Physico-Chemical Studies of Some Aqueous Surfactants in Alcohols

Critical micelle concentration (CMC) values have been determined for aqueous solutions of sodium dodecyl sulphate (SDS), dodecyl trimethyl ammonium bromide (DTAB) and Triton X-100 in mixed solvents (Water + n-propanol, water + iso-propanol) at 298, 308 and 318 K by conductance and surface tension measurements. The observed data have been utilized to evaluate surface properties, i.e., surface excess concentration (T_max), surface pressure at critical micelle concentration (Π_CMC) and thermodynamic parameters of micellization (ΔG⁰_m, ΔH⁰_m and ΔS⁰_m), adsorption (ΔG⁰_ad, ΔH⁰_ad, and ΔS⁰_ad) and transfer (ΔG⁰_m) of surfactant molecules from aqueous solution to mixed solvent. The conductance data have been utilized to evaluate counterion association constant (α). The various parameters have been discussed to explain the micellization behaviour of surfactants in mixed solvent system.