CN114684981B - Treatment method and system for wastewater containing heavy metals - Google Patents
Treatment method and system for wastewater containing heavy metals Download PDFInfo
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- CN114684981B CN114684981B CN202210618371.0A CN202210618371A CN114684981B CN 114684981 B CN114684981 B CN 114684981B CN 202210618371 A CN202210618371 A CN 202210618371A CN 114684981 B CN114684981 B CN 114684981B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
- C02F1/4672—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
- C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
- C02F1/4695—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis electrodeionisation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
Abstract
The invention relates to a method and a system for treating heavy metal-containing wastewater, belonging to the technical field of wastewater recycling treatment. The treatment method comprises the steps of carrying out electrooxidation treatment on the wastewater, filtering the obtained electrooxidation water product by a high-precision filter, injecting the filtered electrooxidation water product into an electrodialyzer for treatment to obtain a heavy metal-containing high-salt solution and a COD-containing low-salt solution, carrying out nanofiltration separation on the heavy metal-containing high-salt solution to obtain a nanofiltration concentrated solution and a nanofiltration filtrate, and injecting the nanofiltration filtrate into a bipolar membrane device for treatment to respectively obtain an alkali liquor and an acid liquor; injecting the acid liquor into a mixed acid separation device for treatment. The method and the system can effectively solve the problems of environmental pollution and resource waste caused by the wastewater containing the heavy metal, realize resource recycling of the miscellaneous salt in the wastewater, and have the characteristics of high treatment efficiency, high acid-base conversion rate, good quality, high heavy metal recovery rate, low operation cost and good system stability.
Description
Technical Field
The invention relates to a method and a system for treating heavy metal-containing wastewater, belonging to the technical field of wastewater recycling treatment.
Background
Can produce a large amount of heavy metal-containing waste water in industrial production processes such as chemical industry, electroplating, metal smelting, electron, wherein heavy metal is mostly poisonous and harmful and difficult by the decomposition destruction, will cause serious harm to natural environment and human health if directly discharging in the natural water body not handling, extravagant a large amount of salt and heavy metal resource moreover. Therefore, the development of an efficient and environment-friendly heavy metal-containing wastewater resource treatment technology reduces the discharge of heavy metal wastewater, improves the recovery rate of heavy metal and miscellaneous salt in the wastewater, and has important significance for the development of heavy metal industry and the ecological environment protection.
At present, methods for treating wastewater containing heavy metals mainly comprise a chemical dosing method, a biological treatment method and a physical method, but have a plurality of problems in the application process. The chemical dosing method has large medicament consumption, large sludge production amount and easy secondary pollution; the biological treatment method has low treatment efficiency and is limited by the content of salt and organic matters in the wastewater; the physical method, the adsorption method and the ion exchange method have the limitations of adsorption capacity and exchange capacity, are easy to be polluted and have high treatment cost. In recent years, membrane separation methods are mostly adopted to treat wastewater containing heavy metals and recycle heavy metal resources, but the treatment cost is higher, the pretreatment is complex, the recovery rate of the heavy metals is lower, the treatment of the obtained miscellaneous salt is difficult, the equipment replacement period is short, and the system stability is poor. Therefore, how to improve the treatment efficiency of the wastewater containing heavy metals and the recovery rate of the heavy metals and waste salt, reduce the system operation cost and improve the equipment stability is a key problem to be solved urgently at present.
Disclosure of Invention
Technical problem to be solved
In order to solve the problems in the prior art, the invention provides a method and a system for treating heavy metal-containing wastewater, which are used for solving the problem of heavy metal wastewater pollution and realizing resource recycling of heavy metal-containing wastewater.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
in one aspect, the invention provides a method for treating heavy metal-containing wastewater, which comprises the following steps:
s1, carrying out electrooxidation treatment on the wastewater containing the heavy metal ions to obtain electrooxidation water;
s2, filtering the electrooxidation water production by a high-precision filter, injecting the electroosmosis water production into an electrodialyzer for treatment, obtaining a heavy metal-containing high-salt solution in a concentrated liquid chamber of the electrodialyzer, and obtaining a COD-containing low-salt solution in a dilute liquid chamber of the electrodialyzer;
s3, carrying out nanofiltration separation on the heavy metal-containing high-salt solution to generate nanofiltration concentrated solution and nanofiltration filtrate;
s4, injecting the nanofiltration filtrate into a bipolar membrane device for treatment to respectively obtain alkali liquor and acid liquor;
and S5, injecting the acid liquor prepared in the step S4 into a mixed acid separation device for treatment.
In the above-mentioned processing method, preferably, in step S1, the anode of the device used in the electro-oxidation process is titanium-based noble metal mixed oxide, the cathode is stainless steel, and the current is 150- 2 (ii) a When COD of the water produced by electrooxidation is less than 180mg/L, the electrooxidation can be stopped for further treatment.
In the treatment method as described above, preferably, in step S2, the high-precision filter is a nano-imprinting membrane with a pore size of 50-200 nm; the polar membrane of the electrodialyzer adopts an anion exchange membrane or a monovalent selective ion exchange membrane.
As described above, preferably, in step S3, the nanofiltration separation uses a positively charged nanofiltration membrane doped with a polymer complex functional separation layer.
In the above processing method, preferably, in step S4, the bipolar membrane device uses a monolithic bipolar membrane containing modified particles, wherein the modified particles are one or more of polypyrrole coated gold nanoparticles, polypyrrole coated carbon nanotubes, polypyrrole coated graphene oxide, polyaniline coated gold nanoparticles, polyaniline coated carbon nanotubes, or polyaniline coated graphene oxide, and the elastic separation net is prepared by weaving bundled polypropylene fibers.
In the treatment method as described above, preferably, in step S5, the mixed acid separation device employs an acid separation positive membrane as the positive membrane, and employs a mono/polyvalent anion selective acid separation negative membrane as the negative membrane, and the separation selectivity is 97.5-99%.
The treatment method as described above, preferably, the COD-containing low salt solution is refluxed to the electrooxidation apparatus; the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled;
the alkali liquor obtained by the treatment of the bipolar membrane device can be recycled.
The device is suitable for common heavy metal ions such as copper ions, cadmium ions, nickel ions, cobalt ions, chromium ions, tin ions, zinc ions and the like.
In the invention, after the wastewater containing heavy metal ions is treated by electrooxidation, organic pollutants contained in the wastewater are removed, the risk of fouling and blocking of the electrodialyzer is reduced, and the quality of the subsequently recovered heavy metals can be effectively ensured. Through a large amount of experimental researches, the optimization is 150-500A/m 2 The current can effectively oxidize and degrade COD in the wastewater, if the current is too small, the reaction efficiency is reduced, the removal effect is influenced, and if the current is too large, the electrode plate is damaged and the operation energy consumption is increased.
The nano-imprinting membrane with the aperture of 50-200nm is preferably selected in the invention, and the nano-imprinting membrane can effectively retain and remove impurity pollutants due to narrow aperture distribution, thereby ensuring the operation stability of a subsequent membrane system. The electrodialyzer selects an anion exchange membrane or a monovalent selective ion exchange membrane as an electrode membrane, and can effectively avoid scaling of electrodialyzer electrode water and precipitation of metal, thereby ensuring the efficiency of the electrode plate, greatly prolonging the replacement period of the electrode plate and reducing the operation cost of the electrode plate.
According to the invention, the positively charged nanofiltration membrane is selected to efficiently intercept multivalent cations (heavy metal ions), and compared with a common conventional nanofiltration membrane (negatively charged), the functional separation layer is doped with the macromolecular complex to positively charge the functional separation layer, so that the interception rate of the multivalent cations is greatly improved, heavy metal resources are fully recycled, and the purity and quality of subsequent acid-base products are ensured. The nanofiltration membrane functional separation layer is doped with a high molecular complex (a divalent cation and a hydrophilic high molecular compound form the high molecular complex), so that the nanofiltration membrane is positively charged.
In step S4, in the present invention, the mechanical properties and conductivity of the bipolar membrane can be effectively enhanced by doping modified particles, and the conductive polymer-coated particles do not cause particle aggregation, and have better compatibility, thereby avoiding the generation of structural defects, so one or more modified monolithic bipolar membranes selected from polypyrrole-coated gold nanoparticles, polypyrrole-coated carbon nanotubes, polypyrrole-coated graphene oxide, polyaniline-coated gold nanoparticles, polyaniline-coated carbon nanotubes, or polyaniline-coated graphene oxide are preferred; in addition, the monolithic bipolar membrane has low resistance, strong ion transfer capacity and good catalytic water dissociation performance, can effectively improve the acid-base conversion rate and the current efficiency of the bipolar membrane, and simultaneously greatly reduces the operating cost of preparing acid and base by the bipolar membrane.
The elastic separation net prepared by weaving the bundled polypropylene fibers can enhance the sealing property of the bipolar membrane compartment, effectively improve the water flow, reduce the resistance, improve the turbulent water flow state and avoid or slow down the concentration polarization phenomenon.
In step S5, the acid separation positive membrane and the mono/polyvalent anion selective acid separation negative membrane of the present invention can separate hydrochloric acid and sulfuric acid efficiently and at low cost; if the separation selectivity is too low, the separation effect is reduced, and the purity of the acid obtained by separation is poor; on the other hand, since too high separation selectivity greatly increases equipment investment and deteriorates operation stability, a membrane having a separation selectivity of 97.5 to 99% is preferable.
On the other hand, the invention also provides a treatment system of the wastewater containing the heavy metals, which comprises an electrooxidation device, a high-precision filter, an electrodialyzer, a nanofiltration device, a bipolar membrane device and a mixed acid separation device which are arranged in sequence;
wherein the water production side of the electrooxidation device is connected with the water inlet of the high-precision filter, and the filtrate side of the high-precision filter is connected with the water inlet of the electrodialyzer and is connected with the fresh water chamber of the electrodialyzer;
the electrodialyzer is provided with a positive electrode and a negative electrode, anode membranes, anion exchange membranes, cation exchange membranes and cathode membranes are alternately stacked between the positive electrode and the negative electrode, wherein the middle part represents that the anion exchange membranes and the cation exchange membranes are repeatedly stacked, a plurality of pairs of anion exchange membranes and cation exchange membranes are stacked according to needs, an anode chamber is formed between the positive electrode and the adjacent anode membrane, an electrodialyzer concentrated solution chamber is formed between the anode membrane and the anion exchange membranes, an electrodialyzer diluted solution chamber is formed between the anion exchange membranes and the cation exchange membranes, a cathode chamber is formed between the negative electrode and the adjacent cathode membrane, and the anode chamber and the cathode chamber are connected in series through a pipeline to form a polar chamber; the filtrate side of the high-precision filter is connected with the water inlet of the electrodialyzer and is connected with the dilute liquid chamber of the electrodialyzer; the concentrated solution chamber of the electrodialyzer is connected with the water inlet of the nanofiltration device, and the dilute solution chamber of the electrodialyzer is connected with the electrooxidation device;
the nanofiltration device is divided into a concentrated solution side and a filtrate side by a nanofiltration membrane, a feed inlet of the nanofiltration device is communicated with the concentrated solution side, the filtrate side of the nanofiltration device is connected with the feed inlet of the bipolar membrane device and is connected with a salt solution chamber of the bipolar membrane device, and the concentrated solution side of the nanofiltration device is used for outputting purified heavy metal solution;
the bipolar membrane device comprises a positive electrode and a negative electrode, wherein a bipolar membrane, a separation net, an anion exchange membrane, the separation net, a cation exchange membrane and the separation net are alternately stacked between the positive electrode and the negative electrode in sequence, an acid liquid chamber is formed between the bipolar membrane and the anion exchange membrane, and an alkali liquid chamber is formed between the bipolar membrane and the cation exchange membrane; a saline chamber is formed between the anion exchange membrane and the cation exchange membrane; the bipolar membrane device acid liquid chamber is connected with the mixed acid separation device, and the bipolar membrane device alkali liquid chamber is used for outputting alkali liquid;
the mixed acid separation device comprises a positive electrode and a negative electrode, and an anode film, a cathode film, an anode film and a cathode film which are repeatedly stacked are sequentially arranged between the positive electrode and the negative electrode; and a mixed acid separation device concentrated liquid chamber is formed between the anode membrane and the adjacent cathode membrane, and a mixed acid separation device diluted liquid chamber is formed between the cathode membrane and the adjacent anode membrane.
In the treatment system as described above, preferably, the connections are each made using a pipe or a combination of a pump and a pipe.
In the above processing system, preferably, the anode of the electro-oxidation device is titanium-based noble metal mixed oxide, the cathode is stainless steel, and the current is 150-500A/m 2 ；
The filtering membrane in the high-precision filter adopts a nano-imprinting membrane, and the aperture of the nano-imprinting membrane is 50-200 nm;
the electrode membrane of the electrodialyzer is an anion exchange membrane or a monovalent selective ion exchange membrane (one of the anion exchange membrane or the monovalent selective ion exchange membrane can be selected as the electrode membrane, the membrane adjacent to the anode and the cathode is called the electrode membrane, the anode adjacent to the anode is an anode membrane, and the cathode adjacent to the cathode is a cathode membrane;
the nanofiltration membrane adopts a positively charged nanofiltration membrane doped with a high-molecular complex functional separation layer;
the bipolar membrane device adopts a monolithic bipolar membrane containing modified particles, wherein the modified particles are one or more of polypyrrole-coated gold nanoparticles, polypyrrole-coated carbon nanotubes, polypyrrole-coated graphene oxide, polyaniline-coated gold nanoparticles, polyaniline-coated carbon nanotubes and polyaniline-coated graphene oxide, and the separation net is an elastic separation net prepared by weaving bundled polypropylene fibers;
the positive membrane in the mixed acid separation device is an acid separation positive membrane, the negative membrane is a single/polyvalent anion selective acid separation negative membrane, and the separation selectivity of the positive membrane and the negative membrane is 97.5-99%.
(III) advantageous effects
The invention has the beneficial effects that:
1. according to the method and the system for treating the wastewater containing the heavy metal, provided by the invention, the wastewater containing the heavy metal is subjected to resource recycling treatment through the electrooxidation device, the high-precision filter, the electrodialyzer, the nanofiltration device, the bipolar membrane device and the mixed acid separation device, so that the heavy metal resource is efficiently recovered, the problems of environmental pollution and resource waste caused by the wastewater containing the heavy metal are effectively solved, meanwhile, the salt solution obtained after treatment is efficiently converted into purified acid and alkali for recycling at low cost, the discharge of waste salt is reduced, the resource recycling of miscellaneous salt in the wastewater is realized, and the problem of salt disposal after wastewater treatment is effectively solved.
2. The method for treating the wastewater containing the heavy metal ions provided by the invention does not relate to medicament addition, has no secondary pollution risk, has a treatment effect not influenced by salt or organic matter content, has high wastewater treatment efficiency, high acid-base conversion rate and good quality, high heavy metal recovery rate, low operation cost, long service life of equipment and good system stability, can be practically applied to treatment of the wastewater containing the heavy metals, and can be popularized and used for resource treatment of other types of wastewater.
3. According to the treatment system for the wastewater containing the heavy metals, provided by the invention, the pore diameter of the nano-imprinting filtering membrane is accurately controlled and is distributed narrowly, so that the precise filtering effect is achieved, the pollution risk of the membrane system is reduced, and the quality of subsequent salt and acid and alkali is improved; an anion exchange membrane or a monovalent selective cation exchange membrane is adopted as an electrodialyzer of the polar membrane, so that heavy metal ions in the solution are effectively prevented from entering a polar chamber to influence the electrode efficiency, and the recovery rate of the heavy metal is improved; by using the positively charged nanofiltration membrane doped with the high-molecular complex functional separation layer, the interception effect of the nanofiltration membrane on heavy metal ions can be greatly improved, and salt and heavy metal ions can be effectively separated; the bipolar membrane device which adopts the bipolar membrane containing the modified particle single-sheet type bipolar membrane and the elastic separation net woven into the bundled polypropylene fibers effectively improves the acid-base conversion rate and the current efficiency of the bipolar membrane, reduces the operating cost of acid-base preparation of the bipolar membrane, effectively improves the turbulent water flow state, and avoids or slows down the concentration polarization phenomenon.
Drawings
FIG. 1 is a schematic flow chart of a preferred method for treating heavy metal-containing wastewater in the present invention.
Detailed Description
The invention has the principle that organic pollutants in wastewater are removed through electrooxidation, the obtained electrooxidation water is filtered by a high-precision filter and then is further purified by an electrodialyzer to contain heavy metal salt solution, heavy metal is separated and recovered through positively charged nanofiltration, nanofiltration filtrate is prepared into alkali (sodium hydroxide solution) and acid (mixture of hydrochloric acid and sulfuric acid) through a bipolar membrane device, hydrochloric acid and sulfuric acid are separated through an acid-mixed separation device, heavy metal ions are effectively recovered, the salt in the wastewater is recycled, and the problem that the salt is difficult to recycle after the wastewater is treated is solved.
The process schematic diagram of the heavy metal-containing wastewater treatment method provided by the invention is shown in figure 1, and the heavy metal-containing wastewater treatment method specifically comprises the following steps:
s1, removing organic pollutants from the heavy metal-containing wastewater by adopting an electrooxidation device with a titanium-based noble metal mixed oxide as an anode and stainless steel as a cathode to reduce the risk of fouling and blocking of an electrodialyzer and ensure the quality of the subsequent recovery of heavy metals, wherein the current is 150-one 500A/m 2 And stopping electrooxidation when COD of the water produced by electrooxidation is less than 180 mg/L.
And S2, filtering the electrooxidation water produced after electrooxidation treatment by a high-precision filter, preferably a 50-200nm nano-imprinting membrane, and treating the filtrate by an electrodialyzer with an anion exchange membrane or a monovalent selective ion exchange membrane as an electrode membrane. The nano-imprinting film can effectively intercept and remove impurities due to narrow pore size distribution, so that the stable operation of a subsequent film system is ensured; an anion exchange membrane or a monovalent selective ion exchange membrane is adopted as an electrode membrane, so that heavy metal ions are effectively prevented from entering electrodialyzer electrode liquid, electrode water scaling and metal precipitation are avoided, and the efficiency of an electrode plate is ensured; in the electrodialysis process, salt ions migrate to enter the concentrated solution chamber of the electrodialyzer, and residual COD in the electroxidation is intercepted in the dilute solution chamber of the electrodialyzer, so that the concentrated solution chamber of the electrodialyser obtains a high-salt solution containing heavy metals, the dilute solution chamber of the electrodialyser obtains a low-salt solution containing COD, and the low-salt solution containing COD flows back to the electroxidation device.
The purpose of refluxing the COD-containing low-salt solution to the electro-oxidation device is as follows: 1. the ion exchange membrane in the electrodialyser is prevented from being polluted and blocked during long-time operation, so that the treatment efficiency of the electrodialyser is reduced, and the operation safety and stability of the electrodialyser can be ensured; 2. the part of the low-salt solution containing COD also contains heavy metal ions and other salts, the recycling rate of heavy metal and salt resources can be further improved through backflow, and the problem of discharge of feed liquid in a dilute solution chamber of the electrodialyzer is solved. The concentration of the low salt is not limited, and the low salt is a salt solution having a high concentration in the electrodialyser concentrate compartment.
And S3, performing nanofiltration separation on the heavy metal-containing high-salt solution by adopting a nanofiltration device of the positively charged nanofiltration membrane doped with the high-molecular complex functional separation layer to obtain nanofiltration concentrated solution and nanofiltration filtrate.
The nanofiltration separation is carried out by adopting the nanofiltration membrane doped with the macromolecular complex (the macromolecular complex is formed by the divalent cation and the hydrophilic macromolecular compound) in the functional separation layer, so that the polyvalent cation (heavy metal ion) can be efficiently intercepted, the heavy metal resource can be fully recovered, the purity of the acid and the alkali prepared subsequently can be ensured, and the generated nanofiltration concentrated solution can be directly recycled for the purified heavy metal solution.
And S4, injecting the nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles to perform acid and alkali preparation treatment to obtain alkali (sodium hydroxide solution) and acid (a mixture of hydrochloric acid and sulfuric acid). Contain modified particle monolithic type bipolar membrane among the bipolar membrane device and can effectively improve the acid-base conversion rate and the current efficiency of bipolar membrane, reduce the operating cost of bipolar membrane preparation acid-base simultaneously by a wide margin, weave the elasticity that bunched polypropylene fiber prepared in the bipolar membrane device and separate the net not only strengthen the leakproofness of bipolar membrane compartment, effectively improve the water output moreover, reduce the resistance, promote the torrent rivers state, avoid or slow down the concentration polarization phenomenon. The bipolar membrane device can be produced by Hangzhou water treatment technology research and development center, wherein the bipolar membrane diaphragm and the separation net can be independently replaced according to needs.
S5, finally, injecting the obtained acid into a mixed acid separation device for treatment, wherein a concentrated solution chamber of the mixed acid separation device can be used for obtaining hydrochloric acid, and a dilute solution chamber of the mixed acid separation device can be used for obtaining sulfuric acid; wherein the positive membrane in the mixed acid separation device adopts an acid separation positive membrane, the negative membrane adopts a single/polyvalent anion selective acid separation negative membrane, the separation selectivity is 97.5-99%, and the mixed acid separation device can select a homogeneous phase electric drive membrane device produced by Hangzhou water treatment technology research and development center, Inc.
The treatment method can adopt a treatment system of the wastewater containing the heavy metal, which comprises an electrooxidation device, a high-precision filter, an electrodialyzer, a nanofiltration device, a bipolar membrane device and a mixed acid separation device which are connected in sequence;
wherein, one side of the electrooxidation device for producing water is connected with the inlet of the high-precision filter through a high-pressure pump and a pipeline, wherein the anode in the electrooxidation device is a titanium-based noble metal mixed oxide, the cathode is stainless steel, and the current can be set to be 150- 2 . The filtrate side of the high-precision filter is connected with a dilute liquid chamber of the electrodialyzer through a pipeline; the polar membrane of the electrodialyzer adopts an anion exchange membrane or a monovalent selective ion exchange membrane.
Specifically, the electrodialyzer comprises a positive electrode and a negative electrode, and an anode membrane, an anion exchange membrane, a cation exchange membrane, and a cathode membrane are alternately stacked between the positive electrode and the negative electrode. Wherein, the negative ion exchange membrane and the positive ion exchange membrane are repeatedly stacked, and a plurality of pairs of negative ion exchange membranes and positive ion exchange membranes are stacked according to the requirement. An anode chamber is formed between the anode and the anode membrane, a concentrate chamber is formed between the anode membrane and the adjacent anion exchange membrane, a dilute chamber is formed between the anion exchange membrane and the cation exchange membrane, and a cathode chamber is formed between the cathode and the adjacent cathode membrane. The filtrate side of the high-precision filter is connected with the water inlet of the electrodialyzer and is connected with the dilute liquid chamber of the electrodialyzer. During operation, ions in the solution in the dilute liquid chamber of the electrodialysis process migrate to the concentrated liquid chamber, so that the concentrated liquid chamber of the electrodialyzer obtains a high salt solution containing heavy metals, and the dilute liquid chamber of the electrodialyzer obtains a low salt solution containing COD. The concentrated solution chamber of the electrodialyzer is connected with the feed inlet of the nanofiltration device, and the dilute solution chamber of the electrodialyzer is connected with the electrooxidation device through a valve and a pipeline.
The nanofiltration device is divided into a concentrated solution side and a filtrate side by a nanofiltration membrane, a feed inlet of the nanofiltration device is communicated with the concentrated solution side, the nanofiltration membrane adopts a positively charged nanofiltration membrane doped with a polymer complex functional separation layer, the filtrate side of the nanofiltration device is connected with the feed inlet of the bipolar membrane device by a pipeline, the feed inlet is connected with a salt solution chamber of the bipolar membrane device, and the concentrated solution side of the nanofiltration device is used for outputting purified heavy metal ion solution. The nanofiltration device can adopt a commercially available product, wherein a positively charged nanofiltration membrane doped with a high-molecular complex functional separation layer needs to be prepared or modified, wherein the hydrophilic high-molecular compound can be polyacrylamide, polyvinylpyrrolidone and the like, the divalent cations can be calcium ions and magnesium ions, the preparation method comprises the steps of enabling a solution containing the divalent cations and the hydrophilic high-molecular compound to generate the functional separation layer on a nanofiltration base membrane (polysulfone base membrane) through an interfacial reaction, and doping the functional separation layer with a high-molecular complex formed by the divalent cations and the hydrophilic high-molecular compound in the reaction process to enable the nanofiltration membrane to be positively charged.
The nanofiltration device is divided into a concentrated solution side and a filtrate side by a nanofiltration membrane, and a feed inlet of the nanofiltration device is communicated with the concentrated solution side. In the separation process of the feed liquid entering the nanofiltration device, one side of the feed liquid penetrating through the nanofiltration membrane is a filtrate side, and the intercepted side of the feed liquid is a concentrated liquid side. The bipolar membrane device comprises a positive electrode and a negative electrode, and the bipolar membrane, the separation net, the anion exchange membrane, the separation net, the cation exchange membrane and the separation net are alternately stacked between the positive electrode and the negative electrode in sequence; namely, the bipolar membranes, the separation net, the anion exchange membranes, the separation net, the cation exchange membranes, the separation net, the bipolar membranes, the separation net and the negative electrode are stacked up in this way, and the bipolar membranes, the separation net, the anion exchange membranes, the separation net, the cation exchange membranes and the separation net can be repeatedly stacked up according to the needs. Wherein an acid liquid chamber is formed between the bipolar membrane and the anion exchange membrane, and an alkali liquid chamber is formed between the bipolar membrane and the cation exchange membrane; a saline chamber is formed between the anion exchange membrane and the cation exchange membrane, and the nanofiltration filtrate is introduced into the saline chamber of the bipolar membrane device. The bipolar membrane device is divided into an acid liquid chamber, a brine chamber and an alkali liquid chamber of the bipolar membrane device in sequence by adopting a single-chip bipolar membrane containing modified particles, an anion exchange membrane and a cation exchange membrane and a single-chip bipolar membrane containing modified particles, partition nets are arranged between the two membranes of the bipolar membrane device, the anion exchange membrane and the cation exchange membrane, the acid liquid chamber of the bipolar membrane device is connected to a mixed acid separation device through a pipeline, and the alkali liquid chamber of the bipolar membrane device is used for outputting alkali liquid. The modified particles are one or more of polypyrrole-coated gold nanoparticles, polypyrrole-coated carbon nanotubes, polypyrrole-coated graphene oxide, polyaniline-coated gold nanoparticles, polyaniline-coated carbon nanotubes and polyaniline-coated graphene oxide, and the elastic separation net is prepared by weaving bundled polypropylene fibers.
The positive membrane in the mixed acid separation device adopts an acid separation positive membrane, the negative membrane adopts a single/polyvalent anion selective acid separation negative membrane, and the separation selectivity of the membrane is 97.5-99%. The device is provided with a mixed acid separation device concentrated liquid chamber and a mixed acid separation device diluted liquid chamber, the structure of the mixed acid separation device is similar to that of an electrodialyzer, and the concentrated liquid chamber and the diluted liquid chamber are formed by alternately arranging anion and cation membranes. Specifically, the concentrated solution chamber and the dilute solution chamber formed in the mixed acid separation device have the same structure as the electrodialyzer, and mainly differ in that the anion-cation exchange membrane adopts an acid separation anode membrane and a mono/polyvalent anion selective acid separation cathode membrane respectively, the concentrated solution chamber of the mixed acid separation device is formed between the anode membrane and the adjacent mono/polyvalent anion selective acid separation anode membrane, the dilute solution chamber of the mixed acid separation device is formed between the mono/polyvalent anion selective acid separation anode membrane and the adjacent acid separation anode membrane, and the dilute solution chamber of the mixed acid separation device is connected with the acid solution chamber of the bipolar membrane device; the concentrated solution chamber of the mixed acid separation device can be used for outputting hydrochloric acid, and the dilute solution chamber of the mixed acid separation device can be used for outputting sulfuric acid.
For a better understanding of the present invention, reference will now be made in detail to the present invention by way of specific embodiments thereof.
Example 1
In this example, the treated wastewater containing heavy metals comprises 3.9% of sodium chloride, 5.2% of sodium sulfate, and 160mg/L, COD mg/L of heavy metal copper ions is 607 mg/L. The treatment method of the wastewater containing the heavy metals comprises the following steps:
s1, removing organic pollutants in the wastewater by adopting an electrooxidation device with an anode of titanium-based noble metal mixed oxide and a cathode of stainless steel, wherein the current is 250A/m 2 (ii) a Obtaining electrooxidation water production, and stopping electrooxidation when COD (chemical oxygen demand) of the electrooxidation water production is less than 180 mg/L;
s2, filtering the electrooxidation water by a 50nm nano-imprinting membrane, treating the filtrate by using an electrodialyzer with an anion exchange membrane as a polar membrane, obtaining a heavy metal-containing high-salt solution from a concentrated liquid chamber of the electrodialyzer, obtaining a COD-containing low-salt solution from a dilute liquid chamber of the electrodialyzer, and refluxing the COD-containing low-salt solution to the electrooxidation device;
s3, performing nanofiltration separation on the heavy metal-containing high-salt solution by using a positively charged nanofiltration membrane doped with the high-molecular complex functional separation layer to obtain nanofiltration concentrated solution and nanofiltration filtrate; the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled;
s4, injecting nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles (polypyrrole-coated graphene oxide) to perform acid-base preparation treatment to obtain a sodium hydroxide solution and a mixture of hydrochloric acid and sulfuric acid;
and S5, finally, injecting the prepared mixed acid into a mixed acid separation device for treatment, wherein a concentrated liquid chamber of the mixed acid separation device obtains hydrochloric acid, and a dilute liquid chamber of the mixed acid separation device obtains sulfuric acid, wherein an acid separation positive membrane is adopted as a positive membrane in the mixed acid separation device, a mono/polyvalent anion selective acid separation negative membrane is adopted as a negative membrane, and the separation selectivity is 98.5%.
After the above treatment, the concentrations of the purified sodium hydroxide solution, hydrochloric acid and sulfuric acid can be obtained by measuring the acid-base concentrations in the bipolar membrane device and the mixed acid separation device respectively. Converting the salt to an acid and a base by a bipolar membrane device, the concentration of the acid and the base increasing as the device operates; in the mixed acid separation device, the hydrochloric acid in the weak solution chamber migrates to the concentrated solution chamber, so the aim of separating the hydrochloric acid and the sulfuric acid is fulfilled, and the concentration of the hydrochloric acid in the concentrated solution chamber gradually increases along with the operation of the device. Finally obtaining 7.5 percent of purified sodium hydroxide solution, 6.1 percent of purified hydrochloric acid and 5.6 percent of purified sulfuric acid, the recovery rate of heavy metal copper is 97.6 percent, and the conversion rate of acid and alkali produced by salt is 96.7 percent.
Example 2
In this example, the wastewater containing heavy metal ions was the same as in example 1. The treatment method of the wastewater containing the heavy metals comprises the following steps:
s1, removing organic pollutants in the wastewater by adopting an electrooxidation device with an anode of titanium-based noble metal mixed oxide and a cathode of stainless steel, wherein the current is 500A/m 2 (ii) a Obtaining electrooxidation water production, and stopping electrooxidation when COD (chemical oxygen demand) of the electrooxidation water production is less than 180 mg/L;
s2, filtering electrooxidation water production by a 50nm nano-imprint membrane, treating filtrate by using an electrodialyzer with an anion exchange membrane as a polar membrane, obtaining a heavy metal-containing high-salt solution from a concentrated liquid chamber of the electrodialyzer, obtaining a COD-containing low-salt solution from a dilute liquid chamber of the electrodialyzer, and refluxing the COD-containing low-salt solution to the electrooxidation device;
s3, performing nanofiltration separation on the heavy metal-containing high-salt solution by using a positively charged nanofiltration membrane doped with the high-molecular complex functional separation layer, wherein the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled;
s4, injecting nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles (gold nanoparticles coated with polypyrrole) to perform acid-base preparation treatment to obtain a sodium hydroxide solution and a mixture of hydrochloric acid and sulfuric acid;
and S5, finally, injecting the prepared mixed acid into a mixed acid separation device for treatment, wherein a concentrated liquid chamber of the mixed acid separation device obtains hydrochloric acid, and a dilute liquid chamber of the mixed acid separation device obtains sulfuric acid, wherein an acid separation positive membrane is adopted as a positive membrane in the mixed acid separation device, a mono/polyvalent anion selective acid separation negative membrane is adopted as a negative membrane, and the separation selectivity is 97.5%.
The 5.7% purified sodium hydroxide solution, 2.9% purified hydrochloric acid and 4.0% purified sulfuric acid are obtained through the treatment, the recovery rate of heavy metals reaches 96.3%, and the conversion rate of the acid and the alkali produced by the salt is 95.9%.
Example 3
In this example, the heavy metal-containing wastewater was the same as in example 1. The treatment method of the wastewater containing the heavy metals comprises the following steps:
s1, removing organic pollutants in the wastewater by adopting an electrooxidation device with an anode of titanium-based noble metal mixed oxide and a cathode of stainless steel, wherein the current is 150A/m 2 (ii) a Obtaining electrooxidation water production, and stopping electrooxidation when COD (chemical oxygen demand) of the electrooxidation water production is less than 180 mg/L;
s2, filtering electrooxidation water production by a 200nm nano-imprint membrane, treating filtrate by using an electrodialyzer with an anion exchange membrane as a polar membrane, obtaining a heavy metal-containing high-salt solution from a concentrated liquid chamber of the electrodialyzer, obtaining a COD-containing low-salt solution from a dilute liquid chamber of the electrodialyzer, and refluxing the COD-containing low-salt solution to the electrooxidation device;
s3, performing nanofiltration separation on the heavy metal-containing high-salt solution by using a positively charged nanofiltration membrane doped with a high-molecular complex functional separation layer, wherein the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled,
s4, injecting nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles (polyaniline-coated carbon nanotubes) to perform acid-base preparation treatment to obtain a sodium hydroxide solution and a mixture of hydrochloric acid and sulfuric acid;
and S5, finally, injecting the obtained mixed acid into a mixed acid separation device for treatment, obtaining hydrochloric acid in a concentrated liquid chamber of the mixed acid separation device, and obtaining sulfuric acid in a dilute liquid chamber of the mixed acid separation device, wherein an acid separation positive membrane is adopted as a positive membrane in the mixed acid separation device, a mono/polyvalent anion selective acid separation negative membrane is adopted as a negative membrane, and the separation selectivity is 99%.
The 10.2 percent purified sodium hydroxide solution, 6.5 percent purified hydrochloric acid and 7.1 percent purified sulfuric acid are obtained through the treatment, the recovery rate of heavy metal reaches 98.4 percent, and the conversion rate of the acid and the alkali produced by the salt is 97.0 percent.
Example 4
In this example, the heavy metal-containing wastewater was the same as in example 1. The treatment method of the wastewater containing the heavy metals comprises the following steps:
s1, removing organic pollutants in the wastewater by adopting an electrooxidation device with an anode of titanium-based noble metal mixed oxide and a cathode of stainless steel, wherein the current is 250A/m 2 (ii) a Obtaining the electrooxidation waterWhen the COD of the water produced by the electrooxidation is less than 180mg/L, stopping the electrooxidation;
s2, filtering electrooxidation water production by a 100nm nano-imprint membrane, treating filtrate by using a monovalent selective ion exchange membrane as an electrodialyzer of a polar membrane, obtaining a heavy metal-containing high-salt solution from a concentrated liquid chamber of the electrodialyzer, obtaining a COD-containing low-salt solution from a dilute liquid chamber of the electrodialyzer, and refluxing the COD-containing low-salt solution to an electrooxidation device;
s3, performing nanofiltration separation on the heavy metal-containing high-salt solution by using a positively charged nanofiltration membrane doped with a high-molecular complex functional separation layer, wherein the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled,
s4, injecting the nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles (polypyrrole-coated carbon nanotubes) to perform acid-base preparation treatment to obtain a sodium hydroxide solution and a mixture of hydrochloric acid and sulfuric acid;
and S5, finally, injecting the prepared mixed acid into a mixed acid separation device for treatment, wherein a concentrated liquid chamber of the mixed acid separation device obtains hydrochloric acid, and a dilute liquid chamber of the mixed acid separation device obtains sulfuric acid, wherein an acid separation positive membrane is adopted as a positive membrane in the mixed acid separation device, a mono/polyvalent anion selective acid separation negative membrane is adopted as a negative membrane, and the separation selectivity is 98%.
The 8.4% purified sodium hydroxide solution, 5.2% purified hydrochloric acid and 5.9% purified sulfuric acid are obtained through the treatment, the recovery rate of heavy metal reaches 97.5%, and the conversion rate of acid and alkali produced by salt is 96.5%.
Example 5
In the example, the wastewater containing heavy metals contains 5.4% of sodium chloride, 2.9% of sodium sulfate and 933mg/L of heavy metal nickel ions at 78mg/L, COD. The treatment method of the wastewater containing the heavy metals comprises the following steps:
s1, removing organic pollutants in the wastewater by adopting an electrooxidation device with an anode of titanium-based noble metal mixed oxide and a cathode of stainless steel, wherein the current is 300A/m 2 (ii) a Obtaining electrooxidation water production, and stopping electrooxidation when COD (chemical oxygen demand) of the electrooxidation water production is less than 180 mg/L;
s2, filtering electrooxidation water production by a 50nm nano-imprint membrane, treating filtrate by using an electrodialyzer with an anion exchange membrane as a polar membrane, obtaining a heavy metal-containing high-salt solution from a concentrated liquid chamber of the electrodialyzer, obtaining a COD-containing low-salt solution from a dilute liquid chamber of the electrodialyzer, and refluxing the COD-containing low-salt solution to the electrooxidation device;
s3, performing nanofiltration separation on the heavy metal-containing high-salt solution by using a positively charged nanofiltration membrane doped with a high-molecular complex functional separation layer, wherein the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled,
s4, injecting nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles (polyaniline-coated graphene oxide) to perform acid-base preparation treatment to obtain a sodium hydroxide solution and a mixture of hydrochloric acid and sulfuric acid;
and S5, finally, injecting the obtained mixed acid into a mixed acid separation device for treatment, wherein a concentrated liquid chamber of the mixed acid separation device obtains hydrochloric acid, and a dilute liquid chamber of the mixed acid separation device obtains sulfuric acid, wherein an anode membrane in the mixed acid separation device adopts an acid-splitting anode membrane, a cathode membrane adopts a mono/polyvalent anion selective acid-splitting cathode membrane, and the separation selectivity is 97.5%.
The above treatment can obtain 9.3% purified sodium hydroxide solution, 7.8% purified hydrochloric acid and 4.6% purified sulfuric acid, the recovery rate of heavy metal nickel is up to 97.9%, and the conversion rate of acid and alkali produced by salt is 97.2%.
Example 6
In the embodiment, the heavy metal-containing wastewater contains 10.1 percent of sodium chloride, 7.2 percent of sodium sulfate and 439mg/L of heavy metal cadmium ions of 104mg/L, COD. The treatment method of the wastewater containing the heavy metals comprises the following steps:
s1, removing organic pollutants in the wastewater by adopting an electrooxidation device with an anode of titanium-based noble metal mixed oxide and a cathode of stainless steel, wherein the current is 200A/m 2 (ii) a Obtaining electro-oxidation water production, wherein COD (chemical oxygen demand) of the electro-oxidation water production is less than 180mg/L, and stopping the electro-oxidation;
s2, filtering electrooxidation water production by a 150nm nano-imprint membrane, treating filtrate by using an electrodialyzer with an anion exchange membrane as a polar membrane, obtaining a heavy metal-containing high-salt solution from a concentrated liquid chamber of the electrodialyzer, obtaining a COD-containing low-salt solution from a dilute liquid chamber of the electrodialyzer, and refluxing the COD-containing low-salt solution to the electrooxidation device;
s3, performing nanofiltration separation on the heavy metal-containing high-salt solution by using a positively charged nanofiltration membrane doped with the high-molecular complex functional separation layer, wherein the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled;
s4, injecting nanofiltration filtrate into a single-chip bipolar membrane device containing modified particles (polypyrrole-coated graphene oxide) to perform acid-base preparation treatment to obtain a sodium hydroxide solution and a mixture of hydrochloric acid and sulfuric acid;
and S5, finally, injecting the obtained mixed acid into a mixed acid separation device for treatment, wherein a concentrated liquid chamber of the mixed acid separation device obtains hydrochloric acid, and a dilute liquid chamber of the mixed acid separation device obtains sulfuric acid, wherein an acid separation positive membrane is adopted as a positive membrane in the mixed acid separation device, a mono/polyvalent anion selective acid separation negative membrane is adopted as a negative membrane, and the separation selectivity is 98.5%.
The above treatment is carried out to obtain 14.9 percent of purified sodium hydroxide solution, 10.5 percent of purified hydrochloric acid and 7.4 percent of purified sulfuric acid, the recovery rate of heavy metal cadmium reaches 99.1 percent, and the conversion rate of the acid and the alkali produced by the salt is 97.7 percent.
Comparative example 1
In this example, the wastewater containing heavy metal ions was the same as in example 1. The steps of the method for treating the wastewater containing the heavy metals are not treated by an electrooxidation device, and other steps are the same as those in the embodiment 1; 6.3 percent of purified sodium hydroxide solution, 4.9 percent of purified hydrochloric acid and 4.2 percent of purified sulfuric acid are obtained through treatment, the recovery rate of heavy metal copper reaches 79.5 percent, and the conversion rate of acid and alkali produced by salt is 84.3 percent.
Comparative example 2
In this example, the wastewater containing heavy metal ions was the same as in example 1. The steps of the method for treating the wastewater containing the heavy metal are the same as those of the embodiment 1 except that a positively charged nanofiltration membrane doped with a high molecular complex functional separation layer is not adopted in nanofiltration separation; 6.8 percent of purified sodium hydroxide solution, 5.5 percent of purified hydrochloric acid and 4.9 percent of purified sulfuric acid are obtained through treatment, the recovery rate of heavy metal copper reaches 85.3 percent, and the conversion rate of acid and alkali produced by salt is 91.4 percent.
Comparative example 3
In this example, the wastewater containing heavy metal ions was the same as in example 1. The steps of the method for treating the heavy metal-containing wastewater are the same as those of the embodiment 1 except that a bipolar membrane device does not adopt a modified particle-containing monolithic bipolar membrane; after treatment, 7.1% purified sodium hydroxide solution, 5.7% purified hydrochloric acid and 5.2% purified sulfuric acid are obtained, the recovery rate of heavy metal copper reaches 95.1%, and the conversion rate of acid and alkali produced by salt is 83.6%.
According to the method, the heavy metal-containing wastewater is subjected to resource recycling treatment through the electrooxidation device, the high-precision filter, the electrodialyzer, the nanofiltration device, the bipolar membrane device and the mixed acid separation device, heavy metal resources can be efficiently recycled, and a good effect cannot be obtained due to the absence of any one-step treatment.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art can change or modify the technical content disclosed above into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.
Claims (5)
1. A treatment method of wastewater containing heavy metals is characterized by comprising the following steps:
s1, carrying out electrooxidation treatment on the wastewater containing the heavy metal ions to obtain electrooxidation water;
s2, filtering the electrooxidation water production by a high-precision filter, injecting the electroosmosis water production into an electrodialyzer for treatment, obtaining a heavy metal-containing high-salt solution in a concentrated liquid chamber of the electrodialyzer, and obtaining a COD-containing low-salt solution in a dilute liquid chamber of the electrodialyzer; wherein, the electrodialyzer comprises a positive electrode and a negative electrode, and an anode membrane, an anion exchange membrane, a cation exchange membrane and a cathode membrane which are repeatedly and alternately stacked are sequentially arranged between the positive electrode and the negative electrode; an electrodialyzer concentrated liquid chamber is formed between the anode membrane and the adjacent anion exchange membrane, and an electrodialyzer dilute liquid chamber is formed between the anion exchange membrane and the cation exchange membrane;
s3, carrying out nanofiltration separation on the heavy metal-containing high-salt solution to generate nanofiltration concentrated solution and nanofiltration filtrate; the nanofiltration separation adopts a positively charged nanofiltration membrane doped with a high molecular complex functional separation layer;
s4, injecting the nanofiltration filtrate into a bipolar membrane device for treatment to respectively obtain alkali liquor and acid liquor; the bipolar membrane device comprises a positive electrode and a negative electrode, wherein bipolar membranes, partition nets, anion exchange membranes, partition nets, cation exchange membranes and partition nets are alternately stacked between the positive electrode and the negative electrode in sequence, bipolar membrane device acid liquid chambers are formed between the bipolar membranes and the anion exchange membranes, and bipolar membrane device alkali liquid chambers are formed between the bipolar membranes and the cation exchange membranes; a saline chamber is formed between the anion exchange membrane and the cation exchange membrane;
s5, injecting the acid liquor prepared in the step S4 into a mixed acid separation device for treatment;
in step S2, a nano-imprinting film is adopted as a filtering film in the high-precision filter, and the aperture is 50-200 nm; the polar membrane of the electrodialyzer adopts an anion exchange membrane or a monovalent selective ion exchange membrane;
in step S4, the bipolar membrane device uses a monolithic bipolar membrane containing modified particles, wherein the modified particles are one or more of polypyrrole-coated gold nanoparticles, polypyrrole-coated carbon nanotubes, polypyrrole-coated graphene oxide, polyaniline-coated gold nanoparticles, polyaniline-coated carbon nanotubes, or polyaniline-coated graphene oxide, and the spacer mesh is an elastic spacer mesh prepared by weaving bundle-formed polypropylene fibers;
in step S5, the mixed acid separation device uses an acid separation positive membrane as the positive membrane, uses a mono/polyvalent anion selective acid separation negative membrane as the negative membrane, and the separation selectivity between the positive membrane and the negative membrane is 97.5-99%.
2. The process as claimed in claim 1, wherein in step S1, the electrooxidation treatment is carried out using an apparatus in which the anode is a mixed oxide of a titanium-based noble metal, the cathode is stainless steel, and the current density is 150-500A/m 2 (ii) a And stopping the electrooxidation when COD of the electrooxidation water production is less than 180mg/L, and carrying out the next treatment.
3. The treatment process according to claim 1, wherein the COD-containing low salt solution is refluxed to the electro-oxidation unit;
the nanofiltration concentrated solution is a purified heavy metal solution and can be directly recycled;
the alkali liquor obtained by the treatment of the bipolar membrane device can be recycled.
4. A treatment system for wastewater containing heavy metals comprises an electrooxidation device, a high-precision filter, an electrodialyzer, a nanofiltration device, a bipolar membrane device and a mixed acid separation device which are sequentially arranged;
wherein the water production side of the electrooxidation device is connected with the high-precision filter, and the filtrate side of the high-precision filter is connected with the electrodialyzer;
the electrodialyzer comprises a positive electrode and a negative electrode, wherein an anode membrane, an anion exchange membrane, a cation exchange membrane and a cathode membrane which are repeatedly and alternately stacked are sequentially arranged between the positive electrode and the negative electrode; an electrodialyzer concentrated liquid chamber is formed between the anode membrane and the adjacent anion exchange membrane, an electrodialyzer dilute liquid chamber is formed between the anion exchange membrane and the cation exchange membrane, the electrodialyzer concentrated liquid chamber is connected with a feed inlet of the nanofiltration device, and the electrodialyzer dilute liquid chamber is connected with the electrooxidation device;
the nanofiltration device is divided into a concentrated solution side and a filtrate side by a nanofiltration membrane, a feed inlet of the nanofiltration device is communicated with the concentrated solution side, the filtrate side of the nanofiltration device is connected with a brine chamber of the bipolar membrane device, and the concentrated solution side of the nanofiltration device is used for outputting purified heavy metal solution;
the bipolar membrane device comprises a positive electrode and a negative electrode, wherein a bipolar membrane, a separation net, an anion exchange membrane, a separation net, a cation exchange membrane and a separation net are sequentially and alternately stacked between the positive electrode and the negative electrode, an acid liquid chamber of the bipolar membrane device is formed between the bipolar membrane and the anion exchange membrane, and an alkali liquid chamber of the bipolar membrane device is formed between the bipolar membrane and the cation exchange membrane; a saline solution chamber is formed between the anion exchange membrane and the cation exchange membrane, the acid solution chamber of the bipolar membrane device is connected with the mixed acid separation device, and the alkaline solution chamber of the bipolar membrane device is used for outputting alkaline solution;
the mixed acid separation device comprises a positive electrode and a negative electrode, and an anode film, a cathode film, an anode film and a cathode film which are repeatedly stacked are sequentially arranged between the positive electrode and the negative electrode; a mixed acid separation device concentrated liquid chamber is formed between the anode membrane and the adjacent cathode membrane, and a mixed acid separation device diluted liquid chamber is formed between the cathode membrane and the adjacent anode membrane;
the anode in the electro-oxidation device is titanium-based noble metal mixed oxide, the cathode is stainless steel, and the current density is 150- 2 ；
The filtering membrane in the high-precision filter adopts a nano-imprinting membrane, and the aperture is 50-200 nm;
the polar membrane of the electrodialyzer is an anion exchange membrane or a monovalent selective ion exchange membrane;
the nanofiltration membrane is a positively charged nanofiltration membrane doped with a high-molecular complex functional separation layer;
the bipolar membrane of the bipolar membrane device is a monolithic bipolar membrane containing modified particles, wherein the modified particles are one or more of polypyrrole-coated gold nanoparticles, polypyrrole-coated carbon nanotubes, polypyrrole-coated graphene oxide, polyaniline-coated gold nanoparticles, polyaniline-coated carbon nanotubes and polyaniline-coated graphene oxide, and the separation net is an elastic separation net prepared by weaving bundled polypropylene fibers;
the positive membrane in the mixed acid separation device is an acid separation positive membrane, the negative membrane is a single/polyvalent anion selective acid separation negative membrane, and the separation selectivity of the positive membrane and the negative membrane is 97.5-99%.
5. The treatment system of claim 4, wherein the connections are made using tubing or a combination of pumps and tubing.
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