Interfacial phenomena of aqueous systems in dense carbon dioxide

The interfacial tensions of initially pure liquids (water, ethanol and corn germ oil) and water-ethanol mixtures against dense carbon dioxide as well as against dense carbon dioxide mixtures with water and ethanol at 313 K and at pressures up to 27 MPa are measured. The wettabilities of ethanol and water on PTFE, glass and steel surrounded by pressurized carbon dioxide are also included in this paper. The interfacial tension results reported are the static values as well as the values which are measured during mass transfer. Generally, it is known that the interfacial tension depends on the composition of the coexisting phases. However, up to now, it is not clear whether only the composition of the interface does have an influence on the interfacial tension or if the composition of the bulk phase also affects this property. The detail discussion on this issue can be found in this paper. In this regard, the estimated pressure difference over the meniscus of a water drop with a diameter of 5 mm is reported. During mass transfer some interesting but scarcely reported drop phenomena such as drop kicking, upwards motion of the continuous phase around the drop, rising bubbles and intense mixing in the drop phase are observed. They are closely related to the interfacial turbulence, free convection, diffusion and stranding of the carbon dioxide molecules. The contact angle of ethanol and water drop over a pressure range of 27 MPa on PTFE, stainless steel and glass surfaces in the presence of dense carbon dioxide are included. (C) 2008 Elsevier B.V. All rights reserved.