Solubility of propane in aqueous solutions of sodium dodecyl sulfate–polyacrylamide with and without NaOH

Abstract

The solubility of propane in aqueous solutions of sodium dodecyl sulfate (SDS)–0.1 wt.% polyacrylamide (PAM) and SDS–0.1 wt.% PAM–NaOH (0.1 mol L^-1) has been determined at 298.15, 308.15 and 318.15 K. The concentration of SDS (m_SDS) is up to 50 mmol kg^-1. The solubility decreases with increasing temperature, and increases linearly with the concentration of SDS above its critical micelle concentration (CMC) or critical aggregation concentration (CAC), indicating that micelles in the solutions solubilize the gas molecules. It was found that the solubilization properties of the micelles bound to PAM and the free micelles are nearly the same. The solubilization property of SDS is changed by addition of PAM, although the solubilizing effect of the polymer alone is not considerable. Addition of NaOH decreases the ability of SDS to solubilize the hydrophobic gas. The standard Gibbs energies for the transfer of propane from bulk phase to the micelle phase are large negative values, indicating that the hydrophobic gas prefers to exist in the hydrophobic interior of the micelles.