9 Kinds Of Effective Methods For Electroplating Wastewater Treatment
Electroplating is one of the three major polluting industries in the world today. According to incomplete statistics, there are more than 10,000 electroplating enterprises in China, and the annual electroplating wastewater generated exceeds 4 billion cubic meters. If we do not deal with direct emissions, it will not only seriously pollute our living environment, but also waste our resources. For environmental protection and sustainable development of society, we must pay attention to the treatment of electroplating wastewater.
With the continuous development of electroplating process, electroplating wastewater treatment methods are also continuously innovating. Many methods of treating wastewater have also achieved recycling of various resources.
Taken together, commonly used and more effective methods include:
1. Activated carbon adsorption
Activated carbon has a very large number of microporous structures and a large surface area, Usually 1g of activated carbon surface area of 700 ~ 1700m2, so it has a strong physical adsorption force, It can effectively absorb heavy metal ions such as hexavalent chromium ions (Cr6+) in wastewater. When the activated carbon reaches the adsorption equilibrium, the adsorbent can also be removed by heating, acid soaking, alkali soaking, etc. to regenerate the activated carbon.
2. Chemical precipitation method
Adding chemicals (NaOH, lime, etc.) to electroplating wastewater, The heavy metal ions in the water react with the hydroxyl ions of the alkali to produce hydroxide precipitates that are hardly soluble in water. The hydroxide precipitate is then separated from water, to achieve the purpose of removing heavy metal ions. The treated water can be reused in production, and chromic acid can be recovered from the precipitated species. Reclaimed barium carbonate and other chemical raw materials.
3. Ion exchange method
For cyanide-containing waste water, free cyanide ions can be first converted into metal ions, ion exchange resins and the like as the exchange agent. The wastewater is passed through a mixed column of cation and anion exchange resins. After the column is saturated, it can be reused after being regenerated with inorganic acid, and the regeneration liquid is neutralized with alkali.
4. Exchange liquid membrane method
Water-in-oil-in-water double emulsion system, liquid film is kerosene and surfactants or additives, The electroplating wastewater is immersed in a carrier-free liquid film, a carrier liquid film, an impregnated liquid film, and the like. The flow carrier selectively complexes heavy metal ions at the outer phase of the membrane. Then it diffuses in the liquid film and resolves at the interface inside the film. Heavy metal ions get enriched in the membrane phase. The flow carrier returns to the interface outside the membrane, and this process is repeated and performed automatically. Wastewater is purified and heavy metals are recycled.
5. Electrolysis reduction method
The electrolytic reduction method uses the electrolysis itself to treat or recover heavy metals. At the same time, the condensation effect of metal hydroxide produced by electrolysis is utilized. It is generally applied to high concentration and single electroplating wastewater, and is particularly suitable for recycling gold, silver, copper, tin, zinc and other metals in concentrated waste liquids.
6 . Reduction precipitation method
The use of reducing agents such as FeSO4, NaHSO3, Na2SO3, SO2, or iron powders, which mainly contain hexavalent chromium ions, reduces the hexavalent chromium ions in wastewater into trivalent chromium ions. Then add NaOH or milk of lime to adjust the pH, so that trivalent chromium ions form chromium hydroxide precipitated and removed.
7. The electro-osmosis method
Using the characteristics of the anion and cation membranes, a yin and yang electrode is placed on both sides of the ion membrane, and the ions are moved after being energized. Thus, the waste water is divided into two types, thick and thin, on both sides of the membrane. Concentrated wastewater facilitate recovery of heavy metals, the diluted solution can be directly reused, or otherwise treated ion exchange discharge or reuse.
8.Biological methods
Biological methods are high-tech biotechnology for treating electroplating wastewater.
Artificially cultivated desulphurization, fungicides, chromate-reducing bacteria, Functional bacteria such as sulfate reducing bacteria can produce electrostatic adsorption of electroplating wastewater. enzymatic conversion, complexation, flocculation, absorbing coprecipitation and buffer the pH. The harmful metals are precipitated in the sludge for recycling, and the discharged water is used for bacteria cultivation and other uses. Biological treatment of electroplating wastewater has low cost, high efficiency, easy management, and no secondary pollution to the environment. Helping to improve the ecological environment is the mainstream of future electroplating wastewater treatment
9. Electroplating wastewater comprehensive treatment system
Firstly, the electroplating wastewater is pretreated and separated, and small molecular weight organic matter and suspended matter are retained. Then, the pretreated permeate is subjected to heavy metal separation using a membrane module. The concentrated solution containing heavy metals is transported to the evaporator for further concentration, and the permeate is recycled for reuse. Finally, the concentrated solution of the membrane module is further concentrated by an evaporator to reach the concentration required for electroplating and recycled to the plating tank for reuse. So that water can be completely recycled back into the environment, The sealing and systemization of electroplating wastewater treatment was achieved.
The 21st century is a century of environmental protection, and it is also a century of high technology. The electroplating industry must proceed from actual conditions, continuously increase the content of science and technology, select appropriate wastewater treatment methods, eliminate pollution to the environment, and take a sustainable approach through the comprehensive utilization of resources. The road to development achieves the three unifications of social, economic and environmental benefits.
With the continuous development of electroplating process, electroplating wastewater treatment methods are also continuously innovating. Many methods of treating wastewater have also achieved recycling of various resources.
Taken together, commonly used and more effective methods include:
1. Activated carbon adsorption
Activated carbon has a very large number of microporous structures and a large surface area, Usually 1g of activated carbon surface area of 700 ~ 1700m2, so it has a strong physical adsorption force, It can effectively absorb heavy metal ions such as hexavalent chromium ions (Cr6+) in wastewater. When the activated carbon reaches the adsorption equilibrium, the adsorbent can also be removed by heating, acid soaking, alkali soaking, etc. to regenerate the activated carbon.
2. Chemical precipitation method
Adding chemicals (NaOH, lime, etc.) to electroplating wastewater, The heavy metal ions in the water react with the hydroxyl ions of the alkali to produce hydroxide precipitates that are hardly soluble in water. The hydroxide precipitate is then separated from water, to achieve the purpose of removing heavy metal ions. The treated water can be reused in production, and chromic acid can be recovered from the precipitated species. Reclaimed barium carbonate and other chemical raw materials.
3. Ion exchange method
For cyanide-containing waste water, free cyanide ions can be first converted into metal ions, ion exchange resins and the like as the exchange agent. The wastewater is passed through a mixed column of cation and anion exchange resins. After the column is saturated, it can be reused after being regenerated with inorganic acid, and the regeneration liquid is neutralized with alkali.
4. Exchange liquid membrane method
Water-in-oil-in-water double emulsion system, liquid film is kerosene and surfactants or additives, The electroplating wastewater is immersed in a carrier-free liquid film, a carrier liquid film, an impregnated liquid film, and the like. The flow carrier selectively complexes heavy metal ions at the outer phase of the membrane. Then it diffuses in the liquid film and resolves at the interface inside the film. Heavy metal ions get enriched in the membrane phase. The flow carrier returns to the interface outside the membrane, and this process is repeated and performed automatically. Wastewater is purified and heavy metals are recycled.
5. Electrolysis reduction method
The electrolytic reduction method uses the electrolysis itself to treat or recover heavy metals. At the same time, the condensation effect of metal hydroxide produced by electrolysis is utilized. It is generally applied to high concentration and single electroplating wastewater, and is particularly suitable for recycling gold, silver, copper, tin, zinc and other metals in concentrated waste liquids.
6 . Reduction precipitation method
The use of reducing agents such as FeSO4, NaHSO3, Na2SO3, SO2, or iron powders, which mainly contain hexavalent chromium ions, reduces the hexavalent chromium ions in wastewater into trivalent chromium ions. Then add NaOH or milk of lime to adjust the pH, so that trivalent chromium ions form chromium hydroxide precipitated and removed.
7. The electro-osmosis method
Using the characteristics of the anion and cation membranes, a yin and yang electrode is placed on both sides of the ion membrane, and the ions are moved after being energized. Thus, the waste water is divided into two types, thick and thin, on both sides of the membrane. Concentrated wastewater facilitate recovery of heavy metals, the diluted solution can be directly reused, or otherwise treated ion exchange discharge or reuse.
8.Biological methods
Biological methods are high-tech biotechnology for treating electroplating wastewater.
Artificially cultivated desulphurization, fungicides, chromate-reducing bacteria, Functional bacteria such as sulfate reducing bacteria can produce electrostatic adsorption of electroplating wastewater. enzymatic conversion, complexation, flocculation, absorbing coprecipitation and buffer the pH. The harmful metals are precipitated in the sludge for recycling, and the discharged water is used for bacteria cultivation and other uses. Biological treatment of electroplating wastewater has low cost, high efficiency, easy management, and no secondary pollution to the environment. Helping to improve the ecological environment is the mainstream of future electroplating wastewater treatment
9. Electroplating wastewater comprehensive treatment system
Firstly, the electroplating wastewater is pretreated and separated, and small molecular weight organic matter and suspended matter are retained. Then, the pretreated permeate is subjected to heavy metal separation using a membrane module. The concentrated solution containing heavy metals is transported to the evaporator for further concentration, and the permeate is recycled for reuse. Finally, the concentrated solution of the membrane module is further concentrated by an evaporator to reach the concentration required for electroplating and recycled to the plating tank for reuse. So that water can be completely recycled back into the environment, The sealing and systemization of electroplating wastewater treatment was achieved.
The 21st century is a century of environmental protection, and it is also a century of high technology. The electroplating industry must proceed from actual conditions, continuously increase the content of science and technology, select appropriate wastewater treatment methods, eliminate pollution to the environment, and take a sustainable approach through the comprehensive utilization of resources. The road to development achieves the three unifications of social, economic and environmental benefits.
