Innovative technology and mechanism for comprehensive recovery of copper, nickel, zinc and iron in electroplating sludge

Electroplating sludge is a product of the purification of the electroplating wastewater by neutralization or flocculation precipitation, which belongs to dangerous solid waste. In the study, copper, nickel, zinc and iron from electroplating sludge were recovered by an innovative sulfidation roasting-flotation-magnetic separation technology. The effects of the crucial parameters on the sulfidation ratio of copper and nickel and the volatilization ratio of zinc during the sulfidation roasting were investigated. Under the optimal condition of the sulfidation roasting, the volatilization ratio of zinc reached 78.10 % and the sulfidation ratios of copper and nickel were 88.55 % and 97.86 %, respectively. The migration rule of valuable metals in the roasting process were illustrated by XRD and SEM-EDS. By the flotation treatment for the roasting products, copper-nickel mixed concentrates containing copper 2.377 % and nickel 10.28 % were obtained, and the recoveries of copper and nickel reached 83.73 % and 85.00 %, respectively. After treatment by the flotation, magnetic separation was carried out to obtain iron concentrate with iron grade and recovery of 73.77 % and 12.41 %. Finally, the toxicity characteristic leaching procedure was employed to prove the excellent stability of the heavy metals in the tailing. The study realized the efficient, comprehensive recovery of copper, nickel, zinc and iron from electroplating sludge, and provided a new idea for the harmless and resource utilization of electroplating sludge.