Method for recycling valuable resources in manganese slag

Abstract

The invention discloses a method for recovering valuable resources in manganese slag, which comprises the following steps: carrying out tempering, fractional precipitation of manganese and magnesium and selective oxidation on washing waste liquid of the manganese slag, and further recovering to obtain high-purity manganous-manganic oxide and high-purity basic magnesium carbonate products; a high-purity ammonium ferrous sulfate product is obtained through homogenization, alkali adjustment, sedimentation and recovery, and a ferrous salt solution capable of being internally circulated is obtained through further alkali adjustment and iron precipitation; the washing waste residues are subjected to catalytic oxidation by adopting a curing agent, so that the washing waste residues are harmless, and dilute ammonia water is recovered; according to the characteristics of the washing waste residues and the washing waste liquid of the manganese residues, high-value recovery of valuable elements in the manganese residues is achieved through process optimization design, and the purpose of no emission of harmful waste water, waste gas, waste residues and the like is basically achieved. In addition, the method also has the advantages of simple overall process flow, low overall operation cost and the like.

Description

Technical Field

[0001] This invention relates to the treatment of electrolytic manganese slag, specifically to a method for recovering valuable resources from manganese slag, belonging to the technical field of valuable resource recovery from electrolytic manganese slag. Background Technology

[0002] Electrolytic manganese slag is a general term for leaching slag, sulfide slag, and iron removal slag generated during the electrolytic manganese production process. It is a dark brown, muddy paste, weakly acidic, and belongs to Class II general industrial solid waste. Generally, producing 1 ton of electrolytic manganese generates 8-10 tons of electrolytic manganese slag. Currently, there is no low-cost method for manganese slag disposal, which has historically constrained the development of the manganese industry.

[0003] Since electrolytic manganese slag generally contains 3-6% manganese and 2-3% ammonia nitrogen, it has certain resource recovery value. Currently, the most economical and reasonable method for treating electrolytic manganese slag is water washing, followed by resource recovery of the resulting washing liquid, and solidification treatment of the washed manganese slag. Regarding the resource utilization of the washing liquid: for example, Chinese patent CN 108483501 A, "A Comprehensive Utilization Method of Washing Liquid from Electrolytic Manganese Slag," involves adding ammonium bicarbonate to the washing liquid to convert manganese into manganese carbonate, and then removing impurities and recovering ammonia through precipitation and deammoniation reactions. Chinese patent CN 112408488 A, "A Method for Recovering Soluble Ammonium Manganese from Electrolytic Manganese Slag," uses an organic phase containing an extractant to extract manganese ions from the washing liquid, and obtains high-purity manganese ions through back-extraction. The raffinate is then used for ammonia recovery through alkaline stripping. Regarding the solidification and stabilization of residual manganese slag: Chinese patent CN 108262336 A, "A method for solidification treatment of electrolytic manganese slag," reports the mixing and solidification of electrolytic manganese slag with alkaline industrial waste slag, blast furnace slag, high-calcium fly ash, composite alkaline agents, and water, followed by storage in a slag silo. Chinese patent CN 103320621 A, "A method for solidifying heavy metals in electrolytic manganese slag and simultaneously producing sulfur," uses calcium sulfide mixed with manganese slag to achieve the stabilization and solidification of heavy metals in the manganese slag. Chinese patent CN 104307849 A, "A method for solidification / stabilization treatment of electrolytic manganese slag," adds alkaline agents and sodium hexametaphosphate for solidification of manganese slag. Chinese patent CN 104307850 A, "A method for solidification / stabilization treatment of high concentration water-soluble manganese in manganese slag," adds active silica and magnesium oxide to achieve solidification of manganese slag. Each of the above methods has its own advantages and disadvantages, but it has not been industrialized. The main reasons are that the cost of resource recovery of washing liquid is relatively high, the product is not pure, and there are also shortcomings such as incomplete solidification and high cost. Summary of the Invention

[0004] To address the problems of high resource recovery costs, low product purity, and poor solidification effect of washing slag in existing electrolytic manganese slag treatment processes, this invention provides a method for recovering valuable resources from manganese slag. By conditioning the manganese slag washing wastewater to reduce the difficulty of subsequent manganese and magnesium separation, high-purity manganese oxide and high-purity basic magnesium carbonate products can be obtained stepwise, increasing the added value of manganese and magnesium products and achieving high-value recovery of manganese and magnesium from the slag. Furthermore, the wastewater after manganese and magnesium recovery is rich in ammonia nitrogen. Through process optimization, high-value ferrous ammonium sulfate product is further recovered, and the remaining residue can be recycled and disposed of within the system without wastewater discharge. Finally, based on the characteristic of the washing waste slag containing iron and manganese, a solidifying agent is used to catalytically oxidize ammonia nitrogen and manganese, ensuring the stability of the washing waste slag and achieving the goal of harmless disposal that meets national standards. The recovered ammonia nitrogen is recycled and disposed of within the system in the form of ammonia water, thus achieving zero discharge of harmful solid waste and exhaust gas.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for recovering valuable resources from manganese slag, the method comprising the following steps: S1: The manganese slag is washed with a washing solution, and after solid-liquid separation, washing waste residue and washing waste liquid are obtained respectively.

[0006] S2: Conditioning agent is used to condition the washing waste liquid. After conditioning, precipitant and oxidant are added in sequence to treat manganese precipitation. After manganese precipitation, solid-liquid separation is performed to obtain manganese oxide precipitate and primary waste liquid.

[0007] S3: Adjust the primary waste liquid to alkaline, then add soluble carbonate for magnesium precipitation. After magnesium precipitation, perform solid-liquid separation to obtain basic magnesium carbonate precipitate and secondary waste liquid.

[0008] S4: Add dilute sulfuric acid and ferrous salt to the secondary waste liquid for a mixed reaction. After the reaction is completed, perform solid-liquid separation to obtain ferrous ammonium sulfate precipitate and tertiary waste liquid.

[0009] S5: Add ammonia to the tertiary waste liquid for iron precipitation. After iron precipitation, perform solid-liquid separation to obtain ferrous hydroxide precipitate and tertiary waste liquid. Mix and homogenize the tertiary waste liquid with the secondary waste liquid and proceed to step S4. Acidify the ferrous hydroxide precipitate and then recycle it to S4 to participate in the mixing reaction.

[0010] S6: First, the washing waste residue is prepared into a slurry, and then a curing agent is added for curing treatment. After curing, a maintenance treatment is carried out to obtain a harmless cured product.

[0011] As a preferred method, the washing of manganese slag with a washing solution specifically involves: first adjusting the water to a weakly acidic state (preferably pH 5-6) with acid, and then using the weakly acidic water to perform multi-stage countercurrent washing of the manganese slag (preferably three-stage countercurrent washing).

[0012] Preferably, the solid-liquid ratio for washing manganese slag is 1:1 to 8, and more preferably 1:2 to 6.

[0013] Preferably, the conditioning agent is one or more of ammonium sulfite, urea, ammonium thiosulfate, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium bicarbonate, with urea being the most preferred.

[0014] Preferably, the amount of conditioning agent added is 0.5-2%, more preferably 1-1.5% (based on the total mass of the washing waste liquid).

[0015] Preferably, the precipitant is one or more of ammonia, sodium hydroxide, potassium hydroxide, and ammonium carbonate, with ammonia being the most preferred.

[0016] Preferably, the amount of precipitant added is such that the pH of the washing waste liquid is 7-8.

[0017] Preferably, the oxidant is one or more of hydrogen peroxide, oxygen, persulfate, and hypochlorite, with hydrogen peroxide being the most preferred.

[0018] Preferably, the amount of oxidant added is 1-3%, more preferably 1.5-2.5% (based on the total mass of the washing waste liquid).

[0019] Preferably, adjusting the primary waste liquid to alkaline pH specifically involves adjusting the pH of the primary waste liquid to 8-9 using an alkali. The alkali is one or more of sodium hydroxide, potassium hydroxide, and ammonia water, preferably ammonia water.

[0020] Preferably, the soluble carbonate is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate, with ammonium carbonate being the most preferred.

[0021] Preferably, the amount of soluble carbonate added is 0.1-1%, more preferably 0.3-0.8% (based on the total mass of the primary waste liquid).

[0022] Preferably, in step S4: dilute sulfuric acid is first added to the secondary waste liquid to obtain a solution system with a pH of 5-6. When the concentration of ammonium sulfate in this solution system is not less than 45 g / L, dilute sulfuric acid is added again to adjust the pH of the solution system to 1-2, and then ferrous salt is added to it for mixing and reaction. When the concentration of ammonium sulfate in this solution system is less than 45 g / L, it is returned to step S1 for use as washing liquid and / or used in subsequent step S6 for pulping the washing waste residue.

[0023] Preferably, the ferrous salt includes one or more of iron powder, ferrous chloride, ferrous sulfate, and ferrous nitrate, with ferrous sulfate being the most preferred. The amount of ferrous salt added is such that the content of ferrous ions in the solution system is 0.2~0.8 mol / L, preferably 0.3~0.5 mol / L.

[0024] Preferably, in step S5, the ammonia water added to the waste liquid is dilute ammonia water, and the amount of dilute ammonia water added is 1 to 2 times the concentration of ferrous ions in the waste liquid, preferably 1.2 to 1.6 times.

[0025] Preferably, in step S5: the precipitate of ferrous hydroxide is acidified to obtain a ferrous salt solution by reacting acid with ferrous hydroxide, preferably by reacting concentrated sulfuric acid (preferably with a mass concentration of not less than 80%) with ferrous hydroxide to obtain a ferrous sulfate solution.

[0026] Preferably, in step S6, the curing agent is one or more of calcium oxide, magnesium oxide, sodium carbonate, phosphate, persulfate, and hypochlorite, preferably a mixture of calcium oxide, phosphate (such as sodium phosphate), and persulfate (such as sodium persulfate) (for example, the mass ratio of calcium oxide, sodium phosphate, and sodium persulfate is 1:0.1~0.4:0.6~0.9).

[0027] Preferably, the curing treatment involves curing in a rotary kiln for 1-5 hours. During the curing process, water is used to absorb the generated ammonia gas to obtain dilute ammonia water.

[0028] Preferably, the amount of curing agent added is 2-8%, more preferably 3-6% (based on the total mass of the washing waste).

[0029] In this invention, based on the characteristics of manganese slag washing liquid and washing slag, the invention achieves the orderly recovery of valuable resources (manganese, magnesium, ammonia nitrogen, etc.) in the manganese slag washing waste liquid through process optimization design, obtaining high-purity and high-value products. At the same time, the washing waste slag is rendered harmless through catalytic solidification. The overall process design is reasonable, with virtually no harmful wastewater, waste slag, or waste gas emissions. This can significantly increase the value of the recovered products and reduce disposal costs, ultimately achieving low-cost resource utilization of manganese slag.

[0030] In this invention, the washing of electrolytic manganese slag mainly adopts a three-stage countercurrent washing process. Through washing, soluble substances such as Mn in the manganese slag can be removed. 2+ NH4 + Mg 2+ SO4 2-After washing and removal, solid-liquid separation yields low-salt washing waste residue and high-salt washing waste liquid. Preferably, the pH of the washing solution is adjusted to 6-7 during washing. This is mainly to prevent strong acid washing from dissolving large amounts of impurities such as iron and increasing acid consumption, and to prevent alkaline washing from causing manganese and magnesium to precipitate and become difficult to remove.

[0031] In this invention, the washing waste liquid of manganese slag mainly contains Mn. 2+ Mg 2+ Ca 2+ Direct alkaline precipitation can lead to co-precipitation, resulting in a product with low purity (low value) and thus secondary waste. To obtain high-purity manganese, conventional methods typically involve first removing magnesium and calcium with fluorides, which is costly and leaves a high amount of residual fluoride ions. This invention utilizes the effects of a conditioning agent and an oxidizing agent to selectively precipitate manganese. Specifically, a certain amount of conditioning agent is added to the washing wastewater, followed by a certain amount of precipitant. After adjusting the pH to 7-8, a certain amount of oxidizing agent is added (to accelerate the oxidation rate of Mn(OH)₂ and shorten the reaction time for the formation of manganese tetroxide). After reacting for a period (e.g., 30-60 minutes), filtration yields high-purity manganese tetroxide. After manganese precipitation, the solution is further pH-adjusted by adding ammonia, followed by the addition of soluble carbonates. This allows magnesium to react with carbonate and hydroxide ions at a pH of 8-9 to form basic magnesium carbonate precipitate. In other words, this invention achieves the stepwise precipitation of manganese and magnesium through conditioning, stepwise precipitation, and selective oxidation, ultimately achieving the goal of high-value recovery of manganese and magnesium. The conditioning agent is a solution of one or more of urea, ammonium sulfite, ammonium thiosulfate, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium bicarbonate (preferably a urea solution). Its main functions include: ① stabilizing the solution pH as much as possible through the buffering effect of the conditioning agent, preventing excessive ammonia water from being used to adjust the pH later, which could lead to the simultaneous precipitation of magnesium and manganese; ② facilitating the slow release of OH- by the conditioning agent. - and CO3 2- Under low alkalinity, it preferentially combines with manganese, providing nuclei for subsequent manganese precipitation and preferentially achieving manganese crystallization; ③ Through the weak reducing property of the conditioning agent, the overall ORP of the solution is reduced, increasing the oxidation rate of manganese during subsequent oxidation, which is more conducive to precipitation under low alkalinity conditions. The oxidizing agent includes one or more of hydrogen peroxide, oxygen, persulfate, and hypochlorite, and its main function is to oxidize manganese ions into manganese tetroxide precipitate under low alkalinity conditions.

[0032] In this invention, after the stepwise recovery of manganese and magnesium from the washing waste liquid, the main component is a sulfate solution containing calcium and ammonia nitrogen. Ammonia nitrogen and sulfate are primarily recovered as ferrous ammonium sulfate. The recovery of ferrous ammonium sulfate is based on the low solubility of ferrous ammonium sulfate as a precipitate. Ammonium sulfate reacts with ferrous sulfate under acidic conditions to convert to ferrous ammonium sulfate. When the concentration of the precipitate exceeds the solubility of ferrous ammonium sulfate, low-cost recovery of ferrous ammonium sulfate can be achieved. The unprecipitated ferrous sulfate is recycled through subsequent alkali neutralization and acid dissolution, reducing the cost of ferrous ammonium sulfate recovery. A certain amount of dilute sulfuric acid is added to the washing waste liquid after the recovery of manganese and magnesium to adjust the pH of the solution to 5-6, and then the concentration of ammonium sulfate in the solution is measured. When the concentration of ammonium sulfate in the solution is below 45 g / L, most of it (generally about 85-95%) is returned to step S1 as washing liquid to wash the manganese slag. This reduces water consumption and achieves the recycling and enrichment of ammonium sulfate. The remaining portion is used in step S6 to mix with the washing waste residue for pulping. When the concentration of ammonium sulfate in the solution is higher than 45 g / L, it enters the subsequent mixing reaction tank. The pH of the solution system is adjusted to 1-2 by adding dilute sulfuric acid, and then ferrous salt is added to it for mixing reaction. High-purity ferrous ammonium sulfate precipitate can be obtained by solid-liquid separation. The filtrate after separation mainly contains ferrous ions (the amount of ferrous added is generally excessive to ensure the removal of ammonia nitrogen). Therefore, ammonia water can be added for neutralization and sedimentation separation to obtain iron-containing precipitate (ferrous hydroxide). The iron-containing precipitate is then acid-dissolved to obtain ferrous salt solution (which can be recycled for the aforementioned ferrous ammonium sulfate recovery step).

[0033] In this invention, the washing waste residue obtained after washing manganese slag still contains small amounts of ammonium sulfate and manganese. The conventional method is to solidify the manganese slag using calcium oxide and calcium sulfate, but this carries the risk of excessive ammonia nitrogen and manganese levels. This invention proposes a catalytic solidification route. Through the catalytic action of iron and manganese in the filter residue, a solidifying agent (such as persulfate or hypochlorite) reacts rapidly with ammonia nitrogen, converting residual ammonia nitrogen in the manganese slag into ammonia gas, and oxidizing and mineralizing residual manganese. This yields harmless manganese slag that meets national standards. The generated ammonia gas is absorbed countercurrently to obtain high-concentration dilute ammonia water, which can be returned to the process for recycling.

[0034] In this invention, the process flow specifically includes (e.g.) Figure 1As shown): 1) Treat the electrolytic manganese slag using a three-stage countercurrent washing process to obtain washing liquid and filter residue. Preferably, the pH of the washing liquid is controlled at 5-6; 2) Add a certain amount of conditioning agent (such as urea) to the washing liquid obtained in step 1), then add a certain amount of precipitant to adjust the pH of the solution to 7-8, then add a certain amount of oxidant to the solution and react for 30-60 minutes. Filter to obtain high-purity manganese tetroxide and solution 1 (i.e., primary waste liquid); 3) Add ammonia to solution 1 obtained in step 2) to adjust the pH of the solution to 8-10, then... Add a certain amount of soluble carbonate to the solution and react for 30-60 minutes. Filter the solution after the reaction to obtain high-purity basic magnesium carbonate precipitate and solution 2 (i.e., secondary waste liquid); 4) Add the residual liquid after iron precipitation (i.e., fourth waste liquid) to solution 2 obtained by filtration in step 3) for homogenization, then add a certain amount of dilute sulfuric acid to adjust the pH of the solution to 5-6, and test the solution density. When the concentration of ammonium sulfate in the solution is lower than 45 g / L, part of it is returned to step 1) for use, and part of it is added to the subsequent solidification step. When the ammonium sulfate concentration in the solution is approximately 45 g / L, proceed to step 5); 5) Continue adding a mixed solution of dilute sulfuric acid and ferrous sulfate to the solution obtained in step 4), controlling the amount of sulfuric acid added to ensure that the pH of the mixed solution is 1-2, and controlling the total amount of ferrous sulfate added to be 50-75 g / L. After reacting for a period of time, the solution is filtered to separate the contents, and the filtration yields high-purity ferrous ammonium sulfate and solution 3 (i.e., the tertiary waste liquid); 6) Add dilute ammonia to solution 3 obtained from the filtration in step 5) for neutralization and precipitation (iron precipitation), and then filter. The process involves separation, filtration, and recovery to obtain ferrous hydroxide and solution 4 (i.e., the fourth waste liquid). The ferrous hydroxide is used for subsequent sulfuric acid acidification and, after mixing with added ferrous sulfate, is returned to step 5) for recycling. Solution 4 is returned to step 4) for recycling. 7) The washing waste residue obtained in step 1) is thoroughly mixed with a portion of the solution obtained in step 4) and the curing agent, with the mixing time controlled to not exceed 30 minutes. 8) The mixed material from step 7) is cured in a rotary kiln for 1-5 hours. After curing, harmless manganese slag is obtained. The waste gas generated during curing is absorbed and recovered using countercurrent absorption to recover dilute ammonia water, which can be recycled in other steps.

[0035] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. This invention addresses the characteristics of manganese slag by introducing a conditioning agent for pretreatment of the washing wastewater, which facilitates the efficient separation and stepwise recovery of manganese and magnesium from the washing wastewater. Furthermore, based on the ammonia nitrogen and sulfate ions abundant in the wastewater after manganese and magnesium recovery, ferrous ammonium sulfate is recovered by homogenizing and adjusting the alkali and adding ferrous salt. The manganese-containing products, magnesium-containing products, and ferrous ammonium sulfate products recovered by this invention have high purity and high economic value. This invention achieves high-value recovery of multiple valuable elements from manganese slag while reducing overall operating costs.

[0036] 2: Based on the characteristics of washing waste containing iron and manganese, this invention introduces a curing agent to catalytically solidify the water-washed filter residue of manganese slag, thereby achieving stable solidification of manganese slag and meeting the national standard requirements for harmless emission.

[0037] 3. The method of the present invention has a simple overall process flow, low wastewater and waste residue discharge, low environmental pollution, high added value of the obtained products, and low overall operating cost. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the process for recovering valuable resources from manganese slag according to the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments. Example 1

[0040] Electrolytic manganese slag was subjected to three-stage countercurrent washing with water (pH 6.8~7.1) at a solid-liquid ratio of 1:4 to obtain washing waste residue and washing waste liquid. Then, 1.3% (based on the mass of washing waste liquid) of urea was added to the washing waste liquid, stirred evenly, and then ammonia water was added to maintain the pH of the mixed solution at about 7.5. 2% (based on the mass of washing waste liquid) of hydrogen peroxide was added to the system and reacted for 40 min. After the reaction was completed, the mixture was filtered, and the resulting filter cake was dried to obtain manganese tetroxide with a purity of about 99.7%.

[0041] Ammonia was added to the filtrate after the manganese tetroxide was filtered out to adjust its pH to about 9.0. Then, 0.3% (based on the mass of the filtrate) of ammonium carbonate was added and the reaction was carried out for 40 minutes. After the reaction was completed, the filtrate was filtered and the resulting filter cake was dried to obtain basic magnesium carbonate with a purity of about 99.3%.

[0042] Dilute sulfuric acid was added to the filtrate after filtering out basic magnesium carbonate to adjust the pH to about 5.5. The concentration of ammonium sulfate in the filtrate was found to be about 58 g / L. Then, dilute sulfuric acid was added to adjust the pH to 1-2, and ferrous sulfate (added in such a way that its concentration in the solution system is about 65 g / L) was added to carry out the mixing reaction. After the reaction was completed, the mixture was filtered. The resulting filter cake was dried to obtain ferrous ammonium sulfate with a purity of about 99.4%.

[0043] Ammonia was added to the filtrate after ferrous ammonium sulfate was filtered out to react and ferrous hydroxide precipitate was obtained. After ferrous hydroxide was filtered out, it was dissolved in concentrated sulfuric acid (mass concentration of about 85%) to obtain ferrous sulfate solution.

[0044] The filtrate after partially filtering out basic magnesium carbonate was mixed with washing waste to form a slurry. Then, 7% (based on the mass of the washing waste) of a curing agent (a mixture of calcium oxide, sodium phosphate, and sodium persulfate in a mass ratio of 50:10:40) was added, and the mixture was reacted for 20 minutes. After the reaction was completed, the mixture was cured in a rotary kiln at room temperature for 3 hours to obtain harmless manganese slag. The waste gas generated during the curing process was absorbed by countercurrent water to obtain dilute ammonia water. After testing, the manganese leaching concentration of the obtained harmless manganese slag was approximately 0.16 mg / L, and the ammonia nitrogen leaching concentration was approximately 1.08 mg / L. Example 2

[0045] Example 1 was repeated, except that the pH of the water used to wash the electrolytic manganese slag was adjusted to 5-5.3. The purity of the intermediate product manganese tetroxide was detected to be approximately 96.0%, the purity of basic magnesium carbonate was approximately 99.2%, the purity of ferrous ammonium sulfate was approximately 99.3%, the manganese leaching concentration of the harmless manganese slag was approximately 0.22 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.94 mg / L. Example 3

[0046] Example 1 was repeated, except that the amount of urea used was 1.5% of the mass of the washing waste liquid. The purity of the intermediate product manganese tetroxide was detected to be approximately 99.8%, the purity of basic magnesium carbonate was approximately 99.5%, the purity of ferrous ammonium sulfate was approximately 99.5%, the manganese leaching concentration of the harmless manganese slag was approximately 0.30 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.82 mg / L. Example 4

[0047] Example 1 was repeated, except that the amount of urea used was 1.9% of the mass of the washing waste liquid. The purity of the intermediate product manganese tetroxide was detected to be approximately 99.9%, the purity of basic magnesium carbonate was approximately 99.7%, the purity of ferrous ammonium sulfate was approximately 99.5%, the manganese leaching concentration of the harmless manganese slag was approximately 0.21 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.76 mg / L. Example 5

[0048] Example 1 was repeated, except that the amount of urea used was 1% of the mass of the washing waste liquid. The purity of the intermediate product manganese tetroxide was detected to be approximately 99.3%, the purity of basic magnesium carbonate was approximately 98.8%, the purity of ferrous ammonium sulfate was approximately 99.4%, the manganese leaching concentration of the harmless manganese slag was approximately 0.32 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.85 mg / L. Example 6

[0049] Example 1 was repeated, except that the amount of urea used was 0.7% of the mass of the washing waste liquid. The purity of the intermediate product manganese tetroxide was detected to be approximately 98.4%, the purity of basic magnesium carbonate was approximately 98.6%, the purity of ferrous ammonium sulfate was approximately 99.3%, the manganese leaching concentration of the harmless manganese slag was approximately 0.36 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.98 mg / L. Example 7

[0050] Example 1 was repeated, except that urea was replaced with ammonium carbonate. The purity of the intermediate manganese tetroxide was detected to be approximately 95.2%, the purity of basic magnesium carbonate was approximately 96.5%, the purity of ferrous ammonium sulfate was approximately 99.6%, the manganese leaching concentration of the harmless manganese slag was approximately 0.45 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.81 mg / L. Example 8

[0051] Example 1 was repeated, except that urea was replaced with ammonium sulfite. The purity of the intermediate manganese tetroxide was detected to be approximately 93.8%, the purity of basic magnesium carbonate was approximately 95.7%, the purity of ferrous ammonium sulfate was approximately 99.3%, the manganese leaching concentration of the harmless manganese slag was approximately 0.39 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.79 mg / L. Example 9

[0052] Example 1 was repeated, except that the ammonia used to adjust the pH of the washing wastewater after adding urea was replaced with sodium hydroxide. The purity of the intermediate product manganese tetroxide was detected to be approximately 88.2%, the purity of basic magnesium carbonate was approximately 93.5%, the purity of ferrous ammonium sulfate was approximately 92.2%, the manganese leaching concentration of the harmless manganese slag was approximately 0.47 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.84 mg / L. Example 10

[0053] Example 1 was repeated, except that the ammonia used to adjust the pH of the washing wastewater after adding urea was replaced with ammonium carbonate. The purity of the intermediate product manganese tetroxide was detected to be approximately 98.8%, the purity of basic magnesium carbonate was approximately 99.1%, the purity of ferrous ammonium sulfate was approximately 99.6%, the manganese leaching concentration of the harmless manganese slag was approximately 0.35 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.83 mg / L. Example 11

[0054] Example 1 was repeated, except that sodium persulfate was replaced with sodium hypochlorite. The purity of the intermediate product manganese tetroxide was detected to be approximately 98.1%, the purity of basic magnesium carbonate was approximately 99.0%, the purity of ferrous ammonium sulfate was approximately 99.1%, the manganese leaching concentration of the harmless manganese slag was approximately 0.81 mg / L, and the ammonia nitrogen leaching concentration was approximately 6.98 mg / L. Example 12

[0055] Example 1 was repeated, except that sodium persulfate was replaced with calcium oxide. The purity of the intermediate product manganese tetroxide was detected to be approximately 98.2%, the purity of basic magnesium carbonate was approximately 99.3%, the purity of ferrous ammonium sulfate was approximately 99.5%, the manganese leaching concentration of the harmless manganese slag was approximately 1.13 mg / L, and the ammonia nitrogen leaching concentration was approximately 21.24 mg / L. Example 13

[0056] Example 1 was repeated, except that the curing agent did not contain sodium persulfate. The purity of the intermediate product manganese tetroxide was detected to be approximately 99.0%, the purity of basic magnesium carbonate was approximately 98.5%, the purity of ferrous ammonium sulfate was approximately 99.4%, the manganese leaching concentration of the harmless manganese slag was approximately 3.24 mg / L, and the ammonia nitrogen leaching concentration was approximately 40.41 mg / L.

[0057] Comparative Example 1 Example 1 was repeated, except that urea was not added to the washing wastewater for conditioning. The purity of the intermediate product manganese tetroxide was detected to be approximately 90.1%, the purity of basic magnesium carbonate was approximately 88.4%, the purity of ferrous ammonium sulfate was approximately 99.3%, the manganese leaching concentration of the harmless manganese slag was approximately 0.36 mg / L, and the ammonia nitrogen leaching concentration was approximately 0.77 mg / L.

[0058] Comparative Example 2 Example 1 was repeated, except that no ammonia was added to the washing wastewater after urea conditioning. The purity of the intermediate product manganese tetroxide was detected to be approximately 88.0%, the purity of basic magnesium carbonate was approximately 72.7%, the purity of ferrous ammonium sulfate was approximately 99.4%, the manganese leaching concentration of the harmless manganese slag was approximately 0.45 mg / L, and the ammonia nitrogen leaching concentration was approximately 1.06 mg / L.

[0059] Comparative Example 3 Example 1 was repeated, except that the amount of curing agent added after mixing the washing waste residue into a slurry was 0. The purity of the intermediate product manganese tetroxide was detected to be approximately 99.5%, the purity of basic magnesium carbonate was approximately 99.0%, the purity of ferrous ammonium sulfate was approximately 99.3%, the manganese leaching concentration of the harmless manganese slag was approximately 145.62 mg / L, and the ammonia nitrogen leaching concentration was approximately 68.87 mg / L.

Claims

1. A method for recovering valuable resources from manganese slag, characterized in that: The method includes the following steps: S1: The manganese slag is washed with a washing solution, and after solid-liquid separation, washing waste residue and washing waste liquid are obtained respectively. S2: The washing waste liquid is conditioned by a conditioning agent. After conditioning, a precipitant and an oxidant are added in sequence to precipitate manganese. After manganese precipitation, solid-liquid separation is performed to obtain manganese oxide precipitate and primary waste liquid respectively. S3: Adjust the primary waste liquid to alkaline, then add soluble carbonate for magnesium precipitation. After magnesium precipitation, perform solid-liquid separation to obtain basic magnesium carbonate precipitate and secondary waste liquid. S4: Add dilute sulfuric acid and ferrous salt to the secondary waste liquid for a mixed reaction. After the reaction is completed, perform solid-liquid separation to obtain ferrous ammonium sulfate precipitate and tertiary waste liquid respectively. S5: Add ammonia to the waste liquid of the third stage for iron precipitation treatment. After the iron precipitation is completed, perform solid-liquid separation to obtain ferrous hydroxide precipitate and waste liquid of the fourth stage. Mix and homogenize the waste liquid of the fourth stage into the waste liquid of the second stage and then proceed to step S4. After acid hydrolysis of the ferrous hydroxide precipitate, it is recycled to S4 to participate in the mixing reaction. S6: First, the washing waste residue is prepared into a slurry, and then a curing agent is added for curing treatment. After curing, a maintenance treatment is carried out to obtain a harmless cured product.

2. The method according to claim 1, characterized in that: The washing of manganese slag with washing solution is specifically as follows: first, the water is adjusted to a weakly acidic state (preferably pH 5-6) with acid, and then the manganese slag is washed in a multi-stage countercurrent wash (preferably a three-stage countercurrent wash) with the weakly acidic water. Preferably, the solid-liquid ratio for washing manganese slag is 1:1 to 8, and more preferably 1:2 to 6.

3. The method according to claim 1 or 2, characterized in that: The conditioning agent is one or more of ammonium sulfite, urea, ammonium thiosulfate, ammonium sulfate, ammonium chloride, ammonium carbonate, and ammonium bicarbonate, preferably urea; Preferably, the amount of conditioning agent added is 0.5-2%, more preferably 1-1.5%.

4. The method according to any one of claims 1-3, characterized in that: The precipitant is one or more of ammonia, sodium hydroxide, potassium hydroxide, and ammonium carbonate, preferably ammonia; Preferably, the amount of precipitant added is such that the pH of the washing waste liquid is 7-8.

5. The method according to any one of claims 1-4, characterized in that: The oxidant is one or more of hydrogen peroxide, oxygen, persulfate, and hypochlorite, preferably hydrogen peroxide; Preferably, the amount of oxidant added is 1-3%, more preferably 1.5-2.5%.

6. The method according to any one of claims 1-5, characterized in that: Adjusting the primary wastewater to alkaline conditions specifically involves: adjusting the pH of the primary wastewater to 8-9 using an alkali; the alkali being one or more of sodium hydroxide, potassium hydroxide, and ammonia water, preferably ammonia water; and / or The soluble carbonate is one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate, preferably ammonium carbonate; Preferably, the amount of soluble carbonate added is 0.1-1%, more preferably 0.3-0.8%.

7. The method according to any one of claims 1-6, characterized in that: In step S4: dilute sulfuric acid is first added to the secondary waste liquid to obtain a solution system with a pH of 5-6. When the concentration of ammonium sulfate in the solution system is not less than 45 g / L, dilute sulfuric acid is added to adjust the pH of the solution system to 1-2, and ferrous salt is added to it for mixing reaction. When the concentration of ammonium sulfate in the solution system is less than 45 g / L, it is returned to step S1 for use as washing liquid and / or used in subsequent step S6 for pulping of washing waste residue. Preferably, the ferrous salt includes one or more of iron powder, ferrous chloride, ferrous sulfate, and ferrous nitrate, with ferrous sulfate being the most preferred; the amount of ferrous salt added is such that the content of ferrous ions in the solution system is 0.2~0.8 mol / L, preferably 0.3~0.5 mol / L.

8. The method according to any one of claims 1-7, characterized in that: In step S5: the ammonia water added to the waste liquid is dilute ammonia water, and the amount of dilute ammonia water added is 1 to 2 times the concentration of ferrous ions in the waste liquid, preferably 1.2 to 1.6 times.

9. The method according to any one of claims 1-8, characterized in that: In step S5: the precipitate of ferrous hydroxide is acidified to obtain a ferrous salt solution by reacting acid with ferrous hydroxide, preferably by reacting concentrated sulfuric acid with ferrous hydroxide to obtain a ferrous sulfate solution.

10. The method according to any one of claims 1-9, characterized in that: In step S6: the curing agent is one or more of calcium oxide, magnesium oxide, sodium carbonate, phosphate, persulfate, and hypochlorite, preferably a mixture of calcium oxide, phosphate, and persulfate; and / or The curing treatment involves curing in a rotary kiln for 1-5 hours; during the curing process, dilute ammonia water is obtained by absorbing the ammonia gas produced by water. Preferably, the amount of curing agent added is 2-8%, more preferably 3-6%.

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