1. Wetting phenomenon:
Wetting is a common phenomenon in nature due to the interfacial action produced by the displacement of the surface of a liquid solid on a solid surface. The surface that is easily wetted is called the lyophilic (water) surface, and its mineral is called lyophilic (water) mineral; otherwise it is called lyophobic (water) surface, lyophobic (water) mineral.
Wettability is one of the important physicochemical characteristics of mineral surface. It is a direct indicator of the good or bad of minerals. It depends on the interaction between the unsaturated bond force of the mineral surface and the dipole water molecule.
2. The meaning of wetting phenomenon in the floating selection:
The wettability of mineral surface and its regulation are the key to realize the separation of various mineral flotation. Therefore, understanding and mastering the difference of mineral surface wettability, variation law and adjustment method are of great significance to the principle and practice of flotation.
At present, there are two main methods for artificially changing the wettability (floating property): physical methods and chemical methods.
Second, the wetted contact angle Wettability is measured by contact angle measurement and wetting measurement method, commonly used contact angle θ.
Three-phase wetting periphery: When the bubble adheres to the surface of the mineral immersed in water, when the wetting equilibrium is reached, the bubble forms a periphery surrounded by three-phase contact points on the surface of the mineral. (change - balance)
Contact angle: the angle δAW between the solid-liquid interface δSW and the solid-liquid interface δSW at any point on the periphery of the three-phase wetting.
The contact angle θ is related to the interfacial tension of the three-phase interface of the contact. When the interfacial tension interaction reaches equilibrium, there is 
The contact angle is a function of the three-phase interfacial tension. Description: It is not only related to the surface properties of minerals, but also related to the interfacial properties of liquid and gas phases. Anything that causes changes in the interfacial tension of any two phases can affect the wettability of the mineral surface.
When θ>90o, δSW > δAW The mineral surface is not easily wetted by water, has a hydrophobic surface, and its mineral is hydrophobic and floatable.
When θ<90o, δSW < δAW The mineral surface is easily wetted by water, has a new water surface, and its mineral has new water and poor floatability.
Therefore, the measure of wettability and floatability of minerals can be defined as:
Wettability = cos θ.
Floatability = 1 - cos θ.
Third, wetting block 1. Wetting block:
During the wetting process, the expansion or movement of the wetted perimeter is hindered, and the equilibrium contact angle is changed. This phenomenon is called wetting retardation.
The influencing factors: wetting sequence, mineral surface composition, chemical hardness, inhomogeneity, roughness, and mineral surface wettability.
Two blocking effects of wetting block: the blocking effect of water exhaust and gas drainage.
(1) Blocking effect when water is exhausted:
There is a frictional force φ0 between the water molecule and the mineral surface.
If The water droplets continue to expand and are in equilibrium:
Therefore: θ1 > θ, cosθ1 < cosθ.
(2) Blocking effect during gas drainage:
The bubbles are unfolded on the surface of the mineral immersed in water, and the friction between the gas molecules and the mineral surface is φ2.
Since φ2 is small, θ2 ≈ θ, so θ2 < θ, cos θ2 > cos θ.
(3) Dynamic block effect:
When the plate is tilted, the water droplets are nearly able to flow along the slope. The front angle θ1 > θ, the back angle θ2 < θ, the front angle water exhaust, the back angle is gas drainage, θ1 > θ > θ2.
2. Effect of wetting resistance on flotation:
In the process of flotation, when the ore particles are attached to the bubbles, they belong to the drainage, that is, in the case where the mineral itself is floatable, the adhesion process is difficult and unfavorable for flotation. When the ore particles fall off from the bubbles, they are water and exhaust, making it difficult for water to discharge the bubbles from the surface of the minerals, preventing the particles from falling off the bubbles, which is beneficial to flotation.
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