintained at a moderate degree of supersaturation. The iron precipitate undergoes an orderly transformation along the thermodynamically stable path of ferrohydrate → goethite → hematite, ultimately forming a precipitate product with good crystallinity and large particle size, which greatly improves the filtration speed.

[0029] (3) In this invention, magnesium-rich steel slag and iron-rich manganese slag are mixed and calcined to generate magnesium-iron spinel (MgFe2O4) structure in situ. This newly generated spinel structure is effective against iron ions (Fe 3+The high lattice matching of this crystal allows it to serve as a highly active heterogeneous nucleation catalytic center, significantly reducing the interfacial activation energy for the directional crystallization of iron into goethite (FeOOH), thereby promoting the crystallization growth of iron precipitates at lower temperatures. Compared to homogeneous nucleation, heterogeneous nucleation requires lower supersaturation, has a faster crystallization rate, and produces products with higher crystallinity. Furthermore, the seed crystals are derived from production solid waste, eliminating the need for additional procurement and achieving resource recycling through waste treatment.

[0030] (4) This invention only requires adjusting the process operating parameters (pH, temperature, hydrogen peroxide addition method) of the existing production line, without adding or modifying the main equipment, and is easy to promote and apply in existing electrolytic manganese enterprises. At the same time, the 60-75℃ low temperature process can significantly reduce the amount of steam used, providing a low-cost alternative for enterprises with limited steam supply. Detailed Implementation

[0031] The present invention will be further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0032] It should be noted that, unless otherwise specified, all chemical reagents involved in this invention were purchased through commercial channels.

[0033] The mass fraction of Fe2O3 in the iron-rich electrolytic manganese slag used in this embodiment of the invention is 41.6%, and the mass fraction of MnO is 9.3%; the mass fraction of CaO in the magnesium-rich steel slag is 43.2%, the mass fraction of MgO is 12.8%, the mass fraction of Fe2O3 is 13.5%, and the mass fraction of SiO2 is 11.7%.

[0034] This invention uses a simulated leaching solution of iron-manganese ore, wherein Fe 2+ Concentration of 5g / L, Mn 2+ The concentration is 50 g / L.

[0035] Example 1 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 70℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add seed crystals to the slurry obtained in step S1 at a rate of 1 g / L, then add 27.5 wt% hydrogen peroxide at a rate of 2.0 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia and heat the reaction at 70°C for 1 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0036] The preparation method of the seed crystal is as follows: take dried and crushed iron-rich manganese slag and magnesium-rich steel slag through a 100-mesh sieve, and ball mill them together at a mass ratio of 4:1 to obtain a mixture; then place the mixture in a muffle furnace, heat it to 800℃ at a rate of 5℃ / min, calcine it for 2 hours, cool it to room temperature after calcine, and grind it through a 100-mesh sieve to obtain the seed crystal.

[0037] Example 2 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 60℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add seed crystals to the slurry obtained in step S1. The amount of seed crystals added is 0.5 g / L. Then add 27.5 wt% hydrogen peroxide. The addition rate of hydrogen peroxide is 1.8 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia. Heat the reaction at 60°C for 1.5 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0038] The preparation method of the seed crystal is as follows: take dried and crushed iron-rich manganese slag and magnesium-rich steel slag through a 100-mesh sieve, and ball mill them together at a mass ratio of 3:1 to obtain a mixture; then place the mixture in a muffle furnace, heat it to 800℃ at a rate of 5℃ / min, calcine it for 2 hours, cool it to room temperature after calcine, and grind it through a 100-mesh sieve to obtain the seed crystal.

[0039] Example 3 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 75℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add seed crystals to the slurry obtained in step S1 at a rate of 2 g / L, then add 27.5 wt% hydrogen peroxide at a rate of 2.7 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia and heat the reaction at 75°C for 0.5 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0040] The preparation method of the seed crystal is as follows: take dried and crushed iron-rich manganese slag and magnesium-rich steel slag through a 100-mesh sieve, and ball mill them together at a mass ratio of 5:1 to obtain a mixture; then place the mixture in a muffle furnace, heat it to 800℃ at a rate of 5℃ / min, calcine it for 2 hours, cool it to room temperature after calcine, and grind it through a 100-mesh sieve to obtain the seed crystal.

[0041] Comparative Example 1 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 70℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add 27.5wt% hydrogen peroxide to the slurry obtained in step S1. The addition rate of hydrogen peroxide is 2.0mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia water and heat the reaction at 70℃ for 1h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0042] Compared with Example 1, no seed crystals were added in Comparative Example 1.

[0043] Comparative Example 2 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 70℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add seed iron-manganese slag to the slurry obtained in step S1. The amount of seed added is 1 g / L. Then add 27.5 wt% hydrogen peroxide. The addition rate of hydrogen peroxide is 2.0 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia. Heat the reaction at 70°C for 1 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0044] Compared with Example 1, the seed crystal in Comparative Example 2 is iron-manganese rich slag.

[0045] Comparative Example 3 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 70℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add α-Fe2O3 seed crystals to the slurry obtained in step S1. The amount of seed crystals added is 1 g / L. Then add 27.5 wt% hydrogen peroxide. The hydrogen peroxide addition rate is 2.0 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia water. Heat the reaction at 70°C for 1 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0046] Compared with Example 1, Comparative Example 3 uses commercial seed crystal α-Fe2O3.

[0047] Comparative Example 4 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 70℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add seed crystals to the slurry obtained in step S1 at a rate of 1 g / L, then add 27.5 wt% hydrogen peroxide at a rate of 3.6 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia and heat the reaction at 70°C for 1 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0048] The preparation method of the seed crystal is as follows: take dried and crushed iron-rich manganese slag and magnesium-rich steel slag through a 100-mesh sieve, and ball mill them together at a mass ratio of 4:1 to obtain a mixture; then place the mixture in a muffle furnace, heat it to 800℃ at a rate of 5℃ / min, calcine it for 2 hours, cool it to room temperature after calcine, and grind it through a 100-mesh sieve to obtain the seed crystal.

[0049] Compared with Comparative Example 4 and Example 1, the hydrogen peroxide addition rate was increased to 3.6 mL / (L·h).

[0050] Comparative Example 5 An iron removal process for electrolytic manganese leaching solution includes the following steps: S1. Take 1000 mL of the prepared simulated iron-manganese ore leaching solution as the test raw material, heat it to 70℃, and use 10 wt% dilute ammonia water as a neutralizing agent to adjust the pH to 4.0 to obtain the slurry. S2. Add seed crystals to the slurry obtained in step S1 at a rate of 1 g / L, then add 27.5 wt% hydrogen peroxide at a rate of 0.9 mL / (L·h) based on the volume of the slurry. Maintain the pH of the system at 4.0 with dilute ammonia and heat the reaction at 70°C for 1 h. S3. After the reaction is complete, keep warm and age for 1 hour, then separate the solid and liquid to obtain manganese-containing purified liquid and iron-containing precipitate residue.

[0051] The preparation method of the seed crystal is as follows: take dried and crushed iron-rich manganese slag and magnesium-rich steel slag through a 100-mesh sieve, and ball mill them together at a mass ratio of 4:1 to obtain a mixture; then place the mixture in a muffle furnace, heat it to 800℃ at a rate of 5℃ / min, calcine it for 2 hours, cool it to room temperature after calcine, and grind it through a 100-mesh sieve to obtain the seed crystal.

[0052] Compared with Comparative Example 5 and Example 1, the hydrogen peroxide addition rate was reduced to 0.9 mL / (L·h).

[0053] The various indicators of the iron removal processes provided in Embodiments 1-3 and Comparative Examples 1-5 of this invention are shown in Table 1.

[0054] Table 1. Indicators of different iron removal processes Finally, it should be noted that the above embodiments do not limit the present invention in any way. Those skilled in the art can make modifications and improvements based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A process for removing iron from an electrolytic manganese leaching solution, characterized in that, Includes the following steps: S1, containing Fe 2+ The electrolytic manganese leaching solution is heated to 60-75℃, and the pH is adjusted to 3.5-4.5 using dilute ammonia as a neutralizing agent to obtain a slurry. S2. Add seed crystals to the slurry obtained in step S1, then add hydrogen peroxide, and maintain the pH of the system at 3.5-4.5 with dilute ammonia, and heat the reaction. S3. After the reaction is complete, keep the mixture at a warm temperature for aging, and then separate the solid and liquid to obtain a manganese-containing purified liquid and an iron-containing precipitate.

2. The iron removal process according to claim 1, characterized in that, In step S1, the mass fraction of dilute ammonia is 5-10%.

3. The iron removal process according to claim 1, characterized in that, In step S2, the seed crystal is prepared as follows: take dried and pulverized iron-rich manganese slag and magnesium-rich steel slag, ball mill and mix them evenly to obtain a mixture; then place the mixture in a muffle furnace for calcination, cool it to room temperature after calcination, grind and sieve it to obtain the seed crystal.

4. The iron removal process according to claim 3, characterized in that, The mass ratio of the iron-rich manganese slag to the magnesium-rich steel slag is 3-5:

1.

5. The iron removal process according to claim 3, characterized in that, The calcination temperature is 750-850℃, and the calcination time is 2-3 hours.

6. The iron removal process according to claim 1, characterized in that, In step S2, the amount of seed crystals added is 0.5-2 g / L.

7. The iron removal process according to claim 1, characterized in that, In step S2, the hydrogen peroxide addition rate is 1.8-2.7 mL / (L·h) based on the volume of the slurry.

8. The iron removal process according to claim 1, characterized in that, In step S2, the temperature of the heating reaction is 60-75℃, and the heating reaction time is 0.5-1.5h.

9. The iron removal process according to claim 1, characterized in that, In step S3, the heat preservation and aging time is 0.5-1.5 hours.

Images