Reprocessing of the old flotation tailings deposited on the RTB Bor tailings pond - a case study

Flotation waste, which was produced through seventy years of copper ore pro- cessing in RTB Bor, Serbia, is deposited in a flotation tailings pond. In total, almost 26.4 Mt could be considered as available for eventual reprocessing and reuse. Chemical analysis has shown that an average concentration of targeted metals in the tailings is: 0.183% Cu, 0.35 g/t Au and 217 g/t Ag. The tailings contain 60 to 70% of SiO2, 10 to 17% of Al2O3 and pyrite 5 to 8%. Flotation tailings reprocessing consisted of acid leaching followed by re-flotation of the leach residue. Leaching of the tailings resulted in leach liquors containing Cu2+ ions from 50 to 580 ppm. The average copper removal degree in the leaching stage was 70%. After re-flotation, the total copper removal degree reached 83 to 85%. Sulphur removal degree reached 77%. Sulphur concentration in the treated tailings was reduced almost 5 times compared to the inlet concentration. An equivalent amount of iron was also reduced through the flotation process. Concentration of total copper was reduced 3 times.