The composition of wastewater in electronic industry, such as electroplating and circuit boards, is very complicated. Besides wastewater containing cyanide (CN-) and acid-base wastewater, heavy metal wastewater is a potentially harmful wastewater in electroplating industry. According to the classification of heavy metal elements contained in heavy metal wastewater, it can generally be 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. A variety of treatment technologies have been developed to eliminate and reduce the discharge of heavy metals by changing toxic treatment into non-toxic and harmful treatment into harmless treatment, recycling precious metals and recycling water. With the rapid development of electroplating industry and the increasing requirement of environmental protection, at present, electroplating wastewater treatment has begun to enter the stage of clean production process, total amount control and circular economy integration, and resource recycling and closed cycle are the mainstream directions of development.

According to the statistics and investigation on the current situation of wastewater treatment in electronic industry in China, there are mainly seven different classification methods widely used: (1) chemical precipitation, which is divided into neutralization precipitation and sulfide precipitation. (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.