The precipitation method for electroplating wastewater treatment is introduced as follows:
(1) Neutralization precipitation method. The alkali is added to the electroplating wastewater containing heavy metals to neutralize the reaction, so that the heavy metals form a water-insoluble hydroxide precipitation form to be separated. The neutralization sedimentation method is easy to operate and is a commonly used method for wastewater treatment.
(2) Chelation precipitation method. The heavy metal trapping precipitant reacts rapidly with heavy metal ions such as Hg2 +, Cd2 +, Cu2 +, Pb2 +, Mn2 +, Ni2 +, Zn2 +, and Cr3 + in the wastewater at room temperature to form an insoluble water chelate salt, and then add a small amount of organic or (and ) Inorganic flocculant, forming flocculent precipitate, so as to achieve the purpose of trapping and removing heavy metals.
(3) Sulfide precipitation method. The method of adding sulfide to precipitate and remove heavy metal ions in electroplating wastewater to form sulfide. Compared with the neutralization precipitation method, the advantages of the sulfide precipitation method are: the solubility of heavy metal sulfide is lower than that of its hydroxide, the reaction pH is between 7-9, and the treated wastewater generally does not need to be neutralized, and the treatment effect better. However, the disadvantage of the sulfide precipitation method is that the sulfide precipitation particles are small, and it is easy to form colloids. The sulfide precipitation remains in the water and generates gas when encountering acids, which may cause secondary pollution.