Treatment process of copper-containing wastewater

Abstract

The invention discloses a copper-containing wastewater treatment process, which relates to six steps of pre-flocculent precipitation, alkaline precipitation, sulfide precipitation, secondary flocculent precipitation, pH regulation of discharged water and solid waste treatment, and utilizes the solubility difference between Cu (OH) 2 precipitation and CuS precipitation to effectively separate copper ion precipitation from other precipitation. And the purity of the copper ion conjugate is improved, so that the copper element is efficiently recovered, and the sludge treatment amount is effectively reduced.

Description

Technical Field

[0001] The invention relates to a treatment process for copper-containing wastewater, and belongs to the technical field of water treatment processes. Background Art

[0002] Electroplating treatment processes are widely used in various fields such as electronics, machinery, automobile industry, and aerospace. In recent years, with the continuous development of high-end manufacturing industries, the scale of the electroplating industry has also continued to expand. There are a large number of medium metal pollutants in electroplating wastewater. How to harmlessly treat electroplating wastewater has become an important issue threatening environmental safety. As for the treatment process of copper-containing wastewater, the current treatment process generally adopts chemical precipitation. This type of treatment method produces a large amount of sludge, and the sludge disposal process accounts for a relatively high proportion of the cost in the overall process; in addition, the additional chemical agents invested in the treatment process are prone to secondary pollution. Therefore, it is necessary to develop a wastewater treatment process with low pollution and low sludge volume. Summary of the invention

[0003] The purpose of the present invention is to provide a treatment process for copper-containing wastewater to solve the technical problems of large amount of sludge and serious environmental pollution in the above technical background.

[0004] The technical solution to achieve the purpose of the present invention is: a process for treating copper-containing wastewater, comprising the following steps:

[0005] S1: Collect raw water and adjust water quality and quantity;

[0006] S2: The sewage that has been regulated in water quality and quantity in S1 is introduced into the first sedimentation tank, and a flocculant is added for stirring and then allowed to stand to complete pre-sedimentation;

[0007] S3: Separate the sewage that has completed pre-precipitation in S2, and let its supernatant enter the second sedimentation tank, add slaked lime water, stir and stand for sedimentation treatment;

[0008] S4: Separate the sewage after the precipitation in S3, and let the supernatant enter the third sedimentation tank, add the metal sulfide solution, stir and stand for precipitation treatment;

[0009] S5: Separate the sewage after the sedimentation in S4, and let the supernatant enter the fourth sedimentation tank, add flocculant, stir and let it stand for sedimentation treatment;

[0010] S6: Separate the supernatant that has completed the precipitation treatment in S5 and adjust the acidity of the supernatant, and discharge it after testing the copper content and finding it qualified.

[0011] The above water treatment process is divided into four stages, which are respectively used for initial sedimentation of coarse particles, Cu 2+ Ion primary precipitation treatment, Cu 2+Ion secondary precipitation treatment and trace sediment capture treatment, in which the coarse particle preliminary precipitation process can capture most of the particles in the sewage, making the water-soluble Cu 2+ Entering the next process ensures the enrichment of Cu element in the next process; Cu 2+ The primary precipitation treatment of ions uses limestone for precipitation treatment to generate a small amount of Cu(OH)2 precipitation in a neutral environment. Its Ksp at 25℃ is 2.2×10-20. 2+ The ion secondary precipitation treatment process uses metal sulfide to generate CuS precipitate, and the Ksp of this precipitate at 25°C is 6.0×10-36. In this process, the main role of limestone is to adjust the pH value. The precipitation process of Cu2+ is mainly in the CuS precipitate. The CuS precipitate is denser than the Cu(OH)2 precipitate, and its particles are larger. The boundary between its treatment process and the connection process of S2 and S5 is clearer. In the treatment process, the supernatant after separation can be used to directly rinse the precipitate, realizing the recycling treatment of the water process, and effectively compressing the sludge volume without increasing the water consumption in the sedimentation and dehydration process.

[0012] In the above treatment process, step S2 and step S5 only involve the coarse particle precipitation process, and do not involve the addition of a large amount of flocculants, which can effectively reduce the addition of organic flocculants in the treatment process and reduce water pollution in the treatment process.

[0013] Further or optionally, the pH value of the water after adjustment in step S1 is less than 3, and the pH value after adding slaked lime water and stirring in step S3 is 5.8-6.5. Within this pH range, the amount of Cu(OH)2 precipitation can be reduced and the amount of H2S generated in the copper sulfide generation step of step S4 can be prevented. According to tests, the waste gas treatment process can be omitted within this range, thereby effectively saving costs.

[0014] Further or optionally, the mass fraction of slaked lime water in step S3 is 5-8%. When the slaked lime has this concentration, the stirring time is controlled to be 3-5 minutes, and the corresponding precipitation time can be completed within a range of 40 minutes to 60 minutes. The pH value after precipitation is relatively stable, which can ensure the purity of the precipitate in step S4.

[0015] Further or optionally, the metal sulfide in step S4 is sodium sulfide or potassium sulfide, and the specific feeding amount needs to be based on the reference of the supernatant in S3 and Cu 2+ The ion concentration is calculated. It is tested that the precipitation efficiency is highest when the feed mass ratio is 0.5-1%. After the precipitation is completed, the filtration separation is carried out. After the separation is completed, the supernatant is further precipitated.

[0016] In order to ensure the purity of the precipitate while saving water consumption in the process, the above-mentioned filtration and separation process adopts a layered screen, and the liquid part after filtration is used to rinse the precipitate. After completing 2 to 3 cycles, the separation liquid is collected, and then the separation liquid is further flocculated to separate small particles in suspension.

[0017] Further or optionally, the flocculant added in steps S2 and S5 is polyaluminium chloride, polyferric sulfate, polyaluminium ferric chloride or a mixture thereof, and the mechanism of action of the above flocculants is to compress the double electric layer, charge neutralization and adsorption bridging to form larger flocs. This process is relatively rough, and the flocs are less recyclable. If the element detection is qualified, it can be treated as general sludge.

[0018] Further or optionally, the flocculant is also used in combination with a coagulant, and the coagulant is polyacrylamide, chitosan, polyethyleneimine, polyethyleneimine or a mixture thereof. The role of the combined use of the agents here is to form larger flocs through the adsorption effect between the active groups on the long-chain structure and the suspended particles to reduce the suspended solids in the water. When the single flocculant is sufficient to complete the sedimentation, and the Cu content of the precipitate produced in S3 and S4 reaches the recoverable standard, costs can be saved without the combined use of agents.

[0019] Further or optionally, the flocculant dosage is 100-200 mg / L, and the coagulant dosage is 10-20 mg / L. The specific dosage needs to be adjusted according to the ion concentration measurement result.

[0020] Further or optionally, the acidity regulator in step S6 is oxalic acid, and the pH end point after the acidity adjustment is 7-8. In actual acidity adjustment, citric acid can be used instead of oxalic acid, which can achieve mild adjustment of acidity and has relatively little impact on the environment.

[0021] Further or optionally, the method further includes a recovery and treatment process of the sediment in steps S3 to S5. Specifically, the flocculated precipitates in steps S2 and S5 are treated as general industrial sludge after compression, dehydration and drying, and the flocculated precipitates in step S3 and the solid precipitates in step S4 are sold to wet metal recyclers as high-copper waste slag after drying and dehydration.

[0022] Further or optionally, the sedimentation time in step S2 is 1 hour, the sedimentation time in step S3 is 1 hour, the sedimentation time in step S4 is 0.5 hour, and the sedimentation time in step S5 is 1 hour. The specific sedimentation time needs to be adjusted according to the diameter of the sedimentation tank and the amount of reagent input.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects:

[0024] (1) The present application relates to a four-stage water treatment process of preliminary flocculation and sedimentation of coarse particles, graded precipitation treatment of copper ions, and further flocculation and sedimentation of microparticles. The copper ion removal efficiency is high and the capture process has a clear boundary compared with the previous and subsequent flocculation and sedimentation processes. The copper element has good separability. While achieving high-efficiency copper ion removal, the amount of sludge generated is small, and the copper ions can be efficiently recycled and utilized, which can effectively reduce the sludge amount without increasing the water consumption.

[0025] (2) The present application uses lime water for preliminary sedimentation and pH adjustment, and the pH range is 5.8 to 6.5. Within this range, the generation of H2S can be avoided, and air purification is not required, and the treatment cost is lower.

[0026] (3) The present invention controls the mass fraction of lime water and the precipitation time. After the precipitation is completed, the pH value is stable and the sedimentation can be completed within 40 to 60 minutes, which can effectively ensure the purity of the product in the next sedimentation process.

[0027] (4) The present application uses sodium sulfide for precipitation under a neutral environment. The generated copper sulfide precipitate is insoluble in water and is dense and compact. The produced precipitate only needs preliminary rinsing and drying before entering the recovery process. Compared with the traditional flocculation precipitation process, the amount of sludge is small. Compared with the direct use of sodium sulfide precipitation method without pretreatment, the treated product has high purity and can be directly used for copper metal recovery and treatment, and the subsequent hazardous waste treatment cost is low.

[0028] (5) In the sedimentation process, the present application uses polyaluminum chloride, polyferric sulfate, and polyaluminum ferric chloride as flocculants and uses polyacrylamide, chitosan, polyethyleneimine, polyethyleneimine and other coagulants to strengthen the sedimentation process. Compared with traditional inorganic flocculants, these materials can reduce the content of residual aluminum and iron, improve the purity of copper precipitation in subsequent treatment processes, and improve the recovery efficiency of copper elements.

[0029] (6) The present application uses oxalic acid or citric acid for pH adjustment, and the adjustment process is gentler and causes less environmental pollution.

[0030] (7) The present application separately recovers and processes the flocculated precipitate and the copper ion precipitate. Compared with the conventional direct flocculation or direct copper sulfide precipitation, the copper ion precipitate has a higher purity and a higher recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments and in conjunction with the accompanying drawings, wherein

[0032] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0033] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0035] All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0036] (Example 1)

[0037] See Figure 1 In the present embodiment, a process for treating copper-containing wastewater is used. 100 tons of copper-containing wastewater from an electroplating plant is injected into a first sedimentation tank as raw water, and its initial copper concentration is measured to be 183 mg / L.

[0038] After the wastewater is filled into the first sedimentation tank, polyaluminium chloride is added as a flocculant at a dosage of 100 mg / L, and polyacrylamide is added as a coagulant at a dosage of 10 mg / L, and the mixture is mechanically stirred for 3 minutes before precipitation.

[0039] After testing, flocculation was completed after about 1 hour, and the upstream water no longer became clearer. At this time, the water inlet of the sedimentation tank was opened to allow the supernatant to flow into the second sedimentation tank. After the supernatant was separated, the discharge port at the bottom of the sedimentation tank was opened and the scraper was turned on. The precipitated flocculated mud was squeezed and dehydrated and then entered the hazardous waste treatment process.

[0040] After the supernatant enters the second sedimentation tank, a 5% lime water solution is added, and its pH value is measured while stirring. When the pH reaches 5.8, the addition is stopped and the sewage in the second sedimentation tank is left to stand. After standing for 1 hour, the floccules no longer increase. The flocs in the second sedimentation tank are separated and processed, and the supernatant enters the third sedimentation tank. The flocs at the bottom of the tank are squeezed and dehydrated and stored separately to wait for copper-containing waste recycling personnel to recycle them.

[0041] After the third sedimentation tank is filled with water, sodium sulfide solution is added to the wastewater to be treated at a dosage of 0.5% by mass ratio, and the concentration of the sodium sulfide solution is 5%. After the addition is completed, the mixture is stirred for 5 minutes. After the stirring is completed, the sewage that has formed a precipitate is allowed to stand for treatment. After standing for 30 minutes, the supernatant is separated and entered into the fourth sedimentation tank. The lower precipitate is dried and stored, waiting for copper-containing waste recycling personnel to recycle it.

[0042] The supernatant of the third sedimentation tank was injected into the fourth sedimentation tank, to which the flocculant polyaluminium chloride was added at a dosage of 100 mg / L, and the coagulant polyacrylamide was added at a dosage of 10 mg / L. After stirring for 3 minutes, the sedimentation was carried out. According to the test, the sedimentation was completed after about 1 hour.

[0043] The supernatant of the wastewater that has completed sedimentation in the fourth sedimentation tank is separated, and the flocculent matter at the bottom is squeezed, dehydrated, bagged and then enters the hazardous waste treatment process.

[0044] The supernatant liquid after separation in the fourth sedimentation tank is added with oxalic acid solution to make its pH reach 7.5 before being discharged.

[0045] The copper concentration of the treated wastewater was tested to be 0.38 mg / L, and the copper removal rate was 99.79%.

[0046] (Example 2)

[0047] See Figure 1 In the present embodiment, a copper-containing wastewater treatment process is used. 100 tons of copper-containing wastewater from an electroplating plant is injected into a first sedimentation tank as raw water, and its initial copper concentration is measured to be 159 mg / L.

[0048] After the wastewater is filled into the first sedimentation tank, add the flocculant polyaluminium chloride at a dosage of 200 mg / L and the coagulant polyacrylamide at a dosage of 20 mg / L, and then stir mechanically for minutes before precipitation.

[0049] After testing, flocculation was completed after about 1 hour, and the upstream water no longer became clearer. At this time, the water inlet of the sedimentation tank was opened to allow the supernatant to flow into the second sedimentation tank. After the supernatant was separated, the discharge port at the bottom of the sedimentation tank was opened and the scraper was turned on. The precipitated flocculated mud was squeezed and dehydrated and then entered the hazardous waste treatment process.

[0050] After the supernatant enters the second sedimentation tank, add 8% lime water solution by mass, and measure its pH value while stirring. When the pH reaches 6.2, stop adding and let the sewage in the second sedimentation tank stand. After standing for 1 hour, the flocculants no longer increase. The floccules in the second sedimentation tank are separated and processed, and the supernatant enters the third sedimentation tank. The floccules at the bottom of the tank are squeezed and dehydrated and stored separately to wait for copper-containing waste recycling personnel to recycle them.

[0051] After the third sedimentation tank is filled with water, sodium sulfide solution is added to the wastewater to be treated at a dosage of 1% by mass ratio, and the concentration of the sodium sulfide solution is 5%. After the addition is completed, the mixture is stirred for 5 minutes. After the stirring is completed, the sewage that has formed a precipitate is allowed to stand for treatment. After standing for 30 minutes, the supernatant is separated and entered into the fourth sedimentation tank. The lower precipitate is dried and stored, waiting for copper-containing waste recycling personnel to recycle it.

[0052] The supernatant of the third sedimentation tank was injected into the fourth sedimentation tank, to which the flocculant polyaluminium chloride was added at a dosage of 100 mg / L, and the coagulant polyacrylamide was added at a dosage of 10 mg / L. After stirring for 3 minutes, the sedimentation was carried out. According to the test, the sedimentation was completed after about 1 hour.

[0053] The supernatant of the wastewater that has completed sedimentation in the fourth sedimentation tank is separated, and the flocculent matter at the bottom is squeezed, dehydrated, bagged and then enters the hazardous waste treatment process.

[0054] The supernatant liquid after separation in the fourth sedimentation tank is added with oxalic acid solution to make its pH reach 7.5 before being discharged.

[0055] The copper concentration of the treated wastewater was tested to be 0.38 mg / L, and the copper removal rate was 99.99%.

[0056] Comparative Example:

[0057] In the present embodiment, a process for treating copper-containing wastewater is used. 100 tons of copper-containing wastewater from an electroplating plant is injected into a first sedimentation tank as raw water, and its initial copper concentration is measured to be 176 mg / L.

[0058] After the first sedimentation tank is filled with wastewater, add flocculant polyaluminum chloride at a dosage of 100 mg / L, add coagulant polyacrylamide at a dosage of 10 mg / L, add 5% lime water solution until the pH of the sewage reaches 8.5, then let it stand for 1 hour, wait for the precipitation to be completed, release the supernatant, add oxalic acid solution to adjust the pH to 7.0, and then discharge it.

[0059] After separation, the sludge is compressed, dehydrated, and bagged and treated as hazardous waste.

[0060] In the above process, the copper concentration of the treated wastewater is 5.33 mg / L, and the copper removal rate is 96.97%.

[0061] It should be understood that the present invention is described by some embodiments, and those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope of protection of the present invention.

Claims

1. A process for treating copper-containing wastewater, characterized in that The steps include: S1: Collect raw water and adjust water quality and quantity; S2: The sewage that has been regulated in water quality and quantity in S1 is introduced into the first sedimentation tank, and a flocculant is added for stirring and then allowed to stand to complete pre-sedimentation; S3: Separate the sewage that has completed pre-precipitation in S2, and let its supernatant enter the second sedimentation tank, add slaked lime water, stir and stand for sedimentation treatment; S4: Separate the sewage after the precipitation in S3, and let the supernatant enter the third sedimentation tank, add the metal sulfide solution, stir and stand for precipitation treatment; S5: Separate the sewage after the sedimentation in S4, and let the supernatant enter the fourth sedimentation tank, add flocculant, stir and let it stand for sedimentation treatment; S6: Separate the supernatant that has completed the precipitation treatment in S5 and adjust the acidity of the supernatant, and discharge it after testing the copper content and finding it qualified.

2. A process for treating copper-containing wastewater according to claim 1, characterized in that: The pH value of the water after adjustment in step S1 is less than 3, and the pH value of the water after adding slaked lime water and stirring in step S3 is 5.8-6.

5.

3. A process for treating copper-containing wastewater according to claim 2, characterized in that: The mass fraction of slaked lime water in step S3 is 5-8%.

4. A process for treating copper-containing wastewater according to claim 1, characterized in that: The metal sulfide in step S4 is sodium sulfide or potassium sulfide, and the mass ratio of the metal sulfide is 0.5-1%.

5. A process for treating copper-containing wastewater according to claim 1, characterized in that: The flocculant added in steps S2 and S5 is polyaluminium chloride, polyferric sulfate, polyaluminium ferric chloride or a mixture thereof.

6. A process for treating copper-containing wastewater according to claim 5, characterized in that: The flocculant is also used in combination with a coagulant, and the coagulant is polyacrylamide, chitosan, polyethyleneimine, polyethyleneimine or a mixture thereof.

7. A process for treating copper-containing wastewater according to claim 6, characterized in that: The flocculant dosage is 100-200 mg / L, and the coagulant dosage is 10-20 mg / L.

8. A process for treating copper-containing wastewater according to claim 1, characterized in that: The acidity regulator in step S6 is oxalic acid or citric acid, and the pH end point after the acidity adjustment is 7-8.

9. A process for treating copper-containing wastewater according to claim 1, characterized in that: It also includes a sediment recovery process in steps S3 to S5.

10. A process for treating copper-containing wastewater according to claim 1, characterized in that: The sedimentation time in step S2 is 1 hour, the sedimentation time in step S3 is 1 hour, the sedimentation time in step S4 is 0.5 hour, and the sedimentation time in step S5 is 1 hour.

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