Comprehensive treatment method for acid mine drainage

Abstract

The application provides a comprehensive treatment method for acid mine wastewater, and belongs to the field of mine wastewater treatment. The method sequentially processes the wastewater through three stages of iron removal pretreatment, copper recovery by replacement and neutralization treatment. First, the pH value of the wastewater is adjusted in the iron removal reaction tank for reaction, and after solid-liquid separation, part of the underflow is backflowed, and the rest is introduced into the pressure filtration system. Then, the liquid after iron removal is introduced into the copper recovery reaction tank, copper is recovered through a reducer and iron powder system, underflow backflow and pressure filtration treatment are performed. Finally, the liquid after copper recovery is adjusted in the neutralization reaction tank, and the pH value is oxidized, and then solid-liquid separation and underflow backflow are performed, so that the wastewater can be finally discharged up to the standard, and deep purification of the acid mine wastewater is realized. The slag produced by the method provided by the application is a general industrial solid waste, which reduces the environmental risk of waste slag storage. The whole process optimizes the reaction efficiency through underflow backflow, realizes efficient recovery of copper and stable treatment of wastewater up to the standard.

Description

Technical Field

[0001] This invention relates to the field of mine wastewater treatment technology, specifically to a comprehensive treatment method for acidic mine wastewater. Background Technology

[0002] Sulfur-rich deposits in non-ferrous metal mines contain a large amount of sulfide minerals. Under the influence of air, water, and microorganisms, these minerals undergo a series of physicochemical and biochemical reactions, including weathering, leaching, oxidation, and hydrolysis, gradually forming acidic liquids containing sulfuric acid, which impact the surrounding environment. Therefore, it is necessary to treat these acidic waters to protect the environment around the mining area.

[0003] Because these acidic wastewaters are generally rich in valuable substances such as copper and iron, the commonly used treatment methods are mainly chemical precipitation methods, including neutralization and sulfidation. Sulfidation is the mainstream process for recovering valuable substances from acidic mine wastewater and is widely used. However, while sulfidation can achieve efficient recovery of copper, it suffers from the problem that sulfiding agents such as sodium hydrosulfide and sodium sulfide in acidic systems easily release hydrogen sulfide, a toxic and harmful gas, causing safety hazards and secondary pollution. Its application is severely limited, especially in environmentally sensitive areas. Therefore, how to rationally optimize the copper recovery process from acidic mine wastewater and avoid the generation of toxic and harmful gases such as hydrogen sulfide is currently a research hotspot in the comprehensive treatment of acidic mine wastewater.

[0004] In view of this, it is necessary to design a comprehensive treatment method for acidic mine wastewater to solve the above problems. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a comprehensive treatment method for acidic mine wastewater, which aims to solve the technical problems of the existing technology, such as the safety and environmental protection hazards of hydrogen sulfide leakage in the sulfide precipitation method, and the large investment and limited application of the iron scrap replacement method due to low reaction efficiency, easy passivation and high equipment requirements.

[0006] This application provides a comprehensive treatment method for acidic mine wastewater, including the following steps:

[0007] S1. Acidic mine wastewater is fed into the iron removal reaction tank, and the pH value is adjusted to 3.5~3.7 by adding the first pH adjuster. The reaction is carried out for 0.25~0.5 hours to obtain iron-removed turbid liquid.

[0008] A flocculant is added to the iron-removing turbid liquid, and after solid-liquid separation, iron-removing underflow and iron-removing overflow are obtained;

[0009] 2-10% of the iron removal underflow is returned to the iron removal reaction tank, 25-35% of the iron removal underflow enters the copper slag collection filter press system, and the remaining iron removal underflow is subjected to filter press dewatering treatment to obtain the first filter press residue and the first filter press liquid.

[0010] S2. Input the iron removal overflow and the first pressure filtrate obtained in step S1 into the copper recovery reaction tank, add a reducing agent to adjust the ORP value to 350~450mV, add the reducing iron powder system reagent, react for 0.25~0.5h, and obtain copper recovery turbid liquid.

[0011] A flocculant is added to the copper-collecting turbid liquid, and after solid-liquid separation, copper-collecting underflow and copper-collecting overflow are obtained;

[0012] 2-10% of the copper recovery underflow is returned to the copper recovery reaction tank. The remaining copper recovery underflow is mixed with the iron removal underflow that enters the copper recovery slag filter press system in step S1. After filter press dewatering treatment, the second filter press residue and the second filter press liquid are obtained.

[0013] S3. Input the copper overflow obtained in step S2 and the second pressure filtrate into the neutralization reaction tank, add the second pH adjuster to adjust the pH value to 8.2~8.8, and introduce oxidant to react for 0.8~1.2h to obtain neutralized turbid liquid;

[0014] A flocculant is added to the neutralized turbid liquid, and after solid-liquid separation, a neutralized underflow and a neutralized overflow are obtained.

[0015] 70-90% of the neutralized underflow is returned to the neutralization reaction tank, and the remaining neutralized underflow is dewatered by pressure filtration to obtain the third pressure filter residue and the third pressure filtrate; the neutralized overflow and the third pressure filtrate are discharged after passing the test.

[0016] As a further improvement of this application, in step S2, the reducing iron powder system reagent includes iron powder, activated carbon, bentonite, diatomaceous earth and zinc oxide, with a mass ratio of 80~95% : 1~3% : 2~10% : 1~6% : 0.5~1%.

[0017] As a further improvement of this application, the dosage of the reducing iron powder system reagent is based on the iron powder content and is added at 1.4 to 2.0 times the theoretical reaction amount of iron powder with copper in acidic mine wastewater.

[0018] As a further improvement of this application, in step S1, the first pH adjuster is one or more of lime, sodium carbonate, sodium hydroxide, and carbide slag.

[0019] As a further improvement of this application, in step S2, the reducing agent is one or more of sodium sulfite, thiosulfate, sodium metabisulfite, and citric acid; and the copper content in the second filter press residue is ≥40%.

[0020] As a further improvement of this application, in step S3, the oxidant is air or hydrogen peroxide, and the second pH adjuster is lime or carbide slag.

[0021] As a further improvement of this application, the oxidant is air, and the gas-liquid volume ratio is 1:(4~5).

[0022] As a further improvement of this application, the oxidant is hydrogen peroxide, and its mass ratio with divalent iron ions in the solution is (0.60~6):1.

[0023] As a further improvement to this application, the flocculant is a non-ionic flocculant, and the addition amount is 0~15g / m³. 3 .

[0024] As a further improvement of this application, the pollutants in the acidic mine wastewater include one or more of copper, iron, zinc, lead, arsenic, manganese, nickel, cadmium, chromium, and beryllium, wherein the copper ion concentration is not less than 100 mg / L; and the temperature of the acidic mine wastewater is ≥5℃.

[0025] The beneficial effects of this application are as follows:

[0026] This application provides a comprehensive treatment method for acidic mine wastewater. The method treats the wastewater through three stages: iron removal, copper recovery, and neutralization. First, in an iron removal reaction tank, the pH of the wastewater is adjusted to 3.5-3.7 for reaction. After solid-liquid separation, part of the underflow is recycled, and the remainder enters a filter press system. Then, the iron-removed liquid is introduced into a copper recovery reaction tank, where copper is recovered through a reducing agent and iron powder system, followed by underflow recycling and filter press treatment. Finally, the copper-recovered liquid is adjusted to pH 8.2-8.8 and oxidized in a neutralization reaction tank, followed by solid-liquid separation and underflow recycling, ultimately achieving compliant discharge. The entire process optimizes reaction efficiency through underflow recycling, achieving efficient copper recovery and stable compliant wastewater treatment.

[0027] The comprehensive treatment method for acidic mine wastewater provided in this application can maintain a high reaction rate even in low-temperature environments, thereby achieving safe, environmentally friendly, and efficient treatment of acidic mine wastewater. After treatment, the target pollutants such as copper, lead, and arsenic in the acidic mine wastewater can meet the strict limits of the Class I discharge standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996) and the direct discharge limit requirements specified in Table 2 of the "Emission Standard of Pollutants for Copper, Cobalt and Nickel Industry" (GB 25467-2010). The comprehensive recovery rate of copper can reach over 94%, and the generated waste residue belongs to general industrial solid waste. It has significant economic, environmental, and social benefits, and provides a new approach for the treatment of acidic mine wastewater, especially in cold regions.

[0028] The comprehensive treatment method for acidic mine wastewater provided in this application addresses the pollution characteristics of acidic mine wastewater rich in valuable substances such as copper. Combining the technological features of current acidic water treatment processes, the method rationally designs the water treatment process, sequentially subjecting the acidic mine wastewater to iron removal pretreatment, copper recovery by displacement, and neutralization. During the iron removal pretreatment, all ferric iron is removed. The copper recovery section achieves efficient recovery of copper ions. Simultaneously, the neutralization process utilizes an oxidant, ensuring that the neutralization overflow and filtrate meet discharge standards, thus achieving deep purification of the acidic mine wastewater. The slag generated by the method provided in this application is all general industrial solid waste, reducing the environmental risks of waste slag storage. The treatment process does not release toxic or harmful gases such as hydrogen sulfide, enabling safe, environmentally friendly, and efficient recovery of copper from acidic mine wastewater.

[0029] The method for comprehensive treatment of acidic mine wastewater provided in this application, by further adjusting parameters such as pH value, ORP value, reducing iron powder system reagent formulation, and reflux ratio in the treatment process, successfully overcomes the problems of large fluctuations in acidic water quality and low water temperature. It can efficiently treat acidic mine wastewater into water that meets discharge standards with a simple process, while achieving efficient recovery of valuable copper, and has high utilization value.

[0030] The method for comprehensive treatment of acidic mine wastewater provided by this invention is simple in process, safe and reliable in operation, and uses common and inexpensive reagents. It can treat acidic mine wastewater into water that meets the discharge standards, while avoiding the risk of hydrogen sulfide gas leakage that is common in conventional methods, and improving the copper recovery rate. It has significant economic, environmental and social benefits, and provides a new approach to the treatment of acidic mine wastewater.

[0031] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0033] Figure 1 A flowchart illustrating the comprehensive treatment method for acidic mine wastewater provided in this application embodiment. Detailed Implementation

[0034] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0036] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0037] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0038] For acidic mine wastewater, the traditional sulfide precipitation method for copper recovery poses safety and environmental hazards due to hydrogen sulfide gas leakage. Meanwhile, the conventional iron scrap replacement copper process suffers from problems such as long reaction time, low reaction rate at low temperatures, easy passivation of iron powder, and high reactor design requirements, resulting in high investment costs and limited application and promotion of the iron scrap replacement copper process.

[0039] To address the safety and environmental hazards, low reaction efficiency, high cost, and limited application of traditional acid mine wastewater treatment methods, this application provides a comprehensive treatment method for acid mine wastewater. This method involves sequentially treating the acid mine wastewater with iron removal pretreatment, copper replacement, and neutralization. A reducing iron powder system is used to replace traditional sulfiding agents, preventing the generation of H2S gas and significantly improving safety. This method is suitable for low-temperature environments, has a high reaction rate, and broadens its application scope.

[0040] Please refer to Figure 1 This application provides a comprehensive treatment method for acidic mine wastewater, comprising the following steps:

[0041] S1. Acidic mine wastewater is fed into the iron removal reaction tank, and the pH value is adjusted to 3.5~3.7 by adding the first pH adjuster. The reaction is carried out for 0.25~0.5 hours to obtain iron-removed turbid liquid.

[0042] A flocculant is added to the iron-removing turbid liquid, and after solid-liquid separation, iron-removing underflow and iron-removing overflow are obtained;

[0043] 2-10% of the iron removal underflow is returned to the iron removal reaction tank, 25-35% of the iron removal underflow enters the copper slag collection filter press system, and the remaining iron removal underflow is dewatered by filter press to obtain the first filter press residue and the first filter press liquid. The leaching toxicity and toxic substance content of the first filter press residue (i.e., iron removal slag) meet the requirements of general industrial solid waste and can be stored in compliance with regulations as general industrial solid waste.

[0044] S2. Input the iron removal overflow and the first pressure filtrate obtained in step S1 into the copper recovery reaction tank, add a reducing agent to adjust the ORP value to 350~450mV, add the reducing iron powder system reagent, react for 0.25~0.5h, and obtain copper recovery turbid liquid.

[0045] A flocculant was added to the copper-collecting turbid liquid, and after solid-liquid separation, copper-collecting underflow and copper-collecting overflow were obtained.

[0046] Two to ten percent of the copper recovery underflow is recycled back to the copper recovery reaction tank, so that the mass concentration of the solid phase in the copper recovery underflow is controlled at 10 to 20% during the circulation process, in order to reduce the processing pressure of the copper recovery underflow filter press section. The remaining copper recovery underflow is mixed with the iron removal underflow that enters the copper slag filter press system in step S1, and then subjected to filter press dewatering treatment to obtain the second filter press residue and the second filter press liquid. The second filter press residue can be sold as copper slag.

[0047] S3. Input the copper overflow and second filtrate obtained in step S2 into the neutralization reaction tank, add a second pH adjuster to adjust the pH value to 8.2~8.8, so that most of the heavy metals and other harmful substances are converted into precipitates, and then introduce an oxidant to react for 0.8~1.2 hours to obtain a neutralized turbid liquid.

[0048] Add flocculant to the neutralized turbid liquid, and then separate the solid and liquid to obtain the neutralized underflow and neutralized overflow;

[0049] 70-90% of the neutralized underflow is recycled back to the neutralization reaction tank, so that the mass concentration of the solid phase in the neutralized underflow is controlled at 15-30% during the circulation process, in order to reduce the processing pressure of subsequent stages. The remaining neutralized underflow is dewatered by pressure filtration to obtain the third pressure filter residue and the third pressure filtrate. The neutralization overflow and the third pressure filtrate are discharged after passing the test. The leaching toxicity and toxic substance content of the third pressure filter residue meet the requirements of general industrial solid waste and can be stored in compliance with regulations as general industrial solid waste.

[0050] In the technical solution of this application embodiment, iron is preferentially precipitated and removed under weakly acidic conditions through stepwise selective precipitation, avoiding interference with subsequent copper recovery. In the wastewater after iron removal, copper ions are efficiently reduced to elemental copper for recovery through the displacement reaction of reduced iron powder, avoiding the safety risks of hydrogen sulfide generation in traditional sulfidation methods. The residual wastewater is neutralized and oxidized, causing the remaining heavy metal ions to form stable precipitates, ensuring that the final effluent meets standards. The entire process improves reaction efficiency and precipitation effect through partial underflow recirculation, and increases the output of sellable copper slag by mixing some iron removal slag with copper slag while ensuring copper grade, achieving a balance between economic and environmental benefits.

[0051] Furthermore, in some embodiments, in step S2, the reducing iron powder system agent includes iron powder, activated carbon, bentonite, diatomaceous earth and zinc oxide, with a mass ratio of 80~95%:1~3%:2~10%:1~6%:0.5~1%.

[0052] In the technical solution of this application embodiment, iron powder can displace copper ions from the solution to generate elemental copper. Iron powder of different particle sizes (80~300 mesh) can be used. Activated carbon adsorbs copper ions in the solution onto its surface, increasing the contact opportunities and local concentration between iron powder and copper ions, thereby significantly accelerating the reaction rate. In addition, the surface of activated carbon can act as a medium for electron transfer, reducing the activation energy of the reaction and further catalyzing the displacement reaction between iron powder and copper ions. The generated fine copper particles can adhere to the activated carbon, forming denser aggregates, which helps with subsequent solid-liquid separation, making the copper slag easier to settle and filter. Bentonite forms a charged colloid in water, which can be used as... The bentonite acts as a nucleus or framework, adsorbing and encapsulating the fine copper particles, iron powder residues, and other suspended matter generated during the reaction, forming larger and denser flocs. This improves settling performance, making solid-liquid separation faster and more thorough. The addition of bentonite gives the final copper slag (second filter cake) better plasticity and structural strength, making it less prone to material loss during filter press dewatering, and resulting in a more regular filter cake. The porous structure of diatomaceous earth forms a highly permeable filter cake, preventing fine copper particles or other impurities from clogging the filter cloth, thereby significantly improving filter press efficiency and filtrate clarity. Zinc oxide helps stabilize the pH of the reaction system within the weakly acidic range most suitable for iron powder replacement, preventing copper re-dissolution. Through the synergistic effect of multiple components, a highly efficient, stable, and multifunctional reaction system is formed, which not only safely and efficiently recovers copper but also optimizes the kinetics and physical properties of the entire reaction and subsequent treatment processes, making the process operation more stable.

[0053] Furthermore, in some embodiments, the dosage of the reducing iron powder system reagent is based on the iron powder content, and is added at 1.4 to 2.0 times the theoretical reaction amount of iron powder with copper in acidic mine wastewater.

[0054] In the technical solution of this application embodiment, the dosage of reducing iron powder in the reagent system helps to compensate for the consumption of side reactions caused by wastewater acidity, dissolved oxygen, and other impurities. Excess reactants drive chemical equilibrium, ensuring a rapid and thorough reaction with low residual copper concentration. Sufficient safety redundancy is provided, allowing the process to adapt to fluctuations in actual water quality and ensuring stable operation. While ensuring treatment effectiveness, reagent costs are controlled, avoiding secondary problems and resource waste caused by excessive addition. Increasing the dosage of iron powder to twice the theoretical value of the iron-copper reaction, raising the reaction temperature of acidic mine wastewater to above 25°C (higher temperatures result in faster reaction rates), and extending the reaction time to above 1 hour can also achieve effective copper recovery from acidic mine wastewater. However, this method increases the investment and operating costs of process equipment (iron powder, heating energy consumption), and due to the large addition of iron powder, the copper slag grade will decrease, and the amount of neutralized slag produced will increase.

[0055] Furthermore, in some embodiments, in step S1, the first pH adjuster is one or more of lime, sodium carbonate, sodium hydroxide, and carbide slag.

[0056] In the technical solution of this application embodiment, acidic wastewater is pretreated by adding a first pH adjuster to reduce its acidity by neutralizing some of the free acid, thereby creating a favorable reaction environment for subsequent iron powder replacement. Simultaneously, this step also promotes the early precipitation of some easily hydrolyzed metallic impurities, achieving preliminary water purification. The pH value needs to be controlled between 3.5 and 3.7. When the pH value is below 3.5, the ferric iron in the acidic mining wastewater cannot be completely precipitated, and the residual ferric iron will consume relevant reagents in the copper recovery section. When the pH value is above 3.7, copper in the acidic mining wastewater will precipitate into the iron slag, leading to copper loss. The amount of iron-removing slag mixed with the copper recovery underflow cannot be too high; otherwise, the copper slag grade will be low and cannot be sold as a copper product. Conversely, the amount of mixed iron-removing slag cannot be too low; otherwise, the copper grade will be too high, while the pricing coefficient remains unchanged, which will affect direct economic benefits. By mixing the iron slag into the copper slag, not only is the amount of solid waste generated reduced and the problem of storage capacity shortage alleviated, but the output of copper slag can also be increased, thereby increasing economic benefits.

[0057] Furthermore, in some embodiments, in step S2, the reducing agent is one or more of sodium sulfite, thiosulfate, sodium metabisulfite, and citric acid; and the copper content in the second filter press residue is ≥40%.

[0058] In the technical solution of this application embodiment, a reducing agent is added to control the ORP value of acidic mine wastewater to 350~450mV, so as to reduce the amount of reagent added to the reducing iron powder system, thereby reducing the amount of subsequent neutralization slag generated; high-grade copper slag can be sold directly as copper concentrate, and the content of harmful impurities in copper slag is relatively low, making it easier to meet the leaching toxicity standards of general industrial solid waste.

[0059] Furthermore, in some embodiments, in step S3, the oxidant is air or hydrogen peroxide, and the second pH adjuster is lime or carbide slag.

[0060] In the technical solution of this application embodiment, oxidation and pH adjustment ensure the efficient removal of residual heavy metals such as Fe and Mn from wastewater. The amount of oxidant used is positively correlated with the content of divalent iron in the neutralization solution.

[0061] Furthermore, in some embodiments, the oxidant is air, and the gas-liquid volume ratio is 1:(4~5).

[0062] In the technical solution of this application embodiment, the gas-liquid volume ratio ensures that there is a sufficient supply of oxygen for the oxidation reaction. If the aeration is insufficient, the oxidation will be incomplete, the reaction rate will be slowed down, and the processing capacity will be reduced.

[0063] Furthermore, in some embodiments, the oxidant is hydrogen peroxide, and its mass ratio to divalent iron ions in the solution is (0.60~6):1.

[0064] In the technical solution of this application embodiment, by precisely controlling the addition ratio of hydrogen peroxide, it is possible to ensure that the oxidation reaction proceeds fully, while avoiding excessive oxidant residue that could lead to a burden on subsequent treatment or the generation of side reactions, thereby optimizing the process economy and treatment effect.

[0065] Furthermore, in some embodiments, the flocculant is a nonionic flocculant, and the addition amount is 0~15g / m³. 3 .

[0066] In the technical solution of this application embodiment, a nonionic flocculant such as nonionic polyacrylamide (PAM) is used for flocculation and sedimentation. In step S1, the amount of flocculant added is 1~10 g / m³. 3 In step S2, the amount of flocculant added is 0~5g / m³. 3 In step S3, the amount of flocculant added is 1~15g / m³. 3 .

[0067] Furthermore, in some embodiments, the pollutants in the acidic mine wastewater include one or more of copper, iron, zinc, lead, arsenic, manganese, nickel, cadmium, chromium, and beryllium, wherein the copper ion concentration is not less than 100 mg / L; and the temperature of the acidic mine wastewater is ≥5°C.

[0068] In the technical solution of this application embodiment, the treatment method can efficiently treat complex components and high concentrations of acidic mine wastewater, and overcomes the problems of large fluctuations in acidic water quality and low water temperature, and has significant economic, environmental and social benefits.

[0069] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0070] Example 1

[0071] This embodiment provides a comprehensive treatment method for acidic mine wastewater containing high concentrations of heavy metals such as copper and iron. Specifically, the copper concentration fluctuates between 150.10 and 1456.21 mg / L, the iron concentration fluctuates between 265.25 and 861.72 mg / L, the arsenic concentration is around 4 mg / L, and the manganese concentration is between 24 and 35.64 mg / L. The water temperature is consistently between 5 and 10°C. A schematic diagram of the process flow is shown below. Figure 1 As shown, the specific steps include:

[0072] S1. Acidic mine wastewater is fed into the iron removal reaction tank, and lime is added to adjust the pH value to 3.6 so that heavy metal ions (mainly ferric iron, arsenic, etc.) can be chemically precipitated so that they can be removed in the solid form of heavy metal precipitation. After reacting for ~0.5h, the iron ion concentration is reduced from 700mg / L to about 200mg / L, and iron-removed turbid liquid is obtained.

[0073] According to 3g / m 3 The dosage of nonionic polyacrylamide is added to the iron removal turbid liquid, and solid-liquid separation is carried out by iron removal thickener to obtain iron removal overflow and iron removal underflow in sludge state.

[0074] 10% of the iron removal underflow is recycled to the iron removal reaction tank, 30% of the iron removal underflow enters the copper slag collection filter press system, and the remaining iron removal underflow is dewatered by the first filter press to obtain the first filter residue and the first filter liquid; the first filter residue meets the requirements of general industrial solid waste and is stored and disposed of in compliance with regulations.

[0075] S2. Input the iron-removed overflow and the first filtrate obtained in step S1 into the copper recovery reaction tank, add 10% sodium sulfite solution as a reducing agent to adjust the ORP value to 400mv, add the reducing iron powder system reagent, the reagent formula is 80 mesh iron powder, 200 mesh iron powder, activated carbon, bentonite, diatomaceous earth and zinc oxide in a mass ratio of 68%:16%:3%:7%:5%:1%, the reducing iron powder system reagent is added according to 1.4 times the theoretical reaction amount of iron powder with copper in acidic mine wastewater, after 0.5h of reaction, the copper concentration in the liquid phase is below 0.5mg / L, and copper recovery turbid liquid is obtained;

[0076] According to 2g / m 3The dosage of nonionic polyacrylamide is added to the copper-collecting turbid liquid, and the solid-liquid separation is performed by a copper-collecting thickener to obtain copper-collecting overflow and copper-collecting underflow in sludge state.

[0077] Eight percent of the copper recovery underflow is returned to the copper recovery reaction tank. The remaining copper recovery underflow is mixed with the iron removal underflow that entered the copper slag filter press system in step S1, and then subjected to filter press dewatering treatment in a second filter press to obtain the second filter residue and the second filter liquid. The second filter residue can be sold as copper slag (its copper grade is 45%).

[0078] S3. Input the copper overflow and second pressure filtrate obtained in step S2 into the neutralization reaction tank, add lime to adjust the pH value to 8.5, and at the same time, introduce air into the neutralization reaction tank to control the gas-liquid ratio to 1:5, further oxidize the residual ferrous ions, and chemically precipitate the heavy metal ions (mainly iron, arsenic, zinc, lead, manganese, nickel, etc.) so that they can be removed through the solid form of heavy metal precipitation. After reacting for 1 hour, a neutralized turbid liquid is obtained.

[0079] According to 8g / m 3 The dosage of nonionic polyacrylamide is added to the neutralized turbid liquid, and the solid-liquid separation is performed by a neutralization thickener to obtain neutralization overflow and neutralization underflow in sludge state.

[0080] 75% of the neutralization underflow is recycled back to the neutralization reaction tank, and the remaining neutralization underflow is dewatered by the third filter press to obtain the third filter residue and the third filter liquid. The target heavy metals in the third filter liquid and the neutralization overflow meet the Class I discharge standards of the "Integrated Wastewater Discharge Standard" (GB 8978-1996) and the direct discharge limits specified in the "Emission Standard of Pollutants for Copper, Cobalt and Nickel Industry" (GB25467-2010), and are discharged in compliance with the standards. The leaching toxicity and toxic substance content of the third filter residue meet the requirements of general industrial solid waste and can be stored in compliance with regulations as general industrial solid waste.

[0081] The influent and effluent water quality of this embodiment were tested, and the results are shown in Table 1.

[0082] Table 1. Water quality of influent and effluent

[0083]

[0084] Note: pH value is dimensionless, and the units for other indicators in the table are "mg / L".

[0085] The results above show that, after treatment by the comprehensive treatment method for acidic mine wastewater provided in this embodiment, the effluent quality meets the corresponding requirements, and the overall treatment process can treat 500 m³ of iron-containing acidic water. 3 / h, achieving efficient treatment of acidic mine wastewater, with a copper recovery rate of 94.2%.

[0086] Comparative Examples 1-5

[0087] Comparative Examples 1-5 each provide a comprehensive treatment method for acidic mine wastewater. Compared with Example 1, the differences are that the pH value in step S1, the ORP value in step S2, the formulation and dosage of the reducing iron powder system reagent, and the pH value in step S3 are changed respectively. The corresponding parameters for each comparative example are shown in Table 2. The remaining steps and parameters are basically the same as those in Example 1, and will not be repeated here.

[0088] Table 2 Process parameters in Example 1 and Comparative Examples 1-5

[0089]

[0090] After treating the iron-containing acidic water according to the methods provided in Comparative Examples 1-5, the quality of the effluent and the generated solid waste were tested, and the results are shown in Table 3.

[0091] Table 3. Experimental Results

[0092]

[0093] As shown in Table 3, controlling the pH value below 3.5 in step S1 directly affects the copper recovery rate. In step S2, if the ORP value cannot be controlled below 450mV, it will consume the reducing iron powder system reagents, reducing the copper recovery rate to 76.2%, which is relatively low. If only reducing iron powder is used to replace copper in acidic mining wastewater, the copper recovery rate will be low. The dosage of the reducing iron powder system reagents is closely related to the copper recovery rate; below 1.2 times the theoretical dosage, the copper recovery rate cannot reach over 80%. In step S3, if the pH value cannot be controlled at around 8.5, it will be impossible to ensure effective treatment of all pollutants in the acidic wastewater, especially Mn. In Comparative Example 5, the concentration after treatment was still as high as 2.5 mg / L, exceeding the standard limit of 2 mg / L.

[0094] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A comprehensive treatment method for acid mine drainage water, characterized by, The method comprises the following steps: S1. Acid mine wastewater is input into an iron removal reaction tank, a first pH regulator is added to adjust the pH value to 3.5-3.7, and reaction is carried out for 0.25-0.5 h to obtain an iron removal turbid liquid; A flocculating agent is added to the iron removal turbid liquid, and solid-liquid separation is carried out to obtain an iron removal underflow and an iron removal overflow; 2-10% of the iron removal underflow is returned to the iron removal reaction tank, 25-35% of the iron removal underflow is input into a copper recovery residue pressure filtration system, and the rest of the iron removal underflow is subjected to pressure filtration dewatering treatment to obtain first pressure filtration residue and first pressure filtration liquid; S2. The iron removal overflow obtained in step S1 and the first pressure filtration liquid are input into a copper recovery reaction tank, a reducing agent is added to adjust the ORP value to 350-450 mV, a reducing iron powder system reagent is added, and reaction is carried out for 0.25-0.5 h to obtain a copper recovery turbid liquid; A flocculating agent is added to the copper recovery turbid liquid, and solid-liquid separation is carried out to obtain a copper recovery underflow and a copper recovery overflow; 2-10% of the copper recovery underflow is returned to the copper recovery reaction tank, and the rest of the copper recovery underflow is mixed with the iron removal underflow input into the copper recovery residue pressure filtration system in step S1, and then subjected to pressure filtration dewatering treatment to obtain second pressure filtration residue and second pressure filtration liquid; The reducing agent is one or more of sodium sulfite, thiosulfate, sodium metabisulfite and citric acid; the grade of copper in the second pressure filtration residue is ≥40%; the reducing iron powder system reagent comprises iron powder, activated carbon, bentonite, diatomite and zinc oxide, and the mass ratio is 80-95%:1-3%:2-10%:1-6%:0.5-1%; S3. The copper recovery overflow obtained in step S2 and the second pressure filtration liquid are input into a neutralization reaction tank, a second pH regulator is added to adjust the pH value to 8.2-8.8, an oxidizing agent is introduced, and reaction is carried out for 0.8-1.2 h to obtain a neutralization turbid liquid; A flocculating agent is added to the neutralization turbid liquid, and solid-liquid separation is carried out to obtain a neutralization underflow and a neutralization overflow; 70-90% of the neutralization underflow is returned to the neutralization reaction tank, and the rest of the neutralization underflow is subjected to pressure filtration dewatering treatment to obtain third pressure filtration residue and third pressure filtration liquid; wherein the neutralization overflow and the third pressure filtration liquid are discharged after detection.

2. The method for comprehensive treatment of acid mine drainage water according to claim 1, characterized in that, The adding amount of the reducing iron powder system reagent is 1.4-2.0 times the theoretical reaction amount of iron powder with copper in the acid mine wastewater based on the iron powder content.

3. The method for comprehensive treatment of acid mine drainage water according to claim 1, characterized in that, In step S1, the first pH regulator is one or more of lime, sodium carbonate, sodium hydroxide and calcium carbide residue.

4. The method for comprehensive treatment of acid mine drainage water according to claim 1, characterized in that, In step S3, the oxidizing agent is air or hydrogen peroxide, and the second pH regulator is lime or calcium carbide residue.

5. The method for comprehensive treatment of acid mine drainage water according to claim 4, characterized in that, When the oxidizing agent is air, the gas-liquid volume ratio is 1:(4-5).

6. The method for comprehensive treatment of acid mine drainage water according to claim 4, characterized in that, When the oxidizing agent is hydrogen peroxide, the mass ratio of hydrogen peroxide to divalent iron ions in the solution is (0.60-6):

1.

7. The method for comprehensive treatment of acid mine drainage water according to claim 1, characterized in that, The flocculant is a non-ionic flocculant, and the addition amount is 0-15 g / m 3 .

8. The method for comprehensive treatment of acid mine drainage water according to claim 1, characterized in that, The pollutants in the acid mine wastewater include one or more of copper, iron, zinc, lead, arsenic, manganese, nickel, cadmium, chromium and beryllium, and the concentration of copper ions is not less than 100 mg / L; the temperature of the acid mine wastewater is ≥5℃.

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