Method for removing and recovering manganese from acid mine wastewater

Abstract

The invention belongs to the technical field of wastewater treatment, and provides a method for removing and recovering manganese from acid mine wastewater. The method comprises the steps that the acid mine wastewater is subjected to iron removal treatment to obtain iron removal supernate, a manganese removal agent is added into the iron removal supernate to obtain manganese precipitation residues and manganese removal supernate, the manganese precipitation residues and sulfuric acid are mixed to obtain leaching liquid and leaching residues, and the leaching liquid is electrolyzed to obtain metal manganese; the manganese removal agent is sodium silicate and / or sodium metasilicate. According to the method, the added manganese removal agent does not enable silicate ions and manganese ions to generate manganese silicate, but enables the silicate ions to generate a hydrated calcium silicate adsorbent or a porous magnesium silicate adsorbent in situ with calcium and magnesium ions by using the calcium and magnesium ions existing in the acid mine wastewater, so that the recovery and removal of manganese are realized; the method disclosed by the invention is simple and low in cost, and not only realizes recovery of manganese resources, but also realizes deep treatment of residual manganese; and the leaching residues generated in the manganese recovery stage can also be used for deeply treating the manganese-removed supernate, so that the generation of waste residues is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a method for removing and recovering manganese from acidic mine wastewater. Background Art

[0002] During the sulfide mining process, acid mine drainage is formed under the action of water, air and bacteria. The pH value of acid mine drainage is usually low, generally 1.8 to 3.0, and contains a large amount of inorganic ions, such as SO4 2- , Ca 2+ Mg 2+ 、Al 3+ 、Fe 2+ 、Fe 3+ 、Mn 2+ 、Cu 2+ , Pb 2+ and Zn 2+ In industry, acid mine wastewater is usually first treated by sulfide precipitation to recover copper ions, and then lime milk is added and aeration is performed to adjust the pH value of the wastewater to 7-8 for neutralization treatment. After neutralization, the Cu 2+ , Pb 2+ 、Zn 2+ The concentration of metal ions such as Mn can generally meet the emission standards, while 2+ The concentration of Mn is usually higher than 15 mg / L, which fails to meet the emission standards (Mn 2+ The emission standard is <2mg / L).

[0003] For Mn in acid mine drainage 2+ An effective method for removing Mn is lime milk neutralization precipitation method, which adjusts the pH value of wastewater to above 9.0 and performs neutralization precipitation treatment. Usually, Mn 2+ The concentration is reduced to below 2 mg / L. However, in fact, because acid mine drainage also contains a large amount of SO4 2- , Ca 2+ Mg 2+ and Al 3+ When lime milk is added to adjust the pH value of wastewater to above 8.4, on the one hand, it will accelerate the scaling of equipment (calcium sulfate scale), on the other hand, Mg 2+ A large amount of precipitation begins, and the generated Al(OH)3 begins to dissolve, which will consume a large amount of lime milk and produce a large amount of precipitated residue. Taking all factors into consideration, the pH value of wastewater is usually controlled at around 7.6 by using lime milk in industry.

[0004] Therefore, industrial manganese removal from acid mine drainage typically involves pre-treatment with lime milk followed by further treatment with strong oxidants such as persulfate, permanganate, or ferrate. However, these strong oxidants are generally expensive, leading to increased operating costs. Furthermore, current treatment of manganese in acid mine drainage primarily relies on direct discharge to meet emission standards, without consideration of manganese resource recovery, which results in a certain degree of resource waste.

[0005] Therefore, providing efficient and low-cost removal of manganese from acidic mine drainage and realizing manganese recovery at the same time is of great significance for wastewater treatment and resource recycling. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for removing manganese from acidic mine wastewater and recovering manganese in view of the shortcomings of the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for removing and recovering manganese from acidic mine wastewater, comprising the following steps:

[0009] 1) removing iron from the acidic mine wastewater to obtain a deironed supernatant;

[0010] 2) adding a manganese removal agent to the iron removal supernatant to obtain a manganese precipitate and a manganese removal supernatant;

[0011] 3) mixing the manganese precipitate residue with sulfuric acid to obtain a leachate and a leach residue;

[0012] 4) electrolyzing the leaching solution to obtain metallic manganese;

[0013] In step 2), the manganese removal agent is sodium silicate and / or sodium metasilicate.

[0014] Preferably, the concentration of manganese ions in the iron removal supernatant in step 1) is ≥50 mg / L, and the total concentration of iron ions and ferrous ions is <0.1 mg / L.

[0015] Preferably, based on 1 L of the iron removal supernatant, the mass ratio of the manganese removal agent in step 2) to the manganese ions in the iron removal supernatant is 1 to 10:1;

[0016] The mass content of manganese in the manganese precipitate slag is 5-35%.

[0017] Preferably, in step 3), the mass ratio of the manganese precipitate to sulfuric acid is 1.5 to 3:1, and the mass fraction of the sulfuric acid is 10 to 30%;

[0018] The concentration of manganese ions in the leachate is 35-45 g / L.

[0019] Preferably, when the concentration of manganese ions in the manganese-removed supernatant in step 2) is ≤2 mg / L, the manganese-removed supernatant is directly discharged;

[0020] When the concentration of manganese ions in the manganese-removed supernatant in step 2) is greater than 2 mg / L, performing deep manganese removal treatment on the manganese-removed supernatant;

[0021] The deep manganese removal treatment comprises: adding the leaching residue of step 3) and / or the manganese removal agent of step 2) to the manganese removal supernatant.

[0022] Preferably, in the deep manganese removal treatment, based on 1 L of manganese removal supernatant, the mass ratio of the leaching residue to the manganese ions in the manganese removal supernatant is 10-50:1, and the mass ratio of the manganese removal agent to the manganese ions in the manganese removal supernatant is 10-30:1.

[0023] Preferably, the iron removal treatment in step 1) comprises aeration oxidation and / or hydrogen peroxide oxidation.

[0024] Preferably, the aeration oxidation time is 5 to 30 minutes;

[0025] In the hydrogen peroxide oxidation, the molar ratio of hydrogen peroxide to ferrous ions in the acid mine wastewater is 1 to 3:1.

[0026] Preferably, the pH value of the acid mine wastewater is 1.7 to 3.8;

[0027] The concentration of manganese ions in the acidic mine wastewater is ≥100 mg / L, the concentration of ferrous ions is ≤600 mg / L, the concentration of calcium ions is 100-1000 mg / L, and the concentration of magnesium ions is 500-2500 mg / L.

[0028] The beneficial effects of the present invention include the following:

[0029] 1) The manganese removal agent added in the present invention does not conventionally cause silicate ions to directly react with manganese ions to form manganese silicate. Instead, it utilizes the calcium and magnesium ions present in large quantities in acidic mine wastewater to cause silicate ions to react with calcium and magnesium ions first, generating in situ hydrated calcium silicate adsorbent or porous magnesium silicate adsorbent, which then adsorbs manganese, thereby achieving manganese recovery and removal.

[0030] 2) The method of the present invention is simple and low-cost, and can not only recover manganese resources but also achieve deep treatment of residual manganese until it meets emission standards. The leaching residue produced in the manganese recovery stage can also be used as an adsorbent to deeply treat the manganese in the manganese-removed supernatant, while reducing the generation of waste residue and facilitating resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1The X-ray diffraction patterns of the precipitated residues generated when powdered instant sodium silicate is used to treat wastewater containing no manganese and calcium and wastewater containing manganese and calcium respectively;

[0032] Figure 2 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats manganese-free and calcium-containing wastewater, where (a) is an element surface scan diagram and (b) is an energy spectrum diagram;

[0033] Figure 3 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats manganese and calcium-containing wastewater, where (a) is an element surface scan diagram and (b) is an energy spectrum diagram;

[0034] Figure 4 The X-ray diffraction patterns of the precipitated residues generated when powdered instant sodium silicate is used to treat wastewater containing no manganese and magnesium and wastewater containing manganese and magnesium respectively;

[0035] Figure 5 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats wastewater containing no manganese and magnesium, where (a) is an element surface scan diagram and (b) is an energy spectrum diagram;

[0036] Figure 6 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate is used to treat manganese and magnesium-containing wastewater, where (a) is the element surface scan diagram and (b) is the energy spectrum diagram. DETAILED DESCRIPTION

[0037] The present invention provides a method for removing and recovering manganese from acidic mine wastewater, comprising the following steps:

[0038] 1) removing iron from the acidic mine wastewater to obtain a deironed supernatant;

[0039] 2) adding a manganese removal agent to the iron removal supernatant to obtain a manganese precipitate and a manganese removal supernatant;

[0040] 3) mixing the manganese precipitate residue with sulfuric acid to obtain a leachate and a leach residue;

[0041] 4) electrolyzing the leaching solution to obtain metallic manganese;

[0042] In step 2), the manganese removal agent is sodium silicate and / or sodium metasilicate.

[0043] In the present invention, the sodium silicate preferably comprises powdered instant sodium silicate and / or water glass, and the modulus of the powdered instant sodium silicate is preferably 2 to 3, more preferably 2.1 to 2.5; the mass fraction of water glass is preferably 30 to 40%, more preferably 35%, based on the total mass of the sodium silicate; the sodium metasilicate preferably comprises zero-hydrate sodium metasilicate and / or pentahydrate sodium metasilicate; the manganese removal agent allows silicate ions to first react with calcium and magnesium ions in the acidic mine wastewater to generate a hydrated calcium silicate adsorbent or a porous magnesium silicate adsorbent in situ, which then adsorbs manganese to achieve manganese recovery and removal; the silicate ions do not directly react with the manganese ions to generate manganese silicate.

[0044] In the present invention, the concentration of manganese ions in the iron removal supernatant in step 1) is preferably ≥50 mg / L, further preferably ≥65 mg / L, and more preferably ≥72 mg / L; the total concentration of ferric ions and ferrous ions is preferably <0.1 mg / L, further preferably <0.08 mg / L, and more preferably <0.07 mg / L.

[0045] In the present invention, based on 1L of the iron-removing supernatant, the mass ratio of the manganese removal agent in step 2) to the manganese ions in the iron-removing supernatant is preferably 1 to 10:1, more preferably 3 to 8:1, and more preferably 3.5 to 6:1;

[0046] The mass content of manganese in the manganese precipitate slag is preferably 5-35%, more preferably 10-29%, and even more preferably 15-26%.

[0047] In the present invention, the mass ratio of the manganese precipitate to sulfuric acid in step 3) is preferably 1.5 to 3:1, more preferably 1.8 to 2.5:1, and more preferably 1.9 to 2.3:1; the mass fraction of sulfuric acid is preferably 10 to 30%, more preferably 15 to 25%, and more preferably 18 to 22%;

[0048] The concentration of manganese ions in the leachate is preferably 35 to 45 g / L, more preferably 38 to 42 g / L, and even more preferably 40 g / L.

[0049] In the present invention, when the concentration of manganese ions in the manganese-removed supernatant in step 2) is ≤2 mg / L, the manganese-removed supernatant is preferably directly discharged;

[0050] When the concentration of manganese ions in the manganese-removed supernatant in step 2) is greater than 2 mg / L, the manganese-removed supernatant is preferably subjected to deep manganese removal treatment;

[0051] The deep manganese removal treatment preferably includes adding the leaching residue from step 3) and / or the manganese removal agent from step 2) to the manganese removal supernatant. The leaching residue is rich in active silica gel, which has a good adsorption effect on manganese ions and can be recycled to the manganese removal supernatant for adsorption and manganese removal.

[0052] In the present invention, in the deep manganese removal treatment, based on 1L of manganese removal supernatant, the mass ratio of the leaching residue to the manganese ions in the manganese removal supernatant is preferably 10 to 50:1, more preferably 20 to 40:1, and more preferably 30:1; the mass ratio of the manganese removal agent to the manganese ions in the manganese removal supernatant is preferably 10 to 30:1, more preferably 15 to 25:1, and more preferably 20:1.

[0053] In the present invention, the iron removal treatment in step 1) preferably comprises aeration oxidation and / or hydrogen peroxide oxidation. 2+ 、Fe 3+ It not only has a great inhibitory effect on the effect of manganese removal agents, but also has a great side effect on the electrolytic recovery of manganese in the leachate. It is necessary to remove Fe in acidic mine wastewater as much as possible before manganese recovery and deep manganese removal treatment. 2+ 、Fe 3+ .

[0054] In the present invention, the aeration oxidation time is preferably 5 to 30 minutes, more preferably 10 to 25 minutes, and more preferably 15 to 20 minutes;

[0055] In the hydrogen peroxide oxidation, the molar ratio of hydrogen peroxide to ferrous ions in the acid mine wastewater is preferably 1 to 3:1, more preferably 1.5 to 2.5:1, and even more preferably 2:1.

[0056] In the present invention, before the iron removal treatment, lime milk is preferably added to the acid mine wastewater to obtain mixed wastewater;

[0057] When aeration oxidation is performed, the amount of lime milk added is preferably such that the pH value of the mixed wastewater is 6 to 6.5, more preferably 6.2 to 6.4;

[0058] When hydrogen peroxide oxidation is performed, the amount of lime milk added is preferably such that the pH value of the mixed wastewater is 4.5 to 6.5, more preferably 5 to 6.3, and even more preferably 6.

[0059] In the present invention, lime milk is added to control the pH value of the mixed wastewater. Under the premise of ensuring the iron removal effect, the amount of lime milk can be reduced, the scaling problem of equipment can be alleviated, and the recovery and removal of manganese can be facilitated.

[0060] In the present invention, the pH value of the acid mine wastewater is preferably 1.7 to 3.8, more preferably 2 to 3.2, and more preferably 2.3 to 2.9;

[0061] The concentration of manganese ions in the acidic mine wastewater is preferably ≥100 mg / L, more preferably ≥120 mg / L, and more preferably ≥150 mg / L; the concentration of ferrous ions is preferably ≤600 mg / L, more preferably ≤500 mg / L, and more preferably ≤400 mg / L; the concentration of calcium ions is preferably 100-1000 mg / L, more preferably 300-800 mg / L, and more preferably 350-600 mg / L; the concentration of magnesium ions is preferably 500-2500 mg / L, more preferably 800-2000 mg / L, and more preferably 1000-1600 mg / L.

[0062] In the present invention, the cathode used in the electrolysis in step 4) is preferably a stainless steel electrode, and the anode is preferably a lead alloy electrode;

[0063] The current density of the electrolysis is preferably 300 to 400 A / m 2 , more preferably 350A / m 2 The pH of the electrolysis is preferably 6.4 to 6.8, more preferably 6.5 to 6.7; the temperature of the electrolysis is preferably 35 to 40°C, more preferably 36 to 37°C.

[0064] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0065] The acid mine wastewater used in the examples and comparative examples of the present invention was taken from the acid mine wastewater treatment plant of Dexing Copper Mine of Jiangxi Copper Group. The pH value of the acid mine wastewater was 2.9, and the Fe 3+ The concentration of Fe is 210 mg / L, 2+ The concentration is 269 mg / L, Al 3+ The concentration of Mn is 746 mg / L, 2+ The concentration of Ca is 124 mg / L, 2+ The concentration is 350mg / L, Mg 2+ The concentration is 1461mg / L, SO4 2- The concentration is 12940 mg / L;

[0066] During the electrolysis process, the cathode is a stainless steel electrode, the anode is a lead alloy electrode, and the current density is 350A / m 2 , pH 6.5, temperature 36°C;

[0067] Powdered instant sodium silicate was purchased from Shanghai MacLean Chemical Reagent Company with analytical grade and a modulus of 2.3-2.5.

[0068] Example 1

[0069] Add lime milk to acid mine wastewater to obtain mixed wastewater with a pH value of 6.3. Aerate the mixed wastewater for 25 minutes to obtain iron removal wastewater. Add polyacrylamide flocculant to the iron removal wastewater (the mass ratio of polyacrylamide flocculant to iron removal wastewater is 3mg:1L), mix well, and then perform solid-liquid separation to obtain iron removal supernatant. 2+ The concentration is 65 mg / L, Fe 2+ and Fe 3+ The total concentration is 0.08 mg / L.

[0070] Based on 1L of the iron removal supernatant, 0.2g of powdered instant sodium silicate was added to the iron removal supernatant, and the mixture was stirred at a speed of 250r / min for 15min and then solid-liquid separation was performed to obtain manganese precipitate (the mass content of manganese in the manganese precipitate was 26%) and manganese removal supernatant (the mass content of Mn in the manganese removal supernatant was 26%). 2+ The concentration of manganese precipitate is 15 mg / L). The manganese precipitate is mixed with 20% sulfuric acid and acid leached for 2 hours to obtain leaching residue and leachate. The mass ratio of manganese precipitate to sulfuric acid is 1.9:1. Mn in the leachate 2+ The concentration of manganese is 40 g / L. The leaching solution is electrolyzed to obtain metallic manganese on the cathode surface.

[0071] The leached residue was dried at 110°C for 2.5 hours and then crushed to a particle size of 75 to 150 μm. The leached residue was then added to the manganese removal supernatant (the amount of leached residue added was 0.3 g based on 1 L of manganese removal supernatant) and subjected to deep manganese removal treatment for 30 minutes. Polyacrylamide flocculant was then added (the mass ratio of polyacrylamide flocculant to the volume ratio of manganese removal supernatant was 2 mg: 1 L). After mixing evenly, solid-liquid separation was performed to obtain a supernatant. Mn in the supernatant was 0.1%. 2+ The concentration is 0.45 mg / L, which meets the discharge standard and the supernatant can be discharged directly.

[0072] Example 2

[0073] Lime milk was added to the acid mine wastewater to obtain a mixed wastewater with a pH value of 6.0. The mixed wastewater was aerated for 10 minutes to obtain a primary iron removal wastewater (Fe 2+ The concentration is 10mg / L). Add 30% hydrogen peroxide (the hydrogen peroxide in the hydrogen peroxide and the Fe 2+ The molar ratio of the two groups was 2:1), and the mixture was stirred at 300 rpm for 10 min to obtain secondary iron removal wastewater. Polyacrylamide flocculant was added to the secondary iron removal wastewater (the volume ratio of the polyacrylamide flocculant to the secondary iron removal wastewater was 3 mg:1 L), mixed evenly, and then solid-liquid separation was performed to obtain iron removal supernatant. Mn in the iron removal supernatant 2+The concentration of Fe is 72 mg / L, 2+ and Fe 3+ The total concentration was 0.07 mg / L.

[0074] Based on 1L of the iron removal supernatant, 0.25g of powdered instant sodium silicate was added to the iron removal supernatant, and the mixture was stirred at a speed of 250r / min for 15min and then solid-liquid separation was performed to obtain manganese precipitate (the mass content of manganese in the manganese precipitate was 29%) and manganese removal supernatant (the mass content of Mn in the manganese removal supernatant was 29%). 2+ The concentration is 18 mg / L). The manganese precipitate is mixed with 20% sulfuric acid for acid leaching for 2 hours to obtain leaching residue and leachate. The mass ratio of manganese precipitate to sulfuric acid is 1.8:1. Mn in the leachate 2+ The concentration is 42 g / L. The leachate is electrolyzed to obtain metallic manganese on the cathode surface.

[0075] The leached residue was dried at 110°C for 2.5h, and then crushed to a particle size of 75-150μm. The leached residue was then added to the manganese removal supernatant (the amount of leached residue added was 0.2g based on 1L of manganese removal supernatant) and subjected to deep manganese removal treatment for 30min to obtain a primary manganese removal supernatant (Mn in the primary manganese removal supernatant was 0.2g). 2+ The concentration is 2.5 mg / L). Powdered instant sodium silicate was added to the supernatant of the primary manganese removal (the amount of powdered instant sodium silicate added was 0.05 g based on 1 L of the primary manganese removal supernatant) and a secondary deep manganese removal treatment was performed for 15 min. Then, polyacrylamide flocculant was added (the volume ratio of the polyacrylamide flocculant to the primary manganese removal supernatant was 2 mg:1 L), mixed well, and then solid-liquid separation was performed to obtain a supernatant. Mn in the supernatant was 0.05 g. 2+ The concentration is 0.13 mg / L, which meets the discharge standard and the supernatant can be discharged directly.

[0076] Comparative Example 1

[0077] Lime milk was added to the acid mine wastewater for neutralization and precipitation to remove manganese. The pH value and Mn content of the wastewater after neutralization and precipitation of manganese were significantly affected by the addition of lime milk. 2+ The concentration and amount of dry residue produced are shown in Table 1.

[0078] Table 1 Effect of lime milk neutralization precipitation and manganese removal

[0079]

[0080] As shown in Table 1, the pH value of the wastewater needs to be adjusted to about 9 to remove manganese by adding lime milk for neutralization and precipitation. 2+ However, at this time, the amount of lime milk added and the amount of slag produced are both large, and because the wastewater contains a large amount of SO42- , which will aggravate the scaling of equipment, affect the manganese removal effect, and cannot be successfully applied in industry.

[0081] Comparative Example 2

[0082] Lime milk was added to acid mine drainage to obtain a mixed wastewater with a pH of 7.5, and then an oxidant was added to deeply remove manganese. The manganese removal effects of different oxidants at different dosages are shown in Table 2.

[0083] Table 2 Manganese removal effects of different oxidants at different dosages

[0084]

[0085] As shown in Table 2, the lime milk pretreatment plus oxidant deep treatment solution requires the addition of 1g / L potassium monopersulfate or 1.5g / L potassium persulfate to meet emission standards. However, the high market prices of potassium monopersulfate and potassium persulfate increase treatment costs and complexity.

[0086] Manganese sulfate (analytical grade) and deionized water were used to prepare Mn 2+ The concentration of simulated wastewater was 60 mg / L. Mn was prepared by using calcium chloride (analytical grade), magnesium chloride (analytical grade), manganese sulfate (analytical grade) and deionized water. 2+ The concentration is 60mg / L, Ca 2+ The concentration is 500mg / L, Mg 2+ Simulated wastewater 2 with a concentration of 1000 mg / L.

[0087] Simulated Wastewater 1 and 2 were treated with different treatment agents: the manganese removal agent of the present invention (powdered instant sodium silicate, analytical grade, available from Shanghai Maclean Chemical Reagent Co., Ltd., modulus 2.3-2.5), commercially available calcium silicate (analytical grade, available from Shanghai Maclean Chemical Reagent Co., Ltd.), and commercially available magnesium silicate (analytical grade, available from Sinopharm Chemical Reagent Co., Ltd.). The treatment time was 15 minutes. The manganese ion concentrations in the treated wastewaters are shown in Table 3.

[0088] Table 3 Manganese ion concentration in treated simulated wastewater

[0089]

[0090]

[0091] As can be seen from Table 3, when the wastewater does not contain calcium and magnesium ions, the manganese removal agent powdered instant sodium silicate has basically no manganese removal effect, which indicates that the silicate ions in the manganese removal agent will not directly combine with the manganese ions in the wastewater to form manganese silicate precipitates; when the wastewater contains calcium and magnesium ions, the addition of the manganese removal agent powdered instant sodium silicate can significantly remove manganese, which indicates that the calcium and magnesium ions in the wastewater play a vital role in the manganese removal effect of the manganese removal agent; in comparison, the manganese removal effects of commercially available calcium silicate and commercially available magnesium silicate are significantly lower than those of the manganese removal agent powdered instant sodium silicate, which indicates that the manganese removal agent of the present invention plays a vital role in the removal and recovery of manganese by in situ generating hydrated calcium silicate adsorbent and porous magnesium silicate adsorbent with calcium and magnesium ions in the wastewater.

[0092] Calcium chloride (analytical grade) and deionized water were used to prepare Ca 2+ The concentration of manganese-free calcium-containing wastewater is 500 mg / L; Mn is prepared using calcium chloride (analytical grade), manganese sulfate (analytical grade) and deionized water. 2+ The concentration is 60mg / L, Ca 2+ Wastewater containing manganese and calcium at a concentration of 500 mg / L was treated with powdered instant sodium silicate (analytical grade, Shanghai MacLean Chemical Reagent Company, modulus 2.3-2.5) at a rate of 200 mg per liter of wastewater.

[0093] Figure 1 The X-ray diffraction diagram of the precipitate generated when powdered instant sodium silicate treats wastewater containing no manganese and calcium and wastewater containing manganese and calcium. Figure 1 It can be seen that diffuse diffraction peaks appear between 20° and 40°, and the diffraction peak is strongest at 29.5°, which is the characteristic diffraction peak of calcium silicate hydrate, indicating the formation of amorphous calcium silicate hydrate; when manganese ions exist in the wastewater, the diffraction peak of the precipitate weakens, which is because the adsorption of manganese ions on the surface of calcium silicate hydrate leads to the weakening of the diffraction peak of calcium silicate hydrate.

[0094] Figure 2 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats manganese-free and calcium-containing wastewater, where (a) is the element surface scan diagram and (b) is the energy spectrum diagram. Figure 3 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats manganese and calcium-containing wastewater, where (a) is the element surface scan diagram and (b) is the energy spectrum diagram. Figure 2 It can be seen that the surface of the sediment from the manganese-free and calcium-containing wastewater is mainly composed of O, Si and Ca, and the distribution is basically the same. The element ratios are 75.56%, 16.86% and 7.44% respectively, indicating that calcium silicate hydrate has been formed. Figure 3It can be seen that the surface of the slag from the wastewater containing manganese and calcium is mainly composed of elements such as Si and O, a small amount of Ca and new Mn. The element ratios of O, Si, Ca and Mn are 69.43%, 16.30%, 3.35% and 10.91% respectively. The proportion of calcium element is significantly reduced, and the proportion of Mn element is significantly increased. The distribution of O and Si elements has no obvious change, and is diffusely distributed on the surface of hydrated calcium silicate with similar distribution positions, indicating that Mn in the wastewater 2+ It is Ca on the surface of calcium silicate hydrate 2+ Ion exchange is carried out, and manganese silicate is not directly generated.

[0095] Magnesium chloride (analytical grade) and deionized water were used to prepare Mg 2+ The concentration of manganese-free and magnesium-containing wastewater is 1000 mg / L; magnesium chloride (analytical grade), manganese sulfate (analytical grade) and deionized water are used to prepare Mn 2+ The concentration is 60mg / L, Mg 2+ Wastewater containing manganese and magnesium at a concentration of 1000 mg / L was treated with powdered instant sodium silicate (analytical grade, Shanghai MacLean Chemical Reagent Company, modulus 2.3-2.5) at a rate of 200 mg per liter of wastewater.

[0096] Figure 4 This is the X-ray diffraction pattern of the precipitate generated when powdered instant sodium silicate treats wastewater containing no manganese and magnesium and wastewater containing manganese and magnesium. Figure 4 It can be seen that diffuse diffraction peaks appear between 20° and 30° and between 55° and 65°, which are the characteristic diffraction peaks of magnesium silicate, indicating that amorphous magnesium silicate precipitates are generated in situ; when manganese ions exist in the wastewater, the diffraction peak of the precipitate weakens, which is because the adsorption of manganese ions on the surface of magnesium silicate leads to the weakening of the diffraction peak of magnesium silicate.

[0097] Figure 5 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats manganese-free and magnesium-containing wastewater, where (a) is the element surface scan diagram and (b) is the energy spectrum diagram. Figure 6 This is a scanning electron microscope energy spectrum analysis diagram of the precipitate generated when powdered instant sodium silicate treats manganese and magnesium-containing wastewater, where (a) is the element surface scan diagram and (b) is the energy spectrum diagram. Figure 5 It can be seen that the surface of the precipitate residue from the wastewater containing no manganese and containing magnesium is mainly composed of elements such as O, Si and Mg, and the distribution is basically the same, with the element ratios being 68.34%, 20.55% and 11.11% respectively, indicating the formation of magnesium silicate. Figure 6It can be seen that the surface of the precipitate of manganese and magnesium-containing wastewater is mainly composed of elements such as Si and O, a small amount of Mg and new Mn. The element ratios of O, Si, Mg and Mn are 72.44%, 16.24%, 5.36% and 5.96% respectively. The proportion of magnesium element is significantly reduced, the proportion of Mn element is significantly increased, and the distribution of O and Si elements has no obvious change, indicating that the Mn in the wastewater 2+ It is Mg on the surface of magnesium silicate 2+ Ion exchange is carried out, and manganese silicate is not directly generated.

[0098] 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for removing manganese from acidic mine wastewater and recovering manganese, characterized in that: The following steps are included: 1) removing iron from the acidic mine wastewater to obtain a deironing supernatant; 2) adding a manganese removal agent to the iron removal supernatant to obtain a manganese precipitate and a manganese removal supernatant; 3) mixing the manganese precipitate residue with sulfuric acid to obtain a leachate and a leach residue; 4) electrolyzing the leaching solution to obtain metallic manganese; In step 2), the manganese removal agent is sodium silicate and / or sodium metasilicate.

2. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 1, characterized in that: In step 1), the concentration of manganese ions in the iron removal supernatant is ≥50 mg / L, and the total concentration of iron ions and ferrous ions is <0.1 mg / L.

3. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 1 or 2, characterized in that: Based on 1 L of the iron-removing supernatant, the mass ratio of the manganese removal agent in step 2) to the manganese ions in the iron-removing supernatant is 1 to 10:1; The mass content of manganese in the manganese precipitate slag is 5-35%.

4. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 3, characterized in that: Step 3) the mass ratio of the manganese precipitate to sulfuric acid is 1.5 to 3:1, and the mass fraction of the sulfuric acid is 10 to 30%; The concentration of manganese ions in the leachate is 35-45 g / L.

5. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 4, characterized in that: When the concentration of manganese ions in the manganese-removed supernatant in step 2) is ≤2 mg / L, the manganese-removed supernatant is directly discharged; When the concentration of manganese ions in the manganese-removed supernatant in step 2) is greater than 2 mg / L, performing deep manganese removal treatment on the manganese-removed supernatant; The deep manganese removal treatment comprises: adding the leaching residue of step 3) and / or the manganese removal agent of step 2) to the manganese removal supernatant.

6. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 5, characterized in that: In the deep manganese removal treatment, based on 1 L of manganese removal supernatant, the mass ratio of the leaching residue to the manganese ions in the manganese removal supernatant is 10-50:1, and the mass ratio of the manganese removal agent to the manganese ions in the manganese removal supernatant is 10-30:

1.

7. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 6, characterized in that: The iron removal treatment in step 1) comprises aeration oxidation and / or hydrogen peroxide oxidation.

8. The method for removing manganese from acid mine wastewater and recovering manganese according to claim 7, characterized in that: The aeration oxidation time is 5 to 30 minutes; In the hydrogen peroxide oxidation, the molar ratio of hydrogen peroxide to ferrous ions in the acid mine wastewater is 1 to 3:

1.

9. The method for removing and recovering manganese from acid mine drainage according to claim 1, characterized in that: The pH value of the acid mine drainage water is 1.7 to 3.8; The concentration of manganese ions in the acidic mine wastewater is ≥100 mg / L, the concentration of ferrous ions is ≤600 mg / L, the concentration of calcium ions is 100-1000 mg / L, and the concentration of magnesium ions is 500-2500 mg / L.

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