Flotation: A method of separating various fine particles according to the difference in physicochemical properties of mineral surfaces.
effect:
(1) The adaptability of flotation is strong
(2) High efficiency of flotation and suitable for processing fine materials
(3) Conducive to the comprehensive recovery of mineral resources
2. The flotation process and the status of its three phases in the sorting.
Flotation process: complex physical and chemical processes completed in gas, liquid, and solid three-phase systems. In fact, the hydrophobic useful mineral adheres to the bubble, and the hydrophilic gangue mineral remains in the water, thereby achieving separation from each other.
In the flotation process of minerals, the solid phase is the sorting object, the liquid phase is the sorting medium, and the gas phase is the sorting carrier. Therefore, this chapter focuses on the structure and properties of each phase of flotation.
3. Classification and structure of crystals.
(1) Ionic crystal
(2) molecular crystal
(3) Atomic crystal
(4) the metal crystals
4. The cause and type of mineral surface polarity and the effect on floatability.
The particles that make up the mineral crystal are not only ordered in a certain spatial geometry, but also the vertices are connected to each other by some kind of bond force. The state of the crystal on the surface of the crystal and the inside of the crystal are not the same. The internal ones are in balance, the particles on the fracture surface have unsaturated bond forces and the unsaturated procedures of the bond forces are also different due to different positions, showing different adsorption capacities and active activities. In particular, after the ore is crushed and finely ground, the specific surface area increases, the angular shape formed increases more, and the "active center" of adsorbing other substances is formed more. The finer the finer ore, the adsorption capacity and the active activity. The stronger it is.
(1) Strong bonding force: covalent bond, ionic bond, metal bond
The particles on the fracture surface have strong polar and chemical activity, polar surface, strong attraction to dipolar water molecules, easy to be wetted by water, and strong hydrophilicity and poor natural floatability. This surface is a hydrophilic surface. Naturally low floatability.
(2) weak bonding force:
The unsaturated bond force exhibited by the fracture surface is mainly intermolecular force, and the polarity is small. It is called a non-polar surface. It has weak interaction with dipolar water molecules, is not easily wetted by water, and exhibits hydrophobicity and easy adsorption to bubbles. Good floatability.
5, affect the structure of the model and its main components of coal to be floating nature.
Structural model:
Coal is a polycyclic aromatic polymer compound composed of a large number of benzene nuclei composed of a multilayer planar carbon network and having an oxygen-containing group and an alkyl side chain.
Impact on floatability:
Coal is an amorphous structure, non-uniform, mainly composed of organisms, the surface of the main body is hydrophobic, and floatable; it has a number of side chains on the aromatic nucleus and is hydrophilic.
The structure of coal contains a certain amount of minerals, so that the surface of the coal is locally polar and hydrophilic;
The degree of metamorphism of coal has a great influence on the floatability of coal;
Coal is easily oxidized.
6. The nature of water and its role in flotation.
Basic properties:
(1) The density of water is the highest at 4 °C. 4 ° C is slightly above freezing point.
(2) has a high valence constant.
(3) It has a high solubility.
(4) The conductivity is low, but it has a large electrode capacity for other compounds.
(5) There is a relatively low dipole moment and strong cooperation.
(6) It has the property of forming a hydrogen bond.
The effect of water on the flotation process:
(1) Association between water molecules: hydrogen bond association, dipole association.
(2) The role of water molecules and mineral surfaces: The result is a hydration or wetting of the mineral surface.
(3) Dissolution capacity of water: It plays a very important role in the flotation process, changing the chemical composition of the mineral surface, the interface electrical properties, and the chemical composition of the liquid phase, and changing the behavior of the mineral during the flotation process.
7. The nature of air and its impact on flotation.
Air is a mixture of typical non-polar materials that have a symmetrical structure. Easy to combine non-polar surface.
The solubility of air in the slurry is related to the pressure, temperature and concentration of other substances dissolved in the water. What makes sense for flotation is the relationship between pressure and solubility.
The role and influence of gas phase in flotation
(1) Carrier effect
(2) The main component can be actively adsorbed on the surface of the mineral to produce a special effect, and directly affect the floatability of the ore. Activator action, the most active of which is oxygen.
8. What is the relationship between the wet contact angle, the contact angle and the interfacial tension, and the floatability.
Wetting contact angle: the tangential line of the gas-liquid interface at any point P on the periphery of the three-phase wetting, and the angle formed by the liquid phase formed between the solid-liquid interface.
The contact angle is related to the interfacial tension of the three-phase interface of the contact. When the interaction with the interfacial tension reaches equilibrium, the contact angle is a function of the three-phase interfacial tension. Not only with mineral surfaces
It is related to nature and related to the interfacial properties of liquid phase and gas phase.
Anything that causes changes in the interfacial tension of any two phases can affect the wettability of the mineral surface.
When it is greater than 900, the mineral surface is not easily wetted by water, has a hydrophobic surface, and its mineral is hydrophobic. Good floatability.
When less than 900, the mineral surface is easily wetted by water, has a new water surface, and its mineral has new water and poor floatability.
9. Wetting block, the effect of wetting block on flotation.
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.
Two Blocking Effects of Wetting Block: Blocking Effect in Water Exhaust and Gas Drainage
Effect of Wetting Block 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.
10. Adhesion work and its relationship with wet contact angle and floatability.
Adhesion work: The change of free energy of the system before and after attachment when the ore particles and bubbles adhere to only a unit area.
Adhesion work ΔE=σAW(1-cosθ)
Wettability = cos θ
Floatability=1-cosθ
ΔE>0, the system free energy is reduced, and it is spontaneous. The larger θ, the larger the ΔE is, the more hydrophobic the mineral surface is, and the more spontaneous the fixation to the bubble is.
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