First, the requirements of flotation on flotation and its classification The concept of flotation foam and foaming agent:
In the pure water in which the heteropolar surface active material is present, the slurry is aerated to form fine and relatively tough bubbles or foams, and the bubbles float to the surface to form a fine bubble collecting layer having a certain stability, and this layer is a foam layer.
Two-phase foam: a foam formed by two phases of gas and liquid.
Three-phase foam: a foam formed by gas, liquid, or solid three-phase foam, or mineralized foam mineralized gas bubbles.
Foaming agent: It can promote the formation of a large number of materials of suitable size and stability foam in the medium.
Type (having foaming properties): organic heteropolar surface active substances such as alcohols, phenols, ketones, aldehydes, ethers, esters, acids, and the like.
2. Requirements for the foaming agent and the conditions it should have
(1) The foaming agent should generally be an organic, heteropolar surface active material having a suitable structure, and the foaming properties are determined by the nature of the polar group and the non-polar hydrocarbon group.
a Polar base:
Best: -OH (hydroxyl), 
Ether group, two kinds of polar groups are ideal polar groups with strong hydration, no trapping effect, and little PH value. In addition, -COOH, -NH2 (amino), -SO3H (sulfonic acid group, etc.) have strong foaming ability, strong affinity, and large pH value.
b non-polar base:
The foaming agent exerts a foaming action on the entire molecule.
Theoretically, the non-polar group may be composed of any type of hydrocarbon group, but the hydrocarbon group length, molecular weight, and structure type properties have an effect on the foaming properties.
c Polar group: The relationship between non-polar groups and foaming properties (described in the next section).
(2) Proper solubility in the slurry.
a High solubility: less adsorption at the gas-liquid interface, even no foaming performance, fast foaming, fragile bubbles, loose foam structure, large amount, H3COH, H3CH2COH.
b Low solubility: retained slurry surface, slow foaming speed, dense foam structure, long bubble life, difficult to control flotation process.
c Appropriate solubility: C4 ~ C10 fatty alcohol, most ideal C5 ~ C8.
(3) No capture of minerals.
(4) It has strong adaptability to the change of pulp pH value and other components in the pulp.
(5) Low dosage, non-toxic and non-polluting environment.
3. Classification of foaming agents
(1) Classification according to the source of the drug:
A, natural product extraction: pine oil, camphor oil;
B, industrial by-products of coal coke extraction: methanol, pyridine;
C, human synthesis, alcohols, ethers, alcohol ethers.
(2) Classification according to molecular structure characteristics:
A, nonionic (alcohol, ether alcohol, ethers, esters);
B, ionic (phenols, heavy pyridine, hydrocarbyl sulfonic acid (sulfate) salts, carboxylic acids and their soaps, amines).
Second, the role of foaming agent and its mechanism of action
1. Reduce the tension at the gas-liquid interface and change the dispersion of the bubbles.
(1) Relationship between δAW and foaming ability When the external power consumption is the same, δAW is lowered, and the air flow is divided to easily form bubbles, and more gas-liquid interfaces for sorting are generated.
The relationship between the two is as follows:
in conclusion:
A, bubble and state can not form a stable foam layer, the actual production is far below the C point value;
B. The size of the foaming ability is not completely determined by the absolute value of the surface tension reduction.
(2) Improve the dispersion of bubbles
When the aeration amount is a certain V, the smaller the bubble diameter is, the larger the gas-liquid separation interface area is, and the higher the dispersion degree of the bubbles in the sorting space is, which is advantageous for sorting.
Requirements for bubble size: According to the requirements of the buoyancy and lifting speed requirements of the sorting, the bubble size is determined. There is no foaming agent in the clear water, the bubble diameter is 4 to 5 mm, and the bubble diameter is 0.8 to 1 mm when there is a foaming agent.
Modern theoretical studies have shown that microbubbles have a reinforcing effect on the flotation process.
2. Block or mitigate the mutual merger (off) of bubbles.
(1) Reasons for bubble merger (off):
Dehydration:
Gravity effect: underwater discharge in the foam layer;
Evaporation: evaporation of the surface water of the foam layer;
Tension effect: △Px= -2δ/R<0
In the border area of ​​Plano: △Py=0
B. Capillary pressure action: The capillary pressure P of different adjacent bubble diameters is different. The bubbles are saturated with the large bubbles and are merged by the large bubbles.
(2) Mechanism of action
A. The orientation of the surfactant at the liquid surface interface forms a hydrated film, which hinders the water from flowing and evaporating, and improves the bubble life.
B. Electrical effect: The same kind of electrical repelling is close to difficulty.
3. Increase the mechanical strength of the bubble and improve the stability of the bubble.
When the bubble is subjected to an external force, the surface is locally deformed, the surface area is increased, the concentration of the foaming agent in the deformation zone is lowered, and the tension is increased to restore the bubble shape.
4. Reduce the speed of bubble rise and fall in the slurry.
(1) Reason: A, the open shape of the rising bubble
When there is no foaming agent: oval, fish shape
When there is a foaming agent: round
B. Hydrogen dipole cohesive attraction;
C. The bubble diameter is small, and the buoyancy and speed are reduced.
(2) Role: A, increase the collision probability of bubbles and ore particles;
B. Reduce collision kinetic energy;
C. Reduce the vibration of the mineralized bubbles, shake, and reduce the probability of falling off.
Third, the role of foaming agent formation
1. The role of a simple foaming agent;
2. Co-adsorption of the foaming agent with the collector .
Fourth, the stability of the foam layer
1. Two-phase foam layer instability
2. Three-phase foam stability
(1) The armor of the ore particles;
(2) the action of the agent, the co-adsorption of the foaming agent and the capture;
(3) The influence of the shape and size of the ore.
3. Secondary enrichment
Fifth, the composition and structure of the foaming agent on the foaming performance
1. Effect of polar groups on foaming performance
(1) affecting solubility;
(2) affecting the degree of dissociation;
(3) The influence of hydration.
2. Effect of non-polar groups on foaming performance
(1) the length of the carbon chain;
(2) Non-polar base properties, structural properties, degree of saturation, and form of chains.
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