A method for treating nickel-containing wastewater

Abstract

The application provides a treatment method of nickel-containing wastewater, which is provided with the following processes: pretreatment, primary coagulation treatment, sludge treatment, secondary coagulation treatment, discharge treatment and accident treatment. The pretreatment includes an adjusting tank and a pH adjusting tank; the coagulation treatment includes an oxidation tank, a coagulation reaction tank and an inclined tube sedimentation tank. The application uses secondary coagulation, and uses silica xerogel, modified polyaluminum chloride and modified polyacrylamide as coagulants in steps, so that the removal capacity of nickel-containing pollutants with different sizes and properties is enhanced. The silica xerogel prepared by the method has high specific surface area, good pore structure and high stability, and these properties make the silica xerogel have high adsorption capacity and filtration effect in the treatment of nickel-containing wastewater. The application modifies polyaluminum chloride and polyacrylamide, and introduces kapok fiber hydrophobic functional groups, so that the hydrophobicity is further improved, and the burden of the sludge treatment process is reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a method for treating nickel-containing wastewater. Background Technology

[0002] Nickel and its metal oxides, due to their excellent physical properties, are widely used in electroplating, chemical engineering, and smelting, bringing great benefits to human life. However, the application of nickel generates nickel-containing wastewater. As a heavy metal, nickel cannot be degraded by organisms in the natural environment. After being ingested by humans or animals through the food chain, metallic nickel accumulates in the body, inhibiting the human enzyme system. Initially, this can cause dizziness and headaches; long-term excessive intake can affect the central nervous system, causing mental confusion. Improper treatment of nickel-containing wastewater not only causes environmental pollution but also affects human health. Therefore, nickel-containing wastewater must be treated to meet national standards before being discharged. Commonly used treatment methods for nickel-containing wastewater include traditional chemical methods, physical methods, and electrochemical methods. Traditional chemical methods can be further divided into chemical precipitation and coagulation. Physical methods can be divided into adsorption, ion exchange, and membrane separation. Electrochemical methods can be divided into electrodialysis and membrane separation. Among these, coagulation is widely used due to its simplicity, ease of operation, and relatively low cost compared to other treatment methods. Existing coagulation methods are mostly primary coagulation treatments, which are insufficient to meet the emission standard of ≤0.1 mg / L total nickel content. Existing coagulants have low nickel removal rates and unstable nickel removal effects, and the resulting sludge has a high water content of up to 98%, placing a significant burden on subsequent sludge treatment processes. Summary of the Invention

[0003] In view of this, the present invention proposes a method for treating nickel-containing wastewater to solve the above problems.

[0004] The technical solution of this invention is implemented as follows:

[0005] A method for treating nickel-containing wastewater includes the following processes: pretreatment, primary coagulation treatment, sludge treatment, secondary coagulation treatment, discharge treatment, and accident handling; specifically, it includes the following steps:

[0006] S1: Pretreatment: including equalization tank and pH adjustment tank. Alkaline agent is added to the pH adjustment tank to adjust the pH to 8-9.

[0007] S2: Primary coagulation treatment: including primary oxidation tank, primary coagulation reaction tank, and primary inclined tube sedimentation tank; oxidant 1 is added to the primary oxidation tank for oxidation reaction, and the reaction is held for 2.0-3.0 hours; then coagulant 1 is added to the primary coagulation reaction tank for coagulation reaction, and the reaction is held for 140-150 minutes; then the mixture is discharged into the primary inclined tube sedimentation tank and held for 50-70 minutes.

[0008] Sludge treatment:

[0009] S3: Sludge treatment: The nickel-containing sludge formed after the primary inclined tube sedimentation is discharged into the sludge tank; a plate and frame filter press is set up, and the nickel sludge after pressing is transported to a designated institution for recycling. The filtrate that passes the test is discharged into the clear water tank, and the filtrate that fails the test is discharged into the secondary oxidation tank for further treatment.

[0010] S4: Secondary coagulation treatment: including a secondary oxidation tank, a secondary coagulation reaction tank, and a secondary inclined tube sedimentation tank; nickel-containing wastewater after primary coagulation treatment and sludge treatment is discharged into the secondary oxidation tank, where oxidant 2 is added for oxidation reaction and held for 1.5-2.0 hours; then coagulant 2 is added to the secondary coagulation reaction tank for coagulation reaction and held for 50-60 minutes; then coagulant 3 is added for coagulation reaction and held for 45-50 minutes; finally, it is discharged into the secondary inclined tube sedimentation tank and held for 40-60 minutes.

[0011] S5: Discharge Treatment: The clear liquid after secondary coagulation treatment is discharged to the clear water tank; if it passes the test, it flows into the plant's water system for continued use; if it fails the test, it flows into the emergency pool; the nickel-containing sludge formed after secondary inclined tube sedimentation is discharged into the sludge tank for nickel-containing sludge treatment in accordance with S3.

[0012] Furthermore, an emergency response pool is also set up. In the event that the effluent fails to meet the standards due to unforeseen circumstances or human error, the nickel-containing wastewater is discharged into the emergency response pool and then discharged into the equalization pool for further treatment.

[0013] Furthermore, the equalization tank, pH adjustment tank, primary oxidation tank, primary coagulation reaction tank, primary inclined tube sedimentation tank, sludge tank, secondary oxidation tank, secondary coagulation reaction tank, secondary inclined tube sedimentation tank, and clear water tank are connected in sequence and are all reinforced steel structures with an internal anti-corrosion layer, which is made of anti-corrosion plates spliced ​​together.

[0014] Furthermore, a mixer is provided between the primary coagulation reaction tank and the secondary coagulation reaction tank. The mixer has a power of 500-1000W and a stirring speed of 50-70r / min.

[0015] Furthermore, the alkaline agent in S1 is either sodium hydroxide or calcium hydroxide.

[0016] Furthermore, the amount of oxidant 1 added in S2 is 50-60 g / m. 3 .

[0017] Furthermore, the coagulant 1 in S2 is silica dry gel, and the amount added is 35-45 g / m³. 3 The silica dry gel is prepared by the following steps:

[0018] S21: Piperidine and ammonia: Mix piperidine (1-10 wt%) and ammonia (15-20 wt%), stir for 1-3 min, and the volume ratio of piperidine to ammonia is (1-1.2):(1-1.5) to obtain solution A, which is ready for use.

[0019] S22: Dissolving tetraethyl orthosilicate: Add tetraethyl orthosilicate to solution A and stir for 10-20 minutes until the solution turns milky white. Stop stirring to obtain a silica gel solution. The mass-volume ratio of tetraethyl orthosilicate to solution A is (0.8-1.2):(2-3).

[0020] S23: Aging and drying: Aging the silica gel solution at room temperature for 1-1.2 hours, then aging it in an aging chamber at 75-85°C for 3.5-4.5 hours, then air-drying it at room temperature for 13-15 hours, and then drying it in a dryer at 75-85°C for 3.5-4.5 hours to obtain silica dry gel.

[0021] Furthermore, in step S4, the oxidant 2 is hydrogen peroxide, and the amount added is 300-600 ml / m. 3 .

[0022] Furthermore, the coagulant 2 in S4 is modified polyaluminum chloride, and the amount of modified polyaluminum chloride added is 100-300 mg / m³. 3 The modified polyaluminum chloride is prepared by the following method: 8-10 parts by weight of polyaluminum chloride and 2-4 parts by weight of kapok fiber are added to 20-24 parts by weight of solvent and stirred for 2-5 minutes to obtain solution C; solution C is placed in an ultrasonic device for ultrasonic oscillation treatment for 20-30 minutes, with the ultrasonic power controlled at 1000-1500W and the ultrasonic frequency controlled at 15-20Hz to obtain solution D; solution D is placed in a centrifuge and rotated at 7000-9000r / min for 5-10 minutes to separate the modified polyaluminum chloride solution; the modified polyaluminum chloride solution is placed in a dryer and dried at 50-60℃ for 20-24 hours to obtain modified polyaluminum chloride.

[0023] Furthermore, the coagulant 3 in S4 is modified polyacrylamide, and the amount of modified polyacrylamide added is 20-40 mg / m³. 3The modified polyacrylamide is prepared by the following method: 7-9 parts by weight of polyacrylamide and 2-3 parts by weight of kapok fiber are added to 18-26 parts by weight of solvent and stirred for 2-5 minutes to obtain solution E; solution E is placed in an ultrasonic device for ultrasonic oscillation treatment for 20-30 minutes, with the ultrasonic power controlled at 1000-1500W and the ultrasonic frequency controlled at 15-20Hz to obtain solution F; solution F is placed in a centrifuge and rotated at 7000-9000r / min for 5-10 minutes to obtain modified polyacrylamide solution; modified polyacrylamide solution is placed in a dryer and dried at 50-55℃ for 18-20 hours to obtain modified polyacrylamide.

[0024] Furthermore, the solvent is prepared by mixing and stirring 1.5-2.5 parts zinc oxide, 6-8 parts sodium hydroxide, 13-14 parts urea, and 70-80 parts purified water for 1-3 minutes, and then placing it in an insulated box and keeping it at a temperature of -10°C to -15°C for 20-25 minutes.

[0025] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention enhances the removal capacity of nickel-containing pollutants of different sizes and properties through a two-stage coagulation treatment. In the first-stage coagulation treatment, larger suspended and colloidal nickel-containing pollutants are removed, while in the second-stage coagulation treatment, smaller nickel-containing pollutants can be removed more effectively. This two-stage treatment method can more comprehensively remove various pollutants from nickel-containing wastewater. The reaction conditions of piperidine and ammonia in this invention are mild, and the prepared silica dry gel has a high specific surface area, good pore structure, and high stability. These properties give the silica dry gel high adsorption capacity and filtration effect in nickel-containing wastewater treatment, effectively removing heavy metal ions and organic pollutants from nickel-containing wastewater. At the same time, the silica dry gel is easier to transport and store than wet silica gel. This invention further improves the hydrophobicity of polyaluminum chloride and polyacrylamide by introducing kapok fiber hydrophobic functional groups into them, reducing the water content in the sludge from 98% to 60%, thus reducing the burden on subsequent processes. Attached Figure Description

[0026] Figure 1 This is a flow chart of the nickel-containing wastewater treatment process of the present invention. Detailed Implementation

[0027] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0028] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0029] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0030] Example 1

[0031] A method for treating nickel-containing wastewater specifically includes the following steps:

[0032] The factory discharges nickel-containing wastewater into a regulating tank to balance the water quality and quantity, where it remains for 10.5 hours.

[0033] Next, the mixture is discharged into a pH adjustment tank, sodium hydroxide is added to adjust the pH to 8, and the mixture is left to stand for 70 minutes.

[0034] Next, it is discharged into the primary oxidation tank, with 50g / m³ added. 3 Oxidizing agent 1 was used for the oxidation reaction, and the reaction was allowed to proceed for 2.0 h.

[0035] Next, it is discharged into the primary coagulation reaction tank, with 35g / m³ added. 3 The silica dry gel was subjected to a coagulation reaction and held for 140 minutes.

[0036] Next, it is discharged into the first-stage inclined tube sedimentation tank and retained for 50 minutes.

[0037] Next, the sludge is discharged into a sludge tank, where a plate and frame filter press is installed. The filtered nickel sludge is then transported to a designated facility for recycling. The filtrate that passes inspection is discharged into a clear water tank; otherwise, it is discharged into a secondary oxidation tank for further treatment.

[0038] Next, it is discharged into the secondary oxidation tank, and 300 ml / m³ is added. 3 Hydrogen peroxide is used for oxidation reaction, and the reaction is allowed to proceed for 1.5 hours.

[0039] Next, it is discharged into the secondary coagulation reaction tank, with 100 mg / m³ added. 3 Modified polyaluminum chloride (PAC) was subjected to a coagulation reaction and held for 50 minutes. The modified PAC was prepared by the following method: 1.5 parts zinc oxide, 6 parts sodium hydroxide, 13 parts urea, and 70 parts purified water were mixed and stirred for 1 minute, then placed in an incubator at -10℃ for 20 minutes to obtain a solvent. 8 parts by weight of PAC and 2 parts by weight of kapok fiber were added to 20 parts of the solvent and stirred for 2 minutes to obtain solution C. Solution C was subjected to ultrasonic oscillation for 20 minutes with an ultrasonic power controlled at 1000W and an ultrasonic frequency controlled at 15Hz to obtain solution D. Solution D was centrifuged at 7000 r / min for 5 minutes to separate the modified PAC solution. The modified PAC solution was then dried in a dryer at 50℃ for 20 hours to obtain modified PAC.

[0040] Next, add 20mg / m 3 Modified polyacrylamide was subjected to a coagulation reaction and held for 45 minutes. The modified polyacrylamide was prepared by the following method: 1.5 parts zinc oxide, 6 parts sodium hydroxide, 13 parts urea, and 70 parts purified water were mixed and stirred for 1 minute, then placed in an incubator and kept at -10℃ for 20 minutes to obtain a solvent. 7 parts by weight of polyacrylamide and 2 parts by weight of kapok fiber were added to 18 parts of the solvent and stirred for 2 minutes to obtain solution E. Solution E was subjected to ultrasonic oscillation for 20 minutes with an ultrasonic power controlled at 1000W and an ultrasonic frequency controlled at 15Hz to obtain solution F. Solution F was centrifuged at 7000r / min for 5 minutes to obtain a modified polyacrylamide solution. The modified polyacrylamide solution was dried in a dryer at 50℃ for 18 hours to obtain modified polyacrylamide.

[0041] Next, it is discharged into a two-stage inclined tube sedimentation tank and held for 40 minutes.

[0042] Next, the wastewater is discharged into the clear water tank and left to stand for 1 hour. If the wastewater passes the test, it flows into the plant's water system for continued use. If the wastewater fails the test, it flows into the emergency response tank. The nickel-containing sludge formed after the secondary inclined tube sedimentation is discharged into the sludge tank and treated according to the above sludge treatment steps.

[0043] The aforementioned equalization tank, pH adjustment tank, primary oxidation tank, primary coagulation reaction tank, primary inclined tube sedimentation tank, sludge tank, secondary oxidation tank, secondary coagulation reaction tank, secondary inclined tube sedimentation tank, clear water tank, and emergency tank are all reinforced steel structures with an internal anti-corrosion layer, which is made of anti-corrosion plates spliced ​​together.

[0044] A mixer is installed between the primary coagulation reaction tank and the secondary coagulation reaction tank. The mixer has a power of 500W and a stirring speed of 50r / min.

[0045] Example 2

[0046] A method for treating nickel-containing wastewater specifically includes the following steps:

[0047] The factory discharges nickel-containing wastewater into a regulating tank to balance the water quality and quantity, where it remains for 11 hours.

[0048] Next, the mixture is discharged into a pH adjustment tank, sodium hydroxide is added to adjust the pH to 9, and the mixture is left to stand for 80 minutes.

[0049] Next, it is discharged into the primary oxidation tank, with 60g / m³ added. 3 Oxidizing agent 1 was used for the oxidation reaction, and the reaction was allowed to proceed for 3.0 h.

[0050] Next, it is discharged into the primary coagulation reaction tank, with 45g / m³ added.3 The silica dry gel was subjected to a coagulation reaction and held for 150 minutes.

[0051] Next, it is discharged into the first-stage inclined tube sedimentation tank and retained for 70 minutes.

[0052] Next, the sludge is discharged into a sludge tank, where a plate and frame filter press is installed. The filtered nickel sludge is then transported to a designated facility for recycling. The filtrate that passes inspection is discharged into a clear water tank; otherwise, it is discharged into a secondary oxidation tank for further treatment.

[0053] Next, it is discharged into the secondary oxidation tank, and 600 ml / m³ is added. 3 Hydrogen peroxide is used for oxidation reaction, and the reaction is carried out for 2.0 h.

[0054] Next, it is discharged into the secondary coagulation reaction tank, with 300 mg / m³ added. 3 Modified polyaluminum chloride was subjected to a coagulation reaction and held for 60 minutes. The modified polyaluminum chloride was prepared by the following method: 2.5 parts zinc oxide, 8 parts sodium hydroxide, 14 parts urea, and 80 parts purified water were mixed and stirred for 3 minutes, then placed in an incubator and kept at -15℃ for 25 minutes to obtain a solvent. 10 parts by weight of polyaluminum chloride and 4 parts by weight of kapok fiber were added to 24 parts by weight of the solvent and stirred for 5 minutes to obtain solution C. Solution C was subjected to ultrasonic oscillation for 30 minutes with an ultrasonic power controlled at 1500W and an ultrasonic frequency controlled at 20Hz to obtain solution D. Solution D was centrifuged at 9000r / min for 10 minutes to separate the modified polyaluminum chloride solution. The modified polyaluminum chloride solution was dried in a dryer at 60℃ for 24 hours to obtain modified polyaluminum chloride.

[0055] Next, add 40mg / m 3 Modified polyacrylamide was subjected to a coagulation reaction and held for 50 minutes. The modified polyacrylamide was prepared by the following method: 2.5 parts zinc oxide, 8 parts sodium hydroxide, 14 parts urea, and 80 parts purified water were mixed and stirred for 3 minutes, then placed in an incubator and kept at -15℃ for 25 minutes to obtain a solvent. 9 parts by weight of polyacrylamide and 3 parts by weight of kapok fiber were added to 26 parts of the solvent and stirred for 5 minutes to obtain solution E. Solution E was subjected to ultrasonic oscillation for 30 minutes with an ultrasonic power controlled at 1500W and an ultrasonic frequency controlled at 20Hz to obtain solution F. Solution F was centrifuged at 9000 r / min for 10 minutes to obtain a modified polyacrylamide solution. The modified polyacrylamide solution was dried in a dryer at 55℃ for 20 hours to obtain modified polyacrylamide.

[0056] Next, it is discharged into a two-stage inclined tube sedimentation tank and held for 60 minutes.

[0057] Next, the wastewater is discharged into the clear water tank and left to stand for 2.0 hours. If the wastewater passes the test, it flows into the plant's water system for continued use. If the wastewater fails the test, it flows into the emergency response tank. The nickel-containing sludge formed after the secondary inclined tube sedimentation is discharged into the sludge tank mentioned above and treated according to the sludge treatment steps described above.

[0058] The aforementioned equalization tank, pH adjustment tank, primary oxidation tank, primary coagulation reaction tank, primary inclined tube sedimentation tank, sludge tank, secondary oxidation tank, secondary coagulation reaction tank, secondary inclined tube sedimentation tank, clear water tank, and emergency tank are all reinforced steel structures with an internal anti-corrosion layer, which is made of anti-corrosion plates spliced ​​together.

[0059] A mixer is installed between the primary coagulation reaction tank and the secondary coagulation reaction tank. The mixer has a power of 1000W and a stirring speed of 70r / min.

[0060] The silica dry gels in Examples 1 and 2 above were prepared by the following steps:

[0061] S21: Piperidine and ammonia: Mix 1 wt% piperidine and 15 wt% ammonia, stir for 1 min, the volume ratio of piperidine to ammonia is 1:1, to obtain solution A, for later use;

[0062] S22: Dissolving tetraethyl orthosilicate: Add tetraethyl orthosilicate to solution A, stir for 10 minutes until the solution turns milky white, then stop stirring to obtain a silica gel solution; the mass-to-volume ratio of tetraethyl orthosilicate to solution A is 0.8:2;

[0063] S23: Aging and drying: The silica gel solution is aged at room temperature for 1 hour, then placed in an aging chamber and aged at 75°C for another 3.5 hours. After being removed, it is left to air dry at room temperature for 13 hours, and then placed in a dryer and dried at 75°C for 3.5 hours to obtain silica dry gel.

[0064] Example 3

[0065] A method for treating nickel-containing wastewater specifically includes the following steps:

[0066] The factory discharges nickel-containing wastewater into a regulating tank to balance the water quality and quantity, where it remains for 10.7 hours.

[0067] Next, the mixture is discharged into a pH adjustment tank, sodium hydroxide is added to adjust the pH to 8.5, and the mixture is left to stand for 75 minutes.

[0068] Next, it is discharged into the primary oxidation tank, with 55g / m³ added. 3 Oxidizing agent 1 was used for the oxidation reaction, and the reaction was allowed to proceed for 2.5 hours.

[0069] Next, it is discharged into the primary coagulation reaction tank, with 30g / m³ added. 3 The silica dry gel was subjected to a coagulation reaction and held for 145 minutes.

[0070] Next, it is discharged into the first-stage inclined tube sedimentation tank and retained for 60 minutes.

[0071] Next, the sludge is discharged into a sludge tank, where a plate and frame filter press is installed. The filtered nickel sludge is then transported to a designated facility for recycling. The filtrate that passes inspection is discharged into a clear water tank; otherwise, it is discharged into a secondary oxidation tank for further treatment.

[0072] Next, it is discharged into the secondary oxidation tank, and 450 ml / m³ is added. 3 Hydrogen peroxide is used for oxidation reaction, and the reaction is carried out for 1.7 hours.

[0073] Next, it is discharged into the secondary coagulation reaction tank, with 200 mg / m³ added. 3 Modified polyaluminum chloride was subjected to a coagulation reaction and held for 55 minutes. The modified polyaluminum chloride was prepared by the following method: 2.0 parts zinc oxide, 7 parts sodium hydroxide, 13.5 parts urea, and 75 parts purified water were mixed and stirred for 2 minutes, then placed in an incubator and kept at -12.5℃ for 22.5 minutes to obtain a solvent. 9 parts by weight of polyaluminum chloride and 3 parts by weight of kapok fiber were added to 22 parts by weight of the solvent and stirred for 3.5 minutes to obtain solution C. Solution C was subjected to ultrasonic oscillation for 25 minutes with an ultrasonic power controlled at 1250W and an ultrasonic frequency controlled at 17.5Hz to obtain solution D. Solution D was centrifuged at 8000 r / min for 7.5 minutes to separate the modified polyaluminum chloride solution. The modified polyaluminum chloride solution was dried in a dryer at 55℃ for 22 hours to obtain modified polyaluminum chloride.

[0074] Next, add 30mg / m 3Modified polyacrylamide was subjected to a coagulation reaction and held for 47.5 min. The modified polyacrylamide was prepared by the following method: 2.0 parts zinc oxide, 7 parts sodium hydroxide, 13.5 parts urea, and 75 parts purified water were mixed and stirred for 2 min, then placed in an incubator and kept at -12.5℃ for 22.5 min to obtain a solvent. 8 parts by weight of polyacrylamide and 2.5 parts of kapok fiber were added to 22 parts of the solvent and stirred for 3.5 min to obtain solution E. Solution E was subjected to ultrasonic oscillation for 25 min with an ultrasonic power controlled at 1250 W and an ultrasonic frequency controlled at 17.5 Hz to obtain solution F. Solution F was centrifuged at 8000 r / min for 7.5 min to obtain a modified polyacrylamide solution. The modified polyacrylamide solution was dried in a dryer at 52.5℃ for 19 h to obtain modified polyacrylamide.

[0075] Next, it is discharged into a two-stage inclined tube sedimentation tank and held for 50 minutes.

[0076] Next, the wastewater is discharged into the clear water tank and left to stand for 1.5 hours. If the wastewater passes the test, it flows into the plant's water system for continued use. If the wastewater fails the test, it flows into the emergency response tank. The nickel-containing sludge formed after the secondary inclined tube sedimentation is discharged into the sludge tank and treated according to the above sludge treatment steps.

[0077] The aforementioned equalization tank, pH adjustment tank, primary oxidation tank, primary coagulation reaction tank, primary inclined tube sedimentation tank, sludge tank, secondary oxidation tank, secondary coagulation reaction tank, secondary inclined tube sedimentation tank, clear water tank, and emergency tank are all reinforced steel structures with an internal anti-corrosion layer, which is made of anti-corrosion plates spliced ​​together.

[0078] A mixer is installed between the primary coagulation reaction tank and the secondary coagulation reaction tank. The mixer has a power of 750W and a stirring speed of 60r / min.

[0079] Next, the above-mentioned silica dry gel is prepared by the following steps:

[0080] S21: Piperidine and ammonia: Mix 5.5 wt% piperidine and 17.5 wt% ammonia, stir for 2 min, the volume ratio of piperidine to ammonia is 1.1:1.3, to obtain solution A, for later use;

[0081] S22: Dissolving tetraethyl orthosilicate: Add tetraethyl orthosilicate to solution A, stir for 15 minutes until the solution turns milky white, then stop stirring to obtain a silica gel solution; the mass-to-volume ratio of tetraethyl orthosilicate to solution A is 1.0:2.5;

[0082] S23: Aging and drying: The silica gel solution was aged at room temperature for 1.1 hours, then placed in an aging chamber at 80°C for 4.0 hours. After being removed, it was air-dried at room temperature for 14 hours, and then placed in a dryer at 80°C for 4.0 hours to obtain silica dry gel.

[0083] Example 4

[0084] A method for treating nickel-containing wastewater specifically includes the following steps:

[0085] The factory discharges nickel-containing wastewater into a regulating tank to balance the water quality and quantity, where it remains for 10.5 hours.

[0086] Next, the mixture is discharged into a pH adjustment tank, where calcium hydroxide is added to adjust the pH to 8, and the mixture is left to stand for 70 minutes.

[0087] Next, it is discharged into the primary oxidation tank, with 50g / m³ added. 3 Oxidizing agent 1 was used for the oxidation reaction, and the reaction was allowed to proceed for 2.0 h.

[0088] Next, it is discharged into the primary coagulation reaction tank, with 35g / m³ added. 3 The silica dry gel was subjected to a coagulation reaction and held for 140 minutes.

[0089] Next, it is discharged into the first-stage inclined tube sedimentation tank and retained for 50 minutes.

[0090] Next, the sludge is discharged into a sludge tank, where a plate and frame filter press is installed. The filtered nickel sludge is then transported to a designated facility for recycling. The filtrate that passes inspection is discharged into a clear water tank; otherwise, it is discharged into a secondary oxidation tank for further treatment.

[0091] Next, it is discharged into the secondary oxidation tank, and 300 ml / m³ is added. 3 Hydrogen peroxide is used for oxidation reaction, and the reaction is allowed to proceed for 1.5 hours.

[0092] Next, it is discharged into the secondary coagulation reaction tank, with 100 mg / m³ added. 3Modified polyaluminum chloride (PAC) was subjected to a coagulation reaction and held for 50 minutes. The modified PAC was prepared by the following method: 1.5 parts zinc oxide, 6 parts sodium hydroxide, 13 parts urea, and 70 parts purified water were mixed and stirred for 1 minute, then placed in an incubator at -10℃ for 20 minutes to obtain a solvent. 8 parts by weight of PAC and 2 parts by weight of kapok fiber were added to 20 parts of the solvent and stirred for 2 minutes to obtain solution C. Solution C was subjected to ultrasonic oscillation for 20 minutes with an ultrasonic power controlled at 1000W and an ultrasonic frequency controlled at 15Hz to obtain solution D. Solution D was centrifuged at 7000 r / min for 5 minutes to separate the modified PAC solution. The modified PAC solution was then dried in a dryer at 50℃ for 20 hours to obtain modified PAC.

[0093] Next, add 20mg / m 3 Modified polyacrylamide was subjected to a coagulation reaction and held for 45 minutes. The modified polyacrylamide was prepared by the following method: 1.5 parts zinc oxide, 6 parts sodium hydroxide, 13 parts urea, and 70 parts purified water were mixed and stirred for 1 minute, then placed in an incubator and kept at -10℃ for 20 minutes to obtain a solvent. 7 parts by weight of polyacrylamide and 2 parts by weight of kapok fiber were added to 18 parts of the solvent and stirred for 2 minutes to obtain solution E. Solution E was subjected to ultrasonic oscillation for 20 minutes with an ultrasonic power controlled at 1000W and an ultrasonic frequency controlled at 15Hz to obtain solution F. Solution F was centrifuged at 7000r / min for 5 minutes to obtain a modified polyacrylamide solution. The modified polyacrylamide solution was dried in a dryer at 50℃ for 18 hours to obtain modified polyacrylamide.

[0094] Next, it is discharged into a two-stage inclined tube sedimentation tank and held for 40 minutes.

[0095] Next, the wastewater is discharged into the clear water tank and left to stand for 1 hour. If the wastewater passes the test, it flows into the plant's water system for continued use. If the wastewater fails the test, it flows into the emergency response tank. The nickel-containing sludge formed after the secondary inclined tube sedimentation is discharged into the sludge tank and treated according to the above sludge treatment steps.

[0096] The aforementioned equalization tank, pH adjustment tank, primary oxidation tank, primary coagulation reaction tank, primary inclined tube sedimentation tank, sludge tank, secondary oxidation tank, secondary coagulation reaction tank, secondary inclined tube sedimentation tank, clear water tank, and emergency tank are all reinforced steel structures with an internal anti-corrosion layer, which is made of anti-corrosion plates spliced ​​together.

[0097] A mixer is installed between the primary coagulation reaction tank and the secondary coagulation reaction tank. The mixer has a power of 500W and a stirring speed of 50r / min.

[0098] Example 5

[0099] A method for treating nickel-containing wastewater specifically includes the following steps:

[0100] The factory discharges nickel-containing wastewater into a regulating tank to balance the water quality and quantity, where it remains for 11 hours.

[0101] Next, the mixture is discharged into a pH adjustment tank, where calcium hydroxide is added to adjust the pH to 9, and the mixture is left to stand for 80 minutes.

[0102] Next, it is discharged into the primary oxidation tank, with 60g / m³ added. 3 Oxidizing agent 1 was used for the oxidation reaction, and the reaction was allowed to proceed for 3.0 h.

[0103] Next, it is discharged into the primary coagulation reaction tank, with 45g / m³ added. 3 The silica dry gel was subjected to a coagulation reaction and held for 150 minutes.

[0104] Next, it is discharged into the first-stage inclined tube sedimentation tank and retained for 70 minutes.

[0105] Next, the sludge is discharged into a sludge tank, where a plate and frame filter press is installed. The filtered nickel sludge is then transported to a designated facility for recycling. The filtrate that passes inspection is discharged into a clear water tank; otherwise, it is discharged into a secondary oxidation tank for further treatment.

[0106] Next, it is discharged into the secondary oxidation tank, and 600 ml / m³ is added. 3 Hydrogen peroxide is used for oxidation reaction, and the reaction is carried out for 2.0 h.

[0107] Next, it is discharged into the secondary coagulation reaction tank, with 300 mg / m³ added. 3 Modified polyaluminum chloride was subjected to a coagulation reaction and held for 60 minutes. The modified polyaluminum chloride was prepared by the following method: 2.5 parts zinc oxide, 8 parts sodium hydroxide, 14 parts urea, and 80 parts purified water were mixed and stirred for 3 minutes, then placed in an incubator and kept at -15℃ for 25 minutes to obtain a solvent. 10 parts by weight of polyaluminum chloride and 4 parts by weight of kapok fiber were added to 24 parts by weight of the solvent and stirred for 5 minutes to obtain solution C. Solution C was subjected to ultrasonic oscillation for 30 minutes with an ultrasonic power controlled at 1500W and an ultrasonic frequency controlled at 20Hz to obtain solution D. Solution D was centrifuged at 9000r / min for 10 minutes to separate the modified polyaluminum chloride solution. The modified polyaluminum chloride solution was dried in a dryer at 60℃ for 24 hours to obtain modified polyaluminum chloride.

[0108] Next, add 40mg / m 3 Modified polyacrylamide was subjected to a coagulation reaction and held for 50 minutes. The modified polyacrylamide was prepared by the following method: 2.5 parts zinc oxide, 8 parts sodium hydroxide, 14 parts urea, and 80 parts purified water were mixed and stirred for 3 minutes, then placed in an incubator and kept at -15℃ for 25 minutes to obtain a solvent. 9 parts by weight of polyacrylamide and 3 parts by weight of kapok fiber were added to 26 parts of the solvent and stirred for 5 minutes to obtain solution E. Solution E was subjected to ultrasonic oscillation for 30 minutes with an ultrasonic power controlled at 1500W and an ultrasonic frequency controlled at 20Hz to obtain solution F. Solution F was centrifuged at 9000 r / min for 10 minutes to obtain a modified polyacrylamide solution. The modified polyacrylamide solution was dried in a dryer at 55℃ for 20 hours to obtain modified polyacrylamide.

[0109] Next, it is discharged into a two-stage inclined tube sedimentation tank and held for 60 minutes.

[0110] Next, the wastewater is discharged into the clear water tank and left to stand for 2.0 hours. If the wastewater passes the test, it flows into the plant's water system for continued use. If the wastewater fails the test, it flows into the emergency response tank. The nickel-containing sludge formed after the secondary inclined tube sedimentation is discharged into the sludge tank mentioned above and treated according to the sludge treatment steps described above.

[0111] The aforementioned equalization tank, pH adjustment tank, primary oxidation tank, primary coagulation reaction tank, primary inclined tube sedimentation tank, sludge tank, secondary oxidation tank, secondary coagulation reaction tank, secondary inclined tube sedimentation tank, clear water tank, and emergency tank are all reinforced steel structures with an internal anti-corrosion layer, which is made of anti-corrosion plates spliced ​​together.

[0112] A mixer is installed between the primary coagulation reaction tank and the secondary coagulation reaction tank. The mixer has a power of 1000W and a stirring speed of 70r / min.

[0113] The silica dry gels in Examples 4 and 5 above were prepared by the following steps:

[0114] S21: Piperidine and ammonia: Mix 10wt% piperidine and 20wt% ammonia, stir for 3 min, the volume ratio of piperidine to ammonia is 1.2:1.5, to obtain solution A, for later use;

[0115] S22: Dissolving tetraethyl orthosilicate: Add tetraethyl orthosilicate to solution A, stir for 20 minutes until the solution turns milky white, then stop stirring to obtain a silica gel solution; the mass-to-volume ratio of tetraethyl orthosilicate to solution A is 1.2:3;

[0116] S23: Aging and drying: The silica gel solution is aged at room temperature for 1.2 hours, then placed in an aging chamber at 85°C for 4.5 hours. After being removed, it is left to air dry at room temperature for 15 hours, and then placed in a dryer at 85°C for 4.5 hours to obtain silica dry gel.

[0117] Determination of Nickel

[0118] The concentration of nickel in the wastewater treated in Examples 1-5 was determined according to the methods and requirements of GB / T 11982-1989 "Determination of Nickel in Water - Flame Atomic Absorption Spectrophotometry". The nickel concentration was calculated using the following formula:

[0119]

[0120] In the formula, c represents the concentration of nickel in the sample (mg / L), m represents the content of nickel in the sample (μg), and v represents the volume of the sample (ml).

[0121] The measurement results are shown in Table 1 below:

[0122] Table 1

[0123] Example 1 Example 2 Example 3 Example 4 Example 5 Nickel concentration (mg / L) 0.06 0.07 0.05 0.08 0.06

[0124] The results above show that the treatment method of the present invention can effectively remove nickel from wastewater. The nickel content in the treated wastewater meets the requirements of Table 2 of Guangdong Provincial Local Standard DB44 1957-2015 "Electroplating Water Pollutant Discharge Standard" for the Pearl River Delta region, which specifies a discharge limit of ≤0.1 mg / L. Example 3 of the method of the present invention shows the best results.

[0125] To verify the treatment results of Example 3, two comparative examples were set up.

[0126] Comparative Example 1

[0127] Compared with Example 3, Comparative Example 1 differs in that it only has one stage of coagulation treatment process. It only has the two-stage coagulation treatment process found in this unit.

[0128] Comparative Example 2

[0129] Comparative Example 2 and Example 3 differ in that an equal mass of commercially available silica gel is used instead of the silica dry gel prepared by the method of the present invention.

[0130] According to the above-mentioned method and formula for determining nickel content, the concentration of nickel in the wastewater treated according to Comparative Examples 1-2 was determined and compared with that in Example 3. The determination results are shown in Table 2 below:

[0131] Table 2

[0132] Example 3 Comparative Example 1 Comparative Example 2 Nickel concentration (mg / L) 0.05 0.21 0.12

[0133] Compared to Comparative Example 1, in Example 3, larger suspended and colloidal nickel-containing pollutants were removed in the first-stage coagulation treatment, while smaller nickel-containing pollutants were removed more effectively in the second-stage coagulation treatment. Therefore, this two-stage treatment method can more comprehensively remove various pollutants from nickel-containing wastewater. Compared to Comparative Example 2, the reaction conditions of piperidine and ammonia in Example 3 are mild, and the prepared silica dry gel has a high specific surface area, good pore structure, and high stability. These properties enable the silica dry gel to have high adsorption capacity and filtration effect in the treatment of nickel-containing wastewater, effectively removing nickel ions from the wastewater.

[0134] Add a comparative example 3 to compare the sludge moisture content with implementation 3.

[0135] Comparative Example 3

[0136] Comparative Example 3 differs from Example 3 in that equal masses of polyaluminum chloride and polyacrylamide are used instead of modified polyaluminum chloride and modified polyacrylamide, respectively.

[0137] Moisture content determination

[0138] The sludge moisture content was determined according to the following steps:

[0139] 1. Take nickel-containing sludge from the secondary coagulation treatment of Example 3 and Comparative Example 3, respectively, and spread it evenly in an aluminum box of known mass. Weigh the total mass of the aluminum box and the sludge using an electronic balance, and record it as m1.

[0140] 2. Then, place the aluminum box in an oven to dry. Set the oven temperature to 105℃ and the drying time to 2 hours. Remove the dried aluminum box and place it in a desiccator to cool. After cooling, weigh the total mass of the dried aluminum box and sludge using an electronic balance and record it as m2.

[0141] The sludge moisture content is calculated using the following formula:

[0142]

[0143] In the formula, x represents the sludge moisture content, m1 represents the total mass of sludge plus aluminum box before drying, and m2 represents the total mass of sludge plus aluminum box after drying. The measurement results are shown in Table 3 below:

[0144] Table 3

[0145] Example 3 Comparative Example 3 sludge moisture content % 60 98

[0146] Compared with Comparative Example 3, Example 3 improved the hydrophobicity of polyaluminum chloride and polyacrylamide by introducing kapok fiber hydrophobic functional groups into them, thereby reducing the water content of sludge from 98% to 60% and reducing the burden on subsequent processes.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 treating nickel-containing wastewater, characterized by: The following processes are set: pretreatment, primary coagulation treatment, sludge treatment, secondary coagulation treatment, discharge treatment and accident treatment; specifically comprising the following steps: S1: pretreatment: including an adjusting tank and a pH adjusting tank, the pH adjusting tank adding an alkaline agent to adjust the pH to 8-9; S2: primary coagulation treatment: including a primary oxidation tank, a primary coagulation reaction tank and a primary inclined tube sedimentation tank; adding an oxidizing agent 1 in the primary oxidation tank for oxidation reaction, staying for 2.0-3.0h; then adding a coagulant 1 in the primary coagulation reaction tank for coagulation reaction, staying for 140-150min; then discharging into the primary inclined tube sedimentation tank, staying for 50-70min; S3: sludge treatment: the nickel-containing sludge formed after the primary inclined tube sedimentation is discharged into a sludge tank; a plate and frame filter press is arranged, the nickel sludge after pressure filtration is transported to a designated institution for recycling, the filtrate after pressure filtration is discharged to a clear water tank after detection, and is discharged to a secondary oxidation tank for further treatment if the detection is not qualified; S4: secondary coagulation treatment: including a secondary oxidation tank, a secondary coagulation reaction tank and a secondary inclined tube sedimentation tank; the nickel-containing wastewater after the primary coagulation treatment and sludge treatment is discharged into the secondary oxidation tank, an oxidizing agent 2 is added into the secondary oxidation tank for oxidation reaction, staying for 1.5-2.0h; then a coagulant 2 is added into the secondary coagulation reaction tank for coagulation reaction, staying for 50-60min; then a coagulant 3 is added for coagulation reaction, staying for 45-50min; then discharging into the secondary inclined tube sedimentation tank, staying for 40-60min; S5: discharge treatment: the clear liquid after the secondary coagulation treatment is discharged to a clear water tank; if the detection is qualified, it flows into the water system of the plant area for further use, and if the detection is not qualified, it flows into an emergency pool; the nickel-containing sludge formed after the secondary inclined tube sedimentation is discharged into a sludge tank for nickel-containing sludge treatment according to S3; The coagulant 2 in the S4 is modified polyaluminum chloride, the adding amount is 100-300 mg / m 3 The modified polyaluminum chloride is prepared by the following method: taking 8-10 parts of polyaluminum chloride, 2-4 parts of kapok fiber, adding the mixture into 20-24 parts of dissolving agent, stirring for 2-5 min to obtain solution C; putting the solution C into ultrasonic equipment for ultrasonic oscillation treatment for 20-30 min, controlling the ultrasonic power at 1000-1500 W, controlling the ultrasonic frequency at 15-20 Hz to obtain solution D; putting the solution D into a centrifuge and rotating at 7000-9000 r / min for 5-10 min to separate the modified polyaluminum chloride solution; putting the modified polyaluminum chloride solution into a drying machine and drying at 50-60 DEG C for 20-24 h to obtain the modified polyaluminum chloride. The coagulant 3 in the S4 is modified polyacrylamide, and the adding amount is 20-40 mg / m 3 The modified polyacrylamide is prepared by the following method: taking 7-9 parts of polyacrylamide and 2-3 parts of kapok fiber by mass, the mixture is added into 18-26 parts of dissolving agent, stirring for 2-5 min to obtain solution E; the solution E is put into ultrasonic equipment for ultrasonic oscillation treatment for 20-30 min, the ultrasonic power is controlled at 1000-1500 W, and the ultrasonic frequency is controlled at 15-20 Hz to obtain solution F; the solution F is put into a centrifuge and rotated at 7000-9000 r / min for 5-10 min to obtain a modified polyacrylamide solution; the modified polyacrylamide solution is put into a drying machine and dried at 50-55℃ for 18-20 h to obtain the modified polyacrylamide. The dissolving agent is obtained by mixing 1.5-2.5 parts of zinc oxide, 6-8 parts of sodium hydroxide, 13-14 parts of urea and 70-80 parts of pure water and stirring for 1-3min, and then placing it in a heat preservation box under the condition of a heat preservation temperature of-10℃ to-15℃ and a heat preservation time of 20-25min.

2. A method of treating nickel-containing wastewater as claimed in claim 1, characterized in that: The adjusting tank, the pH adjusting tank, the primary oxidation tank, the primary coagulation reaction tank, the primary inclined tube sedimentation tank, the sludge tank, the secondary oxidation tank, the secondary coagulation reaction tank, the secondary inclined tube sedimentation tank and the clear water tank are sequentially connected and are all of reinforced structure, are provided with an anticorrosive layer inside, and the anticorrosive layer is formed by splicing anticorrosive plates.

3. The method of treating nickel-containing wastewater of claim 1, wherein: A stirrer is arranged in the middle of the primary coagulation reaction tank and the secondary coagulation reaction tank, the stirrer has a power of 500-1000W and a stirring speed of 50-70r / min.

4. The method of treating nickel-containing wastewater of claim 1, wherein: The alkaline agent in S1 is one of sodium hydroxide and calcium hydroxide.

5. The method of treating nickel-containing wastewater of claim 1, wherein: The amount of oxidizing agent 1 added in S2 is 50-60 g / m 3 .

6. The method of treating nickel-containing wastewater of claim 1, wherein: The coagulant 1 in S2 is a silica xerogel, and the amount added is 35-45 g / m 3 The silica xerogel is prepared by the following steps: S21: piperidine and ammonia water: mixing piperidine with a concentration of 1-10wt% and ammonia water with a concentration of 15-20wt%, stirring for 1-3min, the volume ratio of piperidine to ammonia water being (1-1.2):(1-1.5), to obtain solution A for standby; S22: dissolving tetraethyl orthosilicate: tetraethyl orthosilicate is added into solution A, stirring for 10-20 min, until the solution appears milky white, stop stirring, to obtain a silica gel solution; the mass-volume ratio of tetraethyl orthosilicate to solution A is (0.8-1.2):(2-3); S23: aging, drying: the silica gel solution is aged at room temperature for 1-1.2 h, then placed in an aging box for further aging at 75-85℃ for 3.5-4.5 h, after taking out, it is placed at room temperature for 13-15 h, then placed in a drying machine for drying at 75-85℃ for 3.5-4.5 h, to obtain a silica xerogel.

7. The method of treating nickel-containing wastewater of claim 1, wherein: The oxidizing agent 2 in S4 is hydrogen peroxide, and the amount added is 300-600 ml / m 3 .

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