Novel process to recover valuable metals from hydrometallurgical zinc residues

Zinc residues, i.e., byproducts generated in hydrometallurgical zinc plants, contain valuable elements such as zinc, iron, lead, gallium, indium and silver that are not utilized effectively. In this investigation, zinc residues containing 512-g/t silver were processed by flotation to produce concentrate assaying 4,321.6-g/t silver with an 80.96% silver recovery. The flotation tailings were then pelletized and reduced in a rotary kiln at 1,100 degrees C for two hours. During reduction, the zinc, lead and indium were recovered from the fumes. The roasted pellets were then ground and processed in a magnetic separator to obtain gallium- and germanium-rich iron concentrates. The grades of gallium and germanium in the concentrates reached 1,805 and 1,536 g/t, respectively, with recoveries as high as 94.67% and 93.20%, respectively.