Kinetics of ultrasound-assisted silver leaching from sintering dust using thiourea

In the process of steel manufacture, up to tens of millions of tons of sintering dusts are produced annually in China, which contain noble metals such as Ag. Therefore, the recovery of Ag from sintering dust could be a potential economic and environmental activity. The present work attempts to use ultrasound for leaching silver from the water-leaching residue of sintering dust (WLR-SD) by acidic thiourea at atmospheric pressure. The effects of particle size, leaching temperature, and thiourea concentration were assessed on the leaching efficiency. Mineralogical changes of the WLR-SD were estimated using X-ray fluorescence, X-ray diffraction, and scanning electron microscope. The results have shown that under the conditions used, up to 94% silver could be leached. The leaching kinetics was estimated to follow the first-order kinetic model, and the activation energy was estimated to be 20.7 kJ/mol, confirming an internal diffusion-controlled leaching process. The order of the reaction with respect to the thiourea concentration was estimated to be 0.68.