Foam problems in the water treatment have existed for a long time. Such as initial debugging foam, surfactant foam, bursting foam, peroxide foam and so on. The use of the defoaming agents is more common in water treatment. The mechanism, classification of the defoaming agents are introduced in this article.
Defoaming Agent Mechanism
The defoaming agent, also known as antifoaming agent, has the following mechanism:
1 Decrease the Partial Surface Tension and Causes the Foam to Burst
The origin of this mechanism is to sprinkle the high alcohol or vegetable oil on the foam. When they melt into the foam liquid, the surface tension of the place will be significantly reduced.
Because high alcohol and vegetable oil have poor solubility to water. The surface tension is reduced only in the part of foam. While the surface tension around the foam has hardly been changed. The part of the surface tension decreased strongly extend to the surrounding and finally ruptured.
2 Destroy the Membrane Elasticity and Causes the Foam to Burst
The defoaming agents are added to the foam system, it will spread to the gas-liquid interface. That makes it difficult for the surfactant to recover the membrane elasticity.
3 Promote Liquid Membrane Drainage
Defoaming agents can promote liquid membrane drainage and cause the foam to burst. The drainage rate of foam can reflect its stability. To add a material which accelerates foam drainage also can have the defoaming effect.
4 Add Hydrophobic Solid Particles and Causes Foam to Burst
The hydrophobic solid particles can attract the hydrophobic end of the surfactant. That makes the hydrophobic particles have hydrophilicity and enter the water phase. For this reason, hydrophobic solid particles can defoam the foam.
5 Solubilize the Surfactant and Causes Foam to Burst
Some of the low molecular substances that can be fully mixed with the solution can solubilize the surfactant. That can reduce the effective concentration. This kind of low molecular substances includes octyl alcohol, ethanol, propanol and other alcohols. These low molecular substances not only can reduce the surfactant concentration on the surface layer, but also dissolve in the adsorption layer fo surfactant. That can reduce the compactness of the surfactant molecules. For this reason, the foam stability is weakened.
6 the Electrolyte Dissolves the Surfactant Double Electrode Layer
The surfactant dielectric layer interacts with each other to produce a stable foam fluid. By adding ordinary electrolyte, the dielectric layer of surfactant can be dissolved. So that can defoam the foam.
The commonly used defoaming agents can be divided into silicon (resin), surfactant, alkane and mineral oil.
1 Silicon (Resin) Class
Silicone defoaming agents are also known as emulsion defoaming agent. And the method is to use emulsifying agent (surfactant) emulsifier to the silicone resin dispersed into the wastewater. Silicon dioxide powder is another kind of silicon defoaming agent with good effect.
2 Surfactants Class
This kind of defoaming agents is an emulsifier. That uses the dispersing effect of surfactant to keep the emulsified state of forming foam stable in water. So as to avoid the formation of foam.
3 Chain Alkane Class
Chain alkane defoaming agents are made by emulsifying the chain alkane wax or its derivatives. The use is similar to the emulsified defoaming agents of surfactant.
4 Mineral Oils
The main defoaming components are mineral oil. In order to improve the effect, this kind of defoaming agents sometimes mixed metal soap, silicon oil, silicon dioxide and other materials used together.
In addition, in order to make the mineral oil easily spread to the surface of the foaming liquid. Or to make the metal soap evenly dispersed in the mineral oil. Sometimes it can be added with various surfactants.
In addition to defoaming agents, IRO CHEM also supplies high-quality hydroxyethylidene diphosphonic acid. If you have any requirements, please contact us.