The treatment and reuse of electroplating wastewater plays a vital role in saving water resources and protecting the environment. This article reviews the advantages and disadvantages of various electroplating wastewater treatment technologies, as well as the application of some new materials in electroplating wastewater treatment.
01 Chemical precipitation method
Chemical precipitation method is to convert dissolved heavy metals into water-insoluble compounds and precipitate them by adding chemicals into wastewater, and then separate them from the water. , thereby achieving the purpose of removing heavy metals.
Chemical precipitation method is widely used in electroplating wastewater treatment because of its simple operation, mature technology, low cost, and the ability to remove multiple heavy metals in wastewater at the same time.
1. Alkaline precipitation method
The alkaline precipitation method is to add NaOH, lime, sodium carbonate and other alkaline substances to the wastewater to form hydroxide with low solubility of heavy metals. substances or carbonates are precipitated and removed. This method has the advantages of low cost and simple operation, and is currently widely used.
However, the sludge output of the alkaline sedimentation method is large, which will cause secondary pollution, and the pH of the effluent is high, so the pH needs to be adjusted. NaOH is widely used in engineering because it produces relatively small amounts of sludge and is easy to recycle.
2. Sulfide precipitation method
The sulfide precipitation method is to add sulfides (such as Na2S, NariS, etc.) to form heavy metals in the wastewater into solubility volume ratio hydroxides. For smaller precipitates, the effluent pH is between 7 and 9, and can be discharged without adjusting the pH.
However, the sulfide precipitated particles are small, and flocculants need to be added to assist precipitation, which increases the treatment cost. Sulfide can also produce toxic HS gas in acidic solutions, which has limitations in practical operation.
3. Ferrite method
The ferrite method is developed based on the principle of producing ferrite, which allows various heavy metal ions in the wastewater to form ferrite crystals together. Precipitate out, thereby purifying wastewater. This method mainly adds ferrous sulfate to wastewater, undergoes reduction, precipitation and flocculation, and finally generates ferrite. It is widely used because of its simple equipment, low cost, fast sedimentation, and good treatment effect.
The effects of pH and ferrous sulfate dosage on the removal of heavy metal ions by ferrite method. It is determined that the optimal flocculation pH for nickel, zinc and copper ions are 8.00~9.80, 8.00~10.50 and 10.00 respectively. The molar ratio between the added ferrous ions and them is 2 to 8, while the optimal reduction pH of hexavalent chromium is 4.00 to 5.50, the optimal flocculation pH is 8.00 to 10.50, and the optimal feeding ratio is 20. The nickel content of the effluent is less than 0.5mg/L, the total chromium content is less than 1.0mg/L, the zinc content is less than 1.0mg/L, and the copper content is less than 0.5mg/L, reaching the "Electroplating Pollutant Emission Standard" (GB21900-2008) Table 2" requirements.
Limitations of the chemical precipitation method
With the improvement of wastewater discharge standards, the traditional single chemical precipitation method is difficult to treat electroplating wastewater economically and effectively, and is often used in combination with other processes.
Use ferrite-CARBONITE (a material with physical adsorption and ion exchange functions) combined process to treat high-concentration nickel-containing electroplating wastewater with a Ni content of approximately 4000 mg/L: first use the ferrite method Control the pH to 11.0 in Fe/Fe. The molar ratio was 0.55, the FeSO4·7H2O/Ni mass ratio was 21, and the reaction was stirred for 15 minutes at a reaction temperature of 35°C. The average concentration of Ni in the effluent dropped from 4212.5 mg/L to 6.8 mg/L, and the removal rate reached 99.84; then CARBONITE was used Treatment, when the CARBONITE dosage is 1.5g/L, pH=6.5, and the temperature is 35°C, the Ni removal rate can reach 96.48, and the effluent Ni concentration is 0.24mg/L, reaching "Table 2 in GB21900-2008" "standard.
Using the advanced Fenton-chemical precipitation method to treat wastewater containing chelated heavy metals, using zero-valent iron and hydrogen peroxide to degrade the chelates, and then adding alkali to precipitate heavy metal ions, which can not only remove nickel ions (removal rate up to 98.4), and can reduce COD chemical oxygen demand.
02 Redox method
1. Chemical oxidation method
Chemical oxidation method is particularly effective in treating cyanide-containing electroplating wastewater. This method oxidizes cyanide ions (CN-) in wastewater into cyanate (CNO-), and then oxidizes cyanate (CNO-) into carbon dioxide and nitrogen, which can completely solve the problem of cyanide pollution.
Commonly used oxidants include chlorine-based oxidants, oxygen, ozone, hydrogen peroxide, etc. Among them, alkaline chlorination is the most widely used. The Fenton method is used to treat low-concentration cyanide-containing electroplating wastewater with an initial total cyanide concentration of 2.0 mg/L. The initial pH of the reaction is 3.5, the H202/FeSO4 molar ratio is 3.5:1, the H202 dosage is 5.0g/L, and the reaction time is 60 minutes. Under the optimal conditions, the cyanide removal rate can reach 93%, and the total cyanide concentration can be reduced to 0_3mg/L.
2. Chemical reduction method
Chemical reduction method mainly targets wastewater containing hexavalent chromium in electroplating wastewater treatment. This method is to add reducing agents (such as FeSO, NaHSO3, Na2SO3, SO2, iron powder, etc.) to the wastewater to reduce hexavalent chromium to trivalent chromium, and then add lime or sodium hydroxide for precipitation and separation. The above ferrite method can also be classified as a chemical reduction method.
The main advantages of this method are mature technology, simple operation, large processing capacity, low investment, and good results in engineering applications. However, the large amount of sludge will cause secondary pollution. Ferrous sulfate is used as the reducing agent to treat 80t/d of electroplating wastewater containing total chromium 7O~80mg/L. The total chromium in the effluent is less than 1.5mg/L, and the treatment cost is 3.1 yuan/t, which has high economic benefits.
Using sodium metabisulfite as the reducing agent to treat electroplating wastewater containing 80 mg/L hexavalent chromium and a pH of 6 to 7, the effluent concentration of hexavalent chromium is less than 0.2 mg/L.
03 Electrochemical method
The electrochemical method means that under the action of electric current, heavy metal ions and organic pollutants in wastewater undergo oxidation, reduction, decomposition, precipitation, flotation, etc. removed by a series of reactions.
The main advantages of this method are that it has a fast removal rate, can completely break the metal links in the complex state, is easy to recycle heavy metals, occupies a small area, and has a small amount of sludge. However, it consumes the plates quickly and consumes electricity. The amount is large, and the removal effect of low-concentration electroplating wastewater is not good. It is only suitable for small and medium-sized electroplating wastewater treatment.
Electrochemical methods mainly include electrocoagulation method, magnetic electrolysis method, internal electrolysis method, etc.
The electrocoagulation method uses an iron plate or aluminum plate as an anode. Fe2, Fe or Al is produced during electrolysis. As the electrolysis proceeds, the alkalinity of the solution increases, forming Fe(OH)2, Fe(OH )3 or AI(OH)3, remove pollutants through flocculation and precipitation.
Since the traditional electrocoagulation method will passivate the electrode plate after a long period of operation, in recent years, the high-voltage pulse electrocoagulation method has gradually replaced the traditional electrocoagulation method. It not only overcomes the problem of plate dullness In addition, the current efficiency is increased by 20-30%, the electrolysis time is shortened by 30-40%, the electric energy is saved by 30-40%, the sludge production is small, and the removal rate of heavy metals can reach 96-99%.
Using high-voltage pulse electroflocculation technology to treat electroplating wastewater from an electroplating factory, the removal rates of Cu2O, Ni2, CN1 and COD reached 99.80, 99.70, 99.68 and 67.45 respectively.
Electrocoagulation is usually used in combination with other methods. Electrocoagulation and ozone oxidation are used to jointly treat electroplating wastewater. Iron and aluminum are used as electrode plates to produce hexavalent chromium, iron, nickel, and copper in the water. , zinc, lead, TOC (total organic carbon), and COD removal rates were 99.94, 100.00, 95.86, 98.66, 99.97, 96.81, 93.24, and 93.43 respectively.
In recent years, electrolysis has received widespread attention.
The internal electrolysis method makes use of the principle of the primary battery. Generally, iron powder and carbon particles are added to the wastewater, and the wastewater is used as the electrolyte medium. Through the comprehensive effects of various reactions such as oxidation-reduction, replacement, flocculation, adsorption, and precipitation, it can Remove multiple heavy metal ions at one time.
This method does not require electric energy, has low treatment cost and small amount of sludge. The removal effect of COD and copper ions in simulated electroplating wastewater by the iron-carbon micro-electrolysis method was studied through static experiments, and the removal rates reached 59.01 and 95.49 respectively. However, the operation results of using a micro-electrolysis reaction column to study continuous flow showed that the COD removal rate of the micro-electrolysis effluent after 14 days was only 10 to 15, and the copper removal rate was reduced to between 45 and 50. It can be seen that the packing needs to be replaced regularly or the packing needs to be replaced regularly. Perform regeneration.
04 Membrane separation technology
Membrane separation technology mainly includes microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), electrodialysis ( ED), liquid membrane (Lv), etc., use the selective permeability of the membrane to separate and remove pollutants.
This method has good removal effect, can realize heavy metal recycling and effluent reuse, occupies a small area, and has no secondary pollution. It is a promising technology, but the cost of the membrane is high and it is easy to Contaminated.
The application and effect of membrane technology in electroplating wastewater treatment were analyzed. The results show that: by combining the conventional wastewater treatment process with the membrane bioreactor (MBR) combined process, the water quality of the electroplating wastewater after treatment reaches Discharge standards; after electroplating comprehensive wastewater is treated by the integrated process of UF purification and RO and NF two-stage desalination membranes, the water quality reaches the reuse water standard. The conductivities of RO and NF produced water are respectively lower than 100gS/cm and 1000gS/cm, and the COD is respectively About 5mg/L and 10mg/L; after the nickel plating rinsing wastewater passes through the RO membrane, the nickel is concentrated up to more than 25 times, realizing the recovery of nickel, and the RO water quality reaches the reuse standard.
The investment and operating cost analysis shows that the equipment cost of RO nickel concentration can be recovered after more than one year of project operation.
The liquid membrane method does not use a traditional solid-phase membrane, but a thin layer of emulsion particles suspended in a liquid. It is a new separation technology similar to solvent extraction, including membrane making, separation, Purification and demulsification process.
Dr. Norman N. Li, a Chinese-American, invented the emulsion membrane separation technology, which has the advantages of both extraction and permeation, combining the two steps of extraction and back-extraction. The emulsion membrane method also has the characteristics of high mass transfer efficiency, good selectivity, low secondary pollution, energy saving and low infrastructure investment. It has good effects on the treatment and recycling of heavy metals in electroplating wastewater.
05 Ion exchange method
The ion exchange method uses ion exchangers to exchange and separate harmful substances in wastewater. Commonly used ion exchangers include humic acid substances, zeolites, and ions. Exchange resin, ion exchange fiber, etc. The operation of ion exchange includes four steps: exchange, backwash, regeneration and cleaning.
This method has the characteristics of simple operation, recyclable heavy metals, and low secondary pollution. However, the cost of ion exchanger is high and the consumption of regenerant is large.
Study the treatment process conditions of nickel-containing wastewater with strong acidic ion exchange resin and the nickel recovery method. The results show that a pH of 6 to 7 is beneficial to the removal of nickel ions by strongly acidic cation exchange resin. The suitable temperature for ion exchange nickel removal is 30°C, and the suitable flow rate is 15BV/h (that is, 15 times the resin bed volume per hour). The suitable desorbent is 10% hydrochloric acid, and the flow rate of the desorbent liquid is 2BV/h. The first 4.6BV desorption solution can be reused to prepare electroplating bath solution, and the average nickel ion mass concentration reaches 18.8g/L.
Mei.1ingKong et al. studied the adsorption capacity of CHS-l resin for cr(VI) and found that when Cr(VI) is at a low concentration, the exchange adsorption rate of the resin is controlled by liquid film diffusion and chemical reactions. of. The optimal adsorption pH of CHS-1 resin for Cr(VI) is 2 to 3, and its saturated adsorption capacity is 347.22mg/g at 298K.
CHS-1 resin can be eluted with 5 sodium hydroxide solution and 5 sodium chloride solution, and the adsorption capacity does not decrease significantly after regeneration.
Use titanate coupling agent to polymerize 1-Fe203 and methyl acrylate, and hydrolyze it under alkaline conditions to prepare magnetic weak acid cation exchange resin NDMC-1.
Through the adsorption study of heavy metal Cu, it was found that NDMC-l resin has smaller particle size and larger outer surface area, so it has faster kinetic properties. Contact Sewage Bao for details or see more relevant technical documents.
06 Evaporation concentration method
The evaporation concentration method evaporates electroplating wastewater by heating to concentrate the liquid for reuse. It is generally suitable for treating wastewater containing chromium, copper, silver, nickel and other heavy metals with high concentrations. It consumes a lot of energy and is uneconomical to treat heavy metal wastewater with low concentrations.
In the treatment of electroplating wastewater, the evaporation concentration method is often used together with other methods, which can achieve closed-circuit circulation and achieve good results, such as the combination of an atmospheric pressure evaporator and a countercurrent rinsing system. The evaporation concentration method is simple to operate, has mature technology, and can be recycled. However, the high cost of disposal of concentrated dry solids restricts its application. Currently, it is generally only used as an auxiliary treatment method.
07 Biological treatment technology
Biological treatment method uses microorganisms or plants to purify pollutants. This method has low operating cost, small amount of sludge, and no secondary pollution. For water volume It is the best choice for large, low-concentration electroplating wastewater. Biological methods mainly include bioflocculation, biosorption, biochemical and phytoremediation.
1. Biological flocculation method
Biological flocculation method is a method that uses microorganisms or metabolites produced by microorganisms to flocculate and settle to purify water quality. Microbial flocculants are a type of metabolite produced by microorganisms and secreted out of cells with flocculating activity, which can cause colloidal suspended matter in water to aggregate and precipitate with each other.
Compared with inorganic flocculants and synthetic organic flocculants, biological flocculants have the advantages of safe and non-toxic wastewater treatment, good flocculation effect, and no secondary pollution. However, it is difficult to preserve living biological flocculants. , high production costs and other issues limit its practical application. At present, most bioflocculants are still in the exploratory research stage.
Biological flocculants can be divided into the following three categories:
(1) Direct use of microbial cells as flocculants, such as some bacteria, actinomycetes, fungi, yeast, etc.
(2) Use microbial cell wall extract as a flocculant. The flocculating substances produced by microorganisms are glycoproteins, mucopolysaccharides, proteins and other high molecular substances, such as yeast cell wall glucan, IV-acetylglucosamine, filamentous fungal cell wall polysaccharides, etc., which can be used as good biological flocculants.
(3) Flocculants that utilize metabolites of microbial cells. Metabolites mainly include polysaccharides, proteins, lipids and their complexes.
The biological flocculants reported in recent years are mainly polysaccharides and proteins. The former include ZS-7, ZL-P, H12, and DP. 152 and so on, the latter includes MBF-W6, NOC-l, etc. Tao Ying et al.] conducted a flocculation adsorption study on cr(Ⅳ) using a flocculant prepared from Pseudomonas Gx4-1 extracellular polymer.
The research results show that under suitable conditions, the removal rate of Or(Ⅳ) can reach 51%. Study the treatment effect of bioflocculant v-polyglutamic acid (T-PGA) prepared by Bacillus subtilis NX-2 on electroplating wastewater. Experiments have shown that T-PGA can effectively remove heavy metal ions such as Cr3 and Ni.
2. Biosorption method
Biosorption method uses the chemical structure or composition characteristics of organisms to adsorb heavy metals in water, and then separates heavy metals from water through solid-liquid separation. .
Organisms and their derivatives that can separate heavy metals from solutions are called biosorbents. Biosorbents mainly include biomass, bacteria, yeast, mold, algae, etc. This method has low cost, fast adsorption and desorption rate, easy recovery of heavy metals, selectivity and broad prospects.
The effects of various factors on the adsorption of Cd in electroplating wastewater by Bacillus subtilis were studied. The results showed that the pH was 8, the adsorbent dosage was 10g/L (wet weight), and the stirring speed was 800r/min. , under the condition that the adsorption time is 10 minutes, the removal rate of cadmium in wastewater reaches more than 93%.
After adsorbing cadmium, Bacillus subtilis cells expand, become brighter in color, and adhere to each other. Cd2 undergoes ion exchange adsorption with sodium on the cell surface.
Chitosan is an alkaline natural polymer polysaccharide. It is obtained by deacetylation of chitin extracted from crustaceans in marine organisms. It can effectively remove heavy metal ions in electroplating wastewater.
Chitosan microspheres composed of magnetic silica nanoparticles were prepared by emulsification cross-linking method, and then modified with quaternary ammonium groups obtained by ethylenediamine and glycidyltrimethyl chloride reaction. Biosorbents have high acid resistance and magnetic response.
Use it to remove cr(VI) from acidic wastewater. Under the conditions of pH 2.5 and temperature 25℃, the maximum adsorption capacity is 233.1mg/g, and the equilibrium time is 40~120min [depending on to the initial Cr(VI) concentration. Using a mixture of 0.3mol/LNaOH and 0.3mol/LNaC1 for adsorbent regeneration, the desorption rate reached 95.6, so the biosorbent has high reusability.
3. Biochemical method
Biochemical method means that microorganisms directly react with heavy metals in wastewater to convert heavy metal ions into insoluble substances and be removed.
Three strains of bacteria that can efficiently degrade free cyanogen radicals were screened and isolated from electroplating wastewater. Under optimal conditions, they can remove 80 mg/L CN to 0.22 mg/L. Studies have found that there are many microorganisms that can reduce cr(VI) to low-toxic cr(III), such as Achromobacter, soil bacteria, Bacillus, Desulfovibrio, Enterobacter, Micrococcus, Thiobacillus, and Pseudomonas Among them, except for Escherichia coli, Bacillus, Thiobacillus, and Pseudomonas, which can reduce Cr(VI) under aerobic conditions, most of the other bacterial species can only reduce Cr(VI) under anaerobic conditions.
R.S. Laxman et al. found that Streptomyces griseus can reduce cr(VI) to cr(III) within 24 to 48 hours, and can significantly absorb and remove cr(III). Li Fu, Wu Qianjing and others from the Chengdu Institute of Biology, Chinese Academy of Sciences isolated and screened 35 strains of bacteria from electroplating sludge, wastewater and sewer iron pipes, and obtained the SR series of composite functional bacteria, which can effectively remove Cr(VI) and other The efficacy of heavy metals, and based on this, engineering applications have been carried out and achieved good results.
4. Phytoremediation method
Phytoremediation method uses the absorption, precipitation, enrichment and other functions of plants to treat heavy metals and organic matter in electroplating wastewater to achieve sewage treatment and ecological restoration. purpose.
This method causes less disturbance to the environment, is conducive to environmental improvement, and has low processing cost. Constructed wetlands play an important role in this regard and are a promising treatment method.
Leathery grass is an aquatic plant that can enrich metals and has great potential in removing heavy metals from water. Li's grass was planted in a constructed wetland to treat electroplating wastewater containing chromium, copper, and nickel, reducing their contents by 84.4, 97.1, and 94_3 respectively. When the hydraulic load is less than 0.3m/(m2·d1, the concentration of heavy metals in the effluent meets the requirements of the electroplating pollutant emission standards; when the concentrations of chromium, copper and nickel in the incoming water are 5, 10 and 8 mg/L, the standards can still be met Discharge.
It can be seen that it is feasible to treat electroplating wastewater with medium and low concentrations. The mass balance shows that chromium, copper and nickel are mostly retained in the sediments of the constructed wetland system.
08 Adsorption method
The adsorption method uses porous materials with large specific surface areas to adsorb heavy metals and organic pollutants in electroplating wastewater, thereby achieving the effect of sewage treatment.
Activated carbon is the earliest and most widely used adsorbent. It can adsorb a variety of heavy metals and has a large adsorption capacity. However, activated carbon is expensive, has a short service life, and requires regeneration, which is expensive. Some natural cheap materials, such as zeolite, olivine, kaolin, diatomaceous earth, etc., also have good adsorption capacity, but due to various reasons, they have hardly been used in engineering.
Using zeolite as an adsorbent to treat electroplating wastewater, it was found that under static conditions, the adsorption capacity of zeolite for nickel, copper and zinc reached 5.9, 4.8 and 2.7mg/g respectively. First, magnetic biochar was used to remove electroplating Cr(vI) in wastewater is then separated by an external magnetic field, resulting in a removal rate of cr(VI) of 97.11. After 10rain of magnetic separation, the turbidity dropped from 4075NTU to 21.8NTU. Their research also confirmed that the magnetic biochar still retains its original magnetic separation properties after the adsorption process. In recent years, some new adsorbent materials have been developed, such as the biosorbents and nanomaterial adsorbents mentioned in the article.
Nanotechnology refers to the study and application of atomic and molecular phenomena on the scale of 1 to 100nm. It is a multi-disciplinary science and technology developed from this and is closely linked with basic research and application. Nanoparticles have higher catalytic activity due to their nano-effects that conventional particles do not have.
The surface effect of nanomaterials makes them have high surface activity, high surface energy and high specific surface area, so nanomaterials show great potential in preparing high-performance adsorbents. Lei Li et al. used a mild hydrothermal method to rapidly synthesize titanate nanotubes (TNTs) in one step and applied them to the adsorption of heavy metal ions Pb(II), cd(II) and Cr(III) in water.
The results show that: when pH=5, the equilibrium adsorption capacities of Pb(II), Cd(II) and Cr(III) with initial concentrations of 200, 100 and 50 mg/L respectively on TNTs are respectively 513.04, 212.46 and 66.35mg/L, the adsorption performance is better than traditional adsorption materials. As a new treatment technology that is efficient, energy-saving and environmentally friendly, nanotechnology has been widely recognized by people and has great development potential.
09 Photocatalytic Technology
Photocatalytic treatment technology has the characteristics of small selectivity, high treatment efficiency, complete degradation products, and no secondary pollution.
The core of photocatalysis is photocatalyst, commonly used ones are TiO2, ZnO, WO3, SrTiO3, SnO2 and Fe2O3. Among them, TiO2 has many characteristics such as good chemical stability, non-toxicity, and both oxidation and reduction effects. TiO: When exposed to light with a certain energy, electronic transitions will occur, producing electron-hole pairs.
Photogenerated electrons can directly reduce metal ions in electroplating wastewater, while holes can oxidize water molecules into strongly oxidizing OH radicals, thereby oxidizing many refractory organic substances into COz and H: 0 and other inorganic substances are considered to be one of the most promising and effective water treatment methods.
Using suspended TiO2 as a catalyst, the photocatalytic reaction of complexed copper wastewater is carried out under the action of ultraviolet light. The results show that when the TiO2 dosage is 2g/L and the wastewater pH=4, under the irradiation of a 300W high-pressure mercury lamp and loading 60mL/min air for 40rain, the Cu(II) in the 120mg/LEDTA complexed copper wastewater will The removal rates of COD and COD reached 96.56 and 57.67 respectively. An engineering example of "physical chemistry, photocatalysis and membrane" was implemented to treat electroplating wastewater. The effluent COD removal rate reached more than 70%, and the TiO2 photocatalyst can be reused.
The introduction of the membrane method can greatly improve the water quality, making the treated water quality meet the standards for reclaimed water reuse, improving the resource utilization rate of electroplating wastewater, and the reuse rate reaches more than 85, which greatly saves costs. However, photocatalytic technology suffers from many limitations in practical applications, such as the low adsorption rate of heavy metal ions on the surface of the photocatalyst, the immature catalyst carrier, and the treatment effect drops significantly when encountering wastewater with high color, etc. However, photocatalytic technology, as an efficient, energy-saving, and clean treatment technology, will have great application prospects.
10 Heavy metal collector
Heavy metal collector is also called heavy metal chelating agent. It can produce strong chelation with most of the heavy metal ions in the wastewater, generating high Molecular chelate salts are insoluble in water and can remove heavy metal ions in wastewater through separation.
Most of the remaining heavy metal ion concentrations in the heavy metal wastewater treated with heavy metal collectors can meet the national emission standards. The dithiocarbamate heavy metal ion collector XMT was used to explore the capture effect of different factors on Cu. The Cu removal rate was above 99, the effluent Cu concentration was less than 0.05mg/L, and the effluent was far lower than that of GB21900-2008. "Table 3" standard.
Three commercially available heavy metal collectors were selected for simultaneous deep treatment of Cu2, Zn2, and Ni in actual electroplating wastewater. It was found that trisodium tripolythiocyanate (TMT) had the best removal effect on Cu. Obviously, the dosage is small and the effect is stable, but the Ni removal effect is poor. Methyl-substituted sodium dithiocarbamate (expressed as Me2DTC) has the strongest applicability and has good removal effects on all three heavy metal ions. It can meet the "Table 3" emission standards in GB21900-2008, and at DH= The processing effect is best at 9.70. As for ethyl-substituted sodium dithiocarbamate (Et2DTC), the removal effect of Ni is not good.
Heavy metal collectors are very practical due to their high efficiency, low energy, and relatively low treatment costs.
Conclusion
The composition of electroplating wastewater is complex and should be treated in separate sections as much as possible. When selecting treatment methods, the advantages and disadvantages of various methods should be fully considered, the comprehensive application of various water treatment technologies should be strengthened, and a combined process should be formed to maximize strengths and avoid weaknesses.
Heavy metals have great recycling value and are highly toxic. In the process of electroplating wastewater treatment, heavy metal recycling processes should be used to reduce emissions as much as possible.
Based on many problems such as the large sludge output of chemical precipitation method, high energy consumption of electrochemical method, high cost of membrane components of membrane separation technology and vulnerability to contamination, as far as the existing electroplating wastewater treatment technology is concerned, it should be Improve in the direction of energy saving, high efficiency and no secondary pollution.
At the same time, it can be combined with computer technology to achieve intelligent control. Materials science, biology and other disciplines can also be combined to develop new materials more suitable for treating electroplating wastewater.