Drying Technology
Due to the characteristics of heavy metal wastewater, basic treatment methods cannot decompose and destroy the molecular structure of heavy metal wastewater, but can only transfer their location and change their physical and chemical forms.
Principles of heavy metal wastewater treatment methods:
1) Treated water with heavy metals removed
2) Concentrated products of heavy metals
Disposal methods of heavy metals sewage
1. Chemical Precipitation
A method of converting heavy metals in a dissolved state into heavy metal compounds that are insoluble in water during the treatment of heavy metal wastewater.
In a word, it is to directly add heavy metal trapping agent in the sewage, which is suitable for the treatment of multiple ions exceeding the standard.
The heavy metal capture agent can be applied to a wide range of pH conditions and is not affected by the concentration of heavy metal ions.
2. Electrolysis
Cyanide and heavy metals in wastewater are removed by electrolytic oxidation to decompose cyanide and form hydroxides of heavy metals to precipitate.
This method is widely used to treat cyanide-containing heavy metal wastewater.
3. Solvent extraction and separation
The extraction method is to add an organic solvent that is incompatible with water and has a density less than water into the sewage, and after thorough mixing and contact, the pollutants are redistributed and the solvent is separated.
The solvent used is called the extractant, and the substance proposed is called the extract. Extraction is a liquid-liquid mass transfer process, which uses the difference in solubility of pollutants in water and organic solvents for separation.
It should be noted that this method has certain limitations. The solvent is lost during the extraction process and the energy consumption is large during the regeneration process.
On the other hand, the total power output of the sewage plant in 2016 reached 4.8GWh, which means that the power generation of the plant is 53% more than the power consumption. This excess power will be sold to the national grid, and there is more than 2.5GW of surplus The heat energy is directly used for district heating.
4. Ion exchange method
The method of using ion exchangers to separate harmful substances in wastewater, such as ion exchange resins, zeolites, and so on.
Ion exchange is achieved by ion exchange between the freely movable ions carried by the exchanger itself and the ions in the solution being treated.
The problem of the high regeneration cost of the exchanger cannot be solved, and it is also one of the important factors that restrict the development of this method.
The above are the more common heavy metal wastewater treatment methods. Among them, the chemical precipitation method-heavy metal capture agent, is widely used because of its low cost, simple operation and high removal efficiency.
