Sulphuric Acid Leaching Germanium from Germanium Dust and Fume: Process Optimization Using Response Surface Methodology

Germanium leaching from germanium dust and fume was carried out using sulphuric acid. Response surface methodology, based on a five level, four variable central composite designs, was employed to obtain the best possible combination of liquid/solid ratio, leaching time, sulphuric acid concentration and leaching temperature for germanium leaching. The experimental data obtained were fitted to a one-order polynomial equation using multiple regression analysis and also were analyzed by analysis of variance. The 3-D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. The conditions were: liquid/solid ratio of 10, leaching time of 1 h, sulphuric acid concentration of 15.75 mol/L, and leaching temperature of 87.8. Under these conditions, the germanium leaching rate was 65.14%, which is well in close agreement with the value predicted by the model. The samples were characterized before and after leaching using X-ray diffraction.