Dear Miguel Pereira-Silva, mostly the CMC decreases with increasing salt concentration. Charges screening favors close contact of surfactant molecules and favoring hydrophobic interactions leading to ease of self-assembly (micellization). My Regards

Miguel Pereira-Silva

See new modern ideas about micellization, the influence of salt and how these conclusions can be applied in practice in my answer.

https://www.researchgate.net/post/How_does_polymer_surfactant_charge_influences_CMC_and_micelle_formation

the influence of electrolyte is mainly through interaction with the polar groups of surfactant but to minor extent also by interaction of hydrophobic groups with water. You should read about the effects of 'salting-in and salting out'. Obviously, changing aqueous solubility cmc is shifted. The other side is packing of the hydrophilic groups in micelle - for charged groups the range of electrostatic repulsion is changed, for nonionic ones the repulsion of hydration shells around the polar groups.

Hi! Good day !!

For Ionic,

The addition of salts decreases the CMC of ionic surfactants because of their tendency to screen the electrostatic repulsion at the surface of the micelle.

For non-ionic,

The CMCs of nonionic surfactants are lowered by the addition of salts, but not as much as that of ionic surfactants.

Mechanism:

When salt is added, CMC decreases by decreasing the repulsive action between the charged head groups of the surfactant molecules,

and this mechanism works against micelle formation.

adding salt ions decrease the repulsions, so micelles can form at a lower surface active agent concentration.

Please have a look at these papers to know more about this

Article Salt Effect on Critical Micelle Concentrations of Nonionic S...

Article Influences of Micelle Formation and Added Salts on the Hydro...