AM Gaoden HL缪 (Miay) and HR Spedden have proposed natural floatability criteria: at least when some fracture surfaces are formed, only molecular bonds (Van der Waals bonds or residual bonds) are cleaved. Or when it breaks, it has natural floatability.
The interaction between the solid and the outside depends mainly on the type of rupture bond on the surface of the new solid. The low surface energy surface formed by the molecular bond cleavage (the molybdenite [001] plane is 2.4 × 10 -2 J/m 2 ) mainly acts by van der Waals force. With FM Fox's interfacial tension theory, it is easy to explain that it is hydrophobic. On the contrary, the high-energy surface formed by the covalent bond and the ionic bond cleavage (0.7J/m 2 on the molybdenite spindle) will have a surface chemical reaction with the outside world (when the environment permits), and such a surface is placed in the aqueous medium. An oxidized zone is formed or a strong orientation of water molecules is present to make the face hydrophilic.
In nature, hydrophobic minerals that do not contain hydrophilic regions are rare, and most of them are minerals that contain both "hydrophobic surfaces" and "hydrophilic surfaces", such as molybdenite, talc , and pyrophyllite. DW Fulstenau has a combination of a molecular bond cleavage surface (hydrophobic surface) and an ionic bond and a covalent bond cleavage surface (hydrophilic surface), which is called an "heteropolar surface". Obviously, molybdenite is a typical "heteropolar surface" mineral.
BV Ter good Jinhe ND Sarkar gemcitabine colloidal stability DLVD according to theory, the new criterion hydrophobic mineral floats:
P>O mineral does not float; P
Among them: P-shedding pressure; Pгω-van der Waals pressure; Pe-electric double layer pressure; Ph-solid and liquid film hydration energy and potential energy resistance.
When the molecular force only considers the London dispersion effect, Pгω=AÏs-AÏÏ/6Ï€h 3
Among them: AÏs-liquid-solid interaction Hamek constant; AÏÏ-liquid-solid interaction Hamek constant. When AÏs < AÏÏ, the liquid film is unstable, and the solid is completely hydrophobic.
However, full hydrophobicity is not a sufficient criterion for natural floatability. Since the mineral has a hydrophobic region or a polar region, there is also an oxidized region or a polar region. It makes Pe and Ph more important. For "heteropolar surfaces", the floating interference of Pe and Ph caused by hydrophilic surfaces cannot be ignored. Sometimes, Pe and Ph even play a decisive role. These effects will in turn affect the mineral floatation by ξ-potentials and the like.
S. Chand photographed the wetting state of water droplets on the "face" or "edge" of the molybdenite (see Figure 1).
Fig.1 Moisture pattern of water droplets on different fracture surfaces of molybdenite
Molybdenum ore in the medium of PH2~9, the contact angle does not change. It varies around 80 °C depending on the mineral source and preparation method. The contact angles of some natural hydrophobic minerals reported by DW Fulsing, JD Miller and Kuhn are shown in Table 1. AA certain minerals. Abramov emulsified kerosene plotted in Figure 2 may float changes.
Table 1 Several mineral contact angles
Mineral | Composition | Planes | Contact angle (degrees) |
Stone ink coal Natural sulfur Molybdenite Talc Mine silver iodide | C S MoS 2 (Mg 3 Si 4 O 10 )(OH) 2 AgI | 0001 | 86 30~60 85 75 88 20 |
Figure 2 Effect of floating kerosene on mineral floatability (AA. Abramov)
Obviously, molybdenite is similar to graphite , natural sulfur, and talc. It has a large contact angle and high recovery rate of flotation. It is a typical natural floatable mineral.
In the production of molybdenum ore dressing , in order to improve the recovery rate of molybdenum ore, it is particularly important to reduce Pe and Ph and reduce the dryness of the molybdenum ore in the hydrophilic zone (edge).
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