Solubilities of Ethane in Aqueous Solutions of Sodium Dodecyl Sulfate at Elevated Pressures

Abstract

The solubilities of ethane in aqueous solutions of sodium dodecyl sulfate (SDS) were measured at 313.15 K and at pressures up to 3 MPa. The molalities of SDS (mSDS) in the aqueous solution were 0.0000, 0.0020, 0.0040, 0.0060, 0.0070, 0.0080, 0.0090, 0.0100, 0.0126, 0.0150, 0.0200, and 0.0300. The effect of SDS on the gas solubility in both concentration regions below and above the critical micelle concentration (cmc) was studied. The existence of the micelles of SDS in the solution is favorable to the dissolution of ethane due to the hydrocarbon-like interior of the micelles. The solubilities of ethane in each micelle at different pressures were evaluated based on some assumptions. It was found that the intramicellar solubility of ethane is less than that of the gas in n-dodecane. It was also found that the solubility of ethane in the micelles increases linearly with the partial pressure of ethane. The cmc of SDS was evaluated based on the solubility vs mSDS curves and the effect of dissolved ethane on the cmc was studied. It was observed that the cmc shifts toward a higher value with the increase in dissolved ethane.