The Influence of Backwater Al3+ on Diaspore Bauxite Flotation

Synchrotron Radiation XRD Investigation of the Fine Phase Transformation during Synthetic Chalcocite Acidic Ferric Sulfate Leaching

The fine phase transformation process of chalcocite (Cu2S) leaching in acidic ferric sulfate solution was studied by leaching experiments and synchrotron radiation X-ray diffraction (SRXRD) tests. The results showed that the dissolution process of chalcocite was divided into two stages. In the first stage, Cu2S was firstly transformed to Cu5FeS4 and Cu2−xS, then the galvanic effect between Cu5FeS4 and Cu2−xS accelerated the dissolution process of Cu1.8S → Cu1.6S → CuS, and finally Cu5FeS4 was also transformed to CuS. While in the second stage, CuS was transformed to elemental sulfur, which formed the passivation layer and inhibited the leaching of chalcocite. Specifically, Cu5FeS4 was detected during the chalcocite leaching process by SRXRD for the first time. This research is helpful for revealing the detailed leaching process of chalcocite.

A review of the surface features and properties, surfactant adsorption and floatability of four key minerals of diasporic bauxite resources

Diasporic bauxite represents one of the major aluminum resources. Its upgrading for further processing involves a separation of diaspore (the valuable mineral) from aluminosilicates (the gangue minerals) such as kaolinite, illite, and pyrophyllite. Flotation is one of the most effective ways to realize the upgrading. Since flotation is a physicochemical process based on the difference in the surface hydrophobicity of different components, determining the adsorption characteristics of various flotation surfactants on the mineral surfaces is critical. The surfactant adsorption properties of the minerals, in turn, are controlled by the surface chemistry of the minerals, while the latter is related to the mineral crystal structures. In this paper, we first discuss the crystal structures of the four key minerals of diaspore, kaolinite, illite, and pyrophyllite as well as the broken bonds on their exposed surfaces after grinding. Next, we summarize the surface chemistry properties such as surface wettability and surface electrical properties of the four minerals, and the differences in these properties are explained from the perspective of mineral crystal structures. Then we review the adsorption mechanism and adsorption characteristics of surfactants such as collectors (cationic, anionic, and mixed surfactants), depressants (inorganic and organic), dispersants, and flocculants on these mineral surfaces. The separation of diaspore and aluminosilicates by direct flotation and reverse flotation are reviewed, and the collecting properties of different types of collectors are compared. Furthermore, the abnormal behavior of the cationic flotation of kaolinite is also explained in this section. This review provides a strong theoretical support for the optimization of the upgrading of diaspore bauxite ore by flotation and the early industrialization of the reverse flotation process.

The role of EDTA on rutile flotation using Al3+ ions as an activator

Rutile is a relatively stable mineral, due to its weakly specific adsorption to collectors. The development and application of a high efficiency and low-toxicity activator is the main challenge in rutile flotation. In this study, Al³⁺ ions and EDTA (ethylene diamine tetraacetic acid) as mixed activators were investigated using micro-flotation tests. The results of the micro-flotation tests showed that the flotation recovery was slightly increased (from 65.8% to 69.7%) using single Al³⁺ ions as the activator and surprisingly, the activating effect was sharply improved (from 69.7% to 80.6%) after adding EDTA. The activating mechanism of Al³⁺ ions and EDTA was revealed by adsorption capacity measurements, zeta potential measurements, FT-IR spectroscopy analysis and XPS analysis. Al³⁺ ions were adsorbed on the rutile surface in the form of Al(OH)_n³⁻ⁿ (n = 0, 1, 2), which increased the zeta potential and the activating sites for anionic collector adsorption. The addition of EDTA removed the surplus Al³⁺ ions, and prevented the generation of hydrophilic colloidal Al(OH)₃ over the pH range of optimum flotation.

The adsorption model of Al³⁺ ions, EDTA and SPA on the rutile surface.