The composition of wastewater from electroplating, circuit boards and other electronic industries is very complicated. Besides cyanide-containing wastewater and acid-base wastewater, heavy metal wastewater is a kind of potentially harmful wastewater in electroplating industry. According to the classification of heavy metal elements contained in heavy metal wastewater, it can be generally divided into wastewater containing chromium (Cr), nickel (Ni), cadmium (Cd), copper (Cu), zinc (Zn), gold (Au) and silver (Ag). The treatment of electroplating wastewater has been paid more and more attention at home and abroad. By changing toxic treatment into non-toxic, harmful treatment into harmless treatment, recovering precious metals, recycling water and other treatment technologies, the discharge of heavy metals is eliminated and reduced. With the rapid development of electroplating industry and the increasing requirements of environmental protection, electroplating wastewater treatment has begun to enter the stage of clean production process, total control and circular economy integration, and resource recycling and closed-circuit circulation are the mainstream directions of development.
According to the statistics and investigation on the present situation of wastewater treatment in China's electronics industry, there are seven different classification methods widely used at present: (1) chemical precipitation method, which is divided into neutralization precipitation method and sulfide precipitation method. (2) Redox treatment is divided into chemical reduction method, ferrite method and electrolysis method. (3) Solvent extraction separation method. (4) Adsorption method. (5) Membrane separation technology. (6) ion exchange method. (7) Biological treatment technologies, including biological flocculation, biological adsorption, biochemistry and phytoremediation.