Effects of Alkali Metal Chloride and Carbonate Salts on Micellization of a Nonionic Surfactant

ABSTRACT Despite a substantial number of studies on the effects of salts on micellization behavior in surfactant systems reported in the literature, studies including carbonate salts are not easily found. The effects of salt concentration on nonionic surfactant critical micelle concentrations (CMC) are well known, for example via the linear dependence of the log of CMC on salt concentration. In this study, measurements of CMC of an ethoxylated alcohol surfactant in the presence of chloride and carbonate salts of Li + , Na + , K + , Rb + , and Cs + are presented. It was found that CMC reduction behaviors were different between chloride and carbonate salts. Studies of conductivity showed much higher degrees of salt‐surfactant interaction in carbonate systems. Light scattering studies showed slightly larger micelle sizes in carbonate systems, suggesting higher aggregation numbers or interaction of the salts with the micelle. The differing outcomes in chloride and carbonate systems may have been due to differing degrees to which the salts affect the aqueous bulk phase and the extent to which the salt interacts with the surfactant.