Within the scop e of this study the leaching process of Cu, Zn, Co, Mo from the complex polymetallic sulfide concentrate with high Fe, As, which was produced in Central Kazakhstan using two methods is examined. The metal concentrations in the concentrate were 0.27% Cu, 0.026% Zn, 0.464% Co, 0.057% Mo, 15.51% Fe, 7.38% As. Nitrogen oxides formed in the processes of leaching were absorbed with water, the return of absorption product to the operation of leaching allowed reducing the consumption of nitric acid. The single-stage nitric acid leaching experiment was carried out at the leach concentrate productivity of 170±20 g/h, 80±2 °С, liquid/solid mass ratio (L/S) 6/1, leach time of 10.7 h, and nitric acid (57%) consumption of 0.12±0.01 l/h. The degree of capture of nitrous gases reached 97.8%. In these conditions Cu, Zn, Co, Mo, Fe, As were obtained with dissolution efficiencies of 96.98, 64.92, 99.99, 95.39, 80.13 and 99.80% respectively. Concentrations of NO3–, H+ and redox potential in the leachate were 88.7 g/l, 1.82 mol./l and 741 mV, respectively. The two-stage counter-current nitric acid leaching experiment was carried out at the leach concentrate productivity of 170±20 g/h, 80±2 °С, L/S 6/1, leach time of 26.8 h, and nitric acid (57%) consumption of 0.06±0.006 l/h. The degree of capture of nitrous gases reached 97.8%. In these conditions Cu, Zn, Co, Mo, Fe, As were obtained with dissolution efficiencies of 99.11, 85.23, 100.00, 88.60, 77.24 and 85.56%, respectively. Concentrations of NO3–, H+ and redox potential in the leachate were 46.7 g/l, 0.35 mol/l and 658 mV, respectively. Compared to single-stage leaching, two-stage counter-current nitric acid leaching allo ws the significant economy of nitric acid (256 g of 100% HNO3 per kilogram of concentrate), which is reduction of 48%. Moreover, counter-current leaching enables reduction in concentrations of NO3–, H+ and redox potential in the leachate. The further studies should focus on possible reduction in nitric acid consumption by lowering concentration of NO3– in leachate. The authors appreciate participation of I. A. Parygin, VNIPIpromtekhnologii in this study.
Calculation of HNO2 Concentration from Redox Potential in HNO3-H2O System as an Aid to Understanding the Cathodic Reaction of Nitric Acid Corrosion
