Separation of oxidized zinc minerals from tailings: Influence of flotation reagents

Lead flotation tailings of Dandy mineral processing plant in north-western Iran contain oxidized zinc minerals. Zinc recovery from the tailing was studied in the presence of different flotation reagents. Microscopic analysis showed that the major phases in the tailing were smithsonite and quartz. A sulfidization–flotation method has been used on a laboratory scale to investigate the effect of various reagents such as sodium sulfide as sulfidizing agent, primary amine as collector, dispersants and flocculants. To reach an optimum zinc recovery, different concentrations of the reagents were also studied. Smithsonite is friable and a large amount of fines and slimes produce. Usually de-sliming is used to prevent slime coating and to increase the recovery of zinc. However, analyses have shown that fine particles in the sample mostly contain zinc, thus de-sliming was not suggested. To enhance zinc recovery an effective disperssing reagent could increase the flotation selectivity of these tailings. Among the dispersants tested, sodium hexametaphosphate gave a higher zinc grade of 40.7% and 70% recovery. Comparing to the dispersants used, it seems that the flocculant is not that effective in increasing the zinc recovery, simply coagulating the fine particles.