Advanced oxidation treatment process for chemical nickel and electronickelling wastewater

Abstract

The invention discloses an advanced oxidation treatment process for chemical nickel and electronickelling wastewater, and belongs to the field of industrial wastewater treatment. The process sequentially comprises the steps of three-stage strong oxidation reaction, A / O biological treatment, membrane distillation concentration, sludge treatment and the like, so that high-efficiency purification of wastewater and nickel resource recovery are realized. In the third-stage strong oxidation reaction, the pH is accurately adjusted, a composite catalyst and hydrogen peroxide are added, the reaction conditions are controlled in combination with aeration, complex bonds are gradually broken, and organic matter is degraded; the A / O system further degrades COD; membrane distillation multi-stage concentration enables the concentration of nickel in the concentrated solution to be greater than or equal to 15% and to be reused in the electroplating solution, and membrane produced water reaches the standard and is reused; nickel is recovered from dewatered sludge through acid leaching (the recovery rate is greater than or equal to 95%), and residual sludge is cured and then is safely landfilled. According to the scheme, through the synergistic effect of three-stage gradient strong oxidation and A / O biological treatment, the removal efficiency of COD and nickel ions can be greatly improved, and it is ensured that all indexes of effluent stably reach the standard; the mode of combining membrane distillation multi-stage concentration and sludge acid leaching is adopted, so that efficient recovery of nickel resources is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to a chemical nickel and electroplating nickel wastewater advanced oxidation treatment process. BACKGROUND

[0002] Chemical nickel and electroplating nickel wastewater is one of the most complex and difficult types of wastewater in the electroplating industry to treat, and the core difficulty lies in that the nickel pollutants in the wastewater mainly exist in the form of complexation (such as stable complexes formed with lactic acid, citric acid, EDTA and the like), which leads to that the nickel ions cannot be effectively separated by the conventional precipitation method; meanwhile, the high-concentration hypophosphite (reducing agent) in the wastewater is difficult to be completely converted into precipitable orthophosphate by the traditional oxidation process (such as Fenton method) (the oxidation efficiency is less than 60%), and the ammonia nitrogen (buffering agent) is easy to combine with the nickel ions to form a nickel-ammonia complex, which further hinders the precipitation of nickel under alkaline conditions; in addition, the aging plating solution and cleaning wastewater of chemical nickel also contain high COD (complexing agent and organic matter) and other heavy metals, forming a complex system with the synergistic effect of multiple pollutants, and the existing technologies such as chemical precipitation method have a large amount of sludge and are easy to introduce calcium and magnesium ions to cause evaporation and scaling, ion exchange and membrane separation method can achieve deep purification but has high investment and maintenance costs and outstanding membrane pollution problems, and the biological method has poor tolerance to complexed nickel and toxicity, and a single advanced oxidation technology (such as ozone oxidation) can break the complex but has problems of large reagent consumption and low removal efficiency of ammonia nitrogen and hypophosphite, and especially the electroplating park generally rejects the chemical nickel wastewater, because the mixed wastewater makes the nickel-containing wastewater as a whole into a complex state, greatly increasing the treatment difficulty and cost.

[0003] In addition, the existing process has low resource recovery efficiency and does not meet the requirements of circular economy. For the refractory wastewater containing complexed nickel, it is urgent to develop an integrated technology with the functions of deep oxidation, heavy metal removal and resource recovery. The process solves the problems of incomplete treatment, large reagent consumption and resource waste of the traditional process by three-stage gradient oxidation combined with A / O biological treatment and membrane distillation concentration and recovery of nickel resources, and meets the increasingly stringent environmental protection standards and resource utilization requirements. SUMMARY

[0004] The purpose of the present application is to provide a chemical nickel and electroplating nickel wastewater advanced oxidation treatment process, which aims to solve the problems of incomplete treatment, large reagent consumption and resource waste in the prior art, and realizes the problems of wastewater discharge and efficient recovery of nickel resources.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] A chemical nickel and electroplating nickel wastewater advanced oxidation treatment process, comprising:

[0007] S1, the wastewater is pumped from the water collecting pool to the first strong oxidation reaction pool by the lifting pump, a liquid level sensor is arranged in the pool, when the liquid level reaches 80% to 90% of the preset volume, the sensor triggers the control system to start the submersible stirring device;

[0008] S2, 20% sulfuric acid is added to the first strong oxidation reaction pool, the pH online monitor is used for real-time feedback to accurately adjust the pH of the wastewater to 4.0±0.2;

[0009] S3, a composite catalyst is added, the composition is cobalt nitrate-nickel nitrate supported on activated carbon, the Co / Ni molar ratio is 1:1 to 2:1, the addition amount is 1% to 3% of the mass of the wastewater COD, and stirring is performed for greater than or equal to 5 minutes to uniformly disperse the catalyst;

[0010] S4, hydrogen peroxide is added according to the H2O2 / COD mass ratio of 2:1 to 3:1, and a blower is started simultaneously to perform aeration through a microporous aerator with a pore diameter of 50 to 100 μm, the ORP value is controlled to be 300 to 550 mV, the temperature is 25 to 40℃, and the reaction is performed for 60 to 120 minutes;

[0011] S5, lime milk is added to adjust the pH to 7.0 to 8.0, the mixed solution is pumped into the inclined tube sedimentation pool, and 10 to 50 mg / L of PAC and 0.5 to 2 mg / L of PAM are added for coagulation and sedimentation;

[0012] S6, the supernatant of the first sedimentation is introduced into the second strong oxidation reaction pool, steps S1 to S5 are repeated, hydrogen peroxide is added according to the H2O2 / COD mass ratio of 1:1 to 2:1, the addition of the hydrogen peroxide is based on the residual COD of the supernatant of the first sedimentation, a blower is started simultaneously to perform aeration through a microporous aerator with a pore diameter of 50 to 100 μm, the ORP value is controlled to be 300 to 550 mV, the temperature is 25 to 40℃, and the reaction is performed for 60 to 90 minutes;

[0013] S7, the supernatant of the second sedimentation is introduced into the third strong oxidation reaction pool, hydrogen peroxide is added after adjusting the pH to 4.0±0.2, according to the H2O2 / COD mass ratio of 0.5:1 to 1:1, the addition of the hydrogen peroxide is based on the residual COD of the supernatant of the second sedimentation, an aeration system is started simultaneously, the ORP value is controlled to be 250 to 450 mV, the temperature is 25 to 40℃, and the reaction is performed for 30 to 60 minutes, then lime is added to adjust the pH to greater than or equal to 11.0, and sedimentation is performed for 30 to 45 minutes to remove residual heavy metals and phosphorus;

[0014] S8, after the supernatant of the third sedimentation is adjusted to a pH of 6.5 to 7.5, it is introduced into an A / O system, the anaerobic tank has a specific surface area of the filler of greater than or equal to 500 m 2 / m 3 , the hydraulic retention time is 4 to 6 hours; the aeration amount of the aerobic tank is 2 to 5 L / (m 3 ·h), the sludge concentration is 3000 to 5000 mg / L, and the dissolved oxygen is 2 to 4 mg / L;

[0015] S9, the sludge of each level is concentrated (water content ≤95%) and then dewatered by filter pressing (water content ≤80%), and the recovery rate of nickel resource in the sludge cake is ≥95%.

[0016] As a preferred scheme of the present application, the submersible agitator adopts double-layer turbine paddle, the rotation speed is 80-120 r / min in the medicament adding stage, and is reduced to 40-60 r / min in the reaction stage, and the paddle surface is coated with a polytetrafluoroethylene anticorrosive layer.

[0017] As a preferred scheme of the present application, the composite catalyst is prepared by the following steps:

[0018] The coconut shell activated carbon with a particle size of 3-5 mm is pretreated by 10%-30% nitric acid;

[0019] The molar ratio of Co / Ni in the loaded cobalt nitrate and nickel nitrate is 1:1-2:1, and the constant temperature reaction is carried out at 80-85 ℃ for 8-10 hours;

[0020] Carbonization is carried out at 750-850 ℃ for 2-3 hours to form a cobalt-nickel bimetallic activated carbon catalyst, and the specific surface area is ≥800 m 2 / g.

[0021] As a preferred scheme of the present application, the inclined angle of the inclined pipe of the inclined pipe sedimentation tank is 60°, the pore diameter is 50 mm, the surface load is 1.0-1.5 m 3 / (m 2 ·h), and the PAC adding amount is automatically optimized by the control system based on the influent nickel ion concentration by adding 5-10 mg PAC per 1 mg / L Ni 2+ .

[0022] As a preferred scheme of the present application, the aeration system of the three-stage strong oxidation reaction tank adopts ozone-air mixed aeration, and the ozone adding amount is 10-20 mg / L, which is used for oxidizing hypophosphite to orthophosphate and deeply degrading COD.

[0023] As a preferred scheme of the present application, the sludge reflux ratio of the A / O system is 50%-100%, and the mixed liquor reflux ratio is 200%-300%; the biological filter material is used in the aerobic tank, the particle size is 3-5 mm, the suspended solids and the biodegradation COD are simultaneously intercepted, and the effluent COD is ≤30 mg / L.

[0024] As a preferred scheme of the present application, the nickel in the dewatered sludge is recovered by acid leaching, the recovery rate is ≥95%, and the remaining sludge is safely landfilled after solidification and stabilization.

[0025] As a preferred scheme of the present application, the concentrated water after three-stage strong oxidation is concentrated by multi-stage membrane distillation, each stage adopts series countercurrent operation, the feed of the first stage is the concentrated water after three-stage strong oxidation, after concentration of the first stage, the concentrated water enters the next stage as feed, the operation temperature of each stage decreases by 5-10℃ along the water flow direction, which is 60-80℃ for the first stage and 40-60℃ for the last stage; the membrane module adopts hydrophobic polyvinylidene fluoride material with a molecular weight cut-off of 500-1000 Da, the concentration ratio of each stage is controlled at 2-3 times, the transmembrane pressure difference is maintained at 0.02-0.05 MPa, the water temperature on the condensation side is ≤30℃, the nickel concentration of the concentrated liquid of each stage is tracked in real time through an online monitoring system, when the nickel concentration of the concentrated liquid of the last stage is ≥15%, the concentration is stopped and the concentrated liquid is used for electroplating solution; the water produced by each stage is collected, and the COD is ≤10 mg / L and the total nickel content is ≤0.1 mg / L, and the water is used for production line flushing water after disinfection.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The present scheme can greatly improve the removal efficiency of COD and nickel ions through the synergistic effect of three-stage gradient strong oxidation and A / O biological treatment, and ensure that the indicators of the effluent meet the standards; the combination of multi-stage membrane distillation concentration and sludge acid leaching realizes efficient recovery of nickel resources, and the recovery rate is as high as 95% or more, fully meeting the concept of circular economy; at the same time, by optimizing the dosage of reagents, reaction conditions and using resource recovery technology, the consumption of reagents and sludge production are effectively reduced, and the treatment cost is significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, which together with the embodiments of the present application, serve to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0029] Figure 1 is a process flow diagram of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] Example 1

[0032] 1L of mixed chemical nickel and electroplating nickel wastewater is taken, the initial COD is 1200 mg / L, and the nickel ion concentration is 180 mg / L.

[0033] S1: The wastewater is pumped from the sump by a booster pump to a first strong oxidation reaction tank. A liquid level sensor is provided in the tank. When the liquid level reaches 85% of the preset volume, the sensor triggers the control system to start the submersible stirring device. The submersible stirrer uses double-layer turbine paddles. The paddle surface is coated with a polytetrafluoroethylene corrosion-resistant layer. The paddle speed is 100 r / min during the reagent addition stage and is reduced to 50 r / min during the reaction stage.

[0034] S2: A 20% by mass sulfuric acid is added to the first strong oxidation reaction tank. The pH is adjusted to 4.0 by real-time feedback from an online pH monitor.

[0035] S3: A composite catalyst (cobalt nitrate-nickel nitrate supported activated carbon, Co / Ni molar ratio 1.5:1) accounting for 1.5% of the COD mass of the wastewater is added. The composite catalyst is prepared by the following steps: coconut shell activated carbon with a particle size of 4 mm is pretreated with 20% nitric acid; cobalt nitrate and nickel nitrate (Co / Ni molar ratio 1.5:1) are supported, and the reaction is carried out at a constant temperature of 82°C for 9 hours; carbonization is carried out at 800°C for 2.5 hours to form a cobalt-nickel bimetallic activated carbon catalyst with a specific surface area of 850 m 2 / g.

[0036] S4: Hydrogen peroxide is added at a H2O2 / COD mass ratio of 2.2:1, and a blower is started to aerate through a microporous aerator (pore size 70 μm). The ORP value is controlled at 400 mV, the temperature is 30°C, and the reaction time is 90 minutes.

[0037] S5: Lime milk is added to adjust the pH to 7.5, and the mixture is pumped into a slanted tube sedimentation tank. The slanted tube of the slanted tube sedimentation tank has an inclination angle of 60° and a pore size of 50 mm. The surface load is 1.2 m 3 / (m 2 ·h). PAC (30 mg / L) and PAM (1 mg / L) are added for coagulation and sedimentation. The PAC dosage is automatically optimized by the control system based on the influent nickel ion concentration (6.7 mg PAC is added for every 1 mg / L Ni 2+ ).

[0038] S6: The supernatant from the first stage of sedimentation is pumped into a second strong oxidation reaction tank, and steps S1-S5 are sequentially performed. The parameters of the submersible stirrer are the same as above. A 20% by mass sulfuric acid is added to adjust the pH to 4.0. The above-mentioned composite catalyst accounting for 1.5% of the COD mass of the supernatant from the first stage of sedimentation is added, and the mixture is stirred for 5 minutes. Hydrogen peroxide is added at a H2O2 / COD mass ratio of 1.3:1 (based on the remaining COD of the supernatant from the first stage of sedimentation). Simultaneous aeration is carried out through a microporous aerator with a pore size of 70 μm. The ORP value is controlled at 400 mV, the temperature is 30°C, and the reaction time is 70 minutes. Lime milk is added to adjust the pH to 7.5, and the mixture is pumped into a slanted tube sedimentation tank (parameters are the same as above). PAC (30 mg / L) and PAM (1 mg / L) are added for coagulation and sedimentation.

[0039] S7: The supernatant of the secondary precipitation enters a tertiary strong oxidation tank, and H2O2 is added after adjusting the pH to 4.0 (H2O2 / COD = 0.7:1, calculated based on the residual COD of the supernatant of the secondary precipitation). The aeration system of the tertiary strong oxidation tank uses ozone-air mixed aeration, and the ozone dosage is 15 mg / L. The ozone is used to oxidize hypophosphite to orthophosphate and to deeply degrade COD. The ORP value is controlled at 350 mV, and the temperature is 32°C. After 45 minutes of reaction, lime is added to adjust the pH to 11.5, and the precipitation is performed for 40 minutes to remove residual heavy metals and phosphorus.

[0040] S8: The supernatant of the tertiary precipitation enters an A / O system after adjusting the pH to 7.0. The sludge return ratio of the A / O system is 70%, and the mixed liquor return ratio is 250%. The specific surface area of the filler in the anaerobic tank is 550 m 2 / m 3 , and the hydraulic retention time is 5 hours. The biological filter (particle size 4 mm) is used in the aerobic tank, the aeration rate is 3 L / (m 3 ·h), the sludge concentration is 4000 mg / L, the dissolved oxygen is 3 mg / L, and the suspended solids and COD are simultaneously removed by biological degradation.

[0041] S9: The sludge from each stage of precipitation is concentrated (moisture content 92%) and then pressure-filtered for dewatering (moisture content 78%). The nickel in the dewatered sludge is recovered by acid leaching using a 15% sulfuric acid solution at a liquid-solid ratio of 6:1 at 55°C for 2.5 hours, with a recovery rate of 96%. The remaining sludge is mixed with cement, fly ash, and other solidifying agents at a sludge to solidifying agent mass ratio of 4:1, and then uniformly stirred and cured for 10 days. After testing, it meets the safety landfill standard and is safely landfilled.

[0042] S10: The concentrated water after the tertiary strong oxidation is concentrated by 3-stage serial membrane distillation. The operating temperature is 70°C for the first stage, 60°C for the second stage, and 50°C for the last stage. The membrane assembly is made of hydrophobic polyvinylidene fluoride material with a molecular weight cutoff of 700 Da. The concentration ratio of each stage is controlled at 2.5, and the transmembrane pressure difference is maintained at 0.03 MPa. The water temperature on the condensation side is 25°C. The nickel concentration in the concentrated liquid is tracked in real time through an online monitoring system, and the final nickel concentration in the concentrated liquid reaches 15.2%. The concentrated liquid is reused in the electroplating solution. The COD of the membrane-produced water is 7 mg / L, and the total nickel content is 0.07 mg / L. After ultraviolet disinfection (dose 35 mJ / cm 2 ), it is reused as rinse water in the production line.

[0043] Example 2

[0044] A 2L sample of mixed chemical nickel and electroplating nickel wastewater is used, with an initial COD of 1800 mg / L and a nickel ion concentration of 230 mg / L.

[0045] S1: The wastewater is pumped from the water collecting pool to the first strong oxidation reaction tank by a lifting pump. When the liquid level reaches 80% of the preset volume, the submersible agitator (double-layer turbine paddle, paddle coated with polytetrafluoroethylene corrosion-resistant layer) is started. The rotation speed is 80 r / min during the medicament adding stage and is reduced to 40 r / min during the reaction stage.

[0046] S2: 20% sulfuric acid is added, and the pH is adjusted to 4.1 by the pH online monitor.

[0047] S3: 2% of the COD mass of the wastewater is added to the composite catalyst (Co / Ni molar ratio 2:1). The preparation process is as follows: 3 mm particle size coconut shell activated carbon is pretreated with 10% nitric acid; cobalt nitrate and nickel nitrate (Co / Ni molar ratio 2:1) are loaded, and the reaction is carried out at 80°C for 8 hours; carbonization is carried out at 750°C for 3 hours, and the specific surface area is 800 m 2 / g. The stirring time is 6 minutes.

[0048] S4: H2O2 / COD mass ratio 2.8:1 hydrogen peroxide is added, aeration is carried out by a 50 μm pore size microporous aerator, the ORP value is controlled at 300 mV, the temperature is 25°C, and the reaction time is 110 minutes.

[0049] S5: Lime milk is added to adjust the pH to 7.0, and the sludge is pumped into the inclined pipe sedimentation tank (inclination angle 60°, pore size 50 mm, surface load 1.0 m 3 / (m 2 ·h). PAC (50 mg / L, automatically optimized by the control system based on the nickel ion concentration in the influent, and 10 mg PAC is added for each 1 mg / L Ni 2+ ) and PAM (2 mg / L) are added for coagulation and sedimentation.

[0050] S6: The supernatant of the first stage sedimentation is introduced into the second strong oxidation reaction tank, and S1-S5 are repeated. The hydrogen peroxide addition amount is H2O2 / COD mass ratio 2:1 (based on the residual COD of the supernatant of the first stage sedimentation), the reaction time is 90 minutes, and the other parameters are the same as before.

[0051] S7: The supernatant of the second stage sedimentation is introduced into the third strong oxidation reaction tank, hydrogen peroxide is added after adjusting the pH to 4.1 (H2O2 / COD=1:1), ozone-air mixed aeration is used (ozone addition amount 20 mg / L), the ORP value is controlled at 250 mV, the temperature is 25°C, the reaction time is 60 minutes, lime is added to adjust the pH to 11.0, and the sedimentation time is 45 minutes.

[0052] S8: The supernatant of the third stage sedimentation is introduced into the A / O system after adjusting the pH to 6.5. The sludge return ratio of the A / O system is 50%, and the mixed liquor return ratio is 200%. The specific surface area of the anaerobic tank filler is 500 m 2 / m 3The hydraulic retention time is 4 hours; the aerobic tank uses biological filter media (3mm particle size) with an aeration rate of 2L / (m³). 3 •h), sludge concentration 3000mg / L, dissolved oxygen 2mg / L.

[0053] S9: After the sedimentation sludge is concentrated (moisture content 95%), it is dewatered by filter press (moisture content 80%). The dewatered sludge is acid-leached to recover nickel (10% sulfuric acid, liquid-solid ratio 5:1, stirring reaction at 50℃ for 2 hours), with a recovery rate of 95%. The remaining sludge is solidified and stabilized before being safely landfilled.

[0054] S10: The concentrated water after the third-stage strong oxidation is concentrated by a four-stage tandem membrane distillation process. The operating temperatures are 80℃ for the first stage, 70℃ for the second stage, 60℃ for the third stage, and 50℃ for the final stage. The membrane module is made of hydrophobic polyvinylidene fluoride with a molecular weight cutoff of 500 Da. The concentration factor per stage is 2 times, the transmembrane pressure difference is 0.02 MPa, the condensate side water temperature is 28℃, and the concentrate has a nickel concentration of 17.5% and is recycled to the electroplating solution. The membrane permeate has a COD of 6 mg / L and a total nickel content of 0.05 mg / L. After disinfection, it is recycled to the production line rinsing water.

[0055] Example 3

[0056] Take 3L of mixed wastewater from electroless nickel plating and nickel electroplating, with an initial COD of 1500mg / L and a nickel ion concentration of 200mg / L.

[0057] S1: Wastewater is pumped into the primary strong oxidation reaction tank. When the liquid level reaches 90% of the preset volume, the submersible agitator is started (double-layer turbine blades, the speed is 120r / min during the reagent addition stage and reduced to 60r / min during the reaction stage, and the blades are covered with a polytetrafluoroethylene anti-corrosion layer).

[0058] S2: Add 20% sulfuric acid to adjust the pH to 3.9 (controlled by an online pH monitor).

[0059] S3: A composite catalyst (Co / Ni molar ratio 1.8:1) accounting for 1.8% of the wastewater COD mass was added. Its preparation involved: 5mm coconut shell activated carbon pretreated with 30% nitric acid; loaded with cobalt nitrate and nickel nitrate (Co / Ni molar ratio 1.8:1); reacted at 85℃ for 10 hours; and carbonized at 850℃ for 2 hours, resulting in a specific surface area of ​​900 m². 2 / g, stir for 7 minutes to disperse.

[0060] S4: Add hydrogen peroxide at a mass ratio of H2O2:COD of 2.4:1, aerate through a 100μm microporous aerator, control the ORP value at 550mV, the temperature at 40℃, and react for 60 minutes.

[0061] S5: Add lime slurry to adjust the pH to 8.0, then pump it into the inclined tube sedimentation tank (surface loading 1.5m). 3 / (m 2(·h), other parameters are the same as before), add PAC (10mg / L, per 1mg / L Ni) 2+ Add 5 mg PAC and 0.5 mg / L PAM for coagulation and sedimentation.

[0062] S6: The supernatant of the primary sedimentation enters the secondary strong oxidation reaction tank, and S1-S5 are repeated. The amount of hydrogen peroxide added is 1:1 (based on the remaining COD of the primary sedimentation supernatant) and the reaction is carried out for 60 minutes.

[0063] S7: The supernatant from the secondary sedimentation enters the tertiary strong oxidation reaction tank. After adjusting the pH to 3.9, hydrogen peroxide (H2O2 / COD = 0.5:1) is added, followed by ozone-air mixed aeration (ozone 10mg / L). The ORP value is controlled at 450mV and the temperature at 40℃. After reacting for 30 minutes, lime is added to adjust the pH to 12.0, and sedimentation is allowed for 30 minutes.

[0064] S8: The supernatant from the tertiary sedimentation is adjusted to pH 7.5 before entering the A / O system. The sludge return ratio is 100%, and the mixed liquor return ratio is 300%. The anaerobic tank packing material has a specific surface area of ​​600 m². 2 / m 3 Hydraulic retention time: 6 hours; aerobic tank biological filter media (5mm particle size), aeration rate: 5L / (m³). 3 •h), sludge concentration 5000mg / L, dissolved oxygen 4mg / L.

[0065] S9: Sludge thickening (moisture content 93%), filter press (moisture content 75%), acid leaching to recover nickel (20% sulfuric acid, liquid-to-solid ratio 8:1, stirring reaction at 60℃ for 3 hours), recovery rate 97%, and landfill after solidification of the remaining sludge.

[0066] S10: The concentrated water after three-stage strong oxidation is concentrated by five-stage tandem membrane distillation. The operating temperature is 80℃ for the first stage and 40℃ for the last stage, with a 10℃ decrease for each stage. The membrane module has a molecular weight cutoff of 1000 Da, a concentration factor of 3 times for each stage, and a transmembrane pressure difference of 0.05 MPa. The concentrate has a nickel concentration of 16% and is reused in the electroplating solution. The membrane permeate has a COD of 8 mg / L and a total nickel concentration of 0.08 mg / L, which is reused in the production line.

[0067] Example 4

[0068] The treatment process involved 4L of mixed wastewater from electroless nickel plating and nickel electroplating, with an initial COD of 1400 mg / L and a nickel ion concentration of 210 mg / L.

[0069] S1: The booster pump delivers the wastewater to the primary strong oxidation reaction tank. When the liquid level reaches 82%, the submersible agitator is started (speed 80-120r / min, 40-60r / min during the reaction stage, PTFE corrosion protection).

[0070] S2: Add 20% sulfuric acid to adjust the pH to 4.2.

[0071] S3: Composite catalyst (Co / Ni molar ratio 1:1) was added with 2.5% of COD mass, preparation process: 3mm activated carbon of coconut shell was pretreated with 15% nitric acid; cobalt nitrate and nickel nitrate (1:1) were loaded, 80℃ reaction for 8 hours; carbonization at 750℃ for 3 hours, specific surface area 820m 2 / g, stirring for 6 minutes.

[0072] S4: H2O2 / COD = 3:1, hydrogen peroxide was added, 70μm microporous aeration, ORP 450mV, 35℃ reaction for 80 minutes.

[0073] S5: Lime milk was used to adjust pH to 7.2, inclined tube sedimentation tank (surface load 1.3m 3 / (m 2 ·h), PAC 25mg / L (7mg per 1mg / L Ni 2+ was added), PAM 1.2mg / L coagulation and sedimentation.

[0074] S6: Secondary strong oxidation reaction tank repeated S1-S5, H2O2 / COD = 1.5:1, reaction for 80 minutes.

[0075] S7: Tertiary strong oxidation reaction tank, pH 4.2, H2O2 / COD = 0.8:1, ozone 15mg / L aeration, ORP 380mV, 35℃ reaction for 40 minutes, pH adjustment to 11.2 for 35 minutes of sedimentation.

[0076] S8: A / O system, pH 7.0, sludge return ratio 70%, mixed liquor return ratio 250%; anaerobic tank hydraulic retention 5 hours; aerobic tank aeration amount 4L / (m 3 ·h), sludge concentration 4000mg / L, dissolved oxygen 3mg / L.

[0077] S9: Sludge concentration (94%) filter pressing (78%), acid leaching (15% sulfuric acid, liquid-solid ratio 7:1, 55℃ for 2.5 hours), nickel recovery rate 96%.

[0078] S10: 3-stage membrane distillation concentration, temperature 70-50℃, 10℃ per stage, concentration ratio 2.5 times, concentrated liquid nickel 16.5% for reuse, membrane water production COD 5mg / L, total nickel 0.06mg / L for reuse.

[0079] Example 5

[0080] For 5L of mixed wastewater of chemical nickel and electroplating nickel, initial COD 2000mg / L, nickel ion concentration 260mg / L.

[0081] S1: The water was pumped to the first-stage strong oxidation reaction tank, liquid level 88% to start the stirrer (parameters same as before).

[0082] S2: pH 3.8 adjusted with 20% sulfuric acid.

[0083] S3: Composite catalyst (Co / Ni = 1.2:1) with 3% COD mass added, prepared: 5 mm coconut shell activated carbon pretreated with 25% nitric acid; 85°C for 10 hours after loading; 850°C carbonization for 2 hours, specific surface area 900 m 2 / g, stirring for 5 minutes.

[0084] S4: H2O2 / COD = 2.5:1, 80 μm aeration, ORP 480 mV, 38°C for 100 minutes.

[0085] S5: pH 7.8 adjusted with lime milk, inclined tube sedimentation tank (1.4 m 3 / (m 2 ·h), PAC 40 mg / L (8 mg of Ni 2+ per 1 mg / L), PAM 1.5 mg / L coagulation and sedimentation.

[0086] S6: Secondary strong oxidation H2O2 / COD = 1.8:1, reaction time 75 minutes.

[0087] S7: Tertiary strong oxidation pH 3.8, H2O2 / COD = 0.9:1, ozone 18 mg / L, ORP 320 mV, 38°C for 50 minutes, pH 11.8 sedimentation for 38 minutes.

[0088] S8: A / O system pH 7.2, sludge return 80%, mixed liquor 280%; anaerobic tank 5.5 hours; aerobic tank aeration 4.5 L / (m 3 ·h), sludge 4500 mg / L, dissolved oxygen 3.5 mg / L.

[0089] S9: Sludge concentration 92%, filter pressing 76%, acid leaching recovery of nickel 98%.

[0090] S10: 4-stage membrane distillation, temperature 75-45°C, 7.5°C decrease per stage, concentrated liquid nickel 18.5% for reuse, membrane water production COD 4 mg / L, total nickel 0.04 mg / L for reuse.

[0091] Comparative Example 1

[0092] Take 1 L of electroplating nickel wastewater, initial COD 1200 mg / L, nickel ion concentration 180 mg / L. Directly add lime milk to wastewater to adjust pH to 8.0, add PAC 30 mg / L and PAM 1 mg / L, stir for 30 minutes and then stand for 60 minutes. The supernatant is directly discharged, and the sludge is directly landfilled after concentration and pressure filtration, without nickel recovery. The effluent COD is 850 mg / L, the nickel ion concentration is 72 mg / L, and the nickel recovery rate is 0%.

[0093] Comparative Example 2

[0094] Take 1 L of the same type of wastewater (initial COD 1200 mg / L, nickel ion concentration 180 mg / L), only use one-stage strong oxidation reaction (parameters same as Example 1 one-stage reaction), without secondary and tertiary strong oxidation and A / O biological treatment, directly concentrated by membrane distillation. The concentrated liquid after treatment has a nickel concentration of 8.5%, the membrane product water has a COD of 120 mg / L, a nickel ion concentration of 1.2 mg / L, and a nickel recovery rate of 65%.

[0095] The experimental data table of the examples and comparative examples is as follows:

[0096]

[0097]

[0098] The effluent after treatment of Examples 1-5 has a COD of 4-8 mg / L, a nickel ion concentration of 0.04-0.08 mg / L, a nickel recovery rate of 95%-98%, and a concentrated liquid nickel concentration of 15.2%-18.5%, which are much better than Comparative Example 1 (COD 850 mg / L, nickel 72 mg / L, recovery rate 0%) and Comparative Example 2 (COD 120 mg / L, nickel 1.2 mg / L, recovery rate 65%, concentrated liquid nickel 8.5%); this is because the traditional chemical precipitation method can only remove suspended organic matter and free nickel, and the simplified oxidation process cannot deeply degrade difficult-to-oxidize organic matter and completely break the complex nickel, while the integrated process of "three-stage gradient oxidation and complexation + A / O biological deep degradation + membrane distillation concentration and recovery" in the present scheme realizes the stepwise degradation of organic matter, the complete removal of complex nickel, and the efficient recovery of nickel resources, and performs well in COD removal, heavy metal purification, and resource recovery in three dimensions, with both environmental and economic benefits, suitable for industrial treatment of chemical nickel and electroplating nickel wastewater.

[0099] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent ones. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the advanced oxidation treatment of electroless nickel, electroplating nickel wastewater, characterized in that, Comprise the following steps in turn: S1, the wastewater is pumped from the water collecting pool to the first strong oxidation reaction pool by the lifting pump, a liquid level sensor is arranged in the pool, when the liquid level reaches 80% to 90% of the preset volume, the sensor triggers the control system to start the submersible stirring device; S2, 20% sulfuric acid is added to the first strong oxidation reaction pool, the pH online monitor is used for real-time feedback, and the pH of the wastewater is accurately adjusted to 4.0±0.2; S3, the composite catalyst is added, the composition is cobalt nitrate-nickel nitrate supported activated carbon, the Co / Ni molar ratio is 1:1 to 2:1, the addition amount is 1% to 3% of the wastewater COD mass, and the stirring is greater than or equal to 5 minutes to make it uniformly dispersed; S4, hydrogen peroxide is added according to the H2O2 / COD mass ratio of 2:1 to 3:1, the air blower is started synchronously, and aeration is performed through the microporous aerator with a pore diameter of 50 to 100 μm, the ORP value is controlled to be 300 to 550 mV, the temperature is 25 to 40 ℃, and the reaction is performed for 60 to 120 minutes; S5, lime milk is added to adjust the pH to 7.0 to 8.0, the mixed solution is pumped into the inclined pipe sedimentation tank, and 10 to 50 mg / L of PAC and 0.5 to 2 mg / L of PAM are added for coagulation and sedimentation; S6, the supernatant of the first stage sedimentation is introduced into the second strong oxidation reaction pool, steps S1 to S5 are repeated, hydrogen peroxide is added according to the H2O2 / COD mass ratio of 1:1 to 2:1, the addition of hydrogen peroxide is based on the residual COD of the supernatant of the first stage sedimentation, the air blower is started synchronously, aeration is performed through the microporous aerator with a pore diameter of 50 to 100 μm, the ORP value is controlled to be 300 to 550 mV, the temperature is 25 to 40 ℃, and the reaction is performed for 60 to 90 minutes; S7, the supernatant of the second stage sedimentation is introduced into the third strong oxidation reaction pool, hydrogen peroxide is added after the pH is adjusted to 4.0±0.2, the H2O2 / COD mass ratio is 0.5:1 to 1:1, the addition of hydrogen peroxide is based on the residual COD of the supernatant of the second stage sedimentation, the aeration system is started synchronously, the ORP value is controlled to be 250 to 450 mV, the temperature is 25 to 40 ℃, the reaction is performed for 30 to 60 minutes, then lime is added to adjust the pH to be greater than or equal to 11.0, and sedimentation is performed for 30 to 45 minutes to remove residual heavy metals and phosphorus; S8, the supernatant of the tertiary precipitation is adjusted to pH 6.5-7.5 and then enters the A / O system, the anaerobic tank has a specific surface area of filler ≥500 m 2 / m 3 , and the hydraulic retention time is 4-6 hours; the aerobic tank has an aeration rate of 2-5 L / (m 3 ·h), a sludge concentration of 3000-5000 mg / L, and a dissolved oxygen of 2-4 mg / L; S9, the sludge of each stage of sedimentation is concentrated (the water content is less than or equal to 95%) and then pressure-filtered for dewatering (the water content is less than or equal to 80%), and the nickel resource recovery rate in the sludge cake is greater than or equal to 95%.

2. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 1, characterized in that, The submersible stirrer adopts double-layer turbine paddles, the rotation speed is 80 to 120 r / min in the medicament adding stage, and is reduced to 40 to 60 r / min in the reaction stage, and the paddle surface is coated with a polytetrafluoroethylene anticorrosive layer.

3. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 2, characterized in that: The composite catalyst is prepared through the following steps: The coconut shell activated carbon with a particle size of 3 to 5 mm is pretreated by 10% to 30% nitric acid; The Co / Ni molar ratio of the loaded cobalt nitrate and nickel nitrate is 1:1 to 2:1, and the constant-temperature reaction is performed at 80 to 85 ℃ for 8 to 10 hours; 750~850℃ carbonization 2~3 hours, forming cobalt-nickel double metal active carbon catalyst, specific surface area ≥800m 2 / g.

4. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 3, characterized in that: The inclined tube sedimentation tank has an inclination angle of 60°, an aperture of 50 mm, and a surface loading of 1.0–1.5 m. 3 / (m 2 ·h); The PAC dosage is determined by the control system based on the influent nickel ion concentration according to the ratio of 1 mg / L Ni 2+ Add 5-10 mg of PAC for automatic optimization.

5. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 4, characterized in that: The aeration system of the third strong oxidation reaction pool adopts ozone-air mixed aeration, the ozone addition amount is 10 to 20 mg / L, and is used for oxidizing hypophosphite to orthophosphate and deeply degrading COD.

6. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 5, characterized in that: The sludge reflux ratio of the A / O system is 50% to 100%, and the mixed liquor reflux ratio is 200% to 300%; the aerobic tank adopts biological filter material with a particle size of 3 to 5 mm, simultaneously intercepts suspended solids and biodegrades COD, and the effluent COD is less than or equal to 30 mg / L.

7. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 5, characterized in that: Nickel in the dewatered sludge is recovered by acid leaching, and the recovery rate is greater than or equal to 95%; the residual sludge is safely landfilled after solidification and stabilization.

8. The process for advanced oxidation treatment of electroless nickel and electroplating nickel wastewater according to claim 5, characterized in that: The concentrated water after three-stage strong oxidation is concentrated by membrane distillation in multiple stages; the stages are operated in series and countercurrently; the feed of the first stage is the concentrated water after three-stage strong oxidation; after concentration in the first stage, the concentrated water enters the next stage as feed; the operating temperature of each stage decreases by 5 to 10°C along the water flow direction, and is 60 to 80°C for the first stage and 40 to 60°C for the last stage; the membrane assembly is made of hydrophobic polyvinylidene fluoride material with a molecular weight cut-off of 500 to 1000 Da; the concentration ratio of each stage is controlled to be 2 to 3; the transmembrane pressure difference is maintained at 0.02 to 0.05 MPa; the water temperature on the condensation side is less than or equal to 30°C; the nickel concentration of the concentrated liquid of each stage is tracked in real time through an online monitoring system; when the nickel concentration in the concentrated liquid of the last stage is greater than or equal to 15%, the concentration is stopped and the concentrated liquid is reused for electroplating solution; the water produced by the membranes of all stages is combined, and the COD is less than or equal to 10 mg / L, and the total nickel content is less than or equal to 0.1 mg / L; after disinfection, the water is reused for production line flushing water.

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