The dissolution characteristic of nonionic surfactants in supercritical CO2

Abstract The effects of surfactant structures on the supercritical carbon dioxide (scCO2) solubility are investigated to shed some light on the application of scCO2 in chemical procedures. The dissolution pressure of three nonionic surfactants (TX45, TX100 and OP-10) in scCO2 was measured. Solubility results reveal that surfactant with branched alkyl chains shows better solubility than surfactant with linear alkyl chains. This may be due to the volumes occupied by the hydrophobic tails of these nonionic surfactants. TX45 with the largest tail volume and lowest molecular weight performs the largest solubility in scCO2. In addition, the solubility results of three nonionic surfactants in scCO2 at the temperature range of 305 K to 325 K show that solubility is proportional to the pressure and density of scCO2, and inversely proportional to the experimental temperature. Finally, two density-based models (Chrastil model and Bartle model) are applied to correlate the experimental solubility data, and the results show good agreements for the experimental data of investigated nonionic surfactants. Similar agreements with experimental solubility data of surfactants are obtained by both models and the average absolute relative deviation (AARD) values lower than 2% were obtained.