Recovery treatment process of heavy metal production wastewater

Abstract

The invention discloses a recovery treatment process of heavy metal production wastewater, and relates to the technical field of wastewater treatment. Adjusting the pH value of the wastewater through pretreatment and stirring; 5%-10% of nanometer seed crystals are added in the seed crystal reinforced vulcanization process, a vulcanizing agent is controllably added, and large-particle-size precipitates are generated through pulse stirring; magnetic field separation is performed after magnetic microsphere adsorption; carrying out selective adsorption and acid regeneration on the chitosan-based magnetic resin; micro pollutants are removed through cooperation of the three-dimensional electrode and photocatalysis; concentrating 10-20 times by membrane distillation to enrich heavy metals; metal simple substances with the purity larger than or equal to 99.5% are recycled through pulse electrodeposition; and after deep treatment, the wastewater reaches the standard to be discharged or recycled (the recycling rate is greater than or equal to 70%). The process innovation comprises the steps of enhancing the seed crystal to improve the vulcanization efficiency by 30%, realizing rapid separation by a magnetic material, reducing the energy consumption by 40% by a three-dimensional electrode coupling membrane method, and constructing a vulcanizing agent regeneration (the regeneration rate is greater than or equal to 85%) and heavy metal closed-loop recovery system. Compared with a traditional process, the heavy metal removal rate is larger than or equal to 99.8%, the treatment cost of each ton of water is reduced by 25%-30%, and the method has the advantages of high efficiency, low consumption, environmental protection and recycling and is suitable for multi-metal complex wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a recovery and treatment process for heavy metal production wastewater. Background Art

[0002] With the rapid development of industries such as metallurgy, electroplating, and electronics, the discharge of heavy metal wastewater has been increasing year by year. Such wastewater contains heavy metal ions such as lead, cadmium, mercury, and chromium. If directly discharged without effective treatment, it will pose a serious threat to the ecological environment and human health. Traditional treatment methods such as neutralization precipitation, ion exchange, and electrochemistry have the following defects: Low sulfide precipitation efficiency: The natural nucleation process is slow, the precipitation particles are fine (1 - 2μm), filtration and dehydration are difficult, and the utilization rate of sulfiding agents is only 70% - 80%; Incomplete resource recovery: Traditional processes mostly treat in the form of heavy metal sludge, with low metal recovery rate (95% - 98%), and there is a risk of secondary pollution; High energy consumption cost: Electrochemical treatment relies on high - energy - consuming two - dimensional electrodes, and the membrane separation process is easily blocked by pollutants, resulting in high operating costs; Insufficient co - treatment ability: There is a lack of efficient co - removal means for heavy metal ions and organic pollutants in complex water quality.

[0003] In the prior art, although combined processes have been tried to improve the treatment effect, there are still significant technical bottlenecks in aspects such as the controllability of the precipitation process, selective adsorption of materials, efficient energy utilization, and closed - loop resource recovery. Therefore, there is an urgent need to develop a new process with high - efficiency treatment, low - energy consumption, and resource recovery. Summary of the Invention

[0004] Aiming at the defects of the prior art, the present invention provides a recovery and treatment process for heavy metal production wastewater, achieving: controllability and high efficiency of the sulfide precipitation process, reducing chemical consumption; directional adsorption and deep removal of heavy metal ions, improving resource recovery rate; deep purification and cascade reuse of wastewater, and constructing a green treatment cycle system.

[0005] To solve the above - mentioned technical problems, the technical solution adopted by the present invention is as follows: A recovery and treatment process for heavy metal production wastewater, comprising the following steps: S1. Pretreatment: Introduce the wastewater into an adjustment tank, adjust the pH to the neutral range and stir evenly; S2. Seed - enhanced sulfidation: Add sulfide nanocrystalline seeds accounting for 5% - 10% of the total molar amount of heavy metal ions to the pretreated wastewater, add the sulfiding agent at a controllable flow rate, and control the supersaturation of the reaction system through on - line monitoring and trigger pulse stirring to generate large - particle - size sulfide precipitates; S3. Magnetic solid-liquid separation: Magnetic microspheres are added to form magnetic composite flocs, and the solid-liquid mixture is rapidly separated by a magnetic field. S4. Selective ion adsorption: The filtrate is selectively adsorbed through an exchange column filled with magnetic chelating resin, and the saturated resin is regenerated with an acid solution. S5. Three-dimensional electric field treatment: The wastewater enters a treatment tank equipped with composite electrodes, and a pulsed voltage is applied to form a three-dimensional electric field to synergistically remove trace heavy metal ions and organic pollutants. S6. Membrane distillation concentration and enrichment: The treated wastewater is concentrated through a membrane distillation device to achieve the enrichment of heavy metal ions. S7. Pulsed electroplating recovery: Pulsed current electroplating is used for the concentrated solution to recover heavy metal single elements or alloys. S8. Advanced treatment to meet the standards: The concentrated solution is discharged up to standard or recycled after adsorption and filtration.

[0006] Furthermore, in step S2, the sulfide nanoseeds are bimetallic composite seeds with a particle size of 50 - 100 nm, prepared by the coprecipitation method, and the seed dosage is 5% - 10% of the total molar amount of heavy metal ions.

[0007] Furthermore, in step S3, the magnetic microspheres are Fe3O4 microspheres with a particle size of 1 - 5 μm, the dosage is 50 - 100 mg / L, the magnetic separation intensity is 0.1 - 0.3 T, and the separation time ≤ 5 min.

[0008] Furthermore, in step S4, the magnetic chelating resin is a chitosan-based core-shell structure resin with a particle size of 0.3 - 0.6 mm, the exchange capacity ≥ 2.5 mmol / g, the adsorption flow rate is 5 - 10 BV / h, and the concentration of the regenerating acid solution is 2 - 4 mol / L.

[0009] Furthermore, in step S5, the composite electrodes are a combination of a titanium foam-based coated anode and a graphene-modified cathode, the pulsed voltage applied is 4 - 8 V, the frequency is 50 - 100 Hz, the current density is 15 - 25 mA / cm², and the electrolysis time is 30 - 60 min.

[0010] Furthermore, in step S6, the membrane distillation device uses a polytetrafluoroethylene hollow fiber membrane with a pore size of 0.2 - 0.4 μm, the operating pressure < 5 kPa, the temperature is 40 - 50 °C, and the concentration multiple is 10 - 20 times.

[0011] Furthermore, in step S7, the pulsed electroplating uses a rotating cathode with a rotation speed of 500 - 1000 r / min, the peak current density is 50 - 80 mA / cm², the duty cycle is 1:2, the deposition time is 20 - 30 min, and the heavy metal recovery rate ≥ 99%.

[0012] Further, in step S1, the neutral pH range is 6 - 8, the stirring speed is 100 - 200 r / min, and the stirring time is 10 - 30 min.

[0013] Further, an ultrasonic strengthening step is added between step S2 and step S3, and ultrasonic waves with a frequency of 20 - 40 kHz and a power density of 0.3 - 0.8 W / cm² are used to promote the dispersion and reaction of the seed crystals.

[0014] Further, in step S8, the adsorption filtration uses a combination of an activated carbon adsorption column and a security filter. The pore diameter of the security filter element is 5 - 10 μm, and the quality of the recycled water meets the industrial water standard. Compared with the prior art, the present invention has the following beneficial effects: The heavy metal production wastewater treatment process of the present invention includes: pretreatment to adjust the pH of the wastewater and stir; seed crystal enhanced sulfidation to add nano seed crystals, controllably add a sulfiding agent and pulse stir to generate large - particle precipitates; add magnetic microspheres and then separate by magnetic field; the filtrate is selectively adsorbed by magnetic chelating resin, and the saturated resin is regenerated by acid; three - dimensional electrode synergistic photocatalysis to remove trace pollutants; membrane distillation to concentrate and enrich heavy metals; pulse electro - deposition to recover high - purity metals; after deep treatment, the wastewater meets the discharge standard or is recycled. This process improves the precipitation efficiency through seed crystal enhancement and magnetic separation, enhances the adsorption performance through material innovation, reduces energy consumption through the coupling of three - dimensional electrodes and membrane methods, constructs a closed - loop system to realize reagent regeneration, metal recovery and wastewater recycling, and has the advantages of high efficiency, low consumption, high resource recovery rate and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0018] The present invention provides a recovery and treatment process for heavy metal production wastewater, including the following core steps: 1. Pretreatment Introduce the wastewater into the regulation tank, monitor it in real time through a pH sensor, and add acid / alkali regulators such as NaOH and H2SO4 to adjust the pH to 6 - 8, that is, the neutral range. At the same time, turn on the mechanical stirring device with a stirring speed of 100 to 200 revolutions per minute for 10 to 30 minutes to make the water quality and quantity uniform and stable, creating conditions for subsequent treatment.

[0019] 2. Seed - enhanced sulfidation Add 5% - 10% of sulfide nanoseeds, calculated based on the total molar amount of heavy metal ions, such as CuS / FeS bimetallic composite seeds with a particle size of 50 to 100 nanometers, to the pretreated wastewater. Use a peristaltic pump to uniformly add sodium sulfide solution at a speed of 0.5 to 1.0 milliliters per minute. Monitor the reaction system in real time through an online turbidimeter. When the turbidity reaches 300 to 500 NTU, trigger pulsed stirring with a stirring speed of 200 to 300 revolutions per minute for 10 to 15 seconds. By controlling the supersaturation, promote the oriented nucleation of heavy metal ions on the seed surface to generate large - particle sulfide precipitates with an average particle size of not less than 5 microns. The reaction time is shortened to 15 to 30 minutes, and the dosage of the sulfiding agent is reduced by 25% - 30%.

[0020] 3. Magnetic solid - liquid separation Synchronously add Fe3O4 magnetic microspheres with a size of 1 to 5 microns at a dosage of 50 to 100 milligrams per liter. Use the active sites on the surface of the magnetic microspheres to induce heterogeneous nucleation of sulfide precipitates to form magnetic composite flocs. Rapidly separate the solid - liquid mixture through a magnetic separator with a magnetic field strength of 0.1 to 0.3 T, and the separation time does not exceed 5 minutes. The moisture content of the filter residue is reduced from 85% in the traditional process to below 60%, solving the problem of precipitate dehydration. The separated filter residue can be treated by an alkali leaching process. Use a 5 - 10 mol / L NaOH solution to regenerate sodium sulfide at 150 to 200 °C and 1.0 to 1.5 MPa, and the regeneration rate is not less than 85%, realizing the recycling of the reagent.

[0021] 4. Selective ion adsorption The filtrate enters an ion exchange column filled with chitosan@Fe3O4 core-shell resin. The resin particle size is 0.3 to 0.6 mm, with an exchange capacity of at least 2.5 mmol / g and a controlled flow rate of 5 to 10 BV / h. The shell amino groups specifically chelate heavy metal ions, while the core magnetic particles enable rapid magnetic separation of the resin, with a separation magnetic field strength of 0.1 to 0.3 T. Once the resin is saturated, it is regenerated with 2 to 4 mol / L hydrochloric acid solution at a flow rate of 3 to 5 BV / h for 60 to 90 minutes. The regeneration wastewater is collected separately for heavy metal recovery, ensuring a resin reuse rate of at least 95%.

[0022] 5. Three-dimensional electric field processing Wastewater enters a treatment tank equipped with titanium foam composite electrodes. The anode utilizes a TiO2 / IrO2-Ta2O5-coated titanium foam electrode with a pore size of 0.5 to 1.0 mm, boasting a surface area five times greater than traditional flat electrodes. The cathode utilizes a graphene-modified stainless steel mesh, creating a three-dimensional electrode reaction system. A pulsed voltage of 4 to 8V, a frequency of 50 to 100Hz, a duty cycle of 1:1 to 3:1, and a current density of 15 to 25mA / cm² is applied for 30 to 60 minutes. Through the synergistic effect of the electrode surface micro-electric field and a built-in UV-A light source with a wavelength of 365nm and an intensity of 500 to 1000μW / cm², heavy metal ion electrodeposition and organic pollutant photocatalytic degradation are achieved simultaneously. This reduces energy consumption by 30% compared to traditional two-dimensional electrodes and extends the electrode life to over 2000 hours.

[0023] 6. Membrane Concentration and Enrichment After electrolysis, the wastewater enters a polytetrafluoroethylene hollow fiber membrane distillation device with a pore size of 0.2 to 0.4 microns, an operating pressure of less than 5kPa, and a temperature of 40 to 50°C. The wastewater volume is concentrated 10 to 20 times through membrane distillation, and heavy metal ions are enriched in the concentrated liquid with an enrichment multiple of not less than 15. The residual liquid is returned to the electrochemical treatment process to achieve water resource recycling.

[0024] 7. Pulse electrodeposition recovery The concentrated liquid enters an electrodeposition tank with a rotating cathode at a speed of 500 to 1000 rpm. A pulsed current with a peak current density of 50 to 80 mA / cm² and a duty cycle of 1:2 is used for directional electrodeposition. Within 20 to 30 minutes, the heavy metal recovery rate can reach over 99%, directly obtaining a metal element or alloy powder with a purity of no less than 99.5%, solving the problem of low purity of heavy metal recovery by traditional precipitation methods.

[0025] 8. Deep processing meets standards The concentrated liquid is treated by an activated carbon adsorption column. The particle size of the activated carbon is 0.5 to 1.0 mm, and the flow rate is 3 to 5 BV / h to remove residual organic matter. Then it is filtered through a security filter with a filter element pore size of 5 to 10 microns. The final effluent quality reaches the first-level standard of the Comprehensive Wastewater Discharge Standard (GB8978 - 1996) or the Quality of Reclaimed Water for Industrial Use in Urban Areas (GB / T19923 - 2005), and can be directly discharged or reused in the production process with a reuse rate of not less than 70%.

[0026] Examples of wastewater treatment: The wastewater contains 100 mg / L of Cu²⁺, 60 mg / L of Ni²⁺, and 200 mg / L of COD: Pretreatment: The pH of the wastewater is 5.0. Add NaOH to the adjustment tank to pH = 7.5, with a stirring speed of 150 revolutions per minute for 20 minutes; Seed-enhanced sulfidation: Add CuS / FeS nanoseeds with an addition amount of 8% molar ratio. Dropwise add the sodium sulfide solution at a speed of 0.7 mL per minute. Pulse stir for 15 seconds when the turbidity reaches 400 NTU, and react for 25 minutes; Magnetic separation: Add Fe₃O₄ microspheres with an addition amount of 80 mg / L and separate with a 0.2 T magnetic field for 3 minutes. The Cu²⁺ in the filtrate is reduced to 8 mg / L and the Ni²⁺ is reduced to 5 mg / L; Ion exchange: The flow rate of the resin column is 8 BV / h. After treatment, both Cu²⁺ and Ni²⁺ are less than 0.5 mg / L. The saturated resin is regenerated with 3 mol / L hydrochloric acid; Three-dimensional electrode treatment: The voltage is 5 V, the current density is 20 mA / cm², and electrolyze for 45 minutes. The COD is reduced to 60 mg / L; Membrane distillation concentration: Concentrate 15 times, and the concentration of the heavy metal enrichment liquid is increased to 120 mg / L of Cu²⁺ and 75 mg / L of Ni²⁺; Pulse electroplating: The rotation speed of the rotating cathode is 800 revolutions per minute, the peak current is 60 mA / cm². After 25 minutes, recover the Cu-Ni alloy powder with a purity of 99.6% and a recovery rate of 99.3%; Advanced treatment: After activated carbon adsorption and security filtration, the heavy metal ions in the effluent are less than 0.05 mg / L, and the COD is less than 50 mg / L, which is reused in the electroplating cleaning process.

[0027] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0028] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative style of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A recovery and treatment process for heavy metal production wastewater, characterized in that, It includes the following steps: S1. Pretreatment: Introduce the wastewater into the regulating tank, adjust the pH to the neutral range and stir evenly; 、 S2. Seed-enhanced sulfidation: Add sulfide nanoseeds accounting for 5%-10% of the total molar amount of heavy metal ions to the pretreated wastewater. Add the sulfiding agent at a controllable flow rate, and control the supersaturation of the reaction system through on-line monitoring and trigger pulse stirring to generate large-particle-size sulfide precipitates; S3. Magnetic solid-liquid separation: Add magnetic microspheres to form magnetic composite flocs, and quickly separate the solid-liquid mixture through a magnetic field; S4. Selective ion adsorption: The filtrate is selectively adsorbed through an exchange column filled with magnetic chelating resin, and the saturated resin is regenerated by an acid solution; S5. Three-dimensional electric field treatment: The wastewater enters a treatment tank equipped with composite electrodes, a pulsed voltage is applied to form a three-dimensional electric field to synergistically remove trace heavy metal ions and organic pollutants; S6. Membrane distillation concentration and enrichment: Concentrate the treated wastewater through a membrane distillation device to achieve the enrichment of heavy metal ions; S7. Pulse electroplating recovery: Pulse current electroplating is carried out on the concentrated solution to recover heavy metal single substances or alloys; S8. Advanced treatment to meet the standards: The concentrated solution meets the discharge standards or can be reused after adsorption and filtration.

2. The recycling and treatment process according to claim 1, characterized in that, In step S2, the sulfide nanoseeds are bimetallic composite seeds with a particle size of 50-100 nm, which are prepared by the coprecipitation method, and the seed dosage is 5%-10% of the total molar amount of heavy metal ions.

3. The recycling and treatment process according to claim 1, characterized in that, In step S3, the magnetic microspheres are Fe3O4 microspheres with a particle size of 1-5 μm, the dosage is 50-100 mg / L, the magnetic field separation intensity is 0.1-0.3 T, and the separation time ≤ 5 min.

4. The recycling and treatment process according to claim 1, wherein In step S4, the magnetic chelating resin is a chitosan-based core-shell structure resin with a particle size of 0.3-0.6 mm, an exchange capacity ≥ 2.5 mmol / g, an adsorption flow rate of 5-10 BV / h, and the concentration of the regenerated acid solution is 2-4 mol / L.

5. The recycling process according to claim 1, characterized in that, In step S5, the composite electrode is a combination of a titanium foam-based coated anode and a graphene-modified cathode, a pulsed voltage of 4-8 V is applied, the frequency is 50-100 Hz, the current density is 15-25 mA / cm², and the electrolysis time is 30-60 min.

6. The recycling and treatment process according to claim 1, wherein In step S6, the membrane distillation device uses a polytetrafluoroethylene hollow fiber membrane with a pore size of 0.2-0.4 μm, the operating pressure < 5 kPa, the temperature is 40-50 °C, and the concentration multiple is 10-20 times.

7. The recycling process according to claim 1, wherein In step S7, the pulse electroplating uses a rotating cathode, the rotation speed is 500-1000 r / min, the peak current density is 50-80 mA / cm², the duty cycle is 1:2, the deposition time is 20-30 min, and the heavy metal recovery rate ≥ 99%.

8. The recycling process according to claim 1, characterized in that, In step S1, the neutral range of pH is 6-8, the stirring speed is 100-200 r / min, and the stirring time is 10-30 min.

9. The recycling and treatment process according to claim 1, characterized in that, An ultrasonic strengthening link is added between step S2 and step S3, and ultrasonic waves of 20-40 kHz and 0.3-0.8 W / cm² are used to promote the dispersion and reaction of the seeds.

10. The recycling and treatment process according to claim 1, characterized in that, In step S8, the adsorption filtration is carried out by combining an activated carbon adsorption column and a security filter. The pore diameter of the security filter element is 5 - 10 μm, and the quality of the recycled water meets the industrial water standard.

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