Manganese slag treatment method for centralized utilization of magnesium resources

Abstract

The invention discloses a manganese slag treatment method capable of intensively utilizing magnesium resources, which adopts magnesium-rich water as manganese slag washing water, so that ammonia nitrogen and manganese in manganese slag can be dissolved out, magnesium in the manganese slag is retained, and the subsequent curing and stabilizing effect of washed slag is improved. And a manganese recovery thought of forward two-stage oxidation, iron removal and manganese precipitation is adopted, so that resource recovery of various valuable metals is realized. Ammonia nitrogen is removed by adopting an ammonium ferrous sulfate method, step closed-loop treatment of sulfur dioxide is realized, and the ammonia-removed high-magnesium wastewater is circularly used for water washing treatment of the electrolytic manganese residues. That is to say, three-zero emission of waste residues, waste gas and waste water is achieved by coupling magnesium-rich circulating water washing with two-stage oxidation and removing ammonia nitrogen through an ammonium ferrous sulfite method, and the method has the advantages of being short in technological process and low in input cost.

Description

Technical Field

[0001] The invention relates to resource treatment of electrolytic manganese slag, and in particular to a harmless and resource treatment method of manganese slag for efficient and centralized utilization of magnesium resources, belonging to the technical field of manganese-containing solid waste treatment. Background Art

[0002] Electrolytic manganese slag is a general term for leaching slag, sulfide slag and iron removal slag produced in the process of electrolytic manganese production. It is black-brown muddy and weakly acidic, and belongs to Class II general industrial solid waste. Generally speaking, 8 to 10 tons of electrolytic manganese slag will be produced for every ton of electrolytic manganese produced. Since there is no generally applicable manganese slag disposal technology, most of my country's electrolytic manganese enterprises transport the waste slag to the yard for storage. However, electrolytic manganese slag generally contains 3 to 6% manganese, 2 to 3% ammonia nitrogen and 8 to 10% iron, which has a certain resource recovery value. At present, for the manganese slag produced by the electrolytic manganese process, water washing is often used to remove the soluble valuable components, and then the washing liquid is disposed of.

[0003] Regarding the water washing treatment of electrolytic manganese, the current focus is on how to improve the leaching rate of manganese slag pollutants, the resource disposal of leachate, and the solidification and stabilization of the remaining manganese slag. In terms of improving the leaching rate of manganese slag pollutants: In Chinese patent CN110551898A "A method for treating electrolytic manganese slag", electrolytic manganese anode liquid is combined with a high-voltage impact method to treat electrolytic manganese slag. In Chinese patent CN 201710755518 "A method for microwave extraction of manganese from electrolytic manganese slag", 5-15% sulfuric acid solution is used to slurry the electrolytic manganese slag, and then microwaves are used to promote the dissolution of manganese. In terms of leachate resource disposal: Chinese patent CN108483501 A "A method for comprehensive utilization of electrolytic manganese slag water washing liquid" adds ammonium bicarbonate to the water washing liquid to convert manganese into manganese carbonate, and then removes impurities and recovers ammonia through precipitation and deamination reaction. Chinese patent CN 112408488 A "A method for recovering soluble manganese ammonium in electrolytic manganese slag" uses an organic phase containing an extractant to extract manganese ions, and obtains high-purity manganese ions through stripping, and the raffinate is stripped of ammonia by alkaline blowing to recover ammonia. In terms of the solidification and stabilization of the remaining manganese slag after water washing: Chinese patent CN 108262336A "A method for solidification treatment of electrolytic manganese slag" reports that electrolytic manganese slag is mixed with alkaline industrial waste slag phosphorus slag, slag, high calcium fly ash, composite alkaline agent, water, etc., mixed and stirred for solidification, and then sent to the slag warehouse for storage. Chinese patent CN 103320621A "A method for solidifying heavy metals in electrolytic manganese slag and co-producing sulfur" uses calcium sulfide to mix with manganese slag to achieve the stabilization and solidification of heavy metals in manganese slag. Chinese patent CN 104307849 A "A method for solidification / stabilization treatment of electrolytic manganese slag" adds alkaline agents and sodium hexametaphosphate to solidify manganese slag. Chinese patent CN104307850 A "A method for solidifying / stabilizing high-concentration water-soluble manganese in manganese slag" adds active silicon dioxide and magnesium oxide to achieve the solidification of manganese slag.

[0004] The above methods each have their own advantages and disadvantages, but none of them takes the whole process of harmlessness of manganese slag into consideration, resulting in large energy consumption, high cost, no closed-loop disposal, and insufficient utilization of magnesium resources, which has resulted in the manganese slag not being effectively treated. Summary of the invention

[0005] In view of the problems of large energy consumption, high cost, no closed-loop disposal and under-utilization of magnesium resources in the treatment process of electrolytic manganese slag in the prior art, the present invention provides a manganese slag treatment method for concentrated utilization of magnesium resources. By using magnesium-rich water containing magnesium as circulating water for washing manganese slag, ammonia nitrogen and manganese in the manganese slag can be dissolved, while magnesium in the manganese slag cannot be dissolved, that is, the magnesium content in the manganese slag is well retained, and the ammonia nitrogen and manganese in the manganese slag can be removed at the same time, thereby realizing the rational utilization of valuable metals in the manganese slag.

[0006] In addition, the present invention also uses SO2 / O2 mixed gas as an oxidant under acidic conditions to oxidize divalent manganese ions into manganese dioxide precipitation, thereby realizing the separation of manganese ions from the solution. At the same time, the remaining sulfur dioxide can be absorbed by the absorption liquid and can participate in the ammonia nitrogen precipitation treatment of the ammonia-containing wastewater after manganese precipitation to obtain high-purity ammonium ferrous sulfite with high economic value. A large amount of magnesium ions are retained in the ammonia-removing wastewater, which can be recycled for the water washing treatment of electrolytic manganese slag. That is, the process of the present invention realizes the closed-loop treatment of wastewater and waste gas, and further couples the difficult-to-close-loop elements with resources, thereby improving economic benefits and helping to reduce treatment costs.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is specifically described as follows:

[0008] A method for treating manganese slag for concentrated utilization of magnesium resources, the method comprising the following steps:

[0009] 1) Manganese slag dissolution treatment: The manganese slag is washed with magnesium-containing water, and the dissolution solution and dissolution slag are obtained by solid-liquid separation.

[0010] 2) Oxidative iron removal treatment: Add hydrogen peroxide to the dissolving solution for reaction, and obtain iron removal liquid and iron-containing slag after solid-liquid separation.

[0011] 3) Oxidative manganese precipitation treatment: A mixed gas containing sulfur dioxide and oxygen is introduced into the iron removal liquid for reaction, and after solid-liquid separation, manganese-rich precipitate and ammonia-containing wastewater are obtained. At the same time, an alkaline solution is used to absorb the sulfur-containing tail gas overflowed during the oxidative manganese precipitation process to obtain a sulfur-containing absorption liquid.

[0012] 4) Ammonia nitrogen precipitation treatment: The ammonia-containing wastewater and the sulfur-containing absorption liquid are mixed to obtain mixed wastewater, and then the mixed wastewater is adjusted to neutral or weakly acidic, and then a soluble ferrous salt is added to react, and after solid-liquid separation, ammonium ferrous sulfite precipitation and ammonia-removing wastewater are obtained. The ammonia-removing wastewater is returned to step 1) to participate in the manganese slag dissolution treatment.

[0013] Preferably, the method further comprises:

[0014] 5) Solidification treatment: The leached residue obtained in step 1) is mixed with a mixed solidifying agent to react to obtain a solidified material, wherein the solidifying agent is a mixture containing at least calcium oxide, magnesium oxide, sodium carbonate, phosphate, and sodium hypochlorite.

[0015] Preferably, the manganese slag is magnesium-containing electrolytic manganese slag, wherein the mass content of magnesium is 0.5-5%, preferably 1-3%, for example, one of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.5%, 4%, 4.5%, and 5%.

[0016] Preferably, the curing agent comprises: 40-60% calcium oxide, 30-70% magnesium oxide, 2-10% sodium carbonate, 0.5-2% phosphate, 1-5% sodium hypochlorite, preferably 45-55% calcium oxide, 35-60% magnesium oxide, 3-8% sodium carbonate, 0.8-1.8% phosphate, 1.5-4.5% sodium hypochlorite.

[0017] Preferably, the phosphate is one or more of calcium dihydrogen phosphate, sodium hydrogen phosphate, and sodium phosphate.

[0018] Preferably, in step 1), the magnesium-containing water is an acidic magnesium-containing water after the pH of the magnesium-containing water is adjusted to 2-6 (preferably 3-5) by using an acid. The acid is an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid and optional acidic gas (including but not limited to sulfur dioxide, nitrogen dioxide, hydrogen sulfide and chlorine).

[0019] Preferably, in step 1), the concentration of magnesium ions in the magnesium-containing water is not less than 150 g / L, preferably not less than 200 g / L, and more preferably not less than 250 g / L.

[0020] Preferably, in step 1), the water washing is a three-stage countercurrent water washing. The liquid-to-solid mass ratio in each stage of water washing is 1.5-8:1, preferably 2-6:1, and more preferably 2.5-5:1.

[0021] Preferably, in step 2), the concentration of the hydrogen peroxide is not less than 25wt%, preferably 25-50wt%, more preferably 30-40wt%. The amount of the hydrogen peroxide added is 0.1-0.8 times the total mass of ferrous ions in the dissolution solution, preferably 0.2-0.6 times, more preferably 0.3-0.4 times.

[0022] Preferably, the reaction time of adding hydrogen peroxide is not less than 5 minutes, preferably 0.3-2 hours, more preferably 0.5-1 hour.

[0023] Preferably, in step 3), in the mixed gas containing sulfur dioxide and oxygen, the concentration of sulfur dioxide is not less than 0.5wt%, and the concentration of oxygen is not less than 5wt%. Preferably, the concentration of sulfur dioxide is 0.5-5wt%, and the concentration of oxygen is 5-50wt%. More preferably, the concentration of sulfur dioxide is 1-3wt%, and the concentration of oxygen is 10-20wt%.

[0024] Preferably, the ratio of the total flow rate of the mixed gas of sulfur dioxide and oxygen to the total volume of the iron removal liquid is 20-70:1, preferably 25-60:1, and more preferably 30-50:1.

[0025] Preferably, the reaction time after the mixed gas containing sulfur dioxide and oxygen is introduced is not less than 10 minutes, preferably 0.5-3 hours, more preferably 0.8-2 hours.

[0026] Preferably, in step 3), the sulfur-containing tail gas overflowing from the oxidation manganese precipitation process is absorbed by an alkaline solution in a three-stage countercurrent absorption, specifically: the sulfur-containing tail gas passes through a primary reaction absorber, a secondary reaction absorber and a tertiary reaction absorber in sequence, wherein the pH of the alkaline solution in the primary reaction absorber and the secondary reaction absorber is independently 8-11 (preferably 8.5-10), and the pH of the alkaline solution in the tertiary reaction absorber is 10-14 (preferably 11-12).

[0027] Preferably, the alkali in the alkaline solution is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, preferably sodium hydroxide.

[0028] Preferably, in step 4), adjusting the mixed wastewater to neutral or weakly acidic is to use alkali (preferably sodium hydroxide) or acid (preferably sulfuric acid) to adjust the pH to ≤ 7, preferably to 5-7.

[0029] Preferably, in step 4), the soluble ferrous salt is ferrous sulfate and / or ferrous chloride, preferably ferrous sulfate.

[0030] Preferably, the soluble ferrous salt is added for a reaction time of 0.1-2 h, preferably 0.3-1.5 h.

[0031] In the prior art, the resource treatment of manganese slag mostly focuses on how to extract as much manganese as possible, such as how to improve the leaching rate of manganese in the manganese slag washing solution, how to reduce the content of impurities in the leachate, how to improve the extraction rate or precipitation conversion rate of manganese in the leachate, etc. These methods have their own advantages and disadvantages, but none of them consider the whole process of harmless treatment of manganese slag, resulting in large energy consumption, high cost, no closed-loop disposal, and the loss of other elements (such as magnesium, sulfur, ammonia and other resources) in the manganese slag treatment process. The problem is that the existing manganese slag treatment process has serious deficiencies and the manganese slag has not been truly harmlessly treated.

[0032] In the present invention, according to the characteristic that manganese slag also contains a certain amount of magnesium and sulfur elements, water washing-water solution resource utilization-washed slag solidification are coupled to form an integrated closed-loop waste-free disposal and low-cost treatment plan, which mainly includes circulating water washing with magnesium-rich solution, which can reduce the dissolution of magnesium in manganese slag and retain it in the washed slag, effectively ensuring the feasibility of subsequent washed slag solidification; the manganese-containing dissolution solution after water washing is subjected to two-stage oxidation to remove iron, precipitate manganese and remove ammonia. While achieving high-retention recovery of manganese elements, by adopting specific gaseous oxidants, high-value recovery of sulfide resources and cascade closed-loop utilization of gaseous oxidants are also achieved; the washed slag is reacted with a specially compatible solidifying agent, and on the premise of retaining magnesium in the washed slag, it reacts with residual ammonia nitrogen and manganese therein to stabilize and fix it. The solidified material can meet the landfill pollution control technical requirements of the "Technical Specifications for Pollution Control of Manganese Slag (HJ1241-2022)".

[0033] In general, when industrial water is used to directly wash manganese slag, the washing liquid mainly contains Mn 2+ Mg 2+ NH4 + 、SO4 2- For the subsequent recycling of washing liquid, Mg 2+ NH4 + 、SO4 2- All are low-value resources, generally treated as impurities for removal, not only increasing processing costs and difficulty in vain, but also easily affecting the quality of the manganese products recovered and producing additional waste residues to pollute the environment, therefore, controlling their dissolution can greatly reduce the difficulty of subsequent water washing liquid resource disposal. The present invention, through reasonable design, adopts an aqueous solution rich in magnesium ions (wherein the concentration of magnesium ions is not less than 150g / L, preferably not less than 200g / L, more preferably not less than 250g / L, saturation or near saturation effect is better) to carry out circulating water washing to manganese slag, which can reduce the dissolution of magnesium in manganese slag, allowing it to be retained in the water washing slag, and only selectively dissolving manganese and ammonia nitrogen. The place different from conventional water washing manganese slag is that the water washing slag after the above treatment is mainly low manganese, low ammonia and high magnesium slag, that is, the present invention effectively retains the magnesium in the manganese slag, and magnesium is a promoting effect for forming a stable gel, which helps the efficient solidification treatment of subsequent water washing slag.

[0034] In the present invention, the washing liquid (i.e., the dissolving liquid) after washing the manganese slag mainly contains manganese ions, ammonia nitrogen, ferrous ions, magnesium ions, sulfate, etc. The general operation of the prior art is to use a pretreatment method to remove Mg 2+After removal, manganese is recovered and ammonia nitrogen is subsequently removed, which has a high processing cost. The present invention first uses hydrogen peroxide as an oxidant to oxidize ferrous iron to ferric iron. The precipitation pH of ferric iron is relatively low, and generally precipitation will occur in a solution with a pH of 3 to 5 to achieve removal. However, the oxidizing property of hydrogen peroxide is limited and cannot oxidize manganese ions. Therefore, the present invention also uses a mixed gas composed of SO2 and O2 as an oxidant, and selectively precipitates manganese under acidic conditions. Since the SO2 / O2 mixed gas will form a strongly oxidizing SO5 under acidic conditions. - The group will oxidize the divalent manganese ion to MnO2 precipitation, thereby realizing separation from the solution. Since the precipitation of magnesium is mainly under alkaline conditions, the iron removal and manganese precipitation of the present invention are all acidic environments, so magnesium will not precipitate, and then the efficient separation of iron, manganese, magnesium, etc. can be realized, and finally the positive extraction of manganese is realized, reducing the disposal cost. The sulfur-containing tail gas overflowed during the manganese precipitation process is absorbed by alkali liquid to obtain an absorption liquid containing sodium sulfite, which can be used for subsequent ammonia removal treatment to prevent wastewater and waste gas emissions.

[0035] In the present invention, the solution after iron removal and manganese precipitation also contains a certain concentration of ammonia nitrogen (ammonia-containing wastewater, generally the ammonia nitrogen concentration will reach 10-30g / L). The conventional method is to adjust the solution to alkalinity for stripping or ammonia evaporation, but this will consume a large amount of alkali solution. The present invention is based on the by-product characteristics of the ammonium ferrous sulfite method and manganese precipitation, and adds ferrous sulfate and an absorption liquid containing sodium sulfite to cause a precipitation reaction; that is, by the ammonium ferrous sulfite method: under the condition that the solution pH is 5-7, ammonia nitrogen will combine with ferrous iron and sulfite to form ammonium ferrous sulfite precipitation, wherein the sulfite solution comes from the absorption liquid of sulfur-containing tail gas after manganese precipitation, so as to realize the cascade utilization of sulfur. The whole process of precipitating ammonia nitrogen is weakly acidic and will not cause the precipitation of magnesium in the solution. The opening and resource utilization of ammonia nitrogen are effectively realized. The wastewater after ammonia removal mainly contains magnesium ions, so this part of the magnesium-containing wastewater can be recycled for the washing treatment water of electrolytic manganese slag, and zero discharge of wastewater is truly realized.

[0036] In the present invention, the washed slag obtained after washing is a low-manganese, low-ammonia, high-magnesium slag, in which magnesium is mainly present as magnesium sulfate, which is the core raw material for preparing basic magnesium sulfate cement. Based on the characteristics of the washed slag, the present invention has developed an ionic curing agent with calcium oxide, magnesium oxide, sodium carbonate, phosphate, sodium hypochlorite, etc. as the core, which, after mixing with the washed slag, will undergo complex physical and chemical reactions in the presence of magnesium ions, so that the magnesium in the washed slag is fully utilized, and the residual ammonia nitrogen and manganese in the slag are promoted to achieve stable immobilization. The solidified material after curing meets the landfill pollution control technical requirements of the "Technical Specifications for Pollution Control of Manganese Slag (HJ 1241-2022)". It can be directly used for resource utilization such as road construction, filling, and unburned bricks. Zero discharge of washed waste slag is effectively achieved.

[0037] In the present invention, through experimental research, it is found that the components of the curing agent are: 40-60% calcium oxide, 30-70% magnesium oxide, 2-10% sodium carbonate, 0.5-2% phosphate, 1-5% sodium hypochlorite; preferably 45-55% calcium oxide, 35-60% magnesium oxide, 3-8% sodium carbonate, 0.8-1.8% phosphate, 1.5-4.5% sodium hypochlorite. The mixed curing agent of the above special components has excellent curing and stabilizing effect on low manganese, low ammonia and high magnesium water-washed slag.

[0038] In the present invention, during the oxidation precipitation of manganese, the absorption process of the sulfur-containing tail gas is as follows: the tail gas containing SO2 and the alkali solution are subjected to absorption reaction using a three-stage countercurrent absorption device. The alkali solution can be sodium carbonate or sodium hydroxide, preferably sodium hydroxide. The tail gas containing SO2 passes through a primary reaction absorber, a secondary reaction absorber, and a tertiary reaction absorber in sequence, and the pH in the primary reaction absorber and the secondary reaction absorber are independently controlled to be 8-11 (preferably 8.5-10), and the pH in the tertiary reaction absorber is controlled to be 10-14 (preferably 11-12). By regulation, sodium sulfite is mainly formed in the primary reaction absorber.

[0039] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0040] 1: The present invention adopts magnesium-rich water to wash the electrolytic manganese slag, while realizing the dissolution of manganese and ammonia nitrogen in the manganese slag, effectively retaining the magnesium element in the washed slag, and developing a mixed curing agent specifically according to the characteristics of high magnesium in the washed slag, thereby realizing efficient and stable curing of the electrolytic manganese slag washed slag, and meeting the landfill pollution control technical requirements of the "Technical Specifications for Pollution Control of Manganese Slag (HJ 1241-2022)".

[0041] 2: In the present invention, in view of the high magnesium content in the water wash, the idea of ​​recovering manganese by two-stage forward oxidation to remove iron and precipitate manganese is adopted, which can not consume the magnesium content in the water wash, and simultaneously obtain iron products and high-quality manganese dioxide products, thus realizing the resource recovery of multiple valuable metals.

[0042] 3: The present invention is based on the high-ammonia nitrogen wastewater, high-sulfur absorption liquid, etc. generated by the two-stage oxidation iron removal and manganese precipitation process, and adopts the ammonium ferrous sulfite method to achieve the removal of ammonia nitrogen. Only by adding ferrous ions, the coupled treatment of high-ammonia nitrogen wastewater and high-sulfur absorption liquid can be achieved, and a high-value ammonium ferrous sulfite product can be obtained, realizing the step-by-step closed-loop treatment of sulfur dioxide. The high-magnesium wastewater after ammonia removal is recycled for water washing treatment of electrolytic manganese slag, achieving zero emission of waste gas and wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The present invention is a process flow chart of the manganese slag treatment method for concentrated utilization of magnesium resources. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0045] Example 1

[0046] Magnesium-containing water with a magnesium content of 165 g / L (its pH value is adjusted to about 4 using sulfuric acid) is used to perform a three-stage countercurrent washing treatment on magnesium-containing electrolytic manganese slag (the magnesium-containing electrolytic manganese slag produced by an electrolytic manganese metal plant in Guizhou, and the mass content of magnesium is about 2.06% after being dried to constant weight) (the liquid-to-solid ratio in each stage of washing is 3:1, and the washing liquid is recycled), and finally a dissolving solution (the discharge amount is about 1 times that of the manganese slag) and a dissolving slag are obtained by solid-liquid separation.

[0047] Add 35% hydrogen peroxide (the amount added is 0.3 times the total mass of ferrous ions in the dissolution) to the dissolution solution for 40 minutes, and then obtain iron removal liquid and iron-containing slag after solid-liquid separation.

[0048] A mixed gas containing sulfur dioxide and oxygen (in the mixed gas: the concentration of sulfur dioxide is 1.5wt%, the concentration of oxygen is 7.5wt%) is introduced into the iron removal liquid for reaction for 1 hour, and then a manganese-rich precipitate and ammonia-containing wastewater are obtained after solid-liquid separation. At the same time, a three-stage countercurrent absorption reaction device is used to absorb the overflowed sulfur-containing tail gas to obtain a sulfur-containing absorption liquid.

[0049] The ammonia-containing wastewater and the sulfur-containing absorption liquid are mixed to obtain mixed wastewater, and then the mixed wastewater is adjusted to a pH of about 6, and then ferrous sulfate (the amount of which is 23 g / L) is added to react for 1 hour, and then ammonium ferrous sulfite precipitation and ammonia-removing wastewater are obtained after solid-liquid separation. The ammonia-removing wastewater with a high magnesium content is returned to step 1) as water for washing manganese slag.

[0050] The dissolved slag (whose dry basis weight content of magnesium is about 3.71%) is mixed with a mixed curing agent (the curing agent is composed of 49% calcium oxide, 40% magnesium oxide, 6% sodium carbonate, 1.5% sodium phosphate, and 3.5% sodium hypochlorite) to obtain a solidified material. The leaching toxicity of the solidified material is 0.022 mg / L manganese, 4.06 mg / L ammonia nitrogen, and 1.73% soluble salt, which meets the technical requirements for landfill pollution control in the "Technical Specifications for Manganese Slag Pollution Control (HJ 1241-2022)".

[0051] Example 2

[0052] The magnesium-containing electrolytic manganese slag (the dry basis mass content of magnesium is about 2.06%) is subjected to three-stage countercurrent washing treatment (the liquid-to-solid ratio in each stage of washing is 3:1, and the washing liquid is recycled) with magnesium-containing water with a magnesium content of 200 g / L (the pH value is adjusted to about 4 with sulfuric acid), and finally the dissolution liquid (the discharge amount is about 1 times that of the manganese slag) and the dissolution slag are obtained by solid-liquid separation.

[0053] Add 35% hydrogen peroxide (the amount added is 0.3 times the total mass of ferrous ions in the dissolution) to the dissolution solution for 40 minutes, and then obtain iron removal liquid and iron-containing slag after solid-liquid separation.

[0054] A mixed gas containing sulfur dioxide and oxygen (in the mixed gas: the concentration of sulfur dioxide is 1.5wt%, the concentration of oxygen is 7.5wt%) is introduced into the iron removal liquid for reaction for 1.2 hours, and then a manganese-rich precipitate and ammonia-containing wastewater are obtained after solid-liquid separation. At the same time, a three-stage countercurrent absorption reaction device is used to absorb the overflowed sulfur-containing tail gas to obtain a sulfur-containing absorption liquid.

[0055] The ammonia-containing wastewater and the sulfur-containing absorption liquid are mixed to obtain mixed wastewater, and then the mixed wastewater is adjusted to a pH of about 5, and then ferrous sulfate (the amount of which is 25 g / L) is added to react for 1 hour, and then ammonium ferrous sulfite precipitation and ammonia-removing wastewater are obtained after solid-liquid separation. The ammonia-removing wastewater with a high magnesium content is returned to step 1) as water for washing manganese slag.

[0056] The dissolved slag (whose dry basis weight content of magnesium is about 4.41%) is mixed with a mixed curing agent (the curing agent is composed of 49% calcium oxide, 40% magnesium oxide, 6% sodium carbonate, 1.5% sodium phosphate, and 3.5% sodium hypochlorite) to obtain a solidified material. The leaching toxicity of the solidified material is 0.018 mg / L manganese, 3.62 mg / L ammonia nitrogen, and 1.82% soluble salt, which meets the landfill pollution control technical requirements of the "Technical Specifications for Manganese Slag Pollution Control (HJ 1241-2022)".

[0057] The processes of Examples 1 and 2 were repeated to carry out Examples 3-8 and Comparative Examples 1-12. The specific parameters of each Example and Comparative Example are shown in the following table:

[0058]

[0059]

[0060]

[0061]

Claims

1. A method for treating manganese slag for concentrated utilization of magnesium resources, characterized in that: The method comprises the following steps: 1) Manganese slag dissolution treatment: The manganese slag is washed with magnesium-containing water, and the solid-liquid separation is performed to obtain the dissolution solution and the dissolution slag; 2) Oxidative iron removal treatment: hydrogen peroxide is added to the dissolving solution for reaction, and iron removal liquid and iron-containing slag are obtained after solid-liquid separation; 3) Oxidative manganese precipitation treatment: a mixed gas containing sulfur dioxide and oxygen is introduced into the iron removal liquid for reaction, and after solid-liquid separation, a manganese-rich precipitate and ammonia-containing wastewater are obtained; at the same time, an alkaline solution is used to absorb the sulfur-containing tail gas overflowed during the oxidative manganese precipitation process to obtain a sulfur-containing absorption liquid; 4) Ammonia nitrogen precipitation treatment: the ammonia-containing wastewater and the sulfur-containing absorption liquid are mixed to obtain mixed wastewater, and then the mixed wastewater is adjusted to neutral or weakly acidic, and then a soluble ferrous salt is added to react, and after solid-liquid separation, ammonium ferrous sulfite precipitate and ammonia-removing wastewater are obtained; the ammonia-removing wastewater is returned to step 1) to participate in the manganese slag dissolution treatment.

2. The method for treating manganese slag according to claim 1, characterized in that: The method further includes: 5) Solidification treatment: mixing the leached residue obtained in step 1) with a mixed solidifying agent to obtain a solidified material; wherein the solidifying agent is a mixture containing at least calcium oxide, magnesium oxide, sodium carbonate, phosphate, and sodium hypochlorite; and / or The manganese slag is magnesium-containing electrolytic manganese slag, wherein the mass content of magnesium is 0.5-5%, preferably 1-3%.

3. The method for treating manganese slag according to claim 2, characterized in that: The curing agent comprises: 40-60% calcium oxide, 30-70% magnesium oxide, 2-10% sodium carbonate, 0.5-2% phosphate, 1-5% sodium hypochlorite; preferably 45-55% calcium oxide, 35-60% magnesium oxide, 3-8% sodium carbonate, 0.8-1.8% phosphate, 1.5-4.5% sodium hypochlorite; Preferably, the phosphate is one or more of monocalcium phosphate, sodium hydrogen phosphate, and sodium phosphate.

4. The method for treating manganese slag according to any one of claims 1 to 3, characterized in that: In step 1), the magnesium-containing water is acidic magnesium-containing water after the pH of the magnesium-containing water is adjusted to 2-6 (preferably 3-5) with acid; the acid is an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid and optional acidic gas (including but not limited to sulfur dioxide, nitrogen dioxide, hydrogen sulfide and chlorine).

5. The method for treating manganese slag according to any one of claims 1 to 4, characterized in that: In step 1), the concentration of magnesium ions in the magnesium-containing water is not less than 150 g / L, preferably not less than 200 g / L, and more preferably not less than 250 g / L.

6. The method for treating manganese slag according to any one of claims 1 to 5, characterized in that: In step 1), the water washing is a three-stage countercurrent water washing; the liquid-to-solid mass ratio in each stage of water washing is 1.5-8:1, preferably 2-6:1, and more preferably 2.5-5:

1.

7. The method for treating manganese slag according to any one of claims 1 to 6, characterized in that: In step 2), the concentration of the hydrogen peroxide is not less than 25wt%, preferably 25-50wt%, more preferably 30-40wt%; the amount of the hydrogen peroxide added is 0.1-0.8 times the total mass of ferrous ions in the dissolution solution, preferably 0.2-0.6 times, more preferably 0.3-0.4 times; Preferably, the reaction time of adding hydrogen peroxide is not less than 5 minutes, preferably 0.3-2 hours, more preferably 0.5-1 hour.

8. The method for treating manganese slag according to any one of claims 1 to 7, characterized in that: In step 3), in the mixed gas containing sulfur dioxide and oxygen, the concentration of sulfur dioxide is not less than 0.5wt%, and the concentration of oxygen is not less than 5wt%; preferably, the concentration of sulfur dioxide is 0.5-5wt%, and the concentration of oxygen is 5-50wt%; more preferably, the concentration of sulfur dioxide is 1-3wt%, and the concentration of oxygen is 10-20wt%; Preferably, the ratio of the total flow rate of the mixed gas of sulfur dioxide and oxygen to the total volume of the iron removal liquid is 20-70:1, preferably 25-60:1, more preferably 30-50:1; and / or The reaction time after the mixed gas containing sulfur dioxide and oxygen is introduced is not less than 10 minutes, preferably 0.5-3 hours, and more preferably 0.8-2 hours.

9. The method for treating manganese slag according to any one of claims 1 to 8, characterized in that: In step 3), the sulfur-containing tail gas overflowed during the oxidation precipitation of manganese is absorbed by an alkaline solution for three-stage countercurrent absorption, specifically: the sulfur-containing tail gas passes through a primary reaction absorber, a secondary reaction absorber and a tertiary reaction absorber in sequence, wherein the pH of the alkaline solution in the primary reaction absorber and the secondary reaction absorber is independently 8-11 (preferably 8.5-10), and the pH of the alkaline solution in the tertiary reaction absorber is 10-14 (preferably 11-12); Preferably, the alkali in the alkaline solution is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, preferably sodium hydroxide.

10. The method for treating manganese slag according to any one of claims 1 to 9, characterized in that: In step 4), adjusting the mixed wastewater to neutral or weakly acidic is to use alkali (preferably sodium hydroxide) or acid (preferably sulfuric acid) to adjust the pH to ≤ 7, preferably pH 5-7; and / or In step 4), the soluble ferrous salt is ferrous sulfate and / or ferrous chloride, preferably ferrous sulfate; Preferably, the soluble ferrous salt is added for a reaction time of 0.1-2 h, preferably 0.3-1.5 h.

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