1. Ferrite method
The ferrite precipitation method is developed based on the principle of producing ferrite, which causes various metal ions in the wastewater to form ferrite grains and precipitate together to purify the water. After the precipitation is formed, it can be separated by magnetic force. Can achieve a good separation effect. It usually adds iron salt or ferrous salt to the waste water, heats and stirs under alkaline conditions, adds appropriate amount of additives, and finally forms ferrite. Heavy metal ions replace the position of Fe2 + or Fe3 + in the ferrite lattice through adsorption, wrapping and entrainment to form composite ferrite. The general formula of ferrite is FeO · Fe2O3.
The main advantages of the ferrite method are the wide supply of ferrous sulfate, the low price, the simple treatment equipment, the treated water can reach the standard discharge, and the sludge will not cause secondary pollution; the disadvantage is the large amount of reagent input and the amount of sludge Large, the technical conditions of sludge making ferrite are more difficult to control, consume more heat energy, and the treatment cost is also higher, which is not suitable for the treatment of large amounts of wastewater.
2. Combine chemical precipitation with other methods
Chemical precipitation combined with other methods to treat electroplating wastewater has also proved to be a practical and effective method. Ghosh et al. Used a combination of electrochemical and chemical precipitation methods to treat COD (2 400 mg / L) and Zn2 + (32 mg / L) in man-made fiber wastewater. When using lime precipitation, when the pH was 9 to 10, the 88% COD and 99% ~ 99.3% Zn2 + removal rate.
There are also some reports on the combination of chemical precipitation and ion exchange. Papadopoulos et al. Compared the removal of Ni2 + with ion exchange alone and the treatment of Ni2 + with ion exchange-chemical precipitation combined method. He found that the removal rate of Ni2 + for the former reached 74.8%, while the latter reached 94.2% to 98.3. %, A significant improvement. It can be seen that the use of chemical precipitation methods in combination with other treatment technologies can effectively reduce heavy metals.