Haisheng Han

Anglesite and silver recovery from jarosite residues through roasting and sulfidization-flotation in zinc hydrometallurgy

Hazardous jarosite residues contain abundant valuable minerals that are difficult to be recovered by traditional flotation process. This study presents a new route, roasting combined with sulfidization-flotation, for the recovery of anglesite and silver from jarosite residues of zinc hydrometallurgy. Surface appearance and elemental distribution of jarosite residues was examined by scanning electron microscopy and energy dispersive X-ray spectrometry analysis, respectively. Decomposition and transformation mechanisms of jarosite residues were illustrated by differential thermal analysis. Results showed that after roasting combined with flotation, the grade and recovery of lead were 43.89% and 66.86%, respectively, and those of silver were 1.3 kg/t and 81.60%, respectively. At 600-700 °C, jarosite was decomposed to release encapsulated valuable minerals such as anglesite (PbSO4) and silver mineral; silver jarosite decomposed into silver sulfate (Ag2SO4); and zinc ferrite (ZnO · Fe2O3) decomposed into zinc sulfate (ZnSO4) and hematite (Fe2O3). Bared anglesite and silver minerals were modified by sodium sulfide and easily collected by flotation collectors. This study demonstrates that the combination of roasting and sulfidization-flotation provides a promising process for the recovery of zinc, lead, and silver from jarosite residues of zinc hydrometallurgy.

A novel flotation scheme: selective flotation of tungsten minerals from calcium minerals using Pb–BHA complexes in Shizhuyuan

The similar floatabilities of calcium minerals and the huge difference between scheelite and wolframite have resulted in difficulties during their separation by flotation in Shizhuyuan Mine. In this study, novel collectors, lead complexes of benzohydroxamic acid (Pb–BHA), were introduced to modify the surface properties of scheelite and wolframite, thereby effectively and selectively improving floatability. The Pb–BHA complexes are found to be selective for the separation of scheelite and calcium minerals with little use of depressants and enable the synchronous flotation of scheelite and wolframite. Hence, a novel flotation process was developed for the recovery of tungsten minerals. The process is simplified greatly, and the recovery is improved by almost 10%. Removing or decreasing the amount of water glass contributes to the improvement of tungsten and fluorite recovery and the circulation of water and reagents, which benefits the environment.

A novel method for comprehensive utilization of sintering dust

Abstract A novel process aimed at the comprehensive utilization of sintering dust was developed by combining wetting grinding with sulfidization flotation. The mineralogical characteristics of the sintering dust and products were studied by powder wettability analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and mineral liberation analyzer (MLA). It was found that the primary lead species was laurionite and most of the particles were overwrapped with KCl. Wetting grinding was shown to accelerate the dispersion of sintering dust and transform the KCl overlay to a leachate with 20.78 g/L of K + . A lead and silver concentrate consisting of 40.82% of Pb and 0.96 kg/t of Ag was achieved, while an iron concentrate with 60.89% of Fe was gained as tailings among sulfidization flotation. The recoveries of Pb, Ag and Fe were 89.57%, 87.85% and 88.58%, respectively. The results indicate that this method is a feasible and promising process for the comprehensive utilization of sintering dust.

Activation role of lead ions in benzohydroxamic acid flotation of oxide minerals: New perspective and new practice

Metal ions are commonly used as activators to improve the anionic collector flotation of oxide minerals with an accepted activation mechanism that the prior addition of metal ions can adsorb onto the oxide mineral surface to increase the number of active sites for subsequent attachment of a collector. The improved flotation of cassiterite (or scheelite) with the use of lead nitrate (LN) as the activator and benzohydroxamic acid (BHA) as the collector is a typical example. However, our recent research showed that a soluble metal-organic complex (lead-BHA complex) produced by pre-mixing LN and BHA further improved the collecting ability and selectivity in the flotation of cassiterite and for that, the existing activation mechanism cannot completely explain this further improved performance. We believe that the lead ion and its hydroxide species can directly interact with water molecules to form Pb(H2O)n2+ and Pb(OH)(H2O)n+ complexes in water solution, and those bonded water molecules will in turn affect the interaction of (hydroxide) lead ion with the cassiterite surface and the BHA. In this work, solution chemistry calculation was used to identify the major active components of the lead-BHA complex in water solution at different pH levels, and based on density functional theory, the adsorption energies of different activation mechanisms were calculated via accurate first-principle calculations, indicating a much stronger interaction of the adsorption of HO-Pb-BHA complex on cassiterite surface (-48.11 kcal/mol) compared with that of the sequential adsorption of Pb(OH)(H2O)5+ and BHA anion (-13.29 kcal/mol) at optimal flotation pH 8-9. That is, the difference in two activation systems can be explained based on thermodynamics. With such, a new hypothetic activation model was proposed to explain the improved performance of soluble lead-BHA complex and then, the proposed model was verified by the flotation experiment and adsorption test results. This work can help enrich the activation theory of metal ions in anionic collector flotation of minerals.