Process for the production of electrolytic manganese

Abstract

The present application belongs to the technical field of hydrometallurgy and electrochemical metallurgy, and particularly relates to a preparation process of electrolytic manganese, which comprises the following steps: mixing manganese carbonate concentrate with deionized water, adding sulfuric acid for heating leaching, and then performing pressure filtration to obtain a crude manganese sulfate leaching solution; adding manganese dioxide powder and ammonia water into the crude manganese sulfate leaching solution in sequence for oxidation, neutralization, iron and aluminum removal, adding sulfide to remove heavy metal impurities, and then performing deep adsorption purification through tannic acid modified cross-linked polyethyleneimine diatomite; adding ammonium sulfate, ammonium sulfite and ammonia water into the purified manganese sulfate solution to prepare an electrolyte, and then performing electrolysis in a polypropylene diaphragm electrolytic cell, and finally performing leaching, drying, peeling, crushing and screening to obtain electrolytic manganese. The present application can improve the purification degree of the leaching solution, reduce the interference of impurities on cathode deposition, improve the deposition quality of metal manganese, and take into account the process stability, raw material availability and production cost.

Description

Technical Field

[0001] This invention belongs to the fields of hydrometallurgy and electrochemical metallurgy, and specifically relates to a process for preparing electrolytic manganese. Background Technology

[0002] Electrolytic manganese is an important basic metallic material, widely used in steel smelting, non-ferrous alloys, battery materials, magnetic materials, and fine chemicals. Current electrolytic manganese production typically uses manganese carbonate or manganese oxide ore as raw material, and involves processes such as acid leaching, solid-liquid separation, iron and aluminum removal, sulfidation for impurity removal, electrolyte preparation, and diaphragm electrolysis. With the gradual depletion of high-quality manganese ore resources, the content of impurities such as iron, aluminum, calcium, magnesium, copper, nickel, cobalt, and zinc in the manganese ore raw materials used in industrial production is showing an upward trend, making the composition of the leaching solution more complex. If the leaching temperature, acid dosage, and liquid-solid ratio are not properly controlled, problems such as incomplete manganese leaching, excessively high free acid content, difficulty in slurry filtration, and manganese salt entrainment in the leaching residue can easily occur. This not only reduces the utilization rate of manganese resources but also increases the consumption of subsequent neutralizing agents, purifying agents, and washing water. Some production processes involve high-temperature roasting followed by acid leaching, which can improve the reactivity of some manganese ores. However, this process has drawbacks such as high energy consumption, high equipment investment, heavy flue gas treatment burden, and long production process, making it difficult to balance resource utilization efficiency, production costs, and environmental protection requirements.

[0003] Iron, aluminum, and heavy metal impurities in crude manganese sulfate leachate directly affect subsequent electrolysis processes. Ferrous ions are difficult to completely precipitate under neutralization conditions; they need to be oxidized to ferric ions first, and then hydrolyzed to form a precipitate. If the oxidation and neutralization sequence is not appropriate, incomplete iron removal or loss of manganese ions through co-precipitation can easily occur. The hydrolysis range of aluminum ions is close to the stability range of manganese ions; improper control of the neutralization endpoint can also lead to decreased filtration performance and reduced manganese yield. Even at low residual levels, heavy metal impurities such as copper, nickel, cobalt, and zinc may co-deposit or catalytically evolve hydrogen on the cathode surface, causing pinholes, nodules, dendrites, edge thickening, and localized peeling of the manganese deposition layer. Existing processes often use sulfides for heavy metal precipitation, but insufficient sulfide addition makes deep purification difficult, while excessive addition easily forms manganese sulfide precipitate, resulting in sulfide residue, odor pollution, and increased filtration load. Traditional activated carbon, inorganic powders, and ordinary adsorbents exhibit low selectivity for trace heavy metals in complex manganese sulfate solutions. Furthermore, powder materials are difficult to recover and can easily enter the electrolytic cell and clog the membrane. While ion exchange resins and solvent extraction offer some deep purification effects, they suffer from high material costs, large volumes of regeneration wastewater, complex operating procedures, and organic phase entrainment.

[0004] During the electrolysis stage, the purity, pH level, ammonium salt concentration, and additive composition of the manganese sulfate electrolyte collectively determine the cathode current efficiency and the quality of the manganese layer. Because manganese has a relatively negative deposition potential, the hydrogen evolution reaction at the cathode easily competes with manganese deposition, leading to reduced current utilization and increased power consumption per unit product. Currently, selenium-containing additives are commonly used in production to improve manganese deposition; however, selenium-containing substances may enter the product and wastewater, increasing environmental remediation pressure. Some organic leveling agents can improve the smoothness of the manganese layer under appropriate conditions, but long-term accumulation may cause increased electrolyte viscosity, increased foaming, increased internal stress in the deposition layer, and difficulties in filtration. Furthermore, ordinary stainless steel cathodes and lead-based anodes may also be affected by impurity ions, suspended particles, and local pH changes during long-term electrolysis, resulting in decreased cathode plate peeling performance and increased anode sludge. Therefore, there is an urgent need to develop an electrolytic manganese preparation process that uses readily available raw materials, is simple in process, and has controllable costs. Through reasonable acid leaching, oxidation neutralization, sulfide precipitation, and deep adsorption of functional materials, the iron, aluminum, and heavy metal impurities in the leachate can be reduced. Furthermore, an electrolytic additive system with a low environmental impact can be used to improve the density and stability of manganese deposition, thereby improving the purity, production efficiency, and overall economic benefits of electrolytic manganese. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a process for preparing electrolytic manganese, comprising the following steps:

[0006] S1. By weight, add 95-105 parts of manganese carbonate concentrate to a reaction vessel, add 350-500 parts of deionized water, stir and disperse to obtain manganese carbonate slurry; add 45-80 parts of sulfuric acid to the manganese carbonate slurry, heat and stir to obtain leaching slurry; filter the leaching slurry to obtain crude manganese sulfate leaching solution and leaching residue.

[0007] S2. Transfer the crude manganese sulfate leaching solution to a reaction vessel, heat it, add 0.8-2.5 parts of manganese dioxide powder, and continue stirring at pH 3.5-4.5; add ammonia water, adjust the pH to 5.2-5.6, continue stirring, and filter to obtain the first purified filtrate and iron-aluminum slag; cool the first purified filtrate to 35-45℃, add 0.8-2.0 parts of sodium sulfide, adjust the pH to 5.0-5.4, continue stirring, and filter to obtain the second purified filtrate and metal sulfide precipitate; add 0.5-1.5 parts of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth to the second purified filtrate, continue stirring, filter, and perform precision filtration to obtain a deeply purified manganese sulfate solution;

[0008] S3. Transfer the deeply purified manganese sulfate solution to an electrolyte preparation container, add 110-140 parts ammonium sulfate and 0.15-0.35 parts ammonium sulfite; add ammonia water, adjust the pH, continue stirring, and filter precisely to obtain the manganese sulfate electrolyte.

[0009] S4. The manganese sulfate electrolyte is transported to the polypropylene diaphragm electrolytic cell, with a stainless steel plate as the cathode and a lead-silver alloy plate as the anode, and electrolysis is performed. After electrolysis, the cathode plate is removed, rinsed with deionized water, dried, the metallic manganese layer on the surface of the cathode plate is peeled off, crushed, and sieved.

[0010] According to a preferred embodiment of the present invention, in step S1, the temperature is raised to 75-85°C.

[0011] According to a preferred embodiment of the present invention, in step S2, the temperature is raised to 55-65°C.

[0012] According to a preferred embodiment of the present invention, in step S3, the pH is adjusted to 6.6-7.0.

[0013] According to a preferred embodiment of the present invention, in step S4, the electrolysis time is 18-24 hours; the electrolysis temperature is 36-42°C; and the cathode current density is 350-420 A / m. 2 The electrolysis voltage is 4.5-5.2V.

[0014] According to a preferred embodiment of the present invention, the preparation steps of the tannic acid-modified crosslinked polyethyleneimine diatomaceous earth include:

[0015] A1. By weight, add 95-105 parts of diatomaceous earth filter aid to the reactor, add 30-60 parts of sulfuric acid and 470-640 parts of deionized water, stir and disperse, and heat to 65-80℃ to react and obtain acid-washed diatomaceous earth slurry; filter the acid-washed diatomaceous earth slurry to obtain filter cake; wash the filter cake with deionized water to obtain acid-washed activated diatomaceous earth filter cake;

[0016] A2. Add 95-105 parts of acid-washed and activated diatomaceous earth filter cake to the reactor, add 600-800 parts of deionized water, and stir to disperse; add 8-15 parts of branched polyethyleneimine aqueous solution, and heat to 45-55℃ to react, to obtain polyethyleneimine-loaded diatomaceous earth slurry; filter the polyethyleneimine-loaded diatomaceous earth slurry, wash with deionized water, to obtain polyethyleneimine-loaded diatomaceous earth filter cake;

[0017] A3. Add 95-105 parts of polyethyleneimine-supported diatomaceous earth filter cake to a reactor, add 500-700 parts of deionized water and an aqueous solution containing 1.0-2.5 parts of glutaraldehyde, heat to 40-50℃ and react to obtain the cross-linking reaction product; filter the cross-linking reaction product and wash it with deionized water to obtain glutaraldehyde-crosslinked polyethyleneimine diatomaceous earth filter cake.

[0018] A4. Add 95-105 parts of glutaraldehyde cross-linked polyethyleneimine diatomaceous earth filter cake to the reactor, add 500-700 parts of deionized water, 5-10 parts of tannic acid and 2-4 parts of sodium carbonate, adjust the pH to 8.0-8.6, introduce air, and stir the reaction at 35-45℃ to obtain the functionalized reaction product; filter the functionalized reaction product to obtain the solid product; wash the solid product with deionized water, dry, pulverize and sieve.

[0019] According to a preferred embodiment of the present invention, in step A1, the reaction time is 2-4 hours after heating to 65-80°C.

[0020] According to a preferred embodiment of the present invention, in step A2, the reaction time at 45-55°C is 2-4 hours.

[0021] According to a preferred embodiment of the present invention, in step A3, the reaction time is 2-3 hours after heating to 40-50°C.

[0022] According to a preferred embodiment of the present invention, in step A4, the stirring reaction time at 35-45°C is 3-5 hours.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) In this invention, manganese carbonate concentrate is mixed with deionized water to form a homogeneous slurry, which is then leached with sulfuric acid to convert the manganese-containing components in the manganese carbonate concentrate into the liquid phase. The crude manganese sulfate leachate is obtained by pressure filtration. This process does not require high-temperature roasting and complex reduction steps, which can shorten the production process and reduce equipment investment and energy consumption. By controlling the proportions of manganese carbonate concentrate, deionized water and sulfuric acid, as well as the leaching temperature, it is beneficial to improve the leaching degree of manganese carbonate concentrate, reduce local agglomeration of the slurry and the entrainment of crude manganese sulfate leachate by leaching residue, thereby improving the utilization rate of manganese resources and providing a more stable crude manganese sulfate leachate for subsequent purification.

[0025] (2) This invention uses manganese dioxide powder, ammonia, sodium sulfide, and tannic acid-modified cross-linked polyethyleneimine diatomaceous earth to perform graded purification of crude manganese sulfate leachate. Manganese dioxide powder can promote the conversion of low-valent iron in crude manganese sulfate leachate into high-valent iron that is easily hydrolyzed and precipitated. Ammonia can adjust the acid-base state of crude manganese sulfate leachate, so that iron and aluminum form precipitates and are removed by suction filtration. Sodium sulfide can cause heavy metal impurities such as copper, nickel, cobalt, and zinc to form insoluble precipitates, reducing their interference with the subsequent electrolysis process. Tannic acid-modified cross-linked polyethyleneimine diatomaceous earth uses diatomaceous earth filter aid as a porous carrier and is treated sequentially with branched polyethyleneimine aqueous solution, glutaraldehyde, tannic acid, and sodium carbonate, which can increase the adsorption sites for residual heavy metal impurities. After suction filtration and precision filtration, a highly purified manganese sulfate solution with high purity is obtained.

[0026] (3) This invention uses ammonium sulfate, ammonium sulfite, and ammonia to prepare a deeply purified manganese sulfate solution, giving the manganese sulfate electrolyte suitable conductivity and acid-base properties. Ammonium sulfate helps maintain the ion conductivity of the manganese sulfate electrolyte and the stability of the cathode region composition, while ammonium sulfite helps reduce abnormal oxidation of manganese ions and the side reaction of hydrogen evolution at the cathode, improving the nucleation and deposition state of metallic manganese. Using a polypropylene diaphragm electrolytic cell, stainless steel plate, and lead-silver alloy plate for electrolysis reduces the mutual influence between the cathode liquid and the anolyte, allowing the metallic manganese layer to be uniformly deposited on the surface of the stainless steel plate. After being rinsed with deionized water, dried, peeled, crushed, and sieved, the resulting metallic manganese layer has the characteristics of low impurity content, dense deposition structure, good peeling performance, and easy control of product particle size. Detailed Implementation

[0027] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0028] Example 1

[0029] This embodiment provides a process for preparing electrolytic manganese, the steps of which include:

[0030] Step S1: Select manganese carbonate concentrate with a manganese mass fraction of 34.0%, an iron mass fraction of 3.0%, an aluminum mass fraction of 1.2%, and a particle size D90 not greater than 150 μm. Weigh 100 g of manganese carbonate concentrate and add it to an acid-resistant reaction vessel. Add 425 g of deionized water and stir and disperse at 300 r / min for 30 min to obtain manganese carbonate slurry. Add 62.5 g of 98% sulfuric acid at 300 r / min over 20 min. Control the material temperature not to exceed 60℃ during the addition process. The addition is then completed. The mixture was stirred for another 20 minutes, then heated to 80°C and stirred at 300 r / min for 3 hours. After the reaction was complete, it was cooled to 40°C to obtain the leaching slurry. The leaching slurry was filtered under a pressure of 0.30 MPa, and the leaching residue was washed twice with 100 g of deionized water, using 50 g of deionized water each time. The filtrate and washing liquid were combined to obtain crude manganese sulfate leaching solution and leaching residue. The crude manganese sulfate leaching solution was prepared repeatedly under the same feed amount and operating conditions. The obtained crude manganese sulfate leaching solutions were combined and 1000 g was weighed for use in step S2.

[0031] Step S2: Transfer 1000g of crude manganese sulfate leaching solution to a reaction vessel, stir at 300r / min and heat to 60℃, add 6.0g of 25% ammonia water to adjust the pH to 4.0, add 1.65g of manganese dioxide powder, and continue stirring at 60℃, pH 4.0 and 300r / min for 45min; add 8.0g of 25% ammonia water to adjust the pH to 5.4, and continue stirring at 60℃ and 300r / min for 40min; filter the reaction solution under suction at -0.08MPa, wash the iron-aluminum slag with 50g of deionized water, combine the filtrate and washing liquid to obtain the first purified filtrate and iron-aluminum slag; transfer the first purified filtrate to a reaction vessel, stir at 300r / min and cool to 40℃, add 1.4g of sodium sulfide, and add 1.5g of ammonia containing 0. 15g of sulfuric acid was dissolved in an aqueous solution, and the pH was adjusted to 5.2. The solution was stirred for 30 minutes at 40℃ and 300 rpm. The reaction solution was filtered under vacuum at -0.08 MPa, and the metal sulfide precipitate was washed with 30g of deionized water. The filtrate and washing solution were combined to obtain a second purified filtrate and a metal sulfide precipitate. 1.0g of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth was added to the second purified filtrate, and the solution was stirred for 50 minutes at 40℃ and 300 rpm. The solution was then filtered under vacuum at -0.08 MPa and then finely filtered using a filter medium with a pore size of 1μm to obtain a deeply purified manganese sulfate solution. Step S2 was repeated with the same feed amount and operating conditions. The resulting deeply purified manganese sulfate solutions were combined, and the manganese ion concentration was adjusted to 35.0g / L with deionized water. 1000g of this solution was weighed for step S3.

[0032] Step S3: Transfer 1000g of deeply purified manganese sulfate solution to an electrolyte preparation container, stir at 300r / min, add 125g of ammonium sulfate, stir for 20min, then add 0.25g of ammonium sulfite, and continue stirring for 10min; add 6.0g of 25% ammonia water, adjust the pH to 6.8, and continue stirring at 25℃ and 300r / min for 30min. Perform precision filtration using a filter medium with a pore size of 1μm to obtain the manganese sulfate electrolyte.

[0033] Step S4: A dual-chamber polypropylene diaphragm electrolytic cell is used. The polypropylene diaphragm has a thickness of 1.0 mm and an average pore size of 0.10 μm. A 304 stainless steel plate is used as the cathode, and a lead-silver alloy plate with a silver mass fraction of 0.6% is used as the anode. The effective immersion area of ​​both the cathode and anode plates is 0.0020 m². The cathode and anode plates are arranged parallel to each other with a spacing of 30 mm. Before electrolysis, the stainless steel plate is polished with 800-grit sandpaper, immersed in 100 g of sulfuric acid solution containing 5 g of sulfuric acid for 2 min, and then rinsed with 100 g of deionized water. Manganese sulfate electrolyte is added to the cathode and anode chambers respectively, with 500 g of electrolyte in each chamber. The anolyte and cathode solution were circulated independently at a flow rate of 100 mL / min. Electrolysis was performed using a constant current method with a current of 0.77 A, corresponding to a cathode current density of 385 A / m². The electrolysis temperature was controlled at 39 °C, the stable voltage at 4.85 V, and the electrolysis time at 21 h. No manganese sulfate electrolyte was added or the pH was adjusted during the electrolysis process. After electrolysis, the power was cut off, the cathode plate was removed, and 100 g of deionized water was used to evenly rinse the cathode plate. The cathode plate was then dried at 60 °C for 2 h. After cooling to 25 °C, the metallic manganese layer on the surface of the cathode plate was peeled off, the metallic manganese layer was broken up, and sieved through a sieve with a mesh size of 5 mm to obtain electrolytic manganese.

[0034] Preparation steps of tannic acid-modified crosslinked polyethyleneimine diatomaceous earth:

[0035] Step A1: Weigh 100g of diatomaceous earth filter aid and add it to an acid-resistant reactor. Add 45g of 98% sulfuric acid and 555g of deionized water. Stir and disperse at 300r / min for 30min. Heat to 72.5℃ and react at 72.5℃ and 300r / min for 3h. After the reaction is complete, stop heating, continue stirring and cool to 25℃ to obtain acid-washed diatomaceous earth slurry. Filter the acid-washed diatomaceous earth slurry at -0.08MPa. Wash the obtained filter cake with deionized water in two stages, adding 200g of deionized water each time. Redisperse the filter cake for 5min and then filter again until the pH of the final washing solution is 6.5 and the conductivity is 180μS / cm. A total of 600g of deionized water is used to obtain acid-washed activated diatomaceous earth filter cake.

[0036] Step A2: Based on the solid content measured after drying to constant weight at 105℃, weigh 100g of acid-washed activated diatomaceous earth filter cake (dry basis) and add it to the reactor. Add 700g of deionized water and stir at 300r / min for 30min. Add 11.5g of a 50% (w / w) branched polyethyleneimine aqueous solution containing 5.75g of branched polyethyleneimine. Continue stirring for 20min. The pH of the reaction system is measured to be 10.8. Without adding any acid or alkali adjuster, raise the temperature to 50℃ and react at 50℃ and 300r / min for 3h. After the reaction is complete, cool to 25℃ to obtain polyethyleneimine-loaded diatomaceous earth slurry. Filter the polyethyleneimine-loaded diatomaceous earth slurry at -0.08MPa. Wash the filter cake with deionized water several times, adding 200g of deionized water each time and redispersing for 5min. Use a total of 400g of deionized water to obtain polyethyleneimine-loaded diatomaceous earth filter cake.

[0037] Step A3: Weigh 100g of polyethyleneimine-loaded diatomaceous earth filter cake according to dry weight and add it to the reactor. Add 600g of deionized water and stir at 300r / min for 20min. Add 3.5g of 50% glutaraldehyde aqueous solution, which contains 1.75g ​​of glutaraldehyde. Continue stirring for 20min. The pH of the reaction system is measured to be 8.1. Without adding any acid-base adjuster, raise the temperature to 45℃ and react at 300r / min for 2.5h. After the reaction is completed, cool to 25℃ to obtain the crosslinking reaction product. Filter the crosslinking reaction product under -0.08MPa. Wash the filter cake with deionized water several times, adding 200g of deionized water each time and redispersing for 5min. A total of 400g of deionized water is used to obtain the glutaraldehyde crosslinked polyethyleneimine diatomaceous earth filter cake.

[0038] Step A4: Weigh 100g of glutaraldehyde-crosslinked polyethyleneimine diatomaceous earth filter cake (based on dry weight) and add it to the reactor. Add 600g of deionized water and stir at 300 rpm for 20 min. Add 7.5g of tannic acid and stir for 10 min. Then add 3.0g of sodium carbonate and continue stirring for 20 min. The pH of the reaction system is measured to be 8.3. Use a gas distributor located at the bottom of the reactor to continuously introduce air at a flow rate of 0.20 L / min. Raise the temperature to 40℃ and stir at 300 rpm for 4 h. After the reaction is complete, stop introducing air. The product was air-cooled to 25°C to obtain the functionalized reaction product. The functionalized reaction product was filtered under vacuum at -0.08 MPa, and the obtained solid product was washed with deionized water in two steps. Each time, 200 g of deionized water was added and the product was redispersed for 5 min. A total of 600 g of deionized water was used. The pH of the final washing solution was 6.8 and the conductivity was 190 μS / cm. The washed solid product was vacuum dried at 70°C and -0.08 MPa to constant weight. After cooling to 25°C, it was pulverized and passed through a sieve with a mesh size of 150 μm. The sieve residue was collected to obtain tannic acid modified cross-linked polyethyleneimine diatomaceous earth.

[0039] Example 2

[0040] The difference between this embodiment and Embodiment 1 is that this embodiment provides a process for preparing electrolytic manganese, the steps of which include:

[0041] Step S1: Select manganese carbonate concentrate with a manganese mass fraction of 25.0%, an iron mass fraction of 3.5%, an aluminum mass fraction of 1.5%, and a particle size D90 not greater than 150 μm. Weigh 95 g of manganese carbonate concentrate and add it to a reaction vessel. Add 350 g of deionized water and stir at 300 r / min for 30 min to obtain manganese carbonate slurry. Add 45 g of 98% sulfuric acid within 20 min. After the addition is complete, continue stirring for 20 min. Raise the temperature to 75℃ and stir at 300 r / min for 3 h. After cooling to 40℃, filter under pressure at 0.30 MPa. Wash the leaching residue twice with 100 g of deionized water. Combine the filtrate and washing liquid to obtain crude manganese sulfate leachate. Repeat the preparation under the same feed amount and operating conditions. Combine and weigh 1000 g of crude manganese sulfate leachate for step S2.

[0042] Step S2: Heat 1000g of crude manganese sulfate leaching solution to 55℃, add 8.0g of 25% ammonia water to adjust the pH to 3.5, add 0.8g of manganese dioxide powder, and stir at 55℃ and 300r / min for 45min; continue to add 10.0g of 25% ammonia water to adjust the pH to 5.2, stir at 55℃ for 40min, then filter under vacuum at -0.08MPa, wash the iron and aluminum slag with 50g of deionized water to obtain the first purified filtrate; cool the first purified filtrate to 35℃, add 0.8g of sodium sulfide, and add 0.8g of ammonia containing 0.08% manganese dioxide powder. A sulfuric acid aqueous solution of g sulfuric acid was prepared, and the pH was adjusted to 5.0. The solution was stirred at 35°C and 300 r / min for 30 min, then filtered and the metal sulfide precipitate was washed with 30 g of deionized water to obtain a second purified filtrate. 0.5 g of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth was added, and the solution was stirred at 35°C and 300 r / min for 50 min. The solution was then filtered and subjected to a 1 μm precision filtration to obtain a deeply purified manganese sulfate solution. The purification was repeated under the same conditions, and the resulting deeply purified manganese sulfate solutions were combined. The manganese ion concentration was adjusted to 32.0 g / L with deionized water, and 1000 g of the solution was weighed for step S3.

[0043] Step S3: Add 1000g of deeply purified manganese sulfate solution to the electrolyte preparation container, stir at 300r / min, add 110g of ammonium sulfate, stir for 20min, add 0.15g of ammonium sulfite, continue stirring for 10min, add 4.0g of 25% ammonia water, adjust the pH to 6.6, stir at 25℃ for 30min, and perform 1μm precision filtration to obtain manganese sulfate electrolyte;

[0044] Step S4: A double-chamber polypropylene diaphragm electrolytic cell with the same structure as in Example 1, a 304 stainless steel cathode, and a lead-silver alloy anode are used. The effective immersion area of ​​both the cathode and anode plates is 0.0020 m², and the electrode spacing is 30 mm. 500 g of manganese sulfate electrolyte is added to each chamber, and the cathode and anode solutions are circulated at 100 mL / min. Electrolysis is performed using a constant current method with a current of 0.70 A, corresponding to a cathode current density of 350 A / m². The electrolysis temperature is controlled at 36 °C, the stable voltage is 4.5 V, and the electrolysis is carried out for 18 h. After electrolysis, the cathode plate is rinsed with 100 g of deionized water, dried at 60 °C for 2 h, the metallic manganese layer is peeled off, crushed, and sieved through a 5 mm mesh to obtain electrolytic manganese.

[0045] Preparation steps of tannic acid-modified crosslinked polyethyleneimine diatomaceous earth:

[0046] Step A1: Weigh 95g of diatomaceous earth filter aid and add it to an acid-resistant reactor. Add 30g of 98% sulfuric acid and 470g of deionized water. Stir and disperse at 300r / min for 30min. Heat to 65℃ and react at 65℃ and 300r / min for 2h. After the reaction is complete, cool to 25℃ to obtain acid-washed diatomaceous earth slurry. Filter the acid-washed diatomaceous earth slurry under -0.08MPa. Wash the filter cake with deionized water in two stages, adding 200g of deionized water each time and redispersing for 5min. A total of 600g of deionized water is used. The pH of the final washing solution is 6.3 and the conductivity is 190μS / cm, resulting in acid-washed activated diatomaceous earth filter cake.

[0047] Step A2: Based on dry weight, weigh 95g of acid-washed and activated diatomaceous earth filter cake and add it to the reactor. Add 600g of deionized water and stir at 300r / min for 30min. Add 8.0g of 50% (w / w) branched polyethyleneimine aqueous solution, which contains 4.0g of branched polyethyleneimine. Continue stirring for 20min. The pH of the reaction system is measured to be 10.6. Without adding any acid or base adjuster, raise the temperature to 45℃ and react at 45℃ and 300r / min for 2h. After cooling to 25℃, filter under vacuum at -0.08MPa. Wash the filter cake twice with 400g of deionized water to obtain polyethyleneimine-supported diatomaceous earth filter cake.

[0048] Step A3: Based on dry weight, weigh 95g of polyethyleneimine-loaded diatomaceous earth filter cake and add it to the reactor. Add 500g of deionized water and stir at 300r / min for 20min. Add 2.0g of 50% glutaraldehyde aqueous solution, which contains 1.0g of glutaraldehyde. Continue stirring for 20min. The pH of the reaction system is measured to be 8.0. Without adding any acid-base adjuster, raise the temperature to 40℃ and react at 40℃ and 300r / min for 2h. After cooling to 25℃, filter under vacuum at -0.08MPa. Wash the filter cake twice with 400g of deionized water to obtain glutaraldehyde crosslinked polyethyleneimine diatomaceous earth filter cake.

[0049] Step A4: Weigh 95g of glutaraldehyde-crosslinked polyethyleneimine diatomaceous earth filter cake (based on dry weight) and add it to the reactor. Add 500g of deionized water and stir at 300 rpm for 20 minutes. Add 5.0g of tannic acid and stir for 10 minutes. Then add 2.0g of sodium carbonate and continue stirring for 20 minutes until the pH of the reaction system reaches 8.0. Continuously introduce air at a flow rate of 0.20L / min and raise the temperature to 35℃. Maintain the reaction at 35℃ and 300 rpm. The reaction was stirred for 3 hours. After the reaction was completed, the air supply was stopped and the mixture was cooled to 25°C. The functionalized reaction product was filtered at -0.08 MPa and washed three times with 600 g of deionized water. The pH of the final washing solution was 6.7 and the conductivity was 185 μS / cm. The solid product was vacuum dried at 70°C and -0.08 MPa to constant weight, pulverized, and passed through a sieve with a mesh size of 150 μm to obtain tannic acid modified cross-linked polyethyleneimine diatomaceous earth.

[0050] Example 3

[0051] The difference between this embodiment and Embodiment 1 is that this embodiment provides a process for preparing electrolytic manganese, the steps of which include:

[0052] Step S1: Select manganese carbonate concentrate with a manganese mass fraction of 41.5%, an iron mass fraction of 2.0%, an aluminum mass fraction of 0.8%, and a particle size D90 not greater than 150 μm. Weigh 105 g of manganese carbonate concentrate and add it to a reaction vessel. Add 500 g of deionized water and stir at 300 r / min for 30 min. Add 80 g of 98% sulfuric acid over 20 min. After the addition is complete, stir for 20 min. Raise the temperature to 85℃ and react at 85℃ and 300 r / min for 3 h. After cooling to 40℃, filter under pressure at 0.30 MPa. Wash the leaching residue twice with 100 g of deionized water to obtain crude manganese sulfate leachate. Repeat the preparation under the same conditions and combine 1000 g of crude manganese sulfate leachate for step S2.

[0053] Step S2: Heat 1000g of crude manganese sulfate leachate to 65℃, add 5.0g of 25% ammonia solution to adjust the pH to 4.5, add 2.5g of manganese dioxide powder, and stir at 65℃ and 300r / min for 45min; continue to add 7.0g of 25% ammonia solution to adjust the pH to 5.6, stir at 65℃ for 40min, filter, and wash the iron-aluminum slag with 50g of deionized water to obtain the first purified filtrate; cool the first purified filtrate to 45℃, add 2.0g of sodium sulfide, and add 2.2g of sulfuric acid containing 0.22g of sulfuric acid. The aqueous solution was adjusted to pH 5.4, stirred at 45℃ and 300 rpm for 30 min, filtered, and the metal sulfide precipitate was washed with 30 g of deionized water to obtain the second purified filtrate. 1.5 g of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth was added, stirred at 45℃ and 300 rpm for 50 min, filtered, and then subjected to 1 μm precision filtration to obtain a deeply purified manganese sulfate solution. The purification was repeated under the same conditions, and the resulting deeply purified manganese sulfate solutions were combined. The manganese ion concentration was adjusted to 38.0 g / L with deionized water, and 1000 g was weighed for step S3.

[0054] Step S3: Add 1000g of deeply purified manganese sulfate solution to the electrolyte preparation container, stir at 300r / min, add 140g of ammonium sulfate, stir for 20min, add 0.35g of ammonium sulfite, continue stirring for 10min, add 8.0g of 25% ammonia water, adjust the pH to 7.0, stir at 25℃ for 30min, and perform 1μm precision filtration to obtain manganese sulfate electrolyte;

[0055] Step S4: A double-chamber polypropylene diaphragm electrolytic cell with the same structure as in Example 1, a 304 stainless steel cathode, and a lead-silver alloy anode are used. The effective immersion area of ​​both the cathode and anode plates is 0.0020 m², and the electrode spacing is 30 mm. 500 g of manganese sulfate electrolyte is added to each chamber, and the cathode and anode solutions are circulated at 100 mL / min. Electrolysis is performed using a constant current method with a current of 0.84 A, corresponding to a cathode current density of 420 A / m². The electrolysis temperature is controlled at 42 °C, the stable voltage is 5.2 V, and the electrolysis is carried out for 24 h. After electrolysis, the cathode plate is rinsed with 100 g of deionized water, dried at 60 °C for 2 h, the metallic manganese layer is peeled off, crushed, and sieved through a 5 mm mesh to obtain electrolytic manganese.

[0056] Preparation steps of tannic acid-modified crosslinked polyethyleneimine diatomaceous earth:

[0057] Step A1: Weigh 105g of diatomaceous earth filter aid and add it to an acid-resistant reactor. Add 60g of 98% sulfuric acid and 640g of deionized water. Stir and disperse at 300r / min for 30min. Heat to 80℃ and react at 80℃ and 300r / min for 4h. After the reaction is complete, cool to 25℃. Filter the acid-washed diatomaceous earth slurry under -0.08MPa. Wash the filter cake three times with 600g of deionized water. The pH of the final washing solution is 6.6 and the conductivity is 175μS / cm, thus obtaining the acid-washed activated diatomaceous earth filter cake.

[0058] Step A2: Based on dry weight, weigh 105g of acid-washed and activated diatomaceous earth filter cake and add it to the reactor. Add 800g of deionized water and stir at 300r / min for 30min. Add 15.0g of a 50% (w / w) branched polyethyleneimine aqueous solution containing 7.5g of branched polyethyleneimine. After stirring for 20min, the pH is measured to be 11.0. Without adding any additional acid or alkali adjuster, raise the temperature to 55℃ and react at 55℃ and 300r / min for 4h. After cooling to 25℃, filter the filter cake and wash it twice with 400g of deionized water to obtain polyethyleneimine-loaded diatomaceous earth filter cake.

[0059] Step A3: Based on dry weight, weigh 105g of polyethyleneimine-loaded diatomaceous earth filter cake and add it to the reactor. Add 700g of deionized water and stir at 300r / min for 20min. Add 5.0g of 50% glutaraldehyde aqueous solution, which contains 2.5g of glutaraldehyde. Continue stirring for 20min. The pH is measured to be 8.3. Raise the temperature to 50℃ and react at 300r / min for 3h. After cooling to 25℃, filter the filter cake. Wash the filter cake twice with 400g of deionized water to obtain glutaraldehyde crosslinked polyethyleneimine diatomaceous earth filter cake.

[0060] Step A4: Weigh 105g of glutaraldehyde-crosslinked polyethyleneimine diatomaceous earth filter cake according to dry basis and add it to the reactor. Add 700g of deionized water and stir at 300r / min for 20min. Add 10.0g of tannic acid and stir for 10min. Then add 4.0g of sodium carbonate and continue stirring for 20min to bring the pH to 8.6. Purge air at 0.20L / min and heat to 45℃. Stir at 300r / min for 5h. After cooling, filter and wash three times with 600g of deionized water. The pH of the final wash solution is 6.9 and the conductivity is 195μS / cm. Place the solid product in a vacuum dryer at 70℃ and -0.08MPa to constant weight, pulverize and pass through a sieve with a mesh size of 150μm to obtain tannic acid-modified crosslinked polyethyleneimine diatomaceous earth.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that tannic acid-modified crosslinked polyethyleneimine diatomaceous earth is not added in step S2, while the rest is the same as in Example 1.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that steps A3 and A4 are not performed in the preparation process of tannic acid modified crosslinked polyethyleneimine diatomaceous earth; the rest is the same as in Example 1.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that step A4 is not performed in the preparation process of tannic acid modified crosslinked polyethyleneimine diatomaceous earth; the rest is the same as in Example 1.

[0067] The performance of the electrolytic manganese preparation processes provided in the above embodiments and comparative examples was tested using the following methods:

[0068] Electrolytic manganese products prepared in Examples 1, 2, 3, 1, 2, and 3 were used as test samples. Samples were taken from no less than three locations in each group. The samples were mixed evenly and then reduced in size. Representative samples were tested. Before testing, the samples were dried at 105°C to constant weight. After cooling, they were pulverized using a grinding device so that all samples passed through a 0.125 mm sieve. After being mixed evenly, the samples were stored in a dry and sealed container for later use.

[0069] The manganese content test method is as follows: accurately weigh 0.5000g of the sample and place it in a beaker. Add hydrochloric acid and nitric acid for acid dissolution treatment, heat to completely dissolve the sample, cool, transfer to a volumetric flask and make up to volume. Take a certain amount of the test solution for oxidation treatment to convert the manganese element into a stable determination state. Determine the manganese content by potentiometric titration with a standard titrant. Calculate the manganese content based on the titration consumption, sample mass, and blank test results. The result is expressed as a mass fraction (%).

[0070] The method for testing iron content is as follows: accurately weigh 0.5000g of sample, dissolve it in a mixture of hydrochloric acid and nitric acid, filter to remove insoluble matter, transfer the filtrate to a volumetric flask and make up to volume, take a certain amount of test solution, add a reducing agent to reduce ferrous ions to ferrous ions, add a colorimetric reagent to the buffer system to form a stable colored complex of ferrous ions, measure the absorbance at a wavelength of 510nm, calculate the iron content according to the iron standard working curve, and express the result as a mass fraction (%).

[0071] The copper content test method is as follows: accurately weigh 0.5000g of sample, add hydrochloric acid and nitric acid for digestion treatment to ensure that copper element fully enters the solution system, cool, filter and make up to volume, and use air-acetylene flame atomic absorption spectrometry for detection. Measure the absorbance at the characteristic absorption wavelength of copper element, establish a calibration curve based on copper standard solution, and calculate the copper content in the sample by the concentration corresponding to the absorbance. The result is expressed as mass fraction (%).

[0072] The method for testing nickel content is as follows: accurately weigh 0.5000g of sample, treat with acid, transfer to a volumetric flask and make up to volume. Use air-acetylene flame atomic absorption spectrometry to detect the nickel content. Measure the absorbance at the characteristic absorption wavelength of nickel. Establish a calibration curve using a nickel standard solution. Calculate the nickel content based on the absorbance of the test solution. The result is expressed as a mass fraction (%).

[0073] The cathode current efficiency test method is as follows: Before the electrolysis test begins, the dry and clean stainless steel plate is weighed and the initial mass of the cathode plate is recorded. The manganese sulfate electrolyte prepared in the corresponding examples and comparative examples is added to the polypropylene diaphragm electrolytic cell, and electrolysis is carried out according to the corresponding process conditions. After the electrolysis is completed, the cathode plate is removed, and the residual electrolyte on the surface of the cathode plate is rinsed with deionized water. After drying, the manganese metal layer is peeled off and the actual mass of deposited manganese metal is weighed. At the same time, the current value and electrolysis time during the electrolysis process are recorded. The cathode current efficiency is calculated based on the ratio of the actual mass of deposited manganese metal to the theoretical mass of deposited manganese metal, and the result is expressed as a percentage (%).

[0074] The DC power consumption test method is as follows: During the electrolysis process, the working current, voltage, and duration of the electrolytic cell are continuously recorded. The total power consumption is calculated based on the current, voltage, and time at each time point during the electrolysis process. The total power consumption is divided by the mass of dried electrolytic manganese product obtained within the corresponding time period to obtain the DC power consumed per unit mass of electrolytic manganese product. The result is expressed in kW·h / t. All the above test items use the same sampling method and test conditions. Each group of samples is tested in parallel three times, and the arithmetic mean of the three test results is taken as the final test result.

[0075] The performance test data above are shown in Table 1.

[0076] Table 1: Performance Test Results

[0077]

[0078] As can be seen from the above, the electrolytic manganese products prepared in Examples 1-3 have higher manganese content, lower iron, copper, and nickel impurity content, higher cathode current efficiency, and lower DC power consumption compared to Comparative Examples 1-3. This indicates that by introducing tannic acid-modified cross-linked polyethyleneimine diatomaceous earth into the purification process of manganese sulfate leaching solution, the purification system has a stronger selective adsorption capacity for residual iron ions, copper ions, nickel ions, and other impurity ions, reducing the cumulative concentration of impurity ions after entering the electrolyte, reducing the competitive reduction of impurity ions on the cathode surface, and the resulting cathode passivation phenomenon, thereby improving the stability of the electrolytic manganese deposition process.

[0079] Meanwhile, after iron removal by manganese dioxide powder oxidation, heavy metal removal by sodium sulfide precipitation, and deep adsorption synergistic treatment by tannic acid-modified cross-linked polyethyleneimine diatomaceous earth, the content of impurity elements affecting the purity of manganese deposition in the electrolytes obtained in Examples 1-3 was significantly reduced, resulting in a final electrolytic manganese content of 99.86-99.93%, which is significantly higher than the 99.51-99.76% of Comparative Examples 1-3. Among them, the manganese content in Example 3 reached the highest of 99.93%, indicating that increasing the amount of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth within the scope of the claims can further enhance the deep purification effect.

[0080] In Examples 1-3, the iron content was reduced to 0.004-0.009%, the copper content to 0.0004-0.0010%, and the nickel content to 0.0005-0.0012%. Compared with Comparative Examples 1 and 2, which did not use tannic acid-modified cross-linked polyethyleneimine diatomaceous earth, the contents of iron, copper, and nickel impurities decreased significantly. This indicates that the nitrogen-containing coordination structure provided by polyethyleneimine and the polyhydroxy complex structure provided by tannic acid in the tannic acid-modified cross-linked polyethyleneimine diatomaceous earth can jointly enhance the adsorption and fixation of transition metal impurity ions, effectively solving the problem of insufficient product purity caused by insufficient purification of leaching solution in the existing electrolytic manganese preparation process.

[0081] Furthermore, the cathode current efficiency of Examples 1-3 reached 79.4-82.6%, which was significantly higher than that of Comparative Examples 1-3 (68.5-76.4%), and the DC power consumption was reduced to 5529-6202 kW·h / t, which was lower than that of Comparative Examples 1-3 (6314-7025 kW·h / t). This indicates that the manganese sulfate electrolyte after deep purification can reduce the influence of impurity ions on the cathode hydrogen evolution reaction and manganese deposition process, improve current utilization, and reduce ineffective power consumption.

[0082] Compared to Comparative Example 1, the removal of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth resulted in a decrease in the removal capacity of impurity ions, a reduction in the purity of electrolytic manganese, and an increase in power consumption. Compared to Comparative Example 2, the removal of both tannic acid-modified cross-linked polyethyleneimine diatomaceous earth and ammonium sulfite led to a decrease in the stability of the cathode polarization state during electrolysis, resulting in a further reduction in cathode current efficiency. Compared to Comparative Example 3, which used unmodified diatomaceous earth to replace tannic acid-modified cross-linked polyethyleneimine diatomaceous earth, the lack of functional adsorption structures formed by polyethyleneimine and tannic acid resulted in insufficient removal capacity for trace impurities such as copper and nickel, thus the product purity and electrolysis efficiency were lower than those of Examples 1-3.

[0083] In summary, this invention solves the technical problems of insufficient impurity removal, low electrolysis efficiency, and high energy consumption in the existing electrolytic manganese preparation process by combining the deep purification technology of tannic acid-modified cross-linked polyethyleneimine diatomite with the electrolysis process of manganese sulfate. This results in the preparation of high-purity, high-current-efficiency, and low-energy-consumption electrolytic manganese products.

Claims

1. A process for preparing electrolytic manganese, characterized in that, Includes the following steps: S1. By weight, add 95-105 parts of manganese carbonate concentrate to a reaction vessel, add 350-500 parts of deionized water, stir and disperse to obtain manganese carbonate slurry; add 45-80 parts of sulfuric acid to the manganese carbonate slurry, heat and stir to obtain leaching slurry; filter the leaching slurry to obtain crude manganese sulfate leaching solution and leaching residue. S2. Transfer the crude manganese sulfate leaching solution to a reaction vessel, heat it, add 0.8-2.5 parts of manganese dioxide powder, and continue stirring at pH 3.5-4.5; add ammonia water, adjust the pH to 5.2-5.6, continue stirring, and filter to obtain the first purified filtrate and iron-aluminum slag; cool the first purified filtrate to 35-45℃, add 0.8-2.0 parts of sodium sulfide, adjust the pH to 5.0-5.4, continue stirring, and filter to obtain the second purified filtrate and metal sulfide precipitate; add 0.5-1.5 parts of tannic acid-modified cross-linked polyethyleneimine diatomaceous earth to the second purified filtrate, continue stirring, filter, and perform precision filtration to obtain a deeply purified manganese sulfate solution; S3. Transfer the deeply purified manganese sulfate solution to an electrolyte preparation container, add 110-140 parts ammonium sulfate and 0.15-0.35 parts ammonium sulfite; add ammonia water, adjust the pH, continue stirring, and filter precisely to obtain the manganese sulfate electrolyte. S4. The manganese sulfate electrolyte is transported to the polypropylene diaphragm electrolytic cell, with a stainless steel plate as the cathode and a lead-silver alloy plate as the anode, and electrolysis is performed. After electrolysis, the cathode plate is removed, rinsed with deionized water, dried, the manganese layer on the surface of the cathode plate is peeled off, crushed, and sieved.

2. The preparation process of electrolytic manganese according to claim 1, characterized in that, In step S1, the temperature is raised to 75-85℃.

3. The preparation process of electrolytic manganese according to claim 1, characterized in that, In step S2, the temperature is raised to 55-65℃.

4. The preparation process of electrolytic manganese according to claim 1, characterized in that, In step S3, adjust the pH to 6.6-7.

0.

5. The preparation process of electrolytic manganese according to claim 1, characterized in that, In step S4, the electrolysis time is 18-24 hours; the electrolysis temperature is 36-42℃; and the cathode current density is 350-420 A / m. 2 The electrolysis voltage is 4.5-5.2V.

6. The preparation process of electrolytic manganese according to any one of claims 1-5, characterized in that, The preparation steps of the tannic acid-modified crosslinked polyethyleneimine diatomaceous earth include: A1. By weight, add 95-105 parts of diatomaceous earth filter aid to the reactor, add 30-60 parts of sulfuric acid and 470-640 parts of deionized water, stir and disperse, and heat to 65-80℃ to react and obtain acid-washed diatomaceous earth slurry; filter the acid-washed diatomaceous earth slurry to obtain filter cake; wash the filter cake with deionized water to obtain acid-washed activated diatomaceous earth filter cake; A2. Add 95-105 parts of acid-washed and activated diatomaceous earth filter cake to the reactor, add 600-800 parts of deionized water, and stir to disperse; add 8-15 parts of branched polyethyleneimine aqueous solution, and heat to 45-55℃ to react, to obtain polyethyleneimine-loaded diatomaceous earth slurry; filter the polyethyleneimine-loaded diatomaceous earth slurry, wash with deionized water, to obtain polyethyleneimine-loaded diatomaceous earth filter cake; A3. Add 95-105 parts of polyethyleneimine-supported diatomaceous earth filter cake to a reactor, add 500-700 parts of deionized water and an aqueous solution containing 1.0-2.5 parts of glutaraldehyde, heat to 40-50℃ and react to obtain the cross-linking reaction product; filter the cross-linking reaction product and wash it with deionized water to obtain glutaraldehyde-crosslinked polyethyleneimine diatomaceous earth filter cake. A4. Add 95-105 parts of glutaraldehyde cross-linked polyethyleneimine diatomaceous earth filter cake to the reactor, add 500-700 parts of deionized water, 5-10 parts of tannic acid and 2-4 parts of sodium carbonate, adjust the pH to 8.0-8.6, introduce air, and stir the reaction at 35-45℃ to obtain the functionalized reaction product; filter the functionalized reaction product to obtain the solid product; wash the solid product with deionized water, dry, pulverize and sieve.

7. The preparation process of electrolytic manganese according to claim 6, characterized in that, In step A1, the reaction time is 2-4 hours after heating to 65-80℃.

8. The preparation process of electrolytic manganese according to claim 6, characterized in that, In step A2, the reaction time is 2-4 hours after heating to 45-55℃.

9. The preparation process of electrolytic manganese according to claim 6, characterized in that, In step A3, the reaction time is 2-3 hours after heating to 40-50℃.

10. The preparation process of electrolytic manganese according to claim 6, characterized in that, In step A4, the reaction is stirred at 35-45℃ for 3-5 hours.

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