Method for removing manganese from acidic beneficiation wastewater

Abstract

The application provides a method for removing manganese from acid beneficiation wastewater, wherein the acid beneficiation wastewater is first adjusted in pH by adding alkali liquor in the wastewater, the pH is adjusted to 4.0-6.0, and the reaction time is 10-15 min; then an appropriate manganese removal agent is added into the reaction liquid, the mass ratio of the manganese removal agent to Mn 2+ : is 1:(5-15), and the reaction is carried out for 15-20 min, followed by aeration for 30-60 min; then the pH is adjusted to 6-7 by adding alkali liquor, and solid-liquid separation is carried out, so that the wastewater can be discharged up to the standard. The manganese removal method provided by the application is simple in steps, low in cost, high in removal efficiency, easy to control and low in investment.

Description

Technical Field

[0001] This invention relates to the field of manganese-containing wastewater treatment, and specifically to a method for removing manganese from acidic mineral processing wastewater. Background Technology

[0002] Manganese (Mn) is widely distributed in nature. In groundwater, manganese mainly comes from dissolved manganese carbonates, silicates, and oxides. In surface water, manganese is primarily introduced into the atmosphere through human activities such as manganese mining, dry cell battery production, and municipal incineration pollution, and then enters surface water via rainwater. Manganese exists in nature in valence states from zero to seven, but in water, except for the divalent and tetravalent states, other valence states are prone to disproportionation reactions. Since tetravalent manganese is poorly soluble in water, manganese in water primarily exists in the divalent form. As an important trace element for the human body, manganese is used to construct enzymes necessary for fat metabolism and protein production. It plays a crucial role in bone and connective tissue formation and fat metabolism. Manganese deficiency can impair bone formation, cause growth retardation, and even lead to rickets. Long-term consumption of water with excessive manganese can initially cause neurological dysfunction and neurasthenia, and in later stages may lead to Parkinson's syndrome. Drinking water with excessive manganese can cause irreversible brain diseases such as neurological and psychological disorders.

[0003] Currently, the commonly used methods for manganese removal mainly include natural oxidation, contact oxidation, biological oxidation, and chemical oxidation, all of which have certain limitations.

[0004] The principle of natural oxidation is to aerate the raw water to increase dissolved oxygen, thereby oxidizing manganese. Aeration also removes carbon dioxide and increases the pH value of the water. The manganese removal rate only improves when the pH is greater than 9.5. However, if the pH is too high, acid neutralization is required before the water can be used, which increases the process difficulty and complicates operation and management. Natural oxidation removes manganese slowly, typically requiring a residence time of 2-3 hours, and the process is complex, with high investment costs and less than ideal treatment results.

[0005] Contact oxidation method: In the filter bed, high-valence iron and manganese hydroxides are adsorbed onto the filter media, forming an iron- and manganese-based filter membrane. At this time, the filter media becomes a dark-colored "cooked sand". Under the action of the manganese-based filter membrane (mainly composed of MnO2·xH2O) in the cooked sand, divalent manganese is oxidized to manganese dioxide and adsorbed onto the filter media, continuously renewing the manganese-based filter membrane. The contact oxidation method has many advantages over natural oxidation, such as reduced reaction time, thus reducing operating and investment costs; and no need to adjust the pH of the raw water, as manganese can be removed simply through aeration. However, it also has many problems: manganese has a higher redox potential than iron, and when the raw water contains iron, it will affect the manganese removal efficiency. Furthermore, the oxidation rate of manganese is relatively slow, requiring a longer time to form a manganese-based filter membrane. Frequent backwashing of the filter bed is detrimental to the formation of the manganese-based filter membrane, and the manganese removal effect cannot be guaranteed.

[0006] Biological oxidation method: On the surface of the biological manganese removal filter layer, a large number of iron and manganese oxidizing bacteria exist. Under neutral conditions, divalent manganese (Mn)... 2+ The manganese oxidizing bacteria first adsorb onto the filter membrane surface and, under the action of extracellular enzymes, oxidize into high-valence manganese oxides such as manganese dioxide. The generated manganese oxides are then adsorbed onto the filter media surface, thus renewing the filter membrane. Biological oxidation for manganese removal has been studied for many years and has advantages such as simple process and convenient operation and management. However, current research on engineering design theory and parameter design for manganese removal in biological filters is limited, and corresponding engineering practices are also relatively lacking. Furthermore, a standardized commissioning method is lacking during operation; for example, how backwashing intensity and filtration rate affect the biological stability of the filter layer. The cultivation of manganese-oxidizing bacteria remains at the laboratory stage, and its corresponding manganese removal kinetics need further refinement.

[0007] The principle of chemical oxidation is that the oxidant oxidizes divalent manganese into higher-valence manganese oxides such as manganese dioxide, which are then removed in subsequent treatment units such as coagulation, sedimentation, and filtration. Commonly used oxidants include potassium permanganate, sodium hypochlorite, potassium ferrate, and ozone. Potassium permanganate (KMnO4) is a commonly used strong oxidant. It reacts with divalent manganese in the raw water to form hydrated manganese dioxide with a large specific surface area, which can adsorb divalent manganese in the water. However, the dosage of potassium permanganate must be determined according to the manganese concentration of the raw water. If too little is added, the manganese in the effluent will not meet the standard. If too much is added, the manganese in the permanganate ions will dissolve back, resulting in excessive color in the effluent and an increase in manganese concentration instead of a decrease, thus easily leading to secondary pollution. Sodium hypochlorite (NaClO) can oxidize divalent manganese into insoluble manganese oxides such as manganese dioxide. The main drawback of sodium hypochlorite for manganese oxide is that when reducing substances such as ammonia nitrogen, organic matter, and phenols are present in the water, the actual required effective chlorine content is higher than the theoretical value. The higher the dosage of sodium hypochlorite, the more disinfection byproducts (DBPs) such as chloroform are generated from organic matter. Furthermore, the ferric hydroxide formed by the reaction of sodium hypochlorite with iron and manganese has an amorphous structure, leading to difficult-to-dehydrate sediment. Potassium ferrate (K2FeO4) reacts with heavy metal ions to form ferric hydroxide, which has both adsorption and coagulation functions. When potassium ferrate reacts with manganese, Fe(VI) is reduced to Fe(III). Fe(III) is harmless to the body and has adsorption and flocculation effects, promoting the sedimentation and removal of the product MnO2, thereby promoting manganese removal. However, its treatment cost is high. Ozone (O3) has strong oxidizing properties and can oxidize divalent manganese into insoluble oxides such as manganese dioxide, which can then be removed through simple coagulation and precipitation. Ozone oxidation of manganese can occur at relatively low pH values ​​and does not require an additional catalyst. However, ozone has low solubility in water, and insufficient mixing cannot guarantee effective manganese ion removal. Ozone transportation requires strict control; leaks can cause memory loss, dizziness, and other adverse effects. Furthermore, ozone generators are expensive and cumbersome to operate, and are generally used for advanced treatment in drinking water. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for removing manganese from acidic mineral processing wastewater, so as to solve the technical problems of high cost, large slag volume and unqualified effluent in the existing wastewater manganese removal process.

[0009] This invention is achieved through the following technical solution: (1) Add alkali solution to acidic mineral processing wastewater to adjust pH to 4.0-6.0, and react for 10-15 minutes; (2) Add manganese removal agent to the reaction solution after step (1), according to Mn 2+ The mass ratio of manganese removal agent is 1:(5~15), and the reaction time is 15-20 min. (3) Aerate the liquid after the reaction in step (2) for 30-60 min; (4) Add alkali solution to the solution in step (3), adjust the pH to 6~7, react for 10~15 minutes, separate solid and liquid, and discharge wastewater in compliance with standards.

[0010] Further, in step (2), the manganese removal agent is prepared as follows: (a) Prepare a chitosan solution with a concentration of 20-30 g / L in glacial acetic acid, adjust the pH to 5.0-6.0, and stir for 2-5 minutes. Slowly add a sodium tripolyphosphate solution with a concentration of 2.0-3.0 g / L. The volume ratio of sodium tripolyphosphate to chitosan solution is 1:(1.5-2.0). Let stand at room temperature for 30 minutes to form a chitosan microparticle suspension.

[0011] (b) Dissolve anhydrous sulfite in water to prepare a sulfite solution of 30-50 g / L, wherein the sulfite is at least one of Na2SO3, K2SO3, NaHSO3, and KHSO3.

[0012] (c) Mix sodium sulfite solution and chitosan microparticle suspension at a volume ratio of 1:(25~30) to obtain a sulfite-chitosan microparticle suspension and a manganese removal agent.

[0013] Furthermore, in step (2), a manganese removal agent is added to the wastewater, according to Mn 2+ The mass ratio of manganese removal agent is 1:(5~15), and the reaction time is 20-40 min.

[0014] Furthermore, in step (3), the aeration rate is 8~16 L / min per liter of water.

[0015] Furthermore, the wastewater contains the transition metal Fe. 2+ and Mn 2+ The total content is <500mg / L.

[0016] Compared with existing technologies, the manganese removal agent proposed in this invention can remove manganese under acidic conditions. The innovation of this invention lies in: Sulfite-modified chitosan slowly releases sulfite ions into wastewater, reducing high-valence manganese ions in the wastewater to divalent manganese ions. These divalent manganese ions then combine with sulfite ions to form manganese sulfite, thus initially removing manganese. Under weakly acidic conditions, in the presence of oxygen and transition metal ions (ferrous and manganese ions), sulfite ions can generate highly oxidizing free radicals such as sulfoxyl radicals and hydroxyl radicals, which oxidize and remove residual manganese ions from the wastewater. 2+ Removed with manganese oxide particles. As the oxidation reaction proceeds, some of the modified chitosan is oxidized, with hydroxyl groups being oxidized to carboxyl groups and other groups, which can react with Mn.2+ Complexation further removes manganese from wastewater. The synergistic effect of iron and manganese also contributes to manganese removal. Chitosan, with its porosity, large specific surface area, and hydroxyl groups at the ortho-position of its free amino groups, exhibits strong chelating properties and adsorption chelation capabilities, also removing some manganese ions. Modified chitosan contains phosphate groups, which can complex with manganese in wastewater, achieving deep treatment of manganese-containing wastewater. It also acts as a flocculant, shortening the reaction process. This results in efficient removal of manganese ions from wastewater, with the treated wastewater containing less than 2.0 mg / L, allowing for discharge. This invention features simple steps, low reagent dosage, low cost, high removal efficiency, easy control and operation, low investment, and low operating costs. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for removing manganese from acidic mineral processing wastewater according to the present invention. Detailed Implementation

[0018] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0019] Example 1

[0020] like Figure 1 As shown, this embodiment relates to a method for removing manganese from acidic mineral processing wastewater, the process of which is as follows: Figure 1 As shown; the method steps include: (1) Acidic mineral processing wastewater was used as raw material. The wastewater contained 118.22 mg / L of ferrous ions, 454 mg / L of total iron, 117.60 mg / L of manganese ions, and pH 3.27.

[0021] (2) Use 10% sodium hydroxide to adjust the pH of the original solution to 5.5 and react for 15 min.

[0022] (3) According to the ratio of total manganese in acidic mineral processing wastewater to manganese removal agent mass of 1:10, after adding manganese removal agent, react for 20 minutes to achieve preliminary removal of manganese from wastewater.

[0023] (4) Air is introduced into the liquid after preliminary manganese removal at a rate of 4 L / min per liter of water, and the reaction is carried out for 40 min to further remove manganese; (5) Using 10% liquid alkali, the pH was adjusted to 7.0, the reaction time was 15 min, and after solid-liquid separation, the manganese content in the effluent was 1.83 mg / L, and the manganese removal rate was 98.44%.

[0024] The preparation process of the manganese removal agent is as follows: (a) Chitosan was placed in glacial acetic acid solution to prepare a 20 g / L solution. The pH was adjusted to 5.5. The chitosan solution was stirred for 2 minutes. Then, 2.5 g / L sodium tripolyphosphate solution was slowly added. The volume ratio of sodium tripolyphosphate to chitosan solution was 1:1.5. The solution was allowed to stand at room temperature for 30 minutes to form a chitosan microparticle suspension.

[0025] (b) Dissolve anhydrous sodium sulfite in water to prepare a 50 g / L sodium sulfite solution.

[0026] (c) Mix sodium sulfite solution and chitosan solution at a volume ratio of 1:30 to form sodium sulfite-chitosan microparticle suspension to obtain manganese removal agent.

[0027] Example 2

[0028] This embodiment relates to a method for removing manganese from acidic mineral processing wastewater; the method steps include: (1) Using acidic mineral processing wastewater as raw material, the wastewater contains 181.59 mg / L ferrous ions, 371.73 mg / L total iron, 99.62 mg / L manganese ions, and has a pH of 3.32. (2) Use 10% calcium hydroxide to adjust the pH of the reaction solution in the above steps to 6.0 and react for 10 min.

[0029] (3) According to the ratio of total manganese in acidic mineral processing wastewater to manganese removal agent mass of 1:10, after adding manganese removal agent, react for 15 minutes to achieve preliminary removal of manganese from wastewater.

[0030] (4) Air is introduced into the liquid after preliminary manganese removal at a rate of 16 L / min per liter of water, and the reaction is carried out for 60 min to further remove manganese; (5) Using 10% liquid alkali, the pH of the reaction solution was adjusted to 6.5, the reaction time was 15 min, and after solid-liquid separation, the manganese content in the effluent was 0.41 mg / L, and the manganese removal rate was 99.58%.

[0031] The preparation process of the manganese removal agent is as follows: (a) Chitosan was placed in glacial acetic acid solution to prepare a 25 g / L solution. The pH was adjusted to 5.0. The chitosan solution was stirred for 2 minutes. A 2.5 g / L sodium tripolyphosphate solution was added slowly. The volume ratio of sodium tripolyphosphate to chitosan solution was 1:1.5. The solution was allowed to stand at room temperature for 30 minutes to form a chitosan microparticle suspension.

[0032] (b) Dissolve anhydrous potassium sulfite and potassium bisulfite in water at a mass ratio of 1:1 to prepare a 40 g / L mixed solution of potassium sulfite and potassium bisulfite.

[0033] (c) Mix the potassium sulfite and potassium bisulfite solution with the chitosan solution at a volume ratio of 1:30 to obtain a potassium sulfite-chitosan microparticle suspension, thus obtaining a manganese removal agent.

[0034] Example 3

[0035] This embodiment relates to a method for removing manganese from acidic mineral processing wastewater; the method steps include: (1) Using acidic mineral processing wastewater as raw material, the wastewater contains 273.95 mg / L of ferrous ions, 521.57 mg / L of total iron, 237.31 mg / L of manganese ions, and a pH of 3.19. (2) Use 10% calcium hydroxide to adjust the pH of the reaction solution in the above steps to 4.0 and react for 20 min.

[0036] (3) According to the ratio of total manganese in acidic mineral processing wastewater to manganese removal agent mass of 1:15, after adding manganese removal agent, react for 20 minutes to achieve preliminary removal of manganese from wastewater.

[0037] (4) Air is introduced into the liquid after preliminary manganese removal at a rate of 8 L / min per liter of water, and the reaction is carried out for 40 min to further remove manganese; (5) Using 10% liquid alkali, the pH of the reaction solution was adjusted to 7.0, the reaction time was 15 min, and after solid-liquid separation, the manganese content in the effluent was 0.93 mg / L, and the manganese removal rate was 99.61%.

[0038] The preparation process of the manganese removal agent is as follows: (a) Chitosan was prepared into a 30 g / L solution in glacial acetic acid solution. The pH was adjusted to 6.0. The chitosan solution was stirred for 2 minutes. A 3.0 g / L sodium tripolyphosphate solution was added slowly. The volume ratio of sodium tripolyphosphate to chitosan solution was 1:2.0. The mixture was allowed to stand at room temperature for 30 minutes to form a chitosan microparticle suspension.

[0039] (b) Dissolve anhydrous potassium sulfite, sodium sulfite and sodium bisulfite in water at a mass ratio of 2:2:1 to prepare a 50 g / L mixed solution of anhydrous potassium sulfite, sodium sulfite and sodium bisulfite.

[0040] (c) Mix anhydrous potassium sulfite, sodium sulfite and sodium bisulfite in a volume ratio of 1:25 to form a sulfite-chitosan microparticle suspension to obtain a manganese removal agent.

[0041] Example 4

[0042] This embodiment relates to a method for removing manganese from acidic mineral processing wastewater; the method steps include: (1) Using acidic mineral processing wastewater as raw material, the wastewater contains 172.59 mg / L of ferrous ions, 473.29 mg / L of total iron, 77.31 mg / L of manganese ions, and has a pH of 3.41. (2) Use 10% sodium hydroxide to adjust the pH of the reaction solution in the above steps to 7.5 and react for 15 min.

[0043] (3) According to the ratio of total manganese in acidic mineral processing wastewater to manganese removal agent mass of 1:5, after adding manganese removal agent, react for 20 minutes to achieve preliminary removal of manganese from wastewater.

[0044] (4) Air is introduced into the liquid after preliminary manganese removal at a rate of 12 L / min per liter of water, and the reaction is carried out for 50 min to further remove manganese; (5) Calcium hydroxide was used to adjust the pH of the above reaction solution to 6.0. The reaction time was 15 min. After solid-liquid separation, the manganese content in the effluent was 1.49 mg / L, and the manganese removal rate was 98.03%.

[0045] The preparation process of the manganese removal agent is as follows: (a) Chitosan was placed in glacial acetic acid solution to prepare a 20 g / L solution. The pH was adjusted to 5.5. The chitosan solution was stirred for 2 minutes. A 2.5 g / L sodium tripolyphosphate solution was added slowly. The volume ratio of sodium tripolyphosphate to chitosan solution was 1:2.0. The solution was allowed to stand at room temperature for 30 minutes to form a chitosan microparticle suspension.

[0046] (b) Dissolve anhydrous potassium sulfite in water to prepare a 40 g / L potassium sulfite solution.

[0047] (c) Mix potassium sulfite solution and chitosan solution at a volume ratio of 1:25 to form a potassium sulfite-chitosan microparticle suspension to obtain a manganese removal agent.

[0048] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for removing manganese from acidic mineral processing wastewater, characterized in that, Includes the following steps: (1) Add alkaline solution to acidic mineral processing wastewater to adjust the pH to 4.0-6.0, and react for 10-15 min; (2) Add manganese removal agent to the solution after the reaction in step (1), according to Mn 2+ The mass ratio of manganese removal agent is 1:(5~15), and the reaction time is 15-20 min. (3) Aerate the solution after the reaction in step (2) for 30-60 min; (4) Add alkaline solution to the solution in step (3), adjust the pH to 6-7, react for 10-15 minutes, separate the solid and liquid, and discharge the wastewater in compliance with the standards. The preparation method of the manganese removal agent in step (2) is as follows: a. Place chitosan in glacial acetic acid solution to prepare a solution of 20-30 g / L, adjust the pH to 5.0-6.0, stir for 2-5 minutes to obtain a chitosan solution, slowly add 2.0-3.0 g / L sodium tripolyphosphate solution, the volume ratio of sodium tripolyphosphate to chitosan solution is 1:(1.5-2.0), let stand at room temperature for 30 minutes to form a chitosan microparticle suspension; b. Dissolve anhydrous sulfite in water to prepare a sulfite solution of 30~50g / L; c. Sulfite solution and chitosan microparticle suspension are mixed at a volume ratio of 1:(25~30) to obtain sulfite-chitosan microparticle suspension, thus obtaining manganese removal agent.

2. The method for removing manganese from acidic mineral processing wastewater according to claim 1, characterized in that, In step (3), the aeration rate is 8 to 24 L / min per liter of water.

3. The method for removing manganese from acidic mineral processing wastewater according to claim 1, characterized in that, transition metal Fe in wastewater 2+ and Mn 2+ The total content is <500mg / L.

4. The method for removing manganese from acidic mineral processing wastewater according to claim 1, characterized in that, The sulfite is at least one of Na2SO3, K2SO3, NaHSO3, and KHSO3.

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