Behaviors of Silicon, Aluminum and Iron and Kinetics of Silicon from the Roasted Clinker of Silver Tailings in Water–Acid Leaching Process

Abstract

In order to achieve efficient resource utilization of metal tailings, taking the roasted clinker of silver tailings (RCST) as the object, the dissolution behaviors of Si, Al and Fe in the water–acid two-stage leaching process and the water leaching kinetics of Si were investigated in this study. Single-factor experiments were performed to investigate the effects of the leaching parameters; the XRF, XRD and SEM-EDS methods were used to characterize the leaching residues with different leaching times, and the leaching kinetics models of Si were established. The results demonstrate that, in the water leaching stage, the sodium silicate and a small part of the structurally unstable sodium aluminosilicate in RCST are dissolved, while the nepheline, most of the sodium aluminosilicate and the mixed materials containing iron enter the water leaching residue. The first 5 min of water leaching is controlled by both interfacial transfer and diffusion across the product layer, with an apparent activation energy of 22.36 kJ/mol, and the dissolution reaction during 5–15 min is controlled by the unsteady diffusion of the liquid film, with an apparent activation energy of 14.22 kJ/mol. The structure of the materials in the clinker is completely destroyed, and a great number of fissures and pores are produced by the continued dissolving action of the water. Thus, in the acid leaching stage, the amorphous Si-, Al- and Fe-containing substances in the water leaching residue are rapidly dissolved in the sulfuric acid solution at a lower temperature.