Honghu Tang

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.

Selective adsorption of tannic acid on calcite and implications for separation of fluorite minerals

Selective adsorption of tannic acid (TA) on calcite surfaces and the implications of this process for the separation of fluorite ore were studied by microflotation tests, surface adsorption experiments, zeta potential measurements, UV-vis analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The microflotation tests indicated that TA, when added before sodium oleate (NaOl), could selectively depress calcite from fluorite at pH 7. Surface adsorption experiments revealed that TA hinders the interaction of NaOl with calcite. The zeta potential of calcite became more negative with TA than with NaOl. However, the characteristic features of TA adsorption were not observed on fluorite, suggesting that the dominant adsorption sites are dissimilar on the fluorite and calcite surfaces in the pulp. UV-vis spectroscopy, XPS, and solution chemistry analysis were utilized to obtain a better understanding of the mechanism for selective adsorption of TA as well as the key factors determined by the Ca2+ and Ca(OH)+ components on the mineral surfaces. A possible adsorption mechanism along with an adsorption mode is proposed for the surface interaction between TA and calcite.

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.

Preparation of α-CaSO4·½H2O with tunable morphology from flue gas desulphurization gypsum using malic acid as modifier: A theoretical and experimental study

Huge amount of flue gas desulphurization (FGD) gypsum not only occupies the farmland but also causes severe pollution to the surrounding environment. The most effective way to achieve a high-value utilization of FGD gypsum is to prepare short columnar α-calcium sulfate hemihydrate (α-HH) since short columnar crystals show better mechanical strength than needle-like ones. Here, malic acid, a prolific, inexpensive and environment-friendly modifier was explored for the first time to effectively tune the crystal morphology of α-HH prepared from FGD gypsum in glycerol-water-NaCl solutions. When the concentration of malic acid reached 18.54 × 10-4 mol/kg, α-HH crystals with an average aspect (length-to-diameter) ratio of 1.9 (compared to 29.4 in the absence of malic acid) were prepared. The selective complexation of malic acid with Ca active sites on different α-HH crystal planes played a dominant role in the α-HH crystal morphology transformation, which was then explained by the surface broken bonds theory for the first time. The broken bond number per active Ca atom (Nbper Ca) and broken bond density of Ca atoms (DbCa) on the (2 0 4) end plane were larger than those on the (0 2 0) or (2 0 0) side planes. Therefore, the (2 0 4) end plane was more reactive with organics, resulting in the preferential adsorption of malic acid on the end planes, which reduced the specific surface energy of (2 0 4) and led to an increased exposure of this plane and a decreased exposure of (0 2 0) or (2 0 0) side planes in the final α-HH crystals. Consequently, using malic acid as modifier, the α-HH crystal gradually transformed from a needle-like shape to a short columnar one. This work provided important insights into and perspectives for the selection of crystal modifiers and explanation of the mechanism during the preparation of calcium-containing crystals with controllable morphology.

Size-Tunable Natural Mineral-Molybdenite for Lithium-Ion Batteries Toward: Enhanced Storage Capacity and Quicken Ions Transferring

Restricted by the dissatisfied capacity of traditional materials, lithium-ion batteries (LIBs) still suffer from the low energy-density. The pursuing of natural electrode resources with high lithium-storage capability has triggered a plenty of activities. Through the hydro-refining process of raw molybdenite ore, containing crushing–grinding, flotation, exfoliation, and gradient centrifugation, 2D molybdenum disulfide (MoS2) with high purity is massively obtained. The effective tailoring process further induce various sizes (5, 2, 1 and 90 nm) of sheets, accompanying with the increasing of active sites and defects. Utilized as LIB anodes, size-tuning could serve crucial roles on the electrochemical properties. Among them, MoS2-1 μm delivers an initial charge capacity of 904 mAh g−1, reaching up to 1,337 mAh g−1 over 125 loops at 0.1 A g−1. Even at 5.0 A g−1, a considerable capacity of 682 mAh g−1 is remained. Detailedly analyzing kinetic origins reveals that size-controlling would bring about lowered charge transfer resistance and quicken ions diffusion. The work is anticipated to shed light on the effect of different MoS2 sheet sizes on Li-capacity ability and provides a promising strategy for the commercial-scale production of natural mineral as high-capacity anodes.

An extensive review on restoration technologies for mining tailings

Development of mineral resources and the increasing mining waste emissions have created a series of environmental and health-related issues. Nowadays, the ecological restoration of mining tailings has become one of the urgent tasks for mine workers and environmental engineers all over the world. Aim of the present paper is to highlight the previous restoration techniques and the challenges encountered during the restoration of mine tailings. As it is a common practice that, before restoring of tailings, the site should be evaluated carefully. Studies showed that the mine tailings’ adverse properties, including excessive heavy metal concentration, acidification, improper pH value, salinization and alkalization, poor physical structure and inadequate nutrition, etc., are the major challenges of their restoration. Generally, four restoration technologies, including physical, chemical, phytoremediation, and bioremediation, are used to restore the mining tailings. The working mechanism, advantages, and disadvantages of these techniques are described in detail. In addition, selection of the suitable restoration techniques can largely be carried out by considering both the economic factors and time required. Furthermore, the ecosystem restoration is perceived to be a more promising technology for mine tailings. Therefore, this extensive review can act as a valuable reference for the researchers involved in mine tailing restoration.