Adsorption of surfactants on soiled and washed surfaces

2023-02-23 16:57:06

Adsorption of surfactants (from solution) on soiled and washed surfaces has a major impact on cleaning action. This effect is mainly due to the changes in various properties (such as mechanical properties, electrical properties and chemical properties) of the interface and surface due to adsorption.

For liquid oil stains, the adsorption of surfactants on the oil/water interface mainly leads to a decrease in interfacial tension, which facilitates the cleaning of oil stains. The reduction of interfacial tension is also conducive to the formation of emulsions with greater dispersion. At the same time, the interface film formed by interface adsorption generally has greater strength, and the adsorption film may be charged (if it adsorbs surface active ions). The emulsion has high stability and is not easy to deposit on the surface of the washing.

Suspended solids in oilfield water can be removed with flocculants. A substance that can cause suspended solids in water to form flocs and precipitates is called a flocculant. Suspended solids in water are mainly suspended particles with negative charges on the surface, and the mutual repulsion between them makes it difficult to coalesce and sink. The flocculant can either neutralize the negative charge on the surface of suspended particles, or make the particles that have lost their charge quickly coalesce and sink.

The solubilization of surfactant micelles may have an important impact on the washing process, and there are many facts that are inconsistent with this discussion. But in any case, the emulsification of surfactants is always very important in the washing process, no matter how much oil is stained. To make the emulsification go smoothly, a surfactant with high surface activity must be added to minimize the interfacial tension. In this way, it can be emulsified with only a small amount of mechanical work (slight stirring). While reducing the interfacial tension, interfacial adsorption occurs concomitantly, forming an interfacial film with a certain strength to prevent the coalescence of oil droplets, which is beneficial to the stability of the emulsion, and the oil particles are also deposited on the solid surface in one step. However, it is obvious that only the oil The emulsification and dispersion of the detergent are not enough to effectively complete the washing process, and it is necessary to consider the influence of various factors discussed above according to the specific situation.