Comprehensive treatment method for acidic water containing ferric iron

Abstract

The present invention provides a method for comprehensive treatment of acidic water containing ferric iron, and relates to the field of water treatment. The method sequentially performs iron removal pretreatment, sulfidation and copper collection, and neutralization treatment on the acidic water containing ferric iron, and adds a predetermined amount of reducing agent during the iron removal pretreatment to convert part of the ferric iron into divalent iron, reasonably controls the amount of iron removal precipitate generated, and directly inputs the iron removal turbid liquid obtained after adjusting the pH into the sulfidation and copper collection section without flocculation, and uses an oxidant for treatment in the neutralization process, so that the neutralization overflow and press filtrate obtained in the neutralization process meet the discharge standard, and achieves deep purification of the acidic water containing ferric iron; the above process does not produce iron removal slag, greatly reduces the amount of solid waste generated, and effectively reduces the valuable copper lost with the iron slag liquid phase, and improves the copper recovery rate of the entire acidic water treatment system; and the treated water body and neutralization slag meet the discharge requirements, with significant economic benefits, environmental benefits and social benefits.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection and water treatment, and in particular to a method for comprehensive treatment of acidic water containing ferric iron. Background Art

[0002] Sulfur-rich deposits in nonferrous metal mines contain a large number of sulfide minerals. Under the action of air, water and microorganisms, a series of physical, chemical and biochemical reactions such as weathering, leaching, oxidation and hydrolysis occur, gradually forming acidic liquid containing sulfuric acid, which causes serious pollution to the environment around the mining area. Therefore, it is necessary to treat these acidic waters to protect the environment around the mining area.

[0003] Since these acidic waters are generally rich in valuable substances such as copper and iron, the commonly used treatment method is the step-by-step precipitation method, that is, first perform iron removal pretreatment, then recover the valuable substance copper by sulfidation, and then use the lime neutralization method (HDS method) to remove other heavy metals in the acidic water. For example, the patent with publication number CN108101253A provides a method for treating heavy metal wastewater, which first performs an iron removal operation, adjusts the pH value of the wastewater to 4-5, then adds a flocculant, and removes the iron ions in the wastewater by sedimentation; then adds sodium sulfide and a flocculant to the supernatant obtained by the iron removal operation, and removes the copper ions in the wastewater by sedimentation, and performs a copper precipitation operation; then adjusts the pH value of the supernatant obtained by the copper precipitation operation to 6-7, adds a flocculant, and removes the heavy metal ions in the wastewater by sedimentation, so as to obtain clean water that meets the discharge standards.

[0004] However, although the above method treats the wastewater containing heavy metals into clear water that meets the standards and can be discharged, when the metal content of copper, arsenic, beryllium and other metals contained in the wastewater is relatively high, the copper content in the leaching solution of the iron removal slag formed after the flocculant is added and settled during the iron removal operation is relatively high, and the arsenic content in the solid phase of the iron removal slag is relatively high, resulting in the leaching toxicity of the iron removal slag and the index of the toxic substance content will not meet the requirements of general industrial solid wastes, and it belongs to hazardous waste; and, if the wastewater contains a high concentration of trivalent iron ions, it is also very easy to form hazardous waste iron removal slag mainly composed of iron hydroxide. This not only seriously increases the construction investment and operating costs of the entire water treatment project, but also increases environmental hazards. In addition, the above method will also produce neutralization slag after adding flocculants to settle during the neutralization operation. If the generation of iron removal slag is avoided by simply omitting the iron removal operation, the neutralization slag produced in the subsequent neutralization operation will not meet the requirements of general industrial solid wastes. Therefore, how to reasonably optimize the treatment process of acidic water containing ferric iron, minimize the generation of iron removal slag, and ensure that the neutralization slag produced during the water treatment process can meet the requirements of general industrial solid waste is currently a research hotspot in the treatment of acidic water containing ferric iron.

[0005] In view of this, it is necessary to design an improved method for comprehensive treatment of ferric iron-containing acidic water to solve the above problems. Summary of the invention

[0006] In view of the defects of the above-mentioned prior art, the purpose of the present invention is to provide a method for comprehensive treatment of acidic water containing ferric iron, by reasonably designing the water treatment process and effectively controlling reaction parameters such as pH and ORP value, avoiding the generation of hazardous waste iron removal slag, and making the generated neutralized slag meet the requirements of general industrial solid waste, while achieving efficient recovery of valuable substance copper.

[0007] To achieve the above object, the present invention provides a method for comprehensive treatment of acidic water containing ferric iron, comprising the following steps:

[0008] S1. Inputting ferric iron-containing acidic water into an iron removal reaction tank, adding a predetermined amount of reducing agent, and adjusting the pH value after sufficient reaction to obtain an iron removal turbid liquid;

[0009] S2, inputting the iron removal turbid liquid obtained in step S1 into a sulfidation reaction tank, adding a sulfiding agent to adjust the ORP value, and obtaining a sulfided copper collection turbid liquid; adding a flocculant to the sulfided copper collection turbid liquid, and obtaining a sulfided underflow and a sulfided overflow after solid-liquid separation in a sulfidation thickener; returning a portion of the sulfided underflow to the sulfidation reaction tank, and performing a filter press dehydration treatment on another portion of the sulfided underflow to obtain a first filter press residue and a first filter press liquid;

[0010] S3, inputting the sulfide overflow obtained in step S2 and the first filter press liquid into a neutralization reaction tank as neutralization liquid, adjusting the pH value, and introducing an oxidant at the same time to obtain a neutralized turbid liquid after sufficient reaction; adding a flocculant to the neutralized turbid liquid, and obtaining a neutralization underflow and a neutralization overflow after solid-liquid separation in a neutralization thickener; returning a portion of the neutralization underflow to the neutralization reaction tank, and subjecting another portion of the neutralization underflow to filter press dehydration treatment to obtain a second filter press residue and a second filter press liquid.

[0011] As a further improvement of the present invention, in step S1, the dosage of the reducing agent satisfies the following relationship:

[0012]

[0013] In the above formula, α is the preset copper recovery rate, which is 85% to 99%; γ is 1 to 1.25; m represents the preset copper grade of copper slag, which is greater than or equal to 15%.

[0014] As a further improvement of the present invention, in step S1, the reducing agent is one or more of iron powder, ethylene glycol, trisodium citrate, and hydroxylamine hydrochloride.

[0015] As a further improvement of the present invention, in step S1, the copper ion concentration in the ferric iron-containing acidic water is not less than 100 mg / L, and the method of adjusting the pH is: adding a pH adjuster to adjust the pH to 3.4-3.6, and reacting for 0.25-0.5h; the pH adjuster is lime milk or carbide slag.

[0016] As a further improvement of the present invention, in step S2, the method of adjusting the ORP value is: adding a sulfiding agent to adjust the ORP value to 0-200mv, and reacting for 0.25-0.5h; the sulfiding agent is one of sodium sulfide, sodium hydrosulfide, and hydrogen sulfide gas.

[0017] As a further improvement of the present invention, in step S3, the method of adjusting the pH is: adding a pH adjuster to adjust the pH to 8.0-8.5, and reacting for 1.0-2.0 hours; the pH adjuster is lime milk or carbide slag.

[0018] As a further improvement of the present invention, in step S3, when the oxidant is air, the gas-liquid volume ratio of the oxidant to the neutralizing liquid is 1:4-10; when the oxidant is hydrogen peroxide, the mass ratio of the oxidant dosage to the divalent iron ions in the neutralizing liquid is 0.5-5:1.

[0019] As a further improvement of the present invention, in step S2, 2% to 20% of the sulfidation underflow is refluxed into the sulfidation reaction tank.

[0020] As a further improvement of the present invention, in step S2, the first filter press residue is collected as copper slag, and the copper grade in the copper slag is above 15%.

[0021] As a further improvement of the present invention, in step S3, 60% to 90% of the neutralization underflow is refluxed into the neutralization reaction tank.

[0022] The beneficial effects of the present invention are:

[0023] 1. The method for comprehensive treatment of ferric iron acidic water provided by the present invention is aimed at the pollution endowment characteristics of ferric iron acidic water rich in heavy metals, combined with the process characteristics of current acidic water treatment, and the ferric iron acidic water is subjected to iron removal pretreatment, sulfidation copper collection, and neutralization treatment in sequence by rationally designing the water treatment process, and in the iron removal pretreatment, a predetermined amount of reducing agent is first added to convert part of the ferric iron into divalent iron, and the amount of iron removal precipitate produced is reasonably controlled, and the iron removal turbid liquid obtained after adjusting the pH is directly input into the sulfidation copper collection section without flocculation, and an oxidant is used for treatment in the neutralization process, so that the neutralization overflow and the press filter liquid obtained in the neutralization process can meet the emission standards, and the deep purification of ferric iron acidic water is achieved. Based on the above method, the method provided by the present invention does not produce hazardous wastes such as iron removal slag, greatly reduces the amount of solid waste generated, reduces the environmental risk of waste slag storage, and effectively reduces the valuable copper lost with the iron slag liquid phase, thereby improving the copper recovery rate of the entire acidic water treatment system.

[0024] 2. The method for comprehensive treatment of ferric iron-containing acidic water provided by the present invention successfully overcomes the problem of large fluctuations in acidic water quality by further regulating and controlling parameters such as the amount of reducing agent added, pH value, ORP value, and reflux ratio in the treatment process. The ferric iron-containing acidic water can be efficiently treated into a water body that meets the discharge standards with a simple process. The neutralization slag generated during the neutralization treatment process can also meet the Class I requirements of general industrial solid wastes. At the same time, the generation of hazardous wastes such as iron removal slag is avoided, and efficient recovery of valuable copper is achieved. The generated copper slag can meet the requirements of copper concentrate products and has a high utilization value.

[0025] 3. The method for comprehensive treatment of ferric iron-containing acidic water provided by the present invention has a simple process, safe and reliable operation, and uses common and inexpensive reagents. It can treat ferric iron-containing acidic water into water bodies that meet emission standards, while avoiding the generation of iron removal slag and improving the recovery rate of copper. It has significant economic, environmental and social benefits, and provides a new idea for the treatment of ferric iron-containing acidic water. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic process flow diagram of the method for comprehensive treatment of ferric iron-containing acidic water provided in Example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0029] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0030] The present invention provides a method for comprehensive treatment of acidic water containing ferric iron, comprising the following steps:

[0031] S1. Inputting ferric iron-containing acidic water into an iron removal reaction tank, adding a predetermined amount of reducing agent, and adjusting the pH value after sufficient reaction to obtain an iron removal turbid liquid;

[0032] S2, inputting the iron-removing turbid liquid obtained in step S1 into a sulfidation reaction tank, adding a sulfiding agent to adjust the ORP value, and obtaining a sulfided copper-collecting turbid liquid; adding a flocculant to the sulfided copper-collecting turbid liquid, and obtaining a sulfided underflow and a sulfided overflow after solid-liquid separation in a sulfidation thickener; a part of the sulfided underflow is refluxed into the sulfidation reaction tank, and the other part is subjected to a filter press dehydration treatment to obtain a first filter press residue and a first filter press liquid; wherein the first filter press residue can be sold as copper slag;

[0033] S3, inputting the sulfide overflow and the first filter press liquid obtained in step S2 into a neutralization reaction tank, adjusting the pH value, and introducing an oxidant at the same time, obtaining a neutralized turbid liquid after sufficient reaction; adding a flocculant to the neutralized turbid liquid, and obtaining a neutralization underflow and a neutralization overflow after solid-liquid separation by a neutralization thickener; a part of the neutralization underflow is returned to the neutralization reaction tank, and a part of the neutralization underflow is subjected to filter press dehydration treatment to obtain a second filter press residue and a second filter press liquid; wherein, the neutralization overflow and the second filter press liquid meet the emission standards and can be discharged after being tested to meet the standards; the leaching toxicity and toxic substance content of the second filter press residue meet the requirements of general industrial solid waste, and can be stored in compliance as general industrial solid waste.

[0034] The present invention is based on the problem that trivalent iron in acidic water easily forms a large amount of precipitation in the iron removal section. Through the above-mentioned method, a specific amount of reducing agent is added to partially convert the trivalent iron in the acidic water into divalent iron, so that after the iron hydroxide formed in the iron removal section and the copper sulfide precipitation formed in the sulfide copper removal section are mixed, the copper grade can still meet the external sales requirements, and the generation of hazardous wastes such as iron removal slag is effectively avoided.

[0035] More specifically, in step S1, the ferric iron-containing acidic water may contain several or all pollutants such as copper, iron, zinc, lead, arsenic, manganese, nickel, cadmium, chromium, beryllium, etc., wherein the copper ion concentration is not less than 100 mg / L; the reducing agent is a substance that can reduce ferric iron to divalent iron, and the reducing agent is preferably one or more of iron powder, ethylene glycol, trisodium citrate, and hydroxylamine hydrochloride. The amount of the reducing agent added is determined according to the ferric iron content and the copper ion content in the ferric iron-containing acidic water, and specifically satisfies the following relationship:

[0036]

[0037] In the above formula, 96, 64 and 56 are the molecular weights of copper sulfide, copper and iron respectively; the copper ion content, the ferric iron content and the reducing agent dosage respectively represent the mass or mass concentration of copper ions, ferric iron ions and reducing agent in ferric iron acidic water; the valence change value of the reducing agent is the valence change value of the reducing agent itself after reducing ferric iron to ferrous iron; α is the preset copper recovery rate of the whole process, which is generally between 85% and 99%; γ is related to the content of other substances in acidic water and the control parameters of the iron removal sulfide process, which is specifically determined by experiments and generally takes a value between 1 and 1.25; m represents the preset copper grade of copper slag, which is determined according to the process control requirements and generally takes a value greater than or equal to 15%.

[0038] The dosage of the reducing agent determined in this manner can reduce part of the trivalent iron to divalent iron, and make the copper grade of the first filter press residue obtained in step S2 reach more than 15% to meet sales requirements. After adding the reducing agent, the pH is adjusted by adding a pH adjusting agent to adjust the pH to 3.4-3.6 and reacting for 0.25-0.5h; the pH adjusting agent is lime milk or carbide slag.

[0039] In step S2, the ORP value is adjusted by adding a sulfiding agent to adjust the ORP value to 0-200mv, so that heavy metal ions (mainly copper, etc.) are chemically precipitated, and the reaction time is 0.25-0.5h; the sulfiding agent is one of sodium sulfide, sodium hydrosulfide, and hydrogen sulfide gas. When a part of the sulfidation underflow is refluxed to the sulfidation reaction tank, the reflux ratio is controlled to be 2%-20%, so that the mass concentration of the solid phase in the sulfidation underflow during the circulation treatment process is controlled to be 10%-20%, so as to reduce the processing pressure of the sulfidation underflow filter press section, and control the copper grade in the first filter press residue to be above 15%.

[0040] In step S3, the method of adjusting pH is: adding a pH regulator to adjust the pH to 8.0-8.5, so that most of the harmful substances such as heavy metals (especially manganese) are converted into precipitates, and the reaction time is 1.0-2.0 hours; the pH regulator is lime milk or carbide slag. The reaction time of the oxidant and the neutralization solution is about 1 hour; the oxidant is air or hydrogen peroxide. When the oxidant is air, the gas-liquid volume ratio of the oxidant to the neutralization solution is 1:4-10; when the oxidant is hydrogen peroxide, the mass ratio of the oxidant added to the divalent iron ion in the neutralization solution is 0.5-5:1. When a part of the neutralization underflow is refluxed to the neutralization reaction tank, the reflux ratio is controlled to be 60%-90%, so that the mass concentration of the solid phase in the neutralization underflow during the circulation treatment process is controlled to be 15%-30%, so as to reduce the processing pressure of the subsequent section.

[0041] In the above steps, the flocculants are all non-ionic flocculants, and the amount of flocculants added in S2 is 1-5 g / m 3 The amount of flocculant added in step S3 is 1 to 15 g / m 3 .

[0042] The method for comprehensive treatment of acidic water containing ferric iron provided by the present invention is described below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment provides a method for comprehensive treatment of ferric iron-containing acidic water, which is aimed at ferric iron-containing acidic water containing high concentrations of heavy metals such as copper and iron, wherein the copper concentration fluctuates within the range of 168.64 to 1145.54 mg / L, the ferric iron concentration fluctuates within the range of 234.34 to 938.56 mg / L, the arsenic concentration is about 2.5 mg / L, and the manganese concentration is about 15 mg / L. The process flow diagram is as follows: Figure 1 As shown in the figure (the dotted line in the figure represents the bottom flow in the sludge state), it specifically includes the following steps:

[0045] S1. Iron removal

[0046] The ferric iron-containing acidic water is input into the iron removal reaction tank. According to the measured ferric iron content (845.25 mg / L) and copper ion content (246.56 mg / L) in the ferric iron-containing acidic water, α is set to 94%, γ is set to 1.10, and m is set to 15%. Then, iron powder is used as the reducing agent, and the reducing agent valence change value is 2, and the reducing agent molecular weight is 56. Substitute into the following formula to determine the conditions that the reducing agent dosage needs to meet:

[0047]

[0048] After determining the dosage range of the reducing agent according to the above formula, the dosage of the reducing agent is selected to be 250 mg / L. After adding the reducing agent, the concentration of ferric iron in the ferric iron acidic water is reduced from 845.25 mg / L to about 500 mg / L. Then, 10% lime milk solution is added and the pH value is adjusted to 3.6 to chemically precipitate heavy metal ions (mainly ferric iron, arsenic, etc.) so that they can be removed through the solid form of heavy metal precipitation. After reacting for 0.5 hours, the iron-removing turbid liquid is obtained and enters the sulfidation copper recovery section.

[0049] S2, sulfide copper

[0050] The iron removal turbid liquid obtained in step S1 is input into the sulfidation reaction tank, and 10% sodium hydrosulfide solution is input into the sulfidation reaction tank as a sulfiding agent through the sulfidation mud mixing tank, and the ORP value is adjusted to about 80mv to chemically precipitate heavy metal ions (mainly copper, etc.). After 0.5h of reaction, the copper concentration in the liquid phase is below 0.5mg / L to obtain a sulfidation copper collection turbid liquid. The sulfidation copper collection turbid liquid is input into the sulfidation flocculation reaction tank, and the 3g / m 3 A nonionic flocculant is added in an amount of the amount of the sulfide copper recovery turbid liquid, and then the liquid is input into a sulfide sedimentation tank, and solid-liquid separation is performed through a sulfide thickener to obtain a sulfide overflow and a sulfide underflow in a sludge state; a part of the sulfide underflow is refluxed to the sulfide reaction tank through a sulfide slurry mixing tank, and the reflux ratio is controlled to be 15%; the other part is subjected to filter press dehydration treatment to obtain a first filter press residue and a first filter press liquid; wherein, the first filter press residue can be sold as copper slag (its copper grade is 17%, and the copper recovery rate is 94.5%); the first filter press liquid and the sulfide overflow enter a neutralization section.

[0051] S3, Neutralization

[0052] The sulfide overflow obtained in step S2 and the first press filtrate are input into the neutralization reaction tank, and the lime milk is input into the neutralization reaction tank through the neutralization mud mixing tank to adjust the pH value to 8.3. At the same time, air is introduced into the neutralization reaction tank to control the gas-liquid ratio to 1:6, and the residual divalent iron ions are further oxidized to chemically precipitate the heavy metal ions (mainly iron, arsenic, zinc, lead, manganese, nickel, etc.) so that they can be removed in the solid form of heavy metal precipitation. After reacting for 1.5 hours, a neutralized turbid liquid is obtained. The neutralized turbid liquid is input into the neutralization flocculation reaction tank and the flocculation reaction tank is heated to 8 g / m 3A nonionic flocculant is added to the neutralized turbid liquid in an amount of , and then it is input into the neutralization sedimentation tank, and the neutralization thickener is used for solid-liquid separation to obtain a neutralization overflow and a neutralization underflow in a sludge state; a part of the neutralization underflow is returned to the neutralization reaction tank through the neutralization slurry mixing tank, and the reflux ratio is controlled at 70%; a part of the neutralization underflow is dehydrated by filter pressing to obtain a second filter press residue and a second filter press liquid. Among them, the target heavy metals in the neutralization overflow and the second filter press liquid meet the first-level emission standard of the "Comprehensive Sewage Discharge Standard" (GB 8978-1996), and meet the discharge standards; the leaching toxicity and toxic substance content of the second filter press residue meet the requirements of general industrial solid waste, and can be stored in compliance as general industrial solid waste.

[0053] The water quality of the inlet and outlet water of this embodiment was tested, and the results are shown in the following table.

[0054] Table 1 Inlet and outlet water quality

[0055]

[0056] Note: pH value is dimensionless, and the units of other indicators in the table are "mg / L".

[0057] Application Example Referring to the relevant requirements of the General Standard for Identification of Hazardous Wastes (GB 5085.7-2019), the second filter press residue obtained in step S3 is pre-identified for solid waste properties.

[0058] 1) Flammability analysis

[0059] Spontaneous combustion substances refer to items that are easily oxidized in the air, releasing heat and burning on their own. From the definition, it can be seen that the main feature of this item is that it can generate heat and burn on its own in the air. In this project, the second filter press residue is mainly composed of calcium sulfate and metal precipitates. Preliminary analysis shows that the second filter press residue is not flammable.

[0060] 2) Reactivity analysis

[0061] The second filter press residue produced by the normal process of this project is stable and non-explosive at room temperature and pressure, and does not undergo drastic changes under non-detonation conditions; under standard temperature and pressure (25°C, 101.3kPa), no detonation or explosive decomposition reaction occurs, and preliminary analysis shows that it is not explosive. The second filter press residue produced by the normal process of this project does not produce flammable gas and trace amounts of toxic gas when in contact with water, and cannot produce toxic gas, vapor or smoke that is harmful to human health or the environment when mixed with water. Under acidic conditions, it will not decompose to produce hydrogen cyanide gas and H2S gas. The second filter press residue does not belong to waste oxidants or organic peroxides. Therefore, preliminary analysis shows that it is not reactive.

[0062] 3) Initial screening analysis of acute toxicity

[0063] The second filter press residue produced by the normal process of this project mainly consists of calcium sulfate and metal precipitates, without any acute toxic substances. Preliminary analysis shows that the second filter press residue does not have acute toxicity.

[0064] 4) Corrosion analysis

[0065] According to the "Identification of Corrosiveness of Hazardous Waste Identification Standard" (GB 5085.1-2007), the leaching liquid of the second filter press residue was prepared. After analysis and testing, the pH value of the leaching liquid of the second filter press residue was 7.8, which did not meet the condition of pH ≥ 12.5 or ≤ 2.0. Preliminary analysis showed that the second filter press residue was not corrosive.

[0066] 5) Leaching toxicity analysis

[0067] According to the requirements of “Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method” (HJ / T 299-2007), the second filter press residue was subjected to a toxicity leaching test. The specific results are shown in Table 2.

[0068] Table 2 Results of leaching toxicity analysis of the second filter press residue

[0069]

[0070] Note: The unit of Cu and Mn indicators is mg / L, and the unit of other indicators is μg / L. “L” means below the detection limit.

[0071] From the results in Table 2, it can be seen that, by comparing with the “Identification Standards for Hazardous Wastes - Identification of Leaching Toxicity” (GB 5085.3-2007), it is preliminarily determined that the second filter press residue is general industrial solid waste.

[0072] 6) Toxic substance content

[0073] The components of the second filter press residue were analyzed in accordance with the requirements of the “Identification Standard for Hazardous Wastes - Identification of Toxic Substance Content” (GB 5085.6-2007). The specific results are shown in Table 3.

[0074] Table 3 Analysis results of the second filter press residue components

[0075] index Cu As Cd Cr Second filter press 23500 16.9 4.7 4.4 index Pb Zn Mn Second filter press 220 1140 2340

[0076] Note: The unit of each indicator in Table 3 is "mg / kg".

[0077] The second filter press residue is mainly composed of calcium sulfate and metal hydroxide precipitate. By comparing with the "Identification Standard for Hazardous Wastes - Identification of Toxic Substance Content" (GB 5085.6-2007), it is preliminarily judged that the toxic substances that may exist in the second filter press residue are "arsenic acid and its salts" and "elemental manganese".

[0078] Table 4 Analysis results of harmful substances in the second filter press residue

[0079]

[0080] According to Table 4, the toxic substance content of the second filter press residue is lower than the standard limit of hazardous waste, and it is preliminarily judged that it meets the standard requirements of general industrial solid waste.

[0081] It can be seen from the above results that after being treated by the comprehensive treatment method for ferric iron-containing acidic water provided in this embodiment, the effluent quality and the generated solid waste meet the corresponding requirements. And the overall treatment process can treat 500m3 of ferric iron-containing acidic water. 3 / h, achieving efficient treatment of acidic water containing ferric iron and achieving the effect of harmless slag production.

[0082] Comparative Examples 1 to 4

[0083] Comparative Examples 1 to 4 respectively provide a method for comprehensive treatment of acidic water containing ferric iron. Compared with Example 1, the difference is that the amount of reducing agent added in step S1, the ORP value in step S2, and the pH value in step S3 are respectively changed. The corresponding parameters corresponding to each comparative example are shown in Table 5. The remaining steps and parameters are the same as in Example 1 and are not repeated here.

[0084] Table 5 Process parameters in Comparative Examples 1 to 4

[0085]

[0086] After treating the ferric iron-containing acidic water according to the methods provided in the above comparative examples 1 to 4, the effluent quality and the generated solid waste were tested, and the results are shown in Table 6.

[0087] Table 6 Comparative Example Test Results

[0088]

[0089] As can be seen from Table 6, for acidic wastewater rich in trivalent iron, the amount of reducing agent added in step S1 needs to be appropriate. If the amount of reducing agent added is too low, it will directly affect the grade of copper in copper slag and cannot meet the requirements for the sale of copper concentrate; if the amount of reducing agent added in step S1 is too much, there is a large amount of trivalent iron reduced, although it can improve the copper grade of copper slag, but it will cause the generated divalent iron to precipitate in the neutralization section in large quantities, and the amount of neutralization slag produced will increase; if the ORP value in step S2 cannot be controlled below 200mv, there will be a problem that copper in acidic water cannot be effectively recovered, and the comprehensive recovery rate of copper in comparative example 2 is only 83.6%, and the recovery rate is relatively low. If the pH value in step S3 cannot be controlled at about 8.3, it will not be possible to ensure that each pollutant in acidic water is effectively treated, especially Mn. In the comparative test, the concentration after treatment is still as high as 3.3mg / L, which is much higher than the limit value of 2mg / L required by the standard.

[0090] In summary, the present invention provides a method for comprehensive treatment of acidic water containing ferric iron, and relates to the field of water treatment. The method is to sequentially perform iron removal pretreatment, sulfidation and copper collection, and neutralization treatment on acidic water containing ferric iron, and add a predetermined amount of reducing agent during iron removal pretreatment to convert part of the ferric iron into ferrous iron, reasonably control the amount of iron removal precipitate produced, and directly input the iron removal turbid liquid obtained after adjusting the pH into the sulfidation and copper collection section without flocculation, and use an oxidant to treat it in the neutralization process, so that the neutralization overflow and press filtrate obtained in the neutralization process meet the discharge standard, and achieve deep purification of acidic water containing ferric iron; the above process does not produce iron removal slag, greatly reduces the amount of solid waste generated, and effectively reduces the valuable copper lost with the iron slag liquid phase, and improves the copper recovery rate of the entire acidic water treatment system; and the treated water body and neutralization slag meet the discharge requirements, with significant economic benefits, environmental benefits and social benefits.

[0091] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for comprehensive treatment of ferric iron-containing acidic water, characterized in that: The steps include: S1. Inputting ferric iron-containing acidic water into an iron removal reaction tank, adding a predetermined amount of reducing agent, and adjusting the pH value after sufficient reaction to obtain an iron removal turbid liquid; The dosage of the reducing agent satisfies the following relationship: ×100%≥m In the above formula, α is the preset copper recovery rate, which is 85%~99%; γ is 1~1.25; m represents the preset copper grade of copper slag, which is greater than or equal to 15%; S2, inputting the iron removal turbid liquid obtained in step S1 into a sulfidation reaction tank, adding a sulfiding agent to adjust the ORP value, and obtaining a sulfided copper collection turbid liquid; adding a flocculant to the sulfided copper collection turbid liquid, and obtaining a sulfided underflow and a sulfided overflow after solid-liquid separation in a sulfidation thickener; returning a portion of the sulfided underflow to the sulfidation reaction tank, and performing a filter press dehydration treatment on another portion of the sulfided underflow to obtain a first filter press residue and a first filter press liquid; S3, inputting the sulfide overflow obtained in step S2 and the first filter press liquid into a neutralization reaction tank as neutralization liquid, adjusting the pH value, and introducing an oxidant at the same time to obtain a neutralized turbid liquid after sufficient reaction; adding a flocculant to the neutralized turbid liquid, and obtaining a neutralization underflow and a neutralization overflow after solid-liquid separation in a neutralization thickener; returning a portion of the neutralization underflow to the neutralization reaction tank, and subjecting another portion of the neutralization underflow to filter press dehydration treatment to obtain a second filter press residue and a second filter press liquid.

2. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S1, the reducing agent is one or more of iron powder, ethylene glycol, trisodium citrate, and hydroxylamine hydrochloride.

3. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S1, the copper ion concentration in the ferric iron-containing acidic water is not less than 100 mg / L, and the pH value is adjusted by adding a pH adjuster to adjust the pH to 3.4-3.6 and reacting for 0.25-0.5 h; the pH adjuster is lime milk or carbide slag.

4. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S2, the method of adjusting the ORP value is: adding a sulfiding agent to adjust the ORP value to 0-200 mv, and reacting for 0.25-0.5 h; the sulfiding agent is one of sodium sulfide, sodium hydrosulfide, and hydrogen sulfide gas.

5. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S3, the pH value is adjusted in the following manner: adding a pH adjuster to adjust the pH value to 8.0-8.5, and reacting for 1.0-2.0 hours; the pH adjuster is lime milk or carbide slag.

6. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S3, when the oxidant is air, the gas-liquid volume ratio of the oxidant to the neutralizing liquid is 1:4-10; when the oxidant is hydrogen peroxide, the mass ratio of the oxidant dosage to the divalent iron ions in the neutralizing liquid is 0.5-5:

1.

7. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S2, 2% to 20% of the sulfidation underflow is refluxed into the sulfidation reaction tank.

8. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 7, characterized in that: In step S2, the first filter press residue is collected as copper slag, and the copper grade in the copper slag is above 15%.

9. The method for comprehensive treatment of ferric iron-containing acidic water according to claim 1, characterized in that: In step S3, 60% to 90% of the neutralization underflow is refluxed into the neutralization reaction tank.

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