Bubbles in the water treatment problems a lot of people, debug early bubble, bubble surface active agent, bubble, bubble, peroxide circulating water treatment of cic and non oxidizing bactericide foam, etc., so the water treatment is one of the more common use of removing bubble agent, this paper introduces the principle of defoaming agent, classification, selection and usage.
Foam elimination method
1. Physical methods
Think in terms of physics eliminate foam methods mainly include placed baffle or mesh, mechanical stirring, electrostatic, refrigeration, heating, steam generating, radiation, high speed centrifugal, pressure relief, the high frequency vibration, instantaneous discharge and ultrasonic acoustic liquid (control), etc., of these methods in different extent promoted through rate and liquid membrane on both ends of the gas bubble film of drainage, The stabilizing factors of bubbles are less than the decaying factors, and the number of bubbles gradually decreases. But the common disadvantage of these methods is that the use of environmental factors constraints, defoaming rate is not high, the advantage lies in environmental protection, high reuse rate.
2. Chemical methods
The methods of eliminating foams from chemical point of view mainly include chemical reaction and adding defoamer.
Chemical reaction method refers to the chemical reaction between some reagents and foaming agent to generate insoluble substances, thus reducing the concentration of surfactant in liquid film and promoting the bursting of foam. However, this method has disadvantages such as uncertain foaming agent composition and harmful insoluble substances to system equipment. Now the most widely used defoaming method in all walks of life is the method of adding defoaming agent. The biggest advantage of this method is that it is efficient and convenient to use, but finding suitable and efficient defoaming agent is the key.
Principle of defoamer
Defoaming agent, also known as defoaming agent, has the following principles:
1. The local surface tension of the foam is reduced, resulting in the bursting of the foam
The mechanism begins when a higher alcohol or vegetable oil is applied to the foam, which, when dissolved in the foam, significantly reduces the surface tension there. Because these substances are generally less soluble to water, the reduction in surface tension is limited to a local area of the foam, while the surface tension around the foam barely changes. The part of the reduced surface tension is strongly pulled in all directions, extended, and finally ruptured.
2, destroy the film elasticity and lead to bubble burst
When defoaming agent is added to the foam system, it will diffuse to the gas-liquid interface, making it difficult for the surfactant with foam stabilizing function to recover the elasticity of the film.
3, promote liquid film drainage
Defoaming agent can promote liquid film drainage, resulting in bubble burst, the rate of foam drainage can reflect the stability of foam, adding a material to accelerate foam drainage, can also play the role of defoaming.
4, adding hydrophobic solid particles can lead to bubble burst
Hydrophobic solid particles on the surface of bubbles will attract the hydrophobic end of surfactants, so that hydrophobic particles produce hydrophilicity and enter the water phase, so as to play the role of defoaming.
5, solubilizing foam surfactant can lead to bubble burst
Some low molecular substances that mix well with solution can solubilize the bubbling surfactant and reduce its effective concentration. Low molecular substances with this effect, such as octanol, ethanol, propanol and other alcohols, can not only reduce the surfactant concentration on the surface layer, but also dissolve into the surfactant adsorption layer, reduce the tightness between the surfactant molecules, thus weakening the stability of the foam.
6. Electrolyte dissolves the double layer of surfactant
For the surfactant with the help of foam double electric layer interaction, the stability of foaming liquid, adding ordinary electrolyte can collapse the surfactant double electric layer to play a role in defoaming.
Post time: Mar-08-2022