The effect of adding sodium hypochlorite on the critical micelles concentrations for anionic and cationic surfactants

Abstract

The present paper included studying the effect of adding different concentrations of sodium hypochlorite on the critical micelle concentration (CMC) for each of the sodium dodecylsulfite (SDS) and Cetyltrimethylammonium Bromide (CTAB) at different temperatures. The values of ionization degree (α) and (β) were found, which represent the ratio of the number of counter ions associated with the micelles to the number of molecules which form the micelles (m/n). The thermodynamics functions of micellization, including standard enthalpy ( ), free energy ( ), and entropy ( ) for the micelle formation process were estimated in the absence and presence of sodium hypochlorite. The results showed there is a positive effect on CMC for both types of surfactants due to presence of sodium hypochlorite as the CMC decreased with increasing the concentration of the additive. At the same time, there is a direct relationship between CMC and the temperature. It was observed that there was a decrease in the ionization degree (α) values for SDS due to the presence of sodium hypochlorite, and thus an increase in the (β) (m/n) values, which was attributed to the decrease in the electrostatic repulsions between the polar heads of the SDS molecules. While there is no significant effect on the values of (α) and (β) for CTAB due to the presence of sodium hypochlorite which may be due to the common ion effect.