Optimization of thiourea-assisted silver leaching from sintering dust by response surface methodology

The dust of iron-making sintering process arrested by electrostatic precipitation (sintering dust) that were used as the experimental materials, and the chemical compositions and phases of sintering dust were characterized by XRF, XRD, SEM-EDS techniques, acidic thiourea were applied for silver extraction from sintering dust. The response surface methodology (RSM) was used to optimize the extraction conditions on the basis of single factor experiments in silver leaching process. Silver leaching rate as response indicators, and the process variables (reaction temperature, thiourea concentration, leaching time) as independent factors were investigated with significant effect on silver leaching from sintering dust, then central composite design (CCD) involving three factors at five levels was employed in silver extraction from sintering dust. Optimal process parameters on silver extraction from sintering dust and two order polynomial equation of model with high fitting degree were obtained. The results show that optimum technological conditions are that reaction temperature at 50℃, thiourea concentration at 22 g/L and the leaching time at 90 min. Under the optimum conditions, the theoretical leaching rate of silver of model predicts can reach 89.38%, while the experimental value is 89.9% with a relative stand error is 0.52%. It indicated that the actual value is close to the model prediction value, thus the model can be used to predict the leaching silver from the sintering dust.