During the washing process, it is difficult to remove the surfactant which is difficult to dissolve in water instead of dirt. It is theoretically possible to remove adsorbed surfactants by rinsing and dissolving them with lots of water. However, there is always a small amount of surfactant on the surface of the surface of the coating film and remain in the actual washing conditions. In the precision cleaning process before coating, electroplating, vacuum coating and other processing processes, it is required to solve the problem of removing the surfactant coating film adsorbed on the surface thickness of only about 0.1nm. It is also difficult to remove with water when using surfactants with high degreasing capacity (surfactants with low HLB values). The use of higher temperature water, washing capacity is improved, so generally use the method of increasing the washing temperature to reduce the residual surfactant on the surface. When it is necessary to thoroughly remove the residual surfactant, soak it in ethanol or isopropanol, which have good solubility to the surfactant. Or in the degreasing power of the surfactant to remove dirt, and then use a strong hydrophilic surfactant for washing, in order to remove the strong hydrophilic surfactant, and then rinse the removal of hydrophilic surfactant.

In a word, it is more important to solve the problem of surfactant residue, especially in the field of precision industrial cleaning.

       In the cleaning process, a lot of waste is discharged into the environment, which will cause pollution. Especially, surfactant mixed with washing waste liquid flows into natural water, which is an important factor causing environmental damage. Many surfactants are difficult to biodegrade, such as branched alkyl benzene sulfonate, so use should be avoided to reduce environmental pollution. Currently, it has been replaced by sodium benzenesulfonate, which is biodegradable. In addition, the non-ionic surfactants of alkylphenol polyoxyethylene ether series have poor biodegradability. And their use has been reduced to other types of non-ionic surfactants.

From the point of view of biodegradation, all natural products or substances with similar structures are easy to be degraded, such as surfactants synthesized from high-carbon alcohols, fatty acids and glucose, which have good biodegradability and good compatibility with the environment.