Method for recovering electrolytic manganese industrial waste salt

Abstract

The invention provides a method for recycling electrolytic manganese industrial waste salt, which comprises the following steps: mixing the electrolytic manganese industrial waste salt with calcium oxide, and carrying out first heat treatment and second heat treatment to obtain a treated product; the treated product is subjected to water leaching and solid-liquid separation, and first leaching residues and first leaching liquid are obtained; evaporating and crystallizing the first leachate to obtain a magnesium sulfate product; the first leaching residues and ammonium sulfate are mixed and subjected to ball milling, and a mixture is obtained; roasting the mixture to obtain a roasted product; after the roasted product is subjected to water leaching, second leaching residues and second leaching liquid are obtained; evaporating and crystallizing the second leaching solution to obtain a manganese sulfate product; the second leaching residues are subjected to water washing, solid-liquid separation and drying, and industrial gypsum is obtained. The method is simple in technological process, mild in technological condition, low in energy consumption and low in needed cost, the environmental protection pressure of storage of the electrolytic manganese metal industrial waste salt can be eliminated, efficient recycling of Mg, Mn, NH4 < + > / NH3 and S resources in the electrolytic manganese metal industrial waste salt and recycling of Ca can be achieved, and the purity of recycled manganese sulfate reaches the battery grade.

Description

Technical Field

[0001] The invention belongs to the field of metallurgical solid waste treatment, and in particular relates to a method for recovering electrolytic manganese industrial waste salt by segmented molten salt treatment. Background Art

[0002] As a traditional high-pollution industry, electrolytic manganese production generates a large amount of electrolytic manganese industrial waste salt during the manufacturing process. According to statistics, for every ton of electrolytic manganese produced, 1 to 2 tons of waste salt are generated. China produces more than 1 million tons of electrolytic manganese industrial waste salt every year. The ore raw materials for electrolytic manganese production are accompanied by many Mg and Ca-containing minerals. These minerals dissolve during sulfuric acid leaching, and the released Mg and Ca ions enter the leachate along with the Mn ions. As the electrolytic manganese anode liquid continues to circulate, Mg and Ca are continuously enriched in the solution. When Mg and Ca in the solution system reach a certain concentration, they will be affected by temperature and crystallize and precipitate during the static sedimentation and electrolysis process of electrolytic manganese production. The electrolytic manganese mother liquor is an ammonium sulfate salt aqueous solution system, and the ammonium sulfate concentration is maintained at 90-120g / L. Therefore, Ca and Mg crystals are precipitated simultaneously with some Mn and NH4 + The waste salt from electrolytic manganese industry contains Mg, Mn, NH4 + / NH3, Ca sulfate, the main phases are hexahydrate ammonia magnesium sulfate, hexahydrate ammonium manganese sulfate, ammonium manganese sulfate, epsom salt, hemihydrate gypsum, mixed with a small amount of mud and sand.

[0003] At present, the electrolytic manganese industry waste salt is mainly landfilled together with the electrolytic manganese slag. This disposal method increases the amount of electrolytic manganese slag and increases the soluble salt content in the electrolytic manganese slag, making it more difficult to treat harmlessly. A large amount of soluble salts are washed into the leachate of the slag yard with rainwater, increasing the amount of leachate and its salt concentration, and increasing the risk of pollution to the surrounding soil and water. At the same time, electrolytic manganese industry waste salt can be used as an important Mg, Mn, NH4 + / NH3, Ca, S secondary resources, with great prospects for recycling. Summary of the invention

[0004] In response to the above technical problems, the present application provides a method for recycling electrolytic manganese industrial waste salt.

[0005] To achieve the above objectives, this application proposes the following technical solutions: A method for recovering waste salt from electrolytic manganese industry is provided, comprising: S1. After mixing electrolytic manganese industrial waste salt with calcium oxide, first heating it to a first temperature for a first heat treatment, and then heating it to a second temperature for a second heat treatment to obtain a treated product; the first temperature is lower than the second temperature; the second temperature is 500-700° C.; S2, subjecting the treated product to water leaching and solid-liquid separation to obtain a first leaching residue and a first leaching liquid; the first leaching liquid is evaporated and crystallized to obtain a magnesium sulfate product; S3, after washing and drying the first leaching residue, mixing it with ammonium sulfate and ball milling it to obtain a mixture; the mixture is roasted to obtain a roasted product; S4, water-leaching the roasted product and performing solid-liquid separation to obtain a second leaching residue and a second leaching liquid; the second leaching liquid is evaporated and crystallized to obtain a manganese sulfate product; S5. The second leaching residue is washed with water, then solid-liquid separation and drying are performed to obtain industrial gypsum.

[0006] Furthermore, the calcium oxide and the electrolytic manganese industrial waste salt are mixed in a molar ratio of CaO:(2NH4 + +Mn) = 1:1 to 1.5:1, preferably 1:1 to 1.3:1.

[0007] Furthermore, in step S1, the first temperature is 300-500°C, preferably 400-500°C; the time of the first heat treatment is 20-180min, preferably 45-90min; the atmosphere of the first heat treatment is an oxygen-containing gas, and the oxygen partial pressure of the oxygen-containing gas is 21-100%.

[0008] Furthermore, in step S1, the second temperature is 600-700°C; the reaction time is 30-180 min, preferably 60-120 min; the atmosphere of the second heat treatment is an oxygen-containing gas, and the oxygen partial pressure of the oxygen-containing gas is 21-100%.

[0009] Furthermore, in step S2, the temperature of the water immersion treatment is 25-100°C; the time of the water immersion treatment is 10-60 min; the solid-liquid ratio of the water immersion treatment is 1:2-1:5 g / mL; and the leaching agent of the water immersion treatment is water.

[0010] Furthermore, in step S3, the number of water washing is 1 to 3 times; the temperature of the water washing is 25 to 100° C.; the slurry-solid ratio of the water washing is 2:1 to 5:1 mL / g; the stirring time of the water washing is 5 to 40 min; and the water washing liquid obtained after the water washing is returned to step S2 as a leaching agent for water immersion treatment.

[0011] Further, in step S3, the ammonium sulfate and the first leaching residue are mixed at a molar ratio of SO4 2- :Mn is in a ratio of 1:1 to 1.5:1.

[0012] Furthermore, in step S3, the calcination temperature is 300-550° C.; and the calcination time is 30-180 min.

[0013] Furthermore, the calcination atmosphere is an oxygen-containing gas atmosphere, and the oxygen partial pressure of the oxygen-containing gas is 21 to 100%.

[0014] Furthermore, in step S3, the ball-to-material mass ratio of the ball milling is 20:1 to 2.5:1, and the ball milling time is 30 to 120 minutes.

[0015] Furthermore, in step S4, the water immersion temperature is 25-100° C.; the water immersion time is 10-60 min; the solid-liquid ratio of the water immersion is 1:2-1:5 g / mL; and the leaching agent of the water immersion is water.

[0016] Furthermore, in step S5, the number of water washing is 1 to 3 times; the temperature of the water washing is 25 to 100° C.; the slurry-solid ratio of the water washing is 2:1 to 5:1 mL / g; the stirring time of the water washing is 5 to 40 min; and the washing liquid obtained after the water washing is returned to step S4 as a leaching agent for water immersion.

[0017] Furthermore, in step S1, the flue gas generated by the first heat treatment is absorbed by water to obtain an ammonia solution, or absorbed by a sulfuric acid solution to obtain ammonium sulfate through crystallization; The ammonium sulfate is returned to step S3 for use.

[0018] Furthermore, in step S4, the pH value of the second leachate is adjusted to 4.5-6.5 before evaporation and crystallization.

[0019] Furthermore, the manganese sulfate product is battery-grade manganese sulfate.

[0020] Furthermore, the magnesium sulfate product is industrial grade magnesium sulfate.

[0021] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: The method for recycling and treating electrolytic manganese metal industrial waste salt of the present application is simple in process, mild in process conditions, low in energy consumption, and low in cost, and can eliminate the environmental pressure of electrolytic manganese metal industrial waste salt storage, and can achieve the recovery of Mg, Mn, NH4 + / NH3, S resources and Ca are efficiently recovered, and the purity of the recovered manganese sulfate reaches battery grade.

[0022] The method for recycling and treating electrolytic manganese metal industrial waste salt can return all products except the product to the treatment system for reuse during the treatment process, does not generate secondary waste, is clean and environmentally friendly, reduces the environmental pressure of related enterprises while increasing economic benefits, and is suitable for large-scale industrial applications.

[0023] The method for recycling and treating electrolytic manganese metal industrial waste salt is optimized through process parameter optimization, and the obtained magnesium sulfate product can reach industrial grade, and the recovery rate of Mg and Mn is as high as more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The present invention is a process flow chart of the method for recovering electrolytic manganese industrial waste salt. DETAILED DESCRIPTION

[0026] The present invention provides a method for recovering waste salt from electrolytic manganese industry, comprising: S1. After mixing electrolytic manganese industrial waste salt with calcium oxide, the mixture is first heated to a first temperature for a first heat treatment, and then heated to a second temperature for a second heat treatment to obtain a treated product; the first temperature is lower than the second temperature; the second temperature is 500-700° C.; S2, subjecting the treated product to water leaching and solid-liquid separation to obtain a first leaching residue and a first leaching liquid; the first leaching liquid is evaporated and crystallized to obtain a magnesium sulfate product; S3, after washing and drying the first leaching residue, mixing it with ammonium sulfate and ball milling it to obtain a mixture; the mixture is roasted to obtain a roasted product; S4, water-leaching the roasted product and performing solid-liquid separation to obtain a second leaching residue and a second leaching liquid; the second leaching liquid is evaporated and crystallized to obtain a manganese sulfate product; S5. The second leaching residue is washed with water, then solid-liquid separation and drying are performed to obtain industrial gypsum.

[0027] In some preferred embodiments, the calcium oxide and the electrolytic manganese industrial waste salt are in a molar ratio of CaO: (2NH4 + +Mn) = 1:1 to 1.5:1, preferably 1:1 to 1.3:1, for example, 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, etc.

[0028] In some preferred embodiments, in step S1, the first temperature is 300-500°C, preferably 400-500°C, for example, 400°C, 420°C, 450°C, 480°C, 500°C; the time of the first heat treatment is 20-180min, preferably 45-90min, for example, 45min, 60min, 75min, 90min, etc.; the atmosphere of the first heat treatment is an oxygen-containing gas, and the oxygen partial pressure of the oxygen-containing gas is 21-100%.

[0029] In some preferred embodiments, in step S1, the second temperature is 600-700°C, for example, 600°C, 620°C, 650°C, 680°C, 700°C; the reaction time is 30-180min, preferably 60-120min, for example, 60min, 75min, 90min, 105min, 120min, etc.; the atmosphere of the second heat treatment is an oxygen-containing gas, and the oxygen partial pressure of the oxygen-containing gas is 21-100%.

[0030] In some preferred embodiments, in step S2, the temperature of the water immersion treatment is 25-100°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the time of the water immersion treatment is 10-60min, for example, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.; the solid-liquid ratio of the water immersion treatment is 1:2-1:5g / mL, for example, 1:2g / mL, 1:2.5g / mL, 1:3g / mL, 1:3.5g / mL, 1:4g / mL, 1:4.5g / mL, 1:5g / mL, etc.; the leaching agent of the water immersion is water.

[0031] In some preferred embodiments, in step S3, the number of water washings is 1 to 3 times, for example, 1 time, 2 times, or 3 times; the water washing temperature is 25 to 100°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the liquid-to-solid ratio of the water washing is 2:1 to 5:1 mL / g, for example, 2:1 mL / g. g, 2.5:1mL / g, 3:1mL / g, 3.5:1mL / g, 4:1mL / g, 4.5:1mL / g, 5:1mL / g, etc.; the stirring time of the water washing is 5 to 40min, for example, 5min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, etc.; the washing liquid obtained after the water washing is returned to step S2 as the leaching agent for water immersion treatment.

[0032] In some preferred embodiments, in step S3, the ammonium sulfate and the first leaching residue are mixed at a molar ratio of SO4 2- :Mn is in a ratio of 1:1 to 1.5:1, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc.

[0033] In some preferred embodiments, in step S3, the calcination temperature is 300-550°C, preferably 400-500°C, for example, 400°C, 420°C, 450°C, 480°C, 500°C; the calcination time is 30-180min, preferably 60-120min, for example, 60min, 75min, 90min, 105min, 120min, etc.

[0034] In some embodiments, the calcination atmosphere is an oxygen-containing gas atmosphere, and the oxygen partial pressure of the oxygen-containing gas is 21 to 100%.

[0035] In some preferred embodiments, in step S3, the mass ratio of balls to materials in the ball milling is 20:1 to 2.5:1, for example, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, etc., and the time of the ball milling is 30 to 120 min, for example, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc.

[0036] In some preferred embodiments, in step S4, the water immersion temperature is 25-100°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the water immersion time is 10-60min, for example, 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.; the solid-liquid ratio of the water immersion is 1:2-1:5g / mL, for example, 1:2g / mL, 1:2.5g / mL, 1:3g / mL, 1:3.5g / mL, 1:4g / mL, 1:4.5g / mL, 1:5g / mL, etc.; the leaching agent of the water immersion is water.

[0037] In some preferred embodiments, in step S5, the number of water washings is 1 to 3 times, for example, 1 time, 2 times, or 3 times; the water washing temperature is 25 to 100°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the liquid-to-solid ratio of the water washing is 2:1 to 5:1 mL / g, for example, 2:1 mL / g. / g, 2.5:1mL / g, 3:1mL / g, 3.5:1mL / g, 4:1mL / g, 4.5:1mL / g, 5:1mL / g, etc.; the stirring time of the water washing is 5 to 40min, for example, 5min, 10min, 15min, 20min, 25min, 30min, 35min, 40min, etc.; the washing liquid obtained after the water washing is returned to step S4 as the leaching agent for water immersion.

[0038] In some preferred embodiments, in step S1, the flue gas generated by the first heat treatment is absorbed by water to obtain an ammonia solution, or absorbed by a sulfuric acid solution to obtain ammonium sulfate through crystallization; The ammonium sulfate is returned to step S3 for use.

[0039] In some preferred embodiments, in step S4, the pH value of the second leaching solution is adjusted to 4.5 to 6.5 before evaporation and crystallization, for example, adjusted to 4.5, 5, 5.5, 6, 6.5, etc.

[0040] In some preferred embodiments, the manganese sulfate product is battery-grade manganese sulfate.

[0041] In some preferred embodiments, the magnesium sulfate product is industrial grade magnesium sulfate.

[0042] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0043] Example 1 A method for recycling electrolytic manganese industrial waste salt by segmented molten salt treatment, the process flow chart is as follows Figure 1 As shown, the following steps are included: (1) The electrolytic manganese industrial waste salt and calcium oxide are mixed according to the molar ratio of CaO: (2NH4 + +Mn) = 1 mixed.

[0044] (2) The mixture obtained in step (1) is placed in a muffle furnace at 450° C. and reacted for 60 minutes to obtain a molten salt deamination product.

[0045] (3) The mixture obtained in step (2) is placed in a muffle furnace at 650° C. and reacted for 90 minutes to obtain a molten salt manganese oxide product.

[0046] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 30 minutes, and the leaching rate of Mg was 99.95%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0047] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product that meets the requirements of HG / T 2680-2017. The comprehensive recovery rate of magnesium is 99.5%.

[0048] (6) The leached residue obtained in step (4) was washed twice with water at a temperature of 50°C; the ratio of the slurry to solid was 2:1 mL / g; the stirring time was 20 min, and the residue was dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn = 1.1 are mixed and put into a ball mill with a ball-to-material ratio of 10:1 g / g and the ball milling time is 60 min.

[0049] (7) The mixture obtained in step (6) was placed in a muffle furnace at 500° C. for reaction for 120 min to obtain a reaction product.

[0050] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 25°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 99.32%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0051] (9) The manganese sulfate solution obtained in step (8) is adjusted to pH 6 using concentrated sulfuric acid, and evaporated and crystallized to obtain a MnSO4·H2O product that meets HG / T4823-2015. The comprehensive recovery rate of manganese is 99.1% (comprehensive recovery rate is the total recovery rate, calculated as comprehensive recovery rate of Mn = (mass of Mn contained in MnSO4·H2O product / mass of Mn contained in low-grade manganese oxide ore) × 100%).

[0052] (10) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the slurry was then placed in a 50° C. water bath and stirred for 20 min. The slurry was washed with water three times, and then filtered and dried to obtain a building gypsum product. The comprehensive recovery rate of calcium was 99.5%.

[0053] Example 2 A method for recycling electrolytic manganese industrial waste salt by segmented molten salt treatment, the process flow chart is as follows Figure 1 As shown, the following steps are included: (1) The electrolytic manganese industrial waste salt and calcium oxide are mixed according to the molar ratio of CaO: (2NH4 + + Mn) = 1.2 mixed.

[0054] (2) The mixture obtained in step (1) is placed in a muffle furnace at 500° C. for reaction for 45 minutes to obtain a molten salt deamination product.

[0055] (3) The mixture obtained in step (2) is placed in a muffle furnace at 700° C. for reaction for 60 minutes to obtain a molten salt manganese oxide product.

[0056] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the resulting slurry was placed in a 30°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mg was 99.92%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0057] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product that meets the requirements of HG / T 2680-2017 (industrial grade). The comprehensive recovery rate of magnesium is 99.1%.

[0058] (6) Wash the slag from step (4) 3 times with water at a temperature of 25°C; the ratio of slurry to solids in water washing is 4:1 mL / g; the stirring time for water washing is 30 min, and the slag is dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn = 1.2 are mixed and put into a ball mill with a ball-to-material ratio of 8:1 g / g and a ball milling time of 90 min.

[0059] (7) The mixture obtained in step (6) was placed in a muffle furnace at 550° C. for reaction for 60 min to obtain a reaction product.

[0060] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 40°C water bath for stirring and immersion. The reaction was carried out for 10 minutes, and the leaching rate of Mn was 99.85%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0061] (9) The manganese sulfate solution obtained in step (8) is adjusted to pH 6.5 using concentrated sulfuric acid, and evaporated and crystallized to obtain a MnSO4·H2O product that meets HG / T 4823-2015. The comprehensive recovery rate of manganese is 99.5% (comprehensive recovery rate is the total recovery rate, calculated as comprehensive recovery rate of Mn = (mass of Mn contained in MnSO4·H2O product / mass of Mn contained in low-grade manganese oxide ore) × 100%).

[0062] (10) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the slurry was then placed in a 25° C. water bath and stirred for 30 min. The slurry was washed with water for three times, and then filtered and dried to obtain a building gypsum product. The comprehensive recovery rate of calcium was 99.3%.

[0063] Example 3 A method for recycling electrolytic manganese industrial waste salt by segmented molten salt treatment, the process flow chart is as follows Figure 1 As shown, the following steps are included: (1) The electrolytic manganese industrial waste salt and calcium oxide are mixed according to the molar ratio of CaO: (2NH4 + + Mn) = 1.3 mixed.

[0064] (2) The mixture obtained in step (1) is placed in a muffle furnace at 350° C. and reacted for 150 min to obtain a molten salt deamination product.

[0065] (3) The mixture obtained in step (2) is placed in a muffle furnace at 550° C. and reacted for 120 min to obtain a molten salt manganese oxide product.

[0066] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 3:1 mL / g, and the obtained slurry was then placed in a 70°C water bath for stirring and immersion. The reaction was carried out for 40 minutes, and the leaching rate of Mg was 99.95%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0067] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product that meets the requirements of HG / T 2680-2017. The comprehensive recovery of magnesium exceeds 99.3%.

[0068] (6) Wash the slag from step (4) 3 times with water at 60°C; the ratio of water to solid in water-washing slurry is 3:1 mL / g; the stirring time is 20 min, and the slag is dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn = 1.5 are mixed and put into a ball mill with a ball-to-material ratio of 6:1 g / g and a ball milling time of 60 min.

[0069] (7) The mixture obtained in step (6) was placed in a muffle furnace at 450° C. for reaction for 120 min to obtain a reaction product.

[0070] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 3:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 99.91%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0071] (9) The manganese sulfate solution obtained in step (8) is adjusted to a pH value of 6.5 using concentrated sulfuric acid, and evaporated and crystallized to obtain a MnSO4·H2O product that meets HG / T 4823-2015. The comprehensive recovery of manganese exceeds 99.8%.

[0072] (10) The leached residue obtained in step (8) is slurried with deionized water at a liquid-solid ratio of 2:1 mL / g, and the slurry is then placed in a 50° C. water bath and stirred for 30 min. The slurry is washed with water three times, and then filtered and dried to obtain a building gypsum product. The comprehensive recovery of calcium exceeds 99.9%.

[0073] Example 4 A method for recycling electrolytic manganese industrial waste salt by segmented molten salt treatment, the process flow chart is as follows Figure 1 As shown, the following steps are included: (1) The electrolytic manganese industrial waste salt and calcium oxide are mixed according to the molar ratio of CaO: (2NH4 + +Mn) = 0.7 mixed.

[0074] (2) The mixture obtained in step (1) is placed in a muffle furnace at 450° C. and reacted for 60 minutes to obtain a molten salt deamination product.

[0075] (3) The mixture obtained in step (2) is placed in a muffle furnace at 650° C. and reacted for 90 minutes to obtain a molten salt manganese oxide product.

[0076] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 30 minutes, and the leaching rate of Mg was 99.95%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0077] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product, wherein the Mn content is 3.5 wt.%.

[0078] (6) The leached residue obtained in step (4) was washed twice with water at a temperature of 50°C; the ratio of the slurry to solid was 2:1 mL / g; the stirring time was 20 min, and the residue was dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn = 1.1 are mixed and put into a ball mill with a ball-to-material ratio of 10:1 g / g and a ball milling time of 60 min.

[0079] (7) The mixture obtained in step (6) was placed in a muffle furnace at 500° C. for reaction for 120 min to obtain a reaction product.

[0080] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a water bath at 25° C. and stirred for immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 98.65%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0081] (9) The manganese sulfate solution obtained in step (8) was adjusted to pH 6 using concentrated sulfuric acid, and evaporated and crystallized to obtain a MnSO4·H2O product that meets HG / T4823-2015. The comprehensive recovery rate of manganese was 78.9%.

[0082] (10) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the slurry was then placed in a 50° C. water bath and stirred for 20 min. The slurry was washed with water three times, and then filtered and dried to obtain a building gypsum product. The comprehensive recovery rate of calcium was 99.2%.

[0083] Compared with Example 1, in this example, the CaO in step (1): (2NH4 + In the step (5), the magnesium sulfate obtained in step (5) has a higher Mn content, and the recovery rate of manganese sulfate in step (9) is significantly reduced. According to analysis, this is because the conversion rate of manganese sulfate into manganese oxide is reduced due to insufficient calcium content, which causes part of manganese to enter the magnesium sulfate leachate in the form of manganese sulfate. On the one hand, this leads to a higher Mn content in the magnesium sulfate obtained, and on the other hand, it leads to a reduced recovery rate of manganese sulfate.

[0084] Comparative Example 1 A method for recovering electrolytic manganese industrial waste salt by segmented molten salt treatment comprises the following steps: (1) The electrolytic manganese industrial waste salt and calcium oxide are mixed according to the molar ratio of CaO: (2NH4 + + Mn) = 2 mixed.

[0085] (2) The mixture obtained in step (1) is placed in a muffle furnace at 450° C. and reacted for 60 minutes to obtain a molten salt deamination product.

[0086] (3) The mixture obtained in step (2) is placed in a muffle furnace at 650° C. and reacted for 90 minutes to obtain a molten salt manganese oxide product.

[0087] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 30 minutes, and the leaching rate of Mg was 87.23%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0088] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product that meets the requirements of HG / T 2680-2017. The comprehensive recovery rate of magnesium is 85.4%.

[0089] (6) The leached residue obtained in step (4) was washed twice with water at a temperature of 50°C; the ratio of the slurry to solid was 2:1 mL / g; the stirring time was 20 min, and the residue was dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn = 1.1 are mixed and put into a ball mill with a ball-to-material ratio of 10:1 g / g and the ball milling time is 60 min.

[0090] (7) The mixture obtained in step (6) was placed in a muffle furnace at 500° C. for reaction for 120 min to obtain a reaction product.

[0091] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 25°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 57.72%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0092] (9) The manganese sulfate solution obtained in step (8) was adjusted to pH 6 using concentrated sulfuric acid, and the MnSO4·H2O product was obtained by evaporation and crystallization, wherein the magnesium content was 6.4 wt%.

[0093] (10) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the slurry was then placed in a 50°C water bath and stirred for 20 min, and the washing was repeated three times, and then filtered and dried. The building gypsum product has a manganese content of 4.5 wt.%.

[0094] Compared with Example 1, in this comparative example, the CaO in step (1): (2NH4 ++Mn) is increased to 2.0, in step (4), the leaching rate of Mg is reduced, and in step (8), the leaching rate of Mn is reduced, and in step (9), the impurity Mg content in manganese sulfate is too high, and the Mn content in the building gypsum product is relatively high. After analysis, this is because when the CaO content is too high, the conversion rate of magnesium sulfate to MgO will be too high, resulting in too high leaching rate of Mg, and since the leached residue obtained in step (4) contains not only manganese oxide but also MgO, during the sulfation roasting process in step (7), manganese and magnesium are converted into sulfates. However, the amount of ammonium sulfate is determined according to the amount of manganese. Due to the competitive sulfation of Mn and Mg, the conversion rate of Mn to manganese sulfate is significantly reduced, and some Mn cannot be converted into manganese sulfate. Not only the recovery rate of manganese sulfate is reduced, but also the Mn content in the obtained gypsum residue is increased, and the magnesium content in manganese sulfate is significantly increased, and the quality of manganese sulfate is reduced.

[0095] Comparative Example 2 A method for recovering electrolytic manganese industrial waste salt by segmented molten salt treatment comprises the following steps: (1) The electrolytic manganese industrial waste salt and calcium oxide are mixed according to the molar ratio of CaO: (2NH4 + + Mn) = 1 mixed.

[0096] (2) The mixture obtained in step (1) is placed in a muffle furnace at 650° C. and reacted for 90 minutes to obtain a molten salt manganese oxide product.

[0097] (3) The molten salt reaction product obtained in step (2) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 30 minutes, and the leaching rate of Mg was 90.47%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0098] (4) The magnesium sulfate obtained in step (3) is evaporated and crystallized to obtain a MgSO4·7H2O product that meets the requirements of HG / T 2680-2017. The comprehensive recovery rate of magnesium is 87.4%.

[0099] (5) The leached residue obtained in step (4) was washed twice with water at a temperature of 50°C; the ratio of the slurry to solid was 2:1 mL / g; the stirring time was 20 min, and the residue was dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn=1.1 mixed into a ball mill with a ball-to-material ratio of 10:1 g / g and a ball milling time of 60 min.

[0100] (6) The mixture obtained in step (5) was placed in a muffle furnace at 500° C. for reaction for 120 min to obtain a reaction product.

[0101] (7) The reaction product obtained in step (6) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 25°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 96.16%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0102] (8) The manganese sulfate solution obtained in step (7) was adjusted to pH 6 using concentrated sulfuric acid, and then evaporated and crystallized to obtain a MnSO4·H2O product having a magnesium content of 0.8 wt%.

[0103] (9) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the slurry was then placed in a 50° C. water bath and stirred for 20 min. The slurry was washed with water for three times, and then filtered and dried to obtain a building gypsum product having a manganese content of 0.5 wt.%.

[0104] Compared with Example 1, after step (2) in Example 1 is omitted, the comprehensive recovery rate of Mg is reduced, the Mg content in manganese sulfate is relatively high, resulting in reduced product quality, and a relatively high manganese content enters the building gypsum product. After analysis, this is because after omitting step (2), the reaction is carried out at 650°C, resulting in the decomposition of electrolytic manganese industrial waste salt into sulfur oxides and ammonia, and calcium oxide cannot effectively fix sulfate in electrolytic industrial waste salt. Therefore, in step (2) of this comparative example, the conversion rate of manganese into manganese oxide is reduced. During water leaching in step (3), the incompletely reacted calcium oxide is converted into calcium hydroxide, which reacts with magnesium ions and manganese ions to form hydroxide, resulting in a reduced magnesium leaching rate and more magnesium entering the leached residue. During sulfation roasting in step (6), magnesium and manganese are converted into sulfate. Since ammonium sulfate is added according to the Mn content in the leached residue, part of the manganese cannot be converted into manganese sulfate due to competition. Not only does the obtained manganese sulfate product contain a higher Mg content, the quality of the manganese sulfate product is reduced, but the Mn content in the obtained building gypsum product is increased, and the Mn loss is increased.

[0105] Comparative Example 3 A method for recovering electrolytic manganese industrial waste salt by segmented molten salt treatment comprises the following steps: Steps (1) and (2) are the same as steps (1) and (2) of Example 1; (3) The mixture obtained in step (2) is placed in a muffle furnace at 475° C. and reacted for 90 minutes to obtain a molten salt manganese oxide product.

[0106] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 30 minutes, and the leaching rate of Mg was 94.25%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0107] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product having a manganese content of 1.4 wt.%.

[0108] (6) The leached residue obtained in step (4) was washed twice with water at a temperature of 50°C; the ratio of the slurry to solid was 2:1 mL / g; the stirring time was 20 min, and the residue was dried and mixed with ammonium sulfate at a molar ratio of SO4 2- : Mn = 1.1 are mixed and put into a ball mill with a ball-to-material ratio of 10:1 g / g and a ball milling time of 60 min.

[0109] (7) The mixture obtained in step (6) was placed in a muffle furnace at 500° C. for reaction for 120 min to obtain a reaction product.

[0110] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 25°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 90.43%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0111] (9) The manganese sulfate solution obtained in step (8) was adjusted to pH 6 using concentrated sulfuric acid, and the MnSO4·H2O product was crystallized by evaporation, wherein the magnesium content was 1.2 wt.%.

[0112] (10) The leached residue obtained in step (8) was mixed with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the resulting slurry was placed in a 50° C. water bath and stirred for 20 min. The washing was repeated three times, and then filtered and dried to obtain a gypsum product containing 0.3 wt.% manganese. Compared with Example 1, in this comparative example, the reaction temperature in step (3) is reduced to 475°C, the recovery rate of magnesium sulfate is reduced, and the manganese content is increased. The magnesium content in the obtained manganese sulfate product is also increased, the quality is reduced, and the Mn content in the gypsum product is increased. After analysis, this is because after the reaction temperature in step (3) is reduced, the conversion rate of Mn into manganese oxide is reduced, part of Mn is leached as manganese sulfate during water leaching in step (4), and CaO cannot be completely converted into calcium sulfate. Therefore, when water leaching is performed in step (4), part of magnesium is lost due to the reaction between calcium hydroxide and magnesium sulfate, resulting in a reduction in the leaching rate of Mg. In addition, since part of Mn is also leached, the Mn content in the obtained magnesium sulfate product is increased, and the quality of magnesium sulfate is reduced. At the same time, since part of Mg enters the leaching residue in the form of magnesium hydroxide precipitate, the subsequent leaching residue and sulfur are separated. When the ammonium sulfate is mixed and roasted, part of the Mg and Mn in the leached residue can be converted into sulfate at the same time, and the conversion of Mg is easier than that of Mn. The amount of ammonium sulfate used is configured according to the Mn content, so most of the Mn and part of the Mg in the roasted product are converted into sulfate, and part of the Mn cannot continue to exist completely in the form of oxide. Therefore, on the one hand, the leaching rate of Mn during leaching in step (8) is reduced, and the obtained leachate contains both Mg and Mn, resulting in a decrease in the quality of manganese sulfate obtained by crystallization in step (9). On the other hand, Mn enters the final gypsum product, resulting in an increase in Mn loss.

[0113] Comparative Example 4 A method for recovering electrolytic manganese industrial waste salt by segmented molten salt treatment comprises the following steps: Steps (1) and (2) are the same as steps (1) and (2) of Example 1; (3) The mixture obtained in step (2) is placed in a muffle furnace at 800° C. for reaction for 90 minutes to obtain a molten salt manganese oxide product.

[0114] (4) The molten salt reaction product obtained in step (3) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 50°C water bath for stirring and immersion. The reaction was carried out for 30 minutes, and the leaching rate of Mg was 92.17%. The leaching residue and magnesium sulfate leaching solution were then obtained by filtration.

[0115] (5) The magnesium sulfate obtained in step (4) is evaporated and crystallized to obtain a MgSO4·7H2O product that meets the requirements of HG / T 2680-2017. The comprehensive recovery rate of magnesium is 89.5%.

[0116] (6) The leached residue obtained in step (4) was washed twice with water at a temperature of 50°C; the ratio of the slurry to solid was 2:1 mL / g; the stirring time was 20 min, and the residue was dried and mixed with ammonium sulfate at a molar ratio of SO4 2-: Mn = 1.1 are mixed and put into a ball mill with a ball-to-material ratio of 10:1 g / g and a ball milling time of 60 min.

[0117] (7) The mixture obtained in step (6) was placed in a muffle furnace at 500° C. for reaction for 120 min to obtain a reaction product.

[0118] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 25°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 94.36%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0119] (9) The manganese sulfate solution obtained in step (8) was adjusted to pH 6 using concentrated sulfuric acid, and the MnSO4·H2O product was crystallized by evaporation, wherein the magnesium content was 0.7 wt.%.

[0120] (10) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the slurry was then placed in a 50° C. water bath and stirred for 20 min. The slurry was washed with water three times, and then filtered and dried to obtain a building gypsum product. The comprehensive recovery rate of calcium was 99.4%.

[0121] Compared with Example 1, in this comparative example, the reaction temperature in step (3) is increased to 800°C, the recovery rate of Mg is reduced, and the Mg content in the obtained manganese sulfate is relatively high, resulting in a reduction in the quality of manganese sulfate. After analysis, this is because when the reaction temperature in step (3) is too high, part of the Mn and sulfate in the electrolytic manganese industrial waste salt decompose into manganese oxide, so the calcium oxide content required to fix the manganese ions is reduced, and the excess calcium oxide converts part of the magnesium ions and sulfate ions into calcium sulfate and magnesium oxide in step (3), thereby reducing the recovery rate of Mg, and since part of the Mg enters the leaching residue as magnesium oxide, magnesium oxide will be converted into magnesium sulfate in step (7). Due to the competitive relationship, the conversion rate of manganese oxide into manganese sulfate is reduced, so the leaching rate of Mn is reduced, and since both magnesium sulfate and manganese sulfate are leached into the manganese sulfate solution, the Mg content of the recovered manganese sulfate is increased, resulting in a reduction in the quality of manganese sulfate.

[0122] Example 5 A method for recycling electrolytic manganese industrial waste salt by segmented molten salt treatment, the process flow chart is as follows Figure 1 As shown, the following steps are included: Steps (1) to (6) are the same as steps (1) to (6) in Example 1.

[0123] (7) The mixture obtained in step (6) was placed in a muffle furnace at 650° C. for reaction for 120 min to obtain a reaction product.

[0124] (8) The reaction product obtained in step (7) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the obtained slurry was then placed in a 25°C water bath for stirring and immersion. The reaction was carried out for 20 minutes, and the leaching rate of Mn was 87.32%. The leaching residue and manganese sulfate leaching solution were then obtained by filtration.

[0125] (9) The manganese sulfate solution obtained in step (8) was adjusted to pH 6 using concentrated sulfuric acid, and evaporated and crystallized to obtain a MnSO4·H2O product that meets HG / T4823-2015. The comprehensive recovery rate of manganese was 85.7%.

[0126] (10) The leached residue obtained in step (8) was slurried with deionized water at a liquid-to-solid ratio of 2:1 mL / g, and the resulting slurry was then placed in a 50° C. water bath and stirred for 20 min. The slurry was washed with water three times and then filtered and dried to obtain a building gypsum product having a manganese content of 0.6 wt.%.

[0127] The only difference between this embodiment and embodiment 1 is that, when the roasting temperature in step (7) is increased to 650° C., the recovery rate of Mn is significantly reduced, and the building gypsum contains a relatively high manganese content. After analysis, this is because when the roasting temperature in step (7) is too high, the amount of self-decomposition of ammonium sulfate increases, resulting in the inability to convert part of the manganese oxide in the slag into manganese sulfate, thereby increasing the manganese loss and reducing the recovery rate.

[0128] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering waste salt from electrolytic manganese industry, characterized in that: include: S1. After mixing electrolytic manganese industrial waste salt with calcium oxide, the mixture is first heated to a first temperature for a first heat treatment, and then heated to a second temperature for a second heat treatment to obtain a treated product; the first temperature is lower than the second temperature; the second temperature is 500-700° C.; S2, subjecting the treated product to water leaching and solid-liquid separation to obtain a first leaching residue and a first leaching liquid; the first leaching liquid is evaporated and crystallized to obtain a magnesium sulfate product; S3, after washing and drying the first leaching residue, mixing it with ammonium sulfate and ball milling it to obtain a mixture; the mixture is roasted to obtain a roasted product; S4, water-leaching the roasted product and performing solid-liquid separation to obtain a second leaching residue and a second leaching liquid; the second leaching liquid is evaporated and crystallized to obtain a manganese sulfate product; S5. The second leaching residue is washed with water, then solid-liquid separation and drying are performed to obtain industrial gypsum.

2. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: The calcium oxide and electrolytic manganese industrial waste salt are in a molar ratio of CaO:(2NH4 + +Mn) = 1:1 to 1.5:1, preferably 1:1 to 1.3:

1.

3. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S1, the first temperature is 300-500°C, preferably 400-500°C; the time of the first heat treatment is 20-180min, preferably 45-90min; the atmosphere of the first heat treatment is an oxygen-containing gas, and the oxygen partial pressure of the oxygen-containing gas is 21-100%.

4. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S1, the second temperature is 600-700°C; the time of the second heat treatment is 30-180 minutes, preferably 60-120 minutes; the atmosphere of the second heat treatment is an oxygen-containing gas, and the oxygen partial pressure of the oxygen-containing gas is 21-100%.

5. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S2, the temperature of the water immersion treatment is 25 to 100° C.; the time of the water immersion treatment is 10 to 60 min; the solid-liquid ratio of the water immersion treatment is 1:2 to 1:5 g / mL; the leaching agent of the water immersion treatment is water; In step S3, the number of water washing is 1 to 3 times; the temperature of the water washing is 25 to 100° C.; the slurry-solid ratio of the water washing is 2:1 to 5:1 mL / g; the stirring time of the water washing is 5 to 40 min; and the washing liquid obtained after the water washing is returned to step S2 as a leaching agent for water immersion treatment.

6. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S3, the ammonium sulfate and the first leaching residue are mixed according to a molar ratio of SO4 2- :Mn is in a ratio of 1:1 to 1.5:

1.

7. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S3, the calcination temperature is 300-550°C; the calcination time is 30-180 minutes; The calcination atmosphere is an oxygen-containing gas atmosphere, and the oxygen partial pressure of the oxygen-containing gas is 21 to 100%; In step S3, the ball-to-material mass ratio of the ball milling is 20:1 to 2.5:1, and the ball milling time is 30 to 120 minutes.

8. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S4, the water immersion temperature is 25-100° C.; the water immersion time is 10-60 min; the solid-liquid ratio of the water immersion is 1:2-1:5 g / mL; and the leaching agent of the water immersion is water.

9. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S5, the number of water washing is 1 to 3 times; the temperature of the water washing is 25 to 100° C.; the slurry-to-solid ratio of the water washing is 2:1 to 5:1 mL / g; the stirring time of the water washing is 5 to 40 min; and the washing liquid obtained after the water washing is returned to step S4 as a leaching agent for water immersion.

10. The method for recovering electrolytic manganese industrial waste salt according to claim 1, characterized in that: In step S1, the flue gas generated by the first heat treatment is absorbed by water to obtain an ammonia solution, or absorbed by a sulfuric acid solution, and then crystallized to obtain ammonium sulfate; the ammonium sulfate is returned to step S3 for use; In step S4, the pH value of the second leachate is adjusted to 4.5-6.5 and then evaporated and crystallized; The manganese sulfate product is battery-grade manganese sulfate; The magnesium sulfate product is industrial grade magnesium sulfate.

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