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The heavy metals in wastewater cannot be decomposed and destroyed by various common methods, but can only transfer their location and change their physical and chemical forms. After treatment of heavy metal wastewater, two products are formed, one is the treated water from which heavy metals are basically removed, and the other is the concentrated product of heavy metals.
Heavy metal wastewater treatment methods can be divided into two categories: one is to convert heavy metals in a dissolved state into insoluble heavy metal compounds or elements, which are removed from the wastewater by precipitation and floating. The neutralization precipitation method, the sulfide precipitation method, and the Floating separation method, ion flotation method, electrolytic precipitation or electrolytic floating method, diaphragm electrolysis method, etc.; the second is to concentrate and separate heavy metals in wastewater without changing their chemical form. Reverse osmosis and electrodialysis can be used Method, evaporation method, ion exchange method, etc. The processing principle is as follows:
1) Electrolysis method:
It is widely used to treat cyanide-containing heavy metal wastewater. Cyanide and heavy metals in wastewater are removed by electrolytic oxidation to decompose cyanide and precipitate heavy metals into hydroxides. The electrolysis treatment of mercury sulfide residue can efficiently recover pure mercury or mercury compounds.
2) Float method:
The heavy metal hydroxides and sulfides in the wastewater can also be removed by the air blast floatation method, of which the pressurized dissolved air floatation method is the most effective. Electrolytic floatation process can effectively treat a variety of heavy metal wastewater, especially wastewater containing heavy metal complexes.
3) Ion flotation method:
Add anionic surfactants to the heavy metal wastewater, such as sodium xanthate, sodium dodecylbenzene sulfonate, gelatin, etc., to form a complex or chelate with the heavy metal ions in it. Different surfactants have selective complexation to different metal ions or the same surfactant under different pH values and other conditions, so that heavy metals in wastewater can be floated and separated.
4) Membrane method:
There are mainly electrodialysis and reverse osmosis methods. The characteristic of electrodialysis is that the concentration ratio is limited, and it must be treated by multi-stage electrodialysis to concentrate the useful substances in the wastewater to the extent that it can be reused. The reverse osmosis method is used to treat electroplating rinsing wastewater such as nickel plating, copper plating, zinc plating, and cadmium plating.
When the treated heavy metal wastewater still fails to meet the discharge requirements, it can be directly treated with heavy metal capture agents. The agent has fast reaction speed and excellent treatment effect, is suitable for the post-treatment of heavy metal wastewater, and is a good auxiliary treatment agent.
RJ dewaterintel environment Co.,Ltd founded in 2015, it is a company dedicated to environmental pollution control industry, specializing in the full treatment of organic waste (food and kitchen waste, sludge, livestock and poultry manure, Chinese medicine, etc.) including planning, core equipment R&D, design, engineering construction EPC general contracting and operation maintenance, and the main production equipment includes screw press dehydrator, solid liquid separator, kitchen waste separator, air floatation machine, chemical dosing machine and pump etc. For more information, visit www.dewaterintel.com, or email to [email protected].