Dilute solutions of surfactants follow the law of ideal solutions

2023-01-07 09:05:01

Oxygen-increasing principle of surfactants: Adding surfactants to aquaculture water can increase the saturation solubility of oxygen in aquaculture water. According to the hydrate formation theory and the double-membrane theory, since the solubility of oxygen in water is very small, water-oxygenate is generally first formed at the gas-liquid interface in water, and then slowly diffuses from the gas phase to the liquid phase.

In the water body containing surfactant, due to the solubilization effect of the surfactant, a large amount of oxygen is dissolved in the surfactant micelles formed in the aqueous solution, so that the formation of water-oxygenate in the aqueous surfactant solution can not only It occurs at the gas-liquid interface and can also occur inside the water body at the same time, reducing the water-oxygenate formation time and increasing the solubility of oxygen in the water body.

Dilute solutions of surfactants obey the laws followed by ideal solutions. The adsorption amount of surfactant on the surface of the solution increases with the increase of the concentration of the solution. When the concentration reaches or exceeds a certain value, the adsorption amount does not increase any more. These excessive surfactant molecules are disorderly in the solution, or in some way There is a regular pattern. Both practice and theory show that they form associations in solution, which are called micelles.

Surface pressure of the adsorption film: Surfactant adsorbs on the gas-liquid interface to form an adsorption film. For example, a frictionless movable floating piece is placed on the interface, and the floating piece is used to push the adsorbed plasma membrane along the solution surface, and the membrane generates a pressure on the floating piece. This pressure is called surface pressure. Surface Viscosity: Like surface pressure, surface viscosity is a property exhibited by insoluble molecular films.

Suspend a platinum ring with a thin metal wire, make its plane touch the water surface of the tank, rotate the platinum ring, the platinum ring is hindered by the viscosity of the water, and the amplitude of the vibration gradually attenuates, and the surface viscosity can be measured accordingly. The method is: first on the surface of pure water Carry out an experiment to measure the amplitude attenuation, then measure the attenuation after the surface film is formed, and calculate the viscosity of the surface film from the difference between the two.