Method for improving removal efficiency of COD and total oil in overflow water of copper mine tailings pond

Abstract

The application discloses a method for improving the removal efficiency of COD and total oil in overflow water of a copper mine tailing pond, and comprises the following steps: S1, adjusting the pH of copper mine copper selection alkaline wastewater to 4.5-5.5 by using an acidic agent; S2, the wastewater after pH adjustment is introduced into an iron-carbon micro-electrolysis reaction tank; S4, the wastewater after high-level oxidation treatment is introduced into a neutralization reaction tank, the pH of the wastewater is adjusted to 8-9 by using an alkaline agent, and then a modified high-molecular-weight anionic flocculant solution is added after sufficient reaction. The technical scheme of the process, i.e. 'adjusting the pH of wastewater + iron-carbon micro-electrolysis oxidation-reduction reaction + sodium persulfate high-level oxidation + flocculation and precipitation', can significantly reduce the concentration of pollutants such as COD and total oil in the copper mine copper selection alkaline wastewater, solves the problem of low removal efficiency of COD and total oil in the existing copper mine copper selection wastewater, effectively reduces the risk of environmental impact of the wastewater, and provides a basis for effective utilization of the treated wastewater.

Description

Technical Field

[0001] This invention relates to the technical field of copper mine wastewater treatment and utilization, and in particular to a method for improving the removal efficiency of COD and total oil in tailings overflow water from copper mines. Background Technology

[0002] Overflow water from copper thickeners in copper mines is directly discharged into tailings ponds. This wastewater contains high concentrations of tailings, residual beneficiation reagents, and other pollutants. During its stay in the tailings pond, the wastewater undergoes natural degradation treatment through sunlight, natural oxidation, and sedimentation. Due to the oxidation of sulfur in the tailings and the acidification of the tailings, the pH of the wastewater tends to decrease, from 9-11 to 5-8. Some metal leaching may occur. Artificial aeration is used for some tailings pond wastewater to enhance pollutant degradation and removal. After sedimentation and compression of tailings within the tailings pond, the beneficiation wastewater eventually forms a low-concentration overflow, which is discharged from the tailings pond. Generally, this type of wastewater has a pH of 6.0-9.0. However, due to the influence of meteorological factors such as temperature, rainfall, and sunshine, the water quality of tailings dam overflow fluctuates. The COD in the overflow fluctuates between 15 and 150 mg / L, and the total oil fluctuates between 1.5 and 6.0 mg / L. Under severe conditions, other metals may occasionally exceed the standards, and the pH of the wastewater can drop to 5.0. Therefore, the discharge of this type of wastewater still poses an environmental risk.

[0003] Some copper mine tailings ponds reuse some of the overflow water, while the excess overflow water is discharged for treatment; some mine tailings ponds, due to difficulties in wastewater transportation, have on-site wastewater treatment facilities built for the overflow water or discharge it directly. At present, there are roughly two types of treatment for alkaline wastewater from copper ore beneficiation: (1) Alkaline wastewater from copper ore beneficiation is mixed with acidic wastewater from the mine, and the pH of the two wastewaters is controlled to be 7.0 to 8.5 after neutralization. Then, coagulation and sedimentation are carried out, and the sedimented bottom mud is transported to the tailings pond. The supernatant is discharged directly as wastewater. This type of treatment method can play a certain role in the treatment. However, the acidic wastewater from mines varies greatly due to factors such as rainfall and different mining locations, resulting in a mismatch between the mixing ratio of alkaline wastewater from copper ore beneficiation and acidic wastewater from the mines, and there is still a risk of wastewater discharge. (2) First, sulfuric acid or hydrochloric acid is used to adjust the pH of alkaline wastewater from copper ore beneficiation to weakly acidic, and then lime is used to neutralize it, adjusting the pH of the wastewater to 7-9. Then, coagulation and sedimentation are carried out, and the sedimented bottom mud is transported to the tailings pond. The supernatant is discharged directly as wastewater. The above treatment method can effectively remove heavy metals from the wastewater. However, the reducing substances (COD) and total oil in the wastewater still fluctuate greatly.

[0004] In summary, according to the direct emission limits of the "Emission Standard of Pollutants for Copper, Nickel and Cobalt Industry" (GB 25467-2010), the required discharge limits for wastewater are COD ≤ 60 mg / L and petroleum hydrocarbons ≤ 3.0 mg / L. Clearly, improving the removal efficiency of COD and total oil in copper mine tailings overflow is necessary. Therefore, this application provides a method to improve the removal efficiency of COD and total oil in copper mine tailings overflow to meet this requirement. Summary of the Invention

[0005] The purpose of this application is to provide a method for improving the removal efficiency of COD and total oil in tailings overflow water from copper mines, thereby enhancing the removal depth of COD and total oil in such wastewater and improving treatment efficiency.

[0006] To achieve the above objectives, this application provides the following technical solution: a method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines, comprising the following steps:

[0007] S1: Use acidic reagents to adjust the pH of alkaline wastewater from copper ore beneficiation to 4.5–5.5;

[0008] S2: The wastewater after pH adjustment enters the iron-carbon micro-electrolysis reactor to achieve chain-breaking degradation of organic matter in the wastewater, which is a ring-chain or long-chain mineral processing agent, and decomposes macromolecular pollutants into easily removable small-molecule organic matter.

[0009] S3: Wastewater from the iron-carbon micro-electrolysis reaction enters the sodium persulfate advanced oxidation reaction tank. The Fe produced by micro-electrolysis... 2+ It reacts with added sodium persulfate to generate highly active SO4- ions, which synergistically degrade organic pollutants in wastewater under weakly acidic conditions. Simultaneously, it also causes some Fe... 2+ Oxidized to Fe 3+ This forms Fe(OH)3 colloids that can adsorb or aggregate fine particles;

[0010] Sodium persulfate advanced oxidation fully utilizes the Fe remaining in the wastewater after the iron-carbon micro-electrolysis reaction. 2+ It works synergistically with the highly active SO4- ions generated by sodium persulfate under weakly acidic conditions to degrade pollutants such as residual organic reagents in wastewater.

[0011] S4: The wastewater after advanced oxidation treatment enters the neutralization reaction tank. The pH of the wastewater is adjusted to 8-9 using alkaline agents to ensure a full reaction. Then, a modified polymeric anionic flocculant solution is added to allow the suspended solids, colloids and other fine particles in the wastewater to fully react with the flocculant. Finally, the wastewater is allowed to stand to achieve solid-liquid separation. The supernatant can be directly discharged or recycled, while the underflow is mixed with tailings for treatment or utilization.

[0012] The settling time for the wastewater described in S4 is determined based on a particulate matter settling rate of 0.50–0.65 m³ / (m²·h).

[0013] Acidic agents can be commonly used acidic materials such as sulfuric acid, hydrochloric acid, nitric acid, and oxalic acid, or acidic salts such as ferrous sulfate. However, considering that some acidic materials or salts may lead to an increase in pollutants such as COD and total nitrogen in the treated effluent, sulfuric acid is used as the agent for adjusting the pH of wastewater in this application.

[0014] The technological features of this application

[0015] (1) Adjusting the pH to 4.5-5.5 can satisfy the conversion of iron (equivalent to the negative electrode of the micro battery and the anode of the electrolysis) in iron-carbon materials into ferrous ions: Carbon (equivalent to the positive electrode of a micro-battery and the cathode of an electrolytic cell): , (With sufficient oxygen), this application does not supplement oxygen, maintaining a small amount of oxygen remaining in the wastewater. It can be used as a transfer electron in the subsequent oxidation of sodium persulfate, but it cannot completely oxidize the ferrous ions, otherwise the oxidation efficiency of sodium persulfate will be greatly reduced.

[0016] (2) The iron-carbon micro battery reaction mainly utilizes elemental iron to release electrons and become ferrous ions; it utilizes dissolved oxygen in wastewater and organic matter in wastewater to accept electrons, thereby achieving chain breaking and degradation of organic matter.

[0017] (3) Utilize the weak acid conditions to enhance the oxidation effect of sodium persulfate.

[0018] (4) After oxidation, the pH of the wastewater is increased. Using compound alkali can reduce the amount of sludge produced and the amount of alkaline materials used. In addition, the compound alkali contains carbon powder, which can be used as an adsorbent material to make the fine particles in the wastewater aggregate and settle easily.

[0019] The method of this invention not only effectively removes COD and total oil from the overflow water of copper mine tailings ponds, but also further removes related pollutants such as metals, fluorides, and sulfides from the wastewater.

[0020] In a preferred embodiment of this invention, in step S1, the acidic agent is sulfuric acid, and the concentration of sulfuric acid is 15% to 45%.

[0021] The advantages of using 15%–45% sulfuric acid to adjust wastewater pH are: sulfuric acid has a strong neutralizing ability; its corrosiveness is strongest at a concentration of 47%–50%; and the amount of sulfuric acid used to adjust wastewater pH from 8–9 to 4.5–5.5 is very small, whereas using 98% sulfuric acid directly would be difficult to control. Therefore, using 15%–45% sulfuric acid to adjust wastewater pH ensures neutralization, reduces corrosion of the dosing pipelines and pumps, and guarantees precise dosing.

[0022] In a preferred embodiment of this example, in step S2, the iron and carbon are in the form of tiny particles with a particle size of 1 to 10 mm, and the composition of the iron and carbon is: iron content = 65% to 85% and carbon content = 15% to 35%.

[0023] The advantages of this invention in degrading COD and total oil in wastewater are: controlling the amount of iron and carbon in the iron-carbon material (Fe / C = 0.39~1.21 mol / mol), achieving matching of electron transfer capacity between the anode and cathode, maximizing the concentration of activated hydrogen (·H or [H]), and improving the efficiency of degrading organic matter in wastewater.

[0024] In a preferred embodiment of this invention, in step S2, the iron-carbon micro-electrolysis reactor includes a first tank and a second tank. The first tank is an oxidation-reduction reaction zone, and the second tank is a wastewater and iron-carbon powder separation zone. The stirring device in the first tank is a plate-and-frame stirrer with a rotation speed of 15–30 rpm. The surface loading rate of the sedimentation zone in the second tank is 1.15–1.25 m³ / (m²·h). The underflow generated in the sedimentation zone of the second tank is directly returned to the first tank, achieving full utilization of iron and carbon. Under the acidic conditions of the wastewater, iron and carbon generate nascent H and Fe. 2+ Active reducing media can break down the chains of large molecules and polycyclic organic compounds in wastewater, generating pollutants that are easily degraded, adsorbed, and neutralized.

[0025] The advantage of using a plate and frame agitator in the reaction zone of the iron-carbon microelectrolysis cell is that the iron and carbon reacting with the organic matter in the wastewater are in particulate form. The plate and frame agitator can generate greater disturbance to the wastewater and the iron and carbon materials, which is conducive to the renewal of the iron and carbon surface, promotes full contact between the organic pollutants in the wastewater and the iron and carbon surface, and improves the mass transfer rate between the liquid and solid phase interfaces.

[0026] The sedimentation zone of the iron-carbon micro-electrolysis cell serves to settle larger iron-carbon particles. These settled particles can be returned to the reaction tank within the iron-carbon micro-electrolysis system. The wastewater, carrying a small amount of fine particles (adhered with organic pollutants), enters the subsequent advanced oxidation reaction tank. Due to the high density of iron-carbon particles (1.2–1.5 t / m³) and an average particle size greater than 1 mm, the sedimentation rate is high, resulting in relatively few fine particles in the wastewater. Therefore, the surface loading rate of this sedimentation zone is determined to be 1.15–1.25 m³ / (m²·h), which reduces the required sedimentation area while still meeting efficiency requirements.

[0027] In a preferred embodiment of this example, in step S3, the concentration of sodium persulfate solution is 10%–15%. Sodium persulfate is a strong oxidizing agent, and its concentration is linearly positively correlated with the corrosion rate of carbon steel, stainless steel, copper, etc. To ensure that the equipment, pipelines, and other materials to which sodium persulfate solution is added are not corroded, the concentration of sodium persulfate solution must be controlled below 25%. Therefore, under the premise of ensuring the oxidizing capacity of sodium persulfate solution, experiments have determined that a sodium persulfate solution concentration of 10%–15% is the most effective, the amount of sodium persulfate used is 50–100 g / m³, and the oxidation reaction residence time is 2–4 hours.

[0028] In a preferred embodiment of this invention, the alkaline agent is a composite alkaline solution with a concentration of 20% to 30%.

[0029] Alkaline agents such as compound alkali, lime, caustic soda, and sodium carbonate can be selected. This invention uses compound alkali, which utilizes calcium oxide or calcium hydroxide in the compound alkali to adjust the pH of the wastewater. During the reaction, fine particulate matter is formed, which can be adsorbed by diatomaceous earth, activated carbon, etc. in the compound alkali and aggregate into larger particles. It can also destabilize the colloidal substances in the wastewater and improve the removal efficiency of fine suspended pollutants.

[0030] In a preferred embodiment of this example, in step S4, the modified polymeric anionic flocculant is a sulfonic acid-modified polymeric anionic polyacrylamide, with a concentration of 0.02% to 0.05% and a dosage of 4 to 10 g / m³.

[0031] The modified polymeric anionic flocculant used readily expands in water and forms highly cohesive polymeric complexes, exhibiting strong trapping and bridging capabilities. Experiments showed that when its concentration exceeded 0.1%, it formed a gel-like substance, making it difficult to meter and add to the wastewater. Therefore, the dosage of this flocculant is very small; to ensure optimal performance, its concentration was determined to be 0.02%–0.05%.

[0032] A modified polymeric anionic flocculant comprises 35%–45% polymeric anionic flocculant with a molecular weight greater than 20 million, 2%–5% alkanolamine flocculant synergist, 1%–5% alcohol antioxidant and 55%–62% additives.

[0033] The polymeric anionic flocculant is sulfonated polyacrylamide or polyacrylamide with a molecular weight greater than 20 million.

[0034] The aforementioned amine flocculant is one or more of triethylenetetramine, tetraethylenepentamine, and diethylenetriamine;

[0035] The alcohol antioxidants mentioned are one or more of glycol, dipropylene glycol, and diethylene glycol;

[0036] The additive is one of soluble chloride brine, water, or acid.

[0037] The role of alcohol amine synergists is to introduce some hydrophobic groups into the polymer chain of flocculants by utilizing the intermolecular electrostatics between flocculants and alcohol amines, which is beneficial to the separation of oil and water. The role of antioxidants is that wastewater contains a certain amount of dissolved oxygen. When flocculants dissolve and diffuse in wastewater, they form a network structure, resulting in a very low concentration of flocculants, which are easily oxidized by dissolved oxygen in the water. Introducing water-soluble alcohols into the formulation of flocculants provides attack sites for oxygen in the water and protects the amino, hydroxyl, and other groups of flocculants.

[0038] The larger the molecular weight of anionic polymeric flocculants, the stronger the introduced electrophilic groups, the easier they are to extend in water, and the denser the network structure formed. This is beneficial for the flocculant to capture fine particulate matter and colloidal matter, and allows weakly charged organic pollutants and fine oil to enter the flocs.

[0039] In a preferred embodiment of this invention, the molecular weight of the polymeric anionic flocculant is 22 million to 25 million.

[0040] When the molecular weight of a polymeric anionic flocculant is below 22 million, the flocculant with a lower molecular weight may not be able to form a sufficiently long chain structure, thereby reducing its ability to capture and aggregate suspended particles.

[0041] Flocculants with lower molecular weight form smaller flocs, which settle more slowly in wastewater, thus prolonging the wastewater treatment time.

[0042] Flocculants with lower molecular weights may not be able to effectively adsorb oil, leading to an increase in the amount of oil residue in wastewater;

[0043] When the molecular weight of a high molecular weight anionic flocculant is higher than 25 million, the flocculant with an excessively high molecular weight may have poor solubility in water, making it difficult to disperse evenly during wastewater treatment, which may affect the flocculation effect; flocculants with excessively high molecular weight may also be difficult to completely degrade during wastewater treatment, thus causing secondary pollution in the environment.

[0044] Therefore, setting the molecular weight of the polymeric anionic flocculant to 22 million to 25 million can effectively capture and aggregate suspended particles and dissolved organic matter in wastewater, and it also has a good oil adsorption capacity and a faster settling speed, which helps to shorten the wastewater treatment time.

[0045] In summary, the technical effects and advantages of this invention are as follows:

[0046] This invention has a reasonable structure. The process uses a technical solution of "adjusting the pH of the wastewater + iron-carbon micro-electrolysis oxidation-reduction reaction + sodium persulfate advanced oxidation + flocculation and sedimentation" to significantly reduce the concentration of pollutants such as COD and total oil in the alkaline wastewater of copper ore beneficiation. It solves the problem of low COD and total oil removal efficiency in existing copper ore beneficiation wastewater, which not only effectively reduces the risk of wastewater impact on the environment, but also provides a foundation for the effective utilization of treated wastewater. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Example 1

[0051] The overflow from a copper mine tailings dam has a COD concentration of 85 mg / L, a total oil concentration of 3.5 mg / L, and a pH of 7.8. The treatment steps are as follows: S1. The overflow is introduced into an acidification tank, where sulfuric acid (35.5%) is used to adjust the pH to 4.5. The retention time is 20 min. The acidification tank is constructed with steel lined with rubber. S2. The effluent from the acidification tank enters an iron-carbon micro-electrolysis oxidation-reduction reaction tank. The initial iron-carbon dosage is determined based on the tank volume, and is 100 kg / m³. During the treatment process, the continuous replenishment of iron-carbon is 35 mg / L. The wastewater flow rate is 100 kg / m³, and the retention time in the tank is 2.0 h. The micro-electrolysis reactor is constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S3 iron-carbon micro-electrolysis reactor enters the sodium persulfate advanced oxidation reactor. Sodium persulfate solution is added to the inlet of the advanced oxidation reactor via a dosing pipeline. The concentration of sodium persulfate solution used is 15%, and the dosage of sodium persulfate is determined to be 100 g / m³ based on the wastewater flow rate. The wastewater retention time is 3.0 h. The advanced oxidation reactor is also constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S4 advanced oxidation reactor enters the alkali adjustment tank. A compound alkali suspension is added via a dosing pipeline at the inlet to adjust the pH of the wastewater to 9.0. The mixing reaction time of the alkali solution and wastewater is 15 min, and the agitator speed is 60 rpm. Then, the alkali-adjusted wastewater overflows into the flocculant reaction tank. The flocculant is dripped into the wastewater through the dosing pipeline. The agitator speed in the flocculation tank is 25 rpm, and the wastewater retention time is 10 min. The wastewater after flocculation reaction enters the sedimentation tank, which has a surface loading rate of 0.55 m³ / (m²·h) and a wastewater retention time of 3.0 h. The sedimented effluent can be discharged or reused through the discharge outlet, and the underflow of the sediment is transported to the tailings pond.

[0052] The concentrations of pollutants in the treated effluent were as follows: COD = 10.55 mg / L, total oil = 0.68 mg / L, Cu = 0.065 mg / L, Pb = 0.015 mg / L, As = 0.0025 mg / L, and Mn = 0.0056 mg / L.

[0053] Example 2

[0054] The overflow from a copper mine tailings dam had a COD concentration of 130 mg / L, a total oil concentration of 5.3 mg / L, and a pH of 6.8. The treatment steps were as follows: S1. The overflow was introduced into an acidification tank, where sulfuric acid (25.8%) was used to adjust the pH to 5.5. The retention time was 15 minutes. The acidification tank was constructed with steel lined with rubber. S2. The effluent from the acidification tank entered an iron-carbon micro-electrolysis oxidation-reduction reaction tank. The initial iron-carbon dosage was determined based on the tank volume, and was 100 kg / m³. During the treatment process, the continuous replenishment of iron-carbon was 20 kg / m³. The wastewater flow rate is 1.5 h, and the micro-electrolysis reactor is constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S3 iron-carbon micro-electrolysis reactor enters the sodium persulfate advanced oxidation reactor. Sodium persulfate solution is added at the inlet of the advanced oxidation reactor via a dosing pipeline. The concentration of the sodium persulfate solution used is 10%, and the dosage is determined to be 75 g / m³ based on the wastewater flow rate. The wastewater retention time is 2.3 h. The advanced oxidation reactor is also constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S4 advanced oxidation reactor enters the alkali adjustment tank. A compound alkali suspension is added via a dosing pipeline at the inlet to adjust the pH of the wastewater to 8.5. The mixing and reaction time of the alkali solution and wastewater is 12 min, and the agitator speed is 60 rpm. Then, the alkali-adjusted wastewater overflows into the flocculant reaction tank. Flocculant is dripped into the wastewater through the dosing pipeline. The agitator speed in the flocculation tank is 25 rpm, and the wastewater retention time is 5 min. The wastewater after flocculation enters a sedimentation tank with a surface loading rate of 0.65 m³ / (m²). 2 The wastewater retention time is 2.5 hours. The effluent from the sedimentation can be discharged or reused through the discharge outlet, and the underflow from the sedimentation is transported to the tailings pond.

[0055] The concentrations of pollutants in the treated effluent were as follows: COD = 18.56 mg / L, total oil = 1.52 mg / L, Cu = 0.045 mg / L, Pb = 0.035 mg / L, As = 0.0058 mg / L, and Mn = 0.036 mg / L.

[0056] Example 3

[0057] The overflow from a copper mine tailings dam has a COD concentration of 65 mg / L, a total oil concentration of 4.5 mg / L, and a pH of 6.2. The treatment steps are as follows: S1. The overflow is introduced into an acidification tank, where sulfuric acid (15.0% concentration) is used to adjust the pH to 4.0. The wastewater retention time is 25 min. The acidification tank is constructed with steel lined with rubber. S2. The effluent from the acidification tank enters an iron-carbon micro-electrolysis oxidation-reduction reaction tank. The initial iron-carbon dosage is determined based on the tank volume, and is 100 kg / m³. During the treatment process, the continuous replenishment of iron-carbon is 30 kg / m³. The wastewater flow rate is 1000 kg / h, and the retention time in the tank is 2.5 h. The micro-electrolysis reactor is constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S3 iron-carbon micro-electrolysis reactor enters the sodium persulfate advanced oxidation reactor. Sodium persulfate solution is added to the inlet of the advanced oxidation reactor via a dosing pipeline. The concentration of sodium persulfate solution used is 12%, and the dosage of sodium persulfate is determined to be 85 g / m³ based on the wastewater flow rate. The wastewater retention time is 3.5 h. The advanced oxidation reactor is constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S4 advanced oxidation reactor enters the alkali adjustment tank. A compound alkali suspension is added via a dosing pipeline at the inlet to adjust the pH of the wastewater to 7.5. The mixing reaction time of the alkali solution and wastewater is 20 min, and the agitator speed is 60 rpm. Then, the alkali-adjusted wastewater overflows into the flocculant reaction tank. The flocculant is dripped into the wastewater through the dosing pipeline. The agitator speed in the flocculation tank is 25 rpm, and the wastewater retention time is 8 min. The wastewater after flocculation enters a sedimentation tank with a surface loading rate of 0.50 m³ / (m²). 2 The wastewater retention time is 3.5 hours. The effluent from the sedimentation can be discharged or reused through the discharge outlet, and the underflow from the sedimentation is transported to the tailings pond.

[0058] The concentrations of pollutants in the treated effluent were as follows: COD = 12.35 mg / L, total oil = 2.44 mg / L, Cu = 0.025 mg / L, Pb = 0.028 mg / L, As = 0.0062 mg / L, and Mn = 0.0084 mg / L.

[0059] Example 4

[0060] The overflow from a copper mine tailings dam has a COD concentration of 90 mg / L, a total oil concentration of 6.0 mg / L, and a pH of 8.5. The treatment steps are as follows: S1. The overflow is introduced into an acidification tank, where sulfuric acid (30.0%) is used to adjust the pH to 6.0. The wastewater retention time is 30 minutes. The acidification tank is constructed with steel lined with rubber. S2. The effluent from the acidification tank enters an iron-carbon micro-electrolysis oxidation-reduction reaction tank. The initial iron-carbon dosage is determined based on the tank volume, and is 100 kg / m³. During the treatment process, the continuous replenishment of iron-carbon is 15 kg / m³. The wastewater flow rate is 15%, and the concentration is 45 g / m³. The wastewater retention time is 3.0 h. The wastewater retention time is 3.5 ... The wastewater after flocculation reaction enters the sedimentation tank, which has a surface loading rate of 0.50 m³ / (m²·h) and a wastewater retention time of 4.0 h. The sedimented effluent can be discharged or reused through the discharge outlet, and the underflow of the sediment is transported to the tailings pond.

[0061] The concentrations of pollutants in the treated effluent were as follows: COD = 36.58 mg / L, total oil = 2.85 mg / L, Cu = 0.076 mg / L, Pb = 0.0083 mg / L, As = 0.0034 mg / L, and Mn = 0.015 mg / L.

[0062] Comparative Example 1

[0063] The overflow from a copper mine tailings dam had a COD concentration of 95 mg / L, a total oil concentration of 4.2 mg / L, and a pH of 7.3. The treatment steps were as follows: S1 The overflow was introduced into an acidification tank, where sulfuric acid (98.0% concentration) was used to adjust the pH to 4.0. The wastewater retention time was 20 min. The acidification tank was constructed with steel lined with rubber. S2 The effluent from the acidification tank entered a ferrous sulfate reaction tank. During the treatment process, 65 mg / L of ferrous sulfate was continuously added. The wastewater concentration is 10%, and the hydrogen peroxide concentration is 80 kg / h. The wastewater retention time in the reaction tank is 2.0 h. The reaction tank is constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S3 reaction enters the hydrogen peroxide oxidation reaction tank. Hydrogen peroxide solution is added to the inlet of the oxidation reaction tank via a dosing pipeline. The hydrogen peroxide concentration used is 10%, and the hydrogen peroxide dosage is determined to be 80 kg / h based on the wastewater flow rate. The wastewater retention time is 3.0 h. The oxidation reaction tank is constructed with concrete lined with acid-resistant ceramic tiles. The effluent from the S4 oxidation reaction enters the alkali adjustment tank. Lime slurry suspension is added via a dosing pipeline at the inlet to adjust the pH of the wastewater to 9.0. The alkali solution and wastewater are mixed and reacted for 15 minutes, and the agitator speed is 60 rpm. Then, the alkali-adjusted wastewater overflows into the flocculant reaction tank. PAM flocculant (low molecular weight) is dripped into the wastewater through the dosing pipeline. The agitator speed in the flocculation tank is 25 rpm, and the wastewater retention time is 10 minutes. The wastewater after flocculation enters a sedimentation tank, with a surface loading rate of 0.53 m³ / (m²). 2 The wastewater retention time is 3.0 h. The effluent from the sedimentation can be discharged or reused through the discharge outlet, and the underflow from the sedimentation is transported to the tailings pond.

[0064] The concentrations of pollutants in the treated effluent were as follows: COD = 145.60 mg / L, total oil = 2.52 mg / L, Cu = 0.35 mg / L, Pb = 0.27 mg / L, As = 0.045 mg / L, and Mn = 0.24 mg / L.

[0065] Comparative Example 2

[0066] The COD concentration of the overflow water from a copper mine tailings dam is 75 mg / L, the total oil concentration is 3.7 mg / L, and the pH is 7.8. The treatment steps are as follows: S1. The overflow water is introduced into an acidification tank, and sulfuric acid is used to adjust the pH of the wastewater to 5.2. The concentration of sulfuric acid used is 98.0%, and the wastewater retention time is 30 minutes. The S2 acidification tank is made of steel lined with rubber. The effluent from the S2 acidification tank enters the ferrous sulfate reaction tank. No more ferrous sulfate is added during the treatment process. The wastewater stays in the tank for 3.0 hours. The reaction tank is made of concrete lined with acid-resistant ceramic tiles. The effluent from the S3 reaction enters the hydrogen peroxide oxidation reaction tank. Hydrogen peroxide solution is added to the inlet of the oxidation reaction tank through the dosing pipeline. The concentration of hydrogen peroxide used is 27%. The hydrogen peroxide dosage is determined to be 15 kg / h based on the wastewater flow rate. The wastewater stays for 4.0 hours. The oxidation reaction tank is made of concrete lined with acid-resistant ceramic tiles. The effluent from the S4 oxidation reaction enters the alkali adjustment tank. Lime slurry suspension is added through the dosing pipeline. The dosing point is located at the inlet. The pH of the wastewater is adjusted to 8.0. The reaction time of the alkali solution and wastewater is 30 minutes. The agitator speed is 60 rpm. The alkali-adjusted wastewater then overflows into the flocculant reaction tank. PAM flocculant (low molecular weight) is dripped into the wastewater through the dosing pipe. The agitator in the flocculation tank rotates at 25 rpm, and the wastewater retention time is 20 min. The wastewater after flocculation enters the sedimentation tank, which has a surface loading rate of 0.45 m³ / (m²·h) and a retention time of 4.5 h. The effluent from the sedimentation tank can be discharged or reused through the discharge outlet, and the underflow from the sedimentation tank is transported to the tailings dam.

[0067] The concentrations of pollutants in the treated effluent were as follows: COD = 85.25 mg / L, total oil = 2.80 mg / L, Cu = 0.085 mg / L, Pb = 0.12 mg / L, As = 0.063 mg / L, and Mn = 0.35 mg / L.

[0068] The differences between Comparative Example 1 and the Example are as follows: (1) Comparative Example 1 uses ferrous sulfate as a reducing agent, while the Example uses iron-carbon as an oxidizing-reducing agent; (2) Comparative Example 1 uses hydrogen peroxide as an oxidizing agent, while the Example uses sodium persulfate as an oxidizing agent; (3) Comparative Example 1 uses lime milk as an alkaline agent to adjust the pH of the wastewater, while the Example uses a compound alkali as an alkaline agent to adjust the pH of the wastewater; (4) Comparative Example 1 uses an anionic polyacrylamide (PAM) with a lower molecular weight (approximately 15 million), while the Example uses a high molecular weight anionic polyacrylamide (PAM). Comparing the treated effluent of Comparative Example 1 with that of the Example, the depth and effect of pollutant treatment are both superior to those of Comparative Example 1. Therefore, the technical solution of "iron-carbon micro-electrolysis oxidation-reaction + sodium peroxide advanced oxidation + compound alkali adjustment + high molecular weight anionic flocculant flocculation" adopted in this application is superior.

[0069] The difference between Comparative Example 2 and Comparative Example 1 is that Comparative Example 2 does not add ferrous sulfate as a reducing agent, and the increase in COD concentration in the effluent after treatment in Comparative Example 2 is smaller.

[0070] Both comparative examples showed that the COD concentration in the treated effluent was higher than that in the influent, which is a drawback of the comparative examples. This is because excess hydrogen peroxide and ferrous iron react with potassium dichromate during the measurement process, consuming potassium dichromate and thus affecting the COD measurement.

[0071] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines, characterized in that, Includes the following steps: S1: Use acidic reagents to adjust the pH of alkaline wastewater from copper ore beneficiation to 4.5–5.5; S2: The wastewater after pH adjustment enters the iron-carbon micro-electrolysis reactor to achieve chain-breaking degradation of organic matter in the wastewater, which is a ring-chain or long-chain mineral processing agent, and decomposes macromolecular pollutants into easily removable small-molecule organic matter. S3: Wastewater from the iron-carbon micro-electrolysis reaction enters the sodium persulfate advanced oxidation reaction tank. The Fe produced by micro-electrolysis... 2+ It reacts with added sodium persulfate to generate highly active SO4- ions, which synergistically degrade organic pollutants in wastewater under weakly acidic conditions. Simultaneously, it also causes some Fe... 2+ Oxidized to Fe 3+ This forms Fe(OH)3 colloids that can adsorb or aggregate fine particles; S4: The wastewater after advanced oxidation treatment enters the neutralization reaction tank. The pH of the wastewater is adjusted to 8-9 using alkaline agents to ensure a full reaction. Then, a modified polymeric anionic flocculant solution is added to allow the suspended solids and colloids in the wastewater to fully react with the modified polymeric anionic flocculant. Finally, the wastewater is allowed to stand to achieve solid-liquid separation. The supernatant can be directly discharged or recycled, while the underflow is mixed with tailings for treatment or utilization.

2. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: In step S1, the acidic agent is sulfuric acid, and the concentration of sulfuric acid is 15% to 45%.

3. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: In S2, the iron and carbon are in the form of tiny particles with a particle size of 1 to 10 mm, and the composition of the iron and carbon is: iron content = 65% to 85% and carbon content = 15% to 35%.

4. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: In S2, the iron-carbon micro-electrolysis reactor includes a first tank and a second tank. The first tank is an oxidation-reduction reaction zone, and the second tank is a wastewater and iron-carbon powder separation zone. The stirring device of the first tank adopts a plate and frame stirrer with a rotation speed of 15-30 rpm. The surface loading rate of the sedimentation zone of the second tank is 1.15-1.25 m³ / (㎡·h). The underflow generated in the sedimentation zone of the second tank is directly returned to the first tank, realizing the full utilization of iron and carbon.

5. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: In step S3, the concentration of sodium persulfate solution is 10%–15%, the amount of sodium persulfate used is 50–100 g / m³, and the oxidation reaction residence time is 2–4 h.

6. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: The alkaline agent is a compound alkaline solution with a concentration of 20% to 30%.

7. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: In step S4, the modified polymeric anionic flocculant is a sulfonic acid-modified polymeric anionic polyacrylamide, with a concentration of 0.02% to 0.05% and a dosage of 4 to 10 g / m³.

8. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 1, characterized in that: The modified polymeric anionic flocculant comprises 35%–45% polymeric anionic flocculant with a molecular weight greater than 20 million, 2%–5% alkanolamine flocculant synergist, 1%–5% alcohol antioxidant and 55%–62% additives. The polymeric anionic flocculant is sulfonated polyacrylamide or polyacrylamide with a molecular weight greater than 20 million. The aforementioned amine flocculant is one or more of triethylenetetramine, tetraethylenepentamine, and diethylenetriamine; The alcohol antioxidants mentioned are one or more of glycol, dipropylene glycol, and diethylene glycol; The additive is one of soluble chloride brine, water, or acid.

9. The method for improving the removal efficiency of COD and total oil in tailings dam overflow water of copper mines according to claim 5, characterized in that: The modified polymeric anionic flocculant has a molecular weight of 22 million to 25 million.

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