Abstract
Current challenges in froth flotation are the presence of complex gangues and the use of low-quality waters, such as seawater. In this scenario, the recovery of molybdenum minerals is difficult, mainly due to the hydrophobic faces’ physicochemical changes. In the present study, the natural floatability of pure molybdenite was analyzed by using microflotation assays, and hydrophobicity was measured by performing contact-angle measurements. The impact of two clays, kaolin (non-swelling) and Na-montmorillonite (swelling), was studied. The behavior in freshwater and seawater at pH 8 was compared, considering the current condition of the Cu/Mo mining industries, which use seawater in their operations. The presence of clays lowered the natural floatability of molybdenite precisely because they adhere to the surface and reduce its contact angle. However, the intensity with which they cause this phenomenon depends on the type of water and clay. Kaolin strongly adheres to the valuable mineral in both freshwater and seawater. For its part, Na-montmorillonite does it with greater intensity in a saline medium, but in freshwater, a high concentration of phyllosilicate is required to reduce the hydrophobicity of molybdenite. The clays’ adherence was validated by scanning electron microscopy (SEM) analysis.
Highlights
Molybdenite (MoS2 ) is the most important primary source of molybdenum, which is essential for its several physical properties, such as stability and resistance to high temperatures, high thermal and electrical conductivity, resistance to attack by molten metal, and high rigidity
It should be noted that Qiu et al [25] obtained a contrary trend, with recoveries close to 85% in distilled water, rising to 95% in seawater, at pH 8. The researchers developed their experiments by using a classic collector of the copper industry, potassium amyl xanthate (PAX), but in our study, only a frother agent (MIBC) was applied
This phenomenon is similar to that reported by Yepsen et went down from −35 to −9 mV. This leads to a heterocoagulation in seawater between the al. [26], who studied micas’ effect on the floatability of molybdenite in seawater,6 of and clays and the valuable mineral. This phenomenon is similar to that reported by Yepsen et Ramírez et al [27], who analyzed the impact of kaolinite on molybdenite flotation in seaal. [26], who studied micas’ effect on the floatability of molybdenite in seawater, and water
Summary
Molybdenite (MoS2 ) is the most important primary source of molybdenum, which is essential for its several physical properties, such as stability and resistance to high temperatures, high thermal and electrical conductivity, resistance to attack by molten metal, and high rigidity. The authors explained their results with the DLVO theory, based on the reduction of electrostatic repulsion between the bubbles and the anionic edges of the molybdenite It is common for copper-moly ores to be processed under highly alkaline conditions, avoiding pyrite recovery [15,16]. They have two crystallographically different surfaces, namely the faces that tend to be negatively charged and the edges that vary their charge according to the pH [20] These particles may coagulate with valuable minerals, generating a hydrophilic layer around the surface that impairs contact with the collector and bubbles (coating effect) [21]. In Na-montmorillonite, an octahedral alumina sheet shares oxygen atoms with two silica sheets (TOT; 2:1), resulting in a three-layer mineral These clays have anionic-electric-charge sites on the basal planes, due to substituting the Si and Al in the crystal lattice for cations of lower positive valence. The clays’ adherence was analyzed by using scanning electron microscopy (SEM)
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