Self-sulfidation roasting and flotation of electroplating sludge: An innovative technology for metal recovery

•An innovative technology of self-sulfidation roasting and flotation for the efficient recovery of valuable metal elements in electroplating sludge was proposed.•Copper and nickel sulfidation ratios in the electroplating sludge without addition of sulfidation reagents reached 82.80% and 97.39%, respectively.•Zinc volatilization ratio in the electroplating sludge reached 87.98%.•Copper-nickel concentrate achieved recovery ratios of 64.37% for copper with a grade of Cu 2.7%, and 67.38% for nickel with a grade of Ni 12.84%. Electroplating sludge is classified as a solid hazardous waste, which presents significant environmental and human health risks, while also resulting in substantial depletion of valuable metals. The study proposed an innovative technology of self-sulfidation roasting and flotation for the efficient recovery of valuable metal elements in electroplating sludge. The distinguishing feature lied in utilizing the calcium sulfate present in the electroplating sludge as the sulfidation reagent, thereby achieving self-sulfidation roasting without the need for additional sulfidation reagents. The decomposition process of calcium sulfate and influence factors during self-sulfidation roasting were investigated by thermogravimetric analysis and roasting experiments. Under optimized conditions, copper and nickel sulfidation ratios in the electroplating sludge reached 82.80% and 97.39%, respectively, while zinc volatilization ratio reached 87.98%. XRD and SEM-EDS techniques were employed to reveal phase evolution and surface morphology of the roasted products. Finally, copper-nickel concentrate achieved recovery ratios of 64.37% for copper with a grade of Cu 2.7%, and 67.38% for nickel with a grade of Ni 12.84%. This study presented a novel and effective approach towards secondary utilization of solid wastes.