Interactions of Cationic Surfactant Cetyl-trimethyl ammonium bromide with Ammonium nitrate: Surface and Thermodynamic Studies

The study of interactions between surfactant and salt in aqueous solutions has attracted significant interest in recent years because of their widespread applications and relatively complex behavior. This work reports the systematic study of surface phenomenon and self-aggregation behavior of cationic surfactant cetyltrimethyl ammonium bromide (CTAB) with ammonium nitrate (NH _4 NO _3 ) salt. Surface and thermodynamic properties of cationic surfactant CTAB with NH _4 NO _3 were investigated at different temperatures using different techniques such as conductometry and surface tensiometery. The surface tension measurement was carried out to find out the critical micelle concentration, free energy of adsorption, free energy of micellization, minimum area per molecule, and surface excess concentration. The study reveals that the process of micellization is spontaneous and exothermic in nature. Conductance measurement was carried out to determine critical micelle concentration, degree of ionization and degree of counter ion binding. Addition of NH _4 NO _3 to the surfactant solutions increase the values of degree of ionization and degree of counter ion binding, although it lowers the values of critical micelle concentration showing that the process of micellization is more favorable and spontaneous. The study is very helpful to develop better understanding about interaction between electrolyte and surfactant, which are used in many applications and in different processes (e.g., pharmaceutical, industrial foaming, drug solubilization, oil recovery, and medium for metal nanoparticle formation).