Reverse flotation separation of talc from molybdenite without addition of depressant: Effect of surface oxidation by thermal pre-treatment

Comparison and Mechanism Analysis of Three-Phase Contact Formation onto Hydrophilic/Hydrophobic Mineral Surfaces in the Presence of Cationic/Anionic Surfactants during Flotation Process

This article presents the dynamic process of the three-phase contact (TPC) formation by colliding bubbles onto muscovite and talc surfaces in water and two types of solutions including cationic CTAC surfactant (cetyltrimethyl ammoniumchloride) and anionic NaOL surfactant (sodium oleate). The TPC formation process was observed through the high-speed camera between bubbles and layered silicate minerals (hydrophilic muscovite and hydrophobic talc). It was found that the rupture of the liquid film between the bubbles and the mineral surface is a prerequisite for TPC formation. In the case of muscovite, TPC was formed only with cationic CTAC, and as the surfactant concentration increased, the time needed for TPC formation was shortened. Due to electrostatic repulsion, TPC did not occur in water and NaOL. However, for talc, TPC occurred both in water and in surfactant solutions. In contrast to muscovite, the time of TPC formation on the talc surface was prolonged with the increase in the surfactant concentration. It was concluded that hydrophobic attraction and electrostatic attraction between mineral surfaces and bubbles can significantly promote the localized foam film rupture, which was the main reason for the TPC appearance in water and surfactants. For the hydrophilic muscovite, CTAC adsorption improved the surface hydrophobicity; I3/I1 in fluorescence spectroscopy increased, and the micro-polarity faded, making TPC formation need more time. However, for the natural hydrophobic talc, the increasing surfactant adsorption decreased I3/I1 values and enhanced the local micro-polarity, causing the extension of time for TPC. Therefore, TPC formation for different minerals resulted from different reasons.

Recent progress on research of molybdenite flotation: A review

Molybdenum is an important alloy element for metallurgical industry because of its high temperature stability. As the major mineral reserve for molybdenum, molybdenite (MoS₂) is commonly found in porphyry copper deposits. Molybdenite is naturally floatable and can be separated from copper sulfide mineral using froth flotation. Properties of molybdenite such as mineralogy, microstructure, surface wettability, zeta potential, etc. can have a great effect on its floatability. Organic and inorganic depressants and surface pre-treatment methods are applied to improve the recovery of molybdenite. Electrochemical potential measurements using different electrodes are used to monitor process conditions and enable processing parameter adjustments to improve flotation circuit performance and reduce operating costs. Cations like Ca²⁺ and Mg²⁺ are reported to have negative effects on the flotation of molybdenite in alkaline solution, and dispersants and oil collectors need to be added to restore the flotation of molybdenite. In addition, effects of gangue minerals, particle size, and oil collectors and surfactants on molybdenite recovery are also discussed in this manuscript.