Solubility of surfactant in water is known to decrease with increase in the salt concentration in water.
However, if increase in salt concentration has lead to increase in the solubility of a surfactant, in my case a zwitterionic surfactant, what could be the possible reasons for such behavior ?
I think it depends on the ionic strength and reactions between a particular surfactant and soluble salts. The ionic strength of water could effect on activity, which decreased when ionic strength is increased. When the activity is decreased, the formation of hydrogen bonding between the water molecules and the hydrophilic moiety of surfactants is weakened, so that surfactant aqueous solubility is increased. But maybe there is an optimum ionic strength. You can see this paper: Journal of Hazardous Materials B119 (2005) 195–203
Dear all, for sure not only the solubility is affected but most of other properties, such as micellization. It depends mainly on the type of surfactant in question (neutral, anionic, carbonic, or zwitterionic). At extreem situation, if the screening effect is efficient than phase separation occurs. My Regards
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